Investigation of nitro–nitrito photoisomerization: crystal structures of trans-bis(acetylacetonato-O,O′)(pyridine/4-methylpyridine/3-hydroxypridine)nitrocobalt(III)

Abstract

Study of the crystal structures of the title compounds reveals that the solid-state photochemical nitro–nitrito linkage isomerization is restricted by inter­molecular C—H⋯O,O contacts in the 3-hy­droxy­pyridine phase.

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

“…In turn, as far as nitro complexes of this kind are concerned, to the best of our knowledge, only trans-acac isomers were already described in the literature. 79,80 In the case of the examined [Co(acac) 2 (imH)NO 2 ] complex, recrystallization of the synthesis product via dissolving of the sample upon mild heating in acetonitrile and subsequent slow solvent evaporation leads to two types of crystals in the crystallization batch�small red needles and notably larger red spindle-shaped crystals (Figure 1a). Structural studies revealed that the former type of crystals was formed by the [trans-Co(acac) 2 (imH)NO 2 ] isomer of the studied compound (hereafter trans-Co), whereas the latter by the [cis-Co(acac) 2 (imH)NO 2 ] equivalent (cis-Co).…”

“…Indeed, in the case of the already reported complexes, , crystal structures of cis and/or trans isomers were formed. In turn, as far as nitro complexes of this kind are concerned, to the best of our knowledge, only trans -acac isomers were already described in the literature. , …”

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

“…In a Co III complex, nitro (N-bonded) coordination is thermodynamically more stable than the nitrito (O-bonded) form, but nitro-nitrito linkage isomerization may occur in the solid state by irradiation with visible or UV light (Balzani et al, 1968;Coppens et al, 2002). The crystal structures of trans-[Co(en) 2 (NO 2 )(NCS)]NCS (Ohba, Tsuchimoto & Kurachi, 2018) and trans-[Co(acac) 2 (NO 2 )(pyridine derivative)] (Ohba, Tsuchimoto & Miyazaki, 2018) indicated that a certain geometry of the intermolecular N/C-HÁ Á ÁO contacts restricts the photoisomerization. In the present study, we investigated another type of nitrocobalt complex, trans-[Co(salen)(NO 2 )-(X-py)], where H 2 salen is N,N 0 -bis(salicylidene)-1,2-ethanediamine, and X-py is pyridine in (I) or 4-methylpyridine in (II).…”

“…The photo-reactivities of nitrocobalt complexes in the solid state depend not only on the steric conditions but also on the electronic effects of the co-existing ligands (Miyoshi et al, 1983). The change of the IR spectrum of (I) upon irradiation was less apparent and it disappeared much more quickly after irradiation than that of trans-[Co(acac) 2 (NO 2 )(py)] (Ohba, Tsuchimoto& Miyazaki, 2018), indicating that salen 2À is not as suitable as acac À for stabilization of the nitrito form.…”

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.…”