MAGNETISM IN LITHIUM-METHYLAMINE SOLUTIONS

The magnetic susceptibilities of lithium-methylamine solutions have be en measured for metal concentrations of 2.0, 1.0, and 0.085 mole perce nt metal (MPM) over the temperature range 2 - 300 K. The temperature- and concentration-dependence of the solution-phase magnetic susceptibi lities are consistent with an equilibrium between diamagnetic spin-pai red and paramagnetic spin-unpaired species. Enthalpy and entropy value s for a single equilibrium of this type are derived from an analysis b ased on the susceptibility data for dilute solutions. Calculated susce ptibilities based on this single equilibrium are in good agreement wit h the observed concentration- and temperature-dependence of lithium-me thylamine solution-phase susceptibilities over nearly two orders of ma gnitude variation in concentration and over a 50-degrees-C temperature range. The derived spin-unpairing enthalpy is 12.14 kJ/mol, or 0.125 eV. This value is considerably smaller in magnitude than the correspon ding spin-unpairing enthalpy measured for dilute potassium-ammonia sol utions (congruent-to 0.40 eV), suggesting that the spin-pairing intera ction is weaker in lithium-methylamine solutions.