Vibrational circular dichroism and chiroptical properties of chiral Ir(iii) luminescent complexes

Abstract

The octahedral ionic Ir(iii) complex with a dual stereogenic centre of general formula Δ,Λ-(R,S)-[(ppy)2Ir(Me-Campy)]X, where ppy = 2-phenylpyridine and Me-Campy = 2-methyl-5,6,7,8-tetrahydroquinolin-8-amine, and the complex Λ-(R,S)-[(ppy)2Ir(H-Campy)]X, where ppy = 2-phenylpyridine, H-Campy = 8-amino-5,6,7,8-tetrahydroquinolines and X(-) = Cl(-) as a counterion in both cases, have been characterized by vibrational circular dichroism (VCD), which turns out to be efficacious in diastereomeric discrimination. Moreover, the single crystal X-ray structure of the complex Δ-(R)-[(ppy)2Ir(Me-Campy)]Cl is reported here. Density functional theory (DFT) calculations allow us to conclude that the most important doublet feature in the VCD spectra is associated with a clear vibrational exciton structure located on the two dissymmetrically disposed phenylpyridine ligands. The features in the VCD spectra associated with the (R) or (S)-central chirality configuration are identified and commented on. DFT calculations provide also the interpretation of electronic circular dichroism (ECD) spectra. Finally, circularly polarized luminescence (CPL) spectra are presented as an additional chiroptical characterization of these luminescent iridium complexes.

Computational simulation of vibrationally resolved spectra for spin‐forbidden transitions

“…We finally look at the CPP spectrum of this complex to examine its chiral response. Experimental spectra are not available; however, the CPP sign is expected to be negative in Λ complexes and positive for the Δ configurations, while the magnitude of the dissymmetry factor g should be around 10 −3 …”

“…Experimental spectra are not available; however, the CPP sign is expected to be negative in Λ complexes and positive for the Δ configurations, while the magnitude of the dissymmetry factor g should be around 10 −3 . 8,[99][100][101] Calculated g-values for different functionals can be seen in Table 1. From these results, a remarkable difference between standard and range-separated functionals can be noted, with the latter yielding the expected sign.…”

Circularly Polarized Luminescence: A Review of Experimental and Theoretical Aspects

“…On the right we provide just the experimental CPL spectra of the two enantiomers for which phosphorence effects are possible, as anticipated in Ref. 73 and a few references therein. The only attempt in the literature tackling such a problem is that of Ref.…”

Searching for Models Exhibiting High Circularly Polarized Luminescence: Electroactive Inherently Chiral Oligothiophenes

“…Series of normalized CV stability cycles around the first two oxidation peaks of the oligo-BT 2 -DTP 2 film, in monomer-free solution,a t0.2 Vs À1 scan rate (a cyclea t0.02 Vs À1 is also plotted for comparison). [31][32][33] Care mustb et aken, however,b ecause the magnetic momento ft he two separatem oieties can in some instances prevail on the pure couplede lectric dipole moment mechanism. Secondly, someI Rb ands are weak and this prevents the doublets from havingastrong vibrational excitonc haracter.…”