Dipyrrolylquinoxaline-bridged Schiff bases: a new class of fluorescent sensors for mercury(ii)

Abstract

Novel 2,3-bis(1H-pyrrol-2-yl)quinoxaline-functionalized Schiff bases were prepared and characterized as new fluorescent sensors for mercury(II) ion. The X-ray crystal structures of compounds 4, 5, 4a and 5a were determined. The binding properties of 4 and 5 for cations were examined by UV-vis and fluorescence spectroscopy. The UV-vis and fluorescence data indicate that a 1 : 1 stoichiometric complex is formed between compound 4 (or 5) and mercury(II) ion, and the association constant is (3.81 +/- 0.7) x 10(5) M(-1) for 4 and (3.43 +/- 0.53) x 10(5) M(-1) for 5. The recognition mechanism between compound 4 (or 5) and metal ion was discussed based on their chemical construction and the fluorescence quenching effect when they interact with each other. Competition experiments revealed that compound 4 (or 5) has a highly selective response to mercury(II) ion in aqueous solution.

Syntheses and structures of mononuclear and binuclear transition metal complexes (Cu, Zn, Ni) with (salicylideneglycine and imidazole)

“…The Zn1 centre lies À0.426(5) Å above the N1-O1-N2-O2 coordination plane. The average deviation (14) Å ), but close to that observed in similar complexes [22]. The angles of the N1-Zn1-O1, N1-Zn1-O2, N2-Zn1-O1 and N2-Zn1-O2 are 91.1 (5), 78.0(5), 92.9(5) and 91.4 (5) , respectively.…”

“…Deviation of N1, O1, N6 and O2 from the equatorial plane is À0.032 (2), 0.023(2), À0.028(2) and 0.021(2) Å , respectively. The Ni1-N1 (amino-Schiff base) (2.040(5) Å ) is shorter than Ni1-N from the imidazolyl group (2.101(5) Å , 2.124(5) Å ) and Ni-N6 from 3-methyl-5-pyrazolone ligand (2.098(5) Å ), but longer than the corresponding lengths of the other Ni-Schiff-base complexes [22]. The Ni1-N distances from the imidazolyl group (2.101(5) Å , 2.124(5) Å ) are longer than that of 1.904(5) Å ) in another nickel complex (Ni(bhac)(Himdz), H2bhac ¼ acetylacetone benzoylhydrazone, Himdz ¼ imidazole) with a tridentate Schiff base [23].…”

Gold(III) Macrocycles: Nucleotide-Specific Unconventional Catalytic Inhibitors of Human Topoisomerase I

“…Macrocycles for 1 – 3 and 5 were synthesized by a literature method. 41 Direct metalation of the macrocycle (Route A, Figure S2) was only successful for 1 and 5 (i.e., those macrocycles bridged by a propyl chain). For compounds 2 – 4 with slightly more elaborate alkyl groups linking the imine nitrogen atoms, a metal-templated cyclization had to be employed (Route B).…”

Synthesis and electropolymerization of a new ion sensitive ethylenedioxy-substituted terthiophene monomer bearing a quinoxaline moiety

“…Some quinoxaline derivatives are able to coordinate to various anionic species [15,16], making them amenable as anion sensors. There are also several reports on their use as metal chelators [17,18]. Recently, we have synthesized a series of new fluorescent monomers based on terthienyl systems bearing pendant quinoxaline moieties and found that 4-((2,5-dithiophen-2-yl)thiophen-3-yl)pyrrolo[1,2-a]quinoxaline (TT-Q) monomer and its polymer exhibit high sensitivity towards Fe 3+ ions [19].…”