Cyclometalated platinum(II) complexes bearing o-phenylenediamine derivatives: Synthesis and electrochemical behavior

New cyclometalated Pt(II) complexes bearing 1,2-phenylenediamine (pda) derivatives were synthesized and their chemical and electrochemical properties were investigated. Two Pt complexes, [Pt(bzqn) (pda)](PF6) (bzqn = benzo[h]quinoline, [1](PF6): pda = 1,2-phenylenediamine, [2](PF6): pda = 4,5-dimethyl-1,2-phenylenediamine), were synthesized by the reaction of (Bu4N)[PtCl2(bzqn)] with corresponding pda derivatives. The Pt–pda complexes were converted to Pt–bda (bda = 1,2-benzenediamide) complexes by treatment of 2 mol equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and they showed two-step reversible redox couples in cyclic voltammetry. The cyclometalated ligand gave a strong electronic effect to the bda ligand to take place the negative shift of the bda-based redox potentials.