Synthesis, Crystal Structures, and Density Functional Theory Studies of Two Salt Cocrystals Containing Meldrum's Acid...

Area of Science:

• Crystal Engineering and Solid-State Chemistry
• Materials Science
• Computational Chemistry

Background:

• Salt cocrystals offer tunable properties through molecular design.
• Understanding crystal structures and intermolecular interactions is crucial for materials development.
• Computational methods aid in predicting and validating experimental findings.

Purpose of the Study:

• To synthesize and structurally characterize two novel salt cocrystals, DDD and MDD.
• To investigate the hydrogen bonding patterns and crystal packing in DDD and MDD.
• To computationally model their geometric and electronic properties and compare with experimental spectral data.

Main Methods:

• Single-crystal X-ray diffraction for structural determination.
• Density Functional Theory (DFT) calculations (B3LYP/6-311G(d,p)) for geometric optimization.
• Thermodynamic property calculations and spectral analysis (UV-Vis and fluorescence).

Main Results:

• Crystal structures of DDD (monoclinic, P21/c) and MDD (triclinic, P-1) were elucidated.
• Both cocrystals exhibit 1D-chained structures stabilized by N-H···N and N-H···O hydrogen bonds.
• DFT optimized structures correlate well with crystallographic data; PBEPBE/6-311G(d,p) accurately simulates UV-Vis spectra.
• Fluorescence spectroscopy reveals yellowish-green emission for DDD (570 nm) and purplish-blue for MDD (454 nm).

Conclusions:

• Successful synthesis and structural characterization of two distinct salt cocrystals.
• Established correlation between crystal structure, hydrogen bonding, and observed spectral properties.
• Demonstrated the utility of DFT for predicting structural and spectral characteristics of cocrystals.