1-Aminoanthracene-9,10-dione based chromogenic molecular sensors: effect of nature and number of nitrogen atoms on metal ion sensing behavior

To examine the consequences of nature and number of nitrogen atoms on metal ion sensing properties, four new molecular receptors based on 1-aminoanthracene-9,10-dione as chromogenic moiety and different types of nitrogen atoms viz. arylamine, alkylamine, and pyridyl nitrogen as appendages have been synthesized. These receptors in CH₃OH/H₂O (1:1) (v/v) at pH 7.0, on addition of heavy metal ions show selective and/or semi-selective interactions. These binding interactions are visible to naked eye due to remarkable color change and are associated with λ_max shift by 85-125 nm. Molecular receptor 2, with two sp² hybridized nitrogen atoms and one arylamine nitrogen, selectively binds with Cu²⁺ but 2-Cu²⁺ complex is stable only between pH 7.0 and 8.75. However, the conversion of imine nitrogen to alkylamine in molecular receptor 6, increases the binding ability toward Cu²⁺ along with significant binding affinities toward Ni²⁺ and Co²⁺. Receptor 6 shows the stability of its complexes in the order Cu²⁺>Ni²⁺>Co²⁺ in a broader pH range 6-12. Dipicolylamine based receptor 8, possessing two pyridyl nitrogen atoms, one tertiaryamine and one arylamine nitrogen atoms as ligating sites, also binds semiselectively in the order Cu²⁺>Co²⁺>Ni²⁺. Receptor 10, possessing anilide group in the place of arylamine in receptor 8, on addition of Cu²⁺, Ni²⁺ or Co²⁺ shows bathochromic shift of λ_max associated with color change from yellow to russet (brown) and on addition of Zn²⁺ shows hypsochromic shift of its λ_max associated with disappearance of yellow color. Additionally, all the four chemosensors show ratiometric response toward all these metal ions and thus increase the usability and the dynamic range of estimation.     

Conjugated Polymer Fluorescent Chemosensor： Design Principle and the Concept for Molecular Assembly

共轭高分子作为“分子导线”所特有的信号放大效应,使其在构建高灵敏度的荧光化学传感体系中具有特别的优势。本文首先从分子识别、传感机理和信号输出等方面概述了传感分子设计中需要考虑的一些基本问题;然后以聚对芳撑乙炔类共轭高分子为例,提出基于模板排列组合的分子组装概念,并将之用于合成一系列结构可调的荧光化学传感分子,以满足不同的检测目的;最后通过文献中的具体实例,对多种聚对芳撑乙炔类共轭高分子进行了分子结构和传感应用方面的解析。     

Polyamine Linear Chains Bearing Two Identical Terminal Aromatic Units. Evidence for a Photo Induced Bending Movement

Abstract

Several chemosensors bearing a fluorescent unit at both ends of a linear polyamine chain were synthesised. The protonation as well as the association constants with Cu²⁺ and Zn²⁺ were determined by potentiometry in 0.15 mol dm^?3 NaCl at 298.1 K. In the case of 1,16-bis(1-naphthylmethyl)-1,4,7,10,13,16-hexaazadecane hexahydrochloride (L1), formation of an excimer emission in aqueous acidic solutions was observed. The system was characterized by steady state fluorescence emission and by time resolved fluorescence. In the ground state the molecule is expected to adopt a more or less linear conformation, while in the excited state a bending movement of the chain must occur in order to allow the excimer emission. The system can be viewed as an elementary machine driven by light.     

Photoactive Chemosensors 2: 8-Hydroxyquinoline Based Cu(II) Selective Fluorescent Tripod

8-Hydroxyquinoline based tripod 3 shows selective fluorescence quenching with Cu(II) and can be used for estimation of Cu(II) (1-6 ppm) even in the presence of Ni(II), Cd(II), Zn(II) (1000 ppm), Ag(II) (100 ppm).     

Electro-optical triple-channel sensing of metal cations via multiple signalling patterns

We described two molecular systems containing tricyanovinyl dyes as signalling subunits and crown ether macrocycles as binding sites, which act as triple-channel sensing receptors. Signalling was observed through UV-vis, fluorescence and electro-chemical measurements. With these three techniques sensing of certain metal cations was achieved via multiple signalling patterns.     

Cation and anion fluorescent and electrochemical sensors derived from 4,4′-substituted biphenyl

Five new fluorescent macrocyclic ligands derived from biphenyl are described. These new compounds can be used in cation and anion recognition and sensing. Their fluorescent and electrochemical properties are studied and the influence of the biphenyl conformation on these properties is considered. The X-ray single crystal structure of one of the described ligands has been determined.     

Colorimetric Fluoride‐Anion Sensor Based on Intramolecular Hydrogen Bonding and Enol–Keto Tautomerization of a Phenothiazine Derivative

A colorimetric sensor for fluoride ions based on a new sensing mechanism is reported. The colorimetric sensor contains an isomerizable enol–keto moiety as the recognition site and phenothiazine as chromogenic center. A color change visible to the naked eye is observed upon addition of fluoride ions to the solution of sensor 1 in aprotic solvents such as CHCl₃ and MeCN. The sensor shows no colorimetric response for other halide ions. Enol‐keto tautomerization is proposed to be responsible for the anion sensing of 1 , based on UV/VIS absorption, ¹H‐NMR, and single‐crystal structure analysis.     

Monosubstituted ferrocenyl chalcones: Effect of structural changes upon the ability to detect calcium by absorption spectroscopy

We show how structural changes in the basic framework of ferrocenyl chalcone [(C₅H₅)Fe(C₅ H₄COCHCHC₆H₄NEt₂)] (1) induce different capabilities of detecting calcium by UV/vis absorption spectroscopy. In particular, compound 1, and its derivatives (2) and (3) incorporating a supplementary ethylenic unit into the conjugated link, allow a specific detection of calcium triflate with regard to calcium perchlorate. Investigations related to the unprecedented behaviour of these chalcone-like derivatives are presented. This study confirms that while the interaction of ligands 1-3 with calcium is centred on the CO group, the interaction of ligand 4 with calcium is aza-centered. The strength of these interactions was examined by processing the UV/vis absorption data with a curve fitting model. Remarkably, in the case of compound 4, the set of association constants issued from processing the absorption data was successfully used to fit the NMR data. In addition, mass spectrometry experiments provided strong support for the formation of the different species involved in the interaction of compounds 1-4 with calcium. This work underlines the importance of considering the nature of the salt used as well as the experimental conditions in cation detection processes.     

1,3,5-Triaryl-2-penten-1,5-dione anchored to insoluble supports as heterogeneous chromogenic chemosensor

N-Allyl substituted 1,5-diphenyl-3-(4-N-methylaminophenyl)-2-penten-1,5-dione (1a) has been immobilized on a polystyrene backbone, on the surface of mercaptopropyl-functionalized silica or inside the cavities of zeolite NaY. These solids either in suspension or in films act as chemosensors of Fe³⁺ and other strong Lewis acid metal ions such as Cu²⁺ and Pb²⁺ in buffered water or ethanol. Brönsted acids in low pH aqueous solutions also produce the response of the sensor. For sensing of Fe³⁺, depending on the loading of 1a (typically from 2.5 to 0.5 wt%) the solids can test from 10⁻² to 10⁻⁴ M aqueous solutions. The time response can vary from tens of minutes to below a minute depending on hydrophilic/hydrophobic nature of the support and also on the 1a loading. The solid sensor was reused up to 10 times by regenerating after every use the initial form with NaAcO treatment.     

Organic heterocyclic-based colorimetric and fluorimetric chemosensors for the detection of different analytes: a review (from 2015 to 2022)

Heterocyclic organic compounds, also called heterocycles, are any major class of organic compounds having at least one atom other than carbon in the ring. Due to their excellent electronic and structural features, these compounds exhibit a wide range of biological and nonbiological applications. Among these, indole, benzimidazole, benzothiazole, and benzoxazole are versatile organic heterocyclic compounds widely used in different fields. They show a wide range of applications in polymer, coordination chemistry, pharmacy, dyes, food packages, medicine, and industries. These compounds contain heteroatoms like S-, N-, and O-, through which they interact with metal ions, anions, and neutral species, giving measurable analytical signals that can be used as fluorimetric and colorimetric chemosensors for detecting different analytes in biological, agricultural and environmental samples. This review summarizes indole, benzimidazole, benzothiazole, and benzoxazole-based fluorimetric and colorimetric chemosensors for detecting metal ions, anions, and neutral species. Furthermore, the recognition mechanisms have been discussed in detail, which could help researchers to design efficient, highly selective, and sensitive chemosensors to recognize and determine heavy metal cations.