The First Crystal Structure of an Anti-Geometric Homoleptic Zinc Complex from an Unsymmetric Curcuminoid Ligand

• Published in: Crystals (Basel) Vol. 14; no. 9; p. 751
• Main Authors: Obregón Mendoza, Marco A, Escamilla, Gabriela Marmolejo, Tavera-Hernández, Rosario, Sánchez-Obregón, Rubén, Toscano, Rubén A, Enríquez, Raúl G
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-09-2024
• Subjects: Coordination compounds; Crystal structure; Crystals; curcuminoids; Geometry; hemi-curcuminoids; homoleptic zinc metal complex; Ligands; Molecular structure; NMR; Nuclear magnetic resonance; Single crystals; Software; Solvents; Stereochemistry; Structure; unsymmetric zinc complex; Zinc; Zinc compounds; Argentina; United States > US; Mexico
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst14090751

Curcuminoids are widely studied due to their well-recognized therapeutic properties. These molecules are often derivatized with metals, producing their corresponding homoleptic metal complexes. Numerous crystal structures of homoleptic symmetric curcuminoids with physiologically essential metals are known, although the literature lacks reports of homoleptic metal complexes of unsymmetric curcuminoids (or hemi-curcuminoids) as ligands. Three unknowns must be solved when an unsymmetric curcuminoid ligand is reacted with a metal ion: (a) the degree of coordination (MLn); (b) the spatial geometry; and (c) the conformational nature (syn or anti) of the complex. Herein, we report the structure of the anti-isomer of the Zn complex of the hemi-curcuminoid 5-hydroxy-1-(4-methoxyphenyl)hexa-1,4-dien-3-one. While the NMR shows only one set of signals for this homoleptic complex, the unambiguous stereochemistry was established through single-crystal X-ray diffractometry, revealing an anti-hexacoordinated octahedral ML[sub.2] structure.