University of Southern California Dissertations and Theses

Synthesis of new second-order chromophores and functionalization of sulfur containing donor moieties

(USC Thesis Other)

Synthesis of new second-order chromophores and functionalization of sulfur containing donor moieties

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content SYNTHESIS OF NEW SECOND-ORDER CHROMOPHORES AND FUNCTIONALIZATION OF SULFUR CONTAINING DONOR MOIETIES by Hu Li A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (Chemistry) August 1996 Copyright 1996 Hu Li Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F SOUTHERN CALIFORNIA TH E GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES. CALIFORNIA 9 0 0 0 7 This thesis, written by under the direction of h„i . $. . Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillm ent of the requirements for the degree of Dtsn THESIS COMMITTEE Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS ii During the course of this research, I received help from a great number of people. I would like to extend my greatest appreciation. First, I would like to thank my parents and sister for their encouragement and support; without them I would never be here. Next, I acknowledge my research director Prof. Larry R. Dalton. He showed a great deal of patience, gave me the extreme freedom in research and shared his expertise in the field. I also want to acknowledge my other committee members: Prof. Weber and Prof. Appleman for taking time out of their busy schedule. I also owe thanks to Prof. Charles W. Spangler and Prof. Brenda Spangler. They have been helping me every step of the way and shared their knowledge both in chemistry and in life. They are like family to me. All the other group members have been extremely helpful and made my stay in USC a pleasant one, especially Aaron W. Harper for providing me acceptors for the chromophores I was working on, as well as his friendship. Last but not the least, I would like to thank Christina J. Meyskens. She has always been there for me during some most difficult moments in my life. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Since 1960’ s, nonlinear optics involving organic material has been a explosive field with great potential. Various types of systems have been studied and new chromophores with high nonlinear response have been synthesized, especially for second harmonic generation. Some polymers with high second-order chromophores were tested for device manufacturing. Despite the improvement in second-order NLO material, many problems still exist such as thermal stability and poling efficiency. Jen and coworkers incorporated sulfur containing moieties as donor groups in second-order chromophores and showed they are quite efficient and thermally stable. However, chromophores studied only contain tetracyanovinyl group as acceptor and new donors were not functionalized. In this study, other efficient acceptors were incorporated and functionalization of one of the donor groups was attempted. The first chapter mainly discusses the general background of nonlinear optics and various polymer systems studied, as well as the research objective. First part of the second chapter discusses the synthesis of new chromophores containing 1,3-benzodithiolyldinemethyl group as a donor and various acceptors such as isoxazolone. A .max for most of chromophores is around 585nm in nonpolar solvent and 610nm in polar solvent, 20-25nm red shift from nonpolar to polar solvent; the second part of the second Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. chapter shows the functionalizadon of 2,5,7,9-tetrathiabicyclo{4.3.0]non- l(6)-enyl group, another donor group. Reactions conditions still need to be improved to optimize the yields. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Pages CHAPTER ONE. A Review of Nonlinear Optics and Polymer Systems for Second-Order Nonlinearity 1 1.1 Introduction 1 1.2 Basics of nonlinear optics 3 1.3 Second-order nonlinear optics 11 1.4 Review on second-order polymer systems 17 1.4.1 Guest-host system IS 1.4.2 Side chain polymer system 20 1.4.3 Main chain polymer system 25 1.4.4 Cross-linked system 26 1.5 Research objective 32 1.6 References 34 CHAPTER TWO. Synthesis of New Chromophores and Functionalization of Sulfur Containing Donor Moieties 3 8 2.1 Synthesis of chromophores containing 1,3-benzodithiolyldinemethyl group as donor 38 2.2 Functionalization of 2,5,7,9-tetrathiabicyclo[4.3.0]non- l(6)-enyl group 43 2.3 Conclusion 48 2.4 References 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. v i LIST OF FIGURES Figures Pages 1.1 Second harmonic generation in a second-order NLO material. 7 1.2 Nonlinear electronic response to optical field in term of potential felt by the electrons in the optical medium. 10 1.3 Electronic response to optical fields for linear, second-order nonlinear and third-order nonlinear optical media. 13 1.4 Structures of two 2,4,5-triarylimidazoles 19 1.5 Examples of PMMA polymers with NLO chromophores tethered a side chain. 21 1.6 Thermal stability comparison of G-H system and SC system. 21 1.7 Reaction scheme of a NLO polyimide with excellent thermal stability. 22 1.8 Comparison of SC, isoregic MC and syndioregic MC NLO polymers with the same chromophore. 25 1.9 Reaction scheme for NLO polyimide (II). 26 1.10 Thermal stability comparison of imidized and non-imidized NLO polymers outlined in figure 1.8. 26 1.11 NLO polymer cross-linked with diepoxy compounds (chromophore tethered as side chain). 29 1.12 Diepoxy cross-linked polymer as chromophore incorporated in the backbone. 29 1.13 a) an example e r f a cross-linked system, b) chromophores incorporated in the system. 31 2.1 Reaction scheme for the preparation of phosphonium salt containing 1,3-benzodithiolyldinemethyl group. 39 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2 Reaction scheme for synthesis of chromophores containing 13-benzodithiolyIdinemethyI group. 2.3 Reaction scheme of the functionalization of 2,5,7,9-tetrathiabicyclo[4.3.0]non-l(6)-enyl group. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES Table Page 1.1 Nonlinear optical properties of some important chromophores 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 Chapter One A review of nonlinear optics and polymer systems for second-order non linearity 1.1 Introduction With the high demand in information processing, the electronic technology starts to show its inadequacy. We have pushed the conventional electronic technology to nearly its theoretical limits. Technology involves higher speed transmission and higher density storage for information processing is required. Photonic technology is the best candidate for the "information superhighway" era. One of the areas now under intensive research is the development of electro-optical modulators using nonlinear optical material. Until late 1800's, it was taken for granted that all optical media were linear. It's reflected in following understanding of light and the medium it passes through: 1) the frequency of the light is independent of the medium it passes through; 2) two light beams cannot interact with each other; and 3) optical properties of the medium, such as the refractive index, will not change upon different light intensity. In 1875, J. Kerr observed a change in refractive index of carbon disulfide due to a quadratic electric field. Now this is referred as the Kerr effect. Short after that, in 1883, similar change in quartz induced by a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 linear electric field was reported by F. Pockels, now known as the Pockels effect. These discoveries started a new field: nonlinear optics. However, it was realized to use nonlinear effects an intense light source (10? V/cm) is essential and back then it was almost impossible to achieve such task. In 1960, laser was invented and the following year, P. Franken and coworkers observed second harmonic generation in quartz. Since then, nonlinear optics gradually became a major research interest in the science society. The behavior of light and the media it passes through has been shown to exhibit nonlinear properties, such as 1) frequency of the light can be altered; 2) photons can interact with each other; and 3) the optical properties of a medium can be changed due to high intensity light source. Nonlinearity is a property of the optical media instead of light itself. Thus, researchers have been look for new materials to increase the nonlinear signal to be practical for commercial application. The materials under study include both inorganic and organic nonlinear optical (NLO) compounds. The former one is more mature in its development and optical devices made of inorganic NLO materials, such LiNi03, GaAs/AlGaAs, are commercially available. On the other hand, organic NLO materials are still at their infant stage, but showing very promising results. In comparison, inorganic NLO materials have limited use due to their intrinsic properties. For instance, lithium niobate has a maximum electro- optical coefficient of about 30pm/v and in modulator applications, its high dielectric constant results in an intrinsic bandwidth-length product of only 6 GHzcm which will require special designed electrodes at high frequencies to match the velocity of the light beam and the microwave drive EM Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 radiation. 1 Thus, to drive the electrodes, a high rf power is needed. Inorganic NLO materials also have processing difficulties due to their mechanical properties, such as fragility. Same study done on organic NLO materials showed organic NLO materials have much higher electro-optical coefficient^ , low dielectric constant and fast response t i m e .3 > 4 Furthermore, most of the NLO chromophore incorporated polymer systems have good thermal, chemical stability and higher laser damage threshold, not mentioning the advantage in processing because of the ease in structural m o d i f i c a t i o n . 5 , 6 Different NLO polymer systems studied will be discussed in more detail in section 1.3. 1.2 Basics of nonlinear optics^, 7-10 The optical nonlinearity of a molecules is caused by perturbation of the internal electric field when interacts with applied electromagnetic radiation. If the applied field strength is relatively low, the polarization of the molecule (P) and the field strength (E) correlates linearly as expressed by following equation: P = X(1).E (1.1) where is the polarizability or dielectric susceptibility. The refractive index (n) is independent of field strength and is proportional to %d): Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 n2(co) s 1 + 47t%(l) ( 1.2) As a laser is applied, the molecule starts to show optical nonlinearity. On the molecular level, the polarization of the molecule Q x) can be expressed as a power series of field (E): where j l l o is the permanent ( or ground state) polarization; a is the linear coefficient; P is the second-order molecular susceptibility tensor or first hyperpolarizability and y is the third-order molecular susceptibility or second hyperpolarizability. For a bulk material, the polarization (P) and the field (E) are related in a similar fashion: where x ^ are defined in similar fashion as a, p and y, respectively. The refractive index (n(co)) of a nonlinear optical medium is related to the field (E) in following equation: where Xeff is the effective susceptibility which changes with different applied field. jx = H o + + pHE + yEEE + ••• (1.3) P = Po + x (1>-H+ X (2)*EE + x<3>-EEE + - (1.4) n2(©) = 1 + 47txeff (1.5) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 The applied field can be solved from the Maxwell wave function under the assumptions that the optical medium is insulating and non magnetic and that the interaction with the medium is electric dipolar. The wave equation describing the propagation of an electromagnetic wave is: V1£ = — c2 dt2 where e is the dielectric constant, c is the speed of light and is the Laplace operator which is defined as: ( 1 -7 ) where x, y and z are Cartesian indices. To simplify the problem, we assume that light is traveling as a plane wave in the z direction. The simplified version of equation (1.6) is as following: dzE e d2E dz2 c2 dt2 (1.8) One solution of equation (1.8) is a traveling wave in the z direction with the field E(z, t) as a sinusoidal oscillation : E(z, t) = Eo cos(cot - kz) (1.9) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 where k2 = S E - (l.io) C and Eo is the field strength. Now by substituting E in equation (1.4) with equation (1.9), we get the following expression: p = ^ ( 1) Eo cos(cot - kz) + % (2) Eo^ cos2(©t - kz) +X^)Eo^cos3(o)t - kz) (1.11) After applying proper trigonometric operation, the following equation is obtained: P = x (1 )Eq cos(©r - k z) + [* + cos(2©r - 2 kz)] +X( '3)Eq [jcos(© f - kz) + icos(3fi)r - 3kz) (1. 12) The second and third terms in above equation show new frequency components (2© and 3©) resulted from nonlinear polarization of the optical medium. For instance, the second term (2©) is the second harmonic generation which schematically can be shown as in figure 1.1 : Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 0 ) i l l SHG Figure 1.1 Second harmonic generation in a second-order NLO material. A more complex scenario is that a optical field is applied as the material is exposed to a dc electric field (E(0)). The total field applied now is : E(tot) = E(0) + Eo(cot - kz) (1.13) The same operation is done to obtain : P = [H(0) + Eo cos(cot - kz)]+ %(2) [E(0) + Eo cos(tot - kz)]2 +X(3)[E(0) + Eo cos(ot - kz)]3 (1.14) After the same trigonometric operation, we get the following equation : P = ^(1) Eo cos(cot - kz) + 2%(2) E(0)Eo cos(mt - kz) +3%(3)e2(0)E0 cos(cot - kz) + 3/4 x(3)E3(0)Eo cos(cot - kz) = Xeff E(0) cos(cot - kz) (1.15) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 By the same token, the refractive index can be expressed as: n2 = I + 4* [x(l) + 2X (2) E(0) + 3X (3)e2(0) + 3/4 X (3>e2o] (1.16) Recognizing that E2o = (Sk/c ”) I where I is the intensity and n2 = (n + noXn - no) ~ 2no(n - no), we can plug these two equations into equation (1.16) to rewrite it as : where ni, 1 1 2 and 1 1 3 are the nonlinear refractive indices and can be expressed a s : and they correspond to the Pockels effect, the quadratic electrooptical effect and the Kerr effect. We can see that the X (2) term, ni, is linearly dependent on the incident field E(0), the X (3) term, n2.quadratically dependent on the incident Held and has a linear relationship with the light intensity. For device manufacturing purposes, Kerr effect can be used for optical switching due to its linear relationship with the light intensity as the Pdckels effect can be used for second harmonic generation and optical rectification, etc. n(o>) = no + niE(0) + n2(0)E2(0) + n^co)! (117) m = 4jiX(2)/no nXO ) = Gx x (3)/ no n2 (co) = \2x2yQ)lc no2 (1.18) (1.19) ( 1.20) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 Another way to look at NLO effect is shown in figure 1.2. The three graphs show the potential well that electrons feel in linear optical, second- order NLO and third-order NLO material. The actual mathematical deduction is as following : In a linear optical medium, the equation of the motion is ^ i + 2r — = (1.21) dt dt m where x is the electron coordinate and T is the damping constant. To include the second-order effect, ax2 is added to the motion equation : ^ f + 2 r — + a x 1 = - - B ( 1 .2 2 ) dt2 dt m where a is the parameter describing the second-order nonlinear response. The damping force is therefore : ^restoring = “D M O ^X - max^ (1.23) Thus, the potential energy will simply be an integration of the damping force : U = 1/2 mco2x 2 + 1/3 max^ (1.24) The derivation for third-order nonlinear effect is similar to the one for second-order nonlinear effect except replacing ax2 with bx^ where b is the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 U(x) x Linear optical medium U(x) parabola parabola actual potential x Nonlinear optical parabola parabola x Nonlinear optical centrosymmetric medium Figure 1.2 Nonlinear electronic response to optical field in terms of potential felt by the electrons in the optical medium. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 parameter describing the third-order nonlinearity. As we can see that the potential well that electrons feel is not perfectly parabola except in the first graph corresponding to the first term in equation (1.24) and this causes NLO response. 1.3 Second-order nonlinear optics^, 7-10 Second order nonlinear optical effects "can be visualized as an interaction in terms of the exchange of photons between the various frequency components of the field" where as two photons are destroyed and simultaneously a third photon is created. Depending on different material, sum- or difference- frequency generation can by observed. The second-order susceptibility is denoted as : %Q) (-C O 3; ©1 , ©2), where ©3 = © 1 ± ©2, and the negative sign is a convention to indicate that the momentum is conserved in the process. In a Cartesian coordinate, the ith component of the nonlinear polarization vector P)2 ) can be expressed as : p ? = S X ^ E jEk (1-25) J,K %(?) and |3 (molecular hyperpolarizability) are related as in following equation: X u k ( - ® 3 = N f j ( © 3 ) f j ( © ! ) f k (co2 ) ( p ijk ( - © 3 ; © 1, © 2 ) ) IJK d - 26) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12 where N is the number density of the chromophore, f s are so called "local field factors", the bracket indicates that the term inside is the average |3 value over all orientations. Thus, if chromophores are randomly oriented, this term will be zero resulting in no NLO signal. This determines that noncentrosymmetric medium is essential for second-order NLO response. When NLO material is exposed in a poling field, we can rewrite equation (1.22) a s : X {2) =A7?/2(® )/(2q))(cos3 0) (1.27) where <cos3 0> is the alignment factor that describes the average orientation of all the chromophores in which 0 is the average angle between the orientation of the chromophores before poling field applied and the direction of perfect alignment after applying the poling field. A graphic representation of the necessity of noncentrosymmetric medium is shown in figure 1.3. Part (a) shows a external monochromatic electromagnetic wave; as in part (b), the wave form exhibits no distortion after passing through a linear medium; part (c) displays a wave form distortion after the applied field interacts with a nonlinear, but centrosymmetric medium, however, only odd harmonics of the fundamental frequency are induced. After cancellation , no NLO signal will be observed; part (d) shows both odd and even harmonics of the fundamental frequency are induced while external field interacts with a nonlinear and noncentrosymmetric medium. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13 applied field linear response fiit) nonlinear, cencrosymmetric medium ^(0 nonlinear, noncentrosymmetric medium Figure 1.3 Electronic response to optical fields for linear, second-order nonlinear and third-order nonlinear optical media. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 In the study of second-order NLO effects, instead of > two other coefficients are widely used: dijk and ryk. They are the second harmonic generation coefficient and electrooptic coefficient, respectively and they are define a s : where i, j and k are Cartesian indices. The nonlinear optical phenomena of certain materials can be employed in the manufacture of various optical devices such as electrooptical modulator, optical switch, optical limiter, optical information storage and process devices, etc. How ever, only second-order materials are currently fabricated to build practical devices as the third-order material and higher order nonlinearity are still under investigation due to their small optical nonlinearity. Also, the relationship between the structure and nonlinearity for second-order material is much better understood than the higher order ones. Second-order chromophores have been synthesized in the general form o f : electron donor-7 t electron bridge-electron acceptor. Some of the second-order chromophores are shown in table 1.1.50 (1.28) and r ijk ~~ „ 2 „ 2 ^ ijk n i j (1.29) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 Table 1.1 Nonlinear optical properties of some important chromophores # Molecule pP (10-4 8 esu) Po (10*3 0 esu) 1 HjCO-<0>—NO, 71 (1.9)* 2 / N— —N°2 140(1.3) 12 3 no2 358 (1.3) 25 4 275 (1.9) 5 ^N 330 (1.9) 8 10 & 11 (C H3 )2N — N A - O - V o - n* \ I / " t H y 580(1.9) 800 (138) 1470(1.58) ,C N C N , /=\ C N C N 4100(1.58) i { 1 C N 560(1.9) 106 55 51 10 1 154 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16 12 13 14 15 16 17 18 19 20 N -tQ - N °2 Bu _ CN Bu n 4 c« CN X H CN p CN CN N " \ \ / ( S ' 700(1.9) 1040(1.9) 2190 (1.58) 1300(1.9) 6200 (1.9) ?N 9100(1.9) 2400 (1.9) 104 5320 (1.58) 147 9830 (1.9) 770 * The wavelength in (lm for EFISH measurement. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 1.4 Review on second-order polymer systems Since second-order nonlinearity usually occurs in noncentrosymmetric materials, the major goals are designing high ( 3 chromophores and at least partially aligning them in the same direction. Equation (1.27) shows that second-order nonlinearity % (2) is proportional to chromophore number density (N), the molecular hyperpolarizability (p) and the alignment of the chromophores (<cos30>). There are two methods to incorporate chromophores in a polymer matrix: either by guest-host system or by covalently attaching them to the polymer through side-chain, main-chain and cross-linking systems. The latter one exhibits higher chromophore loading density without losing the qualities of the material. One major reason is in a guest-host system, the incompatibility of NLO chromophore with the polymer matrix. As the loading density gets too high, NLO chromophores start to aggregate or crystallizing, destroying the homogeneity of the polymer film.H Thus, the guest-host system can not be used in device manufacturing. Normally, in a guest-host system, the weight percentage of the chromophore is controlled between 10-30% to ensure the quality of the film while in covalent incorporation method the weight percentage reaches up to 80%. Also, there is health problem involved in dealing with low loading guest-host system due to the transferring of chromophores on the surface of the film to skin by just touching and absorbed through skin. Most chromophore are toxic, mutagenic, teratogenic and carcinogenic. Therefore, guest-host system is Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18 used in preliminary study of chromophores in research labs instead of commercial device manufacturing. 1.4.1 Guest-host system Early study of various chromophores were done in guest-host system considering the simplicity of preparation and the immediate availability for measurement. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) are widely used and good results were reported for such systems. Examples of chromophore studied in PMMA guest-host system are Disperse Red 1 (DRl)i2-15 and4-dicyanovinyl-4'-(dialkylamino) azobenzene (DCV).i^ DR1 h3 ch2 c hoh2ch2c h3 ch2c hoh2ch2c N C CN CN DCV For DR1, loading density (by weight) of only 15% was achieved since higher loading caused phase separation. r33 of 2.5 pm/V at 633nm and d33 of 6.7 pm/V at 1.58 pm were reported. DCV gave much greater d33 value (74 pm/V) at 1.58 pm with 15% loading by weight. However, the signal decayed to 25% of the original in just several days. One method to reduce Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19 the rate of alignment decay is to use bulkier chromophores because they have smaller rotational mobility. *6,17 Boyd and coworkers 18 investigated rotational mobility of a series of chromophores with different molecular volume. Boyd et al. also suggested that hydrogen bonding between chromophore and polymeric backbone will further reduce the poled-order decay. Another factor effects the poled-order is the glass transition temperature (Tg) of the doped system: systems with higher Tg proved to have longer relaxation time. This effect is much more significant for bulkier chromophores. 19-21 Polyimide was intensively investigated; however, due to its low solubility, chromophores were dissolved in its precursor polyamic acid and then cured at a higher temperature after the poling field is applied. Example are two low optical loss poly(ether imides) doped with two 2,4,5-triarylimidazoles shown by General E l e c t r i c .20, 21 Two chromophores used have very good thermal stability (>300 °C) and their structures are shown in figure 1.4. NH NH o c h 3 h3c o Figure 1.4 Structures of two 2,4,5-triarylimidazoles Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 The chromophores are quite soluble in the host Goading of 30% by weight was achieved); but at high loading density, plasticization was observed. At 20% loading, the guest-host system has a Tg of 170 °C and d33 of 12 pm/V at 1.06 |im. The polymer also showed excellent optical signal retention. From above discussion, we can see that guest-host systems have high optical loss due to intramolecular rotation of the chromophores and/or relaxation of the polymer chain. Although intensive research has been done to deal with these problems, there are other ones such as low loading, phase separation, chromophore aggregation, and plasticization, etc. These problems limited the commercial application of the guest-host systems. 1.4.2 Side-chain polymer system In side-chain (SC) polymers, chromophores are incorporated in the polymer matrix as pendent groups which means only one end of the chromophore is chemically bonded to the backbone. The earliest studies on SC NLO polymers were done on methacrylate system. Most of them were synthesized via free radical polymerization of chromophore attached methyl methacrylate and methyl methacrylate.22, 23 Some examples are listed in figure 1.5. PMMA systems usually have fairly low Tg, ranging from 120 - 140 °C. Nonetheless SC system often has much better stability then guest-host system with the same chromophore. One comparison was done on 4- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R = — C H 2 C H 2 n ^ c h 3c h 2 / N N Q j P2q - c h 2c h 2 / — \ - -| _ CH CH / - < > N=N- \ > N =N - O - N 0^ Figure 1.5 Examples of PMMA polymers with NLO chromophores tethered as side chain. 1.0 in 0 -8 ’c 3 0.6 w > I 0.4 v «. •o 0.2 Q .Q 0 5 10 15 20 25 30 35 Time (days) Figure 1.6 Thermal stability comparison of G-H system and SC system. R : 1----------!----------- •S-------------------------------•----------- , — DCV-PMMA side chain polymer 0CV/PMMA Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22 (dicyanovinyl)-4-(dialkylamino)azobenzene substituted m e t h a c r y l a t e 14,24 shown in figure 1.6. no3 o^ - O - no, I n u '_ O ° H DEAD ^ SnCl2 . » ■ Ph3P HC1 N O * > THF SOjCHj ^ (l) DEAD* BOOCS-NCOOa ^ (3) Monomer A ° THF 0 (4a) x = NO-? * Monomer B X = NO2 x (45) x = S0JCH3 Monomer C X = SO2CH3 -------------► To various polyimides Figure 1.7 Reaction scheme of a NLO polyimide (I) with excellent thermal stability. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23 In early 90's, researchers paid much more attention to develop high Tg systems in order to increase film thermal stability so that they will maintain good quality after the semiconductor manufacturing process. This is generally done by replacing the aliphatic groups with aromatic groups. In some cases, by doing so not only increase the thermal stability of the polymer film, but also generates higher [ 3 v a l u e . 2 5 One of high Tg systems under intensive investigation is polyimide. It's a relatively new area; however recent reports showed promising future in this s y s t e m . 2 6 , 2 7 One example is the work done by L. Yu et a l . 2 8 at University of Chicago outlined in figure 1 .7 . Tg of the polyimides are over 2 0 0 °C and d33 values range from 29 to 115pm/V at 532 nm. It's observed that second harmonic generation signal of the films exhibited no decay at room temperature, 90 °C and 120 °C for over 1200 hrs. Furthermore, they are soluble in several polar, aprotic solvents to ensure processibility. 1.4.3 Main-chain polymer system NLO polymers with chromophores incorporated in the backbone are also under extensive investigation. In main-chain (MC) polymer systems, the chromophores are much less mobile than those in side-chain polymers due to the requirement of movement of large polymer chain segment for the chromophores to rotate. This means the sub-Tg relaxation of a poled polymer is significantly inhibited. The trade-off is that poling is more difficult. Another advantage MC polymer has is the improved tensile and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 mechanical properties of the film.^O There are three different chromophore configurations in the MC polymer: head to tail (isoregic)31, head to head ( s y n d i o r e g i c ) 3 2 and random order ( a r e g i c ) 3 3 . Early research in MC polymers were focused on isoregic configuration. Researchers expected a coherent enhancement of the second-order nonlinear optical p r o p e r t i e s ^ , 34 visualizing a simple model of an extended one-dimensional polymer chain in which all chromophores are aligned head-to-tail along the backbone. If that is the case, theoretically the hyperpolarizability of the polymer (Ptot) would simply be the sum of the hyperpolarizability of the individual chromophore unit (P ): ( 1 - 3 0 ) where N is the total number of the chromophores. In reality, as N and the dipole moment of the chromophore get greater, more and more factors become significant, such as motion inhibited due to polymer chain entanglement. This is shown through the study on a series of 4-methoxy-4'- carbomethoxy-a-amino-a'-cyanostilbenes.30 The polymers have fairly high Tg's, ranging from 168-187 °C; however, these polymers showed no enhancement in |ip resulted from the cooperative effects possibly because of the inhibition of chromophore alignment due to polymer chain entanglement. Syndioregic configured MC polymer is a relatively new area in which the chromophores are linked through U-shaped bridging groups designed Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25 to enable chromophore folding resulting in parallel orientation.35-37 This system usually shows no or little second harmonic generation before poling. After poling, this type of polymer exhibits promising results and displays low optical loss at room temperature. A comparison of SC, isoregic MC and syndioregic MC polymers involving same chromophores are shown in figure 1.8. The SC homopolymer^S has Tg of 114 °C and d33 of 22 pm/V; the isoregic MC polymer39 has Tg of 105 °C and d33 of 7 pm/V; the syndioregic MC polymer^O has Tg of 205 °C and d33 of 70 pm/V. NC^5 Figure 1.8 Comparison of SC, isoregic MC and syndioregic MC NLO polymers with the same chromophore. Poiyimide main chain system is also an interest of a great number of researchers. Dalton et al.29 did fairly thorough investigation in main chain poiyimide systems. One scheme is shown in figure 1.9. A comparison in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. HO^n-s.O H < > o o o o O ^ O >' O ^ N '- 0Vlt!C O £© *= , ° ° $ 0 ° pyridine, NMP NO, o ^ o N. O NH4- COOH P i 0 NO, 1. Cast into tfiin film 2. Electric Raid poling 3. Heat to affect imidizaoon N 0 NO, © O --Q -0 N -N.0 v it5CN - - 0 ° 0 o O "o N 0 NO, Rgure 1.9 Reaction scheme for NLO poiyimide (II). t.o o.a 0.6 0.4 0.2 0.0 50 100 iso 200 250 Tem perature (°C) Rgure 1.10 Thermal stability comparison of imidized and non-imidized NLO polymers outlined in figure 1.9. - ^ O q O o "o ec ec3° j °O q 0 c C q 0 q 0 o O 0C o 0 0 o • O q o Imidized • Non-imidized o o o o o o o o o o oo Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27 thermal stability of imidized and non-imidized polymers (outlined in figure 1.9) were done and shown in figure 1.10 : imidized polymer exhibits no significant optical signal up to around 190 °C while non-imidized polymer is stable only up to around 110 °C. 1.4.4 Cross-linked system Inhibition of rotation relaxation after the polymer being poled can be improved by two methods: 1) increase the glass transition temperature of the system; and/or 2) increase the interaction between polymer chains. We have discussed the first one in previous section and the second option leads to a cross-linked system which partially immobilize segments of the polymer chain. Cross-linking process is majorly designed to take place after or during the poling process to lock the NLO units into their aligned orientation. Two pathways were taken to achieve cross-linking : thermal cross-linking and photochemical cross-linking. We will discuss the former one in this section. Three categories of thermal cross-linking systems will be discussed : guest-host system using cross-linked polymer as the host; chromophore chemically incorporated in cross-linked polymer matrix but not involved in cross-linking process ; and polymer cross-linked through bifunctionalized NLO chromophore. Marks and coworker did a great deal of study on the cross-linked guest-host system, as well as the cross-linked system with NLO chromophore incorporated as tethered group (side-chain).41-43 The Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 preparation of the cross-linked guest-host system is similar to the non cross-linked system except sometimes to avoid the dielectric break down caused by strong poling field, partial cross-linking is induced at a low temperature before applying the poling field. Poling field is applied at a higher temperature and taken away after the polymer cools to room temperature. The decay of nonlinear properties is dependent on types of the chromophore incorporated. Generally, the bulkier ones decay slower attribute to the large volume required for mobilization. The thermal stability is much greater than the non-cross-linked guest-host system. For NLO chromophore tethered cross-linking system, Marks et al. incorporated chromophore in a fimctionalized polymer backbone and followed by cross-linking with diepoxy compounds as shown in figure 1.11. Measured d33 values are higher than the corresponding cross-linked guest-host system, as well as better temporal quality. Loss of nonlinear response is only about 10% at room temperature after 350 hrs. With this system, the d33 values vary with different cross-linkers and the stoichiometry of the cross-linker, ranging from 0.6-2.9 pm/V at 1.064 pm. Eich et al.44 reported a cross-linking system with chromophore incorporated in the polymer backbone but not involved in the cross-linking process shown in figure 1.12. Tg of the polymer rose slowly to the curing temperature (140 °C) in 12-16 hrs. The d33 value was determined to be 13.5 pm/V at 1.064 pm. The film exhibited excellent thermal stability : no second harmonic signal decay at room temperature after 500 hrs. At 85 °C, the signal held steady for 40 min. Similar but improved work was done by Jungbauer et al.45 as they reported d33 value of 50 pm/V at 1.06 pm with Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 N H j r \ | ^ q d ( Q r N H j+ 2 n o 2 NPOA OH j— CH2 — CH — CH2 \/ OH I C H jC H C H j— 0 OH N I 1 ^CH.CHCH.j- N O , ^ C H jC H C H ,— 0 OH b isA -N P O A f H ’ C I CH. 1 ° j CH, I 3 C CH, Figure 1.11 NLO polymer cross-linked with diepoxy compound (chromophore tethered as side chain). (— C H ,- CH + (— CH,— CH 4 * + \ I In NaH \ I /n U “ * (Q O , n> “CH2OTs OH N02 0-M «t NPPTos ( _ c „ _ c h ^ ( _ ch, _ c h ) . o o OH “NPP _ ° > /W v or OH OH + V ^ ~ V ' 1 ' ] y \ / W \ A ? C r o s s l i n k s P o ly m ar NPP-PHS A. poling Rgure 1.12 Diepoxy cross-linked polymer as chromophore incorporated in the backbone. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30 loading density of 63% by weight. The cross-linked polymer is extremely stable, showing no signal decay at room temperature and only 10-15% loss at 80 °C after 50 hrs, mostly occurred within first 15 min. Out of all the possibilities, the most stable NLO polymer is a three dimensional network cross-linked through double ended chromophores. Dalton et al .46 did extensive research on this type of system and reported quite promising results. One such polymer investigated is outlined in figure 1.13. This particular example shows cross-linking after a prepolymer containing NLO chromophore being prepared. The r33 values for this polymer system range from 7-13 pm/V and 14-20 pm/V if using nitro group as acceptor. r33 values sustained for 1000 hrs at 90 °C and 200 hrs at 125 °C. With the same system, high |x(3 chromophore incorporated polymers have electro-optical coefficient up to 45 pm/V even without optimization of poling protocols. Other routes to prepare cross-linked film are also discussed.29 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 A) I.) E J -B li.) A- D-a { ^ f j - C 2D + • ( t - ' Z H -(-C3D- XL * crosslinking groups 1. Rim casting 2. Electric lieU poling 3. Crosslinking ^Xv\XvvXv* I' . fcsi s Dipolar NLO Chromophore 1. Rim casting 2. Electric field poling 3. Crosslinking v\XvvCvwv* B) N O * s i r " J* (C H * ), o=s=o N ' /V " '- 'V V ' ' Rgure 1.13 a) an example of a cross-linked system, b) chromophores incorporated in the system. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32 1.5 Research objective Sulfur containing moieties like 1,3-benzodithiolyldinemethyl (1) and 2,5,7,9-tetrathiabicylco[4.3.0.]non-l(6)-enyl (2) groups were first investigated for their conducting properties in compounds (3) and (4). o o R * Oc S\ | / R /I V 1,3-benzodithiolyldinemethyl group 2,5,7,9-tetrathiabicylco[4,3,0]non-1 (6)-enyl group 0 X 0 O X O 2,2'-bi[l ,3-benzodithiolyldene] bis(ethylenedithio)tetrathiafuvalene The use of compound 1 as electron donor in NLO study was reported by Katz et al.22 Lehn and coworkers47,48 also discussed compound 1 as an efficient electron donor. But no data on their optical nonlinearity and thermal stability were reported. Jen et al.49 synthesized a series of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 33 chromophores with different sulfur containing moieties as donors. Collected data showed that this type of sulfur containing moieties are efficient and thermally stable donors.However, tetracyanoethylene group was the only acceptor studied in this type of chromophore. Also, functionalization of the donor group was not reported. The objective of this research is to explore new chromophores with sulfur containing moiety 1 as donor and different acceptors, and to functionalize sulfur containing moiety 2 with hydroxyl group. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 1.6 References 1. Dalton, L. R.; Harper, A. W.; Wu, B.; Ghosn, R.; Laquindanum, J.; Liang, Z.; Hubei, A.; Xu, C. Adv. Mater. 1995, 7, 519. 2. Prasad, P. N.; Williams, D. J. Introduction to Nonlinear Optical Effects in Molecules and Polymers, John Wiley & Sons, New York, 1991. 3. Williams, P. J., Ed., Nonlinear Optical Properties o f Organic and Polymeric Materials, American Chemical Society, Washington, DC., 1983. 4. Prasad, P. N. Ulrich, D. R., Eds. Nonlinear Optical and Electroactive Polymers, D. R., Eds. Plenum, New York, 1989. 5. Heeger, A. J.; Orenstein, J.; Ulrich, D. R., Ed. Nonlinear Optical Properties of Polymers, Materials Research Society, Pittsburgh, 1988. 6. Heeger, A. J.; Moses, D.; Sinclair, M. Synth. Met., 1986, 15, 85. 7. Burland, D. M.; Miller, R. D.; Walsh, C. A. Chem. rev., 1994, 94, 31. 8. Boyd, R. W. Nonlinear Optics, Academic Press, San Diego, 1992. 9. Saleh, B. E. A.; Teich, M. C. Fundamentals of Photonics, John Wiley & Sons, New York, 1991. 10. Shen, Y. R. The Principles o f Nonlinear Optics, John Wiley & Sons, New York, 1984. 11. Leslie, T. M.; et al. Mol. Cryst. Liq. Cryst., 1987, 153, 451. 12. Singer, K. D.; Sohn, J. E.; Lalama. S. J. Appl. Phys. Lett. 1986, 49, 248. 13. Singer, K. D.; Kuzyk, M.; Sohn, J. E. J. Opt. Soc. Am. B1987, 4, 968. 14. Singer, K. D.; Kuzyk, M.; Holland, W. R.; Sohn, J. E.; Lalama, S. J.; Comizzoli, R. B.; Katz, H.; Schilling, M. Appl. Phys. Lett., 1988, 53, 1800. 15. Mortazavi, M.; Knoesen, A.; Kowel, S.; Higgins, B.; Diene, A. J. Opt. Soc. Am. B1989, 6, 733. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35 16. Hampsch, H. L.; Yang, J.; Wang, G. K.; Torkelson, J. M. Polym. Commun., 1989, 30 (2), 40. 17. Hampsch, H. L.; Yang, J.; Wang, G.K.; Torkelson, J. Macromolecules, 1988, 21, 526. 18. Boyd, G.;Francis, C.; Trend, J.; Ender, D., J. Opt. Soc. Am. B1991, 8, 887. 19. Stahelin, M.; Burland, D.; Ebert, M.; Miller, R.; Smith, B.; Twieg, R.; Volksen, W.; Walsh, C. Appl. Phys. Lett. 1992, 61, 1626. 20. Walsh, C.; Burland, D.; Lee, V.; Miller, R.; Smith, B.; Twieg, R.; Volksen, W. Macromolecules, 1993, 26, 3720. 21. Stahelin, M.; Walsh, C.; Burland, D.; Miller, R.; Twieg, R.; Volksen, W. J. Appl Phys. 1993, 73, 8471. 22. Katz, H.; Singer, K.; Sohn, J.; Dirk, C.; King, L.; Gordon, H. J. Am. Chem. Soc. 1987, 109, 6561. 23. Matsumoto, S.; Kubodera, K.; Kurihara, T.; Kaino, T. Appl. Phys. Lett. 1987, 51, 1. 24. Singer, K.; Holland, W.; Kuzyk, M.; Wolk, G.; Katz, H.; Schilling, M.; Cahill, P. Proc. SPIE, 1989, 1143, 233. 25. Carter, K. R.; Hedrick, J. L.; Twieg, R. J.; Matray, T. J.; Walsh, C. A. Macromolecules, 1994, 27, 4851. 26. Moylan, C. R.; Twieg, R. J.; Lee, V. Y.; Swanson, S. A.; Betterton, K. M.; Miller, R. D. J. Am. Chem. Soc. 1993, 115, 12599. 27. Lindsay, G. A.; et al. Proc. SPIE, 1994, 2143, 19. 28. Yu, D.; Peng, Z.; Gharavi, A.; Yu, L.; Lindsay, G. A. Eds. Polymer for Second-Order Nonlinear Optics, American Chemical Society, Washington, DC., 1994. 29. Dalton, L. R.; Wu, B.; Harper, A. W.; Ghosn, R.; Ra, Y.; Liang, Z.; Montgomery, R.; Kalluri, S.; Shi, Y.; Steier, W. H.; Jen, A. K-Y.; Lindsay, G. A. Eds. Polymer for Second-Order Nonlinear Optics, American Chemical Society, Washington, DC., 1994. 30. Mitchell, M.; Mulvaney, J.; Hall, H. K., Jr.; Willand, C.; Hampsch, H.; Williams, D. Polym. Bull. 1992, 28, 381. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36 31. Fuso, F.; Padia, A.B.; Hall, H.K., Jr. Macromolecules, 1991, 24, 1710. 32. Tao, X. T.; Watanabe, T.; Shimoda, S.; Zou, D. C.; Sato, H.; Miyata, S. Chem. Mater. 1994, 6, 1961. 33. Xu, C.; Wu, B.; Dalton, L. R.; Ranon, P. M.; Shi, Y.; Steier, W. H.; Becker, M. W. Chem. Mater. 1993, 5, 1439. 34. Willand, C.; Williams, D. Ber. Bunsen-Ges. Phys. Chem. 1987, 91, 1304. 35. Lindsay, G.; Nee, S.; Hoover, J.; Stenger-Smith, J.; Henry, R.; Seltzer, M. SPIE Proc. Nonlinear Opt. Prop. Org. Mat. TV, 1991, 1560, 443. 36. Lindsay, G.; Stenger-Smith, J.; Henry, R.; Hoover, J.; Nissan, R.; Wynne, K. Macromolecules, 1992, 25, 6075. 37. Lindsay, G.; Henry, R.; Stenger-Smith, J. SPIE Proc. 1993, 1775, 425. 38. Rondon, P.; Van Beylen, M.; Samyn, C.; S'heeren, G.; Persoons, A. Macromol. Chem. 1992, 193, 3045. 39. Stenger-Smith, J.; Fischer, J. W.; Henry, R. A.; Hoover, J. M.; Lindsay, G. A. Macromol. Chem. Rapid Commun. 1990, 11,141. 40. Stenger-Smith, J. D.; Henry, R. A.; Chafin, A. P.; Merwin, L. H.; Nissan, R. A.; Yee, R. Y.; Nadler, M. P.; Lindsay, G. A.; Hayden, L. M.; Brower, S.; Mokal, N.; Kokron, D.; Herman, W. N.; Ashley, P. Lindsay, G. A. Eds. Polymer for Second-Order Nonlinear Optics, American Chemical Society, Washington, DC., 1994. 41. Hubbard, M. A.; Minami, N.; Ye, C.; Marks, T. J.; Yang, J.; Wong, G. K. SPIE Proc. Nonlinear Opt. Prop. Org. Mat. 1988, 971, 136. 42. Hubbard, M. A.; Marks, T. J.; Yang, J.; Wong, G. K. Chem. Mater. 1989, 1, 167. 43. Park, J.; Marks, T. J.; Yang, J.; Wong, G. K. Chem. Mater. 1990, 2, 229. 44. Eich, M.; Bjorklund, G. C.; Yoon, D. Y. Polym. Adv. Technol. 1990, 1, 189. 45. Jungbauer, D.; Reck, B.; Twieg, R.; Yoon, D.; Wilson, C.; Swalen, J. Appl. Phys. Lett. 1990, 56, 2610. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37 46. Xu, C.; Wu, B.; Dalton, L. R.; Ranon, P. M.; Kalluri, S.; Shi, Y.; Steier, W. H. Mater. Res. Soc. Symp. Proc. 1994, 328, 461. 47. Blanchard-Desce, M.; Ledoux, L; Lehn, J. M.; Malthete, J.; Zyss, J. J. Chem. Soc. Chem. Commun. 1988, 736. 48. Meyers, F.; Bredas, J. L.; Zyss, J. J. Am. Chem. Soc. 1992, 114, 2914. 49. Jen, A. K-Y.; Rao, V. P.; Drost, K. J.; Wong, K. Y.; Cava, M. J. Chem. Soc. Chem. Commun. 1994, 2057. 50. Chengzhen Xu's doctoral thesis. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 Chapter Two Synthesis of New Choromophores and Functionalization of of Donor Group Containing Sulfur Moieties 2.1 Synthesis of chromophores containing 1,3- benzodithiolyldinemethyl as donor The general scheme of the preparation of chromophores containing 1,3- benzodithiolyldinemethyl is as following: first 2-alkoxy-l,3-benzodithiole was prepared and then converted to a phosphonium salt; second the bridging group (in this case thiophene) was attached via Wittig reaction; and last the acceptor was attached via Knovenagel condensation. The preparation of 2-methoxy-l,3-benzodithiole was first accomplished by 1,3- dipolar cycloaddition of carbon disulfide with benzyne generated by oxidation of 1-aminobenzotriazole, 1 and the resulting carbene was quenched by addition of methanol^ But the synthesis of the precursor 1- aminobenzotriazole was difficult on a large scale. Nakayama^ reported a simpler synthesis of 2-alkoxy-l,3-benzodithiole with respectable yield. 2- alkoxy-l,3-benzodithiole can be easily converted to a tetrafluoroborate salt by addition to tetrafluoroboric acid^ and subsequent phosphonium salt can be prepared by reacting the tetrafluoroborate salt with phosphines in acetonitrile at room temperature.5 These reactions have yield around 90%. The preparation of the chromophores is outlined in figure 2.1. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39 C C - ^ c r T - ^ d H ?U + CSi + ROH + hbf4 O c v P f pr3 . bf4 - Figure 2.1 Reaction scheme for the preparation of phosphonium salt containing 1,3-benzodithiolyldinemethyl group. Compound 1 2.5g (5mmol) of 1,3-benzodithiolylium tetrafluoroborate and 0.78g (5mmol) of 5-bromo-2-thiophenecarboxylaldehyde were dissolved in 50ml of DMF. 7.5 ml of sodium ethoxide (1M in ethanol, 7.5mmol) was added dropwise to the reaction mixture. The reaction mixture then was heated at 95 °C for 48 hrs. Water was added to precipitate the crude product which was collected by vacuum filtration. The pure product was obtained after recrystallization in ethanol. Yield: 0.88g (66%). NMR (CDCI3): 6.67 (d, 2H), 6.99 (d, 1H), 7.15 (dd, 2H), 7.27 (dd, 2H). Elemental analysis for C i2H7S3Br calc. C 44.04, H2.16, S 29.39; found C 44.25, H 2.06, S 29.31 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 NtOEt S ^Pt<3. BF,- B r - s ^ s x^C H O ^ j j I.i-BuU/-7S‘C 2.DMH-20-C ^ i- UM T/-ZU Q P - S f V ^ — O Q - v CHO CF. piperidine > N c f 3 , piperidine , piperidine K C f3 c Ph , piperidine 6 Figure 2.2 Reaction scheme for synthesis of chromophores containing 1,3-benzodithiolyldinemethyl group. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41 Compound 2 6ml of 1.7M t-butyl lithium was added dropwise to a solution of 1.5g (4.58 mmol) of compound 1 in dry THF at -78 °C. After the addition was complete, the reaction mixture was warmed up to -20 °C slowly and 2ml of DMF was added. The reaction mixture was stirred for 2 hrs at room temperature and 10ml of 3N HC1 was added. The product was extracted with diethyl ether and washed with saturated sodium bicarbonate solution and then brine solution. Rotary evaporated the solvent and recrystallized the product in ethanol. Yield: 1.2g (95%). *H NMR (CDCI3): 6.87 (d, 2H), 6.98 (d, 1H), 7.22 (dd, 2H), 7.4 (dd, 2H), Elemental analysis for C 13H8S3O calc. C 56.49, H 2.92, S 34.8; found C 56.35, H 3.01, S 34.84 Compound 3 0.28g (lmmol) of aldehyde (compound 2) and 0.31g (lmmol) of 3- trifluoromethyl-l-(4-sulfonomidophenyl)pyrozolin-5-one were dissolved in 50ml warm ethanol. Two drops of piperidine was then added and the reaction mixture was heated at 75 °C for 12 hrs. Ethanol was then evaporated and the residue was purified through column chromatography (20% ethyl acetate/hexane). Yield: 0.16g (28.3%). UV-VIS: 585nm (in dioxane), 610nm (in methanol). iH NMR (CDCI3): 4.22 (s, 2H), 7.01 (d, 2H), 7.16 (d, 1H), 7.18 (d, 1H), 7.51 (m, 4H), 7.56 (m, 4H). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42 Compound 4 0.28g (lmmol) of aldehyde (compound 2) and 0.16g (lmmol) of coumarin-4-one were suspended in 50ml of ethanol. After addition of two drops of piperidine, the reaction mixture was heat at 75 °C for 10 hrs. Solvent was then evaporated and the product was purified via column chromatography (20% ethyl acetate/hexane; then methylene chloride). Yield: 0.2g (47.6%). UV-VIS: 577nm (in dioxane), 603nm (in methanol). 1H NMR (CDCI3): 6.997 (d, 2H), 7.14 (d, 1H), 7.17 (d, 1H), 7.58 (m, 4H), 7.93 (m, 4H). Compound 5 0.18g (0.65mmol) of aldehyde (compound 2) and O.lg (0.65mmol) of 3-trifluoromethyl-5-isoxazolone were suspended in 40ml of ethanol and two drops of piperidine was added. The reaction mixture was heated at 70 °C for 8 hrs. After evaporation of the solvent, the product was purified via column chromatography (10% ethyl acetate/ hexane). Yield:0.14g (53.1%). UV-VIS: 585nm (in dioxane), 602.5nm (in methanol). iH NMR (CDCI3): 7.0 (d, 2H), 7.13 (d, 1H), 7.16 (d, 1H), 7.43 (m, 4H). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 Compound 6 0.47g (1.7mmol) of compound 2 and 0.28g (1.7mmol) of 3-phenyl-5- isoxazolone were dissolved in 50ml of warm ethanol. After addition of two drops of piperidine, the reaction mixture was heated at 70 °C for 4hrs. Then, the solvent was evaporated and the residue was purified via column chromatography (20% ethyl acetate/ hexane). Yield: 0.38g (53%). UV- VIS: 537nm (in dioxane), 549nm (in acetone), iff NMR (CDCI3): 7.01 (d, 2H), 7.13 (d, 1H), 7.16 (d, 1H), 7.56 (m, 4H), 7.73 (m, 5H). 2.2 Functionalization of 2,5,7,9-tetrathiabicylco[4.3.0.]non-l(6)-enyl group In figure 2.2 is shown a reaction scheme to prepare a hydroxyl group functionalized phosphonium salt containing 2,5,7,9-tetrathiabicylco[4.3.0.]non-l(6)-enyl group. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44 Na + CS2' DMF ZnCl2 N E t4 B r -o c v x v - S S "— • s 2&Et4 8 S , ,S>^(CH2 ) 4 O H 85 - 90 °C <cr Ac20/pyridine S S 10 L . DMS, 90 °C, 30min 2. AcjO, 0 °C, lOtnin A c O d H jC ) AcCUlHjC)^^ S \ r r - ' \ NaBH4 T If y — SM e. b f4 - HBF4 Et20/Ac20 Ae0* W J) Sns - ^ S I J L / - " ” ’4 ' PPh3 r.t., 4hrs Ac04(H2C) XXX .B F | 12 Figure 2.3 Reaction scheme of the functionalization of 2,5,7,9-tetrathiabicyclo[4.3.0]non-l(6)-enylgroup Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Compound 7 45 Weighed out 23g (lmol) of sodium and transferred into a 1L round- bottomed flask with 180ml of carbon disulfide and 200ml of DMF. Refluxed for 48 hrs and then cooled down to room temperature. Vacuum distilled of the DMF and excess carbon disulfide (caution: don't let the oil bath heat over 65 °C. Intermediate will decompose). The residue was redissolved in 600ml of methanol and 300ml of water. After transferring the solution to a 4L Erlenmeyer flask, 20g of zinc chloride in 500ml of methanol and 500ml of ammonium hydroxide, and 43g of tetraethyl ammonium salt were added. Let the reaction mixture stand for 24hrs and the precipitate was collected via vacuum filtration. The precipitate was then washed with water three times and dried in vacuo. Yield: 63.9g (71%). m.p. 200-205 °C. Compound 8 3.5g (4.87mmol) of zinc complex (compound 7) was dissolved in 40ml of acetone in a 200ml round-bottomed flask. The reaction vessel was cooled in a dry ice/acetone bath to -50 °C. 2.75g (10.83mmol) of iodine in 40ml of abs. ethanol was then added dropwise as the temperature was controlled at -50 °C. After the addition completed, the product was collected via vacuum filtration and washed with ethanol, water and acetone. Dried the product in vacuo. Yield: 1.91g (100%). m.p.: 130 °C (decompose). Elemental analysis calc. C 18.35; found C 18.32 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46 Compound 9 6.02g (30.66mmol) of oligomer 8 was suspended in 120ml of dry toluene. 3.41g (33.72mmol) of 5-hexen-l-ol was added to the suspension. The reaction mixture was heated at 85-90 °C for 10 hrs. Remaining solid was filtered off as the mixture was still hot and the solvent was then evaporated. The residue was redissolved in hot ethanol and decolorized with activated charcoal two to three times. The solution was then concentrated to 100-125ml and cooled in fridge. Yellow solid was collected via vacuum filtration and dried in vacuo. Yield: 5.73g (63%). NMR: 1.6-1.9 (hr, m, 6H), 3.18 (dd, 1H), 3.4 (dd, 1H), 3.6 ("ddt", 1H), 3.7 (t, 2H). Elemental analysis for C9H 12S5O calc. C 36.46, H 4.08, S 54.07; found C 36.28, H 4.1, S 54.11 Compound 10 1.54g (5.2mmol) of alcohol 9 was dissolved in 4ml of pyridine and 3ml of acetic anhydride. The reaction mixture was stirred for 24 hrs and then 15 ml of water was added. The mixture was stirred for 2 more hrs. The precipitate was collected via vacuum filtration, redissolved in ethyl ether, washed with water, saturated sodium bicarbonate solution, water, brine solution and then dried over anhydrous magnesium sulfate. After solvent evaporation, a yellow solid was obtained and dried in vacuo. Yield: 1.69g (97%). 1H NMR (CDCI3): 1.6-1.9 (br, m, 6H), 2.05 (s, 3H), 3.2 (dd, 1H), Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47 3.4 (dd, 1H), 3.65 ("ddt", 1H), 4.1 (t, 2H). D R . showed complete conversion of the hydroxyl group to acetate. Compound 11 A suspension of 1.7g (5mmol) of compound 10 in 5ml of dimethyl sulfate was heated at 95-100 °C for 45 min. The mixture was cooled to 0°C and 1ml of acetic anhydride was added and stirred for 10 min. 0.94g (5mmol) of fluoroboric acid diethyl ether complex (85%) was added and stirred for a further 10 min. as the temperature was controlled at 0 °C. The reaction mixture was then cooled to room temperature and 75ml of ether was added. The resulting oil was separated and washed thoroughly with ether. (The methylated tetrafluoroborate salt was used without further purification.) The oil was dissolved in 30ml of dry actonitrile and 0.19g (5mmol) of sodium borohydride was added portion wise over 30 min. under nitrogen. The mixture was stirred for 3 hrs at room temperature and then 40 ml of water was added. The product was extracted with methylene chloride (3 x 30ml) and dried over anhydrous magnesium sulfate. After solvent evaporation, the product was dried in vacuo. The product was purified via column chromatography eluting with hexane/methylene chloride (2:1 v/v). Yield: 0.88g (51%). 1H NMR (CDCI3): 1.5-1.9 (br, m, 6H), 2.2 (s, 3H), 2.45 (s, 3H), 3.18 (dd, 1H), 3.4 (dd, 1H), 3.6 ("ddt", 1H), 3.7 (t, 2H), 5.31 (s, 1H). Elemental analysis for C12H 18S5O2 calc. C 40.65, H 5.12, S 45.21; found C 40.7, H 5.2, S 45.09 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 Compound 12 0.88g (2.54mmol) of compound 11 was dissolved in 8ml of acetic anhydride. 0.47g (2.54mmol) of fluoroboric acid diethyl ether complex (85%) was added dropwise over 10 min period at 0 °C under nitrogen. The reaction mixture was stirred at room temperature for 1 hr. 20ml of anhydrous ethyl ether was added. The precipitated oil (sometimes solid) was separated and washed thoroughly with ether and dried. The resulting oil (or solid) was redissolved in 20ml of dry acetonitrile. 0.67g (2.54mmol) of triphenylphosphine was added and reaction mixture was stirred for 4 hrs at room temperature. 40ml of anhydrous diethyl ether was added to precipitated the product. The product was collected via vacuum filtration and reprecipitated from methanol/ether. Yield: 0.7g (42%). !H NMR (CDC13): 1.42-1.86 (br, m, 6H), 2.04 (s, 3H), 2.58 (dd, 1H), 2.77 (dd, 1H), 3.0 ("ddt", 1H), 3.1 (t, 2H), 7.82 (m, 15H). Elemental analysis for C29H30S4O2PBF4 cacl. C 53.05, H 4.61, S 19.54; found C 53.37, H 4.73, S 19.35 2.3 Conclusion Chromophores containing 1,3-benzodithiolyldinemethyl as donor group have been synthesized. Their appearances vary from pink to blue in nonpolar solvent (dioxane) and from purple to green in polar solvent (methanol). The Umax's vary from 537nm to 610nm and A A ,max S for most of the chromophores are around 20nm red shift from nonpolar to polar Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 solvent, showing signs of good chromophores. Preparation of chromophore with longer bridge(containing two thiophene rings) was also attempted. How ever, the attempt wasn't successful due to the low solubility of the precursor aldehyde. The fiinctionalization of 2,5,7,9-tetrathiabicylco[4.3.0.]non-l(6)-enyl group involves some low yield reactions because the reaction conditions haven't been optimized. This fimctionalized sulfur moiety can be incorporated in chromophores in the same fashion as 1,3- benzodithiolyldinemethyl group. Based on past experience, 2,5,7,9- tetrathiabicylco[4.3.0.]non-l(6)-enyl group is expected to have better solubility so that bridge extension is possible. Both donor groups can be fimctionalized and be covalently incorporated in polymer systems. Study of these two systems are still in their infancy and has already showed promising results to be efficient and thermally stable donor groups. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 2.4 References 1. Campbell, C. D.; Rees, C. W. J. Chem. Soc. [c] 1969, 742, 748, 752. 2. Nakayama, J. Chem. Commun. 1974, 166. 3. Nakayama, J. Synthesis, 1975, 38. 4. Nakayama, J.; Fujiwara, K.; Hoshino, M. Chem. Lett. 1975, 1099. 5. Ishikawa, K.; Akiba, K-Y.; inamoto, N. Tetrahedron Lett. 1976, 41, 3695. 6. Steimecke, G.; Sieler, H-J.; Kirmse, R.; Hoyer, E. Phosphorus and Sulfur, 1979, 7, 49. 7. Neiland, O. Y.; Katsens, Y. Y. UDC 547.494.04,1989, 592. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zed) Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI N u m b er: 1 381593 UMI Microform 1381593 Copyright 1996, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Fluorinated carbocations and carboxonium ions

PDF

Synthesis and functionalization of polymer nanospheres

PDF

Synthesis and metal cation-promoted hydrolysis of (hydroxyimino)phosphonoacetic acid derivatives

PDF

Study and modification of organic species formed in HSAPO-34 cages during methanol-to-olefin catalysis by ex situ analysis

PDF

Nafion-H® catalyzed organic transformations

PDF

Design and synthesis of a new phosphine pincer porphyrin

PDF

Nitration of arylboronic acids

PDF

Synthesis of novel solid superacids

PDF

Synthesis and photochemistry of hydrogen telluride

PDF

Structural analyses of the potassium and cesium salts of silver(I) mercaptonicotonate

PDF

Design and synthesis of novel second order nonlinear optical materials

PDF

Mid-infrared laser source based on Raman shifting in para-hydrogen crystal

PDF

Derivatization chemistry of mono-carboranes

PDF

Development of a 20-femtosecond tunable ultraviolet laser source towards study of the photochemistry of liquid water

PDF

Evaluation of muscle function in Six5 knock-out and (CTG) repeat overexpresser mice

PDF

Path integral simulations of helium and hydrogen droplets

PDF

Novel phenylpolyene-bridged second-order nonlinear optical chromophores and new thermally stable polyurethanes for electro-optic applications

PDF

Monodisperse polymer nanospheres: Fabrication, chemical modifications and applications

PDF

I. Layered nano fabrication. II. Adhesion layers for hippocampal neurons

PDF

Infrared spectroscopy and ab initio studies of carbon dioxide van der Waals complexes

Asset Metadata

Creator Li, Hu (author)

Core Title Synthesis of new second-order chromophores and functionalization of sulfur containing donor moieties

School Graduate School

Degree Master of Science

Degree Program Chemistry

Degree Conferral Date 1996-08

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, organic,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-5204

Unique identifier UC11336743

Identifier 1381593.pdf (filename),usctheses-c16-5204 (legacy record id)

Legacy Identifier 1381593.pdf

Dmrecord 5204

Document Type Thesis

Rights Li, Hu

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA