查看文章

Two polymorphic crystal forms of m-nisoldipine (1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 2-methylpropyl ester) were characterized by X-ray powder diffraction and IR-spectroscopy. The solubility of the two polymorphs in water at 25, 31, 37, 42, and 49°C was investigated; the values obtained were used to calculate the thermodynamic parameters of the phase transition. The results show that the two forms A and B are enantiotropic. The temperature of polymorphic phase transition was 47°C, and the values of ΔG_A,B^θ, ΔH_A,B^θ, and ΔS_A,B^θ at 25°C were 2.47, 36.01, and 112.48J·mol⁻¹·K⁻¹, respectively. Form A is thermodynamically stable below the transition temperature; it accorded with interaction energies of the two forms obtained from Density Function Theory (DFT) calculations on the hydrogen-bonding and π-stacking interactions. The character of the solid-state …