Synthesis, electrochemical, optical and biological properties of new carbazole derivatives

[Display omitted] •The environment significantly influences on the absorption and emission spectra.•EDG substituents reduce the excitation energy and EWG increases.•The -OCH3 group reduce the de-excitation energy and -CH3 group increases.•The dye shows the intramolecular charge transfer.•For bioimaging, the presence of -COOC2H5 and -OCH3 will be particularly desirable.•The tested dyes are very promising for using as fluorescent markers in bioimaging.•The tested derivatives should be treated as safe for the human body. Carbazole skeleton is the key structural motif of many biologically active compounds including synthetic and natural products. Based on the (E)-2-(2-(4-9H-carbazol-9-yl)benzylidene) hydrazinyl)thiazole as skeleton, three novel carbazole dyes were synthesized. The scientific analysis includes the effect of changing the strength of the activating substituents and their exchange for the deactivating substituent on the chemical and biological properties. The presented research showed a significant influence of the CH3, OCH3 and CH2COOC2H5 groups on the spectral properties of the tested derivatives. Their significant influence is also visible in electrochemical, nonlinear-optic and biological properties. The study also included the analysis of the use of the presented derivatives as potential fluorescent probes for in vivo and in vitro tests. Quantum-chemical calculations complement the conducted experiments.