Dicationic Salts Research Articles

Development of dicationic 1,2,4-triazolium salts and their application as solid-state electrolyte for energy storage

Here, in this study we report the synthesis and characterizations of novel electrolyte based on dicationic salts 1,3-bis(1-alkyl-1,2,4-triazolium)mesitylene bis(tetrafluoroborate). Two cations were linked by mesitylene as spacer. Using 1H NMR, 13C NMR, FTIR and RAMAN spectroscopy methods the structural characterization of synthesized salts were done. Cyclic voltammetry, electrochemical impedance spectroscopy, thermogravimetry analysis, and differential scanning calorimetry have all been used to examine their thermal, electrochemical, and transport properties. Their suitability for energy storage was examined by fabricating a cell out of it in a Swagelok, where ionic liquid gel polymer electrolyte (ILGPE) was used as electrolyte and the graphite-PTFE sheet functioned as an electrode to construct a symmetrical EDLC. A wide working electrochemical potential window range of 0 to 4.5 V was obtained after studying the electrochemical cell performance, indicating that the dicationic salts can be employed as a promising electrolyte. It provided an effective areal capacitance of 63.13 F/cm2. Even after 2000 consecutive cycles of charging and discharging, the fabricated device continues to retain about 80 % of its initial capacitance. The GCD curves provided computed values for energy and power density of 1.1 μWh and 317.5 μW/cm2, respectively.

Unprecedented C-F bond cleavage in perfluoronaphthalene during cobaltocene reduction.

The C-F bond activation of perfluoronaphthalene by 5-SIDipp led to the formation of dicationic salts with two fluorides (3·2HF2 ) or heptafluorodiborate (3·2B2F7) as counter-anions. The anion exchange reaction of 3·2B2F7 with NBu4PF6 afforded a highly luminescent 3·2PF6. The in situ addition of cobaltocene in the reaction mixture of 5-SIDipp and perfluoronaphthalene led to a distinct Co(I) species.

Synthesis and N-C bond cleavage reactions for cyclic phosphazenium dications.

Phosphazenium cations were first characterized 60 years ago and yet little is known of their reactivity. The bidentate phosphonium dicationic salts [(C6H4)(PPh2F)2][B(C6F5)4]22 and [(C6H4)(PPh2Cl)2][Cl]23 were prepared. Reaction of 2 with (Me3Si)2NMe gave the phosphazenium dication [(C6H4)(PPh2)2(μ-NMe)][B(C6F5)4]24, while reaction of 3 with two equivalents of Me2N(SiMe3) gave the related dication [(C6H4)(PPh2NMe2)2][Cl]25. Compound 3 also reacted with (Me3Si)2NH affording the monocationic salt [(C6H4)(PPh2)2(μ-N)]Cl 6, with the liberation of HCl. Interestingly 4 reacted with [nBu4N]Cl generating the related salt [(C6H4)(PPh2)2(μ-N)][B(C6F5)4] 6' with concurrent formation of MeCl. This reactivity was extended to [(C2H4)(PPh2F)2][B(C6F5)4]27 which afforded [(C2H4)(PPh2)2(μ-NR)][B(C6F5)4]2 (R = Me 8, CH2CHCH29, CH2Ph 10) upon reaction with (Me3Si)2NR. These dications were shown to react with [nBu4N]Cl affording [(CH2PPh2)2(μ-N)][B(C6F5)4] 11 and the corresponding alkyl-chloride. The mechanism of these N-C bond cleavage reactions is considered.

Controlling the Energetic Properties of N-Methylene-C-Linked 4-Hydroxy-3,5-dinitropyrazole- and Tetrazole-Based Compounds via a Selective Mono- and Dicationic Salt Formation Strategy.

In the quest to synthesize high-performing insensitive high-energy density materials (HEDMs), the main challenge is establishing an equilibrium between energy and stability. For this purpose, we explored 4-hydroxy-3,5-dinitropyrazole- and tetrazole-based energetic scaffolds connected via a N-methylene-C bridge. The hydroxy functionality between nitro groups on the pyrazole ring promotes physical stability via inter- and intramolecular hydrogen bonding and contributes to oxygen balance, supporting better energetic performance. Due to two acidic sites (OH and NH) with different reactivities, a series of monocationic and dicationic salts were synthesized, and their overall performance was compared. All compounds synthesized in this study have high physical stability with impact sensitivity >40 J and friction sensitivity >360 N. Monocationic salts were generally found to have better thermal stability with respect to their corresponding dicationic energetic salts, which showed better energetic performance. The salt formation strategy effectively improved the thermal stability of 2 (Td = 168 °C), where most energetic salts have decomposition temperatures higher than 220 °C. All of the compounds were characterized through IR, multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. The structure-property relationship was studied using Hirshfeld surface analysis, noncovalent interaction (NCI) analysis, and electrostatic potential studies.

Development of New Plastic‐Crystal Based Electrolytes using Pyrrolidinium‐ Bis(fluorosulfonyl)imide Dicationic Salts

Dicationic organic salts are an interesting class of solid-state electrolyte materials due to their unique structure. Here we present, for the first time, the synthesis and characterization of three dicationic-FSI salts, 1,2-bis(N-methylpyrrolidinium)ethane bi(bis(fluorosulfonyl)imide) ([C2 -Pyrr1][FSI]2 ), 1,2-bis(N-ethylpyrrolidinium)ethane bi(bis(fluorosulfonyl)imide) ([C2 -Pyrr2][FSI]2 ) and 1,2-bis(N-n-propylpyrrolidinium)ethane bi(bis(fluorosulfonyl)imide) ([C2 -Pyrr3][FSI]2 ). The structure and dynamics of the organic salts were probed using variable temperature solid-state NMR and were compared with the thermal and transport properties. The investigation revealed that [C2 -Pyrr1][FSI]2 , with shorter alkyl-side chains on the dication, displayed increased transport properties compared to [C2 -Pyrr2][FSI]2 and [C2 -Pyrr3][FSI]2 . To determine the proficiency of these dicationic-FSI salts as electrolyte materials for battery applications, 10 mol% and 50 mol% lithium bis(fluorosulfonyl)imide (LiFSI) was mixed with [C2 -Pyrr1][FSI]2 and [C2 -Pyrr2][FSI]2 . Increased transport properties were observed for [C2 -Pyrr1][FSI]2 /10 mol % LiFSI in comparison to [C2 -Pyrr2][FSI]2 /10 % LiFSI, while pulse field gradient NMR analysis revealed the highest Li+ self-diffusion ratio for [C2 -Pyrr1][FSI]2 /50 % LiFSI out of the four Li-salt-containing mixtures.

Strong dual-state emission of unsymmetrical and symmetrical thiazolothiazole-bridged imidazolium salts

A novel thiazolothiazole-bridged imidazole derivative (1) was found to exhibit blue fluorescence in gaseous state or in methanol and yellow fluorescence in solid state. The N-alkylation of imidazole subunit(s) in 1 using n-propyl iodide generated unsymmetrically or symmetrically alkylated thiazolothiazole-bridged imidazolium salts with good water solubility and remarkably strong emission in solution. Furthermore, the replacement of iodide counter-anion by triflate or bis(trifluoromethane sulfonyl)imide achieved remarkably strong emission in solid state and in solution as well as good water solubility. The strong fluorescence of dicationic salts with triflate and NTf2– counter-anions in solid state can be ascribed to their twisted and rigid structures induced by interionic C−H···F hydrogen bonding.

Plastic crystal-based electrolytes using novel dicationic salts.

The unique structures of dications increase the number of possible combinations of cations and anions that can be used to obtain new materials with a wide range of physicochemical properties. However, structure-property relationships related to dicationic organic salts are seldom explored. Here, we report the synthesis and characterization of two new dicationic salts, 1,2-bis(N-ethylpyrrolidinium)ethane bis(trifluoromethanesulfonyl)imide ([C2-Pyrr2][TFSI]2) and 1,2-bis(N-n-propylpyrrolidinium)ethane bis(trifluoromethanesulfonyl)imide ([C2-Pyrr3][TFSI]2). To investigate the physicochemical properties of the organic salts, local structure and dynamics were investigated by variable temperature solid-state NMR and correlated with the thermal analysis and ionic conductivity. These studies revealed that [C2-Pyrr3][TFSI]2, with the longer alkyl-side chain on the dication, showed improved transport properties compared to [C2-Pyrr2][TFSI]2. Further exploration of the organic salts as potential electrolyte materials was conducted by mixing with 10 mol% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). This study demonstrates the effect that lithium salt addition has on thermal and ionic conductivity properties, where the largest increase in conductivity was found for [C2-Pyrr3][TFSI]2/LiTFSI (10 mol% LiTFSI). Solid-state NMR analysis revealed that Li+ and [TFSI]- ions acted as the major contributors to ionic conductivity while the dications in the bulk structure showed lower mobility.

Green Energetic Dicationic Azine Salts for Wireless Ignition

Green Energetic Dicationic Azine Salts for Wireless Ignition

Linking the Thermal and Electronic Properties of Functional Dicationic Salts with Their Molecular Structures

The two major properties that underpin ionic liquids are tunability and the potential to create task-specific media. Together, these properties allow ionic liquids to surpass the roles long held by traditional molecular solvents. However, at elevated temperatures or under prolonged heating, the structural components that impart such properties decompose or degrade. Dicationic pyridine salts present new opportunities to extend functionality and tunability to high temperatures because they are coordinating and thermally robust. In this work, we present three structurally related series of dicationic pyridine salts, which have been characterized by a wide array of techniques to link thermal and electronic properties to structural variation. The phase transitions and thermal stabilities of the salts were significantly influenced by small structural changes, and several new candidates for high-temperature-based applications were identified. The electron density, and therefore the electron donating ability, of the pyridine functional group could also be controlled by structural variation of cations and anions. Therefore, dicationic pyridine salts are highly tunable choices for task-specific solvents at elevated temperatures. Importantly, thermally robust solvents not only extend operational ranges but also reduce the need to replace or replenish solvents that degrade over time at temperatures commonly employed in industrial settings (i.e., 150–200 °C); solvent lifetimes are extended, and production is reduced. This is a critical requirement for complex media such as ionic liquids, which have high economic and environmental production costs.

Synthesis and Characterization of Peralkylated Pyrrole-Fused Azacoronene.

A hexapyrrolohexaazacoronene (HPHAC) with 12 less-bulky peripheral ethyl groups than its aryl-containing HPHAC counterpart was synthesized to investigate the innate character of HPHAC. X-ray diffraction analysis revealed that HPHAC had a planar structure and close packing because of CH-π interactions between the alkyl groups and the HPHAC core. Compared to the previously reported HPHAC decorated with 12 peripheral aryl groups, this electron-rich π-system exhibited reversible multistep oxidations at low potentials and easily formed mono- and dicationic salts and charge-transfer (CT) complexes with 7,7,8,8-tetracyano-p-quinodimethane. These oxidized species exhibited clear changes in the bond-length alternation of the pyrrole units in the crystal state, indicating charge and spin delocalization. The distinct upfield shift of the central carbon signal of the dication in the 13C NMR spectrum affirms the global aromaticity from the viewpoint of a magnetic criterion. In the UV-vis/NIR spectra, broad absorption in the NIR region was observed only for HPHAC2+ and not the structurally similar cyclo[6]pyrrole. Magnetic circular dichroism measurements and time-dependent density functional theory calculations revealed that the broad absorption was assigned to the CT transition from the central benzene ring to the outer pyrrole rings.

Organic Salts Based on Isoniazid Drug: Synthesis, Bioavailability and Cytotoxicity Studies

Tuberculosis is one of the ten causes of morbidity and mortality worldwide caused by Mycobacterium tuberculosis complex. Some of the anti-tuberculosis drugs used in clinic studies, despite being effective for the treatment of tuberculosis, present serious adverse effects as well as poor bioavailability, stability, and drug-resistance problems. Thus, it is important to develop approaches that could provide shorter drug regimens, preventing drug resistance, toxicity of the antibiotics, and improve their bioavailability. Herein, we reported the use of organic salts based on the isoniazid drug, which can act as an organic cation combined with suitable organic anions such as alkylsulfonate-based (mesylate, R or S-Camphorsulfonate), carboxylate-based (glycolate, vanylate) and sacharinate. The synthesis, characterization, and cytotoxicity studies comparing with the original isoniazid drug have been performed. The possibility to explore dicationic salts seems promising in order to improve original bioavailability, and promote the elimination of polymorphic forms as well as higher stability, which are relevant characteristics that the pharmaceutical industry pursues.

The Interconnection of Two Positive Charges by Conjugation and Cross‐Conjugation in Bis‐Quinolinium Ethynyls

1,4‐Diethynylbenzene was used as conjugated all‐carbon and rigid spacer between the 2‐, 3‐ and 4‐positions of two 1‐methylquinolinium rings. Thus, for a systematic study, a series of dicationic salts with 2,2‐, 3,3‐, 4,4‐, 3,2‐, and 3,4‐interconnections of the two positive charges was prepared, in which all even‐numbered substitution patterns are conjugated, and all odd‐numbered substitution patterns are cross‐conjugated. As a consequence, conjugated/conjugated, cross‐conjugated/cross‐conjugated, and conjugated/cross‐conjugated dications have been prepared. The different combinations result in considerably different charge distributions of the positive charges within the π‐electron systems according to the rules of resonance which translate into different DFT‐calculated frontier orbital profiles and spectroscopic properties such as 13C NMR chemical shifts, IR and Raman absorptions, and the measured as well as calculated UV/Vis spectra.

Stable dicationic dioxoliums and fate of their dioxolyl radicals

A glimpse into uncharted territory: the synthesis and study of dicationic dioxolium salts allow for assessing the fate of the corresponding elusive dioxolyl radicals.

Wurster-Type Nanographenes as Stable Diradical Dications.

Three new and stable diradical dications based on the 4,10-dibromoanthanthrone have been synthesized and characterized. In their dicationic state, the amines show a biradical character in the ground state. Their magnetic properties have been investigated by NMR and EPR spectroscopies. The dicationic salts shows strong and broad optical absorption in the near-infrared region. The main driving force to obtain a ground state biradical is the high steric hindrance that prevents planarization of the diphenylamines with the anthanthrone aromatic core. The radical cations are isolated in two perpendicular π-systems as demonstrated by X-ray diffraction structures. This work provides a new bridging unit in the search for biradical bis(triarylamines) salts.

Dicationic and monocationic benzobisthiazolium salts as potential NLO chromophores

Dicationic salts derived from linear and angular benzobisthiazole skeleton were prepared by methylation under microwave conditions. The following condensation with aromatic aldehydes afforded two-armed conjugated molecules, which represent quadrupolar systems. Monocationic angular derivatives were also prepared to study the differences in properties between the quadrupolar and dipolar structures. Absorption and fluorescence characteristics were determined, in the case of dipolar derivatives solvatochromism was studied as well. Quantum chemical calculation of absorption spectra and nonlinear optical properties (first and second hyperpolarizability) were performed. The predicted values correlate well with the experimental ones and helped to explain the split character of the main band in absorption spectra of quadrupolar angular derivatives. Although high values of second hyperpolarizability are predicted for the linear compounds, their very low solubility in common solvents is a strongly limiting factor when practical use is considered. On the contrary, the applicability of one dicationic and one monocationic angular dye, with better solubility, was successfully verified in confocal laser scanning microscopy with nonlinear excitation.

A new class of bicyclic dicationic salts based on the 7-azoniabicyclo[2.2.1]heptane scaffold

A new class of dicationic ionic salts has been developed based on two 7-azoniabicyclo[2.2.1]heptane moieties and a variable spacer. The construction of the 7-azabicyclo[2.2.1]heptane skeleton and introduction of the two- to ten-atom spacer occurred concurrently in a one-pot reaction. Quaternization and subsequent metathesis afforded the dicationic salts consisting of two linked quaternized bicyclic moieties and bis(trifluoromethylsulfonyl)imide or dicyanamide as counterions. These salts are liquids at room temperature if the spacer length was larger than seven atoms. X-ray diffraction analysis revealed a linear conformation of the spacer and RS/SR stereochemistry of the quaternized nitrogens.

Polymerised ionic liquid crystals bearing imidazolium and bipyridinium groups

ABSTRACTNovel kinds of polymerised ionic liquid crystals (PILCs) bearing imidazolium and bipyridinium groups were synthesised and characterised in this work. Some bromo-polyesters were synthesised in an esterification chain reaction using 2,3-dibromosuccinyl dichloride, isophthaloyl chloride and 4,4′-biphenol. The polyester imidazolium bromides (PIBs) and polyester dipyridinium bromides (PDBs) were obtained by a quaternisation reaction between the bromo-polyesters, N-methylimidazole and 4-4′-bipyridine, respectively. The polyester imidazolium tetrafluoroborates (PITs) and polyester dipyridinium tetrafluoroborates (PDTs) were synthesised using the corresponding PIBs and PDBs in an anion-exchange reaction. The chemical structures, liquid crystalline properties and molecular weights of these polymers were characterised by multiple experimental techniques. All the PILCs including PIBs, PDBs, PITs and PDTs display smectic A phase on heating and cooling cycles. The liquid-crystalline properties of bromo-polyesters are influenced by the length of flexible spacer and composition of polyester backbones, while those of PILCs are determined by the ionic groups as additional important influent factors. In comparison with those of the mother bromo-polyesters, the d-spacing of PILCs reduced slightly due to Im+–Br−, Dp+–Br−, Im+–BF4− and Dp+–BF4− ion pairs in the polymer systems. Monocationic imidazolium salts display weaker interionic and intermolecular interaction, higher mobility and lower viscosity than dicationic dipyridinium salts.

Exploring the Use of Ionic Liquid Mixtures to Enhance the Performance of Dicationic Ionic Liquids

Dicationic ionic liquids (DILs) of diverse structural architectures (including symmetrical and asymmetrical ammonium, phosphonium and heterodications and the bis(trifluoromethylsulfonyl)amide (NTf2−) anion) have been prepared and used as additives to N-methyl-N-ethoxyethylpyrrolidinium (P1EOE) NTf2, a relatively high-performing IL in terms of its transport properties (viscosity 53 mPa s). The three-ion, binary IL mixtures were characterized for their thermal and transport properties using differential scanning calorimetry, temperature dependent viscosity, conductivity and Pulsed Gradient Spin Echo (PGSE) NMR. Variable temperature 1H, 19F and 31P self-diffusion coefficients were determined at 25, 60 and 75°C. The order of the diffusion coefficients was D(P1EOE+) > D(anion) > D(dication), and the composition of the dication had a strong effect on the degree to which diffusion of all three species is more or less coupled. IL mixtures containing about 30 mol % of the dicationic NTf2 and 70 mol % of P1EOE NTf2 resulted in a significant decrease in glass transition temperatures and viscosities compared to the pure DIL. The mixtures extended the liquid range and potential for practical applications significantly. The data obtained here provides insight into the future design of dicationic salts tailored to exhibit lower viscosity and higher conductivities.

Flexible, dicationic imidazolium salts for in situ application in palladium‐catalysed Mizoroki–Heck coupling of acrylates under aerobic conditions

The synthesis, characterization and in situ catalytic performance of new unsymmetric N,N′‐disubstituted imidazolium‐based dicationic salts in Mizoroki–Heck coupling of acrylates with aryl bromides under aerobic conditions are described. A series of flexible dicationic salts with varying steric and electronic properties were synthesized in good to excellent yields. All the salts were well characterized using spectroscopic techniques. X‐ray diffraction analysis of two salts with the same dicationic backbone and different counter anions shows that the ligand adopts two different conformations which are influenced by the nature of the anion. Thus, the ligand is capable of changing its conformation according to the change in environment due to its flexible nature. All the synthesized imidazolium salts were found to be active in in situ palladium‐catalysed Mizoroki–Heck coupling under aerobic conditions. Amongst the salts, the hydroxyl‐functionalized imidazolium salt, incorporating the features of both bidentate chelating O,O ligand and carbene, shows the maximum catalytic activity. A variety of aryl and heteroaryl methyl and ethyl cinnamates were synthesized using these imidazolium salts as preligands. In addition, NMR studies confirm in situ generation of normal N‐heterocyclic carbenes from the C‐2 position of imidazol‐2‐ylidene ring. The mercury poisoning test was also performed to ascertain the nature of catalytically active palladium species. Aerobic conditions, low catalytic loading (0.5 mol%), shorter reaction times, broad functional group tolerance and good to excellent isolated yields are some of the significant features of the novel catalytic systems described here. Copyright © 2016 John Wiley & Sons, Ltd.

Direct Carbonization of Cyanopyridinium Crystalline Dicationic Salts into Nitrogen-Enriched Ultra-Microporous Carbons toward Excellent CO2 Adsorption.

A family of nitrogen-enriched ultramicroporous carbon materials was prepared by direct carbonization of task-specifically designed molecular carbon precursors of cyanopyridinium-based crystalline dicationic salts (CISs). Varying the molecular structure of CISs, large surface area (918 m(2) g(-1)), high N content (20.10 wt %), and narrow distributed ultramicropores (0.59 nm) can be simultaneously achieved on the sample PCN-14 derived from methyl-linked 4-cyanopyridinium D[4-CNPyMe]Tf2N. It therefore exhibited exceptional performance in greenhouse gas CO2 capture, i.e., simultaneously possessing (1) high CO2 adsorption uptakes: 5.33 mmol g(-1) at 273 K, and 3.68 mmol g(-1) at 298 K (both at 1.0 bar); (2) unprecedented selectivity of CO2 versus N2: 156; and (3) a high adsorption ratio of CO2 to N2: 148 (at 1.0 bar). This is the first time such a high selectivity and adsorption ratio over carbon materials has been achieved, which is among the highest values over solid adsorbents.