posted on 2020-03-18, 12:06authored byAndrés
F. Molina-Osorio, David Cheung, Colm O’Dwyer, Andrew A. Stewart, Manuel Dossot, Grégoire Herzog, Micheál D. Scanlon
One
of the many evolved functions of photosynthetic organisms is
to synthesize light harvesting nanostructures from photoactive molecules
such as porphyrins. Engineering synthetic analogues with optimized
molecular order necessary for the efficient capture and harvest of
light energy remains challenging. Here, we address this challenge
by reporting the self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrins
into films of highly ordered nanostructures. The self-assembly process
takes place selectively at the interface between two immiscible liquids
(water|organic solvent) with the kinetically stable interfacial nanostructures
formed only at pH values close to the pKa of the carboxyphenyl groups. Molecular dynamics simulations suggest
that the assembly process is driven by an interplay between the hydrophobicity
gradient at the interface and hydrogen bonding in the formed nanostructure. Ex situ X-ray diffraction (XRD) analysis and in
situ UV–vis and steady-state fluorescence indicate
the formation of chlathrate type nanostructures that retain the emission
properties of their monomeric constituents. The self-assembly method
presented here avoids the use of acidic conditions, additives such
as surfactants, and external stimuli, offering an alternative for
the realization of light-harvesting antennas in artificial photosynthesis
technologies.