Stability of Few-Charge Systems in Quantum Mechanics

We consider non-relativistic systems in quantum mechanics interacting through the Coulomb potential, and discuss the existence of bound states which are stable against spontaneous dissociation into smaller atoms or ions. We review the studies that have been made of specific mass configurations and also the properties of the domain of stability in the space of masses or inverse masses. These rigorous results are supplemented by numerical investigations using accurate variational methods. A section is devoted to systems of three arbitrary charges and another to molecules in a world with two space-dimensions.Comment: 101 pages, review articl

Butyl­trichlorido{2-[(diisopropyl­ammonio)­meth­yl]phen­yl}tin(IV) dichloro­methane monosolvate

The title compound, [Sn(C4H9)(C13H21N)Cl3]·CH2Cl2, was obtained by recrystallization of [2-(diisopropyl­amino­meth­yl)phen­yl]tin(IV) butyl dichloride from a CH2Cl2/n-hexane mixture (1:4 v/v) in the presence of ambient moisture. Partial hydrolysis led to the title compound, the hydro­chloric acid adduct of the dichloride, having a penta­coordinated Sn atom with a trigonal–bipyramidal C2SnCl3 core. The N atom of the 2-[(diisopropyl­ammonio)­meth­yl]phenyl ligand forms a strong intra­molecular N—H⋯Cl hydrogen bond, resulting in a zwitterionic species, [2-(iPr2HN+CH2)C6H4]SnBuCl3 −·CH2Cl2. Disorder was found in the n-butyl group, which was refined as disordered over three positions, with site occupancies of 0.22 (1), 0.51 (1) and 0.27 (2)

Bis[2-(morpholinometh­yl)phen­yl]phenyl­phosphane

The title compound, C28H33N2O2P, contains a penta­coordinated P atom as a result of the weak N→P intra­molecular inter­actions, with three C atoms, two N atoms and the lone pair arranged in a dicapped pseudo-tetra­hedral geometry. The morpholine rings exhibit an almost ideal chair conformation. In the crystal, two weak C—H⋯O hydrogen-bond inter­actions link the mol­ecules in layers stacked along the a axis; there are no further inter­actions between the layers

A new ortho­rhom­bic polymorph of 1,1′-seleno­bis­(N,N-diethyl­sulfanecarbothio­amide)

The title compound [systematic name: N,N-dieth­yl({[(diethyl­carbamothio­yl)sulfan­yl]selan­yl}sulfan­yl)carbothio­amide], C10H20N2S4Se, crystallizes in a new form in the space group Pca21: the previously reported polymorph crystallizes in the space group P212121. The new phase contains two independent mol­ecules in the asymmetric unit. The Se atoms are tetra­coordinated, with a distorted square-planar geometry. The ligands coordinate asymmetrically to the Se atoms, with one strong Se—S bond [range 2.2833 (13)–2.3041 (15) Å] and one weaker bond [range 2.7318 (14)–2.7873 (12) Å]

Substitutional disorder in a hypervalent diorganotin(IV) dihalide

The structure of bromidochloridobis[2-(dimethyl­amino­meth­yl)phen­yl]tin(IV), [SnBr0.65Cl1.35(C9H12N)2], contains two 2-(Me2NCH2)C6H4 units bonded to a Sn atom which lies on a twofold axis. The compound exhibits substitutional disorder of the halide atoms bonded to the Sn, with 1.35 occupancy for Cl and 0.65 for Br; it is isomorphous with the corresponding dichloride. The Sn atom is hexa­coordinated with a (C,N)2SnX 2 (X = Cl/Br) distorted octa­hedral core as a result of the strong intra­molecular N→Sn coordination trans to the Sn—X bonds (N1—Sn1—X1 = 165.8°). As a result of the inter­molecular contacts, viz. H⋯X and H⋯benzene inter­actions, the mol­ecules are arranged in a three-dimensional supra­molecular manner in the crystal structure

Hydrogen bonding in substitutionally disordered di-μ-hydroxido-bis­{aqua­tri[bromido/chlorido(1/2)]tin(IV)} acetone disolvate

The structure of the title compound, [Sn2Br1.97Cl4.03(OH)2(H2O)2]·2C3H6O, contains two hexa­coordinated Sn atoms bridged symmetrically by two hydroxide groups, with an inversion center in the middle of the planar Sn2O2 ring, half of the mol­ecule being generated by inversion symmetry. The other sites of the distorted octa­hedral coordination geometry are occupied by halide atoms and water mol­ecules. The structure exhibits substitutional disorder of the halide atoms bonded to the Sn atom, with 0.672 (4) occupancy for Cl and 0.328 (4) for Br for each halide position. The compound crystallizes with two acetone mol­ecules, which are involved in intra- and inter­molecular O—H⋯O contacts. The water mol­ecules coordinated to the Sn atoms are also involved in O—H⋯O and O—H⋯X contacts, leading to a polymeric array along the a axis

Di-μ-chlorido-bis­{[2-(morpholinometh­yl)phenyl-κ2 C 1,N]palladium(II)}

The title compound, [Pd2(C11H14NO)2Cl2], has a dimeric structure with Cl atoms bridging the two Pd atoms, one half of the mol­ecule being generated by symmetry due to the crystallographic inversion centre located in the middle of the perfectly planar Pd2Cl2 ring. The five-membered ring adopts an envelope conformation, while the morpholino group has a chair conformation. The geometry around the metal centres is distorted square-planar, as a result of a strong intra­molecular N→Pd coordination trans to a Pd—Cl bond. In the crystal structure, the dimeric structure is strengthened by inter­molecular C—H⋯Cl hydrogen bonds. C—H⋯Cphen­yl inter­actions link the dimers into a columnar supra­molecular array along the a axis; the dimers are further connected by C—H⋯Ph inter­actions into a three-dimensional supra­molecular arrangement

2,6-Dichloro­pyridine-3,5-dicarbonitrile

In the crystal, essentially planar (r.m.s. deviation = 0.003 Å) mol­ecules of the title compound, C7HCl2N3, form chains along the b axis by means of C—H⋯N inter­actions. These chains are further linked into layers parallel to the ab plane by C—Cl⋯N inter­actions

Second bound state of the positronium molecule and biexcitons

A new, hitherto unknown bound state of the positronium molecule, with orbital angular momentum L=1 and negative parity is reported. This state is stable against autodissociation even if the masses of the positive and negative charges are not equal. The existence of a similar state in two-dimension has also been investigated. The fact that the biexcitons have a second bound state may help the better understanding of their binding mechanism.Comment: Latex, 8 pages, 2 Postscript figure

N,N-Bis(2-bromo­ethyl)aniline

The mol­ecule of the title compound, C10H13Br2N, has a twofold rotation axis along the N—Cphen­yl bond. The compound shows a slightly distorted trigonal planar geometry around the N atom. The structural study shows the presence of inter­molecular C—H⋯Br inter­actions, resulting in a three-dimensional supra­molecular architecture