Issue 44, 2019

Chloranilate bridged dinuclear copper(ii) complexes: synanti geometry tuned by the steric factor and supramolecular interactions

Abstract

Four dinuclear Cu(II) coordination compounds, [(CuL1)2CA]·CH3OH (1), [(CuL1)2CA]·CH3CN (1A), [(CuL2)2CA] (2) and [(CuL3)2CA] (3) (where, CA = chloranilate anion, HL1 = 2-[1-(2-dimethylamino-ethylimino)-methyl]-phenol, HL2 = 2-[1-(2-methylamino-ethylimino)-methyl]-phenol, HL3 = 2-[1-(methylamino-propan-2-ylimino)-ethyl] phenol, have been synthesized by the self-assembly of copper–Schiff base precursors together with chloranilate anions as bridging ligands. The complexes are characterized by elemental analyses, IR spectroscopy, thermal analyses, and single crystal X-ray crystallography. Structural analyses reveal that complexes 1 and 1A are in the syn-conformation while 2 and 3 are in the anti-conformation with respect to the metal coordinated Schiff-base ligands. Theoretical calculations show that for all three ligands, the anti-conformations are energetically favorable and the unfavourable syn-conformation in 1 or 1A is stabilized through CH⋯π and hydrogen bonding interactions between the [(CuL1)2CA] unit and a co-crystallised solvent molecule. The M06-2X/def2-TZVP level of theory and NCI plot explicitly show that unlike in the case of 2 and 3, which form a 1D supramolecular chain by chelate ring⋯chelate ring π-stacking and cuprophilic interactions between neighbouring dimers, in 1 and 1A, steric interactions between neighbouring dimeric units, incorporated by one extra methyl group of the Schiff-base moiety, restrict these structures into dimeric units. Variable-temperature magnetic susceptibility measurements suggest weak antiferro- and ferromagnetic coupling in 1 (syn-conformation) and 3 (anti-conformation) with coupling constants of −2.11 and 3 cm−1, respectively.

Graphical abstract: Chloranilate bridged dinuclear copper(ii) complexes: syn–anti geometry tuned by the steric factor and supramolecular interactions

Supplementary files

Article information

Article type
Paper
Submitted
08 May 2019
Accepted
02 Oct 2019
First published
02 Oct 2019

CrystEngComm, 2019,21, 6886-6893

Chloranilate bridged dinuclear copper(II) complexes: synanti geometry tuned by the steric factor and supramolecular interactions

P. Kar, A. Franconetti, A. Frontera and A. Ghosh, CrystEngComm, 2019, 21, 6886 DOI: 10.1039/C9CE00705A

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