Spectrochemical properties of 2,3-dihydronaphtho[1,8 -de] [1,2] diazepine- 1, 4-dione and its derivatives

Abstract

The electronic absorption and fluorescence properties of 2,3-dihydronaphtho[1,8 -de] [1,2] diazepine-1, 4-dione -1 A -dione (<b>II</b>), 6-nitro-

2,3-dihydronaphtho[1,8 -de] [1,2] diazepine -1, 4-dione (<b>III</b>) and 6-amino-2,3-dihydronaphtho[1,8-de] [1,2] diazepine-1,4-dione (<b>IV</b>) have been studied in different solvents. The compounds show variation from the characteristic electronic absorption spectra of naphthalene moiety. The electron withdrawing and donating groups in <b>III </b>and <b>IV</b> facilitate longitudinal polarization causing a red shirt in the ¹B_b and ¹L_b transitions. Proton donating solvents cause a blue shift. A new intramolecular charge transfer band is noticed as a result of capdati ve effect of electron donating amino substituent. The fluorescence studies show that the excitation maximum of <b>III</b> is always closer to that of the absorption maximum, while in <b>IV</b> these are separated indicating that <b>IV </b>undergoes association in the excited state, Stokes shirts for the substituted naphth ylhydrazides vary from 33.4 to 133nm. Compound <b>IV</b> exhibits larger Stokes shirts than compound <b>III. </b>The relative fluorescence intensities and the quantum yields of compound <b>IV</b> are always higher than that of <b>III </b>in the respective solvents. The presence of the electron donating amino group enhances the fluorescence properties of compound IV. The steady state fluorescence properti es of these hydrazides do not bear any linear relationship with solvent polarity function. However, a subtle relationship is found to exist when the solvents

are categorized into proton donating, accepting and inert solvents, indicating the existence of a specific interaction between the fluorophore and the solvent. Compound <b>IV</b> exhibits a reasonably high lifetime, which is solvent sensitive and is a better fluorophore in comparison to the other hydrazides studied.