Metal Dependence on the Bidirectionality and Reversibility of the Singlet Energy Transfer in Artificial Special Pair-Containing Dyads

Abstract

The demetalation of a precursor dyad, 3, built upon a zinc(II)-containing artificial special pair and free-base antenna, leads to a new dyad, 4, for singlet energy transfer composed of cofacial free-base porphyrins (acceptor), [Fb] bridged by a 1,4-CH group to a free-base antenna (donor), [Fb]. This dyad exhibits the general structure [M]-CH-[Fb], where [M] = [Fb], and completes a series reported earlier, where [M] = [Mg] (2) and [Zn] (3). The latter dyads exhibit a bidirectional energy-transfer process at 298 K for 2 and at 77 K for 3. Interestingly, a very scarce case of cycling process is observed for the zinc-containing dyad at 298 K. The newly reported compound 4 exhibits a quasi unidirectional process [Fb]*→[Fb] (major, k = 2 × 10 s at 298 K), where the remaining is [Fb]*→[Fb] (minor, k = 8 × 10 s at 298 K), thus completing all possibilities. The results are analyzed in terms of molecular orbital couplings (density functional theory computations), Förster resonance energy transfer parameters, and temperature dependence of the decay traces. This study brings major insights about artificial special pair-containing dyads and clearly contributes to a better understanding of the communication between the two main components of our models and those already described in the literature.

Impressive near-infrared brightness and singlet oxygen generation from strategic lanthanide–porphyrin double-decker complexes in aqueous solution

“…Previous calculations of the energy levels of double-decker complexes have shown poor agreement with experiments 47,48 . Herein, the absorption spectrum was modeled from the optimized structure by two programs.…”

Melting Behavior of a DNA Four-Way Junction Using Spectroscopic and Calorimetric Techniques

“…To gain a better understanding of which stems are melting together, fluorescence spectroscopy was performed on modified FWJ oligonucleotides, where adenine was replaced with 2-aminopurine (2AP) (Figure (left)). The 2AP absorption maxima occurs at a longer wavelength than standard purine and pyrimidine bases, and quenching of its fluorescence is sensitive to base-stacking and collisional interactions, with the amount of quenching dependent on the identity of the nearest nucleotides. − Thus, the fluorescence of 2AP is responsive to changes in its local environment and allows for determination of some structural changes. ,− Not only is 2AP sensitive to its surrounding structure, its base-pair stacking is similar to the AT base pair stack and thus causes minor effects to the thermal stability (between 2 and 10 °C depending on the structure). Incorporation of 2AP into each of the three arms that contains an adenine allows for us to distinguish which arms are melting in the two transitions visible by DSC.…”

Solvent dependent triplet state delocalization in a co-facial porphyrin heterodimer

“…[15][16][17][18][19] As a result, there are very few studies of the electronic and physical properties of co-facial porphyrin dimers. 16,20,21 Recently, we reported the characterization of the co-facial porphyrin heterodimer AlPor-O-PPorÁPF 6 in which Al(III) porphyrin and P(V) porphyrin are linked via a m-oxo bridge (Fig. 1a).…”