Structural,vibrational, and bonding analysis of M2?SiO (M=Li or Ag) using density functional theory

The spectroscopic properties of the M₂ SiO (M=Li or Ag) complexes were studied using density functional theory. It is shown that the global minimum of Li₂ SiO corresponds to a doubly bridged silonyl structure, while that of Ag₂ SiO is a phosgenelike structure. The calculated binding energies of the M₂ SiO complexes relative to M₂+SiO are −47.8 and −4.0 kcal mol⁻¹ for M=Li and Ag, respectively. In the case of Ag₂ SiO, the calculated SiO stretching frequency as well as its isotopic shifts are in good agreement with the experimental data. For Li₂ SiO, the SiO vibrational frequency is calculated to be greatly red‐shifted by 493.4 cm⁻¹ (≈40% of free ν_SiO) upon complexation. According to the natural population analysis, the charge transfer from metal to ligand is 0.79 e⁻ for each Li and is only of 0.15 e⁻ for each Ag. The bonding was also investigated using the topological analysis of the charge density. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 499–503, 1999     

Structures,Bonding Analyses and Reactivity of a Dicationic Digallene and Diindene Mimicking trans-bent Ditetrylenes

The reaction of bisdicyclohexylphosphinoethane (dcpe) and the subvalent M^I sources [M^I(PhF)₂][pf] (M=Ga⁺, In⁺; [pf]⁻=[Al(OR^F)₄]⁻; R^F=C(CF₃)₃) yielded the salts [{M(dcpe)}₂][pf]₂, containing the first dicationic, trans-bent digallene and diindene structures reported so far. The non-classical M^I⇆M^I double bonds are surprisingly short and display a ditetrylene-like structure. The bonding situation was extensively analyzed by quantum chemical calculations, QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis with the combination of Natural Orbitals for Chemical Valence) analyses and is compared to that in the isoelectronic and isostructural, but neutral digermenes and distannenes. The dissolved [{Ga(dcpe)}₂]²⁺([pf]⁻)₂ readily reacts with 1-hexene, cyclooctyne, diphenyldisulfide, diphenylphosphine and under mild conditions at room temperature. This reactivity is analyzed and rationalized.     

On the Volume Chemistry of Solid Compounds: the Legacy of Wilhelm Biltz

For the calculation of the atomic or ionic volumes the Quantum Theory of Atoms In Molecules method was applied. The regions (basins) around the nuclei confined by the zero‐flux surfaces in the electron density gradient are called QTAIM atoms. They are non‐overlapping and completely fill the space. The volume of the basins gives volumes of atoms or ions. The integration of the electron density within the volumina yields effective charges, defining neutral or ionic character of the given QTAIM species. Present investigations refer to metal hydrides, metal nitrides and to intermetallic compounds of the system Al‐Pt. A linear relation between the ionic volumina of hydrogen or nitrogen established according to QTAIM and after Biltz has been found with (homodesmic) binary metal hydrides and binary metal nitrides, but has been observed merely as a trend with stronger deviations for heterodesmic compounds, such as ternary hydrido‐ and nitridometallates A_a[M_mX_x] (A – alkali or alkaline earth metal, M – transition metal and X – H or N). The deviation from linearity for heterodesmic compounds is caused by the different kinds of chemical bonds being present within the [M_mX_x] anions on the one hand and between the anions and the cations on the other hand reflected by the calculated volumes and the QTAIM charges of M and X components. Concerning the intermetallic compounds of the system Al‐Pt, the quantum chemical calculations reveal negative charges for the platinum atoms and positive ones for the aluminium atoms in accordance with their electronegativities. Introducing the variation of the atomic volume with the composition extends the Vegard's approach and gives a non‐linear slope for the concentration dependence of mean atomic volume which explains qualitatively the experimental results.     

Binding behaviors of para-dicyclohexanocucurbit[6]uril and meta-tricyclohexanocucurbit[6]uril with dialkyl viologens

The binding behaviours of para-dicyclohexanocucurbit[6]uril (Cy₂Q[6]) and meta-tricyclohexanocucurbit[6]uril (Cy₃Q[6]) with a series of dialkyl viologens (MV²⁺, EV²⁺, PV²⁺, BV²⁺, FV²⁺ and HV²⁺) have been investigated by various methods. In the aqueous solution, ¹H NMR spectra suggest that the alkyl chains are more favourably encapsulated into the hydrophobic cavities of both hosts than the aromatic rings. Cyclic voltammograms (CV) curves show that the Cy₂Q[6] or Cy₃Q[6] bind the charged viologens more strongly than the reduced viologens. Isothermal titration calorimetry (ITC) data reveal that the binding processes of both hosts with viologens are enthalpic driven. In the solid state, the PV²⁺, BV²⁺ guests and two Cy₃Q[6] hosts generated dumbbell-shaped structures, with two Cy₃Q[6] hosts residing over two terminal alkyl chains of the guests.     

Seventeen‐Coordinate Actinide Helium Complexes

The geometries and electronic structures of molecular ions featuring He atoms complexed to actinide cations are explored computationally using density functional and coupled cluster theories. A new record coordination number is established, as AcHe₁₇³⁺, ThHe₁₇⁴⁺, and PaHe₁₇⁴⁺ are all found to be true geometric minima, with the He atoms clearly located in the first shell around the actinide. Analysis of AcHe_n ³⁺ (n =1–17) using the quantum theory of atoms in molecules (QTAIM) confirms these systems as having closed shell, charge‐induced dipole bonding. Excellent correlations (R ²>0.95) are found between QTAIM metrics (bond critical point electron densities and delocalization indices) and the average Ac−He distances, and also with the incremental He binding energies.     

Palladium Complexes Based on Ylide-Functionalized Phosphines (YPhos): Broadly Applicable High-Performance Precatalysts for the Amination of Aryl Halides at Room Temperature

Palladium allyl, cinnamyl, and indenyl complexes with the ylide-substituted phosphines Cy₃P⁺−C⁻(R)PCy₂ (with R=Me ( L1 ) or Ph ( L2 )) and Cy₃P⁺−C⁻(Me)PtBu₂ ( L3 ) were prepared and applied as defined precatalysts in C−N coupling reactions. The complexes are highly active in the amination of 4-chlorotoluene with a series of different amines. Higher yields were observed with the precatalysts in comparison to the in situ generated catalysts. Changes in the ligand structures allowed for improved selectivities by shutting down β-hydride elimination or diarylation reactions. Particularly, the complexes based on L2 (joYPhos) revealed to be universal precatalysts for various amines and aryl halides. Full conversions to the desired products are reached mostly within 1 h reaction time at room temperature, thus making L2 to one of the most efficient ligands in C−N coupling reactions. The applicability of the catalysts was demonstrated for aryl chlorides, bromides and iodides together with primary and secondary aryl and alkyl amines, including gram-scale applications also with low catalyst loadings of down to 0.05 mol %. Kinetic studies further demonstrated the outstanding activity of the precatalysts with TOF over 10.000 h⁻¹.     

Synthesis,Isolation and Crystal Structures of the Metalated Ylides [Cy3P-C-SO2Tol]M (M = Li,Na, K)

The preparation and isolation of the metalated ylides [Cy₃PCSO₂Tol]M ( ^Cy1-M ) (with M = Li, Na, K) are reported. In contrast to its triphenylphosphonium analogue the synthesis of ^Cy1-M revealed to be less straight forward. Synthetic routes to the phosphonium salt precursor ^Cy1 - H₂ via different methods revealed to be unsuccessful or low-yielding. However, nucleophilic attack of the ylide Cy₃P = CH₂ at toluenesulfonyl fluoride under basic conditions proved to be a high-yielding method directly leading to the ylide ^Cy1-H . Metalation to the yldiides was finally achieved with strong bases such as nBuLi, NaNH₂, or BnK. In the solid state, the lithium compound forms a tetrameric structure consisting of a (C–S–O–Li)₄ macrocycle, which incorporates an additional molecule of lithium iodide. The potassium compound forms a C₄-symmetric structure with a (K₄O₄)₂ octahedral prism as central structural motif. Upon deprotonation the P–C–S linkage undergoes a remarkable contraction typical for metalated ylides.     

Novel Metal Complexes Unit of Phenanthroline Derivative for Being Used as Auxiliary Electron Acceptor in Dye Sensitizer Molecules

Donor-acceptor-π bridge-acceptor (D−A−π−A) motif dyes are promising dye sensitizers in dye-sensitized solar cells (DSSCs). In this study, to strengthen with-drawing electron force of the auxiliary electron acceptors(A) in D−A−π−A motif dye sensitizers, the metal complexes unit is be used as auxiliary electron acceptor(A) instead of organic electron-withdrawing monomer. The four polymeric metal complexes were designed, synthesized, and characterized, which used metal complexes of phenanthroline derivatives as auxiliary acceptors (A), benzodithiophene-dithiophene derivatives (BDTT) as donors (D), and 8-hydroxyquinoline derivatives as π-bridges and acceptors of the dye sensitizers, and have been used for dye sensitizers. Under AM 1.5 G (100 mW cm⁻²), the photovoltaic test results indicated that the short-circuit photocurrent density (J_sc) of the DSSCs based four polymeric metal complexes are 11.26, 13.68, 14.42 and 15.57 mA cm⁻² and power conversion efficiency (PCE) are 5.96 %, 7.83 %, 8.07 %, 9.28 % respectively. Both J_sc and PCE value of the four polymeric metal complexes increased in order. This may be due to the fact that larger radius of metal ion under the same change number can enhance the coordination bond and cause stronger electron-withdrawing ability of auxiliary acceptor and stronger charge-transfer ability between the donor and the acceptor, which results in higher J_sc and higher PCE of the polymeric complex dye sensitizer.     

Interactions of Zn(II) with single and multiple amino acids. Insights from density functional and ab initio calculations

Calculations were performed to study the interactions of metal ions (M) with (multiple) amino acids (AA) and fill the gap between single AA and proteins. A complete conformational search results in nine and eleven ZnGly isomers at B3P86 and MP2 levels, respectively, and four populated conformers of glycine are responsible for production of these isomers. For all M, the isomers via the OO and NO binding modes are the main constituents, and the OO mode is favored by stronger electrostatic interactions. Binding with more glycines causes larger structural distortions, improves relative stabilities of monodentate binding isomers and generates new binding modes (e.g. ZnB_III via only the hydroxyl group). The scaling factor of Zn(Gly)_n structures, the ratio of its binding affinity versus the sum of comprising ZnGly isomers, is linear with glycine number (n), and the linear relationship may not be altered by mutations of glycines and M. It thus allows to estimate M(AA)_n binding affinities (n ≥ 2) from the comprising MAA structures and analyze their structures with kinetic methods. The DFT and MP2 results become comparable by increasing metal coordination, e.g. the ZnB_III versus ZnA_I (zwitterionic) relative energy differs by 41.9 kcal mol^?1 at B3P86 and MP2 levels and is close by addition of three water molecules (4.1 kcal mol^?1). The presence of water solvent improves the relative stabilities of monodentate binding isomers and results in a broader conformational distribution. Copyright © 2012 John Wiley & Sons, Ltd.     

All-Metallic Zn=Zn Double-π Bonded Octahedral Zn2M4 (M=Li,Na) Clusters with Negative Oxidation State of Zinc

Zn=Zn double bonded-especially double-π bonded-systems are scarce due to strong Coulomb repulsion caused by the Zn atom's internally crowded d electrons and very high energy of the virtual π orbitals in Zn₂ fragments. It is also rare for Zn atoms to exhibit negative oxidation states within reported Zn−Zn bonded complexes. Herein, we report Zn=Zn double-π bonded octahedral clusters Zn₂M₄ (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state. Especially in D_4h−Zn₂Na₄, the natural population analysis shows that the charge of the Zn atom reaches up to −0.89 |e| (−1.11 |e| for AIM charge). Although this cooperation inevitably increases the repulsion between two Zn atoms, the introduction of the s¹-type ligands results in occupation of degenerated π orbitals and the electrons being delocalized over the whole octahedral framework as well, in turn stabilizing the octahedral molecular structure. This study demonstrates that maintaining the degeneracy of the π orbitals and introducing electrons from equatorial plane are effective means to construct double-π bonds between transitional metals.     

Near IR Bandgap Semiconducting 2D Conjugated Metal-Organic Framework with Rhombic Lattice and High Mobility

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs) are emerging as a unique class of electronic materials. However, 2D c-MOFs with band gaps in the Vis-NIR and high charge carrier mobility are rare. Most of the reported conducting 2D c-MOFs are metallic (i.e. gapless), which largely limits their use in logic devices. Herein, we design a phenanthrotriphenylene-based, D_2h-symmetric π-extended ligand ( OHPTP ), and synthesize the first rhombic 2D c-MOF single crystals ( Cu₂(OHPTP) ). The continuous rotation electron diffraction (cRED) analysis unveils the orthorhombic crystal structure at the atomic level with a unique slipped AA stacking. The Cu₂(OHPTP) is a p-type semiconductor with an indirect band gap of ≈0.50 eV and exhibits high electrical conductivity of 0.10 S cm⁻¹ and high charge carrier mobility of ≈10.0 cm² V⁻¹ s⁻¹. Theoretical calculations underline the predominant role of the out-of-plane charge transport in this semiquinone-based 2D c-MOF.     

Binding Interaction of Captopril with Metal Ions: A Fluorescence Quenching Study

The binding interaction of captopril (CPL) with biologically active metal ions Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ was investigated in an aqueous acidic medium by fluorescence spectroscopy. The experimental results showed that the metal ions quenched the intrinsic fluorescence of CPL by forming CPL‐metal complexes. It was found that static quenching was the main reason for the fluorescence quenching. The quenching constant in the case of Cu²⁺ was highest among all quenchers, perhaps due to its high nuclear charge and small size. Quenching of CPL by metal ions follows the order Cu²⁺>Ni²⁺>Co²⁺>Ca²⁺>Zn²⁺>Mn²⁺>Mg²⁺. The quenching constant K_sv, bimolecular quenching constant K_q, binding constant K and the binding sites "n" were determined together with their thermodynamic parameters at 27 and 37°C. The positive entropy change indicated the gain in configurational entropy as a result of chelation. The process of interaction was spontaneous and mainly ΔS‐driven.     

Atomvolumina und Ladungsverteilungen in Nitridometallaten

Atom Volumina and Charge Distributions in Nitridometalates The linear relation between the nitride volumina calculated by use of the QTAIM‐method developed by Bader and those derived from the tables of volume increments reported by Biltz does not hold for nitridometalates A_a[M_mN_n] (A = alkali or alkaline earth metal, M = transition metal). The clear deviation from linearity is caused by the different kinds of chemical bonds being present within the complex [M_mN_n] anions on the one hand and between the complex anions and the cations on the other hand. The significant covalency of the chemical bonds within the complex [M_mN_n] anions is reflected by the calculated volumina and the charge distributions between the M and N atoms using the Bader method. By comparing the oxidation numbers of the atoms forming the complex anions with their calculated charge assignments (QTAIM method) a significant charge reduction becomes evident.     

[{μ‐Cy8Si8O13}2Ca(DME)Ca(THF)2] – The First Metallasilsesquioxane Derivative of a Heavier Alkaline Earth Metal

[{μ‐Cy₈Si₈O₁₃}₂Ca(DME)Ca(THF)₂] ( 2 ), the first metallasilsesquioxane derivative of a heavier alkaline earth metal, has been prepared by a reaction of Cy₇Si₇O₉(OH)₃ ( 1 ) with metallic Ca in liquid ammonia / THF followed by recrystallization from DME. In the course of the reaction ligand rearrangement under formation of the (Cy₈Si₈O₁₃)^? dianion takes place. In the dinuclear calcium complex 2 the anionic silsesquioxane cages act as bridging ligands. The Ca²⁺ ions are unsymmetrically coordinated by THF and DME molecules.     

Geometry and electronic properties of alkali metal (rubidium) doped boron clusters

Alkali metal-doped boron clusters have captured much attention because of their novel electronic properties and structural evolution. In the study of RbB_n^0/− (n = 2–12) clusters, the minimum global search of the potential energy surface and structure optimization at the level of PBE1PBE by using the CALYPSO method and Gaussian package coupled with DFT calculation; the geometrical structures and electronic properties are systematically investigated. At n = 8, the ground-state structures are composed of an Rb atom above B atoms, forming a structurally stable pagoda cone. By stability analysis and charge transfer calculation, the RbB₈⁻ cluster shows more stability. It found that s-p hybridization between Rb atom and B atoms as well as s-p hybridization between B atoms is one of the reasons for the outstanding stability exhibited in the RbB₈^0/− clusters by using DOS and HOMO–LUMO orbital contour maps. The chemical bonding of the RbB₈^0/− groups was analyzed by using the AdNDP method, and B atoms with larger numbers readily form multi-center chemical bonds with the Rb atom. From the results of the bonding analysis, the interaction between the Rb atom and B atoms strengthens the stability of the RbB₈^0/− clusters. It is hoped that this work provides a direction for experimental manipulation.     

Metal–Helix Frameworks Formed by μ3-NO3− with Different Orientations and Connected to a Heterometallic CuII10DyIII2 Folded Cluster

Metal nanoclusters have a certain rigidity due to their specific coordination patterns and shapes; thus, they face extreme difficulty in folding into a specific direction to form a double-helix structure and in further interconnecting to form metal–helix frameworks (MHFs). To date, no MHFs have been produced by the formation of heterometallic clusters. Selecting the appropriate “bonding molecules” to bond metal nanoclusters in a specific multiple direction is one of the most effective strategies for designing synthetic MHFs. In this study, we realized for the first time the control of different orientations of μ₃-NO₃⁻ to join heterometallic clusters (Cu₁₀Dy₂) and subsequently form a left-handed double helix chain, which further joins to form MHFs. In the structure of the MHFs, four different directions of bridging μ₃-NO₃⁻ exist, three of which are involved in the linkage of the double-helix chain. Each μ₃-NO₃⁻ is connected to three adjacent Cu₁₀Dy₂. Herein, we extend a new method for designing synthetic double-helix structures and MHFs, thereby further laying the foundation for the development of similar DNA double-helix structures and nucleic acid secondary structures in vitro.     

Bond strengths in cyclopentadienyl metal carbonyl anions

Energy-resolved collision-induced dissociation of metal cyclopentadienyl carbonyl anions CpM(CO)_x⁻(Cpc-C₅H₅, MV, Cr, Mn, Fe, Co) is used to determine metal–carbonyl bond energies in these systems. These bond energies are, in general, slightly stronger than those for the corresponding homoleptic metal carbonyl anions. The bond strength in CpCo(CO)₂⁻, a 19-electron complex, is notably weaker than most of the others. D[CpMn⁻-CO] is also weak; this is attributed to a mismatch in the electronic ground states of CpMn⁻ and CpMnCO⁻. D[CpCo⁻-CO], on the other hand, is substantially larger than the others, and is comparable to the bond energy measured in solution for CpMn(CO)₃.     

Boosting Electroreduction Kinetics of Nitrogen to Ammonia via Atomically Dispersed Sn Protuberance

Atomically dispersed metal catalysts show potential advantages in N₂ reduction reaction (NRR) due to their excellent activity and efficient metal utilization. Unfortunately, the reported catalysts usually exhibit unsatisfactory NRR activity due to their poor N₂ adsorption and activation. Herein, we report a novel Sn atomically dispersed protuberance (ADP) by coordination with substrate C and O to induce positive charge accumulation on Sn site for improving its N₂ adsorption, activation and NRR performance. The extended X-ray absorption fine structure (EXAFS) spectra confirmed the local coordination structure of the Sn ADPs. NRR activity was significantly promoted via Sn ADPs, exhibiting a remarkable NH₃ yield (R_NH3) of 28.3 μg h⁻¹ mg_cat⁻¹ (7447 μg h⁻¹ mg_Sn⁻¹) at −0.3 V. Furthermore, the enhanced N₂H_x intermediates was verified by in situ experiments, yielding consistent results with DFT calculation. This work opens a new avenue to regulate the activity and selectivity of N₂ fixation.     

The Analysis of Os≡C Bond and Electric Field Influence on the Properties in the Osmium Carbyne Complex OsCl3 (≡CCH2CMe3 )(PH3 )2: A Theoretical Insight

In this paper, we study the effect of electric field on the dipole moment, electronic structure, and frontier orbital energy in the osmium carbyne complex OsCl₃ (≡CCH₂CMe₃ )(PH₃ )₂ using MPW1PW91 quantum chemical computations. We demonstrate the nature of the chemical bond between the [OsCl₃ (PH₃ )₂]⁻ and [CCH₂CMe₃ ]⁺ fragments through energy and charge decomposition analyses. We also estimate the percentage composition in terms of the specified groups of frontier orbitals for this complex to investigate the feature in the metal–ligand bonds. Quantum theory of atoms in molecules (QTAIM ) is applied to elucidate the Os≡C bond in the complex. Also, the influence of external electric field on the energy, frontier orbital energies, and HOMO–LUMO gap values is analyzed.     

CuAg nanoparticles formed in situ on electrochemically pre‐anodized screen‐printed carbon electrodes for the detection of nitrate and nitrite anions

CuAg nanoparticles (CuAgNPs) were electrochemically formed in situ on pre‐anodized, screen‐printed carbon electrodes (SPCEs) that possessed many oxygen‐containing functional groups capable of adsorbing metal ions, namely Cu²⁺ and Ag⁺. Pre‐anodization was achieved using continuous cyclic voltammetry in the range of potential 0.3–2.0 V under a scan rate of 50 mV/s. Cu²⁺ and Ag⁺ ions were adsorbed on the pre‐anodized SPCE by immersing the electrode in solutions containing both metal ions, and then CuAgNPs were formed in situ via electrochemical reduction in a deaerated, neat NaClO₄ solution after the electrode was ultrasonicated to remove physically adsorbed metal ions. Although CuNPs showed higher activity than AgNPs toward both nitrate (NO₃⁻) and nitrite (NO₂⁻) ions, the instability of CuNPs hindered the application, so CuAgNPs were employed to achieve a compromise between sensitivity and stability. The SPCE/anodized/CuAgNP electrodes showed activity toward the electrochemical reduction of NO₃⁻ and NO₂⁻, respectively, with the limit of detection (LOD) of 15.6 μM (0.97 ppm) and 11.1 μM (0.51 ppm), which is sufficient to fit the allowed values (50 and 3 ppm, respectively) in drinking water as suggested by the World Health Organization (WHO).