Mineral Particles as Nucleating Agents for Controllable Polymorphic Forms of ROY

The crystallization behavior of the organic molecule 5-methyl-2-[(2-nitrophenyl) amino]-3-thiophenecarbonitrile (known as ROY for its red, orange, and yellow crystals) was systematically regulated by using various natural mineral particles as heterogeneous nucleating agents. Polarized light microscopy and X-ray diffraction demonstrated that different types of mineral nucleating agents significantly influenced the resulting polymorphic forms of ROY, establishing a clear correlation between the nucleating agent type and the crystal form. Scanning electron microscopy and in situ video microscopy provided detailed insights into the nucleation sites and crystal growth dynamics. Remarkably, these nucleating agents consistently induced specific polymorphs under different crystallization methods and conditions while also modulating the dominant crystal facets. This study highlights the critical role of mineral nucleating agents in manipulating the crystallization process and tailoring the resulting crystal products.