Controlling the electronic density of the [Ru2(DPhF)3(O2CR)] core to obtain one-dimensional compounds

The substitution of the acetate ligand in [Ru₂Cl(DPhF)₃(O₂CMe)] (DPhF⁻ = N,N′-diphenylformamidinate) by the pentafluorobenzoate group gives the complex [Ru₂Cl(DPhF)₃(O₂CC₆F₅)(OH₂)] (1), and the reaction of 1 with AgSO₃CF₃ leads to the compound [Ru₂(DPhF)₃(O₂CC₆F₅)(OH₂)₂]SO₃CF₃ (2). The low donor character of the pentafluorobenzoate ligand compared to the acetate group decreases the electron density of the Ru₂⁵⁺ unit which permits ligands to bond at both axial positions of the diruthenium moiety. The use of the [Au(CN)₂]⁻ group yields the new complex {[Ru₂(DPhF)₃(O₂CC₆F₅)][Au(CN)₂]} (3). Complexes 1–3 are characterized by elemental analysis, ¹⁹F{¹H} NMR, IR and electronic spectroscopy, mass spectrometry and variable-temperature magnetic measurements. The crystal structure of 2·H₂O is also reported. The magnetic properties of complex 1 is in accordance with the ground-state configuration σ²π⁴δ²(π*δ*)³. In contrast, the slope of representation of the magnetic moment towards temperature in complex 2 indicates a gradual transition from essentially high spin (S = 3/2) to low spin (S = 1/2) configuration.     

FT Raman and DFT Study on a Series of All‐anti Oligothienoacenes End‐Capped with Triisopropylsilyl Groups

Herein, we study the π‐conjugational properties of a homologous series of all‐anti oligothienoacenes containing four to eight fused thiophene rings by means of FT Raman spectroscopy and DFT calculations. The theoretical analysis of the spectroscopic data provides evidence that selective enhancement of a very limited number of Raman scatterings is related to the occurrence in these oligothienoacenes of strong vibronic coupling between collective ν(C?C) stretching modes in the 1600–1300 cm^?1 region and the HOMO/LUMO frontier orbitals (HOMO=highest occupied molecular orbital; LUMO=lowest unoccupied molecular orbital). The correlation of the Raman spectroscopic data and theoretical results for these all‐anti oligothienoacenes with those previously collected for a number of all‐syn oligothienohelicenes gives further support to the expectation that cross‐conjugation is dominant in heterohelicenes. Fully planar all‐anti oligothienoacenes display linear π conjugation which seemingly does not reach saturation with increasing number of annulated thiophene rings in the oligomeric chain at least up to the octamer.     

A new method for exact integration of some perturbed stiff linear systems of oscillatory type

This article presents a new family of real functions with values within the ring of M(m,R) matrices, Φ-functions for perturbed linear systems and a numerical method adapted for integration of this type of problem. This method permits the system solution to be expressed as a series of Φ-functions. The coefficients of this series are obtained through recurrences in which the perturbation intervenes.The Φ-functions series method has the advantage of being exactly integrated in the perturbed problem. For this purpose an appropriate B matrix is selected and used to construct the operator described in this article, thus annihilating the disturbance terms, transforming the system into a homogenous second-order system, which is exactly integrated with the two first Φ-functions.The article ends with a detailed study of four perturbed systems which illustrate how the method is used in stiff problems or in highly oscillatory problems, contrasting its behaviour by studying its accuracy in comparison with other well-known codes.     

Regularized state-constrained boundary optimal control of the Navier-Stokes equations

The numerical solution of the Dirichlet boundary optimal control problem of the Navier-Stokes equations in presence of pointwise state constraints is investigated. Two different regularization techniques are considered. First, a Moreau-Yosida regularization of the problem is studied. Optimality conditions are derived and the convergence of the regularized solutions towards the original one is proved. A source representation of the control combined with a Lavrentiev type regularization strategy is also presented. The analysis concerning optimality conditions and convergence of the regularized solutions is carried out. In the last part of the paper numerical experiments are presented. For the numerical solution of each regularized problem a semi-smooth Newton method is applied.     

Platinum(II)-Based Optical Probes for Imaging Quadruplex DNA Structures via Phosphorescence Lifetime Imaging Microscopy

G-quadruplex DNA is a non-canonical structure that forms in guanine-rich regions of the genome. There is increasing evidence showing that G-quadruplexes have important biological functions, and therefore molecular tools to visualise these structures are important. Herein we report on a series of new cyclometallated platinum(II) complexes which, upon binding to G-quadruplex DNA, display an increase in their phosphorescence, acting as switch-on probes. More importantly, upon binding to G-quadruplexes they display a selective and distinct lengthening of their emission lifetime. We show that this effect can be used to selectively visualise these structures in cells using Phosphorescence Lifetime Imaging Microscopy (PLIM).     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.     

Novel Synthetic Approach towards Amino-Substituted Polycyclic Aromatic Hydrocarbons through Electrocyclization of Keteniminium Salts

Polycyclic aromatic hydrocarbons (PAHs) are an important family of molecules in science and technology. Amino-substituted PAHs are promising building blocks to create attractive molecules for materials science. However, the synthetic limitations have hampered to produce diverse structures of amino-substituted PAHs. Here we describe a novel efficient synthetic method to access amino-substituted PAHs through the electrocyclization of highly reactive keteniminium species. We demonstrated the synthesis of various amino-substituted PAHs and disclosed some of their photophysical properties. Furthermore, combination with theoretical calculation revealed that the multiple electrocyclization reactions of keteniminium species is a stepwise process and the fusion of additional aromatic ring to the substrate accelerates the electrocyclization.