Photoluminescent materials, that are now ubiquitous in our everyday life, have particularly attracted the attention of the scientific community these past few years due to potential important applications such as in bioimaging, sensing, or optoelectronics. In this context, relatively few different families of molecules have been reported to exhibit fluorescence in the aggregated or solid-state through the excited-state intramolecular proton transfer (ESIPT) photochemical process. The preparation and subsequent determination of photochemical properties of an underexplored family of 1,5-benzodiazepin-2-one derivatives are reported. From these data and X-ray diffraction analysis study, it emerged that photoluminescence (in the range 520–655 nm) was mostly attributed to ESIPT. The photoluminescent potential of 1,5-benzodiazepin-2-ones, their facile access, and functionalization were demonstrated through the preparation of two fluorogenic probes for the selective detection of biothiols.