The synthesis and photophysical studies of cyclometalated Pt(II) complexes with C,N,N-ligands containing imidazolyl donors

Two new C,N,N-type ligands (HL₂ and HL₃), containing a C_phenyl, a N_pyridyl, and a N_imidazolyl donor, and their cycloplatinated complexes, [Pt(L₂)Cl] (1), [Pt(L₃)Cl] (2), [Pt(L₂)(PPh₃)]+ (3) and [Pt(L₃)(PPh₃)]+ (4), have been successfully synthesized and characterized. Spectroscopic and ³MLCT luminescent properties of these Pt(II) cyclometalated complexes were found to be pH dependent. This was attributed to the protonation/deprotonation of the acidic 1-imidazolyl-NH moieties on the ligands. All the cycloplatinated complexes (both protonated and deprotonated forms) possessed two-photon excitability with two-photon absorption cross-sections ranging from 6.0 to 30.0 GM (protonated forms) and from 16.2 to 24.9 GM (deprotonated forms). Copyright © 2012 The Royal Society of Chemistry.