Photosensitizers Based on Bichromophoric Dyads Combining Ru(II)-Polypyridyl Complexes and Dissymmetric Perylene Monoimide Derivatives: The Nontrivial Role of Ligand Substitution.

The covalent modification of Ru(II) polypyridyl complexes (RPCs) with organic chromophores is a powerful strategy to obtain metal-based photosensitizer agents (PSs) with improved performance for application in photodynamic therapy (PDT). In this respect, perylene-imides are of particular interest due to their rich chemical-physical repertoire, and it is therefore quite surprising that their combination with RPCs has been poorly considered so far. Herein, we report on the photophysical behavior of two newly synthesized RPCs bearing a perylene monoimide appendant (PMI-Ad).

Nitroimidazole-Based Ruthenium(II) Complexes: Playing with Structural Parameters to Design Photostable and Light-Responsive Antibacterial Agents.

5-Nitroimidazole (5NIMH), chosen as a molecular model of nitroimidazole derivatives, which represent a broad-spectrum class of antimicrobials, was incorporated into the ruthenium complexes [Ru(tpy)(phen)(5NIM)]PF () and [Ru(tpy)(dmp)(5NIM)]PF () (tpy = terpyridine, phen = phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline). Besides the uncommon metal coordination of 5-nitroimidazole in its imidazolate form (5NIM), the different architectures of the spectator ligands (phen and dmp) were exploited to tune the "mode of action" of the resulting complexes, passing from a photostable compound where the redox properties of 5NIMH are preserved () to one suitable for the nitroimidazole phototriggered release () and whose antibacterial activity against , chosen as cellular model, is effectively improved upon light exposure. This study may provide a fundamental knowledge on the use of Ru(II)-polypyridyl complexes to incorporate and/or photorelease biologically relevant nitroimidazole derivatives in the design of a novel class of antimicrobials.

Highly Charged Ruthenium(II) Polypyridyl Complexes as Effective Photosensitizer in Photodynamic Therapy.

A comparative study between two novel, highly water soluble, ruthenium(II) polypyridyl complexes, [Ru(phen) L'] and [Ru(phen) Cu(II)L'] (L and L-Cu ), containing the polyaazamacrocyclic unit 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridilophane (L'), is herein reported. L and L-Cu interact with calf-thymus DNA and efficiently cleave DNA plasmid when light-activated. They also possess great penetration abilities and photo-induced biological activities, evaluated on an A375 human melanoma cell line, with L-Cu being the most effective.

A Photochromic Azobenzene Peptidomimetic of a β-Turn Model Peptide Structure as a Conformational Switch.

The insertion of azobenzene moiety in complex molecular protein or peptide systems can lead to molecular switches to be used to determine kinetics of folding/unfolding properties of secondary structures, such as α-helix, β-turn, or β-hairpin. In fact, in azobenzene, absorption of light induces a reversible trans ↔ cis isomerization, which in turns generates a strain or a structure relaxation in the chain that causes peptide folding/unfolding. In particular azobenzene may permit reversible conformational control of hairpin formation.

Correspondence between light-absorption spectrum and nonequilibrium work distribution as a mean to access free energy differences between electronic states.

The problem of recovering the free energy difference between two electronic states has been investigated by Frezzato [Chem. Phys. Lett.

Silver nanowires as infrared-active materials for surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS) is increasing in significance as a bioanalytical tool. Novel nanostructured metal substrates are required to improve performances and versatility of SERS spectroscopy. In particular, as biological tissues are relatively transparent in the infrared wavelength range, SERS-active materials suitable for infrared laser excitation are needed.

Non-covalent interactions in anisole-(CO) (n = 1, 2) complexes.

Non-covalent interactions are ubiquitous and represent a very important binding motif. The direct experimental measurement of binding energies in complexes has been elusive for a long time despite its importance, for instance, for understanding and predicting the structure of bio-macromolecules. Here, we report a combined experimental and computational analysis on the 1 : 1 and 1 : 2 clusters formed by anisole (methoxybenzene) and carbon dioxide molecules.

Photochemical Reactivity of 1,6-Methano[10]annulene.

1,6-Methano[10]annulene solutions in cyclohexane have been subjected to continuous and pulsed UV irradiation. Photolysis occurs in both cases, giving naphthalene as a minor and major product, respectively. The wavelength dependence of the reaction in solution indicates that the photochemical process occurs, exciting 1,6-methano[10]annulene in the second and third singlet electronic excited states.

Nonequilibrium Candidate Monte Carlo Simulations with Configurational Freezing Schemes.

Nonequilibrium Candidate Monte Carlo simulation [Nilmeier et al., Proc. Natl.

Computing Free Energy Differences of Configurational Basins.

A simulation-based approach is proposed to estimate free energy differences between configurational states A and B, defined in terms of collective coordinates of the molecular system. The computational protocol is organized into three stages that can be carried on simultaneously. Two of them consist of independent simulations aimed at sampling, in turn, A and B states.

A fluorescent receptor for halide recognition: clues for the design of anion chemosensors.

The chemosensing properties of the polyaza-macrocycle 1-(6,7)-acridine-3,6,9,12-tetraaza-tridecaphane have been investigated by means of emission fluorescence spectroscopy, considering halide ions as substrates. As in the case of the free ligand, the fluorescence emission of the complexes is due to the acridinium species which are formed after photoinduced proton transfer reaction. The complexation constants have been obtained for the bi- and tri-protonated ligands in deoxygenated aqueous solutions.

Binding energies of the π-stacked anisole dimer: new molecular beam-laser spectroscopy experiments and CCSD(T) calculations.

Among noncovalent interactions, π-π stacking is a very important binding motif governed mainly by London dispersion. Despite its importance, for instance, for the structure of bio-macromolecules, the direct experimental measurement of binding energies in π-π stacked complexes has been elusive for a long time. Only recently, an experimental value for the binding energy of the anisole dimer was presented, determined by velocity mapping ion imaging in a two-photon resonant ionisation molecular beam experiment.

Annealed importance sampling with constant cooling rate.

Annealed importance sampling is a simulation method devised by Neal [Stat. Comput. 11, 125 (2001)] to assign weights to configurations generated by simulated annealing trajectories.

Combining path-breaking with bidirectional nonequilibrium simulations to improve efficiency in free energy calculations.

An important limitation of unidirectional nonequilibrium simulations is the amount of realizations of the process necessary to reach suitable convergence of free energy estimates via Jarzynski's relationship [C. Jarzynski, Phys. Rev.

Path-breaking schemes for nonequilibrium free energy calculations.

We propose a path-breaking route to the enhancement of unidirectional nonequilibrium simulations for the calculation of free energy differences via Jarzynski's equality [C. Jarzynski, Phys. Rev.

Tuning the emission properties of fluorescent ligands by changing pH: the unusual case of an acridine-containing polyamine macrocycle.

Synthesis and characterization of a new macrocyclic compound, composed by a triethylentetraamine chain linking the 4 and 5 positions of an acridine moiety, are reported. The molecule, devised as a fluorescent chemosensor for anions, has revealed an intriguing pH-dependent spectroscopic behavior, whose features are the specific object of this article. Ligand protonation in aqueous solution has been analyzed by means of potentiometric, (1)H NMR, UV-vis, and fluorescence emission measurements.

Noncovalent interactions in the gas phase: the anisole-phenol complex.

The present paper reports on an integrated spectroscopic study of the anisole-phenol complex in a molecular beam environment. Combining REMPI and HR-LIF spectroscopy experimental data with density functional computations (TD-M05-2X/M05-2X//N07D) and first principle spectra simulations, it was possible to locate the band origin of the S(1) ← S(0) electronic transition and determine the equilibrium structure of the complex, both in the S(0) and S(1) electronic states. Experimental and computational evidence indicates that the observed band origin is due to an electronic transition localized on the phenol frame, while it was not possible to localize experimentally another band origin due to the electronic transition localized on the anisole molecule.

Integrated experimental and computational spectroscopy study on π-stacking interaction: the anisole dimer.

Integrated experimental and computational results help to clarify the nature of the intermolecular interactions in a simple, isolated π-stacked dimer prepared in a molecular beam. The properties of bimolecular anisole complexes are examined and discussed in terms of the local/supramolecular nature of the electronic wavefunctions. Experimental resonance-enhanced multi-photon ionization spectra of clusters with different isotopic compositions confirmed the fundamentally localized nature of the S(1)←S(0) electronic transition.

Isotopomeric conformational changes in the anisole-water complex: new insights from HR-UV spectroscopy and theoretical studies.

Resonance enhanced multiphoton ionization and rotationally resolved S1<--S0 electronic spectra of the anisole-2H2O complex have been obtained. The experimental results are compared with high level quantum mechanical calculations and with data already available in the literature. Quite surprisingly, the equilibrium structure of the anisole-2H2O complex in the S0 state shows some non-negligible differences from that of the isotopomer anisole-1H2O complex.

On the properties of microsolvated molecules in the ground (S0) and excited (S1) states: the anisole-ammonia 1:1 complex.

State-of-the-art spectroscopic and theoretical methods have been exploited in a joint effort to elucidate the subtle features of the structure and the energetics of the anisole-ammonia 1:1 complex, a prototype of microsolvation processes. Resonance enhanced multiphoton ionization and laser-induced fluorescence spectra are discussed and compared to high-level first-principles theoretical models, based on density functional, many body second order perturbation, and coupled cluster theories. In the most stable nonplanar structure of the complex, the ammonia interacts with the delocalized pi electron density of the anisole ring: hydrogen bonding and dispersive forces provide a comparable stabilization energy in the ground state, whereas in the excited state the dispersion term is negligible because of electron density transfer from the oxygen to the aromatic ring.

Direct quantification of lycopene in products derived from thermally processed tomatoes: optothermal window as a selective, sensitive, and accurate analytical method without the need for preparatory steps.

The concept of the optothermal window (OW) is proposed as a reliable analytical tool to rapidly determine the concentration of lycopene in a large variety of commercial tomato products in an extremely simple way (the determination is achieved without the need for pretreatment of the sample). The OW is a relative technique as the information is deduced from the calibration curve that relates the OW data (i.e.