Resorcinarene-dendrimers with stilbene moieties for optoelectronics

Dendrimers with resorcinarene core and π-conjugated dendron branches with 16 and 32 stilbene groups have been synthesized and characterized by 1H and 13C NMR, FTIR, UV–vis, fluorescence spectroscopy, MALDI-TOF, electrospray or FAB+ mass spectrometry, and elemental analysis. Homogeneous thin films of resorcinarene-dendrimers deposited on quartz, glass or ITO substrates were prepared by spin-coating. All the materials showed absorption in the UV region in both chloroform solutions and thin films. The band gap energies (Eg) determined from both UV–vis spectroscopy and voltammetry were in the semiconducting range. A slight decrease in the Eg values was observed when passing from the first generation of dendrimers to the second one, which can be attributed to an increase in the π-conjugated system. The fluorescence quantum yield of the molecules in solution was low and practically null in the solid state. Nevertheless, a very interesting behavior was observed in the reductive voltammetric cycle, where electrochromism from transparent to blue forms occurred in the film by n-doping process; property that makes these materials suitable for the development of electrochromic devices such as smart windows.