Structural insights into methyl‐ or methoxy‐substituted 1‐(α‐aminobenzyl)‐2‐naphthol structures: the role of C—H…π interactions

Aminobenzylnaphthols are a class of compounds containing a large aromatic molecular surface which makes them suitable candidates to study the role of C—H…π interactions. We have investigated the effect of methyl or methoxy substituents on the assembling of aromatic units by preparing and determining the crystal structures of (S,S)‐1‐{(4‐methylphenyl)[(1‐phenylethyl)amino]methyl}naphthalen‐2‐ol, C₂₆H₂₅NO, and (S,S)‐1‐{(4‐methoxyphenyl)[(1‐phenylethyl)amino]methyl}naphthalen‐2‐ol, C₂₆H₂₅NO₂. The methyl group influenced the overall crystal packing even if the H atoms of the methyl group did not participate directly either in hydrogen bonding or C—H…π interactions. The introduction of the methoxy moiety caused the formation of new hydrogen bonds, in which the O atom of the methoxy group was directly involved. Moreover, the methoxy group promoted the formation of an interesting C—H…π interaction which altered the orientation of an aromatic unit.     

Microwave Irradiation in Micro‐ Meso‐Fluidic Systems; Hybrid Technology has Issued the Challenge

A combination of microwave irradiation and flow chemistry has been described as a promising smart and hyphenated technology that can fuse and synergize the benefits of the techniques. The cells and tissues of all living organisms promote a huge number of bioorganic reactions that occur as flow systems and not the batch‐type conditions typically used by chemists and biotechnologists. Microwave‐assisted chemical conversion carried out in continuous flow mode with micro‐ or meso‐channel reactors can offer significant processing advantages, including improved thermal exchange, energy efficiency, safety, mixing control, a wider range of reaction conditions, repeatability and scalability as well as dramatic reductions in side‐reactions and degradations. This review will discuss relevant examples of organic synthesis and nanoparticles production performed in continuous flow mode with integrated microwave irradiation in micro‐ or mesofluidic systems.     

Template effect of tetrathiafulvalene in the formation of cyclobis(paraquat-p-phenylene)

[reaction: see text] The template effect exerted by tetrathiafulvalene (TTF) in the ring-closure reaction of the trication 5(3+) yielding cyclobis(paraquat-p-phenylene) has been quantitatively evaluated in acetonitrile at 62 degrees C with UV-vis spectrophotometry. The rate of ring closure of the trication 5(3+) largely increases in the presence of the template (a maximum increase of ca. 80 times at [TTF] approximately 0.14 M). The results are compared with those of other aromatic templates, 2 and 3, that were provided with polyethereal sidearms and indicate that the template ability of tetrathiafulvalene is comparable or better than that of the others.     

The electron transfer rate of large TPA based compounds: a joint theoretical and electrochemical approach

A series of triphenylamine (TPA) based compounds is investigated by means of density functional theory and cyclic voltammetry. Using the Nicholson's formalism, the measured deltaE(p) are correlated with B3LYP/6-31G* calculated reorganisation energies (lambda), elucidating the trend followed by the electron transfer rate of these compounds. Besides the direct dependency upon the dimension of the cationic fragment contributing to the hole stabilisation, the lambdas are tuned by the symmetry local to the TPA units, as evidenced by the structural relaxation of the cations. MDTAB shows the interesting combination of low ionisation potential (IP) and low lambda. This can make this compound interesting for practical applications in organic light emitting diode (OLEDs) devices, due to the direct correlation of the IP and lambda with the hole transfer efficiency to the anode, along with the hole mobility.     

Lyapunov Characteristic Exponents for smooth dynamical systems and for hamiltonian systems; A method for computing all of them. Part 2: Numerical application

Summary The present paper, together with the previous one (Part 1: Theory, published in this journal) is intended to give an explicit method for computing all Lyapunov Characteristic Exponents of a dynamical system. After the general theory on such exponents developed in the first part, in the present paper the computational method is described (Chapter A) and some numerical examples for mappings on manifolds and for Hamiltonian systems are given (Chapter B).

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Sommario Questo articolo, insieme con il precedente (Parte 1: Teoria, pubblicato in questa stessa rivista) è inteso a fornire un metodo esplicito per il calcolo di tutti gli esponenti caratteristici di Lvapunov per un sistema dinamico. Dopo la teoria generale su tali esponenti sviluppata nella prima parte, qui si illustra il metodo di calcolo (Capitolo A) e si danno esempi numerici per applicazioni di varietà in sè e per sistemi Hamiltoniani (Capitolo B).

     

Resolution of 13C-19F interactions in the 13C NMR of spinning solids and liquid crystals

Anomalous line-broadenings of carbon resonances close to 19F have commonly been reported in the 13C NMR of liquid crystals and solids. We have previously shown that these effects in static liquid-crystal samples are related to the difficulty of 1H decoupling in the presence of strong 1H-19F dipolar interactions. We here extend this work to spinning samples (both liquid crystals and solids). A number of different line-broadening mechanisms are elucidated: analogous decoupling effects, magic angle misset, and 19F lifetime-broadening. In relatively mobile systems, such as liquid crystals or soft solids, the limiting factor on 13C resolution (and the ability to directly quantify the 13C-19F interactions) is found to be the efficiency and robustness of the 1H-decoupling. In rigid solids, the lifetime of the 19F spin-states is found to be an additional critical factor.     

Synthesis of new polyoxapolycarboxylic ligands for lanthanide(III) ions complexation

The multidentate polyoxapolycarboxylic ligands 1 and 2 were obtained by a two-step synthesis from easily available chemicals. Preliminary data on their coordination properties are reported.     

Novel squalene-hopene cyclase inhibitors derived from hydroxycoumarins and hydroxyacetophenones

Squalene-hopene cyclase (SHC) is a useful model enzyme for predicting molecular interactions with oxidosqualene cyclase (OSC). Structure--activity relationships were investigated for numerous coumarin-derived inhibitors of SHC, and structural simplifications are suggested. Both umbelliferone and 2,4-dihydroxyacetophenone provide convenient starting nuclei for the design of SHC inhibitors. Derivatives bearing an omega-epoxyfarnesyl moiety or just a plain alkyl chain showed an inhibitory effect on a recombinant SHC from Alicyclobacillus acidocaldarius expressed in Escherichia coli.     

A Lagrange multiplier method for the finite element solution of elliptic interface problems using non-matching meshes

Summary. In this paper we propose a Lagrange multiplier method for the finite element solution of multi-domain elliptic partial differential equations using non-matching meshes. The interface Lagrange multiplier is chosen with the purpose of avoiding the cumbersome integration of products of functions on unrelated meshes (e.g, we will consider global polynomials as multiplier). The ideas are illustrated using Poissons equation as a model, and the proposed method is shown to be stable and optimally convergent. Numerical experiments demonstrating the theoretical results are also presented.Mathematics Subject Classification (2000): 65N30, 65N12     

Spectral multipliers for sub-Laplacians with drift on Lie groups

We study spectral multipliers of right invariant sub-Laplacians with drift on a connected Lie group G. The operators we consider are self-adjoint with respect to a positive measure , whose density with respect to the left Haar measure λ_G is a nontrivial positive character of G. We show that if p≠2 and G is amenable, then every spectral multiplier of extends to a bounded holomorphic function on a parabolic region in the complex plane, which depends on p and on the drift. When G is of polynomial growth we show that this necessary condition is nearly sufficient, by proving that bounded holomorphic functions on the appropriate parabolic region which satisfy mild regularity conditions on its boundary are spectral multipliers of . Work partially supported by the EC HARP Network “Harmonic Analysis and Related Problems”, the Progetto Cofinanziato MURST “Analisi Armonica” and the Gruppo Nazionale INdAM per l'Analisi Matematica, la Probabilità e le loro Applicazioni. Part of this work was done while the second and the third author were visiting the “Centro De Giorgi” at the Scuola Normale Superiore di Pisa, during a special trimester in Harmonic Analysis. They would like to express their gratitude to the Centro for the hospitality.