Twisted π-system electro-optic chromophores. A CIS vs. MRD-CI theoretical investigation

Twisted, merocyanine-type molecules are investigated theoretically as chromophores, whose optical and electro-optic responses can be controlled via steric repulsion-mediated tuning of the central dihedral angle. Employing multi-reference determinant computational methods results in significant modifications to the quantitative aspects of the response properties, compared to values computed using a single determinant ground state, and leads to computed hyperpolarizabilities even larger than previously estimated. Using either computational approach demonstrates that fine control of the sharp variations in response properties can be achieved by using substituent-induced steric repulsions to modify the internal dihedral twist angles.