Synthesis and Structure of Acetonitrile Solvates of Copper(II) Monofluoroacetate and Silver(I) Trifluoroacetate, [Cu2(CH2FCOO)4· 2CH3CN](CH3CN) and Ag3(CF3COO)3(CH3CN)2

Compounds [Cu₂(CH₂FCOO)₄· 2CH₃CN](CH₃CN) (I) and Ag₃(CF₃COO)₃(CH₃CN)₂(II) were synthesized and studied by X-ray structural analysis. Crystals Iare monoclinic, space group C2/c, a= 27.854(6), b= 8.286(2), c= 19.428(4) Å, = 106.82(3)°, V= 4292(2) ų, Z= 8, R ₁= 0.0426; crystals IIare triclinic, space group , a= 8.676(2), b= 9.819(2), c= 11.961(2) Å, = 95.27(3), = 109.59(3)°, = 104.60(3)°, V= 911.4(3) ų, Z= 2, R ₁= 0.0252. Structure Iis composed of the structural units (lanterns) typical of copper(II) carboxylates. The presence of an additional acetonitrile molecule noncoordinated by the copper atoms makes it possible to consider compound Ias a lattice clathrate. Structure IIhas no analogs among the silver carboxylates. It simultaneously contains silver atoms with coordination numbers varying from 2 to 4.     

The solvent influence on some physicochemical properties of Cu(NO3)2·3H2O-(CH3)2SO solutions

The electrical conductance of Cu(NO₃)₂·3H₂O solutions (0.00886–2.82 mol L^?1) in dimethylsulfoxide at 288–318 K has been studied by conductometry.     

Intramolecular Rearrangements of >Si(O–C·=O)(CH2–CH3) and >Si(CH2–CH·–CH3)(CH2–CH3) Radicals

Using ESR and IR spectroscopy, the structures of >Si(O–C^·=O)(CH₂–CH₃) (1) and >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) (2) radicals were deciphered. The directions and kinetic parameters of reactions of intramolecular rearrangements in these radicals were determined. The reactions of hydrogen atom abstraction in radical (1) from the CH₂ and CH₃ groups were studied. It was found that the endothermic reaction of hydrogen atom abstraction from the methyl group occurs at a higher rate than the exothermic reaction with the methylene group. The differences are determined by changes in the size of a cyclic transition state. Based on the experimental data, the strengths of separate C–H bonds in surface fragments are compared. The rearrangement >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) >Si(C^·(CH₃)₂)(CH₂–CH₃) was discovered and its mechanism was determined. One of its steps is the skeletal isomerization Si- (2)- _. (1)Si- (1)- _. (2). Experimental data are analyzed using the results of quantum-chemical calculations of model systems.     

Effects of excitation energy on the autodetachment lifetimes of small iodide-doped ROH clusters (R═H-, CH3-, CH3CH(2)-)

The effect of excitation energy on the lifetimes of the charge-transfer-to-solvent (CTTS) states of small (4 ≤ n ≤ 10) iodide-doped water and alcohol clusters was explored using femtosecond time-resolved photoelectron imaging. Excitation of the CTTS state at wavelengths ranging from 272 to 238 nm leads to the formation of the I···(ROH)(n)(-) (R═H-, CH(3)-, and CH(3)CH(2)-) species, which can be thought of as a vibrationally excited bare solvent cluster anion perturbed by an iodine atom. Autodetachment lifetimes for alcohol-containing clusters range from 1 to 71 ps, while water clusters survive for hundreds of ps in this size range. Autodetachment lifetimes were observed to decrease significantly with increasing excitation energy for a particular number and type of solvent molecules. The application of Klots' model for thermionic emission from clusters to I(-)(H(2)O)(5) and I(-)(CH(3)OH)(7) qualitatively reproduces experimental trends and reveals a high sensitivity to energy parametrization while remaining relatively insensitive to the number of vibrational modes. Experimental and computational results therefore suggest that the rate of electron emission is primarily determined by the energetics of the cluster system rather than by details of molecular structure.     

Transition dipole moments between the low-lying Ω(g,u)(+∕-) states of the Rb2 and Cs2 molecules

For the Rb(2) and Cs(2) molecules, the adiabatic potential-energy curves and the transition dipole moments of the 43 Ω((+∕-)) (g,u) low-lying states dissociating adiabatically to the limits up to ns+(n-1)d (n = 5,6 for Rb(2) and Cs(2), respectively), have been computed as a function of the internuclear distance R for a large and dense grid. Each molecule was treated as a two-electron system. We used an ab initio approach involving a relativistic non-empirical pseudo-potential for Rb and Cs cores, core-valence polarization potentials, and full valence configuration interaction calculations for the two valence electrons. Spin-orbit effects were taken into account through semi-empirical spin-orbit pseudopotentials. Equilibrium distances, transition energies, rotational constants, and harmonic frequencies as well as depths of wells and heights of barriers are reported for all the molecular states investigated in Hund's cases (a) and (c). Extensive tables of energy values and transition dipole moments are given in an auxiliary (EPAPS) files as a database for future studies on Rb(2) and Cs(2).     

Crystal structures of the selenium- and bromo-bridged copper(I) dimers [Cu2(μ2-Br)2(SePPh3)2 · (NCCH3)2] and [Cu2I2(μ3-dppm-Se,Se)2] · 2CH3CN

Reactions of copper(I) halides with Se-donor ligands, namely, triphenylphosphine selenide (Ph₃PSe) and bis(diphenylselenophosphinyl)methane (dppm-Se,Se) yielded bromo-bridged [Cu₂(μ₂-Br)₂(SePPh₃)₂(NCCH₃)₂] (1), and selenium-bridged, [Cu₂I₂(μ₃-dppm-Se,Se)₂]?· 2CH₃CN (2) dimers, whose crystal structures are described. Acetonitrile stabilizes 1 by coordinating and helps to stabilize the packing in crystals of 2.     

Syntheses and Characterizations of （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 and （NH3CH2CH2NH3）2Bi2I10

The title compounds have been respectively synthesized by solution process and solvothermal reaction, and their crystal structures were determined by X-ray diffraction method. For （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 1, it crystallizes in tficlinic, space group P1^- with Mr = 2049.76, a = 8.5719（1）, b = 11.7461（3）, c = 15.700（1）A, V = 1451.4（1）A^3, Z = 1, Dc = 2.345 g/cm^3, F（000） = 924, μ（MoKα） = 8.907 mm^-1, T = 293（2） K, the final R = 0.0655 and wR = 0.0804 for 2399 observed reflections with I 〉 2σ（I）. For （NH3CH2CH2NH3）2Bi2I10 2, it crystallizes in monoclinic, space group P21/n with Mr= 1811.20, a = 8.434（4）, b = 13.862（6）, c = 13.362（6）A, V = 1499.9（12）A^3, Z = 2, Dc = 4.010 g/cm^3, F（000） = 1536,μ（MoKα） = 22.007 mm^-1, T = 293（2） K, the final R = 0.0584 and wR = 0.1451 for 1798 observed reflections with I 〉 2σ（I）. The structures of 1 and 2 contain halobismuthate monomer and dimers, respectively. It is noteworthy that the dimers and their organic counters in 2 connect each other by N…I hydrogen bonds to form a layered structure, and the electrostatic interactions and crystal packing forces between layers give rise to the packing of the crystal. The optical absorption spectra of 1 and 2 reveal the appearance of sharp optical gaps of 2.13 and 2.01 eV, respectively.     

A photoionization study of the ion-neutral complexes CH3CH +CH 3 · CH2CH3] and CH3CH2CH+CH 3 · CH3 in the gas phase: Formation,H-transfer and C—C bond formation between partners,and channeling of energy into dissociation

Photoionization mass spectrometry was used to investigate the dynamics of ion-neutral complex-mediated dissociations of the n-pentane ion (1). Reinterpretation of previous data demonstrates that a fraction of ions 1 isomerizes to the 2-methylbutane ion (2) through the complex CH₃CH⁺CH ₃ ^· CH₂CH₃ (3), but not through CH₃CH⁺CH₂CH ₃ ^· CH₃ (4). The appearance energy for C₃Hin ₇ ⁺ formation from 1 is 66 kJ mol^?1 below that expected for the formation of n-C₃H ₇ ⁺ and just above that expected for formation of i-C₃H ₇ ⁺ . This demonstrates that the H shift that isomerizes C₃H ₇ ⁺ is synchronized with bond cleavage at the threshold for dissociation to that product. It is suggested that ions that contain n-alkyl chains generally dissociate directly to more stable rearranged carbenium ions. Ethane elimination from 3 is estimated to be about seven times more frequent than is C-C bond formation between the partners in that complex to form 2, which demonstrates a substantial preference in 3 for H abstraction over C-C bond formation. In 1 → CH₃CH⁺CH₂CH₃ + CH₃ by direct cleavage of the C1–C2 bond, the fragments part rapidly enough to prevent any reaction between them. However, 1 → 2 → 4 → C4H ₈ ⁺ + CH₄ occurs in this same energy range. Thus some of the potential energy made available by the isomerization of n-C₄H₉ in 1 is specifically channeled into the coordinate for dissociation. In contrast, analogous formation of 3 by 1 → 3 is predominantly followed by reaction between the electrostatically bound partners.     

Hydrothermal Synthesis,Crystal Structure and Thermal Stability Properties of the Complex [Cd2(phen)2(C14HuO3)4(CH3CH2OH)]·(CH3OH)·(H2O)

T A dinuclear cadmium complex[Cd2(phen)2(C14H11O3)4(CH3CH2OH)]·(CH3OH)·(H2O)has been synthesized with benzilic acid and 1,10-phenanthroline by hydrothermal method.The crystal structure was determined bv X-ray diffraction with crystal parameters as follows:triclinic system with space group P-1,α=1.21298(10),b=1.32586(1 1),c=2.4815(2)nm,α=76.2630(10),β=81.4500(10),γ=69.1700(10)°V=3.6143(5)nm3,Dc=1.438g/cm3,Z=1,F(000)=1600,the final GOOF=0.937,R=0.0521 and wR=0.1328.In the title complex,the dinuclear structure is defined by carboxyl oxygen atoms adopting a monodentate bridged coordination mode.The coordination environment of Cd(Ⅱ)ion is CdO4N2,giving a distorted octahedral coordination geometry.TG analysis shows that the title complex is stable under 140℃.     

Influence of axial ligands and anions on the Ni–Ni distances in trinickel string complexes: synthesis,structure, and properties of [Ni3(dpa)4(CH3CN)2] · (ClO4)2 · (CH3CN) · H2O

A cation–anion metal string complex with neutral axial ligands, [Ni₃(dpa)₄(CH₃CN)₂] · (ClO₄)₂ · (CH₃CN) · H₂O (1) where dpa^? is 2,2′-dipyridylamine anion, was synthesized and characterized by elemental analysis, IR, fluorescence, UV, and CV spectroscopic methods, and single crystal X-ray analysis. The Ni–Ni distances in 1 are longer than those in [Ni₃(dpa)₄(CH₃CN)₂] · (PF₆)₂ · 3.14CH₃CN (2) and [Ni₃(dpa)₄F₂] · [Ni₃(dpa)₄(H₂O)₂] · (BF₄)₂ · 2CH₃OH, indicating that the counter anions affect the Ni–Ni distances of trinickel string complexes. Compared with Ni₃(dpa)₄Cl₂ and Ni₃(dpa)₄(ClO₄)₂, 1 also has different fluorescence, UV, and CV properties. Therefore, this study clearly indicates that ligands and counter anions largely influence the structures and properties of trinickel string complexes.     

Vibrational spectra of bis(halomercurio)methanes CH2(HgX)2 (X  Cl,Br and I) in poly- and monocrystalline states

Vibrational spectra of polycrystalline bis(chloromercurio)methane CH₂(HgCl)₂ (space group Pnma, Z = 4), and of the deuterated analogue, as representatives of the bis(halomercurio)methanes, are preliminarily assigned. Low-temperature Raman and IR spectra of CH₂(HgCl)₂ reveal correlation splittings between g and u species, and partly within the sets of g and u modes, as predicted by unit-cell group analysis. Single-crystal Raman studies not only confirm the suggested assignments but are also the only method to unequivocally assign some bands. The limitations of the applicability of unit-cell group analysis in the present case are discussed.     

Primary amino-functionalized N-heterocyclic carbene ligands as support for Au(I)···Au(I) interactions: structural, electrochemical, spectroscopic and computational studies of the dinuclear [Au2(NH2(CH2)2imMe)2][NO3]2

The N-heterocyclic carbene (NHC) precursor, 1-(2-aminoethyl)-3-methylimidazolium nitrate, [NH(2)(CH(2))(2)imMe)]NO(3) ([3][NO(3)]) reacted with Ag(2)CO(3) in dimethyl sulfoxide readily yielding a Ag(I)-(NHC-NH(2)) complex presenting limited stability in solution. The in situ carbene transfer reaction of the latter with [Au(tht)Cl] afforded the first example of a dinuclear gold(I) complex [Au(2)(NH(2)(CH(2))(2)imMe)(2)][NO(3)](2) ([5][NO(3)](2)) bearing a primary amino-functionalized NHC ligand. The complex has been characterized by NMR, mass spectrometry, X-ray crystallography and cyclic voltammetry; the electrochemical behaviour and photophysical properties of [5][NO(3)](2) have been also investigated and the experimental data have been compared with density functional theory (DFT) and Time Dependent (TDDFT) calculations. Single-crystal structural studies showed that the Au(I)-carbene compound contains dinuclear (AuL)(2) cations in which pairs of gold(I) centres are linked by a pair of bridging ligands, with a Au···Au aurophilic contact of 3.2332(17) ? that is maintained in solution as documented by the DFT calculations. Complex [5][NO(3)](2) is photoluminescent in solution at room temperature and the high energy emission peak at 410 nm is remarkably shifted with respect to the absorption band centered at 260 nm.     

Synthesis and structure of [Cr3O(CH3COO)6(H2O)3][UO2 (CH3COO)3] · 3H2O

Crystals of [Cr₃O(CH₃COO)₆(H₂O)₃][UO₂(CH₃COO)₃]·3H₂O (I) were synthesized for the first time and studied by X-ray crystallography. The crystals of I are orthorhombic: a = 8.3561(3) ?, b = 16.8421(5) ?, c = 25.7448(9) ?, V = 3623.2(2) ?³, space group P2₁2₁2₁, Z = 4, R = 0.0409. The structure is composed of trinuclear [Cr₃O(CH₃COO)₆(H₂O)₃]⁺ complexes and mononuclear [UO₂(CH₃COO)₃]^? complexes classified with crystal-chemical groups A₃M³B ₆ ² M ₃ ¹ (A = Cr³⁺, M³ = O^2?, B² = CH₃COO^?, M¹ = H₂O) and AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?), respectively. The complexes are bound to each other by electrostatic interactions and hydrogen bonds involving outer-sphere water molecules. The results of IR spectroscopic study of I are in good agreement with the structural data for the crystal.     

Multiple pathways of dissociative attachment: CH3Br on Si(100)-2×1

We describe the dissociative attachment (DA) of methyl bromide to form chemisorbed CH(3) and Br on a Si(100)-2×1 surface at 270 K. The patterns of DA were studied experimentally by ultra-high vacuum scanning tunneling microscopy (STM) and interpreted by ab initio theory. The parent molecules were found to dissociate thermally by breaking the C-Br bond, attaching the resulting fragments CH(3) and Br at adjacent Si-atom sites. The observed DA resulted in three distinct attachment geometries: inter-row (IR, 88%), inter-dimer (ID, 11%), and on-dimer (OD, 1%). Ab initio computation agreed in predicting these three DA reaction pathways, with yields decreasing down the series, in accord with experiment. The three computed physisorption geometries, each of which correlated with a preferred outcome, IR, ID, or OD, exhibited similar heats of adsorption, the choice of pathway being governed by the energy barriers to DA chemisorption predicted to increase along the series: E(IR) = 0.48 eV, E(ID) = 0.57 eV, and E(OD) = 0.63 eV.     

The influence of molecular interaction on polymerization—11: A study of the influence of the solvent on the tacticities of poly(2-naphthyl methacrylated) and poly(cumylphenyl methacrylate) obtained in various solvents

Polymerizations of 2-naphthyl methacrylate and 4(1-methylphenethyl)phenyl methacrylate (cumylphenyl methacrylate) have been carried out in solvents with different dielectric constants and donor numbers (DN). By means of ¹H-NMR and fluorescence spectroscopy, the tacticities of the polymers were studied. It was found that the structures of the polymers depend on the dielectric constant of the solvent and not on its donor number. In solvents with high dielectric constant, the contents of isotactic triads are higher than for solvents with low dielectric constants.     

Internal rotation and halogen bonds in CF3I···NH3 and CF3I···N(CH3)3 probed by broadband rotational spectroscopy

The rotational spectra of CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) are measured between 6.7 and 18 GHz using a chirped-pulse Fourier transform microwave spectrometer. Transitions in each spectrum are assigned to A and E species associated with ground and excited internal rotor states respectively. Rotational constants, B(0), centrifugal distortion constants, D(J), D(Jm), D(JKm), nuclear quadrupole coupling constants of the (14)N and (127)I atoms, χ(aa)(N) and χ(aa)(I), are determined for each complex. D(JK) is additionally determined for CF(3)I···NH(3). Results are presented for both (14)N and (15)N-substituted isotopologues. All data are consistent with C(3v) symmetric top structures for both complexes. The nuclear quadrupole coupling constants of iodine are determined to be -2230.030(83) MHz and -2241.61(17) MHz in CF(3)I···(14)NH(3) and CF(3)I···(14)N(CH(3))(3) respectively. The data are interpreted through a model that accounts for the internal dynamics of the complexes in order to determine the length of the halogen bond between the iodine and nitrogen atoms, r(N···I). Values of r(N···I) are thus determined to lie in the ranges 3.054 ? > r(N···I) > 3.034 ? and 2.790 ? > r(N···I) > 2.769 ? for CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) respectively.