On justification of Cu(II) environment in mononuclear complexes: Joint X-ray and AIM studies

Interaction of copper(II) acetate with benzoic acid (benzene-1,3,5-tricarboxylic acid = H3-btc and 3,5-dinitro-benzoic acid = H-dnb) and pyridine (Py) resulted in two mononuclear square-planar complexes with the compositions [Cu(H2-btc)2(Py)2] (1) and [Cu(dnb)2(Py)2] (2). The recrystallization of 2 from dimethylsulfoxide (DMSO) yielded the square-bipyramidal complex [Cu(dnb)2(DMSO)2(H2O)2] (3). Crystal structures of 1–3 were determined by single crystal X-ray diffraction at 100 K. The square-planar Cu(II) geometry with the Cu–O and Cu–N distances of 1.924(2), 1.925(2) and 2.024(3) and 2.025(3) Å in 1, and 1.930(4) and 2.033(5) Å in 2 was found. The extended H-bonding system in 1 built on the robust carboxylic synthons is giving rise to the high-ordered porous layered structure. Insight into metal center environment and stabilizing intramolecular short interactions is obtained through quantum theory of atoms in molecules (QTAIM). As revealed by QTAIM, in octahedral complex 3 Cu-dnb and Cu-DMSO bonds are stronger than Cu–N bonds in 1 and 2.

Interaction of copper(II) acetate with benzoic acid (benzene-1,3,5-tricarboxylic acid = H3-btc and 3,5-dinitro-benzoic acid = H-dnb) and pyridine (Py) resulted in two mononuclear square-planar complexes with the compositions [Cu(H2-btc)2(Py)2] (1) and [Cu(dnb)2(Py)2] (2). The recrystallization of 2 from dimethyl sulfoxide (DMSO) yielded the square-bipyramidal complex [Cu(dnb)2(DMSO)2(H2O)2] (3). Crystal structures of 1–3 were determined by single crystal X-ray diffraction at 100 K. Insight into metal center environment and stabilizing intramolecular short interactions is obtained through quantum theory of atoms in molecules (QTAIM).Figure optionsDownload as PowerPoint slideHighlights
► Preparation of three mononuclear Cu(II) complexes with tricarboxylic and benzoic acid derivatives as ligands.
► Joint X-ray single-crystal and quantum theory of atoms in molecules (AIM) studies.
► The square-planar primary coordination sphere in four-coordinated complexes was justified using X-ray and AIM results.