Copper ion luminescence on/off sensing by a quinoline-appended ruthenium(II)-polypyridyl complex in aqueous media

Naphthalimide-based new architecture for fluorescence turn-on sensing of Cu2+ and colorimetric detection of F-/CN. Methods 2024;225:13-19. [PMID: 38438060 DOI: 10.1016/j.ymeth.2024.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

A new molecular structure 1 has been developed on naphthalimide motif. The amine and triazole binding groups have been employed at the 4-position of naphthalimide to explore the sensing behavior of molecule 1. Single crystal x-ray diffraction and other spectroscopic techniques confirm the identity of 1. Compound 1 exhibits high selectivity and sensitivity for Cu2+ ions in CH3CN. The binding of Cu2+ shows ∼ 70-fold enhancement in emission at 520 nm. The binding follows 1:1 interaction and the detection limit is determined to be 6.49 × 10-7 M. The amine-triazole binding site in 1 also corroborates the detection of F- through a colour change in CH3CN. Initially H-bonding and then deprotonation of amine -NH- in the presence of F- are the sequential steps involved in F- recognition with a detection limit of 4.13 × 10-7 M. Compound 1 is also sensible to CN- like F- ion and they are distinguished by Fe3+ ion. Cu2+-ensemble of 1 fluorimetrically recognizes F- among the tested anions and vice-versa. The collaborative effect of amine and triazole motifs in the binding of both Cu2+ and F-/CN- has been explained by DFT calculation.

An Indole-based Chromofluorogenic Probe for Detection of Trivalent Al3+, Ga3+, In3+ and Fe3+ Ions

An easily synthesizable indole-derived chromofluorogenic probe InNS has been demonstrated for recognition of trivalent metal ions (i. e., Al3+, Ga3+, In3+ and Fe3+). Both UV-Vis and emission spectral studies have been employed to assess the cation sensing ability of InNS in semi-aqueous medium. This probe exhibited a chromogenic response for these metal ions, and the related change was accompanied with the appearance of a new absorption near 376 nm. An obvious color change from pale yellow to dark yellow could also be noticed upon addition of the aforementioned metal ions to the probe's solution. Distinctively from the UV-Vis analysis, the fluorescence behavior of InNS was completely different; it displayed a 'turn-on' fluorescence response for only Al3+ among all the studied cations. The detection limit and the association constant (Ka) for Al3+ were determined to be 12.5 nM and 6.85×106 M-1, respectively. A potential 1 : 1 binding mode of Al3+-InNS has been established based on Job's plot, 1H NMR and DFT analyses. The reversibility experiment was conducted using strongly chelating EDTA ion, and a corresponding logic gate has been devised. In terms of practical applications, the InNS has been utilized to detect Al3+ in human breast carcinoma (MCF-7) cell lines displaying promising 'turn-on' bioimaging experiments.

Turn-on detection of Al3+ and Zn2+ ions by a NSN donor probe: reversibility, logic gates and DFT calculations

An efficient dual functional naphthalene-derived Schiff base NpSb probe has been synthesised and evaluated for its fluorescence and chromogenic response towards metal ions. The NpSb probe was capable of selectively recognising Al3+ and Zn2+ ions when they were excited at the same wavelength in an aqueous organic solvent system. Almost non-fluorescent NpSb displayed a 'turn-on' fluorescence response when treated with Zn2+ (λem = 416 nm) and Al3+ (λem = 469 nm) ions due to the chelation-enhanced fluorescence (CHEF) effect. The limit of detection (LoD) values for Al3+ and Zn2+ have been determined to be 38.0 nM and 43.0 nM, respectively. The binding constants for Al3+ and Zn2+ were found to be 1.18 × 106 M-1 and 3.5 × 105 M-1, respectively. The NpSb also acted as a colorimetric sensor for Al3+ as the colour of the probe's solution turned to pale green from colourless upon Al3+ addition. The binding mechanism between NpSb and Zn2+/Al3+ was supported by the ESI-MS, Job's plot, NMR, and DFT studies. The reversibility experiments were carried out with an F- ion and EDTA with the development of corresponding logic gates. Moreover, NpSb could be applied to detect Al3+ ions in real samples such as tap water, distilled water and soil samples.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

Determination and Imaging of Small Biomolecules and Ions Using Ruthenium(II) Complex-Based Chemosensors

Luminescence chemosensors are one of the most useful tools for the determination and imaging of small biomolecules and ions in situ in real time. Based on the unique photo-physical/-chemical properties of ruthenium(II) (Ru(II)) complexes, the development of Ru(II) complex-based chemosensors has attracted increasing attention in recent years, and thus many Ru(II) complexes have been designed and synthesized for the detection of ions and small biomolecules in biological and environmental samples. In this work, we summarize the research advances in the development of Ru(II) complex-based chemosensors for the determination of ions and small biomolecules, including anions, metal ions, reactive biomolecules and amino acids, with a particular focus on binding/reaction-based chemosensors for the investigation of intracellular analytes' evolution through luminescence analysis and imaging. The advances, challenges and future research directions in the development of Ru(II) complex-based chemosensors are also discussed.

Ruthenium(II) Complexes with (3-Polyamino)phenanthrolines: Synthesis and Application in Sensing of Cu(II) Ions

This work deals with the development of water-soluble optical sensors based on ruthenium(II) tris(diimine) complexes that exhibit high molar absorptivity and are emissive in aqueous media. Palladium-catalyzed arylation of polyamines with 3-bromo-1,10-phenanthroline (Brphen) and [Ru(bpy)2(Brphen)](PF6)2 (bpy = 2,2’-bipyridine) was explored to prepare Ru2+ complexes with 1,10-phenanthrolines (phen) substituted by linear polyamines (PAs) at position 3 of the heterocycle ([Ru(bpy)2(phen⎼PA)](PF6)2). The most convenient synthetic pathway leading to the target molecular probes includes the preparation of phen⎼PA ligands, followed by ruthenium complexation using cis-Ru(bpy)2Cl2. Complexes bearing a polyamine chain directly linked to phenanthroline core are emissive in aqueous media and their quantum yields are comparable to that of parent [Ru(bpy)3](PF6)2. Their structure can be easily adapted for detection of various analytes by modification of amine groups. As an example, we prepared the emissive complex Ru(N2P2phen) which is suitable for the dual channel (spectrophotometry and luminescence (ON–OFF probe)) selective detection of Cu2+ ions at the physiological pH levels with limits of detection (LOD) by spectrophotometry and fluorescence spectroscopy equal to 9 and 6 μM, respectively, that is lower than the action level in drinking water for copper as prescribed by the US Environmental Protection Agency.

Recent advances (2017-20) inthe detection of copper ion by using fluorescence sensors working through transfer of photo-induced electron (PET), excited-state intramolecular proton (ESIPT) and Förster resonance energy (FRET)

An essential trace element copper plays several physiological roles in living systems. But at excess concentration, it exerts toxicity and becomes associated with numerous disorders. In this article, we have reviewed the recent developments (from 2017 to 2020) in the field of fluorescence-based chemosensors for the detection of Cu²⁺ ion. The sensing probes which were built to work through transfer of photo-induced electron (PET), excited-state intramolecular proton (ESIPT) and Förster resonance energy (FRET) mechanisms have been included in this review. Emphasis is given on the design, sensitivity and response of the probe molecules for the detection of Cu²⁺ ion. Using suitable examples, applications of these three recognition mechanisms for the probing of copper ion have been addressed.

Development of a method for the detection of Cu2+ in the environment and live cells using a synthesized spider web-like fluorescent probe

A macrocyclic Schiff base fluorescent probe [1,2-phenylenediamine-2,6-pyridinedialdehyde macrocyclic Schiff base] (BP-MSB) based on 2,6-pyridinedialdehyde was synthesized for use in the detection of Cu²⁺ in environmental water samples and live cells imaging by the method of specific recognition. The free fluorescent probe BP-MSB shows strong fluorescence in DMSO/H₂O. The probe shows high sensitivity and selectivity for Cu²⁺ through "turn-off" fluorescence response in DMSO/H₂O buffer solution (pH = 6.5), with a detection limit of 0.83 nM, which is far below the maximum allowable drinking water content of 20.0 μM specified by the US Environmental Protection Agency. The BP-MSB fluorescence quenching method was used for the determination of Cu²⁺ in Xiang Jiang water samples and tap-water. Furthermore, addition of the same number of moles of ethylene diamine tetraacetic acid (EDTA) can realize the reversible recognition of Cu²⁺ by the probe BP-MSB. Most importantly, the fluorescence imaging of live cells after incubation of BP-MSB with GM12878 cells showed good imaging performance, confirming the sensitivity of the fluorescent probe BP-MSB in vivo. The probe was also used to form an analog logic gate. This probe has the advantages of good stability, simple operation and high selectivity, which provides a broad prospect for environmental monitoring, intracellular detection and practical application of POCT.

Recognition, mechanistic investigation and applications for the detection of biorelevant Cu2+/Fe2+/Fe3+ ions by ruthenium(ii)-polypyridyl based fluorescent sensors

Selective recognition of biorelevant Cu²⁺ and Fe²⁺/Fe³⁺ ions using fluorescent Ru(ii)-polypyridyl based sensors via both “turn-on” and “turn-off” emissive response is the main focus of present article.