Intramolecular Hydrogen Bond in Biologically Active o-Carbonyl Hydroquinones

Molecules

Maximiliano Martínez-Cifuentes²  Boris E. Weiss-López¹  Leonardo S. Santos² 

[1] Departamento de Química, Facultad de Ciencias, Universidad de Chile, Santiago, Casilla 653, Chile; E-Mail:;Laboratorio de Síntesis Asimétrica, Instituto de Química de los Recursos Naturales, Universidad de Talca, Talca, Casilla 747, Chile; E-Mail:

关键词: hydroquinone;    hydrogen bond;    DFT;    molecular electrostatic potential;    natural bond orbital;   

DOI  :  10.3390/molecules19079354

来源: mdpi

【 摘 要 】

Intramolecular hydrogen bonds (IHBs) play a central role in the molecular structure, chemical reactivity and interactions of biologically active molecules. Here, we study the IHBs of seven related o-carbonyl hydroquinones and one structurally-related aromatic lactone, some of which have shown anticancer and antioxidant activity. Experimental NMR data were correlated with theoretical calculations at the DFT and ab initio levels. Natural bond orbital (NBO) and molecular electrostatic potential (MEP) calculations were used to study the electronic characteristics of these IHB. As expected, our results show that NBO calculations are better than MEP to describe the strength of the IHBs. NBO energies (∆E_ij⁽²⁾) show that the main contributions to energy stabilization correspond to LP→σ* interactions for IHBs, O₁^…O₂-H₂ and the delocalization LP→π* for O₂-C₂ = C_α(β). For the O₁^…O₂-H₂ interaction, the values of ∆E_ij⁽²⁾ can be attributed to the difference in the overlap ability between orbitals i and j (F_ij), instead of the energy difference between them. The large energy for the LP O₂→π* C₂ = C_α(β) interaction in the compounds 9-Hydroxy-5-oxo-4,8, 8-trimethyl-l,9(8H)-anthracenecarbolactone (VIII) and 9,10-dihydroxy-4,4-dimethylanthracen-1(4H)-one (VII) (55.49 and 60.70 kcal/mol, respectively) when compared with the remaining molecules (all less than 50 kcal/mol), suggests that the IHBs in VIII and VII are strongly resonance assisted.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.