Waly SM, Karlsson JKG, Waddell PG, Benniston AC, Harriman A. Light-Harvesting Crystals Formed from BODIPY-Proline Biohybrid Conjugates: Antenna Effects and Excitonic Coupling.
J Phys Chem A 2022;
126:1530-1541. [PMID:
35230124 PMCID:
PMC9097531 DOI:
10.1021/acs.jpca.2c00035]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
A boron dipyrromethene (BODIPY) derivative
bearing a cis-proline residue at the meso-position crystallizes
in the form of platelets with strong (i.e., ΦF =
0.34) red fluorescence, but the absorption and emission spectra differ
markedly from those for dilute solutions. A key building block for
the crystal is a pseudo-dimer where hydrogen bonding
aligns the proline groups and separates the terminal chromophores
by ca. 25 Å. Comparison with a covalently linked bichromophore
suggests that one-dimensional (1D) excitonic coupling between the
terminals is too small to perturb the optical properties. However,
accretion of the pseudo-dimer forms narrow channels
possessing a high density of chromophores. The resultant absorption
spectrum exhibits strong excitonic splitting, which can be explained
quantitatively using the extended dipole approach and allowing for
coupling between ca. 30 BODIPY units. Fluorescence, which decays with
a lifetime of 2.2 ns, is assigned to a delocalized and (slightly)
super-radiant BODIPY dimer situated at the interface and populated
via electronic energy transfer from the interior.
Collapse