Organic fluorophores are widely used for the detection of specific analytes. We have designed and prepared a series of π-conjugated molecules for covalent capture and fluorescence turn-on detection of toxic cyanide anion. Taking advantage of the benzimidazole unit to function as both hydrogen bond donor (HBD) and acceptor (HBA) group, a latent fluorophore was constructed to support multiple HBD-HBA pairs. A combination of 1D/2D 1H NMR spectroscopic and X-ray crystallographic studies has established the functional role of tightly-knit hydrogen bonding arrays to (i) shift the tautomer equilibrium, (ii) enhance the electrophilicity of the cyanide capturing site, and eventually (iii) elicit a large fluorescence turn-on response through conformational rigidification of the cyanohydrin adduct. A direct side-by-side comparison of eight different structural derivatives that differ in the number or positioning of the HBD-HBA units supported our mechanistic model. In this presentation will be discussed key design principles, synthetic implementations, and important structure-property-reactivity relationships underpinning this chemistry.