Tunable Trimers: Using Temperature and Pressure to Control Luminescent Emission in Gold(I) Pyrazolate-Based Trimers

C. H. Woodall, S. Fuertes, C. M. Beavers, L. E. Hatcher, A. Parlett, H. J. Shepherd, J. Christensen, S. J. Teat, M. Intissar, A. Rodrigue-Witchel, Y. Suffren, C. Reber, C. H. Hendon, D. Tiana, A. Walsh, P. R. Raithby, Chem. Eur. J. 2014, 20, 16933-16942

A systematic investigation into the relationship between the solid-state luminescence and the intermolecular Au···Au interactions in a series of pyrazolate-based gold(I) trimers; tris(m2-pyrazolato-N,N’)-tri-gold(I) (1), tris(m2-3,4,5-trimethylpyrazolato-N,N’)-tri-gold(I) (2), tris(m2-3-methyl-5-phenylpyrazolato-N,N’)-tri-gold(I) (3) and tris(m2-3,5-diphenylpyrazolato-N,N’)-tri-gold(I) (4) has been carried out using variable temperature and high pressure X-ray crystallography, solid-state emission spectroscopy, Raman spectroscopy and computational techniques. Single-crystal X-ray studies show that there is a significant reduction in the intertrimer Au···Au distances both with decreasing temperature and increasing pressure. In the four complexes, the reduction in temperature from 293 to 100 K is accompanied by a reduction in the shortest intermolecular Au···Au contacts of between 0.04 and 0.08. The solid-state luminescent emission spectra of
1 and 2 display a red shift with decreasing temperature or increasing pressure. Compound 3 does not emit under ambient conditions but displays increasingly red-shifted luminescence upon cooling or compression. Compound 4 remains emissionless, consistent with the absence of intermolecular Au···Au interactions. The largest pressure induced shift in emission is observed in 2 with a red shift of approximately 630 cm1 per GPa between ambient and 3.80 GPa.
The shifts in all the complexes can be correlated with changes in Au···Au distance observed by diffraction.

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