title: CO2 triggering and controlling orthogonally multiresponsive photochromic systems.
abstract: We report a new generic method of reversibly controlling the photochromism of spiropyrans. It was found that the photochromic effect of spiropyrans can be reversibly switched on and off by addition and removal of carbon dioxide (CO(2)) to spiropyran in alcohol solutions containing an amidine (i.e., DBU) that acts as a CO(2) sensitizer. Spiropyrans are not photochromic in the presence of DBU but photochromic when CO(2) is subsequently added to the solution. The CO(2) is readily removed by inert gas bubbling, thus allowing facile activation and deactivation of the photochromic effect. Carbon dioxide, without the presence of the sensitizing amidine, had no effect on photochromism of the spiropyrans. Other photochromic dyes classes such as spirooxazines and chromenes are not affected by this CO(2)/DBU stimulus. As a result, orthogonal activation of mixtures of spirooxazines and spiropyrans was achieved to provide four color states (clear, yellow, green, and blue) by varying the combinations of the stimuli of UV, visible light, CO(2), and CO(2) depleted. This finding now permits the many applications using spiropyrans to be CO(2) responsive.
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia. tamim.darwish@ansto.gov.au
authors.forename: Tamim A
authors.initials: TA
authors.lastname: Darwish
authors.forename: Richard A
authors.initials: RA
authors.lastname: Evans
authors.forename: Michael
authors.initials: M
authors.lastname: James
authors.forename: Nino
authors.initials: N
authors.lastname: Malic
authors.forename: Gerry
authors.initials: G
authors.lastname: Triani
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Hanley
mesh_terms: D000578:Amidines / Q000737:chemistry; D001578:Benzopyrans / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry*; D055668:Photochemical Processes
chemical_list: D000578:Amidines; D001578:Benzopyrans; D007211:Indoles; D009574:Nitro Compounds; C088184:spiropyran; D002245:Carbon Dioxide