Donor substituted stilbenes

Malicki M, Guan Z, Ha SD, Heimel G, Barlow S, Rumi M, Kahn A, Marder SR (2009) Preparation and characterization of 4 -donor substituted stilbene-4-thiolate monolayers and their influence on the work function of gold. Langmuir 25(14) 7967-7975... 

Donor-Acceptor and Donor-Donor Substituted Stilbenes... 

The coupling of bromo- or iodobenzene to styrene yields regioselectively a mixture of E- and Z-stilbenes 12 and 13. An electron-withdrawing substituent at the olefinic double bond often improves the regioselectivity, while an electron-donor-substituted alkene gives rise to the formation of regioisomers. 

Stimulated by extensive research activities on donor/acceptor substituted stilbenes, Mullen and Klarner have reported a donor/acceptor substituted poly(4,4 -biphenyl-diylvinylene) derivative (85) in which the NR2 donor and CN acceptor substituents are located on the vinylene unit [111]. The synthesis is based on a C-C-coupling reaction of in situ generated carbanion functions with a (pseudo)cation function, followed by a subsequent elimination of MeSH with formation of the olefinic double bond. 

Lapouyade R, Czeschka K, Majenz W, Rettig W, Gilabert E, Rulliere C (1992) Photophysics of donor-acceptor substituted stilbenes. A time-resolved fluorescence study using selectively bridged dimethylamino cyano model compounds. J Phys Chem 96(24) 9643-9650... 

Very recently, donor-acceptor substituted stilbenes and related dye systems have been studied within the context of possible TICT formation. Examples are... 

Scheme 1. Three-state kinetic scheme as minimal basis to explain the photophysics of donor-acceptor substituted stilbenes. E (primary excited n, n state, essentially planar geometry) and P ( Phantom Singlet state , twisted double bond) are the classical states discussed for stilbene, A (twisted single bonds, state(s) of TICT nature, up to 4 different possibilities in donor-acceptor substituted stilbenes like DNS) correspond to motions along different reaction coordinates than for P ...

Distyrylbenzenes with the general structure 58 have become one of the most widely used compounds for applications in TP photosciences. The TPA of these chromophores is higher compared to that of donor substituted polyenes 57. Thus, the (phenylene-vinylene) moiety is presumably a better re-bridge to increase 8 compared to the diphenylpolyene in 57. Increase of the re-bridge in 58 has an impact on Moi and M12, respectively, resulting in an increase of 8 because for such chromophores 8 is proportional to (Moi M12)2, Eq. (27). Furthermore, substitution of stilbene and distyrylbenzene by amino groups at the chromophore ends results in a three- to fourfold increase of M12 while... 

Three novel organic optical materials, 4 -(N,N-dihydroxyethylamino)-4-(pyridine-4-vinyl) stilbene, N- ((4- N, N-dihydroxyethylamino)benzylidene) -4- (pyridine-4-vinyl) aniline, and 4 -(N,N-dihydroxyethylamino)-4-(pyridine-4-vinyl)azobenzene, were synthesized [105]. Tolunitriles reacted vdth donor-substituted aromatic aldehydes in high yielding reactions of the synthesis of donor-acceptor cyanostilbenes without the need of inert atmosphere. The keys to this reaction were the use of anhydride DMF solvent and the phase transfer agent - tris(3,6-dioxaheptyl)amine (TDA). High yields of stilbenes were also obtained with amino-substituted aromatic aldehydes [106]. 

A complex antibody-donor-acceptor-substituted stilbene has been investigated (Figure 1.27) [152]. Photophysical and structural analyses indicated that antibody binding alters the excited-state behavior of stilbene. The authors suggested that such complexes may find in vivo application as fluorescent biosensors. 

These data can be explained in terms of the high stabilization energy resulting from solvation of the excited t state. High p values in these cases indicate that the polar solvent-solute intermolecular stabilization ofthe zwitterionic excited t state is very sensitive to intramolecular substituent effects. In contrast, there is no dependence of Stokes shifts on a-constants in cyclohexane, which is nonpolar aprotic solvent, where the vibrational relaxation ofthe Franck-Condon state plays a primary role in stabilizing the excited state. This implies that the vibrational relaxation is not sensitive to intramolecular donor-acceptor interactions. The observations showed that the ultrafast intra- and intermolecular electronic polarization plays a major role in determining the position of the Franck-Condon zwitterionic state and its sensitivity to the relaxation of polar-substituted stilbenes. 

Antibodies to the donor-acceptor-substituted stilbene trans-4-N,N-dimethyl-amino-4 -cyanostilbene (DCS) and other donor-acceptor-substituted stilbenes were... 

The various processes occurring in the stilbene molecule after its excitation exhibit different sensitivity to intramolecular donor-acceptor effects of substituents. This sensitivity was quantitatively characterized by p-constant of the linear Hammett-like relationships [54]. It has been shown that the Stokes shift in nonpolar cyclohexane was not dependent on the structure of the stilbene molecule (Section 3.4.1) [12, 31). Therefore, the substituent effects on vibrational relaxation in the nonpolar solvent can be neglected. Nevertheless, these intramolecular electronic effects on the excitation energy of the substituted stilbenes were found to be very essential even in the nonpolar media (the excitation energy difference between stilbenes substituted with weak and strong donor-acceptor groups can reach 20kcal/mol). 

The photoisomerization rate of the 4-(CH3)2N-suhstituted stilbenes from the second stilbene group decreases considerably compared to the weak donor-acceptor-substituted stilbenes from the first group, hut usually follows the same trends of... 

Some examples of ehromophores that were ineorporated into side ehains and main ehains of polymers are donor/aeeeptor substituted stilbenes and azobenzenes.Another example are the two eompounds shown below ... 

The palladium-catalyzed Heck reaction proved to be a very efficient and atom economical approach to synthesize stilbene derivatives on polymers as disparate as polysiloxanes and polyimides. A variety of different donor-acceptor substituted stilbenes have been synthesized. The regiospecific brominationand Heck reactions clearly show the utility and the generality of these processes to controllably and efficiently modify polymers. 

It can be determined from the higher effect of the p-substitution compared with the 7-substitution and the high donor ability of the stilbene (ECT = 200 kJ mol-1 x(HOMO) = 0.504 qa = qp = 1.000), that an even electron distribution in the n-system of the donor causing a high electron density in the vicinity of the monomer double bond is important for the strength of the EDA interaction between 71-donor and 7t-acceptor. 

Photoaddhion of electron donor olefins such as vinyl ethers and stilbene to variously methyl and halogeno-substituted 1,4-benzoquinones resulted in the formation of dihydrobenzofurans via a dienone-phenol rearrangement of the primary product spirooxetanes <96H(43)619>. High-temperature water seems to be an alternative to use of acid catalysts or organic solvents by the cyclization of allyl phenyl ethers to dihydrobenzofurans <96JOC7355>. 

Many other organic and some organometallic materials have been examined by the powder SHG method and/or tested by EFISH techniques. They will not be discussed in detail here but are listed by structural classes for completeness. Several compendia of materials responses have been published. (38,54,55) Clearly, the largest single class of second order materials consists of donor-acceptor substituted aromatics. The class has been extended to stilbenes and diarylacetylenes and... 

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