Photophysical properties and electronic structure of bacteriochlorin-chalcones with extended near-infrared absorption.
Synthetic bacteriochlorins enable systematic tailoring of substituents about the bacteriochlorin chromophore and thereby provide insights concerning the native bacteriochlorophylls of bacterial photosynthesis. Nine free-base bacteriochlorins (eight prepared previously and one prepared here) have been examined that bear diverse substituents at the 13- or 3,13-positions. The substituents include chalcone (3-phenylprop-2-en-1-onyl) derivatives with groups attached to the phenyl moiety, a "reverse chalcone" (3-phenyl-3-oxo-1-enyl), and extended chalcones (5-phenylpenta-2,4-dien-1-onyl, retinylidenonyl). The spectral and photophysical properties (τs, Φf, Φ(ic), Φ(isc), τT, k(f), k(ic), k(isc)) of the bacteriochlorins have been characterized. The bacteriochlorins absorb strongly in the 780-800 nm region and have fluorescence quantum yields (Φf) in the range 0.05-0.11 in toluene and dimethylsulfoxide. Light-induced electron promotions between orbitals with predominantly substituent or macrocycle character or both may give rise to some net macrocycle ↔ substituent charge-transfer character in the lowest and higher singlet excited states as indicated by density functional theory (DFT) and time-dependent DFT calculations. Such calculations indicated significant participation of molecular orbitals beyond those (HOMO - 1 to LUMO + 1) in the Gouterman four-orbital model. Taken together, the studies provide insight into the fundamental properties of bacteriochlorins and illustrate designs for tuning the spectral and photophysical features of these near-infrared-absorbing tetrapyrrole chromophores.
Department of Chemistry, Washington University, St. Louis, MO, USA.
Eunkyung
E
Yang
Christian
C
Ruzié
Michael
M
Krayer
James R
JR
Diers
Dariusz M
DM
Niedzwiedzki
Christine
C
Kirmaier
Jonathan S
JS
Lindsey
David F
DF
Bocian
Dewey
D
Holten
D001429:Bacteriochlorophylls / Q000737:chemistry; D047188:Chalcones / Q000737:chemistry*; D004121:Dimethyl Sulfoxide; D004583:Electrons; D007700:Kinetics; D018716:Molecular Mimicry; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents; D019265:Spectroscopy, Near-Infrared; D045725:Tetrapyrroles / Q000737:chemistry*; D013816:Thermodynamics; D014050:Toluene
D001429:Bacteriochlorophylls; D047188:Chalcones; D011166:Porphyrins; D012997:Solvents; D045725:Tetrapyrroles; C452433:bacteriochlorin; D014050:Toluene; D004121:Dimethyl Sulfoxide