Ana M. V. M. Pereira

Porphyrin–Phthalocyanine/Pyridylfullerene Supramolecular Assemblies

The synthesis and photophysical properties of several porphyrin (P)-phthalocyanine (Pc) conjugates (P-Pc; 1-3) are described, in which the phthalocyanines are directly linked to the β-pyrrolic position of a meso-tetraphenylporphyrin. Photoinduced energy- and electron-transfer processes were studied through the preparation of H(2)P-ZnPc, ZnP-ZnPc, and PdP-ZnPc conjugates, and their assembly through metal coordination with two different pyridylfulleropyrrolidines (4 and 5). The resulting electron-donor-acceptor hybrids, which were formed by axial coordination of compounds 4 and 5 with the corresponding phthalocyanines, mimicked the fundamental processes of photosynthesis; that is, light harvesting, the transduction of excited-state energy, and unidirectional electron transfer. In particular, photophysical studies confirmed that intramolecular energy-transfer resulted from the S(2) excited state as well as from the S(1) excited state of the porphyrins to the energetically lower-lying phthalocyanines, followed by an intramolecular charge-transfer to yield P-Pc(.+)⋅C(60)(.-). This unique sequence of processes opens the way for solar-energy-conversion processes.

Diporphyrinylamines: Synthesis and Electrochemistry

The synthesis of three possible diporphyrinylamines is described. All compounds were obtained by using the Buchwald-Hartwig aromatic amination reaction. The electronic spectra of the three porphyrin dimers showed characteristic features found in highly delocalized systems. The first oxidation of these compounds took place on the connecting amine function.

A New Synthetic Approach to N-Arylquinolino[2,3,4-at]porphyrins from β-Arylaminoporphyrins

A new reaction leading to porphyrins bearing fused rings is described. Novel N-arylquinolino[2,3,4-at]porphyrins 2 were obtained by thermal oxidative cyclization of beta-arylaminoporphyrins 1. The starting beta-arylaminoporphyrins were prepared by two routes: (i) nucleophilic displacement of the nitro group from 2-nitro-5,10,15,20-tetraphenylporphyrin by anilines and (ii) palladium-catalyzed amination of bromobenzene derivatives with (2-amino-5,10,15,20-tetraphenylporphyrinato)nickel(II). The N-arylquinolino[2,3,4-at]porphyrins show interesting UV-vis spectra with strong absorption bands in the red region.

Synthesis of extended porphyrins by connection of meso-aryl groups with β-pyrrolic positions

This review focuses on synthetic strategies leading to extended porphyrins, but is limited to examples in which at least one β-pyrrolic carbon is linked to a meso-aryl substituent. Friedel–Crafts reactions are covered first because historically they were the first reactions employed to link β-pyrrolic carbons with meso-aryl groups, thus creating new six-membered fused rings. Other reactions inserting heteroatoms follow. Direct cyclizations between an ortho-carbon and a β-pyrrolic position are presented next. Finally, new highly extended chromophores are described. These compounds are generally obtained in two consecutive reactions. First a Suzuki coupling is used to introduce an aryl group in one or two meso positions. Then the new fused rings are generated by oxidative cyclizations.

Recent developments in the synthesis of homo- and heteroarrays of porphyrins and phthalocyanines

Here, we report the progress in the chemistry of porphyrin-phthalocyanine and phthalocyanine-phthalocyanie multinuclear systems being developed by the organic chemistry groups of Cavaleiro and Torres.

Inexpensive and Efficient Ullmann Methodology To Prepare Donor-Substituted Porphyrins

The preparation of porphyrins functionalized with one or two carbazoles (or phenoxazines) is described. The electron donors were introduced into one or two porphyrin meso positions by using the inexpensive Ullmann coupling procedure. Very good yields were obtained, and for two new compounds, the X-ray structures were solved. Preliminary electrochemical data coupled with electronic spectroscopy are also reported.

A new approach to N-phenylquinolino[2,3,4-at]porphyrins: Electrochemical and photochemical studies

A new route to N-phenylquinolino[2,3,4-at]porphyrins is described and the electrochemical and photochemical properties of the synthesized derivatives were investigated. The electrochemical studies (cyclic voltammetry and rotating disk voltammetry) of the free-base and the corresponding Ni, Cu and Pd complexes have shown that the presence of the phenyl group is responsible for the formation of stable radical cations. The capacity of the N-phenylquinolino[2,3,4-at]porphyrins to generate singlet oxygen was evaluated and some of them have promising features as photosensitizers.

A new porphyrin dimer as an unexpected side-product

The synthesis of new diporphyrinylamines is described. In particular, the possibility to use the Buchwald or Ullmann amination reactions to obtain these compounds is detailed. Attempts to obtain symmetrical diporphyrinylamines linked by a tertiary amine are exposed and the obtention as side-product of an unexpected unsymmetrical porphyrin dimer with a meso–β linkage is described.

A Deep Learning Approach for Red Lesions Detection in Video Capsule Endoscopies.

The wireless capsule endoscopy has revolutionized early diagnosis of small bowel diseases. However, a single examination has up to 10 h of video and requires between 30–120 min to read. Computational methods are needed to increase both efficiency and accuracy of the diagnosis. In this paper, an evaluation of deep learning U-Net architecture is presented, to detect and segment red lesions in the small bowel. Its results were compared with those obtained from the literature review. To make the evaluation closer to those used in clinical environments, the U-Net was also evaluated in an annotated sequence by using the Suspected Blood Indicator tool (SBI). Results found that detection and segmentation using U-Net outperformed both the algorithms used in the literature review and the SBI tool.

Electronic and magnetic interactions in diporphyrinylamines

The synthesis of new metalated diporphyrinylamines is described. The electronic ≪communication≫ through the amino function linking the two porphyrins was clearly demonstrated by electronic spectroscopy. In addition, intramolecular magnetic interactions were measured between two copper(II) ions located in the two linked porphyrins. Compared to the reported value (J ∼ -2 K) for Osuka’s triply fused bis-copper(II) porphyrin dimer, a relatively high antiferromagnetic coupling constant was determined in our compound (J = -11 K).