Exchange Coupling in the Alternating Chain Compounds Catena-Di-micron-chlorobis(4-Methylpyridine)Copper(II), Catena-Di-micron-bromobis-(N-Methylimidazole)Copper(II), Catena-hexanedionebis(Thiosemicarbazato)Copper(II), and Catena-o

摘要

Magnetic susceptibility data have been collected for catena-octanedionebis-(thiosemicarbazonato)copper(II), Cu-OTS, and catena-hexane-dionebis(thiosemicarbazonato(copper(II), Cu-HTS, in the temperature range 1.8-120 K, and the data analyzed in terms of an alternating chain Heisenberg exchange model to yield J = -10.1 + or - 0.2/cm, alpha = 0.91 + 0r - 0.02, and g = 2.06 + or - 0.02 for Cu-HTS and J = 12.9 + or - 0.2 alpha = 0.90 + or - 0.02, and g = 2.11 + or - 0.02 for Cu-OTS. Anomalies in the temperature dependent capacitance data for catena-di-micron-chlorobis(4-methylpyridine)copper(II) and catena-di-micron-bromo(N-methylimidazole)copper(II) provide evidence for structural phase transitions presumably from uniform chain structures at room temperature to alternating chain structures at low temperatures. Magnetic parameters for Cu(4-methylpyridine)2Cl2 are J = -9.6 + or - 0.2/cm, g = 2.17 + or - 0.02 and alpha = 0.67 + or - 0.02. An expression for the magnetic susceptibility of a Heisenberg alternating chains of S = 1/2 ions has been developed in terms of the alternation parameter, the exchange coupling constant, and the g factor. (Author)