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Reactions of copper(II) and nickel(II) hexafluoroacetylacetonates with pyridine‐based amides: synthesis and characterization

The rational design of functional molecular solids is one of the main challenges in crystal engineering. Properties of crystalline solids are closely connected with the manner in which building units are aligned and linked together in the solid state. Understanding and controlling noncovalent interactions, in particular hydrogen bonds, is essential for establishing reliable connections between molecular and supramolecular structure. Strong directionality, sufficient strength, tunability and selectivity of hydrogen bonds enables synthesis of desired supramolecular architectures. The employing of rather weak and reversible intermolecular interactions in the building of organic networks is well known, but their role as well as the role of conventional hydrogen bonds in the assembly of metal- containing architectures is still much less studied. In our attempts to control molecular geometry and supramolecular assembly we synthesized a series of copper(II) and nickel(II) coordination compounds. We employed neutral hexafluoroacetylacetonates, [Cu(hfa)2(H2O)2] and [Ni(hfa)2(H2O)2] (hfa = hexafluoroacetylacetonate ion) to react with N- heterocyclic ligands equipped with the amide functionality, and to produce our desired metal‐containing building blocks. Hexafluoroacetyacetonate ligand was used due to the strong electron withdrawing capability of the terminal –CF3 groups to lessen the hydrogen- bond acceptor capability of the donating oxygen atoms. On the fifth and sixth coordination site we introduced pyridine‐based ligands (4‐ acetamidopyridine, 4‐acpy ; 4‐ propaneamidopyridine, 4‐propy) bearing the amide group, well established supramolecular functionality in purely organic systems. The compounds were characterized by single crystal X‐ ray structure analysis and IR spectroscopy. Thermal stability of coordination compounds was investigated by TGA/SDTA analysis.

copper(II), nickel(II), hexafluoroacetylacetonate, pyridine‐based amide

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