Narrow Results

A variety of aromatic and aliphatic aldehydes were oxidized to the corresponding carboxylic acids in the presence of platinum porphyrin, sunlight and air in acetonitrile solvent under mild conditions. Nitrobenzaldehydes were found to be very efficient ¹O₂ scavengers that quench the formation of acids from any aldehyde in the presence of free-base porphyrin sensitizers. However, nitrobenzaldehydes were converted to the corresponding acids in the presence of platinum porphyrins. The platinum porphyrins are very good and efficient catalysts for a wide range of applications in the aerobic conversion of aldehydes to acids.

3${}^{\mathrm{\text{2}}}$-Carboxy-pyropheophorbides-$a$ possessing a variety of $N$-substituted carbamoyl groups at the 17${}^{\mathrm{\text{2}}}$-position were prepared by modifying naturally occurring chlorophyll-$a$. 3${}^{\mathrm{\text{2}}}$-Methoxycarbonyl-pyropheophorbide-$a$ was obtained via the protection of the 17${}^{\mathrm{\text{2}}}$-carboxy group with an allyl group, and amidated with various primary and secondary amines at the free 17-propionate residue, followed by the acidic hydrolysis of the methyl ester in the 3-substituent to give the desired pyropheophorbide-$a$ secondary and tertiary amides, respectively, bearing the trans-3${}^{\mathrm{\text{2}}}$-COOH. The synthetic pigments potentially usable for dye-sensitized solar cells gave almost the same optical properties in a solution.

In order to improve the efficacy of photochemical properties for photodynamic therapy (PDT) applications, carboxylic acid groups axially conjugated with silicon(IV) and at the peripheral position with zinc(II) phthalocyanine skeletons for new photosensitizers to investigate the influence of the COOH group positions on the photophysicochemical performance are described in this study. Silicon (IV) (3 and 5) and zinc (II) (7) phthalocyanines were characterized by UV-vis, FTIR, ¹H-NMR, MALDI-TOF MS and elemental analysis spectral data. Furthermore, the photophysical (fluorescence quantum yields and fluorescence quenching studies), photochemical (photodegradation and singlet oxygen generation) and aggregation properties of the newly synthesized phthalocyanines were investigated in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solutions. The results were compared with that of zinc and silicon phthalocyanines. Singlet oxygen quantum yields ranged from 0.23 to 0.63 via Type II mechanism under the experimental conditions studied. The fluorescence of the phthalocyanine complexes (3, 5 and 7) is effectively quenched by 1,4-benzoquinone (BQ) in DMSO, DMF and THF.

Four asymmetric Zn(II) phthalocyanines (Pc1–Pc4) bearing a carboxylic acid group in the peripheral position have been designed and synthesized to investigate the influence of the distance between COOH group and the phthalocyanine core on their photophysical and photochemical properties. The novel phthalocyanine complexes were characterized by ${}^{\mathrm{\text{1}}}$H, ${}^{\mathrm{\text{13}}}$C NMR, IR, and UV-vis spectroscopies, elemental analysis and matrix-assisted laser desorption ionization mass spectrometry (MALDI). The aggregation behavior, photophysical and photochemical properties such as fluorescence lifetime and quantum yields and singlet oxygen quantum yields of Pc1–Pc4 were explored in tetrahydrofuran (THF) to the determination of the potential use of these novel phthalocyanines as photosensitizers for different applications such as photovoltaic technologies and photodynamic therapy (PDT). Pc1–Pc4exhibited high singlet oxygen generation quantum yields (0.84, 0.66, 0.88 and 0.65, respectively). Fluorescence quantum yields could be obtained for Pc1, Pc2, Pc3 and Pc4 (0.13, 0.31, 0.10 and 0.25, respectively) in THF.

Four asymmetric Zn(II) phthalocyanines (Pc1–Pc4) bearing a carboxylic acid group in the peripheral position have been designed and synthesized to investigate the influence of the distance between COOH group and the phthalocyanine core on their photophysical and photochemical properties. The novel phthalocyanine complexes were characterized by ¹H, ¹³C NMR, IR, and UV-vis spectroscopies, elemental analysis and matrix-assisted laser desorption ionization mass spectrometry (MALDI). The aggregation behavior, photophysical and photochemical properties such as fluorescence lifetime and quantum yields and singlet oxygen quantum yields of Pc1–Pc4 were explored in tetrahydrofuran (THF) to the determination of the potential use of these novel phthalocyanines as photosensitizers for different applications such as photovoltaic technologies and photodynamic therapy (PDT). Pc1–Pc4 exhibited high singlet oxygen generation quantum yields (0.84, 0.66, 0.88 and 0.65, respectively). Fluorescence quantum yields could be obtained for Pc1, Pc2, Pc3 and Pc4 (0.13, 0.31, 0.10 and 0.25, respectively) in THF.

Today, fossil carbon provides us with fuels (energy), polymers (packaging, insulating and building materials, household utensils, glues, coatings, textiles, 3D-printing inks, furnitures, vehicle parts, toys, electronic and medical devices, etc.) and biologically active substances (drugs (Chapter 9), flavorings, fragrances, food additives, plant protection products, etc.). In this chapter we discover the modern materials of our civilization which are very often polymers derived from oil. They are referred to as “plastics” (annual world production: 380 × 10⁶ tons). Their production consumes 8% of the crude oil extracted (ca. 5 billion tons per year). An increasing part of the plastics originates from renewable resources (less than 10% today, see Section 11.10, bio-sourced plastics). Plastics make life easy for us, but at the underestimated cost of damage to our environment (Figure 8.1) and our health. They contaminate the hydrosphere and the agricultural soil. The atmosphere is also contaminated by microplastics…

Syngas is a mixture of carbon monoxide (CO) and molecular hydrogen (H₂) that can be converted into a host of industrial feedstocks including fuels such as gasoline, fuel oil and kerosene. We examine what are the most abundant sources of these two gases and describe some important transformations that continue to fascinate scientists because, with a reactant as simple as CO, which contains only one carbon atom, catalysts allow to condense it with H₂ and to form C–C bonds even though all oligomers of the (CO)_n type (n = 2, 3, …) are kinetically and thermodynamically unstable. Let us recall here that thanks to photosynthesis, Nature builds C–C bonds (e.g. D-glucose) from CO₂ and H₂O and solar light! (Section 1.4.2, reaction (1.8), Figure 1.10)…