Cyanides and Isocyanides of Zinc,Cadmium and Mercury: Matrix Infrared Spectra and Electronic Structure Calculations for the Linear MNC,NCMCN, CNMNC,NCMMCN, and CNMMNC Molecules

Cadmium atoms from laser ablation react with cyanogen, NC=CN, in excess argon during co-deposition at 4 K, and even more on UV irradiation of the cold samples. Final annealing to 35 K increases bands at 2187.3 and 2089.2 cm⁻¹ at the expense of weaker bands at 2194.6 and 2092.2 cm⁻¹ through addition of another cadmium atom. Reaction products were identified by comparison with B3LYP and CCSD(T) computed frequencies and energies, through frequency differences between Zn and Cd products, and by cyanogen isotopic substitution. The CN radical, ZnNC, and CdNC were observed on sample deposition. Hg arc ultraviolet (UV) irradiation activates the insertion of Cd and Zn to form the NCCdCN, CNCdNC, NCZnCN and CNZnNC molecules. Next annealing increased the dimetal products NCCdCdCN, CNCdCdNC, NCZnZnCN, and CNZnZnNC at the expense of their single metal analogs. Laser ablated mercury amalgam also produced NCHgCN, NCHg−HgCN, CNHgNC and CNHg−HgNC. The Group12 metals form both cyanide and isocyanide products, and the argon matrix also traps the higher energy but much more intensely absorbing isocyanides. In the isocyanide case bond polarity results in very intense infrared absorptions. Group 12 metals produce shorter M−M bonds in the dimetal cyanides NCM−MCN and isocyanides CNM−MNC than in the M−M itself, and their computed M−M bond lengths compare favorably with those measured for dimetal complexes stabilized by large ring containing molecular ligands.     

Mercury Cyanides and Isocyanides: NCHgCN and CNHgNC as well as NCHgHgCN and CNHgHgNC: Simple Molecules with Short,Strong Hg−Hg Bonds

Mercury atoms, laser‐ablated from an amalgam dental filling target, react with cyanogen in excess argon during condensation at 4 K to form two major products in the 2200 cyanide M?C?N stretching region of the IR spectrum, which were assigned to NCHgCN and NCHgHgCN from their antisymmetric C?N stretching mode absorptions at 2213.8 and 2180.1 cm^?1. Two broader bands in the isocyanide region at 2098.2 and 2089.6 cm^?1 were assigned to CNHgNC and CNHgHgNC. The N‐bonded isomers were computed to be 603/33 and 823/69 times more intense IR absorbers than the C‐bonded isomers at the CCSD level of theory. The dissociation energy for the NCHg?HgCN molecule into two HgCN molecules was calculated to be 296 kJ mol^?1 and that for CNHg?HgNC into two HgNC molecules is 304 kJ mol^?1. These simple molecules with two cyanide or two isocyanide ligands have two of the shortest and strongest known Hg?Hg single bonds as the two electronegative CN ligands withdraw antibonding electron density from the bonding region.     

(Noble Gas)n-NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations

An investigation of pulsed-laser-ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co-deposition with laser-ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo-dissociation product. A new band at 1933.4 cm⁻¹ in the region of the CN and CN⁺ gas-phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar)_nCN⁺, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN⁺ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm⁻¹. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm⁻¹. H¹³CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for ¹³CN⁺ itself in the gas phase and in the argon matrix. The CN⁺ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)₂⁺+CN→Ar+CN⁺→(Ar)_nCN⁺.     

Reactions of Group V Metal Atoms with Hydrogen Sulfide:Argon Matrix Infrared Spectra and Theoretical Calculations

The reaction of laser-ablated vanadium, niobium and tantalum atoms with hydrogen sulfide has been investigated using matrix isolation FTIR and theoretical calculations. The metal atoms inserted into the H-S bond of H₂S to form the HMSH molecules (M=V, Nb, Ta), which rearranged to H₂MS molecules on annealing for Nb and Ta. The HMSH molecule can also further react with another H₂S to form the H₂M(SH)₂ molecules. These new molecules were identified on the basis of the D₂S and H₂³⁴S isotopic substitutions. DFT (B3LYP and BPW91) theoretical calculations are used to predict energies, geometries, and vibrational frequencies for these novel metal dihydrido complexes and molecules. Reaction mechanism for formation of group V dihydrido complex was investigated by DFT internal reaction coordinate calculations. The dissociation of HVSH gave VS+H₂ on broad band irradiation and reverse reaction happened on annealing. Based on B3LYP calculation releasing hydrogen from HVSH is endothermic only by 13.5 kcal/mol with lower energy barrier of 16.9 kcal/mol.     

An Insight into nd10 Metal Cyanide-based Coordination Polymers Through ab-initio Calculations: Electronic Properties and Optical Response

Semiconductors are essential for modern life since they are the basis of many current technologies that are related to better living standards. Some of them, characterized by the periodic assembling of metal cyanides with filled d-shell (nd¹⁰) constitute an interesting series of cyanide-based coordination polymers with physical properties such like anomalous anisotropic thermal expansion and quantum confinement effects related to the polymer's width that can be exploited for technological applications. Herein, the electronic structure of nd¹⁰ metal cyanide-based systems were studied both experimentally and through Density Functional Theory. The band gap found for one-dimensional (1D) −M−C≡N− (M=Cu, Ag, Au) and tetrahedral M−(C≡N)₂ (M=Zn, Cd, Hg) systems can be attributed to Laporte-allowed π π* (Metal to Ligand Charge Transfer mechanism) combined with metal center (d s,p) electronic transitions. Aurophilic bonding was found on the AuCN structure, and a new forbidden electronic transition associated to its band gap is reported. Computed effective and reduced masses from carriers revealed that carrier mobility and quantum confinement effects are greater in 1D systems.     

ChemInform Abstract: Matrix Infrared Spectra and Electronic Structure Calculations of the First Actinide Borylene: FB=ThF2.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Gas‐Phase Infrared Spectra of Three Compounds of Astrochemical Interest: Vinyl,Allenyl, and Propargyl Isocyanides

Isocyanides, isomers of the cyanides detected in the interstellar medium, are also possible components of this medium. The infrared spectra (5000–500 cm^?1) of gaseous vinyl isocyanide, allenyl isocyanide, and propargyl isocyanide have been recorded at 0.1 cm^?1 resolution. When prepared on a gram scale to produce a partial pressure of 10 mbar after evaporation in the cell, these three isocyanides, which have previously been reported to be kinetically unstable, do not display any sign of decomposition when recording the spectra. Geometry optimizations and harmonic and anharmonic vibrational frequencies were calculated using the LCCSD(T) method with the cc‐pVTZ basis set. Anharmonic frequencies of fundamental, overtone, and combination transitions were calculated using a variational approach implemented in the P Anhar.v2.0 code, to assign the experimental data for each compound. These results improve our knowledge of these under‐investigated compounds and pave the way for other physicochemical studies on functionalized isocyanides.     

Cyclic M(SO2) (M=Zn,Cd) and its Anions: Matrix Infrared Spectra and DFT Calculations

Reaction of laser ablated zinc and cadmium atoms with SO₂ molecules was studied by low temperature matrix isolation infrared spectroscopy. Cyclic M(SO₂) and anion M(SO₂)^- (M=Zn, Cd) were produced in excess argon and neon, which were identified by ³⁴SO₂ and S¹⁸O₂ isotopic substitutions. The observed infrared spectra and molecular structures were confirmed by density functional theoretical calculations. Natural charge distributions indicated significant electron transfer from s orbitals of zinc or cadmium metal atom to SO₂ ligand and cyclic M(SO₂) complexes favored “ion pair” M⁺(SO₂)^- formation, which were trapped in low temperature matrices. In addition Zn-O or Cd-O bond in M(SO₂) exhibited strong polarized covalent character. Reaction of Hg atom with SO₂ was also investigated, but no reaction product was observed, due to the relativistic effect that resulted in the contraction of 6s valence shell and high ionization potential of Hg atom     

Syntheses and structures of highly hindered N-functionalised alkyl and amido group 12 complexes MR2 (M=Zn, Cd, and Hg), [MRCl]2 (M=Zn and Hg)

The reaction of MCl₂ (M=Zn, Cd and Hg) with Li(2-(C(SiMe₃)₂)(6-Me-C₅H₃N)), [Li(MeR)], affords mononuclear metal(II) alkyls. These, in the solid state, show intramolecular M-N interactions in their four-membered chelate rings, which progressively weaken down the series, the C-M-C angles becoming more open (〈M-N〉= 2.30(2), 2.52(2), 2.913(4) Å, C-M-C=160.7(2), 168.5(2), 180(-)°). Alkylmercury chloride complexes have been prepared by the reaction of HgCl₂ with [Li(MeR)], Li(2-(C(SiMe₃)₂)(C₅H₄N)), [Li(HR)], or Li(2-(NSiMe₃)(6-Me-C₅H₃N)), [Li(mpsa)], or from the redistribution reaction of the dialkyl (or amido) mercury complex with HgCl₂. The alkylmercury chloride complexes are dimeric or polymeric in nature with near-linear 2-coordination; (Hg-Cl=2.329(5), 2.318(4), 2.272(8) Å, Cl-Hg-C(N)=175.0(4), 174.7(4), 175.6(5)°). Cd(2-(CH(SiMe₃))(6-Me-C₅H₃N))₂(tmen), prepared from the reaction of Li(2-(CH(SiMe₃))(6-Me-C₅H₃N)) and CdCl₂ in the presence of tmen, has also been structurally authenticated as the rac isomer with the ipso protons directed towards the tmen.     

Quaternary Sulfide Ba6Zn6ZrS14: Synthesis,Crystal Structure,Band Structure,and Multiband Physical Properties

Ba₆Zn₆ZrS₁₄ was synthesized by a traditional salt‐melt method with KI as flux. The pale yellow crystals of Ba₆Zn₆ZrS₁₄ crystallize in the tetragonal space group I4/mcm with a=16.3481 (4) Å and c=9.7221(6) Å. The structure features unique one‐dimensional parallel [Zn₆S₉]^6? and [ZrS₅]^6? straight chains. The D_2h‐symmetric [Zn₆S₉]^6? cluster serves as the building block of the [Zn₆S₉]^6? chains. A powder sample was investigated by X‐ray diffraction, optical absorption, and photoluminescence measurements. The compound shows multiple‐absorption character with three optical absorption edges around 1.78, 2.50, and 2.65 eV, respectively, which are perfectly consistent with the results of first‐principles calculations. Analysis of the density of states further revealed that the three optical absorption bands are attributable to the three S(3p⁶)→Zr(4d⁰) transitions due to the splitting of the Zr 4d orbitals in the D_4h crystal field. The multiband nature of Ba₆Zn₆ZrS₁₄ also results in photocatalytic activity under visible‐light irradiation and three band‐edge emissions.     

Direct bonds between metal atoms: Zn, Cd, and Hg compounds with metal-metal bonds

The synthesis and characterization of [Zn(2)(eta(5)-C(5)Me(5))(2)], a stable molecular compound with a Zn-Zn bond and the first example of a dimetallocene structure, has opened a new chapter in the organometallic chemistry of zinc and in metallocene chemistry. The existence of two directly bonded zinc atoms demonstrates that the [Zn-Zn](2+) unit, the lightest Group 12 homologue of the well-known [Hg-Hg](2+) ion, can be stabilized by appropriate ligands. Activity in this area has increased enormously in the few years since the determination of the structure of this molecule. Numerous theoretical studies have been devoted to the investigation of the electronic, structural, and spectroscopic properties of this and related compounds, and new metal-metal coordination and organometallic compounds of zinc, cadmium, and mercury have been synthesized and structurally characterized. This Minireview gives an overview of activity in this field during the past three to four years.     

Co-Y共掺杂ZnO光电性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Co和Y单掺杂ZnO、Co-Y不同配位共掺杂ZnO的电子结构和光学性质。计算结果表明,在本文的掺杂浓度下,Co和Y单掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性,Co-Y共掺时ZnO半导体进入简并状态,呈现金属性。Co掺杂ZnO会在可见光和近紫外区域发生吸收增强现象,而Y掺杂ZnO可以提高体系在紫外区域的吸收,其中由于Co离子和Y离子之间的协同效应,Co-Y共掺ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加,因此Co-Y共掺杂ZnO可以用于制作光电感应器件。     

Co-Y共掺杂ZnO光电性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Co和Y单掺杂ZnO、Co-Y不同配位共掺杂ZnO的电子结构和光学性质。计算结果表明,在本文的掺杂浓度下,Co和Y单掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性,Co-Y共掺时ZnO半导体进入简并状态,呈现金属性。Co掺杂ZnO会在可见光和近紫外区域发生吸收增强现象,而Y掺杂ZnO可以提高体系在紫外区域的吸收,其中由于Co离子和Y离子之间的协同效应,Co-Y共掺ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加,因此Co-Y共掺杂ZnO可以用于制作光电感应器件。     

Low-Energy Electronic Excitations of N-Substituted Heteroacene Molecules: Matrix Isolation Spectroscopy in Concert with Quantum-Chemical Calculations

N-Heteropolycycles are attractive as materials in organic electronic devices. However, a detailed understanding of the low-energy electronic excitation characteristics of these species is still lacking. In this work, the matrix isolation technique is applied to obtain high-resolution absorbance spectra for a series of tetracene and core-substituted N-analogues. The experimental electronic excitation spectra obtained for matrix-isolated molecules are then analysed with the help of quantum-chemical calculations. Additional lower energy excitation bands in the spectrum of the core-substituted N-derivatives of tetracene could be explained in terms of intensity borrowing from dipole-forbidden transitions due to Herzberg–Teller vibronic coupling. In the case of tetracene, evidence for the additional formation of London dimers (J aggregates) is found at higher tetracene concentrations in the matrix.     

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Tetrahydrides crystallizing in the ThCr₂Si₂ structure type have been predicted to become stable for a plethora of metals under pressure, and some have recently been synthesized. Through detailed first-principles investigations we show that the metal atoms within these symmetry MH₄ compounds may be divalent, trivalent or tetravalent. The valence of the metal atom and its radius govern the bonding and electronic structure of these phases, and their evolution under pressure. The factors important for enhancing superconductivity include a large number of hydrogenic states at the Fermi level, and the presence of quasi-molecular H units whose bonds have been stretched and weakened (but not broken) via electron transfer from the electropositive metal, and via a Kubas-like interaction with the metal. Analysis of the microscopic mechanism of superconductivity in MgH₄, ScH₄ and ZrH₄ reveals that phonon modes involving a coupled libration and stretch of the H units leading to the formation of more complex hydrogenic motifs are important contributors towards the electron phonon coupling mechanism. In the divalent hydride MgH₄, modes associated with motions of the hydridic hydrogen atoms are also key contributors, and soften substantially at lower pressures.     

邻苯二甲酸锌配合物的合成,红外光谱和晶体结构

邻苯二甲酸锌配合物的合成、红外光谱和晶体结构孙聚堂＊王东利张克立王春林（武汉大学化学系武汉４３００７２）（武汉大学测试中心武汉）关键词邻苯二甲酸，锌，晶体结构，红外光谱１９９６－１２－１６收稿，１９９７－０６－１６修回国家自然科学基金资助课题掺杂微量...     

Synthesis,Structural Characterization,Electronic Structure,and Magnetic Properties of the Zintl Phase Eu10Cd6Bi12

A new transition‐metal‐containing Zintl phase, Eu₁₀Cd₆Bi₁₂, was synthesized by combining the elements in excess molten Cd. Single‐crystal X‐ray diffraction studies indicated that this compound crystallizes in the orthorhombic space group Cmmm (No. 65) with a=7.840(2), b=24.060(7), and c=4.7809(14) Å. The crystal structure of Eu₁₀Cd₆Bi₁₂ can be viewed as a stacking of a series of [Cd₆Bi₁₂] double layers, which are arranged alternately along the b axial direction. The layers are composed of corner‐ and edge‐shared CdBi₄ tetrahedra, a common feature in the crystal chemistry of many transition‐metal Zintl phases. Electronic‐band‐structure calculations confirm the closed‐shell configuration of all constituent elements and corroborate the electron count inferred by the Zintl formalism, that is, [Eu²⁺]₁₀[Cd²⁺]₆[Bi^3?]₈[Bi^2?]₄. Magnetic‐susceptibility measurements confirm the divalency of europium and show the existence of a long‐range antiferromagnetic order of the Eu spins below 12.3 K.     

Investigation of 4f-Related Electronic Transitions of Rare-Earth Doped ZnO Luminescent Materials: Insights from First-Principles Calculations

Rare-earth (RE) doped zinc oxides (ZnO) are regarded as promising materials for application in versatile color-tuned devices. However, the understanding of underlying luminescence mechanism and the rule of 4 f-related electronic transition is still limited, which is full of significance for the exploration of advanced RE-based ZnO phosphors. Thus, a series of ZnO : RE (RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb) phosphors have been investigated by means of first-principles calculations. Meanwhile, we also consider the effect of native defects (V_O, V_Zn) on the luminescence of ZnO : RE phosphors. Accordingly, four types of electric-dipole allowed transition processes are figured out in ZnO : RE family. Additionally, we manifest that the V_O can further improve the luminescent performance of ZnO : RE phosphors, and give insightful guidance to design desired RE-based ZnO materials with excellent luminescence.