Subchromophore interactions in tricyanovinyl-substituted triarylamines -: a combined experimental and computational study

The electronic coupling between the phenyl substituents of mono-, bis-, and tris(tricyanovinyl)-substituted triphenylamines (1, 2, 2-OMe and 3) have been investigated by various methods: the splitting of excited states was taken as a measure of the interaction. These splittings can be seen in the optical absorption spectra; exciton coupling theory was also used to estimate electronic coupling of the excited states; redox potentials gave coupling energies of charged ground state species as well as Hush analysis of intervalence charge-transfer bands (IV-CT), which were observed by UV-Vis-NIR spectroelectrochemistry, and finally, the quadratic hyperpolarisability measured by hyper-Rayleigh scattering was used to estimate excited state couplings. The results of these methods were compared to semiempirical AM1 calculations and suggest the subchromophore interactions to be weak compared to the band width of the UV-spectra. Nevertheless, the quadratic hyperpolarisability is enhanced in the two-dimensional tris(tricyanovinylphenyl)amine compared to its one-dimensional analogue.