Micro-thermal analysis,FTIR-and Raman-microscopy of (R,S)-proxyphylline crystal forms

摘要

Three modifications of (R,S)-proxyphylline have been characterized by hot stage microscopy,FTIR-and FT-Raman microspectroscopy as well as differential scanning calorimety,X-ray powder diffractometry and helium pycnometry,Mod I(m.p.136degC) is thermodynamically stable in the entire temperature range and the only form which crystallizes from organic solvents or water.The metastable mod.II(m.p.113-116degC) was prepared in gram quantities from the supercooled melt and shows considerable kinetic stability under dry atmospheric conditions. Mod.III(m.p.82-85degC) is a new,kinetically very unstable form,which can only be produced in microscopic amounts aong with mod.II.The metastable forms are monotropically related to mod.I.FTIR-and FT-Raman micro-spectroscopy,in combination with thermal analysis,are demonstrated to be pwerful tools for the characterization of microphases and unstable modifications of polymorphic systems,providing information beyon dthe commonly phenomenological reports on such forms.