Multichromophoric arrays provide one strategy for assembling molecules with intense absorptions across the visible spectrum but are generally focused on systems that efficiently produce and manipulate singlet excitations and therefore are burdened by the restrictions of (a) unidirectional energy transfer and (b) limited tunability of the lowest molecular excited state. In contrast, we present here a multichromophoric array based on four boron dipyrrins (BODIPY) bound to a platinum benzoporphyrin scaffold that exhibits intense panchromatic absorption and efficiently generates triplets. The spectral complementarity of the BODIPY and porphryin units allows the direct observation of fast bidirectional singlet and triplet energy transfer processes (k ST(1BDP→1Por) = 7.8×1011 s-1, kTT(3Por→3BDP) = 1.0×1010 s-1, kTT(3BDP→ 3Por) = 1.6×1010 s-1), leading to a long-lived equilibrated [3BDP][Por]=[BDP][3Por] state. This equilibrated state contains approximately isoenergetic porphyrin and BODIPY triplets and exhibits efficient near-infrared phosphorescence (λem = 772 nm, φ = 0.26). Taken together, these studies show that appropriately designed triplet-utilizing arrays may overcome fundamental limitations typically associated with core-shell chromophores by tunable redistribution of energy from the core back onto the antennae. © 2010 American Chemical Society.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of the American Chemical Society|
|State||Published - Jan 12 2011|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-015-21
Acknowledgements: Funding for this research was provided by the Center for Advanced Molecular Photovoltaics (CAMP) (KUS-C1-015-21) of the King Abdullah University of Science and Technology (KAUST) and the Global Photonic Corporation. The quantification of absorbance at AM1.5G illumination and femto-second transient absorption measurements were carried out with support from the Department of Energy's Energy Frontier Research Center program (Center for Energy Nanoscience, Award DE-SC0001011). S.T.R. acknowledges support from the National Science Foundation in the form of an ACC-F fellowship (CHE-0937015), and A.C.D. acknowledges support from the NSF Center for Chemical Innovation (CCI Powering the Planet, Grants CHE-0802907 and CHE-0947829). We are also grateful to Dr. Jay Winkler and the Beckman Institute Laser Resource Center at the California Institute of Technology for assistance with nanosecond transient absorption measurements. We dedicate this manuscript to Professor Harry B. Gray, pioneer of inorganic photochemistry, on the occasion of his 75th birthday.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.