TITLE:
Dynamic NMR and Twisted Intramolecular Charge Transfer Excited States
AUTHORS:
Iraj Parchamazad, Debra Hornyak, Melvin Miles
KEYWORDS:
Twisted Intramolecular Charge Transfer State, Back Electron Transfer, Twisted Excited State, Dynamic NMR, Rotation around B-N Bond, Molecular Photochemistry inside NMR Probe, Customized Optical Probe, Solvent Effect, Low Temperature Spectra
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.6 No.5,
March
31,
2015
ABSTRACT: In this paper the results of dynamic NMR
studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or
without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom-made optical
probe and with our custom-made 450 watts (W) monochromatic light
sources. The molecular photochemistry including twisted intramolecular
charge-transfer-excited-state (TICT) of the EMABPB in several solvents has been
investigated. These results indicate that the aminoborane demonstrates multiple
configurations in CD3Cl and CD2Cl2 resulting
in the shifts of the signals of the alkyl groups on the nitrogen and boron.
This indicates that there are some time-dependent changes at constant
temperature over the irradiation interval. At ﹣60°C and the presence of light (λ = 265 nm), we observed a large change
in the populations of the two sites, and this by itself indicates a
modification in the rotation around the boron nitrogen bond in the excited
state. By considering the existence of the TICT state, many important energy
technologies may be developed with higher efficiency by controlling the
back-electron transfer processes.