Spin Switching with Triazolate-Strapped Ferrous Porphyrins

Abstract

Fe­(III) porphyrins bridged with 1,2,3-triazole ligands were synthesized. Upon deprotonation, the triazolate ion coordinates to the Fe­(III) ion, forming an overall neutral high-spin Fe­(III) porphyrin in which the triazolate serves both as an axial ligand and as the counterion. The second axial coordination site is activated for coordination and binds p-methoxypyridine, forming a six-coordinate low-spin complex. Upon addition of a phenylazopyridine as a photodissociable ligand, the spin state of the complex can be reversibly switched with ultraviolet and visible light. The system provides the basis for the development of switchable catalase- and peroxidase-type catalysts and molecular spin switches.

Dendronised Ni(ii) porphyrins as photoswitchable contrast agents for MRI

“…Further studies are devoted to improving the switching efficiency and relaxivity by the replacement of the pyridine ligand by imidazole, 24 or by replacing Ni 2+ with Fe 3+ within the porphyrin core. 28,29…”

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

“…Another promising approach towards coordination-based, photoswitchable catalysts are photodissociable ligands. These ligands coordinate in their trans form and decoordinate in the cis configuration driven by steric hindrance [14,34,35].…”

Molecular Sensors Operating by a Spin‐State Change in Solution: Application to Magnetic Resonance Imaging

“…In a significant synthetic effort to explore the merits of an Fe(III) system for the design of a CISSS sensor, [61] the group led by Herges prepared a triazole‐containing macrocycle embedding a porphyrine, a system reminiscent of porphyrine‐quinone cyclophanes prepared from the mid‐80s (Scheme 8). [62] Synthetic access to such sophisticated systems is notoriously difficult, and the present system is no exception.…”