Streams, cascades, and pools: various water cluster motifs in structurally similar Ni(ii) complexes

Abstract

Hydrogen bonding (HB) interactions are well known to impact the properties of water in the bulk and within hydrated materials. A series of Ni(II) complexes based on chelates containing N-(2-aminoethyl)-1-methylimidazole-2-carboxamide have been synthesized and fully characterized by single crystal X-ray diffraction, spectroscopic methods, and thermal analysis. The complexes reveal a variety of water cluster motifs dependent on the packing arrangement in the solid state. A key feature is the orientation of the carboxamide moiety, which leads to the formation of void spaces that accommodate water through HB interactions. The water motifs contain 1D water chains (streams), 2D tapes of infused rings (cascades), and isolated water dimers (pools). The HB motifs in the hydrated structures vary as a function of the crystal packing of the host molecules. Thermal analyses show a correlation between the HB motif in the hydrated crystals and the temperature range of the dehydration process. The conductivity of the hydrated crystals varies as a function of the crystal packing interactions between metal complexes.