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.