A novel Cu(II) co-crystal compound, [Cu2(μ-acetate-κ1:κ1-O,O’)4(Isn)2][Cu(acetate-κ1-O)2(Isn)2(H2O)]⋅5H2O (1), (where Isn = isonicotinamide), was synthesized in ethanolic solution at room temperature. The compound was characterized by single-crystal X-ray diffraction, which revealed that it crystallizes in the monoclinic space group P2₁/c. The complex features two centrosymmetric paddle-wheel dicopper(II) moieties, a mononuclear unit, and five hydrogen-bonded water molecules. Both the lattice water molecules and the uncoordinated carboxylate oxygen atoms in the mononuclear moiety form a strong O–H⋯O hydrogen bonding network. Compound 1 represents a cocrystal structure formed by the incorporation of two chemically distinct copper complexes, one mononuclear and one dinuclear, into a single, ordered crystal lattice. Further analysis using FT − IR/FIR/Raman, NIR-Vis-UV spectroscopy, and computational methods, including Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) theory, was conducted to investigate intra- and intermolecular interactions. Two distinct complexes were identified in the unit cell: the mononuclear copper complex (M) and the dinuclear copper complex (D). Key intra-cell interactions were analyzed by examining two representative pairwise configurations: DD, consisting of two M units, and MD, formed by one M and one D unit. The interaction energies for DD and MD were − 27.3 kcal/mol and − 34.0 kcal/mol, respectively, after correcting for non-basis set superposition error (BSSE). The DD is stabilized by N–H···O hydrogen bonds, while the MD exhibits both π-π and hydrogen bond interactions, promoting enhanced stability and stacking along the b-axis. A frontier orbital gap of 2.6 eV suggests its potential for electronic, photonic, and sensing applications. Biological assays highlighted compound M’s significant antimicrobial activity, outperforming reference compounds like Cu(OAc)₂·H₂O and isonicotinamide against Candida albicans, MRSA, E. coli, and S. typhi. Molecular docking confirmed strong binding to C. albicans, with a binding energy of − 6.89 kcal/mol, whereas compound D showed moderate activity. Graphical Abstract

Theoretical and spectroscopic insights into a unique copper(II) carboxylate co-crystal: π-stacking, hydrogen bonding network, structural features, semiconductor potential, antimicrobial, and molecular docking studies

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发表日期：

2025年9月1日

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Abiodun A. Ajibola,
Néstor Cubillán,
Faith J. Olaitan,
Agnieszka Wojciechowska,
Lesław Sieroń,
Waldemar Maniukiewicz

摘要

A novel Cu(II) co-crystal compound, [Cu₂(μ-acetate-κ¹:κ¹-O,O’)₄(Isn)₂][Cu(acetate-κ¹-O)₂(Isn)₂(H₂O)]⋅5H₂O (1), (where Isn = isonicotinamide), was synthesized in ethanolic solution at room temperature. The compound was characterized by single-crystal X-ray diffraction, which revealed that it crystallizes in the monoclinic space group P2₁/c. The complex features two centrosymmetric paddle-wheel dicopper(II) moieties, a mononuclear unit, and five hydrogen-bonded water molecules. Both the lattice water molecules and the uncoordinated carboxylate oxygen atoms in the mononuclear moiety form a strong O–H⋯O hydrogen bonding network. Compound 1 represents a cocrystal structure formed by the incorporation of two chemically distinct copper complexes, one mononuclear and one dinuclear, into a single, ordered crystal lattice. Further analysis using FT − IR/FIR/Raman, NIR-Vis-UV spectroscopy, and computational methods, including Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) theory, was conducted to investigate intra- and intermolecular interactions. Two distinct complexes were identified in the unit cell: the mononuclear copper complex (M) and the dinuclear copper complex (D). Key intra-cell interactions were analyzed by examining two representative pairwise configurations: DD, consisting of two M units, and MD, formed by one M and one D unit. The interaction energies for DD and MD were − 27.3 kcal/mol and − 34.0 kcal/mol, respectively, after correcting for non-basis set superposition error (BSSE). The DD is stabilized by N–H···O hydrogen bonds, while the MD exhibits both π-π and hydrogen bond interactions, promoting enhanced stability and stacking along the b-axis. A frontier orbital gap of 2.6 eV suggests its potential for electronic, photonic, and sensing applications. Biological assays highlighted compound M’s significant antimicrobial activity, outperforming reference compounds like Cu(OAc)₂·H₂O and isonicotinamide against Candida albicans, MRSA, E. coli, and S. typhi. Molecular docking confirmed strong binding to C. albicans, with a binding energy of − 6.89 kcal/mol, whereas compound D showed moderate activity.

Graphical Abstract