Experimental and Computational Study of the Thermodynamic Properties of Trivalent Cobalt Schiff Base Complexes with Cyclic Amines

Abstract

Some cobalt(III) complexes with a potentially tetradentate unsymmetrical NNOS Schiff base ligand have been synthesized and characterized using IR, 1 HNMR, UV-Vis spectroscopy and elemental analysis. The equilibrium constants were measured spectrophotometrically for 1:1 adduct formation of the cobalt(III) complexes with some cyclic amines in acetonitrile as solvent at constant ionic strength (I = 0.1 M NaClO 4 ), and at various temperatures. In addition, the ground state geometries of the complexes were optimized using density functional theory (DFT) at B3LYP/6-311G** level. Binding energy, thermodynamic parameters, structural parameters and electronic structures of complexes are investigated. The theoretical investigations were done for comparing with the experimental results. Our comparison between the computational and experimental results revealed that the cobalt(III) complexation process is spontaneous, exothermic and entropically unfavorable.

Formation constants and thermodynamic parameters of bivalent Co, Ni, Cu and Zn complexes with Schiff base ligand: Experimental and DFT calculations

“…The [NiL] complex adopts a nearly perfect square planar geometry: (i) the bond lengths associated with the nickel atom are virtually equal (Table 2), (ii) the two diagonal angles 3N-Ni-5O and 2N-Ni-4S of 179 and 179, respectively, barely deviate from linearity, (iii) the sum of the angles at nickel is very close to 360º, and (iv) as a result, the metal centre is located 0.003Å from the mean NNOS plane. Such a behavior is similar to those observed in related Ni(II) unsymmetrical Schiff base complex reported by us [26].…”

“…The analytical ligand concentration was kept constant and different concentration of metal ions (10 -5 -10 -4 M) in DMF were prepared and used as titrant. After preparation of the samples solution the time of one hour was given to the samples until they reach to the same as previous work [20,[25][26][27]. UV-Vis spectra were recorded in the range 250-700 nm.…”

Copper(II) Schiff Base Complexes with Catalyst Property: Experimental, Theoretical, Thermodynamic and Biological Studies

“…59 Therefore, for the calculation of hardness the following equation η = ½(E HOMO -E LUMO ) was used for all titled compounds. 60 As can be seen in Table 7, the H 2 L 2 ligand and [CuL 1 ] complex have a higher hardness and lower chemical reactivity and higher stability than the other compounds.…”