Impact of the Replacement of a Triphenylamine by a Diphenylmethylamine Unit on the Electrochemical Behavior of Pentaerythritol-Based Push-Pull Tetramers

The synthesis of a tetra-functionalized pentaerythritol core decorated with N-methyl-N,N-diphenylamine-based push-pull chromophores and its electropolymerization to 3D push-pull networks are described. The electrochemical and absorption behaviors of the tetramer are compared with the one of two reference linear push-pull compounds, carrying triphenylamine (TPA) or methyldiphenylamine (MeDPA) donor groups, a thienyl linker and a dicyanovinyl acceptor group (DCV). We found that substituting the outer phenyl with a methyl group causes important differences in the radical cation stability, such that MeDPA chromophore generates stable dimers and TPA is reversibly oxidized. Interestingly, DFT calculations suggest that steric hindrance and electrostatic interactions dominate the radical cation reactivity.