Title: UV, FTIR and DFT studies of Pyrazolines in polar protic and polar aprotic solvent mixtures
Abstract:UV and FTIR spectroscopic studies containing 0.01 and 0.001m some Pyrazolines with electron donating and withdrawing groups were done in 10 -90% (w/w) methanol (ME) in DMSO/DMF solvent mixtures at roo...UV and FTIR spectroscopic studies containing 0.01 and 0.001m some Pyrazolines with electron donating and withdrawing groups were done in 10 -90% (w/w) methanol (ME) in DMSO/DMF solvent mixtures at room temperature.The λmax of solutes vary with the % of ME.The decrease was more in ME + DMSO than in ME + DMF.The amount of blue shift (lower wave length) has been used as a measure to the strength of hydrogen bond.Absence of n →* excitation in solute + ME + DMSO/ DMF was ascribed due to hydrogen bond formation.An irregular trends in OH, C=O, S=O, C-Cl ,C-H ,NH etc. with increase of ME in solution at a particular concentration of solute indicated structure of the medium changed with ME content.In certain compositions of 0.01 and 0.01m, no changes in vibration frequencies were detected.OH/NH for Pyrazolines in both concentrations (0.01 and 0.001m) in all ME + DMF are greater than those of ME + DMSO, thereby indicating possibility of intramolecular hydrogen within Pyrazolines and intermolecular hydrogen bond among solvent molecule Hydrogen bond formation of ME with C-Cl of Pyrazolines was well supported by shifting of normal C=O to 1650 -1640 cm -1 .Geometry optimizations of heterocyclic compounds, pure solvents and their 1:1 and 1:1:1 complex were carried out using the DFT/B3LYP method with medium size 6-31G(d) basis set available in G03(W) series of programs All optimized geometries were viewed through Gauss View 4.1 software to know exact nature of intermolecular interaction.Read More