Photo credit: www.sciencedaily.com
A collaborative research effort between the Universities of Amsterdam and Zurich has yielded a groundbreaking molecular system capable of controlling the release of iron. By combining ferrocene, known for its unique structure that sandwiches an iron atom, with a carbon ‘nanohoop’, the team developed a mechanism that enables the release of Fe2+ ions when exposed to harmless green light. This innovative work has been detailed in a paper recently published in the Journal of the American Chemical Society (JACS), where it graces the cover of the latest issue.
The research was spearheaded by Dr. Tomáš Šolomek from the University of Amsterdam’s Van ‘t Hoff Institute for Molecular Sciences and Dr. Peter Štacko from the University of Zurich’s Department of Chemistry. Both researchers specialize in the field of photocages—molecular photochemical instruments that provide precise control over the activity of specific substrates using light as a stimulus. Photocages are pivotal not only in examining biochemical processes and dynamics but also hold the potential for therapeutic innovations, including applications in photoactivated chemotherapy.
In their latest findings published in JACS, the team shifted their investigation from organic molecules to a critical element in biological systems: iron. Iron is well-known for its essential functions in transporting oxygen within the body, facilitating vital energy-producing redox reactions in mitochondria, synthesizing deoxyribonucleotides, and safeguarding cells against oxidative stress.
Strain-induced photorelease
While nature has a sophisticated protein-based system for regulating iron uptake and balance, the researchers presented a simpler yet effective synthetic alternative designed to store and release iron on demand.
This system utilizes ferrocene as the carrier for iron, integrated within a carbon nanohoop that facilitates the control of its functionality. Ferrocene, an organometallic compound, securely holds an iron atom between two cyclopentadienyl rings, exhibiting remarkable stability and light resistance. The integration into a molecular nanohoop alters this stability, creating a configuration that subjects the ferrocene to mechanical stress. This tension makes the system responsive to green light irradiation, triggering the release of the iron.
According to their findings, the researchers demonstrated that effective release of iron can be achieved through light activation. They anticipate that this innovative approach—inducing mechanical stress to enhance molecule responsiveness—may have far-reaching implications, extending beyond photocages into new types of materials in the domains of supramolecular, organometallic, or polymer chemistry.
Abstract, as published with the paper
The study details the synthesis, structural characteristics, and extraordinary reactivity of the first carbon nanohoop that incorporates ferrocene within its macrocyclic framework. The significant strain applied to the ferrocene by the curved configuration of the nanohoop enables unprecedented photochemical reactivity from this otherwise non-reactive metallocene. Activation with visible light results in a ring-opening event in the nanohoop that entirely dissociates the Fe-cyclopentadienyl bonds in conjunction with 1,10-phenanthroline. This mechanism effectively uncages Fe2+ ions encapsulated in the form of the [Fe(phen)3]2+ complex, achieving high chemical yields and efficient operation in aqueous solutions with green light excitation. Notably, the quantum yields of [Fe(phen)3]2+ formation indicate that embedding ferrocene within a strained nanohoop amplifies its photoreactivity by three orders of magnitude compared to unstrained analogs, or ferrocene itself. The findings suggest that dissociation occurs through an interaction between the photoexcited triplet state of the nanohoop and a nucleophilic solvent or external ligand. The methodology illustrated in this research opens pathways for developing new, tunable reactivity within similar metallamacrocycles, facilitating advancements in responsive materials designed for metal ion delivery and broader applications in supramolecular, organometallic, or polymer chemistry.
Source
www.sciencedaily.com