The extended Hulburt–Hirschfelder‐long‐range oscillator model for direct‐potential‐fit analysis

In the present work, an extended Hulburt–Hirschfelder oscillator model is proposed as a means of simplifying potential energy functions for direct‐potential‐fit analyses. The new potential energy function is joined smoothly to the long‐range inverse‐power dispersion energy expression. The new model is employed in direct‐potential‐fits using spectroscopic line positions that involve the ground electronic states of the principal isotopologues of hydrogen iodide and carbon monoxide, and the ground and first singlet‐sigma excited states of hydrogen fluoride and hydrogen chloride. The present methodology is found to lead to compact, flexible, and robust representations for the potential energy that compare favorably with the results of past work where more complicated models were employed.     

Calculation of excited‐state ionization potential for boron‐like sequence

Excited‐state ionization potentials for boron‐like sequence with Z = 5–19 are studied systematically, using the weakest bound electron potential model theory (WBEPM theory) and iso‐spectrum‐level series conception. Nonrelativistic ionization energy is derived from the theory. Relativistic effects are included in the Breit–Pauli approximation. Comparison of the calculated excited‐state ionization potential with available experimental data is carried out for 1s²2s²2p ²P, 1s²2s²3s ²S_1/2, 1 s²2s²3p ²P, 1s²2s²3d ²D_5/2, 1s²2s²4d ²D_5/2, 1s²2s²5d ²D_5/2, and 1s²2s²6d ²D_5/2 series. The present results depart from experimental results by no more than 0.133 eV for all 81 results for which experimental data are available. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Reversible adsorption change of 2‐amino‐4,5‐imidazoledicarbonitrile on Ag electrode surfaces by potential‐dependent surface‐enhanced Raman scattering

The potential‐induced adsorption change of 2‐amino‐4,5‐imidazoledicarbonitrile (AIDCN) on Ag electrode surfaces has been examined by surface‐enhanced Raman scattering (SERS) in an applied potential range between ?1.0 and 0.2 V. Upon adsorption, AIDCN has a substantial interaction with the Ag metal surfaces via its two nitrile groups. The CN stretching peaks at ～2200 cm^?1 appeared to be more intensified and redshifted at a negative potential. The deconvolution peak analysis of the CN bands at various voltages suggests that there should be a change in binding modes of AIDCN on Ag surfaces. This potential‐dependent orientation change appeared to be reversible. The density functional theory (DFT) calculation of AIDCN on Ag cluster atoms is used to explain its potential‐dependent adsorption. Copyright © 2010 John Wiley & Sons, Ltd.     

Grid potential analysis,virtual screening studies and ADME/T profiling on N‐arylsulfonylindoles as anti‐HIV‐1 agents

A grid potential analysis employing a novel approach of 3D quantitative structure–activity relationships (QSAR) as AutoGPA module in MOE2009.10 was performed on a dataset of 42 compounds of N‐arylsulfonylindoles as anti‐HIV‐1 agents. The uniqueness of AutoGPA module is that it automatically builds the 3D‐QSAR model on the pharmacophore‐based molecular alignment. The AutoGPA‐based 3D‐QSAR model obtained in the present study gave the cross‐validated Q² value of 0.588, r²_pred value of 0.701, r²_m statistics of 0.732 and Fisher value of 94.264. The results of 3D‐QSAR analysis indicated that hydrophobic groups at R₁ and R₂ positions and electron releasing groups at R₃ position are favourable for good activity. To find similar analogues, virtual screening on ZINC database was carried out using generated AutoGPA‐based 3D‐QSAR model and showed good prediction. In addition to those mentioned earlier, in‐silico ADME absorption, distribution, metabolism and excretion profiling and toxicity risk assessment test was performed, and results showed that majority of compounds from current dataset and newly virtually screened hits generated were within their standard limit. Copyright © 2013 John Wiley & Sons, Ltd.     

Trans‐3,5‐dihydroperoxy‐3,5‐dimethyl‐1,2‐dioxalane/HBr System as New,Effective, Mild and Non‐toxic Reagent for Synthesis of 2‐Aryl‐1H‐benzothiazoles and 2‐Aryl‐1‐arylmethyl‐1H‐benzimidazoles

Ttrans‐3,5‐dihydroperoxy‐3,5‐dimethyl‐1,2‐dioxalane has been used as new, effective, solid, inexpensive and nontoxic oxidant for in situ generation of Br⁺ from HBr. This system has been applied as catalyst for synthesis of 2‐aryl‐1H‐benzothiazoles and 2‐aryl‐1‐arylmethyl‐1H‐benzimidazoles at room temperature in excellent yields and high purity.     

Combined experimental and computational modeling studies on 4‐[(2‐hydroxy‐3‐methylbenzylidene) amino]‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one

The Schiff base compound, 4‐[(2‐hydroxy‐3‐methylbenzylidene)amino]‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one, has been synthesized and characterized by IR, UV–vis, and X‐ray single‐crystal determination. Molecular geometry from X‐ray experiment of the title compound in the ground state have been compared using the density functional method (B3LYP) with 6‐31G(d,p) basis set. Calculated results show that density functional theory (DFT) can well reproduce the structure of the title compound. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6‐31G(d,p) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provided more stable structure than Onsager's method. By using TD‐DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD‐DFT method and the experimental one is determined. The predicted nonlinear optical properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential and NBO analysis were performed at B3LYP/6‐31G(d,p) level of theory. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A Novel Conversion of 2, 4‐Diaryl‐2, 3‐dihydro‐1 H‐1, 5‐benzodiazepines into 2, 4‐Diaryl‐3 H‐1, 5‐benzodiazepines

A novel conversion of 2, 4‐diaryl‐2, 3‐dihydro‐1 H‐1, 5‐benzodiazepins into 2, 4‐diaryl‐3 H‐1, 5‐benzodiazepines by the reaction with m‐chloroperbenzoic acid (MCPBA) was reported.     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

Cyclic Voltammetric Study of Some Anti‐Chagas‐Active 1,4‐Dioxidoquinoxalin‐2‐yl Ketone Derivatives

The electrochemical properties of 24 1,4‐dioxidoquinoxalin‐2‐yl ketone derivatives with varying degrees of anti‐Chagas activity were investigated in the aprotic solvent dimethylformamide (DMF) by cyclic voltammetry and first‐derivative cyclic voltammetry. For this group of compounds, the first reduction in DMF was either reversible or quasireversible and consistent with reduction of the N‐oxide functionality to form the radical anion. The second reduction process for these compounds was irreversible under the conditions used. The reduction potentials correlated well with molecular structure. Substitution in the 3‐, 6‐, and 7‐ positions of the quinoxaline ring by electron‐withdrawing substituents directly affected the ease of reduction and improved the biological activities of these compounds, whereas substitution by electron‐donating groups had the opposite effect. The electrochemical results, when combined with previous work on their mechanism of action against Chagas disease and their measured anti‐Chagas activities, indicated that the quinoxaline 1,4‐dioxide system serves as a promising starting point for chemical modifications aimed at improving the T. cruzi activity via a possible bioreduction mechanism.     

New Approach to N‐substituted‐1,2,3,6‐tetrahydro‐pyridine‐4‐carbaldehyde,a Precursor for Synthesizing Aricept®, Isoguvacine,and Deethylibophyllidine

A new route towards the synthesis of N‐substituted‐4‐formylpiperidine using N‐benzyl or tryptaminyl‐sulfonylacetamide and α,β‐unsaturated ester as starting materials is described. Formal synthesis of Aricept^®, deethylibophyllidine, and isoguvacine, which have potential biological activities, were synthesized via this strategy.     

Isocyanide‐Based Three‐Component Synthesis of Highly Substituted 1,6‐Dihydro‐6,6‐dimethylpyrazine‐2,3‐dicarbonitrile, 3,4‐Dihydrobenzo[g]quinoxalin‐2‐amine,and 3,4‐Dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine Derivatives

A novel and efficient isocyanide‐based multicomponent reaction between alkyl or aryl isocyanides 1 , 2,3‐diaminomaleonitrile ( 2 ), naphthalene‐2,3‐diamines ( 6 ) or benzene‐1,2‐diamine ( 9 ), and 3‐oxopentanedioic acid ( 3 ) or Meldrum's acid ( 4 ) or ketones 7 was developed for the ecologic synthesis, at room temperature under mild conditions, of 1,6‐dihydropyrazine‐2,3‐dicarbonitriles 5a – 5f in H₂O without using any catalyst, and of 3,4‐dihydrobenzo[g]quinoxalin‐2‐amine and 3,4‐dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine derivatives 8a – 8g and 10a – 10e , respectively, in the presence of a catalytic amount of p‐toluenesulfonic acid (TsOH) in EtOH, in good to excellent yields (Scheme 1).     

The investigation of proton transfer and fluorescence‐sensing mechanisms of [2‐(2‐hydroxy‐phenyl)‐1H‐benzoimidazol‐5‐yl]‐phenyl‐methanone

Given the tremendous potential of fluorescence sensors in recent years, in this present work, we theoretically explore a novel fluorescence chemosensor [2‐(2‐Hydroxy‐phenyl)‐1H‐benzoimidazol‐5‐yl]‐phenyl‐methanone (HBPM) about its excited state behaviors and probe‐response mechanism. Using density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods, we explore the S₀‐state and S₁‐state hydrogen bond dynamical behaviors and confirm that the strengthening intramolecular hydrogen bond in the S₁ state may promote the excited state intramolecular proton transfer (ESIPT) reaction. In view of the photoexcitation process, we find that the charge redistribution around the hydroxyl moiety plays important roles in providing driving force for ESIPT. And the constructed potential energy curves further verify that the ESIPT process of HBPM should be ultrafast. That is the reason why the normal HBPM fluorescence cannot be detected in previous experiment. Furthermore, with the addition of fluoride anions, the exothermal deprotonation process occurs spontaneously along with the intermolecular hydrogen bond O–H?F. It reveals the uniqueness of detecting fluoride anions using HBPM molecules. As a whole, the fluoride anions inhibit the initial ESIPT process of HBPM, which results in different fluorescence behaviors. This work presents the clear ESIPT process and fluoride anion‐sensing mechanism of a novel HBPM chemosensor.     

Self‐Assembled PAA‐Based Nanoparticles as Potential Gene and Protein Delivery Systems

A series of nanoparticles is prepared via layer‐by‐layer assembly of oppositely charged, synthetic biocompatible polyamidoamine polymers as potential carriers. Particle size, surface charge and internal chain mobility are quantified as a function of the polymer type and number of layers. The effect of addition of surfactant is examined to simulate the effects of nanoparticle dissolution. The cyctotoxicity of these particles (in epithelia and murine cell lines) are orders of magnitude lower than polyethyleneimine controls. Stable nanoparticles may be prepared from mixtures of strongly, oppositely charged polymers, but less successfully from weakly charged polymers, and, given their acceptable toxicity characteristics, such modularly designed constructs show promise for drug and gene delivery.

     

An experimental and theoretical approach to the molecular structure of 3‐{[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐ indol‐2‐one

The title molecule, 3‐{[4‐(3‐methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐indol‐2‐one (C₂₂H₂₀N₄O₁S₁), was prepared and characterized by ¹H NMR, ¹³C NMR, IR, UV–visible, and single‐crystal X‐ray diffraction. The compound crystallizes in the monoclinic space group P21 with a = 8.3401(5), b = 5.6976(3), c = 20.8155(14) Å, and β = 95.144(5)°. Molecular geometry from X‐ray experiment and vibrational frequencies of the title compound in the ground state has been calculated using the Hartree–Fock with 6‐31G(d, p) and density functional method (B3LYP) with 6‐31G(d, p) and 6‐311G(d, p) basis sets, and compared with the experimental data. The calculated results show that optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies values show good agreement with experimental data. Density functional theory calculations of the title compound and thermodynamic properties were performed at B3LYP/6‐31G(d, p) level of theory. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Paper‐Based Electrochemiluminescent 3D Immunodevice for Lab‐on‐Paper,Specific, and Sensitive Point‐of‐Care Testing

Recent research on microfluidic paper‐based analytical devices (μPADs) has shown that paper has great potential for the fabrication of low‐cost diagnostic devices for healthcare and environmental monitoring applications. Herein, electrochemiluminescence (ECL) was introduced for the first time into μPADs that were based on screen‐printed paper‐electrodes. To further perform high‐specificity, high‐performance, and high‐sensitivity ECL on μPADs for point‐of‐care testing (POCT), ECL immunoassay capabilities were introduced into a wax‐patterned 3D paper‐based ECL device, which was characterized by SEM, contact‐angle measurement, and electrochemical impedance spectroscopy. With the aid of a home‐made device‐holder, the ECL reaction was triggered at room temperature. By using a typical tris(bipyridine)ruthenium–tri‐n‐propylamine ECL system, this paper‐based ECL 3D immunodevice was applied to the diagnosis of carcinoembryonic antigens in real clinical serum samples. This contribution further expands the number of sensitive and specific detection modes of μPADs.     

Synthesis of 2‐Thioxohydropyridine‐3‐Carbonitrile, 2‐Alkylthiopyridine,Thienopyridine, Pyrazolopyridine Derivatives and Their Theoretical Calculations

Cyanothioacetamide ( 1 ) reacted with but‐2‐enal ( 2 ) to give the corresponding 4‐methyl‐2‐sulfanylpyridine‐3‐carbonitrile ( 7 ) which was used as a good starting material for the synthesis of 1‐(3‐amino‐4‐methylthieno[2,3‐b]pyridin‐2‐yl)ethan‐1‐one ( 10 ), 3‐amino‐4‐methylthieno[2,3‐b]pyridine‐2‐carboxamide ( 15 ), 3‐amino‐4‐methylthieno[2,3‐b]pyridine‐2‐carboxylate ( 18 ) and 3‐amino‐4‐methylthieno[2,3‐b]pyridin‐2‐ylarylketone 25a‐c through its reactions with each of (1‐chloroacetone ( 8 ), 3‐chloropentane‐2,4‐dione ( 11 ) or ethyl 2‐chloro‐3‐oxo‐butanoate ( 19 )), 2‐chloroacetamide ( 13 ), ethyl 2‐chloroacetate ( 16 ) and 2‐bromo‐1‐arylethan‐ 1 ‐one 23a‐c , respectively. Considering the data of elemental analyses, IR, ¹HNMR, mass spectra and theoretical calculations, structures of the newly synthesized heterocyclic compounds were elucidated.