Plug-in Spectrometry with Optical Fibers as a Novel Analytical Tool for Nanoparticles Technology: Application to the Investigation of the Emulsion Polymerization of the Alkylcyanoacrylate

This paper advances a simple technique to follow, in situ, the emulsion polymerization of isobutylcyanoacrylate (IBCA) performed in different conditions. The method is based on the monitoring of the optical density of the polymerization medium using a plug-in spectrometer equipped with optical fibers since during polymerization the optical density of the medium increases. The technique is demonstrated using poly(alkylcyanoacrylate) nanoparticles developed as carrier for the delivery of drugs in vivo. These nanoparticles are produced by emulsion polymerization of alkylcyanoacrylates (ACA) which are among the highest reactive monomers. The results showed that the spontaneous anionic polymerization of IBCA induced by water could be controlled at pH 1. It was initiated after a delay whereas an immediate and extremely rapid polymerization could be monitored when it was initiated using a combination of cerium IV and dextran allowing the radical polymerization to occur. At higher pH, the spontaneous anionic polymerization could not be controlled. The method developed in this study appeared suitable to monitor emulsion polymerization of ACA and to highlight different mechanisms of polymerization.     

Molecular orbitals and photoelectron spectra of some titanium(IV) organometallic compounds

The photoelectron spectra of some titanium(IV) organometallic compounds are reported, and the data and the bonding in the compounds are discussed with the aid of extended CNDO/2 calculations.     

A Theoretical design of new inorganic ring systems as potential antitumor agents

Quantum calculations of electronic structures and ring stabilities along the (NCMe)_3?x(NPMe₂)_x and (NCNMe₂)_3?x(NPMe₂)_x predict that the aziridinyl mixed terms (x = 1 and 2) of these two families may be anticancer agents even more efficient than (NCAz)₃(TEM) and (NPAz₂)₃(MYKO 63).     

How to use a very simple microcomputing system for a dynamical conformational analysis of versatile molecules. The case of some anticancer inorganic ring systems

A very simple use of a suitable microcomputing system allows discrimination of a set of X-ray structures of anticancer drugs which (i) are the “natural” preferred conformations and (ii) are the direct relationships logically linking these conformations together. Such an approach appears the main interest for a deep understanding of the relative antitumour activities of drugs, whatever the target may be.     

An answer to the spiro versus ANSA dilemma in cyclophosphazenes : Part IX. The first genuine ANSA derivatives from N3P3Cl6 itself

The reaction of the simplest Lehn's ligand, H₂N---(CH₂)₂---O---(CH₂)₂---NH₂, on N₃P₃Cl₆ in suitable stoichiometric conditions leads quite neatly to the first genuine MONOANSA and DIANSA derivatives.     

Structure electronique des complexes acide-base de Lewis. I. Structure electronique et conformation moléculaire des molécules F3P·BH3 et F2HP·BH3

The electronic structure and preferred conformations of F₃P·BH₃ and F₂HP·BH₃ are investigated in the framework of the CNDO /2 approximation. In complete agreement with microwave data, the staggered conformations are predicted to be the most stable ones. The barriers to internal rotation are in good agreement with experimental values (F₃P·BH₃: calc. = 3.03 kcal/mole, exp. = 3.24 ± 0.15 kcal/mole; F₂HP·BH₃: calc. = 3.63 kcal/mole, exp. = 4.05 ± 0.45 kcal/mole) and a bicentric energy partitioning shows that the variations of the total energy are completely reflected by the only variation of the interaction energy between phosphorus and H atoms bonded to boron. The analysis of the electron densities reveals the importance of the 3s(P) → 2p_x(B) transfer in the formation of the co-ordination. Finally, the computed dipole moment value and direction agree with corresponding experimental data.     

A CNDO/2 approach to electron delocalization in N4S4 and N4S4F4

The electronic structure of N₄S₄ and N₄S₄F₄ molecules is investigated within the framework of the CNDO/2 approximation. A pure alternated system is obtained for the fluorinated compound with respect to the Wiberg bond populations. On the other hand, the N₄S₄ molecule appears to be composed of three highly delocalized “islands”, as defined by Dewar in the case of cyclophosphazenes. The “tub form” of N₄S₄ is due to a strong spatial interaction between non-bonded sulphur atoms and, for this reason, the N₄S₄ molecule may be called the “inorganic cyclooctatetraene”.     

Structure électronique de quelques cyclophosphazènes halogénés de symétrie Dnh

The electronic structure of some D_nh cyclophosphazenes is investigated by the /2 approximation of the method. The results allow a critical analysis of ideas previously developed by Craig et al. and Dewar et al. This work supports the localised model of Dewar and tests the Faraday effect experimentally.     

Interprétation quantique des propriétés physico-chimiques - et notamment de l'inversion des échelles d'acidite en solution et en phase gazeuse

The trend of some physico-chemical properties in the saturated alcohols series is investigated within the framework of the CNDO/2 approximation on the basis of an intentional choice of a standard rigid geometrical pattern. It thus enables us to explain the origin of the inversion of the acidity scale which is observed experimentally in solution or in the gas phase. Jano's formalism appears to be highly suitable for the calculation of solvation energies.     

Theoretical conformational analysis (CNDO/2 method) and electronic structure of BIS(Difluorophosphino) ether,F2POPF2

The conformational analysis of F₂POPF₂ is investigated within the framework of the CNDO/2 approximation using the geometrical electron diffraction sets B and C proposed by Arnold and Rankin. The first one appears to be preferential on the basis of the criterion of minimal energy. The theoretical (20, 120) preferred conformation is very close to the experimental one (56.2, 122.0) because of the flexibility of the molecule, as demonstrated by the smooth trend of the energy map around the potential well. Such a conformation has no symmetry elements as a result of a medley of numerous energy terms. Therefore, F₂POPF₂ appears to be one of the scarce molecules in nature which has by itself such a lack of symmetry.