Supramolecular structures modeling photosynthetic reaction center function

Conference · Thu Aug 20 04:00:00 EDT 1992

OSTI ID:7037164

Wasielewski, M R; Gaines, III, G L; Gosztola, D; Niemczyk, M P; Svec, W A

Work in our laboratory has focused on the influence of solvent motion on the rates and energetics of photochemical charge separation in glassy solids. The efficiencies of many nonadiabatic electron transfer reactions involving photochemical electron donors with relatively low excited state energies, such as porphyrins and chlorophylls, are poor in the solid state. Recent work has shown that placing a porphyrin-acceptor system in a glassy solid at low temperature significantly raises the energy of ks ion-pair state. This destabilization can be as much as 0.8 eV relative to the ion pair state energy in a polar liquid. This contrasts sharply with photosynthetic reaction centers, which maintain medium-independent electron transfer rates with relatively small free energies of charge separation. Using this information we have set out to design photochemical systems that produce long-lived radical ion pairs in glassy solids with high quantum efficiency. These systems maintain their efficiency when placed in other glassy matrices, such as polymers. An important consequence of this effort is the design of molecules that minimize the electronic interaction between the oxidized donor and reduced acceptor. This minimization can be attained by careful design of the spacer groups linking the donor and acceptor and by using more than a single electron transfer step to increase the distance between the separated charges as is done in natural photosynthesis.

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7037164
• Report Number(s): ANL/CP-76566; CONF-9208155--1; ON: DE92041123
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
550200 -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BIOMIMETIC PROCESSES
CARBOXYLIC ACIDS
CHEMISTRY
CHLOROPHYLL
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LASERS
MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMISTRY
PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE