Cold photo-carving of halogen-bonded co-crystals of a dye and a volatile co-former using visible light

• Published in: Nature chemistry 2022-05, Vol.14 (5), p.574-581
• Main Authors: Borchers, T. H., Topić, F., Christopherson, J.-C., Bushuyev, O. S., Vainauskas, J., Titi, H. M., Friščić, T., Barrett, C. J.
• Format: Article
• Language: English
• Subjects: 639/638/298/398; 639/638/541/961; 639/638/541/963; Analytical Chemistry; Azo compounds; Azo dyes; Biochemistry; Bonding strength; Burning; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Covalent bonds; Crystallization; Crystals; Dyes; Electromagnetic absorption; Engraving; Evaporation; Fluorination; Inorganic Chemistry; Ion beams; Irradiation; Laser beams; Lasers; Machining; Materials selection; Metals; Organic Chemistry; Physical Chemistry; Polymers; Pyrazine; Recrystallization
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/s41557-022-00909-0

The formation of co-crystals by the assembly of molecules with complementary molecular recognition functionalities is a popular strategy to design or improve a range of solid-state properties, including those relevant for pharmaceuticals, photo- or thermoresponsive materials and organic electronics. Here, we report halogen-bonded co-crystals of a fluorinated azobenzene derivative with a volatile component—either dioxane or pyrazine—that can be cut, carved or engraved with low-power visible light. This cold photo-carving process is enabled by the co-crystallization of a light-absorbing azo dye with a volatile component, which gives rise to materials that can be selectively disassembled with micrometre precision using low-power, non-burning laser irradiation or a commercial confocal microscope. The ability to shape co-crystals in three dimensions using laser powers of 0.5–20 mW—substantially lower than those used for metals, ceramics or polymers—is rationalized by photo-carving that targets the disruption of weak supramolecular interactions, rather than the covalent bonds or ionic structures targeted by conventional laser beam or focused ion beam machining processes. Halogen-bonded co-crystals of a fluorinated azobenzene derivative and a volatile co-former can be cut, carved or engraved with micrometre-scale precision using low-power visible light. The proposed mechanism involves the local evaporation of the volatile component followed by recrystallization of the azobenzene co-former near the edge of the irradiation area.