Possible Superconductivity for Layered Metal Boride Carbide Compounds MBC (M = Alkali, Alkaline-Earth, or Rare-Earth Metals).

The possible emergence of superconductivity in layered metal boride carbide compounds MBC (M = Sc, Y, Be, Ca) was investigated using density functional theory calculations upon the topology of a boron-carbon network and the nature of the metal. ScBC and YBC show metallic and superconductive properties with low critical temperatures (s). The semiconducting BeBC compound may show superconductivity upon carrier doping with a high of 47.

Enhancement of Thermoelectric Performance through Transport Properties Decorrelation in the Quaternary Pseudo-Hollandite Chalcogenide RbBaCrSe.

The novel quaternary compound RbBaCrSe was synthesized and characterized in both single crystal and polycrystalline forms. Crystallizing in the monoclinic crystal system (space group 2/, cell parameters = 18.7071(4) Å, = 3.

Bimetallic Perthiocarbonate Complexes of Cobalt: Synthesis, Structure and Bonding.

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{-TePh}{-TeBH-Te,H}{Cp*Co}] (Cp* = -CMe) () in the presence of CS afforded the bimetallic perthiocarbonate complex [(Cp*Co)(-CS-S:S')(-S-S″:S‴)] () and the dithiolene complex [(Cp*Co)(-CS-S,S'] (). Complex contains a four-membered metallaheterocycle (CoS) comprising a perthiocarbonate [CS] unit and a disulfide [S] unit, attached opposite to each other.

Protic Processes in an Extended Pyrazinacene: The Case of Dihydrotetradecaazaheptacene.

Pyrazinacenes are linearly fused heteroaromatic rings, with N atoms replacing all apical CH moieties. Component rings may exist in a reduced state, having NH groups instead of N, causing cross-conjugation. These compounds have interesting optical and electronic properties, including strong fluorescence in the near-infrared region and photocatalytic properties, leading to diverse possible applications in bio-imaging and organic synthesis, as well as obvious molecular electronic uses.

Theoretical and DFT Study of Atypical Pentanuclear [(PrP)Ni]H ( = 4, 6, 8) Clusters: What are the Rules?

The structure, bonding, and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron-rich PrP of the type [(PrP)Ni]H ( = 4, 6, 8; , , ) and their anionic models where PrP are substituted by H (, , ) were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with small singlet-triplet gaps for and , similar to previously reported experimental values.

Synthesis, Crystal and Electronic Structure, and Thermal Conductivity Investigation of the Hollandite-like CsCrTe Phases (0.73 < < 1).

This article presents a comprehensive study on the synthesis and structural and thermal conductivity properties of cesium-inserted chromium tellurides of formula CsCrTe. Single crystals of three different compositions ( = 0.73, 0.

16-Vertex --titanaborane [(Cp*Ti)BH].

Although Lipscomb predicted in 1977 that supra-icosahedral boron clusters would be viable, their synthesis has been impeded by the unavailability of appropriate synthetic methodologies. Herein, we report the first examples of the open 16-vertex --titanaborane clusters [(Cp*Ti)BHR] (1: R = H; 2: R = Me) having a non-Wadean 19-skeletal-electron-pair count. Interestingly, these clusters show a six-membered [TiB] open face, which could lead to -19-vertex clusters.

Monocarboxylate-protected two-electron silver nanoclusters with high photothermal conversion performance.

The first series of monocarboxylate-protected silver nanoclusters was synthesized and fully characterized by X-ray diffraction, fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and electrospray ionization mass spectrometry (ESI-MS). Specifically, compounds [Ag(L)(9-AnCO)] (L = PhP (I), (4-ClPh)P (II), (2-furyl)P (III), and PhAs (IV)) were prepared by a solvent-thermal method under alkaline conditions. These clusters exhibit a similar unprecedented structure containing a [Ag@Ag] metal kernel, of which the 2-electron [Ag] inner core shows a flattened and puckered hexagonal bipyramid of symmetry.

From 8- to 18-Cluster Electrons Superatoms: Evaluation via DFT Calculations of the Ligand-Protected W@Au(dppm) Cluster Displaying Distinctive Electronic and Optical Properties.

The iconic W@Au icosahedral bare cluster reaches the favorable closed-shell superatomic electron configuration 1S 1P 1D, making it an 18-cluster electron (18-ce) superatom. Here, we pursue the evaluation of a ligand-protected counterpart based on the construction of a fully phosphine-protected [W@Au(dppm)] cluster strongly related to the characterized [Au(dppm)] homometallic counterpart. The later cluster has the same total number of valence electrons as the former but is considered an 8-ce superatom with 1S 1P configuration.

Eu- and Tb-adsorbed SiN and GeN: tuning the colours with one luminescent host.

Phosphor-converted white light emitting diodes (pc-LEDs) are efficient light sources for applications in lighting and electronic devices. Nitrides, with their wide-ranging applicability due to their intriguing structural diversity, and their auspicious chemical and physical properties, represent an essential component in industrial and materials applications. Here, we present the successful adsorption of Eu and Tb at the grain boundaries of bulk β-SiN and β-GeN by a successful combustion synthesis.

Trimetallic Chalcogenide Species: Synthesis, Structures, and Bonding.

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl] (Cp* = -CMe) with four equivalents of Li[BHE] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)(-Se)(BH)(-Se)] () and the homocubane-like cluster [(NbCp*)(-Se)(-Se)(BH)(-Se)] (). Interestingly, the tri-niobium framework of stabilizes a selenaborate {SeBH} ligand.

Electronic Configurations of 3d Transition-Metal Compounds Using Local Structure and Neural Networks.

Machine learning (ML) methods extract statistical relationships between inputs and results. When the inputs are solid-state crystal structures, structure-property relationships can be obtained. In this work, we investigate whether a simple neural network is able to learn the 3d orbital occupations for the transition-metal (TM) centers in crystalline inorganic solid-state compounds using only the local structure around the transition-metal centers described by rotationally invariant fingerprints based on spherical harmonics and one-hot elemental encoding.

Ligand-Induced Cuboctahedral versus Icosahedral Core Isomerism within Eight-Electron Heterocyclic-Carbene-Protected Gold Nanoclusters.

The controlled structural modification of ligand-protected gold clusters is evaluated by a proper variation of the size and shape of N-heterocyclic carbene (NHC) ligands. Density functional theory calculations show that the Au core of [Au(NHC)Br] can be shaped into an icosahedron and/or a so far unexpected cuboctahedron depending on the sterical effect inferred by the NHC ligand side arms. As a result, the cluster properties can be modified, encouraging further exploration on controlled core isomerization in ligated gold cluster chemistry.

Methyl Viologens of Bis-(4'-Pyridylethynyl)Arenes - Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology.

A series of bis-(4'-pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds.

Looking at platinum carbonyl nanoclusters as .

Although the chemistry of carbonyl-protected platinum nanoclusters is well established, their bonding mode remains poorly understood. In most of them, the average Pt oxidation state is zero or slightly negative, leading to the apparent average configuration 5d 6s ( = 0 or very small) and the apparent conclusion that metal-metal bonding cannot arise from the completely filled 5d shell nor from the empty (or almost empty) 6s orbitals. However, DFT calculations show in fact that in these species the actual average configuration is 5d 6s, which provides to the whole cluster a significant total number of 6s electrons that ensures metal-metal bonding.

Insight Into the Stability and Electronic and Optical Properties of N-Heterocyclic Carbene Analogues of Halogen/Phosphine-Protected Au Superatomic Clusters.

Atomically precise gold nanoclusters (AuNCs) belong to a relevant area offering useful templates with tunable properties toward functional nanostructures. In this work, we explored the feasible incorporation of N-heterocyclic carbenes (NHCs), as part of the protecting-ligand shell in AuNCs. Our results, which are based on the substitution of phosphine ligands in experimentally characterized AuNCs by NHCs in various eight-electron superatoms Au and MAu (M = Cu, Ag), indicate similar electronic structure and stability but somewhat different optical properties.

Two-photon absorption properties of multipolar triarylamino/tosylamido 1,1,4,4-tetracyanobutadienes.

The synthesis and characterization of four new tetracyanobutadiene (TCBD) derivatives (1, 3c and 4b-c) incorporating tosylamido and 4-triphenylamino moieties are reported. Along with those of five closely related or differently branched TCBDs derivatives (2, 3a-b, 4c and 5), their linear and (third-order) nonlinear optical properties were investigated by electronic absorption spectroscopy and Z-scan measurements. Among these compounds, the tri-branched compounds 3c and 5 are the most active two-photon absorbers, with effective cross-sections of 275 and 350 GM at 900 nm, respectively.

On Heteronuclear Isoelectronic Alternatives to [Au(dppe)Cl]: Electronic and Optical Properties of the 18-Electron Os@[Au(dppe)Cl] Cluster from Relativistic Density Functional Theory Computations.

The development of well-defined atomically precise heteronuclear nanoclusters passivated by protecting ligands is presently a booming area, owing to the fact that doping well-known homonuclear nanostructures allows fine-tuning of their properties. Here, we explore by means of density functional theory calculations the possibility of doping the central gold atom in the classical [Au(dppe)Cl]cluster () by Os. Although both [Au(dppe)Cl] and [Os@Au(dppe)Cl] have the same total number of electrons, we show that they are not isoelectronic within the formalism of the superatom model, being respectively an 8- and an 18-electron species.

Crystal, electronic and magnetic structures of a novel series of intergrowth carbometalates RCoC (R = Y, Gd, Tb).

A series of new ternary isostructural RCoC (R = Y, Gd, Tb) carbides was synthesized by annealing of arc-melted stoichiometric samples. The crystal structure of TbCoC [space group P2/m, Pearson symbol mP18, a = 12.754(2) Å, b = 3.

Chemistry of group 5 metallaboranes with heterocyclic thiol ligands: a combined experimental and theoretical study.

Thermolysis of [(Cp*Nb)(BH)], 1b (Cp* = η-CMe), with 2-mercaptobenzothiazole, CHNSCSH (MBT), and 2-mercaptobenzoxazole, CHNOCSH (MBO), yielded hydrogen substituted compounds 2 and 3 with a general formula [(Cp*Nb)(BH)(BHL)] (2: L = CHNSCS and 3: L = CHNOCS). A similar reaction of 1b with PhSe yielded the monosubstituted derivative [(Cp*Nb)(BH){BH(PhSe)}], 4. All further efforts towards persubstitution of 1b under various drastic conditions were unfruitful.

2- and 2,7-Substituted para-N-Methylpyridinium Pyrenes: Syntheses, Molecular and Electronic Structures, Photophysical, Electrochemical, and Spectroelectrochemical Properties and Binding to Double-Stranded (ds) DNA.

Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm .

Zwitterionic Mixed-Valence Species for the Design of Neutral Clocked Molecular Quantum-Dot Cellular Automata.

Mixed-valence compounds can be used for the design of molecular quantum-dot cellular automata (QCA). Here, we investigate the QCA properties of a three-dot "Y"-shaped functionalized zwitterionic neutral -carborane model 1-(3,5-{Cp(dHpe)Fe-C≡C-}(CH))-10-Cp(dHpe)Fe-C≡C--1-CBH () (Cp = cyclopentadienyl (η-CH) and dHpe = 1,2-bis(phosphino)ethane (HPCHCHPH)) as a neutral clocked molecular half-cell. DFT results clearly demonstrate that can display simultaneously the two most basic properties necessary for clocked QCA operation, i.

Toward the Formation of N-Heterocyclic-Carbene-Protected Gold Clusters of Various Nuclearities. A Comparison with Their Phosphine-Protected Analogues from Density Functional Theory Calculations.

The structure and bonding of a series of selected phosphine-protected gold clusters () of nuclearity varying from = 6 to 13 were investigated by density functional theory (DFT) calculations and compared to those of the hypothetical homologues in which phosphines were replaced by N-heterocyclic carbene (NHC) analogues (). Both the and series exhibit similar stabilities and structural features, except for = 6, where some differences are noted. The NHC ligands are found to be even slightly more strongly bonded to the gold core (by a few kilocalories per mole per ligand) than phosphines.

Electron count and electronic structure of bare icosahedral Au and Au ionic nanoclusters and ligated derivatives. Stable models with intermediate superatomic shell fillings.

DFT calculations were carried out on bare Au32 and Au33 nanoclusters with various charges, in order to analyze their stability with respect to different cluster electron numbers. Results indicate that in addition to the neutral Au32 hollow species, significant HOMO-LUMO gaps are computed for [Au32]8+ (hollow) and [Au32]4+ (two-shell structure). Species with smaller HOMO-LUMO gaps can reach stability upon "passivation" by a ligand shell, as experimentally exemplified.