A new rhodamine-based fluorescent chemosensor for transition metal cations synthesized by one-step facile condensation

A Novel Rhodamine-Phenolphthalein Architecture for Selective Mercury Ion Detection in Aqueous Media

In this study, the primary objective is to synthesize a novel fluorescent Rh-PP-Rh compound and explore its extensive range of photochemical behaviors. Initially, the synthesis of the novel Rh-PP-Rh was carried out for this purpose. Subsequently, UV-Vis and fluorescence spectroscopy were employed to investigate the interactions between Rh-PP-Rh and a diverse array of ions in aqueous solvent systems. Through fluorescence and UV-Vis studies, it was observed that Rh-PP-Rh demonstrated turn-on sensor properties in the presence of Hg2+ ions. Furthermore, the limits of detection (LOD) and association constant (Ka) values for Rh-PP-Rh/Hg2+ were determined as 334 nM and 9.13×1011 M-2, respectively. Additionally, the reversible studies demonstrated a switchable on/off response upon alternate addition of HgCl2 and [Bu4N]F to Rh-PP-Rh. These findings suggest that the probe Rh-PP-Rh also possesses specific sensor properties for F- ions in the presence of mercury. In addition, the investigation encompassed an assessment of the visual analysis of the color alterations of Rh-PP-Rh both on filter paper and in an EtOH/H2O solution. The findings demonstrated that Rh-PP-Rh can be successfully utilized in solutions containing mercury, as it generates significant color transformations.

Novel schiff base as Fe3+ sensor as well as an antioxidant and its theoretical studies

A novel Schiff base derivative L (N1-(thiophene-2-ylmethylene)benzene-1,2-diamine) was synthesized via condensation reaction of 3-thiophene carboxaldehyde and 1,2-diamino benzene. The synthesized compound was authenticated using 1 H NMR, 13 C NMR, HRMS, and IR spectroscopy. The compound L was found to be a Fe3+ sensor with the complexation ratio of 1 : 3 as revealed by Job’s plot with maximum absorption at 318 nm. The photophysical properties were studied using absorption and emission spectra. DFT and TD-DFT studies were carried out in order to support the photophysical outcomes of compound L. An antioxidant behaviour of compound L was studied using TAC, FRAP, and DPPH assays and it was found to be showing better TAC activity than the used standard i.e. gallic acid.

Novel fluorescein- and pyridine-conjugated schiff base probes for the recyclable real-time determination of Ce3+ and F. Methods Appl Fluoresc 2019;8:015002. [PMID: 31622961 DOI: 10.1088/2050-6120/ab4ee7]

The effect of aminopyridines substituted at different positions on the fluorescence properties deserves to be studied. Since 2-aminopyridyl-based probes have been reported, the effects of 3-aminopyridine and 4-aminopyridine on the performance of fluorescein probes were discussed in here. Two Schiff base fluorescein probes FN-1, FN-2 were designed and synthesized. Among them, since the ligand shows a highly selective and sensitive response to metal charge transfer (LMCT), the fluorescence of FN-1 can be quenched by Ce³⁺ ions in PBS buffer. At the same time, a specific precipitation reaction between Ce³⁺ and F^- releases the free probe to restore the fluorescence of FN-1. Therefore, FN-1 can be used for the recyclable 'ON-OFF-ON' detection of Ce³⁺and F^-. The detection limits for Ce³⁺and F^- are 4.48 μM and 11.58 μM in concentration range of 0-50 μM and 0-150 μM. However, due to the para position of N and amino groups on 4-aminopyridine, the spatial structure of FN-2 cannot be complexed with ions, resulting in poor selectivity. Polyvinylidene fluoride (PVDF) membrane containing FN-1 were prepared for the real-time qualitative detection of Ce³⁺and F^- in real water samples. FN-1 exhibits high water solubility and biocompatibility and has been successfully applied to biological imaging in vascular smooth muscle cells (VSMCs).

A New pH-Dependent Macrocyclic Rhodamine B-Based Fluorescent Probe for Copper Detection in White Wine

For efficiently measuring copper (II) ions in the acidic media of white wine, a new chemosensor based on rhodamine B coupled to a tetraazamacrocyclic ring (13aneN₄CH₂NH₂) was designed and synthesized by a one-pot reaction using ethanol as a green solvent. The obtained chemosensor was characterized via NMR, UV and fluorescent spectra. It was marked with no color emission under neutral pH conditions, with a pink color emission under acidic conditions, and a magenta color emission under acidic conditions where copper (II) ions were present. The sensitivity towards copper (II) ions was tested and verified over Ca²⁺, Ag⁺, Zn²⁺, Mg²⁺, Co²⁺, Ni²⁺, Fe²⁺, Pb²⁺, Cd²⁺, Fe³⁺, and Mn²⁺, with a detection limit of 4.38 × 10^-8 M in the fluorescence spectrum.

Crystal structure of (E)-2-(((6-bromopyridin-2-yl)methylene)amino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one, C34H34N5O2Br

C34H34N5O2Br, orthorhombic Pca21 (no. 29), a = 21.3626(13) Å, b = 11.8358(8) Å, c = 12.0998(9) Å, Z = 4, V = 3059.38(4) Å3, R gt(F) = 0.0507, wR ref(F 2) = 0.1401, T = 173 K.

Highly selective chemosensor for repetitive detection of Fe3+in pure water and bioimaging

Combining octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) with amine-containing polyacrylamide (OV-POSS co-poly(acrylamide)) gives a new fluorescent polymeric chemo-sensor with complete water solubility.

First Chemosensor for Selective Detection and Quantification of L-4-Hydroxyproline in Collagen and Other Bio Samples

Amino pyridine-based rhodamine conjugate (APR) has been developed as a first chemosensor for selective detection and quantification of L-4-Hydroxyproline (Hyp). The "turn-on" fluorescence property of the chemosensor makes it unique for easy estimation of Hyp in collagen and biological samples.

Sensitive and Selective "Turn-On" Chemodosimetric Probes for Fe3+ Based on a Skeleton of 2-Hydroxy-1-Naphthaldehyde

A naked-eye colored chemodosimeteric probes 4a-f, based on Schiff-azo dye conjugates were synthesized and characterized. All compounds 4a-f exhibited excellent selectivity and high sensitivity in absorbance toward detection of Fe³⁺ in alcoholic solutions under neutral pH conditions. The detection limit of the probe was shown to be up to 0.05 ppm. A simple paper test strip system for the rapid monitoring of Fe³⁺ was developed, indicating their convenient use in environmental samples. Electrochemical analysis of metal free conjugates and iron chelated probes confirmed the chelation of ligands. Graphical Abstract.

Novel triphenylamine based rhodamine derivatives: synthesis, characterization, photophysical properties and viscosity sensitivity

Five novel triphenylamine based deep red to NIR emitting rhodamine derivatives were synthesized and characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis.

A new type of triphenylamine based coumarin–rhodamine hybrid compound: synthesis, photophysical properties, viscosity sensitivity and energy transfer

A series of novel core modified triphenylamine coumarin–rhodamine systems (compounds MCMR, MCDR and DCMR) was designed and synthesized by incorporating a coumarin moiety on one and a rhodamine moiety on the other phenyl ring of the triphenylamine molecular skeleton.

Studies directed towards nonyl acridine orange analogues having the potential to act as FRET donors with the PDT drug Pc 4

Analogues of nonyl acridine orange (NAO) were made by quaternization of substituted acridine oranges. The Pc 4-FRET occurrence of these NAO analogues in cells was investigated.

A series of selective and sensitive fluorescent sensors based on a thiophen-2-yl-benzothiazole unit for Hg2+

Different types of fluorescent probes for Hg²⁺ based on the 5-thiophen-2-yl-benzothiazole derivatives (TBT, CTBT, DTBT and NTBT) were realized by changing the subsituents, including the fluorescence quenching probe, the fluorescence enhancement probe and the ratiometric fluorescent probe.

Dipicolylamine coupled rhodamine dyes: new clefts for highly selective naked eye sensing of Cu2+and CN−ions

The dipicolylamine (DPA) motif has been utilized in devising rhodamine labeled compounds1and2for Cu²⁺ions.

A Multisite-Binding Switchable Fluorescent Probe for Monitoring Mitochondrial ATP Level Fluctuation in Live Cells

Adenosine triphosphate (ATP), commonly produced in mitochondria, is required by almost all the living organisms; thus fluorescent probes for monitoring mitochondrial ATP levels fluctuation are essential and highly desired. Herein, we report a multisite-binding switchable fluorescent probe, ATP-Red 1, which selectively and rapidly responds to intracellular concentrations of ATP. Live-cell imaging indicated that ATP-Red 1 mainly localized to mitochondria with good biocompatibility and membrane penetration. In particular, with the help of ATP-Red 1, we successfully observed not only the decreased mitochondrial ATP levels in the presence of KCN and starvation state, but also the increased mitochondrial ATP levels in the early stage of cell apoptosis. These results indicate that ATP-Red 1 is a useful tool for investigating ATP-relevant biological processes.

A New Schiff Base Chemodosimeter for Fluorescent Imaging of Ferric Ions in Living Cells

A new and efficient chemodosimeter for ferric ions has been developed. The visual and fluorescent behaviors of the compound toward various metal ions were investigated: ferric ions are distinguished from other cations by selective color change and unusual fluorescence enhancement in mixed aqueous solution. Fluorescence microscopy experiments showed that this receptor is effective for detection of Fe(3+) in vitro, developing a good image of the biological organelles. The sensing mechanism is shown to involve a hydrolysis process.

Introduction of luminescent rhenium(i), ruthenium(ii), iridium(iii) and rhodium(iii) systems into rhodamine-tethered ligands for the construction of bichromophoric chemosensors

Several classes of rhenium(i), ruthenium(ii), iridium(iii) and rhodium(iii) complexes tethered with a rhodamine moiety have been synthesized and characterized, and their photophysical and ion-binding properties were investigated.

A rhodamine derivative as selective fluorescent and colorimetric chemosensor for mercury (II) in buffer solution, test strips and living cells

In this paper, we reported a new rhodamine derivative bearing 2,4-dichloroquinazoline as a selective fluorescent chemosensor for Hg(2+). The ring-opening process of spirolactam enabled the large fluorescent enhancement and colorimetric change by Hg(2+) induced configuration transformation of the rhodamine. Moreover, the fluorescence changes of the chemosensor were dramatically specific for Hg(2+) in the presence of other metal ions, which could meet the selective requirements for practical application. Under optimized experimental conditions, the linear response range covered the concentration range of Hg(2+) from 0 to 1.0×10(-6)M, and the limit of detection was calculated to be 2.7×10(-8)M. In addition, the probe was also successfully applied to the determination of Hg(2+) in water samples, test strips and living cells.

A new rhodamine-derived fluorescent chemodosimeter for Cu2+in aqueous solution and its application in living cell imaging

A new rhodamine-derived fluorescent chemodosimeter for imaging of Cu²⁺in living cells was developed under a coordination-promoted hydrolysis mechanism.

Switching selectivity between Pb2+ and Hg2+ ions through variation of substituents at xanthene end; ‘turn-on’ signalling responses by FRET modulation

Substitution at amino groups attached to the xanthene core modulates the stereo-electronic situation to switch selectivity; a FRET mediated signalling with a distinctive coupling of fluorophores.

Rhodamine-based fluorescent off–on sensor for Fe3+ – in aqueous solution and in living cells: 8-aminoquinoline receptor and 2 : 1 binding

A rhodamine-based Fe³⁺ sensor of a rigid 8-aminoquinoline receptor shows a 2 : 1 binding according to 1D and 2D-¹HNMR experiments.

Zn(II)-coordination modulated ligand photophysical processes - the development of fluorescent indicators for imaging biological Zn(II) ions

Molecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered photophysical processes that are pertinent to developing Zn(II) indicators. The main aim is to show how small organic Zn(II) indicators work under the constraints of specific requirements, including Zn(II) detection range, photophysical requirements such as excitation energy and emission color, temporal and spatial resolutions in a heterogeneous intracellular environment, and fluorescence response selectivity between similar cations such as Zn(II) and Cd(II). In the last section, the biological questions that fluorescent Zn(II) indicators help to answer are described, which have been motivating and challenging this field of research.

Determination of iron(III) based on the fluorescence quenching of rhodamine B derivative

A new method for determination of iron(III) has been developed using a kind of rhodamine B derivative fluorescent probe, rhodamine amide (RHA), in acidic HAc-NaAc buffer solution. In this approach, the heavy atom effect of I₃(-) was applied to quench the fluorescence of RHA. When iron(III) and KI coexisted in HAc-NaAc buffer solution, iron(III) reacted with the excess KI to produce I₃(-) that quenched the fluorescence of RHA through the formation of a non-fluorescence compound. The results showed that the fluorescence intensity decrease of RHA presented a good linear relationship with the iron(III) concentrations in the range from 0.5 to 5.0 μmol L(-1) with the correlation coefficient of 0.9970, and the detection limit was 0.3 μmol L(-1) iron(III). The approach was applied to determination of iron(III) in water samples, and the recovery was found to be from 80.7% to 100. 8%.

Tricolor emission of a fluorescent heteroditopic ligand over a concentration gradient of zinc(II) ions

The internal charge transfer (ICT) type fluoroionophore arylvinyl-bipy (bipy = 2,2'-bipyridyl) is covalently tethered to the spirolactam form of rhodamine to afford fluorescent heteroditopic ligand 4. Compound 4 can be excited in the visible region, the emission of which undergoes sequential bathochromic shifts over an increasing concentration gradient of Zn(ClO(4))(2) in acetonitrile. Coordination of Zn(2+) stabilizes the ICT excited state of the arylvinyl-bipy component of 4, leading to the first emission color shift from blue to green. At sufficiently high concentrations of Zn(ClO(4))(2), the nonfluorescent spirolactam component of 4 is transformed to the fluorescent rhodamine, which turns the emission color from green to orange via intramolecular fluorescence resonance energy transfer (FRET) from the Zn(2+)-bound arylvinyl-bipy fluorophore to rhodamine. While this work offers a new design of ratiometric chemosensors, in which sequential analyte-induced emission band shifts result in the sampling of multiple colors at different concentration ranges (i.e., from blue to green to orange as [Zn(2+)] increases in the current case), it also reveals the nuances of rhodamine spirolactam chemistry that have not been sufficiently addressed in the published literature. These issues include the ability of rhodamine spirolactam as a fluorescence quencher via electron transfer, and the slow kinetics of spirolactam ring-opening effected by Zn(2+) coordination under pH neutral aqueous conditions.