A Detailed Study of the Vapochromic Behavior of {Tl[Au(C6Cl5)2]}n

Résumé

The linear-chain polymer {TI[Au(C6Cl5) 2]}n, 1, reacts in the solid state and in solution with different volatile organic compounds such as tetrahydrofuran, acetone, tetrahydrothiophene, 2-fluoropyridine, acetonitrile, acetylacetone, and pyridine. Solid-state exposure of 1 to vapors of the above VOCs produces a selective and reversible change in its color that is perceptible to the human eye and even deeper under UV irradiation, allowing 1 to function as a sensor for these VOCs. Heating the samples exposed to the VOCs for a few minutes at 100° C regenerates the original material without degradation, even after several exposure/heating cycles. The reversibility is further confirmed by X-ray powder diffraction measurements of complex 1 before and after exposure to vapors and again after heating the samples. The products obtained by reactions of complex 1 with the above VOCs as ligands in solution contain extended linear chains of alternating gold and thallium centers with two molecules of the organic ligands attached to each thallium atom. The stoichiometry of these materials has been confirmed by single-crystal X-ray diffraction as {TI(THF)2[Au(C6Cl5)2]}, 3, and {TI(acacH)2[Au(C6Cl5)2]}, 5. Comparison of FT-IR, UV-vis, and luminescence spectra at room temperature and at 77 K of the solid samples of complexes 2-9 with the spectra of complex 1 after its exposure to VOCs suggests interaction occurs between the organic VOCs and thallium in each case. Thermogravimetric analyses data indicate that all the thallium centers in these derivatives of complex 1 are neither fully nor equally coordinatively saturated. The materials formed appear to be intermediates between complex 1 with no VOCs attached and complexes 3-9 which contain two organic ligands coordinated to each thallium. A crystal structure analyses of one of these intermediates, {TI(THF)0.5[Au(C 6Cl5)2]}, 1·0.5THF, confirms this. Density functional calculations are in accord with the observed experimental results. Analysis reveals a substantial participation of the metal atoms in transitions that give rise to the observed emissions. Crystallographic data are as follows. For 1·0.5THF: triclinic, P1, a = 8.9296(1) Å, b = 11.2457(1) Å, c = 21.2465(3) Å, α = 96.7187(7)°, β = 92.5886(6)°, γ = 98.5911(8)°, V = 2090.87(4) Å3, and Z = 2. For 3: monoclinic, P21/c1 a = 26.4163(6) Å, b = 12.1619(2) Å, c = 28.0813(6) Å, α = 90°, β = 161.9823(6)°, γ = 90°, V = 2790.51(10) A3, and Z = 4. For 5: monoclinic, P21/c1, a = 9.8654(2) Å, b = 29.8570(5) Å, c = 11.6067(2) Å, α = 90°, β = 114.5931(6)°, 7 = 90°, V = 3108.64(10) Å3, and Z = 4.