Naslov
Synthesis and cation binding properties of fluorescent calix[4]arene derivatives bearing tryptophan units at the lower rim

Autori
Galić, Nives ; Burić, Nataša ; Tomaš, Renato ; Frkanec, Leo ; Tomišić, Vladislav

Izvornik
Supramolecular chemistry (1061-0278) 23 (2011), 5; 389-397

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
calixarenes ; alkali metal cations ; europium(III) ; stability constants ; fluorescence

Sažetak
The fluorescent peptidocalixarenes, 5, 11, 17, 23-tetra-tert-butyl-25, 26, 27, 28-tetrakis(O-methyl-L-tryptophanylcarbonylmethoxy)calix[4]arene (1) and 5, 11, 17, 23-tetra-tert-butyl-25, 27-di(O-methyl)-26, 28-bis(O-methyl-L-tryptophanylcarbonylmethoxy)calix[4]arene (2), were prepared by introducing tryptophan subunits at a lower calixarene rim. Coordination abilities of 1 and 2 towards europium(III) and alkali metal cations were studied by spectrophotometric, spectrofluorimetric, conductometric and potentiometric titrations in acetonitrile at 25 oC. Rather strong complexation was observed for smaller alkali metal cations Li+ and Na+ (log KLi1 > 6, log KLi2 > 6, log KNa1 = 8.25, logKNa2 = 6.94), and moderate for K+ (log KK1 = 5.09, log KK2 = 4.09). Larger Rb+ and Cs+ cations did not fit in the ion-binding site of 1 so no complexation was detected, whereas the more flexible ligand 2 accommodated Rb+ cation (log KRb2 = 3.44). The fluorescence of 1 (ex = 280 nm, em = 340 nm) was remarkably quenched by Eu(III). Stability constant of 1:1 (Eu3+:1) complex determined spectrofluorimetrically amounted to log KEu1 = 6.16.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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