Triflate Salts\nas Alternative Non-Chlorinated Oxidants\nfor the Oxidative Chemical Vapor Deposition and Electronic Engineering\nof Conjugated Polymers

Oxidative chemical vapor deposition (oCVD) stands as\nan attractive\napproach for the synthesis, engineering, and integration of conjugated\npolymers for advanced electronic and optoelectronic applications.\nIn oCVD, the oxidant significantly influences the conformational and\noptoelectronic properties of the resulting conjugated polymer thin\nfilms. In this work, triflate salts of iron(III) and copper(II) (Fe(OTf)<sub>3</sub> and Cu(OTf)<sub>2</sub>, respectively) are investigated for\nthe first time as suitable alternative oxidants to the widely used\niron(III) chloride (FeCl<sub>3</sub>) for the oCVD of conjugated polymers.\nStructural and compositional characterizations of the resulting thin\nfilms evidenced the successful polymerization of cobalt(II) 5,15-diphenyl\nporphyrin using either Fe(OTf)<sub>3</sub> or Cu(OTf)<sub>2</sub>.\nAlong with an intermolecular dehydrogenative C–C coupling reaction,\nthe occurrence of side reactions, such as the inclusion of −CF<sub>3</sub> groups and demetalation and subsequent insertion of copper(II)\nin the porphyrin macrocycle when using Cu(OTf)<sub>2</sub>, were evidenced.\nInterestingly, the inclusion of −CF<sub>3</sub> groups into\nthe polymer backbone when using triflate salts results in a deepening\nof the frontier energy levels, while the insertion of copper(II) contributes\nto a reduction in the band gap energy. This work demonstrates that\nthe careful selection of the oxidant agent in oCVD enables fine-tuning\nthe optoelectronic properties of conjugated polymers to suit specific\napplication requirements.