摘要:
                                A series of compounds of formula [{Cu(2)(OOCC(m)H(2m+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(H) tetracarboxylate, where the central coordination sphere in [{Cu(2)(OOCC(5)H(11))(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) Angstrom through the apical positions of two dimers. Urea molecules (Cu-O 2.114(2) Angstrom) occupy both outside apical positions of the resulting tetranuclear units. A strong antiferromagnetic behaviour has been shown for [{Cu(2)(OOCC(5)H(11))(4)(urea)}(2)] (-2J = 261.4(4) cm(-1)), and compared with related isolated dinuclear and polymeric hexanoate compounds [CU(2)(OOCC(5)H(11))(4)(urea)(2)], [CU(2)(OOCC(5)H(11))(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 CuO(4)O chromophores. A solid-to-solid phase transition for [{Cu(2) (OOCC(5)H(11))(4)(urea)}(2)] was observed by magnetic measurement and analysed for the whole series [{CU(2)(OOCC(m)H(2m+1))(4)(urea)}(2)] by TG, DTA, and variable temperature XRD studies. (C) 2004 Elsevier B.V. All rights reserved.