Journal article
Isotopic exchange in solid cobalt phthalocyanine—I: Thermal treatment and charge transfer interactions
Journal of inorganic & nuclear chemistry, v 43(2), pp 271-280
1981
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Abstract
Isotopic exchange of α and ß-cobalt phthalocyanine (CoPc) doped with carrier-free
57CoCl
2 was studied at different temperatures in presence, and absence of oxygen. In samples sealed in evacuated vials, the exchange is induced by electrons released from multi-depth donors. The results show that ß-CoPc has a smaller density of donors and a deeper distribution in depths, as compared to α-CoPc. The mode of population of traps with electrons (or holes) during the preparation is discussed.
Thermal treatment of CoPc in air and followed by doping with
57CoCl
2 (and radiochemical analysis) gives us the magnitude of isotopic exchange induced by holes, which are injected by virtue of charge transfer interactions between molecules of CoPc and O
2. Our observations indicate that the rate of diffusion of O
2 into CoPc crystallites depends on the temperature and the period of thermal treatment. The diffusion continues well beyond 1 week even at relatively high temperatures. The concentration of the injected holes and therefore the magnitude of exchange depends on the size of particles. The diffusion and chemisorption of O
2 seems to be facilitated considerably when the microcrystallites of CoPc are suspended in oxygenated water (as compared to the dry powder).
When aliquots of
57Co
2+-doped CoPc are compacted with
o-chloranil or iodine, strong charge transfer interactions between CoPc, and
o-chloranil, and (to a lesser extent) iodine molecules, inject high concentrations of holes and thereby induce considerable exchange.
When samples of
57Co
2+-doped α- or ß-CoPc are heated in air, either detrapped electrons or injected holes may induce exchange. In ball-milled samples, consisting of very fine particles, the contributions towards exchange by electrons and holes, become additive. This amazing observation indicates that large non-equilibrium concentrations of electrons and holes co-exist for considerable lengths of time without recombination.
In conclusion, the dopant
57Co
2+ in CoPc constitutes a good probe and we have obtained a wealth of information which would be difficult to obtain by purely physical measurements.
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Details
- Title
- Isotopic exchange in solid cobalt phthalocyanine—I: Thermal treatment and charge transfer interactions
- Creators
- Mohanan Kalliat - Drexel UniversityAmar Nath - Drexel University
- Publication Details
- Journal of inorganic & nuclear chemistry, v 43(2), pp 271-280
- Publisher
- Elsevier
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- [Retired Faculty]
- Web of Science ID
- WOS:A1981KZ35800008
- Scopus ID
- 2-s2.0-27544509441
- Other Identifier
- 991019173841304721
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- Web of Science research areas
- Chemistry, Inorganic & Nuclear