Publication Date: 2008
Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry (09750975)47(7)pp. 979-985
Internal energy of liquid methane has been obtained based on the pair-wise additive approximation for the effective pair potential of dense fluids using (12,6) Lennard-Jones model for the intermolecular potential function. This internal energy has been compared with the internal pressure via the equation of state (EoS) expression. Thus, the effective pair potential parameters (EPPP) through some given EoSs for dense fluids have been calculated. A relation between the potential parameters with EoS parameters has been obtained. Using the obtained EPPPs and applying the pair-wise additive approximation, one could calculate accurately the thermodynamics functions such as total energy. The results of such calculations for the total energy of the liquid methane obtained via the EPPPs from different EoSs indicate a good agreement with the experimental data. Physical interpretation for the state dependencies of the obtained EPPPs from given EoSs is also presented.
Publication Date: 2019
Journal Of The Iranian Chemical Society (1735207X)16(12)pp. 2629-2637
In this work, four types of data mining methods, namely adaptive neuro-fuzzy inference system, artificial neural network—multilayer perceptron algorithm (ANN-MLP), artificial neural network—radial basis function algorithm (ANN-RBF), and group method of data handling (GMDH) have been used to predict the enhancement of the relative thermal conductivity of a wide range of nanofluids with different base fluids and nanoparticles. The total number of experimental data used in this work is 483 from 18 different nanofluids. The input parameters are thermal conductivity of base fluid and nanoparticles, volume fraction percent, the average size of nanoparticles, and temperature. Although the results showed that all four models are in relatively good agreement with experimental data, the ANFIS method is the best. The average absolute relative deviations (AARD%) between the experimental data and those of obtained using ANFIS, ANN-MLP, ANN-RBF, and GMDH methods were calculated as 2.7, 2.8, 4.2, and 4.3, respectively, for the test sets and as 1.1, 2.4, 3.9, and 4.5, respectively, for the training sets. Comparison between the predictions of the proposed ANN-MLP, ANN-RBF, ANFIS, and GMDH models and those predicted by traditional models, namely Maxwell and Bruggeman models showed that much better agreements can be obtained using the four models especially ANFIS model. Accordingly, the ANFIS method can able us to predict the relative thermal conductivity of new nanofluids in different conditions with good accuracy. © 2019, Iranian Chemical Society.
Sedighi, M.,
Talaie m.r., M.R.,
Sabzyan, H.,
Aghamiri, S. Publication Date: 2023
Sustainable Materials and Technologies (22149929)38
To develop an appropriate metal-organic framework to capture CO2 from dry flue gas, understanding the roles of structural modifications, location of primary adsorption sites and underlying adsorption mechanisms is crucial. Herein, effects of type, position and concentration of nitrogen-containing functional groups and C/N-substituted ligands are investigated on overall CO2/N2 adsorption process performance and mechanism of pristine and metal-substituted MIL-101 MOFs. In this investigation, density functional theory computations, grand-canonical Monte-Carlo, and molecular dynamics simulations are applied. Taguchi-based overall evaluation criteria objective function is also used to assess the overall adsorption performances of these MIL-101 MOFs in terms of CO2 uptake capacity, CO2/N2 selectivity, isosteric heat of adsorption and mass transfer resistance. The PBE/DZVP computations resulted in the CO2-framework binding energies ranging from −3.85 to −21.01 kJ/mol implying an acid-base type of physisorption. A correlation is introduced to estimate the CO2 uptake capacity from binding affinity and pore diameter of these MIL-101 MOFs. Mechanistic investigations show that to enhance CO2 uptake capacity and CO2/N2 selectivity, functionalization of the linker ligands is more successful than functionalization of the open metal sites having strong interactions with CO2 molecules. Results also showed that the best possible scenario to improve the overall adsorption process performance of MIL-101 is to substitute the C atom(s) of the BDC ligands with the N atom(s), regardless of the central metal atom type. The comprehensive molecular design approach introduced in this work can be used as a methodology by scientists for the development of new MOFs for practical CO2 capture applications. © 2023 Elsevier B.V.
Publication Date: 2020
Journal of Molecular Liquids (18733166)298
A molecular dynamics (MD) study on the behavior of some ion gels consists of two biodegradable aliphatic cholinium-based naphthenic acid ionic liquids (CBNAILs) confined in the BN nanostructures has been reported in this work. The structural and dynamical properties of these ILs between two h-BN nanosheets (h-BNNSs) as a function of intersheet separation were analyzed. Also, the confinement effects of these CBNAILs inside the BN nanotubes (BNNTs) as a function of nanotube diameter along with the solvation effects of these ILs outside the BNNTs were studied. The results of radial distribution functions (RDFs), number densities, charge densities, the number of hydrogen bonds, coordination numbers, mass density contours and also diffusion coefficients showed that how the structure and dynamics of these ILs changes under confinement conditions. Generally, the strength of ion−BN nanostructure interactions decreases with increasing nanopore size for both anions and cations and the dynamics of confined ions are slower than that of the bulk fluid, i.e. the ions move faster into the larger nanopores (h-BNNSs or BNNTs) than the smaller ones. The results have been compared with the recent studies of the adsorption of these ILs on one h-BN sheet and also with the behavior of confined aromatic CBNAILs. The results showed the ability of the biodegradable aliphatic CBNAILs to interact with BN nanosystems for developing specific applications such as super capacitors, lubricants, gas adsorption, dispersion of nanostructures, etc. © 2019 Elsevier B.V.
Publication Date: 2004
Journal of Physics B: Atomic, Molecular and Optical Physics (09534075)37(20)pp. 4143-4157
Ionization of the hydrogen molecular ion under linearly polarized intense laser fields is simulated by direct solution of the fixed-nuclei time-dependent Schrödinger equation for X = 790 nm and 1 = 1 × 1014 W cm-2. Different adaptive grids used in this study produced very similar results. The results are in agreement with, and thus support, the results of recent calculations carried out by other researchers. Detailed structure of the ionization rates is presented which has not been reported so far in the literature. The use of the virtual detector method resulted in more details of the ionization rates of the hydrogen ion molecule and hydrogen atom. This method especially allowed a simultaneous detection of the parallel and perpendicular components of the ionization rates.
Publication Date: 1997
International Journal of Thermophysics (15729567)18(5)pp. 1197-1216
A general equation of state, originally proposed for compressed solids by Parsafar and Mason, has been successfully applied to dense fluids. The equation was tested with experimental data for 13 fluids, including polar, nonpolar, saturated and unsaturated hydrocarbons, strongly hydrogen bonded, and quantum fluids. This equation works well for densities larger than the Boyle density ρB [1/ρB = TB dB2(TB)/dT, where B2(TB) is the second virial coefficient at the Boyle temperature, at which B2 = 0] and for a wide temperature range, specifically from the triple point to the highest temperature for which the experimental measurements have been reported. The equation is used to predict some important known regularities for dense fluids, like the common bulk modulus and the common compression points, and the Tait-Murnaghan equation. Regarding the common points, the equation of state predicts that such common points are only a low-temperature characteristic of dense fluids, as verified experimentally. It is also found that the temperature dependence of the parameters of the equation of state differs from those given for the compressed solids. Specifically they are given by Ai(T) = ai + biT + ciT2 - diT ln(T).
Publication Date: 2015
Physical Chemistry Research (23452625)3(4)pp. 347-360
The compressibility factor of nonassociated chain molecules composed of hard convex core Yukawa segments was derived with SAFT-VR and an extension of the Barker-Henderson perturbation theory for convex bodies. The temperature-dependent chain and dispersion compressibility factors were derived using the Yukawa potential. The effects of temperature, packing fraction, and segment number on the compressibility factor were investigated for chains of the prolate sphereocylinder segments. A comparison of hard core Yukawa chain compressibility factor values and hard chain compressibility factor values showed that the type of interaction potential has more effect on those chain molecules with higher segment numbers. The results demonstrated that in reduced temperatures 1.4 and 2.4, the Yukawa chain of the compressibility factor is insensitive to temperature, while the dispersion term of the compressibility factor changes remarkably with the temperature. The derived equation of state can fairly predict the SAFT-VR results of the hard sphere core chain molecules in the limit of α= 1.
Publication Date: 2014
Match (03406253)72(2)pp. 359-373
An asymmetry index (AI) is introduced to measure deviation of the electron density distribution in a molecule from any given symmetry. This AI is calculated by summing all point-wise differences between electron density distributions before and after symmetry operation. A minimum asymmetry index (MAI) rule is also introduced to evaluate uniquely the extent of asymmetry of a molecule with respect to any reference symmetry operation. This MAI rule prescribes where to locate the reference element of symmetry. The overall MAI for a given molecule with respect to a certain symmetry point group is calculated by averaging over AIs of all symmetry elements appearing in its character table. The proposed AI and the MAI rule are used to measure electron density asymmetry of the NX3, NX2Y/NXY2 and NXYZ (X, Y, Z = H, F, Cl, Br) series of molecules referenced to the C3V symmetry.
Publication Date: 2020
Physical Chemistry Chemical Physics (14639084)22(23)pp. 13070-13083
In this paper, we have reported a molecular dynamics (MD) study on the properties of three different magnetic imidazolium-based ionic liquids in the absence and presence of an external magnetic field. In this regard, the volumetric properties such as density and isobaric expansion coefficient, dynamical properties, namely, viscosity, mean square displacement of ions, diffusion coefficients, transport numbers of cations and anions, and electrical conductivity, and structural properties such as radial distribution function (RDF) and spatial distribution function (SDF) of [emim][FeCl4], [bmim][FeCl4] and [hmim][FeCl4] have been studied at different temperatures using molecular dynamics simulations. After studying the different volumetric, structural, and dynamical properties of the above-mentioned magnetic ILs in the absence of a magnetic field, we investigated the effect of an external magnetic field on the structural properties of one of these systems, i.e., [bmim][FeCl4]. In this regard, we established different contributions in the interactions between the external magnetic field and the studied magnetic ionic liquid (MIL). The number density profiles of the studied MIL before and after imposing an external magnetic field of 1.5 T showed a significant variation in the molecular distribution. The results indicated that the external magnetic field reduced the intensity of RDFs due to the reduction in the interactions between different ion sites as a result of changes in their orientations. After applying the external magnetic field, it was observed that due to the oppositely directed forces on the cations and anions, they moved in opposite directions. The snapshots showed that the static motion of the anion was smaller because of its small size. In the presence of an external magnetic field, the ions distributed more homogeneously compared to that observed in the absence of this field. The results of this study can be used in the rational and accurate design of viscomagnetic fluids and reaction systems in the presence and absence of magnetic fields. © the Owner Societies.
Nickmand, Z.,
Aghamiri, S.,
Reza talaie khozanie, M.,
Sabzyan, H. Publication Date: 2014
Separation Science and Technology (15205754)49(4)pp. 499-505
Grand canonical Monte Carlo (GCMC) simulation is used to model adsorption of CO 2 and SO 2 molecules by the pure and functionalized single walled carbon nanotubes (SWCNT and FSWCNT). Simulations are conducted for two cases: i) without and ii) with a 5.75 Å clearance between the CNT wall and the walls of the simulation box. Results show that the adsorption capacity for the SO 2 molecules is generally higher than that of the CO 2 molecules, especially at low pressures. Although for both molecules, the inside adsorption is higher at low pressures, the outside adsorption becomes larger above 10 and 2 bar for CO 2 and SO 2, respectively. At 5 bar, the total amounts of adsorption for case (ii) is higher by ∼ 42% and ∼ 271% for CO 2 and SO 2, respectively, compared with those for case (i). Functionalization does not show significant effect on the adsorption of the CO 2 and SO 2 gases. Adsorption of CO 2 and SO 2 gases in the FSWCNT are rather more sensitive to the parameters of the force field, especially those used for the functionalized carbon atoms, than the number of carbon atoms affected by functional groups. The effects of non-spherical interactions on the adsorption isotherms have also been examined. © 2014 Copyright Taylor and Francis Group, LLC.
Khosravi-darani, K.,
Sabzyan, H.,
Zeini-isfahani, A.,
Parsafar, G. Publication Date: 2004
Iranian Journal Of Chemistry And Chemical Engineering (10219986)23(2)pp. 45-53
In this work, a more accurate prediction of liquid evaporation flux has been achieved. The statistical rate theory approach, which is recently introduced by Ward and Fang and exact estimation of vapor pressure in the layer adjacent to the liquid-vapor interface have been used for prediction of this flux. Firstly, the existence of an equilibrium layer adjacent to the liquid-vapor interface is considered and the vapor pressure in this layer and its thickness calculated. Subsequently, by using the Fick's second law, an appropriate vapor pressure expression for the pressure of equilibrium layer is derived and by this expression and the statistical rate theory approach, evaporation flux is predicted more accurately than the previous work. Finally, some novel steady state evaporations are simulated and the effects of both liquid and vapor temperature and the effect of the length of the evaporation chamber on the evaporation flux are investigated.
Publication Date: 2004
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM (01661280)678(1-3)pp. 67-76
Intermolecular potential energy surface for the F2-F2 system has been obtained using MP2/6-31G* computations for 20,724 different geometries with F-F bond length left relaxed to be optimized. Counterpoise correction has been used to eliminate the basis set superposition error. Characteristics of the potential energy curves such as well-depth, position of the potential minimum, well-width and hard-sphere collision diameter have been studied in detail. Molecular volume, vibrational harmonic frequencies and thermochemical stabilities (compared to the two isolated F2 monomers) corresponding to the optimized structures of the F2-F 2 complex have also been calculated and studied. © 2004 Elsevier B.V. All rights reserved.
Hymas, M.,
Wongwas, S.,
Roshan, S.,
Whittock, A.L.,
Corre, C.,
Omidyan, R.,
Stavros, V.G. Publication Date: 2024
The Journal Of Physical Chemistry Letters (19487185)15(29)pp. 7424-7429
Mycosporine glycine (MyG) was produced by the fermentation of a purposely engineered bacterial strain and isolated from this sustainable source. The ultrafast spectroscopy of MyG was then investigated in its native, zwitterionic form (MyGzwitter), via femtosecond transient electronic absorption spectroscopy. Complementary nonadiabatic (NAD) simulations suggest that, upon photoexcitation to the lowest excited singlet state (S1), MyGzwitter undergoes efficient nonradiative decay to repopulate the electronic ground state (S0). We propose an initial ultrafast ring-twisting mechanism toward an S1/S0 conical intersection, followed by internal conversion to S0 and subsequent vibrational cooling. This study illuminates the workings of the archetype mycosporine, providing photoprotection, in the UV-B range, to organisms such as corals, macroalgae, and cyanobacteria. This study also contributes to our growing understanding of the photoprotection mechanisms of life. © 2024 The Authors. Published by American Chemical Society.
Mandegani, Z.,
Asadi, M.,
Asadi, Z.,
Mohajeri, A.,
Iranpoor, N.,
Omidvar, A. Publication Date: 2015
Green Chemistry (1463-9262)17(6)pp. 3326-3337
A new nano tetraimine Pd(0) complex was successfully prepared by the complexation of palladium acetate with an N,N-bisimine ligand. The structural features of the catalyst and the ligand were characterized using different microscopic and spectroscopic techniques such as FT-IR, XRD, XPS, UV-Vis, NMR, and elemental analysis. The morphology of the catalyst was determined using FE-SEM and TEM. The catalyst was effectively employed in the palladium-catalyzed Heck-Mizoroki reaction in water as a green solvent. The catalyst was reusable and recycled six times without any decrease in its catalytic activity. The ICP analysis showed that the catalyst has very little Pd leaching (0.2%) during the reaction process, demonstrating that our catalyst is stable and heterogeneous in practice. Furthermore, we have theoretically explored the feasibility of two neutral and cationic pathways in the density functional theory framework. The geometries and energies of all species involved in the reaction mechanism are analyzed. © The Royal Society of Chemistry 2015.
Publication Date: 2016
Fluid Phase Equilibria (03783812)409pp. 59-71
In the present study, a new equation of state (EOS) was derived by using the thermodynamic equation of state and the intermolecular potential (3, 9, 12). It was shown that the EOS is applicable in low and high ranges of temperature, pressure and density for gaseous, liquid and supercritical fluids and even in liquid-gas phase transition region. The new EOS is applicable for a variety of fluids such as polar, nonpolar, rare gases, short-chain and long-chain hydrocarbon fluids. The absolute percent deviation of the calculated density for gaseous, liquid and supercritical fluids is very low. The common bulk modulus point and the common compression point regularities were predicted by the new EOS. The new EOS was compared with some equations of state which had been derived similarly. It is shown that the repulsive potential used in the EOS derivation is effective in predicting correct fluid properties. © 2015 Elsevier B.V..
Publication Date: 2012
Journal of Molecular Liquids (18733166)174pp. 117-123
A new proposed equation of state (EoS) for pure liquid alkali metals has been extended to predict the volumetric and thermodynamic properties of alkali metal alloys at different temperatures, pressures, and compositions. The new equation which is valid over the whole liquid range is based on a suggested potential function and the interactions of nearest neighbors are according to the characteristics of the soft repulsive interaction in dense and large attractive interaction in expanded liquid alkali metals. The composition dependencies of the parameters of the equation of state are assumed as quadratic functions of mole fraction considering the mean geometry approximation MGA. In this paper, the calculated results of liquid density and other thermodynamic properties such as isobaric expansion coefficient, α P, isothermal compressibility, κ T, and internal pressure, P i, of binary molten alloys of Na-K and Cs-K from the freezing point up to several hundred degrees above the boiling point are presented. The results show good agreement between the density values obtained from this equation and the experimental and literature data. To show the ability of this EoS in prediction of density of alkali metal alloys, the results have been compared with some other equations. Although there is no corresponding literature data to compare the results obtained for derived thermodynamic properties, the variations of these properties with temperature and composition show proper trends for these alloys. © 2012 Elsevier B.V.
Publication Date: 2012
Fluid Phase Equilibria (03783812)329pp. 63-70
In this paper, we have derived an equation of state (EoS) for liquid alkali metals based on a suggested potential function over the whole liquid range including metal-nonmetal transition. This EoS is based on the interaction of nearest neighbors according to the characteristics of the soft repulsive interaction in dense and large attractive interaction in expanded liquid alkali metals. PVT data of dense liquid alkali metals obey the equation (2Z-1)V m=A+Bρ over the whole range of liquid densities, where Z, V m, and ρ are compression factor, molar volume, and molar density, respectively. The intercept A and slope B of this equation are related to the attractive and repulsive parts of suggested potential function, respectively, and both depend on temperature. The new EoS has been used to calculate the molar density and other thermodynamic properties such as isobaric expansion coefficient, α P; isothermal compressibility, κ T; and internal pressure, P i; of liquid alkali metals at any temperature and pressure over the whole liquid range. The results show good agreement between the values obtained using this equation and the experimental and literature data. To show the ability of this EoS in prediction of thermodynamic properties of liquid alkali metals over the whole liquid range, the results have been compared with some other equations. © 2012 Elsevier B.V.
Publication Date: 2019
Materials Science and Engineering C (09284931)94pp. 410-416
Accurate and fast measurement of the iron ion in biological, pharmaceutical and medical samples is of great applied importance. In this work, a novel optical sensor (optode) for the Fe(III) ion is fabricated based on the immobilization of morin (2′,3,4′,5,7-pentahydroxyflavone) on a triacetylcellulose membrane. Chemical binding of the Fe(III) ion with the immobilized morin is monitored spectrophotometrically at 334 nm. The prepared optode shows excellent response over a wide range of concentrations from 1.06 × 10−10 to 4.73 × 10−5 M with a detection limit of 4.23 × 10−11 M Fe(III). Effects of the factors determining sensitivity of the optode are studied and optimized. The prepared optical sensor shows good selectivity toward the Fe(III) ion in the presence of a number of other metal ions. The developed sensor is applied successfully and satisfactorily for the determination of iron in three pharmaceutical, one plasma and two serum samples. In addition, concentration of the Fe(III) ion in two tap water samples is measured using standard addition method. Density functional theory (TD) B3LYP/6-311++G** method is used to investigate structure and binding characteristics, and calculate the UV–Vis spectrum of the Fe(III)-morin complex. © 2018
Kargar, H.,
Fallah-mehrjardi, M.,
Moghadam, M.,
Omidvar, A.,
Zare-mehrjardi, H.R.,
Dege, N.,
Ashfaq, M.,
Munawar, K.S.,
Tahir, M.N. Publication Date: 2024
Polyhedron (02775387)249
In this study, a new 1D polymeric Cu(I) complex [Cu(L2Cl)I]n, where L = N,N′-bis(2-chlorobenzylidene)ethane-1,2-diamine, was synthesized and characterized using different analytical approaches, comprising 1H NMR, FT-IR, and CHN analysis. The geometrical features of the complex were determined through the single crystal X-ray diffraction (SC-XRD) method, which revealed that the copper atom is coordinated to the N atoms of the Schiff base. The bond angles surrounding Cu(I) ion indicated a somewhat distorted trigonal planar geometry of the complex. Hirshfeld surface analysis (HSA) was used to investigate the non-covalent intermolecular interactions, while theoretical studies were conducted utilizing DFT with B3P86/Def2-TZVP level of theory. The consistency between theoretical findings and experimental bond lengths of the [Cu(L2Cl)I]n confirmed the reliability of the theoretical conclusions. To better understand the intermolecular charge transfer features of the [Cu(L2Cl)I]n, the natural bond orbital as well as Atoms in Molecules analyses were also performed. The electrochemical behavior of the Cu(I) complex was explored at 25 °C using cyclic voltammetry in a pH 7.0 buffered solution. It is established that the quasi-reversible mechanism is consistent with the Cu(II)/Cu(I) redox system. Additionally, the catalytic action of this complex as a new catalyst was evaluated in the synthesis of derivatives of tetrahydropyrimidine by reacting 1,3-propylenediamine with various aryl nitriles under conventional thermal conditions. © 2023 Elsevier Ltd
Rastegari, F.,
Asghari, S.,
Mohammadpoor baltork, I.,
Sabzyan, H.,
Tangestaninejad, S.,
Moghadam, M.,
Mirkhani, V. Publication Date: 2024
Journal of Hazardous Materials (0304-3894)476
A novel imine-linked COF is synthesized by the condensation of 2,4,6-tris(4-aminophenyl)−1,3,5-triazine (TAPT) and 2-hydroxy-5-methoxyisophthalaldehyde (HMIPA) under solvothermal conditions. This COF adsorbs preferentially the neutral dye Neutral Red (NR) over the positively charged dye Methylene Blue (MB) at pH 7, and the negatively charged Methyl Orange (MO) over the positively charged Methylene Blue (MB) at pH 3. The maximum adsorption capacities (qe) obtained within very short times (11–60 min) under optimized conditions were 108, 185 and 429 mg.g−1 for the MB, MO, and NR dyes, respectively. These adsorptions obey the Langmuir isotherm and pseudo-second-order kinetics. The prepared TAPT-HMIPA-COF is used successfully for the removal of the dyes from real water and treated wastewater samples. The adsorption data, BET, FTIR, and zeta potential measurements show that the electrostatic, π-π stacking and hydrogen bond interactions are responsible for the adsorption of organic dyes on the surface of the prepared COF. Due to recyclability, high capacity and efficiency for the adsorption of positive, negative and neutral organic dyes, this COF can be considered promising for simultaneous removal of various dyes from aqueous solutions at adjusted pHs. © 2024 Elsevier B.V.
Publication Date: 2020
Physical Chemistry Research (23452625)8(4)pp. 629-644
Reactive molecular dynamics simulations (RMDS) with the ReaxFF force field are used to study nucleation and growth of silica nanoparticles during flame synthesis from tetramethoxysilane (TMOS). Two reactive systems (A and B) are considered and formation and/or consumption of various reactants, intermediates and products are followed. In the RMDSs of system A (TMOS, O2, SiO2 and Ar), the temperature-dependence of the formation of initial SimOn seeds show that formation of transient SiO3C3H9 intermediate is an important stage in the conversion of TMOS to the initial SimOn seeds, which then aggregate to produce silica nanoparticles. Increasing temperature speeds up this conversion. Results of the RMDSs on system B (TMOS, O2, Ar and (SimOn); the SimOn seeds play the role of the initial silica nanoparticles) show that at 2100 K, application of weak EFs (~1 V/A) narrows the size distribution of the silica nanoparticles compared to that in the absence of EF while by application of stronger EFs (4-8 V/A), the initial SimOn nanoparticles split into smaller species. In the absence of EF, increasing temperature from 1500 K to 3000 K increases sizes of the nanoparticles. The radial distribution functions, coordination numbers, and atomic compositions are used to characterize nanoparticles and evolution of the reaction. © 2020 Iranian Chemical Society.
Publication Date: 2016
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH (08885885)55(22)pp. 6517-6529
Proton nuclear magnetic resonance (H-1 NMR), diffusion-ordered NMR spectroscopy (DOSY-NMR), and ultraviolet-visible (UV-vis) spectroscopy techniques were used to study the specific intermolecular interactions within the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroburate, [bmim]BF4, and poly(ethylene glycol), PEG, with different average molecular weights (i.e., 200, 400, 600, and 1000) in the whole composition range. Also, the electrical conductivity and the viscosity of these four mixtures were measured at different compositions and temperatures. The results of 1H NMR spectra show that the change in proton chemical shifts of ionic liquid (IL) and PEG molecules in the mixtures is more than that of the pure ones. DOSY-NMR was used to measure the diffusion coefficients of the ionic species in the mixtures. Also, the other parameters such as hydrodynamic radii, transport numbers of anions and cations, and dissociation and association degrees of IL molecules were calculated from the diffusion coefficient and viscosity data. The overall results show that the behavior of the mixtures of [bmim]BF4 + PEG400, PEG600, and PEG1000 which show the synergistic effect on their viscosity is completely different from the IL + PEG200 mixture, and this difference can be interpreted well according to the special interactions occurring at the molecular level in these mixtures. Accordingly, in these mixtures, larger hydrodynamic radii and lower transport numbers of anions with respect to the cations may be attributed to the trapping of small anions in the polymeric clusters. Increasing the chain length and the concentration of PEG increases the association degree of the IL molecules due to increasing intermolecular interactions. The continuous decrement of electrical conductivity with increasing PEG concentration in these three mixtures confirms the cluster formation in the mixtures. The UV-vis spectra showed more hydrogen bonding interactions between unlike molecules in the mixtures containing higher molecular weight PEGs with respect to the lower ones.
Publication Date: 2015
RSC Advances (20462069)5(118)pp. 97619-97628
The second order approximate Moller-Plesset (MP2) and coupled cluster (CC2) methods have been employed to investigate the geometry, electronic transition energies and photophysics of the isoindole-pyridine and quinoline-pyrrole complexes. The most stable geometry of both isoindole-pyridine and quinoline-pyrrole complexes has been predicted to be a perpendicular structure. It has also been found that the first electronic transition in both complexes is responsible for UV absorption owing to its 1ππ∗ nature, while a charge transfer 1ππ∗ state governs the nonradiative relaxation processes of both complexes. In this regard, excited state intermolecular hydrogen/proton transfer (ESHT/PT) via the charge transfer electronic states plays the most prominent role in non-radiative deactivation. In the HT/PT reaction coordinate, the minimum potential energy profile of the lowest CT-1ππ∗ state predissociates the local 1ππ∗ state, connecting the latter to a curve crossing with the S0 state. At the region of this curve crossing, the S0 and CT state become degenerate, enabling the 1ππ∗ state to proceed as the predissociative state and finally direct the excited system to the ground state. © 2015 The Royal Society of Chemistry.
Publication Date: 2015
Photochemical and Photobiological Sciences (1474905X)14(12)pp. 2261-2269
The geometry, electronic structures and potential energy profiles of protonated furan and thiophene have been extensively investigated, using the RI-MP2 and RI-CC2 methods. According to RI-CC2 calculated results, the adiabatic S1(1ππ∗)-S0 transition energies of protonated furan and thiophene, have been predicted to be 4.41 eV and 3.70 eV respectively. Thus, protonation is accompanied by a large red shift effect on the first 1ππ∗ transition of the title systems (ΔE > 1.5 eV). The significant spectral-movements, predicted based on the calculated results of this work, indicate an essential effect of protonation on the geometry, electronic structures and optical characters of the five membered heterocyclic systems. In addition, it has been found that excitation of protonated furan and thiophene, with sufficient excess energy above the band origin of S1(1ππ∗)-S0 transition, is accompanied by the S-C or O-C bond breaking. This mechanism is mostly governed by a dissociative 1πσ∗ PE profile in both protonated systems. © The Royal Society of Chemistry and Owner Societies 2015.
Publication Date: 2025
RSC Advances (20462069)15(59)pp. 50766-50774
Polyoxometalates (POMs) are versatile inorganic compounds that can be integrated into hybrid materials due to their unique properties, which allow them to interact effectively with organic components. In this study, we designed a series of donor–acceptor (D–A) type hybrids in which dithieno[3,2-b:2′,3′-d] pyrrole (DTP)-derived building blocks served as donors and the Keggin-type POM acted as the acceptor moiety. The electronic structures, UV-visible absorption spectra, and photovoltaic properties of these hybrid compounds, along with their potential applications in n-type dye-sensitized solar cells, were investigated using density functional theory (DFT) and time-dependent DFT methods. Key parameters such as excitation energies (Ever), maximum absorption wavelengths (λmax), oscillator strengths (f), charge-transfer percentages, local excitation percentages, and Δr values for the principal molecular orbitals were systematically computed. To better understand intramolecular charge-transfer processes, natural transition orbitals and the charge density differences between the excited state and the ground state were analyzed. Research shows that among the 12 designed hybrid compounds, TD/POM, SN5/POM, DTP/POM, and DBTP/POM exhibited the highest Δr and CT charge values, making them the most effective sensitizers for dye-sensitized solar cells due to their superior LHE and high VOC. This journal is © The Royal Society of Chemistry, 2025
Publication Date: 2005
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM (01661280)731(1-3)pp. 239-239
