Quantum-chemical simulation of structure and conformational flexibility of 5,7-di(tert-butyl)-2-(8-hydroxyquinolin-2-yl)-1,3-tropolone

摘要

Density functional theory [DFT B3LYP/6-311++G(d,p)] simulation has revealed stable tautomers and conformers of polydentate ligand system based on 5,7-di(tert-butyl)-2-(8-hydroxyquinolin-2-yl)-1,3-tropolone with different structures of the coordination nodes, capable of formation of metal chelates. It has been shown that the tautomeric NH- and OH- forms with exo and endo location of the hydroxy group in the quinoline fragments (close in energy, Delta E (ZPE) = 0.2-2.4 kcal/mol) are stabilized by intramolecular hydrogen bonds. Energy barriers of the interconversion of these forms via rotation about the C-OH bond of the phenolic fragment are of Delta E (ZPE) (not equal) = 2.1-4.2 kcal/mol, whereas the barrier of rotation about the bond between the quinoline and tropolone fragments is higher (Delta E (ZPE) (not equal) = 18.2 and 19.6 kcal/mol).