Photo- and ionochromism of 5’-(4,5-diphenyl-1,3-oxazol-2-yl) substituted spiro[indoline-naphthopyrans]

Photo- and ionochromism of two spiro[indoline-naphthopyran] derivatives with a 4,5-diphenyl-1,3-oxazol-2-yl substituent at the 5’-position has been investigated. The cyclic forms exhibit fluorescence and phosphorescence. In the presence of metal ions such as Zn(II), Cu(II), Mn(II), Co(II), Ni(II), Cd(II) the merocyanine isomers of the 5’-(4,5-diphenyl-1,3-oxazol-2-yl) substituted spironaphthopyrans forms metal complexes whose composition and stability strongly depends on the nature of a metal ion. Zn(II), Cd(II) and Mn(II) ions form 1:1 complexes, whereas with Co(II), Ni(II) and Cu(II) ions the formations of 1:2 complexes was also observed. For the first time stepwise stability constants and spectral properties of the prepared mono- and bis-complexes have been determined. The complexes formed by Cd(II) and Zn(II) ions exhibit fluorescence in 580–700 nm spectral region. Complexes with Mn(II) at 77 K display unusual narrow band fluorescence with a maximum at 730–760 nm. At room temperature solutions of the complexes with Cd(II), Zn(II), Mn(II) demonstrate negative photochromic behavior which make them promising building blocks for the construction of photodynamic chemosensors for metal ions.