Azophenine as Central Core for Efficient Light Harvesting Devices. Issue 5 (10th January 2018)

• Record Type: Journal Article
• Authors: Lei, Hu; Karsenti, Paul‐Ludovic; Harvey, Pierre D.
• Is Part Of: Chemphyschem. Volume 19:Issue 5(2018)
• Page Start: 596
• Page End: 611
• Publication Date: 2018-01-10
• Subjects: azophenine -- Bodipy -- Dexter energy transfer -- FRET -- porphyrin; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201701183
• Languages: English
• ISSNs: 1439-4235

Abstract

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 −1 ; DFT; B3LYP). The rates for energy transfer, k ET (S1 ), for 1 Bodipy*→Q are in the order of 10 10 –10 11 s −1 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 C6 H4 C≡CC6 H4 arms, thus favoring the double electron exchange mechanism. In the mixed‐antenna Bodipy–porphyrin star molecule, the rate for 1 Bodipy*→porphyrin has also been evaluated (≈ 16×10 10 s −1 ) 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 C6 H4 C≡CC6 H4 and C≡CC6 H4 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. Abstract : Fast transfer : Two Bodipy and zinc(II)porphyrin antennas were connected to an uncycled azophenine, which became fluorescent in the near‐IR region and mediated two unexpectedly ultrafast S1 energy transfers: 1 Bodipy*→Q ( k ET =10 10 –10 11 s −1 ) and 1 Bodipy*→porphyrin ( k ET ≈ 16×10 10 s −1 ), due to the rather low absorptivity properties of the lowest energy charge transfer excited state of azophenine. The Dexter mechanism is the dominent process.