[eng] Ab initio calculations were performed on complexes between cations and s-triazine, which has a small and positive quadrupole moment. Minimum energy ð-complexes were found between s-triazine and cations. Minimum ð-complexes with anions were previously reported. This ability of s-triazine to form stable complexes with either anions or cations is studied using several theoretical methods. A likely explanation of this duality is the stabilization obtained from the ion-induced polarization.