Enantioselective fluorescent sensor for dibenzoyl tartrate anion based on chiral binaphthyl derivatives bearing an amino acid unit

Spectral studies on anthracene based dual sensor for Hg2+ and Al3+ ions with two distinct output modes of detection

A simple and easily synthesized colorimetric and fluorescent chemosensor 1, based on aromatic OH and imine moieties as a binding and anthracene as signaling unit, has been synthesized in a one-step procedure. The chemosensor 1 is developed as a dual chemosensor for detection of Hg²⁺ and Al³⁺ ions in CH₃OH, which exhibited a color change from light yellow to dark yellow with Hg²⁺ ions, enabling 1 a suitable "bare eye" indicator for Hg²⁺ ions. On the other hand, fluorescent enhancement with blue shift along with brilliant cyan fluorescence was observed upon binding with Al³⁺ ions. A possible sensing mechanism has been proposed by means of Job's plot and ¹H NMR titration.

'Naked-eye' detection of biologically important anions in aqueous media by colorimetric receptor and its real life applications

A colorimetric receptor R 2-[(2-Hydroxy-naphthalen-1-ylmethylene)-hydrazonomethyl]-quinolin-8-ol has been designed and synthesized with good yield and characterized by the standard spectroscopic techniques such as FT-IR, UV-Visible, ¹H NMR, ¹³C NMR and ESI-MS. The receptor R showed naked-eye detection and spectral change in the presence of F^-, AcO^- and H₂PO₄^- over other anions. Interestingly, receptor R displaying high selective recognition towards F^-, AcO^- ion with a drastic color change from pale yellow to red in dry DMSO solvent and orange in mixed solvent DMSO/H₂O (9:1, v/v). The behavior of receptor R towards F^-, AcO^- ion was investigated using UV-Vis and ¹H NMR experiment. The detailed ¹H NMR experiment result revealed that the receptor R is forming the hydrogen bonding between imine nitrogen and phenolic OH proton towards anions. The receptor R is able to detect sodium salts of flouride (NaF) and acetate (NaAcO) in aqueous medium and it exhibited dramatic color change from pale yellow to red. The receptor R demonstrated itself to be useful for real life application by detecting flouride and acetate ion in sea-water and commercially available product such as toothpaste, mouthwash and vinegar solution.

Recognizing the Limited Applicability of Job Plots in Studying Host-Guest Interactions in Supramolecular Chemistry

Continuous variation method, known as Job plot, is the most commonly applied method for the determination of stoichiometry of complex chemical entities for over 100 years. Although, the method was proven successful in the analysis of very stable metal-ligand complexes, we demonstrate that its use in supramolecular chemistry often provides false results. We support this statement with multiple simulations as well as cases studies of several real host-guest systems. We propose an alternative, general method relying on the analysis of residual distribution in titration data fitting. The latter method is more convenient compared to the Job plot and unlike it gives correct results in all real cases studied.

Dual mode ratiometric recognition of zinc acetate: nanomolar detection with in vitro tracking of endophytic bacteria in rice root tissue

Structurally characterized naphthalene-based ratiometric probe detects zinc acetate (ZA) by colorimetric and fluorescence tools. In vitro tracking of ZA in endophytic bacteria in rice root tissue and human breast cancer cells (MCF7) is possible.

Chiral recognition of carboxylates by a static library of thiourea receptors with amino acid arms

Chiral recognition is based on a large network of very subtle interactions whose outcome is difficult to predict. A combinatorial approach is therefore the most suitable to search for the most efficient receptor and obtain a structure-enantioselectivity correlation. We synthesized a set of 12 receptors constructed with 1,9-diaminoantracene and α-amino acid esters, linked via thiourea groups. The association constants and enantioselectivities for the complexes with mandelate and N-acetylphenylalanine were determined by competitive NMR titrations. Association constants quite regularly depend on the substituents in the receptor structure, but the distribution of enantioselectivities across the library could not easily be rationalized.

A single probe for sensing both acetate and aluminum(iii): visible region detection, red fluorescence and human breast cancer cell imaging

A single probe (L) can recognise both AcO⁻ and Al³⁺ as prepared by coupling 2-hydroxy-1-naphthaldehyde with hydrazine. The probe allows both colorimetric and fluorescence detection of both the ions.

l-Amino acid derived pyridinium-based chiral compounds and their efficacy in chiral recognition of lactate

A series ofl-amino acid derived pyridinium-based chiral compounds have been designed and synthesized. Among them, somel-valine derivatives show enantioselective recognition ofd-lactate in fluorescence.

A highly selective ratiometric chemosensor for Ni2+in a quinoxaline matrix

The monohydrazone of quinoxaline aldehyde (HOQA) is found to be a ratiometric and colorimetric probe for Ni²⁺.HOQAshows a remarkable color change from colorless to yellow upon specific and selective binding to nickel.

Fluorescent sensors for Ca(2+) and Pb(2+) based on binaphthyl derivatives

Two novel binaphthyl compounds have been synthesized for the selective fluorescent recognition of Ca(2+) or Pb(2+). By introducing different terminal groups to the receptor unit, the fluorescence signals of the receptors are significantly changed: 1 is fluorescence enhancement for Ca(2+), 2 is fluorescence quenching for Pb(2+). The binding properties for metal ions were examined by the absorption and fluorescence spectra. The fluorescence intensity enhancement was ascribed to the complex formation between Ca(2+) and 1 which blocked the photo-induced electron transfer process.