In:
European Journal of Inorganic Chemistry, Wiley, Vol. 2007, No. 20 ( 2007-07), p. 3188-3194
Abstract:
The five‐coordinate ferric azide complex of 2,7,12,17‐tetrapropylporphyrcene [Fe(TPrPc)N 3 ] was characterized with proton NMR, electron paramagnetic resonance (EPR), Mössbauer, and IR techniques. The paramagnetic NMR showed the pyrrole‐H signal that exhibits anomalous anti ‐Curie type of 1/ T ‐dependence over a 310–190 K range. The EPR of the solid sample resolved a signal with g = 5.42, 5.40, and 2.00 at 5 K. The quadrupole splitting parameter of the Mössbauer spectrum was 2.20 mm s –1 at 290 K, and the magnetic moment was 4.70 μ B at 290 K for the microcrystalline sample. These results suggest that [Fe(TPrPc)N 3 ] is not pure high‐spin ( S = 5/2) but a spin mixture of the S = 5/2, 3/2 states. The azide in [Fe(TPrPc)N 3 ] exhibited split IR bands ascribed to the two spin isomers at 2066 and 2049 cm –1 . The 2049‐cm –1 band, assigned to the S = 3/2 species, was reversibly intensified with decreasing temperature. The IR results demonstrate that the S = 3/2, 5/2 states are not quantum‐mechanically admixed but in thermal equilibrium. The thermodynamic parameters associated with the spin equilibrium, Δ H = –3 990 cal mol –1 and Δ S = –16.5 cal mol –1 K –1 , were obtained from the NMR shift analysis, and the population of the S = 3/2 isomer was calculated to be 0.19 at 293 K. A minimum lifetime of the two spin isomers was estimated to be 0.3 ps with IR. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Type of Medium:
Online Resource
ISSN:
1434-1948
,
1099-0682
DOI:
10.1002/ejic.v2007:20
DOI:
10.1002/ejic.200601183
Language:
English
Publisher:
Wiley
Publication Date:
2007
detail.hit.zdb_id:
1475009-0
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