Synthesis, spectral properties and DFT/TDDFT study on novel methyl heteroazulene derivative

Paper introduces new heteroazulene derivative, 10-methoxy-6-methyl-6H-5,6,7-triazadibenzo[f,h]naphtho[3,2,1-cd]azulene (MMTNA), including chemical aspects of its synthesis likewise optical absorption and fluorescence spectra measured in several organic solvents of different polarity. The obtained experimental results are subjected to the quantum-chemical analysis based on DFT/TDDFT/PCM calculations at the B3LYP/6-31+G(d,p) level of theory. MMTNA demonstrates insignificant solvatochromism of both first absorption and fluorescence bands caused mainly by a weakly polar feature of its ground and lowest excited states. Despite this the emission bands appears to be considerably red shifted with respect to relevant first absorption bands resulting thus to a substantial Stokes shift. Its origin is dominated by the conformational relaxation in the excited state whereas the solvent relaxation has practically no influence on the emission spectra. Low sensitivity to the host environment makes MMTNA dye perspective for a number of applications, particularly in those cases when a high stability of the emission wavelength (color) is demanded.

► Synthesis of methoxy methyl triazadibenzo-naphthoazulene (MMTNA) is described.
► Optical absorption and fluorescence spectra of MMTNA are reported.
► Measured absorption and fluorescence spectra are compared with the TDDFT calculations.
► Weak solvatochromism of MMTNA makes this dye perspective in a number of applications.