Influence of original and simulated microscopic units on SHG response in semiorganic NLO materials†
Exploring chromophores which determine band gap sizes and nonlinear optical (NLO) activity is of importance for material design. In this study, the electronic structures and optical properties of a class of the semiorganic NLO materials ASr[C4H2O6B(OH)2]·4H2O (A = K and Rb) and simulated virtual compounds ASr[C4O6B(OH)2]·4H2O (A = K and Rb) with CC bonding after removing H atoms have been investigated to clarify the role of microscopic units. It was found that introducing π-conjugated microscopic units could increase the SHG effect but decrease the band gap. Whether the band gap red shift or the electronic transfer induced by π-conjugated microscopic units should be responsible for the change of the SHG effect is explored by combining the electronic structure, SHG density and molecular orbital analysis.