Theoretical investigation of the second-order nonlinear optical properties of calix[4]arene molecules

We investigate theoretically the second-order nonlinear optical properties of a new class of compounds presenting more than one [Donor-π conjugated segment-Acceptor] unit in a single molecule: the calix[4]arenes. We calculate the second-order polarizabilities β for four conformers of calix[4]arenes; namely, the cone, partial cone, 1,2-alternate and 1,3-alternate conformations. The theoretical results are compared with Electric-Field-Induced Second Harmonic Generation (EFISGH) and Hyper Rayleigh Scattering (HRS) experimental data. We describe the evolution of the β response with the change of conformation and point out the presence of strong π-π cofacial interactions which shift the charge transfer bands to shorter wavelengths.