Second-order nonlinear optical properties of cyclometallated Ir(III) and Pt(II) complexes

The second-order NLO properties of various cyclometallated cationic Ir(III) and neutral Pt(II) complexes were determined by both Electric Field Induced Second Harmonic generation (EFISH) and Harmonic Light Scattering (HLS) techniques. Cationic 1,10-phenanthroline and bipyridine iridium(III) complexes (1, 2) are characterized by high negative EFISH β values which decrease when the ion-pair strength between the cation and the counterion (PF6–, C12H25SO3–) increases. Neutral Pt(II) complexes (3, 4) are also characterized by a good to high negative NLO response. For all these cyclometallated complexes, the EFISH response is mainly controlled by MLCT/L'LCT processes. Interestingly, a combination of HLS and EFISH techniques, used to evaluate both the dipolar and octupolar contributions to the total quadratic hyperpolarizability, shows that the major contribution is controlled by the octupolar part. [...] 1. V. Aubert, L. Ordronneau, M. Escadeillas, J. A. G. Williams, A. Boucekkine, E. Coulaud, C. Dragonetti, S. Righetto, D. Roberto, R. Ugo, A. Valore, A. Singh, J. Zyss, I. Ledoux-Rak, H. Le Bozec, V. Guerchais, Inorg. Chem. 2011. ASAP