Photo- and Dehydration-Induced Charge Transfer Processes Accompanied with Spin Transition on CoFe(CN)5NH3·6H2O
✍ Scribed by Z.-Z. Gu; Y. Einaga; O. Sato; A. Fujishima; K. Hashimoto
- Book ID
- 102610637
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 329 KB
- Volume
- 159
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The coexistence of di4erent valences of iron and cobalt in cobalt pentacyanoferrate, CoFe(CN) 5 NH 3 ' 6H 2 O, was con-5rmed by the infrared spectrum, in which two distinct peaks for the C+N stretch at 2162 cm ؊ 1 and 2117 cm ؊ 1 were assigned to CN in Fe III +CN+Co II and Fe II +CN+Co III respectively, and by the MoK ssbauer spectrum, in which Fe III and Fe II exhibited doublets with di4erent isomer shifts and di4erent quadrupole splitting. Photo-irradiation of this compound with red light changed the population of these two electronic states due to the internal electron transfer from Fe II to Co III . As a result, the ferrimagnetic properties of this pentacyanometalate at low temperature can be changed by photo-irradiation similar to the case of the hexacyanometalate, K 0.2 Co 1.4 Fe(CN) 6 ' 6.9H 2 O reported previously (O. Sato et al., Science 272, 704 (1996)). Moreover, the fraction of these two electronic states in this pentacyanoferrate is sensitive to the number of water molecules, which induces a charge transfer from Co II and Fe III . As a result, dehydration increases the fraction of Fe II +CN+Co III and causes the compound to be paramagnetic even at low temperature.