Aqueous Fluorometric and Colorimetric Sensing of Phosphate Ions by a Fluorescent Dinuclear Zinc Complex

Abstract

A fluorescent dinuclear zinc complex (1) has been prepared by an easy "one pot" method in which the lysine-based Schiff base ligand is generated in situ. The compound is characterized in detail by various spectroscopic techniques and single-crystal X-ray diffraction. Crystal data: monoclinic, C2, a = 18.31(13) A, b = 8.45(7) A, c = 11.20(8) A, beta = 90.11(6) degrees, V = 1733.6(2) A(3). Z = 2, R1 = 0.0442, wR2 = 0.1068, Flack(x) parameter = 0.03(2). Compound 1 is highly fluorescent, in both the solution phase and as a solid. Under neutral aqueous conditions (0.01 M HEPES buffer, pH 7.4), compound 1 exhibits intense blue fluorescence (lambda(ex) = 352 nm, lambda(em) = 453 nm, Phi(F) = 0.17). The complex was tested with several anions, such as F(-), Br(-), I(-), AcO(-), HCO(3)(-), H(2)PO(4)(-), HPO(4)(2-), PO(4)(3-), and a variety of biologically relevant phosphate anions, such as adenosine monophosphate (AMP), cyclic adenosine monophosphate (cAMP), inorganic pyrophosphate (PPi, P(2)O(7)(4-)), adenosine diphosphate (ADP), and adenosine triphosphate (ATP), in water at physiological pH. The dizinc species was found to act as a highly selective sensor for PPi in particular by fluorescence ON-OFF signaling. Both the fluorometric and colorimetric (indicator displacement assays) titration results suggest that compound 1 is a highly selective sensor for phosphate ions with the order PPi > or = ATP > ADP.

Unravelling the correlation between metal induced aggregation and cellular uptake/subcellular localization of Znsalen: an overlooked rule for design of luminescent metal probes

“…There are several examples of water soluble Znsalens that were found to be monomeric species in aqueous solutions, 27,28,61 and thus the effect of water on the aggregation of ZnL 1 in water needs to be further discussed. Generally, water is a Lewis base and a coordinating solvent, and can compete with the intermolecular Zn···O interaction, and hence may prevent aggregation.…”

“…Previous studies demonstrated that anions such as phosphate 23,27,61 and Br – 25 are able to coordinate Zn and dissociate Znsalen aggregates, however, with much smaller binding constants than pyridine. 61,62 In this work, we chose PO 4 3– (PBS buffer), Br – ( n Bu 4 NBr) and HBSS buffer (containing various inorganic anions), which are relevant to biological studies.…”

Synthesis, structure, spectral characterization and DNA binding affinity of new water soluble trinuclear copper(II) complexes with partial cubane Cu3O4 cores

“…In general, copper(II) ion is known as fluorescence quencher. Recently, it has also been observed in the literature that the fluorescence emission of DNA and other substrates have significantly been quenched due to the binding with copper(II) ions [60][61][62]. Therefore, theoretical calculations strongly suggest that the binding of DNA with complexes 1 and 2 occurs more possibly through the copper centers which have been further supported by the fluorescence titration experiments having the significant quenching effect.…”

Solvothermal in situ synthesis of (Schiff-base)-containing dinuclear cobalt compound

“…By contrast, in our previous work we for the first time disclosed a distinct approach to target (Schiff base)-containing compound, where the in situ formation of Schiff base ligand is explored [19]. Further similar attempts are also achieved by Powell and Churchill [20,21]. However, the detailed experiment conditions are very different.…”