Studies on Properties of p-Nitrophenylazo Calixarene Derivatives

The p nitrophenylazo calixarene derivatives 1a-1d with nonlinear optical (NLO) properties were prepared by the diazo coupling reaction of calixarene with p nitrophenyl diazonium. The diazotization reaction of p nitroaniline was carried out with isoamyl nitrite as a source of nitrous acid in EtONa/EtOH under refluxing condition. X Ray crystallographic analysis and 1H 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 nitrophenylazo calixarenes 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 calixarene (2) with longer alkyl chains can form monolayer at the air/water interface.