The formation mechanism of hollow spherulites and molecular conformation of curcumin and solvate

Abstract

In this study, curcumin 1,4-dioxane solvates (CUR–DIO) were obtained in two molecular ratios of 1 : 1.5 (CUR–DIO-1.5) and 1 : 1 (CUR–DIO-1) at different temperatures. In the two single crystal structures, the molecular conformation of curcumin is a planar structure and a curved structure, respectively. Moreover, the length of the hydrogen bond between the curcumin molecule and the 1,4-dioxane molecule indicates that with the increase in the system temperature, the difficulty of solvate formation increases, the solvent ratio decreases, and the inter-molecular hydrogen bond energy increases. In addition, with the increase in temperature, the crystal morphology changes from spherulites to rod-shaped crystals. The hollow spherulites of CUR–DIO-1 were obtained at 25 °C, and based on the ReactRaman data and microscope recording, a new formation mechanism of hollow spherulites was proposed. The formation mechanism and preparation method of organic small molecule hollow spherulites will play an important role in promoting the application of the hollow spherulite structures in the fields of drug loading, slow release and multifunctional drugs.