Phosphorescence Resulting from Interaction between Two Non‐equivalent Metals on a Helical π‐Conjugated Surface

Abstract

A [7]helicene bis-ruthenium complex, with one ruthenium atom bound to the cyclopentadienyl (Cp) ring and the other coordinated to the arene ring at the edge of the helicene, was synthesized. This complex showed phosphorescence both in butyronitrile (Φ=31 %, 77 K) and in the solid state (Φ=18 %, 77 K). The two non-equivalent ruthenium metal atoms, attached to the helicene ligand, interact with each other upon photoabsorption and emission.

Asymmetric Synthesis and Chiroptical Properties of Enantiopure Helical Ferrocenes

“…Despite the great achievements performed up to date in this field, to the best of our knowledge, there are only a few examples of helical ferrocenes in which the central iron atom of the ferrocene unit is bounded directly into the helicene framework through the ortho -annulation to several aromatic rings (Figure a–c). − In all cases reported, the synthetic strategy was based on the initial formation of the helicene framework containing one or two cyclopentadienyl rings, followed by formation of the ferrocene unit. Thus, it is worth mentioning the pioneering work of Katz, who in 1982 described the first synthesis of a racemic [7]-helicene with the ferrocene unit at the edge of its skeleton (Figure a) .…”

“…In 2007, Thiel reported the synthesis of a series of ferrocenes with the dibenzo­[c,g]­fluorenyl (Dbf) ligand, in which the ferrocene unit is situated at the middle of the [5]-helicene structure (Figure b), although racemization proceeded rapidly at room temperature in solution . This problem was solved by Nozaki in 2017 by synthesizing an enantiopure [7]-helicene analogue (Figure c), with a high racemization barrier, through chiral HPLC resolution of the corresponding racemic derivative . This helical ferrocene showed large optical rotations and intense circular dichroism (CD) responses.…”