M. David Maree

Effects of axial ligands on the photophysical properties of silicon octaphenoxyphthalocyanine

The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.

Silicon octaphenoxyphthalocyanines: photostability and singlet oxygen quantum yields

Abstract Photochemical properties of series of axially substituted silicon octaphenoxyphthalocyanines with aryloxy, siloxy, aminoalkoxy, esters of carboxylic acids and sulphonic acid esters residues as axial ligands were studied in dimethylsulfoxide (DMSO) solution. It was found, that under Q-band excitation axial ligands in compounds studied have the propensity to be changed by hydroxyl groups with quantum yields in the range 10 −5 to 10 −2 depending on the nature of the axial ligand. Axial substituent phototransformation was followed by slow photobleaching of dihydroxysilicon octaphenoxyphthalocyanine (photoproduct) in self-sensitized singlet oxygen mediated oxidation of the macrocycle. Singlet oxygen quantum yields were found to be in the range 0.15–0.20 for majority of the phthalocyanines (Pc) studied.

Influence of cyclodextrins on the fluorescence, photostability and singlet oxygen quantum yields of zinc phthalocyanine and naphthalocyanine complexes

The effects of formation of cyclodextrin inclusion complexes on the photochemical and photophysical properties of zinc phthalocyanine (ZnPc) and various peripherally substituted zinc phthalocyanines as well as zinc naphthalocyanine (ZnNPc) are investigated. The cyclodextrins employed were the hydroxypropyl-γ-cyclodextrin and unsubstituted β-cyclodextrin. Jobs plots were employed to confirm the stoichiometry of the inclusion complexes and showed 2:1 and 4:1 (cyclodextrin:phthalocyanine) inclusion behavior. The phthalocyanine inclusion complexes showed larger singlet oxygen quantum yield (ϕΔ) values when compared to the free phthalocyanines before inclusion, for complexes 1 (zinc naphthalocyanine), 2 (zinc tetranitrophthalocyanine) and 4 (zinc tetra-tert-butylphenoxyphthalocyanine). The fluorescence quantum yields generally remained unchanged following inclusion.

Synthesis, electrochemical and spectroelectrochemical studies of octaphenylthio-substituted phthalocyanines

Cobalt (4) and iron (5) phenylthio-substituted phthalocyanines (MPc(SR)8) have been synthesized and characterized. Cyclic square wave voltammetry in dimethylformamide containing tetrabutylammonium perchlorate revealed five and six redox processes, respectively, for complexes 4 and 5. The complexes are easier to reduce compared to the corresponding unsubstituted MPc and to butylthio substituted derivatives. The first oxidation and reduction occurs on the metal for both complexes. Spectroelectrochemistry (in dimethylformamide containing tetrabutylammonium perchlorate) was employed to assign the cyclic voltammetry peaks, and gave spectra characteristic of FeIPc for reduction of 5 and CoIPc for the reduction of 4. The spectrum of the former is particularly of importance since such species have not received much attention in the literature.

Synthesis and photophysical properties of a covalently linked porphyrin-phthalocyanine conjugate

The synthesis of a phthalocyanine-porphyrin heteropentamer (zinc(II) tetra(5-phenoxy-10,15,20-triphenylporphyrin)) zinc(II) phthalocyanine, (ZnPc-(ZnTPP)4), containing four units of zinc tetraphenylporphyrin linked to a central zinc phthalocyanine macrocycle via an ether linkage is reported. The photophysical parameters of the pentamer are reported in toluene and dimethyl sulfoxide (DMSO). The observed differences in the fluorescence behavior of the pentamer in the two solvents is explained in terms of emission from different states; charge transfer state in DMSO and locally excited state in toluene. The rate constants for fluorescence, intersystem crossing, internal conversion, and of charge and energy transfer are reported for the pentamer. Quantum yields for fluorescence, internal conversion, triplet state and of charge and energy transfer are also reported for the pentamer, ZnPc-(ZnTPP)4 and the mixture of ZnPc and ZnTPP. The latter two parameters are higher in the pentamer compared to a mixture containing ZnPc and ZnTPP.

Solvent-free axial ligand substitution in octaphenoxyphthalocyaninato silicon complexes using microwave irradiation

Several axially substituted octaphenoxy silicon phthalocyanines were prepared by condensation of the complexes used as axial ligands with octaphenoxyphthalocyaninato (dichloro) silicon under microwave irradiation.

Effect of oligomerization on the photochemical properties of silicon octaphenoxyphthalocyanine

Abstract The photochemical properties of silicon octaphenoxyphthalocyanines (SiOPPc) oligomerized were studied in dimethylsulfoxide (DMSO) solutions. Oligomers containing 2–5 and 9 SiOPPc rings linked with terephthalate linkages were synthesized. Singlet oxygen quantum yields were found to be in the range 0.11–0.34, and increased with the number of rings up to five rings, a decrease in the quantum yield was observed for nine rings. This is explained in terms of the high aggregation of the oligomer containing nine rings.

Photochemical and photophysical properties of pentoxy- and naphthaloxy appended magnesium and zinc phthalocyanines

Photochemical and photophysical measurements were conducted on pentoxy and naphthaloxy appended zinc and magnesium phthalocyanines. We describe in this paper the synthesis as well as unexpected photodegradation behavior of naphthaloxy appended magnesium phthalocyanines. General trends are described for quantum yields of photodegradation, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds.

Synthesis and photochemical characterization of a zinc phthalocyanine–zinc porphyrin heterotrimer and heterononamer

The synthesis of two phthalocyanine-porphyrin covalently linked heteromolecules are described. Intramolecular energy transfer is investigated and quantified in terms of the quantum yield of energy transfer and found to be highly effective in both molecules. The photophysical properties of both molecules are modified greatly by the presence of the porphyrin moieties on the phthalocyanine core.

The observation of room temperature delayed fluorescence in various non-peripherally substituted phthalocyanines

The first observation of direct room temperature delayed fluorescence from non-peripherally substituted phthalocyanines is reported. The quantum yields of delayed fluorescence and delayed fluorescence lifetimes were determined and are discussed. The normal fluorescence quantum yields and photodegradative quantum yields of these compounds were also determined.