Aggregation of Halogen Atoms in Crystalline Isomers

A comparison of halogen (Hal) atom aggregation patterns was made for 26 groups of crystalline C _m H _n Hal _p isomers (position isomers with different locations of halogen atoms and/or alkyl/phenyl groups and stereoisomers were primarily compared). A total of 58 substances with low halogen contents are considered. It is found that crystals of some isomers with similar molecular structures have fully identical Hal aggregates. In most cases, however, the Halaggregation patterns turn out to be only partly similar; i.e., isomers have either the same type of aggregates (finite or infinite in one, two, or three dimensions) or close local characteristics, such as k(Hal) (coordination number of halogen atoms with respect to neighboring halogen atoms) and r (mean distance to k nearest neighbors). Different positions of methyl groups in isomer molecules have no effect on the characteristics of Hal aggregates in the examined substances, whereas different positions of ethyl and phenyl groups lead to significant changes in the Halaggregation pattern.     

Microcalorimetric determination of enthalpies of solution of methyl alkanes in glacial acetic acid

An empirical equation H _{s, m}=0.84n gives the enthalpy of solution of 30 branched, linear and cyclic alkanes in glacial acetic acid. The parametern is an effective carbon number which expresses the number of carbon atoms in the longest chain plus one half of the pendant methyl groups.     

Approximate formulas for the characteristics of interelectronic angle densities

The accuracies of approximate formulas are examined for several characteristics of the interelectronic angle density A(₁₂), where ₁₂ (0₁₂) is the angle subtended by the position vectors r₁ and r₂ of two electrons. Numerical results for 102 atoms show that simple approximations have sufficient accuracies for the moments with n=1–4, the central moments _n with n=2, 4, and the kurtosis, when measured by the absolute and relative errors. For heavy atoms, however, the relative errors for the third central moment ₃ and the skewness are large.     

1D and 2D Systems Derived from Polynuclear [ ML(N 3) 2] n ( M?=?Zn(II) or Cd(II) and L is 2-Picoline- N-oxide or 4-Methylpyrimidine)

Four new polynuclear complexes: [Zn(2picNO)(N₃)₂]_n, [Zn(4Mepym)(N₃)₂]_n, [Cd(2picNO)(N₃)₂]_n, and [Cd(4Mepym)(N₃)₂]_n (2picNO=2-picoline-N-oxide and 4Mepym=4-methylpyrimidine) have been synthesized and characterized by single-crystal X-ray diffraction. The structures of the zinc(II) complexes feature five-coordinate zinc atoms, (-1,1) azido bridges, monodentate organic ligands, and 1D chains. The cadmium(II) azide complexes contain distorted octahedral metal atoms linked by alternate di-(-1,1) and di-(-1,3) azido bridges in cis arrangement and these chains are connected by 2picNO bridges giving a honeycomb 2D framework or by 4Mepym bridges forming extended 2D network structure.     

Collisional process involving atomic cluster ions

Collision of Ar cluster ions, Ar _n ⁺ (n=3–16), with He and Ne atoms was investigated by use of mass spectroscopic techniques. The cross sections for the production of Ar _n ⁺ (nn) were measured as functions of the size of the parent cluster ion and the collision energy (0.1–10 eV in the center-of-mass frame). These results were analyzed in the scheme of hard-sphere spectator collision with RRK theory. It was concluded that the reaction proceeds via collisional excitation of the parent cluster ion and following sequential loss of the constituent Ar atoms.This paper was originally submitted in connection with the 2nd. Int. Conference on Atomic and Nuclear Clusters held in Santorini from 28. June-2. July 1993 and is published here as a regular article after an independent refereeing procedure according to the standards of Z. Phys. D     

Density functional study of hydrogen adsorption and dissociation on small Pdn (n = 1–7) clusters

Density functional theory has been performed to investigate the interaction of H₂ and Pd_n clusters (n = 1–7). The local minima configurations for different H₂ molecule approach modes towards Pd_n clusters are presented. Our results show that in some cases H₂ is physically adsorbed around Pd atom, and in other cases H₂ is dissociated to be H atoms. Except for PdH2, Pd_n clusters with H atoms dissociatively adsorbed are most stable. For these most stable PdnH2 clusters (n  2), the binding energy of hydrogen atom decreases as the number of Pd atom increases until n = 4, and when n  4, the binding energy almost keeps constant with the H atoms bound sites changing from Pd–Pd bonds to Pd triangle planes. Besides, the adsorption of H₂ on other low-lying isomers of Pd_n clusters is also discussed.     

Force constant calculations of the LAM-1 modes ofn-alkanes and their substituted α-Monohalo- and α,ω-dihalo- species in their extended zig-zag planar configurations as found in urea inclusion compounds

Force constants were determined for the C₈, C₁₀, C₁₂ and C₁₄ series ofn-alkanes C _n H_{2n + 2} using an approximate SVFF calculation and observed LAM = 1 wave numbers. In this calculation the hydrogen atoms were neglected and only the carbon backbone chain and terminal atoms were considered; this was valid since only low-frequency vibrations were under consideration. Using force constant transfer, the wavenumbers of the LAM = 1 accordion modes for the analogous -C_n H_2n + 1 X and ,-C_n H_2nX₂ species, where X = C1, Br or I were calculated. For -chloroalkanes and ,-dichloroalkanes, them = 1 accordion modes are calculated to be in the 220–130 cm^–1 and 200–120 cm^–1 regions, respectively. For the bromo- and iodo-analogues them = 1 accordion modes are calculated to be in the 200–100 cm^–1, 150–90 cm^–1 and in the 170–100, 135–80 cm^–1 regions, respectively.     

Sodium doped binary clusters I: Ionization potentials of SinNam clusters

Sodium doped silicon clusters (Si_nNa_m, 3n11, 1m4) were produced by two independent laser vaporization methods and their ionization potentials were measured by scanning the wavelength of the UV dye laser. The IPs of most Si_nNa_m clusters decrease monotonously with the number of Na atoms, but IPs of Si₇Na_m and Si₁₀Na_m clusters show an apparent even-odd alternation; odd numbers of Na atoms efficiently decrease the IP but even numbers of Na atoms never significantly decrease the IPs. In addition, the reactivity of Si_nNa_m clusters for NO molecules was investigated with a fast flow reactor, and an anti-correlation between IP and the reactivity was clearly observed; clusters having high IP show low reactivity andvice versa.     

1D and 2D Systems Derived from Polynuclear [ ML(N 3) 2] n ( M?=?Zn(II) or Cd(II) and L is 2-Picoline- N-oxide or 4-Methylpyrimidine)

Summary. Four new polynuclear complexes: [Zn(2picNO)(N₃)₂]_n, [Zn(4Mepym)(N₃)₂]_n, [Cd(2picNO)(N₃)₂]_n, and [Cd(4Mepym)(N₃)₂]_n (2picNO=2-picoline-N-oxide and 4Mepym=4-methylpyrimidine) have been synthesized and characterized by single-crystal X-ray diffraction. The structures of the zinc(II) complexes feature five-coordinate zinc atoms, (-1,1) azido bridges, monodentate organic ligands, and 1D chains. The cadmium(II) azide complexes contain distorted octahedral metal atoms linked by alternate di-(-1,1) and di-(-1,3) azido bridges in cis arrangement and these chains are connected by 2picNO bridges giving a honeycomb 2D framework or by 4Mepym bridges forming extended 2D network structure.     

The influence of sodium-n-alkyl sulphates on positively and negatively charged AgI systems

Summary The influence of sodium-n-alkyl sulphates with even number of C atoms (from 6 to 16) on the positively and negatively charged AgI systems was examined. The coagulation concentrations for each alkyl sulphate for positively charged AgI was determined. The critical concentrations of alkyl sulphates for a process similar to coagulation on negatively charged AgI systems were also determined. In both cases, the in statu nascendi method was employed. The coagulation concentrations and critical concentrations are in linear relationship with the number of C atoms of the sodium-n-alkyl sulphates.

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Zusammenfassung Es wurde die Wirkung von Natrium-n-Alkylsulfaten mit 6, 8, 10, 12, 14 und 16 C-Atome in der Alkylkette auf positiv sowie negativ geladene AgJ-Systeme untersucht. Dabei wurden die Koagulationskonzentrationen der erwähnten Alkylsulfate für positiv geladene AgJ-Systeme und die kritischen Konzentrationen derselben einen der Koagulation ähnlichen Proze bei den negativ geladenen AgJ-Systemen bestimmt. In beiden Fällen wurde eine in statu nascendi Methode angewandt. Die Koagulationskonzentration sowie die kritischen Konzentrationen zeigen eine lineare Abhängigkeit von der C-Atomanzahl im betreffenden Natrium-n-Alkylsulfat.

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With 3 figures and 1 table     

Exactly Soluble Hamiltonian with a Squared Cotangent Potential

The exact ground and first-excited state eigenvalues and eigenfunctions are given for a one-dimensional Hamiltonian with the potential n(n–1)cot²(x) on the domain x[0,]. Furthermore, an exact eigenvalue spectrum is proposed for all n>1 and the exact eigenfunctions are proposed for n=3. These are simply finite linear combinations of sin(mx) for integer m.     

The n→π* optical activity of chiral carbonyl compounds predicted to be optically inactive by the octant rule

The one-electron model of n* optical activity in chiral carbonyl compounds is carried to second-order in perturbation theory and the results are applied to systems which are predicted by the octant rule to yield zero n* optical activity. It is shown that second-order contributions to the n* rotatory strength lead to sector rules which are qualitatively different from those obtained from first-order contributions. Inclusion of three-way interactions involving the carbonyl chromophore and two different extrachromophoric perturbing groups (or atoms) lead to second-order contributions to the rotatory strength which can account for the n* optical activity in chiral carbonyl systems predicted to be optically inactive by the conventional quadrant and octant rules. These results are shown to be in agreement with the conclusions derived by Ruch and Schönhofer from a purely algebraic theory of molecular chirality.     

Das Helixmodell der „Chimney-Ladder”-Strukturen

A general idealized model for the class of chimney-ladder structures with chemical formulaT _n B _2n–m is proposed on the basis of a helical arrangement of theT andB atoms. By means of this model it is possible to understand from the geometrical point of view the observed formation of pseudohomogeneous regions of microphases with only extremely small differences in their composition, and the different space groups of their crystal structures as a function ofn andm.The special diffraction patterns of the chimney-ladder structures with their sometimes enormous number of not-space-group-required extinctions are explained by the theory of diffraction by helical structures. According to the periodicity 2n–m and the pitch of the helices formed by theB atoms, only superstructure reflections withl =t(2n–m)–s(n–m) (t, s ... integral numbers) ands=0, ±1, ±2, ±3 are expected to be relatively strong.The deviations of the real structures from the helical model are discussed.

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Mit 1 Abbildung

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Herrn Prof. Dr.O. Hoffmann-Ostenhof zum 60. Geburtstag gewidmet.     

Direct and stepwise intercalation of alkylalcohols intoα-zirconium phosphate

Intercalation of alkylalcohols into -zirconium phosphate was investigated at 25°C and/or under reflux.n-Alcohols having two to five carbons and 2-propanol were taken up at 25°C. These alcohols, andn-hexanol and heptanol, also intercalated under reflux.n-Alcohols having eight to eighteen carbon atoms intercalated when a stepwise method was employed. 2-Butanol and tertiary amylalcohols intercalated under reflux using a butanol intercalate as a starting material. Ethanol-to-butanol intercalates were unstable at room temperature, losing alcohols and changing to -zirconium phosphate. The particle size of the -zirconium phosphate did not affect the intercalation of alcohols.     

Formation of radicals in stepwise thermolysis of polyunsaturated polycarbosilane —[(Me2SiC≡C)4Me2SiCH=CH] n —

The onset temperature of radical formation in the stepwise thermolysis of polyunsaturated polycarbosilane —[(Me₂SiCC)₄Me₂SiCH=CH] _n — with n > 2 was found by ESR spectroscopy. Beginning from 230°C two types of radicals are formed. The first radical arises on heating to 240°C due to the delocalization of unpaired electrons over the polyunsaturated polymer systems to H atoms of the Et groups of the polymer. The second radical appears at temperatures 240°C due to delocalization to H atoms of the Me groups through the vacant 3d-orbital of the Si atom.     

Synthesis,crystal structure and magnetism of a three-dimensional manganese(II) complex with carbamyldicyanomethanide anion (<Emphasis Type="Italic">cda</Emphasis>) as a bridging ligand

A three-dimensional complex {[Mn(cda)₂]·2MeOH}_n has been synthesized and its crystal structure determined by X-ray crystallography. In the complex each Mn ion is located in a distorted octahedral environment with two oxygen atoms O(1D) and O(1E) from two amide groups, and four nitrogen atoms N(2), N(2A), N(3B) and N(3C) from four nitrile groups of four cda anions, respectively; each cda anion as a ₃-bridging ligand provides two nitrile nitrogen atoms, and an amide oxygen atoms to coordinate three Mn ions. Thus, a three-dimensional network consisting of Mn ions and cda bridging ligands is constructed with solvent MeOH molecules trapped in the cavities. The variable-temperature magnetic susceptibility of the complex was measured in the 5–300K range. The magnetic coupling parameter is consistent with an antiferromagnetic exchange and generates the antiferromagnetic coupling parameter, 2J=–0.2cm^–1.     

An ab Initio Study on the Chemical Bond and Reactivity of Molybdenum–Sulfur Clusters with a Mo2O n S4−n (n=1–3) Core

Using the ab initio method and natural bond analysis, the reactivity and chemical bond of dinuclear molybdenum sulfur clusters with Mo₂O _n S_4–n (n=1–3) core were studied. The results show that the Mo--Mo bonds in these clusters are significantly affected by the delocalization effects of the multicenter d--p and Mo--X ₁ bonds, besides the direct interactions between Mo atoms. The substitution reactions of the cluster core are also discussed, and it is indicated that sulfur atoms have a preference for the bridging sites and the oxygen atoms tend to attach to the terminal sites.     

Subshell-pair interelectronic angles of atoms in momentum space

Average angles between linear momenta of an electron in a subshell nl and another electron in a subshell nl are examined for the 102 atoms He through Lr in their ground states, where n and l are the principal and azimuthal quantum numbers, respectively. Congruency in the mathematical structures of the average interelectronic angles in position and momentum spaces leads to the theoretical results that with even |l–l| are exactly equal to 90°, while with odd |l–l| are always larger than 90°. Numerical analyses of 3,275 subshell-pair angles with odd |l–l| in the 102 atoms clarify that deviations of the total average interelectronic angles from 90° are mainly governed by subshell pairs with |n–n|1 and |l–l|=1, in contrast to the position-space results where only subshell pairs with n=n and |l–l|=1 are important.Acknowledgments. We thank Mr. T. Shimazaki for his assistance in the compilation of data. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education of Japan.     

Hydrothermal Synthesis and Crystal Structure of a Europium(III) Coordination Polymer with 5-Sulfoisophthalate Trivalent Anions and Free 4,4′-Bipyridine Molecules

A novel europium(III) coordination polymer [Eu(Sip)(H₂O)₅]_n · nH₂O · 1.5n(Bipy) (I) (Sip is 5-sulfo-isophthalate trivalent anion and Bipy is 4,4-bipyridine) is hydrothermally synthesized and determined by the single crystal X-ray diffraction method. Polymer I crystallizes in the monoclinic system, space group C2/c with a=30.7515(6) , b=10.9577(2) , c=17.5545(4) , =112.040(1)°, V=5483.0(2) ³, Z=4, final R ₁=0.0253 and wR ₂=0.0606. In I, each Eu³⁺ ion is coordinated by four oxygen atoms from two carboxylate groups of two different Sip anions and five oxygen atoms from five coordinated water molecules to complete a deformed monocap square antiprism. Moreover, each Sip anion acts as a tetradentate ligand to connect two adjacent Eu³⁺ ions through its two chelating carboxylate groups, resulting in one-dimensional linear chains. In addition, fifteen different kinds of hydrogen-bonding interactions link the chains, lattice water molecules, and free Bipy molecules to engender a complicated hydrogen-bonding network.__________From Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 391–396.Original English Text Copyright © 2005 by Hu Mao Lin, Cai Xiao Qing, Miao Qian, Xiao Hong Ping.This text was submitted by the authors in English.