Exploration of the solid state metallosupramolecular chemistry of mononuclear nickel(II) complexes with α-hydroxycarboxylates and 2,2′-dipyridylamine

Six new nickel(II) complexes have been synthesized by the reaction of the nitrogen donor coligand 2,2′-dipyridylamine (dipyam) and three different α-hydroxyacids (H2L′) with different levels of bulkiness, namely lactic, 2-methyllactic and mandelic acids. Two types of compounds have been obtained: neutral complexes of formula [Ni(HL′)2(dipyam)] and the cationic metal complexes of general formula [Ni(HL′)(dipyam)2](HL′). The structures of the cationic metal complexes have been elucidated by single-crystal X-ray diffraction. The role of the second coordination sphere in the metallosupramolecular organization through different hydrogen-bonding patterns has been analysed. The thermal behaviour of all new compounds has been investigated.