New copper carboxyl-ate pyrene dimers: synthesis, crystal structure, Hirshfeld surface analysis and electrochemical characterization.

Two new copper dimers, namely, bis-(dimethyl sulfoxide)-tetra-kis-(μ-pyrene-1-carboxyl-ato)dicopper( Cu - Cu ), [Cu 2 (C 17 H 9 O 2 ) 4 (C 2 H 6 OS) 2 ] or [Cu 2 (pyr-COO - ) 4 (DMSO) 2 ] ( 1 ), and bis-(di-methyl-formamide)-tetra-kis-(μ-pyrene-1-carboxyl-ato)dicopper( Cu - Cu ), [Cu 2 (C 17 H 9 O 2 ) 4 (C 3 H 7 NO) 2 ] or [Cu 2 (pyr-COO - ) 4 (DMF) 2 ] ( 2 ) (pyr = pyrene), were synthesized from the reaction of pyrene-1-carb-oxy-lic acid, copper(II) nitrate and tri-ethyl-amine from solvents DMSO and DMF, respectively. While 1 crystallized in the space group P , the crystal structure of 2 is in space group P 2 1 / n . The Cu atoms have octa-hedral geometries, with four oxygen atoms from carboxyl-ate pyrene ligands occupying the equatorial positions, a solvent mol-ecule coordinating at one of the axial positions, and a Cu⋯Cu contact in the opposite position. The packing in the crystal structures exhibits π-π stacking inter-actions and short contacts through the solvent mol-ecules. The Hirshfeld surfaces and two-dimensional fingerprint plots were generated for both compounds to better understand the inter-molecular inter-actions and the contribution of heteroatoms from the solvent ligands to the crystal packing. In addition, a Cu 2+ /Cu 1+ quasi-reversible redox process was identified for compound 2 using cyclic voltammetry that accounts for a diffusion-controlled electron-donation process to the Cu dimer.