Synthesis, crystal structure, Hirshfeld surface and DFT analysis of bis(4-oxo-4-phenylbut-2-en-2-olato-κ ² <i>O</i> , <i>O</i> ′)copper(II)

In the title compound, [Cu(C₁₀H₉O₂)₂], which crystallizes in space group <i>P</i>2₁/<i>n</i>, the central Cu^II ion is four-coordinate and closely approaches an ideal square-planar geometry: Cu-O = 1.9173 (18)-1.920 (2) Å, O-Cu-O = 93.34 (7)°, τ₄ = 0.00, CShM(square-planar) = 0.085. The crystal packing features offset chains along [011] consolidated by π-π inter-actions [<i>Cg</i>⋯<i>Cg</i> = 3.1293 (1) Å], weak π-metal contacts [<i>Cg</i>⋯Cu = 3.390 (2) Å], and C-H⋯O contacts; Hirshfeld surface analysis shows dominant H⋯H contacts (54.8%), followed by H⋯C (18.8%) and O⋯H (11.3%). DFT (UB3LYP, ECP on Cu) yields <i>E</i>(HOMO) = -6.19 eV, <i>E</i>(LUMO) = -1.83 eV, Δ<i>E</i> = 4.36 eV; the HOMO has a significant metal contribution while the LUMO is ligand π* in character, indicating mixed metal-to-ligand charge-transfer (MLCT)/ligand-centered transitions and high electronic stability.