Development of highly selective fluorescent ferrocenyl-iminopyridine chemosensor for biologically relevant Fe3

Design, synthesis, characterization, and ion detection studies of two ferrocene-appended Schiff bases namely N-(2-[ferrocenylamino]ethyl)-5-nitropyridin-2-amine (1) and ferrocenylamino-1H-imidazole-4-carboxamide (2) been reported. Both the chemosensors have been thoroughly characterized using Fourier transfer infrared, 1 H and 13 C nuclear magnetic resonance, high resolution mass spectrometry, and ultraviolet/visible (UV/visible) and fluorescence spectral techniques. Probes 1 and 2 were designed with the aim of appending the ferrocenyl group with pyridine ring having an amine substitution (for 1) and imidazole ring with an amide substitution (for 2). Interaction of these probes with a series of cations and anions was examined through UV/vis and fluorescence spectral techniques. Probe 2 exhibited an insignificant response towards anions and loss of selectivity for cations, whereas 1 displayed highly selective detection towards biologically important Fe3+ in 2:1 (probe:cation) stoichiometry. Notably, none of the cations and anions could interfere the selectivity of Fe3+ ensured by 1 in aqueous medium. The limit of detection for Fe3+ detection using 1 was determined to be 0.2 ppm. The results strongly suggest that 1 could find promising future application as a chemosensor for Fe3+ in biological systems for quantification and qualitative analysis.

A rhodamine based dual chemosensor for Al3+ and Hg2+: Application in the construction of advanced logic gates

A rhodamine-based compound (RBO), which has been constructed from the reaction between N-(rhodamine-6G)lactam-ethylenediamine and 2,1,3-benzoxadiazole-4-carbaldehyde, is reported here as a selective chemosensor for both Al³⁺ and Hg²⁺ ions in 10 mM HEPES buffer in water:ethanol (1:9, pH = 7.4). Absorption intensity of RBO increases considerably at 528 nm with these cations. It shows fluorescence enhancement at 550 nm by 1140- and 524-fold in the presence of Al³⁺ and Hg²⁺, respectively. LOD has been determined as 6.54 and 16.0 nM for Al³⁺ and Hg²⁺, respectively. Quantum yield and lifetime of RBO enhances with these metal ions. Fluorescence intensity of Al-probe complex or Hg-probe complex is quenched in the presence of fluoride or sulfide ion, respectively, opening a path for the construction logic gates. DFT analysis has been used to understand the spectral transitions. We have constructed a systematic development from single to five inputs complex circuit, and for the first time a time dependent five input complex logic circuit is reported herein.

Schiff base-functionalized silatrane-based receptor as a potential chemo-sensor for the detection of Al3+ ions

Excess Al³⁺ ions are considered toxic to living organisms.

The first report of X-ray characterized organosilatrane-based receptors for the electrochemical analysis of Al3+ ions

The electrochemical behaviour of aryl–alkyl ether functionalized organosilatranes has been studied by square wave voltammetry (SWV) using a gold electrode.

TICT fluorescent probe for Al3+: Sequential detection of PPi, ATP and ADP in semi-aqueous medium and real-life applications

A ditopic Schiff base ligand, H₂L has been synthesized and characterized by all spectroscopic techniques. It is highly selective and specific towards Al³⁺ in semi aqueous medium (DMF/H₂O mixture) by exhibiting a drastic increase in the fluorescence intensity. The emission studies, spectroscopic data, life time and quantum yield results have been used to understand its binding mode, explore its specificity and establish its efficacy. The intensity difference is remarkable in physiological pH range. Due to its reversible behavior this ditopic fluorescent chemosensor can be used multiple times to make it cost effective. Detection limit for this chemosensor was found to be 0.65 μM. Experiments with TLC plates show that it can be used as a practical and portable sensor for studying environmental samples in real life. The L-Al³⁺ complex generated in the solution acts as a sensor to sequentially detect pyrophosphate groups present in inorganic pyrophosphates, ATP and ADP among other anions by turning off the fluorescence. Inhibit logic gate and its corresponding truth table has been developed to aid in further exploiting its multidimensional applications.

A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al3+ and Its Application in Water Samples and Cell Imaging

An easily prepared benzothiazole-based probe (BHM) was prepared and characterized by general spectra, including ¹H NMR, ¹³C NMR, HRMS, and single-crystal X-ray diffraction. Based on the synergistic mechanism of the inhabitation of intramolecular charge transfer (ICT), the BHM displayed high selectivity and sensitivity for Al³⁺ in DMF/H₂O (v/v, 1/1) through an obvious blue-shift in the fluorescent spectrum and significant color change detected by the naked eye, respectively. The binding ratio of BHM with Al³⁺ was 1:1, as determined by the Job plot, and the binding details were investigated using FT-IR, ¹H NMR titration, and ESI-MS analysis. Furthermore, the BHM was successfully applied in the detection of Al³⁺ in the Songhua River and on a test stripe. Fluorescence imaging experiments confirmed that the BHM could be used to monitor Al³⁺ in human stromal cells (HSC).

A reusable multichannel anthraimidazoledione-based receptor for Hg2+and Cu2+ions: ultrasensitive, economical and facile detection of Hg2+in real water sources through fluorescence readout

A multichannel, ultrasensitive and selective receptor (1) has been developed for practical detection of Hg²⁺in various drinking waters.

A single chemosensor for bimetal Cu(ii) and Zn(ii) in aqueous medium

A new quinazoline-based bimetal chemosensor for Cu(ii) and Zn(ii) in aqueous medium was synthesized. It can act as a “turn-off” sensor for Cu(ii) with the excitation wavelength of 356 nm, and a “turn-on” sensor for Zn(ii) when excited at 416 nm.

Cu(ii) complex-based fluorescence chemosensor for cyanide in aqueous media

A Cu²⁺ complex-based fluorescence “off–on” chemosensor for the direct detection of CN⁻ in the environment and in living cells was designed and prepared.

Synthesis and characterization of a novel, ditopic, reversible and highly selective, “Turn-On” fluorescent chemosensor for Al3+ ion

A ditopic Schiff base fluorescent chemosensor, L (OFF state), selectively senses Al³⁺ by inhibition of ESIPT/GSIPT, CN isomerization and CHEF (ON state).

Metal ion-assisted ring-opening of a quinazoline-based chemosensor: detection of copper(ii) in aqueous media

A fluorescence chemosensor for Cu(ii) in aqueous media was synthesized. The experiments and theoretical calculations confirmed that the Cu(ii) ion assisted the ring-opening of the quinazoline derivative, forming a Cu(ii) Schiff base during the detection.

Binding site-driven sensing properties of a quinazoline derivative with metal cations

A quinazoline derivative showed high sensitivity and selectivity for Al³⁺, Cr³⁺ and Fe³⁺ ions in methanol solution.

Detection of copper(ii) and aluminium(iii) by a new bis-benzimidazole Schiff base in aqueous media via distinct routes

Synthesis and characterization of a bis-benzimidazole appended Schiff base ligand, 2-(3,5-bis(1H-benzimidazole-2-yl)-phenyliminomethyl)phenol (H3L) displaying excellent selectivity towards Cu²⁺and Al³⁺in mixed aqueous media.