Structure of bis(nitrato)tetrakis(pyrazole)cobalt(II): Fine tuning in the stabilization of coordination entities by using intramolecular hydrogen bonding

•A tetragonal molecular structure with strong intramolecular hydrogen bonding.•Intermolecular hydrogen bonding of nitrates anions competes with intramolecular hydrogen bonding.•A correlation is observed between ν(N–H) and the donor–acceptor (N⋯O) contact distance.

The crystal and molecular structure of the title compound is presented and discussed in detail, and compared with some related pyrazole compounds. Focus is given on the often overlooked intramolecular hydrogen-bond stabilization that determines the structural conformation and also explains some unusual spectral properties. Ligand-field, EPR and infrared spectra are presented to illustrate the case on the title compound and also on a few related Cu(II) and Co(II) pyrazole-based compounds, compared with earlier reported Zn and Ni compounds. The observed N–H⋯O H-bond contacts correlate with the observed N–H stretching vibrations.

Graphical abstractThe nitrate anion in bis(nitrato)tetrakis(pyrazole)cobalt has a special role in intermolecular and intramolecular hydrogen bond stabilization.Figure optionsDownload full-size imageDownload as PowerPoint slide