Luminescent cyclometallated Ir(III) and Pt(II) complexes with beta-diketonate ligands as highly active second-order NLO chromophores

[Ir(ppy)(2)(RCOCR'COR)] and [Pt(ppy)(RCOCHCOR)] (ppy = cyclometallated 2-phenylpyridine; R = Me, Ph; R' = H, 2,4-dinitrophenyl) complexes show an unexpected large second order non linear optical response, as evidenced by the EFISH technique, which can be attributed by an SOS-TDDFT investigation mainly to intraligand charge transfer transitions involving the cyclometallated ligands.