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Indian Journal of Chemistry -Section A (IJC-A) >
IJC-A Vol.50A [2011] >
IJC-A Vol.50A(09-10) [September-October 2011] >
| Title: | Models for photosynthetic reaction center: Synthesis, structure and electrochemical properties of a cofacial di-palladium bisporphyrin |
| Authors: | Chaudhary, Arvind
Patra, Ranjan
Rath, Sankar Prasad |
| Keywords: | Porphyrins
Palladium
Porphyrin dimers
Pi-pi interactions
Molecular motions
Electrochemical properties |
| Issue Date: | Sep-2011 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | A novel cofacial dipalladium(II) bisporphyrin (Pd2DEP) of
Pacman-type is reported herein. Structural characterization suggests very
strong π-π interactions between two planar porphyrins that closely mimic the spatial orientation
observed in the so called ‘special pair’. The electrochemical
response reveals four consecutive ring-centered oxidations in CH2Cl2,
indicative of strong through-space electronic communication between two redox-active
Pd-porphyrins. At 0.66V, one
Pd-porphyrin unit is oxidized to generate a radical cation at a potential much
lower than that of monomeric unit (PdOEP), owing to the increased electron
density in the bisporphyrin scaffold.
However, due to the presence of strong
inter-macrocyclic interactions, the second Pd-porphyrin is then oxidized at a
significantly higher potential (0.97 V) to produce radical cation species. In
the bis(radical cation) state, electrostatic repulsion induces change in the
geometry due to flexible spacer which eventually forces an increase in the
porphyrin-porphyrin distance. As a result, the second oxidation of both the porphyrin
radical cations is observed at 1.42 V as a single reversible two-electron
process. The
overall oxidation process thus demonstrates strong electrostatic communication
between the two macrocycles in Pd2DEP and also provides a means of switching, in a clapping
motion, from a closed to an open Pacman structure under electrochemical
stimulus. |
| Page(s): | 1436-1442 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-0975(Online); 0376-4710(Print) |
| Source: | IJC-A Vol.50A(09-10) [September-October 2011]
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