Photochem, Volume 5, Issue 2 (June 2025) – 4 articles

Visible-light photoredox catalysis using biacetyl (BA) as a low-cost photosensitizer enables the efficient formation of triarylethylenes (TAEs) via a Mizoroki–Heck-type coupling. The reaction proceeds efficiently in acetonitrile upon blue LED irradiation under anaerobic conditions. Alternatively, supramolecular viscoelastic gels have also been explored as reaction media, allowing the possibility of working under aerobic atmosphere. Mechanistic investigations by means of transient absorption spectroscopy and quenching experiments support a charge-separated intermediate pathway. Reaction quantum yield measurements further validate the efficiency of BA, demonstrating its potential as an alternative to transition-metal catalysts. Overall, this work presents a sustainable and scalable strategy for TAEs synthesis, integrating photoredox catalysis with soft material engineering. These findings pave the way for broader applications in green chemistry and functional materials. Full article

IR-780 is a heptamethine cyanine dye that exhibits strong absorbance in the near-infrared region. Herein, we report IR-780 dye as a dual sensor for chromogenic cyanide detection and azide’s fluorogenic sensing in acetonitrile. Cyanide and hydroxide cause instant, dramatic color changes in the dye solution from green to yellow and dramatic spectral changes in the UV-Vis spectrum. The interaction of cyanide and hydroxide with the dye caused a dramatic decrease in the intensity of the strong absorption band at 780 nm and a concomitant band appearance at 435 nm. Other monovalent ions, including fluoride, chloride, bromide, iodide, dihydrogen phosphate, thiocyanate, acetate, and dihydrogen arsenate, caused no significant color or spectral changes. UV-Vis studies showed that the IR-780 dye is sensitive and selective to both ions. The detection limits for cyanide and azide are 0.39 µM and 0.50 µM, respectively. Interestingly, the IR-780 dye exhibited strong fluorescence at 535nm upon interaction with azide, while its initial emission at 809 nm was quenched. Both UV-Vis and fluorescence spectroscopy accomplished the detection of cyanide and azide using IR-780. Furthermore, the sensor’s effectiveness in fluorescence imaging of intracellular CN⁻ ions is demonstrated in live HeLa cells. Full article

This review examines the production of terephthalic acid via the oxidation of p-xylene, comparing catalytic and photocatalytic approaches. The commercial AMOCO process employs a cobalt/manganese/bromide catalyst system but requires harsh conditions, including high temperatures and acidic environments, raising environmental and safety concerns. While effective, its complexity and severe reaction conditions highlight the need for further optimization. In contrast, photocatalytic oxidation under milder conditions offers a more sustainable alternative. However, research on truly heterogeneous photocatalysts remains limited. The development of hybrid catalysts that exclude expensive noble metals holds promise for selective terephthalic acid production with minimal by-products. Advances in photocatalyst design—particularly in non-metallic and hybrid systems—could address key challenges such as limited light absorption and charge recombination, enhancing overall efficiency. Despite these advancements, maintaining high selectivity for terephthalic acid while minimizing by-product formation remains a critical challenge. Additionally, scaling up the photocatalytic process for industrial applications requires overcoming issues related to catalyst stability, recyclability, and cost-effectiveness. Continued research on improving catalyst performance and long-term stability will be essential for establishing photocatalytic oxidation of p-xylene as a viable and environmentally friendly route for terephthalic acid production. Full article

Porphyrins play important roles in biological systems including oxygen transport and catalysis. Due to their tetrapyrrole core structure, they exhibit exceptional photophysical and electrochemical properties and find many applications in both technical and life science fields, including photodynamic therapy and neurosurgery. The irradiation of porphyrins may cause modifications to their molecular structure or their degradation. Such photobleaching processes potentially affect the success and sensitivity of photosensitizer applications. While there have been many studies using fluorescence spectroscopy to investigate this phenomenon, reports about analytically validated structures of photoproducts are scarce. It is, however, necessary to know the individual contributions of different molecules to the fluorescence signal in order to evaluate it correctly. This review provides a summary of the current state of knowledge in this respect, discussing especially the validated hydroxyaldehyde and formyl photo-oxidation products of protoporphyrin IX. Full article