Combined solid state NMR and ONIOM studies of reversible crystalline phase reaction for nickel coordination compounds

Ni(II) with bis(acetylacetone)ethylenediamine ligand forms complexes which crystallizes as semi-hydrate with C2/c space group in monoclinic system and anhydrous form with Pna2(1) space group in orthorhombic system. 13C and 15N CP/MAS experiments were employed for structural characterization of both forms and searching of process of reversible water exchange in the crystal lattice. Comparative analysis of 13C and 15N principal elements of chemical shift tensors for ligand and complexes showed the sensitivity of δii elements both for complexation and phase reaction processes. Theoretical 13C and 15N NMR shielding parameters σii were computed employing ONIOM approach and correlated with experimental δii data. The applicability of ONIOM in structural analysis of coordination compounds (CC) is discussed.