Supramolecular Bimetallic Systems Constructed through π‐π Stacking and Hydrogen Bond Interactions

Five new bimetallic compounds have been synthesized and crystallographically characterized: [{Cu(acac)(phen)}₂{Ni(CN)₄}] · H₂O (1), [{Cu(acac)(bipy)}₂{Ni(CN)₄}] (2); [Cu(acac)(bipy)(H₂O)]₂[Ni(CN)₄] (3), [(Cu(acac)(Me₂bipy)]₂[Ni(mnt)₂] (4), [Cu(acac)(bipy)][Ni(mnt)₂] (5) (Me₂bipy=4,4′‐dimethyl‐2,2′‐bipyridine; mnt=maleonitriledithiolate). The molecular structures of complexes 1 and 2 are similar: they consist of neutral [{Cu(acac)(BB)}₂{Ni(CN)₄}] entities, which result by connecting two [Cu(acac)(BB)]⁺ ions through two trans‐cyano groups from the bridging ligand, [Ni(CN)₄]²⁻ (BB=1,10‐phenanthroline and, respectively, 2,2′‐bipyridine). The intermolecular π‐π stacking interactions established between the organic ligands attached to the copper ions lead to supramolecular chains. In the ionic compound 3, the [Ni(CN)₄]²⁻ anions and the [Cu(acac)(bipy)(H₂O)]⁺ cations generate a 3D supramolecular architecture by convolution of hydrogen bonding with π‐π stacking interactions. The crystal structure of compound 4, [(Cu(acac)(Me₂bipy)]₂[Ni(mnt)₂], consists of cationic, [(Cu(acac)(Me₂bipy)]⁺, and anionic species, [Ni(mnt)₂]²⁻, which are connected through Cu ··· S interactions, resulting in supramolecular {CuNiCu} trimers. Crystal 5 is an ionic compound containing [Cu(acac)(bipy)]⁺ and [Ni(mnt)₂]⁻ ions.

Keywords:

• copper complexes
• nickel complexes
• cyano‐complexes
• dithiolene complexes
• stacking interactions
• hydrogen bonding