Tracking an Ultrafast C-S Bond Breaking in the UV-induced Sulfur-substituted 2-aminoazole

Numerous biologically active compounds in medicine derive their therapeutic properties from sulfur-bearing five-membered aromatic rings. These compounds are inherently photoactive, and their transient accumulation beneath the skin of living organisms or in sunlit water may lead to photodegradation under sunlight. Among them, 2-aminothiazole is widely known as a molecular scaffold employed in therapeutics, but its photochemical properties remain unknown. Our UV-irradiation experiments and quantum-chemical calculations reveal that substituting a ring sulfur in the 2-aminoazoles family enables absorption in the UV-B range and initiates an ultrafast ring-opening photochemical process through C-S bond cleavage. The resulting reactive intermediate, with a lifetime of ~80 ps, can undergo a reversal to the initial structure or the addition of water molecules to its structure, potentially altering therapeutic agents. Consequently, modified pharmaceutics might not perform their intended functions, trigger harmful effects on living organisms and could become pollution for the biosphere.