Solvatochromic and Photochromic Behavior of Spiropyran-cored PAMAM Dendron and Cu2+-Selective Sensing

Spiropyran-cored polyamidoamine (PAMAM) dendrons (SP-PAMAMs) were prepared and their solvatochromic and photochromic properties investigated. As with simple merocyanine (MC), MC-PAMAM shows negative solvatochromism. On UV irradiation, colorless SP-PAMAM transforms into colored MC-PAMAM and the reaction occurs a little faster in a more polar solvent. In the dark, MC-PAMAM returns to SP-PAMAM much more slowly in a more polar solvent. On addition of Cu2+, the color of SP-PAMAM solution in acetonitrile changes from colorless to orange, whereas neither color change nor absorption spectral changes are observed with the addition of other metal cations.