The role of intermolecular interactions in the assemblies of FeII and CoII tetrakis-isothiocyanatometalates with tris(1,10-phenanthroline)-RuII: Crystal structures of two dual-metal assemblies featuring octahedral cationic and tetrahedral anionic modules

Two new dual-metal assemblies: 2[Ru(phen)3]2+·[Fe(SCN)4]2−·2SCN−·4H2O 1 and [Ru(phen)3]2+·[Co(SCN)4]2−2, (phen:1,10-phenanthroline), have been prepared and their structures were characterized by X-ray diffraction. In 1, the cationic octahedral enantiomers are arranged with a ΛΔΛΔΛ sequence supported by π–π stacking and the anionic inorganic tetrahedral units are oriented between these stacks by interacting with the nearby water molecules through strong O–H⋯O and O–H⋯S hydrogen bonds. In 2, homochiral double helices in the b-direction are revealed, with tetrakis-isothiocyanate CoII anions arranged in the crystal to furnish one-dimensional (1D)-helical chains with S⋯S intermolecular interactions at 3.512(2) and 3.966(2) Å supporting [Ru(phen)3]2+Λ- and Δ-helices with Ru⋯Ru shortest distance of 8.676(7) Å. In both 1 and 2, the supramolecular assembly is maintained by C–H⋯S hydrogen bonds extending between the phenanthroline aromatic carbons in the cationic nodes and the sulphur atoms of the isothiocyanates anions. Analysis of S⋯S interactions in isothiocyanate containing compounds using Cambridge structural database (CSD) showed an angle dependence categorizing these interactions into “type-I” and “type-II”.

Graphical abstractSide projection in 2 showing the crankshaft caused by S⋯S interactions in [Co(NCS)4]2− in-between [RuII(phen)3]2+ helices. Only isothiocyanates arms of [Co(NCS)4]2− that are part of S⋯S interactions are shown and [RuII(phen)3]2+ are presented as polyhedra.Figure optionsDownload full-size imageDownload as PowerPoint slide