The Synergy of Ligand Methylation and Steric Hindering in Co(Salen)-Type Complexes to Control Electrochemical Doping of Their Polymers

Intermolecular interactions in electrochemically active polymers define their properties substantially. Electrochemistry of polymeric square planar transition metal complexes with Salen-type ligands is the focus of research due to easy structure modification and a great variety of proven and potential applications of these materials. The main tool for tuning intermolecular interactions in square planar complexes is introducing steric bulky substituents out of the molecular plane. Methylation of the benzene ring strongly affects the intermolecular interaction in aryl compounds. In this work, we explore cobalt complexes of methylated Salen-type ligand with sterically hindered and unhindered structures. We discuss methylation- and steric hindering-induced features of monomeric complexes and their polymers. With the EQCM technique, we found that synergy of steric bulkiness around cobalt center and aromatic rings methylation provides a great effect on mass transport at electrochemical oxidative polymer doping.