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A kinetic model for photoswitching of magnetism in the high spin molecule $[Mo(IV)(CN)_2(CN Cu(II)(tren))_6](ClO_4)_8$

Raghunathan, Rajamani and Ramasesha, S and Mathoniere, Corine and Marvaud, Valerie (2008) A kinetic model for photoswitching of magnetism in the high spin molecule $[Mo(IV)(CN)_2(CN Cu(II)(tren))_6](ClO_4)_8$. In: Physical Chemistry Chemical Physics, 10 (35). pp. 5469-5474.

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The heptanuclear complex $[Mo(IV)(CN)_2(CN–CuL)_6]^{8+} $switches from a paramagnetic dark state corresponding to six spin-1/2 Cu(II) ions to a predominantly high spin S = 3 state, on prolonged irradiation with 406 nm laser radiation at low temperature. The system returns to a paramagnetic state on warming to room temperature. The temperature dependence of the $w_MT$ vs. T curve depends upon duration of irradiation. An earlier microscopic model showed that the excitation cross sections in different spin manifolds are similar in magnitude and that photomagnetism is not due to preferential excitation to the S = 3 state. In this paper, we attribute photomagnetism to a long lived S = 3 charge transfer excited state for which there appears to be sufficient experimental evidence. Based on this postulate, we model the photomagnetism by employing a kinetic model which includes internal conversions and intersystem crossings. The key feature of the model is the assumption of the existence of two kinds of S = 3 states: one of which has no direct pathway for internal conversion and the other characterized by slow kinetics for internal conversion to the low-energy states. The trapped S = 3 state can decay via a thermally activated barrier to the other S = 3 state. The experimental $w_MT$ vs. T for two different

Item Type: Journal Article
Publication: Physical Chemistry Chemical Physics
Publisher: Royal Society of Chemistry
Additional Information: Copyright of this article belongs to Royal Society of Chemistry
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 14 May 2009 07:03
Last Modified: 19 Sep 2010 04:51
URI: http://eprints.iisc.ac.in/id/eprint/16280

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