NLO characteristics of D-π-A coumarin-thiophene bridged azo dyes by Z-scan and DFT methods

The structural, electronic, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties of the donor-pi-acceptor (D-pi-A) azo linked dyes bearing coumarin thiophene bridge with different acceptors were inspected by Z-scan and DFT methods. The dye 3a exhibits bathochromic absorption maxima (649 and 650 nm) in the near IR region in DMF and DMSO. The dye 3a holds low HOMO-LUMO gap elucidated by CV and DFT indicating strong ICT character. The thermal stability is high for 3a and it shows enhanced NLO property by Z-scan and DFT methods as predicted in both global and range-separated hybrid functionals. The molecular geometry was optimised using B3LYP/6-311 + g(d,p). The ICT characteristics are correlated with NLO properties obtained by Z-scan and DFT techniques.