Ruthenium-Vinylhelicenes: Remote Metal-Based Enhancement and Redox Switching of the Chiroptical Properties of a Helicene Core

Abstract

Introducing metal-vinyl ruthenium moieties onto [6]helicene results in a significant enhancement of the chiroptical properties due to strong metal-ligand electronic interactions. The electro-active Ru centers allow the achievement of the first purely helicene-based redox-triggered chiroptical switches. A combination of electrochemical, spectroscopic, and theoretical techniques reveals that the helicene moiety is a noninnocent ligand bearing a significant spin density.

Enantioseparation on Riboflavin Derivatives Chemically Bonded to Silica Gel as Chiral Stationary Phases for HPLC

“…The racemates were commercially available or were prepared by the usual or reported methods. [29][30][31] The synthesis of new [6]helicene derivatives (26-28) will be reported elsewhere. Porous spherical silica gel (Daiso gel SP-120-7P, N-silica) with a mean particle size of 7 µm and a mean pore diameter of 12 nm was kindly supplied from Daicel (Tokyo, Japan).…”

“…However, CSPC and CSPE immobilized at the3-N-position could not resolve the helicenes at all, indicating that the interaction of the original isoalloxazine ring of CSPA and CSPB with the polyaromatic helicenes may be the major driving force for their efficient chiral recognition of the helicenes rather [7]helicene (30) on CSPA and CSPB was identical to that on the reported riboflavin-coated silica gel CSP, 20 judging from the Cotton effect sign of the first-eluted enantiomer of 30 at 350 nm. 20,33 More interestingly, most of the helicene derivatives, in particular, the [6]helicene derivatives (25 and 27), [7]helicene (30), and an [8]helicene analog (31) were better resolved on the 3-Nbonded CSPD composed of the fully-acetylated ribityl residue, and 25 and 31 (Fig. 3C) were completely separated.…”

Redox‐triggered chiroptical switching activity of ruthenium(III)‐bis‐(β‐diketonato) complexes bearing a bipyridine‐helicene ligand

“…3 In this context, several classes of organometallic helicene-based complexes have been investigated in our groups, including (1) ruthenium(II)-vinyl- 4,5 and iron(II)-ethynyl-carbo [6] helicenes 6 displaying redox-triggered switching of not only ECD and OR responses but also vibrational circular dichroism and, in the case of the Fe system, even resonance Raman optical activity spectra, (2) cycloplatinated bipyridine- [6]helicene-based systems demonstrating acid/base-triggered tuning of ECD and circularly polarized luminescence signals, 7 and (3) a bis-helicenic terpyridine derivative revealing an efficient absorption and emission switching activity through zinc(II) coordination/decoordination processes. Herein, we describe the synthesis of stable octahedral Ru(III) complexes ( [4] .+ ,PF 6 − , Scheme 1) bearing a helicenic bipyridine and two tmhd (tmhd: 2,2,6,6-tetramethyl-3,5heptanedionato) ligands. Herein, we describe the synthesis of stable octahedral Ru(III) complexes ( [4] .+ ,PF 6 − , Scheme 1) bearing a helicenic bipyridine and two tmhd (tmhd: 2,2,6,6-tetramethyl-3,5heptanedionato) ligands.…”

“…[11][12][13][14] These novel chiral propeller-like systems have been characterized via electrochemistry examinations, UV-vis and ECD spectroscopy, and first-principles calculations. 7,15 2.2 | Synthesis of racemic [4] .+ ,PF 6 − To a solution of 2 (20 mg, 0.03 mmol) in DMF (3 mL) was added a solution of rac-3 (12 mg, 0.03 mmol) in DMF (3 mL). 2 and racemic and enantiopure bipyridine-carbo [6]helicene (rac-, P-, or M-3) were prepared according to literature procedures.…”

Dioxygen‐Triggered Transannular Dearomatization of Benzo[5]helicene Diols: Highly Efficient Synthesis of Chiral π‐Extended Diones

“…[5] Recently, optically pure helicenes having diverse functional groups are employed in several different fields, such as highoptical-rotation complexes, [6] organoelectronics, [7] asymmetric gold catalysis, [8] redox-triggered chiroptical switches, [9] and proteinlike tetrameric aabb-heteroaggregates.…”