A new class of platinum (II) vapochromic salts

Luminescent chloride and hexaflurophosphate salts of Pt(Me2bzimpy)Cl+ (Me2bzimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine) are reported. As solids, both compounds are vapochromic, undergoing pronounced and reversible changes of color and emission in the presence of volatile organic compounds. The chloride salt responds to vapors of methanol, chloroform, ethanol, and acetonitrile, undergoing a distinct change in color from yellow to red within seconds. The PF6- salt responded selectively to acetonitrile vapor, changing from yellow to violet while sorbing 1.0 +/- 0.1 equiv. For either salt, leaving vapor-exposed samples in air for several days or heating for several minutes restored the original color. UV-visible absorption spectra and solid-state room temperature and 77 K emission spectra are reported, and the accumulated data are consistent with a decrease in Pt...Pt separation accompanying vapor sorption.