Effect Of Dimer Formation Via Hydrogen Bonding On Static And Dynamic Nonlinear Optical Characteristics Of Chromophores

The effect of head-to-tail azochromophore dimer formation on the values of static and dynamic first hyperpolarizability is studied on the basis of calculations performed at M06-2X/aug-cc-pVDZ and omega B97X-D/aug-cc-pVDZ computational levels; the results are compared with those obtained at second-order Moller-Plesset pertubation theory (MP2)/aug-cc-pVDZ. Azochromophores DO3 and AAB-DCV, participating in the dimer formation, contain nitro- or dicyanovinylene acceptor moieties. The structure of the studied dimers is obtained at the B3LYP-D3/6-31++G (d,p) level with basis set superposition error (BSSE) correction. Dynamic first hyperpolarizabilities are calculated at radiation frequencies of 0.65 eV, 0.918 eV and 1.165 eV. The essential effect of dimer formation is demonstrated: it results in almost a 3.5 times increase of the first hyperpolarizability. In the series D1-D2-D3, beta(2 omega) values at 0.65 eV increase in a way similar to the static case: beta(2 omega) for D2 and D3 are 1.5 and 1.8 times higher than that for D1. The notable resonance enhancement of beta(2 omega) for the studied hydrogen-bonded dimers is demonstrated at radiation frequency of 1.165 eV.