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

Platinum(II) complex [Pt(Me3SiCCbpyC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 CH3I, 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·CHCl3, 1·1/2(CH2ClCH2Cl), and 1·1/2(toluene) revealed a staggered packing for 1·CHCl3 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) Å in 1·CHCl3, whereas it is >4.0 Å in the other three structures. Complex 1 displays bright orange luminescence in dichloromethane solution, arising from π(phenylacetylide)→π*(Me3SiCCbpyCCSiMe3) 3LLCT and d(Pt)→π*(Me3SiCCbpyCCSiMe3) 3MLCT triplet states which are supported by DFT calculation. The solid-state emission occurs at approximately 762 nm for 1·VOC (VOC = CH2Cl2, CHCl3, and CH3I), whereas it was at approximately 562 (603sh) or 603 (562sh) nm for 1 and other 1·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 CH3I are induced by a reversible conversion of the emissive state from 3MLCT/3LLCT character to 3MMLCT/3LLCT state.

铂(II)配合物（Platinum(II) complex）[Pt(Me₃SiC≡CbpyC≡CSiMe₃)(C≡CPh)₂]（记为化合物1）以5,5-双(三甲基硅基乙炔基)-2,2'-联吡啶（5,5-bis(trimethylsilylethynyl)-2,2′-bipyridine，缩写为Me₃SiC≡CbpyC≡CSiMe₃）与苯乙炔（phenylacetylene，PhC≡CH）为配体合成，其对二氯甲烷（CH₂Cl₂）、三氯甲烷（CHCl₃）、碘甲烷（CH₃I）等挥发性有机化合物（volatile organic compounds, VOCs）表现出罕见的发光蒸气变色行为，可用于检测分子量小于150的单碳卤代烃。对化合物1及其加合物1·CHCl₃、1·1/2(CH₂ClCH₂Cl)、1·1/2(甲苯)的晶体结构解析结果表明，1·CHCl₃中的平面铂(II)结构单元呈现交错堆积模式，而其余三种加合物的平面铂(II)结构单元则为反平行堆积；1·CHCl₃中的Pt···Pt间距为3.302(1) Å，其余三种结构中的该间距均大于4.0 Å。化合物1在二氯甲烷溶液中展现出明亮的橙色发光，其发光起源于π(苯乙炔基)→π*(Me₃SiC≡CbpyC≡CSiMe₃)三重态配体到配体电荷转移（³LLCT）以及d(铂)→π*(Me₃SiC≡CbpyC≡CSiMe₃)三重态金属到配体电荷转移（³MLCT），该结论得到密度泛函理论（DFT）计算的佐证。化合物1的加合物1·VOC（VOC为CH₂Cl₂、CHCl₃、CH₃I）的固态发射波长约为762 nm，而纯化合物1及其他加合物的固态发射波长约为562(603sh)或603(562sh) nm，对应的蒸气变色响应位移约为160~200 nm。化合物1对CH₂Cl₂、CHCl₃或CH₃I蒸气所展现出的显著蒸气变色与蒸气发光行为，是由激发态从³MLCT/³LLCT特征可逆转变为³MMLCT/³LLCT特征所诱导产生的。