Perylene-Based Coordination Polymers: Synthesis, Fluorescent J-Aggregates, and Electrochemical Properties.

The incorporation of electroactive organic building blocks into coordination polymers (CPs) and metal-organic frameworks (MOFs) offers a promising approach for adding electronic functionalities such as redox activity, electrical conductivity, and luminescence to these materials. The incorporation of perylene moieties into CPs is, in particular, of great interest due to its potential to introduce both luminescence and redox properties. Herein, we present an innovative synthesis method for producing a family of highly crystalline and stable coordination polymers based on perylene-3,4,9,10-tetracarboxylate (PTC) and various transition metals (TMs = Co, Ni, and Zn) with an isostructural framework. The crystal structure of the PTC-TM CPs, obtained through powder X-ray diffraction and Rietveld refinement, provides valuable insights into the composition and organization of the building blocks within the CP. The perylene moieties are arranged in a herringbone pattern, with short distances between adjacent ligands, which contributes to the dense and highly organized framework of the material. The photophysical properties of PTC-Zn were thoroughly studied, revealing the presence of J-aggregation-based and monomer-like emission bands. These bands were experimentally identified, and their behavior was further understood through the use of quantum-chemical calculations. Solid-state cyclic voltammetry experiments on PTC-TMs showed that the perylene redox properties are maintained within the CP framework. This study presents a simple and effective approach for synthesizing highly stable and crystalline perylene-based CPs with tunable optical and electrochemical properties in the solid state.

Porphyrin NanoMetal-Organic Frameworks as Cancer Theranostic Agents.

Metal-Organic Frameworks (MOFs) are hybrid multifunctional platforms that have found remarkable applications in cancer treatment and diagnostics. Independently, these materials can be employed in cancer treatment as intelligent drug carriers in chemotherapy, photothermal therapy, and photodynamic therapy; conversely, MOFs can further be used as diagnostic tools in fluorescence imaging, magnetic resonance imaging, computed tomography imaging, and photoacoustic imaging. One essential property of these materials is their great ability to fine-tune their composition toward a specific application by way of a judicious choice of the starting building materials (metal nodes and organic ligands). Moreover, many advancements were made concerning the preparation of these materials, including the ability to downsize the crystallites yielding nanoporous porphyrin MOFs (NMOFs) which are of great interest for clinical treatment and diagnostic theranostic tools. The usage of porphyrins as ligands allows a high degree of multifunctionality. Historically these molecules are well known for their reactive oxygen species formation and strong fluorescence characteristics, and both have proved helpful in cancer treatment and diagnostic tools. The anticipation that porphyrins in MOFs could prompt the resulting materials to multifunctional theranostic platforms is a reality nowadays with a series of remarkable and ground-breaking reports available in the literature. This is particularly remarkable in the last five years, when the scientific community witnessed rapid development in porphyrin MOFs theranostic agents through the development of imaging technologies and treatment strategies for cancer. This manuscript reviews the most relevant recent results and achievements in this particular area of interest in MOF chemistry and application.

Multifunctionality in an Ion-Exchanged Porous Metal-Organic Framework.

Porous robust materials are typically the primary selection of several industrial processes. Many of these compounds are, however, not robust enough to be used as multifunctional materials. This is typically the case of Metal-Organic Frameworks (MOFs) which rarely combine several different excellent functionalities into the same material. In this report we describe the simple acid-base postsynthetic modification of isotypical porous rare-earth-phosphonate MOFs into a truly multifunctional system, maintaining the original porosity features: [Ln(H3pptd)]·xSolvent [where Ln3+ = Y3+ (1) and (Y0.95Eu0.05)3+ (1_Eu)] are converted into [K3Ln(pptd)]·zSolvent [where Ln3+ = Y3+ (1K) and (Y0.95Eu0.05)3+ (1K_Eu)] by immersing the powder of 1 and 1_Eu into an ethanolic solution of KOH for 48 h. The K+-exchanged Eu3+-based material exhibits a considerable boost in CO2 adsorption, capable of being reused for several consecutive cycles. It can further separate C2H2 from CO2 from a complex ternary gas mixture composed of CH4, CO2, and C2H2. This high adsorption selectivity is, additionally, observed for other gaseous mixtures, such as C3H6 and C3H8, with all these results being supported by detailed theoretical calculations. The incorporation of K+ ions notably increases the electrical conductivity by 4 orders of magnitude in high relative humidity conditions. The conductivity is assumed to be predominantly protonic in nature, rendering this material as one of the best conducting MOFs reported to date.

Inclusion Compound of Efavirenz and γ-Cyclodextrin: Solid State Studies and Effect on Solubility.

Efavirenz is an antiretroviral drug of widespread use in the management of infections with human immunodeficiency virus type 1 (HIV-1). Efavirenz is also used in paediatrics, but due to its very poor aqueous solubility the liquid formulations available resort to oil-based excipients. In this report we describe the interaction of γ-cyclodextrin with efavirenz in solution and in the solid state. In aqueous solution, the preferential host-guest stoichiometry was determined by the continuous variation method using 1H NMR, which indicated a 3:2 host-to-guest proportion. Following, the solid inclusion compound was prepared at different stoichiometries by co-dissolution and freeze-drying. Solid-state characterisation of the products using FT-IR, 13C{1H} CP-MAS NMR, thermogravimetry, and X-ray powder diffraction has confirmed that the 3:2 stoichiometry is the adequate starting condition to isolate a solid inclusion compound in the pure form. The effect of γ-cyclodextrin on the solubility of efavirenz is studied by the isotherm method.

Membrane-Supported Layered Coordination Polymer as an Advanced Sustainable Catalyst for Desulfurization.

The application of a catalytic membrane in the oxidative desulfurization of a multicomponent model diesel formed by most refractory sulfur compounds present in fuel is reported here for the first time. The catalytic membrane was prepared by the impregnation of the active lamellar [Gd(H4nmp)(H2O)2]Cl·2H2O (UAV-59) coordination polymer (CP) into a polymethyl methacrylate (PMMA, acrylic glass) supporting membrane. The use of the catalytic membrane in the liquid-liquid system instead of a powder catalyst arises as an enormous advantage associated with the facility of catalyst handling while avoiding catalyst mass loss. The optimization of various parameters allowed to achieve a near complete desulfurization after 3 h under sustainable conditions, i.e., using an aqueous H2O2 as oxidant and an ionic liquid as extraction solvent ([BMIM]PF6, 1:0.5 ratio diesel:[BMIM]PF6). The performance of the catalytic membrane and of the powdered UAV-59 catalyst was comparable, with the advantage that the former could be recycled successfully for a higher number of desulfurization cycles without the need of washing and drying procedures between reaction cycles, turning the catalytic membrane process more cost-efficient and suitable for future industrial application.

Site-Selective Modification of a Porpholactone-Selective Synthesis of 12,13- and 17,18-Dihydroporpholactones.

The reaction of meso-tetrakis(pentafluorophenyl)porpholactone with azomethine ylides and nitrones affords pyrrolidine-fused and isoxazolidine-fused dihydroporpholactones that display, respectively, isobacteriochlorin- and chlorin-type UV-Vis spectra. These reactions are site-selective, yielding, respectively, 17,18- or 12,13-dihydroporpholactones. The crystal and molecular features of pyrrolidine-fused and isoxazolidine-fused dihydroporpholactones were unveiled from single-crystal X-ray diffraction studies.

A Convenient Synthesis of Pentaporphyrins and Supramolecular Complexes with a Fulleropyrrolidine.

A simple and straightforward synthesis of diporphyrins and pentaporphyrins is reported here. The supramolecular interactions of the new porphyrin derivatives with C60 and PyC60 (a pyridyl [60]fulleropyrrolidine) were evaluated by absorption and fluorescence titrations in toluene. While no measurable modifications of the absorption and fluorescence spectra were observed upon addition of C60 to the porphyrin derivatives, the addition of PyC60 to the corresponding mono-Zn(II) porphyrins resulted in the formation of Zn(porphyrin)-PyC60 coordination complexes and the binding constants were calculated. Results show that the four free-base porphyrin units in pentaporphyrin 6 have a significant contribution in the stabilization of the 6-PyC60 complex. The crystal and molecular features of the pentaporphyrin Zn5 were unveiled using single-crystal X-ray diffraction studies.

Bifunctional Porphyrin-Based Nano-Metal-Organic Frameworks: Catalytic and Chemosensing Studies.

The use of 5,10,15,20-tetrakis( p-phenylphosphonic acid)porphyrin (H10TPPA) as a linker in the preparation of porphyrin-based metal-organic frameworks (Por-MOFs) through coordination to lanthanides cations is reported. The resulting unprecedented materials, formulated as [M(H9TPPA)(H2O) x]Cl2· yH2O [ x + y = 7; M3+ = La3+ (1), Yb3+ (2), and Y3+ (3)], prepared using hydrothermal synthesis, were extensively characterized in the solid-state, for both their structure and thermal robustness, using a myriad of solid-state advanced techniques. Materials were evaluated as heterogeneous catalysts in the oxidation of thioanisole by H2O2 and as chemosensors for detection of nitroaromatic compounds (NACs). Nano-Por-MOFs 1-3 proved to be effective as heterogeneous catalysts in the sulfoxidation of thioanisole, with Por-MOF 1 exhibiting the best catalytic performance with a conversion of thioanisole of 89% in the first cycle and with a high selectivity for the sulfoxide derivative (90%). The catalyst maintained its activity roughly constant in three consecutive runs. Por-MOFs 1-3 can be employed as chemosensors because of a measured fluorescence quenching up to 70% for nitrobenzene, 1,4-dinitrobenzene, 4-nitrophenol, and phenol, with 2,4,6-trinitrophenol exhibiting a peculiar fluorescence profile.

A Comparative Study of Molybdenum Carbonyl and Oxomolybdenum Derivatives Bearing 1,2,3-Triazole or 1,2,4-Triazoles in Catalytic Olefin Epoxidation.

The molybdenum(0)-carbonyl-triazole complexes [Mo(CO)3(L)3] [L = 1,2,3-triazole (1,2,3-trz) or 1,2,4-triazole (1,2,4-trz)] have been prepared and examined as precursors to molybdenum(VI) oxide catalysts for the epoxidation of cis-cyclooctene. Reaction of the carbonyl complexes with the oxidant tert-butyl hydroperoxide (TBHP) (either separately or in situ) gives oxomolybdenum(VI) hybrid materials that are proposed to possess one-dimensional polymeric structures in which adjacent oxo-bridged dioxomolybdenum(VI) moieties are further linked by bidentate bridging triazole (trz) ligands. A pronounced ligand influence on catalytic performance was found and the best result (quantitative epoxide yield within 1 h at 70 °C) was obtained with the 1,2,3-triazole oxomolybdenum(VI) hybrid. Both molybdenum oxide-triazole compounds displayed superior catalytic performance in comparison with the known hybrid materials [MoO3(trz)0.5], which have different structures based on organic-inorganic perovskite-like layers. With aqueous H2O2 as the oxidant instead of TBHP, all compounds were completely soluble and active. A pronounced ligand influence on catalytic performance was only found for the hybrids [MoO3(trz)0.5], and only the 1,2,4-trz compound displayed reaction-induced self-precipitation behavior. An insight into the type of solution species that may be involved in the catalytic processes with these compounds was obtained by separately treating [MoO3(1,2,4-trz)0.5] with excess H2O2, which led to the crystallization of the complex (NH4)1.8(H3O)0.2[Mo2O2(µ2-O)(O2)4(1,2,4-trz)]·H2O. The single-crystal X-ray investigation of this complex reveals an oxo-bridged dinuclear structure with oxodiperoxo groups being further linked by a single triazole bridge.

Robust Multifunctional Yttrium-Based Metal-Organic Frameworks with Breathing Effect.

Phosphonate- and yttrium-based metal-organic frameworks (MOFs), formulated as [Y(H5btp)]·5.5H2O (1), [Y(H5btp)]·2.5H2O (2), (H3O)[Y2(H5btp)(H4btp)]·H2O (3), and [Y(H5btp)]·H2O·0.5(MeOH) (4), were prepared using a "green" microwave-assisted synthesis methodology which promoted the self-assembly of the tetraphosphonic organic linker [1,1'-biphenyl]-3,3',5,5'-tetrayltetrakis(phosphonic acid) (H8btp) with Y3+ cations. This new family of functional materials, isolated in bulk quantities, exhibits a remarkable breathing effect. Structural flexibility was thoroughly studied by means of X-ray crystallography, thermogravimetry, variable-temperature X-ray diffraction, and dehydration and rehydration processes, ultimately evidencing a remarkable reversible single-crystal to single-crystal (SC-SC) transformation solely through the loss and gain of crystallization solvent molecules. Topologically, frameworks remained unaltered throughout this interconversion mechanism, with all compounds being binodal 6,6-connected network with a Schäfli symbol of {413.62}{48.66.8}. Results show that this is one of the most stable and thermally robust families of tetraphosphonate-based MOFs synthesized reported to date. Porous materials 2 and 3 were further studied to ascertain their performance as heterogeneous catalysts and proton conductors, respectively, with outstanding results being registered for both materials. Compound 2 showed a 94% conversion of benzaldehyde into (dimethoxymethyl)benzene after just 1 h of reaction, among the best results registered to date for MOF materials. On the other hand, the protonic conductivity of compound 3 at 98% of relative humidity (2.58 × 10-2 S cm-1) was among the highest registered among MOFs, with the great advantage of the material to be prepared using a simpler and sustainable synthesis methodology, as well as exhibiting a good stability at ambient conditions (temperature and humidity) over time when compared to others.

Photoluminescent thermometer based on a phase-transition lanthanide silicate with unusual structural disorder.

The hydrothermal synthesis of the novel Na[LnSiO4] (Ln = Gd, Eu, Tb) disordered orthorhombic system is reported. At 100 K, and above, these materials are best described in the centrosymmetric orthorhombic Pnma space group. At lower temperatures (structure solved at 30 K) the unit cell changes to body-centered with Imma symmetry. The materials exhibit unique photophysical properties, arising from both, this phase transformation, and the disorder of the Ln(3+) ions, located at a site with D2d point symmetry. Na[(Gd0.8Eu0.1Tb0.1)SiO4] is an unprecedented case of a luminescent ratiometric thermometer based on a very stable silicate matrix. Moreover, it is the first example of an optical thermometer whose performance (viz., excellent sensitivity at cryogenic temperatures <100 K) is determined mainly by a structural transition, opening up new opportunities for designing such devices.

Phosphonate appended porphyrins as versatile chemosensors for selective detection of trinitrotoluene.

Fluorescent molecular probes based on phosphonate-functionalized porphyrin derivatives have been designed for selective detection of nitroaromatics. It is shown that molecular recognition is based on cooperative hydrogen bonding and π-π stacking interactions with electron-deficient molecules (nitroaromatic compounds, NACs), displaying superior detection toward trinitrotoluene (TNT). The P═O functional groups decrease the lowest unoccupied molecular orbital (LUMO) energy level of the porphyrins and, consequently, facilitate the electron inoculation to TNT through a photoinduced electron transfer (PET) process. The hydroxyl groups of the phosphonates and pyrrole -NH protons are further engaged in donor-acceptor interactions with TNT by strong intermolecular hydrogen bonding interactions (as evidenced by single crystal X-ray, NMR, and density functional theory (DFT)) showing turn off fluorescence behavior. The nonplanarity of the porphyrins induced by protonation at the central core of the porphyrin H4TPPA(2+) undergoes additional interactions, furnishing an anomalous increase in the selectivity of TNT at nanomolar levels in solution (limit of detection, LOD ∼ 5 nM). Porphyrin-doped hybrid PMMA [poly(methyl methacrylate)] polymer films demonstrate the reversibility of the fluorescence behavior and exhibit high photostability. The formation of discrete molecular aggregates on the surface of hybrid films and efficient diffusion of TNT vapors (10 ppb) displayed high selectivity in the solid state. The hybrid films are further used to demonstrate the detection of NACs in the aqueous medium, ultimately providing a platform for a practical strategy and implementation for the detection of toxic NACs.

Crystal Structure and Catalytic Behavior in Olefin Epoxidation of a One-Dimensional Tungsten Oxide/Bipyridine Hybrid.

The tungsten oxide/2,2'-bipyridine hybrid material [WO3(2,2'-bpy)]·nH2O (n = 1-2) (1) has been prepared in near quantitative yield by the reaction of H2WO4, 2,2'-bpy, and H2O in the mole ratio of ca. 1:2:700 at 160 °C for 98 h in a rotating Teflon-lined digestion bomb. The solid-state structure of 1 was solved and refined through Rietveld analysis of high-resolution synchrotron X-ray diffraction data collected for the microcrystalline powder. The material, crystallizing in the orthorhombic space group Iba2, is composed of a one-dimensional organic-inorganic hybrid polymer, ∞(1)[WO3(2,2'-bpy)], topologically identical to that found in the previously reported anhydrous phases [MO3(2,2'-bpy)] (M = Mo, W). While in the latter the N,N'-chelated 2,2'-bpy ligands of adjacent corner-shared {MO4N2} octahedra are positioned on the same side of the 1D chain, in 1 the 2,2'-bpy ligands alternate above and below the chain. The catalytic behavior of compound 1 for the epoxidation of cis-cyclooctene was compared with that for several other tungsten- or molybdenum-based (pre)catalysts, including the hybrid polymer [MoO3(2,2'-bpy)]. While the latter exhibits superior performance when tert-butyl hydroperoxide (TBHP) is used as the oxidant, compound 1 is superior when aqueous hydrogen peroxide is used, allowing near-quantitative conversion of the olefin to the epoxide. With H2O2, compounds 1 and [MoO3(2,2'-bpy)] act as sources of soluble active species, namely, the oxodiperoxo complex [MO(O2)2(2,2'-bpy)], which is formed in situ. Compounds 1 and [WO(O2)2(2,2'-bpy)] (2) were further tested in the epoxidation of cyclododecene, trans-2-octene, 1-octene, (R)-limonene, and styrene. The structure of 2 was determined by single-crystal X-ray diffraction and found to be isotypical with the molybdenum analogue.

Multidimensional transition metal complexes based on 3-amino-1H-1,2,4-triazole-5-carboxylic acid: from discrete mononuclear complexes to layered materials.

The synthesis and structural characterization of five transition metal complexes with different dimensionality and incorporating residues of 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H2atrc) is reported: [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2), [Fe2(Hatrc)4(OH)2]·6H2O (3), [Cd(Hatrc)2(H2O)]n (4), and [Mn(atrc)(H2O)]n·nH2O (5). These materials could be prepared from solution (1-3), diffusion (4), or hydrothermal reactions (5) with various anions and L:M ratios. Structural details were revealed by single crystal X-ray diffraction. The discrete units composing compounds 1-3, the polymeric 1D chain of 4 and the 2D layer of 5 are further extended into 3D supramolecular architectures through the formation of hydrogen bonds.

Synthesis, structural elucidation, and catalytic properties in olefin epoxidation of the polymeric hybrid material [Mo3O9(2-[3(5)-pyrazolyl]pyridine)]n.

The reaction of [MoO2Cl2(pzpy)] (1) (pzpy = 2-[3(5)-pyrazolyl]pyridine) with water in an open reflux system (16 h), in a microwave synthesis system (120 °C, 2 h), or in a Teflon-lined stainless steel digestion bomb (100 °C, 19 h) gave the molybdenum oxide/pyrazolylpyridine polymeric hybrid material [Mo3O9(pzpy)]n (2) as a microcrystalline powder in yields of 72­79%. Compound 2 can also be obtained by the hydrothermal reaction of MoO3, pzpy, and H2O at 160 °C for 3 d. Secondary products isolated from the reaction solutions included the salt (pzpyH)2(MoCl4) (3) (pzpyH = 2-[3(5)-pyrazolyl]pyridinium), containing a very rare example of the tetrahedral MoCl4(2­) anion, and the tetranuclear compound [Mo4O12(pzpy)4] (4). Reaction of 2 with excess tert-butylhydroperoxide (TBHP) led to the isolation of the oxodiperoxo complex [MoO(O2)2(pzpy)] (5). Single-crystal X-ray structures of 3 and 5 are described. Fourier transform (FT)-IR and FT Raman spectra for 1, 4, and 5 were assigned based on density functional theory calculations. The structure of 2 was determined from synchrotron powder X-ray diffraction data in combination with other physicochemical information. In 2, a hybrid organic­inorganic one-dimensional (1D) polymer, ∞(1)[Mo3O9(pzpy)], is formed by the connection of two very distinct components: a double ladder-type inorganic core reminiscent of the crystal structure of MoO3 and 1D chains of corner-sharing distorted {MoO4N2} octahedra. Compound 2 exhibits moderate activity and high selectivity when used as a (pre)catalyst for the epoxidation of cis-cyclooctene with TBHP. Under the reaction conditions used, 2 is poorly soluble and is gradually converted into 5, which is at least partly responsible for the catalytic reaction.

Carriers for metal complexes on tumour cells: the effect of cyclodextrins vs CNTs on the model guest phenanthroline-5,6-dione trithiacyclononane ruthenium(II) chloride.

The complex [Ru[9]aneS3(pdon)Cl]Cl (pdon = 1,10-phenanthroline-5,6-dione) was readily obtained from the stoichiometric reaction of Ru[9]aneS3(dmso)Cl2 with pdon. Recrystallisation in ethanol using salicylic acid as a co-crystallisation helper afforded single-crystals suitable for the collection of X-ray diffraction data which afforded a reasonable structural description. Two different kinds of molecular carriers were tested as vehicles for this complex: carbon nanotubes (CNTs) and cyclodextrins. CNTs had an insufficient loading rate for the ruthenium complex at CNT concentrations deemed non-cytotoxic on cultured cells. The cyclodextrin (CD) carriers, ß-CD and TRIMEB (standing for permethylated ß-CD), were able to form two adducts, studied by powder X-ray diffraction, thermogravimetric analysis (TGA), (13)C{(1)H} CP/MAS NMR and FT-IR spectroscopies. The DNA thermal denaturation studies showed that the complex 1 is able to intercalate with DNA. The in vitro cytotoxicity of the free complex [Ru[9]aneS3(pdon)Cl]Cl (1) and of its two CD adducts (2 and 3) was assessed on both rodent and human cell lines. By using the mouse K1735-M2 melanoma cell line and the non-tumour rat H9c2 cardiomyoblasts, the results showed that 1 and 2 significantly inhibited the growth of the tumour cell line while displaying a good safety profile on cardiomyoblasts. Compound 3 at 100 µM inhibited the proliferation of both cell lines, with a higher activity towards the melanoma cell line. The cytotoxicity of the compounds 1-3 was further assessed on human breast cancer cell lines. Against the MDA-MB-231 line, growth inhibition occurred only with 1 and 3 at the incubation time of 96 h, both with approximate inhibition rates of 50 %; against the MCF-7 line, mild cytotoxicity was observed at 48 h of incubation, with IC50 values calculated above 100 µM for 1, 2 and 3.

Exploring the Luminescence, Redox, and Magnetic Properties in a Multivariate Metal-Organic Radical Framework.

Persistent neutral organic radicals are excellent building blocks for the design of functional molecular materials due to their unique electronic, magnetic, and optical properties. Among them, triphenylmethyl radical derivatives have attracted a lot of interest as luminescent doublet emitters. Although neutral organic radicals have been underexplored as linkers for building metal-organic frameworks (MOFs), they hold great potential as organic elements that could introduce additional electronic properties within these frameworks. Herein, we report the synthesis and characterization of a novel multicomponent metal-organic radical framework (PTMTCR@NR-Zn MORF), which is constructed from the combination of luminescent perchlorotriphenylmethyl tricarboxylic acid radical (PTMTCR) and nonemissive nonradical (PTMTCNR) organic linkers and Zn(II) ions. The PTMTCR@NR-Zn MORF structure is layered with microporous one-dimensional channels embedded within these layers. Kelvin probe force microscopy further confirmed the presence of both organic nonradical and radical linkers in the framework. The luminescence properties of the PTMTCR ligand (first studied in solution and in the solid state) were maintained in the radical-containing PTMTCR@NR-Zn MORF at room temperature as fluorescence solid-state quenching is suppressed thanks to the isolation of the luminescent radical linkers. In addition, magnetic and electrochemical properties were introduced to the framework due to the incorporation of the paramagnetic organic radical ligands. This work paves the way for the design of stimuli-responsive hybrid materials with tunable luminescence, electrochemical, and magnetic properties by the proper combination of closed- and open-shell organic linkers within the same framework.

Design of Promising Thiazoloindazole-Based Acetylcholinesterase Inhibitors Guided by Molecular Docking and Experimental Insights.

Alzheimer's disease is characterized by a progressive deterioration of cognitive function and memory loss, and it is closely associated with the dysregulation of cholinergic neurotransmission. Since acetylcholinesterase (AChE) is a critical enzyme in the nervous system, responsible for breaking down the neurotransmitter acetylcholine, its inhibition holds a significant interest in the treatment of various neurological disorders. Therefore, it is crucial to develop efficient AChE inhibitors capable of increasing acetylcholine levels, ultimately leading to improved cholinergic neurotransmission. The results reported here represent a step forward in the development of novel thiazoloindazole-based compounds that have the potential to serve as effective AChE inhibitors. Molecular docking studies revealed that certain of the evaluated nitroindazole-based compounds outperformed donepezil, a well-known AChE inhibitor used in Alzheimer's disease treatment. Sustained by these findings, two series of compounds were synthesized. One series included a triazole moiety (Tl45a-c), while the other incorporated a carbazole moiety (Tl58a-c). These compounds were isolated in yields ranging from 66 to 87% through nucleophilic substitution and Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reactions. Among the synthesized compounds, the thiazoloindazole-based 6b core derivatives emerged as selective AChE inhibitors, exhibiting remarkable IC50 values of less than 1.0 µM. Notably, derivative Tl45b displays superior performance as an AChE inhibitor, boasting the lowest IC50 (0.071 ± 0.014 µM). Structure-activity relationship (SAR) analysis indicated that derivatives containing the bis(trifluoromethyl)phenyl-triazolyl group demonstrated the most promising activity against AChE, when compared to more rigid substituents such as carbazolyl moiety. The combination of molecular docking and experimental synthesis provides a suitable and promising strategy for the development of new efficient thiazoloindazole-based AChE inhibitors.

Synthesis of enantiopure 2-C-glycosyl-3-nitrochromenes.

A novel methodology has been developed to obtain enantiopure 2-C-glycosyl-3-nitrochromenes. First, (Z)-1-bromo-1-nitroalkenes were prepared from the corresponding sugar aldehydes through a sodium iodide-catalyzed Henry reaction with bromonitromethane followed by elimination of the resulting 1-bromo-1-nitroalkan-2-ols. In the next step, reaction of the sugar-derived (Z)-1-bromo-1-nitroalkenes with o-hydroxybenzaldehydes afforded enantiopure (2S,3S,4S)-3-bromo-3,4-dihydro-4-hydroxy-3-nitro-2H-1-benzopyrans, which, upon SmI2-promoted ß-elimination, yielded chiral enantiopure 2-C-glycosyl-3-nitrochromenes.

Hydrothermal synthesis, crystal structure, and catalytic potential of a one-dimensional molybdenum oxide/bipyridinedicarboxylate hybrid.

The reaction of MoO3, 2,2'-bipyridine-5,5-dicarboxylic acid (H2bpdc), water, and dimethylformamide in the mole ratio 1:1:1730:130 at 150 °C for 3 days in a rotating Teflon-lined digestion bomb leads to the isolation of the molybdenum oxide/bipyridinedicarboxylate hybrid material (DMA)[MoO3(Hbpdc)]·nH2O (1) (DMA = dimethylammonium). Compound 1 was characterized by scanning electron microscopy, FT-IR and (13)C{(1)H} CP MAS NMR spectroscopies, and elemental and thermogravimetric analyses. The solid state structure of 1 was solved and refined through Rietveld analysis of high resolution synchrotron X-ray powder diffraction data in conjunction with information derived from the above techniques. The material, crystallizing in the noncentrosymmetric monoclinic space group Pc, is composed of an anionic one-dimensional organic-inorganic hybrid polymer, ∞(1)[MoO3(Hbpdc)](-), formed by corner-sharing distorted {MoO4N2} octahedra, which cocrystallizes with charge-balancing DMA(+) cations and one water molecule per metal center. In the crystal structure of 1, the close packing of individual anionic polymers, DMA(+) cations, and water molecules is mediated by a series of supramolecular contacts, namely strong (O-H···O, N(+)-H···O(-)) and weak (C-H···O) hydrogen bonding interactions, and π-π contacts involving adjacent coordinated Hbpdc(-) ligands. The catalytic potential of 1 was investigated in the epoxidation reactions of the bioderived olefins methyl oleate (Ole) and DL-limonene (Lim) using tert-butylhydroperoxide (TBHP) as the oxygen donor and 1,2-dichloroethane (DCE) or (trifluoromethyl)benzene (BTF) as cosolvent, at 55 or 75 °C. Under these conditions, 1 acts as a source of active soluble species, leading to epoxide yields of up to 98% for methyl 9,10-epoxystearate (BTF, 75 °C, 100% conversion of Ole) and 89% for 1,2-epoxy-p-menth-8-ene (DCE, 55 °C, 95% conversion of Lim). Catalytic systems employing the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as solvent could be effectively recycled.