Photochromic spiropyran dendrimers: 'Click' syntheses, characterization, and optical properties

Resorting to 'click chemistry', four photochromic dendrimers, A-Tri-SP, B-Tri-SP, C-Tri-SP, and D-Hex-SP, have been synthesized facilely in sound yields of 85, 88, 94, and 80%, respectively. These dendrimers have been obtained by the straightforward coupling of azido-attached photochromic spiropyran units to acetylenic-terminated dendritic cores. The photochromic dendrimers show typical photochromic properties both in tetrahydrofuran solution and in poly (methyl methacrylate) film. They are demonstrated to be endowed with superior performance in comparison to the corresponding spiropyran monomer in terms of larger optical density, better stability of the open ring form, higher sensitivity towards the coordination of ferric ions, and better two-photon absorption properties.