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Abstract
The photoisomerisation pathways of substituted aminoazobenzenes with cyano-containing acceptor moieties, AAB-DCV and AAB-TCV, are revealed by TD-DFT at B3LYP/6-31G** level. Stationary and transition points on ground and excited state potential energy surfaces are localised; both inversion and rotation trans- and cis-isomerisation mechanisms are considered and the former is shown to be the preferable for both chromophores in the ground state. UV/vis spectra of isomeric forms of AAB-DCV and AAB-TCV are calculated by TD-DFT in chloroform at CAM-B3LYP/PCM//def2-TZVP level, the effect of acceptors on the spectrum shape and absorption maximum is revealed. It is found that S0→S2 excitation determines the most intensive π-π* band in the case of AAB-DCV trans-isomer, while in the case of AAB-TCV this band is due to S0→S1 excitation. λmax is bathochromically shifted when passing from AAB-DCV to AAB-TCV for trans-isomers. As for cis-isomers, the spectrum shape is determined by several excitations up to S0→S4, corresponding transitions having close intensities. Switching ability of the composite nonlinear-optical polymer material is demonstrated at both molecular and macroscopic levels: first hyperpolarisability of trans- and cis-forms differs three times in favour of the former; estimations of macroscopic quadratic electric susceptibility, χ(2), performed for model PMMA-based doped materials reveal the corresponding almost twofold difference.
GRAPHICAL ABSTRACT
Acknowledgements
Financial support of the Program for fundamental research of the Presidium of RAS No 13 «Fundamental backgrounds for nanostructures and nanomaterials technologies» is gratefully acknowledged.
Disclosure statement
No potential conflict of interest was reported by the author(s).