The Impact of the Phenyl Spacer on the Electronic Structure and Spectra of Porphyrin Dimers

Quantum-chemical investigation of the electronic structure and properties of the excited states of porphyrin dimers, in which monomeric subunits are linked by the phenyl spacer, is performed by semiempirical methods. The molecular orbitals of the monomeric subunits are shown to interact with each other via molecular orbitals of the phenyl ring. Comparison of the experimental absorption data and quantum-chemical calculations of electronic absorption spectra for different conformations of Zn-tetraphenylporphyrin dimer is performed and the main conformation of the dimer in a solution at 295 K, in which the planes of tetrapyrrole macrocycles are located at an angle of about 60°, is substantiated.     

Evidence of Ternary Inclusion Complexes Formation Using Factorial Design and Determination of Their Formation Constant

Evidence of the interaction among the [PbAc]⁺ and[PbEDTA]^-2 with the v9tt332821247/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (v9tt332821247/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD)is shown, using a 2⁴ factorial design. The factors used werethe [Pb(II)], [v9tt332821247/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD], [Ac^-] and [EDTA] concentrationsat pH = 6.2. The statistical results indicate that the changes inchemical response for these species are associated to theinteraction among these factors. Spectrophotometric andelectrochemical studies were undertaken to assess the interactions.The equilibrium constants for inclusion complexes were determinedFor v9tt332821247/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD-[PbAc]⁺ and v9tt332821247/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD-[PbEDTA]^-2.     

Orders on Braid Groups

It is shown that the braid group v656m373/10469_2004_Article_469355_TeX2GIFIE1.gif" alt=" $$B\left( n \right)\left( {n \geqslant 3} \right)$$ " align="middle" border="0"> defies lattice ordering.     

Zinc(II)-porphyrin Receptors in Multi-point Molecular Recognition: Recent Progress

The tremendous efforts made in order to control the coordination chemistry of hemoprotein models have considerably enhanced the synthesis of functionalized porphyrins, whose carefully designed architectures allowed for selective bindings of exogenic substrates. The common use of zinc(II) in place of pentacoordinated iron(II) has induced the use of zinc(II) porphyrins as building blocks for selective receptors. These receptors offer a convenient combination of multi-point recognition of substrates, and monitoring of the complexation due to the chromophoric nature of the tetrapyrrolic unit. This review is dedicated to recent progress made in the field of molecular recognition involving multi-point selective binding processes, in whichthe establishment of a strong coordination bond is finely tuned by one or more weak interactions adequately introduced in the architecture of a functionalized zinc(II)-porphyrin.     

Are the Elements Elementary? Nineteenth-Century Chemical and Spectroscopical Answers

We analyze the role and influence of a tradition of research linked to the concept of vaat31dee30v5t/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0">primary mattervaat31dee30v5t/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> in nineteenth-century studies on the nature of the elements.The suggestion of William Prout (1785-1850) in 1816 that the atomic weights of pure chemical elements are whole numbers and multiples of the atomic weight of hydrogen, taken as unity, was met with serious confutations,which in turn prompted several attempts to save Proutvaat31dee30v5t/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s hypothesis.We discuss these attempts in detail and the objections raised against them, for instance by Dmitry Ivanovich Mendeleev (1834-1907). We pay particular attention to the use of spectroscopy as a method for proving the existence of elementary forms of matter inside atoms. Leaders in this field of research were two English scientists, the astrophysicist Norman Lockyer (1836-1920) and the chemist William Crookes (1832- 1919). Both of their approaches involved the idea of primary matter. However, while Crookesvaat31dee30v5t/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s approach proved to be incorrect, Lockyervaat31dee30v5t/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s ideas survived for several years and supported the discovery of the electron by J.J.Thomson (1856-1940).     

On the Operator Semirings of a Γ-Semiring

In this paper we introduce the notion of operator semirings of a v085/xxlarge915.gif" alt="Gamma" align="BASELINE" BORDER="0">-semiring to study v085/xxlarge915.gif" alt="Gamma" align="BASELINE" BORDER="0">-semirings. It is shown that the lattices of all left (right) ideals (two-sided ideals) of a v085/xxlarge915.gif" alt="Gamma" align="BASELINE" BORDER="0">-semiring and its right (respectively left) operator semiring are isomorphic. This has many applications to characterize various v085/xxlarge915.gif" alt="Gamma" align="BASELINE" BORDER="0">-semirings.AMS Subject Classification (2000): 16Y60, 16Y99     

Metric and Complete Metric σ-Frames

A v5502736n5406h88/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0">-frame is a lattice in which countable joins exist and binary meets distribute over countable joins. In this paper, the category Mv5502736n5406h88/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0">Frm, of metric v5502736n5406h88/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0">-frames, is introduced, and it is shown to be equivalent to the category MLFrm _u, of metric Lindelöf frames.Finally, it is shown that the complete metric v5502736n5406h88/xxlarge963.gif" alt="sgr" align="BASELINE" BORDER="0">-frames are exactly the cozero parts of complete metric Lindelöf frames.     

On non-measurability of in its second dual

We show that with the weak topology is not an intersection of Borel sets in its Cech-Stone extension (and hence in any compactification). Assuming (CH), this implies that has no continuous injection onto a Borel set in a compact space, or onto a Lindelöf space. Under (CH), this answers a question of Arhangel'ski.

     

Variational representations of Varadhan functionals

Motivated by the theory of large deviations, we introduce a class of non-negative non-linear functionals that have a variational ``rate function" representation.

     

Spectral‐Luminescence and Generation Properties of 1‐Aza‐2‐Methyl‐6‐Aminopyrene and of Its Protolytic Forms

Spectral manifestations of protolytic forms of 1v7802126541151h1/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">azav7802126541151h1/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">2v7802126541151h1/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">methylv7802126541151h1/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">6v7802126541151h1/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">aminopyrene in ethanol and aqueous solutions are investigated. The ionization constants of the protolytic forms are determined. The generation properties and photostability of a neutral molecule and a cation in excitation by an excimer XeCl laser are studied.