Dication Salts Research Articles

Dicationic salt of β-alkyl substituted sapphyrin-type porphyrinoid: Acid-basic properties, thermal stability and quantum-chemical calculations

The UV-Vis spectra of the dicationic salt of 2,3,7,13,17,18,18,22,23-octamethyl-8,12-diethylsapphyrin {H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text]} in solutions with different polarity and acid-basic properties have been investigated. The tautomeric and acid-base equilibria of H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text] in the presence of organic bases have been examined by spectrophotometric titration. It was demonstrated that an addition of small amounts of 1,8-diazabicyclo[5.4.0]undecene (DBU) and tetramethylammonium hydroxide (Me4NOH) dissolved in methylene chloride (DCM) and MeOH, respectively results in a stepwise detachment of two protons from the basic nitrogen atoms of the macrocycle, with no anionic forms of sapphyrin being registered. The results obtained were supported using quantum-chemical calculations (DFT, B3LYP, cc-pVDZ including NBO analysis). The interactions of 2,3,7,13,17,18,18,22,23-octamethyl-8,12-diethylsapphyrin (H3β-Me8Et2Sap) with a series of compounds of different acidity and basicity were studied and the formation of very weak hydrogen bond of H3β-Me8Et2Sap as NH-acid with N,N-dimethylformamide (DMF) molecule with the value of the interaction energy (E[Formula: see text] equal -16.40 kJ/mol was revealed. The low acidity of bonds NH in the sapphyrin molecule was confirmed on the base of thermogravimetric data obtained for the solid samples of H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text] evaporated from DMF and DCM concentrated solutions.

Synthese und Charakterisierung eines stabilen Nickelocenium‐Dikation‐Salzes

AbstractWir berichten über die Synthese und Charakterisierung der Nickelocenium‐Kationen [NiCp2]⋅+ und [NiCp2]2+ als deren [F‐{Al(ORF)3}2]− (Cp = C5H5; RF=C(CF3)3) Salze. Das diamagnetische [NiCp2]2+ ist das erste Beispiel für die Isolierung eines unsubstituierten Metallocen Dikations. Beide Salze wurden durch Reaktion von neutralem NiCp2 mit [NO]+[F‐{Al(ORF)3}2]− in 1,2,3,4‐Tetrafluorbenzol (4FB) erzeugt. Die Salze konnten durch Einkristall‐Röntgenbeugung charakterisiert werden, wobei kürzere Metall‐Ligand‐Bindungslängen für das höher geladene Salz gemessen wurden. Pulver‐Röntgenbeugung zeigte, dass die Salze phasenrein erhalten wurden. Cyclovoltammetrie in 4FB ergab quasi‐reversibel Redoxwellen bei −0.44 (0→1) und +1.17 V (1→2) gegen Fc/Fc+. Das 1H NMR von [NiCp2]2+ weist ein Singulett bei 8.6 ppm auf, während das paramagnetische [NiCp2]⋅+ deutlich Hochfeld auf −103.1 ppm verschoben ist.

Synthesis and Characterization of a Stable Nickelocenium Dication Salt.

We report the synthesis and characterization of the nickelocenium cations [NiCp2 ]⋅+ and [NiCp2 ]2+ as their [F-{Al(ORF )3 }2 ]- (Cp = C5 H5 ; RF =C(CF3 )3 ) salts. Diamagnetic [NiCp2 ]2+ represents the first example for the isolation of an unsubstituted parent metallocene dication. Both salts were generated by reacting neutral NiCp2 with [NO]+ [F-{Al(ORF )3 }2 ]- in 1,2,3,4-tetrafluorobenzene (4FB). The salts were characterized by single crystal X-ray diffraction (XRD), indicating shorter metal-ligand bond lengths for the higher charged salt. Powder XRD shows the salts to be phase pure, cyclic voltammetry in 4FB gave quasi reversible redox waves at -0.44 (0→1) and +1.17 V (1→2) vs Fc/Fc+ . The 1 H NMR of [NiCp2 ]2+ is a singlet at 8.6 ppm, whereas paramagnetic [NiCp2 ]⋅+ is significantly shifted upfield to -103.1 ppm.

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.

Synthesis and Chemical Redox Studies of Half-Sandwich Chromium Carbonyl Azobenzenes

Chemical oxidation of piano-stool complexes Cr(CO)3(TripN═NTrip) (1) and Cr(CO)3(TripN═NTrip)Cr(CO)3 (2) was investigated, which led to a CAArN cation (cyc-1+) and a 17-electron chromic radical cation (2•+) upon one-electron oxidation reactions, respectively. The reactivity of cation cyc-1+ was extensively investigated. The electrophilicity enables cyc-1+ to form Lewis adducts with Me3P. Cyc-1+ can be reduced by metal K to form neutral monoradical cyc-1• and react with p-benzoquinone to produce a diradical dication salt (X). The electronic properties of 2•+ were investigated by single-crystal X-ray diffraction and EPR spectroscopy, in conjunction with DFT calculations.

Doped semiconducting polymer nanoantennas for tunable organic plasmonics

Optical nanoantennas are often based on plasmonic resonances in metal nanostructures, but their dynamic tunability is limited due to the fixed permittivity of conventional metals. Recently, we introduced PEDOT-based conducting polymers as an alternative materials platform for dynamic plasmonics and metasurfaces. Here, we expand dynamic organic plasmonic systems to a wider class of doped polythiophene-based semiconducting polymers. We present nanodisks of PBTTT semiconducting polymer doped with a dicationic salt, enabling a high doping level of around 0.8 charges per monomer, and demonstrate that they can be used as nanooptical antennas via redox-tunable plasmonic resonances. The resonances arise from the polymer being optically metallic in its doped state and dielectric in its non-conducting undoped state. The plasmonic resonances are controllable over a 1000 nm wavelength range by changing the dimensions of the nanodisks. Furthermore, the optical response of the nanoantennas can be reversibly tuned by modulating the doping level of the polymer. Simulations corroborate the experimental results and reveal the possibility to also modulate the optical nearfield response of the nanoantennas.

Construction and Functionalization of Highly Strained N -Doped Zigzag Hydrocarbon Belts

Construction and Functionalization of Highly Strained <i>N</i> -Doped Zigzag Hydrocarbon Belts

Triazolium Salt Organocatalysis: Mechanistic Evaluation of Unusual Ortho-Substituent Effects on Deprotonation

Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an NMR kinetic method for the analysis of C(3)-H/D exchange, we determined log kex–pD profiles for three ortho-substituted N-aryl triazolium salts, which enables a detailed analysis of ortho-substituent effects on deprotonation. This includes N-5-methoxypyrid-2-yl triazolium salt 7 and di-ortho-methoxy and di-ortho-isopropoxyphenyl triazolium salts 8 and 9, and we acquired additional kinetic data to supplement our previously published analysis of N-pyrid-2-yl triazolium salt 6. For 2-pyridyl triazoliums 6 and 7, novel acid catalysis of C(3)-H/D exchange is observed under acidic conditions. These kinetic data were supplemented by DFT analyses of the conformational preferences of 6 upon N-protonation. A C(3) deprotonation mechanism involving intramolecular general base deprotonation by the pyridyl nitrogen of the N(1)-deuterated dicationic triazolium salt is most consistent with the data. We also report kDO values (protofugalities) for deuteroxide-catalyzed exchange for 6–9. The protofugalities for 8 and 9 are the lowest values to date in the N-aryl triazolium series.

Ion conformation and orientational order in a dicationic ionic liquid crystal studied by solid-state nuclear magnetic resonance spectroscopy

Ionic liquids crystals belong to a special class of ionic liquids that exhibit thermotropic liquid-crystalline behavior. Recently, dicationic ionic liquid crystals have been reported with a cation containing two single-charged ions covalently linked by a spacer. In ionic liquid crystals, electrostatic and hydrogen bonding interactions in ionic sublayer and van der Waals interaction in hydrophobic domains are the main forces contributing to the mesophase stabilization and determining the molecular orientational order and conformation. How these properties in dicationic materials are compared to those in conventional monocationic analogs? We address this question using a combination of advanced NMR methods and DFT analysis. Dicationic salt 3,3′-(1,6-hexanediyl)bis(1-dodecylimidazolium)dibromide was studied. Local bond order parameters of flexible alkyl side chains, linker chain, and alignment of rigid polar groups were analyzed. The dynamic spacer effectively “decouples” the motion of two ionic moieties. Hence, local order and alignment in dicationic mesophase were similar to those in analogous single-chain monocationic salts. Bond order parameters in the side chains in the dicationic smectic phase were found consistently lower compared to double-chain monocationic analogs, suggesting decreasing contribution of van der Waals forces. Overall dication reorientation in the smectic phase was characterized by low values of orientational order parameter S. With increased interaction energy in the polar domain the layered structure is stabilized despite less ordered dications. The results emphasized the trends in the orientational order in ionic liquid crystals and contributed to a better understanding of interparticle interactions driving smectic assembly in this and analogous ionic mesogens.

Synthesis, Structure, and Electrochemical Properties of Extended Tetrathiafulvalene Dimers Linked by Flexible Butylene Chain

Abstract Tetrathiafulvalene derivatives bridged by butylene units were successfully synthesized. X-ray structure analysis of the dimeric EBDT 1 revealed that C–C bonds have staggered arrangement and all substituents are arranged anti to each other in the butylene bridge. Cyclic voltammograms of the molecules 1 and the fused TTF analog 2 consisted of two-pairs of two-electron and four pairs of two-electron redox waves, respectively. X-ray structure analysis and calculation of overlap integrals of a dicationic salt of unsubstituted-1 (1Aa) indicated that the EBDT units are stacked with strong dimerization. Coin-type cells using the molecule 2 (2Ce) as a positive electrode material showed initial discharge capacity of 179 mAh g−1, initial energy density of 600 mWh g−1, and an average voltage of 3.35 V.

Understanding the dopant induced effects on SFX-MeOTAD for perovskite solar cells: a spectroscopic and computational investigation

First-time spectroscopic and computational investigations to elucidate the role of a dicationic salt in the optical, electrical and electronic properties of a triarylamine hole transport material, SFX-MeOTAD.

A Magnetically Robust Triplet Ground State Sulfur-Hydrocarbon Diradical Dication.

The one- and two-electron oxidation reactions of tetrathiolated di-tert-butylpyrene compound 1 with NO[Al(ORF)4] (ORF = OC(CF3)3) resulted in radical cation salt 1•+[Al(ORF)4]- and diradical dication salt 12+••·2[Al(ORF)4]-, respectively. Both salts were isolated as stable crystals and investigated by single-crystal X-ray diffraction, EPR spectroscopy, SQUID measurements, and UV-vis spectroscopy. The electron spin density is delocalized on one single sulfur-doped ring in 1•+ and on both sulfur-doped rings in 12+••. The diradical dication 12+•• features a robust triplet ground state, representing the first example of a high-spin sulfur-hydrocarbon diradical.

Stable Radical Cation and Dication of an N-Heterocyclic Carbene Stabilized Digallene: Synthesis, Characterization and Reactivity.

One- and two-electron oxidation of a digallene stabilized by an N-heterocyclic carbene afforded the first stable gallium-based radical cation and dication salts, respectively. Structural analysis and theoretical calculations reveal that the oxidation occurs at the Ga=Ga double bond, leading to removal of π electrons of the double bond and a decrease of the bond order. The spin density of the radical cation mainly locates at the two gallium centers as demonstrated by EPR spectroscopy and theoretical calculations. Moreover, the reactivity of the radical cation salt toward nBu3 SnH and cyclo-S8 was studied; a digallium-hydride cation salt containing a Ga-Ga single bond and a gallium sulfide cluster bearing an unprecedented ladder-like Ga4 S4 core structure were obtained, respectively.

Stable Radical Cation and Dication of an N‐Heterocyclic Carbene Stabilized Digallene: Synthesis, Characterization and Reactivity

AbstractOne‐ and two‐electron oxidation of a digallene stabilized by an N‐heterocyclic carbene afforded the first stable gallium‐based radical cation and dication salts, respectively. Structural analysis and theoretical calculations reveal that the oxidation occurs at the Ga=Ga double bond, leading to removal of π electrons of the double bond and a decrease of the bond order. The spin density of the radical cation mainly locates at the two gallium centers as demonstrated by EPR spectroscopy and theoretical calculations. Moreover, the reactivity of the radical cation salt toward nBu3SnH and cyclo‐S8 was studied; a digallium–hydride cation salt containing a Ga−Ga single bond and a gallium sulfide cluster bearing an unprecedented ladder‐like Ga4S4 core structure were obtained, respectively.

Stabilization and isolation of radical cation and dication salts of a tetrathiafulvalene derivative functionalized with amino groups

The radical cation and dication salts of a tetrathiafulvalene derivative functionalized with amino groups have been stabilized and isolated by chemical oxidation. Comprehensive research on their structure–property relationship was fully performed.

Serendipitous isolation of a triazinone-based air stable organic radical: synthesis, crystal structure, and computation

Here we report the synthesis, isolation, and characterization of a dication salt, namely 4,6-bis(4,4′-bipyridinium)-1,3,5-triazin-2-one {12+(PF6)22−·2H2O1(PF6)2·2H2O}, and its radical cation salt, namely 4,6-bis(4,4′-bipyridinium)-1,3,5-triazin-2-one (1+˙PF6−1˙PF6).

Cluster core growth upon the decarbonylation of cyclopentadienyl-iron-dicarbonyl ferrocenyltelluride CpFe(CO)2TeFc: Fe1Te1 to Fe3Te3

Formal substitution of aryl group on to the ferrocenyl in [CpFe(CO)(μ-TeR)]2 (R = Ar, Fc) complex dramatically changes its Fe2Te2 core structure and chemical properties. Introduction of electron-rich and bulky ferrocenyl moiety instead of Ph in [CpFe(CO)TePh]2 provide flattening of Fe2Te2 core in [CpFe(CO)(μ-TeFc)]2 (1), further photochemical decarbonylation resulting unusual [(CpFe)3(μ-TeFc)3(μ-CO)(CO)] cluster (2). The electrochemical oxidation of 1 shows two reversible one-electron oxidation waves attributed to oxidation of Fe2Te2 core. Chemical oxidation of 1 is accompanied by isomerization of its core and results in dicationic salt cis-[CpFe(CO)(μ-TeFc)]2 (PF6)2 (3).This study also provides an illustrative example of the increasing nuclearity in Fe1 → Fe2 → Fe3 row, upon the stepwise electron-compensating decarbonylation of iron-carbonyl complexes and (apart from this) insight into the distribution of toluene molecules inclusion inside the channels of crystals of compound 2.

LiTFSI‐Free Spiro‐OMeTAD‐Based Perovskite Solar Cells with Power Conversion Efficiencies Exceeding 19%

AbstractTo date, the most efficient perovskite solar cells (PSCs) employ an n–i–p device architecture that uses a 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) hole‐transporting material (HTM), which achieves optimum conductivity with the addition of lithium bis(trifluoromethane)sulfonimide (LiTFSI) and air exposure. However, this additive along with its oxidation process leads to poor reproducibility and is detrimental to stability. Herein, a dicationic salt spiro‐OMeTAD(TFSI)2, is employed as an effective p‐dopant to achieve power conversion efficiencies of 19.3% and 18.3% (apertures of 0.16 and 1.00 cm2) with excellent reproducibility in the absence of LiTFSI and air exposure. As far as it is known, these are the highest‐performing n–i–p PSCs without LiTFSI or air exposure. Comprehensive analysis demonstrates that precise control of the proportion of [spiro‐OMeTAD]+ directly provides high conductivity in HTM films with low series resistance, fast hole extraction, and lower interfacial charge recombination. Moreover, the spiro‐OMeTAD(TFSI)2‐doped devices show improved stability, benefitting from well‐retained HTM morphology without forming aggregates or voids when tested under an ambient atmosphere. A facile approach is presented to fabricate highly efficient PSCs by replacing LiTFSI with spiro‐OMeTAD(TFSI)2. Furthermore, this study provides an insight into the relationship between device performance and the HTM doping level.

Iodine Clathrated: A Solid-State Analogue of the Iodine-Starch Complex.

Co-crystallizing iodine with a simple dicationic salt (1,8-diammoniumoctane chloride) results in the clathration of the iodine (I2 ) molecules inside trigonal and hexagonal helical channels of the crystal lattice with 72 wt % overall I2 loading. The I2 inside the bigger trigonal channel forms a I-I⋅⋅⋅I-I⋅⋅⋅I-I halogen-bonded infinite helical chain, while the I2 in the smaller hexagonal channel is disordered. In both channels the I2 interaction with the channel wall happens through I-I⋅⋅⋅Cl- halogen bonds. The helical channels in the crystal lattice are constructed via the strong charge-assisted H2 N+ H⋅⋅⋅Cl- hydrogen bonds between the dications and the chloride anions. The structure shows a marked similarity with the well-known starch-I2 system, and thus may provide insight for the yet unresolved structure of the I2 in the helical starch channel.

Task-Specific Organic Salts and Ionic Liquids Binary Mixtures: A Combination to Obtain 5-Hydroxymethylfurfural From Carbohydrates.

The increase in energy demand and depletion of fossil fuels are among major issues of modern society. Valorization and transformation of raw materials in products of industrial value represent a challenge. This justifies the growing interest of scientific research toward the identification of suitable media and methodologies able to pursue above goals, paying attention to matter of sustainability. On this subject, we studied sulfonic-acid functionalized diimidazolium salts as catalysts for the conversion of fructose and sucrose to 5-hydroxymethylfurfural (5-HMF) in an ionic liquid mixture. In general, using these salts allowed us to obtain 5-HMF in good yields from both substrates in mild conditions. Indeed, at 60°C and in the presence of 20 mol% of catalyst, 5-HMF yields of 60 and 30% were obtained from fructose and sucrose, respectively. The catalytic system was recycled and used up to six times observing no appreciable loss in yield for the first four cycles. Moreover, we gathered mechanistic information by in situ 1H NMR monitoring the dehydration of fructose. To dissect the role of acidity on the reaction, we determined the Hammett acidity function of each salt. Comparison of these results with yields and reactivity observed in the presence of related monocationic salts and with a dicationic salt bearing only one sulfonic acid group, allowed stating that the reactivity observed is the result of the combined action of acidity and structural features of the catalysts. Overall, the approach proposed here could contribute to pave the way to increase sustainability in the raw material valorization processes.