Azophenine as Central Core for Efficient Light Harvesting Devices

Abstract

The notoriously non-luminescent uncycled azophenine (Q) was harnessed with Bodipy and zinc(II)porphyrin antennas to probe its fluorescence properties, its ability to act as a singlet excited state energy acceptor and to mediate the transfer. Two near-IR emissions are depicted from time-resolved fluorescence spectroscopy, which are most likely due to the presence of tautomers of very similar calculated total energies (350 cm ; DFT; B3LYP). The rates for energy transfer, k (S ), for Bodipy*→Q are in the order of 10 -10 s and are surprisingly fast when considering the low absorptivity properties of the lowest energy charge transfer excited state of azophenine. The rational is provided by the calculated frontier molecular orbitals (MOs) which show atomic contributions in the C H C≡CC H arms, thus favoring the double electron exchange mechanism. In the mixed-antenna Bodipy-porphyrin star molecule, the rate for Bodipy*→porphyrin has also been evaluated (≈16×10 s ) and is among the fastest rates reported for Bodipy-zinc(II)porphyrin pairs. This astonishing result is again explained from the atomic contributions of the C H C≡CC H and C≡CC H arms thus favouring the Dexter process. Here, for the first time, this process is found to be sensitively temperature-dependent. The azophenine turns out to be excellent for electronic communication.

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

“…This value is indeed faster than the limit determined using the Streak camera above (i.e., >1.9 × 10 10 s −1 at 298 K and >7.4 × 10 10 s −1 at 77 K; note that k ET is not strongly temperature dependent as only the J‐integral may change). This rate is also considered ultrafast and is in full agreement that the recently reported rate for energy transfer mediated by an imine bridge to the zinc(II)porphyrin acceptor in a BODIPY‐azophenine‐zinc(II)porphyrin assembly; that is, 1 BODIPY* → zinc(II)porphyrin ( k ET = 1.6 × 10 11 s −1 ) . In a similar manner, this relationship can be applied to S 2 and T 1 as well.…”

“…This rate is also considered ultrafast and is in full agreement that the recently reported rate for energy transfer mediated by an imine bridge to the zinc(II)porphyrin acceptor in a BODIPY-azophenine-zinc(II)porphyrin assembly; that is, 1 BODIPY* → zinc(II)porphyrin (k ET = 1.6 × 10 11 s −1 ). [21] In a similar manner, this relationship can be applied to S 2 and T 1 as well. The corresponding rates are k ET (S 2 ) = 3.4 × 10 12 s −1 and k ET (T 1 ) = 3.1 × 10 8 s −1 .…”

Redox Chemistry of BODIPY Dyes

“…The illumination of organic reactions utilizing a photoredox catalyst, a light-sensitive compound that mediates the transfer of electrons (via single-electron transfer events) between chemical compounds when illuminated, can promote reactions that progress slowly or not at all. Dye molecules are attractive photoredox catalyst motifs due to their strong light absorbing capabilities [32][33][34][35].…”