Zn²⁺‐Ion Sensing by Fluorescent Schiff Base Calix[4]arene Macrocycles

Abstract

A macrocyclic ligand (H L) containing two o,o'-bis(iminomethyl)phenol and two calix[4]arene head units has been synthesized and its coordination chemistry towards divalent Ni and Zn investigated. The new macrocycle forms complexes of composition [ML] (M=Zn, M=Ni) and [ZnL(py) ], which were characterized by elemental analysis; IR, UV/Vis, and NMR spectroscopy; electrospray ionization mass spectrometry (ESI-MS); and X-ray crystallography (for [ZnL(py) ] and [NiL]). H L allows the sensitive optical detection of Zn among a series of biologically relevant metal ions by a dual fluorescence enhancement/quenching effect in solution. The fluorescence intensity of the macrocycle increases by a factor of ten in the presence of Zn with a detection limit in the lower nanomolar region.

Alkali Blues: Blue‐Emissive Alkali Metal Pyrrolates

“…Restriction of intramolecular motion by aggregation and in the solid state, leading to enhanced fluorescence quantum yields, is a very common strategy (aggregation induced emission, AIE) . Similarly, emission enabled by confinement through metal‐ion chelation has been increasingly reported and is called the chelation‐enhanced fluorescence effect (CHEF effect) . Typically, the metal center itself is not directly involved in the excited states in these cases, as demonstrated, for example, by Hahn and Strassert for fluorescent tetra‐N‐heterocyclic carbene silver(I) complexes …”

“…[45,46] Similarly, emission enabled by confinement through metal-ion chelation has been increasingly reported and is called the chelation-enhanced fluorescencee ffect( CHEF effect). [47][48][49] Typically,t he metal center itself is not directly involved in the excited states in these cases, as demonstrated, for example, by Hahn and Strassertf or fluorescentt etra-N-heterocyclicc arbene silver(I) complexes. [50] Consequently,w ew ere interested in whether the RIM concept of enabling fluorescencet hrough rigidification of 2-iminopyrrolatol igands with simple alkali metal ions is af easible alternative to chelation of transition metal ions or to covalent linking by boryl fragments (CHEF effect by alkali metal ions).…”

Diversifying the luminescence of phenanthro-diimine ligands in zinc complexes

“…[13][14][15] In solution, such easily detectable responses allow for efficient luminescence sensing of the Zn(II) ion by a variety of organic probes. [16][17][18][19][20][21][22] In the solid state, in addition to intramolecular effects, the non-covalent intermolecular interactions, e.g. hydrogen/ halogen bonding and π-stacking, govern the organization of the constituting conjugated moieties, and often play a decisive role in modulating the physical characteristics of the bulk materials.…”

Dinuclear lanthanide complexes supported by a hybrid salicylaldiminato/calix[4]arene-ligand: synthesis, structure, and magnetic and luminescence properties of (HNEt3)[Ln2(HL)(L)] (Ln = SmIII, EuIII, GdIII, TbIII)

“…Hybrid ligands of this sort are known to complex first-row transition metals readily, but their lanthanide chemistry remains largely unexplored. [51][52][53][54][55][56][57] This study demonstrates that H 4 L supports dinuclear lanthanide complexes (for Ln = Sm, Gd, Eu, and Tb)a property which contrasts the mononucleating behavior of the double and fourfold functionalized calix [4]arene amides. Their synthesis and characterization along with the investigation of photophysical, magnetic and structural properties are presented herein.…”