TY - JOUR
T1 - Magnetic circular dichroism spectroscopy of weakly exchange coupled transition metal dimers: A model study
AU - Piligkos, S.
AU - Slep, L.D.
AU - Weyhermuller, T.
AU - Chaudhuri, P.
AU - Bill, E.
AU - Neese, F.
N1 - JEnglishReviewNeese, F, Univ Bonn, Inst Phys & Theoret Chem, Wegelerstr 12, D-53115 Bonn, [email protected] SCIENCE SALAUSANNEPO BOX 564, 1001 LAUSANNE, SWITZERLANDCOORD CHEM REVOCTSp. Iss. SIDiscipline: Chemistry, Inorganic & Nuclear496QT
PY - 2009
Y1 - 2009
N2 - A detailed study of the magnetic circular dichroism (MCD) spectra of weakly exchange coupled transition metal heterodimers is reported. The systems consist of three isostructural complexes of the type [LM(III)(PyA)(3)M(II)](ClO4)(2) where L represents 1,4,7-trimethyl-1,4,7-triazacyclonanane and PyA- is the monoanion of pyridine-2-aldoxime. The trivalent metal ion M(III) is either diamagnetic Ga(III) or paramagnetic Cr(III) (S-Cr = 3/2). The divalent metal ion M(II) is either diamagnetic Zn(II) or paramagnetic Ni(II) (S-Ni = 1). The three systems 1 (CrZn), 2 (GaNi) and 3 (CrNi) have been structurally and magnetically characterized through magnetic susceptibility measurements. For I the zero-field splitting is D = 0.6 cm(-1) while for 2 the value D = 3.5 cm(-1) was found. These values have been fixed in analyzing 3 which was found to be characterized by an antiferromagnetic interaction Of J(CrNi) = -8.4 cm(-1) (H = -2JS(A)S(B)). These values served as benchmarks in the MCD analysis. The zero-field splitting of I and 2 was qualitatively recovered using a multi-wavelength analysis of the variable-temperature variable-field (VTVH) MCD data. The observed ligand field bands were assigned to individual d(3) and d(8) multiplets. Using an extension of an earlier developed theory of the nonlinear MCD response, the stunningly complex multiwavelength VTVH-MCD curves of 3 could be quantitatively reproduced with only the relative transition polarizations as input into the fitting procedure. Interestingly, the MCD bands of the minority spin Ni(II) ligand field bands were observed to change sign relative to the parent complex 2. This behavior has been analyzed. The present work hence provides a benchmark study for the application of MCD spectroscopy to weakly interacting transition metal dinners. (C) 2008 Elsevier B.V. All rights reserved
AB - A detailed study of the magnetic circular dichroism (MCD) spectra of weakly exchange coupled transition metal heterodimers is reported. The systems consist of three isostructural complexes of the type [LM(III)(PyA)(3)M(II)](ClO4)(2) where L represents 1,4,7-trimethyl-1,4,7-triazacyclonanane and PyA- is the monoanion of pyridine-2-aldoxime. The trivalent metal ion M(III) is either diamagnetic Ga(III) or paramagnetic Cr(III) (S-Cr = 3/2). The divalent metal ion M(II) is either diamagnetic Zn(II) or paramagnetic Ni(II) (S-Ni = 1). The three systems 1 (CrZn), 2 (GaNi) and 3 (CrNi) have been structurally and magnetically characterized through magnetic susceptibility measurements. For I the zero-field splitting is D = 0.6 cm(-1) while for 2 the value D = 3.5 cm(-1) was found. These values have been fixed in analyzing 3 which was found to be characterized by an antiferromagnetic interaction Of J(CrNi) = -8.4 cm(-1) (H = -2JS(A)S(B)). These values served as benchmarks in the MCD analysis. The zero-field splitting of I and 2 was qualitatively recovered using a multi-wavelength analysis of the variable-temperature variable-field (VTVH) MCD data. The observed ligand field bands were assigned to individual d(3) and d(8) multiplets. Using an extension of an earlier developed theory of the nonlinear MCD response, the stunningly complex multiwavelength VTVH-MCD curves of 3 could be quantitatively reproduced with only the relative transition polarizations as input into the fitting procedure. Interestingly, the MCD bands of the minority spin Ni(II) ligand field bands were observed to change sign relative to the parent complex 2. This behavior has been analyzed. The present work hence provides a benchmark study for the application of MCD spectroscopy to weakly interacting transition metal dinners. (C) 2008 Elsevier B.V. All rights reserved
M3 - Journal article
SN - 0010-8545
VL - 253
SP - 2352
EP - 2362
JO - Coordination Chemistry Reviews
JF - Coordination Chemistry Reviews
IS - 19-20
ER -