Investigation of solid-state photochemical nitro-nitrito linkage isomerization: crystal structures of -bis-(ethyl-enedi-amine)(iso-thio-cyanato)-nitritocobalt(III) salts: thio-cyanate, chloride monohydrate, and perchlorate-thio-cyanate-(0.75/0.25).

The reaction cavities of the nitro groups in the crystals of the title compounds, -[Co(NO)(NCS)(CHN)]·, = SCN (I), Cl·HO (II), and (ClO )(SCN) (III), have been investigated, revealing that the geometry of the inter-molecular N-H⋯O hydrogen bonds in (I) is unsuitable for nitro-nitrito photo-isomerization. The common main building block of these crystal structures is a centrosymmetric pair of complex cations connected by pairwise N-H⋯O(nitro) hydrogen bonds forming an (4) ring, which is a narrow diamond shape in (I) but is approximately square in (II) and (III). The structure of (I) was reported earlier [Börtin (1976 ▸). , , 503-506] but is described here with an improved disorder model for the thio-cyanate anions and to higher precision.