Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers

Greg Brewer; Raymond J Butcher; Peter Zavalij

doi:10.3390/ma13071595

Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers

Materials (Basel). 2020 Mar 31;13(7):1595. doi: 10.3390/ma13071595.

Authors

Greg Brewer¹, Raymond J Butcher², Peter Zavalij³

Affiliations

¹ Department of Chemistry, Catholic University, Washington, DC 20064, USA.
² Department of Chemistry, Howard University, Washington, DC 20059, USA.
³ Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.

Abstract

The 3:1 condensation of 5-methyl-1H-pyrazole-3-carboxaldehyde (MepyrzH) with tris(2-aminoethyl)amine (tren) gives the tripodal ligand tren(MePyrzH)₃. Aerial oxidation of a solution of cobalt(II) with this ligand in the presence of base results in the isolation of the insoluble Co(tren)(MePyrz)_3. This complex reacts with acids, HCl/NaClO₄, NH₄ClO₄, NH₄BF₄, and NH₄I to give the crystalline compounds Co(tren)(MePyrzH)₃(ClO₄)₃, {[Co(tren)(MePyrzH_0.5)₃](ClO₄)_1.5}₂ {[Co(tren)(MePyrzH_0.5)₃](BF₄)_1.5}₂ and [Co(tren)(MePyrzH)₃][Co(tren)(MePyrzH)₃]I_2. The latter three complexes are dimeric, held together by three N_pyrazole -H^…N_pyrazolate hydrogen bonds. The structures and symmetries of these homochiral dimers or pseudodimers are discussed in terms of their space group. Possible applications of these complexes by incorporation into new materials are mentioned.

Keywords: cobalt; crystal structure; dimer; hydrogen bonding; pyrazole; supramolecular.