Abstract
The role of cobalt and iron phthalocyanines in catalytic CO2 reduction has been studied. Chemical, photochemical, and radiolytic reductions of the metal phthalocyanines (Pc) have been carried out in organic solvents, and reduction of their tetrasulfonated derivatives (TSPc) in aqueous solutions. CoIIPc and FeIIPc are readily reduced to [CoIPc]- and [FeIPc]-, which do not react with CO2. Reduction of [CoIPc]- yields a product which is characterized as the radical anion, [CoIPc·-]2-, on the basis of its absorption spectra in the visible and IR regions. This species is stable under dry anaerobic conditions and reacts rapidly with CO2. Catalytic formation of CO and formate is confirmed by photochemical experiments in DMF and acetonitrile solutions containing triehylamine (TEA) as a reductive quencher. The photochemical yields are greatly enhanced by the addition of p-terphenyl (TP). The radical anion. TP·-, formed from the reductive quenching of the singlet excited state with TEA, reduces the phthalocyanines very rapidly. The rate constants for reduction of CoIIPc, [CoIPc]-, and [FeIPc]- by TP·-, determined by pulse radiolysis in DMF solutions, are nearly diffusion-controlled. The mono-reduced species formed from [CoIPc]- is unstable under the pulse radiolysis conditions but is longer-lived under the flash photolysis conditions. The interaction of this species with CO2 is either too weak or too slow to detect in the current experiments, where a competing reaction with protons predominates.
| Original language | English |
|---|---|
| Pages (from-to) | 11332-11339 |
| Number of pages | 8 |
| Journal | Journal of Physical Chemistry A |
| Volume | 104 |
| Issue number | 48 |
| DOIs | |
| Publication status | Published - Dec 7 2000 |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
Cite this
Reduction of cobalt and iron phthalocyanines and the role of the reduced species in catalyzed photoreduction of CO2 . / Grodkowski, J.; Dhanasekaran, T.; Neta, P.; Hambright, P.; Brunschwig, B. S.; Shinozaki, K.; Fujita, Etsuko.
In: Journal of Physical Chemistry A, Vol. 104, No. 48, 07.12.2000, p. 11332-11339.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Reduction of cobalt and iron phthalocyanines and the role of the reduced species in catalyzed photoreduction of CO2
AU - Grodkowski, J.
AU - Dhanasekaran, T.
AU - Neta, P.
AU - Hambright, P.
AU - Brunschwig, B. S.
AU - Shinozaki, K.
AU - Fujita, Etsuko
PY - 2000/12/7
Y1 - 2000/12/7
N2 - The role of cobalt and iron phthalocyanines in catalytic CO2 reduction has been studied. Chemical, photochemical, and radiolytic reductions of the metal phthalocyanines (Pc) have been carried out in organic solvents, and reduction of their tetrasulfonated derivatives (TSPc) in aqueous solutions. CoIIPc and FeIIPc are readily reduced to [CoIPc]- and [FeIPc]-, which do not react with CO2. Reduction of [CoIPc]- yields a product which is characterized as the radical anion, [CoIPc·-]2-, on the basis of its absorption spectra in the visible and IR regions. This species is stable under dry anaerobic conditions and reacts rapidly with CO2. Catalytic formation of CO and formate is confirmed by photochemical experiments in DMF and acetonitrile solutions containing triehylamine (TEA) as a reductive quencher. The photochemical yields are greatly enhanced by the addition of p-terphenyl (TP). The radical anion. TP·-, formed from the reductive quenching of the singlet excited state with TEA, reduces the phthalocyanines very rapidly. The rate constants for reduction of CoIIPc, [CoIPc]-, and [FeIPc]- by TP·-, determined by pulse radiolysis in DMF solutions, are nearly diffusion-controlled. The mono-reduced species formed from [CoIPc]- is unstable under the pulse radiolysis conditions but is longer-lived under the flash photolysis conditions. The interaction of this species with CO2 is either too weak or too slow to detect in the current experiments, where a competing reaction with protons predominates.
AB - The role of cobalt and iron phthalocyanines in catalytic CO2 reduction has been studied. Chemical, photochemical, and radiolytic reductions of the metal phthalocyanines (Pc) have been carried out in organic solvents, and reduction of their tetrasulfonated derivatives (TSPc) in aqueous solutions. CoIIPc and FeIIPc are readily reduced to [CoIPc]- and [FeIPc]-, which do not react with CO2. Reduction of [CoIPc]- yields a product which is characterized as the radical anion, [CoIPc·-]2-, on the basis of its absorption spectra in the visible and IR regions. This species is stable under dry anaerobic conditions and reacts rapidly with CO2. Catalytic formation of CO and formate is confirmed by photochemical experiments in DMF and acetonitrile solutions containing triehylamine (TEA) as a reductive quencher. The photochemical yields are greatly enhanced by the addition of p-terphenyl (TP). The radical anion. TP·-, formed from the reductive quenching of the singlet excited state with TEA, reduces the phthalocyanines very rapidly. The rate constants for reduction of CoIIPc, [CoIPc]-, and [FeIPc]- by TP·-, determined by pulse radiolysis in DMF solutions, are nearly diffusion-controlled. The mono-reduced species formed from [CoIPc]- is unstable under the pulse radiolysis conditions but is longer-lived under the flash photolysis conditions. The interaction of this species with CO2 is either too weak or too slow to detect in the current experiments, where a competing reaction with protons predominates.
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U2 - 10.1021/jp002709y
DO - 10.1021/jp002709y
M3 - Article
VL - 104
SP - 11332
EP - 11339
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 48
ER -