Recognition of Oxalate by a Copper(II) Polyaza Macrobicyclic Complex

Abstract

A new polyamine macrobicyclic compound was synthesised through a [1+1] "tripod-tripod coupling" strategy and using a Schiff base condensation reaction, followed by sodium borohydride reduction. The resulting compound is a heteroditopic cage (btpN(7)) in which one of the head units is appropriate for the coordination of copper(II), whereas the other head is available for additional hydrogen-bonding and electrostatic interactions with substrates. The acid-base behaviour of the new compound, the stability constants of its complex with the Cu(2+) ion and the association constants of the copper(II) cryptate with oxalate (oxa(2-)), malonate (mal(2-)), succinate (suc(2-)), maleate (male(2-)) and fumarate (fum(2-)) were determined by potentiometry at 298.2 K in aqueous solution and at an ionic strength of 0.10 mol dm(-3) in KNO(3). These studies revealed a clear preference of the receptor [CuH(h)btpN(7)H(2)O]((2+h)+) for oxa(2-) over the other dicarboxylate substrates. This arises from co-operativity between metal-anion coordination and electrostatic and hydrogen-bonding interactions, in accordance with the ideal size of this dicarboxylate, which allow it to take full advantage of the potential binding sites of the receptor. A qualitative indicator-displacement study, in agreement with the potentiometric studies, demonstrated that the copper cryptate receptor can be used as a selective visual sensor for oxalate.

Colorimetric detection of oxalate in aqueous solution by a pyrogallol red‐based Cu2+ complex

“…As there have been some reports on the complex formation between oxalate and Cu 2+ in an aqueous solution, to examine the sensing selectivity of PR–Cu 2+ toward oxalate, an absorption spectral study of PR–Cu 2+ (40 μM) was performed upon addition of various anions (80 μM) such as F − , Cl − , Br − , I − , NO 3 − , SO 4 2− , PO 4 3− , HPO 4 2− , H 2 PO 4 − , CO 3 2− , HCO 3 − , acetate, oxalate, malonate, succinate, citrate, AMP, ADP, ATP and PPi in 10 mM acetate buffer solution at pH 5.0 (Figure ). The addition of oxalate to the PR–Cu 2+ instantly yielded a characteristic colorimetric change as a decrease in the absorbance at 555 nm and an increase in the absorbance at 435 nm.…”

“…Therefore, new colorimetric chemosensors that can achieve naked‐eye detection of a colour change in the visible wavelength region, have attracted considerable attention. However, to the best of our knowledge, very few colorimetric sensors for oxalate in pure aqueous solution have been reported . These sensors were developed using metal–indicator complexes, namely chemosensing ensemble methods, which have the distinct advantages of simple measurement in aqueous medium, decrease in complicated organic synthesis, and easy preparation of various metal–indicator complexes using different metal ions .…”

“…Pyrogallol red (PR) is a commercially available and water‐soluble triphenylmethane trihydroxy dye with xanthene cycle as shown in Scheme , and has been widely used as a metal sensitive dye due to the chelation of various metal ions . Among the sensors for oxalate in aqueous solution, significant progress has been made in the detection of oxalate with Cu 2+ ‐containing receptors by colorimetric and fluorescent methods . PR shows a distinct colorimetric response to Cu 2+ in a pure aqueous solution (10 mM acetate buffer, pH 5.0).…”

Formation and Reactivity of a Biomimetic Hydroperoxocopper(II) Cryptate

“…A correlation indeed exists between coordination geometry and anion size in cryptand complexes. [17] Further studies are in progress to render the ligand less sensitive to oxidation and stabilize the intermediate species to enable a more complete characterization.…”

Colorimetric Recognition of Oxalate in Water by a New Carbazole-Zn(II) Based Chemosensing Ensemble

“…[14][15][16][17][18][19][20][21][22][23][24][25] However, only limited oxalate sensors that can operate in 100% water solution have been documented. [17][18][19][20][21][22]26 Therefore, it is still imperative to develop water soluble chemosensors for the detection of oxalate under physiological conditions. Owing to the strong hydration effect of anions in aqueous solution, anion sensing in water is difficult and remains as a challenging task.…”