Circularly Polarized Luminescence Accessory

CIRCULARLY POLARIZED LUMINESCENCE

 

No matter if it is for characterization of lanthanide complexes, pharmaceutical compounds or chemiluminescent polymers—the Circularly Polarized Luminescence (CPL) accessory is an indispensable tool to probe the emission polarization of chiral luminophores.

CPL and CD with the same setup

The CPL accessory is compatible with standard CD measurements. CPL and CD mode are easily switched through a drop-down menu in the Chirascan software, requiring no hardware changes.

CPL Mode

 

CD Mode

 

 

 

Optics for optimization

Including all optics for optimizing the experimental setup, the CPL accessory adapts to individual sample requirements.

  • Focusing lens and iris control light throughput
  • Cut-off filter removes excitation light
  • Scanning Emission Monochromator (SEM) selects emission wavelength and bandwidth
  • Horizontal polarized excitation beam and a vertically polarized emission polarizer with a 90 degree geometry minimizes photoselection artifacts

Technical Specifications

Further Information
 

Applications and Case Studies

The Chirascan CPL accessory has applications from materials physics to biology. It is used to characterize the excited states of chiral molecules, for example:

  • Metal ion environments

    e.g. lanthanide complexes as chiral probes and in liquid crystal displays

  • Biological polymers

    e.g. chemiluminescence in some firefly species

  • Simple organic molecules

    Polycyclic aromatics, e.g. some anticancer drugs

    Stereo-dynamic probes for analytics

Case Study: Eu(facam)3 as a CPL benchmark

 

Eu(facam)3 (Europium tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate]) is a europium complex consisting of three small molecules structurally very similar to camphor sulfonic acid (CSA) as they share the same bicyclic core of camphor.

CSA is a conventional calibration standard for CD spectroscopy and, likewise, Eu(facam)3 is a known reference for CPL. Unlike CSA, Eu(facam)3 also has a conjugated π system that lends it its luminescence.

Here, Eu(facam)3 in 5.5 mM DMSO was used for proof-of-principle CPL measurements performed with a 1 cm pathlength using a Chirascan V100TM.

Results

Measurements with the Chirascan CPL accessory yielded results in line with the known spectral profiles of Eu(facam)3, i.e. ΔI and glum with negative peaks at ~585 nm and ~595 nm and a positive peak at ~613 nm and I  with positive peaks at these wavelengths.

Conclusions

Performance of the Chirascan CPL accessory together with the Chirascan V100 can easily be scrutinized using Eu(facam)3.

Case Study: Characterization of Quinolone Cycles

Quinolone antibiotics are often used to treat genitourinary infections. A polymer consisting of quinolone cycles with the bicyclic core structure of 4-quinolone connected by amide bonds (molecular formula: C472H476N66O68, Molecular weight: 8605.89 Da) was analysed with a the CPL accessory installed on a Chirascan V100TM. Polymer samples at different concentrations in dichloromethane were analysed in a 1 cm pathlength cuvette.

Results

CPL measurements yielded differential fluorescence, ΔI (AC), with a maximum at ~460 nm, a total fluorescence, I (DC), with a maximum at ~465 nm and the luminescence dissymmetry ratio, glum, with a maximum at ~425 nm. As glum is calculated from ΔI and I, any dependence on sample concentration is removed.

In addition to CPL data, CD and absorbance data was obtained without changing the experimental setup. For CD measurements, a total absorbance between about 0.4 AU and 1.6 AU but no greater than 2 AU is optimal. Within this range, glum was virtually constant.

As an identical glum is obtained over a wide range of sample concentrations, sample concentration can be optimized for CD so that both CD and CPL data can be obtained for the same sample.

Conclusions

The Chirascan CPL accessory enables comprehensive analysis of chiral luminophores and is compatible with CD measurements.

  • CPL and CD measurements with the same instrument setup and sample
  • Multiple ways for optimizing light throughput
  • Full software integration for easy acquisition of both CD and CPL measurements