Organic Molecular Salt Research Articles

Crystal Structure, Quantum Chemical, Hirshfeld Surface and Molecular Docking of Organic Molecular Salt: 2‐Amino‐5‐Chloropyridinium‐2,4‐Dihydroxybenzoate

AbstractAn organic molecular salt, 2‐amino‐5‐chloropyridinium‐2,4‐dihydroxybenzoate (ACP‐DHB) is synthesized by the slurry method followed by crystallization from methanol. The formation of molecular salt is initially confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectral data. Single crystal X‐ray diffraction (XRD) analysis shows that the crystal belongs to the monoclinic crystal system with space group, P21/n. Further, the supramolecular assembly involved the extensive network of N+−H···O− and N−H···O hydrogen bonds as well as C‐Cl···O halogen bond. Using UV‐Visible spectral data, the optical band gap is calculated and found to be 4.21 eV. Photoluminescence studies indicate the crystal has blue light emission properties. TG/DTA analysis shows that ACP‐DHB is thermally stable up to 162 °C. The quantum chemical calculations and natural bond analysis (NBO) are performed at B3LYP/6‐311G++ (d,p) basis set using Gaussian 09 software. The relative contributions of various intermolecular connections are discussed using Hirshfeld surface analysis and fingerprint plot illustration. The antibacterial and antifungal activity exhibits better inhibitory capacity against pathogens. Molecular docking revealed that ACP‐DHB efficiently binds with the 1UAG and 5KEE targets and has strong binding ability to the proteins. ADMET factors and Lipinski's rule of five are used to predict drug likeness property.

Unusual Nonlinear Conductivity in Charge-Ordered α-(BEDT-TTF)2I3

Unusual nonlinear conduction is detected in organic molecular salt α-(BEDT-TTF)2I3. The observed third-order nonlinear conductivity implies a quadrupole instability hidden in this charge-ordered organic salt.

Supramolecular synthons in 4-chloroanilinium-5-sulfosalicylate monohydrate: In vitro antioxidant and antimicrobial studies

An organic molecular salt hydrate crystal, 4-chloroanilinium-5-sulfosalicylate monohydrate (4CA5SSA) was obtained in 2:2:1 ratio. A proton of SO3H group in 5-sulfosalicylic acid was transferred to nitrogen atom of 4-chloroaniline leading to form primary NH…O hydrogen bonding in its crystal structure. R22(8) motif is also observed due to homo dimmer synthon of carboxylic acid. Further, the strong NH…O and OH…O hydrogen bonding interactions construct the supramolecular architecture whereas weak CH…O hydrogen bonds play the dominant role in controlling the interactions between layers in 4CA5SSA salt hydrate. The thermal stability of title crystal was determined by TG/DTA thermogravimetric analysis. The in vitro antimicrobial activity of 4CA5SSA crystal was investigated against bacterial and fungal pathogens. The title compound was also evaluated for its in vitro antioxidant susceptibilities through DPPH radical scavenging methods.

Synthesis, growth, structural characterization and biological investigation of hydrogen bonded organic molecular salt: N, N-diethylanilinium-5-sulphosalicylate

N, N-diethylanilinium-5-sulphosalicylate was successfully synthesized and good optical quality single crystals were grown employing slow solvent evaporation solution growth technique at ambient temperature. The CHN analysis indicates that the titled crystal is composed of stoichiometric proportion of the constituent ions, free from impurities and devoid of water molecules. The UV–Visible absorption spectrum exhibits the bands due to π-π* and n- π* transitions occurring in the salt. FT-IR spectral studies were performed to identify the different vibrational modes present in the titled crystal. The formation of salt and the molecular structure were initially confirmed by 1H and 13C NMR spectroscopic Studies. Single crystal XRD analysis indicates that the titled crystal belongs to monoclinic crystal system with centrosymmetric space group, P21/c. The hydrogen bonding parameter reveals that the salt crystal possesses N–H⋯O, O–H⋯O and C–H⋯O types of hydrogen bonding which are responsible for the stabilization of the crystal structure. TG/DTA Analyses reveal that the crystal is thermally stable up to 270 °C. The Vickers microhardness study reveals the soft nature of the titled crystal. Further, the titled salt was screened for its antimicrobial and antioxidant activities. The antimicrobial studies reveal that the synthesized salt has significant antibacterial and antifungal activities comparable to the standard compounds. The antioxidant activities of the titled salt show that the synthesized salt exhibits moderate activity against DPPH radical.

Redox-active organic molecular salt of 1,2,4-benzenetricarboxylic acid as lithium-ion battery anode

Hybrid organic–inorganic materials, particularly with a framework structure, have recently attracted much attention as redox electrode. In this work, we report for the first time, the electrochemical properties of redox-active organic molecular Li-salt derived from 1,2,4-benzenetricarboxylic acid (1,2,4-H3BTC) as lithium-ion battery (LIB) anode. The organic molecular salt (1,2,4-Li-BTC), prepared by a simple low temperature (80°C) solvothermal process, delivers a first cycle charge capacity of 162mAhg−1. Further, it is shown that preparing a composite electrode with 8wt% MWCNT improves charge transport and alleviates the dissolution problem, resulting in steady cycling behaviour and good rate performance. The results show promise for this new class of anode with flat charge discharge profiles and a convenient working potential of ∼1.2Vvs. Li+/Li.

Thermopower and specific heat of the organic molecular salt(TMTSF)2ClO4: observation of the narrow band response

Measurements of thermopowerSa(T) along the highlyconducting a axis and specific heat of the Bechgaard salts(TMTSF)2ClO4 for various cooling rates through the anion ordering temperatureTa = 24 K were carried out.Sign reversal in Sa(T) is found below Ta and it decreases with increasing cooling rate, which is attributed to the change of a narrow bandfilling level as the temperature and the cooling rates change. The crossover from 2D to 3D inSa(T) is observed around 15 K. The onset temperature of anion ordering inSa(T) decreases from 29.8 to 24.2 K as the cooling rate increases. Meanwhile, the electronic specific heatcoefficient γ has a pronounced change within this temperature region, giving strong evidence for a narrow bandcontribution. The difference in the specific heat between the quenched and relaxed states follows aT-cubic law from 5 to 24 K, implying a lattice distortion by the ordered anion only.The entropy estimated from the specific heat peak between 28 and 15 K isRln (4/3) lower thanthe value Rln2, consistent with the thermopower result that some anions have been ordered far aboveTa for the relaxed state.

Electro-optic modulation using single-crystal film of an organic molecular salt in a Fabry-Perot cavity

Electro-optic modulation using single-crystal film of an organic molecular salt placed in a Fabry-Perot cavity has been measured at 633 and 750nm. Large modulation depth (80%) at a low applied field (0.5V∕μm) has been observed in the field-induced birefringence geometry (mirror reflectivity ∼70%) for a bias point which was controlled by moving one of the mirrors. A modulation of about 60% with a higher throughput was obtained when no analyzer was used and the incident polarization was parallel to the dipole-axis.

On the electro-optic measurements in organic single-crystal films

We present a detailed study of the electro-optic modulation in single-crystal thin films of organic materials, taking into account the effects due to multiple internal reflections and absorption of optical radiation in the crystal film and the substrate. Optical transmission expressions are derived for the widely employed field-induced birefringence measurement configuration by developing a coupled optical cavity formalism and incorporating complex electro-optic coefficient tensor elements and refractive indices in Maxwell's wave equation. This treatment is applied to the electro-optic measurements in the single-crystal films of an important and popular organic molecular salt, 4′-dimethylamino-N-methyl-4-stilbazolium tosylate. The results show that the conventional interpretation of the measured responses, where the aforesaid effects are neglected for simplicity, would lead to substantial errors in the determination of the electro-optic coefficients, which is validated by the wide variation of reported experimental results in the literature.

Measurement of two-photon absorption cross-section in organic molecular salt with linear and circular polarized radiation

We report on the investigation of two-photon absorption (TPA) in 4′-Diethylamino-N-Methyl-4-Stilbazolium Tosylate (DEST) with 40 picosecond, 1064 nm linear and circular polarization laser radiation. The TPA cross-section σ2 measured is larger for linear polarized radiation (948 GM) than that for the circular polarized radiation (840 GM). The large TPA cross-section of DEST facilitates highly directional and efficient TPA induced upconverted emission in the range of 590–640 nm even though the fluorescence efficiency of DEST is very low (∼0.5%). The net single pass efficiency of upconversion is ∼7%.

Higher-order optical nonlinearities in 4 ′-dimethylamino- N-methyl-4-stilbazolium tosylate

Higher-order optical nonlinearities in an organic molecular salt, 4 ′-dimethylamino- N-methyl-4-stilbazolium tosylate (DAST), are investigated by a two-beam self-diffraction technique using a picosecond laser under single photon as well as two-photon absorption. The intensity dependence of the diffracted signals is measured. At a low concentration (1.0 × 10 −4mol/l) the ratio of χ eff (5)/ χ eff (3) is found to be 0.24 × 10 −6 cm 3/erg. A diffraction efficiencies of 1.2% and 0.02% are observed in the first and sixth-order signals, respectively.

Single-crystal thin films of organic molecular salt may lead to a new generation of electro-optic devices

Single-crystal films of an organic molecular salt, 4-dimethylamino- N -methyl-4-stilbazolium tosylate (DAST) with exceptional optical quality are prepared by a modification of the shear method. Electro-optic modulation for light propagating perpendicular to the film is measured at 720 and 750 nm wavelengths with electric fields over the frequency range of 2 kHz to 100 MHz. A modulation depth of 80% was measured at 750 nm for a field of 4 V/μm in a 4-μm-thick film. The measured electro-optic response is flat over the frequency range used (2 kHz to 100 MHz), indicating electronic origin of the electro-optic effect. The results show that these films may lead to a new generation of electro-optic devices.

Electro-optic modulation at 1.5 GHz using single-crystal film of an organic molecular salt

Electro-optic modulation using single-crystal film of an organic molecular salt with light propagating perpendicular to the film (transverse configuration) has been recently reported. In this letter, we report results of measurements at high speed (up to 1.5 GHz) using such films in the same configuration. Excellent signal-to-noise ratio has been observed even at a low applied voltage (1 V across 15 μm gap) for a 3 μm thick film. The magnitudes of the electro-optic coefficients are: r11=445 pm/V and r21=148 pm/V at 750 nm. A wide range of applications of these films are predicted.

Highly efficient mirrorless laser-like emission in an organic molecular salt

Unusually high conversion efficiency in laser-like emission has been observed in solutions of an organic molecular salt, styrylpyridinium cyanine dye, at a low threshold input pulse energy. Pumped with frequency-doubled 55 ps pulses from a Nd:YAG laser, a conversion efficiency as high as 40% was achieved without incorporating external mirrors. The spectrally narrowed output beam was observed to be polarized and having a low divergence. The exceptionally low threshold (<1 μJ with excitation area ∼5 mm2) and high conversion efficiency at a high molar concentration in spite of a very small photoluminescence quantum efficiency (<0.3%) can be attributed to the large dipole moments associated with the charge-transfer transitions of these molecules favoring strong cooperative emission.

Single-pass thin-film electro-optic modulator based on an organic molecular salt

Single crystal films of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) with excellent optical quality have been prepared by modified shear method. Electro-optic modulation for light propagating perpendicular to the film surface was measured at a wavelength (720 nm) where absorption is small. Very large electro-optic modulation (20%) was demonstrated in a 3 μm thick film at a low ac field (1 V/μm, at 4 kHz). Electro-optic modulation in such thin films is suitable for a wide range of applications in free-space interconnects and various modulator structures with light propagating perpendicular to the film. The magnitude of the electro-optic coefficient at 720 nm, r11∼530 pm/V, is significantly larger than that of bulk crystals.