Characterization of a photoswitching chelator with light-modulated geometric, electronic, and metal-binding properties.

Photoswitching molecules are utilized for a variety of applications where the rapid manipulation of the molecules' chemical properties and spatial orientations allows for new spatiotemporal control over molecular-scale interactions and processes. Here, we present a hydrazone-containing transition metal chelator, HAPI ((E)-N'-[1-(2-hydroxyphenyl)ethyliden]isonicotinoylhydrazide), that displays dual-wavelength photoswitching behavior. Several of its metal complexes, however, are inert to photoreaction and thereby add another layer of control over the photoswitch system. The light-induced twist in HAPI structure is accompanied by a dramatic change in electronic properties as well as chelator strength. This work introduces HAPI as the prototype for a class of molecules with properties that may be optimized for a variety of experimental applications that take advantage of phototriggered molecular changes.