Wavelength-Selective\nXanthene-Based Monochromophoric\nPhotoremovable Protecting Groups for Tuning Soft Matter Material Properties

Photocontrolled deprotection of specific functional groups\nhas\ngarnered significant interest over the past two decades. Notably,\nthe selective deprotection of distinct groups based on wavelength\nhas emerged as a prominent focus in recent research. The achievement\nof this objective has primarily involved the utilization of linker-based\nbichromophoric systems and diverse cocktail mixtures of photoresponsive\nprotecting groups (PRPGs), each responsive to varying wavelengths\nof light. Herein, we present the first wavelength-selective monochromophoric\nsystem based on a hydroxanthene moiety, enabling the wavelength-selective\nrelease of two distinct functionalities under 450 and 600 nm light,\nrespectively. The mechanism of the wavelength-selective photodegradation\nwas thoroughly investigated by <sup>1</sup>H NMR, UV–vis, and\nfluorescence spectroscopy, suggesting a proton-coupled electron transfer\nmechanism in the first photorelease step and electron transfer based\narylmethyl type of photorelease in the second step. The utility of\nthe xanthene-based wavelength-selective PRPGs was demonstrated in\nthe multistep degradation of microparticles and dual-color tuning\nof polymer chain architecture, thus opening an avenue to design advanced\nphotoreactive wavelength-controlled systems for applications in soft\nmatter materials.