Influence of isomeric phthaloperinone monomers on the formation of π-dimers and σ-bonded segments in electrochemically-crosslinked products

Abstract A mixture of three constitutional isomers containing terminal reactive phthaloperinone units was obtained by the condensation of 4,4’-(4,4’-isopropylidenediphenoxy)bis(phthalic anhydride) with 1,8-naphthalenediamine. Both terminal units underwent an addition reaction via electrochemical oxidation and subsequent reduction at the perimidine core and isoindolinone, respectively, to create a multi-directional crosslinked product. The course of electropolymerization depended significantly on the isomer used, which was related to the intermediate products formed during electrooxidation: π-dimers formed in the precursor solution with stronger π-π interactions between radical cations and/or products containing π-conjugated segments: bis-isoindolinone, bis-perimidine (bonded via 3/4 and 3’/4’ positions) and protonated σ-bonded bis-perimidine via 1/6 and 1’/3’/4’/6’ positions, where hydrogen bonds stabilized these latter adducts and prevented their deprotonation. The polymers were characterized by a mixed structure, which had different effects on the long-range interactions, stability of hydrogen bonds providing a redox center located on the protonated dicationic bis-perimidine segment underwent reversible reduction to stable radical cation.