Electronic structure and bridge geometric distortion in push–pull imine-bridged triads. A theoretical study

Abstract

The Intramolecular Electron Transfer (IET) in a wide set of imine-bridged triads as well as some model ethylene-bridged compounds and directly linked donor–acceptor diads was explored, using ferrocene and quinone groups as prototypical donor and acceptor subunits, respectively. For this purpose, the electric charge transferred from and to each subunit was analysed and some global electronic descriptors (dipole moment and chemical hardness) were computed. Ferrocene geometric distortion parameters (namely the Fe–Cp distance, total transannular deflection angle and the fulvenization HOMFc descriptor) also provided a reliable picture of IET for only ferrocenyl-substituted diads or triads. A new “Harmonic Oscillator Model of Conjugated Ethylene character” (HOMCEc) parameter was proposed in order to estimate the extension to which the bridge is engaged in IET taking place in ethylene-bridged compounds and derivatives (e.g. imines).