Bistable Photochromic Organometallics Based on Linkage Isomerization:  Photochemistry of Dicarbonyl(η⁵-methylcyclopentadienyl)manganese(I) Derivatives with a Bifunctional, Nonchelating Ligand

Abstract

Cyclopentadienylmanganese complexes of the general formula (η5-C5H4CH3)Mn(CO)2L, where L is a nonchelatable, bifunctional ligand, were found to be photochromic. Irradiation of (η5-C5H4CH3)Mn(CO)2L(3-cyanomethylpyridine) with alternating visible and UV light produced alternating yellow and red solutions, and fatigue of this response was inhibited when free 3-(cyanomethyl)pyridine was present during irradiation. Similar results were observed when L is pyridine in the presence of dispersed acetonitrile. Irradiation of (η5-C5H4CH3)Mn(CO)3 and a pyridine derivative RC5H4N (R = 3-CH2CN, 2-CH2CN, 4-CHCHPh, 4-CHCH2) generated (η5-C5H4CH3)Mn(CO)2L in situ, which likewise showed a photochromic response. The results demonstrate that the linkage isomerization occurs by unimolecular and bimolecular processes and that linkage isomerization is an effective photochromic mechanism for organometallics.

Manganese phosphinocarbodithioate for RAFT polymerisation with sunlight-induced chain end post-treatment

“…These observations may be explained by the photosensitivity of the Mn-RAFT chain end under visible light, which is well-documented for such manganese(I) phosphine complexes. [41][42][43] Because of the long reaction times needed for St polymerisation, the polymer chain ends probably start to degrade over time, allowing chain coupling through the metal centre (Scheme 3, pathway A). To a lesser extent, we already observed a similar gradual loss of control with Mocarbonyl complexes in St polymerization for long reaction times.…”

Electron transfer triggered sulfoxide isomerization in ruthenium and osmium complexes

“…For example, linkage isomerization in Cp*Mn(CO) 2 L, where L is 3-cyanomethylpyridine, has been investigated by UV-vis spectroscopy. The two isomers are associated with cyano vs. pyridyl coordination [63]. Both unimolecular and bimolecular pathways for isomerization were observed.…”

Dynamic magnetic MOFs

“…126 The influence of external physical stimuli on linkage isomerization processes is well-known in coordination chemistry, 127,128 and several examples of bistability have been reported. 129,130 Surprisingly, until very recently the possibility of tuning the magnetization of Prussian blue analogues via this structural rearrangement has not been explored, despite the fact that cyanide is a nonsymmetric ligand and linkage isomerization can be operative in these bimetallic systems. In this context, the first example showing the importance of linkage isomerism in the reversible switching of the magnetization induced by pressure was reported by our group in 2005 in polycrystalline samples of iron(II) hexacyanochromate.…”