We report the synthesis and characterisation of new examples of meso-hydroxynickel(II) porphyrins with 5,15-diphenyl and 10-phenyl-5,15-diphenyl/diaryl substitution. The OH group was introduced by using carbonate or hydroxide as nucleophile by using palladium/phosphine catalysis. The NiPor-OHs exist in solution in equilibrium with the corresponding oxy radicals NiPor-O . The 15-phenyl group stabilises the radicals, so that the H NMR spectra of {NiPor-OH} are extremely broad due to chemical exchange with the paramagnetic species. The radical concentration for the diphenylporphyrin analogue is only 1 %, and its NMR line-broadening was able to be studied by variable-temperature NMR spectroscopy. The EPR signals of NiPor-O are consistent with somewhat delocalised porphyrinyloxy radicals, and the spin distributions calculated by using density functional theory match the EPR and NMR spectroscopic observations. Nickel(II) meso-hydroxy-10,20-diphenylporphyrin was oxidatively coupled to a dioxo-terminated porphodimethene dyad, the strongly red-shifted electronic spectrum of which was successfully modelled by using time-dependent DFT calculations.

No abstract

A strategy to tackle the synthesis of azoporphyrins with unsubstituted terminal meso positions was investigated. It comprised the combination of diaza‐Diels–Alder (DADA) reaction of 1,3‐dienes with dialkyl azodicarboxylates, decarboxylative hydrolysis of the bis(carbamates), palladium‐catalyzed amination of bromoporphyrin precursors, and retro‐DADA reactions to release the ultimate targets. The somewhat confused historical results on the DADA reactions of 1,3‐cyclohexadiene were clarified, but the hydrolyses yielded extremely air‐sensitive amines which decomposed completely in minutes via autooxidation and retro‐DADA reaction. With anthracene or 2,3‐dimethyl‐1,3‐butadiene as the diene, the synthesis of azoporphyrin was not achieved but three amino‐substituted porphyrins were obtained in moderate yields under mild conditions. The X‐ray crystal structures of several of the intermediates and the final aminoanthracene‐porphyrin nickel(II) complex were determined.

No abstract

No abstract