Synthesis, characterization and spectroscopic studies of cyclometalated platinum(II) complexes containing meta-bis(2-pyridoxy)benzene

A series of mononuclear and binuclear cyclometalated platinum(II) complexes containing new terdentate meta-bis(2-pyridoxy)benzene ligands: 3,5-bis(2-pyridoxy)toluene (L1H) and 3,5-bis(2-pyridoxy)-2-dodecylbenzene (L2H): [Pt(L1)Cl] (1), [Pt(L2)Cl] (2), [Pt(L1)(CH3CN)](ClO4) (3), {[Pt(L1)]2(μ-dppm)}(ClO4)2 (4), {[Pt(L2)]2(μ-dppm)}(ClO4)2 (5), {[Pt(L1)]2(μ-pyrazole)}(ClO4) (6), {[Pt(L2)]2(μ-pyrazole)}(ClO4) (7), {[Pt(L1)]2(μ-imidazole)}(ClO4) (8) and {[Pt(L2)]2(μ-imidazole)}(ClO4) (9), have been synthesized and characterized. These ligands are coordinated to platinum(II) in a “pincer”-like manner and the presence of pyridyl donors enhances the availability of the ligand π∗ orbitals for electronic transition. Spectroscopic properties of these cyclometalated complexes were studied. While the non-coplanar nature of the ligands hinders ligand–ligand and metal–metal interactions in these cyclometalated complexes, the presence of long hydrocarbon side chain on ligand L2H seems to alleviate such hindrance. Intermolecular π–π, and possibly Pt–Pt interactions were observed in complex 2 at high concentration.