Influence of substituent position in aromatic diamines on coumarin derivative

Abstract

The Influence of substituent position in aromatic diamines such as ortho-phenylenediamine (OPD) and para-phenylenediamine (PPD) on 7-methoxy-4-azido methyl coumarin (7MCA) has been studied in different solvents. A hypsochromic shift in the absorption maximum of 7MCA in the presence of aromatic diamine indicates the formation of the complex. From the 1H NMR study, it is understood that there is an H-bonding between the NH2 proton of OPD and 7MCA. A shift in the N–H stretching band of OPD observed in FT-IR spectra towards lower frequency indicates H-bonding between 7MCA and OPD. But the nature of the interaction between PPD and 7MCA cannot be determined from NMR and FT-IR study. Non-linear S-V plots obtained from the fluorescence quenching study reveals the involvement of both static and dynamic quenching processes. The value of the quenching rate parameter for para-phenylenediamine is more than ortho-phenylenediamine in protic solvents. But the value of the quenching rate parameter for ortho-phenylenediamine is more than its para isomer in aprotic solvents. Electrochemical analysis reveals that there is no electron transfer from these amino anilines to coumarin derivatives. The Nature of force between 7MCA and aromatic diamine (OPD and PPD) is hydrophobic in methanol since the change in enthalpy and entropy are positive but these thermodynamic parameters have negative values in DMF solvent indicating, a weak van der Waals force between 7MCA and amino anilines.