TY - JOUR
T1 - Hydrogen-bonded supramolecular structures of cobalt(III) complexes with unsymmetrical bidentate ligands
T2 - mer/fac interconversion induced by hydrogen-bonding interactions
AU - Mitsuhashi, Ryoji
AU - Suzuki, Takayoshi
AU - Hosoya, Satoshi
AU - Mikuriya, Masahiro
N1 - Funding Information:
We thank Ms. Rina Ogawa and Mr. Masatoshi Mori (Okayama University) for 1H NMR measurements. R.M. appreciates support from the JSPS Research Fellowship for Young Scientists. This work was partially supported by Grants-in-Aid for JSPS Fellow No. 258041 (to R.M.) and for Scientific Research No. 26410080 (to M.M.) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/4
Y1 - 2017/1/4
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.cgd.6b01438
DO - 10.1021/acs.cgd.6b01438
M3 - Article
AN - SCOPUS:85022341749
SN - 1528-7483
VL - 17
SP - 207
EP - 213
JO - Crystal Growth and Design
JF - Crystal Growth and Design
IS - 1
ER -