Swain-Lupton Parameters Research Articles

Synthesis of novel 1,2,4-oxadiazine derivatives and the substituent effect study on 13C NMR spectra

In this study, eight mostly new 6-Methyl-4-phenyl-3-(substituted-phenyl)-4H-1,2,4-oxadiazin-5(6H)-one (OXA-ON) and eight new 6-Methyl-4-phenyl-3-(substituted-phenyl)-4H-1,2,4-oxadiazine-5(6H)-thione (OXA-TY) were synthesized. The synthesized heterocycle structures were characterized by IR, 1H NMR, 13C NMR and HRMS analyses. The carbons of interest in the OXA-ON and OXA-TY compounds are CH3, CH, C=N and C=O (C=S). The 13C NMR experimental chemical shifts (ppm) (SCS) of the CH3, CH, C=N, C=O (C=S) carbons of these OXA-ON and OXA-TY derivatives were correlated with the Hammett substitution constants and Swain-Lupton parameters, using the single substituent parameter (SSP) and dual substituent parameter (DSP) methods. Negative ρ values were detected for C=N and C=O carbons in OXA-ON derivatives and for C=N and C=S carbons in OXA-TY derivatives (reverse substituent effect). Positive ρ values were detected for CH carbon in OXA-ON derivatives and for CH3 and CH carbons in OXA-TY derivatives (normal substituent effect). According to the results of all statistical analyses, SCS (ppm) values of C=N, C=O carbons of OXA-ON derivatives, and C=N, C=S carbons of OXA-TY derivatives showed excellent correlation. The SCS (ppm) of CH carbon of OXA-ON and the CH3 and CH carbons of OXA-TY showed good correlation. The excellent and good correlations implied that the substituent effects are electronic in nature.

Fine-tuning of the spin-crossover properties of Fe(III) complexes via ligand design.

Exploring the chemical space of a given ligand aiming to modulate its ligand field strength is a versatile strategy for the fine-tuning of physical properties such as the transition temperature (T1/2) of spin-crossover (SCO) complexes. The computational study presented herein aims at systematically exploring the extent to which the ligand substituent effects can modulate T1/2 in two families of Fe(III) SCO systems with a N4O2 coordination environment and at identifying the best descriptors for fast and accurate prediction of changes in T1/2 upon ligand functionalization. B3LYP* calculations show that the attachment of substituents to β-ketoiminato fragments (L1) leads to drastic changes in T1/2, while functionalization of phenolato moieties (L2) allows for a finer degree of control over T1/2. Natural Bond Orbital (NBO) charges of the donor atoms, Hammett parameters for both para and meta-functionalization of L2, and Swain-Lupton parameters for L1 and para-functionalization of L2 have been found to be the suitable descriptors for predicting the changes in T1/2. Further analysis of the ligand-field splitting in such systems rationalizes the observed trends and shows that ligand substituents modify both the σ and π bonds between the Fe(III) center and the ligands. Thus, we provide simple yet reliable guidelines for the rational design of new SCO systems with specific values of T1/2 based on their ligand design.

Molecular electrostatic potential as a general and versatile indicator for electronic substituent effects: statistical analysis and applications.

It is necessary to quantitatively determine substituent effects to accurately elucidate reaction mechanisms in the field of organic chemistry. This paper reports that the molecular electrostatic potential (MESP) can be used as a general and versatile measure for the substituent effects in various chemical reactions by performing extensive density functional theory (DFT) calculations for more than 400 molecules, followed by statistical analyses. We observed a robust and linear correlation between the electrostatic potential and the substituent parameters for various cases of reactive systems, regardless of the DFT functionals, basis sets, and solvation models used. In addition, we statistically analysed the normality of the residuals from the linear regression to demonstrate that strong linear relationships hold universally, which indicates that the electrostatic potential can serve as a physically meaningful quantity for the predictive estimation of substituent effects. In contrast, conventionally used methods based on the charge deviation in the aromatic carbons, as computed using various charge analysis methods, (e.g., Hirshfeld charge analysis) do not demonstrate the statistical normality. Furthermore, we illustrate that MESP can be extensively adopted to strengthen the validity of the linear free energy relationships (LFERs) under various chemical conditions. The results revealed that the MESP shift derived by a functional group on a mono-substituted benzene ring is a strong predictor for the substituent effects on the electronic behaviours in chemical reactions; thus, it can serve as an alternative to other empirical parameters such as the Hammett or Swain-Lupton parameters, or the charge shift.

Synthesis and substituent effect study on 13C NMR chemical shifts of 4-(substitue-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one

The twelve novel 4-(substituted-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one derivatives were synthesized by the reactions of N-Substituted-phenyl-benzamide oximes with 2-bromopropionyl chloride. The synthesized 1,2,4-oxadiazin-5-one derivatives were characterized by their physical constants and IR, 1H NMR, 13C NMR and LC/TOF-MS analyses data. The experimental 13C NMR chemical shifts (ppm) (SSC) of the C=O, C=N, CH and CH3 carbons of these 1,2,4-oxadiazin-5-one derivatives were correlated with the various Hammett substitution constants and Swain-Lupton parameters, using single (SSP) and multi-linear (DSP) regression analysis. Negative ρI and ρR values were found for correlations of C=O, C=N and CH3 carbons (reverse substituent effect). For the other carbon (CH), positive ρI (normal substitution effect) and negative ρR (reverse substitution effect) values were calculated by DSP regression analysis. As a result of DSP regression analysis, the 13C NMR chemical shift of the C=O, C=N and CH carbons of the oxadiazine ring showed a satisfactory correlation (r > 0.90), while excellent correlation was observed at the CH3 carbon (r = 0.99). The 13C NMR chemical shift values of the C=O, C=N, CH and CH3 carbons of the p-Br-substituted 1,2,4-oxadiazin-5-one derivative were estimated using the equations obtained by the DSP regression analysis. These predicted 13C NMR chemical shifts were compared with experimental 13C NMR chemical shifts for 4-(4-bromophenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazine-5(6H)-one derivatives.

Substituent effect study on the experimental 13C NMR chemical shifts of 3-(substituted phenyl)-3a,4,8,8a-tetrahydro-1,3-dioxepino[5,6-d] [1,2] isoxazoles

Novel heterocyclic derivatives containing isoxazole ring were synthesized by the 1,3-dipolar cycloaddition reaction of substituted nitrile oxides with cis-4,7-dihydro-1,3-dioxepin in the present study. These 3-(substituted phenyl)-3a,4,8,8a-tetrahydro-1,3-dioxepino[5,6-d] [1,2] isoxazole derivatives were characterized by their physical constants and IR, 1H NMR, 13C NMR and HRMS data. 13C NMR spectra of studied molecules were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced experimental 13C NMR chemical shifts (δ, ppm) (SSC) of C=N, C4, C5, C7, C9 and C10 carbons of these isoxazole derivatives have been correlated with various Hammett substituent constants, and Swain-Lupton parameters using single (SSP) and multi-linear (DSP) regression analysis. Negative ρ values were found for correlations of C=N, C4 and C5 carbons. The other carbons were found to have positive ρ values for the electronic effect of substituent on 13C NMR chemical shifts.

Predictable Substituent Control of CoIII/II Redox Potential and Spin Crossover in Bis(dipyridylpyrrolide)cobalt Complexes.

A family of five easily prepared tridentate monoanionic 2,5-dipyridyl-3-(R1)-4-(R2)-pyrrolide anions (dppR1,R2)-, varying in the nature of the R1 and R2 substituents [R1, R2 = CN, Ph; CO2Et, CO2Et; CO2Me, 4-Py; CO2Me, Me; Me, Me], has been used to generate the analogous family of neutral [CoII(dppR1,R2)2] complexes, two of which are structurally characterized at both 100 and 298 K. Both the oxidation and spin states of these complexes can be switched in response to appropriate external stimuli. All complexes, except [CoII(dppMe,Me)2], exhibit gradual spin crossover (SCO) in the solid state, and SCO activity is observed for three complexes in CDCl3 solution. The cobalt(II) centers in the low spin (LS) complexes are Jahn-Teller tetragonally compressed along the pyrrolide-Co-pyrrolide axis. The complexes in their high spin (HS) states are more distorted than in the LS states, as is also usually the case for SCO active iron(II) complexes. The reversible CoIII/II redox potentials are predictably tuned by choice of substituents R1 and R2, from -0.95 (Me,Me) to -0.45 (CN,Ph) V vs Fc+/Fc, with a linear correlation observed between E1/2(CoIII/II) and the Swain-Lupton parameters of the pyrrolide substituents.

How Do Amides Affect the Electronic Properties of Pyrene?

The electronic properties of amide linkers, which are intricate components of biomolecules, offer a wealth of unexplored possibilities. Herein, we demonstrate how the different modes of attaching an amide to a pyrene chromophore affect the electrochemical and optical properties of the chromophore. Thus, although they cause minimal spectral shifts, amide substituents can improve either the electron-accepting or electron-donating capabilities of pyrene. Specifically, inversion of the amide orientation shifts the reduction potentials by 200 mV. These trends indicate that, although amides affect to a similar extent the energies of the ground and singlet excited states of pyrene, the effects on the doublet states of its radical ions are distinctly different. This behavior reflects the unusually strong orientation dependence of the resonance effects of amide substituents, which should extend to amide substituents on other types of chromophores in general. These results represent an example where the Hammett sigma constants fail to predict substituent effects on electrochemical properties. On the other hand, Swain–Lupton parameters are found to be in good agreement with the observed trends. Examination of the frontier orbitals of the pyrene derivatives and their components reveals the underlying reason for the observed amide effects on the electronic properties of this polycyclic aromatic hydrocarbon and points to key molecular-design strategies for electronic and energy-conversion systems.

Synthesis, Evaluation of Substituent Effect and Antimicrobial Activities of Substituted (E)-1-(3-bromo-4-morpholinophenyl)-3-phenylprop-2-en-1-one Compounds

A series of ten substituted (E)-1-(3-bromo-4-morpholinophenyl)-3-phenylprop-2-en-1-one compounds were synthesized by Crossed-Aldol condensation of 3-bromo-4-marpholino acetophenone with various substituted and unsubstituted benzaldehydes in presence of sodium hydroxide. The entire ten compounds are novel and these have been newly synthesized compounds. The synthesized substituted 3-phenylprop-2-en-1-one were characterized by their physical constants and UV, IR, NMR spectral data. These observed UV absorption maximum (λ max nm) value. The group frequencies of infrared absorption (cm -1 ) of νCO s-cis and s-trans, deformation modes of νCH out of plane and in-plane, νCH=CH out of plane, ν>C=C<out of plane values, 1 H chemical shifts (ppm) vinyl protons, 13 C chemical shifts (ppm) carbonyl carbons and vinyl carbons values were correlated with various Hammett substituent constants, and Swain-Lupton parameters using single and multi-regression analyses. From the results of statistical analysis, the effects of substituents on the functional group frequencies were studied. The antimicrobial activities of these synthesized substituted (E)-1-(3-bromo-4-morpholinophenyl)-3-phenylprop-2-en-1-ones have been screened using Kirby-Bauer method. DOI: http://dx.doi.org/10.17807/orbital.v9i1.852

A high‐level theoretical study into the atmospheric phase hydration, bond dissociation enthalpies, and acidity of aldehydes

CBS‐Q//B3, G4(MP2), and G4 composite method calculations were used to estimate atmospheric phase standard state (298.15 K, 1 atm) free energies of hydration (ΔhydrG°(g)), hydration equilibrium constants (log Khydr,(g)), bond dissociation enthalpies (BDEs), and enthalpies (ΔdH°(g)) and free energies (ΔdG°(g)) of aldehydic proton acid dissociation for various substituted aldehydes with electron withdrawing and electron releasing groups. Good quality log Khydr,(g) correlations with the Swain–Lupton resonance effect parameters R and R+ were found, allowing extension of the model to predict log Khydr,(g) values for 487 substituted aldehydes having available R‐values and 108 substituted aldehydes having available R+ values. Good correlations were also found between experimental aqueous phase hydration equilibrium constants (log Khydr,(aq)) and summative R/R+ values for peripheral substituents on a range of carbonyl derivatives (aldehydes, ketones, esters, and amides), suggesting that the structure–reactivity modeling approach can be extended to include all possible combinations of R1C(O)R2 carbonyl substitution in both gas and aqueous systems. Computationally derived BDEs and ΔdH°(g)/ΔdG°(g) were in good agreement with the limited experimental and theoretical datasets. BDEs did not generally correlate with any of the Hammett substituent constants or Swain–Lupton parameters considered. Gas phase acidities exhibited high correlation coefficients with Hammett inductive substituent constants (σI) and field effect parameters (F), allowing these to be employed as surrogates for estimating the gas phase aldehydic proton acidities of a larger potential compound range. The resulting models will be of use in predicting the environmental behavior for a broad range of environmentally relevant compounds containing carbonyl functionalities. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Correlation analysis and antimicrobial activities of substituted aryl imines

Substituted (E)-N-(4-bromobenzylidene) benzeneamines were synthesized using Fly-ash:PTS catalyzed solvent free reaction between 4-bromoaniline and substituted benzaldehydes. The synthesized Schiff's bases were characterized by UV, IR, 1H, and 13C NMR spectral data. These data were correlated with various Hammett substituent constants, F and R Swain-Lupton parameters using single and multi-regression analysis. From the results of statistical analysis, the effects of the substituents were studied. The antimicrobial activities of all the synthesized Schiff's bases were studied. The results of the study demonstrated the reaction protocol to be simple, eco-friendly, non-hazardous with easier work-up procedure and good yield. Good antimicrobial activity was observed in all imines against bacterial and fungal strains.

Infrared and &lt;sup&gt;13&lt;/sup&gt;C NMR Spectral Studies of some Aryl Hydrazides: Assessment of Substituent Effects

A series of some aryl hydrazides have been synthesized. These hydrazides purities were analyzed by physical constants and spectral data. The assigned spectral group frequencies were correlated with Hammett substituent constants and Swain-Lupton parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the spectral group frequencies has been discussed

Infrared and &lt;sup&gt;13&lt;/sup&gt;C NMR Spectral Studies of some Aryl Hydrazides: Assessment of Substituent Effects

A series of some aryl hydrazides have been synthesized. These hydrazides purities were analyzed by physical constants and spectral data. The assigned spectral group frequencies were correlated with Hammett substituent constants and Swain-Lupton parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the spectral group frequencies has been discussed

SiO2-H2SO4 catalysed, microwave-assisted cyclization cum acetylation of 2-propenones under solvent-free condition: Synthesis and spectral correlations of some 1-acetyl pyrazolines

Some 1N-acetyl pyrazoles, including 3-phenyl-(5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-yl)ethanones, were synthesized by solvent-free cyclization cum acetylation of chalcones of substituted styryl phenyl ketones with hydrazine hydrate and acetic anhydride in the presence of a SiO2-H2SO4 catalyst. The yield of these N-acetyl pyrazole derivatives was greater than 80%. The synthesized derivatives were characterized by their physical constants and spectral data. The infrared spectral νCN and CO (cm−1) frequencies, nuclear magnetic resonance chemical shifts (δ, ppm) of Ha, Hb, Hc, CH3 protons, CN, CO and CH3 carbons of 3-phenyl-(5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-yl)ethanones were assigned and correlated with Hammett substituent constants and Swain–Lupton parameters by single and multiple regression analyses. The results of the statistical analyses indicated that the substituents affect the frequencies and chemical shifts of acetylated pyrazoles.

Synthesis, Spectral Correlations and Biological Evaluation of Some Aryl (E)-N-Benzylidene-3-nitrobenzenamines

Assessment of substituent effects in a series of aryl imines through spectral correlation has been studied since they have close pharmacological association with diverse pharmacological properties. A series of aryl imines have been synthesized from 3-Nitro aniline with various substituted benzaldehydes were refluxed for 4h with 20 mL of absolute ethanol. The purity of all imines has been checked using their physical constants and spectral data. The UV λmax(nm), infrared νC=N(cm -1 ), NMR δ(ppm) of CH=N and C=N spectral data have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. The single parameter correlation with few Hammett constants and F and R parameters gave satisfactory correlation coefficients whereas all multiple correlations gave satisfactory correlation coefficients with Resonance, Field and Swain-Lupton's parameters. The antimicrobial activities of all imines have been studied using Bauer-Kirby method. Aryl imine compounds with 2-Cl, 4-Br and 2-OCH3 substituents have shown good antibacterial activity against S.aureus and those with 3-NO2 and 4-NO2 substituents have shown good antifungal activity against T.viridi.,

Spectral correlation, antimicrobial and insect antifeedant activities of some 1-naphthyl keto-oxiranes

Thirteen optically active (αS,βR) 1-naphthyl keto-oxiranes (1-naphthyl-4-yl[3-(substituted phenyl)oxiran-2-yl]methanones) have been synthesised by phase transfer catalysed epoxidation of 1-naphthyl chalcones. The yields of oxiranes are more than 95%. The synthesized oxiranes have been characterized by IR, 1H, 13C and MS spectra. The spectral data are correlated with Hammett substituent constants and Swain–Lupton parameters. From the regression analysis the effect of substituent on the group frequencies has been predicted. The antimicrobial and insect antifeedant activities of all synthesised oxiranes have been evaluated.

IR and NMR spectral studies of some 2-hydroxy-1-naphthyl chalcones: Assessment of substituent effects

A series of substituted styryl 2-hydroxy-1-naphthyl ketones have been synthesized by crossed-Aldol condensation reaction. These ketones are characterized by their physical constants, IR and NMR data. The IR carbonyl stretching and deformation modes ν (cm−1) of vinyl portion frequencies and 1H and 13C NMR spectral chemical shifts δ (ppm) of ethylenic protons, carbons and carbonyl carbons are correlated with various Hammett sigma constants, field, and resonance and Swain–Lupton parameters by single and multi-regression analysis. From the statistical analysis the effect of substituents on the group frequencies is studied.

Synthesis, spectral studies, antimicrobial, antioxidant and insect antifeedant activities of some 9 H-fluorene-2-yl keto-oxiranes

Thirteen ee (α S, β R) 9 H-fluorene-2-yl keto-oxiranes (2-(9 H)-fluorene-4-yl[3-(substituted phenyl)oxiran-2-yl]methanones) have been synthesized by phase transfer catalysed epoxidation of 9 H-fluorene-2-yl chalcones. The yields of oxiranes are more than 95%. The synthesized oxiranes have been characterized by IR, 1H, 13C and GC–MS spectral data. The spectral data are correlated with Hammett substituent constants and Swain–Lupton parameters. From the regression analysis, the effect of substituents on the group frequencies has been predicted. The antimicrobial, antioxidant and insect antifeedant activities of all the synthesized oxiranes have been studied.

Synthesis, spectral studies, antimicrobial and insect antifeedant potent keto oxiranes

A series of ee (αS, βR) biphenyl keto oxiranes (biphenyl-4-yl[3-(substituted phenyl)oxiran-2-yl]methanones) have been synthesized by phase transfer catalysed epoxidation of biphenyl 2E-chalcones. The yields of oxiranes are more than 95%. The synthesized oxiranes have been characterized by IR, 1H, 13C and GC–MS spectra. The spectral data are correlated with Hammett substituent constants and Swain–Lupton parameters. From the regression analyses, the effect of substituent on the group frequencies has been predicted. The antimicrobial and insect antifeedant activities of all synthesized oxiranes have been evaluated.

Gas phase hydration, bond dissociation enthalpies, and acidity of aldehydes: A CBS-Q//B3, G4MP2, and G4 theoretical study of substituent effects

AbstractCBS-Q//B3, G4MP2, and G4 composite method calculations were used to estimate gas phase standard state (298.15 K, 1 atm) free energies of hydration (Δ~hydr~G°~(g)~), hydration equilibrium constants (log K~hydr,(g)~), bond dissociation enthalpies (BDEs), and enthalpies (Δ~d~H°~(g)~) and free energies (Δ~d~G°~(g)~) of aldehydic proton acid dissociation for various substituted aldehydes with electron withdrawing and electron releasing groups. Good quality log K~hydr,(g)~ correlations with the Swain-Lupton resonance effect parameters R and R^+^ were found, allowing extension of the model to predict log K~hydr,(g)~ values for 487 substituted aldehydes having available R-values and 108 substituted aldehydes having available R^+^-values. Good correlations were also found between experimental aqueous phase hydration equilibrium constants (log K~hydr,(aq)~) and summative R/R^+^-values for peripheral substituents on a range of carbonyl derivatives (aldehydes, ketones, esters, and amides), suggesting the structure-reactivity modeling approach can be extended to include all possible combinations of R~1~C(O)R~2~ carbonyl substitution in both gas and aqueous systems. Computationally derived BDEs and Δ~d~H°~(g)~ / Δ~d~G°~(g)~ were in good agreement with the limited experimental and theoretical datasets. BDEs did not generally correlate with any of the Hammett substituent constants or Swain-Lupton parameters considered. Gas phase acidities exhibited high correlation coefficients with Hammett inductive substituent constants (σ~I~) and field effect parameters (F), allowing these to be employed as surrogates for estimating the gas phase aldehydic proton acidities of a larger potential compound range.

Correlations between 13C NMR chemical shifts of [(1-R-η3-C3H4)PdCl]2 and Na[(1-R-η3-C3H4)PdCl2] and substituent constants

Linear correlations between 13C NMR chemical shifts of unsubstituted terminal carbon atom of the allylic ligand in [(1-R-η3-C3H4)PdCl]2 and Na[(1-R-η3-C3H4)PdCl2] and the modified Hammett constants were established. Two-parameter correlations using the Swain-Lupton parameters R+, R−, and F were obtained.