Luminescence Vapochromism of a Platinum(II) Complex for Detection of Low Molecular Weight Halohydrocarbon

Platinum(II) complex [Pt(Me3SiC Cbyc CSiMe3)(C CPh)(2)] (1) with 5,5-bis(trimethylsilylethynyl)-2,2'-bipyridine (Me3SiC CbpyC CSiMe3) and phenylacetylene (PhC CH) exhibits unusual luminescence vapochromism to volatile organic compounds (VOCs) including CH2Cl2, CHCl3, and CH(3)l, which is useful for detection of volatile halohydrocarbon with one carbon atom and molecular weight less of than 150. Crystal structural determination of 1,1 center dot CHCl3, 1 center dot 1/2(CH2ClCH2Cl), and 1 center dot 1/2(toluene) revealed a staggered packing for 1 center dot CHCl3 whereas there was an antiparalle packing for other three structures in stacking of planar platinum(II) moieties. The Pt center dot center dot center dot Pt distance is 3.302(1) angstrom in 1 center dot CHCl3, whereas it is > 4.0 angstrom in the other three structures. Complex 1 displays bright orange luminescence in dichloromethane solution, arising from pi(phenylacetylide)->pi(star)(Me3SiC CbpyC CSiMe3) (LLCT)-L-3 and d(Pt)->pi(star)(Me3SiC CbpyC CSiMe3) (MLCT)-M-3 triplet states which are supported by DFT calculation. The solid-state emission occurs at approximately. 762 nm for 1 center dot VOC (VOC = CH2Cl2, CHCl3, and CH(3)l), whereas it was at approximately 562 (603sh) or 603 (562sh) nm for 1 and other 1 center dot VOC, corresponding to a vapochromic response shift of approximately 160-200 nm. The dramatic vapochromism and vapoluminescence of 1 to the vapor of CH2Cl2, CHCl3, or CH(3)l are induced by a reversible conversion of the emissive state from (MLCT)-M-3/(LLCT)-L-3 character to (MMLCT)-M-3/(LLCT)-L-3 state.