Potential Fluorescent Sensor Research Articles

Solvent-Regulated Formation of Metal/Metal-Oxo Nodes in Two Indium Metal-Organic Frameworks: Syntheses, Structures, Selective Gas Adsorption and Fluorescence Sensor Properties.

Two water-stable indium metal-organic frameworks, (NH2Me2)3[In3(BTB)4] ⋅ 12DMA ⋅ 4.5H2O (In-MOF-1) and (NH2Me2)9[In9O6(BTB)8(H2O)4(DMSO)4] ⋅ 27DMSO ⋅ 21H2O (In-MOF-2) (BTB=4,4',4''-benzene-1,3,5-tribenzoate) with 3D interpenetrated structure has been constructed by regulating solvents. Structure analysis revealed that In-MOF-1 has a three-dimensional (3D) structure with a single metal core, while In-MOF-2 features an octahedron cage constructed by three kinds of metal clusters to further form a 3D structure. The fluorescence investigations showed that In-MOF-1 and In-MOF-2 are potential MOF-based fluorescent sensors to detect acetone and Fe3+ ions in EtOH or water with high sensitivity, excellent selectivity, recyclability and a low limit of detection. Moreover, the fluorescence mechanisms of In-MOF-1 and In-MOF-2 toward acetone and Fe3+ ions were further explained. In addition, In-MOF-2 has higher thermal and framework stability than In-MOF-1. The activated In-MOF-2 presents a high BET surface area of 998.82 m2g-1 and a pore size distribution of 8 to 16 Å. At the same time, In-MOF-2 exhibits high selective CO2 adsorption for CO2/CH4 and CO2/N2, respectively. Furthermore, the adsorption sites and adsorption isotherms were predicted using grand canonical Monte Carlo (GCMC) simulations, and the adsorption energy of the lowest-energy adsorption configuration was calculated using molecular dynamics (MD) simulations.

Regulation on the ligand fluorescence in UiO-66-Y metal-organic frameworks for effective detection of nitro-aromatic explosives

Rapid, sensitive and highly selective detection of nitro-aromatic explosives (NAEs) has become one of the most pressing environmental and safety issues. Metal-organic frameworks (MOFs) offer new possibilities for the development of new photoactive materials with excellent sensing properties. In this paper, three robust UiO-66-type fluorescent MOFs were prepared from the self-assembly of yttrium cations (Y3+) and linear dicarboxylic acid ligands, named terephthalic acid (BDC), 2-hydroxyterephthalic acid (OHBDC) and 2,5-dihydroxyterephthalic acid (DHBDC). The solid and solution fluorescence properties of three MOFs were successfully modulated by regulating the number of –OH functional groups from zero to two. At 370 nm excitation, Y-BDC MOF without –OH group was almost non-fluorescent, Y-OHBDC MOF with one –OH group emitted blue fluorescence, and Y-DHBDC MOF with two –OH groups emitted green fluorescence. Thanks to the suitable porous structures and stable frameworks, Y-OHBDC and Y-DHBDC MOFs both can quantificationally detect at least seven nitro-aromatic explosives (NAEs) by a fluorescence quenching process. Remarkably, the detection performance for 2,4,6-trinitrophenol (TNP) is the most outstanding with the KSV values of 8.4 × 104 M−1 and 2.1 × 105 M−1. Fast response, high sensitivity, strong anti-interference ability and good reusability make UiO-66-Y MOFs potential fluorescent sensors for TNP.

A molecule with aggregation-induced emission for the pH sensing and anti-counterfeiting applications

In this paper, a meaningful pH sensor (E)-4-(4-(1,2,2-triphenylvinyl) styryl)quinoline (TPQ) with aggregation-induced emission (AIE) effect was synthesized based on the conjugated 4-(1,2,2-triphenylvinyl)benzaldehyde and 4-methylquinoline connected by a CC bond. The conjugated quinoline moiety acts as a proton acceptor, and the small variations of pH value in the linear range of 4.01–7.03 and 7.96–9.45 can cause obvious fluorescence fluctuations. The TPQ has good selectivity and reversibility in pH detection, and importantly, it can detect pH fluctuations in real-time in practical applications by fluorescent means. Moreover, TPQ can also be used as a potential viscosity fluorescence sensor for organic solvents. In addition, by combining various color changes of TPQ caused by acid, alkali, water and ammonia stimulation under sunlight and 365 nm ultraviolet light irradiation, it provides a novel concealed optical anti-counterfeiting technique with high security. Therefore, TPQ is a multifunctional molecule with great potential for applications in pH, viscosity sensing and anti-counterfeiting.

Highly selective fluorescence turn-on sensor for·thiol compounds detection

As a kind of commonly-used synthetic materials for many pesticides, thiol compounds, once being leaked, can cause serious harm to the environment and humans. Therefore, the efficient detection of thiol compounds is essential. In this study developed a turn-on fluorescent probe (Cu@Zn-CP) for the highly sensitive fluorescence detection of thiol compounds. The probe was constructed based on a zinc coordination polymer (Zn-CP), whose fluorescence was quenched through the effective doping of Cu2+ ions. After the introduction of methyl thioglycolate (MTC), a rapid fluorescence turn-on response was generated within 90 s with a low detection limit of 23 ppb. Even after being reused for five cycles, the sensor maintains excellent detection performance and demonstrates good recyclability. It can also detect MTC in river water, with a spike recovery rate between 98–103 %. Furthermore, the designed Cu@Zn-CP exhibits good universality for detecting multifarious thiol compounds, including L-cysteine, glutathione, monothioglycerol, and 2-hydroxy-1-ethanethiol. This result provides a potential recyclable fluorescent sensor for thiol compounds.

Hectorite/Phenanthroline-Based Nanomaterial as Fluorescent Sensor for Zn Ion Detection: A Theoretical and Experimental Study

The development of fluorescent materials that can act as sensors for the determination of metal ions in biological fluids is important since they show, among others, high sensitivity and specificity. However, most of the molecules that are used for these purposes possess a very low solubility in aqueous media, and, thus, it is necessary to adopt some derivation strategies. Clay minerals, for example, hectorite, as natural materials, are biocompatible and available in large amounts at a very low cost that have been extensively used as carrier systems for the delivery of different hydrophobic species. In the present work, we report the synthesis and characterization of a hectorite/phenanthroline nanomaterial as a potential fluorescent sensor for Zn ion detection in water. The interaction of phenanthroline with the Ht interlaminar space was thoroughly investigated, via both theoretical and experimental studies (i.e., thermogravimetry, FT-IR, UV-vis and fluorescence spectroscopies and XRD measurements), while its morphology was imaged by scanning electron microscopy. Afterwards, the possibility to use it as sensor for the detection of Zn2+ ions, in comparison to other metal ions, was investigated through fluorescent measurements, and the stability of the solid Ht/Phe/Zn complex was assessed by different experimental and theoretical measurements.

Two Cd(Ⅱ)/Mn(Ⅱ) complexes based on multinuclear metal clusters for Fe(Ⅲ) and Cr(Ⅵ) fluorescence detection and magnetic properties

Two novel complexes, {[Cd3(L)2(H2O)2]·(H2O)4}n (1) and {[Mn(HL)(H2O)2]·(H2O)}n (2), which are synthesized by the reaction of 3-(2, 4-dicarboxyphenyl)-4-carboxypyridine ligand with cadmium and manganese metal ions under the solvothermal method. The complex 1 is a 3D framework based upon trinuclear [Cd3(μ2-COO)4(μ1-COO)4(N)2] SBUs, and the complex 2 is a one-dimensional metal oxygen chain based upon binuclear [Mn2(μ2-COO)2(μ1-COO)2(N)2] SBUs. The solid fluorescence analysis of complex 1 reveals that the emission peak of 451 nm when its excitation peak is 336 nm. The fluorescence detection experiments of complex 1 showed that Fe3+, Cr2O72− and CrO42− can effectively to be detected. Furthermore, their limits of detection are 1.47 × 10−3 M, 1.31 × 10−3 M and 1.25 × 10−3 M, respectively. It has good recovery properties as a potential multifunctional fluorescence sensor. Besides, the quenching mechanism of fluorescence sensing is also discussed. In addition, the magnetic studies of complex 2 show strong antiferromagnetic interactions between its neighboring Mn(II) ions.

Carbon dots-based fluorescent films to act as a potential antioxidant agent and pH ratiometric sensor for skin applications

The wound healing process is accompanied by changes in pH values. Monitoring this physicochemical parameter can indicate the effectiveness of the applied treatment and act as early identification of wound infection. This study focuses on the development of a fluorescent film-based polyvinyl alcohol (PVA) and carbon dots (CDs) derived from lemon bagasse (CD-L) and ortho-phenylenediamine (CD-oPD) named to act as antioxidants and potential ratiometric fluorescent pH sensors, in wound applications. The I460/I550 intensity ratio, as a function of pH value for the dual-system CDs prepared from the mixture of CD-L and CD-oPD, named CD-L/oPD, was investigated. The fit corresponded to a sigmoidal function in the pH range of 5–10, with a relationship having a r2 = 0.992. The variation in the values of the I460/I550 ratio allows for the visualization of the color change from yellowish-green to green with increasing pH. Through a simulated ex vivo pig skin model, it was possible to note that the films prepared from mixed of the CD-L and CD-oPD carbon dots incorporated in a matrix PVA named CD-L/oPD-F was more efficient at visually discriminating color in relation to changes in pH than the films prepared from both individual CD-L (CD-L-F) and CD-oPD (CD-oPD-F) carbon dots. CD-L and CD-oPD demonstrated antioxidant capacity against reactive oxygen species (ROS). The IC50 values for CD-L and CD-oPD were 56.7 and 39.5 μg mL−1 in the DPPH● inhibition assay, and 25.1 and 63.4 μg mL−1 in the HOCl scavenging one, respectively. MTT viability assays using human non-tumoral skin fibroblast (HFF-1) cell showed a cell survival rate of over 80% for both CDs up to a concentration of 1,000 μg mL−1. Finally, the developed films can act in a bifunctional way, by monitoring healing through pH changes and by acting as an antioxidant agent in the treatment of wounds.

A naked-eye visible aluminium (III)-based complex fluorescence sensor for sensitive detection of mesotrione

Mesotrione, which is a kind of herbicide to control broad-leaved weeds, has been increasingly used due to its excellent selectivity, rapid process and low toxicity. However, the excessive application of mesotrione have led to widespread contamination. Herein, a turn-on competitive coordination-based fluorescent probe, 2-hydroxy-1-(9-purin)-methylidenehydrazinenaphthalene (HPM), has been successfully synthesized. HPM could effectively detect Al3+ in CH3OH/HEPES (1/9, v/v) with low limit of detection (LOD) being 0.2 µM via coordination. HPM also exhibited excellent imaging capabilities for Al3+ in living cells with low cytotoxicity. On the basis of the competitive coordination of HPM with Al3+, the [HPM-Al3+] complex could also serve as a potential fluorescence sensor for detecting mesotrione with the LOD of 0.2 µM. Furthermore, [HPM-Al3+] complex was applied for the detection of mesotrione in real samples and test paper. Finally, the mechanism of [HPM-Al3+] for sensing mesotrione was investigated deeply as well. This work designed a new convenient method for on-site detection of mesotrione without the large-scale equipment or complicated pre-treatment.

Nanoscale semiconducting polymer dots with rhodamine spirolactam as fluorescent sensor for mercury ions in living systems

Mercury ion (Hg2+), as one of the most poisonous heavy metal ions, could seriously damage mental and neurological functions thus causing severe diseases. A fluorescent ratiometric sensor based on semiconducting polymer dots (Pdots) and rhodamine spirolactam derivate was developed for the detection of Hg2+. The Pdots were prepared by Poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-diphenylene-vinylene-2-methoxy-5-{2-ethylhexyloxy}-benzene)] (PDDB) with emitting strong green fluorescence. The organic fluorescence dye N-(rhodamine-B) lactam-hydrazine (RhBH), as Hg2+-recognizing monomer, was conjugated to the surface of Pdots. Hg2+ could specifically trigger ring-opening process of RhBH and thus induce strong Förster resonance energy transfer (FRET) effect, resulting in the green fluorescence decrease of Pdots (energy donor) and red emission derived from the ring-opened RhBH (energy acceptor) increasing. PDDB@RhBH showed a sensitive and reversible response toward Hg2+ and had a great performance on resisting interferences from various biological analytes. Additionally, both fluorescent imaging in living cells and zebrafish, and systemic toxicity analysis in rats demonstrated that PDDB@RhBH was a great potential fluorescent sensor for quantitative Hg2+ imaging in living systems.

A novel dual emission ratiometric fluorescence sensor Eu3+/CDs@UiO-66 to achieve Cu2+ detection in water environment

A novel dual-emission ratiometric fluorescent sensor Eu3+/CDs@UiO-66 was synthesized by post-synthesis modifying of UiO-66, a zirconium-based MOF formed by 1,4-phthalic acid (PTA) and Zr4+ , with europium ion (Eu3+) and carbon dots (CDs) and utilized for the determination of Cu2+ ions. The prepared composites not only maintain the excellent optical properties of CDs and Eu3+ but also have good stability in an aqueous solution. At the excitation wavelength of 299 nm, Eu3+/CDs@UiO-66 has two distinct emission peaks at 394 nm and 615 nm, respectively. More interestingly, when the material was dispersed in an aqueous solution containing Cu2+ ions, the characteristic peak of Eu3+ at 615 nm decreased significantly, while the characteristic peak of CDs at 394 nm remained unchanged. In the range of 0–500 μM, the relative fluorescence intensity ratio (F394/F615) linearly increased with increasing Cu2+ ion concentration, and the detection limit was calculated to be 51 nM (3Sb/Ksv). At the same time, the material can also be effectively applied to the detection of Cu2+ in environmental water samples. So Eu3+/CDs@UiO-66 can be developed as a potential ratiometric fluorescent sensor to detect Cu2+ ions.

A ratiometric fluorescent sensor for the detection of phosphate.

Over the past few years, ratiometric fluorescent nanoprobes have garnered substantial interest because of their self-calibration characteristics. This research developed a ratiometric fluorescent sensor to detect phosphate. Through encapsulating luminescent materials, gold nanoclusters (AuNCs) and carbon dots (CDs) into a zeolitic imidazolate framework-8 (ZIF-8), the fluorescence signal of AuNCs was enhanced, while that of CDs was suppressed. After phosphate was added, it could decompose ZIF-8, and AuNCs and CDs were released, which weakened the fluorescence signal of the AuNCs while restoring that of the CDs. Thereby, this makes CDs/AuNCs@ZIF-8 a potential fluorescent sensor for phosphate determination. The ratiometric sensor had facile synthesis, good selectivity, and a low detection limit. Therefore, this sensor was an effective tool for the detection of phosphate.

A Robust Strontium Coordination Polymer with Selective and Sensitive Fluorescence Sensing Ability for Fe3+ Ions.

Exploration of sensitive and selective fluorescence sensors towards toxic metal species is of great importance to solve metal pollution issues. In this work, a three-dimensional (3D) strontium coordination polymer of Sr2(tcbpe) (H4tcbpe = 1,1,2,2-tetrakis(4-(4-carboxy-phenyl)phenyl)ethene) has been synthesized and developed as a fluorescent sensor to Fe3+ ions. Sr2(tcbpe) shows a mechanochromic fluorescence with emission shifting from blue of the pristine to green after being ground. Notably, based on a fluorescence quenching mechanism, Sr2(tcbpe) displays a sensitive and selective fluorescent sensing behavior to Fe3+ ions with a detection limit of 0.14 mM. Moreover, Sr2(tcbpe) exhibits high tolerance to water in a wide pH range (pH = 3-13), demonstrating that Sr2(tcbpe) is a potential fluorescent sensor of Fe3+ in water.

AIEE active stilbene based fluorescent sensor with red-shifted emission for vapor phase detection of nitrobenzene and moisture sensing

A unique π-electron rich stilbene-based sensor with significantly enhanced red-shifted fluorescence emission has been synthesized via a Mizoroki-Heck cross-coupling reaction. The strong fluorescence properties of stilbene derivative as a potential fluorescent sensor have been investigated for sensitive and selective detection of hazardous and threatening nitrobenzene (NB) in both solution and vapor phase. The fluorescence emission intensity of stilbene sensor 1 at 474 nm was quenched upon interaction with NB. The fluorescence quenching was attributed to the combined effect of dominant smaller and adjustable size of NB and photo-induced electron transfer (PET) process. Stilbene sensor 1 is the first active bathochromic shifted fluorescent sensor with AIEE property was developed for both solution and vapor phase detection of NB. Possible interactions of stilbene sensor 1 with NB was evaluated by UV–vis., fluorescence, density functional theory (DFT) calculations, and 1H NMR titration experiment. Additionally, non-covalent interaction (NCI), Frontier molecular orbitals (FMOs) and interaction energy were studied by using Gaussian 09 software. Moreover, test strips were fabricated to accomplish contact mode detection of NB. Further, stilbene sensor 1 was successfully applied for trace detection of NB in real water samples.

A potential sensor for assessing thorium (IV) based on Albuterol sulfate fluorescence enhancement: A density functional theory (DFT) study

• Introducing a new fluorescent sensor for assessing Th(IV) in environmental samples. • Fluorescence mechanism was discussed. • HOMO and LUMO energy levels has been calculated by DFT. This study introduces a potential fluorescence sensor for assessing thorium (Th(IV)) in aquatic environments. In the presence of Th(IV), Albuterol Sulfate ( ABS ) 4-[2-( tert -butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol; sulfuric acid exhibits significant fluorescence enhancement at 600 nm. The current ABS ligand sensor shows wide linear range from 6.0 × 10 −8 – 2.5 × 10 −7 mol/L and pH range of 4–6. Interestingly, when all evaluated interference ions coexisted, the change in fluorescence emission intensity of ABS -Th complex was roughly 2.3 %. The binding mode is studied and indicating a 2:1 complex formation between ABS ligand and Th (IV). Density functional theory (DFT) has been utilized to examine the interaction characteristics between the present ABS ligand sensor and Th(IV) and to compute the geometric configuration of the ABS and ABS -Th through the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. The interaction properties exhibit considerable effect on the HOMO and LUMO properties of the complexes, as well as a fluorescence enhancement that could be attributable to the heavy atom effect of Th (IV). The ABS sensor shows remarkable features and provides good performance compared to some of the optical sensors, making it a potential new fluorescence sensor for Th(IV) assessment.

Helicene-Hydrazide Encapsulated Ethyl Cellulose as a Potential Fluorescence Sensor for Highly Specific Detection of Nonanal in Aqueous Solutions and a Proof-of-Concept Clinical Study in Lung Fluid.

Over the past years, lung cancer has been one of the vital cancer-related mortalities worldwide and has inevitably exhibited the highest death rate with the subsequent need for facile and convenient diagnosis approaches to identify the severity of cancer. Previous research has reported long-chain aldehyde compounds such as hexanal, heptanal, octanal, and nonanal as potential biomarkers of lung cancer. Herein, the helicene dye-encapsulated ethyl cellulose (EC@dye-NH) nanosensors have been applied for the potentially sensitive and specific detection of long-chain aldehydes in aqueous media. The sensors contain the intrinsic hydrazide group of dye-NH, which is capable of reacting an aldehyde group via imine formation and the EC backbone. This offers the synergistic forces of hydrophobic interactions with alkyl long-chain aldehydes, which could induce self-assembly encapsulation of EC@dye-NH nanosensors and strong fluorescence responses. The addition of long-chain aldehyde would induce the complete micellar-like nanoparticle formation within 15 min in acetate buffer pH 5.0. The limit of detection (LOD) values of EC@dye-NH nanosensors toward heptanal, octanal, and nonanal were 40, 100, and 10 μM, respectively, without interference from the lung fluid matrices and short-chain aldehydes. For practical applicability, this sensing platform was developed for quantification of the long-chain aldehydes in lung fluid samples with 98-101% recoveries. This EC@dye-NH nanosensor was applied to quantify nonanal contents in lung fluid samples. The results of this method based on EC@dye-NH nanosensors were then validated using standard gas chromatography-mass spectrometry (GC-MS), which gave results consistent with the proposed method. With intracellular imaging application, the EC@dye-NH nanosensors demonstrated excellent intracellular uptake and strong green fluorescence emission upon introducing the nonanal into the lung cancer cells (A549). Thus, the developed nanosensing approach served as the potential fluorescent probes in medical and biological fields, especially for lung cancer disease diagnosis based on highly selective and sensitive detection of long-chain aldehydes.

Metal ions recognition by pyrene labeled poly(acrylic acid)

In the present work, we assessed the sensing of multiple transition metal ions (Men+) using pyrene labeled poly(acrylic acid) (PAA25Py3). The UV–vis, steady-state (excitation and emission) and time-resolved fluorescence as well as FTIR measurements were performed. The comparative effect of Ag+, Cu2+ and Fe3+ on the optical properties (the monomer and excimer maximum intensity, the polarity/conformational index as well as the fluorescence quantum yield and lifetime) of the pyrene (Py) label was evaluated. The influence of the other metal ions (i.e., Li+, K+, Na+, Ba2+, Ca2+, Zn2+, Ni2+ and Al3+) on the Py photophysics was investigated. The fluorescence quenching of both Py monomer and excimer by appropriate amounts of Ag+, Cu2+ and Fe3+ was revealed. The quenching curves of Py were analyzed with the Stern-Volmer equation. The detection limit, the quenching and the binding constants were calculated. The fluorescent polymer showed higher sensitivity, selectivity and binding ability for Fe3+ than Cu2+ and Ag+. It was revealed the occurrence of the electron transfer from the amide group of PAA25Py3 to Py label, the formation of coordination complexes between several Cu2+/Fe3+ ions and carboxylic units of PAA25Py3 as well as the photoinduced electron transfer from excited Py to complexed Men+. The results proved that the pyrene labeled poly(acrylic acid) can be used as a potential fluorescent sensor to detect both Fe3+ and Cu2+ ions.

POSS‐based fluorescence sensor for rapid analysis of β‐carotene in health products

In recent years, fluorescent organic-inorganic hybrid nanomaterials have received much interest as potential fluorescent sensor materials. In this study, fluorescent organic-inorganic hybrid nanomaterials (POSS@ANT) were created using polyhedral oligomeric silsesquioxane as the precursor and 9,10-bromoanthracene as the monomer. The morphology and composition of POSS@ANT, as well as its pore characteristics and fluorescence properties were studied. POSS@ANT displayed steady fluorescence emission at an excitation wavelength of 374 nm. Next, a β-carotene fluorescence sensor was developed using the capacity of β-carotene to quench the fluorescence of POSS@ANT. The quenching process is linked to acceptor electron transfer and energy transfer, and the sensor has a high selectivity for β-carotene. This β-carotene fluorescence analysis method that we established has a linear range of 0.2-4.3mg/L and a detection limit of 0.081 mg/L. Finally, it was used to quantify β-carotene in health products, the recovery rate was 91.1-109.9%, the relative standard deviation (RSD) was 2.2-4.3%, and the results were comparable with the results of high-performance liquid chromatography. The approach is reliable and can be used to determine β-carotene in health products.

1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research.

This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review.

Fluorescent sensing framework based on mixed-ligand as a highly sensitive probe for selective detection of Fe3+ cations, Cr2O72− and nitrobenzene

Using 4'-(4′-pyridyl)-2,2':6′,2″-terpyridine (PYTPY) and 3,5-bis-(3-carboxy-benzyloxy)-benzoic acid (H3bcb) as ligands and transition metals cadmium (II) and iron (III) synthesized two metal organic frameworks [Cd(H2bcb)2(PYTPY)] (1) and [Fe(H2bcb)2(PYTPY)]n (2). The structure was confirmed and characterized by single crystal X-ray diffraction and elemental analysis. The structure analysis shows that complexes 1 and 2 are further connected through π-π interactions and hydrogen bonds to form a 3D supramolecular network. In addition, complex 1 shows high sensitivity to Fe3+, Cr2O72− and nitrobenzene in solutions containing mixed metal ions, anionic groups and aromatic compounds. Which makes it be a promising crystalline material as luminescent probe to Fe3+ Cr2O72− and nitrobenzene. This property makes complex 1 a potential fluorescence sensor for these chemicals. The present investigation clearly demonstrates selective, recyclable detection of lethal environmental pollutants such as Fe3+, Cr2O72− and NB in aqueous media which has relevance in the context of environmental protection and homeland security. Moreover, complex 2 exhibits weak antiferromagnetic interactions at low temperature. It lays a good foundation for the future research and design of molecular based magnets.

Metal-Organic Frameworks with Novel Catenane-like Interlocking: Metal-Determined Photoresponse and Uranyl Sensing.

The assembly of two tripyridinium-tricarboxylate ligands and different metal ions leads to seven isostructural MOFs, which show novel 2D→2D supramolecular entanglement featuring catenane-like interlocking of tricyclic cages. The MOFs show tripyridinium-afforded and metal-modulated photoresponsive properties. The MOFs with d10 metal centers (1-Cd, 1-Zn, 2-Cd, 2-Zn) show fast and reversible photochromism and concomitant fluorescence quenching, 1-Ni displays slower photochromism but does not fluoresce, and 1-Co and 2-Co are neither photochromic nor fluorescent. It is shown here that the network entanglement dictates donor-acceptor close contacts, which enable fluorescence originated from interligand charge transfer. The contacts also allow photoinduced electron transfer, which underlies photochromism and concomitant fluorescence response. The metal dependence in fluorescence and photochromism can be related to energy transfer through metal-centered d-d transitions. In addition, 1-Cd is demonstrated to be a potential fluorescence sensor for sensitive and selective detection of UO2 2+ in water.