1-萘甲酰苯胺和2-萘甲酰苯胺的分子内电荷转移研究

A series of 1-naphthanilides (1) and 2-naphthanilides (2) with varied substituents at the para- or meta-position of anilino phenyl ring were prepared and their absorption and fluorescence spectra in a nonpolar solvent cyclohexane were investigated. An abnormal long wavelength emission assigned to the charge transfer (CT) state was found for all of the prepared naphthanilides in cyclohexane. A linear free energy correlation between the CT emission energies and the Hammett constants of the substituent was found within series 1 and 2. The value of the linear slope with 1 (0.42 eV) was higher than that with 2 (0.32 eV) being close to that of the substituted benzanilides 3 (0.31 eV) The higher slope value suggested higher charge separation extent in the CT state of 1 than that of 2. It was found that the corresponding linear slope of anilino-substituted benzanilides remained unchanged when para-, meta-, ortho-, or ortho, ortho-methyls were introduced into the anilino moiety, which ruled out the possible contribution of the difference in the steric effect and the electron accepting ability of the naphthoyl acceptor in 1 and 2. Compared with the early reported N-substituted-benzoyl-aminonaphthalene derivatives 4 and 5, it was considered that 1-naphthoyl enhanced the charge transfer in 1 and the proximity of its ^1La and ^1Lb states was suggested to be responsible. It was shown that 1- and/or 2-substituted naphthalene cores acting as either electron acceptor (naphthoyl) or electron donor (aminonaphthalene) were different in not only electron accepting (donating) ability but also shaping the charge transfer pathway.     

Correlation of substituted aromatic β‐diketones' characteristic protons chemical shifts with Hammett substituent constants

Influence of dibenzoylmethane's substituents in meta and para positions on chemical shift values of tautomers' characteristic protons was investigated in four solvents with ¹H NMR spectroscopy: acetone‐d₆, benzene‐d₆, CDCl₃ and deuterated dimethyl sulfoxide (DMSO‐d₆). It was proved that the influence of substituents on chemical shifts strongly depends on the kind of the solvent; the greatest changes were observed in benzene‐d₆ and the smallest in CDCl₃. In acetone‐d₆ and DMSO‐d₆, the influence of substituents on chemical shifts is similar and the most regular. It allowed a fair correlation of chemical shifts of para‐substituted dibenzoylmethane derivatives' characteristic protons with Hammett substituent constants in these solvents. In CDCl₃, characteristic protons' chemical shifts were near ¹H NMR spectroscopy measurement error limits, and, therefore, correlation with Hammett substituent constants in this solvent was unsatisfactory. In benzene, although the changes of chemical shifts are the most evident, the changes are also the most irregular, and, therefore, correlation in this solvent failed completely. Results of meta‐substituted derivatives were much more irregular, and their correlation with Hammett substituent constants was poor in all investigated solvents. Copyright © 2013 John Wiley & Sons, Ltd.     

The ortho‐Substituent Effect on the Ag‐Catalysed Decarboxylation of Benzoic Acids

A combined experimental and computational investigation on the Ag‐catalysed decarboxylation of benzoic acids is reported herein. The present study demonstrates that a substituent at the ortho position exerts dual effects in the decarboxylation event. On one hand, ortho‐substituted benzoic acids are inherently destabilised starting materials compared to their meta‐ and para‐substituted counterparts. On the other hand, the presence of an ortho‐electron‐withdrawing group results in an additional stabilisation of the transition state. The combination of both effects results in an overall reduction of the activation energy barrier associated with the decarboxylation event. Furthermore, the Fujita–Nishioka linear free energy relationship model indicates that steric bulk of the substituent can also exert a negative effect by destabilising the transition state of decarboxylation.     

Structure–Reactivity Relationships in Negishi Cross‐Coupling Reactions

Competition experiments have been performed to determine the relative reactivities of substituted bromobenzenes and of different arylzinc reagents in the [Pd(PPh₃)₄]‐catalyzed Negishi cross‐coupling reaction in THF at 25 °C. The cross‐coupling reactions are accelerated by electron acceptors in the bromobenzenes, the effect of which increases in the order ortho <meta <para. On the other hand, electron acceptors in the arylzinc halides diminish the reaction rates. Hammett correlations show that substituent variations in the bromobenzenes (ρ=+2.5) have a larger effect than substituent variations in the arylzinc halides (ρ=?0.98).     

Functionalization of Hexa‐peri‐hexabenzocoronenes: Investigation of the Substituent Effects on a Superbenzene

We have demonstrated that the iridium‐catalyzed direct borylation of hexa‐peri‐hexabenzocoronene (HBC) enables regioselective introduction of boryl groups to the para‐, ortho‐, and meta‐substituted HBCs in high yields. The boryl groups have been transformed into various functionalities such as hydroxy, cyano, ethynyl, and amino groups. We have elucidated that the substituents significantly influence the photophysical properties of HBCs to enhance fluorescence quantum yields. DFT calculations revealed that the origin of the substituent effect is the lift in degeneracy in the frontier orbitals by an interaction with electron‐donating and electron‐withdrawing substituents at the para‐ and ortho‐positions. The change in molecular orbitals results in an increase of the transition probability from the S₀→S₁ states. In addition, the two‐photon absorption cross‐section values of para‐substituted HBCs are significantly larger than those of ortho‐ and meta‐substituted HBCs.     

Studies on the kinetics of imidazolium fluorochromate oxidation of some meta‐ and para‐substituted anilines in nonaqueous media

The imidazolium fluorochromate (IFC) oxidation of meta‐ and para‐substituted anilines, in seven organic solvents, in the presence of p‐toluenesulfonic acid (TsOH) is first order in IFC and TsOH and is zero order with respect to substrate. The IFC oxidation of 15 meta‐ and para‐substituted anilines at 299–322 K complies with the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies within the experimental range. The specific rate of oxidizing species‐anilines reaction (k₂) correlates with substituent constants affording negative reaction constants. The rate data failed to correlate with macroscopic solvent parameters such as ε_r and E^N_T. A correlation of rate data with Kamlet–Taft solvatochromic parameters (α, β, π*) suggests that the specific solute–solvent interactions play a major role in governing the reactivity, and the observed solvent effects have been explained on the basis of solute–solvent complexation. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 166–175, 2006     

Solvent and substituent effects on the electrochemical oxidation of substituted benzylamines in 2‐methylpropan‐2‐ol/water medium

Electrochemical oxidation of various para‐ and meta‐substituted benzylamines in different mole fractions of 2‐methylpropan‐2‐ol in water has been investigated in the presence of 0.1 M sulfuric acid as supporting electrolyte. The oxidation potential data of benzylamines correlates well with Hammett's substituent constants affording negative reaction constants (?1.112 < ρ > ?1.529). The correlation of the oxidation potential values with macroscopic solvent parameters is nonlinear, suggesting the operation of both specific and nonspecific solvent–solvent–solute interaction mechanisms. Correlation of the experimental data with Kamlet–Taft solvatochromic parameters is excellent (100r² > 98%) and the results reveal that the reactivity is influenced by the preferential solvational effects. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 371–377, 2007     

Structure–property relationship of phenoxyimine ligands/metal chloride initiating systems for controlled cationic polymerizations of alkyl vinyl ethers

The catalyst structure–property relationships of the phenoxyimine complexes in controlled cationic polymerization of vinyl ethers were investigated based on the Hammett correlation. The correlation analyses of a series of experiments using the phenoxyimine ligands/TiCl₄ initiating systems indicated that the substituents on the N‐aryl phenoxyimine ligands affected the polymerization rate and stereoselectivity. Importantly, a linear correlation was observed between the Hammett substituent constants and the polymerization rates, which indicates that the Lewis acidity of the complex is affected by the electron‐withdrawing and ‐donating effects of the substituents. The tacticity of product polymers correlated to the Hammett substituent constants. Unlike the relationship with the polymerization rates, the σ^– values, which account for the enhanced resonance effects, were more appropriate for the relationship with the tacticity than the normal σ values. In contrast, the polymerization behavior using o‐substituted ligands exhibited a trend different from those using p‐ or m‐substituted ligands. The structural change, which was caused by the rotation of the C? N bonding, most likely triggered the acceleration effect in the case of the o‐substituents. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2021–2029     

Substituent effects in mass spectrometry—II. The effect of substituents on the dissociation of para and meta disubstituted benzenes

The effect of substituents on the activation energy for primary dissociation processes in the molecular ions of mono- and para and meta di-substituted benzenes has been examined. Where the daughter ion retains the substituent group, variation of the energy of activation derives from a combination of the effects of substituents on the ionisation potential of the molecular ion and the appearance potential of the daughter ion. An equation relating the energy of activation for the fragmentation of the molecular ion of a mono-substituted benzene to that of related para and meta di-substituted benzenes is presented.     

A correlation of substituent effects with proton chemical shifts in aromatic tetrazolic acids

The effect of substituents on the proton chemical shifts and spin–spin coupling constants in ortho-, meta- and para-substituted 5-phenyltetrazoles (tetrazolic acids) in DMSO–CH₃CN (1:1, v/v) was studied. With the meta- and para- substituted compounds the additivity rule of chemical shifts was obeyed, thereby enabling increments characterizing the effects of individual substituents in monosubstituted benzenes to be determined. By employing the Smith and Proulx equation, the chemical shifts of the aromatic protons were correlated with the F, R and Q substituent constants. The values of these constants are 1.02, ?0.004 and 5.49, respectively, for the tetrazolyl substituent.     

Ultrafast Spectroscopy of Hydroxy‐Substituted Azobenzenes in Water

Ultrafast UV/Vis pump/probe experiments on ortho‐, meta‐ and para‐hydroxy‐substituted azobenzenes (HO‐ABs), as well as for sulfasalazine, an AB‐based drug, were performed in aqueous solution. For meta‐HO‐AB, AB‐like isomerisation behaviour can be observed, whereas, for ortho‐HO‐AB, fast proton transfer occurs, resulting in an excited keto species. For para‐HO‐AB, considerable keto/enol tautomerism proceeds in the ground state, so after excitation the trans‐keto species isomerises into the cis form. Aided by TD‐DFT calculations, insight is provided into different deactivation pathways for HO‐AB, and reveals the role of hydroxy groups in the photochemistry of ABs, as well as their acetylation regarding sulfasalazine. Hydroxy groups are position‐specific substituents for AB, which allow tuning of the timescale of thermal relaxation, as well as the amount and contribution of the keto species to photochemical processes.     

Linear Free‐Energy Relationships Applied to the 13C NMR Chemical Shifts in 4‐Substituted N‐[1‐(Pyridine‐3‐ and ‐4‐yl)ethylidene]anilines

Two series of 4‐substituted N‐[1‐(pyridine‐3‐ and ‐4‐yl)ethylidene]anilines have been synthesized using different methods of conventional and microwave‐assisted synthesis, and linear free‐energy relationships have been applied to the ¹³C NMR chemical shifts of the carbon atoms of interest. The substituent‐induced chemical shifts have been analyzed using single substituent parameter and dual substituent parameter methods. The presented correlations describe satisfactorily the field and resonance substituent effects having similar contributions for C1 and the azomethine carbon, with exception of the carbon atom in para position to the substituent X. In both series, negative ρ values have been found for C1′ atom (reverse substituent effect). Quantum chemical calculations of the optimized geometries at MP2/6‐31G++(d,p) level, together with ¹³C NMR chemical shifts, give a better insight into the influence of the molecular conformation on the transmission of electronic substituent effects. The comparison of correlation results for different series of imines with phenyl, 4‐nitrophenyl, 2‐pyridyl, 3‐pyridyl, 4‐pyridyl group attached at the azomethine carbon with the results for 4‐substituted N‐[1‐(pyridine‐3‐ and ‐4‐yl)ethylidene]anilines for the same substituent set (X) indicates that a combination of the influences of electronic effects of the substituent X and the π₁‐unit can be described as a sensitive balance of different resonance structures.     

Proximity effects in pyridines. Proton chemical shifts in substituted methyl pyridinecarboxylates

Ring and ester proton chemical shifts in six series of substituted methyl pyridinecarboxylates have been measured. Results for ring protons ortho and para to the substituent can generally be accounted for by additive substituent, ester and nitrogen effects. Shifts for protons meta to the substituent, when compared with analogous shifts in monosubstituted benzenes, provide evidence of substituent–nitrogen interactions. In particular, a special effect is noted for series where both the proton and substituent are adjacent to the nitrogen. The origin of this effect is discussed. The ester proton results lead to essentially the same conclusions. Although this probe is much less sensitive to substituent effects, the same special effect is evident for the methyl 6-X-picolinate series.     

A stress tensor and QTAIM perspective on the substituent effects of biphenyl subjected to torsion

The Quantum Theory of Atoms in Molecules (QTAIM) defines quantities in 3D space that can be easily obtained from routine quantum chemical calculations. The present investigation shows that local properties can be related quantitatively to measures traditionally connected to experimental data, such as Hammett constants. We consider the specific case of substituted biphenyl to quantify the effects of a torsion φ, 0.0° ≤ φ ≤ 180.0°, of the C—C bond linking the two phenyl rings for C₁₂H₉‐x, where x = N(CH₃)₂, NH₂, CH₃, CHO, CN, NO_2, on the entire molecule. QTAIM interpreted Hammett constants, aΔH( r_b ) are introduced and constructed using the difference between the H( r_b ) value of C₁₂H₉‐x and the C₁₂H₉‐H, biphenyl which is the reference molecule, with a constant of proportionality a. This investigation unexpectedly yields very good or good agreement for the x groups with the Hammett para‐, meta‐, and ortho‐substituent constants and is checked against para‐substituted benzene. We then proceed to present the interpreted substituent constants of seven new biphenyl substituent groups, where tabulated Hammett substituent constant values are not available; y = SiH₃, ZnCl, COOCH₃, SO₂NH₂, SO₂OH, COCl, CB₃. Consistency is found for the QTAIM interpreted biphenyl substituent constants of the seven new groups y independently using the stress tensor polarizability P_σ. In addition, a selection of future applications is discussed that highlight the usefulness of this approach. © 2016 Wiley Periodicals, Inc.     

A Convenient Synthesis of N‐Aryl Benzamides by Rhodium‐Catalyzed ortho‐Amidation and Decarboxylation of Benzoic Acids

The rhodium‐catalyzed amidation of substituted benzoic acids with isocyanates by directed C?H functionalization followed by decarboxylation to afford the corresponding N‐aryl benzamides is demonstrated, in which the carboxylate serves as a unique, removable directing group. Notably, less common meta‐substituted N‐aryl benzamides are generated readily from more accessible para‐ or ortho‐substituted groups by employing this strategy.     

meta‐ and para‐Phenylenediamine‐Fused Porphyrin Dimers: Synthesis and Magnetic Interactions of Their Dication Diradicals

meta‐ and para‐Phenylenediamine‐fused nickel(II) porphyrin dimers were synthesized by S_NAr reaction of meso,β,β‐trichloro nickel(II) porphyrin with meta‐ and para‐phenylenediamines and subsequent Pd‐catalyzed intramolecular C?H arylation. Their tetrachlorinated dication diradicals are very stable, allowing SQUID magnetometry and revealing clear open‐shell characters for both meta and para isomers with ferro‐ and anti‐ferromagnetic interactions, respectively. The nitrogen analogue of Thiele's hydrocarbon usually displays predominant closed‐shell nature but its hidden diradical characters increase either in a twisted conformation or upon insertion of an additional phenylene spacer. The observed distinct diradical nature of the para‐congener indicates that diradical properties can be enhanced also by efficient spin delocalization.     

Haloaza‐closo‐dodecaboranes

The bromo‐ and iodoaza‐closo‐dodecaboranes HNB₁₁H₁₀Hal (Hal = Br, I), MeNB₁₁H₉Br₂, and MeNB₁₁H₈Br₃ are formed from [NB₁₁H₁₁]^– and MeNB₁₁H₁₁, respectively, by electrophilic halogenation with elementary halogen in the presence of acidic catalysts. Hydrogen in para‐ or in para‐ and meta‐position with respect to the cluster‐N atom is substituted by halogen. With iodine chloride as halogenation agent, all the 11 boron bound H atoms of MeNB₁₁H₁₁ are substituted to give HNB₁₁Cl₅I₆ with iodine in the para‐ and meta‐ and chlorine in the ortho‐positions, presumably via electrophilic (I) and nucleophilic substitution (Cl). The products are characterized by their NMR spectra, the product HNB₁₁Cl₅I₆ also by crystal structure analysis.     

Photoisomerization of Trans Ortho‐, Meta‐, Para‐Nitro Diarylbutadienes: A Case of Regioselectivity

A series of ortho‐, meta‐ and para‐substituted trans‐nitro aryl (phenyl and pyridyl) butadienes have been synthesized and characterized. The effect of substitution and positional selectivity on their fluorescence and photoisomerization were systematically investigated. Among all dienes, meta‐ and para‐nitro phenyl‐substituted derivatives exhibit remarkable solvatochromic emission shifts due to intramolecular charge transfer. On the other hand, ortho derivatives undergo regioselective isomerization upon photoexcitation in contrast to inefficient isomerization of para and meta nitro‐substituted dienes. Single crystal X‐ray analysis revealed existence of intramolecular hydrogen bonding between the nitro group and the hydrogen of the proximal double bond. This restricts the rotation of the proximal double bond thereby allowing regioselective isomerization. The observations were also supported by NMR spectroscopic studies.     

The stability of columns comprising alternating triphenylene and hexaphenyltriphenylene molecules: variations in the structure of the hexaphenyltriphenylene component

Previous investigations of complementary polytopic interaction (CPI) columnar mesophases, in which the columns are built up of alternating hexaalkoxytriphenylene (HAT) and hexaphenyltriphenylene (PTP) molecules, concentrated mainly on the effect of variations in the structure of the HAT component. This investigation is concerned with the effect of variations in the structure of the PTP component and, in particular, variations in the position of an alkoxy side chain in the phenyl ring. Stable columnar mesophases are obtained when a hexyloxy substituent is placed in the meta‐ or para‐position but not in the ortho‐position. In the case of the meta‐ and para‐substituted systems, the two‐component CPI columnar phases are stable over a considerably larger temperature range than the one‐component HAT systems. The evidence suggests that unfavourable PTP/PTP stacking is as much a driving force for the formation of these mixed stacks as is favourable PTP/HAT stacking, but both need to be explained in terms of the sum of atomically dispersed van der Waals and coulombic interactions. On cooling from the isotropic into the Col_h phase, the columnar phase based on a 1:1 mixture of hexakis(hexyloxy)tripenylene and the meta‐hexyloxy‐substituted PTP gives an unusual texture consisting of ‘viking‐axe’‐shaped structures.     

Synthesis of Chiral Pyridylphenols for the Enantioselective Addition of Diethylzinc to Aldehydes

Chiral 8‐substituted 2‐(8,10,10‐trimethyl‐6‐aza‐tricyclo[7.1.1.0^2,7]undeca‐2(7),3,5‐trien‐5‐yl)‐phenols were prepared from a high enantiopurity (>97% ee) of (1R)‐(+)‐α‐pinene, and assessed in the enantioselective addition of diethylzinc to substituted benzaldehydes, giving the (S)‐alcohols with enantiomeric excess ranging from 33% to 89%. Interestingly, in all cases, except for those of ortho‐chlorobenzaldehyde, ortho‐ and para‐methoxybenzaldehydes, the ee was >71%. The plot of the Hammett substitution constants vs. enantiomeric excess of the diethylzinc addition to either the ortho‐ or para‐substituted benzaldehydes shows a linear correlation.