Molecular structure investigation of organic cocrystals of 1,10-phenanthroline-5,6-dione with aryloxyacetic acid: A combined experimental and theoretical study

• Cocrystals were synthesized via solvent mediated crystallization and neat grinding methods.
• Cocrystal 1 is stabilized through H-bonding as well as π–π interaction.
• Cocrystals 1 and 2 are stable up to 210 °C.
• Binding energy of cocrystal 2 is higher than that of cocrystal 1.
• Formation of H-bonding in cocrystals 1 and 2 is confirmed by MEP and NBO analysis.

Two organic cocrystals namely, 1,10-phenanthroline-5,6-dione:2-naphthoxyacetic acid [(phendione)(2-naa)] (1) and 1,10-phenanthroline-5,6-dione:2-formylphenoxyacetic acid [(phendione)(2-fpaa)] (2) were synthesized and studied by single crystal XRD, FT-IR, NMR, thermogravimetric, and powder X-ray diffraction analysis. The molecular properties of cocrystals were studied using density functional theory (DFT), basis set B3LYP/6-31G(d,p). Both cocrystals are stabilized through intermolecular hydrogen bonding (OH⋯N). The total electron density and molecular electrostatic potential surfaces of the cocrystals were constructed by NBO analysis using B3LYP/6-31G(d,p) method to display the electrostatic potential (electron + nuclei) distribution. The energy gap between HOMO and LUMO was measured for both cocrystals.

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