Shedding Light on the Photochemistry of Coinage-Metal Phosphorescent Materials: A Time-Resolved Laue Diffraction Study of an Ag^I–Cu^I Tetranuclear Complex

Abstract

The triplet excited state of a new crystalline form of a tetranuclear coordination d10–d10-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing AgI and CuI metal centers has been explored using the Laue pump–probe technique with ≈80 ps time resolution. The relatively short lifetime of 1 μs is accompanied by significant photoinduced structural changes, as large as the Ag1···Cu2 distance shortening by 0.59(3) Å. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag···Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag···Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronuclear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies.

Exploring the structural changes on excitation of a luminescent organic bromine-substituted complex by in-house time-resolved pump-probe diffraction

“…Photodeformation maps : Photodeformation maps (Fournier and Coppens, 2014 and Jarzembska et al ., 2014) are calculated using the LASER refined model parameters. They represent the difference between the densities calculated with the excited state parameters and those of the GS structure.…”

Luminescence Thermochromism of Gold(I) Phosphane–Iodide Complexes: A Rule or an Exception?

“…For the di-andp olynuclear d 10 complexes, such changes are often related to shortening of the metalmetal contacts; [33,35] this also seems to be ar easonables cenario for 6 and 7.I ti se ssential that significant involvement of the ligand orbitalsi nto the T 2 state and possible mixingw ith the T 1 state in 6 and 7 potentially offersa na ppealingp ossibility of tuning the dual emission, with respect to the wavelengths and energy barrierbetween the triplet excitedstates. For the di-andp olynuclear d 10 complexes, such changes are often related to shortening of the metalmetal contacts; [33,35] this also seems to be ar easonables cenario for 6 and 7.I ti se ssential that significant involvement of the ligand orbitalsi nto the T 2 state and possible mixingw ith the T 1 state in 6 and 7 potentially offersa na ppealingp ossibility of tuning the dual emission, with respect to the wavelengths and energy barrierbetween the triplet excitedstates.…”

“…Nevertheless, ligand Xh as an oninnocent influence on luminescencee fficiency because the iodide induces aboutathreefold increase in the radiativer ate constant (k r = 1.5 10 5 s À1 for 10 vs. 5.8 10 4 s À1 for [(AuCN)(tpdp)]), and consequently,e nhances the quantumy ield of 10 (F em = 0.35) by af actor of four,w ith respectt oi ts cyanide congener (F em = 0.08). [13,33] The crucial importance of the ordered solid matrix is demonstrated by bimetallic luminophores 6 and 7,w hich reveal the presence of two coupled triplet excited states T 2 and T 1 of IL 3 pp*a nd 3 (X + M)C (mixedw ith 3 XLCT) origin, respectively.D ue to the energy barrier between T 2 and T 1 ,c rystalline 6 and 7 exhibit HE and LE emissionsw ith thermally variable intensity ratios. Eur.J.…”

Perspective: On the relevance of slower-than-femtosecond time scales in chemical structural-dynamics studies

“…Comparison of results of isolated-molecule calculations with calculations in which the lattice is taken into account confirms such differences. Large differences are often observed, as in the recent study of a Ag-Cu coinage metal complex, in which theoretical contraction of −0.534 and −0.932 Å, were reduced to −0.345 and 0.438 Å, respectively, when the environment was taken into account in the calculation, in much better agreement with the experimental results (Jarzembska et al , 2014). The photodifference maps and the structural changes on excitation are illustrated in Fig.…”