Hydrogen-Bonded Supramolecular Structures of Cobalt(III) Complexes with Unsymmetrical Bidentate Ligands: mer/fac Interconversion Induced by Hydrogen-Bonding Interactions

作者：Mitsuhashi Ryoji^*; Suzuki Takayoshi; Hosoya Satoshi; Mikuriya Masahiro

来源：Crystal Growth & Design, 2017, 17(1): 207-213.

DOI：10.1021/acs.cgd.6601438

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. H-1 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-tetrahydropyrimidin-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-irnidazolyl)-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 forrnation of a supramolecular assembly of hydrogen-bond networks.

• 出版日期2017-1