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Towards artificial photosynthesis : resolving supramolecular packing of artificial antennae chromophores through a hybrid approach
of fundamental building blocks like chlorophylls, which interact to form
photosystem, which performs the complex function of water splitting. The key
challenge in artificial photosynthesis is to learn how to design systems that can
adapt and optimize their topologies in line with self-assembly of natural
photosystem. In this thesis I combine different techniques of cross polarization
Magic angle spinning Nuclear Magnetic Resonance and Transmission Electron
Microscopy with simulation and modeling, to resolve the global packing of
molecules which are potential candidates for efficient solar fuel cell devices. This
thesis focuses on the packing analysis of three-dimensional structures, which are
heterogeneous in nature. I demonstrate a new and general structure
determination approach that, in combination with first-principles quantum...Show more
Photosynthesis is a highly cross linked process. However, we can distinguish a set
of fundamental building blocks like chlorophylls, which interact to form
photosystem, which performs the complex function of water splitting. The key
challenge in artificial photosynthesis is to learn how to design systems that can
adapt and optimize their topologies in line with self-assembly of natural
photosystem. In this thesis I combine different techniques of cross polarization
Magic angle spinning Nuclear Magnetic Resonance and Transmission Electron
Microscopy with simulation and modeling, to resolve the global packing of
molecules which are potential candidates for efficient solar fuel cell devices. This
thesis focuses on the packing analysis of three-dimensional structures, which are
heterogeneous in nature. I demonstrate a new and general structure
determination approach that, in combination with first-principles quantum
chemical calculations, establishes the structures of molecularly ordered antenna
complexes that lack long-range 3D atomic crystalline order. This is possible
despite the absence of a priori information on the space group or atomic
coordinates.
Chapter 2 describes DATZnS(3ʹ-NMe) parallel stacking in an antiparallel
framework with the P2/c space group. 13C CP/MAS NMR yields number of
asymmetric sites in the structure and recognition motif. This in conjunction with
unit cell parameters and diffraction spots from the Fourier transformation of a
TEM image is used to resolve the structure. Supramolecular recognition motif is a
characteristic of the packing of the DATZnS(3ʹ-NMe) molecule. The molecular
recognition and molecular symmetry steer the packing into a racemic mixture with
a c-glide plane and inversion symmetry to release the steric hindrance. Simulation
of the LGCP build up curve between specific pairs and electron diffraction were
used to validate the proposed packing.
Chapter 3 describes the centerosymmetric dimer formation with NMI
extending outwards to capture the solar energy. MAS NMR chemical shifts were
used to generate a truncated 1,7-perylene-3,4,9,10-tetracarboxylic monoimide
dibutylester motif. This motif is further optimized and used for molecular
replacement approach to generate a partial 3D electron density approach. The P-1
symmetry obtained from Electron Nano Crystallography is used to graft the naphathelene monoimide substituents. The alkyl chains are modeled using the
intermolecular correlation observed in HETCOR. Naphthalene monoimide
antennas projecting out from the rows of dimers formed out of rod type D1A2
could capture the light energy and transfer to dimers through FRET.
Finally, in chapter 4 C2 molecular symmetry obtained from MAS NMR and
DFT modeling is used as the core motif to propose the packing of the DATZnS(4H).
Intermolecular correlations obtained from the HETCOR shows the folding of the
tails along the phenazine moiety. The analogous modeling showed how the
packing could be steered by the NCH3 functional group between antiparallel and
parallel dipoles. This understanding opens the way for the evidence based design
of light harvesting antenna.
In summary, a novel methodology to resolve the structure of chromophore
antenna from a structural background with static and dynamic heterogeneity that
strongly limits the diffraction response is shown. Furthermore, I anticipate that the
insights into packing of the antenna are key to the design of the organic solar fuel
cell device in the future.
- All authors
- Thomas, B.
- Supervisor
- Groot, H.J.M. de
- Co-supervisor
- Grip, W.J. de
- Committee
- Kentgens, A.P.M.; Brouwer, J.; Lammertsma, K.; Pandit, A.; Pannu, N.S.
- Qualification
- Doctor (dr.)
- Awarding Institution
- Institute of Chemistry , Science , Leiden University
- Date
- 2016-11-10
- ISBN (print)
- 9789462955189