Crystal structure and magnetic behavior of Cu-3(O2C16H23)(6) center dot 1.2 C6H12. An unexpected structure and an example of spin frustration

A copper(II) carboxylate has been obtained from the reaction of basic coppe r carbonate. CuCO3. Cu(OH)(2), with 2,4,5-triisopropylbenzoic acid. It cont ains a trinuclear Cu-3(6+) core with three-fold symmetry, with each pair of copper atoms bridged by two carboxylate ligands. The Cu . . . Cu separatio ns are 3.131(3) Angstrom, precluding any direct bonding. Magnetic susceptib ility data from 1.8 to 380 K at 1000 G indicate a doublet ground state, (g approximate to 2.1) between 10-50 K (mu (eff) = 1.80 mu (B)) Above 50 K, th e magnetic moment increase to 2.69 mu (B) at 380 K, as expected for an equi lateral triangular system of CuII with antiferromagnetic interactions betwe en spin carriers. (C) 2001 Academie des sciences / Editions scientifiques e t medicales Elsevier SAS.