Tripodal aza crown ether calix[4]arenes, 5a, 5b, 6a and 6b, have been synthesized. The structure of protonated 5a was elucidated by X-ray crystallography to be a self-threaded rotaxane. Complexation studies of 5a and 5b towards anions using Na+ as countercation were carried out by H-1 NMR titration in dimethylsulfoxide-d(6) and the mixture of chloroform-d and methanol-d(4), respectively. Ligands 5a and 5b were able to form 1:1 complexes with Br-, I- and NO3- and the complexation stability varied as follows: NO3- >I->Br-. The effect of countercation on anion complexation was also investigated. The results showed that the association constants of 5a towards Br- in the presence of various cations varied as K+>Bu4N+>Na+. The enhancement in anion complexation ability of 5a may result from the rearrangement of the tripodal ammonium unit in the presence of K+. The neutral forms, 6a and 6b, were able to form complexes with transition metal ions such as Co2+, Ni2+, Cu2+ and Zn2+. The stability of the complexes followed the sequence: Ni2+