The development of Laue techniques for single-pulse diffraction of chemical complexes: time-resolved Laue diffraction on a binuclear rhodium metal-organic complex

Abstract

A modified Laue method is shown to produce excited-state structures at atomic resolution of a quality competitive with those from monochromatic experiments. The much faster data collection allows the use of only one or a few X-ray pulses per data frame, which minimizes crystal damage caused by laser exposure of the samples and optimizes the attainable time resolution. The method has been applied to crystals of the α-modification of Rh(2)(μ-PNP)(2)(PNP)(2) (BPh(4))(2) [PNP = CH(3)N(P(OCH(3))(2))(2), Ph = phenyl]. The experimental results show a shortening of the Rh-Rh distance in the organometallic complex of 0.136 (8) Å on excitation and are quantitatively supported by quantum-mechanical (QM)/molecular-mechanics (MM) theoretical calculations which take into account the confining effect of the crystal environment, but not by theoretical results on the isolated complex, demonstrating the defining effect of the crystal matrix.

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

“…Photodifference maps: Photodifference maps (Kim et al ., 2002; Zheng et al ., 2007; Makal et al ., 2011; Fournier and Coppens, 2014; and Jarzembska et al ., 2014) illustrate the light-induced changes in terms of the differences between laser-ON and laser-OFF electron density distributions. They are important for the selection of parameters in the following least squares refinements.…”

“…S1(b)). For the second refinement, individual datasets were scaled and combined as described earlier (Makal et al , 2011) to obtain a single combined scaled/merged data set. It resulted in a 5.55% excited state population (Table II, last row).…”

“…Subsequently, a combined scaled/merged data set was obtained by scaling of the individual data sets by a scale factor k ( η ) set  = ⟨| η |⟩ all / ⟨| η |⟩ set ; in which ⟨| η |⟩ all  = the average over all the measured reflections and ⟨| η |⟩ set  = the averages over all measured reflections in a specific data set (Makal et al , 2011). The combined scaled data sets were then merged using the SORTAV program.…”

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

“…Additional examples of excited state studies of metalloorganic complexes are the 100 ps study of Rh 2 (μ-PNP) 2 (PNP) 2 _BPh 4 (Makal et al , 2011) (Fig. 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).…”

“…The initial studies at monochromatic sources were followed by the development of the “pink” Laue technique, first applied to the dynamics of biological systems (Ren and Moffat, 1995; Moffat, 2001), and more recently to the analysis of the structure of fleeting molecular triplet states (Makal et al , 2011) (Fig. 3), and an Ag-Cu containing coinage metal complex (Jarzembska et al , 2014).…”