Carboxylate Coordination Assisted Aggregation for Quasi‐Tetrahedral and Partial‐Dicubane [Cu4] Coordination Clusters

Abstract

AbstractThe reaction of three copper(II) carboxylate (R = Me, Ph and H in RCO2−) salts in MeOH with H3L resulted three [Cu4] aggregates: [Cu4(μ4‐O)(μ‐H2L)2(μ1,3‐O2CCH3)4] (1), [Cu4(μ4‐O)(μ‐H2L)2(μ1,3‐O2CPh)(PhCO2)3]⋅H2O (2⋅H2O), and [Cu4(μ3‐OH)2(μ‐H2L)2(μ1,1‐HCO2)2(HCO2)2]⋅2H2O (3⋅2H2O). Three different carboxylate groups showing varying coordination modes were responsible for the self‐aggregation of two ligand bound [Cu2(H2L)]3+ units. The [Cu4O] and [Cu4(OH)2] cores were generated from water‐derived oxido and hydroxido nucleating groups to provide quasi‐tetrahedral and partial‐dicubane topologies. In complexes 1 and 2⋅2H2O the μ1,3 bridging mode of the carboxylate bridges were responsible for the entrapment of μ4‐O unit, whereas μ1,1 bridge by formato groups resulted in trapping of two μ3‐OH units in complex 3⋅2H2O. Complex 3⋅2H2O is the first reported example of a μ1,1‐formato bridged [Cu4] aggregate. Long range van der Waals forces, in presence of hydrogen bonding interactions, also play significant role in the [Cu4] aggregation process. These have been analyzed by DFT calculations and Hirshfeld surface analysis.