8-(Pyridin-2-yl)quinolin-7-ol as a Platform for Conjugated Proton Cranes: A DFT Structural Design

• Main Authors: Anton Georgiev, Liudmil Antonov
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Micromachines
• Subjects: proton crane; 7-hydroxyquinoline; DFT; proton transfer; tautomerism; ESIPT
• Online Access: https://www.mdpi.com/2072-666X/11/10/901

Theoretical design of conjugated proton cranes, based on 7-hydroxyquinoline as a tautomeric sub-unit, has been attempted by using ground and excited state density functional theory (DFT) calculations in various environments. The proton crane action request existence of a single enol tautomer in ground state, which under excitation goes to the excited keto tautomer through a series of consecutive excited-state intramolecular proton transfer (ESIPT) steps with the participation of the crane sub-unit. A series of substituted pyridines was used as crane sub-units and the corresponding donor-acceptor interactions were evaluated. The results suggest that the introduction of strong electron donor substituents in the pyridine ring creates optimal conditions for 8-(pyridin-2-yl)quinolin-7-ols to act as proton cranes.