MAlH4(M=Li,Na)储氢材料*

氢能是一种新型的清洁能源,有望替代碳经济,而氢的储存是氢能应用的关键。近年来,研究集中在具有储氢容量高和可逆性好等优点的固态储氢材料上。许多新型储氢材料不断出现,其中以MAlH₄(M=Li, Na)为代表的金属复合氢化物体系被认为是最有前景的储氢材料之一。本文综述了MAlH₄(M=Li, Na)作为可逆储氢材料的研究现状,主要从吸放氢反应、储氢性能、反应机理、理论计算和存在的问题等方面进行了讨论,并指出其相关发展趋势。     

Les systemes binaires AlPO4−M3PO4 (M=Li,Na, K)

The liquid-solid phase diagram of the binary systems AlPO₄?M₃PO₄(M=Li, Na, K) have been established. The additional compounds Na₃Al(PO₄)₂, Na₃Al₂(PO₄)₃ and K₃Al₂(PO₄)₃ have been found again. A new compound K₃Al(PO₄)₂ is observed. The melting point of Na₃PO₄ is 1545°C and K₃PO₄ does not melt up to 1700°C.     

Octacoordination of the nitrogen atom in M4NO 4 + systems (M = Li, Na, K)

The electronic and geometric structures of M₄NO ₄ ⁺ compounds (M = Li, Na, K) in classical and nonclassical isomeric forms were studied by the ab initio (MP2(full)/6-311+G**) and density functional theory (B3LYP/6-311+G**) methods. For all M atoms, structurally stable nonclassical isomers were found with octacoordinated nitrogen atoms and tetracoordinated oxygen atoms. For Li₄NO ₄ ⁺ , the classical structure with the tetracoordinated nitrogen atom is energetically more stable, whereas nonclassical structures with the octacoordinated nitrogen center are more stable for Na₄NO ₄ ⁺ and K₄NO ₄ ⁺ .     

Probing Lewis acidity of Y(BH4)3 via its reactions with MBH4 (M = Li, Na, K, NMe4)

High-energy milling of Y(BH(4))(3) (containing LiCl as a by-product, which has not been removed) with MBH(4) (M = Li, Na, K, (CH(3))(4)N) leads to the first two examples of quasi-ternary yttrium borohydrides: KY(BH(4))(4) and (CH(3))(4)NY(BH(4))(4), while no chemical reaction is observed for LiBH(4) and NaBH(4). KY(BH(4))(4) is isostructural to NaSc(BH(4))(4) (Cmcm, a = 8.5157(4) ?, b = 12.4979(6) ?, c = 9.6368(5) ?, V = 1025.62(9) ?(3), Z = 4), while (CH(3))(4)NY(BH(4))(4) crystallises in primitive orthorhombic cell, similarly to KSc(BH(4))(4) (Pnma, a = 15.0290(10) ?, b = 8.5164(6) ?, c = 12.0811(7) ?, V = 1546.29(17) ?(3), Z = 4). The thermal decomposition of hydrogen-rich KY(BH(4))(4) (8.6 wt.% H) involves the formation of an unidentified intermediate at 200 °C and recovery of KBH(4) at higher temperatures; at 410 °C, KCl and YH(2) are observed. The thermal decomposition of (CH(3))(4)NY(BH(4))(4) occurs via two partly overlapping endothermic steps with concomitant emission of H(2) and organic compounds. Heating of a NaBH(4)/Y(BH(4))(3) mixture above 165 °C results in a mixed-cation mixed-anion borohydride, NaY(BH(4))(2)Cl(2), but not NaY(BH(4))(4). The reduced reactivity of Y(BH(4))(3) towards borohydride Lewis bases when compared to hypothetical scandium borohydride can be explained by the lower Lewis acidity of Y(BH(4))(3) than Sc(BH(4))(3).     

Rules on pair electron correlation in MOH (M=H,Li, Na)

In this article, the transferable property of pair correlation energies of OH components is discussed for a series of OH containing compounds MOH (M=H, Li, Na). In this series of compounds, from OH free radicals through HOH, LiOH, NaOH to OH^?, both the intra‐ and interpair correlation energies and intra‐ and intershell correlation energies of the inner orbital electrons change little. The 1s$_{\mathrm{O}}^{2}$ is very much alike in all the above OH containing systems and such a pair correlation is transferable. But the interpair correlation and intrashell correlation energies of the valence electrons are large and change a lot in all systems. In MOH molecules, the OH correlation energy contribution increases with the increase of the ionic bond strength of the compound and this contribution is always between the correlation energy values of OH free radicals and OH^? atomic groups. For strong ionic compounds, we present a very simple method to estimate the correlation energy by adding the correlation energies of its component ions within the chemical accuracy (2 kcal/mol). © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 311–317, 2001     

Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M = Li, Na, or Rb)

Phase equilibria in the systems M₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ (M = Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ system with the molar ratios of the starting components equal to 5: 1: 1 (S ₂) and 1: 1: 1 (S ₁). Proceeding from that the isostructurality of Rb₅FeHf(MoO₄)₆ and S ₂ the unit cell, parameters are determined for S ₂.     

Structure determination and relative properties of novel cubic borates MM'4(BO3)3 (M = Li, M' = Sr; M = Na, M' = Sr, Ba)

A series of novel borates, MM'4(BO3)3 (M = Li, M' = Sr; M = Na, M' = Sr, Ba), have been successfully synthesized by standard solid-state reaction. The crystal structures have been determined from powder X-ray diffraction data. They crystallize in the cubic space group Iad with large lattice parameters: a = 14.95066(5) A for LiSr4(BO3)3, a = 15.14629(6) A for NaSr4(BO3)3, and a = 15.80719(8) A for NaBa4(BO3)3. The structure was built up from 64 small cubic grids, in which the M' atoms took up the corner angle and the BO3 triangles or MO6 cubic octahedra filled in the interspaces. The isolated [BO3]3- anionic groups are perpendicular to each other, distributed along three 100 directions. The anisotropic polarizations were counteracting, forming an isotropic crystal. Sr and Ba atoms were found to be completely soluble in the solid solution NaSr(4-)xBax(BO3)3 (0 < or = x < or = 4). The photoluminescence of samples doped with the ions Eu2+ and Eu3+ was studied, and effective yellow and red emission was detected, respectively. The results are consistent with the crystallographic study. The DTA and TGA curves of them show that they are chemically stable and congruent melting compounds.     

Aromatic N-Heterocyclic superalkali M@C4H4N2 complexes (M=Li,Na, K); A promising potential hydrogen storage system

In search of a potential hydrogen storage material, we have used three different aromatic N-heterocyclic systems; Pyrazine, Pyrimidine, and Pyridazine. The alkali (Li, Na, and K) metallated heterocyclic systems (M@C₄H₄N₂) are stabilized as cation found to be superalkali with a vertical electron affinity ranges from 4.42 to 3.97 ​eV. First principle calculations reveal that M@heterocylclic systems can adsorb up to 10–18H₂ molecules with gravimetric wt% of 17. It has been observed that all the trapping process belongs to physisorption as H₂ are almost in a molecular form with a slight increase in bond length. Binding energy values favor gradual H₂ adsorbtion. Superalkali nature is gradually increasing upon the increasing number of H₂ molecules but attains a constant value after certain numbers. Among three isomers Pyrazine, Pyrimidine, and Pyridazine, Li@Pyrazine complex is found to be the most suitable for H₂ storage.     

(NH4)4M(Zr(Hf))3F17 · 2HF Complexes (M = Li,Na): Synthesis and Physicochemical Properties

Monoclinic crystals of ammonium hydrofluoride fluoro complexes of zirconium and hafnium (NH₄)₄M(Zr(Hf))₃F₁₇ · 2HF (M = Li, Na) are synthesized and studied. Their unit cell parameters are determined. IR spectra of the synthesized compounds are measured in the range of 350–4000 cm^–1.     

Immobilization of molten salt waste into MZr2(PO4)3 (M=Li, Na, Cs, Sr)

Summary Amorphous zirconium phosphate (Zr(HPO₄)₂^.nH₂O, AM-ZP) has been investigated as a material for selective removal of Cs or Sr from molten salt waste at aqueous state and its ceramic waste form. NZP (MZr₂P₃O₁₂, M=Li, Na, Cs, and Sr), was synthesized by three methods and evaluated their durability by the Product Consistency Test (PCT) method. AM-ZP has a high selectivity on Cs and Sr even in the presence of Li with high concentration. From the leaching data, the leached fractions (LF_∞) of each product at a given time in infinite leachate volume can be calculated by a semi-empirical equation. The LF_∞ of Li, Na, Cs and Sr on the product prepared by composition-adjusting process were 0.143, 0.078, 0.017, and 0.034, respectively. It can be concluded that AM-ZP is an effective material for selective removal of radionuclides from molten salt waste and its metal-loaded ZP can be changed into a durable waste form close to NZP structure by a composition-adjusting process.     

Water-dependent reactions of diiron(II) carboxylate complexes

Carboxylate-rich diiron(II) compounds with varying numbers of water ligands have been characterized, including the first complex with a {Fe2(mu-OH2)2(mu-O2CArTol)}3+ unit. The isolation of these complexes reveals how water can alter the structural properties of carboxylate-bridged diiron(II) core similar to those that occur in a variety of dioxygen-activating metalloenzyme cores. M?ssbauer and variable temperature, variable field magnetic susceptibility experiments indicate that the compound [Fe2(mu-OH2)2(mu-O2CAr4F-Ph)(O2CAr4F-Ph)3(THF)2(OH2)] has a high-spin diiron(II) core with little significant magnetic exchange coupling.     

Nonlinear optical properties of the M @ C60 endohedrals (M = Cs,Li, and Na)

The Hartree–Fock (HF) approximation and the Single‐excitation configuration interaction (single‐CI) method are used, with sum‐over‐state (SOS) approach, in order to determine the static (ω = 0) and frequency dependent linear and non linear optical (NLO) properties of the M @ C₆₀ endohedrals (M = Cs, Li, and Na). We discuss the effects of displacement, movement direction, and type of atom on the (hyper) polarizability of the M at C₆₀ endohedrals. A HF‐single‐CI model yields the (hyper) polarizability magnitudes and spectra, which are in agreement with experiment. Our results indicate that the movement of the atom (M) effect on the NLO spectra of M @ C₆₀ endohedrals is dramatic. These results may provide new means to design some new types of NLO materials. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

不饱和类硅烯H2C＝SiMBr (M＝Li, Na)的DFT研究

采用密度泛函理论方法, 在B3LYP/6-311G (d,p)水平上研究了不饱和类硅烯H₂C＝SiMBr (M＝Li, Na)的结构. 结果表明, 不饱和类硅烯H₂C＝SiLiBr与H₂C＝SiNaBr各有三种平衡构型, 其中非平面的p-配合物型构型能量最低, 是这两种不饱和类硅烯存在的主要构型. 对平衡构型间异构化反应的过渡态进行了计算, 求得了转化势垒. 计算预言了最稳定构型的振动频率和红外强度.     

New examples of metalloaromatic Al-clusters: (Al4M4)Fe(CO)3 (M = Li, Na and K) and (Al4M4)2Ni: rationalization for possible synthesis

Ab initio calculations reveal that all-metal antiaromatic molecules like Al4M4 (M = Li, Na and K) can be stabilized in half sandwich (Al4M4)Fe(CO)3 and full sandwich (Al4M4)2Ni complexes. The formation of the full sandwich complex [(Al4M4)2Ni] from its organometallic precursor depends on the stability of the organic-inorganic hybrid (C4H4)Ni(Al4Li4).     

Synthesis and structures of some heterometallic [(Li, Y)2, (M3, Ce) (M = Li or Na), (Li, Zr2) and (Li, Zr)4] oligomeric diamides derived from 1,2-bis(neopentylamino)benzene

The following crystalline, X-ray-characterised heterometallic oligomeric diamides have been prepared in good yield under mild conditions in diethyl ether from the dilithio or disodio derivative of the N,N'-dineopentyl-1,2-diaminobenzene [{N(H)(CH2Bu(t))}2C6H4-1,2] (abbreviated as H2L):[Y(L)(mu-Cl)2Li(OEt2)2]2 (1), [Li(OEt2)2Li(mu2-Cl)4(mu3-Cl)2{Zr(L)}2]2 (2), [Zr(L)2(mu-Cl){Li(OEt2)2}(mu2-Cl)2Zr(L)] (3), [Ce{(mu-L)M}3(OEt2)(1/2)] (3M = Li(1.82)Na(1.18)) (4), [Ce{(mu-L)Na}3(OEt2)] (5) and [Ce{(mu-L)Na}3] (6). Compounds 1-3 were obtained from Li2(L) and YCl3 (the colourless 1) or ZrCl4 (the red 2 and 3), while the red 4 and 5 were isolated from CeCl3 and M2(L) (3M = Li(1.82)Na(1.18)) (4) or Na2(L) (5). Attempted oxidation of 5 with Br2 in hexane yielded the black 6. The ligand is N,N'-chelating to each of the d- or f-block metals in 1-6; and in 4-6 L is also acting as a bridge between Ce and the alkali metal, to which L is thus also chelating.     

Phase formation in the Re-Se-Br-MBr systems (M = Li, Na, K, Rb, Cs)

Phase formation in the Re-Se-Br-MBr systems (M = K, Rb, Cs) was studied by NMR spectroscopy and powder X-ray diffraction. The reactions taking place in alkali metal halide melts were found to give, among the series of cluster anions [{Re₆Se_{8 − n} Br _n }Br₆]^{(4 − n)}− (0 ≤ n≤ 4), polymeric complexes Re₆Se₈Br ₂ and M₂Re₆Se₈Br₄ (M = Cs, Rb) and salts containing cluster anions [Re₆Se₆Br₈]²⁻ and [Re₆Se₇Br₇]³⁻ as the major products. The effect of the alkali metal cation on the product composition and ratio was established. Original Russian Text ? S.S. Yarovoi, Yu.V. Mironov, S.V. Tkachev, V.E. Fyodorov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 344–349.     

Semiempirical calculations on WO3 and MXWO3 crystals (M = H,Li, Na)

The monoclinic structure of tungsten trioxide WO₃ has been studied by combining a modified intermediate neglect of differential overlap (INDO) method and the supercell model. The fitted semiempirical parameters describe very well the features of the band structure and crystal structure. Calculations of H, Li, and Na impurities in a WO₃ crystal have been performed to study the absorption spectra and the equilibrium geometries of intercalated impurities. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 729–735, 1997     

Developments in heterobimetallic s-block systems: synthesis and structural survey of molecular M/Ae (M=Li, Na, K, Cs; Ae=Ca, Sr) aryloxo complexes

A series of novel heterobimetallic group 1/strontium and group 1/calcium aryloxo complexes having the composition [MAe(Odpp)3] [Ae=Sr and M=Na (1), K (2, 3), Cs (4); Ae=Ca and M=Na (5), K (6), Cs (7)] or [M2Ae(Odpp)4] [M=Li and Ae=Sr (9), Ca (10)] have been prepared using 2,6-diphenylphenol (HOdpp) as the ligand. Through the use of solid-state direct metalation, these compounds were obtained either directly from the reaction vessel or after workup in toluene. The Lewis base adduct [KCa(Odpp)3(thf)] (8) was obtained by treatment of [KCa(Odpp)3] (6) with tetrahydrofuran (thf). All of the compounds displayed extensive metal-pi-arene interactions, which provide significant stabilization in these reactive species. The thermal stabilities and volatilities of representative heterobimetallic strontium and calcium complexes were investigated using thermogravimetric analysis.