Mechanistic Insight into the Light-Triggered CuAAC Reaction: Does Any of the Photocatalyst Go?

The attainment of transition-metal catalysis and photoredox catalysis has represented a great challenge over the last years. Herein, we have been able to merge both catalytic processes into what we have called "the light-triggered CuAAC reaction". Particularly, the CuAAC reaction reveals opposite outcomes depending on the nature of the photocatalyst (eosin Y disodium salt and riboflavin tetraacetate) and additives (DABCO, Et₃N, and NaN₃) employed. To get a better insight into the operating processes, steady-state, time-resolved emission, and laser flash photolysis experiments have been performed to determine reactivity and kinetic data. These results, in agreement with thermodynamic estimations based on reported data, support the proposed mechanisms. While for eosin Y (EY), Cu(II) was reduced by its triplet excited state; for riboflavin tetraacetate (RFTA), mainly triplet excited RFTA state photoreductions by electron donors as additives are mandatory, affording RFTA^•- (from DABCO and NaN₃) or RFTAH^• (from Et₃N). Subsequently, these species are responsible for the reduction of Cu(II). For both photocatalysts, photogenerated Cu(I) finally renders 1,2,3-triazole as the final product. The determined kinetic rate constants allowed postulating plausible mechanisms in both cases, bringing to light the importance of kinetic studies to achieve a strong understanding of photoredox processes.

Synthesis of vinyl-1,2,3-triazole derivatives under transition metal-free conditions

Synthesis of vinyl triazole derivatives with alkynes and triazoles promoted by an inorganic base under transition metal-free conditions is reported.

Nano- to Micro-Self-Aggregates of New Bisimidazole-Based Copoly(ionic liquid)s for Protecting Copper in Aqueous Sulfuric Acid Solution

This study presents the synthesis of two new bisimidazole-based copoly(ionic liquid)s (PILs) through multistep preparation routes. It is shown that the target PILs can display orderly molecular stacking, and nano- to micro-self-aggregates are yielded in aqueous sulfuric acid solution, which are characterized by various technologies including scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. The studied PIL aggregates show strong chemical adsorption onto the copper surfaces demonstrated by Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the anticorrosion performance of the studied PIL aggregates is shown using polarization curves and impedance spectroscopy. As a result, the target PIL aggregates show great corrosion inhibition performance to protect copper in aggressive acid medium.