Thermal and photochemical control of nitro–nitrito linkage isomerism in single-crystals of [Ni(medpt)(NO₂)(η²-ONO)]

Abstract

The known complex [Ni(medpt)(η

The impact of hydrogen bonding on 100% photo-switching in solid-state nitro–nitrito linkage isomers

“…The results of this, and previous, 16 photocrystallographic studies confirm that intermolecular hydrogen bonding involving the photo-active group will influence the progress of nitro → nitrito conversion in the solid-state. However, in contrast to previous work, this study has illustrated that the presence of such intermolecular interactions does not necessarily limit the crystal system to only a low photo-activation level.…”

“…This hydrogen bond motif is significant, as it directly involves the potentially photo-active nitro-(η 1 -NO 2 ) groups. The hydrogen bonds must be disrupted for photo-isomerisation to proceed and, given the literature precedent, 16 could be likely to hinder high photo-conversion in 1. The OTf anions sit in discrete pockets, with each OTf participating in short contacts with 6 nearest neighbour cations.…”

“…An example is [NiIJMeDPT)IJNO 2 ) 2 ], which contains two, crystallographically distinct nitro-(η moderately strong hydrogen bonds through both of its oxygen atoms. 16 This result suggests that, when designing new linkage isomer switches, fragments containing hydrogen bond donor groups should be avoided. This would be an unfortunate design limitation, given that hydrogen bonds are traditionally one of crystal engineering's most important and useful tools.…”

“…In line with thermal lattice expansion, the NIJ3)-HIJ3)⋯OIJ1) hydrogen bonds are significantly longer at higher temperature, consistent with these interactions becoming weaker on warming. If, as expected, hydrogen bonds to the GS NO 2 ligand inhibit photo-isomerism, 16 the weaker interaction at high temperature is expected to facilitate higher conversion. Secondly, it has been previously shown that "reaction cavity" analysis -where a reaction cavity is defined as the volume encapsulating the photo-active groupprovides insight into local structural changes and helps to rationalize how or why a photo-reaction proceeds.…”

Monitoring photo-induced population dynamics in metastable linkage isomer crystals: a crystallographic kinetic study of [Pd(Bu4dien)NO2]BPh4

“…The earliest photocrystallographic studies with linkage isomers were carried out on metal-nitrosyl complexes, including seminal work by Coppens et al on sodium nitroprusside. 5 Since then, several linkage isomer switches have been studied using photocrystallographic methods, including nitrosyl, [6][7][8][9] sulfur dioxide [10][11][12][13] and nitrite [14][15][16][17][18][19] compounds.…”