Abstract: Photothermographic materials comprise heat-bleachable antihalation compositions in antihalation layers. These compositions comprise a hexaarybiimidazole and one or more infrared radiation absorbing compounds that are represented by the following Structure I: A1—L1—A2  I wherein A1 represents a group derived from a dye base, a heterocyclic group, or an electron-donating aromatic group, A2 represents a group derived from a dye base, a heterocyclic group, a group derived from a dye acid, or an electron-donating aromatic group, and L1 represents a conjugated linking group that maintains electron delocalization between A1 and A2 to provide infrared absorbance. The antihalation composition is typically bleached when subjected to a temperature of at least 90° C. for at least 0.5 seconds.