Dependence of Electrochemical and Electrogenerated Chemiluminescence Properties on the Structure of BODIPY Dyes. Unusually Large Separation between Sequential Electron Transfers

Abstract

Electrochemistry and electrogenerated chemiluminescence (ECL) of selected substituted BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes have been studied. The location and nature of substituents on positions 1-8 are important in predicting the behavior, and especially the stability, of the radical ions formed on electron transfer. Dyes with unsubstituted positions 2, 6, and 8 show a kinetic contribution to both oxidation and reduction. Dyes with only unsubstituted positions 2 and 6 and a substituted 8 position show chemically reversible reduction but irreversible oxidation. Unsubstituted positions 2 and 6 tend to show dimer formation on oxidation. Completely substituted dyes show nernstian oxidation and reduction. Oxidation and reduction studies of simple BODIPY dyes show an unusually large separation between the first and second reduction peaks and also the first and second oxidation peaks, of about 1.1 V, which is very different from that observed for polycyclic hydrocarbons and other heteroaromatic compounds, where the spacing is usually about 0.5 V. Electronic structure calculations confirmed this behavior, and this effect is attributed to a greater electronic energy required to withdraw or add a second electron and a lower relative solvation energy for the dianion or dication compared with those of the polycyclic hydrocarbons. ECL was generated for all compounds either by annihilation or by using a co-reactant.

Electrochemistry, Electrogenerated Chemiluminescence, and Electropolymerization of Oligothienyl-BODIPY Derivatives

“…The diffusion coefficient decreases linearly upon addition of each thiophene.Because compounds 4 and 5 are similar and differ by a hexyl substituent, the average value was taken for the plot. Extrapolating to 0 gives a diffusion coefficient of 2E-6 cm 2 s -1 , which agrees well with previously reported work for unsubstituted BODIPY species in various non-aqueous media [57]. …”

Improved Photon Yield from a Green Dye with a Reducing and Oxidizing System

“…The Bodipy-Fl redox potentials are taken from ref. [13]. In buffer T, BFl fluorescence exhibits a poor signal-to-noise ratio (SNR) compared to cyanine dyes such as Cy3 or Cy5.…”

Physical and structural properties of [Cu(BOT1)Cl]Cl, a fluorescent imaging probe for HNO

“…Anodic scans reveal the presence of an irreversible oxidation at approximately 1 V. Based on previous electrochemical studies of BODIPY compounds [28], the quasi-reversible reduction at −570 mV and the irreversible oxidation are both assigned to BODIPYcentered redox processes. The oxidation of BODIPY chromophores often gives rise to radical cations, which dimerize rapidly forming additional electroactive species [29]. The observation of two resolved peaks and the increased current density for the oxidation feature of [Cu(BOT1)Cl]Cl may arise from the oxidation of electrochemically generated dimers.…”