Luminescent square-planar platinum(II) complexes with tridentate 3-bis(2-pyridylimino)isoindoline and monodentate N-heterocyclic ligands.

A series of platinum(II) complexes with 1,3-bis(2-pyridylimino)isoindoline (BPI) derivatives were prepared by substitution of the coordinated Cl in the precursor complex Pt(BPI)Cl with a N-heterocyclic ligand such as pyridine, phthalazine or phenanthridine. These complexes display orange to red luminescence in fluid dichloromethane solutions and in the solid states at room temperature. The photophysical properties were tuned by introducing electron-withdrawing -NO(2) or electron-donating -NH(2) to the BPI ligand. The DFT computational studies suggest that the emission in the N-heterocyclic ligand substituted platinum(II) complexes originates mainly from the (3)[π→π*(BPI)] (3)IL triplet excited state, mixed with some (3)[dπ(Pt)→π*(BPI)] (3)MLCT character. Compared with the precursor Pt(BPI)Cl, both the low-energy absorption and the emission in the N-heterocyclic ligand substituted platinum(II) complexes exhibits a distinct blue-shift due to an obviously enhanced contribution from the (3)IL state and a reduced (3)MLCT character.