“…Light-responsive agents have found application in a variety of areas, including polymer synthesis, sensor design, manipulation of intracellular biochemistry, , and drug delivery. − For example, light-triggered drug delivery offers the promise of diseased site targeting and consequent reduced side effects. ,, Nitrobenzyl, , hydroxyphenacyl, , coumarin-4-yl, , and a wide assortment of other derivatives have long served in the capacity of light-absorbing/photorelease scaffolds. However, within the last decade, attention has shifted to the design of molecular scaffolds that absorb long-wavelength visible and near-infrared (IR) light, which has the advantage of deeper tissue penetration than that of shorter wavelengths. , These scaffolds include Bodipy analogs, − cyanine derivatives, − [Ru(bpy) 3 ] 3+ complexes, − and others. , In this regard, we have found that cobalamin (Cbl; vitamin B12) serves as an unusually flexible molecular launch pad for therapeutic agents that can be tuned to wavelengths in the red, far red, and near IR .…”