Tetrastyryl-BODIPY-Based Dendritic Light Harvester and Estimation of Energy Transfer Efficiency

Abstract

Versatile BODIPY dyes can be transformed into bright near-IR-emitting fluorophores by quadruple styryl substitutions. When clickable functionalities on the styryl moieties are inserted, an efficient synthesis of a light harvester is possible. In addition, clear spectral evidence is presented showing that, in dendritic light harvesters, calculations commonly based on quantum yield or emission lifetime changes of the donor are bound to yield large overestimations of energy transfer efficiency.Efficient harvesting of solar radiation requires judiciously designed absorbers. Considering the fact that it would be difficult to have a single molecule with strong absorptions in the entire visible spectrum and near-IR (perfect black dye), it makes more sense to seek multichromophoric dye ensembles. Different chromophoric units can be brought together either by covalent bonds or by noncovalent interactions. In either case, excitation energy transfer (EET) from the donor chromophores (shorter wavelength absorption) to the acceptor (longer wavelength absorbing core) module is expected. The efficiency of energy transfer from the antenna chromophores to the central core is very important. In such multichromophoric light harvesters, energy transfer can be either through-space 1 or through-bond. 2 Through-space energy transfer is also possible between two or more free chromophoric units. This kind of energy transfer has been thoroughly studied, and in fact, the F€ orster (throughspace) energy transfer model is built on the interaction of such transition dipole coupled chromophoric pairs. Three important parameters determine the efficiency of energy transfer: donorÀacceptor distance, relative orientations of the transition dipoles, and the spectral overlap between the relevant absorption and emission bands. In proteins, either utilizing endogenous fluorescence of tryptophan or using fluorescent labels, EET efficiency calculations based on quantum yield or lifetime changes have been successful, but proteins are large and flexible enough for orientation of the dipoles to be averaged, and typically, reference fluorophores are in the same microenvironment. This simplified energy transfer calculation approach was later carried out on covalently linked multichromophoric light harvesters. In these energy transfer cassettes, energy funnels, or dendritic light harvesters, energy transfer efficiency is calculated assuming that the original bimolecular model can be directly related to an energy transfer process in a

Bodipy-ruthenium(II) tris-bipyridyl dyads for homogeneous photochemical oxidations

“…Their molecular structures were unambiguously assigned by using 1 H, 13 C, 19 F and 11 B NMR spectroscopy, electrospray mass spectrometry and elemental analysis. Both dyads analysed by ESI-MS gave an intense molecular peak with the expected isotopic profile corresponding to the loss of two PF 6 -counter anions assigned to a doubly charged species.…”

“…5 On the other hand, the use of 4,4-difluoro-4-bora-3a,4a-diazas-indacene (Bodipy) as a chromophore has become very popular owing to its exceptional optical properties, photostability, and ease of preparation and purification. Very complicated structures have been prepared based on dendritic scaffolds, 6 cassette lightharvesters 7 or multi-dyads showing the versatility of such dyes. 8 They can be easily functionalised to tune redox and optical properties to meet the demands for the water oxidation reaction.…”

Broad-Band N∧N Pt(II) Bisacetylide Visible Light Harvesting Complex with Heteroleptic Bodipy Acetylide Ligands

“…In order to study the intramolecular energy transfer (RET) in Pt-1, the luminescence excitation spectra of Pt-1 were compared with those of that UV−vis absorption spectra ( Figure 7a). 52 First, the emission of the coordinated 2-ethynyl Bodipy ligand at 680 nm in Pt-1 was used as the monitoring wavelength in the measurement of the excitation spectrum. Two excitation bands were observed ( Figure 7a).…”

Multistimuli Sensitive Behavior of Novel Bodipy‐Involved Pillar[5]arene‐Based Fluorescent [2]Rotaxane and Its Supramolecular Gel

“…In the present case, the π–π interactions between the phenylene moieties of neighboring pillar[5]arene rings of [2]rotaxane BC12P5, as well as between the Bodipy–Bodipy stacking, Bodipy, and imidazolium moieties, with the help of the van der Waals forces between long alkyl chains in the neighboring [2]rotaxane BC12P5 systems result in the formation of 1D supramolecular arrays, which subsequently self‐assemble into the cross‐linked network depending on the similar intermolecular interactions as mentioned above between neighboring [2]rotaxane BC12P5 systems in different 1D arrays, Scheme 2 . This 3D network then entraps the DMSO molecules with its porous structure, leading to the formation of a novel supramolecular gel containing Bodipy fluorescence chromophore depending mainly on the hydrogen bonding interaction between the solvent DMSO molecules and [2]rotaxane BC12P5 systems 19. The critical gelation concentration for [2]rotaxane BC12P5/DMSO was about 11.2 wt%.…”