Two-photon excited white-light emission from natural camptothecin derivatives

Developing single-molecule white-light-emitting (WLE) materials from natural resources is significant in sustainable optoelectronics, however, achieving efficient emission via nonlinear optical processes remains challenge. Herein, we report a generalized strategy to achieve tunable multicolor and high-quality two-photon excited white-light emission from camptothecin (CPT) and a diverse library of its derivatives including 9-(dimethylamino)-10-hydroxycamptothecin (9NCPT), 7-Ethyl-10-hydroxycamptothecin (7ECPT), 10-Methoxycamptothecin (10MOCPT), which was regulated via solvent-mediated excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) processes. Through precise modulation of the equilibrium between neutral and ionized species of CPT derivatives within binary solvent systems, complementary blue and yellow emissions are combined to yield white light with high quantum efficiency. These natural scaffolds were found to possess exceptional intrinsic two-photon absorption (TPA) cross-sections, with 10MOCPT reaching 833.58 GM, firstly enabling two-photon excited white-light emission from natural product-derived scaffolds under near-infrared excitation. Furthermore, the versatility of these emitters is highlighted through the construction of a supramolecular WLE system via host-guest assembly with a ruthenium-based metal-organic cage. This work not only connects natural product chemistry with nonlinear optics but also provides a novel platform for designing multifunctional, sustainable two-photon luminescent materials.