The Measurement of Circular Polarization in the Near-IR Luminescence from Chiral Complexes of Yb(III) and Nd(III)

Abstract

This work describes the measurement and analysis of circular polarization in the luminescence (CPL), in the near-IR spectral region, from chiral complexes of Yb(III) and Nd(III) in solution. The experimental technique is based upon previous measurements of CPL in the visible region. Instrumentation design, performance, and calibration are discussed. The experimental technique has been applied to several related complexes of Yb(III) and Nd(III) with chiral macrocyclic ligands based on 1,4,7,10-tetraazacyclododecane that have approximate C 4 symmetry. In addition, CPL from D 3 complexes of Yb(III) with 2,6-pyridinedicarboxylate, which were prepared as a solution of enriched enantiomers by the addition of (+)-dimethyltartrate, is also presented. It is demonstrated that CPL from the 2F5/2 → 2F7/2 transition of Yb(III) at 980 nm is particularly suited for CPL studies because this transition satisfies magnetic-dipole selection rules. The luminescence from the 4F3/2 → 4I9/2 and 4F3/2 → 4I11/2 transitions of Nd(III) centered at 880 and 1060 nm, respectively, showed only weak CPL signals. The usefulness of these types of polarization measurements in the near-IR is discussed.

Lanthanide Circularly Polarized Luminescence: Bases and Applications

“…However, so far, only few pioneering works concerning the measurement of CPL in the NIR region have been reported, [72][73][74] and therefore it remains a relatively novel field to explore. However, so far, only few pioneering works concerning the measurement of CPL in the NIR region have been reported, [72][73][74] and therefore it remains a relatively novel field to explore.…”

“…Another asset worth employing is the luminescence of different lanthanides extending to the near-infrared (NIR) region; this would allow one to obtain molecules with circularly polarized emission in a region that cannot be easily reached with chiral organic emitters. However, so far, only few pioneering works concerning the measurement of CPL in the NIR region have been reported, [72][73][74] and therefore it remains a relatively novel field to explore. Fig.…”

Static and Dynamic Stereochemistry of Chiral Ln DOTA Analogues

“…[41] Chirality has been introduced at an even more remote position, outside the first coordination sphere, by derivatizing the carboxyl group with a chiral amine, as occurs for example with the amide DOTAMNp (Scheme 2). [42][43][44][45] It may appear surprising that in spite of the distance between the chiral centre and the DOTA scaffold, Yb DOTAMNp is completely rigid and does not show any dynamic process, in a wide range of solvents [methanol, dimethyl sulfoxide (DMSO), acetonitrile]. [42] The common problem of conformational assignment has been solved in the literature by detailed analysis of the NMR data, but at this stage of our discussion a much easier solution is provided by the direct inspection of the NIR-ECD spectrum, shown in Figure 9.…”

Survey of factors determining the circularly polarised luminescence of macrocyclic lanthanide complexes in solution

“…6,11 The preferred isomer is a regular mono-capped square antiprismatic structure and for an S-configuration at C, the D-(kkkk) isomer adopts the most stable structure in which arm rotation is also believed to be slow on the NMR and luminescence emission timescales. 11 In the naphthyl analogue Eu:3bH 2 O 3 , strong exciton coupling has been observed between pairs of naphthyl chromophores 6 and relatively intense CPL emission (g em~0 .2À0.3) may also be obtained in the visible (Eu, Tb) 11 or near-IR (Yb, Nd) 12,13 following direct or indirect excitation of the lanthanide ion.…”