Hammett Substituent Constants Research Articles

Infrared and <sup>13</sup>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 <sup>13</sup>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

Fine tuning of frontier orbital energy levels in dithieno[3,2-b:2′,3′-d]silole-based copolymers based on the substituent effect of phenyl pendants

A series of dithieno[3,2-b:2′,3′-d]silole-based π-conjugated copolymers containing thieno[3,4-c]pyrrole-4,6-dione or thieno[3,4-b]thiophene units bearing 4-substituted phenyl pendants were synthesized and their thermal stability, optical properties and frontier orbital energy levels were systematically investigated. The introduction of electron-withdrawing substituents on the phenyl rings lowered their frontier orbital energy levels without deteriorating their thermal and optical properties. By replacing an electron-donating methoxy group with an electron-withdrawing trifluoromethyl group, both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital energy levels of the polymers were deepened by more than 0.3 eV. A relatively linear relationship was observed between the HOMO energy levels and the Hammett substituent constants.

Spectral Correlations in some Substituted Styryl (<i>E</i>)-4-((2-Oxopropyl)Diazenyl) Benzoic Acids

A series of titled compounds were prepared and analyzed their purities by literature method. The infrared and NMR spectral group frequencies of the compounds were assigned and correlated with Hammett substituent constants, F and R constants using single and multi linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral frequencies was discussed.

Spectral Correlations in some Substituted Styryl (<i>E</i>)-4-((2-Oxopropyl)Diazenyl) Benzoic Acids

A series of titled compounds were prepared and analyzed their purities by literature method. The infrared and NMR spectral group frequencies of the compounds were assigned and correlated with Hammett substituent constants, F and R constants using single and multi linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral frequencies was discussed.

Spectral Correlation Analysis of Hammett Substituent Constants and Biological Activities of some (<i>E</i>)-1-(4-Phenoxyphenyl)-3-Phenylprop-2-en-1-Ones

A series of aryl chalcones have been synthesized from 4-phenoxyacetophonone with various substituted benzaldehydes. The purity of all chalcones has been checked using their physical constants and spectral data. These 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 chalcones have been studied using Bauer-Kirby method.

Infrared and NMR Spectral Hammett Correlations in 4-(2-Naphthyl)-5,6-Dihydro-6-(Substituted Phenyl)-<sup>4</sup>H-1,3-Oxazine-2-Amines

A series containing ten titled compounds have been synthesised and recorded the IR and NMR spectra. From the spectra the infrared νNH, C=N, C-O-C stretches, NMR chemical shifts of (δ, ppm) NH and C=N were assigned and correlated with Hammett substituent constants, F and R parameters using single regression analysis. From the results, the effects of substituent on the above spectral frequencies were discussed.

Spectral Correlation Analysis of Hammett Substituent Constants and Biological Activities of some (<i>E</i>)-1-(4-Phenoxyphenyl)-3-Phenylprop-2-en-1-Ones

A series of aryl chalcones have been synthesized from 4-phenoxyacetophonone with various substituted benzaldehydes. The purity of all chalcones has been checked using their physical constants and spectral data. These 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 chalcones have been studied using Bauer-Kirby method.

Infrared and NMR Spectral Hammett Correlations in 4-(2-Naphthyl)-5,6-Dihydro-6-(Substituted Phenyl)-<sup>4</sup>H-1,3-Oxazine-2-Amines

A series containing ten titled compounds have been synthesised and recorded the IR and NMR spectra. From the spectra the infrared νNH, C=N, C-O-C stretches, NMR chemical shifts of (δ, ppm) NH and C=N were assigned and correlated with Hammett substituent constants, F and R parameters using single regression analysis. From the results, the effects of substituent on the above spectral frequencies were discussed.

Novel Near‐Infrared Squaraine Sensitizers for Stable and Efficient Dye‐Sensitized Solar Cells

A new molecular design strategy for tuning the energy levels of cis‐configured squaraine sensitizers for dye‐sensitized solar cells is described. The Hammett substituent constant and the π‐conjugation length are used as quantitative indicators to modify the central squarate moiety of the sensitizer dyes; specifically, novel near‐infrared squaraine dyes HSQ3 and HSQ4 are synthesized by incorporation of an electron‐withdrawing and π‐extending ethyl cyanoacetate unit on the central squarate moiety. The solution absorption maximum of HSQ4 occurs at 703 nm, and the energy levels of the lowest unoccupied molecular orbital and the highest occupied molecular orbital are in the ideal range for energetically efficient electron injection and regeneration of the oxidized dye. A solar cell sensitized with HSQ4 exhibits a broad incident photo­n‐to‐current conversion efficiency spectrum, extending into the near‐infrared region with a maximum value of 80% at 720 nm, which is is the highest value reported for a squaraine dye–based dye‐sensitized solar cell. The HSQ4‐sensitized solar cell also exhibits excellent durability during light soaking, owing to the double anchors attaching the dye to the TiO2 surface and to the long alkyl chains extending outward from the surface.

Synthesis, IR and NMR spectral correlations in some symmetrical diimines

A series of diimines have been synthesized by coupling of diamine with substituted benzaldehydes. The purities of these diimines were checked by their analytical and spectroscopic data. The spectral frequencies νCN (cm-1), NMR chemical shifts (δ, ppm) of C-H and C=N of these diimines have been correlated with Hammett substituent constants, 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. KEY WORDS: Diimines, IR and NMR spectra, Spectral correlation, Hammett sigma constants Bull. Chem. Soc. Ethiop. 2014, 28(1), 73-79.DOI: http://dx.doi.org/10.4314/bcse.v28i1.9

Hammett Spectral Correlations in Benzofuranyl Flavonols

A series containing eleven benzofuranyl flavonols have been prepared by cyclization of 3-hydroxybenzofuranyl chalcones with 30% hydrogen peroxide in the presence of sodium bicarbonate. The synthesized flavonols were characterized by their physical constants, analytical and spectroscopic data. The infrared spectral νOH, CO stretches(cm-1), NMR chemical shifts of OH, CO(δ, ppm) of these flavonols were assigned and correlated with Hammett substituent constants, F and R parameters using single and multi linear regression analysis. From the results of statistical analyses, the effects of substituents on the above group frequencies were discussed.

Solvent-free one-pot cyclization and acetylation of chalcones: Synthesis of some 1-acetyl pyrazoles and spectral correlations of 1-(3-(3,4-dimethylphenyl)-5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-yl) ethanones

One-pot synthesis of some 1N-acetyl pyrazoles including 1-(3-(3,4-dimethylphenyl)-5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-yl) ethanones has been achieved via solvent-free microwave irradiation using substituted chalcones, hydrazine hydrate and acetic anhydride in the presence of catalytic amount of fly-ash: PTS catalyst. The yield of these 1N-acetyl pyrazole derivatives is more than 75%. The synthesized 1N-acetyl pyrazoline derivatives were characterized by their physical constants and spectral data. The infrared spectral νCN and CO (cm−1) frequencies, NMR chemical shifts (δ, ppm) of Ha, Hb, Hc, CH3 protons, CN, CO and CH3 carbons of 1-(3-(3,4-dimethylphenyl)-5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-yl) ethanones have been assigned and correlated with Hammett substituent constants and Swain-Lupton’s parameters using single and multi-regression analysis. From the results of statistical analyses, the effect of substituents on the above group frequencies and chemical shifts of the acetylated pyrazoles were discussed.

Hammett Spectral Correlations in Benzofuranyl Flavonols

A series containing eleven benzofuranyl flavonols have been prepared by cyclization of 3-hydroxybenzofuranyl chalcones with 30% hydrogen peroxide in the presence of sodium bicarbonate. The synthesized flavonols were characterized by their physical constants, analytical and spectroscopic data. The infrared spectral νOH, CO stretches(cm-1), NMR chemical shifts of OH, CO(δ, ppm) of these flavonols were assigned and correlated with Hammett substituent constants, F and R parameters using single and multi linear regression analysis. From the results of statistical analyses, the effects of substituents on the above group frequencies were discussed.

Post-Polymerization Electrochemical Functionalization of a Conducting Polymer: Diazonium Salt Electroreduction at Polypyrrole Electrodes

In this paper we report the functionalization of conductive polypyrrole (PPY) films via electrochemical reduction of the aryl diazonium salts in a manner that is similar to the one employed for other conductive surfaces. To understand the general trends of the grafting behavior of diazonium salts and to establish the optimal conditions for the covalent functionalization of the PPY films, we have compared the grafting behavior of four p-substituted phenyldiazonium salts: p-nitrophenyl diazonium tetrafluoroborate (PNBDBF4−), p-tolyl diazonium tetrafluoroborate (TDBF4−), p-fluorophenyl diazonium tetrafluoroborate (FPDBF4−) and 4-diazo-N,N-dimethylaniline tetrafluoroborate (DDMABF4−). The selection of the molecules to be grafted was done both for their electroactivity after grafting and the contrasted electronegativityof the substituents at the benzene ring. For all investigated diazonium salts, a linear relationship between their reduction potential at the PPY electrodes and Hammett substituent constants was obtained, suggesting a similar electrochemical reaction mechanism. The functionalization of the polypyrrole films has been evaluated using electrochemical methods like EQCM, CV and EIS. The presence at the polymeric films surface of the functional groups introduced by the electrochemical reduction of diazonium salts was evidenced also by XPS. This approach enables new functionalities on PPY that could otherwise not withstand the polymerization conditions.

CuAAC and RuAAC with Alkyne-functionalised Dihydroazulene Photoswitches and Determination of Hammett σ-Constants for Triazoles

Dihydroazulene (DHA)–vinylheptafulvene (VHF) photoswitches have attracted attention as potentially useful components in molecular electronics. The π-conjugated dihydroazulene system is a rigid structure and can be strategically functionalised to place handles for further elaboration. Here we show that alkyne-functionalised dihydroazulenes can be subjected to copper and ruthenium catalysed azide–alkyne cycloadditions (CuAAC and RuAAC) with tolylazide, furnishing 1,4- and 1,5-disubstituted triazoles. The rates of ring-closure of the corresponding vinylheptafulvenes were compared with those of reference systems, which allowed determination of Hammett substituent constants (meta and para) for N-tolyl-substituted 1,2,3-triazoles.

Solvent-Free Synthesis and Assessment of Substituent Effects from IR & NMR Spectra of some Substituted Benzylidene-5-Ethyl-1,3,4-Thiadiazole-2-Amines

A series containing ten titled compounds were synthesized by SiO2:H3PO4 catalyzed solvent-free condensation of substituted benzaldehydes and 2-amino-5-ethyl-1,3,4-thiadiazole under microwave irradiation. The yields of prepared amines are more than 90%. The synthesized amines were characterized by their physical constants and spectroscopic data reported in literature earlier for known compounds. The assigned spectral group frequencies such as infrared νC=N, C-S-C, N-N (cm-1) and NMR chemical shifts (δ, ppm) of CH, C=N have been correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. From the results of statistical analyses, the effects of substituent on the above spectral data have been discussed.

Spectroscopic and quantum chemical investigations of substituent effects on the azo-hydrazone tautomerism and acid–base properties of arylazo pyridone dyes

A series of 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone dyes was synthesized and the structure of the dyes was confirmed by UV–Vis, FT-IR, 1H NMR and 13C NMR spectroscopic techniques. The azo-hydrazone tautomeric equilibrium was found to depend on the substituents as well as on the acidity and basicity of the media. Ionization constant, pKa, of the dyes was determined by UV–Vis spectroscopy and correlated with the Hammett substituent constants, σp and σI. The interpretation of the effect of different substituent in phenyl ring of arylazo pyridone dyes on their spectroscopic and structural properties was based on quantum chemical calculations performed by the density functional theory (DFT/M06-2X) method. The DFT calculations confirmed the existence of two forms in water solution: hydrazone form in acidic and neutral media and anionic form in basic media. The different contribution of azo and hydrazone canonical forms of anionic form is observed for dyes with electron-donating and dyes with electron-withdrawing groups. The dependence of absorption spectra and determined pKa values to the substituent type seems to be mostly due to azo/hydrazone canonical structure ratio in their anionic form.

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.

Solvent-Free Synthesis and Assessment of Substituent Effects from IR & NMR Spectra of some Substituted Benzylidene-5-Ethyl-1,3,4-Thiadiazole-2-Amines

A series containing ten titled compounds were synthesized by SiO2:H3PO4 catalyzed solvent-free condensation of substituted benzaldehydes and 2-amino-5-ethyl-1,3,4-thiadiazole under microwave irradiation. The yields of prepared amines are more than 90%. The synthesized amines were characterized by their physical constants and spectroscopic data reported in literature earlier for known compounds. The assigned spectral group frequencies such as infrared νC=N, C-S-C, N-N (cm-1) and NMR chemical shifts (δ, ppm) of CH, C=N have been correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. From the results of statistical analyses, the effects of substituent on the above spectral data have been discussed.