The synthesis of a novel class of molecules for second order nonlinear optics, i.e. calixarenes with extended π-systems, is described. These compounds are obtained via Wittig-Horner reactions of the formylated calixarenes 5 and 6 to give the stilbene derivatives 7-9, or by diazotization of calixarene, 1, followed by alkylation to give the phenylazocalixarenes 11 and 12. The molecular second order nonlinear optical properties (βz) of these calixarenes have been measured by electric field-induced second harmonic generation. The influence of different acceptors as well as the influence of the different conformations of the calixarenes on βz values were determined. Surprisingly, the wavelength of the charge-transfer band λmax is lower when βz increases upon increasing the number of acceptors.