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Non-covalent assemblies of negatively charged boronated porphyrins with different cationic moieties

“…Figs. [4][5][6][7] show some examples of the absorption spectra of the monomeric ionic porphyrins and their mixture, all at the same molar concentration of each porphyrin. The characteristics of the absorption spectra of the porphyrin Scheme 1.…”

“…Unfortunately, the available porphyrin assemblies, which could serve as simple salt-bridge-containing energy or electron transfer model systems, are all 0022-328X/$ -see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2004.07.029 characterized by a face-to-face orientation between the relevant redox active partners [6,7]. Thus, there is a clear need at present for electrostatically assembled donoracceptor systems that enforce alternative geometries.…”

Radiative Deactivation of Lowest Singlet and Triplet Excited States of Water-Soluble Porphyrins

“…Water-soluble porphyrins occupy a special place among numerous tetrapyrrole derivatives because they have great potential for practical applications in medicine, biology, and industry as drugs, catalysts, and reaction inhibitors and sensitizers [1,2]. Water-soluble porphyrins have ionizable peripheral substituents, in contrast with their hydrophobic analogs, and can be salts of acids or bases [2][3][4]. The ionizable peripheral substituents carry either a negative (H 2 T4SPP) or positive charge (H 2 T4MPYP) that is responsible for the hydrophilic properties of the porphyrin as a whole although the tetrapyrrole macrocycle itself is hydrophobic.…”

Fluorescence quenching of water-soluble porphyrins by molecular oxygen

“…Depending on the conditions, the counterions either dissociate or form ion pairs with the tetrapyrrole macrocycles [3]. Electronic absorption and vibrational spectra in addition to rate constants of intramolecular transitions change markedly as a result of intermolecular interaction of the tetrapyrrole with its own counterions [3,4]. Fluorescence quenching of tetrapyrroles by oxygen has been studied in detail [5,6].…”

“…Results and Discussion. As the amount of ethanol in aqueous ethanol solutions of H 2 TSPP is increased (tõ 40-50 vol %), the porphyrin converts from the dissociated form to the undissociated one [3,4,7,12]. This lengthens the fluorescence lifetime of H 2 TSPP from ~10.6 to ~13.5 nsec (Fig.…”