In-situ solid-state NMR spectroscopy reveals competing crystallization pathways for a system that forms structurally...

Area of Science:

• Solid-state chemistry
• Crystallization science
• Materials science

Background:

• Crystallization processes are fundamental in chemistry and materials science.
• Understanding the structural evolution of crystalline phases is crucial for process control.
• In situ monitoring techniques offer mechanistic insights into crystallization pathways.

Purpose of the Study:

• To investigate the structural evolution of crystalline phases during the crystallization of 1,10-dihydroxydecane and urea in methanol.
• To apply in situ solid-state ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy for real-time monitoring.
• To identify and characterize the different crystalline phases formed during the process.

Main Methods:

• In situ solid-state ¹³C NMR spectroscopy was employed.
• Crystallization was performed from a methanol solution containing 1,10-dihydroxydecane and urea.
• Structural characterization of solid phases was achieved through NMR spectral analysis.

Main Results:

• Two structurally diverse crystalline phases were identified: a urea inclusion compound and a 1,10-dihydroxydecane-(urea)₂ co-crystal.
• The urea inclusion compound formed initially, followed by the stoichiometric co-crystal.
• The urea inclusion compound was found not to be an intermediate but persisted alongside the co-crystal, which then grew rapidly.

Conclusions:

• In situ solid-state NMR is a powerful tool for monitoring the structural evolution of multicomponent crystalline phases during crystallization.
• The study elucidated the formation of distinct crystalline phases and their dynamic interplay during the crystallization of 1,10-dihydroxydecane and urea.
• The findings highlight the capability of NMR to provide mechanistic details of complex crystallization processes.