Ferrocene–BODIPYmerocyanine dyads: new NIR absorbing platforms with optical properties susceptible to protonation

Abstract

Ferrocene-BODIPYmerocyanine dyads 5 and 6 were prepared and characterized by a variety of spectroscopic, electrochemical, and theoretical methods. Experimental and theoretical data on these NIR absorbing compounds are suggestive of unusual susceptibility (for BODIPY chromophores) of the delocalized π-system in 5 and 6 to protonation and low-potential oxidation of their π-systems.

Redox Chemistry of BODIPY Dyes

“…Introduction of a ferrocenyl fragment generated reversible ferrocene-based oxidations 230-360 mV more positive than free ferrocene, irreversible BODIPY-based oxidations 990-1190 mV more positive than free ferrocene, and reversible BODIPY-based reductions 1010-1110 mV more negative than free ferrocene. Similar results have been observed by several other groups that have incorporated ferrocene fragments into BODIPY cores [14][15][16][17][18]. Although incorporation of a ferrocenyl fragment into a BODIPY dye can introduce an additional oxidation wave, the reduction of the BODIPY dye is nearly unaffected by the presence of ferrocene moieties, which is primarily due to the added electron residing on the BODIPY core [19].…”

“…Non-interacting redox centers normally display a difference of 35 mV between their redox potentials [20]. If a small splitting is observed between the two oxidation waves associated with the ferrocene oxidations, then the difference in oxidation potentials is attributed to electrostatic effects [18]. Although small separations between the ferrocene oxidations are [21].…”

Ferrocene: An unrivaled electroactive building block for the design of push-pull dyes with near-infrared and infrared absorptions

“…In the ferrocene-BODIDY-merocyanine triads BDP-58 and BDP-59, elongation of the π-conjugated system on the merocyanine side was determined as destabilizing the π-centered mole cular orbitals, what was confirmed by electrochemistry and by time-resolved photophysics. Due to the presence of the long-conjugated spacer between the BODIPY core and merocyanine end-group, protonation of this latter with a strong acid was examined for BDP-58 and BDP-59, and a drastically modification of the photophysical properties was found [101]. In fact, modification of the optical properties of BODIPY-merocyanine conjugates by protonation was reported prior to this work [102][103][104][105][106][107][108], but the combination of the three partners within a single molecule is unprecedented.…”

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.…”