Uncovering the Influence Mechanism of Solvent on Crystal Morphology via a Combined Experimental and Theoretical Method: The Case of Aceclofenac

Aceclofenac (ACF) is a kind of antipyretic, analgesic, and antiarthritic drug, which is clinically suitable for the treatment of rheumatoid arthritis. However, the morphology of ACF produced in the crystallization process is easily regulated by different solvents, which has a significant effect on the powder properties of the ACF crystals. Therefore, the study of crystal habits is needed for producing ACF with a better performance. In this study, the effects of different solvents on the growth of the ACF crystal were studied by analyzing the morphology of ACF in various solvents and comprehensive simulation calculations. It was found that the ACF crystals in ethanol (EAL) and acetonitrile (ACE) were quadrangular in shape. In methyl acetate (MA), acetone (ACT), and n-propanol (NPL), the lateral aspect of the (101̅) facet is clearly prominent. More interestingly, pentagonal crystals are found only in methanol (MEL), and the (002) facet eventually disappears as they grow. Through molecular dynamics simulations, we have found that the attachment energy Eatt of crystal facets, the Connolly surface coefficient R, and solvent effects Es are the main factors influencing the growth of ACF crystals. The competitive adsorption of ACF and solvent molecules onto crystal facets accounts for morphology change during the growth process. By establishing a strong link between experimental observations and simulation results, this study favors the morphology control of the ACF crystal.