Photoinduced intramolecular electron transfer in ruthenium and osmium polyads: insights from theory

Ru(II) and Os(II) complexes (P) of [4'-(p-phenyl)]terpyridyl ligand (ptpy) derivatized with an electron acceptor (A) of the triphenylpyridinium (H3TP+) type have been recently proposed as functional models for electron-transfer (ET) processes in the context of artificial photosynthesis. These inorganic dyads, P-A, are expected to undergo intramolecular photoinduced ET to form a charge separated (CS) state of pivotal interest. To draw a complete picture of possible ET processes, the ground- and excited-state properties of these complexes, both in their native and monoreduced forms, have been studied by the means of density functional theory (DFT). A time-dependent-DFT approach (TDDFT) was used to interpret the electronic spectra, while additional spectroscopic measurements have been carried out in order to complete the available experimental information and to further confirm the theoretical issues. Besides the noticeable quantitative agreement between computed and experimental absorption spectra, our results allow us to clarify, by first principles, the actual nature and interplay of the electronic and geometrical coupling between the acceptor moiety and the photosensitizer. The possibility of a direct (optical) ET from the ground state to the targeted *[P+-A-] CS state is theoretically postulated and found to be consistent with available photophysical data (transient absorption spectroscopy). Concerning backward ET (from the CS state), the occurrence of a quinoidal-like electronic redistribution inherent to the photoreduced acceptor-ligand is proposed to favor efficient charge recombination.     

Electropolymerized Manganese Tetraaminophthalocyanine Thin Films onto Platinum Ultramicroelectrode for the Electrochemical Detection of Peroxynitrite in Solution

Peroxynitrite, ONOO^? also so‐called PON, is a very powerful oxidant and cytotoxic agent produced in biological systems by the recombination of nitric oxide and superoxide anion radical. Most of the techniques for assaying PON (chemiluminescence, fluorescence, UV‐visible spectroscopy, immunochemistry and EPR ) use indirect methods relying on measurements of secondary species. We report in this study the calibration of a chemically modified Pt ultramicroelectrode by electropolymerized manganese tetraaminophthalocyanine film (MnTAPc) for the determination of PON in aqueous solution. The obtained result allows showing for the first time a real‐time calibration curve of the amperometric determination of stable PON in aqueous solution. The sensitivity of the sensor is 14.6 nA mM^?1 and its detection limit is 5 μM.     

Elements of harmonic analysis related to the third basic zero order Bessel function

This paper is devoted to the study of some q-harmonic analysis related to the third q-Bessel function of order zero. We establish a product formula leading to a q-translation with some positive kernel. As an application, we provide a q-analogue of the continuous wavelet transform related to this harmonic analysis.     

Conformationally gated photoinduced processes within photosensitizer-acceptor dyads based on osmium(II) complexes with triarylpyridinio-functionalized terpyridyl ligands: insights from experimental study

[(ttpy)Os(tpy-ph-TPH(3)(+))](3+) (2), [(ttpy)Os(tpy-xy-TPH(3)(+))](3+) (3), [(ttpy)Os(tpy-ph-TPH(2)(NO(2))(+))](3+) (4), and [(ttpy)Os(tpy-xy-TPH(2)(NO(2))(+))](3+) (5) are a series of dyads made of an Os(II) bis-tpy complex (tpy = 2,2':6',2"-terpyridine) as the photosensitizer (P) and 2,4,6-triarylpyridinium group (TP(+)) as the electron acceptor (A). These dyads were designed to form charge-separated states (CSS) upon light excitation. Together with analogous Ru(II) complexes (7-10), they have been synthesized and fully characterized. We describe herein how intramolecular photoinduced processes are affected when the electron-accepting strength of A (by nitro-derivatization of TP(+)) and/or the steric hindrance about intercomponent linkage (by replacing a phenyl spacer by a xylyl one) are changed. Electronic absorption and electrochemical behavior revealed that (i) chemical substitution of TP(+) (i.e., TP(+)-NO(2)) has no sizable influence on P-centered electronic features, (ii) reduction processes located on TP(+) depend on the intercomponent tilt angle. Concerning excited-state properties, photophysical investigation evidenced that phosphorescence of P is actually quenched in dyads 4 and 5 only. Ultrafast transient absorption (TA) experiments allowed attributing the quenching in conformationally locked dyad 5 to oxidative electron transfer (ET) from the (3)MLCT level to the TP(+)-NO(2) acceptor (k(el) = 1.1 x 10(9) s(-)(1)). For 4, geometrically unlocked, the (3)MLCT state was shown to first rapidly equilibrate (reversible energy transfer; k(eq) approximately 2 x 10(9) s(-)(1)) with a ligand centered triplet state before undergoing CSS formation. Thus, the pivotal role of conformation in driving excited-state decay pathways is demonstrated. Also, inner P structural planarization as a relaxation mode of the (3)MLCT states has been inferred from TA experiments.     

Modelling of the surface plasmon resonance waveguide sensor with Bragg grating

The operation of a novel device – a waveguide surface plasmon resonance sensor with a UV-written Bragg grating – is theoretically analysed using two methods. In the simple perturbation approach, the metal/dielectric layer system supporting the resonance excitation of the surface plasma wave is considered to be a perturbation of the original dielectric waveguide with Bragg grating that is analysed using a coupled-mode theory. The second approach consists of the rigorous method of bi-directional mode expansion and propagation using the Floquet mode formalism developed recently for the analysis of waveguide grating structures. The results of both approaches are mutually compared, and the operation characteristics of this novel sensing device are briefly described.     

Ground state and phonon spectrum of NiSi2

We have studied structural, electronic, elastic and dynamical properties of NiSi₂ by employing the plane wave pseudopotential method based on density functional theory within the local density approximation. The calculated lattice constant, bulk modulus and first-order pressure derivative of the bulk modulus are reported and compared with earlier available experimental and theoretical calculations. Numerical first-principles calculations of the elastic constants were used to calculate C₁₁, C₁₂ and C₄₄ for NiSi₂. The calculated electronic band structure has been compared with angle-resolved photoemission spectroscopy experimental data along the [100] and [111] symmetry directions. A linear response approach to density functional theory is used to derive the phonon dispersion curves and phonon partial density of states. Atomic displacement patterns for NiSi₂ at the Γ, X and L symmetry points are also presented.     

Multiband small zeroth-order metamaterial antenna

A novel resonant metamaterial antenna based on the Composite Right/Left-Handed (CRLH) transmission line (TL) model is presented. The proposed small antenna is designed to operate simultaneously over multiple wireless services (UMTS-WLAN-WIMAX)     

A Lagrangean-based heuristics for the target covering problem in wireless sensor network

We study the target coverage problem in wireless sensor networks. The problem consists in maximizing the network lifetime by grouping the sensors in disjoint set covers of the targets. A binary integer programing model is formulated to maximize the network lifetime. Since the problem is NP-complete, we provide an iterative approximation based on Lagrangean relaxation and subgradient optimization.     

Uncertainty Principles for the Segal-Bargmann Transform

We recall some properties of the Segal-Bargmann transform; and we establish for this transform qualitative uncertainty principles: local uncertainty principle, Heisenberg uncertainty principle, Donoho-Stark''s uncertainty principle and Matolcsi-Sz\"ucs uncertainty principle.     

Some Examples of Extremal Functions on the Dunkl-Type Fock Space $$F_k(\mathbb {C})$$

In this work, we recall some properties of the generalized Fock space \(F_k(\mathbb {C})\) and the Hilbert space \(H_k(\mathbb {C})\) (defined by the squared norm \(\Vert f\Vert ^2_{H_k(\mathbb {C})}:=\Vert f\Vert ^2_{F_k(\mathbb {C})}+\langle zf',f\rangle _{F_k(\mathbb {C})}\)). Next, we give the best approximation of the bounded operators \(L:F_k(\mathbb {C})\rightarrow H_k(\mathbb {C})\). As applications, we come up with some results regarding the approximate formulas for the difference operator, the Dunkl difference operator and the primitive operator.