Interfacial Activity of the Diprotonated 222 Cryptand at the Water/"Oil" Interface Revealed by Molecular Dynamics Simulations

Abstract

Orange II (I) is easily soluble in H₂O. It requires several months for the formation of needle-like crystals from a 0.16 M (saturated) aqueous solution. But when 0.03 M γ-cyclodextrin (γ-CD) is added to an equivalent of (I) at RT, the solution exhibits enhancement of the viscosity in an hour, and the microscopic viewing indicates the formation of a pine needle-like aggregate. Enough old millet jelly-like one shows well arranged stripe pattern upon rubbing. In the induced c.d. spectrum, the π→π* band of this complex appears at ～500 nm in the solution state, but in the aggregate state, it changes to the J-band due to the head-to-tail stacking of (I) and the H-band due to parallel stacking. When MeOH is poured onto the aggregate, the latter changes colour from orange to silver-gray, but keeps the same shape. The driving force for the aggregate formation may be 1. van der Walls contact between γ-CD and two molecules of (I),

2. π-π interaction between the two molecules of (I) in γ-CD,

3. H-bonding and stacking effects between γ-CD.

In this chiral aggregate, γ-CD works as an adhesive for the azo dye.     

Invariant generalized ideal classes – structure theorems for <Emphasis Type="BoldItalic">p</Emphasis>-class groups in <Emphasis Type="BoldItalic">p</Emphasis>-extensions

We give, in sections 2 and 3, an english translation of: Classes généralisées invariantes, J. Math. Soc. Japan, 46, 3 (1994), with some improvements and with notations and definitions in accordance with our book: Class Field Theory: From Theory to Practice, SMM, Springer-Verlag, 2nd corrected printing 2005. We recall, in section 4, some structure theorems for finite \(\mathbb {Z}_{p}[G]\)-modules (\(G \simeq \mathbb {Z}/p\,\mathbb {Z}\)) obtained in: Sur les ?-classes d’idéaux dans les extensions cycliques relatives de degré premier ?, Annales de l’Institut Fourier, 23, 3 (1973). Then we recall the algorithm of local normic computations which allows to obtain the order and (potentially) the structure of a p-class group in a cyclic extension of degree p. In section 1973, we apply this to the study of the structure of relative p-class groups of Abelian extensions of prime to p degree, using the Thaine–Ribet–Mazur–Wiles–Kolyvagin ‘principal theorem’, and the notion of ‘admissible sets of prime numbers’ in a cyclic extension of degree p, from: Sur la structure des groupes de classes relatives, Annales de l’Institut Fourier, 43, 1 (1993). In conclusion, we suggest the study, in the same spirit, of some deep invariants attached to the p-ramification theory (as dual form of non-ramification theory) and which have become standard in a p-adic framework. Since some of these techniques have often been rediscovered, we give a substantial (but certainly incomplete) bibliography which may be used to have a broad view on the subject.     

The vibrational energy pattern in ethylene (12C2H4)

All known vibrational energies in ¹²C₂H₄([Xtilde]¹ A_g ) are collected. A block-diagonalized vibrational matrix Hamiltonian is set up, combining a Dunham expansion with the 2/10,10, 11/2,12, and the 5,5/9,9, 1,1/11,11,1,9/5,11 and 1,11/5,9 anharmonic resonances, with the normal modes numbered according to the most usual conventions in the previous literature. A step by step fitting procedure is applied. Vibrational constants are obtained, and vibrational assignments are provided and discussed. A slightly modified ensemble of vibrational constants is also produced by taking care of a more extended set of resonances between the CH-type vibrations. A new constant of the motion N = 3ν₁ + 3ν₅ + 3ν₉ + 3ν₁₁ + 2ν₂ + ν₁₀ + ν₁₂ is demonstrated to support the latter vibrational energy pattern.     

FTIR free-jet set-up for the high resolution spectroscopic investigation of condensable species

An existing experimental set-up combining Fourier transform infrared (FTIR) spectroscopy and free-jet cooling has been modified significantly to allow high resolution studies of the spectrum of monomer species which are liquid under standard conditions. Evaporation of the liquid samples is controlled by a condenser apparatus which is described. A supersonic planar expansion issuing from a narrow aperture is preferred for its very high cooling rate. Such an expansion, probed with a pitot tube, has a zone of limited temperature gradient close to the nozzle exit. The continuum isentropic model appears well suited to describing the thermodynamic properties of the flow up to a high number of nozzle diameters downstream. High resolution spectra of benzene and methanol have been recorded in the 3 μm wavelength range, and their analysis demonstrates a well defined rotational temperature in the 20–25 K range.     

Ab initio calculations of the photoionization of diatomic molecules

A review is presented of the calculation of photoionization spectra, particularly in the spectral range where electron autoionization of diatomic molecules takes place. In addition to some interesting results obtained over years that compare favourably with experiment, the emphasis here is put on the relation between the methods developed for the calculation of observables associated with the continuum energy spectrum of the electrons and the Alchemy system of programs. This system of programs serves as a basis for initial and intermediate calculations. The examples presented show that diatomic molecules not only in gas phase but also oriented in space or physisorbed at surfaces may be studied readily.     

Investigation of the fine structure in overtone absorption bands of 12C2H4

A Fourier transform interferometer was used to record the slit-jet cooled overtone absorption spectrum of ¹²C₂H₄ between 3900 and 7900cm^?1, at a spectral resolution of 0.02cm^?1 and a rotational temperature of 53 K. Some 17 bands were observed and rotationally analysed, leading to effective vibration—rotation constants for all upper states. Coriolis perturbations were identified and refined vibration—rotation constants were produced for seven upper states as well as for 12 Coriolis interacting dark states. Symmetry conventions different from those of the previous literature are selected in the present work.     

Interaction of the t-butylcalix[4]arene Anion with Ammonium Cations in Acetonitrile: Host–Guest Complexes or exo Counterions? A Molecular Dynamics Investigation

We report a theoretical study of the NR4+salts (R = H; Me; Et) of the t-butylcalix[4]arenemonooxyanion L- inacetonitrile solution, to compare the endocomplexes NR4+ inside the cone of thehost) with the exo ones. For a given cation, wefind that the complexes display structures of similartype in the gas phase and in acetonitrile solution.Intrinsically, the endo forms are more stablethan exo ones, but they are less well solvated.As a result, exo complexes are predicted to bemore stable than the endo ones in acetonitrile.In the gas phase and in solution, the exocomplexes of NMe4+ and NEt4+display interesting examples of fluctional intimateion pairs, where the cation oscillates between theoxygen lower rim region of L- and exo stacking with the phenolic rings ofL-. Based on free energy perturbation calculations,we compare endo NH4+/NMe4+complexes and find that the hypotheticalNH4+ complex is more stable in acetonitrile solution.