Formation and decay of zinc tetrakis(N-methyl-4-pyridinio)porphyrin. pi. -radical cation in aqueous solutions containing azide ions and a polyelectrolyte

Journal Article · Thu Jul 28 04:00:00 EDT 1988 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100326a023· OSTI ID:6951156

Nahor, G S ^[1]

---

1. National Bureau of Standards, Gaithersburg, MD (USA)

The formation and decay of the {pi}-radical cation of zinc tetrakis(N-methyl-4-pyridinio)porphyrin (ZnTMPyP{sup 4+}) were studied by using the pulse radiolysis technique. The radical cation (ZnTMPyP{sup 5+}) was produced in N{sub 2}O-saturated, aqueous solutions containing azide ions. Its formation and decay kinetics were monitored by following its absorbance at 700 nm. The formation kinetics and the initial absorbance were found to depend on both ZnTMPyP{sup 4+} and azide concentrations. The decay kinetics were second order with respect to (ZnTMPyP{sup 5+}) and depended on (N{sub 3}{sup {minus}}), (ZnTMPyP{sup 4+}), and the ionic strength. The results are explained by multicomplexation of ZnTMPyP{sup 5+} with azide and by a decay via an equilibrium process involving the ZnTMPyP{sup 5+}/N{sub 3}{sup {minus}} complexes, ZnTMPyP{sup 4+}, and the dication ZnTMPyP{sup 6+}. When a negatively charged polyelectrolyte, poly(styrenesulfonate) (PSS), was added, a decrease in the rate of the ZnTMPyP{sup 5+} formation was observed as well as a decrease in the initial absorbance. These results are related to the binding of the porphyrin to the oppositely charged polyelectrolyte. A slight increase in the decay rate was also observed, which was interpreted by dynamics of the binding polyelectrolyte. A slight increase in the decay rate was also observed, which was interpreted by dynamics of the binding process, or aggregation. Optimal conditions are suggested for utilization of ZnTMPyP{sup 4+} in the photooxidation of water.

• DOE Contract Number: AI05-83ER13108
• OSTI ID: 6951156
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 92:15; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AQUEOUS SOLUTIONS
AZIDES
AZINES
CARBOXYLIC ACIDS
CATIONS
CHARGED PARTICLES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COMPLEXES
DATA
DISPERSIONS
ELECTROLYTES
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
MIXTURES
NITROGEN COMPOUNDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
PYRIDINES
RADICALS
SOLUTIONS
SYNTHESIS
ZINC COMPLEXES