nitrosyl linkage isomers in the solid state

‘Photocrystallography ’ is a rapidly developing technique that involves the deter-mination of the full three-dimensional structure of a molecule or array material, using single-crystal X-ray diffraction techniques, while the molecular components are in a photoactivated metastable or short-lived high-energy state (Coppens et al., 2005). The photoactivation is usually achieved by irradiating the single crystal with a laser or a set of LED lights in the ultra-violet or visible wavelength range. The term ‘photocrystallography ’ was originally coined by Philip Coppens, one of the pioneers in the field (Coppens et al., 1998). To date, photocrystallography has been used to study the structures of metastable linkage isomers of transition metal coordination complexes, and to investigate the changes in coordination geometry in mononuclear complexes or the length of metal– metal interactions in dinuclear metal complexes (Hatcher & Raithby, 2013). In a complex that undergoes linkage isomerism, the compound contains one or more ligands that are capable of bonding to the metal centre in more than one way. For example, as elegantly illustrated by Casaretto et al. (Casaretto et al., 2015) the nitrosyl ligand, NO, can coor