Hydrogen-bonded supramolecular structures of cobalt(III) complexes with unsymmetrical bidentate ligands: mer/fac interconversion induced by hydrogen-bonding interactions

Ryoji Mitsuhashi, Takayoshi Suzuki, Satoshi Hosoya, Masahiro Mikuriya

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Cobalt(III) complexes with three unsymmetrical bidentate ligands containing a noncoordinating N−H bond and a phenolate-O donor as hydrogen-bond donor and acceptor, respectively, were prepared and characterized.1H NMR spectroscopy indicated that all the tris-chelate Co(III) complexes prepared favor the mer configuration in solution. [Co(Hthp)3] and [Co(Himn)3] also possess the mer configuration in the crystals (Hthp = 2-(1,4,5,6-tetrahydro-pyrimidin-2-yl)phenolate, Himn = 2-(2-imidazolinyl)-phenolate). On the other hand, [Co(Himl)3] takes the fac configuration in the crystal (Himl = 2-(2-imidazolyl)-phenolate). These Co(III) complexes showed three types of characteristic supramolecular structures: ladder, distorted hexagonal sheet, and honeycomb sheet structure, constructed by intermolecular hydrogen bonds. Heating [Co(Himn)3] and [Co(Himl)3] in methanol selectively afforded precipitates of the fac isomer due to the low solubility of the hydrogen-bonded supramolecular structures. This mer to fac isomerization upon crystallization in methanol is presumably induced by the formation of highly ordered hydrogen-bond networks via the methanol molecule. The fac isomers remained intact in dimethyl sulfoxide (DMSO) for longer than a week at room temperature. Upon heating, however, fac to mer geometrical isomerization of both fac-[Co(Himn)3] and fac-[Co(Himl)3] was observed in DMSO. Thus, mer/fac interconversion was achieved by heating in two different solvents, due to the formation of a supramolecular assembly of hydrogen-bond networks.

Original languageEnglish
Pages (from-to)207-213
Number of pages7
JournalCrystal Growth and Design
Volume17
Issue number1
DOIs
Publication statusPublished - Jan 1 2017

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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