Journal of Porphyrins and Phthalocyanines

The valence electronic properties of some unsubstituted and peripherally substituted oxo-titanium phthalocyanines are reported. Semiempirical quantum chemical calculations show that the nature of peripheral substituents has a strong bearing on the valence electronic properties, including the state dipole moments and absorption wavelength. The non-linear optical response was measured around the the Q-band resonance. The effect of different substituents and substitution patterns on the non-linear behaviour of the samples was determined. The combined results suggest that tuning of electronic and optical properties is effectively achieved by functionalization of the edges of the conjugated ring.

Soluble and less soluble phthalocyaninatocopper(II) derivatives (4a and 4b) were prepared from the corresponding 7-[(4′-benzo-15-crown-5)oyl]-15, 16-dibromo-2,3,6,7,8,9,11,12-octahydro-5H-benzo[e]-[1,4,10,13,7] tetraoxaazacyclopentadecine (3a) and 7-(2′-tosylaminoethyl)-15, 16-dibromo-2,3,6,7,8,9,11, 12-octahydro-5H-benzo[e]-[1,4,10,13,7] tetraoxaazacyclopentadecine (3b) and CuCN in pyridine. A less soluble novel multifunctionalized scorpiand macrocycle-substituted phthalocyanine (4c) in which an NH₂CH₂CH₂— chain is appended to a monoazacrown ether ring was obtained by detosylation of 4b with concentrated sulfuric acid.

Experimental and calculated absorption spectra are compared for four different porphyrin dimers covalently linked by alkyl- or phenyl bridges. The spectra of the corresponding monomers were used as a reference to determine the experimental exciton,ic shift(s) of the absorption spectrum in the Soret region. The excitonic interaction was calculated using the point dipole approximation and taking into account the restricted conformational freedom of the monomeric units in the dimers due to steric constraints. The constraints were independently verified by magnetic dipole-dipole broadening of the EPR spectra of several (CuTPP)_2^-substituted dimers. The observed and calculated absorption spectra agree at least semiquantitatively.

We report on the synthesis of cobalt 2,3,9,10,16,17,23,24-octakis(2-ethylhexyloxy)phthalocyanine. This complex, when pre-adsorbed onto graphite electrodes, is active for the electro-oxidation of 2-mercaptoethanol. Its activity is higher than that of cobalt phthalocyanine and cobalt tetrasulfonated phthalocyanine adsorbed on graphite. The voltammetric response of adsorbed cobalt 3,4-octaethylhexyl- oxyphthalocyanine exhibits both Co(II)/Co(I) and Co(III)/Co(II) reversible processes. However, the Co(III)/Co(II) couple shows a pH dependence that is different from that reported for other cobalt phthalocyanine derivatives. The much higher activity of cobalt 3,4-octaethylhexyloxyphthalocyanine compared with cobalt tetrasulfonated phthalocyanine and cobalt phthalocyanine is attributed to the electron-donating ability of the ethylhexyloxy substituents on the periphery of the phthalocyanine ligand.

The luminescence properties at room temperature and 77 K of octamethylcorrole are reported for the first time, together with the photophysical behaviour of corrole-corrole and porphyrin-corrole dyads covalently linked through the 10-position with a phenyl bridge. The photophysical properties of corrole free base are very similar to those of the porphyrin analogues, whereas the dimeric systems show luminescence bands different from those of the parent monomers, indicating an unexpectedly high degree of interaction between the chromophores. The porphyrin-corrole dyad undergoes photocatalysed ring opening of the corrole moiety to give the corresponding porphyrin-biliverdin species.

The new phthalocyanine-like macrocycle tetrakis(selenodiazole)porphyrazine, TSeDPzH₂, and its Mg(II) and Cu(II) complexes have been prepared and their general, spectroscopic (IR, UV-vis), and magnetic properties investigated. It has been observed that the peripheral selenodiazole rings of the TSeDPz skeleton can be opened by the action of H₂S, with release of the Se atoms and formation of a new macrocycle, i.e. octaaminoporphyrazine, which is easily converted into tetrakis(pyrazino)porphyrazine derivatives.

In order to apply photodynamic therapy to pigmented neoplasms, comparative photosensitizing studies of B16 pigmented melanoma in C57B1/6 mice were carried out with haematoporphyrin derivative (HpD), zinc(II) phthalocyanine (ZnPc), zinc(II) naphthalocyanine (ZnNc) and tetrabenzamido-substituted zinc(II) naphthalocyanine (ZnNcA). By injection of the optimal drug concentration and application of the optimal dose of light irradiation (the emission of the laser dye corresponding to the λ_max value of the respective sensitizer) a phototherapeutic effect was observed only after photosensitization with the longest-wavelength-absorbing sensitizer, namely ZnNcA. It is supposed that the detected, through different assessment criteria, promising phototherapeutic effect after ZnNcA photosensitization of B16 pigmented melanoma in mice is due to suitable structural, photophysical and photochemical properties of this sensitizer, but not due to a hyperthermic effect. This assumption is supported by the results obtained after irradiation of B16 pigmented melanoma-bearing mice with the same fluence rate and fluence but without the sensitizer. In this case the tumour temperature did not increase by more than 35 °C and no changes in the mean tumour diameter or in the malignant subcellular components were detected.