A newly synthesized 1,4,8,11-tetraazacyclotetradecane derivative (L), functionalized with a diazo moiety as the reporter functionality, is found to bind specifically to Hg2+ with an associated change in color that could be visually detected. With biologically benign beta-CD, it forms an inclusion complex (L center dot 2 beta-CD), which shows a much higher solubility in water, and this helps in developing a more intense color on binding to Hg2+ in a CH3CN-HEPES buffer medium. The nontoxic nature of L was checked with the living cells of a Gram negative bacterium, Pseudomonas putida. Further, experiments revealed that these two reagents could be used as staining agents for the detection of Hg2+ present in this microorganism.