Green synthesis of xanthene derivatives through visible light-driven photocatalysis using blackberry dye-sensitized TiO₂

Researchers are actively exploring novel approaches to sustainable chemistry, aiming to reduce environmental harm while optimizing efficiency. One promising approach is visible light photocatalysis, which enables organic transformations under mild conditions. This research investigation focuses on the synthesis of xanthene derivatives (12-Aryl/hetroaryl-8,9,10,12-tetrahydrobenzo [a] xanthen-11-oness) via a three-component, one-pot condensation reaction of 2-naphthol, dimedone, and aldehydes using visible light-responsive TiO₂ nanoparticles sensitized with blackberry dye. A comparative analysis was conducted between pristine TiO₂ nanoparticles and blackberry dye-sensitized TiO₂ (BB dye-TiO₂) to evaluate their photocatalytic activities. The results unequivocally demonstrated the superior photocatalytic activity of BB dye-TiO₂ compared to pristine TiO₂ nanoparticles. The study determined the optimal operating conditions for achieving an efficient photocatalytic synthesis of xanthene derivatives and proposed a mechanism for the photocatalytic process. The optimized conditions for photocatalytic synthesis with a yield of 98% included a reaction time of 30 min, a light intensity of 100 mW/cm², and a photocatalyst concentration of 1 g/L. Moreover, the reusability test revealed that the BB dye-TiO₂ maintained its photocatalytic activity for up to four runs, with only a slight decrease observed. This study highlights the immense potential of natural dye sensitization and visible light photocatalysis for sustainable chemical synthesis, effectively bridging the realms of green chemistry and synthetic organic chemistry.