The role of hydrogen bonding interactions and their fluctuations are well known to determine the properties of water. The key to understanding the behavior of water in its interactions with materials is to collect precise structural data of various H-bonded water networks in diverse environments. Numerous studies have characterized discrete water clusters in crystal hosts. This has significantly advanced our understanding of how these clusters link together to form a larger network of water molecules. This presentation will focus on a series of N-(2-aminoethyl)-1-methylimidazole-2-carboxamide containing chelates that have been synthesized and used to prepare Ni(II) complexes with N3O, N3S, and N6 donors sets. The complexes have been structurally characterized by single crystal X-ray diffraction, which reveals a variety of water cluster motifs in these structurally similar nickel(II) complexes. All of the complexes are hydrates with water molecules in crystal lattice connected via hydrogen bonds to carboxamido oxygens of ligand backbone. Based on changes in the ligand structure, the pattern and dimensionality of H-bonding expansion are unique in these complexes. Specifically, complexes with N3S donors display the 1D water chains whereas the water clusters in complexes with N3O donors are expanded in two and three dimensions. Thermal analysis is consistent with the differences in the hydrogen bonding motifs in the different structures. In complexes with N3S donors, dehydration and complex degradation occur simultaneously in a single step. For complexes with N3O donors, dehydration precedes complex degradation, which requires a higher temperature. These results demonstrate that how small changes in ligand structure and donor type impact the formation and stability of water clusters. These results can be helpful to better understand the structure and behavior of water molecules in crystalline lattices for the design of new materials.

Variation of water cluster motifs in structurally similar Ni(II) complexes: Synthesis, characterization, and thermal analyses

255th National Meeting (2018)

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