Effect of Twist Angle on Calculated Second Order Non Linear Responses of Novel Charge Transfer Molecular Systems

Motivation. Molecules with large optical non-linearities have extensively been studied due to their potential applications in the area of materials science and various photonic technologies, including optical switching and data processing. Semi-empirical quantum chemical calculations are performed on the class of compounds shown in Figure 1 which show very large non-linear optical activity. The effect of twist angle (1234) on the static hyperpolarizability was investigated. Method. Geometries of all molecules were optimized at the semi-empirical level of the theory using AM1 Hamiltonian using MOPAC 6.0 computational package. The static hyperpolarizabilities, β, and frontier molecular orbital energies are studied as a function of the twist angle (1234), between the diaminomethylene unit and the six membered fused rings as shown in Figure1 using AM1 Hamiltonian within MOPAC 6.0 computational chemistry package. Results. All the β values that we report here are the magnitude of static hyperpolarizability. The enormous enhancement of the hyperpolarizability for a particular dihedral angle of these designed novel molecular systems is also reported. Conclusions. The study reveals that these classes of organic compounds show a very large hyperpolarizability and hence in general may have potential applications in the development of non linear optical materials