Quantum Chemical Methods for the Design of Molecular Non-Linear Optical Materials

The quantum chemical design of new molecular materials for non-linear applications requires a fundamental understanding of electronic structure and properties. Targeted synthesis of candidates greatly reduces the costs and timescales of an empirical search and this is aided by prior calculation of excited state energies, energy relaxation and transfer rates, molecule-environment interactions and excited state chemistry.Essentially, the problems encountered in the routine application of standard quantum chemical methods are caused by the large size of the molecules of interest. This necessitates either the design of ultra-fast computers or numerical methods which facilitate the application of ‘exact’ techniques or the development of less resource intensive approximate methods with proven accuracy.We shall outline the theories used in the calculation of optical properties and review their computational implementation. Calculations on annellated tetraazaporphyrazines will be presented in illustration.