5 research outputs found
Crystalline Graphdiyne Nanosheets Produced at a Gas/Liquid or Liquid/Liquid Interface
Synthetic two-dimensional
polymers, or bottom-up nanosheets, are
ultrathin polymeric frameworks with in-plane periodicity. They can
be synthesized in a direct, bottom-up fashion using atomic, ionic,
or molecular components. However, few are based on carbon–carbon
bond formation, which means that there is a potential new field of
investigation into these fundamentally important chemical bonds. Here,
we describe the bottom-up synthesis of all-carbon, π-conjugated
graphdiyne nanosheets. A liquid/liquid interfacial protocol involves
layering a dichloromethane solution of hexaethynylbenzene on an aqueous
layer containing a copper catalyst at room temperature. A multilayer
graphdiyne (thickness, 24 nm; domain size, >25 μm) emerges
through
a successive alkyne–alkyne homocoupling reaction at the interface.
A gas/liquid interfacial synthesis is more successful. Sprinkling
a very small amount of hexaethynylbenzene in a mixture of dichloromethane
and toluene onto the surface of the aqueous phase at room temperature
generated single-crystalline graphdiyne nanosheets, which feature
regular hexagonal domains, a lower degree of oxygenation, and uniform
thickness (3.0 nm) and lateral size (1.5 μm)
Crystalline Graphdiyne Nanosheets Produced at a Gas/Liquid or Liquid/Liquid Interface
Synthetic two-dimensional
polymers, or bottom-up nanosheets, are
ultrathin polymeric frameworks with in-plane periodicity. They can
be synthesized in a direct, bottom-up fashion using atomic, ionic,
or molecular components. However, few are based on carbon–carbon
bond formation, which means that there is a potential new field of
investigation into these fundamentally important chemical bonds. Here,
we describe the bottom-up synthesis of all-carbon, π-conjugated
graphdiyne nanosheets. A liquid/liquid interfacial protocol involves
layering a dichloromethane solution of hexaethynylbenzene on an aqueous
layer containing a copper catalyst at room temperature. A multilayer
graphdiyne (thickness, 24 nm; domain size, >25 μm) emerges
through
a successive alkyne–alkyne homocoupling reaction at the interface.
A gas/liquid interfacial synthesis is more successful. Sprinkling
a very small amount of hexaethynylbenzene in a mixture of dichloromethane
and toluene onto the surface of the aqueous phase at room temperature
generated single-crystalline graphdiyne nanosheets, which feature
regular hexagonal domains, a lower degree of oxygenation, and uniform
thickness (3.0 nm) and lateral size (1.5 μm)
π‑Conjugated Trinuclear Group‑9 Metalladithiolenes with a Triphenylene Backbone
Previously,
we synthesized π-conjugated trinuclear metalladithiolene complexes
based on benzenehexathiol (<i>J. Chem. Soc., Dalton Trans.</i> <b>1998</b>, 2651; <i>Dalton Trans.</i> <b>2009</b>, 1939; <i>Inorg. Chem.</i> <b>2011</b>, <i>50</i>, 6856). Here we report trinuclear complexes with a triphenylene
backbone. A reaction with triphenylenehexathiol and group 9 metal
precursors in the presence of triethylamine gives rise to trinuclear
complexes <b>9</b>–<b>11</b>. The planar structure
of <b>11</b> is determined using single crystal X-ray diffraction
analysis. The ligand-to-metal charge transfer bands of <b>9</b>–<b>11</b> move to longer wavelengths compared with
those of mononuclear <b>12</b>–<b>14</b>. Electrochemical
measurements disclose that the one-electron and two-electron reduced
mixed-valent states are stabilized thermodynamically. UV–vis–NIR
spectroscopy for the reduced species of <b>9</b> identifies
intervalence charge transfer bands for <b>9</b><sup>–</sup> and <b>9</b><sup>2–</sup>, substantiating the existence
of electronic communication among the three metal nuclei. These observations
prove that the triphenylene backbone transmits π-conjugation
among the three metalladithiolene units
π‑Conjugated Nickel Bis(dithiolene) Complex Nanosheet
A π-conjugated nanosheet comprising planar nickel
bisÂ(dithiolene)
complexes was synthesized by a bottom-up method. A liquid–liquid
interfacial reaction using benzenehexathiol in the organic phase and
nickelÂ(II) acetate in the aqueous phase produced a semiconducting
bulk material with a thickness of several micrometers. Powder X-ray
diffraction analysis revealed that the crystalline portion of the
bulk material comprised a staggered stack of nanosheets. A single-layer
nanosheet was successfully realized using a gas–liquid interfacial
reaction. Atomic force microscopy and scanning tunneling microscopy
confirmed that the π-conjugated nanosheet was single-layered.
Modulation of the oxidation state of the nanosheet was possible using
chemical redox reactions
Redox Control and High Conductivity of Nickel Bis(dithiolene) Complex π‑Nanosheet: A Potential Organic Two-Dimensional Topological Insulator
A bulk
material comprising stacked nanosheets of nickel bisÂ(dithiolene)
complexes is investigated. The average oxidation number is −3/4
for each complex unit in the as-prepared sample; oxidation or reduction
respectively can change this to 0 or −1. Refined electrical
conductivity measurement, involving a single microflake sample being
subjected to the van der Pauw method under scanning electron microscopy
control, reveals a conductivity of 1.6 × 10<sup>2</sup> S cm<sup>–1</sup>, which is remarkably high for a coordination polymeric
material. Conductivity is also noted to modulate with the change of
oxidation state. Theoretical calculation and photoelectron emission
spectroscopy reveal the stacked nanosheets to have a metallic nature.
This work provides a foothold for the development of the first organic-based
two-dimensional topological insulator, which will require the precise
control of the oxidation state in the single-layer nickel bisdithiolene
complex nanosheet (cf. Liu, F. et al. <i>Nano Lett.</i> <b>2013</b>, <i>13</i>, 2842)