A very large Rh–Rh bond shortening on excitation of the [Rh₂(1,8-diisocyano-p-menthane)₄]²⁺ion by time-resolved synchrotron X-ray diffraction

Abstract

A very large Rh-Rh contraction of approximately 0.85 A occurs on excitation of the [Rh(2)(1,8-diisocyano-p-menthane)(4)](2+) ion to its triplet state.

Synchrotron ultrafast techniques for photoactive transition metal complexes

“…As in the Pt-POP case, a significant difference in the entity of metal-metal bond contraction has been highlighted, comparing results from solution and crystal phase characterization. For instance, the dramatic shortening of 1.4 Å with respect to the long-distance GS isomer is greater than the values found via steady-state XRD studies on the analogue Rh-containing compound [Rh 2 (dimen) 4 ] 2+ [217]. The authors explained such discrepancy with the absence of crystal packing forces, leading to an intensification of secondary deformation mechanisms already present in the crystal case.…”

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

“…A contraction of the molecule on excitation, resulting from a promotion of an electron from an anti-bonding to a weakly bonding orbital, was observed when the first results on the 50  μ s lifetime 16 K excited state structure of [Pt 2 (P 2 O 5 H 2 ) 4 ] 4− became available (Novozhilova et al , 2003; Kim et al , 2002). Contractions of binuclear complexes on excitation have since been observed in several systems (Coppens et al , 2004; Zheng et al , 2005; and Makal et al , 2011). Structural modifications have been determined for spin-crossover systems, which can be switched between low- and high-spin states by light irradiation, temperature variation, and other external perturbations, with parallel changes occurring in magnetic and optical properties (Cailleau et al , 2010).…”

The dramatic development of X-ray photocrystallography over the past six decades

“…3), and the very large shortening of the Rh-Rh distance of 0.85 Å in [Rh 2 (1,8-diisocyano-p-menthane) 4 ] 2+ (Coppens et al , 2004). …”