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 TbIII·(CAS)2 and TbIII·TCAS, respectively, which were utilized as a host for cationic guests. Addition of 1-ethylpyridinium guest quenched luminescence of TbIII·(CAS)2 in accordance with the Stern-Volmer (SV) relation with a low detection limit (D.L.) of 5.94 × 10−8 M (S/N = 3, M ≡ mol dm−3). On the other hand, 1-ethylquinolinium quenched luminescence of TbIII·TCAS most efficiently, affording a very low D.L. (6.71 × 10−10 M). The agreement of the SV coefficients obtained with luminescent intensity (KSV,all = 6.74 × 106 M−1) and lifetime (KSV,Tb = 6.50 × 106 M−1) implied that dynamic quenching of 5D4 excited state of TbIII was predominant in the quenching processes. The quenching rate was estimated to be kq,Tb = 9.94 × 109 M−1 s−1, which was as fast as diffusion-limited rate. Quenching of TbIII·(CAS)2 was also applied to detection of NAD+, with a D.L. of 2.78 × 10−7 M.