Ferrocene‐Based Small Molecules for Multichannel Molecular Recognition of Cations and Anions

A ferrocene-based chemo-dosimeter for colorimetric and electrochemical detection of cyanide and its estimation in cassava flour

A simple chemo-dosimeter VDP2 bearing a ferrocene moiety was designed, synthesized, and characterized, and exhibited both chromogenic and electrochemical responses selectively for CN- in H2O-DMSO (9 : 1, v/v) medium. The probe VDP2 showed an instantaneous color change from colorless to yellow with CN- that can readily be observed visually. The deprotonation of the benzimidazole -NH, followed by nucleophilic addition of CN- to the olefinic C-atom, as evidenced by 1H and 13C NMR titration experiments, caused the colorimetric and electrochemical responses. The mass spectral study, CV, FTIR and Mulliken charges computed well supported the proposed mechanism. The electrochemical limit of detection was calculated to be 72 nM. The results of DFT and TD-DFT calculations suggested that the colorless nature of the probe VDP2 is due to weak intramolecular charge transfer (ICT) transition and the yellow color of the VDP2+CN adduct is due to through-space ICT transition. Above all, the probe could be an ideal candidate for monitoring cyanide in water samples and cassava flour with practical significance. A simple and convenient colorimetric method was developed to determine cyanide content in cassava flour.

Ferrocenyl-triazole complexes and their use in heavy metal cation sensing

Complexes tris((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)amine (3), bis((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)amine (6), bis((1-ferrocenyl-1H-1,2,3-triazol-4-yl)methyl)ether (7), and 1-ferrocenyl-1H-1,2,3-triazol-4-yl)methanamine (9) were synthesized using the copper-catalyzed click reaction. Complexes 3, 6, 7, and 9 were characterized using NMR (1H and 13{1H}) and IR spectroscopy, elemental analysis, and mass spectrometry. Structures of 3, 7, and 9 in the solid state were determined using single-crystal X-ray diffraction. It was found that the triazole rings were planar and slightly twisted with respect to the cyclopentadienyl groups attached to them. Chains and 3D network structures were observed due to the presence of π⋯π and C-H⋯N interactions between the cyclopentadienyl and triazole ligands. A reversible redox behavior of the Fc groups between 239 and 257 mV with multicycle stability was characteristic for all the compounds, revealing that the electrochemically generated species Fc+ remained soluble in dichloromethane. Electrochemical sensor tests demonstrated the applicability of all the complexes to enhance the quantification sensing behavior of the screen-printed carbon electrode (SPCE) toward Cd2+, Pb2+, and Cu2+ ions.

A Review on Metal Ion Sensors Derived from Chalcone Precursor

Disclosure of new molecular probes as chromogenic and fluorogenic cation sensors is scientifically exigent work. Recently chalcone derivatives gained more attention because of their structural variability. A suitable donor and acceptor groups separated by delocalized π-orbitals display excellent chromogenic and fluorogenic properties because of intramolecular charge transfer (ICT). These designed molecular frameworks provide the coordination sites to the incoming metal ions results in small changes in the optical properties. In a typical sensing behavior, coordination leads to a large conjugation plane with the probe resulted in hypo/hyperchromic shifts or red/blue shifts. In this review, we tried to converge the reported chalcone-derived sensors and explored the design, synthesis, metal ion sensing mechanism, and practical application of the probes. We expect that this review gives a basic outline for researchers to explore the field of chalcone-based sensors further.

Fluorescent chemosensors containing redox-active ferrocene: a review

The redox-active ferrocene containing two cyclopentadienyl rings and iron was extensively employed in the field of sensing, catalysis, medicine, biotechnology etc., due to the structural stability, solubility in common solvents and easy structural modification to make a wide variety of ferrocene derivatives. The ferrocene moiety can be linked suitably with fluoro-chromogenic units and applied for the multichannel (fluorescent, chromogenic and redox) sensing of various bioactive and toxic analytes. This review was narrated to compile some important ferrocene based fluorescent chemosensors developed for the detection of metal ions, anions and neutral analytes. The analytical novelty and sensing mechanisms of the summarized chemosensors are discussed to open new scopes for future research.

A novel near-infrared optical and redox-active receptor for the multi-model detection of Hg2+ in water and living cells

A key issue for constructing optical and redox-active receptors is how to conjugate a specific sensing kernel with a multi-signal-responsive system to carry out multi-feature analysis. Mercury is considered to be highly toxic to human health and ecological security. In this work, we present a novel near-infrared optical and redox-active receptor that can sense Hg²⁺ at ppb level in aqueous media via multi-model monitors with a low detection limit of 8.4 × 10^-9 M (1.68 ppb). This receptor features a visible detection, 'off-on' fluorescence response, and efficient electrochemistry assessment, as well as pH-insensitivity to Hg²⁺ with high sensitivity. In view of its marked near-infrared emission and fluorescence enhancement, we successfully applied this receptor to visualize Hg²⁺ in live cells. Furthermore, a possible sensing model was established and rationalized with theoretical studies.

Y-shaped ferrocene/non-ferrocene conjugated quinoxalines for colorimetric and fluorimetric detection of picric acid

New Y-shaped ferrocene and non-ferrocene conjugated quinoxaline derivatives {[R-(CH)₂-N=CH-)₂C₁₀H₄], R = C₅H₅-Fe-C₅H₅ (1) and R = C₆H₄-OCH₃ (2)} have been synthesized and characterized using analytical and spectroscopic techniques. The thermal stability of the compounds 1 and 2 were examined by thermogravimetric analysis (TGA), both were stable up to 250 °C. The optical properties were studied using UV-Visible and fluorescence spectroscopic methods and Y-shaped ferrocene appended quinoxaline derivative 1 show a weak emission due to the quenching nature of ferrocene. The compound 2 shows enhanced fluorescence intensity in their aggregation state due to Restricted Intramolecular Rotation (RIR). Hence, the compound 2 have further utilized for the detection of picric acid (PA) by fluorimetric method and the detection limit of 1.37 × 10^-6 M was obtained. Further, paper sensor was made using compound 2 which resulted in the instant 'naked eye' response for trace detection of picric acid. Consequently, the compound 2 acts as a colorimetric sensor and can be used as a new probe for the detection of nitro aromatic explosives.

Comparative cation sensing properties of a newly designed urea linked ferrocene-benzimidazole dyad: a DFT study

Herein, our primary motivation was to elucidate the electronic and physicochemical properties of a novel molecular dyad consisting of ferrocene (Fc; electron donor), urea (u; linker), and amphoteric benzimidazole (BI; electron acceptor) entities. The sensor responses were investigated for various divalent transition metal cations (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) and the selectivity of this cationophore molecule (Fc-u-BI) to copper ion (Cu²⁺) was demonstrated by using B3LYP/LANL2DZ method. According to the thermochemical calculations, we justified that Fc-u-BI⋯Cu²⁺ reached to the lowest binding energy (∆E), enthalpy (∆H), and Gibbs free energy (∆G) changes. In the light of the calculated global descriptors, Fc-u-BI⋯Cu²⁺ was found to be the softer and thus the most reactive complex. The complex stabilities and their corresponding non-covalent interactions were also investigated by NBO and NCI analyses, respectively. The mechanistic insight into metal cation sensing by the modeled cationophore dyad.

A reaction-type receptor for the multi-feature detection of Hg2+ in water and living cells

The first optical and redox-active receptor of reaction-type has been developed for efficiently multi-model survey of Hg²⁺.

Novel mesoporous organosilica nanoparticles with ferrocene group for efficient removal of contaminants from wastewater

Traditional method to functionalize mesoporous silica nanoparticles with organic groups for removal of contaminants from wastewater was surface modification. However, this surface modification could not cover the entire surface, leading to incomplete utilization of the high surface area of MSNs. In this work, we designed and prepared a novel inorganic-organic hybrid nanomaterial: ferrocene incorporated mesoporous organosilica nanoparticles (MONs). Owing to the mesoporous structure, large surface area and the ferrocene group in the framework, MONs could adsorb phosphate anion more efficiently with adsorption capacities up to 1299 mg/g than surface modified MSNs (SiO₂-Fe) (488 mg/g). Congo red (CR) and Pb²⁺ were also used as the model contaminants, and the results indicated that MONs is a superior absorbent comparing with ferrocene surface modified MSNs.

A simple urea-based multianalyte and multichannel chemosensor for the selective detection of F−, Hg2+ and Cu2+ in solution and cells and the extraction of Hg2+ and Cu2+ from real water sources: a logic gate mimic ensemble

Herein, a hydrazine-based chromogenic, fluorogenic and electrochemical chemosensor BCC [1,5-bis(4-cyanophenyl) carbonohydrazide] was reported.

Benzothiazole integrated into a cryptand for ESIPT-based selective chemosensor for Zn2+ ions

A novel 2(2′-hydroxyphenyl) benzothiazole-based cryptand (L) exhibits high fluorescence intensity in the presence of Zn²⁺ ions by stopping the excited state intramolecular proton transfer (ESIPT) process with a detection limit of 0.20 μM.

Azines: synthesis, structure, electronic structure and their applications

Azines (2,3-diaza-1,3-butadienes): structure, electronic structure, tautomerism, and their applications in organic synthesis, medicinal chemistry and materials chemistry.

A novel ferrocenyl–naphthalimide as a multichannel probe for the detection of Cu(ii) and Hg(ii) in aqueous media and living cells

The first reported probe that has been used for the bifunctional fluorescent monitoring Cu²⁺ and Hg²⁺ ions in living cells.

Ferrocene amphiphilic D–π–A dyes: synthesis, redox behavior and determination of band gaps

We reported the synthesis, optical and redox behavior of six ferrocenyl D–π–A dyes. Optical and electrochemical band gaps were determined and corroborated by TD-DFT calculations. Compounds4exhibit the smallest band gap of this series.

Synthesis, Crystal Structures and Properties of Ferrocenyl Bis-Amide Derivatives Yielded via the Ugi Four-Component Reaction

Ten ferrocenyl bis-amide derivatives were successfully synthesized via the Ugi four-component reaction by treating ferrocenecarboxylic acid with diverse aldehydes, amines, and isocyanides in methanol solution. Their chemical structures were fully characterized by IR, NMR, HR-MS, and X-ray diffraction analyses. They feature unique molecular morphologies and create a 14-membered ring motif in the centro-symmetric dimers generated in the solid state. Moreover, the electrochemical behavior of these ferrocenyl bis-amides was assessed by cyclic voltammetry.

Windmill-shaped octanuclear Zn/Ln (LnIII = Dy, Tb, Ho) heterometallic ensembles supported by a tetraferrocene scaffold

Utilizing a new ferrocene-based compartmental ligand, H₄L (1), a series of novel heterometallic complexes [{LZn(μ-OAc)Dy}₄(μ₄-H₂O)] (2), [{LZn(μ-OAc)Tb}₄(μ₄-H₂O)] (3), [{LZn(μ-OAc)Ho}₄(μ₄-H₂O)] (4), [L = Fe[(C₅H₄){-C(Me)[double bond, length as m-dash]N-N[double bond, length as m-dash]C₆H₃-(o-O)(m-O)}]₂] were synthesized and characterized. 2 and 3 crystallize in the monoclinic crystal system in the I2/m space group, whereas 4 crystallizes in the tetragonal crystal system in the I4/m space group. The tetra deprotonated ligand L^4- has two distinct coordination compartments: one pocket (2N, 2O) suitable for the transition metal (3d) ions and another pocket (4O) suitable for lanthanide (4f) metal ions. Additionally, the terminal phenoxo group can be utilized for cluster expansion. In all the complexes, the Zn^II ion is in a perfect square pyramidal (2N, 3O) geometry whereas the lanthanide ion has a coordination number of eight (8O) in a distorted biaugmented trigonal-prism geometry. The electrochemical properties of 2 and 3 along with ligand H₄L (1) were studied by cyclic voltammetry (CV). All the complexes display a similar type of electrochemical behavior viz., one quasi-reversible oxidation typical of a ferrocene/ferrocenium motif. The magnetic properties of all the complexes have also been investigated.