Spectroscopic Study of Ni(II)-4, 4’, 4’’, 4’ ’’ – Tetrasulfophthalocyanine In Aqueous Solution

Authors

Issa Ishaq Jabra

Publication Date

12-1978

Advisor(s) - Committee Chair

R. D. Farina, J. T. Riey, L. W. Shank

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

It was determined spectrally that a monomer-dimer equilibrium exists in aqueous solutions of Ni-TSPC^4- over a concentration range of 5 x 10^-8 – 10^-4 M. Equilibrium measurements were made under natural ionic strength conditions at 29°, 39° and 49°C. The values obtained for the equilibrium constants at 29°, 39° and 49°C were 2.4 x 10⁸, 6.6 x 10⁷ and 2.9 x 10⁷ M^-1, respectively. These results indicated that the equilibrium strongly favors dimer formation. This study also showed that nickel is second to copper in enhancing the dimerization of metallotetrasulfophthalocyanine complexes. However, metals in general inhibit dimer formation relative to the free ligand. The dimerization reaction of Ni-TSPC^4- is exothermic with thermodynamic parameters of ΔG° = -11.6 kcal/mole, ΔH = -20.9 kcal/mole, and ΔS = -31 e.u. The dimerization process is thus favored from an energetic point of view despite the unfacorable entropy change.

Spectral measurements made on Ni-TSPC^4- in aqueous pyridine solutions in the concentration range of .05 - 6.0% pyridine (by volume) indicated a dipyridinated dimer complex of Ni-TSPC^4- was formed. Using a modified version of the Benesi-Hildebrand equation, the following equilibrium was proposed : D + 2Py = D(Py)₂. The overall equilibrium constants for this system at 15°, 21°, 30° and 40°C were 1.7, 1.9, 2.8, 3.6 and 4.4 M^-2, respectively. The equilibrium reaction is endothermic with thermodynamic parameters of: ΔG=6.2 kcal/mole, ΔH =6.9 kcal/mole, and ΔS=25 e.u. Thus, the equilibrium reaction was favored thermodynamically due to the favorable entropy change associated with the process.

Ligand studies indicated that only pyridine and polupyridine ligands bind to Ni-TSPC^4- and cause a spectral change. This study also showed that Ni-TSPC^4- cannot be used as an oxygen carrier in biological systems.

Disciplines

Chemistry

Recommended Citation

Jabra, Issa Ishaq, "Spectroscopic Study of Ni(II)-4, 4’, 4’’, 4’ ’’ – Tetrasulfophthalocyanine In Aqueous Solution" (1978). Masters Theses & Specialist Projects. Paper 1700.
https://digitalcommons.wku.edu/theses/1700