Over the last ten years, the binding properties of calix[n]pyrrole macrocycles with anions (fluoride, chloride, acetate, dihydrogen phosphate etc.) have been explored. Because the parent system is a colorless non-fluorescing solid, NMR and microcalorimetry have been the methods of choice to evaluate binding. As the field developed, a few examples of fluorescent and colorimetric derivatives were prepared, opening up additional analytical pathways. The synthesis of a novel class of calix[4]pyrrole macrocycles containing pendant phenyldiazene groups will be discussed. The mono- and tetra-substituted derivatives have been prepared in a straight forward manner from benzenediazonium tetrafluoroborate and the parent calix[4]pyrrole. The products were brick red solids that slowly decompose and degas under prolonged storage at elevated temperatures. A preliminary binding profile of the tetra-substituted congener was constructed by adding ten equivalents of tetrabutylammonium anion to a 1 μM solution of calix[4]. For the corresponding salts of fluoride and acetate, we saw a red shift in the spectrum from 445 to 530 nm. Dihydrogen phosphate gave a more intermediate result, suggesting either partial or more complex binding at 10 equivalents. Chloride and perrhenate gave no response at these levels. Surprisingly, the tetraphenyldiazene-substituted calix[4]pyrrole exceeded the absorbance limit of 3.0 for the spectrophotometer at a mere 10 μM. Given this result, the visible limits for this system were pushed through successive dilutions. Though faint, the 10 nM solution was still detectable by the naked eye.