Fe(III), Mn(II), Co(II), and Ni(II) 3,4,5-trihydroxybenzoate (gallate) dihydrates; a new family of hybrid framework materials

摘要

We report the synthesis, crystal structures, magnetic properties, and thermal behavior of a family of isostractural transition metal galiate dihy-drates containing infinite chains of trans-corner-sharing MO_6 octahedra. The gallates crystallize in the enantiomorphic space groups P3_1 21 and P3_221, chirality being imparted by helical motifs in the structure. Ni(C_7O_5H_4) cnetre dot 2H_2O: a = 8.824(2) A, c = 10.644(2) A; Mn(C_7O_5H_4) centre dot 2H_2O: a = 9.063(2) A, c = 10.947(2) A; Co(C_7O_5H_4) centre dot 2H_2O: a = 8.910(2) A, c = 10.887(2) A. The Co(II) and Ni(II) gallates exhibit antiferromagnetic behavior, with T_N = 43 and 19 K, respectively, while Mn(II) gallate is paramagnetic down to 5 K. High-temperature X-ray powder diffraction indicates that crystallinity is lost near 200 deg C in all of the compounds. Decarboxylation of the gallate moieties is believed to facilitate this thermal decomposition.