New large refractive-index change materials: Synthesis and photochemical valence isomerization of the calixarene derivatives containing norbornadiene moieties

We have examined the synthesis of cyclic oligomers with pendant norbornadiene (NBD) moieties based on the calixarenes [p-tert-butylcalix[8]arene (BCA), p-methylcalix[6]arene (MCA), calix[4]resorcinarene (CRA), 2,8,14,20-tetra-decylcalix[4]resorcinarene (CRA(10)), and 2,8,14,20-tetrakis(p-hydroxyphenyl)calix[4]resorcinarene (CRA(ph))]. The photochemical valence isomerization of the obtained calixarene derivatives containing NBD moieties proceeded very smoothly to afford the corresponding quadricyclane (QC) moieties, and it was found that the large refractive-index changes (Deltan's = 0.028-0.061) before and after photo-isomerization.