Synthesis, characterization, and magnetic properties of new complexes based on self-assembled homotrinuclear units Cu~(II)-Cu~(II)-Cu~(II)

摘要

Three new supramolecular entities of Cu~(II) have been synthesized and characterized" [Cu_2(H_2O)_2(tmen)_2(#mu#-Cu(H_2O)(pba)](PF_6)_2 (1), [{Cu_2(H_2O)(tmen)_2(#mu#-Cu(bpa))}(#mu#-SeCN)]_n(ClO_4)_n·2nH_2O (2) and [{Cu_2(H_2O)(tmen)_2(#mu#-Cu(pba))}(#mu#-SeCN)]_n(PF_6)_n·2nH_2O (3), where pba = 1,3-propanediylbis(oxamato) and tmen = N, N,N',N'-tetramethylethylene-diamine. The crystal structures of 1 and 2 were solved. Complex 1 is the precursor of 3; complex 2 is derived from the ClO_4~- analogue of 1. The two complexes have a central core in common: a trinuclear Cu~(II) complex with the two terminal Cu~(II) ions blocked by N,N,N'N'-tetramethylethylenediamine and with the same environment in the Cu~(II) central atom. In the case of complex 1, the structure is a double chain of trinuclear entities linked by hydrogen bonds owing to coordinated water molecules. In the case of complex 2, the selenocyanate ligands produce intermolecular linkages giving a one-dimensional system. The counter anions PF_6~- and ClO_4~- do not participate directly in the formation of the supramolecular entities. For complex 3 we propose a one-dimensional structure such as found for complex 2. The magnetic properties of the three complexes were studied by susceptibility measurements vs. temperature; a fit was made by the irreducible tensor formalism (ITO). The values obtained were: J_1 = - 342.1 cm~(-1), J_2 = 0.61 cm~(-1) for 1, J_1 = - 282.2 cm~(-1), J_2 = 2.6 cm~(-1) for 2 and J_1 = - 245.4 cm~(-1), J_2 = 1.3 cm~(-1) for 3.