2-((E)-{2-[(E)-2,3-Dihydroxy-benzyl-ideneamino]-5-methyl-phen-yl}iminiometh-yl)-6-hydroxy-phenolate

Area of Science:

• Crystallography
• Organic Chemistry
• Materials Science

Background:

• Schiff base compounds are versatile organic molecules with diverse applications.
• Understanding the solid-state structure of Schiff bases is crucial for predicting their properties and designing new materials.
• The title compound, C(21)H(18)N(2)O(4), presents an interesting case for structural investigation due to its potential for complex intermolecular interactions.

Purpose of the Study:

• To elucidate the detailed crystal structure of the Schiff base compound C(21)H(18)N(2)O(4).
• To analyze the conformational variations among independent zwitterions within the asymmetric unit.
• To investigate the types and significance of intermolecular interactions (hydrogen bonding, C-H···π, π-π stacking) that stabilize the crystal lattice.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the molecular and crystal structure.
• Analysis of bond lengths, bond angles, and dihedral angles provided insights into molecular geometry.
• Identification and analysis of intra- and intermolecular hydrogen bonds, along with C-H···π and π-π interactions, were performed to understand crystal packing.

Main Results:

• The asymmetric unit contains four independent zwitterions (A, B, C, D) with similar conformations.
• A methyl group in each molecule exhibits positional disorder with varying occupancies.
• Dihedral angles between aromatic rings show significant variations across the independent molecules.
• Intramolecular hydrogen bonds form S(6) ring motifs in all molecules.
• Intermolecular O-H···O and C-H···O hydrogen bonds link molecules into a two-dimensional network parallel to the ab plane.
• C-H···π and π-π interactions further stabilize the crystal structure, with centroid-centroid distances ranging from 3.5153(14) to 3.7810(15) Å.

Conclusions:

• The crystal structure of the Schiff base C(21)H(18)N(2)O(4) is characterized by multiple independent zwitterions and significant disorder.
• A combination of intra- and intermolecular hydrogen bonds, along with C-H···π and π-π stacking interactions, dictates the overall crystal packing and stability.
• The detailed structural analysis provides a foundation for understanding the structure-property relationships of this class of compounds.