Guest to framework photoinduced electron transfer in a cobalt substituted RWLC-2 metal organic framework

Abstract

Photoinduced electron transfer (PET) between donors and acceptors in porous materials is a key element in the development of light harvesting applications. Metal organic frameworks (MOFs) are ideal materials for PET processes due to their tunable pore size and diversity in framework building units. Here, PET between excited [Ru(2,2'-bipyridine)3]2+ (RuBpy) and Co-carboxylate clusters composing the metal building blocks of a RWLC-2 metal organic framework is described. The lifetime of the RuBpy decreases from ∼600 ns in deaerated solution to 9.5 ns (kET ∼ 1 × 108 s-1) when encapsulated within CoRWLC-2. The decrease in lifetime is attributed to PET between the 3MLCT of RuBpy to the Co ion cluster composing the MOF building blocks. A fit of the lifetime vs. temperature data to the semi-empirical Marcus equation gives a reorganizational energy of 1.6 eV and an electronic coupling factor (HAB) of 0.006 eV.

Metal–Metalloligand Coordination Polymer Embedding Triangular Cobalt–Oxo Clusters: Solvent- and Temperature-Induced Crystal to Crystal Transformations and Associated Magnetism

“…The strong luminescence is severely quenched in the coordination polymer of I , indicating that the iridium electronic state is influenced by that of the cobalt (Figure b). This is not the case for a different polymer with either Zn­(II) or Cd­(II). , Given the good overlap of the emission spectrum of Ir­(ppy-COOH) 3 and the absorption spectrum of the polymer, we postulate that the emission from the excited state upon irradiation of the polymers is consumed by slightly low energy Co­(II) nodes through resonant energy transfer. , …”

“…16,23 Given the good overlap of the emission spectrum of Ir(ppy-COOH) 3 and the absorption spectrum of the polymer, we postulate that the emission from the excited state upon irradiation of the polymers is consumed by slightly low energy Co(II) nodes through resonant energy transfer. 17,24 Transformations and Crystal Structures. Compound I undergoes a first transformation to the phase II by immersing the crystals of I in dry acetone for 7 days under ambient conditions.…”

Tuning photoactive metal–organic frameworks for luminescence and photocatalytic applications

“…Typically, this is achieved by using an appropriate organic linker in the MOF structure, though light-harvesting guests can also be incorporated into the voids of the porous framework. [38] In some rarer cases, direct excitation of metal ions or metal clusters is also possible, for example, in Fe III -based MOFs containing {Fe III 3 (l 3 -O)} 7+ clusters. [39] By varying the organic linker, MOFs can be designed to absorb light in specific regions of the UV-visible spectrum.…”

Applications of reticular diversity in metal–organic frameworks: An ever-evolving state of the art

“…The observed phosphorescence is due to the metal-to-ligand charge transfer (MLCT), which leads to oxidation of Ru II to Ru III and reduction of the polypyridine ligand [545]. Due to their high redox-activity, Ru II often shows additional photo-induced electron transfer in MOFs, as between [Ru(bpy) 3 ] 2+ (Rubpy) and co-carboxylate clusters [546]. Bpy-based complexes in combination with Os II or Re I are equally attractive due to the long-lived and intense luminescence and redox activity.…”