Synthesis, Spectral Correlations and Antimicrobial Activities of 2-Pyrimidine Schiff’s Bases

Abstract

ABSTRACT. In the present study, a series of substituted (E)-N-benzylidene-2-aminopyrimidine compounds have been synthesized by condensation reaction with 2-aminopyrimidine and meta-and para-substituted benzaldehydes. These synthesized Schiff's base compounds are confirmed by their physical constants, UV, IR and NMR spectral data. All the observed UV absorption maximum λ max (nm), IR frequencies νC=N(cm -1 ), NMR δ(ppm) of C-H & C=N chemical shifts have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analyses in order to study the effect of substituents on these spectral data has been studied. The antimicrobial activities of all the synthesized Schiff's base compounds have been studied using Bauer-Kirby disc diffusion method. 1.INTRODUCTION Schiff's bases are an important class of organic compounds possessing biological activities and structural significance. It has been proved that the incorporation of this molecule into the biologically active azomethine linkage (-CH=N-) produces compounds with high pharmacological activity [1]. Schiff's bases are represented by the general formula RCH=NR' where >C=N is the azomethine group [2]. The colour of the Schiff's bases is due to the presence of this azomethine (>C=N) linkage and can vary by introducing other auxochromic groups. When functional groups, such as -OH, -SH, -COOH are present in these ligands in suitably tailored positions, they enable them to be powerful chelating, biological and analytical reagents. On this basis of such groups present, the Schiff's bases may be di, tri, tetra or polydentate in nature. Compounds containing azomethine group are basic in nature, as N atom of this group has a lone pare of electrons and the double bond has electron donating character. Schiff's bases displayed the phenomenon of tautomeris[3], thermochromy and photochromy[4] and geometrical isomerism [5]. They possess both types of hydrogen bonding i.e. intra-molecular as well as inter-molecular [6]. Schiff's bases are widely studied and used in the fields of organic synthesis and metal ion complexation [7] for a number of reasons: their physiological and pharmacological activities [8] their use in ionselective electrodes [9] in the determination of heavy metals ions in environmental samples [10] and in the extraction of metals ions [11,12] and their many catalytic applications (e.g. for epoxidation of olefins, alkene cyclopropanation [13,14] trimethylsilylcyanation of ketones [15] asymmetric oxidation of methyl phenyl sulfide enantioselective epoxidation of silylenol [16] and ring-opening polymerization of lactide [17]. In recent years, correlation analysis has been applied by chemists for solving the effect of substituents on Schiff's bases through spectral data. Literature survey shows that there is no information available regarding the study of UV, IR and NMR spectral correlation and antimicrobial activities of substituted (E)-N-benzylidene-2-aminopyrimidine compounds. Hence the authors have taken efforts fo...

Spectral LFER Studies on Some Sydnone Chalcones

“…The general structure of (E)-4-(N-(4-cinnamoylphenyl)sulfamoyl)-3-(p-tolyl)-1,2,3-oxadiazol-3-ium-5-olates are shown in Fig.1. [13][14][15][16][20][21][22][23][24][25][26][27][28][29][30][31]of these data with Hammett substituent constants and Swain-Lupton's [33] parameters. In this correlation, the Hammett equation was taken in the form as(1).…”

“…The Chemical shifts (δ, ppm) of vinyl protons, NH and methyl protons of synthesised sydnone chalcones were presented in Table 3. These chemical shifts(δ, ppm) have been correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis [13][14][15][16][20][21][22][23][24][25][26][27][28][29][30][31][32]. In this correlation the Hammett equation was taken in the form as (20) δ = ρσ + δ o (20) where δ o is the frequency for the parent member of the series.…”

“…The spectral correlation of infrared and carbon-13 NMR data of quinoxaline and phenazine derivatives were studied by Thirunaryanan et al [27,28]. Senbagam et al, have studied the effects of substituents on some substituted (E)-N-benzylidene-4H-1,2,4-triazol-4-amines [29]. Vijayakumar et al, have investigated the spectral correlation analysis on some (E)-2-benzylidenehydrazine carbothioamides [30].…”

Synthesis, Hammett Spectral Correlations and Antimicrobial Activities of (<i>E</i>)-1-Benzylidene-2-(4-Chlorophenyl)Hydrazines

“…The results of statistical analysis [34][35][36][37] are shown in Table 2. From Table 2, it is evident that the UV absorption maximum λ max (nm) values of all the substituted (E)-1-benzylidene-2-(4-chlorophenyl)hydrazines have shown poor correlations (r < 0.900) with Hammett substituent constants namely, σ, σ + , σ I, σ R and F and R parameters.…”

“…The assigned infrared stretching frequency νC=N (cm -1 ) values of all the substituted (E)-1-benzylidene-2-(4-chlorophenyl)hydrazines are presented in Table- The results of the statistical analysis [34][35][36][37] are presented in 1-benzylidene-2-(4-chlorophenyl)hydrazines, except those with 3-NO 2 substituent have shown satisfactory correlations with Hammett constant σ R (r =0.906) and Swain-Lupton R (r =0.907) parameters. When these substituents that have been given exception are included in regression they reduce the correlations considerably.…”