Monosubstituted Derivatives Research Articles

A New Phosphine Oxide Host based on ortho‐Disubstituted Dibenzofuran for Efficient Electrophosphorescence: Towards High Triplet State Excited Levels and Excellent Thermal, Morphological and Efficiency Stability

An efficient host for blue and green electrophosphorescence, 4,6-bis(diphenylphosphoryl)dibenzofuran (o-DBFDPO), with the structure of a short-axis-substituted dibenzofuran was designed and synthesised. It appears that the greater density of the diphenylphosphine oxide (DPPO) moieties in the short-axis substitution configuration effectively restrains the intermolecular interactions, because only very weak π-π stacking interactions could be observed, with a centroid-to-centroid distance of 3.960 Å. The improved thermal stability of o-DBFDPO was corroborated by its very high glass transition temperature (T(g)) of 191 °C, which is the result of the symmetric disubstitution structure. Photophysical investigation showed o-DBFDPO to be superior to the monosubstituted derivative, with a longer lifetime (1.95 ns) and a higher photoluminescent quantum efficiency (61 %). The lower first singlet state excited level (3.63 eV) of o-DBFDPO demonstrates the stronger polarisation effect attributable to the greater number of DPPO moieties. Simultaneously, an extremely high first triplet state excited level (T(1)) of 3.16 eV is observed, demonstrating the tiny influence of short-axis substitution on T(1). The improved carrier injection ability, which contributed to low driving voltages of blue- and green-emitting phosphorescent organic light-emitting diodes (PHOLEDs), was further confirmed by Gaussian calculation. Furthermore, the better thermal and morphological properties of o-DBFDPO and the matched frontier molecular orbital (FMO) levels in the devices significantly reduced efficiency roll-offs. Efficient blue and green electrophosphorescence based on the o-DBFDPO host was demonstrated.

Comparison of the substituent effects in tetrazole systems and benzene. A computational study

Natural Population Analysis of two tautomeric forms of 16 tetrazole derivatives substituted at carbon atom (AlH 2, BeH, BH 2, CCH, CF 3, CHO, Cl, CN, F, Me, NH 2, NO, NO 2, OH, SH, SiH 3) was carried out at B3LYP/6-31G(d,p) level of theory and compared with data for monosubstituted benzene derivatives. The individual occupancies of 2p z orbitals at all atoms of the tetrazole and benzene derivatives were correlated with the sum of occupation overall 2p z orbitals, named pEDA( A) or pEDA( B), respectively. These characteristics correlate well with the Hammett-like substituent constants. Acceptable correlations between the individual atom occupancies at the 2p z orbital and pEDA were found for all atoms except N4.

ChemInform Abstract: A New Synthesis of Pyrazoles Through a Lewis Acid Catalyzed Union of 3‐Ethoxycyclobutanones with Monosubstituted Hydrazines.

AbstractThe reaction is catalyzed by SnCl4 for tosyl hydrazine and by BF3·Et2O for all other monosubstituted hydrazine derivatives.

X-ray diffraction investigation of cyclohexane derivatives at 293 K

This paper reports results of the X-ray diffraction structural studies of liquid cyclohexylamine C 6H 11–NH 2 and cyclohexanol C 6H 11–OH performed at 293 K. The method of X-ray scattering and Fourier analysis enabled the determination of the mean structural parameters of the liquids studied. The wide-angle X-ray scattering (WAXS) method provided new information on mutual arrangement and orientation of the molecules of the above mentioned compounds in the liquid phase. The measurements of scattered radiation intensity were performed in a wide range of wave vector (from S min =0.925 Å −1 to S max =14.311 Å −1), with the use of X-ray radiation MoK α ( λ=0.71069 Å). Angular distributions of X-ray scattered intensity were measured, and differential radial distribution functions of electron density (DRDFs) were calculated. The mean distances between the neighbouring molecules and the mean radii of coordination spheres were found. A simple model of short-range arrangement of the molecules was proposed, which seems to be valid for other polar monosubstituted cyclohexane derivatives in the liquid phase.

Regioselectivity in Electrophilic Aromatic Substitution: Insights from Interaction Energy Decomposition Potentials

AbstractThe SEAr reaction was scrutinized using a quantitative, fragment‐based interaction energy decomposition analysis (EDA) as implemented in the ADF program. The interaction energy between monosubstituted benzene derivatives and a model electrophile at the onset of the reaction was studied and decomposed into Pauli repulsion, electrostatic interaction and orbital interaction terms for a plane parallel to the molecular plane. As such experimentally observed selectivity patterns arise in the orbital interaction, stressing again the role of both electrophile and benzene derivative in determining the regioselectivity. Using the HSAB principle and MO theory, the orientation mechanism of the SEAr is further explored.

Synthesis of Unsymmetrical, Monosubstituted Bis-terpyridine Derivatives via Suzuki-Miyaura Cross-Coupling

As building blocks for metallo-supramolecular polymers, novel, unsymmetrical, monosubstituted bis-terpyridine derivatives with one electron-donating (OMe) or electron-withdrawing (CN or COOMe) group have been synthesized via the Suzuki― Miyaura cross-coupling reaction. This method is quick, efficient and suitable for the introduction of various substituents at the periphery of pyridine.

DFT investigation of the thermodynamics and mechanism of electrophilic chlorination and iodination of arenes

Quantum chemical calculations at the B3LYP/6-311G level have been carried out in order to investigate the reaction mechanisms of the iodination of benzene and its monosubstituted derivatives with ICl, I(+), I (3) (+) and reagents containing N-I and O-I bonds as the iodinating agents. The results are compared with those obtained for chlorination by Cl(+) and Cl(2), both in the gas phase and in methanol solution using the PCM solvent model. We have also used the MP2/DGDZVP level of theory and the IEFPCM model to perform comparisons in a few cases. The thermodynamic parameters for the reactions have been calculated, the structures of the intermediate products (π- and σ-complexes) and transition states have been optimized, and the profiles of the free energy surfaces have been constructed.

In Vivo Trypanosomicidal Activity of Imidazole- or Pyrazole-Based Benzo[g]phthalazine Derivatives against Acute and Chronic Phases of Chagas Disease

The in vivo trypanosomicidal activity of the imidazole-based benzo[g]phthalazine derivatives 1-4 and of the new related pyrazole-based compounds 5 and 6 has been studied in both the acute and chronic phases of Chagas disease. As a rule, compounds 1-6 were more active and less toxic than benznidazole in the two stages of the disease, and the monosubstituted derivatives 2, 4, and 6 were more effective than their disubstituted analogs. Feasible mechanisms of action of compounds 1-6 against the parasite have been explored by considering their inhibitory effect on the Fe-SOD enzyme, the nature of the excreted metabolites and the ultrastructural alterations produced. A complementary histopathological analysis has confirmed that the monosubstituted derivatives are less toxic than the reference drug, with the behavior of the imidazole-based compound 4 being especially noteworthy.

Liquid crystalline PEDOT derivatives exhibiting reversible anisotropic electrochromism and linearly and circularly polarized dichroism

The multifunctional poly(3,4-ethylenedioxythiophene) [PEDOT] derivatives that exhibit liquid crystallinity, reversible anisotropic electrochromism, and linearly and circularly polarized dichroism are developed. A series of copolymer-type liquid-crystalline PEDOT (LC PEDOT) derivatives are synthesized and evaluated in terms of optical and electrochromic properties. Two of the polymers are monosubstituted LC PEDOT derivatives with phenylcyclohexyl (PCH) or cyanobiphenyl (CB) mesogenic side chain moieties linked to the main chain via an ester bond. Four are disubstituted polymers bearing PCH or CB side chain moieties linked to the main chain via an ester or an ether bond. All of the polymers showed thermotropically nematic LC (N-LC) phases of an enantiotropic nature. Macroscopically aligned LC PEDOT derivatives were prepared by rubbing the polymer films in their N-LC phases, yielding linearly polarized fluorescence and anisotropic electrochromism. The morphologies of the polymer films reversibly changed between the neutral and oxidized states through electrochemical dedoping and doping procedures. The electrochromism between the neutral and oxidized states occurred in the parallel and perpendicular directions of the aligned polymer film, affording a novel anisotropic electrochromism. The chiral nematic LC (N*-LC) phases were also induced in the polymers by adding chiral binaphthyl derivatives as chiral inducer into the LC PEDOT derivatives. The polymer films with the induced N*-LC phase exhibited circular dichroism, implying the formation of an interchain helically π-stacked structure or intrachain helically twisted structure.

An asymmetric TTF derivative bearing a phenyl β-diketone group as an efficient ligand towards functional materials

A novel asymmetric tetrathiafulvalene (TTF) derivative bearing a conjugated phenyl β-diketone moiety 1-(4-tetrathiafulvalyphenyl)-4,4,4-trifluorobutane-1,3-dione (TTF-ph-tfacH) has been synthesized using feasible methods and fully characterized. The chelating ability of its enolate anion (TTF-ph-tfac) has been investigated with [MIICl2·xH2O] (M = Zn and Co) leading to complexes [Zn(TTF-ph-tfac)2(CH3OH)2] (2a) and [Co(TTF-ph-tfac)2(CH3OH)2] (2b), where the metal center is coordinated with two TTF-ph-tfac ligands and two methanol molecules. This redox active ligand shows promising features for the elaboration of hybrid organic–inorganic building blocks. The magnetic analysis for 2b reveals very weak antiferromagnetic interactions between spin centers, which would be a precursor for magnetic conductors. The herein reported mono-substituted TTF derivative interconnected via the phenyl group, which is of extended conjugation, enhanced planarity, and asymmetric geometry, shows a great promise to multifunctional (conducting, non-linear optical, and magnetic) materials.

Synthesis of mono-substituted derivatives of 6-aminoquinoline

Abstract Several 6-aminoquinoline derivatives, which could be used in drug design, have been synthesized. The reaction conditions were comparatively studied, and the p -chloroaniline was used as optimum oxidant in Skraup–Doebner–Von Miller reaction. The nitro group was reduced effectively by SnCl 2 with no halo-removed occurred.

α‐Cyclodextrin Host–Guest Binding: A Computational Study of the Different Driving Forces

AbstractFree‐energy differences govern the equilibrium between bound and unbound states of a host and its guest molecules. The understanding of the underlying entropic and enthalpic contributions, and their complex interplay are crucial for the design of new drugs and inhibitors. In this study, molecular dynamics (MD) simulations were performed with inclusion complexes of α‐cyclodextrin (αCD) and three monosubstituted benzene derivatives to investigate host–guest binding. αCD Complexes are an ideal model system, which is experimentally and computationally well‐known. Thermodynamic integration (TI) simulations were carried out under various conditions for the free ligands in solution and bound to αCD. The two possible orientations of the ligand inside the cavity were investigated. Agreement with experimental data was only found for the more stable orientation, where the substituent resides inside the cavity. The better stability of this conformation results from stronger Van der Waals interactions and a favorable antiparallel host–guest dipole–dipole alignment. To estimate the entropic contributions, simulations were performed at three different temperatures (250, 300, and 350 K) and using positional restraints for the host. The system was found to be insensitive to both factors, due to the large and symmetric cavity of αCD, and the nondirectional nature of the host–guest interactions.

THE EFFECT OF THE CHAIN LENGTH OF BONDED PHASE ON RETENTION OF AROMATIC SOLUTES IN RP LC WITH PURE WATER AS MOBILE PHASE

Retention factors (log kw ) in pure water were calculated for a homologous series of alkylbenzenes, PAHs, and aromatic monosubstituted derivatives for column C18, C8, and C4, using the numerical method based on the linear form of the Ościk's equation, which were correlated with the log kw values determined by the linear extrapolation method from the log k dependence on methanol volume fraction in binary eluent. The chromatographic parameters (log kw ), being the hydrophobicity measure, were compared with the experimental partition coefficients in n-octanol/water system (log P). The author examined the contribution of the substituents (‒CH2‒, ‒OH, ‒Cl, ‒NO2, and ‒CHO) in the substance retention in pure water for columns of different hydrocarbon chain length of the bonded phase. Moreover, the transfer thermodynamics of the particular functional groups from water to the stationary phase, as well as the influence of the kind of the stationary phase on the thermodynamics of this process were studied. For this purpose the standard free enthalpy (ΔG o) of the functional groups transfer from water to the stationary phase and from the gas to stationary one was calculated.

Design, synthesis, and evaluation of a new fluorescent probe for measuring polymyxin–lipopolysaccharide binding interactions

Fluorescence assays employing semisynthetic or commercial dansyl-polymyxin B have been widely employed to assess the affinity of polycations, including polymyxins, for bacterial cells and lipopolysaccharide (LPS). The five primary γ-amines on diaminobutyric acid residues of polymyxin B are potentially derivatized with dansyl-chloride. Mass spectrometric analysis of the commercial product revealed a complex mixture of di- or tetra-dansyl-substituted polymyxin B. We synthesized a mono-substituted fluorescent derivative, dansyl[Lys] 1polymyxin B 3. The affinity of polymyxin for purified gram-negative LPS and whole bacterial cells was investigated. The affinity of dansyl[Lys] 1polymyxin B 3 for LPS was comparable to polymyxin B and colistin, and considerably greater ( K d < 1 μM) than for whole cells ( K d ∼ 6–12 μM). Isothermal titration calorimetric studies demonstrated exothermic enthalpically driven binding between both polymyxin B and dansyl[Lys] 1polymyxin B 3 to LPS, attributed to electrostatic interactions. The hydrophobic dansyl moiety imparted a greater entropic contribution to the dansyl[Lys] 1polymyxin B 3–LPS reaction. Molecular modeling revealed a loss of electrostatic contact within the dansyl[Lys] 1polymyxin B 3–LPS complex due to steric hindrance from the dansyl[Lys] 1 fluorophore; this corresponded with diminished antibacterial activity (MIC ⩾16 μg/mL). Dansyl[Lys] 1polymyxin B 3 may prove useful as a screening tool for drug development.

Diiron Complexes with a [2Fe3S] Core Related to the Active Site of [FeFe]H2ases

AbstractSix‐membered heterocycles, 1,4‐dithiane and 1,4‐thioxane, were treated with [Fe2(CO)6(μ‐pdt)] (pdt = propanedithiolate) in order to synthesise [2Fe3S] complexes with well positioned heteroatoms as potential base. Monosubstituted compounds of general formula [Fe2(CO)5L(μ‐pdt)] (L = 1,4‐dithiane, 1,4‐thioxane) were mainly obtained and characterised by 1H NMR, IR, elemental analysis and X‐ray diffraction studies. Electrochemical behaviour of these monosubstituted derivatives was investigated by cyclic voltammetry. An original tetranuclear cluster with a [4Fe8S] core was also isolated as a minor product and structurally characterised.

Intramolecular Vibrational Energy Redistribution in Aromatic Molecules of Type C6H5X (X = H, D, F, Cl, CH3, CF3)

Femtosecond IR pump UV probe spectroscopy was employed in the gas phase to study intramolecular vibrational energy redistribution (IVR) in benzene and five monosubstituted derivatives thereof. After selective excitation of the first overtone of the ring CH-stretch vibration, all molecules showed the same two-step redistribution dynamics characteristic for nonstatistical IVR. The nature of the substituent influences mainly the second, slower IVR component. The presence of an internal rotor does not alter the redistribution rate or pathway compared to that of a monatomic substituent of equal mass. Coupling order model calculations reflect the experimental trends well if the polyatomic substituents are regarded as decoupled from the intra-ring dynamics and modeled as point masses.

Photocatalytic oxidation of benzene derivatives in aqueous suspensions: Synergic effect induced by the introduction of carbon nanotubes in a TiO2 matrix

Nanostructured composite catalysts produced using multi-walled carbon nanotubes (CNT) and titanium dioxide were prepared by means of a modified acid catalyzed sol–gel method. Materials were extensively characterized by XRD, TG, N2 adsorption–desorption isotherms, TEM, UV–vis spectroscopy and TPD. Composite catalysts with different CNT contents were tested in the photo-oxidation of phenol under different irradiation wavelengths. A correlation between CNT content and the changes in the UV–vis absorption properties is observed especially in the visible spectral range. The introduction of CNT into the titanium matrix induced a synergic effect when irradiating in the near-UV to visible spectral range. This effect may be explained in terms of a strong interphase interaction between CNT and TiO2 in the composite catalysts. CNT with different surface chemical groups were used to produce CNT–TiO2 composites. The presence of mild concentrations of oxygen containing surface groups, mainly carboxylic acids and phenols, appears to produce a beneficial effect in the photocatalytic activity of CNT–TiO2 composite catalysts. The photocatalytic oxidation of other monosubstituted benzene derivatives such as, aniline, nitrobenzene and benzoic acid, has been investigated under visible irradiation. The primary intermediates of photocatalytic reaction are single substituted hydroxy derivatives. The photoefficiency of the composite catalyst showed to be affected by the aromatic ring reactivity properties of the substrate.

ChemInform Abstract: Convenient and Efficient Palladium‐Catalyzed Coupling Reaction Between Ferroceneboronic Acid and Organic Triflates.

A simple and efficient palladium (Pd)–catalyzed Suzuki cross-coupling reaction between ferroceneboronic acid and organic triflates for the preparation of monosubstituted ferrocene derivatives has been developed. A systematic study of various solvents, bases, and catalysts revealed that the combination of Pd(PPh3)4 (0.025 equiv) and K3PO4 (2 equiv) in refluxing dioxane gave reproducible and excellent yields of the coupling products. The reaction could be applied to a wide variety of aryl and vinyl triflates in good to excellent yields, and the electronic and steric effects were observed for ortho-, meta-, and para-substituents of aryl triflates.

Theoretical study of Diels-Alder reaction: Role of substituent in regioselectivity and aromaticity

A comparative study on the influence of the substituents on the Diels-Alder reaction was performed. The energy profiles for 11 sets of Diels-Alder reaction between monosubstituted derivatives of butadiene and ethylene have been studied and the structures of all transition states were located at B3LYP/6-31+G* level. Four pathways were independently investigated; the reaction between substituted ethylene and 1-substituted butadiene leading to ortho (a1) and meta (a2) adducts, and in the same manner, the reaction between substituted ethylene and 2-substituted butadiene yields para (b1) and meta (b2) adducts. Inspection of both the activation barriers and the reaction energies for 44 reactions revealed that the pathway b1 is both thermodynamically and kinetically more favorable in all types of Diels-Alder reactions; while the pathway a1 can be labeled only as kinetic pathway. The aromaticity of all 44 transition state structures was measured using para delocalization index to study the effect of aromaticity on the reaction path. The calculations suggest that in normal and neutral DA reactions there is a gain in aromatic stabilization of the transition state which reduces slightly the activation barrier of the kinetic pathway a1.

Derivation of Correlation Functions to Predict Bond Properties of Phenyl−CH Bonds Based on Vibrational and1H NMR Spectroscopic Quantities

The study of electron density properties significantly contributes to the determination of important chemical relations. The experimental determination of the electron density distribution is limited to single crystals. However, equivalent information is often desired for molecules, which do not crystallize in a sufficient manner. Furthermore, it is of high impact to study changes in the electron density distribution (i.e., related reactivities) upon environmental variations. Consequently, here we investigate methods to derive electron density properties from spectroscopic data. In particular correlation functions are introduced, which are able to predict electron density properties in all five CH-bonds of monosubstituted benzene derivatives at once. The prediction performance for electron densities and the corresponding Laplacians is lower as compared to previously introduced local functions [Presselt et al. J. Phys. Chem. A 2009, 113, 3210], but far less spectroscopic input data are needed. However, for ellipticities a higher prediction performance than this obtained for the previously derived local functions could be obtained despite the fact that less spectroscopic data were used. Thus, ellipticities are best predicted using (1)H NMR data for the para position of monosubstituted benzene derivatives.