A tandem mass spectrometric study of C2H5I+CH3 ions: A search for the non-classical ethyl cation stabilized by methyl iodide

The results of this study have shown that the C₂H₅I⁺CH₃ ion containing classical and non-classical forms of the ethyl group can be generated by gas-phase ion—molecule reactions. The classical ions fragment by CH₄ and CH₃? losses, the latter without loss of positional identity of H atoms in the ethyl group. Hydrogen scrambling, however, precedes ethene loss, taking place in an ion of non-classical form. The latter is produced directly from ion—molecule reactions and from energy-rich classical ions. The relative energies of the classical and non-classical ions could not be determined, although the former was proposed to be the global minimum. Finally, the classical ion serves as a source for the ylid ion CH₃ICH₂^+., which previously had eluded preparation.     

Quantum effects on the stability of the He5I2 van der Waals conformers

We present 15-dimensional quantum multiconfiguration time-dependent Hartree calculations of the vibrational levels of the He₅I₂ van der Waals (vdW) complex employing an ab initio-based potential energy surface (PES). The energies and spatial features of such bound structures are analyzed, providing predictions on the structures and relative stabilities of its three lowest isomers. We found that the most stable isomer corresponds to all five He atoms encircling the I₂ molecule, indicating that in this case the anharmonic quantum effects do not stabilize the isomers involving a He atom in a linear configuration as reported previously for the smaller He_NI₂ systems. Such finding provides information on the overall structuring of the finite-size-solvent systems, highlighting the intriguing interplay between weak intermolecular interactions and quantum effects. © 2019 Wiley Periodicals, Inc.     

Nuclear quantum and H/D isotope effects on three-centered bonding diborane: Path integral molecular dynamics simulations

Nuclear quantum and H/D isotope effects of bridging and terminal hydrogen atoms of diborane (B₂H₆) molecules were systematically studied by classical ab initio molecular dynamics (CLMD) and ab initio path integral molecular dynamics (PIMD) simulations with BHandHLYP/6-31++G** level of theory at room temperature (298.15 K). Calculated results clearly show that H/D isotope effect appears in the distribution of hydrogen (deuterium) of B₂H₆ (B₂D₆). Geometry of B₂H₆ also plays a significant role in the nuclear quantum effect proved by PIMD simulations, but slightly deviated from its equilibrium structure when simulated via CLMD simulation. The bond lengths between boron atoms R (B1 … B2) and the bridging hydrogen atoms R_HH (H_B1 … H_B2) of the B₂H₆ molecule obtained from PIMD simulations are slightly longer than those of the deuterated form of the diborane (B₂D₆) molecule. The principal component analysis (PCA) was also employed to distinguish the important modes of bridging hydrogen as related to the nuclear quantum and H/D isotope effects. The highest level of contribution obtained from PCA of PIMD simulations is bending, while various mixed vibrations with less contribution were also found. Therefore, the nuclear quantum and H/D isotope effects need to be taken into account for a better understanding of diborane geometry.     

A new polymorph of physcion

The structure of the title compound, 7‐methoxy‐2‐methyl‐4,5‐dihydroxyanthracene‐9,10‐dione, C₁₆H₁₂O₅, was originally reported by Ulickýet al. [Acta Cryst. (1991). C 47 , 1879–1881] in the space group P2₁2₁2₁ [polymorph (Io)]. The new polymorph, (Im), crystallizes in the space group P2₁/c. The molecular structures are closely similar, with both –OH groups forming intramolecular hydrogen bonds to one of the neighbouring quinone O atoms, thus slightly lengthening this C=O bond; the pattern of C—C bond lengths in the ring system is consistent with some contribution from a resonance form with a negative charge at the hydrogen‐bonded quinone O atom and an aromatic region around its neighbouring C atoms. The packing of (Im) is simpler than the extensively crosslinked pattern of (Io), with molecular tapes connected by classical (but three‐centre) and `weak' hydrogen bonds, parallel to [20].     

Effect of solvents on dielectric,spectroscopic and thermodynamic manifestations of intermolecular interactions. Iodine complexes of pyridine and picoline

Dipole moments of pyridine and γ-picoline complexes with I₂ in a number of nonpolar and weakly polar solvents were determined and the contributions of the dative structure F_N in the ground state were estimated. The results are consistent with those calculated from the force constants of stretching vibrations v(N-l) and v (I-I). A good correlation of F_N was found with respect to the solvent shift of the transition energy {ie355-1} in the I₂ molecule bounded to amines and also to empirical parameters of solvent activities like rate constants of the Menshutkin reaction or the Dimroth-Reichardt parameter. No correlation exists between the solvent induced enhancement of the dipole moment and dielectric permittivity in terms of the Onsager reaction field theory.     

Photodissociation of an I2 supersonic beam in the nozzle expansion region: Influence on cluster spectra

Iodine clusters are obtained by free expansion of iodine vapour. The I₂ molecule is then photodissociated by a cw laser in the nozzle expansion region. Hot dissociated 1 atoms partially prevent nucleation, allowing accurate probing of the nucleation region. Moreover, I atoms can act as germs for the formation of odd clusters I_2n-1, leading to an increase of the ratio (number of I_2n-1⁺/number of I_2n⁺).     

Synthesis,characterization, and crystal structure of cobalt(II) and zinc(II) complexes with a bulky Schiff base derived from rimantadine

Two novel complexes, C₃₈H₄₈CoN₂O₂ (I) and C₃₈H₄₈N₂O₂Zn (II), were prepared through an analogous procedure with a corresponding metal chloride and a bulky Schiff base ligand (HL) which derived from rimantadine and salicylaldehyde in appropriate solvents, respectively. They were structurally characterized by the means of IR, UV-Vis, elemental analysis, molar conductance, PXRD and single-crystal X-ray diffraction (CIF files nos. 946735 (I), 893304 (II)). Single-crystal X-ray diffraction analysis reveals that I belongs to the triclinic system, \(P\overline 1 \) space group; each asymmetric unit consists of one cobalt(II) complex and one lattice ethanol molecule. In each complex molecule, cobalt(II) atom is four-coordinated via two oxygen atoms and two nitrogen atoms from the deprotonated Schiff base ligands, forming an approximate planar geometry. The crystal structure also involves strong O–H···O intermolecular hydrogen bonds between the solvent alcoholic and phenol O atoms of complex molecule. Complex II belongs to the monoclinic system, Cc space group. Each asymmetric unit consists of one zinc(II) ion and two deprotonated ligands. Zinc(II) atom lies on a twofold rotation axis and is four-coordinated via two nitrogen atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.     

Proof of the Existence of a Linear,Centrosymmetric Polyiodide Ion I: the crystal structure of Cu(NH3)4 I4

Tetrammine-copper(II)-tetraiodide Cu(NH₃)₄I₄ crystallizes in the monoclinic space group C 2/m. The crystal structure has been determined from X-ray diffractometer data and refined to R_w = 2.2%. Four coplanar nitrogen atoms and two axial iodine atoms form an octahedral coordination around Cu(II) with a pronounced 4 + 2 tetragonal distortion. A connection of the Cu(II) atoms by linear, centrosymmetric I polyiodide ions results in infinite chains of [Cu(NH₃) I]-units. The central I-I-bond distance in I is 2.802(1) Å; a considerable amount of I-I bonding is indicated by the distance of 3.342(1) Å found for the terminal bonds. These intramolecular bond distances correspond to calculated I-I-bond orders of 0.80 and 0.43.     

A three‐dimensional polymeric potassium complex of 5‐sulfonobenzene‐1,2,4‐tricarboxylic acid: poly[μ‐aqua‐aqua‐μ9‐(2,4‐dicarboxy‐5‐sulfonatobenzoato)‐dipotassium(I)]

The asymmetric unit in the structure of the title compound, [K₂(C₉H₄O₉S)(H₂O)₂]_n, consists of two eight‐coordinated K^I cations, one 2,4‐dicarboxy‐5‐sulfonatobenzoate dianion (H₂SBTC²⁻), one bridging water molecule and one terminal coordinated water molecule. One K^I cation is coordinated by three carboxylate O atoms and three sulfonate O atoms from four H₂SBTC²⁻ ligands and by two bridging water molecules. The second K^I cation is coordinated by four sulfonate O atoms and three carboxylate O atoms from five H₂SBTC²⁻ ligands and by one terminal coordinated water molecule. The K^I cations are linked by sulfonate groups to give a one‐dimensional inorganic chain with cage‐like K₄(SO₃)₂ repeat units. These one‐dimensional chains are bridged by one of the carboxylic acid groups of the H₂SBTC²⁻ ligand to form a two‐dimensional layer, and these layers are further linked by the remaining carboxylate groups and the benzene rings of the H₂SBTC²⁻ ligands to generate a three‐dimensional framework. The compound displays a photoluminescent emission at 460 nm upon excitation at 358 nm. In addition, the thermal stability of the title compound has been studied.     

On the fixed-nuclei approximation as applied to rotational excitation of molecules by atoms

The applicability of the fixed-nuclei approximation to the rotational excitation of a diatomic molecule by an atom is investigated. The approximation is shown to predict accurate quantum cross sections for the model system H₂ + N₂ at thermal collision energies. A quasi-classical Monte-Carlo study of the same problem is also performed, and the success of the fixed-nuclei approximation is interpreted by investigating in detail a number of coplanar classical trajectories.     

Polyiodide amide complexes of transition metals: Structures and raman spectra

The Raman spectra of the polyiodide complexes of d elements with urea (Ur) and acetamide (AA), namely, [M(Ur)₆][I₃]₃ (M = Cr, Fe), Co(Ur)₆][I₃]₂ · 2Ur, [Mn(Ur)₆][I₈], [Ni(AA)₆][I₃]₂, [M(AA)₆][I₁₀ (M = Fe, Co, Cd), and [Co(AA)₄(H₂O)₂][I₁₂], are studied. The structure of [Cr(Ur)₆][I₃]₃ is studied. The crystals of [Cr(Ur)₆][I₃]₃ are monoclinic: space group C2/c, a = 15.260(5), b = 11.941(3), c = 20.506(6) Å, β = 106.14(3)°, Z = 4, V = 3589.4(18) ų. The I-I bond length in the CdI₂ · 4BA · 2I₂ polyiodide complex amorphous to X-rays is estimated by a correlation between the I-I bond length and the frequency of vibrations of this bond in the Raman spectra.     

Centrifugal mechanism for molecular dissociation in high-energy collisions with solid surfaces

A simple model is proposed for molecular dissociation probabilities in impulsive collisions with surfaces. Dissociation is assumed to follow rotational excitation high enough to break the molecule. The model was tested against exact classical simulations for I₂, Li₂ colliding with smooth surfaces. Agreement is better than a factor of 2 over a wide range of energies.     

Performance of 3D‐space‐based atoms‐in‐molecules methods for electronic delocalization aromaticity indices

Several definitions of an atom in a molecule (AIM) in three‐dimensional (3D) space, including both fuzzy and disjoint domains, are used to calculate electron sharing indices (ESI) and related electronic aromaticity measures, namely, I_ring and multicenter indices (MCI), for a wide set of cyclic planar aromatic and nonaromatic molecules of different ring size. The results obtained using the recent iterative Hirshfeld scheme are compared with those derived from the classical Hirshfeld method and from Bader's quantum theory of atoms in molecules. For bonded atoms, all methods yield ESI values in very good agreement, especially for C–C interactions. In the case of nonbonded interactions, there are relevant deviations, particularly between fuzzy and QTAIM schemes. These discrepancies directly translate into significant differences in the values and the trends of the aromaticity indices. In particular, the chemically expected trends are more consistently found when using disjoint domains. Careful examination of the underlying effects reveals the different reasons why the aromaticity indices investigated give the expected results for binary divisions of 3D space. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011.     

Electronic quantum motions in hydrogen molecule ion

The hydrogen molecule ion is a two‐center force system expressed under the prolate spheroidal coordinates, whose quantum motions and quantum trajectories have never been addressed in the literature before. The momentum operators in this coordinate system are derived for the first time from the Hamilton equations of motion and used to construct the Hamiltonian operator. The resulting Hamiltonian comprises a kinetic energy T and a total potential V_Total consisting of the Coulomb potential and a quantum potential. It is shown that the participation of the quantum potential and the accompanied quantum forces in the force interaction within H₂⁺ is essential to develop an electronic motion consistent with the prediction of the probability density function |Ψ|². The motion of the electron in H₂⁺ can be either described by the Hamilton equations derived from the Hamiltonian H = T_K + V_Total or by the Lagrange equations derived from the Lagrangian H = T_K ? V_Total. Solving the equations of motion with different initial positions, we show that the solutions yield an assembly of electronic quantum trajectories whose distribution and concentration reconstruct the σ and π molecular orbitals in H₂⁺. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Synthesis, properties, and crystal structure of the tin(IV) complex with N-(2-hydroxyethyl)ethylenediaminetriacetic acid [Sn(μ-Hedtra)(μ-OH)SnCl3(H2O)] · 3H2O

The binuclear tin(IV) complex with N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (H₄Hedtra) is synthesized. The compound is characterized by elemental analysis, thermogravimetry, and IR spectroscopy. An X-ray diffraction analysis of complex Sn(μ-Hedtra)(μ-OH)SnCl₃(H₂O)] · 3H₂O (I) is carried out. Structure I is formed by the binuclear complexes and molecules of water of crystallization. One of the tin atoms coordinates six “active” sites Hedtra^4? (the alcohol branch is deprotonated and forms a bridge between two tin atoms) and the bridging hydroxo group. The polyhedron is a pentagonal bipyramid. The octahedral environment of the second tin atom is formed by two bridging oxygen atoms, three chlorine atoms (fac isomer), and a coordination water molecule.     

Stability and molecular and crystal structure of 9-amino-10-methylacridinium triiodide

Mixing of equimolar amounts of 9-amino-10-methylacridinium iodide and elemental iodine yields 9-amino-10-methylacridinium triiodide. The complexation in the organic cation iodide-elemental iodine system has been studied by spectrophotometry. The composition and the stability constant of the complex formed in a chloroform solution have been determined. The compound [C₁₄H₁₃N₂]⁺[I₃]^? has been isolated as dark red plate crystals and studied by X-ray diffraction. The structure is formed by linear I ₃ ^? anions and 9-amino-10-methylacridinium cations assembled through π-π stacking. The cations in the stacks are shifted by approximately one ring with respect to one another. The triiodide ion is linear, the average I-I bond length (2.915 Å) is close to the standard value. The stacking reflects the specific nature of the organic cation, while the presence of the I ₃ ^? counterion results in extension of the system of hydrogen bonds.     

Nickel(II) and copper(II) complexes with chiral bis-α-thiooxime,the derivative of natural terpenoid (+)-3-carene: Synthesis and structures

Chiral bis-α-thiooxime (H₂L¹), the derivative of the natural monoterpenoid (+)-3-carene, was synthesized and used to prepare paramagnetic complexes of the composition M(H₂L¹)Cl₂ (M=Ni, Cu). The crystal structures of [Ni(H₂L¹)Cl₂] (I) and [Cu(H₂L¹)Cl₂] (II) were determined by X-ray diffraction analysis. Crystals I and II consist of mononuclear acentric molecules. The Ni²⁺ ion in a molecule of complex I coordinates two N atoms and two S atoms of a tetradentate chelating ligand (the H₂L¹ molecule) and two Cl atoms. The NiCl₂N₂S₂ coordination core forms octahedron compressed along the apical N atoms. In a molecule of complex II, the Cu²⁺ ion coordinates two S atoms and the N atom of a tridentate chelating H₂L¹ ligand and two Cl atoms. The CuCl₂NS₂ coordination core forms a trigonal bipyramid.     

Slow motions undergone by surfactant molecules in micelles. A 1H and 14N nuclear magnetic relaxation study

Surfactant motion in spherical micelles of the system cetyltrimethylammonium bromide/D₂O has been investigated by ₁H and ¹⁴N longitudinal relaxation at different frequencies. Such measurements allow extraction of the correlation time characterizing the overall reorientation of the surfactant molecule, which includes micelle tumbling and lateral diffusion around the micelle. The proton data, which reflect the alkyl chain mobility, require the definition of a local director, distinct from the normal to the aggregate surface, thus making possible the occurrence of an additional slow motion. Conversely ¹⁴N data can be analyzed accord- ing to the classical two-step model; this yields a correlation time associated with the slow motion of as ≈5 ns leading to a value of 4× 10⁻⁷ cm² s⁻¹ for the lateral diffusion coefficient.