Stepwise synthesis of new porphyrinoid hybrids

Mashnoy, Ibtesam (2025) Stepwise synthesis of new porphyrinoid hybrids. Doctoral thesis, University of East Anglia.

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Abstract

This thesis aims to develop new synthetic strategies for stepwise, controlled construction of novel core-modified phthalocyanine hybrids – specifically diazabenzoporphyrin derivatives with one isoindole unit replaced by methine-linked thiophene (“tribenzodiazathiaporphyrins”). Treating benzamidine with 2,5-diethynylthiophene under copper-free Sonogashira cross-coupling reaction conditions led to the successful formation of bisaminoisoindoline thiophene as the required intermediate for the formation of the target macrocycles. Reaction of this intermediate with phthalonitrile gave the new macrocycles, and initial synthetic investigations involved substituting this top isoindole unit through using a range of phthalonitriles. The substituted phthalonitrile was reacted with the intermediate to form the desired macrocyclic structures. The different substituents on the top isoindole of the macrocycle has only a small effect on the absorption and emission properties; a slight red shift was observed in the Q band of the non-peripherally phenyl substituted derivative.

Modifying the synthetic route allowed substitution of both side isoindoles of the macrocycle so that the effect of modification on top and side fragments could be investigated. Again, a minimal effect was observed in the absorption and fluorescence emission properties across this series.

Isomeric macrocycles (S-confused, cis-diazatribenzothiophenyl porphyrins) were also synthesised using a similar approach, starting from 2,4-diethynylthiophene. However, in this case, we focused on the 2,4-positions of the thiophene moiety. The effect of modifying the position was also investigated in terms of the macrocycle’s properties. This macrocycle, which is not aromatic, showed a significant blue shift of ~100 nm in comparison with tribenzodiazathiaporphyrins, where the longest wavelength peak appears around 644 nm.

Alternative reactants such as diamines, dicarbonyls and di-carboxylic acid chlorides, were also used to attempt macrocycle formation from our intermediate bisaminoisoindoline thiophene. Unfortunately, these attempts were unsuccessful and did not yield any of the desired macrocycles. The reaction of bisaminoisoindoline thiophenes with phthaloyl chloride formed a bisphthalimide derivative rather than the macrocycle. Replacement of the thiophene unit with bithiophene or pyridine was also investigated, but indicated no macrocycle formation.

The final part of the thesis describes an attempt to synthesis different macrocycles with distinct patterns of π-conjugation, specifically using triphenylene as a building block. A 2,11-diaminoisoindoline-triphenylene intermediate was produced by coupling triphenylene-2,11-diacetylene with bromobenzamidine using the same strategy that had been successfully used earlier. Attempts to produce a macrocycle by inserting a phthalonitrile unit were unsuccessful. However, attempts to cyclise the intermediate directly led to interesting new materials. We found evidence for intramolecular cyclisation, but the dominant product resulted from dimerization and spectroscopic (NMR) evidence suggests a complex, twisted conformation for this large macrocycle because there is a clear indication that symmetry is broken.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Depositing User:	Kitty Laine
Date Deposited:	04 Nov 2025 14:42
Last Modified:	04 Nov 2025 14:42
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100899
DOI:

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