AgOTf Research Articles

Silver Nanoparticles Anchored on Single-Walled Carbon Nanotubes via a Conjugated Polymer for Enhanced Sensing Applications.

Single-walled carbon nanotubes (SWCNTs) are candidate matrices for loading metal nanoparticles (NPs) for sensor and catalytic applications owing to their high electron conductivity and mechanical strength, larger surface area, excellent chemical stability, and ease of surface modification. The performance of the formed NP/SWCNT composites is dependent on the NP size, the physical and chemical interactions between the components, and the charge transfer capabilities. Anchoring metal complexes onto the surface of SWCNTs through noncovalent interactions is a viable strategy for achieving high-level metal dispersion and high charge transfer capacities between metal NPs and SWCNTs. However, traditional metal complexes have small molecular sizes, and their noncovalent interactions with SWCNTs are limited to provide excellent sensing and catalytic capability with restricted efficiency and durability. Here, we selected poly(9,9-di-n-dodecylfluorenyl-2,7-diyl-alt-2,2'-bipyridine-5,5') (PFBPy) to increase the noncovalent interactions between silver nanoparticles (AgNPs) and SWCNTs. A silver triflate (Ag-OTf) solution was added into a PFBPy-wrapped SWCNT solution to form Ag-PFBPy complexes on the nanotube surface, after which Ag+ was photoreduced to AgNPs to form a Ag-PFBPy/SWCNT composite in the solution. In various feeding molar ratios of Ag-OTf over the BPy unit (0.4-50), the size of the formed AgNPs may be well-controlled at sub-nm levels to provide them with an energy level comparable to that of the SWCNTs. Additionally, the 2,2'-bipyridine (BPy) unit of the polymer provided a coordinating interaction with Ag+ and the formed AgNPs as well. The 5,5'-linage of BPy with the fluorene unit in PFBPy ensured a straight main chain structure to retain strong π-π interactions with nanotubes before and after Ag+ chelation. All of these factors confirmed a tight contact between the formed AgNPs and SWCNTs, promoting the charge transfer between them and enhancing the sensing capabilities with a 5-fold increase in humidity sensing sensitivity.

Binuclear homo- and hetero-metallic complexes containing [(Me3tacn)Ru] units

Reaction of (Me3tacn)RuCl3·H2O and three equivalents of zinc acetate afforded a binuclear heterometallic species (Me3tacn)RuII(µ-Cl)(µ-CH3CO2)2ZnCl (1) (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane). Treatment of (Me3tacn)RuCl3·H2O with three equivalents of silver triflate or equivalent cadmium acetate in alcohol got trichloro-bridged binuclear homometallic complexes [(Me3tacn)Ru(µ-Cl)3Ru(Me3tacn)]X2 (X = CF3SO3, 2; Cl, 3) with metal–metal Ru-Ru bonds. When three equivalents of manganese acetate and cadmium acetate was employed, such reactions led to isolations of [(Me3tacn)RuIII(µ-O)(µ-CH3CO2)2RuIII(Me3tacn)]2+ species (4/5), with [MnCl4]2− and [CdCl4]2− acting as the counter anions only. The crystal structures of complexes 1–5 have been determined. All complexes have been characterized by infrared, UV–vis spectroscopies and their electrochemical properties were also investigated. Moreover, the catalytic property of ruthenium(III) complexes 4/5 towards oxidation of isopropanol was accordingly investigated.

Synthesis of a tetratopic bisphosphine ligand derived from pyrimidine and its incorporation into gold and silver coordination polymers

Herein we present the synthesis of a tetratopic bisphosphine ligand derived from 4,6-disubstituted pyrimidine scaffold. This new ligand (2) was doubly alkylated using iodomethane to give bisphosphonium dication (3) as an iodide salt, and was also coordinated to both gold(I) chloride to give the metal complex (4) and to silver(I) triflate to give a coordination polymer (5), respectively. All compounds have been fully characterized using multinuclear NMR spectroscopy as well as single crystal X-ray diffraction. Gold complex 4 was also found to exhibit weak emission at λmax = 530 nm due to Au(I)–Au(I) aurophilic interactions. Additionally we demonstrated that bisphosphine ligand 2 can be used as a tetratopic ligand, as evidenced by the formation of the coordination polymer 5 in which both phosphine → silver and nitrogen → silver interactions were observed.

Hybrid Quinoline Telluroether Ligand Derived Copper and Silver Complexes: Synthesis, Structural and Electronic Properties

AbstractThe tetradentate organotelluroether (C9H6NTe)2CH2 ligand has been synthesized and its coordination behaviour with a stoichiometric amount of copper(II) and silver(I) perchlorate and triflate salts has been experimentally investigated. The isolated ligand and metal complexes are characterized by multinuclear (1H, 13C, 125Te) NMR spectroscopy, single crystal X‐ray diffraction, and DFT calculations. The X‐ray analysis revealed the formation of self‐assembled bimetallic complexes with the molecular formula of 2[M(C9H6NTe)2CH2]+ X− [M+=Cu, Ag; X−=ClO4, CF3SO3]. Further, it has been noticed that the metal ions act as a bridging unit to form cationic 8‐membered metallamacrocycles in the chair conformation. The atoms in molecule (AIM) and non‐covalent interactions (NCI) analysis display a weak intramolecular Te⋅⋅⋅Te interaction. Natural bond orbital (NBO) calculations suggest that the tellurium has a rich electron donating ability toward metal ions than the quinoline nitrogen in the complexes.

Estimation for rotational barriers of unsymmetrical tert-amide-containing pyridine ligands and their silver(I) complexes

Structures of silver(I) complexes with unsymmetrical tert-amide-containing pyridine ligand isomers (1a-1d) are reported. Because these ligands exist as s-cis and s-trans forms in solution, the ratios of s-cis and s-trans forms in solution and their rotational barriers were estimated by 1H NMR experiments. Despite the presence of s-cis and s-trans-form in solution, silver(I) complexes with these ligands were all s-trans form in the solid-state. Because of the semi-flexible properties of isomers (1a-1d), various ligand shapes showed the coordination networks depending on the direction of the pyridine nitrogen. For example, on the silver(I) triflate complexations, the tertiary amide incorporating two 4‑pyridyl units (1a) yields a wavy 2D coordination polymer. On the other hand, the complexation of 1b afforded double-stranded 1D coordination polymer. Furthermore, the complexations of 1c and 1d afforded 2D coordination polymer and cyclic dimer, respectively. The complexations of isomers (1a-1d) with AgBF4 instead of AgOTf were also investigated. As a result, the AgBF4 complexations of 1a, 1c, and 1d gave 1D, 2D, and 1D structures, respectively.

Design, Synthesis, and Anticancer Studies of a p-Cymene-Ru(II)-Curcumin Organometallic Conjugate Based on a Fluorescent 4-Amino-1,8-naphthalimide Tröger's Base Scaffold.

A unique V-shaped "chiral" supramolecular scaffold, N-(4-pyridyl)-4-amino-1,8-naphthalimide Tröger's base (TBNap), was synthesized in good yield from a precursor N-(4-pyridyl)-4-amino-1,8-naphthalimide (Nap). TBNap was characterized using different spectroscopic methods and the molecular structure was elucidated by diffraction analysis. A new p-cymene-Ru(II)-curcumin conjugate (TB-Ru-Cur) was designed by reacting TBNap dipyridyl donor and ruthenium-curcuminato acceptor [RuCur = (p-cymene)Ru-(curcuminato)Cl] in the presence of silver triflate. TB-Ru-Cur was isolated in quantitative yield and characterized using Fourier transform infrared (FT-IR), NMR (1H, 13C, and 19F), and electrospray ionization mass spectrometry (ESI-MS), and the molecular structure has been predicted using a computational study. Both TBNap and TB-Ru-Cur exhibited intramolecular charge transfer (ICT)-based fluorescence emission. Furthermore, the anticancer properties of TBNap, Ru-Cur, and TB-Ru-Cur were assessed in different cancer cell lines. Gratifyingly, the conjugate TB-Ru-Cur displayed fast-cellular internalization and good cytotoxicity against HeLa, HCT-116, and HepG2 cancer cells and the estimated IC50 value was much lower than that of the precursors (TBNap and Ru-Cur) and the well-known chemotherapeutic drug cisplatin.

Synthesis and mesomorphism of 3,4-dialkoxyphenylpyridine complexes of silver(I)

3,4-Dialkoxyphenylpyridine complexes with silver dodecyl sulfate or silver triflate are liquid crystalline. The complexes are polycatenar and show one or both of a cubic and a columnar hexagonal phase depending on the chain length of the dialkoxyphenylpyridine and the anion associated with the silver. Their mesomorphism is compared both with the analogous and very well-studied silver complexes of dialkoxystilbazole ligands as well as closely related N-phenylpyridinium analogues. The slightly shorter nature of the dialkoxyphenylpyridines is important in determining the mesomorphism when compared to the dialkoxystilbazole complexes, whereas there are appreciable differences with the N-phenylpyridinium salts. The notable stabilisation of the Colh phase remains a feature of all three families of materials.

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

Total Synthesis of 12,13‐Dibenzyl‐banistenoside B and Analogs

AbstractBanistenosides A and B possessing a unique “azepino(1,2‐a)tetrahydro‐β‐carboline” carbon framework were isolated from the stem of Banisteriopsis caapi and showed MAO‐A inhibition. Herein, we report the total synthesis of dibenzyl derivative of the untouched natural product in the last two decades, Banistenoside B. The key steps involve construction of 6.5.6.7 tetracyclic core using Pictet−Spengler reaction and intramolecular amide coupling. The stereoselective glycation was achieved through Hotha's protocol using gold catalyst, and silver triflate in the late stage of synthesis. The stereochemistry of most of the essential compounds were confirmed by X‐ray crystallography.

Silver‐Catalyzed Nucleophilic Deoxydifluoromethylthiolation of Activated Aliphatic Alcohols with BT−SCF2H

AbstractDeoxygenative conversion of alcohols into difluoromethylthioethers is reported using 2‐((difluoromethyl)thio)‐3‐methylbenzo[d]thiazol‐3‐ium triflate (BT−SCF2H) as a source of −SCF2H anions. The presence of silver(I) triflate as a catalyst was found to be crucial for stabilizing the in situ‐generated anion, while the concomitant formation of a reactive 2‐(alkoxy)benzothiazolium electrophile likely ensures a fast onward substitution reaction, avoiding the build‐up of −SCF2H. To the best of our knowledge, this process represents the first report of a direct nucleophilic substitution reaction with −SCF2H and delivers products containing the medicinally relevant difluoromethylthio motif in a single step from widely available alcohols.

Silver Triflate Catalyzed Domino Reactions of o‐Alkynylanilines: An Approach Toward Unsymmetrical Diarylacetates and Triarylmethanes

AbstractStraightforward and efficient Ag(I) catalyzed domino reactions for the synthesis of unsymmetrical diarylacetate and triarylmethane derivatives has been reported. These reactions proceed via an initial 5‐endo‐dig cyclization of o‐alkynylanilines to result in the indole motif which further reacts with various electrophiles resulting in a wide range of unsymmetrical diarylacetates, diaryl ketones, and triarylmethanes. The strategy is versatile, displays broad substrate scope, and provides excellent yields of the products.

Catalytic Intramolecular Cyclization of Alkynyl Cyclic Acetals via Chemoselective Activation Leading to a Phenanthrene Core

Abstract An intramolecular cyclization reaction of alkynyl cyclic acetals to synthesize various phenanthrene derivatives in the presence of silver triflate (AgOTf) or boron trifluoride etherate (BF3·OEt2) as catalysts has been developed. By using AgOTf or BF3·OEt2 appropriately depending on the substituents various alkynyl cyclic acetals were converted to the corresponding phenanthrene derivatives. Investigations of reaction mechanisms, X-ray structure of the product, and computational density functional theory (DFT) study suggested that the reaction proceeds via alkyne activation (π-activation) or acetal activation (σ-activation) pathways based on π- or σ-Lewis acidities.

Cationic gold(I)-catalyzed glycosylation with glycosyl N-1,1-dimethylpropargyl carbamate donors.

A mild and efficient cationic gold(I)-catalyzed O-glycosylation methodology involving the use of bench-stable glycosyl N-1,1-dimethylpropargyl carbamate donors has been developed. In the presence of 1-2 mol% [tris(2,4-di-tert-butylphenyl)phosphite]gold(I) chloride and 5 mol% silver triflate, both "armed" and "disarmed" glycosyl N-1,1-dimethylpropargyl carbamate donors react with various sugar acceptors at room temperature to afford the corresponding glycosides in good to excellent yields. These glycosyl N-1,1-dimethylpropargyl carbamates are found to be orthogonal to regular phenyl thioglycoside donors. The utilization of this method has been demonstrated in the synthesis of a trisaccharide.

Efficient Synthesis of Isoquinoline Derivatives through Sequential Cyclization–Deoxygenation Reaction of 2-Alkynylbenzaldoximes

AbstractWe describe a novel, simple, robust, and efficient cyclization/deoxygenation approach for the synthesis of functionalized isoquinoline derivatives. Over the course of continued studies on o-alkynylbenzaldoxime cyclization reactions, the formation of cyclic nitrones through 6-endo-dig cyclization was achieved using silver triflate or bromine as an electrophile, and subsequently, the deoxygenation process was carried out in the presence of CS2 in good to high yields.

In situ localization of tris(2,3-dibromopropyl) isocyanurate in mouse organs by MALDI-IMS with auxiliary matrix strategy

Tris(2,3-dibromopropyl) isocyanurate (TBC) is one of the novel brominated flame retardants that has been widely used in consumer goods. Humans may be exposed to TBC daily. Studies showed that TBC can induce significant toxicity. However, there is currently no report on its in situ localization in organs. In this study, we aimed to develop a reliable and reproductive method to determine the in situ localization of TBC in mouse organs by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). As commercially available matrices were not able to detect TBC in tissue section, we then developed a novel MALDI-IMS method based on 1,5-diaminonaphthalene hydrochloride and silver trifluoromethanesulfonate (NDA/AgOTf) as the matrix for the in situ localization of TBC. AgOTf used as the auxiliary matrix in the negative-ion mode showed an excellent MS signal of TBC. The detection limit of [2AgOTf + Br]- was at the μg/mL level. The developed MALDI-IMS method was successfully employed to obtain the TBC spatial distribution in the mouse organs collected from mice exposed to 160 mg/kg/day of TBC for 30 days. High-pressure liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS) was also used to evaluate the accumulation of TBC in liver, kidney, heart, and brain. The combination of MALDI-IMS and HPLC-MS/MS showed that TBC can accumulate in mice organs and it is mainly distributed in the renal parenchyma. In summary, an innovative method was developed for the analysis of TBC spatial distribution by MALDI-IMS using a novel NDA/AgOTf matrix, extending the application of MALDI-IMS in environmental pollutants.

Hexadentate Poly‐Lewis Acids Based on 1,3,5‐Trisilacyclohexane

AbstractWe report the preparation of hexadentate poly‐Lewis acids (PLA) based on 1,3,5‐trisilacyclohexane backbones bearing two alkynyl groups attached to each of the silicon atoms. A rigid hexadentate PLA bearing six Lewis‐acidic catecholatoboryl‐substituents was prepared by a tin‐boron exchange reaction. Its structure, determined by X‐ray diffraction, is the first of a Lewis‐acid‐functionalised donor‐free trisilacyclohexane. Flexible hexadentate PLA were prepared by hydroboration or hydrosilylation of hexavinyltrisilacyclohexane, resulting in PLA with six 9‐BBN, SiCl3, SiCl2Me or SiClMe2 groups. The Lewis‐acidity of the last one was increased by conversion with silver triflate, resulting in a PLA with six highly acidic silyl triflate groups attached to the 1,3,5‐trisilacyclohexane unit as TfOSiMe2‐C2H4‐ groups. Host‐guest experiments of the above PLA demonstrated the suitability of the flexible representatives for complexation of neutral Lewis‐based guest molecules under formation of 1 : 6 adducts (host: guest).

Synthesis, Structures, and Reactivities of Iron Complexes Bearing an Isoindoline‐Based, Polyprotic Pincer‐Type Pyrazole Ligand

AbstractThe synthesis and properties of polyprotic NNN pincer‐type bis(pyrazole) iron complexes derived from a 1,3‐bis(pyrazol‐3‐ylimino)isoindoline 1 were investigated. When 1 was treated with iron(II) chloride, the paramagnetic, square‐pyramidal complex [FeCl2(LH3)] (2; LH3=3‐(5‐tert‐butylpyrazol‐3‐ylamino)‐1‐(5‐tert‐butylpyrazol‐3‐ylimino)‐1H‐isoindole) was obtained. Reaction of 2 with two equiv. of silver triflate followed by addition of two equiv. of trimethylphosphine yielded the diamagnetic, octahedral complex [Fe(OTf)(PMe3)2(LH3)]OTf (3), which was converted to the carbonyl complex [Fe(CO)(PMe3)2(LH3)](OTf)2 (4). Treatment of 4 with triethylamine led to deprotonation of the chelate backbone to give the isoindolin‐2‐yl complex [Fe(CO)(PMe3)2(LH2)]OTf (5). The structures of the LH3 and LH2 ligands were compared in details. The NH groups in the pincer ligand in 2–5 are accompanied by hydrogen bonds, showing their Brønsted acidic nature. In addition, 3 catalyzed disproportionation of hydrazine, although the catalytic activity was lower than that of a related pyridine‐based pincer complex 6 a.

Silver Salt-Mediated Allylation Reactions Using Allyl Bromides.

A facile, efficient, and chemoselective synthesis of allylic amides has been developed. Allyl bromides were used as the precursors activated by silver triflate. A Ritter-type reaction readily proceeded to give various allyl amides under mild conditions. The reaction protocol was also applicable to different nucleophilic partners to give a wide range of allyl-substituted products in the absence of a base.

Halogen addition to some 1-C-substituted pyranoid glycals

Addition of bromine and chlorine to O-peracylated 1-CN-, COOMe- and CONH2-substituted glycals was studied under ionic and radical conditions. The main or exclusive products were the corresponding 2,3-trans-diaxial (3-bromo-3-deoxy-α-d-heptopyranosylbromide)onic acid derivatives. Bromination of the O-peracetylated d-lyxo-hept-2-enopyranosononitrile and all chlorinations proved selective towards the 2-axial-3-equatorial (3-halogeno-3-deoxy-α-d-heptopyranosylhalide)onic acid derivatives. Silver triflate promoted glycosylation of methanol was successful with each 2,3-trans-diaxial (3-bromo-3-deoxy-α-d-heptopyranosylbromide)onic acid derivative, however, several attempted nucleophilic substitution and elimination reactions gave the parent glycal only.

Silica-Supported Phosphine-Gold Complexes as an Efficient Catalytic System for a Dearomative Spirocyclization.

The combination of metal catalyst and inorganic silica frameworks provides a greener approach to recyclable catalysis. In this study, three phosphine-gold chloride complexes have been successfully covalently grafted onto chiral silica nanohelices. The resulting 3D ensembles showed chiroptical properties that allowed the monitoring of the supported ligands. The heterogeneous gold chloride catalysts in cooperation with silver triflate exhibited high reactivity in various reactions, especially in the spirocyclization of aryl alkynoate esters, for which a catalytic loading of 0.05 mol % could be employed. The heterogeneous catalysts could be easily recovered and recycled seven or eight times without any loss of efficiency. By adding more silver triflate, 25 cycles with full conversion were achieved owing to a complex catalytic system based on silica and metallic species.