Supramolecular Assemblies of Nucleobase Derivative 1-Mecyt with Mg(II) and Ni(II) and Solid-State Transformation of Ni(II) Phase:  A Comprehensive Evidence of Their Different Reactivity toward 1-Mecyt [1-Mecyt = 1-Methylcytosine]

The synthesis and crystal structure of the compounds [Mg(H<sub>2</sub>O)<sub>6</sub>(1-Mecyt)<sub>2</sub>]Cl<sub>2</sub> (<b>1</b>), [Ni(H<sub>2</sub>O)<sub>6</sub>(1-Mecyt)<sub>2</sub>]Cl<sub>2</sub> (<b>2</b>), and [Ni(1-Mecyt)<sub>2</sub>Cl<sub>2</sub>] (<b>3</b>) (where 1-Mecyt = 1-Methylcytosine) are reported. Compounds <b>1</b> and <b>2</b> consist of hexaaquo ions, 1-Mecyt molecules, and chloride ions self-assembled through an extended network of hydrogen-bonding interactions. Compound <b>3</b> is made of [Ni(1-Mecyt)<sub>2</sub>Cl<sub>2</sub>] units, with the 1-Mecyt molecules directly coordinated to the metal centers through the N(3) and O(2) atoms. When crystals of compound <b>2</b> are allowed to stand in air for 1 week, a solid transformation occurs. The results of our investigation clearly suggest that a solid-state reaction takes place in <b>2</b>, leading to <b>3</b>.