Butadiyne-linked bis(chlorin) and chlorin-porphyrin dyads and an improved synthesis of bis[octaethylporphyrinatonickel(II)-5-yl]butadiyne using the Takai iodoalkenation

Abstract

meso-EthynylNiOEC (OEC=dianion of octaethylchlorin) was obtained by dehydrohalogenation of the novel meso-(2'-bromovinyl)NiOEC, prepared from NiOEC-CHO by low-temperature Wittig bromoalkenation. An improved synthesis of the known conjugated bis(porphyrin) NiOEP-C-4-NiOEP (OEP=dianion of octaethylporphyrin) was achieved via the previously unreported meso-(2'-iodovinyl)NiOEP, which was prepared by Takai iodoalkenation (CHI3, CrCl2) of meso-formylNiOEP. The Takai chemistry was also applied to the NiOEC aldehyde, but the yield was much lower than for the Wittig bromoalkenation. The reaction was unsuccessful for H2OEP-CHO, ZnOEP-CHO and CuOEP-CHO. The ethynyl chlorin was homocoupled to give the first example of a conjugated alkyne-linked bis(chlorin), and heterocoupled with 5-ethynylNiDPP (DPP=dianion of 5, 15-diphenylporphyrin) to give the first chlorin-alkyne-porphyrin dyad. The first meso,meso-butadiyne-linked heteroporphyrin dyad NiOEP-C-4-NiDPP was also prepared.