Nonlinear optical properties of polychlorotriphenylmethyl radicals: towards the design of `super-octupolarʹ molecules

Molecular quadratic hyperpolarizability (βc) of substituted polychlorinated triphenylmethyl radicals, 1–8, has been determined by using the harmonic light scattering (HLS) technique. Results showed that this opens-shell family known to possess a good chemical stability also exhibited a very large SONLO response. The presence of a permanent dipole moment in the ground state for some of these octupolar compounds makes them attractive candidates for further orientation by the poling technique. Data of compounds 1–8 have been discussed on the basis of a model describing the evolution of the βc response for D3h and C2v symmetry groups.