Detection of cationic guest molecules by quenching of luminescence of a self-assembled host molecule consisting of terbium(III) and calix[4]arene-p-tetrasulfonates.

By self-assembly in aqueous solution, calix- (CAS) and thiacalix[4]arene-p-tetrasulfonate (TCAS) formed luminescent complexes Tb(III).(CAS)2 and Tb(III).TCAS, respectively, which were utilized as a host for cationic guests. Addition of 1-ethylpyridinium guest quenched luminescence of Tb(III).(CAS)2 in accordance with the Stern-Volmer (SV) relation with a low detection limit (D.L.) of 5.94 x 10(-8) M (S/N=3, M identical with mol dm(-3)). On the other hand, 1-ethylquinolinium quenched luminescence of Tb(III).TCAS most efficiently, affording a very low D.L. (6.71 x 10(-10) M). The agreement of the SV coefficients obtained with luminescent intensity (K(SV,all)=6.74 x 10(6) M(-1)) and lifetime (K(SV,Tb)=6.50 x 10(6) M(-1)) implied that dynamic quenching of 5D4 excited state of Tb(III) was predominant in the quenching processes. The quenching rate was estimated to be k(q,Tb)=9.94 x 10(9) M(-1) s(-1), which was as fast as diffusion-limited rate. Quenching of Tb(III).(CAS)2 was also applied to detection of NAD+, with a D.L. of 2.78 x 10(-7) M.