Synthesis, Characterization, and Electron‐Transfer Properties of Ferrocene–BODIPY–Fullerene Near‐Infrared‐Absorbing Triads: Are Catecholopyrrolidine‐Linked Fullerenes a Good Architecture to Facilitate Electron‐Transfer?

Abstract

As eries of covalent ferrocene-BODIPY-fullerene triads with the ferrocene groups conjugated to the BODIPY p-systema nd the fullerene acceptorl inked at the boron hub by ac ommon catecholpyrrolidine bridge were prepared and characterizedb y1 Da nd 2D NMR, UV/Vis, steady-state fluorescence spectroscopy, high-resolution mass spectrometry, and, for one of the derivatives, X-ray crystallography.R edox processes of the new compounds were investigated by electrochemical (CV and DPV) methods and spectroelectrochemistry.D FT calculations indicate that the HOMOin all triads was delocalized between ferrocene and BODIPY p-system, the LUMO was always fullerene-centered, and the catecholcentered occupied orbitalw as close in energy to the HOMO. TDDFT calculations were indicative of the low-energy,l ow-in-tensity charge-transfer bands originated from the ferrocene-BODIPY core to fullerene excitation, which explainedt he similarity of the UV/Vis spectra of the ferrocene-BODIPY dyadsa nd ferrocene-BODIPY-fullerene triads. Photophysical properties of the new triadsa sw ell as reference BODIPYfullerenea nd ferrocene-BODIPY dyads were investigated by pump-probe spectroscopy in the UV/Vis and NIR spectralr egions following selective excitation of the BODIPY-based antenna.I nitial charget ransfer from the ferrocenet ot he BODIPY core was shown to outcompetes ub-100 fs deactivation of the excited state mediated by the catecholb ridge. However, no subsequente lectron transfer to the fullerene acceptorw as observed. The initial charge separated state relaxes by recombination with at ime constanto f1 50-380 ps.[a] Dr.We attempted to obtain single crystals of triads 3a-d.I nt he majority of cases, crystals were too small for X-ray crystallographic measurements, with typical reflection datal imited to Scheme1.Synthetic pathway for preparation of the ferrocene-BODIPY-fullerene triads 3a-d.

Triplet BODIPY and AzaBODIPY Derived Donor‐acceptor Dyads: Competitive Electron Transfer versus Intersystem Crossing upon Photoexcitation

“…On the contrary, current and previous reports from our collaborator and our own groups, where catecholopyrrolidine linker was used to couple an electron donor to the fullerene acceptor we were able to see a successful electron transfer. A closer look of the BODIPY derivatives reported in the above mentioned article reveal that the BODIPY donor unit used to be much electron deficient due to peripheral ester groups. Consequently, the harder oxidation and easier reduction of their BODIPY derivative with first oxidation and reduction potentials of 0.86 V and –1.2 V, respectively, geometrical positioning and conjugated styryl linker connecting BODIPY and ferrocene lead to reductive electron transfer from ferrocene to excited BODIPY instead of oxidative electron transfer to fullerene.…”

Transient Absorption Spectra of Metal‐Free and Transition‐Metal 5,10,15,20‐Tetraferrocene Porphyrins: Influence of the Central Metal Ion, Solvent Polarity, and the Axial Ferrocene Ligand

“…First, this long‐lived component was only observed in the polar solvent with a low yield (ca 10 %). In addition, these lifetimes are too short for the triplet states and are within the range of the relaxation energies observed for the charge‐separated states in the ferrocene‐BODIPYs [15a,e,h,16a,g] and ferrocene‐aza‐BODIPYs [19] . Since DMF can weakly bound to the central metal ions in ZnTFcP, PdTFcP, and FcInTFcP as well as form weak hydrogen bonds with the inner NH protons in H 2 TFcP, we speculate that the third, long‐lived component observed in the transient absorption spectra of these complexes is reflective of such weak coordination.…”

Light‐Activated Carbon Monoxide Prodrugs Based on Bipyridyl Dicarbonyl Ruthenium(II) Complexes

“…A new band in the visible region at 509 nm appeared in the absorbance spectrum (Figure , left, red line). The transition band at 509 nm is characteristic for the BODIPY core and it is due to π BODIPY–π* BODIPY transitions …”