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Phase transitions and antiferromagnetism in copper(II) hexanoates: a new tetranuclear type of copper carboxylate paddle-wheel association |
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| Authors: | Bojan Kozlev?ar Ivan Leban Saša Petri?ek Jan Reedijk |
| Institution: | a Department of Inorganic Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ašker?eva 5, P.O. Box 537, 1001 Ljubljana, Slovenia b Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ro?na dolina, C VIII/34, 1000 Ljubljana, Slovenia c Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands |
| Abstract: | A series of compounds of formula {Cu2(OOCCmH2m + 1)4(urea)}2] (m=5-11) have been characterized. X-ray structure analysis for the hexanoate compound reveals a new type of tetranuclear dicopper(II) tetracarboxylate, where the central coordination sphere in {Cu2(OOCC5H11)4(urea)}2] is composed of two dinuclear dicopper tetracarboxylates, connected via two inter-dinuclear Cu-O coordination bonds at a distance 2.222(2) Å through the apical positions of two dimers. Urea molecules (Cu-O 2.114(2) Å) occupy both outside apical positions of the resulting tetranuclear units. A strong antiferromagnetic behaviour has been shown for {Cu2(OOCC5H11)4(urea)}2] (−2J=261.4(4) cm−1), and compared with related isolated dinuclear and polymeric hexanoate compounds Cu2(OOCC5H11)4(urea)2], Cu2(OOCC5H11)4]n, respectively. Only small differences in the magnetic susceptibility have been found, while EPR spectroscopy showed significantly different results for all three hexanoate compounds, also with the dicopper tetracarboxylate central core and square-pyramidal CuO4O chromophores. A solid-to-solid phase transition for {Cu2(OOCC5H11)4(urea)}2] was observed by magnetic measurement and analysed for the whole series {Cu2(OOCCmH2m + 1)4(urea)}2] by TG, DTA, and variable temperature XRD studies. |
| Keywords: | Copper Hexanoates Urea Structure Dinuclear EPR |
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