Roles of bridges on Electronic, linear and nonlinear optical Properties: A computational study on zwitterions with N-methyl pyridinium and p-Dicyanomethanide phenylene

This contribution reports structure–property correlations for a series of interesting zwitterions. All the molecules have N-methyl pyridinium as common acceptor (A), dicyanomethanide substituted p-phenylene as common donor (D), coupled through several mono aromatic rings as the bridges. Computations were carried out using HF, B3LYP, CAM-B3LYP and ωB97xD methodologies. The current report deals with a complete methodical study on the effects of various possible mono aromatic rings as bridges, on dipole moments (μ), polarizabilities (α), hyperpolarizabilities (β) and adiabatic absorption properties. This work shows that compared to literature reported traditional bridges, aromatic bridges indeed showed enhanced nonlinear optical responses (10-fold enhanced β in some cases). Results show that unlike the TICT approach, one can be able to design a wide range of non-TICT chromophores by suitable manipulations through aromatic bridges. Aromatic control on the bridges is suggested as an effective approach in the designing of a wide range of efficient molecular chromophores.