Substituent Effect on the Circularly Polarized Luminescence of C₁‐Symmetric Carbene‐Copper(I) Complexes

Abstract

The substituent effect on the magnitude of the circularly polarized luminescence (CPL) of MentCAAC‐Cu‐X (X=F, Cl, Br, I, BH4, B3H8; CAAC=cyclic (alkyl)(amino)carbenes) complexes is experimentally investigated. This study examines seven pairs of enantiomeric complexes with small anionic substituents (halides, borohydrides, hydride). The complexes are fully characterized, including single crystal X‐ray diffraction studies, and chiroptical measurements show that small covalent anions induce a larger CPL magnitude. These results demonstrate that the magnitude of the CPL can be manipulated without making any modifications to the chiral ligand.

Helicenic N-heterocyclic carbene copper(i) complex displaying circularly polarized blue fluorescence

“…4 b ,6 However, there are still very few chiral emissive Cu( i ) complexes, and only two recent examples of enantiopure Cu–X (X = F, Cl, Br, I, BH 4 , B 3 H 8 ) molecular systems bearing a chiral menthyl–CAAC ligand that display circularly polarized luminescence (CPL). 7 Introduction of novel chiral NHC–based Cu( i ) complexes is attractive for the development of circularly polarized (CP) OLEDs, a fast-growing research field for light-emitting device technology. 8…”

“…To our knowledge, this study constitutes the first example of a CPL-active, chiral NHC-based copper complex comprising a helicenic ligand. 7…”

Synthesis and Photophysical Studies of Copper(I) CAAC Half-Sandwich Complexes as a Highly Modifiable Class of Emitters

“…On the one hand, if the discrimination of photons of opposite circular polarization measured by the absorption dissymmetry factor g abs is high, the compounds might be interesting candidates in chiral induction of energy transfer or imaging . On the other hand, these compounds are readily available in an enantiomerically pure form, and as information about the chiroptical properties of carbene copper(I) complexes is so far limited to 2-Cl and related halides and borohydrides, it seems useful to increase the understanding of the correlation between complex structures and interaction with circular polarized light. , The dissymmetry of absorption in dependence of the wavelength is provided by g normala normalb normals = normalΔ ε ε = ε normalL − ε normalR ε where ε L and ε R are the left- and right-handed circular polarization-dependent extinction coefficients, respectively (Figure ). It appears that the lowest energy transition bands exhibit moderate ECD with g abs (365 nm) = 1.4 × 10 –4 and g abs (420 nm) = −1.0 × 10 –4 for 2-Cp and 2-Cp* , respectively, which is lower than the one we observed for 2-Cl (2.6 × 10 –3 ) (Figure S15).…”

“…59 On the other hand, these compounds are readily available in an enantiomerically pure form, and as information about the chiroptical properties of carbene copper(I) complexes is so far limited to 2-Cl and related halides and borohydrides, it seems useful to increase the understanding of the correlation between complex structures and interaction with circular polarized light. 52,60 The dissymmetry of absorption in dependence of the wavelength is provided by…”

Recent Advances in the Domain of Cyclic (Alkyl)(Amino) Carbenes

“…Moreover, as demonstrated by Braker et al in the recent report, the magnitude of the circularly polarized luminescence in cAACÀ Cu(I)À X complexes can be changed by varying the type of X ligand. [227] This suggests that the luminescence properties can be tuned without modification of the main molecular skeleton.…”