On new solvatomorphs of the metalloligand [Ni(o-van-en)]
The Schiff-base bis(2-hydroxy-3-methoxybenzylidene)ethylenediamine, denoted H2(o-van-en), is a versatile two-compartment polydentate ligand that can bring different guests, such as a transition metal and a lanthanoid, into close proximity to produce novel complexes with potentially singular properties. The base, which is prepared by the condensation of o-vanillin with ethylenediamine, reacts with nickel(II) carbonate to yield a microcrystalline product which upon recrystallization from acetone, ethanol and isopropanol, yielded three solvatomorphs of [Ni(o-van-en)]. These products, the hydrate [Ni(o-van-en)]⋅nH2O (n = 1.17, 1), the ethanol–water solvate [Ni(o-van-en)]⋅H2O⋅EtOH (2) and the isopropanol-water solvate [Ni(o-van-en)]⋅H2O⋅iPrOH (3), all contain the molecular complex [Ni(o-van-en)], as characterized by single-crystal x-ray diffraction. The [Ni(o-van-en)] fragment, which has been developed as a metalloligand for the preparation of mixed-metal (Tr-Ln) complexes with novel magnetic properties, here forms solvatomorphs whose crystals display pronounced differences in morphology and stability. The Ni(II) center in each of the three solvatomorphs is coordinated by the (o-van-en)2- ligand in a square geometry with a cis-N2O2 donor set. Each solvatomorph contains water solvate molecules; and in addition, ethanol and isopropanol solvate molecules are present in 2 and 3, respectively. Full Interaction Maps were used for comparison of the intermolecular interactions, by way of understanding the factors leading to the different solvation behavior. A review of the known structures containing o-van-en fragments is used as a contextual backdrop for a discussion of the new solvatomorph structures. Calculations based on an energy-decomposition model are used to characterize the interactions within dimeric aggregates observed in the structures of 2 and 3.