Pt(II)-activated coupling of aminoethylferrocene with benzonitrile. A facile access route to a new redox-active bis(ferrocenyl-amidine) anion sensor

A new heterometallic electroactive compound having the ferrocenyl moiety attached to the platinum atom through an amidine functionality has been prepared via Pt(II)-mediated nucleophilic addition of β-aminoethylferrocene to a benzonitrile ligand. This neutral receptor shows remarkable electrochemical anion-sensing redox response to H(2)PO(4)(-).     

Mechanism of the Deprotonation Reaction of Alkyl Benzyl Ethers with n‐Butyllithium

Kinetic study of the α‐lithiation of benzyl methyl ether (BME) by nBuLi has revealed that increasing the concentration of the organolithium compound does not necessarily increase the reactivity, and this is a consequence of the reactivities of the different nBuLi aggregates present in solution. We propose a dimer‐based mechanism, in which a pre‐complexation step is a key process for substrates bearing a donor oxygen atom that can interact with the lithium cation to form mixed dimers. For these studies, we have developed a system based on UV/Vis spectroscopy that allows kinetic measurements to be conducted at ?80 °C under argon.     

Conformational selection of the AGA*IA(M) heparin pentasaccharide when bound to the fibroblast growth factor receptor

The interaction of the synthetic pentasaccharide AGA*IA(M) (GlcNS,6S-GlcA-GlcNS,3S,6S-IdoA2S-GlcNS,6S-Me) with the extracellular Ig2 domain of the fibroblast growth factor receptor (FGFR2) has been studied by NMR and computational methods. Analysis of the heparin pentasaccharide in the free state and in the complex indicates the existence of a conformational selection process. Although an equilibrium exists between the (1)C(4) and (2)S(0) conformers (ratio 60:40) of the 2-O-sulfo-α-L-iduronate ring (IdoA2S) in the free state, FGFR2 selects only the unique twisted-boat (2)S(0) conformation of this IdoA2S residue. In addition, the protein residues involved in the binding with AGA*IA(M) have also been characterized. The NMR results obtained, from both the ligand and protein perspective, were employed to model the bound conformation of the pentasaccharide by a combined docking and molecular dynamic simulation approach.     

Adsorption thermodynamics of a lattice–gas model with non-additive lateral interactions

In the present paper, we study the adsorption thermodynamics of a lattice–gas model with non-additive interactions between adsorbed particles. We have assumed that the energy which links a certain atom with any of its nearest neighbors strongly depends on the state of occupancy in the first coordination sphere of that adatom. By means of Monte Carlo simulations in the grand canonical ensemble the adsorption isotherms, isothermal susceptibility (or equivalently the mean square density fluctuations of adparticles), and isosteric heat of adsorption were calculated and their striking behavior was analyzed and discussed in terms of the low temperature phases formed in the system.     

Self-isospectrality, special supersymmetry, and their effect on the band structure

We study a planar model of a nonrelativistic electron in periodic magnetic and electric fields that produce a 1D crystal for two spin components separated by a half-period spacing. We fit the fields to create a self-isospectral pair of finite-gap associated Lamé equations shifted for a half-period, and show that the system obtained is characterized by a new type of supersymmetry. It is a special nonlinear supersymmetry generated by three commuting integrals of motion, related to the parity-odd operator of the associated Lax pair, that coherently reflects the band structure and all its peculiarities. In the infinite-period limit it provides an unusual picture of supersymmetry breaking.     

Qubits and chirotopes

We show that qubit and chirotope concepts are closely related. In fact, we prove that the qubit concept leads to a generalization of the chirotope concept, which we call qubitope. Moreover, we argue that a possible qubitope theory may suggest interesting applications of oriented matroid theory in at least three physical contexts, in which qubits make their appearance, namely string theory, black holes and quantum information.     

Holstein-Primakoff/Bogoliubov Transformations and the Multiboson System

As an aid to understanding the displacement operator definition of squeezed states for arbitrary systems, we investigate the properties of systems where there is a Holstein-Primakoff or Bogoliubov transformation. In these cases the ladder-operator or minimum-uncertainty definitions of squeezed states are equivalent to an extent displacement-operator definition. We exemplify this in a setting where there are operators satisfying [A, A^å] = 1, but the A's are not necessarily the Fock space a's; the multiboson system. It has been previously observed that the ground state of a system often can be shown to to be a coherent state. We demonstrate why this must be so. We close with a discussion of an alternative, effective definition of displacement-operator squeezed states.     

NMR study of the coordinating behavior of 2,6‐bis(benzimidazol‐2′‐yl)pyridine

The coordination sites of 2,6‐bis(benzimidazol‐2′‐yl)pyridine ( 1 ) toward protons and the diamagnetic metal ions Li⁺, Na⁺, and Co³⁺ were investigated by NMR spectroscopy. Variable temperature ¹H and ¹³C NMR experiments were performed on 1 in order to evaluate the tautomeric equilibrium and hydrogen bonding. Imidazole dicoordinated aromatic nitrogen atoms were protonated by trichloroacetic acid and the three N‐dicoordinated atoms by fuming H₂SO₄. Reactions of the ligand 1 and benzimidazole 2 with metallic sodium or LiH afforded anionic species; the alkali metal ions appeared solvated by THF, but not by the ligands 1 or 2 . In contrast, reaction of 1 with Co(III) produces the stable cation [Co( 1 ‐H)₂]⁺ with cobalt ion coordinated by two molecules of the monodeprotonated ligand. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:392–398, 2000