Monoterpene-based metallophthalocyanines: Sustainable synthetic approaches and photophysical studies

Tetra-substituted zinc(II) and copper(II) phthalocyanines bearing peripheral alkoxy-monoterpene groups were prepared by conventional vs. non-conventional synthetic approaches (ultrasound and microwave irradiation). The synthesis of (1[Formula: see text]-(–)-myrtenol (a) and (1[Formula: see text],2[Formula: see text],5[Formula: see text]-([Formula: see text]-menthol (b) derived phthalonitrile precursors was performed through ipso-nitro aromatic substitution reactions, with optimal conditions being obtained using ultrasound irradiation, which allowed us to achieve full conversions in 4.5 h, with isolated yields up to 74%. The subsequent cyclotetramerization of monoterpene-based phthalonitriles was carried out using Zn(II) or Cu(II) salts as metal templates, and also using conventional and non-conventional heating methods. Microwave-assisted synthesis was shown to be the most efficient approach, providing complete conversions in 1 h, yielding the target monoterpene-based metallophthalocyanines in up to 70% isolated yields. Furthermore, photophysical and photochemical studies revealed that Zn(II) phthalocyanines possess fluorescence quantum yields in the range of [Formula: see text] 0.27–0.29, while Cu(II) phthalocyanines exhibited room temperature phosphorescence. In addition, the monoterpene-based Zn(II) phthalocyanines led to high singlet oxygen quantum yields ([Formula: see text] 0.55–0.69).

Nitrobenzene method: A keystone in meso-substituted halogenated porphyrin synthesis and applications

This review article briefly describes the available synthetic approaches for meso-arylporphyrins giving particular emphasis for one-pot nitrobenzene and nitrobenzene/NaY methods regarding the synthesis of meso-halogenated arylporphyrins. The review also describes the relevant applications of these halogenated porphyrins and their metalloporphyrin counterparts, prepared via nitrobenzene method, as photosensitizers for therapy (PDT and PDI), diagnostic (molecular contrast agents) and also for catalytic oxidation and CO2 cycloaddition reactions to epoxides.

Synthesis of meso-substituted porphyrins using sustainable chemical processes

The easy access and low price of pyrrole and aldehydes, conjugated with the simplicity in preparing meso-substituted porphyrins, makes this type of porphyrins very attractive for a broad range of applications. However, there is an increasing demand for the development of new synthetic processes involving more sustainable chemical principles substituting, whenever possible, dangerous organic solvents by alternative solvents, chromatographic purifications by precipitations and energy-intensive procedures by alternative energy sources such as microwaves and ultrasounds. In this review we will address some recent strategies to synthesize meso-substituted porphyrins using alternative energy sources, reaction media and catalysts, namely microwave irradiation, water as solvent, or solid microporous acid catalysts.