The Polymorphism of Orlyum White 520T, an Ultraviolet Luminescent Security Ink

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Polymorphism is crucial for security inks, impacting stability and performance.
• Orlyum White 520T is an ultraviolet luminescent security ink with a known crystalline form.

Purpose of the Study:

• To investigate the polymorphism of Orlyum White 520T.
• To identify and characterize new polymorphic forms with enhanced stability.
• To understand the factors influencing the formation of different polymorphs.

Main Methods:

• Single-crystal X-ray diffraction
• Powder X-ray diffraction (PXRD)
• Fourier-transform infrared spectroscopy (FT-IR)
• Nuclear magnetic resonance (NMR) spectroscopy
• Elemental analysis
• Hirshfeld surface analysis
• Lattice energy calculations
• Thermogravimetric evolved gas analysis (TG/DTA-EGA-MS)

Main Results:

• Two new polymorphic forms (Form I and Form II) of Orlyum White 520T were successfully synthesized, exhibiting higher melting points (197-198 °C and 195-196 °C) than the known Form III (184.8-185.2 °C).
• Identical elemental composition and NMR spectra confirm the chemical identity across polymorphs, while distinct PXRD and FT-IR patterns reveal structural differences.
• Single-crystal structure analysis of Form II and redetermination of Form III elucidated differences in crystal packing, secondary interactions, and molecular conformations.
• Hirshfeld surface analysis and lattice energy calculations provided insights into the factors governing the distinct melting points.
• Thermogravimetric evolved gas analysis suggested that solvents or organic contaminants play a significant role in the nucleation and growth of specific polymorphic forms.

Conclusions:

• The study reveals new, more stable crystalline forms of Orlyum White 520T, expanding the understanding of its solid-state properties.
• Differences in crystal packing and intermolecular interactions are key determinants of the observed variations in melting points among polymorphs.
• Controlling crystallization conditions, particularly the presence of solvents or impurities, is critical for reproducible synthesis of desired polymorphic forms.