Time-dependent and coupled-perturbed DFT and HF investigations on the absorption spectrum and non-linear optical properties of push-pull M(II)-porphyrin complexes (M = Zn, Cu, Ni)

We report time-dependent (TD) and coupled-perturbed (CP) DFT/HF investigations, on the linear and non-linear optical properties of M(II)-complexes of [5-[(4 0 -dimethylaminophenyl)-ethynyl]-15-[(4 00 -nitrophenyl)ethynyl]-10,20-diphenylporphyrin], with M = Zn, Cu, Ni. The TD-DFT absorption spectrum is in good agreement with the experimental one, allowing us to identify the transitions mainly responsible of the NLO response. CP-DFT/CP-HF calculations provide similar hyperpolarizability values for the three complexes, suggesting an irrelevant role of the metal center. A sharp hyperpolarizability increase is calculated at an incident laser wavelength of 1.064 lm compared to 1.907 lm, which seems to be responsible for the large differences between Zn, Cu and Ni complexes reported experimentally.