Novel monoanionic diphenate-nicotinamide/N,N-diethylnicotinamide complexes of NiII, ZnII. Synthesis, structural investigations and hydrogen adsorption study

Abstract Mixed ligand complexes containing monoanionic diphenate (Hdiphen-), dianionic diphenate (diphen2−)-nicotinamide (nic)/N,N-diethylnicotinamide (denic) ligands of Ni(II) and Zn(II) transition metal cations were synthesized, their structural characterizations and molecular simulation for hydrogen adsorption were performed. It is the salt type coordination compound of the Ni(II) complex, complementing the metal octahedral environment with 2 mol of nic and 4 mol of aqua ligands. Two moles of Hdiphen- ligand is monoanionic located outside the coordination sphere and provides the charge equivalence of the complex. In the Zn(II) complex structure, denic and diphen2− ligand is located within the coordination sphere. In the Zn(II) coordination compound structure, diphen2− ligands, which are located in the structure of a bridge between two different metal centres, make the structure polymeric. The binding properties of complexes to metal cations are also elucidated by infrared spectra. It has also been clarified whether the diphenate ligand is bonded to monovalent or bivalent. The mixed ligand complexes of diphenate [Ni(nic)(H2O)4].2(Hdiphen) (I) and [Zn(denic)(diphen)(H2O)]·H2O (II) distorted octahedral, and they have P-1 space group and triclinic crystal systems. The thermal decomposition of the complexes begins with dehydration steps and continues with the decomposition of organic ligands. As a result of the thermal analysis, it is determined that the oxides of the relevant metal cations remain as the final decomposition products of the molecules. The hydrogen storage of nickel complex is 0.153 wt% and the zinc complex is 0.289 wt% at 77 K and 10 bars.