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The physicochemical properties and solubilities of NaH2PO2-Zn(H2PO2)(2)-H2O, NaH2PO2-NaCl-H2O, and NaCl-Zn(H2PO2)(2)-H2O ternary systems and in NaH2PO2-NaCl-Zn(H2PO2)(2)-H2O quaternary system at 298.15 K were investigated-via the isothermal method. Invariant point compositions represent the quaternary system were characterized as the following: 10.65% mass NaCl, 32.51% mass NaH2PO2, 6.50% mass Zn(H2PO2)(2) and 50.34% mass H2O. In solid phases, the salts of Zn(H2PO2)(2)center dot H2O, NaCl and NaH2PO2 center dot H2O were recognized. The crystallization area of the salts were obtained as (i) 79.04% Zn(H2PO2)(2), (ii) 18.62% NaCl and (iii) 2.34% NaH2PO2. Being the least soluble salt, Zn(H2PO2)(2) has the largest crystallization area when compared with other salts present in the medium. According to the results, the crystallization area of was the largest in comparison with those of other salts and at the same time it was the least soluble salt.

The asymmetric unit of the title compound, [Cu(C7H4FO2)(2)(C6H6N2O)(2)(H2O)]center dot 0.5C(6)H(6)N(2)O center dot 3H(2)O, contains two aquabis(4-fluorobenzoato)bis(nicotinamide)copper(II) molecules, one nicotinamide solvent molecule and six water molecules. The Cu-II ion is coordinated by two O atoms from two 4-fluorobenzoate ligands, two N atoms from two nicotinamide ligands and one water O atom in a distorted square-pyramidal geometry. In the crystal, O-H center dot center dot center dot O, O-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds consolidate the crystal packing, which also exhibits pi-pi interactions between the aromatic rings [centroid-centroid distances 3.692 (2)-3.794 (2) angstrom].

The title Cu-II complex, [Cu(C7H4BrO2)(2)(C10H14N2O)(2)-(H2O)(2)], contains two 4-bromobenzoate (PBB), two diethylnicotinamide (DENA) monodentate ligands and two water molecules. The four O atoms in the equatorial plane around the Cu-II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by two N atoms of the DENA ligands in the axial positions. Intramolecular O-H center dot center dot center dot O hydrogen bonds link the water molecules to the carboxylate groups. The dihedral angles between the carboxylate groups and the adjacent benzene rings are 3.1 (3) and 3.74 (17)degrees, while the pyridine rings and the benzene rings are oriented at dihedral angles of 6.81 (10) and 3.38 (12)degrees. In the crystal, intermolecular O-H center dot center dot center dot O hydrogen bonds link the molecules into double chains along the b axis. C-H center dot center dot center dot O interactions are also observed. pi-pi contacts between pyridine rings [centroid-centroid distance = 3.485 (2) angstrom] may further stabilize the crystal structure.

The asymmetric unit of the title mononuclear Cu-II complex, [Cu(C7H4FO2)(2)(C10H14N2O)(2)(H2O)(2)], contains one-half of the molecule. The Cu-II ion is located on an inversion centre, and is coordinated by two N atoms from two diethylnicotinamide ligands, two O atoms from two 4-fluorobenzoate (PFB) ligands and two water molecules in a distorted octahedral geometry. In the PFB ligand, the carboxylate group is twisted at an angle of 2.10 (14)degrees from the attached benzene ring. In the crystal structure, intermolecular O-H center dot center dot center dot O hydrogen bonds link molecules related by translation along the a axis into chains. Weak intermolecular C-H center dot center dot center dot O hydrogen bonds and pi-pi interactions between the pyridine rings of neighbouring molecules [centroid-to-centroid distance = 3.571 (2) angstrom] further consolidate the crystal packing.

In the centrosymmetric dinuclear title compound, [Mn-2(C7H4BrO2)(4)(C6H6N2O)(2)(H2O)(2)], the Mn-II atom is coordinated by one N atom from one bridging nicotinamide ligand and one O atom from another symmetry-related bridging nicotinamide ligand, three O atoms from two 4-bromobenzoate ligands and one water molecule in a distorted octahedral geometry. The dihedral angles between the carboxylate groups and the adjacent benzene rings are 10.89 (16) and 8.4 (2)degrees, while the benzene rings are oriented at a dihedral angle of 6.09 (13)degrees. Intermolecular O-H center dot center dot center dot O, N-H center dot center dot center dot O and weak C-H center dot center dot center dot O hydrogen bonds link the molecules into a three-dimensional network. pi-pi interactions, indicated by short centroid-centroid distances [3.845 (2) angstrom between the benzene rings, 3.650 (2) angstrom between the pyridine rings and 3.700 (3) angstrom between the benzene and pyridine rings] further stabilize the structure.

In the mononuclear Ni-II title complex, [Ni(C7H4FO2)(2)(C6H6N2O)(2)(H2O)(2)], the Ni-II atom, located on an inversion center, is coordinated by two nicotinamide and two 4-fluorobenzoate ligands and two water molecules in a distorted N2O4 octahedral geometry. The dihedral angle between the carboxylate group and the adjacent benzene ring is 8.95 (8)degrees, while the pyridine ring and the benzene ring are oriented at a dihedral angle of 75.01 (7)degrees. The water molecule links the adjacent carboxylate O atom via an intramolecular O-H center dot center dot center dot O hydrogen bond. In the crystal, O-H center dot center dot center dot O, N-H center dot center dot center dot O, C-H center dot center dot center dot O and C-H center dot center dot center dot F hydrogen bonds link the molecules into a three-dimensional network. pi-pi stacking between parallel pyridine rings [centroid-centroid distance = 3.7287 (11) angstrom] is also observed.