3 research outputs found
Synthesis and Photoinduced Electron Transfer Studies of a Tri(Phenothiazine)–Subphthalocyanine–Fullerene Pentad
A novel donor–acceptor pentad featuring subphthalocyanine and fullerene as the primary electron donor and acceptor, and three phenothiazine entities as secondary hole transferring agents, have been newly synthesized and characterized as an photosynthetic reaction center model compound. Occurrences of ultrafast photoinduced electron transfer (PET) and slower charge recombination are witnessed in the pentad from the femtosecond and nanosecond transient absorption studies
Control over Photoinduced Energy and Electron Transfer in Supramolecular Polyads of Covalently linked azaBODIPY-Bisporphyrin ‘Molecular Clip’ Hosting Fullerene
A ‘molecular clip’ featuring a near-IR
emitting fluorophore,
BF<sub>2</sub>-chelated tetraarylazadipyrromethane (aza-BODIPY) covalently
linked to two porphyrins (MP, M = 2H or Zn) has been newly synthesized
to host a three-dimensional electron acceptor fullerene via a ‘two-point’
metal–ligand axial coordination. Efficient singlet–singlet
excitation transfer from <sup>1</sup>ZnP* to aza-BODIPY was witnessed
in the dyad and triad in nonpolar and less polar solvents, such as
toluene and <i>o</i>-dichlorobenzene, however, in polar
solvents, additional electron transfer occurred along with energy
transfer. A supramolecular tetrad was formed by assembling bis-pyridine
functionalized fullerene via a ‘two-point’ metal–ligand
axial coordination, and the resulted complex was characterized by
optical absorption and emission, computational, and electrochemical
methods. Electron transfer from photoexcited zinc porphyrin to C<sub>60</sub> is witnessed in the supramolecular tetrad from the femtosecond
transient absorption spectral studies. Further, the supramolecular
polyads (triad or tetrad) were utilized to build photoelectrochemical
cells to check their ability to convert light into electricity by
fabricating FTO/SnO<sub>2</sub>/polyad electrodes. The presence of
azaBODIPY and fullerene entities of the tetrad improved the overall
light energy conversion efficiency. An incident photon-to-current
conversion efficiency of up to 17% has been achieved for the tetrad
modified electrode
Bisdonor–azaBODIPY–Fullerene Supramolecules: Syntheses, Characterization, and Light-Induced Electron-Transfer Studies
Achieving ultrafast light-induced
charge separation requires carefully
selected donor and acceptor entities often held together in a closer
proximity. In the present investigation, two tetrads featuring a near-IR-emitting
sensitizer, BF<sub>2</sub>-chelated dipyrromethene (azaBODIPY), covalently
linked to a fullerene through the central boron atom and two electron-donor
entities, namely, <i>N</i>,<i>N</i>-dimethylaminophenyl,
or bithiophene in close proximity to the fullerene entity were designed
and synthesized, and the results were compared to the earlier-reported
bisferrocene–azaBODIPY–fullerene tetrads in this series.
The tetrads synthesized by establishing a multistep procedure exhibited
typical spectral, redox, and photo reactivities of the individual
components with some degree of intramolecular interaction. The X-ray
structure of one of the precursor triads was also solved as part of
this investigation. Ultrafast photoinduced electron transfer was witnessed
in the case of both tetrads by femtosecond transient absorption spectroscopy
studies. The significance of electron-donor entities was clear for
the tetrad derived from <i>N</i>,<i>N</i>-dimethylaminophenyl
entities, while for the bithiophene-derived tetrad, the charge separation
involved mainly the azaBODIPY and fullerene entities. The charge recombination
process involved populating the triplet excited state of azaBODIPY
prior to returning to the ground state for both tetrads, as demonstrated
by nanosecond transient absorption studies