engleski

One-dimensional self-assembling by weak Cu-C intermolecular interactions in copper(II) beta-diketonates

Tetracoordinated divalent metal atoms of the first transition series strive to achieve higher coordination number. One possible way for coordination saturation is association (self-assembling) with neighbouring molecules. Oligomers and polymers formed in such a way posses specific physical and chemical properties. Association is ussualy achieved by weak interactions. The influence of these weak attractions to some of the compound properties (e.g. to the crystal growth) can generaly be of great importance. The determination of the crystal and molecular structure of bis(3-benzyl-2,4-pentanedionato)copper(II) provided more evidences for marked influence of copper-to-carbon interactions to the molecular assembling in crystalline state. This Cu-C contact is comparable with the sum of van der Waals radii. Searching for such contacts in related cupric beta-diketonates [J.W. Carmichael et al., J. Chem. Phys. 43 (1965) 3959-3964; Hon et al., Inorg. Chem. 5 (1965) 516-521] revealed some new facts that have to be investigated by UV/VIS spectroscopy. Better understanding of this type of interactions will surely throw new light on the nature of weak attractions. The central moiety defined by the Cu and four O atoms is essentially planar. The chelate rings are slightly folded in two along O1, O2 line[dihedral angle between planes defined by C1, C2, C3, O1, O2 and Cu, O1, O2 atoms amounts 2.5(3) degrees]. The C2 benzyl substituent phenyl ring is almost perpendicular to the chelate plane. Severe distortion of the tetrahedral angle at the C6 carbon atom results probably from the crystal packing forces and not from the intramolecular steric hindrances. The Cu-C2 contact distance between neighbouring molecules is 326,4(2) pm. This interactions affect to the molecular stacking linking the molecules in infinite one-dimensional ribbons.

intermolecular self-assembling; copper(II) beta diketonates

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