Investigation of nitro–nitrito photoisomerization: crystal structures of trans-{2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}(pyridine/4-methylpyridine)nitrocobalt(III)

Abstract

The crystal structures of the title compounds have been studied to clarify the characteristics of the NO2 − ligand as a C—H⋯O hydrogen-bond acceptor, in relation to the solid-state photochemical linkage isomerization.

Impact of Cis–Trans Isomerism on Crystal Packing and Photo-Activity of a Cobalt(III) Room-Temperature Photoswitch

“…It should be noted that the Co−N bond lengths are on average slightly longer than the Co−O ones, which is in accordance with literature reports on similar compounds. 46,79 In turn, regarding the N-donor ligands, the bond between the metal center and nitro moiety is shorter than that with the imidazole ring; however, both bonds are longer for the trans isomer with respect to cis. Altogether this shows that the coordination sphere of the cis isomer is tighter than that of trans-Co (Supporting Information).…”

“…It has turned out that in the case of Ni complexes working, temperatures are usually rather low, i.e., below 240 K. ,,, On the other hand, the less studied Co-based photoswitches appeared to be a promising alternative. To date, only a couple of Co III nitrite complexes have been studied, mainly spectroscopically, toward linkage isomerism. − Some of them, however, exhibited RT photoswitching behavior, such as the lately reported by us simple trinitro cobalt­(III) complex . In the mentioned case, it was possible to achieve about 55% population of the PLI under ambient conditions in a single crystal without losing its crystallinity (the conversion could have been even higher, roughly 90%, but then a significant crystal degradation was observed).…”

Investigation of nitro–nitrito photoisomerization: crystal structure oftrans-chloridonitro(1,4,8,11-tetraazacyclotetradecane-κ4N,N′,N′′,N′′′)cobalt(III) chloride

“…The photochemical reactions of metal complexes in the solid state attract much attention from crystallographers and chemists (Coppens et al, 2002;Vittal & Quah, 2017). The present authors have investigated photochemical linkage isomerization of a series of the nitrocobalt(III) complexes, trans-[Co(en) 2 (NO 2 )(NCS)]ClÁH 2 O and other salts, (Ohba, Tsuchimoto & Kurachi, 2018), trans-[Co(acac) 2 (NO 2 )(pyridine derivative)] (Ohba, Tsuchimoto & Miyazaki, 2018), and trans-[Co(salen)(NO 2 )(pyridine derivative)] (Ohba, Tsuchimoto & Yamada, 2018). In the present study, we describe our investigations of another type of nitrocobalt complex, trans-[Co(cyclam)(NO 2 )Cl]Cl, (I), where cyclam stands for 1,4,8,11tetraazacyclotetradecane.…”