Luminescence vapochromism of a platinum(II) complex for detection of low molecular weight halohydrocarbon.

Platinum(II) complex [Pt(Me(3)SiC[triple bond]CbpyC[triple bond]CSiMe(3))(C[triple bond]CPh)(2)] (1) with 5,5-bis(trimethylsilylethynyl)-2,2'-bipyridine (Me(3)SiC[triple bond]CbpyC[triple bond]CSiMe(3)) and phenylacetylene (PhC[triple bond]CH) exhibits unusual luminescence vapochromism to volatile organic compounds (VOCs) including CH(2)Cl(2), CHCl(3), and CH(3)I, 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 x CHCl(3), 1 x 1/2(CH(2)ClCH(2)Cl), and 1 x 1/2(toluene) revealed a staggered packing for 1 x CHCl(3) whereas there was an antiparallel packing for other three structures in stacking of planar platinum(II) moieties. The Pt...Pt distance is 3.302(1) A in 1 x CHCl(3), whereas it is >4.0 A in the other three structures. Complex 1 displays bright orange luminescence in dichloromethane solution, arising from pi(phenylacetylide)-->pi*(Me(3)SiC[triple bond]CbpyC[triple bond]CSiMe(3)) (3)LLCT and d(Pt)-->pi*(Me(3)SiC[triple bond]CbpyC[triple bond]CSiMe(3)) (3)MLCT triplet states which are supported by DFT calculation. The solid-state emission occurs at approximately 762 nm for 1 x VOC (VOC = CH(2)Cl(2), CHCl(3), and CH(3)I), whereas it was at approximately 562 (603sh) or 603 (562sh) nm for 1 and other 1 x VOC, corresponding to a vapochromic response shift of approximately 160-200 nm. The dramatic vapochromism and vapoluminescence of 1 to the vapor of CH(2)Cl(2), CHCl(3), or CH(3)I are induced by a reversible conversion of the emissive state from (3)MLCT/(3)LLCT character to (3)MMLCT/(3)LLCT state.