Heterobimetallic One-Dimensional Coordination Polymers M I Cu II (M = Li and K) Based on Ferromagnetically Coupled Di- and Tetracopper(II) Metallacyclophanes

摘要

The synthesis, crystal structure and magnetic properties of the coordination polymers of formula [EDAP{Li 6 (H 2 O) 8 [(Cu 2 (μ-mpba) 2 ) 2 (H 2 O) 2 ]}] n ( 1 ) and [(EDAP) 2 {K(H 2 O) 4 [Cu 2 (μ-mpba) 2 (H 2 O) 2 ]}Cl·2H 2 O] n ( 2 ), in which mpba = N , N ′-1,3-phenylenebis(oxamate) and EDAP 2+ = 1,1′-ethylenebis(4-aminopyridinium) are described. Both compounds have in common the presence of the [Cu 2 (mpba) 2 ] 4? tetraanionic unit which is a [3,3] metallacyclophane motif in which the copper(II) ions are five-coordinate in a distorted square pyramidal surrounding. The complex anion in 1 is dimerized through double out-of-plane copper to outer carboxylate-oxygen atoms resulting in the centrosymmetric tetracopper(II) fragment [Cu 4 (μ-mpba) 4 (H 2 O) 2 ] 8? which act as a ligand toward six hydrated lithium(I) cations leading to anionic ladder-like double chains whose charge is neutralized by the EDAP 2+ cations. In the case of 2 , each dicopper(II) entity acts as a ligand towards tetraquapotassium(I) units to afford anionic zig zag single chains of formula {K(H 2 O) 4 [Cu 2 (μ-mpba) 2 (H 2 O) 2 ]} n 3n? plus EDAP 2+ cations and non-coordinate chloride anions. Cryomagnetic measurements on polycrystalline samples 1 and 2 show the occurrence of ferromagnetic interactions between the copper(II) ions across the –N amidate –(C–C–C) phenyl –N amidate – exchange pathway [ J = +10.6 ( 1 ) and +8.22 cm ?1 ( 2 )] and antiferromagnetic ones through the double out-of-plane carboxylate-oxygen atoms [ j = ?0.68 cm ?1 ( 1 ), the spin Hamiltonian being defined as H = ? J ( S C u 1 · S C u 2 + S C u 2 i · S C u 1 i ) ? j ( S C u 2 · S C u 2 i ) ].