Triethylammonium Cations Research Articles

Two New 2p–3d Metal Complexes with a Nitronyl-Nitroxide Ligand Derived from o-Vanillin: Synthesis, Crystals Structures and Magnetic Properties

Two new 2p–3d complexes, (Et3NH)[ML(hfac)2], have been obtained using the nitronyl-nitroxide radical (HL) derived from 2-hydroxy-3-methoxy-5-nitrobenzaldehyde (M = Mn 1; Co 2). The two compounds are isomorphous and their structures consist of anionic mononuclear species, [M(hfac)2L]−, M = Mn 1; Co 2, and triethylammonium cations, Et3NH+. The metal ions adopt an octahedral geometry, being coordinated by phenoxido and aminoxyl oxygen atoms from the ligand and four oxygen atoms from the hexafluoroacetylacetonato (hfac−) ligand. The cryomagnetic behaviors of the two compounds reveal relatively strong antiferromagnetic M(II)-Rad interactions (JMnRad = −191 cm−1, JCoRad = −166 cm−1 with H = −JSMSRad). The EPR spectra (X- and Q-band) of compound 1 below 70 K show the characteristical features of a S = 2 spin system with zero field splitting terms of D = 0.26 cm−1 and E = 0.031 cm−1.

Hydrazine-derived salts: Unveiling their diverse potential through synthesis, characterization, pharmacology, and theoretical analysis

This study focuses on newly synthesized compounds derived from hydrazine derivatives, specifically methyl carbazate (MCZ, C2H6N2O2) and 2-thiobarbituric acid (2-TBA, C4H4N2O2S). The reaction between MCZ and 2-TBA resulted in the formation of three types of salts with the following compositions: [(C2H7N2O2)+(C4H3N2O2S)−(1), (C2H7N2O2)+(C4H3N2O2S)−(C2H6N2O2) (2), and (C2H7N2O2)+(C6H16N)+(C4H3N2O2S)2−(3) [(C6H16N)+ represents the triethyl ammonium cation]. The prepared salts were comprehensively characterized, showing that compound (3) exhibited a monoclinic crystal structure and met Lipinski’s rules, indicating significant drug-like properties. Molecular docking analysis revealed that these compounds exhibited strong binding affinities toward bacterial proteins, particularly Staphylococcus aureus and Escherichia coli, indicating their potential as antibacterial agents. The synthesized compounds demonstrated remarkable free radical-scavenging abilities, as evidenced by DPPH assays. The results of pharmacological evaluations, including brine shrimp lethality assays, antibacterial tests, and anticancer studies on MCF-7 cell lines, revealed that the compounds exhibit highly significant activities, particularly cytotoxic effects, suggesting their potential as anticancer agents. The compound (3) emerged as the most effective anticancer agent against MCF-7 cells. These findings underscore the broad potential of these compounds, especially (3), as promising agents with significant antibacterial, antioxidant, and anticancer activities, suggesting that they may contribute to the field of medicinal chemistry with implications for therapeutic applications.

Synthesis and crystal structure of an ionic phenyltin(iv) complex of N-salicylidene-valine

Abstract Triethylammonium dichloro[N-[(2-oxyphenyl)methylidene]valinato]-phenyl-tin(iv) was prepared and characterized by spectroscopic methods and single crystal X-ray crystallography. The compound consists of a triethylammonium cation and a tin complex as anion. The tin complex is composed of a tridentate O,N,O-Schiff base ligand coordinated to a SnCl2Ph unit. The tin atom is in distorted octahedral coordination geometry. NMR spectroscopic studies have shown that the unusual hexa-coordinated tin complex was formed as a kinetically controlled product. Storage of the solid product for several years led to a transformation into a thermodynamically stable penta-coordinated tin complex.

Effect of di- and tri-ethylammonium cations on the structure and physicochemical properties of dioxido vanadium(V) Schiff base complexes

Four dioxido vanadium(V) complexes with formula [VO2(L)]− (where L = Schiff base ligand, formed by reacting 3‑hydroxy-2-naphtoic hydrazide with 5-chlorosalicylaldehyde or 5-bromosalicylaldehyde) have been isolated and structurally characterized based on elemental analysis, IR and UV–Vis spectra results. The X-ray crystal structure diffraction analyses of all complexes indicate a distorted square pyramidal geometry for the vanadium(V) atom, being coordinated by the tridentate Schiff base and two oxido groups. The complexes are charge-balanced by triethylammonium or diethylammonium cations, and the hydrogen bond interactions between the ionic species are discussed. Ionic vanadium complexes are characterized by better solubility in water compared to neutral molecules, and this represents an important feature if these compounds have to be used as pharmaceuticals. The stability of the complexes at pH = 2 and 7 was established by UV–Vis spectroscopy and compared to the previously studied potential insulin-mimetic vanadium(III-V) complexes with Schiff base ligands. The effect of the cation on the solubility of the complexes in water and their stability in solution has been described in detail.

Triethylammonium thiocyanate ionic liquid electrolyte-based supercapacitor fabricated using coconut shell-derived electronically conducting activated charcoal electrode material

Organic solvents are commonly used as commercial electrolytes in supercapacitors, but they have several drawbacks, such as high volatility, toxicity, and environmental issues. To overcome these problems, ionic liquids are used though their high costs hamper commercial applications. In this study, a novel and low-cost ionic liquid based on triethylammonium cation and thiocyanate anion were synthesized and used as the electrolyte in a low-cost supercapacitor fabricated using electronically conducting activated carbon derived from cleaned coconut shells as electrode material. The temperature dependence of electrolyte conductivity was investigated, in the frequency range of 1 Hz-500 kHz, using AC impedance analysis, in the temperature range from 30 °C - 90 °C in ten-degree increments and found to be in the range of 4.5 to 14.4 mS cm−1. The ion transport kinetics behaves according to the Vogel-Tammann-Fulcher (VTF) model with an activation energy (Ea) and the pre-exponential factor (AσT) of 0.0158 eV and 114.9 S m−1 K1/2, respectively. The activated carbon material developed has a high porosity and high electronic conductivity. The electrode fabrication methodology was optimized by varying the polyvinylpyrrolidone (PVP) binder amount with respect to the mass of activated carbon on a titanium sheet as a function of heat treatment temperature. The supercapacitor that gives the highest specific capacitance is based on the electrode constructed using 5 % w/w PVP in 0.50 g of activated carbon deposited on a titanium sheet by heat treating at 200 °C for 20 min. At the scan rate of 5 mV s−1, two-electrode CV studies revealed a specific capacitance of 36.8 F g−1 for the optimized supercapacitor assembly. The electrolyte triethylammonium thiocyanate (TAT) demonstrated good electrochemical stability and a large operating voltage window of 1.8 V and high stability, with 94.4 % capacity retention after 1000 cycles. The AC impedance studies also gave comparable results. Prime novelty statementThe manuscript describes a method to prepare a novel and low-cost ionic liquid material triethylammoniumthiocyanate starting from triethylamine and ammonium thiocyanate, and its application as the ionic liquid electrolyte in a low-cost supercapacitor. The electrode material used in the supercapacitor was fabricated using electronically conducting activated carbon derived from cleaned coconut shells, which were deposited firmly adhering to titanium sheets using polyvinylpyrrolidone binder under optimized heat treatment conditions. As such, both the ionic liquid electrolyte and the activated carbon electrode material are novel and attractive materials for the commercial production of low-cost supercapacitors.

The Influence of Deuterium Isotope Effects on Structural Rearrangements, Ensemble Equilibria, and Hydrogen Bonding in Protic Ionic Liquids.

We report strong isotope effects for the protic ionic liquid triethylammonium methanesulfonate [TEA][OMs] by means of deuterium solid-state NMR spectroscopy covering broad temperature ranges from 65 K to 313 K. Both isotopically labelled PILs differ in non-deuterated and fully deuterated ethyl groups of the triethyl ammonium cations. The N-D bond of both cations is used as sensitive probe for hydrogen bonding and structural ordering. The 2 H NMR line shape analysis provides the deuteron quadrupole coupling constants and the characteristics of a broad heterogeneous phase with simultaneously present static and mobile states indicating plastic crystal behavior. The temperatures where both states are equally populated differ by about 80 K for the two PILs, showing that deuteration of the ethyl groups in the trialkylammonium cations tremendously shifts the equilibrium towards the static state. In addition, it leads to a significant less cooperative transition, associated with a significantly reduced standard molar transition entropy.

Synthesis of 1T WSe2 on an Oxygen-Containing Substrate Using a Single Precursor.

The metallic property of metastable 1T' WSe2 and its promising catalytic performance have attracted considerable interest. A hot injection method has been used to synthesize 1T' WSe2 with a three-dimensional morphology; however, this method requires two or more precursors and long-chain ligands, which inhibit the catalytic performance. Here, we demonstrate the synthesis of 1T' WSe2 on a substrate by a simple heating-up method using a single precursor, tetraethylammonium tetraselenotungstate [(Et4N)2WSe4]. The triethylamine produced after the reaction is an electron donor that yields negatively charged WSe2, which is stabilized by triethylammonium cations as intercalants between layers and induces 1T' WSe2. The purity of 1T' WSe2 is higher on oxygen-containing crystalline substrates than amorphous substrates because the strong adhesion between WSe2 and the substrate can produce sufficient triethylammonium (TEA) intercalation. Among the oxygen-containing crystal substrates, the substrate with a lower lattice mismatch with 1T' WSe2 showed higher 1T' purity due to the uniform TEA intercalation. Furthermore, 1T' WSe2 on carbon cloth exhibited a more enhanced catalytic performance in the hydrogen evolution reaction (197 mV at 10 mA/cm2) than has been reported previously.

Effects of the Cationic Structure on the Adsorption Performance of Ionic Polymers toward Au(III): an Experimental and DFT Study.

Ionic polymers have been proven to be promising adsorbents in recovering Au(III) due to their advantages of simple synthesis and high adsorption efficiency. However, the unclarity of the relationship between the adsorption ability of ionic polymers and their cationic structures hinders further optimization of their adsorption performance. This study synthesized a series of ionic polymers with pyridinium, imidazolium, piperidinium, pyrrolidinium, and triethylammonium cations to discover the effects of the cationic structure on their adsorption properties. Experimental results show that the existence of anion-π interaction between aromatic cations and [AuCl4]- makes the aromatic cations-anion interaction stronger, which does not enhance the adsorption performance of the aromatic-based ionic polymer. This is due to the charge delocalization in the aromatic ring, resulting in a lower electrostatic potential (ESP) of aromatic cations than that of aliphatic cations with a localized charge. The higher the ESP of cations, the better the adsorption performance of the corresponding ionic polymer. This study serves as a deep understanding of the cationic structure-adsorptive performance relationship of the ionic polymer at the molecular level and further provides a theoretical guidance to optimize the adsorption performance of ionic polymers.

Structure, hydrogen bond dynamics and phase transition in a model ionic liquid electrolyte.

We show that solid-state NMR spectroscopy is a suitable method for characterizing the structure, hydrogen bond dynamics and phase transition behavior in protic ionic liquids (PILs). Deuteron line shape and spin relaxation time analysis provide a description of the structural and dynamical heterogeneity in the solid state of the model PIL triethyl ammonium bis(trifluoromethanesulfonyl)amide [TEA][NTf2]. Therein, we observed two deuteron quadrupole coupling constant for the ND bond of the TEA cation, indicating differently strong hydrogen bonds to the nitrogen and oxygen atoms of the NTf2 anion, as we could confirm by DFT calculations. The transition processes in the dynamically heterogeneous phase are characterized by two standard molar enthalpies and thus different stages of melting. We provide geometry, rates and energetics of the cation in the solid and liquid states of the PIL. Comparison with PILs having stronger interacting anions shows higher enthalpy change between the solid and liquid states, lower activation barriers of tumbling motion and higher amplitude of librational motion for the TEA cation in the presence of the weakly interacting anion NTf2. We provide reasonable relations between microscopic and macroscopic properties, as is relevant for any kind of application.

Chloride Salts of Triethyl- and Benzyl-Triethyl-Ammonium: A New Antifungal for Giant Bamboo <i>(Dendrocalamus asper) </i>Preservation

In this study, quarternary ammonium salts based on triethylammonium and benzyltriethylammonium cations with the anion of chloride are successfully used for giant bamboo (Dendrocalamus Asper) preservation. These salts are new biocides as well as new salts which penetrate bamboo well. The prepared salts with hydrogen and benzyl substituent at the cation and consisted of chloride anion, exhibited fungicidal activity against Aspergillus Flavus. The effective and lethal doses were measured by the agar-plate method. In their activity against bamboo degrading fungi, salt of benzyl-triethyl-ammonium chloride was comparable with commercially available benzalkonium chloride and didecyldimethylammonium. Keywords: Triethylammonium, Benzyltriethylammonium, chloride, antifungal, and giant bamboo (Dendrocalamus Asper) and Aspergillus Flavus

A new series of Schiff base Ni(II)4 cubanes: Evaluation of magnetic coupling via carboxylate bridges

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, –CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1–3 possesses tetranuclear cubane-like structures containing [Ni4L4(R3COO)2]2− complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1–3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

Probing relaxation models by means of Fast Field-Cycling relaxometry, NMR spectroscopy and molecular dynamics simulations: Detailed insight into the translational and rotational dynamics of a protic ionic liquid

A combination of temperature dependent Fast Field-Cycling (FFC) relaxometry and high-resolution NMR spectroscopy provides more than five orders of magnitude in frequency range for studying translational and rotational dynamics of ionic liquids. However, to make use of this broad frequency range, certain requirements have to be met: The viscosity of the liquid has to be of the right order of magnitude, and the material has to exhibit a sufficiently broad liquid range. In addition, NMR sensitive nuclei have to be present (ideally) on both, cation and anion, and appropriate relaxation models properly describing the molecular dynamics have to be available. For the latter, Molecular Dynamics (MD) simulations are ideally suited to suggest meaningful relaxation models. In this study we employ the protic ionic liquid triethylammonium bis(trifluoromethylsulfonyl)-imide [TEA][NTf2] as model compound to gain insight into details of the molecular dynamical processes. By addressing different NMR sensitive nuclei on both ions, 1H nuclei on the triethylammonium cation, and 19F on the NTf2 anion, we are able to obtain translational dynamics as well as rotational dynamics for both species at the same time. The obtained temperature dependent translatoric diffusion coefficients are consistent with our MD simulations, and are found to be in agreement with data reported in the literature. In addition, two types of NMR relaxation processes are employed to investigate the intramolecular relaxation: (1) dipolar relaxation at low frequencies (employing FFC) addressing 1H and 19F nuclei, and (2) quadrupolar relaxation at high frequencies addressing 2H nuclei. In near quantitative agreement with MD simulations, we show that both, dipolar relaxation obtained via FFC and quadrupolar relaxation obtained via high-field NMR are leading to consistent rotational correlation times, suggesting that the rotational motion of the cation is dominantly isotropic. Hence, the intramolecular 1H relaxation rate of the cation determined via FFC can be appropriately expressed by a single rotational correlation time, compatible with the Bloembergen Purcell Pound (BPP) approach. MD simulations of the NTf2 anion, however, suggest that its reorientational dynamics is strongly anisotropic. Consequently, the proper description of the intramolecular 19F relaxation rate of the anion requires a more complex model beyond the BPP approach employing at least two correlation times: By taking internal rotation of the CF3 groups into account, we are able to determine correlation times compatible with our MD simulations.

Synthesis, Structures, Electrochemistry, and Catalytic Activity towards Cyclohexanol Oxidation of Mono-, Di-, and Polynuclear Iron(III) Complexes with 3-Amino-2-Pyrazinecarboxylate

The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the heteronuclear Fe(III)/Na(I) two-dimensional coordination polymer [Fe(N3)(μ-L)2(μ-O)1/2(Na)(μ-H2O)1/2]n (4), are reported. Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with iron(III) chloride under different reaction conditions were studied, and the obtained compounds were characterized by elemental analysis, Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray single-crystal diffraction. Compound 1 is a neutral mononuclear complex, whereas 2 is mono-anionic with its charge being neutralized by triethylammonium cation. Compounds 3 and 4 display a di-methoxido-bridged dinuclear complex and a two-dimensional heterometallic Fe(III)/Na(I) polynuclear coordination polymer, respectively. Compounds 3 and 4 are the first examples of methoxido- and oxido-bridged iron(III) complexes, respectively, with 3-amino-2-pyrazinecarboxylate ligands. The electrochemical study of these compounds reveals a facile single-electron reversible Fe(III)-to-Fe(II) reduction at a positive potential of 0.08V vs. saturated calomel electrode (SCE), which is in line with their ability to act as efficient oxidants and heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation (with tert-butyl hydroperoxide) of cyclohexanol to cyclohexanone (almost quantitative yields after 1 h). Moreover, the catalysts are easily recovered and reused for five consecutive cycles, maintaining a high activity and selectivity.

А New Series of Schiff Base Ni(II)4 Cubanes: Evaluation of Magnetic Coupling Via Carboxylate Bridges

The Schiff base ligand H 2 L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction with Ni(OOCR 3 ) 2 , R = H in 1 , -CH 3 in 2 , Cl in 3 , to yield three new tetranuclear Ni(II) complexes The ligands and the complexes have been characterized by elemental analysis, IR- and NMR- spectroscopy. Their structures were determined by single-crystal X-ray diffraction. Compounds 1 - 3 possesses tetranuclear cubane-like structures containing [Ni 4 L 4 (R 3 COO) 2 ] 2- complex as anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time,. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1-3 , in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

Co-crystallization of Oxalate Salts of Monoprotonated Amines with a Double Sn-Ph Bond Cleavage

Two oxalate compounds [(C4H7N2)3][Sb(C2O4)3] (1) and [(Et3NH)][SnPhCl(C2O4)2] (2), have been isolated and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P21/c with a=13.3944 (6) A, b=11.3554 (5) A, c=16.3314 (7) A, β=107.206 (1), V=2372.82 (18) A3 and Z=4. Compound 2 crystallizes in the monoclinic system, space group P21/n with a=8.6903 (4) A, b=15.3844 (8) A, c=20.3144 (10) A, β=100.869 (2), V=2667.2 (2) A3 and Z=4. The complex-anion [Sb(O2CCO2)3]3- of the compound 1 adopts a distorted pentagonal pyramidal arrangement with monochelating oxalates. The asymmetric unit of 1 consists of three 2-methyl-1H-imidazolium cations, C4H7N2+, three oxalate anions, C2O42-, and one antimony (III) ion, Sb3+. From a supramolecular point of view, in 1 complex-anions are connected by cations through N-H•••(O,O) and N-H•••O hydrogen bonds involving the two oxalates of the basal plane into sheets which are then connected via the remaining oxalate and cations through N-H•••O hydrogen bonds to give rise to a three-dimensional structure. The complex-anion of 2 is comprised of a tin centre linked to a chlorine atom and a phenyl group, and cis-chelated by two oxalates in a distorted octahedral fashion. Each triethylammonium cation is connected to the complex-anion through bifurcated N-H•••(O,O) hydrogen bonds. These interactions lead to a discrete structure. A double Sn-C bond cleavage has occurred during the process of the formation of the compound 2. In both complounds 1 and 2, one cation exhibits some positional disorder.

A Novel Chromium(III) Hybrid Salt, Triethylammonium <i>Trans</i>-Diaquabis(Oxalato-<i>κ</i><sup>2</sup>O<sup>1</sup>,O<sup>2</sup>) Chromate(III), (C<SUB>6</SUB>H<SUB>16</SUB>N)[Cr(C<SUB>2</SUB>O<SUB>4</SUB>)<SUB>2</SUB>(H<SUB>2</SUB>O) <SUB>2</SUB>]: Synthesis, Spectroscopic Studies, Thermal Behavior and Crystal Structure

A novel organic-inorganic chromium(III) hybrid salt, triethylammonium trans-diaquabis(oxalato-κ2O1,O2)chromate(III), (C6H16N)[Cr(C2O4)2(H2O)2] (1), has been synthesized in aqueous solution and characterized by elemental and thermal analyses, FTIR and UV-Vis spectroscopies, and by single crystal X-ray structure determination. Compound 1 crystallizes in the orthorhombic system, Pbcn space group with the unit cell parameters a = 11.1776(10), b = 7.6105(10), c = 17.5654(2) Å, α = β = γ = 90°, V = 1494.24(3) Å3, Z = 4 and Z’ = 1/2. The structure of 1 consists of [Cr(C2O4)2(H2O)2]− mononuclear anions and triethylammonium [(C2H5)3NH]+ cations. In the anionic unit, the CrIII ion is six coordinated, in a distorted octahedral geometry, by four equatorial O atoms of two oxalate anions acting as chelating ligands and two O atoms from trans-coordinated water molecules occupying the apical positions with longer metal-oxygen distances. In the solid, O-H … O and N-H … O intra and inter molecular hydrogen bonding interactions connect the components into a 3D network. The triethylammonium cations are disordered among two possible orientations with occupancies rates around 50% for C4, N1, C1a, C1b, C4ii, N1ii, C1aii, C1bii (ii = −x + 1, y, − z + 1/2). The IR spectrum of 1 is consistent with the presence of the various molecular building constituents. The UV-Vis spectrum shows two absorption bands around 564 and 416 nm which are compatible with an anionic chromium (III) complex in an octahedral environment. Thermal studies carried out in air between 25°C and 700°C confirm the anhydrous character of 1 and show that it is stable up to 210°C.

PH-induced phase transition and crystallization of soft-oxometalates (SOMs) into polyoxometalates (POMs): a study on crystallization from colloids.

In this work, we demonstrate a simple approach for growing 1D (one-dimensional) inorganic chains of K(C6H16N)3Mo8O26·H2O polyoxometalates (POMs) from its colloidal soft-oxometalate (SOM) phase through the variation of pH. The structure is composed mainly of a 1D inorganic chain with a β-Mo8O264- binding node linked using K+ via Mo-O-K linkages, which results in a cuboctahedral geometry for the K+ ions. Crystal structure and Hirshfeld surface studies reveal the role of triethylammonium cations in restricting the growth of the 1D chain into 2D/3D (two-/three-dimensional) structures. During the nucleation process from the heterogeneous SOM phase, some of the intermolecular interactions in the dispersion phase are retained in the crystal structure, which was evidenced from residual O...O interactions. The crystallization of the species from its colloidal form as a function of pH was studied by the use of Raman spectroscopy and it was found that the increase in volume fraction of the β-Mo8O264- species in the crystallizing colloidal mixture with the decrease in pH is responsible for the nucleation. This was monitored by time-dependent DLS (dynamic light scattering) measurement and zeta-potential studies, revealing the co-existence of both the crystal and the colloidal forms at pH 3-2. This brings us to the conclusion that in the crystallization of POMs, the colloidal SOM phase precedes the crystalline POM phase which occurs via a phase transition. This work could open up avenues for the study of POM formation from the stand-point of colloidal chemistry and SOMs.

Triethylammonium picrate: An above-room-temperature phase transition material to switch quadratic nonlinear optical properties

To switch quadratic nonlinear optical (NLO) effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here, we report an organic picrate-based binary molecular crystal, triethylammonium picrate (TEAP), which undergoes an above-room-temperature phase transition at Tc=319K, being solidly confirmed by the thermal and dielectric measurements. A large thermal hysteresis of ∼7K discloses the first-order feature for its phase transition. More strikingly, the quadratic NLO effects of TEAP can be switched in the vicinity of Tc. That is, TEAP exhibits NLO-active response of ∼1.5 times as large as that of KDP below Tc (i.e., NLO-on state), while its NLO effects totally disappear above Tc (NLO-off state). Structure analyses disclose that the order-disorder transformations of triethylammonium cations and picrate anions collectively contribute to its phase transition, as well as switchable NLO behaviors. This work opens up a new pathway to the designing and assembling of stimuli-responsive materials.

Characterization of Doubly Ionic Hydrogen Bonds in Protic Ionic Liquids by NMR Deuteron Quadrupole Coupling Constants: Differences to H-bonds in Amides, Peptides, and Proteins.

We present the first deuteron quadrupole coupling constants (DQCCs) for selected protic ionic liquids (PILs) measured by solid-state NMR spectroscopy. The experimental data are supported by dispersion-corrected density functional theory (DFT-D3) calculations and molecular dynamics (MD) simulations. The DQCCs of the N-D bond in the triethylammonium cations are the lowest reported for deuterons in PILs, indicating strong hydrogen bonds between ions. The NMR coupling parameters are compared to those in amides, peptides, and proteins. The DQCCs show characteristic behavior with increasing interaction strength of the counterion and variation of the H-bond motifs. We report the similar presence of the quadrupolar splitting pattern and the narrow liquid line in the NMR spectra over large temperature ranges, indicating the heterogeneous nature of PILs.

Ab Initio Study of Structural Features and H-Bonding in Alkylammonium-Based Protic Ionic Liquids

The structural and energetic characteristics of protic ionic liquids (PILs) based on ethyl-, diethyl-, or triethylammonium cations with anions of phosphorus, trifluoroacetic, or p-toluenesulfonic acids have been investigated by density functional theory calculations at the B3LYP/6-31++G(d,p) level of theory. As a result of the interaction between acid and alkylamine, the H-bonded molecular complexes or H-bonded ion pairs have been obtained. The increasing number of ethyl groups attached to the nitrogen atom of amine and H-bond donor ability of acid causes a stronger H-bonding interaction leading to the formation of ion pairs. For all systems, the proton transfer between ion pairs and molecular complexes has been examined. Solvation effects have been also investigated using the solvent polarizable continuum model (CPCM).