Magnetic and structural properties of Mn(SCN)2(ROH)2 compounds

Abstract

Three new members of the title series, where R=CH3, C2H5, i-C3H7 or n-C3H7, have been studied in addition to the previously examined ethanol homologue. A crystal structure for the methanol compound reveals a two-dimensional network of manganese ions bridged by thiocyanate groups with methanols separating they layers. The situation is somewhat similar to that occurring for the ethanol compound, in which magnetic quasi-two-dimensionality was apparent. On the other hand, for the isopropanol compound a crystal structure suggests more nearly one-dimensional magnetic character. Weiss constants in Curie–Weiss fits to high-temperature data are −22.4, −20.9, −20.5, and −37.2 K for the methanol, ethanol, n-propanol, and isopropanol systems, respectively. The susceptibilities exhibit broad maxima at about 12.7 K for the methanol and n-propanol systems and about 16.0 K for the isopropanol system. All but the isopropanol exhibit a phase transition at about 10 K. For the methanol and ethanol systems weak ferromagnetism occurs below the ordering temperature; this appears not to occur for the n-propanol system. Susceptibility data are analyzed on the basis of two-dimensional (methanol, n-propanol) or one-dimensional (isopropanol) S=5/2 antiferromagnetic Heisenberg models. The exchange interaction is substantially stronger in the isopropanol than in the other members of the series.