38 research outputs found
Cupriphication of gold to sensitize d10âd10 metalâmetal bonds and near-unity phosphorescence quantum yields
Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reductionuponcupriphicationofcyclic trinucleartrigonal-planargold(I) complexes are found to sensitize ground-state Cu(I)âAu(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(ÎŒ-C2,N3-EtIm)4Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(ÎŒ-C2,N3-BzIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (1) and [Au2(ÎŒ-C2, N3-MeIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(ÎŒ-C2,N3-MeIm)Cu2(ÎŒ3,5-(CF3)2Pz)2], (3b) and [Au(ÎŒ-C2,N3-EtIm)Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(ÎŒ-C2,N3-BzIm)]3[Cu(ÎŒ-3,5-(CF3)2Pz)]3, (2)} formuponreactingAu3 {[Au(ÎŒ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R =benzyl/methyl/ethyl =BzIm/MeIm/EtIm)} with Cu3 {[Cu(ÎŒ-3,5(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via twoAu(I)âŻCu(I)metallophilicinteractions,whereas 4a exhibitsa hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10âd10 polar-covalent bond with ligandunassisted Cu(I)âAu(I) distances of 2.8750(8) Ă
eachâthe shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a âmetalâmetal bondâ vis-Ă -vis âmetallophilic interaction.â Density-functional calculations estimate 35â 43kcal/molbindingenergy,akintotypicalMâMsingle-bondenergies. Congruently, FTIR spectra of4a showmultiple far-IR bands within 65â 200 cmâ1, assignable to vCu-Au as validated by both the HarveyâGray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilicsensitizationinextinctioncoefficientandsolid-state photoluminescence quantum yields approaching unity (ΊPL = 0.90â0.97 vs. 0â0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications
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Photochemical and Photophysical Properties of Mononuclear and Multinuclear Closed Shell D10 Coinage Metal Complexes and Their Metallo-organometallic Adducts
This dissertation covers the studies of two major topics: the photochemistry of mononuclear and multinuclear gold(I) complexes and synthetic approaches to tailor photophysical properties of cyclic trinuclear d10 complexes. First a detailed photochemical examination into the photoreactivity of neutral mononuclear and multinuclear gold(I) complexes is discussed, with the aim of gold nanoparticle size and shape control for biomedical and catalysis applications. Next is a comprehensive systematic synthetic approach to tailor the photophysical properties of cyclic trinuclear d10 complexes. This synthetic approach includes an investigation of structure-luminescence relationships between cyclic trinuclear complexes, an examination into their Ï-acid/Ï-base reactivity with heavy metal cations and an exploration into the photophysical properties of new heterobimetallic cyclic trinuclear complexes. These photophysical properties inspections are used to screen materials for their employment in molecular electronic devices such as organic light-emitting diodes (OLEDs) and thin film transistors (OTFTs)
Eutectoid flux growth and physical properties of single crystal Ln117Ni54-ySn112-z (Ln = Gd-Dy)
Ln117Ni53-ySn112-z (Ln = Gd-Dy) have been grown via the eutectoid flux growth method, characterized using single crystal X-ray diffraction, and determined to have a face centered cubic unit cell with lattice parameters of a = 30.070(4), 29.862(5), and 29.823(4) Ă
for the Gd, Dy, and Tb analogues. The compounds contain over 1100 atoms per unit cell with a complex bonding network and multiple magnetic sublattices. In addition, disorder is prevalent throughout the structure. These physical characteristics are ideal when searching for ultralow thermal conductivity materials. Magnetic susceptibility and electrical properties are presented, and all analogues exhibit positive Curie-Weiss constants, suggesting ferromagnetic interactions in each compound, in addition to a spin-glass component to the magnetic behavior
Soft metal cations trigger sandwich-cluster luminescence of a new Au(I)-vinylimidazolate cyclic trinuclear complex
The formation of heterobimetallic complexes from parent cyclic trinuclear complexes (CTCs) of gold(I) has become straightforward in recent years with this team and others showing that the strategy leads to strengthened Au-Mâ bonding and optoelectronic properties. A new gold(I)-vinylimidazolate CTC, 1, was prepared and the formation of highly-emissive sandwich adducts with the soft metal cations Cu+, Ag+, and Tl+, 2 â 4, respectively, was investigated. Compound 1 does not exhibit peculiar emissive properties at room or cryogenic temperatures as the adducts do. Its unit cell packing displays an unprecedented collection of repeating units for CTCs. While the intermolecular AuâŠAu distances are versatile (3.470, 3.673, and 4.045 Ă
), they connect only single Au centres from adjacent CTCs and form extended circular networks. Hirshfeld surface analyses mapped the new CTC contours underlining the possible cooperative effects of not only metallophilic interactions but also C-HâŠÏ and hydrogen bonding in the packing of 1 (as opposed to the dominance of the former in most other reported CTCs). DFT calculations validate the formation of sandwich-like structures for compounds 2 - 4 with averaged AuâM distances of 2.665 Ă
, 2.802 Ă
, and 3.036 Ă
, respectively, close by to experimental crystal data obtained for similar sandwich compounds
Putting ScTGa<sub>5</sub> (T = Fe, Co, Ni) on the Map: How Electron Counts and Chemical Pressure Shape the Stability Range of the HoCoGa<sub>5</sub> Type
We explore the factors stabilizing
one member of the diverse structures
encountered in LnâTâE systems (Ln = lanthanide or similar
early d-block element, T = transition metal, E = p-block element):
the HoCoGa<sub>5</sub> type, an arrangement of atoms associated with
unconventional superconductivity. We first probe the boundaries of
its stability range through the growth and characterization of ScTGa<sub>5</sub> crystals (T = Fe, Co, Ni). After confirming that these compounds
adopt the HoCoGa<sub>5</sub> type, we analyze their electronic structure
using density functional theory (DFT) and DFT-calibrated HuÌckel
calculations. The observed valence electron count range of the HoCoGa<sub>5</sub> type is explained in terms of the 18-<i>n</i> rule,
with <i>n</i> = 6 for the Ln atoms and <i>n</i> = 2 for the T sites. The role of atomic sizes is investigated with
DFT-chemical pressure (DFT-CP) analysis of ScNiGa<sub>5</sub>, which
reveals negative pressures within the Ga sublattice as it stretches
to accommodate the Sc and T atoms. This CP scheme is consistent with
HoCoGa<sub>5</sub>-type gallides only being observed for relatively
small Ln and T atoms. These conclusions account for the relative positions
of the HoCoGa<sub>5</sub>, BaMg<sub>4</sub>Si<sub>3</sub>, and Ce<sub>2</sub>NiGa<sub>10</sub> types in a structure map, demonstrating
how combining the 18-<i>n</i> and CP schemes can guide our
understanding of LnâTâE systems
Polymorphic, Porous, and HostâGuest Nanostructures Directed by MonolayerâSubstrate Interactions: Epitaxial Self-Assembly Study of Cyclic Trinuclear Au(I) Complexes on HOPG at the SolutionâSolid Interface
Synthesis, crystallographic characterization,
and molecular self-assembly
of two novel cyclotrimeric goldÂ(I) complexes, Au<sub>3</sub>[3,5-(COOEt)<sub>2</sub>Pz]<sub>3</sub> (Au<sub>3</sub>Pz<sub>3</sub>) and Au<sub>3</sub>[(<i>n</i>-PrâO)ÂCî»NÂ(Me)]<sub>3</sub> (Au<sub>3</sub>Cb<sub>3</sub>) was studied. Single crystal X-ray
crystallography data reveal that both goldÂ(I) complexes have one-dimensional
stacking patterns caused by intermolecular AuÂ(I)···AuÂ(I)
aurophilic interactions. The Au<sub>3</sub>Pz<sub>3</sub> trimer units
stack with two alternate and symmetrical AuÂ(I)···AuÂ(I)
interactions while the Au<sub>3</sub>Cb<sub>3</sub> units have three
alternating and nonsymmetrical AuÂ(I)···AuÂ(I) interactions.
Molecular self-assembly of the goldÂ(I) complexes on the 1-phenyloctane/highly
ordered pyrolytic graphite (HOPG) (0001) solutionâsolid interface
is studied with scanning tunneling microscopy (STM). The goldÂ(I) cyclotrimers
form epitaxial nanostructures on the HOPG surface. At a concentration
of âŒ1 Ă 10<sup>â4</sup> M, Au<sub>3</sub>Pz<sub>3</sub> complexes exhibit a single morphology, while Au<sub>3</sub>Cb<sub>3</sub> complexes exhibit polymorphology. Two polymorphs,
one nonporous and the other porous, are observed at 22.0 ± 2.0
°C for Au<sub>3</sub>Cb<sub>3</sub> complexes. A nonporous, low-surface-density
(0.82 molecules/nm<sup>2</sup>) Au<sub>3</sub>Cb<sub>3</sub> nanostructure
forms first and then transforms into a high-density (1.43 molecules/nm<sup>2</sup>) porous nanostructure. This is the first time any porous
surface nanostructure is reported for an organometallic system. The
porous structure is thought to be stabilized by a combination of hydrogen
bonding and monolayerâsubstrate interactions. These pores are
utilized to incorporate pyrene into the film, rendering this the first
organometallic hostâguest system imaged at the solidâsolution
interface. Molecular and periodic density functional theory (DFT)
calculations shed light on the two-dimensional topography and polymorphic
self-assembly revealed by STM; these calculations suggest significant
electronic hybridization of the Au<sub>3</sub> trimer orbitals and
HOPG. The multiple-technique approach used herein provides insights
concerning moleculeâsubstrate and moleculeâmolecule
interactions
Eutectoid Flux Growth and Physical Properties of Single Crystal Ln<sub>117</sub>Ni<sub>54â<i>y</i></sub>Sn<sub>112â<i>z</i></sub> (Ln = GdâDy)
Ln<sub>117</sub>Ni<sub>53â<i>y</i></sub>Sn<sub>112â<i>z</i></sub> (Ln = GdâDy) have been
grown via the eutectoid flux growth method, characterized using single
crystal X-ray diffraction, and determined to have a face centered
cubic unit cell with lattice parameters of <i>a</i> = 30.070(4),
29.862(5), and 29.823(4) Ă
for the Gd, Dy, and Tb analogues.
The compounds contain over 1100 atoms per unit cell with a complex
bonding network and multiple magnetic sublattices. In addition, disorder
is prevalent throughout the structure. These physical characteristics
are ideal when searching for ultralow thermal conductivity materials.
Magnetic susceptibility and electrical properties are presented, and
all analogues exhibit positive CurieâWeiss constants, suggesting
ferromagnetic interactions in each compound, in addition to a spin-glass
component to the magnetic behavior
Eutectoid Flux Growth and Physical Properties of Single Crystal Ln<sub>117</sub>Ni<sub>54â<i>y</i></sub>Sn<sub>112â<i>z</i></sub> (Ln = GdâDy)
Ln<sub>117</sub>Ni<sub>53â<i>y</i></sub>Sn<sub>112â<i>z</i></sub> (Ln = GdâDy) have been
grown via the eutectoid flux growth method, characterized using single
crystal X-ray diffraction, and determined to have a face centered
cubic unit cell with lattice parameters of <i>a</i> = 30.070(4),
29.862(5), and 29.823(4) Ă
for the Gd, Dy, and Tb analogues.
The compounds contain over 1100 atoms per unit cell with a complex
bonding network and multiple magnetic sublattices. In addition, disorder
is prevalent throughout the structure. These physical characteristics
are ideal when searching for ultralow thermal conductivity materials.
Magnetic susceptibility and electrical properties are presented, and
all analogues exhibit positive CurieâWeiss constants, suggesting
ferromagnetic interactions in each compound, in addition to a spin-glass
component to the magnetic behavior
Polymorphic, Porous, and HostâGuest Nanostructures Directed by MonolayerâSubstrate Interactions: Epitaxial Self-Assembly Study of Cyclic Trinuclear Au(I) Complexes on HOPG at the SolutionâSolid Interface
Molecular and Electronic Structure of Cyclic Trinuclear Gold(I) Carbeniate Complexes: Insights for Structure/Luminescence/Conductivity Relationships
An
experimental and computational study of correlations between
solid-state structure and optical/electronic properties of cyclotrimeric
goldÂ(I) carbeniates, [Au<sub>3</sub>(RNî»CORâČ)<sub>3</sub>] (R, RâČ = H, Me, <sup>n</sup>Bu, or <sup>c</sup>Pe), is reported.
Synthesis and structural and photophysical characterization of novel
complexes [Au<sub>3</sub>(MeNî»CO<sup>n</sup>Bu)<sub>3</sub>], [Au<sub>3</sub>(<sup>n</sup>BuNî»COMe)<sub>3</sub>], [Au<sub>3</sub>(<sup>n</sup>BuNî»CO<sup>n</sup>Bu)<sub>3</sub>], and
[Au<sub>3</sub>(<sup>c</sup>PeNî»COMe)<sub>3</sub>] are presented.
Changes in R and RâČ lead to distinctive variations in solid-state
stacking, luminescence spectra, and conductive properties. Solid-state
emission and excitation spectra for each complex display a remarkable
dependence on the solid-state packing of the cyclotrimers. The electronic
structure of [Au<sub>3</sub>(RNî»CORâČ)<sub>3</sub>] was
investigated via molecular and solid-state simulations. Calculations
on [Au<sub>3</sub>(HNî»COH)<sub>3</sub>] models indicate that
the infinitely extended chain of eclipsed structures with equidistant
Au--Au intertrimer aurophilic bonding can have lower band gaps, smaller
Stokes shifts, and reduced reorganization energies (λ). The
action of one cyclotrimer as a molecular nanowire is demonstrated
via fabrication of an organic field effect transistor and shown to
produce a p-type field effect. Hole transport for the same cyclotrimerîždoped
within a polyÂ(9-vinylcarbazole) hostîžproduced a colossal increase
in current density from âŒ1 to âŒ1000 mA/cm<sup>2</sup>. Computations and experiments thus delineate the complex relationships
between solid-state morphologies, electronic structures, and optoelectronic
properties of goldÂ(I) carbeniates