Significant Substituent Effect Research Articles

The Substituent Effects of Suzuki Coupling in Aqueous Micelles.

The Suzuki coupling in aqueous micelles has received much attention, but few attempts focus on its substituent effects. In view of the significant substituent effects on this reaction, it is necessary and practical to investigate its substituent effects. Herein, the substituent effects of Suzuki coupling in aqueous micelles are well established through Hammett plots and kinetic studies. In the cases of aryl halides, the rate-determining step of the reaction will shift from the oxidation addition step to the transmetalation step as the substituents' electron withdrawing ability increases, so aryl halides with weak electron-withdrawing groups exhibit better reactivity than ones containing strong electron-withdrawing or electron-donating groups. For arylboronic acids, the electron donating groups are beneficial to the Suzuki reaction, while the electron withdrawing group is unfavorable for the reaction. The Suzuki reactions of substituent exchange between arylboronic acids and aryl halides further confirm these substituent effects.

π-Extended dibenzo[g,p]chrysenes

Two different series of π-extended dibenzo[g,p]chrysenes are synthesized. The experimental and DFT data showed the significant effects of both position and substituent on the optoelectronic and charge delocalization behavior.

Electronic effects on polypyridyl Co complex-based water reduction catalysts.

Three new isomeric cobalt complexes of TPA (tris(2-pyridylmethyl)amine) based on methoxy substitution at the ortho, meta and para positions, respectively, were constructed and their photocatalytic proton reduction efficiencies were compared. It was found that there are good linear correlations with the Hammett constants of the substituents for the computed Co–N bond lengths, redox potentials of CoII/I and CoI/0 events, and the photocatalytic activities of the complexes. The ortho-substituted Co complex distinguished itself from the others remarkably in all these comparisons, demonstrating the presence of a steric effect besides the electronic effect. For other examined complexes, a stronger electron-donating substituent may lead to a higher hydrogen evolution efficiency, suggesting that the formation of a Co(iii) hydride intermediate is the rate-limiting step.

Reaction Mechanisms on [3 + 2] Cycloaddition of Azides with Metal Carbyne Complexes: Significant Effects of Aromaticity, Substituent, and Metal Center.

Density functional theory calculations were used to investigate the reaction mechanisms on [3 + 2] cycloaddition reactions of azides with metal carbyne complexes. Our results reveal that the formation of a 1,4-metallatriazole regioisomer is a kinetically favorable process in comparison with the formation of 1,5-metallatriazole. Aromaticity plays an important role in stabilizing the products in these reactions. Further analyses show that the electron-donating ligand on metal centers or the electron-withdrawing group on the azide could accelerate the [3 + 2] cycloaddition reaction. All of these findings could be useful for experimental chemists to develop "click reactions" in organometallic chemistry.

Experimental and theoretical approaches to the study of the reactivity and mechanism of the substitution of phenyl 1‐(2,4‐dinitronaphthyl) ether with anilines derivatives

AbstractReactions of aniline derivatives in dimethyl sulfoxide with phenyl 1‐(2,4‐dinitronaphthyl) ether yield aryl 1‐(2,4‐dinitronaphthyl) amine, which results in substitution of the phenoxy groups at the naphthyl ipso carbon atom. Rate constants were measured spectrophotometrically, and reaction proton transfer was rate limiting. The values of the rate coefficients indicate a rate‐limiting proton transfer mechanism with significant substituent effects. The calculated activation parameters were of regular variation with substituents in 4‐ and 3‐position in the aniline nucleophile, and the reaction proceeded through a common mechanism. Hammett's reaction constant showed that the reaction rate constants depend on the electron density of the nitrogen atom of aniline derivative, whereas the coefficient value obtained from the Brönsted relation indicated that the reaction was significantly associative and quite zwitterion like. Computational studies of the substitution were carried out based on density functional theory, and theoretical to the experimental agreement was achieved.

A novel approach for rhodium(iii)-catalyzed C-H functionalization of 2,2'-bipyridine derivatives with alkynes: a significant substituent effect.

We described a novel approach for the C-H functionalization of 2,2'-bipyridine derivatives with alkynes. DFT calculations and experimental data showed a significant substituent effect at the 6-position of 2,2'-bipyridine, which weakened the adjacent N-Rh bond and provided the possibility of subsequent rollover cyclometalation, C-H activation, and functionalization.

Probing the tautomerization of disilenes and disilabenzenes with their isomeric silylenes: significant substituent, aromaticity and base effects.

Disilene has attracted considerable interest due to the trans-bending geometry which is significantly different from the planar alkene. However, the equilibrium between disilene and isomeric silylsilylene has not been fully understood. Here, we report a density functional theory (DFT) study on this equilibrium. Calculations reveal significant effects of substituent, aromaticity and base. Specifically, the parent disilene is thermodynamically more stable than the isomeric silylene. When the methoxy substituent is introduced, the corresponding silylene becomes thermodynamically more stable, which could be rationalized by the Bent's rule. Interestingly, disilabenzene becomes thermodynamically more stable than the isomeric silylene when the concept of aromaticity is taken into account. Finally, once the base is introduced, the silylene could become thermodynamically more stable than the isomeric disilabenzene. The kinetic effect of the tautomerization with several typical substituents (F, Me and OMe) has also been investigated. Some species with a bridged form have been found to have a higher thermodynamic stability over the nonbridged ones. All these findings could be particularly useful to develop the chemistry of disilenes and silylenes.

Reaction mechanisms of iron(iii) catalyzed carbonyl–olefin metatheses in 2,5- and 3,5-hexadienals: significant substituent and aromaticity effects

Theoretical calculations reveal significant substituent and aromaticity effects on Fe(iii)-catalyzed carbonyl–olefin metatheses of hexadienals.

Synthesis and Stereochemical Analysis of Dynamic Planar Chiral Nine-Membered Diallylic Amide: Significant Substituent Effect on Stereochemical Stability

Synthesis and Stereochemical Analysis of Dynamic Planar Chiral Nine-Membered Diallylic Amide: Significant Substituent Effect on Stereochemical Stability

Optically transparent aromatic poly(ester imide)s with low coefficients of thermal expansion. 2: Effect of the introduction of alkyl‐substituted p‐biphenylene units

AbstractA series of ester‐linked tetracarboxylic dianhydrides (TA‐X) were synthesized from trimellitic anhydride chloride and 4,4′‐biphenol analogs containing different numbers and positions of methyl substituents. Aromatic poly(ester imide)s (PEsIs) were polymerized from TA‐Xs and 2,2′‐bis(trifluoromethyl)benzidine to investigate the film properties systematically. A significant substituent effect on the target properties (Tg, optical transparency, the linear coefficient of thermal expansion (CTE) and ductility) was observed. A PEsI containing 2,2′,3,3′,5,5′‐hexamethyl‐substituted p‐biphenylene units was chemically imidized in a homogeneous state. It was highly soluble at room temperature, even in less hygroscopic non‐amide solvents such as cyclopentanone (CPN), and provided a stable CPN solution with a high solid content. The CPN‐cast PEsI film was almost colorless as suggested from the rather low yellowness index (3.2), high light transmittance at 400 nm (71.5%) and very low haze (1.15%). This PEsI film also had a high Tg (294 °C, determined by thermomechanical analysis) in addition to a low CTE (21.7 ppm K−1), moderate film ductility and very low water uptake. A structural modification of the PEsI by copolymerization with a tetracarboxylic dianhydride with a rigid/linear structure was effective in further reducing the CTE while maintaining the other excellent target properties. Thus, some of the PEsIs developed in this work are promising candidates as novel plastic substrates for use in image display devices. © 2017 Society of Chemical Industry

Structural and Computational Investigation of Intramolecular N···H Interactions in α‐ and β‐Fluorinated 7‐Azaindoline Amides

Novel fluorinated N1‐acylated 7‐azaindolines have been synthesized and their conformations analyzed by X‐ray diffraction and NMR spectroscopy: Unusual intramolecular interactions between the 7‐nitrogen and amide α‐hydrogen atoms were identified. The strength of these interactions correlate with the electron‐withdrawing character of the amide α substituents. A combination of experimental and computational approaches revealed a significant substituent effect when the substituent (H, OMe, F, CN) at the 4‐position of the 7‐azaindoline scaffold was varied. As these intramolecular interactions also occur in non‐fluorinated N1‐acylated 7‐azaindolines and similar heterocycles, this study is relevant to medicinal chemistry: The results will facilitate the prediction of the predominant conformations of N1‐acylated‐7‐azaindoline‐containing bioactive molecules and thus potentially contribute to drug discovery programs.

Probing Ultrafast Dissociation Dynamics of Chloroiodomethane in the B Band by Time-Resolved Mass Spectrometry**Supported by the National Natural Science Foundation of China under Grant Nos 11304157, 21303255 and 11475229, the ‘Six Talent Peaks’ Project in Jiangsu Province under Grant No 2015-JNHB-011, and the College Students Practice Innovative Training Program of Nuist under Grant No 201610300042.

Ultrafast dissociation dynamics of chloroiodomethane (CH2ICl) in the B band is studied by femtosecond time-resolved time-of-flight (TOF) mass spectrometry. Time-resolved TOF mass signal of parent ion (CH2ICl+) and main daughter ion (CH2Cl+) are obtained. The curve for the transient signal of CH2ICl+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function. The decay constant determined to be less than 35 fs reflects the lifetime of the B band. Significant substituent effects on photodissociation dynamics of CH2ICl compared with CH3I are discussed. The dissociation time from the parent ion CH2ICl+ to the daughter ion CH2Cl+ is determined in the experiment. The optimized geometry of the ionic state of CH2ICl and the ionization energy are calculated for further analysis of the measurements. In addition, compared with the parent ion, a new decay component with time constant of ∼596 fs is observed for CH2Cl+, and reasonable mechanisms are proposed for the explanation.

An efficient computational scheme for electronic excitation spectra of molecules in solution using the symmetry-adapted cluster-configuration interaction method: the accuracy of excitation energies and intuitive charge-transfer indices.

Solvent effects on electronic excitation spectra are considerable in many situations; therefore, we propose an efficient and reliable computational scheme that is based on the symmetry-adapted cluster-configuration interaction (SAC-CI) method and the polarizable continuum model (PCM) for describing electronic excitations in solution. The new scheme combines the recently proposed first-order PCM SAC-CI method with the PTE (perturbation theory at the energy level) PCM SAC scheme. This is essentially equivalent to the usual SAC and SAC-CI computations with using the PCM Hartree-Fock orbital and integrals, except for the additional correction terms that represent solute-solvent interactions. The test calculations demonstrate that the present method is a very good approximation of the more costly iterative PCM SAC-CI method for excitation energies of closed-shell molecules in their equilibrium geometry. This method provides very accurate values of electric dipole moments but is insufficient for describing the charge-transfer (CT) indices in polar solvent. The present method accurately reproduces the absorption spectra and their solvatochromism of push-pull type 2,2'-bithiophene molecules. Significant solvent and substituent effects on these molecules are intuitively visualized using the CT indices. The present method is the simplest and theoretically consistent extension of SAC-CI method for including PCM environment, and therefore, it is useful for theoretical and computational spectroscopy.

Substituent effect on the electroluminescence efficiency of amidinate-ligated bis(pyridylphenyl) iridium(iii) complexes

A significant substituent effect on the EL properties was observed and a heteroleptic iridium(iii) complex with a t-Bu substituted amidinate ligand [(ppy)2Ir{(t-BuN)2CPh}] showed high current and power efficiency.

Significant Substituent Effect on the Anomerization of Pyranosides: Mechanism of Anomerization and Synthesis of a 1,2‐cis Glucosamine Oligomer from the 1,2‐trans Anomer

Aminoglycosides containing a 2,3-trans carbamate group easily undergo anomerization from the 1,2-trans glycoside to the 1,2-cis isomer under mild acidic conditions. The N-substituent of the carbamate has a significant effect on the anomerization reaction; in particular, an N-acetyl group facilitated rapid and complete α-anomerization. The differences in reactivity due to the various N-substituents were supported by the results of DFT calculations; the orientation of the acetyl carbonyl group close to the anomeric position was found to contribute significantly to the directing of the anomerization reaction. By exploiting this reaction, oligoaminoglycosides with multiple 1,2-cis glycosidic bonds were generated from 1,2-trans glycosides in a one-step process.

Substituent effects on indirect carbon–carbon couplings, J(CC), in substituted thiophenes, pyrroles, and furans studied by experiment and theory

An excellent linear correlation is found between a large set of experimental spin–spin carbon–carbon coupling constants, J(CC), in thiophene, pyrrole, and furan systems and the corresponding B3PW91/6‐311++G(2d,p)//B3PW91/6‐311++G(2d,p) calculated estimates. The correlation does not differ significantly from the simplest relationship possible, J(CC)exp. = J(CC)calcd., within a small and random spread of about 1 Hz. There are 285 experimental values considered, and 202 out of these are new and come from the present work. The character of the correlation indicates that rovibronic effects on aromatic J(CC)'s, and those of nuclear motions on aromatic J(CC)'s are practically negligible. All of this is in a perfect agreement with our recent extensive studies on aromatic J(CC)'s in pyridine and benzene ring systems. As has been shown by computations, not only large one‐bond couplings but also almost all long‐range ones occurring between the carbons of the heteroaromatic rings are, with a few exceptions, positive. Significant substituent effects experimentally observed in the one‐bond as well as long‐range couplings are very accurately reproduced by the computation. The experimental coupling magnitudes vary from ca. 1 to 98 Hz. The J(CC)'s computed for the model variously substituted trimethylsilyl and fluoro derivatives, which are not easily accessible experimentally, span a range of about 130 Hz, from ca. −2 in up to ca. +125 Hz . Copyright © 2012 John Wiley & Sons, Ltd.

Ethylene and Ethylene/α-Olefin (Co)Polymerization Behavior of Bis(phenoxy−imine)Ti Catalysts: Significant Substituent Effects on Activity and Comonomer Incorporation

The ethylene and ethylene/α-olefin (co)polymerization behavior of bis(phenoxy−imine)Ti complexes 1−7 possessing a series of substituents ortho to the phenoxy O's (ortho substituents 1, iPr; 2, cyclohexyl; 3, cyclooctyl; 4, cyclododecyl; 5, tBu; 6, CMe2Ph; 7, Ph) with dried methylaluminoxane activation was investigated. At 50 °C, all complexes displayed some of the characteristics of living ethylene polymerization and produced polyethylenes (PEs) with very narrow molecular weight distributions (Mw/Mn 1.08−1.19, Mw 14 900−62 100), albeit under limited conditions. Generally, the Ti complexes with sterically bulkier ortho substituents exhibited higher activities [e.g., 6: activity 93.2 kg of PE/(mol of cat. min)]; the ortho substituents with quaternary α-C atoms attached to the phenoxy rings, providing higher activities than those with tertiary α-C atoms on the basis of the steric bulk of the entire ortho substituent. To our surprise, complex 7 incorporating an ortho phenyl group displayed the highest activit...

The first solution-processable n-type phthalocyaninato copper semiconductor: tuning the semiconducting nature via peripheral electron-withdrawing octyloxycarbonyl substituents

A series of unsymmetrical phthalocyaninato copper complexes simultaneously incorporating electron-withdrawing and electron-donating substituents at the phthalocyanine periphery Cu{Pc(15C5)[(COOC8H17)6]} (2), Cu{Pc[(adj-15C5)2][(COOC8H17)4]} (3), Cu{Pc[(opp-15C5)2][(COOC8H17)4]} (4), Cu{Pc(15C5)3[(COOC8H17)2]} (5) were prepared and isolated. For comparative studies, symmetrical analogues including 2,3,9,10,16,17,24,25-octakis(octyloxycarbonyl)phthalocyaninato copper complex Cu[Pc(COOC8H17)8] (1) and 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato copper complex Cu[Pc(15C5)4] (6) were also prepared. Their electrochemistry was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). With the help of a solution-based self-assembly process, these compounds were fabricated into organic field effect transistors (OFETs) with top contact configuration on hexamethyldisilazane (HMDS)-treated SiO2/Si substrate. In line with the electrochemical investigation results, a p-type OFET with a carrier mobility (for holes) of 0.06 cm2 V−1 s−1 was shown for Cu[Pc(15C5)4] (6) with electron-donating 15-crown-5 as the sole type of peripheral substituent. In contrast, n-type devices with a carrier mobility (for electrons) of 6.7 × 10−6–1.6 × 10−4 cm2 V−1 s−1 were achieved for 1–5 with electron-withdrawing octyloxycarbonyl substituents at the peripheral positions of phthalocyanine ring, indicating the significant effect of electron-withdrawing octyloxycarbonyl substituents on tuning the nature of phthalocyanine organic semiconductors. The present results represent the first example of solution-processed n-type phthalocyanine-based OFET devices.

ChemInform Abstract: Chiral 1‐Phenylethylamine‐Derived Phosphine—Phosphoramidite Ligands for Highly Enantioselective Rh‐Catalyzed Hydrogenation of β‐(Acylamino)acrylates: Significant Effect of Substituents on 3,3′‐Positions of Binaphthyl Moiety.

AbstractIntroduction of phenyl substituents at the phosphoramidite backbone of PEAPhos ligand (PEAPP) significantly increases its catalytic activity in the Rh‐catalyzed asymmetric hydrogenation of β‐(acylamino)acrylates.

Two-Step Alkylation of Single-Walled Carbon Nanotubes: Substituent Effect on Sidewall Functionalization

A two-step alkylation of single-walled carbon nanotubes was investigated. The functionalized SWNTs were characterized with vis-NIR and Raman spectrometers, scanning electron microscope, and thermogravimetric analysis. This one-pot alkylation of SWNTs with alkyllithium followed by alkyl halide is useful for the sidewall functionalization of SWNTs. This reaction shows significant substituent effects on the degree of functionalization of SWNTs. The degree of functionalization on SWNTs sidewall upon SWNTs may influence their characteristic properties on SWNTs sidewall by the substituent effects.