Array based vapor sensing has emerged as a powerful approach toward the detection of chemically diverse analytes. Based on cross-responsive sensor elements, these systems aim to produce composite responses unique to each odorant, in a fashion similar to the mammalian olfactory system. We have recently discovered [Rakow, N. A.; Suslick, K. S. "A Colorimetric Sensor Array for Odour Visualization" Nature, 2000, 406, 710-714.; Suslick, K. S.; Rakow, N. A. "Colorimetric Artificial Nose Having an Array of Dyes and Method for Artificial Olfaction" U.S. Patent 6,368,558; April 9, 2002. Suslick, K. S.; Rakow, N. A.; Sen, A. "Colorimetric Artificial Nose Having an Array of Dyes and Method for Artificial Olfaction: Shape Selective Sensors" U.S. Patent 6,495,102 B1; Dec. 17, 2002. ] a new and simple approach to array detection of odorants using the colorimetric response from a library of immobilized vapor-sensing dyes. We call this technique "smell-seeing".

     As inorganic chemists have long realized, compounds that bind to metal ions are nearly always highly odiferous. For this reason, metal-containing dyes, such as metalloporphyrins, provide a way of reporting the presence of odors by changes in color. We use a two-dimensional display of metalloporphyrins as sensor elements for the visual identification of a wide range of olfactants (including alcohols, amines, ethers, phosphines, phosphites, thioethers, and thiols) and even weakly-ligating solvent vapors (arenes, halocarbons, and ketones). The solid-state color changes are similar to those known for metal ligation in solution. The array shows good linear response to single analytes and interpretable responses to analyte mixtures. Water vapor does not interfere with other analytes. Unique color fingerprints can be obtained below 1 ppm, and responses to analyte concentrations below 100 ppb have been observed. Applications for this sensing array include general-purpose vapor dosimeters and analyte-specific detectors (e.g., for insecticides, drugs, or neurotoxins).

     Metalloporphyrins provide a versatile synthetic base on which to design desired properties: i.e., molecular engineering. To tailor our molecular recognition of olfactants, we have used sterically hindered, "bis-pocket" porphyrins to control the response of our array sensors. In this work with synthetic metalloporphyrins and with dendrimer-porphyrins, we are developing superstructured macrocycles as shape, size, and polarity selective oxidation catalysts and as selective molecular sensors.

     In other recent work, we have made the connection complete by finding a conserved metal ion binding site in the mammalian olfactory recetors. Wang, J.; Luthey-Schulten, Z.; Suslick, K. S. "Is the Olfactory Receptor A Metalloprotein?" Proc. Natl. Acad. Sci. U.S.A., 2003, 100, 3035-3039.