We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 ± 0.5%) under Ar, representing ca. 3600 cm(-1) blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

An experimental and computational study of correlations between solid-state structure and optical/electronic properties of cyclotrimeric gold(I) carbeniates, [Au3(RN═COR')3] (R, R' = H, Me, (n)Bu, or (c)Pe), is reported. Synthesis and structural and photophysical characterization of novel complexes [Au3(MeN═CO(n)Bu)3], [Au3((n)BuN═COMe)3], [Au3((n)BuN═CO(n)Bu)3], and [Au3((c)PeN═COMe)3] are presented. Changes in R and R' 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 [Au3(RN═COR')3] was investigated via molecular and solid-state simulations. Calculations on [Au3(HN═COH)3] 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 cyclotrimer-doped within a poly(9-vinylcarbazole) host-produced a colossal increase in current density from ∼1 to ∼1000 mA/cm(2). Computations and experiments thus delineate the complex relationships between solid-state morphologies, electronic structures, and optoelectronic properties of gold(I) carbeniates.

Outer-shell s 0 /p 0 orbital mixing with d 10 orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)-Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au 4 Cu 2 {[Au 4 (μ-C 2 ,N 3 -EtIm) 4 Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4a)}, Au 2 Cu {[Au 2 (μ-C 2 ,N 3 -BzIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (1) and [Au 2 (μ-C 2 , N 3 -MeIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (3a)}, AuCu 2 {[Au(μ-C 2 ,N 3 -MeIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (3b) and [Au(μ-C 2 ,N 3 -EtIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4b)} and stacked Au 3 /Cu 3 {[Au(μ-C 2 ,N 3 -BzIm)] 3 [Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 , (2)} form upon reacting Au 3 {[Au(μ-C 2 ,N 3 -(N-R)Im)] 3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu 3 {[Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 (3,5-(CF 3 ) 2 Pz = 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 two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d 10 -d 10 polar-covalent bond with ligandunassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d 10 centers so as to deem it a "metal-metal bond" vis-à-vis "metallophilic interaction." Density-functional calculations estimate 35-43 kcal/mol binding energy, akin to typical M-M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65-200 cm −1 , assignable to v Cu-Au as validated by both the Harvey-Gray 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 cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (Φ PL = 0.90-0.97 vs. 0-0.83 for Au 3 and Cu 3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications. Here, we show that outer 4s/p (Cu I ) and 6s/p (Au I ) orbitals can admix with the respective valence 3d and 5d orbitals to sensitize a bona fide polar-covalent metal-metal bond between two d 10 centers manifest by two rather short, 2.8750(8) Å, Cu(I)-Au(I) bonds without any ligand-bite-size assistance. The reduced symmetry in this family of complexes is also shown to impart higher extinction coefficients and phosphorescence quantum yields than those attained by the parent homometallic precursor complexes.Heterometallic complexes are remarkable molecules owing to their unique catalytic and optoelectronic properties (2, 3). Heterometallic species involving coinage metals have received immense attention owing to their fascinating structural a...

The diimine-dithiolato ambipolar complexes Pt(dbbpy)(tdt) and Pt(dmecb)(bdt) (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine; tdt(2-) = 3,4-toluenedithiolate; dmecb = 4,4'-dimethoxyester-2,2'-bipyridine; bdt(2-) = benzene-1,2-dithiolate) are prepared herein. Pt(dmecb)(bdt) exhibits photoconductivity that remains constant (photocurrent density of 1.6 mA/cm(2) from a 20 nm thin film) across the entire visible region of the solar spectrum in a Schottky diode device structure. Pt(dbbpy)(tdt) acts as donor when combined with the strong nitrofluorenone acceptors 2,7-dinitro-9-fluorenone (DNF), 2,4,7-trinitro-9-fluorenone (TRNF), or 2,4,5,7-tetranitro-9-fluorenone (TENF). Supramolecular charge transfer stacks form and exhibit various donor-acceptor stacking patterns. The crystalline solids are "black absorbers" that exhibit continuous absorptions spanning the entire visible region and significant ultraviolet and near-infrared wavelengths, the latter including long wavelengths that the donor or acceptor molecules alone do not absorb. Absorption spectra reveal the persistence of donor-acceptor interactions in solution, as characterized by low-energy donor/acceptor charge transfer (DACT) bands. Crystal structures show closely packed stacks with distances that underscore intermolecular DACT. (1)H NMR provides further evidence of DACT, as manifested by upfield shifts of aromatic protons in the binary adducts versus their free components, whereas 2D nuclear Overhauser effect spectroscopy (NOESY) spectra suggest coupling between dithiolate donor protons with nitrofluorenone acceptor protons, in correlation with the solid-state stacking. The NMR spectra also show significant peak broadening, indicating some paramagnetism verified by magnetic susceptibility data. Solid-state absorption spectra reveal further red shifts and increased relative intensities of DACT bands for the solid adducts vs solution, suggesting cooperativity of the DACT phenomenon in the solid state, as further substantiated by νC-O and νN-O IR bands and solid-state tight-binding computational analysis.

Synthesis, crystallographic characterization, and molecular self-assembly of two novel cyclotrimeric gold­(I) complexes, Au3[3,5-(COOEt)2Pz]3 (Au3Pz3) and Au3[(n-Pr–O)­CN­(Me)]3 (Au3Cb3) was studied. Single crystal X-ray crystallography data reveal that both gold­(I) complexes have one-dimensional stacking patterns caused by intermolecular Au­(I)···Au­(I) aurophilic interactions. The Au3Pz3 trimer units stack with two alternate and symmetrical Au­(I)···Au­(I) interactions while the Au3Cb3 units have three alternating and nonsymmetrical Au­(I)···Au­(I) interactions. Molecular self-assembly of the gold­(I) complexes on the 1-phenyloctane/highly ordered pyrolytic graphite (HOPG) (0001) solution–solid interface is studied with scanning tunneling microscopy (STM). The gold­(I) cyclotrimers form epitaxial nanostructures on the HOPG surface. At a concentration of ∼1 × 10–4 M, Au3Pz3 complexes exhibit a single morphology, while Au3Cb3 complexes exhibit polymorphology. Two polymorphs, one nonporous and the other porous, are observed at 22.0 ± 2.0 °C for Au3Cb3 complexes. A nonporous, low-surface-density (0.82 molecules/nm2) Au3Cb3 nanostructure forms first and then transforms into a high-density (1.43 molecules/nm2) 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 monolayer–substrate interactions. These pores are utilized to incorporate pyrene into the film, rendering this the first organometallic host–guest system imaged at the solid–solution 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 Au3 trimer orbitals and HOPG. The multiple-technique approach used herein provides insights concerning molecule–substrate and molecule–molecule interactions.

Single crystals of LnM x Ga 3 (Ln = Ho, Er; M = Fe, Co; x < 0.2) were grown from a Ga self-flux. The compounds crystallize in a "stuffed" variant of the AuCu 3 -structure type where Fe or Co partially occupies the body-centered position of the unit cell surrounded by six Ga atoms. The insertion of Fe or Co guest atoms into the AuCu 3 -structure type causes a structural change in the host material where chemical pressure is exerted on Ga-Ga contacts surrounding the filled octahedra. This in turn affects the stability of the AuCu 3 -structure type and the intrinsic properties of the materials. With increasing Ho−Ho distances of 4.2355(5), 4.2377(5), and 4.2441(3) Å, HoCo 0.16(2) Ga 3 , HoFe 0.11(1) Ga 3 , and HoFe 0.16(2) Ga 3 order antiferromagnetically with decreasing Néel temperatures of T N = 10.2, 7.2, and 6.5 K, respectively. ErCo 0.06(2) Ga 3 , ErFe 0.06(1) Ga 3 , and ErFe 0.11(2) Ga 3 order antiferromagnetically with Néel temperatures of T N = 3.3, 5.2, and 6.2 K. The magnetic properties are attributed to changes in the coupling strength of local magnetic moment with conduction electrons as a function of transition metal and rare earth.

Ln 117 Ni 53−y Sn 112−z (Ln = Gd−Dy) have been grown via the eutectoid flux growth method, characterized using single crystal Xray 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) Å 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.

We explore the factors stabilizing one member of the diverse structures encountered in Ln–T–E systems (Ln = lanthanide or similar early d-block element, T = transition metal, E = p-block element): the HoCoGa5 type, an arrangement of atoms associated with unconventional superconductivity. We first probe the boundaries of its stability range through the growth and characterization of ScTGa5 crystals (T = Fe, Co, Ni). After confirming that these compounds adopt the HoCoGa5 type, we analyze their electronic structure using density functional theory (DFT) and DFT-calibrated Hückel calculations. The observed valence electron count range of the HoCoGa5 type is explained in terms of the 18-n rule, with n = 6 for the Ln atoms and n = 2 for the T sites. The role of atomic sizes is investigated with DFT-chemical pressure (DFT-CP) analysis of ScNiGa5, which reveals negative pressures within the Ga sublattice as it stretches to accommodate the Sc and T atoms. This CP scheme is consistent with HoCoGa5-type gallides only being observed for relatively small Ln and T atoms. These conclusions account for the relative positions of the HoCoGa5, BaMg4Si3, and Ce2NiGa10 types in a structure map, demonstrating how combining the 18-n and CP schemes can guide our understanding of Ln–T–E systems.