Abstract
Copper(II) azacyclam complexes (azacyclam = 1,3,5,8,12-pentaazacyclotetradecane) containing naphthyl or dansyl subunits can be prepared by template synthesis involving proper sulfonamide derivatives as locking fragments. The macrocyclic complexes are very poorly emissive due to the fluorescence-quenching behavior displayed by Cu2+ ions. However, the fluorescence can be recovered as a result of the decomposition of the complexes, which induces the release of free light-emitting subunits to the solution. This reaction takes place very slowly in neutral water but its rate is increased by the presence of sulfite. Therefore, [Cu(azacyclam)]2+ derivatives have been investigated as simple chemical probes for the fluorogenic detection of sulfite both on laboratory and real samples. Preliminary tests performed on samples of white wine provided sulfite concentration values that are in agreement with those obtained by a standard analytical method.
Highlights
Sulfite and related sulfiting agents are well-known as preservatives and antioxidants and are widely used as food and drink additives [1–3].They may sometimes occur spontaneously in some alimentary products [4,5]
On the other hand, when such [Cu(azacyclam)]2+ complexes undergo decomposition the release of the light-emitting locking fragments should take place and an intense turn-on of the emission could be expected. Starting from this assumption, we investigated the behavior of three different azacyclam complexes, namely [Cu(1)]2+, [Cu(2)]2+, and [Cu(3)]2+, which have been prepared by using p-toluenesulfonamide, 2-naphthalenesulfonamide, and dansylamide as locking fragment” (LF), respectively (Scheme 1)
The copper complexes of azacyclam ligands 1–3 were prepared according to the previously reported metal-template route, which is depicted in Scheme 1 [65]
Summary
Sulfite and related sulfiting agents (i.e., bisulfite and metabisulfite) are well-known as preservatives and antioxidants and are widely used as food and drink additives [1–3].They may sometimes occur spontaneously (i.e., without external addition) in some alimentary products [4,5]. Sulfite and related sulfiting agents (i.e., bisulfite and metabisulfite) are well-known as preservatives and antioxidants and are widely used as food and drink additives [1–3]. Some individuals exhibit extremely high sensitivity even to very low levels of these compounds [6], resulting in a wide variety of adverse clinical effects that can range from mild-to-life-threatening reactions [3,6,7]. Due to these potential health concerns, in many countries the content of sulfite and/or its related compounds has been strictly limited in recent decades, in foodstuffs and drinks (e.g., wine and beer) [8–11]
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