DOI: 10.1002/chem.201504441
Communication
&
Supramolecular Chirality
Induced Circular Dichroism in Phosphine Gold(I) Aryl Acetylide
Urea Complexes through Hydrogen-Bonded Chiral Co-Assemblies
ture.[10] Obviously, the incorporation of gold complexes in
Abstract: Phosphine gold(I) aryl acetylide complexes
equipped with a central bis(urea) moiety form 1D hydro-
other chiral matrices can offer interesting alternatives.[11]
Notably, chiral supramolecular polymers constitute robust
gen-bonded polymeric assemblies in solution that do not
platforms for chirality transfer and amplification.[12] Supra-
display any optical activity. Chiral co-assemblies are
molecular polymers are often in dynamic exchange, and co-
formed by simple addition of an enantiopure (metal-free)
polymers can be prepared by simply mixing different types of
complementary monomer. Although exhibiting an intrinsi-
complementary monomers. Since the chiral information is
cally achiral linear geometry, the gold(I) aryl acetylide frag-
transferred (and possibly amplified) along the polymeric back-
ment is located in the chiral environment displayed by
bone, co-polymers with a strong helical bias are formed, which
the hydrogen-bonded co-assemblies, as demonstrated by
are composed of two types of monomers: the monomer bear-
induced circular dichroism (ICD).
ing the chiral information (commonly called the sergeant) and
the achiral monomer (the soldier). Up to now, sergeants-and-
soldiers experiments have been mostly conducted with struc-
Inducing chirality to metal complexes,[1] nanoparticles,[2] and
turally similar monomers in the purpose of probing the chirali-
surfaces[3] is a central topic of chemical sciences, and it is moti-
vated by important applications in the fields of chiral recogni-
tion, sensing, and catalysis. Notably, non-covalent interactions
have been designed to place intrinsically achiral metal com-
plexes in the chiral environment provided by various types of
chiral species.[4] Chirality induction is usually confirmed by the
presence of a Cotton effect in the spectral region in which
only the metal complex absorbs.[5] The observation of such an
induced circular dichroism[6] (ICD) signal reflects the specific
electronic charge distribution within the thus-formed chiral
supramolecular entities.
ty amplification properties of supramolecular polymers.[4e,12]
By adapting the sergeants-and-soldiers principle, we design
a new strategy for the incorporation of metal complexes in
a dynamic and modular chiral environment in solution. One-di-
mensional (1D) co-assemblies are targeted which contain ser-
geants and soldiers that differ not only by their chiral nature
but also by the functionality located in their side chain. More
precisely, we investigate mixtures containing: 1) a bis(urea)
monomer bearing only the chiral information (the sergeant)
and 2) a metal-functionalized bis(urea) monomer (the soldier).
The two urea moieties, connected through an aromatic spacer,
constitute a well-known self-complementary hydrogen-bonded
unit for the assembly of 1D supramolecular polymers in solu-
tion.[13] Also, the co-assemblies formed by structurally simple
non-metal-functionalized sergeants and soldiers are chiral and
display strong chirality amplification effects.[14] We expect that
the intrinsically achiral metal fragment, located at the periph-
ery of the co-assemblies, will be a reporter of the chirality dis-
played by the central supramolecular helices. The formation of
such metal-functionalized co-assemblies seems particularly at-
tractive since: it would allow to independently control 1) the
electronic characteristics of the metal complex soldier and
2) the degree of chirality induction/amplification within the co-
assemblies through the design of a metal-free sergeant.
Herein we describe the proof-of-principle of our strategy
using racemic gold complexes as the soldiers and enantiopure
monomers as the sergeants. The observation of an ICD signal
clearly demonstrates that the gold aryl acetylide complexes
are located in the chiral environment displayed by the co-as-
semblies.
Gold(I) species have attracted considerable attention since
the discovery of their catalytic and spectroscopic properties in
solution and their potential use in a wide range of applica-
tions.[7] However, since gold(I) has a known preference for
a linear coordination geometry, the induction of chirality in
gold(I) complexes is actually a non-trivial task. In the realm of
asymmetric catalysis, an effective degree of enantioinduction is
observed only for a few classes of chiral covalent ligands or
anions.[8] Alternatively, ICD signals have been observed for
achiral gold complexes embedded into chiral surfactants[9] or
self-assembled within a semicrystalline chiral organized struc-
[a] Dr. J. Dubarle-Offner, Dr. J. Moussa, Dr. H. Amouri, Dr. B. Jouvelet,
Dr. L. Bouteiller, Dr. M. Raynal
Sorbonne UniversitØs, UPMC Univ Paris 06
CNRS, Institut Parisien de Chimie MolØculaire
4 Place Jussieu, 75005 Paris (France)
Our investigated gold(I) complexes 1·AuPPh3 and 1·AuPCy3
(Scheme 1) contain the following structural elements: 1) a cen-
Supporting information for this article is available on the WWW under
Chem. Eur. J. 2016, 22, 3985 – 3990
3985
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