Conductive Directly Fused Poly(Porphyrin) Coatings by Oxidative Chemical Vapour Deposition - From Single- to Triple-Fused

While the solution-phase synthesis of directly fused porphyrin tapes has been successfully developed in recent years, the deposition of these promising compounds in thin film form has remained a challenge. In this study, we report the simultaneous synthesis and deposition of conductive directly fused poly(porphyrin) coatings based on a substrate independent and up-scalable oxidative chemical vapor deposition (oCVD) approach. A particular emphasis is given to the selection and sublimation conditions of the oxidant. The direct fusion of nickel(II) 5,15-(diphenyl)porphyrin (NiDPP) is successfully achieved using three different oxidants, namely iron(III) chloride (FeCl3), copper(II) chloride (CuCl2) and copper(II) perchlorate hexahydrate (Cu(ClO4)(2)6H(2)O). FeCl3 is demonstrated as the most suitable oxidant, allowing the formation of mainly singly-fused poly(NiDPP) or conductive mainly doubly or triply-fused poly(NiDPP) that strongly absorb in the NIR. High-resolution mass spectrometry evidences the chlorination of the formed compounds as a side reaction. This chlorination can either be considered as a drawback by preventing the formation of large directly fused NiDPP oligomers or as an asset when targeting the formation of fully insoluble directly fused poly(NiDPP) coatings. Overall, the described oCVD approach opened up the possibility to tune the band gap, conductivity, and solubility of directly fused P(NiDPP) coatings.