Synthesis, structure and DFT calculation of a hexanuclear mixed-valence copper cluster supported by 2,3-disulfidobenzoate and 3-carboxybenzene-1,2-bis(thiolate)

A homoleptic hexanuclear Cu cluster, [(Cu(DSB)(CBT))2(Cu2Br)2][PPh4]2 (1-PPh4) [DSB = 2,3-disulfidobenzoate; CBT = 3-carboxybenzene-1,2-bis(thiolate)] was synthesized as dark green crystals by the reaction of CuCl2 with 2,3-dimercaptobenzoic acid in acetate buffer solution. The X-ray crystal study of 1-PPh4 revealed its unique structural features: (1) one of two types of crystallographically distinct Cu centers adopted a square planer geometry and the other center had a tetrahedral geometry, and (2) intermolecular H-bonding interactions connected between carboxylic acid group of CBT and the carboxylate group of DSB led to the construction of an unprecedented topologic architecture of a zigzag patterned infinite sheet. In addition, taking into account the total charge of the molecule, which contained 2,3-disulfidobenzoate and 3-carboxybenzene-1,2-bis(thiolate), and the diamagnetic nature of 1-PPh4, 1-PPh4 led to it is assignment as a mixed-valence Cu(I)/Cu(III) cluster. Such mixed valence states of Cu atoms were also examined by density functional theory calculation.

Graphical abstractA mixed-valence hexanuclear Cu cluster, [(Cu(DSB)(CBT))2(Cu2Br)2][PPh4]2 (where DSB = 2,3-disulfidobenzoate and CBT = 3-carboxybenzene- 1,2-bis(thiolate)) with four tetrahedral Cu(I) and two square planer Cu(III) centers, was constructed with an unprecedented topologic architecture of a zigzag patterned infinite sheet through unique intermolecular H-bonding interactions in solid state.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hexanuclear mix valance Cu(I/II) cluster with asymmetric dithiolene ligand. ► 2,3-dimercaptobenzoic acid served as bi and tridentate ligand under controlled acetate buffer. ► 2D H-bonding network afforded unique topologic architecture of a zigzag patterned infinite sheet. ► DFT calculation explained mix valence state of Cu atom which is well agreement with experimental results.