Heteroleptic platinum(ii) isocyanide complexes: Convenient synthetic access, polymorphs, and vapoluminescence

A convenient synthetic scheme was developed to access a series of square-planar Pt(ii) complexes of the form (TBA)[Pt(CN)₃(CNR)] (TBA = tetra-n-butyl ammonium cation, R = CH₃, c-C₆H₁₁, p-(C₂H₅)-C₆H₄). These heteroleptic complexes were characterized by combustion analyses, single-crystal X-ray structure determinations, HRFAB-MS, ¹H NMR, ATR-IR, solution UV-Vis, and solid-state emission spectroscopies. Surprisingly, each of these complexes exhibit low energy room temperature solid-state luminescence in the absence of intermolecular Pt-Pt interactions. Additionally, the polymorphic behavior of (TBA)[Pt(CN)₃(CN-c-C₆H₁₁)] was elucidated through a combination of single-crystal X-ray structure determinations, X-ray powder diffraction, and mass uptake experiments. Vapoluminescence and polymorphic transformations of (TBA)[Pt(CN)₃(CN-c-C₆H₁₁)] were concomitant with water vapor absorption. A new double-salt complex [Pt(terpy)Cl] [Pt(CN)₃(CNCH₃)] (terpy = 2,2′,6′,2′′-terpyridine) was also synthesized and characterized by combustion analysis, ATR-IR, HRFAB-MS, and solid-state UV-Vis and emission spectroscopies. The vapoluminescent properties of this salt in response to water were examined by mass uptake experiments, ATR-IR, and solid-state emission spectroscopy. A principal component analysis (PCA) of the solid-state emission changes induced by water vapor confirmed the presence of an intermediate emissive species.