Synthesis and spectroscopic studies of some naphthalimide based disperse azo dyestuffs for the dyeing of polyester fibres

A series of monoazo disperse dyestuffs derived from some naphthalimide derivatives were prepared. 4-Amino-N-methyl (alternatively N-ethyl, N-propyl, N-butyl) derivatives of naphthalimide were used as the diazo components and β-naphthol, N,N-diethyl-m-toluidine and p-aminoacetophenone constituted the coupling components.The various 4-aminonaphthalimide derivatives mentioned above were all prepared by standard reactions from acenaphthene as the starting material. The reaction conditions were varied in order to obtain optimal yields for each stage of the preparation to obtain the corresponding 4-aminonaphthalimide derivative as the diazo component which was subsequently purified. The coupling components were purchased and were of analytical grade. Diazotisation and coupling reactions were carried out in order to obtain the final dyestuffs. Again maximal yields were sought after and the reaction conditions were varied accordingly.The final dyestuffs were recrystallised in order to be attained in a purified form. The obtained dyestuffs and their corresponding intermediates were characterized by the use of elemental analysis, DSC, FTIR, H NMR, and UV–visible spectroscopic techniques.Spectrophotometric investigations of the prepared dyestuffs in different solvents were carried out in order to obtain their absorption maxima, halochromic effects and various intensities. The dyestuffs were finally dyed on polyester fibres in order to investigate their dyeing properties and the obtainable colour gamut.