Chromone-Based Cd(II) Fluorescent Coordination Polymer Fabricated to Study Optoelectronic and Explosive Sensing Properties

Here, electrical conductivity and explosive sensing properties of multifunctional chromone-Cd(II)-based coordination polymers (CPs) (1-4) have been explored. The presence of different pseudohalide linkers, thiocyanate ions, and dicyanamide ions resulted in 1D and 3D architecture in the CPs. Thin film devices developed from CPs 1-4 (complex-based Schottky devices, CSD1, CSD2, CSD3, and CSD4, respectively) showed semiconductor behavior. Their conductivity values increased under photo illumination (1.37 × 10-5, 1.85 × 10-5, 1.61 × 10-5, and 2.01 × 10-5 S m-1 under dark conditions and 5.06 × 10-5, 8.78 × 10-5, 7.26 × 10-5, and 10.21 × 10-5 S m-1 under light). The nature of the I-V plots of these thin film devices under light irradiation and dark are nonlinear rectifying, which has been observed in Schottky barrier diodes (SBDs). All four CPs (1-4) exhibited highly selective fluorescence quenching-based sensing properties toward well-known explosives, 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP). The limit of detection (LOD) values are 55, 28, 27, and 31 μM for TNP and 78, 44, 32, and 41 μM for DNP for complexes 1-4, respectively. A structure property correlation has been established to explain optoelectronic and explosive sensing properties.

A Soluble Porous Coordination Polymer for Fluorescence Sensing of Explosives and Toxic Anions under Homogeneous Environment

In the past decades, porous coordination polymers (PCPs) based fluorescent (FL) sensors have received intense attention due to their promising applications. In this work, a soluble Zn-PCP is presented as a sensitive probe towards explosive molecules, chromate, and dichromate ions. In former reports, PCP sensors were usually ground into fine powders and then dispersed in solvents to form FL emulsion for sensing applications. However, their insoluble characters would cause the sensing accuracy which is prone to interference from environmental effects. While in this work, the as-made PCP could be directly soluble in organic solvents to form a clear solution with bright blue emission, representing the first soluble PCP based fluorescence sensor to probe explosive molecules under a homogeneous environment. Moreover, the FL PCP solution also shows sensitive detection behaviors towards the toxic anions of CrO42- and Cr2O72-, which exhibit a good linear relationship between the fluorescence intensity of Zn-PCP and the concentrations of both analytes. This work provides a reference for designing task-specific PCP sensors utilized under a homogeneous environment.

A Cerium Organic Framework with {Cu2I2} Cluster and {Cu2I2}n Chain Modules: Structure and Fluorescence Sensing Properties

In this work, a copper iodine module bearing a coordination polymer (CP) with a formula of [(Cu₂I₂)₂Ce₂(INA)₆(DMF)₃]·DMF (1, HINA = isonicotinic acid, DMF = N,N'-dimethyl formamide) is presented. The title compound features a three dimensional (3D) structure, in which the {Cu₂I₂} cluster and {Cu₂I₂}_n chain modules are coordinated by N atoms from a pyridine ring in INA^- ligands, while the Ce³⁺ ions are bridged by the carboxylic groups of INA^- ligands. More importantly, compound 1 exhibits an uncommon red fluorescence (FL) with a single emission band maximized at 650 nm belonging to near infrared (NIR) luminescence. The temperature dependent FL measurement was applied to investigate the FL mechanism. Remarkably, 1 could be used as a FL sensor to cysteine and the nitro-bearing explosive molecule of trinitropheno (TNP) with high sensitivity, demonstrating its potential FL sensing applications for biothiol and explosive molecules.

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.

Synthesis of a Heterometallic [Zn2Ca] Pinwheel Array Stabilized by Amide-Amide Synthons

The rational design of heterometallic compounds bearing s-block metal ions have been a difficult task for chemists owing to their lack of preferential geometries. However, some strategies, such as the design of coordinating pockets with different sizes and/or donor atoms, have offered great results. In this work, this strategy has been tested using Ca(II) as an s-block metal ion and a compound previously obtained by our group with the formula [Zn3(μ-ACA)6(4-phpy)2], which contains tetrahedral N,O- and octahedral O-coordinating pockets as a model structure. From this work, the corresponding heterometallic compound with the formula [Zn2Ca(μ-ACA)6(4-phpy)2]·EtOH (1) has been successfully synthesized, and fully characterized, and its crystal structure has been elucidated. Furthermore, we have compiled all the crystal structures containing [Zn2M] pinwheel secondary building units (SBUs), where M stands for an s-block metal ion, and the observed tendencies, as well as the promising applications as template SBUs for the preparation of 1D–3D coordination polymers, have been discussed. Finally, solid-state UV-Vis and photoluminescence have been recorded and compared with the homometallic [Zn3(μ-ACA)6(4-phpy)2] compound.

A Dihydrotetrazine-Functionalized Metal-Organic Framework as a Highly Selective Luminescent Host-Guest Sensor for Detection of 2,4,6-Trinitrophenol

Pore decoration of metal-organic frameworks (MOFs) with functional groups is a useful strategy to attain high selectivity toward specific analytes, especially in the presence of interfering molecules with similar structures and energy levels, through selective host-guest interactions. In this work, we applied a dihydrotetrazine-decorated MOF, TMU-34, with the formula [Zn(OBA)(H₂DPT)_0.5]_n·DMF, where H₂OBA is 4,4'-oxybis(benzoic acid) and H₂DPT is 3,6-bis(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, for the highly selective detection of phenolic NACs, especially TNP (94% quenching efficiency, detection limit 8.1 × 10^-6 M, K_SV = 182663 mol L^-1), in the presence of other substituted NACs especially -NH₂-substituted NACs. Investigations reveal that the quenching mechanism is dominated by photoinduced MOF-to-TNP electron transfer through possible hydrogen-bonding interactions between the phenolic hydroxyl group of TNP and dihydrotetrazine functions of TMU-34. Despite extensive publications on the detection of TNP in the presence of other NACs, the significance of this work will be elucidated if attention is paid to the fact that TMU-34 is among the rare and highly selective MOF-based TNP sensors in the presence of -NH₂-substituted NACs as the serious interferers.

Two new supramolecular Ag(I) coordination polymers: luminescent properties and treatment activity on glioblastoma

Two new Ag(I) coordination polymers, namely [Ag(bpp)]·0.5 n(1,5-NDSA)·n(H₂O) (1) and [Ag₂(bpp)₂]_n·n(2,7-NDSA)·2 n(H₂O)·n(CH₃CN) (2) (Na₂(1,5-NDSA) = sodium 1,5-naphthalenedisulfonate dibasic, Na₂(2,7-NDSA) = sodium 1,5-naphthalenedisulfonate dibasic, bpp is 1,3-bis(4-pyridyl)propane), were generated via the solution evaporation method under room temperature. Moreover, the solids of these two compounds display strong luminescence emission at RT. And the application values of the compounds against the glioblastoma treatment were determined, and the corresponding mechanism was simultaneously tested. The analysis of CCK-8 was first implemented and the glioblastoma viability was measured. The real-time RT-PCR was next performed, and the signaling pathway activation of VEGF in glioblastoma cells was tested after treating by the above compound.

Tuning Chromophore-Based LMOF Dimensionality to Enhance Detection Sensitivity for Fe3+ Ions

Herein, we report the synthesis of two new manganese-based luminescent metal-organic frameworks (LMOFs) [Mn_0.5(tipe)(1,4-ndc)] _n (1) and [Mn(tipe)(1,4-ndc) (H₂O)·(DMF)₂·(H₂O)₃] _n (2) [tipe = 1,1,2,2-tetrakis(4-(1H-imidazol-1-yl)phenyl)ethene (tipe) and 1,4-ndc = 1,4-naphthalenedicarboxylic acid] constructed from an aggregation-induced emission (AIE) chromophore ligand. Compound 1 can undergo a facile single-crystal-to-single-crystal transformation to form compound 2, which results in an increase in dimensionality from a two-dimensional (2D) network to a three-dimensional (3D) network. Both compounds demonstrate excellent performance for the solution-phase detection of Fe³⁺ ions through a significant and rapid quench in luminescence emission. Fluorescence titration experiments reveal that compound 2 is more selective toward Fe³⁺ compared to compound 1 because of its 3D stacking mode. The K _sv value for compound 2 (32 378 M^-1) is twice as large as that for compound 1 (15 854 M^-1) for the detection of Fe³⁺ ions. We attribute this significant increase in performance to the increase in dimensionality. In addition, compound 2 demonstrates high selectivity and sensitivity for the detection of Cr³⁺ cations and Cr₂O₇ ^2- anions.

Heterometallic coordination polymers: Treatment activity on diabetic foot by reducing the excess inflammatory response in the plantar tissue

Two new heterometallic coordination polymers formulated as {[LaCo(2.5-pydc)2(H2O)4]Cl·4H2O}n (1, 2,5-H2pydc = pyridine-2,5-dicarboxylic acid) and {[LaCo2Cl3(4,4′-bpdc)2(H2O)3]·H2O}n (2, 4,4′-H2bpdc = 2,2′-bipyridyl-4,4′-dicarboxylic acid) have been solvothermally synthesized using the coordination between rare earth/transition metal ions and pyridinedicarboxylic acids. To develop new candidates for enhancing the therapeutic effect of improved negative pressure suction for diabetic foot, the activities of compounds 1 and 2 were studied. First, the ELISA (enzyme linked immunosorbent assay) detection kit was used and the inflammatory cytokines in the plantar tissue were measured. Besides, the TLR-4-NF-κB signaling pathway was measured with real-time reverse transcription-polymerase chain reaction.

Regioisomeric monopyridine-functionalized triarylethene: small AIEgens with isomeric effect and an efficient platform for the selective and sensitive detection of Pd2+ and Fe3+

Regioisomeric monopyridine functionalized triarylethenes are established as small AIEgens. These compounds are utilized to detect Fe⁺³ and Pd⁺² selectively in nM range. The detection is further extended for the on-site applications.

Novel alkaline earth metal–organic frameworks with thiophene groups for selective detection of Fe3+

This work demonstrates that the alkaline earth ion radii play an important role in coordination numbers and topologies for constructing MOFs, and these MOFs can be used as fast-response fluorescence sensors for the detection of Fe³⁺.

Sensing organic analytes by metal–organic frameworks: a new way of considering the topic

In this review, our goal is comparison of advantageous and disadvantageous of MOFs about signal-transduction in different instrumental methods for detection of different categories of organic analytes.

New perspective on the fluorescence and sensing mechanism of TNP chemosensor 2-(4,5-bis(4-chlorophenyl)-1H-imidazol-2-yl)-4-chlorolphenol

For TNP chemosensor 2-(4,5-Bis(4-Chlorophenyl)-1H-Imidazol-2-yl)-4-Chlorolphenol (HPICI), previous thought with no theoretical basis was that excited-state intramolecular proton transfer (ESIPT) process and the ground-state HPICI-TNP complex are mainly responsible for its fluorescence emission and the detection of TNP. However, this interpretation has been proved to be wrong by the present theoretical DFT/TDDFT explorations. Actually, the strong fluorescence of HPICI is mainly induced by the local excitation of the enol form HPICI(E) without ESIPT, and the fluorescence quenching by TNP is due to the photo-induced electron transfer (PET) process together with the cooperative effect of hydrogen-bonding interaction and π-π stacking interaction coexisting in the HPICI-TNP complex. The strengthened excited-state hydrogen bond promotes the PET process, thus facilitates the fluorescence quenching. This mechanism is proposed on the basis of the theoretical analyses on molecule geometry, binding energy, Gibbs free energy, electronic transitions, and frontier molecular orbitals (FMOs).

A water-stable 3D Eu-MOF based on a metallacyclodimeric secondary building unit for sensitive fluorescent detection of acetone molecules

A Eu-MOF with high water stability constructed using a systematic metallacyclodimeric motif as a potential chemical sensor for acetone is reported.

Amino acid-derived alternating polyampholyte luminogens

A unique polyampholyte luminogen comprised of alternatively placed oppositely charged moieties onto the poly(styrene-alt-maleimide) skeleton was synthesized, and used for the specific detection of carbon disulfide (CS₂) in both solution and vapor phases.

Mg2+ incorporated Co-based MOF precursors for hierarchical CNT-containing porous carbons with ORR activity

The light and abundant Mg²⁺ was introduced as a heteroatom into a Co-MOF to synthesize a series of Mg-Co bimetallic MOFs, further acting as excellent precursors for hierarchically CNTs-containing nanoporous carbons.

A channel-structured Eu-based metal–organic framework with a zwitterionic ligand for selectively sensing Fe3+ ions

A novel Eu-based MOF [Eu(IMS1)₂]Cl·4H₂O (1) was successfully constructed based on a semi-rigid zwitterionic 1,3-bis(4-carboxylbenzyl)-imidazolium (IMS1) ligand, featuring a 3-fold interpenetrating dia net structure with a point symbol of 6⁶ and charged permanent micropores. Considering its excellent luminescent property as well as thermal and chemical stability, complex 1 was explored as a potential sensor for detecting Fe³⁺ ions. The results show that complex 1 has a high sensitivity and selectivity for Fe³⁺ based on a ‘turn-off’ effect, for which the electrostatic interaction between Fe³⁺ ions and the inner surface of the micropores may play a critical role. The fluorescence quenching mechanism reveals that dynamic quenching and competitive adsorption between Fe³⁺ and 1 lead to the quenching effect of 1.

A channel-structured Eu-based metal–organic framework with a zwitterionic ligand may serve as a sensor for selectively detecting Fe³⁺ ions.