The
possibility to design alkali-metal-free coinage metalides as
alternative species to the unstable alkalides has been explored by
constructing a series of M-1-M’ (M; M’
= Cu, Ag, and Au) based on the facially polarized all-cis 1,2,3,4,5,6-hexafluorocyclohexane (1) in this work.
Under the joint action of inherent polarization of 1 and
the electronegativity difference between M’ and M, the s electron
of Cu/Ag atom can be ejected to the Au atom, forming the diffuse excess
electron around the Au– anions in the Cu+
-1-Au– and Ag+
-1-Au– complexes. Hence, they can be regarded as the
first examples of alkali-metal-free coinage metalides. These two compounds
not only have higher stability (larger VIE and E
c values) than previously reported alkalides but also exhibit
remarkably larger β0 values than the reported coinage
metalides M+
-1-Au– (M =
Li, Na, and K), demonstrating their great potential to serve as new
molecular materials with considerable NLO responses. Taking Cu+
-1-Cu– and Cu+
-1-Ag– as examples, it is proved that the
rest of the M-1-M’ compounds can also be converted
into coinage metalides under oriented external electric fields (OEEFs),
which provides an approach to obtain novel NLO molecular switches.
This work will pave the way to design stable NLO materials by using
coinage metal atoms instead of alkali metals, which are more likely
to be synthesized in the laboratory.