Intramolecular hydrogen bond in biologically active o-carbonyl hydroquinones
Martínez Cifuentes, Maximiliano
Weiss López, Boris
Santos, Leonardo S.
Araya Maturana, Ramiro
Cita de ítem
Molecules 2014, 19, 9354-9368
Artículo de publicación ISI
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 (ΔEij
(2)) show that the main contributions to energy stabilization
correspond to LPσ* interactions for IHBs, O1
…O2-H2 and the delocalization LPπ* for
O2-C2 = Cα(β). For the O1
…O2-H2 interaction, the values of ΔEij
(2) can be attributed to the
difference in the overlap ability between orbitals i and j (Fij), instead of the energy difference
between them. The large energy for the LP O2π* C2 = Cα(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.
We are grateful to FONDECYT grants 1140753, FONDECYT/POSTDOCTORADO 3140286
(M.M-C) and ACT grant 1107.