Abstract: The search for light-sensitive moieties which allow a controlled spatio-temporal triggering of chemical and biological relevant molecules within cellular systems represents an important challenge in chemical biology. Caging strategies make use of photochemically removable protecting groups to mask the activity of biologically relevant molecules and release the bioactive species upon irradiation with light of appropriate wavelength [1].The use of fluorescent caging groups allows the visualization, quantification, and the follow-up of spatial distribution, localization, and depletion of the active compound through the monitoring of its fluorescent caged precursor using fluorescent techniques. As a continuation of our research work concerning the synthesis of new fluorescent heterocyclic compounds, their application on the design of fluorescent conjugates of biologically relevant molecules and studies on their photorelease [2], the present study aims to give a contribution to the development of novel photoactivable groups based on azaheterocycles, namely carbazole and acridine. A model carboxylic acid was used for the preparation of novel ester conjugates of acridine and carbazole, in order to be compared with the corresponding 2-nitrobenzyl derivative (a widely known caging group). The resulting compounds were evaluated in a photochemical reactor under irradiation at 254, 300, 350 and 419 nm and the monitoring of the photocleavage process was carried out by HPLC and 1H NMR. [1] Furuta, T. in Dynamic Studies in Biology: Phototriggers, Photoswitches and Caged Biomolecules, M. Goeldner, R. S. Givens (Eds.), Wiley-VCH, New York, 2005. [2] a) Piloto A.M., Soares A.M.S., Hungerford G., Costa S.P.G.; Goncalves, M.S.T. Eur. J. Org. Chem. 2011, 5447-5451. b) Piloto A.M., Hungerford G., Costa S.P.G. Gonçalves M.S.T., Photochem. Photobiol. Sci. 2012, in press DOI:10.1039/C2PP25261A.