Narrow Results

Theoretical calculations have been carried out to study the mechanism of intermolecular hydroacylation of acetylene with acetaldehyde. The results indicate that the generally accepted mechanism, C–H oxidative addition followed by hydrometallation and reductive elimination, is the most favorable pathway. The intermolecular hydroacylation reaction of acetylene is shown to suffer from three problems: (1) the formation of a stable bis-acetylene intermediate, which leads to a facile dimerization side-reaction; (2) higher activation barrier of the rate-determining C–H (carbonyl) bond activation; and (3) "fatal" easy decarbonylation from hydrometalated intermediate and subsequent reductive elimination to give decarbonylation product. Our calculations indicate that the above three problems can all be overcome by the use of a tethered carbonyl substrate with a chelation-forming basic donor ligand such as alkylthio group.

A new luminescent and thermally stable platinum(II) polyyne polymer trans-[–Pt(PBu₃)₂C≡CArC≡C–]_n (P1) containing the 2,7-fluorene chromophoric spacer substituted by pendant carbazolyl group via long alkyl bridges. The regiochemical structures of these compounds were studied by various spectroscopic analyses. We report the photophysical properties of this group 10 polymetallayne and a comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt₃)₂C≡CArC≡CPt(Ph)(PEt₃)₂] (M1) as well as to those with non-carbazole-containing fluorene spacer (P2 and M2). Upon photoexcitation, each of P1 and M1 emits an intense purple-blue fluorescence emission in the near-UV to visible region in dilute fluid solutions at room temperature. Harvesting of organic triplet emissions harnessed through the strong heavy-atom effects of platinum metal was examined and at 77 K, each of the metalated compounds displayed dual emission bands, viz. both the fluorescence and the lower-lying phosphorescence. Spectroscopic results revealed that the formation of excimers was suppressed by introducing carbazole side groups. The spatial extent of the lowest singlet and triplet excitons in P1 and M1 was fully elucidated. Such organometallic poly(fluorenyleneethynylene)s anchored with the carbazole pendants was found to have an improved thermal stability and suppressed aggregation.

The review aims at being an exhaustive summary of the use of Huisgen azide-alkyne dipolar addition in the synthesis of tetrapyrrolic compounds, mainly porphyrins, phthalocyanines, chlorins and bacteriochlorins.

Click chemistry has become a very popular and efficient concept for synthetic chemists for the construction of new molecules. Among the click chemistry approaches known to date, it is undoubted that the copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) has played a key role. Such reactions in general offer virtually unlimited possibilities to prepare new molecules for $e.g$. materials science applications. As such, the synthesis of porphyrin–fullerene conjugates obtained via CuAAC are summarized within the present review article.

To improve conjugation between a central porphyrin core and its peripheral fluorenyl antennae, we have introduced in the meso-tetrafluorenyl porphyrin (TFP-Bu) unit an ethynyl spacer at the meso positions. By this means, we have synthesized and characterized a new meso-alkynyl fluorenyl porphyrin (TAFlP). We discuss the effect of this extra extension of the $\pi$ manifold on the optical properties. This enlarged porphyrin core, TAFlP, is foreseen as a key building block for the design of new dendrimers for theranostic applications. The constant improvement of porphyrin-based dendrimers featuring conjugated fluorenyl dendrons is recalled herein and demonstrates the important role of the central core structure in determining linear and nonlinear optical properties. Further improvement of these properties seems possible with TAFlP-like structures based on observations made for dendrimers recently obtained. This makes the exploration of such new molecular architectures appealing for photodynamic therapy (PDT) and related applications.

We report routes towards synthesis of novel $\pi$-conjugated freebase cobalt, copper, gallium and manganese meso-alkynylcorroles. UV-vis spectra show that extensive peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of $\pi$-conjugation. Using density functional theory (DFT), we have carried out a first theoretical study of the electronic structure of these metallocorroles. Decreased energy gaps of about 0.3–0.4 eV between the HOMO and LUMO orbitals compared to the corresponding copper, gallium and manganese meso-5,10,15 triphenylcorrole are observed. In all cases, the HOMO energies are nearly unperturbed as the $\pi$-conjugation is expanded. The contraction of the HOMO–LUMO energy gaps is attributed to the lowered LUMO energies.

To improve conjugation between a central porphyrin core and its peripheral fluorenyl antennae, we have introduced in the meso-tetrafluorenyl porphyrin (TFP-Bu) unit an ethynyl spacer at the meso positions. By this means, we have synthesized and characterized a new meso-alkynyl fluorenyl porphyrin (TAFlP). We discuss the effect of this extra extension of the π manifold on the optical properties. This enlarged porphyrin core, TAFlP, is foreseen as a key building block for the design of new dendrimers for theranostic applications. The constant improvement of porphyrin-based dendrimers featuring conjugated fluorenyl dendrons is recalled herein and demonstrates the important role of the central core structure in determining linear and nonlinear optical properties. Further improvement of these properties seems possible with TAFlP-like structures based on observations made for dendrimers recently obtained. This makes the exploration of such new molecular architectures appealing for photodynamic therapy (PDT) and related applications.

Some people think that carbon and sustainable development are not compatible. This textbook shows that carbon dioxide (CO₂) from the air and bio-carbon from biomass are our best allies in the energy transition, towards greater sustainability. We pose the problem of the decarbonation (or decarbonization) of our economy by looking at ways to reduce our dependence on fossil carbon (coal, petroleum, natural gas, bitumen, carbonaceous shales, lignite, peat). The urgent goal is to curb the exponential increase in the concentration of carbon dioxide in the atmosphere and hydrosphere (Figures 1.1 and 1.2) that is directly related to our consumption of fossil carbon for our energy and materials The goal of the Paris agreement (United Nations COP 21, Dec. 12, 2015) of limiting the temperature increase to 1.5 degrees (compared to the pre-industrial era, before 1800) is becoming increasingly unattainable (Intergovermental Panel on Climate Change (IPCC), report of Aug. 6, 2021). On Aug. 9, 2021 Boris Johnson, prime minister of the United Kingdom, declared that coal needs to be consigned to history to limit global warming. CO₂ has an important social cost…

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…