CPL Measurement of Camphorquinone Using CPL-300 Circularly Polarized Luminescence Spectrometer

Download PDF February 14, 2018

Introduction

CPL-300 Circularly Polarized Luminescence Spectrophotometer
CPL-300 Circularly Polarized Luminescence Spectrophotometer

When chiral compounds are excited with unpolarized light, the difference in emission intensities of left- and right-handed circularly polarized light can be measured. This phenomenon is called circularly polarized luminescence (CPL). While circular dichroism provides information about the ground state of chiral molecules, CPL spectroscopy probes the excited states of chiral molecules.

By combining CPL with ECD, more structural information regarding chiral molecules can be obtained. To measure sharp CPL peaks at a high resolution, the CPL spectrometer uses two prism monochromators. Both the emission and excitation monochromators are equipped with continuously variable slit drives, which allow for an appropriate wavelength and band width selection.

This application note demonstrates the measurement and analysis of camphorquinone using two complimentary techniques: circular dichroism and circularly polarized luminescence.

Experimental

18 mM of (1R)-(-) – and (1S)-(+)-camphorquinone was prepared in ethanol.

Measurement Conditions
CDCPL
Data Pitch0.1 nmExcitation Wavelength440 nm
Scan Speed50 nm/minExcitation Bandwidth16 nm
D.I.T.2 secData Pitch0.1 nm
Bandwidth1 nmEmission Bandwidth10 mm
Accumulations1Scan Speed50 nm/min
D.I.T.4 sec
Accumulations16

Keywords

Circularly polarized luminescence, Circular dichroism, CD-0031, Materials

Results

The CPL and fluorescence spectra of (1R)-(-)- and (1S)-(+)- camphorquinone were measured using a CPL-300, while CD and absorption were collected using a J-1500. The CD and CPL signals were normalized as gabs =Δ ε/ε and glum = ΔI/I, respectively. The spectra are shown in Figure 1.

Figure 1. The (a) CD and CPL spectra, (b) absorbance and fluorescence spectra, and (c) gabs and glum spectra of the (1R)-(-)- (bluered) and (1S)-(+)- (bluered) camphorquinone ethanol solution.

Conclusion

The results are in good agreement with the camphorquinone CPL spectrum previously reported.1

References

1. Chun Ka Luk and F. S. Richardson, JACS. 1974, 96, 2006-2009.

About the Author

Leah Pandiscia received her PhD from Drexel University where she studied Biophysical Chemistry. She is a Spectroscopy Applications Scientist at JASCO.