Characteristic vapochromic detection of platinum(II) 3,8-bis-(2-triisopropylsilylethynyl)-phenanthroline organometallic complexes with bis-arylethynyl derivatives

Abstract

The vapochromism of square-planar platinum(II) complexes has been widely studied because of its potential as a useful chemical sensor of harmful volatile organic compounds (VOCs). We synthesized six platinum(II) organometallic complexes with 3,8-bis-(triisopropylsilyl)ethynyl-1,10-phenanthroline (PhenTIPS) and six respective arylethynyl ligands with different substituents (Pt(PhenTIPS)(-Ph-R)2: R = 4-Me (1TIPS), 4-CF3 (2TIPS), 4-t-Bu (3TIPS), 3,5-di-Me (4TIPS), 3,5-di-CF3 (5TIPS), 3,5-di-t-Bu (6TIPS)), as well as two complexes with 3,8-bis-(trimethylsilyl)ethynyl-1,10-phenanthroline (PhenTMS) and 3,8-bis-(triethylsilyl)ethynyl-1,10-phenanthroline (PhenTES) including a 3,5-dimethyl-phenylethynyl ligand: Pt(PhenTMS)(-Ph-3,5-di-Me)2 (4TMS) and Pt(PhenTES)(-Ph-3,5-di-Me)2 (4TES). These complexes were characterized by their luminescence in solution and in the solid state by photoluminescence spectroscopy and showed the phosphorescence from the mixed transition of triplet metal-to-ligand charge transfer (3MLCT)/triplet ligand-to-ligand charge transfer (3LLCT) or the transition of a triplet metal-metal-to-ligand charge transfer (3MMLCT) including the Pt-Pt interaction in the solid state. In vapoluminescence experiments, we found that three complexes (3TIPS, 4TIPS, and 4TMS) in the solid state showed unique luminescent color changes against the vapors of specific VOCs. Also, in vapoluminescence experiments, the solid-state photoluminescence spectra of 3TIPS and 4TMS showed a blue shift in phosphorescence from the 3MMLCT transition to the 3MLCT/3LLCT mixed transition against the vapors of specific VOCs. The vapoluminescence experiment with 4TIPS against 13 species of VOCs showed only the characteristic selective detection against CHCl3 with a bright green emission.