posted on 2024-01-08, 22:03authored bySanoop
Mambully Somasundaran, Srinath V. K. Kompella, Hridya Valia Madapally, E. Krishnan Vishnu, Sundaram Balasubramanian, K. George Thomas
Understanding
the mechanism of chirality transfer from a chiral
surface to an achiral molecule is essential for designing molecular
systems with tunable chiroptical properties. These aspects are explored
herein using l- and d-isomers of alkyl valine amphiphiles,
which self-assemble in water as nanofibers possessing a negative surface
charge. An achiral chromophore, acridine orange, upon electrostatic
binding on these surfaces displays mirror-imaged bisignated circular
dichroism and red-emitting circularly polarized luminescence signals
with a high dissymmetry factor. Experimental and computational investigations
establish that the chiroptical properties emerge from surface-bound
asymmetric H-type dimers of acridine orange, further supported by
fluorescence lifetime imaging studies. Specifically, atomistic molecular
dynamics simulations show that the experimentally observed chiral
signatures have their origin in van der Waals interactions between
acridine orange dimers and the amphiphile head groups as well as in
the extent of solvent exposure of the chromophore.