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

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C4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C4NiDPP was also prepared.