Structural and Magnetic Properties of a {GdCu5}2 Metallacrown Dimer with a Disulfonate Linker

Abstract

The complex {Na2(H2O)8[GdCu5(GlyHA)5(H2O)4L]2}L2 ⋅ 2.5DMF ⋅ 10.5H2O (1, where GlyHA2−= glycinehydroxamate, L2−= 4,4′-bis(2-sulfonatostyryl)biphenyl) was obtained as the outcome of the metathesis reaction of previously reported [GdCu5(GlyHA)5(CO3)(NO3)(H2O)5] ⋅ 3.5H2O with an excess of the disulfonate‘s sodium salt. X-Ray analysis of 1 shows a dimeric structure in which 15-metallacrown-5 units {GdCu5}3+ are arranged in an “edge-to-edge” manner by way of two linking disulfonates, L2−. Magnetic studies of polycrystalline 1 over a temperature range of 2–300 K revealed both Gd-Cu ferromagnetic and Cu-Cu antiferromagnetic interactions within the metallacrown unit. Experimental χMT vs. T data for 1 were fitted using different theoretical models. A two-J model, which takes into account both exchange interactions between adjacent copper(II) ions and the Gd-Cu exchange interactions allows fitting of the χMT vs. T data in the whole temperature range. The values obtained for the exchange parameters are in accord with previously reported parameters for Ln(III)-Cu(II) 15-metallacrowns-5. The 240 GHz powder EPR spectra for 1 were recorded between 30 and 150 K.