1,1′‐Diethyl‐4,4′‐bipyridine‐1,1′‐diium bis(1,1,3,3‐tetracyano‐2‐ethoxypropenide): multiple C—H...N hydrogen bonds form a complex sheet structure

In the title salt, C₁₄H₁₈N₂²⁺·2C₉H₅N₄O⁻, the 1,1′‐diethyl‐4,4′‐bipyridine‐1,1′‐diium dication lies across a centre of inversion in the space group P2₁/c. In the 1,1,3,3‐tetracyano‐2‐ethoxypropenide anion, the two independent –C(CN)₂ units are rotated, in conrotatory fashion, out of the plane of the central propenide unit, making dihedral angles with the central unit of 16.0 (2) and 23.0 (2)°. The ionic components are linked by C—H...N hydrogen bonds to form a complex sheet structure, within which each cation acts as a sixfold donor of hydrogen bonds and each anion acts as a threefold acceptor of hydrogen bonds.     

4‐[2‐(4‐Cyano­phenyl)ethenyl]‐N‐methyl­pyridinium tetra­phenyl­borate

In the title compound, C₁₅H₁₃N₂⁺·C₂₄H₂₀B⁻, the pyridyl ring of the cation makes a dihedral angle of 1.6° with the benzene ring. Each is rotated in the same direction with respect to the central –C—CH=CH—C– linkage, by 3.8 and 5.3°, respectively. The anions have a slightly distorted tetra­hedral geometry. Mol­ecular packing analysis was carried out using the packing energy portioning scheme in the program OPEC. Around each anion in the crystal structure there are eight anions, which inter­act with the central anion through C—H⋯π inter­actions. The cations are hydrogen bonded in a head‐to‐tail fashion, forming chains along [10].     

Novel Cyclic Sulfonium‐Based Ionic Liquids: Synthesis,Characterization, and Physicochemical Properties

A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO₃]^? and [NTf₂]^? ions exhibit organic plastic crystal behaviors, and all the saccharin‐based salts display relatively high refractive indices (1.442–1.594). In addition, some ionic liquids with the [NTf₂]^? ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA]^? ion show lower viscosities (34.2–62.6 mPa s at 20 °C) and much higher conductivities (7.6–17.6 mS cm^?1 at 20 °C) than most traditional 1,3‐dialkylimidazolium salts.     

Hexa­methyl­enetetraminium 2,4,6‐tri­nitro­phenolate

In the title complex, the 1:1 ionic adduct of hexa­methyl­enetetraminium and 2,4,6‐tri­nitro­phenolate, C₆H₁₃N₄⁺·­C₆H₂N₃O₇^?, the cation acts as a donor for bifurcated hydrogen bonds to the O atoms of the phenolate and one of the nitro groups of the 2,4,6‐tri­nitro­phenolate anion. The crystal structure is built from sheets of cations and anions, and is stabilized by intermolecular C—H?O and C—H?π interactions.     

Pentazol‐Derivate und daraus entstehende Azide: [O3S—p‐C6H4—N5]— und [O3S—p‐C6H4—N3]— als Kalium‐Kronenether‐Salze

Pentazole Derivates and Azides Formed from them: Potassium‐Crown‐Ether Salts of [O₃S—p‐C₆H₄—N₅]^— and [O₃S—p‐C₆H₄—N₃]^{— —}O₃S—p‐C₆H₄—N₂⁺ was reacted with sodium azide at —50 °C in methanol, yielding a mixture of 4‐pentazolylbenzenesulfonate and 4‐azidobenzenesulfonate (amount‐of‐substance ratio 27:73 according to NMR). By addition of KOH in methanol at —50 °C a mixture of the potassium salts K[O₃S—p‐C₆H₄—N₅] and K[O₃S—p‐C₆H₄—N₃] was precipitated (ratio 60:40). A solution of this mixture along with 18‐crown‐6 in tetrahydrofurane yielded the crystalline pentazole derivate [THF‐K‐18‐crown‐6][O₃S—p‐C₆H₄—N₅]·THF by addition of petrol ether at —70 °C. From the same solution upon evaporation and redissolution in THF/petrol ether the crystalline azide [THF‐K‐18‐crown‐6][O₃S—p‐C₆H₄—N₃]·THF was obtained. A solution of the latter in chloroform/toluene under air yielded [K‐18‐crown‐6][O₃S—p‐C₆H₄—N₃]·1/3H₂O. According to their X‐ray crystal structure determinations [THF‐K‐18‐crown‐6][O₃S—p‐C₆H₄—N₅]·THF and [THF‐K‐18‐crown‐6][O₃S—p‐C₆H₄—N₃]·THF have the same kind of crystal packing. Differences worth mentioning exist only for the atomic positions of the pentazole ring as compared to the azido group and for one THF molecule which is coordinated to the potassium ion; different orientations of the THF molecule take account for the different space requirements of the N₅ and the N₃ group. In [K‐18‐crown‐6][O₃S—p‐C₆H₄—N₃]·1/3H₂O there exists one unit consisting of one [K‐18‐crown‐6]⁺ and one [O₃S‐C₆H₄—N₃]^— ion and another unit consisting of two [O₃S‐C₆H₄—N₃]^— ions joined via two [K‐18‐crown‐6]⁺ ions and one water molecule. The rate constants for the decomposition [O₃S‐C₆H₄—N₅]^— → [O₃S‐C₆H₄—N₃]^— + N₂ in methanol were determined at 0 °C and —20 °C.     

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy,X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Ten [C₈C₁Im]⁺ (1‐methyl‐3‐octylimidazolium)‐based ionic liquids with anions Cl^?, Br^?, I^?, [NO₃]^?, [BF₄]^?, [TfO]^?, [PF₆]^?, [Tf₂N]^?, [Pf₂N]^?, and [FAP]^? (TfO=trifluoromethylsulfonate, Tf₂N=bis(trifluoromethylsulfonyl)imide, Pf₂N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C₈C₁C₁Im]⁺ (1,2‐dimethyl‐3‐octylimidazolium)‐based ionic liquids with anions Br^? and [Tf₂N]^? were investigated by using X‐ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While ¹H NMR spectroscopy is found to probe very specifically the strongest hydrogen‐bond interaction between the hydrogen attached to the C² position and the anion, a comparative XPS study provides first direct experimental evidence for cation–anion charge‐transfer phenomena in ionic liquids as a function of the ionic liquid’s anion. These charge‐transfer effects are found to be surprisingly similar for [C₈C₁Im]⁺ and [C₈C₁C₁Im]⁺ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.     

Site‐Directed Dimerization of Bowl‐Shaped Radical Anions to Form a σ‐Bonded Dibenzocorannulene Dimer

Designed site‐directed dimerization of the monoanion radicals of a π‐bowl in the solid state is reported. Dibenzo[a,g]corannulene (C₂₈H₁₄) was selected based on the asymmetry of the charge/spin localization in the C₂₈H₁₄^.? anion. Controlled one‐electron reduction of C₂₈H₁₄ with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs⁺(diglyme)}₂(C₂₈H₁₄?C₂₈H₁₄)^2?] ( 1 ), as revealed by single crystal X‐ray diffraction study performed in a broad range of temperatures. The C?C bond length between two C₂₈H₁₄^.? bowls (1.560(8) Å) measured at ?143 °C does not significantly change upon heating of the crystal to +67 °C. The single σ‐bond character of the C?C linker is confirmed by calculations. The trans‐disposition of two bowls in 1 is observed with the torsion angles around the central C?C bond of 172.3(5)° and 173.5(5)°. A systematic theoretical evaluation of dimerization pathways of C₂₈H₁₄^.? radicals confirmed that the trans‐isomer found in 1 is energetically favored.     

DFT Study of the Geometrical and Electronic Structures of Geminal Dicationic Ionic Liquids 1,3‐Bis[3‐methylimidazolium‐1‐yl]hexane Halides

In this work, the geometrical and electronic properties of the mono cationic ionic liquid 1‐hexyl‐3‐methylimidazolium halides ([C₆(mim)]⁺_X^?, X=Cl, Br and I) and dicationic ionic liquid 1,3‐bis[3‐methylimidazolium‐1‐yl]hexane halides ([C₆(mim)₂X₂], X=Cl, Br and I) were studied using the density functional theory (DFT). The most stable conformer of these two types ionic liquids (IL) are determined and compared with each other. Results show that in the most stable conformers, in both monocationic ILs and dicationic ILs, the Cl^? and Br^? anions prefer to locate almost in the plane of the imidazolium ring whereas the I^? anion prefers nearly vertical location respect to the imidazolium ring plan. Comparison of hydrogen bonding and ionic interactions in these two types of ionic liquids reveals that these ionic liquids can be formed hydrogen bond by Cl^? and Br^? anion. The calculated thermodynamic functions show that the interaction of cation — anion pair in the dicationic ionic liquids are more than monocationic ionic liquids and these interactions decrease with increasing the halide anion atomic weight.     

Discrete Cationic Zinc and Magnesium Complexes for Dual Organic/Organometallic‐Catalyzed Ring‐Opening Polymerization of Trimethylene Carbonate

We describe herein an original approach for the efficient immortal ring‐opening polymerization (iROP) of trimethylene carbonate (TMC) under mild conditions using dual‐catalyst systems combining a discrete cationic metal complex with a tertiary amine. A series of new zinc and magnesium cationic complexes of the type [{NNO}M]⁺[anion]^? ({NNO}^?=2,4‐di‐tert‐butyl‐6‐{[(2′‐dimethylaminoethyl)methylamino]methyl}phenolate; M=Zn, [anion]^?=[B(C₆F₅)₄]^? ( 2 ), [H₂N‐ {B(C₆F₅)₃}₂]^? ( 3 ), and [EtB(C₆F₅)₃]^? ( 4 ); M=Mg, [anion]^?=[H₂N{B(C₆F₅)₃}₂]^? ( 7 )) have been prepared from the corresponding neutral compounds [{NNO}ZnEt] ( 1 ) and [{NNO}‐ Mg(nBu)] ( 6 ). Compounds 2 – 4 and 7 exist as free ion pairs, as revealed by ¹H, ¹³C, ¹⁹F, and ¹¹B NMR spectroscopy in THF solution, and an X‐ray crystallographic analysis of the bis(THF) adduct of compound 7 , 7? (THF)₂. The neutral complexes 1 and 6 , in combination with one equivalent or an excess of benzyl alcohol (BnOH), initiate the rapid iROP of TMC, in bulk or in toluene solution, at 45–60 °C (turnover frequency, TOF, up to 25–30 000 mol(TMC)?mol(Zn)?h^?1 for 1 and 220–240 000 mol(TMC)?mol(Mg)?h^?1 for 6 ), to afford H‐PTMC‐OBn with controlled macromolecular features. ROP reactions mediated by the cationic systems 2 /BnOH and 7 /BnOH proceeded much more slowly (TOF up to 500 and 3 000 mol(TMC)?mol(Zn or Mg)?h^?1 at 110 °C) than those based on the parent neutral compounds 1 /BnOH and 6 /BnOH, respectively. Use of original dual organic/organometallic catalyst systems, obtained by adding 0.2–5 equiv of a tertiary amine such as NEt₃ to zinc cationic complexes [{NNO}Zn]⁺[anion]^? ( 2 – 4 ), promoted high activities (TOF up to 18 300 mol(TMC)?mol(Zn)?h^?1 at 45 °C) giving H‐PTMC‐OBn with good control over the M_n and M_w/M_n values. Variation of the nature of the anion in 2 – 4 did not significantly affect the performance of these catalyst systems. On the other hand, the dual magnesium‐based catalyst system 7 /NEt₃ proved to be poorly effective.     

Benzyl­triethyl­ammonium 2,2,2,4‐tetra­chloro‐2,5‐di­hydro‐1,2λ5‐oxatellurole

The geometry around the Te atom in the anion in C₁₃H₂₂N⁺·C₃H₃Cl₄OTe^? is distorted pseudo‐octahedral with three Cl atoms and the O atom forming the equatorial plane, and the C atom lying opposite the tellurium lone pair. Distances and angles are: Te—O 2.0120 (18), Te—C 2.072 (2), Te—Cl 2.5239 (7), 2.5283 (7) and 2.5577 (7) Å; O—Te—C 81.61 (9), O—Te—Cl 90.69 (6), 90.99 (6) and 168.13 (5), C—Te—Cl 87.13 (8), 86.64 (8) and 86.59 (8), and Cl—Te—Cl 87.02 (2), 90.00 (3) and 173.24 (3)°. The anions are arranged in an infinite zigzag chain parallel to the a axis through a secondary Te?Cl bond [3.8391 (8) Å].     

Linkage isomerism of organoplatinum(II) compounds coordinated by two 1,3‐di­methyl­barbiturate anions

In two linkage isomers, bis[1,3‐di­methyl‐2,4,6(1H,3H,5H)‐pyrimidine­trionato]‐C⁵,O⁴‐(ethyl­enedi­amine‐N,N′)platinum(II), [Pt(C₆H₇N₂O₃)₂(C₂H₈N₂)], (I), and bis[1,3‐di­methyl‐2,4,6(1H,3H,5H)‐py­rim­idine­tri­on­ato‐C⁵](ethyl­enediamine‐N,N′)­plati­num(II) di­hyd­rate, [Pt(C₆H₇N₂O₃)₂(C₂H₈N₂)]·2H₂O, (II), crystal­lized from the same aqueous solution containing [Pt(en)(OH)₂] and 1,3‐di­methyl­barbituric acid (Hdmbarb) in a 1:2 molar ratio, a pair of monodentate dmbarb^? anions coordinate to the Pt atom at tetrahedral C atoms for (II), while one dmbarb^? anion coordinates at the carbon and the other at a deprotonated enol oxy­gen for (I). The Pt—C distances in (I) and (II) are comparable: 2.112 (4) Å for (I), and 2.114 (4) and 2.117 (4) Å for (II).     

trans‐4‐[4‐(Dimethylamino)phenyl­iminomethyl]‐N‐phenylpyridinium hexafluorophosphate

The crystal structure of the dipolar chromophoric title compound, C₂₀H₂₀N₃⁺·PF₆^?, is described. The phenyl­ene and pyridyl rings are almost coplanar [dihedral angle 7.5 (2)°], but the phenyl substituent forms a dihedral angle of 56.6 (1)° with the pyridyl ring. The compound crystallizes in the non‐centrosymmetric space group Cc and is a likely candidate for the display of quadratic non‐linear optical effects.     

The salt‐type 1:2 adduct of meso‐5,5,7,12,12,14‐hexa‐C‐methyl‐1,4,8,11‐tetraazacyclotetradecane (tet‐a) and 5‐nitroisophthalic acid forms a hydrogen‐bonded sheet ­structure containing two configur­ational isomers of [(tet‐a)H2]2+

The title compound, meso‐5,7,7,12,14,14‐hexa­methyl‐4,11‐di­aza‐1,8‐diazo­nia­cyclo­tetra­decane bis(3‐carboxy‐5‐nitro­benz­oate), C₁₆H₃₈N₄²⁺·2C₈H₄NO₆^?, is a salt in which the cation is present as two configurational isomers, disordered across a common centre of inversion in P, with occupancies of 0.847 (3) and 0.153 (3). The anions are linked into chains by a single O—H?O hydrogen bond [H?O 1.71 Å, O?O 2.5063 (15) Å and O—H?O 156°] and the cations link these anion chains into sheets by means of a range of N—H?O hydrogen bonds [H?O 1.81–2.53 Å, N?O 2.718 (5)–3.3554 (19) Å and N—H?O 146–171°].     

A novel PtII–dibenzo‐18‐crown‐6 (DB18C6) complex

The novel Pt^II–dibenzo‐18‐crown‐6 (DB18C6) title complex, μ‐[tetrakis­(thio­cyanato‐S)­platinum(II)]‐N:N′‐bis{[2,5,8,­15,18,21‐hexa­oxa­tri­cyclo­[20.4.0.1^9,14]­hexa­cosa‐1(22),9(14),10,12,23,25‐hexaene‐κ⁶O]­potassium(I)}, [K(C₂₀H₂₄O₆)]₂[Pt(SCN)₄], has been isolated and characterized by X‐ray diffraction analysis. The structure analysis shows that the complex displays a quasi‐one‐dimensional infinite chain of two [K(DB18C6)]⁺ complex cations and a [Pt(SCN)₄]^2? anion, bridged by K⁺?π interactions between adjacent [K(DB18C6)]⁺ units.     

N,N′‐Di­methyl­piperazinium(2+) phos­phonoacetate: hydrogen‐bonded anion sheets containing cation‐templated R66(28) rings

In the title compound, C₆H₁₆N₂²⁺·2C₂H₄O₅P^?, the cations lie across centres of inversion; in the anions, two of the H‐atom sites have 0.50 occupancy. The anions are linked by short O—H?O hydrogen bonds [O?O 2.465 (3)–2.612 (3) Å and O—H?O 165–171°] into sheets of alternating R(12) and R(28) rings, both of which are centrosymmetric; the cations lie at the centres of the larger rings linked to the anion sheet by N—H?O hydrogen bonds [N?O 2.642 (2) Å and N—H?O 176°].     

Exploring Sustainable Rocket Fuels: [Imidazolyl−Amine−BH2]+‐Cation‐Based Ionic Liquids as Replacements for Toxic Hydrazine Derivatives

The application of hypergolic ionic liquids as propellant fuels is a newly emerging area in the fields of chemistry and propulsion science. Herein, a new class of [imidazolyl?amine?BH₂]⁺‐cation‐based ionic liquids, which included fuel‐rich anions, such as dicyanamide (N(CN)₂^?) and cyanoborohydride (BH₃CN^?) anions, were synthesized and characterized. As expected, all of the ionic liquids exhibited spontaneous combustion upon contact with the oxidizer 100 % HNO₃. The densities of these ionic liquids varied from 0.99–1.12 g cm^?3, and the heats of formation, predicted based on Gaussian 09 calculations, were between ?707.7 and 241.8 kJ mol^?1. Among them, the salt of compound 5 , that is, (1‐allyl‐1H‐imidazole‐3‐yl)?(trimethylamine)?dihydroboronium dicyanamide, exhibited the lowest viscosity (168 MPa s), good thermal properties (T_gT_d>130 °C), and the shortest ignition‐delay time (18 ms) with 100 % HNO₃. These ionic fuels, as “green” replacements for toxic hydrazine‐derivatives, may have potential applications as bipropellant formulations.     

Ionic thermo‐responsive copolymer with multi LCST values: easy and fast LCST‐change through anion exchange

An ionic thermo‐responsive copolymer with multiple lower critical solution temperatures (multi‐LCSTs) has been developed, and the multi‐LCSTs were easily changeable according to the various counter anion types. The multi‐LCST values were achieved by introducing an ionic segment with an imidazolium moiety within the p‐NIPAAm polymer chain to produce poly(NIPAAm‐co‐BVIm) copolymers, [p‐NIBIm]⁺[Br]^?, and changing the counter anion type to produce [p‐NIBIm]⁺[X]^? (X = Cl, AcO, HCO₃, BF₄, CF₃SO₃, PF₆, SbF₆). The as‐prepared temperature‐responsive copolymers were physicochemically characterized via proton nuclear magnetic resonance spectroscopy (¹H‐NMR), Fourier‐transform infrared, X‐ray photoelectron spectroscopy, and thermogravimetric analysis. Their various LCST values, micelle sizes, and surface charges were determined using an Ultraviolet‐visible spectrophotometer and a Zeta (ξ) sizer, which were fitted with temperature and stirring control. The copolymers showed a broad LCST spectrum between 39°C and 52°C. The Zeta (ξ) potential values at a pH = 7 decreased from about +9.7 for [p‐NIBIm]⁺[X]^? (X = Cl ≈ Br) to about +2.0 mV for [p‐NIBIm]⁺[X]^? (X = PF₆ ≈ SbF₆). The micelle size (or volume) of the copolymers with different anionic species gradually increased from 181.2 nm (or 2.49 × 10^?17 cm^?3) for [p‐NIBIm]⁺[Br]^? to 229.2 nm (or 5.04 × 10^?17 cm^?3) for [p‐NIBIm]⁺[CF₃SO₃]^?, showing a clear effect of the anion on the micelle size (or volume) at a constant temperature, such as body temperature. The fact that the most important physicochemical properties for the thermo‐responsive copolymers, such as the LCST value, micelle size (or volume), and surface charge, could be easily controlled only through the anion exchange suggests these are highly applicable as ionic thermo‐responsive copolymers in a drug (or gene, protein) delivery system. Copyright © 2015 John Wiley & Sons, Ltd.     

1‐Methyl‐4‐nitraminopyridinium nitrate and 4‐nitraminopyridinium methanesulfonate

In the title compounds, C₆H₈N₃O₂⁺·NO₃^? and C₅­H₆­N₃­O₂⁺·­CH₃SO₃^?, respectively, the cations are almost planar; the twist of the nitr­amino group about the C—N and N—N bonds does not exceed 10°. The deviations from coplanarity are accounted for by intermolecular N—H?O interactions. The coplanarity of the NHNO₂ group and the phenyl ring leads to the deformation of the nitr­amino group. The C—N—N angle and one C—C—N angle at the junction of the phenyl ring and the nitr­amino group are increased from 120° by ca 6°, whereas the other junction C—C—N angle is decreased by ca 5°. Within the nitro group, the O—N—O angle is increased by ca 5° and one O—N—N angle is decreased by ca 5°, whereas the other O—N—N angle remains almost unchanged. The cations are connected to the anions by relatively strong N—H?O hydrogen bonds [shortest H?O separations 1.77 (2)–1.81 (3) Å] and much weaker C—H?O hydrogen bonds [H?O separations 2.30 (2)–2.63 (3) Å].     

{2,6‐Bis­[(di­methyl­amino)­methyl]­phenyl‐N2,C1,N6}di­phenyl­tin(II) bromide monohydrate

In the title compound, [Sn(C₆H₅)₂(C₁₂H₁₉N₂)]Br·H₂O, the Sn^IV atom lies on a twofold axis and is coordinated by a C and two N atoms from the 2,6‐bis­[(di­methyl­amino)­methyl]­phenyl ligand in a tridentate fashion and by two phenyl groups. The resulting geometry is intermediate between square pyramidal and trigonal bipyramidal, with three C atoms in equatorial and the two N atoms in axial positions. The main deformation from ideal trigonal‐bipyramidal geometry is seen for the N—Sn—N angle [152.18 (7)°]. The Br^? anion and the water solvate mol­ecule are on an inversion centre and twofold axis, respectively. They form an infinite chain of Br?H—O—H?Br hydrogen bonds [Br?O 3.529 (2) Å] without contributing to the primary coordination sphere of the Sn atom.     

Charge‐Scaling Effect in Ionic Liquids from the Charge‐Density Analysis of N,N′‐Dimethylimidazolium Methylsulfate

The charge scaling effect in ionic liquids was explored on the basis of experimental and theoretical charge‐density analyses of [C₁MIM][C₁SO₄] employing the quantum theory of atoms in molecules (QTAIM) approach. Integrated QTAIM charges of the experimental (calculated) charge density of the cation and anion resulted in non‐integer values of ±0.90 (±0.87) e. Efficient charge transfer along the bond paths of the hydrogen bonds between the imidazolium ring and the anion was considered as the origin of these reduced charges. In addition, a detailed QTAIM analysis of the bonding situation in the [C₁SO₄]^? anion revealed the presence of negative π_O→σ*_S‐O hyperconjugation.