Tricyanovinyl acceptors

Kato et al. (1983) studied PVK containing three different intramolecular charge-transfer complexes, each containing a carbazole donor chromophore and a tricyanovinyl acceptor. The results were compared to PVK TNF and PVKiTCNE (telracyanoethylene) intermolecular complexes. Relative to the intermolecular complexes, intramolecular complexes show high primary quantum yields. The thermalization distances were about 22 A, less than 28 to 35 A for the intermolecular complexes. Differences in the structure of the intramolecular complexes caused slight differences in the primary quantum yield, but did not cause significant differences in the thermalization distance. 

In principle, the behaviour of any molecular species in forming donor-acceptor complexes depends on its ionization potential, electron affinity and polarizability. However, the donor (or acceptor) ability of a substance depends strongly on the requirements and properties of its partners. The same compound may act as a donor towards strong acceptor compounds or as an acceptor towards donor compounds. This is the case of the TT-amphoteric p-tricyanovinyl-AA/V-dimcthylaniline (41) which is a donor towards 2,4,7-trinitrofluorenone and an acceptor towards /V,/V-dirnclhy Ian Mine138. 

The approach by Drost, Jen, and Rao was to incorporate into typical nonlinear optics materials electron-rich five-membered heteroaromatic groups, like thiophene as part of an all n conjugation between the donor and acceptor substituents. The function of the conjugating unit is to transfer electrons. In addition, they also incorporated a very active acceptor, a tricyanovinyl group into the thiophene-based moiety... 

Although tricyanovinylthiophene derivatives (30) had been previously used as the acceptor moiety in donor-acceptor 7c-extended conjugated compounds with nonlinear optical properties [51], isolated tricyanovinylthiophenes had not been examined as acceptors for the preparation of CT complexes or CT salts. These easily soluble acceptors showed a slight deviation from planarity, the angle defined by the least-squares plane formed by the thiophene ring and the tricyanovinyl substituent being 9(1)° (Figure 1.8). 

The NLO properties of a series of random copolymers of methylmethacrylate and azo dye-substituted methacrylate were reported by Sohn et al. [102] (Scheme 2). The dicyano- and tricyanovinyl were stronger acceptors... 

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