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Theoretical Study of the Remote Control of Hydrogen Bond Strengths in Donor–Bridge–Acceptor Systems: Principles for Designing Effective Bridges with Substituent Tuning
Author(s) -
Lo ShihJung,
Li WanSheung,
Chen YungHsiang,
Chao Ito
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500473
Subject(s) - intramolecular force , protonation , pyrrole , chemistry , substituent , hydrogen bond , acceptor , lone pair , imine , moiety , photochemistry , conjugated system , computational chemistry , molecule , stereochemistry , organic chemistry , polymer , ion , physics , condensed matter physics , catalysis
Remote control of hydrogen bond strengths has been studied based on conjugated donor–bridge–acceptor (pyrrole–bridge–imine) systems. The neutral and protonated states of the imine can change the hydrogen bonding ability of the pyrrole because, in the protonated state, significant partial intramolecular charge transfer (ICT) is induced that causes partial delocalization of the positive charge onto the pyrrole moiety. An efficient bridge, regardless of its length, should help electrons to flow out of pyrrole. A previously developed design strategy for the bridge (low bridge HOMO/LUMO) leads to the study of cyano‐ and fluoro‐substituted conjugated systems. Substitution positions are found to be of key importance for maximizing the protonation‐induced response from the donor–bridge–acceptor systems. Our results not only help to identify useful bridge substitution patterns, but also highlight interesting issues regarding the bridge conformation and the fluorine lone‐pair effect.