Theoretical study of the remote control of hydrogen bond strengths in donor-bridge-acceptor systems: principles for designing effective bridges with substituent tuning.
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.
Lo
Shih-Jung
SJ
Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan.
Li
Wan-Sheung
WS
Chen
Yung-Hsiang
YH
Chao
Ito
I
D003198:Computer Simulation; D004583:Electrons; D004735:Energy Transfer; D005461:Fluorine / Q000737:chemistry*; D006860:Hydrogen Bonding; D007097:Imines / Q000737:chemistry*; D008956:Models, Chemical; D008962:Models, Theoretical; D011758:Pyrroles / Q000737:chemistry*
D007097:Imines; D011758:Pyrroles; D005461:Fluorine