Studies on Properties of p ‐Nitrophenylazo Calix[4]arene Derivatives

The p ‐nitrophenylazo calix[4]arene derivatives 1a‐1d with nonlinear optical (NLO) properties were prepared by the diazo‐coupling reaction of calix[4]arene with p ‐nitrophenyl diazonium. The diazotization reaction of p ‐nitroaniline was carried out with isoamyl nitrite as a source of nitrous add in EtONa/EtOH under refluxing condition. X‐Ray crystallographic analysis and 1 H NMR spectra reveal that they exist as cone conformation in crystal state or in solution. HRS measurements at 1064 nm in THF indicate that p ‐nitro‐phenylazo calix[4]arenes have higher hyperpolarizability β z values than the corresponding reference compound 4‐(4‐nitrophenylazo)‐2, 6‐dimethyl‐phenol, without red shift of the charge transfer band. The tetrakis p ‐nitrophenylazo calix[4]arene (2) with longer alkyl chains can form monolayer at the air/water interface.