Hydroxybenzoate salts of cobalt(II), manganese(II), and nickel(II): synthesis, crystal structure, Hirshfeld surface analyses, and thermal behavior

The reaction of hydroxybenzoates with divalent first row transition metal ions afforded four mononuclear complexes, [M(OH2)(6)](dhbzc)(2)center dot 2H(2)O (M = Co2+, 1 or Mn2+, 2), [Ni(OH2)(6)](hbzc)(2)center dot 2H(2)O (3) and [Ni(OH2)(5)(hbzc)](hbzc)center dot 3H(2)O (4) (where dhbzc(-) = 2,6-dihydroxybenzoate and hbzc(-) = 4-hydroxybenzoate). The complexes were characterized by single crystal and powder X-ray diffraction analyses, infrared spectroscopy, and thermogravimetric analysis. Results showed that the hydrogen bonds present in dhbzc(-) impaired its coordination to Co2+ and Mn2+. Thereafter, Hirshfeld surface analyses (HS) and 2D fingerprint plots were used to investigate the intermolecular contacts in 1-4. The offset pi center dot center dot center dot pi stacking of the dhbzc(-) counterions in 1 and 2 lead to C center dot center dot center dot C close contacts over C center dot center dot center dot H/H center dot center dot center dot C ones. Complexes 3 and 4 presented the usual herringbone aromatic-based packing for the hbzc(-) rings with a predominance of C center dot center dot center dot H/H center dot center dot center dot C close contacts. The existence of water molecules in the crystal lattices of 1-4 was determined by TG analyses, which proved the presence of coordinated and uncoordinated water molecules. The thermal decomposition patterns were analyzed in light of the percentage of the strongest intermolecular close contacts.