Porous Crystalline Materials Based on Tetrathiafulvalene and Its Analogues: Assembly, Charge Transfer, and Applications.

ConspectusThe directed synthesis and functionalization of porous crystalline materials pose significant challenges for chemists. The synergistic integration of different functionalities within an ordered molecular material holds great significance for expanding its applications as functional materials. The presence of coordination bonds connected by inorganic and organic components in molecular materials can not only increase the structural diversity of materials but also modulate the electronic structure and band gap, which further regulates the physical and chemical properties of molecular materials. In fact, porous crystalline materials with coordination bonds, which inherit the merits of both organic and inorganic materials, already showcase their superior advantages in optical, electrical, and magnetic applications. In addition to the inorganic components that provide structural rigidity, organic ligands of various types serve as crucial connectors in the construction of functional porous crystalline materials. In addition, redox activity can endow organic linkers with electrochemical activity, thereby making them a perfect platform for the study of charge transfer with atom-resolved single-crystal structures, and they can additionally serve as stimuli-responsive sites in sensor devices and smart materials.In this Account, we introduce the synthesis, structural characteristics, and applications of porous crystalline materials based on the famous redox-active units, tetrathiafulvalene (TTF) and its analogues, by primarily focusing on metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). TTF, a sulfur-rich conjugated molecule with two reversible and easily accessible oxidation states (i.e., radical TTF•+ cation and TTF2+ dication), and its analogues boast special electrical characteristics that enable them to display switchable redox activity and stimuli-responsive properties. These inherent properties contribute to the enhancement of the optical, electrical, and magnetic characteristics of the resultant porous crystalline materials. Moreover, delving into the charge transfer phenomena, which is key for the electrochemical process within these materials, uncovers a myriad of potential functional applications. The Account is organized into five main sections that correspond to the different properties and applications of these materials: optical, electrical, and magnetic functionalities; energy storage and conversion; and catalysis. Each section provides detailed discussions of synthetic methods, structural characteristics, the physical and chemical properties, and the functional performances of highlighted examples. The Account also discusses future directions by emphasizing the exploration of novel organic units, the transformation between radical cation TTF•+ and dication TTF2+, and the integration of multifunctionalities within these frameworks to foster the development of smart materials for enhanced performance across diverse applications. Through this Account, we aim to highlight the massive potential of TTF and its analogues-based porous crystals in chemistry and material science.

A Benzothiadiazole-Based Zn(II) Metal-Organic Framework with Visual Turn-On Sensing for Anthrax Biomarker and Theoretical Calculation.

2,6-pyridine dicarboxylic acid (DPA) is an exceptional biomarker of notorious anthrax spores. Therefore, the rapid, sensitive, and selective quantitative detection of DPA is extremely significant and urgent. This paper reports a Zn(II) metal-organic framework with the formula of {[Zn6(NDA)6(DPBT)3] 2H2O·3DMF}n (MOF-1), which consists of 2,6-naphthalenedicarboxylic acid (2,6-NDA), 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole (DPBT), and Zn(II) ions. Structural analysis indicated that MOF-1 is a three-dimensional (3D) network which crystallized in the monoclinic system with the C2/c space group, revealing high pH, solvent, and thermal stability. Luminescence sensing studies demonstrated that MOF-1 had the potential to be a highly selective, sensitive, and recyclable fluorescence sensor for the identification of DPA. Furthermore, fluorescent test paper was made to detect DPA promptly with color changes. The enhancement mechanism was established by the hydrogen-bonding interaction and photoinduced electron transfer transition between MOF-1 and DPA molecules.

N-Heterocyclic Carbene-Catalyzed Atroposelective Synthesis of Axially Chiral α-Carbolinones via Heterocycle Formation.

An NHC-catalyzed atroposelective synthesis of axially chiral α-carbolinones from α,ß-unsaturated iminoindole derivatives and α-chloroaldehydes was developed. The reaction proceeds through a cascade process including [4 + 2] annulation and then oxidative dehydrogenation with concomitant central-to-axial chirality conversion under mild conditions. The developed method opens a new avenue to efficiently access axially chiral α-carbolinones in moderate to good enantioselectivities.

A pH-Stable Tb-MOF as Luminescence Sensor for Highly Sensitive Detection of Amino Acids through Diverse Sensing Mechanism.

A luminescent Tb-MOF with excellent stability and dual-emitting properties was constructed with an amide-functionalized tetracarboxylate ligand. Tb-MOFs were initially assembled on one-dimensional Tb3+ chains, then formed a two-dimensional double-decker layer through the synergistic linking of organic ligands and bridging formic acid anions, and further fabricated the final three-dimensional structure through the connection of the organic ligands. Powder X-ray diffraction experiments revealed that Tb-MOFs not only exhibited excellent stability in water but also maintained structural integrity in the pH range of 2-12. Importantly, this Tb-MOF provided the first example of a metal-organic framework (MOF)-based luminescence sensor that can simultaneously detect two acid amino acids (aspartic and glutamic acids) through a turn-off sensing mechanism and two basic amino acids (lysine and arginine acids) through unusual turn-on and turn-off-on sensing mechanisms. Moreover, high sensitivity, low detection limit, and excellent recyclability of this sensor endow Tb-MOFs with great potential as a highly efficient amino acid fluorescence sensor in chemical detection and biological environments.

Two Stable Bifunctional Zinc Metal-Organic Frameworks with Luminescence Detection of Antibiotics and Proton Conduction.

Functionalized crystalline solids based on metal-organic frameworks (MOFs) enable efficient luminescence detection and high proton conductivity, making them crucial in the realms of environmental monitoring and clean energy. Here, two structurally and functionally distinct zinc-based MOFs, [Zn(TTDPa)(bodca)]·H2O (1) and [Zn(TTDPb)(bodca)]·H2O (2), were successfully designed and synthesized using 3,6-di(pyridin-4-yl)thieno[3,2-b]thiophene (TTDPa) and 2,5-di(pyridin-4-yl)thieno[3,2-b]thiophene (TTDPb) as ligands, in the presence of bicyclo[2.2.2]octane-1,4-dicarboxylic acid (H2bodca). Both 1 and 2 display a three-dimensional (3D) structure with 5-fold interpenetration, and notably, 2 forms a larger one-dimensional pore measuring 17.16 × 10.81 Å2 in size. Fluorescence experiments demonstrate that 1 and 2 can function as luminescent sensors for nitrofurantoin (NFT) and nitrofurazone (NFZ) with low detection limits, remarkable selectivity, and good recyclability. A comprehensive analysis was conducted to investigate the differing sensing effects of compounds 1 and 2 and to explore potential sensing mechanisms. Additionally, at 328 K and 98% relative humidity, 1 and 2 exhibit proton conductivity values of 2.13 × 10-3 and 4.91 × 10-3 S cm-1, respectively, making them suitable proton-conducting materials. Hence, the integration of luminescent sensing and proton conductivity in monophasic 3D Zn-MOFs holds significant potential for application in intelligent multitasking devices.

Uranyl Polyoxotungstate Cluster for Visible-Light-Driven Heterogeneous C-H Selective Fluorination.

The selective fluorination of C-H bonds at room temperature using heterogeneous visible-light catalysts is both interesting and challenging. Herein, we present the heterogeneous sandwich-type structure uranyl-polyoxotungstate cluster Na17{Na@[(SbW9O33)2(UO2)6(PO3OH)6]}·46H2O (denoted as U6P6) to regulate the selective fluorination of the C-H bond under visible light and room temperature. This is the first report in which uranyl participates in the fluorination reaction in the form of an insoluble substance. U6P6 is capable of the effective selective fluorination of cycloalkanes and the recyclability of the photocatalyst due to the synergistic effect of multiple uranyl (UO2)2+ and the insolubility of organic reagents of polyoxotungstate. In situ electron paramagnetic resonance spectroscopy captured the generation of cycloalkane radicals during the photoreaction, confirming the mechanism of direct hydrogen atom transfer.

A Novel Cold-Adapted and High-Alkaline Alginate Lyase with Potential for Alginate Oligosaccharides Preparation.

Alginate oligosaccharides (AOs) prepared through enzymatic reaction by diverse alginate lyases under relatively controllable and moderate conditions possess versatile biological activities. But widely used commercial alginate lyases are still rather rare due to their poor properties (e.g., lower activity, worse thermostability, ion tolerance, etc.). In this work, the alginate lyase Alyw208, derived from Vibrio sp. W2, was expressed in Yarrowia lipolytica of food grade and characterized in order to obtain an enzyme with excellent properties adapted to industrial requirements. Alyw208 classified into the polysaccharide lyase (PL) 7 family showed maximum activity at 35 °C and pH 10.0, indicating its cold-adapted and high-alkaline properties. Furthermore, Alyw208 preserved over 70% of the relative activity within the range of 10-55 °C, with a broader temperature range for the activity compared to other alginate-degrading enzymes with cold adaptation. Recombinant Alyw208 was significantly activated with 1.5 M NaCl to around 2.1 times relative activity. In addition, the endolytic Alyw208 was polyG-preferred, but identified as a bifunctional alginate lyase that could degrade both polyM and polyG effectively, releasing AOs with degrees of polymerization (DPs) of 2-6 and alginate monomers as the final products (that is, DPs 1-6). Alyw208 has been suggested with favorable properties to be a potent candidate for biotechnological and industrial applications.

A Tetrathiafulvalene/Naphthalene Diimide-Containing Metal-Organic Framework with fsc Topology for Highly Efficient Near-Infrared Photothermal Conversion.

Metal-organic frameworks (MOFs) provide broad prospects for the development of new photothermal conversion materials, while their design and synthesis remain challenging. A new Zn-MOF (1) containing both tetrathiafulvalene (TTF) as an electron donor and naphthalene diimide (NDI) as an electron acceptor was constructed by using a space limiting effect. The material exhibited wide absorption peaks in the near-infrared region, indicating that there was strong charge transfer interaction between the TTF and NDI units and providing the possibility of photothermal conversion. 1 shows efficient near-infrared photothermal conversion performance. Under 808 nm laser (0.4 W cm-2) illumination, the temperature of 1 increased rapidly from room temperature to 250 °C, with good thermal stability and cycle durability. This work provides an efficient strategy for promising materials in photothermal therapy.

Dysprosium(III) Metal-Organic Framework Demonstrating Ratiometric Luminescent Detection of pH, Magnetism, and Proton Conduction.

A multifunctional metal-organic framework, (Hdmbpy)[Dy(H2dobdc)2(H2O)]·3H2O (Dy-MOF, H4dobdc = 2,5-dihydroxyterephthalic acid, dmbpy = 4,4'-dimethyl-2,2'-bipyridine), was synthesized and structurally characterized. The metal center DyIII is connected by four carboxyl groups to form the [Dy2(CO2)4] binuclear nodes, which are further interconnected by eight separate H2dobdc2- ligands to form a three-dimensional (3D) framework including hydrophilic triangular channels and abundant hydrogen-bonding networks. Dy-MOF has good stability in aqueous solution as well as in harsh acidic or alkaline solutions (pH range: 2.0-12.0). Furthermore, the luminescence signal of Dy-MOF undergoes a visualized color change as the acidity of the solution alters, which is the typical behavior of pH ratiometric probe. At a 100% relative humidity, Dy-MOF exhibits a high proton conductivity σ (1.70 × 10-4 S cm-1 at 303 K; 1.20 × 10-3 S cm-1 at 343 K) based on the proton hopping mechanism, which can be classified as a superionic conductor with σ exceeding 10-4 S cm-1. Additionally, the ferromagnetic interaction and magnetic relaxation behavior are simultaneously achieved in Dy-MOF. Herein, the combination of luminescence sensing, magnetism, and proton conduction in a single-phase 3D MOF may offer great potential applications in smart multitasking devices.

Chromatographic fingerprint combined with quantitative analysis of multi-components by single-marker for quality control of total lignans from Fructus arctii by high-performance liquid chromatography.

INTRODUCTION: The total lignans from Fructus arctii (TLFA) is a mixture of a series of lignans isolated from dried ripe fruit of Arctium lappa L. We previously reported on the pharmacological activity of TLFA that is related to diabetes. An accurate and practical TLFA quantitative analysis method for utilising it needs to be established. OBJECTIVE: This study aimed to develop an effective quantitative analysis method for assessing the TLFA quality. METHODS: A total of 11 marker components were confirmed by analysing the high-performance liquid chromatography fingerprints of 24 batches of TLFA samples. The samples were prepared from TLFA and structurally identified as lappaol H, lappaol C, arctiin, arctignan D, arctignan E, matairesinol, arctignan G, isolappaol A, lappaol A, arctigenin, and lappaol F. In the quantitative analysis of multi-components by the single-marker (QAMS) method and with arctiin as an internal reference substance, the content of these lignans in TLFA was simultaneously determined according to their relative correction factors with arctiin. RESULTS: There was no significant difference between results measured by the QAMS and traditional external standard methods. Hierarchical cluster and principal component analyses were performed to evaluate 24 TLFA batches based on the contents of 10 marker components. The results revealed that QAMS method combined with chemometric analyses could accurately measure and clearly distinguish the different quality samples of TLFA. CONCLUSION: The QAMS method is a reliable and promising quality control method for TLFA. It can provide a reference for promoting quality control of complex multi-component systems, especially for traditional Chinese medicine.

Human Lower Limb Motion Capture and Recognition Based on Smartphones.

Human motion recognition based on wearable devices plays a vital role in pervasive computing. Smartphones have built-in motion sensors that measure the motion of the device with high precision. In this paper, we propose a human lower limb motion capture and recognition approach based on a Smartphone. We design a motion logger to record five categories of limb activities (standing up, sitting down, walking, going upstairs, and going downstairs) using two motion sensors (tri-axial accelerometer, tri-axial gyroscope). We extract the motion features and select a subset of features as a feature vector from the frequency domain of the sensing data using Fast Fourier Transform (FFT). We classify and predict human lower limb motion using three supervised learning algorithms: Naïve Bayes (NB), K-Nearest Neighbor (KNN), and Artificial Neural Networks (ANNs). We use 670 lower limb motion samples to train and verify these classifiers using the 10-folder cross-validation technique. Finally, we design and implement a live detection system to validate our motion detection approach. The experimental results show that our low-cost approach can recognize human lower limb activities with acceptable accuracy. On average, the recognition rate of NB, KNN, and ANNs are 97.01%, 96.12%, and 98.21%, respectively.

Cytotoxic lanostane triterpenoids from the ethanol extract of Schisandra viridis.

Three new lanostane triterpenoids, designated as 6-hydroxyl schiglausin A (1), 29-hydroxyl schiglausin D (2), and 6-hydroxyl schiglausin G (3), were isolated from the ethanol extract of the stems of Schisandra viridis. Structural elucidation of all the compounds were performed by spectral methods such as 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated compounds were tested in vitro for cytotoxic activities. As a result, compound 1 exhibited cytotoxic activities for all six tested human lung cancer cell lines with IC50 values less than 10 µM.

Charge Transfer Metal-Organic Framework Containing Redox-Active TTF/NDI Units for Highly Efficient Near-Infrared Photothermal Conversion.

Metal-organic frameworks (MOFs), as a class of new inorganic-organic hybrid crystal materials, could have important applications in near-infrared (NIR) photothermal conversion. Herein, a new charge-transfer MOF (Co-MOF) with mixed ligands of H4 TTFTB and bpmNDI incorporating redox-active tetrathiafulvalene/naphthalene diimide (TTF/NDI) units into one system is reported. Due to the presence of TTF/NDI oxidative and reductive couples, stable radicals can be observed in the MOF. In addition, charge transfer from the electron donor (TTF) to the acceptor (NDI) results in a broad absorption in the NIR region. The Co-MOF exhibited an efficient photothermal effect induced by irradiation with a NIR laser. Under the 808 nm laser (0.7 W cm-2 ) illumination, the temperature of the Co-MOF increased from room temperature to 201 °C in only 10 s. Furthermore, a series of polydimethylsiloxane (PDMS) films doped with trace amounts of Co-MOF showed efficient NIR photothermal conversion. When a Co-MOF@PDMS (0.6 wt %) film is irradiated by 808 nm laser with power of 0.5 W cm-2 , it's temperature can reach a plateau at 62 °C from 20 °C within 100 s. Our experimental results from the Co-MOF@PDMS film demonstrate that the effectiveness and feasibility of the material is promising for photothermal applications.

Rare-Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox-Switchable Single-Molecule Magnets.

Using the redox-active tetrathiafulvalene tetrabenzoate (TTFTB4- ) as the linker, a series of stable and porous rare-earth metal-organic frameworks (RE-MOFs), [RE9 (µ3 -OH)13 (µ3 -O)(H2 O)9 (TTFTB)3 ] (1-RE, where RE=Y, Sm, Gd, Tb, Dy, Ho, and Er) were constructed. The RE9 (µ3 -OH)13 (µ3 -O) (H2 O)9 ](CO2 )12 clusters within 1-RE act as segregated single-molecule magnets (SMMs) displaying slow relaxation. Interestingly, upon oxidation by I2 , the S=0 TTFTB4- linkers of 1-RE were converted into S= 1 / 2 TTFTB.3- radical linkers which introduced exchange-coupling between SMMs and modulated the relaxation. Furthermore, the SMM property can be restored by reduction in N,N-dimethylformamide. These results highlight the advantage of MOFs in the construction of redox-switchable SMMs.

Sandwich-Type Uranyl Phosphate-Polyoxometalate Cluster Exhibiting Strong Luminescence.

A pure inorganic uranyl phosphate-polyoxometalate of Na17{Na@[(SbW9O33)2(UO2)6(PO3OH)6]}·xH2O (abbreviated as Na@U6P6, with x ≈ 46) featuring a sandwich-type structure was prepared using Keggin-type trilacunary [α-B-SbW9O33]9- units as building blocks, which were formed in situ by SbCl3 and Na2WO4·2H2O. Crystal structural analysis showed that six UO22+ cations and six PO3OH2- anions generated a wheel-like cluster unit with a Na+ center ([Na@(UO2)6(PO3OH)6]+) that is stabilized by two [α-B-SbW9O33]9- units. Na@U6P6 displayed a solid-state photoluminescence quantum yield of 33% at 300 K. The temperature-dependent fluorescence emission spectra showed that Na@U6P6 has temperature-sensitive fluorescence in which its emission intensity decreased by 77% as the temperature increased from 200 to 300 K. These results suggest that such uranyl phosphate-polyoxometalate clusters could serve as potential temperature-sensitive molecular materials.

Enantioselective Synthesis of Axially Chiral Benzothiophene/Benzofuran-Fused Biaryls by N-Heterocyclic Carbene Catalyzed Arene Formation.

Axially chiral biaryl scaffolds are prevalent in natural products, chiral ligands, and organocatalysts. However, N-heterocyclic carbene (NHC) catalyzed de novo construction of an aromatic ring with concomitant axial chirality induction for the synthesis of biaryl atropisomers is far less developed, and the efficient synthesis of axially chiral tetra-ortho-substituted biaryls remains an unsolved problem under NHC catalysis. Reported here is an NHC-catalyzed de novo synthesis of axially chiral benzothiophene/benzofuran-fused biaryls from enals and 2-benzyl-benzothiophene/benzofuran-3-carbaldehydes through a [2+4] annulation, decarboxylation, and oxidative aromatization cascade with central-to-axial chirality conversion. The developed method provides efficient and general access to novel axially chiral benzothiophene/benzofuran-fused biaryls in high enantioselectivities and works well for the synthesis of tetra-ortho-substituted biaryls.

A Metal-Organic Framework Based on a Nickel Bis(dithiolene) Connector: Synthesis, Crystal Structure, and Application as an Electrochemical Glucose Sensor.

Functionalizing the redox-active tetrathiafulvalene (TTF) core with groups capable of coordination to metals provides new perspectives on the modulation of architectures and electronic properties of organic-inorganic hybrid materials. With a view to extending this concept, we have now synthesized nickel bis(dithiolene-dibenzoic acid), [Ni(C2S2(C6H4COOH)2)2], which can be considered as the inorganic analogue of the organic tetrathiafulvalene-tetrabenzoic acid (H4TTFTB). Likewise, [Ni(C2S2(C6H4COOH)2)2] is a redox-active linker for new functional metal-organic frameworks, as demonstrated here with the synthesis of [Mn2{Ni(C2S2(C6H4COO)2)2}(H2O)2]·2DMF, (1, DMF = N,N-dimethylformamide). 1 is isomorphic to the reported [Mn2(TTFTB)(H2O)2] (2) but is a better electrochemical glucose sensor due to the multiple oxidation-reduction states of the [NiS4] core, which allow glucose to be oxidized to glucolactone by the high oxidation state [NiS4] center. As a non-enzymatic glucose sensor, 1 on Cu foam (CF), 1-CF, was synthesized by a one-step hydrothermal method and exhibited an excellent electrochemical performance. The fabricated 1-CF electrode offers a high sensitivity of 27.9 A M-1 cm-2, with a wide linear detection range from 2.0 × 10-6 to 2.0 × 10-3 M, a low detection limit of 1.0 × 10-7 M (signal/noise = 3), and satisfactory stability and reproducibility.

Insight into the Construction of (3,6)-Connected rtl, ant, and Chiral anh Nets Based on Structural Investigation of Several MOFs via Steric Tuning of Linkers.

Six cobalt-organic frameworks (1-6) were solvothermally constructed with a tritopic pyridine-carboxylate linker (L-H) and its methyl- and methoxy-functionalized derivatives (L-OCH3 and L-CH3). Due to incorporated multiple substituents with various steric hindrances, the tritopic linkers adopt different molecular configurations, Y-shaped and T-shaped, which further combine octahedral or trigonal-prismatic inorganic nodes to afford diverse (3,6)-connected nets. Consequently, 1 and 2 are rtl nets and 3 and 4 are ant nets. Notably, 5 and 6 present rarely observed chiral anh (flu-3) networks with left-handed double helical chains. The structural investigation indicates that the steric tuning of linkers may essentially dictate the resulting diverse MOF structures. Furthermore, the MOFs presented here can be regarded as an ideal structural platform for a better understanding of the assembly of (3,6)-connected rtl, ant, and chiral anh nets, which are closely related to the shape and geometric configuration/conformation of tridentate organic nodes as well as inorganic building nodes.

Crosstalk between PKC and MAPK pathway activation in cardiac fibroblasts in a rat model of atrial fibrillation.

OBJECTIVE: Atrial fibrillation (AF) is the most frequent form of cardiac arrhythmia and major cause of cardiac ischemia. Defective calcium homeostasis due to anomalous expression of ryanodine receptor type 2 (RyR2) or its hyperactivation by phosphorylation by serine threonine kinases has been implicated as a central mechanism of AF pathogenesis. Given the role of protein kinase C (PKC) isoforms in cardiac function we investigated role of PKC in AF using a rat model. RESULTS: PMA induced global increase in protein synthesis in cardiac fibroblasts isolated from AF rats, but not healthy controls, and the increase was inhibited by PKC inhibition. PMA mediated activation of both PKC and ERK and either inhibition of PKC by Go6983 or ERK by the MEK inhibitor Trametinib attenuated both P-ERK and P-PKC in both cardiac fibroblasts isolated from AF rats or from healthy rats but transduced with PKC-delta. The PKC and ERK mediated induction of global protein synthesis was found to be mediated by increased phosphorylation of the ribosomal protein S6. CONCLUSION: Our findings provide a foundation for future testing of PKC and MEK inhibitors to treat AF in pre-clinical models. It also needs to be determined if PKC and MAPK pathway activation is functioning via RyR2 or some yet undefined substrates.

Characterization of a New Intracellular Alginate Lyase with Metal Ions-Tolerant and pH-Stable Properties.

Alginate lyases play an important role in alginate oligosaccharides (AOS) preparation and brown seaweed processing. Many extracellular alginate lyases have been characterized to develop efficient degradation tools needed for industrial applications. However, few studies focusing on intracellular alginate lyases have been conducted. In this work, a novel intracellular alkaline alginate lyase Alyw202 from Vibrio sp. W2 was cloned, expressed and characterized. Secretory expression was performed in a food-grade host, Yarrowia lipolytica. Recombinant Alyw202 with a molecular weight of approximately 38.3 kDa exhibited the highest activity at 45 °C and more than 60% of the activity in a broad pH range of 3.0 to 10.0. Furthermore, Alyw202 showed remarkable metal ion-tolerance, NaCl independence and the capacity of degrading alginate into oligosaccharides of DP2-DP4. Due to the unique pH-stable and high salt-tolerant properties, Alyw202 has potential applications in the food and pharmaceutical industries.