期刊
INORGANICA CHIMICA ACTA
卷 399, 期 -, 页码 67-78出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.ica.2012.12.042
关键词
Macrocyclic compounds; Clathrochelates; Cobalt complexes; Iron complexes; Phase transitions; Paramagnetic shifts
资金
- RFBR [10-03-00837, 10-03-00613, 11-03-00652, 11-03-00986, 11-03-12181, 12-03-00961, 12-03-00955, 12-03-33107, 12-03-90431]
- Council of the President of the Russian Federation [NSh 5943.2012.3]
- RAS [6, 7, P8]
The n-butyl- and n-hexadecylboron-capped macrobicyclic iron and cobalt(II) tris-dioximates were synthesized by the direct template condensation of the aliphatic and aromatic alpha-dioximes with alkylboronic acids on either a Fe2+ or a Co2+ cation as a matrix. The clathrochelates obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis, H-1 and C-13{H-1} NMR, Fe-57 Mossbauer and EPR spectroscopies, magnetochemistry, and by X-ray crystallography; their redox properties were studied by cyclic voltammetry (CV). These low-spin complexes undergo no spin transitions in the temperature range from 5 to 300 K. Their trigonal prismatic (TP)-trigonal antiprismatic (TAP) molecular geometry is mainly governed by the nature of an encapsulated metal ion and that of their ribbed substituents. The encapsulated cobalt(II) ions are shifted from the centers of their CoN6 coordination polyhedra due to Jahn-Teller distortion, and their anisotropic displacement parameters proved the energetical preference for only one distorted structure. The hexadecylboron-capped clathrochelates undergo the temperature-driven phase transitions. The EPR and NMR data suggest that the length of the apical alkyl groups has no impact on the magnetic properties of the cobalt complexes, whereas that of the ribbed substituents affects a distribution of the spin density. The CV data showed that these electron-donor groups stabilize the oxidized and destabilize the reduced clathrochelate species. (C) 2013 Elsevier B.V. All rights reserved.
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