Reaction of Metcar Ti8C12 with Halogen-Containing Addends

Ab initio electron density functional method in the discrete-variational scheme was used to perform self-consistent calculations of the electronic structure of Ti₈C₁₂Cl₂ and Ti₈C₁₂(CHCl₃), i.e., the adducts of reaction between the Ti₈C₁₂ metallocarbohedrene and halogen-containing addends (Cl₂ and CHCl₃ molecules). The electronic states, charge distributions, and chemical bonds of the obtained adducts were analyzed. The results were compared with calculations of the Ti₈C₁₂Cl complex that can be treated as a model of the destruction stage of the addends. General conditions for the interaction of halogenated addends with metcars in the molecular and crystalline states are discussed based on the data obtained.     

The Electronic Structure of Mixed Metcars Ti7MC12 (M = Y,Zr, Nb,..., Ag)

The electronic structures of a series of mixed metallocarbohedrenes (metcars) Ti₇MC₁₂formed as a result of replacement of the titanium atom in the Ti₈C₁₂metcar by 4dtransition metal ions (M = Y, Zr, Nb, ..., Ag) are established using the ab initioelectron density functional method in the discrete-variational scheme. The dependences of electronic structure, charge distributions, and chemical bonds in the Ti₇MC₁₂metcars on the cluster symmetry (T _hor T _d) and position of the 4datom in a molecular cage are discussed. The electronic states of 4datoms in molecular titanium carbide (Ti₈C₁₂metcar) are compared with those in crystal titanium carbide (cubic TiC phase with rock salt structure). The effect of doping of the Ti₈C₁₂metcar with 4datoms on its reactivity is studied.     

Electronic structure study of the reactivity centres in Ti8C12 clusters

The reactivity centres of Ti₈C₁₂, for the three structures suggested in conformity with experimental observations, are studied by extended Huckel theory, The C₂ unit can complex with transition metal fragments such as Pt(PH₃)₂ with the unusual net result of transferring two electrons to Ti₈C₁₂. The metal centre, Ti can accommodate extra two-electron donors like CO. Model systems are used to explain the carbon and metal environment in Ti₈C₁₂.     

New Quasi-One-Dimensional Crystals of Metallocarbohedrenes (Sc,Ti,V)8C12 in (12,0) Boron–Nitrogen Nanotubes: Quantum-Chemical Simulation

A quantum-chemical model was made of new quasi-one-dimensional crystals, consisting of regular chains of metallocarbohedrenes Sc₈C₁₂, Ti₈C₁₂, and V₈C₁₂ (isomers with T _h symmetry) inside a single-wall (12,0) boron–nitrogen nanotube. Their electronic characteristics, the nature of the interatomic bonds, and the relative stability in relation to the electronic concentration in the (Sc₈C₁₂@(12,0)BN-NT Ti₈C₁₂@(12,0)BN-NT V₈C₁₂@(12,0)BN-NT) systems and the mutual arrangement of the metallocarbohedrenes and the nanotube are discussed.     

Novel ion pairs obtained from the reaction of titanium(IV) halides with simple arsane ligands

The compounds tert‐butylarsenium(III) tri‐μ‐chlorido‐bis[trichloridotitanium(IV)], (C₄H₁₂As)[Ti₂Cl₉] or [^tBuAsH₃][Ti₂(μ‐Cl)₃Cl₆], (II), and bis[bromidotriphenylarsenium(V)] di‐μ‐bromido‐μ‐oxido‐bis[tribromidotitanium(IV)], (C₁₈H₁₅AsBr)₂[Ti₂Br₈O] or [Ph₃AsBr]₂[Ti₂(μ‐O)(μ‐Br)₂Br₆], (III), were obtained unexpectedly from the reaction of simple arsane ligands with Ti^IV halides, with (II) lying on a mirror plane in the unit cell of the space group Pbcm. Both compounds contain a completely novel ion, with [^tBuAsH₃]⁺ constituting the first structurally characterized example of a primary arsenium cation. The oxide‐bridged titanium‐containing [Ti₂(μ‐O)(μ‐Br)₂Br₆]²⁻ dianion in (III) is also novel, while the bromidotriphenylarsenium(V) cation is structurally characterized for only the second time.     

Halides of Titanium in Lower Oxidation States

New investigations on the di‐ and trihalides of titanium, TiX₂ and TiX₃ (X = Cl, Br, I), with their 3d² and 3d¹ electronic configurations, confirm the early observations and conclusions of Klemm. At sufficiently low temperatures, Ti–Ti single bonds are formed in the one‐dimensional trihalides, i.e., Ti–Ti dimers are observed. Equally, in the two‐dimensional dihalides, {Ti₃} triangles occur with three single bonds. Phase transitions were detected from single‐crystal or powder X‐ray diffraction data, from magnetic measurements and thermal analysis. Except for the binary halides a number of ternary halides ATiX₃ (extended chains of facesharing octahedra), K₄Ti₃Br₁₂ (triples of face‐sharing octahedra), Na₂Ti₃Cl₈ (triangular trimers), A₃Ti₂X₉ (dimers of face‐sharing octahedra), and A₃TiX₆ (isolated octahedra) as well as the mixed‐valent halides CsTi₂I₇ (tetrahedra and octahedra) and Na₅Ti₃Cl₁₂ (chains of octahedra) have been observed. Except for the triangles in titanium(II) halides, cluster compounds are rare but include K₄[{OTi₄}I₁₂] and {CTi₆}Cl₁₄.     

Structures and electronic properties of C<Subscript>12</Subscript>Si<Subscript>8</Subscript>X<Subscript>8</Subscript> (X = H,F, and Cl)

The structural stabilities and electronic properties of C₁₂Si₈X₈ where X = H, F, and Cl are probed on the basis of density functional theory at the B3LYP/6-311++G**//B3LYP/6-31+G* level. Vibrational frequency calculations show that all the systems are true minima. The infrared spectra of the most stable C₁₂Si₈X₈ molecules are simulated to assist further experimental characterization. The functionalized structures and energy gaps between the highest occupied molecular orbital, HOMO, and the lowest unoccupied molecular orbital, LUMO, have been systematically investigated. It seems that C₁₂Si₈H₈ has more stability against electronic excitations via increasing the HOMO–LUMO gap comparing with C₁₂Si₈Cl₈ and C₁₂Si₈F₈. High charge transfer on the surfaces of our stable compounds, provokes further investigations on their possible application for hydrogen storage. The addition reaction energies of C₁₂Si₈X₈ are high exothermic, and C₁₂Si₈F₈ is more thermodynamically accessible.     

Crystal and molecular structures of the complexes of cobalt dichloride with 1-isopropenylimidazole and 1-vinylimidazole

The crystal and molecular structures of bis(1-isopropenylimidazole)dichlorocobalt (C₁₂H₁₆Cl₂·N₄Co) [R 0.036 (R _W 0.089) for 3229 unique reflections with I > 2σ(I)] and tetra(1-vinylimidazole)dichlorocobalt (C₂₀H₂₄Cl₂N₈Co) [R 0.031 (R _W 0.072) for 1863 unique reflections with I > 2σ(I)] were determined. In these molecular complexes, the monodentate terminal 1-alkenylimidazole ligands coordinate to the metal via a “pyridine” nitrogen atom. In C₁₂H₁₆Cl₂N₄Co, the Co atom has a distorted tetrahedral 2N,2Cl coordination. The coordination polyhedron of cobalt in C₂₀H₂₄Cl₂N₈Co is a strongly elongated 4N,2Cl octahedron. The Co-N and Co-Cl bonds [Co-N 2.015(2) and 2.032(4) Å; Co-Cl 2.229(2) Å] in the tetrahedral complex C₁₂H₁₆Cl₂N₄Co are shorter than those in the octahedral complex C₂₀H₂₄Cl₂N₈Co [Co-N 2.134(2) and 2.157(2) Å; Co-Cl 2.518(1) Å]. In the structures of both complexes there are short contacts involving the Cl atoms.     

Structure and electronic properties of TI8C12 cluster

Structure and electronic properties of recently discovered Ti₈C₁₂ molecule are studied using the discrete variational method within the framework of local density approximation. The geometry of this novel cluster is optimized to be a distorted dodecahedron by varing the bond lengths of Ti-C and C-C while maintaining theT _h symmetry, and the electronic states and the chemical bonding are discussed.     

In situ decoration of CoP/Ti3C2Tx composite as efficient electrocatalyst for Li-oxygen battery

Application of Li-oxygen (Li-O₂) battery is in urgent need of bifunctional ORR/OER electrocatalyst. A surface-functionalization CoP/Ti₃C₂T_x composite was fabricated theoretically, with the optimized electronic structure and more active electron, which is beneficial to the electrochemical reaction. The accordion shaped Ti₃C₂T_x is featured with large specific surface area and outstanding electronic conductivity, which is beneficial for the adequate exposure of active sites and the deposition of Li₂O₂. Transition metal phosphides provide more electrocatalytic active sites and present good electrocatalytic effect. The CoP/Ti₃C₂T_x composite served as the electrocatalyst of Li-O₂ battery reaches a high specific discharge capacity of 17,413 mAh/g at 100 mA/g and the lower overpotential of 1.25 V, superior to those of the CoP and Ti₃C₂T_x individually. The composite of transition metal phosphides and MXene are applied in Li-O₂ battery, not only demonstrating higher cycling stability of the prepared CoP/Ti₃C₂T_x composite, but pointing out the direction for their electrochemical performance improvement.     

An experimentally based description of the ground-state wavefunction for two weakly coupled electrons by photoelectron spectroscopy and magnetic susceptibility measurements

It is possible to extract values for the transfer energy, t, and the Coulomb interaction, U, in hydrogen-like systems from a combination of photoelectron and magnetic data, as both the form of the photoelectron spectrum and the exchange splitting are determined by these quantities. This procedure is used to evaluate the ground-state wavefunction for the two weakly coupled Ti 3d electrons in (C₁₀H₈)(C₅H₅)₂Ti₂Cl₂.     

Structure and electronic properties of 3,3′-diamino-4,4′-azo-1,2,4-triazole nitrate and perchlorate

Based on density functional theory with regard to the dispersion interaction the crystal structure and electronic properties of C₄H₈N₁₂O₆ and C₄H₈N₁₀Cl₂O₈ are studied. Atomic structural parameters, bond populations, atomic charges, energy and spatial electron distributions are calculated. Differences in the studied characteristics caused by the non-equivalence of atoms are shown. A partially covalent nature of anion-cation bonds is revealed. The cationic nature of the lower unoccupied states is established, which results in a small band gap of ~1.7 eV as compared to other nitrates and perchlorates.     

Atomic structure and electronic properties of nanopeapods: Isomers of endohedral dititanofullerenes Ti2@C80 in carbon nanotubes

The atomic structure, charge and electronic parameters, and energies of formation of new “hybrid” nanostructures-nanopeapods Ti₂@C₈₀@C-NTs, regular linear ensembles of seven isomers of endohedral dititanofullerenes Ti₂@C₈₀ encapsulated into a carbon zigzag (19.0) nanotube—have been calculated by the self-consistent density functional tight-binding method (DFTB). The results are discussed in comparison to the “free” isomers of C₈₀ fullerenes and Ti₂@C₈₀ endofullerenes, as well as to all-carbon nanopeapods, i.e., C₈₀ isomers inside a carbon nanotube (C₈₀@C-NT). It is demonstrated that the type of Ti₂@C₈₀ isomer determines the energy effect of its encapsulation into the tube (exo-or endothermic), the orientational arrangement of end-ofullerenes in the tube, the charge states of the Ti₂@C₈₀ and tube atoms, and the electronic properties of nanopeapods (semiconducting or metallic).     

Topological aspects of metals in carbon cages: Analogies with organometallic chemistry

Metals can interact with carbon cages in the following ways: (1) stable carbon cages (i.e., fullerenes) function as electronegative olefins in their exohedral η₂ bonding to transition metals; (2) endohedral metallofullerenes with a highly electropositive lanthanide (Ln) inside the carbon cage can be considered to be ionic with lanthanide cations, Ln³⁺, and fullerene anions; (3) fullerenes too small for independent existence can be stabilized by internal covalent bonding to an endohedral metal atom using the central carbon atoms of pentagon triplets,i.e triquinacene, units, in complexes such as M@C₂₈ (M=Ti, Zr, Hf, and U), derived from the tetrahedral fullerene C₂₈; (4) metal atoms can occur as vertices of binary mixed metal-carbon cages in both early transition metal complexes of the types M₁₄C₁₃, M₈C₁₂, and M₁₃C₂₂ (e.g., M=Ti) and copper-carbon cages of the types Cu_2n +1C_2n ⁺ (n≤10), Cu₇C₈ ⁺, Cu₉C₁₀ ⁺ and Cu₁₂C₁₂ ⁺. The presence of metal atoms as vertices of carbon cages changes radically their stoichiometries and thus their structures. Thus, early transition metals form cages such as Ti₁₄C₁₃ assumed to have titanium atoms at the vertices and face midpoints of a 3×3×3 cube and carbon atoms at the edge midpoints and center of the cube and Ti₁₃C₂₂ assumed to have titanium atoms at the edge midpoints and center of a 3×3×3 cube as well as C₂ units and carbon atoms at the vertices and face midpoints, respectively, of the cube. Elimination of the face metal atoms from the Ti₁₄C₁₃ structure as well as the center carbon atom, which has been achieved experimentally by photofragmentation, leads to the Ti₈C₁₂ cluster. The structure of this cluster is based on a tetracapped tetrahedron withT _d symmetry with two distinct quartets of titanium atoms, six distinct C₂ pairs, and 36 direct Ti−C interactions. The copper-carbon cages of various stoichiometries are suggested to have prismatic, antiprismatic, or cuboctahedral structures in which the electronic configurations of the copper atoms approach the favored 18-electron rare gas configuration. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 862–869, May, 1998.     

A structural study of Si6‐ring‐containing [Si6Cl14]2− chlorosilicates

The crystal structures of four substituted‐ammonium dichloride dodecachlorohexasilanes are presented. Each is crystallized with a different cation and one of the structures contains a benzene solvent molecule: bis(tetraethylammonium) dichloride dodecachlorohexasilane, 2C₈H₂₀N⁺·2Cl⁻·Cl₁₂Si₆, (I), tetrabutylammonium tributylmethylammonium dichloride dodecachlorohexasilane, C₁₆H₃₆N⁺·C₁₃H₃₀N⁺·2Cl⁻·Cl₁₂Si₆, (II), bis(tetrabutylammonium) dichloride dodecachlorohexasilane benzene disolvate, 2C₁₆H₃₆N⁺·2Cl⁻·Cl₁₂Si₆·2C₆H₆, (III), and bis(benzyltriphenylphosphonium) dichloride dodecachlorohexasilane, 2C₂₅H₂₂P⁺·2Cl⁻·Cl₁₂Si₆, (IV). In all four structures, the dodecachlorohexasilane ring is located on a crystallographic centre of inversion. The geometry of the dichloride dodecachlorohexasilanes in the different structures is almost the same, irrespective of the cocrystallized cation and solvent. However, the crystal structure of the parent dodecachlorohexasilane molecule shows that this molecule adopts a chair conformation. In (IV), the P atom and the benzyl group of the cation are disordered over two sites, with a site‐occupation factor of 0.560 (5) for the major‐occupied site.     

Derivate des Imidazols. XXIV [1].[Li12O2Cl2(ImN)8(THF)4] · 8 THF: Ein Peroxo-Komplex des Lithiums mit neuartiger Käfigstruktur

Imidazole Derivatives. XXIV. [Li₁₂O₂Cl₂(ImN)₈(THF)₄] · 8 THF: a Peroxo Lithium Fragment in a Novel Cage Structure 1,3-dimethyl-2-iminoimidazoline ( 8 , ImNH) reacts with methyl lithium to give [ImNLi]_n ( 9 ). In tetrahydrofuran, crystals of C₅₆H₉₆Cl₂Li₁₂N₂₄O₆ · 8 C₄H₈O ( 10 ) are obtained. The structure of 10 consists of a Li₁₂Cl₂N₈O₂ core in which a peroxo unit is incorporated into a stack of ladder fragments. Over all, four tetrahydrofuran and eight imidazoline ligands are attached at the lithium and nitrogen atoms.     

Electroactive Polymerization Behaviors of Fused-Pentagon Chlorofullerenes: <Superscript>#1809</Superscript>C<Subscript>60</Subscript>Cl<Subscript>8</Subscript> and <Superscript>#271</Superscript>C<Subscript>50</Subscript>Cl<Subscript>10</Subscript>

The fullerenes that violate isolated pentagon rule (IPR) have unusual electronic properties resulting from their fused-pentagon structures. Numerous non-IPR fullerenes have now been captured by chlorination, affording opportunity to go insight into the properties involved in non-IPR fullerenes in the forms of chlorofullerenes (CFs). Here cyclic voltammetry (CV) is employed to probe the electrochemical properties of non-IPR ^#1809C₆₀Cl₈ in comparison with those of ^#271C₅₀Cl₁₀. Differing from IPR-satisfying CFs such as C₆₀Cl₈ and C₆₀Cl₁₀ (referring to I _h-symmetric C₆₀), the two non-IPR CFs exhibit divergent electroactive polymerization characters. In addition, the electrocatalytic effect of ferrocene that is otherwise employed as internal reference has been shown in the CV process of CFs.     

Lithium storage properties of Ti3C2Tx (Tx = F,Cl, Br) MXenes

In this work, Ti₃C₂T_x MXene with -F, -Cl and -Br surface terminations are synthesized and the effect of these halogen terminations on the lithium storage properties is investigated. A maximum Li⁺ storage capacity of 189 mAh/g is achieved with Ti₃C₂Br_x MXene much higher than Ti₃C₂Cl_x and Ti₃C₂F_x with 138 mAh/g and 123 mAh/g, respectively. Density functional theory (DFT) calculation shows that the adsorption formation energy of halogen atoms on Ti atoms follows the trend of Ti-F > Ti-Cl > Ti-Br, leading to the same trend in the content of terminations on corresponding MXenes. In addition, inevitable exposure of MXene to oxygen causes competition between halogen and oxygen. Theoretical results show Ti₃C₂Br_x MXene has the highest Ti to O ratio and the lowest Ti to Br ratio, the high lithium affinity of O explains the maximum Li-ion storage capacity with Ti₃C₂Br_x MXene. This work shed light on the opportunity for achieving improved lithium storage properties of MXene electrodes by regulating the surface chemistry.     

Ni(II) and Co(II) complexes with 2,4-dichlorophenoxyacetic acid and 2-(2,4-dichlorophenoxy)-propionic acid

Nickel(II) and cobalt(II) complexes with the commercial herbicides 2,4-dichlorophenoxyacetic acid (2,4D; C₈H₆O₃Cl₂) and 2-(2,4-dichlorophenoxy)-propionic acid (2,4DP; C₉H₈O₃Cl₂) were prepared and characterized. On the basis of the results of elemental analysis and Ni and Co determination, the following molecular formulae were proposed for the obtained compounds: Ni(C₈H₅O₃Cl₂)₂·6H₂O, Co(C₈H₅O₃Cl₂)₂·6H₂O, Ni(C₉H₇O₃Cl₂)₂·2H₂O and Co(C₉H₇O₃Cl₂)₂·2H₂O. X-ray powder analysis was carried out. The IR, electronic (VIS) spectra and conductivity data were discussed. Water solubility of the synthesized complexes at room temperature was examined. Thermal decomposition of the compounds was studied. Dehydration processes occur during heating in air. The anhydrous compounds decompose via different intermediate products to oxides. TG/MS studies indicate formation of gaseous mass fragments of decomposition including H₂O⁺, OH⁺, CO₂ ⁺, HCl⁺, Cl₂ ⁺, CH₃Cl⁺, CH₂O⁺, C₆H₆ ⁺ and other. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and electrochemical properties of spinel Li4Ti5O12−x Cl x anode materials for lithium-ion batteries

Li₄Ti₅O_12−x Cl _x (0 ≤ x ≤ 0.3) compounds were synthesized successfully via high temperature solid-state reaction. X-ray diffraction and scanning electron microscopy were used to characterize their structure and morphology. Cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge cycling performance tests were used to characterize their electrochemical properties. The results showed that the Li₄Ti₅O_12−x Cl _x (0 ≤ x ≤ 0.3) compounds were well-crystallized pure spinel phase and that the grain sizes of the samples were about 3–8 μm. The Li₄Ti₅O_11.8Cl_0.2 sample presented the best discharge capacity among all the samples and showed better reversibility and higher cyclic stability compared with pristine Li₄Ti₅O₁₂. When the discharge rate was 0.5 C, the Li₄Ti₅O_11.8Cl_0.2 sample presented the superior discharge capacity of 148.7 mAh g⁻¹, while that of the pristine Li₄Ti₅O₁₂ was 129.8 mAh g⁻¹; when the discharge rate was 2 C, the Li₄Ti₅O_11.8Cl_0.2 sample presented the discharge capacity of 120.7 mAh g⁻¹, while that of the pristine Li₄Ti₅O₁₂ was only 89.8 mAh g⁻¹.