Antenna effects in truxene-bridged BODIPY triarylzinc(ii)porphyrin dyads: evidence for a dual Dexter–Förster mechanism

Abstract

The antenna process from an energy donor (BODIPY; 4',4'-difluoro-1',3',5',7'-tetramethyl-4'-bora-3a',4a'-diaza-s-indacene) in its singlet state to two acceptors (two zinc(II) 5,15-p-tolyl-10-phenylporphyrin) bridged by a central truxene residue (5',5'',10',10'',15',15''-hexabutyltruxene), 5, has been analysed by means of comparison of the energy transfer rates with those of a structurally similar β-substituted BODIPY-(zinc(II) 5,10,15-p-tolyl-porphyrin), 6, where no conjugation is present between the donor and the two acceptors using the Förster resonance energy transfer (FRET) approximation. It is estimated that the energy transfer in operates mostly via a Dexter mechanism (>99%), and the remaining proceeds via a Förster mechanism (<1%). This information is useful for the design of future molecular devices aimed at harvesting light.

Synthesis of 3,8‐Dichloro‐6‐ethyl‐1,2,5,7‐tetramethyl–BODIPY from an Asymmetric Dipyrroketone and Reactivity Studies at the 3,5,8‐Positions

“…However, these compounds show low fluorescence quantum yields ( Φ f <0.1), as a result of the greater freedom of rotation of the thienyl and furyl groups in comparison with phenyl, which increases the amount of energy lost to nonradiative decay to the ground state. [20, 31] The monostyryl-BODIPY 16 showed the most redshifted fluorescence emission ( λ max =617 nm) of all the BODIPYs investigated, and a high quantum yield ( Φ f =0.73). On the other hand, the significant redshift in the absorption and emission of formyl-BODIPY 17 relative to 6c is due to the conjugation of the carbonyl group with the BODIPY π-system, as indicated by the nearly co-planarity seen in the X-ray structure (Figure 6).…”

Cross Conjugated Organometallic Polymers Exhibiting Ultrafast Excitation Energy Channeling: Drastic Effect of the Connectivity

“…In this situation, the ultrafast rate (>1.9 × 10 10 s −1 at 298 K, and >7.4 × 10 10 at 77 K) is explained by a contribution of both Förster and Dexter mechanisms. The latter is most likely to be dominant owing to the presence of conjugation . This conclusion was confirmed by examining the fs‐TAS data of P1 , P2, and PdTTPNH 2 , where the two latter are the comparative species.…”

“…These latter smaller values are prone to π‐orbital overlap throughout the conjugated system, thus favoring a Dexter mechanism (i.e., double electron exchange), which relies entirely upon MO contact between the donor and the acceptor. This phenomenon has previously been tested on compounds containing porphyrin units . In conclusion, to explain the significantly faster k ET for P1 , one must take into account a Dexter mechanism (presumably dominant) in addition to the Förster.…”

Excited State N−H Tautomer Selectivity in the Singlet Energy Transfer of a Zinc(II)‐Porphyrin–Truxene–Corrole Assembly

“…We report the synthesis and analysis of a donor–acceptor system, [Zn‐COR 2 ] , based on Zn‐porphyrin, [Zn] , and free‐base corrole, [COR] , bridged by a central ( C 3 v point group) truxene scaffold, an aromatic species known for promoting fast singlet energy transfer . This efficient [Zn] *→ [COR] process is needed to adequately probe the selectivity of one excited‐state tautomer over the other.…”

“…We also measured the rate of excited‐state tautomerization in the donor–acceptor dyad [Zn‐COR 2 ] as well as for two model compounds [COR] and [COR 2 ] (Scheme ). The preparation of the investigated compounds was performed according to a previously published method and is summarized in Scheme . The energy transfer processes is examined from the point of view of both the FRET and Dexter theories, and a strong Dexter dependence is assumed for these systems in relation to the results that were obtained for similar compounds …”