Protonation of cyclen-based chelating agents containing fluorescent moieties

Abstract

The synthesis of three new polyamine receptors based on a common 1,4,8,11-tetraazacyclododecane (cyclen) platform with appended, via a methylene linker, a single quinoline (Q) or 8-hydroxy-quinoline (8-OH-Q) moiety (L1 and...

Glyphosate sensing in aqueous solutions by fluorescent zinc(ii) complexes of [9]aneN3-based receptors

“…S1 (ESI†) the distribution diagrams of the species formed in solution are reported. The protonation constants are quite similar to those determined in water in a previous study, 39 and account for the protonation of the macrocyclic ring in the first two protonation steps, while the quinoline nitrogen atom results in protonation in the last protonation step occurring at acidic pH values. Zn( ii ) gives a stable 1 : 1 complex with L1 in solution, in which the metal is likely coordinated by the four amine groups of the [12]aneN 4 moiety.…”

“…Solvents for other purposes and starting materials were purchased from commercial sources where available. L1 , 39 L2 38 and L3 37 a were prepared by published methods.…”

“…The [9]aneN 3 and [12]aneN 4 derivatives considered in the present study are reported in Scheme 1. [37][38][39] In all cases, quinoline is used as a fluorogenic fragment(s) linked to the cyclic frameworks via a methylene bridge (L1) or an amide function (s) (L2 and L3). As previously described, L2 and L3 exhibit an optical response towards Zn(II) via an OFF-ON Chelation Enhancement of the Fluorescence (CHEF) effect in MeCN/H 2 O (1 : 4 v/v at pH = 7.4, MOPS buffer) following metal complexation.…”