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The electrochemical sensing applications of a series of water-stable 2D metal–organic framework (MOF)-modified screen-printed carbon electrodes (SPCEs) are reported. The MOF materials in this study are [M(bipy)(C4O4)(H2O)2]·3H2O, in which bipy = 4,4′-bipyridine and M = Mn, Fe, Co and Zn. The MOF materials are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing that the MOFs have a layer-by-layer rod structure with a smooth surface. We use the nitrofurazone molecule as a probe to investigate the influence of the metal ions of MOFs on electrochemical sensing ability. Cyclic voltammetry demonstrated that the Mn-MOF electrode of interest delivered stronger signals than that of other electrodes. Through first-principles calculations, we also revealed that the change in the spin polarization of divalent metal ions passing from the free ion state to the MOF environment appeared to be significantly correlated with the enhancement in the peak response current. The theoretical and experimental results consistently indicate that Mn-MOF has the smallest bandgap and good sensitivity among these MOF materials. Accordingly, we proposed a simple model to illustrate this observation and disclosed the importance of the electron configuration of the transition metal constructing the MOF materials used in improving electrochemical sensing applications.

The electrochemical sensing applications of a series of water-stable 2D metal-organic framework (MOF)-modified screen-printed carbon electrodes (SPCEs) are reported. The MOF materials in this study are [M(bipy)(C

A two-dimensional (2D) coordination polymer, [Co(4-dpds)(bdc)(H2O)2]&middot, 4-dpds (1) (4-dpds = 4,4&prime, dipyridyldusulfide and bdc2&minus, = dianion of benzenedicarboxylic acid), has been synthesized and structurally determined by single-crystal X-ray diffractometer. In 1, the bdc2&minus, and 4-dpds both act as bridging ligands connecting the Co(II) ions to form a 2D wrinkled-like layered coordination polymer. Two wrinkled-like layered coordination polymers are mutually penetrated to generate a doubly interpenetrated framework, and then extended to its 3D architecture via the supramolecular forces between doubly interpenetrated 2D frameworks and free 4-dpds ligands by intermolecular O&ndash, H&sdot, &sdot, N hydrogen bonding interaction. Crystal packing arrangements were characterized by fingerprint plots, which were derived from the Hirshfeld Surfaces analysis, and showed that intermolecular hydrogen bonding interactions are the most important interactions on the construction of the crystal 1.

We use the discrete solvent reaction field model to evaluate the linear and second-order nonlinear optical susceptibilities of 3-methyl-4-nitropyridine-1-oxyde crystal. In this approach, crystal environment is created by supercell architecture. A self-consistent procedure is used to obtain charges and polarizabilities for environmental atoms. Impact of atomic polarizabilities on the properties of interest is highlighted. This approach is shown to give the second-order nonlinear optical susceptibilities within error bar of experiment as well as the linear optical susceptibilities in the same order as experiment. Similar quality of calculations are also applied to both 4-N,N-dimethylamino-3-acetamidonitrobenzene and 2-methyl-4-nitroaniline crystals.

We used force-field based grand-canonical Monte Carlo simulation method and density functional theory to study adsorption characteristics of carbon dioxide (CO2) molecules in a metal-organic framework (MOF) compound, [Zn(bdc)(dpds)]n. The studied MOF include a metal ion (Zn(II)), an anion organic linker (dianion of benzene dicarboxylicacid, bdc2−) and a neutral organic linker (4,4′-dipyridyldisulfide, dpds). Results from calculated adsorption isotherms and enthalpies of adsorption agree with the experimental data. The interactions between the adsorbed CO2 and the organic linkers were examined in simulations. Calculated results show available absorption sites are surrounded by two dpds ligands in which an S-S bond as an N-N′ spacer connect two pyridines. In contrast, the bdc2− ligand does not give a significant contribution to the substantial adsorption amount even though it contains the carboxylate group that provides available bonding site to CO2.

Based on the configurations generated by molecular dynamics (MD) simulations using the on-the-fly density-functional tight-bonding (DFTB) force field, we investigated performance of the discrete solvent reaction field (DRF) model coupled to time-dependent density functional theory (TD-DFT) for solvatochromic effect of one- and two-photon absorption phenomena. Dimethylaminonitrostilbene (DANS) molecule solvated in chloroform, dichloromethane, and dimethyl sulfoxide solvents was selected as a model system for our research purpose. For every selected MD/DFTB configuration, within the context of the DRF, solute molecule is represented by TD-DFT and solvent molecules are described by atomic charges and polarizabilities. The calculated one-photon absorption energies reproduce well the positive solvatochromic behavior of solvated DANS and are in good agreement with available experimental data. For the two-photon absorption cross section, even though our approach overshot the experimental data by about 20% in absolute magnitude, experimentally observed solvatochromic change was captured qualitatively in this work. At last, we examined the contributions of atomic charges and polarizabilities of solvent molecules to the solvatochromic shifts of properties of interest.

Density functional theory has been used to calculate the μ·β(−2ν;ν,ν,0) on a series of solution-phase hydrazones. Using the experimental and MP2(Full) calculated data as references, the qualitative trend of the Hartree–Fock, M06-HF and range-separated hybrids have been examined. Our results propose methods with long-range corrections, and without short-range exact exchange, are capable of qualitatively predicting the nonlinear optical responses of the hydrazones when reliable geometries have been provided. The same conclusion can also be applied to solution-phase push–pull phenylpolyenes.

This article presents an assessment of methods to study the second harmonic generation (SHG) response of organic molecular crystal. We incorporated the discrete solvent reaction field model, density functional theory, and the local field approximation (designated as the LF-DRF/DFT) to investigate the SHG susceptibilities of the chromophore of 2-carboxylic acid-4-nitropyridine-1-oxide (POA). In experiment, the POA appears in two different polymorphic crystal structures easily identified by noticeable differences in the melting points and SHG susceptibilities. In this work, we tried to utilize the LF-DRF/DFT in a supermolecular framework to differentiate the two crystals. While focusing on the ratio of the calculated SHG susceptibilities for the two crystals, at optical wavelength of 1064 nm, the S12 g and SSB-D exchange–correlation functionals within a 5 × 5 × 5 extended architecture produced 2.16 and 2.08, differing from the experimental estimate of 2.16 by 0 and 3.7 %, respectively.

This study explored the planar structure of ( E )-benzaldehyde phenylhydrazone in ethanol, using MP2(Full), B2PLYP-D and B3LYP. Explicit few solvent molecules incorporating in polarized continuum model were used to address solvent–solute interaction. The calculated maximum absorption from time-dependent density functional theory using PBE0 with 6-311+G(2d,p) and 6-311++G(3df,3pd) basis sets based on the calculated structures resulting from different levels of theory were gauged against experimental values. In addition, the effects of both basis set and explicit solvent molecules on the geometrical parameters of concern were examined. The results of this study suggested ( E )-benzaldehyde phenylhydrazone in ethanol adopted a non-planar structure with a pyramidal amino nitrogen atom and a significant distortion of the two phenyls.

We presented the time-dependent density functional theory calculated ultraviolet–visible (UV-vis) spectra for derivatives of phenylhydrazones, semicarbazones and pyrrole hydrazones in ethanol. We employed the B3LYP, PBE0, CAM-B3LYP, LC–ωPBE, LC–PBE and ωB97X-D functionals. We gauged the performance of the six hybrid functionals of choice in determination of the K-band λmax values of the UV-vis spectra. The PCM-TD-PBE0/6-311+G(2d,p)//PCM-PBE0/6-311G(d,p) approach provided the smallest error with an average absolute deviation limited to 14 nm. We also investigated the impacts of including explicit solvent molecules and considering vibrational envelope with the Franck–Condon Herzberg–Teller method.

The purpose of this study is to compare solvent effects of the polarizable continuum model (PCM) and ONIOM (our Own N-layered Integrated molecular Orbital molecular Mechanics) model. The test was performed by calculating Gibbs energies of reaction and activation for the Z / E thermal isomerization reaction of acetaldehyde N , N -dimethylhydrazone at 298.15 K in the solvent of cyclohexane. Four density functional theory typed methods, B3LYP, BB1K, MPW1B95 and MPWB1K with the 6-311++G(3df,2p)//6-31G(2df,p) basis sets were employed to give estimates of Gibbs energies. We compared the calculated results with the available experimental observation (established by Clarke et al. [Clarke et al., J. Chem. Soc. Perkin Trans II 11 (1991) 1649.]). As a result of the calculations, it is found that with the ONIOM model the four density functional theory typed computations gave estimates of Gibbs energy of activation in agreement with the experimental observation while the PCM calculated values overestimated the energy of activation by about 3 or 4 kcal/mol. For the calculated free energies of reaction, the four density functional theory typed computations with the PCM and the ONIOM models gave very close results with a range of about 1 kcal/mol.

The optimized structures at the equilibrium, cis and trans configurations and the barrier heights for the cis and trans saddle points for hydrogen peroxide, obtained using the diffusion quantum Monte Carlo simulations are reported. The Monte Carlo calculated torsional barriers, Δ E trans = 386(26) cm −1 and Δ E cis = 2526(41) cm −1 are in very good agreement with experimental values, Δ E trans = 385/387 cm −1 and Δ E cis = 2488/2563 cm −1 .

In this study, 18 synthetic naphthalene derivatives were tested for their inhibitory effects on the activation of neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristic acetate (PMA). Some of these compounds showed significant antiinflammatory activities. In general, esterification of 1-naphthalene to compound 14 (2-hydroxymethyl-1-naphthol diacetate; TAC) enhanced the antioxidant activity. Compound 15, N,N-bis(2-hydroxy-1-naphthylmethyl) amine, has moderate inhibitory activity on neutrophils stimulated with fMLP as compared to Mannich bases of naphthylene derivatives. Either substitution at 1 or 2 position, except TAC, disfavored the inhibitory effects evoked by PMA stimulation. The influence of these compounds on the release of granule enzyme lysozyme-induced by fMLP was measured. TAC had the highest potency on the inhibition of lysozyme release from rat neutrophil degranulation. The effects of TAC on ionic currents in a mouse neuroblastoma and rat glioma hybrid cell line, NG105-18, were also investigated with the aid of the whole-cell patch- clamp technique. TAC caused an inhibitory effect on voltage-dependent L-type Ca 2þ current (ICa,L) with an IC50 value of 0.8 mM. The inhibitory effect of TAC on ICa,L may not be caused by its inhibition of superoxide formation. Such an effect may, also in part, affect neuronal function. Drug. Dev. Res. 60: 261-269, 2003. � c 2003 Wiley-Liss, Inc.

The potential energy curve of hydrogen fluoride was calculated using the Ornstein-Uhlenbeck diffusion quantum Monte Carlo method. There are two choices in the determination of the trial wave function: a full optimization of all parameters of the trial wave functions and a partial optimization of the coefficients of different configuration wave functions. A full optimization gave an excellent result while comparing with results of other theoretical calculations as well as the experiment. A partial optimization described a wrong behavior in large separation but provided a good alternative in calculating the behavior near the equilibrium distance while considering the computational demandings.

The total atomization energies and equilibrium dipole moments of some small first-row polyatomic molecules are calculated at the Ornstein–Uhlenbeck diffusion quantum Monte Carlo with the floating spherical Gaussians. By using explicitly correlated wave functions built from the spherical Gaussian-type orbitals and geminals to be the trial wave function, this work gives accuracy that is comparable to or better than previously theoretical estimates. The accuracies are less than 0.6 kcal mol−1 and 0.007 D for total atomization energies and equilibrium dipole moments, respectively. We also compare the performance of three different approximations in estimating expectation values of equilibrium dipole moment.

Electronic energies have been calculated for the electronic ground states of BH and HF at their equilibrium bond lengths by using the Ornstein–Uhlenbeck diffusion quantum Monte Carlo method. The dissociation energy ( D e ) and electronic energies of some points along the potential energy curve of HF were also calculated. The trial wave function built from the floating spherical Gaussian orbitals and the spherical Gaussian geminals is used to guide the random walks without significant time-size step error. The calculations give 93% and 98.6% of correlation energy for BH and HF at their equilibrium bond lengths, respectively. The dissociation energy of HF is also in excellent agreement with experimental data.

We have assessed six range-separated hybrids (CAM-B3LYP, LC-PBE, ωB97, ωB97X, ωB97X-D and M11) in evaluating the dynamic quadratic polarizability along the direction of the molecular dipole moment, β μ (−2ν; ν; ν; 0), by comparing with MP2(Full)-calculated data. There are 104 solution-phase organic molecules included in the set. Both geometry optimizations and β μ (−2ν; ν; ν; 0) computations have been carried out by the same functional. Calculated results showed that simultaneous modeling geometrical and electronic effects improved significantly the nonlinear optical (NLO) property of interest. More generally, our numerical assessment revealed that the CAM-B3LYP functional could be the reasonable choice for NLO property computations.

A diffusion quantum Monte Carlo method, based on a trial wave function, built from floating spherical Gaussian orbitals and geminals, is reported. The ability to precisely sample the Gaussian function by using the Ornstein–Uhlenbeck random walks process, to treat electron correlation effect explicitly, and to apply the Hellmann–Feynman theorem are the important consequences of this approach. Floating functions, which remedy deficiency of electron density around nuclei, satisfy the Hellmann–Feynman theorem. Gaussian geminals, which correlate the electron pair directly, are used to treat correlation energy and to improve the quality of the trial wave function. Applying this type of trial wave function, within fixed-node approximation, in diffusion quantum Monte Carlo (QMC) calculation of ground state energies of lithium hydride molecule, provides very good estimates of the electronic energy and dipole moment. We also compare the results with several previous QMC results and experiments.

In this work, we examined the conformational population of a highly fluorinated hydrazone, 2H-perfluoro-2-methyl-3-pentanone, by density functional theory computations in four Lewis basic solvents: acetonitrile, diethyl ether, tetrahydrofuran and dimethyl sulfoxide. Various 1:1 hydrogen-bonded clusters of rotamer and solvent were embedded in the solvent employing the polarized continuum model in the computations. The calculated results showed the strength of the intermolecular interaction between the hydrogen bonding acceptor of solvent and the hydrogen atom of amino group in the fluorinated hydrazone played an important role in the experimental observation for the relative population. The combined approach that involves attaching a single explicit solvent molecule to the hydrazone, and then surrounding the resulting 1:1 cluster by a dielectric continuum, significantly improves the agreement between the calculated relative Gibbs energy and experiment, whereas, the implicit treatment of solvent gave an error in the prediction of relative stability for the fluorinated hydrazone in the four Lewis basic solvents.

The present study investigated the effects of 2-hydroxymethyl-1-naphthol diacetate (TAC) on cell proliferation and K + currents in RPMI-8226 human myeloma cells. In cells with intracellular Ca 2+ concentration ([Ca 2+ ] i ) = 10 nM, depolarizing square pulses from a holding potential of -80 mV elicited instantaneous outward current with slow inactivation, corresponding to voltage-activated K + current. TAC (1-100 μM) inhibited I K(V) in a concentration-dependent manner. A23187 (1 μM), a Ca 2+ ionophore, can potentiate Ca 2+ -activated K + current (I K(Ca) ). Tetraethylammonium chloride (10 mM) caused a small decrease in the amplitude of I K(Ca) elicited by A23187, whereas TAC (30 μM) and quinidine (10 μM) decreased I K(Ca) more effectively. The present results show that TAC directly blocks voltage- and Ca 2+ -activated K + currents in human myeloma cells. TAC inhibited both cell proliferation and voltage-activated K + current with an effective dose inducing half-maximum effects at 3.8 ± 0.8 μM and 10 ± 1.5 μM, respectively. The present study suggests that the cytotoxic effect of TAC in cancer cells may be partially explained by blockade of K + channels. The delocalization energy of TAC and other analogs was employed to compare their ability to block the voltage-activated K + channel in myeloma cells. It was found that naphthol derivatives-mediated blockade of voltage-activated K + channel might relate to the level of delocalization energy and molecular volume.

MP4/6-31+G* level calculations are performed to study the reductive bond-breaking reaction of the C-X bond in halomethanes, CH3X and CH2X2 where X is a fluorine atom or chlorine atom. This type of reaction involves a radical anion, after attaching an extra electron to the halomethane molecule, in which a C-X bond-breaking takes place. Products are a radical and a halogen anion. The equilibrium geometry and bond dissociation energy of the C-X bond thus found are in good agreement with previous theoretical and experimental results. The anomeric effect, electrostatic effect, and radical re-stabilization effect, are investigated to find their influences on bond length and bond dissociation energy in CH3X and CH2X2. Potential energy curves are calculated for the reductive bond-cleavage process, and trends in activation energy for various cases are discussed.

The dynamic second-order hyperpolarizability from the third-harmonic generation experiment, 〈γ〉(−3ω;ω;ω;ω), of 59 solution-phase organic molecules has been theoretically calculated and compared with available experimental data. The DFT/6-311+G(2d,p)//(CAM-)B3LYP/6-31G(2df,p) level of theory with the polarizable continuum model was employed to evaluate the static second-order hyperpolarizability. The theoretical static values were then corrected to dynamic estimates of 〈γ〉(−3ω;ω;ω;ω) by employing a two-level approximation (Chen et al. in J Chem Phys 101(7):5860–5864, 1994). Calculated results showed that for the property of interest, the range-separated hybrids provided more accurate and consistent estimate than the global hybrids and the CAM-B3LYP optimized geometry delivered more accurate estimate than the B3LYP optimized geometry.

To verify the performance of the fixed-node diffusion quantum Monte Carlo method in electron affinities calculations, the adiabatic electron affinities of C(2) and BO molecules calculated by the fixed-node Ornstein-Uhlenbeck diffusion quantum Monte Carlo simulations guiding by trial wave functions constructed from the floating spherical Gaussian orbitals and spherical Gaussian geminals are presented in this work. The random walk based results, 3.264(43) and 2.507(32) eV for C(2) and BO, respectively, are compared with the available best experimental determined values, 3.269(6) and 2.508(8) eV for C(2) and BO, respectively, and the results of other theoretical calculations.

Various hybrid functionals (B3LYP, B97-2, PBE0, BMK, BH&HLYP, CAM-B3LYP, and LC-ωPBE) implemented in density functional theory were applied to give estimate of static first hyperpolarizabilty (β0) of (E)-benzaldehyde phenylhydrazone designated as (E)-BPH. Against those of MP2 computations as a function of the underlying density functional, good agreement was obtained with the BH&HLYP and CAM-B3LYP functionals. The LC-ωPBE functional and the B3LYP, PBE0, B97-2, and BMK functionals underestimated and overestimated β0, respectively. The basis set effect on the calculated β0 was also investigated. It turned out that the 6-311+G(2d,p) basis set provided excellent converged value of β0. On the basis of the calculated results, we investigated the substituent effect on β0 of donor–acceptor (D-A) substituted (E)-BPH systematically by using the BH&HLYP and CAM-B3LYP computations with the 6-311+G(2d,p) basis set. We proposed a Zwitterion structure to explain the calculated trend in the substituent effect and the enhanced hyperpolarizability of type II compounds (A-(E)-BPH-D) than type I compounds (D-(E)-BPH-A). Natural bonding orbital analysis carried out at BH&HLYP/6-311+G(2d,p)//B3LYP/6-31G(2df,p) level of theory substantiated the claim. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011

In this article, we examined the Gibbs energy of activation for the Z/E thermal isomerization reaction of (1Z)-acetaldehyde hydrazone and (1Z)-acetaldehyde N,N-dimethylhydrazone, at 298.15 K in the solvent of cyclohexane. We carried out computations employing both the Gaussian-4 (G4) theory and the coupled cluster method using both single and double substitutions and triple excitations noniteratively, CCSD(T). The CCSD(T) energy is extrapolated to the complete basis set (CBS). We compared the calculated results to the available experimental observation. It appeared that both G4 and CCSD(T)/CBS computations overestimated the experimental value by as much as about 6 and 12 kcal/mol in the present two cases. We discussed possible sources of error and proposed the experimental kinetic data could be questionable.

For a test set of 17 first-row small molecules, the equilibrium structures are calculated with Ornstein-Uhlenbeck diffusion quantum Monte Carlo simulations guiding by trial wave functions constructed from floating spherical Gaussian orbitals and spherical Gaussian geminals. To measure performance of the Monte Carlo calculations, the mean deviation, the mean absolute deviation, the maximum absolute deviation, and the standard deviation of Monte Carlo calculated equilibrium structures with respect to empirical equilibrium structures are given. This approach is found to yield results having a uniformly high quality, being consistent with empirical equilibrium structures and surpassing calculated values from the coupled cluster model with single, double, and noniterative triple excitations [CCSD(T)] with the basis sets of cc-pCVQZ and cc-pVQZ. The nonrelativistic equilibrium atomization energies are also presented to assess performance of the calculated methods. The mean absolute deviations regarding experimental atomization energy are 0.16 and 0.21 kcal/mol for the Monte Carlo and CCSD(T)/cc-pCV(56)Z calculations, respectively.

We investigated thermal isomerization and absorption spectra of trimethylacetaldehyde N,N-dimethylhydrazone in vacuum and cyclohexane by density functional theory (DFT). Also G3B3 model chemistry has been used to check the accuracy of DFT computations.

Against experimental values obtained from solution-phase dc electric field induced second-harmonic generation measurements at a fundamental wavelength of 1910 nm, the performance of 20 exchange-correlation functionals in density functional theory in evaluation of solvent modulated dynamic first hyperpolarizabilities of 82 organic molecules in chloroform, 1,4-dioxane, and/or dichloromethane was evaluated. The used exchange-correlation functionals consisted of generalized gradient approximation (GGA), meta-GGA, global hybrids, and range-separated hybrids. The PCM-X/6-311+G(2d,p)//PCM-B3LYP/6-31G(2df,p) level of theory was employed. The calculated results showed functionals with the exact asymptote of the exchange potential gave satisfying linear correlation with R(2) of 0.95 between experimental data and theoretical values. With a linear correction, these functionals also provided a better accuracy with mean absolute error of 5 × 10(-30) esu than other functionals. The solvent effect and solvation scheme on the calculated property were also studied.

The accuracy of equilibrium bond lengths and harmonic frequencies for 12 doublet first-row diatomic radicals is presented as predicted by the fixed-node diffusion quantum Monte Carlo method based on the Ornstein-Uhlenbeck random walk guided by the floating spherical Gaussian orbital and spherical Gaussian geminal-type trial wave function. Compared to the experimental determined values, the random-walk-based approach gives the absolute mean deviations of 0.0019 A and 18 cm-1 for the equilibrium bond length and harmonic frequency, respectively. We also compare the random-walk-based results with some coupled-cluster-based values.

Ab initio calculations of transition state structure and reaction enthalpy of the F + H2--HF + H reaction has been carried out by the fixed-node diffusion quantum Monte Carlo method in this study. The Monte Carlo sampling is based on the Ornstein-Uhlenbeck random walks guided by a trial wave function constructed from the floating spherical Gaussian orbitals and spherical Gaussian geminals. The Monte Carlo calculated barrier height of 1.09(16) kcal/mol is consistent with the experimental values, 0.86(10)/1.18(10) kcal/mol, and the calculated value from the multireference-type coupled-cluster (MRCC) calculation with the aug-cc-pVQZ(F)/cc-pVQZ(H) basis set, 1.11 kcal/mol. The Monte Carlo-based calculation also gives a similar value of the reaction enthalpy, -32.00(4) kcal/mol, compared with the experimental value, -32.06(17) kcal/mol, and the calculated value from a MRCC/aug-cc-pVQZ(F)/cc-pVQZ(H) calculation, -31.94 kcal/mol. This study clearly indicates a further application of the random-walk-based approach in the field of quantum chemical calculation.

The conventional method for determining ergot alkaloids in fermentation media is laborious and time consuming, largely because of the chloroform extraction procedure employed. A new and simplified method, without chloroform extraction, for measuring alkaloid in culture liquid and in colonies has been developed. The details of the procedure and its application are described. Estimates of alkaloid by the new method were about 6% higher than by the conventional method. The advantages of the new method are that it is accurate, rapid, safe and versatile in use, especially in the large scale screening of strains of the ergot fungus.