Fluorescence from an H-aggregated naphthalenediimide based peptide: photophysical and computational investigation of this rare phenomenon.
Fluorescence associated with J-aggregated naphthalenediimides (NDIs) is common. However, in this study an NDI based synthetic peptide molecule is found to form a fluorescent H-aggregate in a chloroform (CHCl3)-methylcyclohexane (MCH) mixture. An attempt has been made to explain the unusual fluorescence property of this H-aggregated NDI derivative. Time correlated single photon counting (TCSPC) shows that the average lifetime of the NDI based molecule is on the order of a few nanoseconds. It is revealed from the computational study that the transition from the second exited state (S2) to the ground energy state (S0) is responsible for the fluorescence as S1 is a dark state. Such rare violation of Kasha's rule accounts for the unusual fluorescence properties of this type of NDI molecule in the H-aggregated state.
Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India. bcab@iacs.res.in.
Shibaji
S
Basak
Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India. bcab@iacs.res.in.
Nibedita
N
Nandi
Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India. spad@iacs.res.in.
Kalishankar
K
Bhattacharyya
Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India. spad@iacs.res.in.
Ayan
A
Datta
Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India. bcab@iacs.res.in.
Arindam
A
Banerjee
D005453:Fluorescence; D007094:Imides / Q000737:chemistry*; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory
D007094:Imides; D009281:Naphthalenes; D010455:Peptides; C542131:naphthalenediimide