THEORETICAL INVESTIGATION OF THE 2ND-ORDER NONLINEAR-OPTICAL PROPERTIES OF CALIX[4]ARENE MOLECULES

We investigate theoretically the second-order nonlinear optical proper ties of a new class of compounds presenting more than one [Donor-pi co njugated segment-Acceptor] unit in a single molecule: the calix[4]aren es. We calculate the second-order polarizabilities beta for four confo rmers 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 H yper Rayleigh Scattering (HRS) experimental data. We describe the evol ution of the beta response with the change of conformation and point o ut the presence of strong pi-pi cofacial interactions which shift the charge transfer bands to shorter wavelengths.