Vapor- and Mechanical-grinding-triggered Color and Luminescence Switches for Bis(σ-fluorophenylacetylide) Platinum(II) Complexes

Square-planar bis(σ-fluorophenylacetylide) platinum(II) complexes [Pt(Me(3)SiC≡CbpyC≡C-SiMe(3))(C≡CC(6)H(4)F)(2)] (C≡CC(6)H(4)F-2 for 2, C≡CC(6)H(4)F-3 for 3, and C≡CC(6)H(4)F-4 for 4; Me(3)SiC≡CbpyC≡CSiMe(3)=5,5'-bis(trimethylsilylethynyl)-2,2'-bipyridine) were prepared and were characterized by spectroscopic and luminescence studies, and X-ray crystallography. The color and luminescence of crystalline complex 3 is specifically sensitive to CHCl(3) vapor to afford 140-180 nm of luminescence vapochromic redshift, which is useful for specific detection of CHCl(3) vapor. Complex 4 displays selective luminescence vapochromic properties to CH(2)Cl(2) and CHCl(3) vapors with a luminescence vapochromic shift response of ca. 150-200 nm. Interestingly, complexes 2-4 exhibit reversible, and naked-eye perceivable, mechanical stimuli-responsive color and luminescence changes. When solid species 2-4 are crushed gently or ground, the crystalline state is converted to an amorphous phase. Meanwhile, bright yellow-orange luminescence in the crystalline species is converted to dark red under UV light irradiation with 100-160 nm of mechanochromic shift response. A vapochromic or mechanochromic cycle was monitored by dynamic variations in emission spectra and X-ray diffraction (XRD) patterns. The halohydrocarbon vapor- or mechanical-grinding-triggered color and luminescence switches are most likely correlated to a shorted intermolecular Pt-Pt distance as that revealed in vapochromic species 4·0.5 CH(2)Cl(2) by X-ray crystallography, thus leading to an increased contribution from intermolecular Pt-Pt interaction as demonstrated by DTF computational studies.