Cyclam-Based “Clickates”: Homogeneous and Heterogeneous Fluorescent Sensors for Zn(II)

Abstract

In an effort to improve upon the recently reported cyclam based zinc sensor 1, the "click"-generated 1,8-disubstituted analogue 2 has been prepared. The ligand shows a 2-fold increase in its fluorescence emission compared to 1 exclusively in the presence of Zn(II) that is typical of switch-on PET fluorescent sensors. Single crystal X-ray diffraction of complexes of model ligand 10 reveals that the configuration adopted by the macrocyclic framework is extremely sensitive to the metal ion to which it coordinates. For Zn(II), Mg(II), and Li(I) the metal ions adopt an octahedral geometry with a trans III configuration of the cyclam ring. In contrast for Ni(II) the ligand adopts the rare cis V configuration, while for Cu(II) a clear preference for five-coordinate geometry is displayed with a trans I configuration of the macrocyclic ring being observed in two essentially isostructural compounds prepared via different routes. The ligand displays an increased selectivity for Zn(II) compared to 1 in the majority of cases with excellent selectivity upheld over Na(I), Mg(II), Ca(II), Mn(II), Ni(II), Co(II), and Fe(III). In contrast for Cu(II) and Hg(II) little improvement was observed for 2 compared to 1 and for Cd(II) the selectivity of the new ligand was inferior. In the light of these findings and the slower response times for ligand 2, our original "click"-generated cyclam sensor system 1 was employed in a proof of concept study to prepare a heterogeneous sol-gel based material which retains its PET response to Zn(II). The versatile nature of the sol-gel process importantly allows the simple preparation of a variety of nanostructured materials displaying high surface area-volume ratio using fabrication methods such as soft lithography, electrospinning, and nanopipetting.

[12]aneN3-based BODIPY as a selective and sensitive off–on sensor for the sequential recognition of Cu2+ ions and ADP

“…Because of their protonation property at physiological conditions, macrocyclic polyamines often act as positive-charged units in constructing DNA condensation agents and non-viral gene vectors [5][6][7][8]. As a binding unit, macrocyclic polyamines have been frequently applied in the development of artificial nucleases [9][10][11][12] and a number of chemical sensors to monitor biologically-and environmentally-relevant metal and anion ions [13][14][15][16]. Our group has recently focused on the design and synthesis of various macrocyclic polyamine [12]aneN 3 compounds and their applications in artificial nucleases, DNA condensation agents, non-viral gene vectors, and chemical sensors [17][18][19][20][21].…”

A Click Fluorophore Sensor that Can Distinguish CuII and HgII via Selective Anion‐Induced Demetallation

“…[8] The development of heterogeneous sol-gel sensors based on 1 has also been explored. [9] An alternative approach has involved compound 2, with the pendant biotin molecule acting as a binding site for avidin, and the loss of triazole coordination at the metal in the presence of avidin signalled by changes in the EPR spectrum. [10] We now outline the synthesis of a cyclam-based fluorescent sensor 3 featuring a novel triazole pendant, linked to the macrocycle via the N1 position rather than C4.…”

Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

“…It is interesting to emphasize here that despite the dramatic upturn in usage of click chemistry over the last few years, applications to prepare azacrown macrocycle derivatives remain scarce. [26] This is rather surprising since the formed 1,4-disubstituted 1,2,3-triazole shares sim- [27] complexes with copper, [15,[28][29][30][31] zinc, [30][31][32][33] nickel, [31] silver, [28,34] iron, [33,35,36] ruthenium, [33,35,37] or palladium [38] have been reported, for instance. Recently, we published the synthesis of the L1 ligand and the characterization of its complex with Cu 2+ , which, to the best of our knowledge, was the first solid-state structural study of a copper complex that involved coordinated diaza [18]crown-6 and 1,2,3-triazolyl ligands.…”