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 (E_g) determined from both UV–vis spectroscopy and voltammetry were in the semiconducting range. A slight decrease in the E_g 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.