Spectroscopic Determination of Magnetic Exchange Parameters and Structural Geometry for Trinuclear Compounds: (CuL)2Mn·xB (L = N-(4-Methyl-6-oxo-3-azahept-4-enyl)oxamato
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- 作者：Olivier Cador ; Corine Mathoniè ; re ; Olivier Kahn ; Jean-Pierre Costes ; Marc Verelst ; and Pierre Lecante
- 刊名：Inorganic Chemistry
- 出版年：1999
- 出版时间：May 31, 1999
- 年：1999
- 卷：38
- 期：11
- 页码：2643 - 2648
- 全文大小：96K
- 年卷期：v.38,no.11(May 31, 1999)
- ISSN：1520-510X
文摘
The optical absorption spectroscopy for the trinuclear compounds Mn(CuL)2·xB with L standing for N-(4-methyl-6-oxo-3-azahept-4-enyl)oxamato and B = (CH3)2SO (x = 2) (1) or H2O (x = 5) (2) has been investigated in the4-300 K temperature range. The crystal structure of 1 was known; it consists of isolated and neutral trinuclearunits in which the central MnII ion is linked to two CuL complex ligands and two (CH3)2SO molecules in a cisconfiguration. The Cu-Mn-Cu linkage is bent with an angle of 127
. The spectra for 1 and 2 exhibit narrow andintense MnII spin-forbidden transitions in the 24000-28000 cm-1 range, activated by an exchange mechanism.The temperature dependences of the main feature corresponding to the 6A1 
4A1, 4E(G) MnII transitions havebeen recorded. Using a model proposed first by Tanabe and co-workers and adapted to the CuMnCu topology,a theoretical expression for the temperature dependence of the intensity of the transition has been derived andcompared to the experimental data. The parameters of this expression are the angle 
(2 = 180 - CuMnCu)and the interaction parameter between the local ground states, J (H = -JSMn·(SCu1 + SCu2)). For 1, = 26.5was known from the structural data, and J has been found as -38 cm-1. For 2, J has been estimated as -32.6cm-1 with = 0. The spectra for 2 exhibit cold and hot bands; the energy difference between these bandsdepends on both J and the interaction parameter J* between the CuII ions in their ground state and the MnII ionin its spin flip excited state. J* has been estimated as +35 cm-1. The linear geometry of the Cu-Mn-Cu linkagefor 2 has been confirmed by a WAXS (wide-angle X-ray scattering) study. The intramolecular Cu···Cu distancehas been estimated as 10.2 Å. These results have been discussed in relation to the information deduced frommagnetic measurements.
. The spectra for 1 and 2 exhibit narrow andintense MnII spin-forbidden transitions in the 24000-28000 cm-1 range, activated by an exchange mechanism.The temperature dependences of the main feature corresponding to the 6A1 4A1, 4E(G) MnII transitions havebeen recorded. Using a model proposed first by Tanabe and co-workers and adapted to the CuMnCu topology,a theoretical expression for the temperature dependence of the intensity of the transition has been derived andcompared to the experimental data. The parameters of this expression are the angle (2 = 180 - CuMnCu)and the interaction parameter between the local ground states, J (H = -JSMn·(SCu1 + SCu2)). For 1, = 26.5was known from the structural data, and J has been found as -38 cm-1. For 2, J has been estimated as -32.6cm-1 with = 0. The spectra for 2 exhibit cold and hot bands; the energy difference between these bandsdepends on both J and the interaction parameter J* between the CuII ions in their ground state and the MnII ionin its spin flip excited state. J* has been estimated as +35 cm-1. The linear geometry of the Cu-Mn-Cu linkagefor 2 has been confirmed by a WAXS (wide-angle X-ray scattering) study. The intramolecular Cu···Cu distancehas been estimated as 10.2 Å. These results have been discussed in relation to the information deduced frommagnetic measurements.