Shedding new light on quadrupolar 1,4-dihydropyrrolo[3,2-]pyrroles: impact of electron-deficient scaffolds over emission.

In this work, we disclose a series of seven quadrupolar centrosymmetric 1,4-dihydropyrrolo[3,2-]pyrroles (DHPPs) linked to the two peripheral, strongly electron-accepting heterocycles such as benzoxadiazole, benzothiadiazole and benzoselenadiazole. This represents the first study probing the influence of electron-deficient heterocycles, rather that small electron-withdrawing substituents, on photophysics of DHPPs. These new acceptor-donor-acceptor hybrid dyes exhibit an appreciable combination of photophysical properties including absorption maxima in the range of 470-620 nm, and emission in the range of 500-720 nm with fluorescence quantum yields reaching 0.

Nonradiative Deactivation of the Fluorescent Ag-DNA and Ag-DNA Emitters: The Role of Water.

The luminescent quantum yield of silver-cluster emitters stabilized by short oligonucleotides (Ag-DNA) may be efficiently tuned by replacing nucleobases in their stabilization DNA matrices with analogues. In the present study, we proposed a valuable and straightforward theoretical methodology for assessing the photophysical behaviors emerging in Ag-DNA emitters after excitation. Using green Ag-DNA and near-IR Ag-DNA emitters we demonstrate how point guanine/inosine replacement could affect the photophysical rate constants of radiative/nonradiative processes.

Nitrogen Photoelectrochemical Reduction on TiB Surface Plasmon Coupling Allows Us to Reach Enhanced Efficiency of Ammonia Production.

Ammonia is one of the most widely produced chemicals worldwide, which is consumed in the fertilizer industry and is also considered an interesting alternative in energy storage. However, common ammonia production is energy-demanding and leads to high CO emissions. Thus, the development of alternative ammonia production methods based on available raw materials (air, for example) and renewable energy sources is highly demanding.

So Close, Yet so Different: How One Donor Atom Changes Significantly the Photophysical Properties of Mononuclear Cu(I) Complexes.

The manipulation of the photophysical properties of molecular emitters can be realized by composing the close environment of the metal center with the "heavier pnictogen atom" effect. Replacing a nitrogen atom with a heavier phosphorus atom in otherwise isostructural molecular systems results in a significant change of the photophysical parameters. Herein, we report on the synthesis of four pairs of novel phosphinine-based and isostructural diimine-based Cu(I) complexes, which feature peculiar photophysical properties, and show how these parameters depend on the "heavier pnictogen atom" effect.

Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands.

Imidoylamidinate-based heteroleptic bis(2-phenylbenzothiazole)iridium(III) and -rhodium(III) complexes [()M(NN)] ( = 2-phenylbenzothiazole, NN = '-(benzo[]thiazol-2-yl)acetimidamidyl ( and ), '-(6-fluorobenzo[]thiazol-2-yl)acetimidamidyl (), '-(benzo[]oxazol-2-yl)acetimidamidyl (), '-(1-methyl-1-benzo[]imidazol-2-yl)acetimidamidyl (); yields 70-84%) were obtained by the reaction of the in situ-generated solvento-complex [()M(NCMe)]NO and benzo[]thia/oxa/-methylimidozol-2-amines in the presence of NaOMe. Complexes - exhibited intense orange photoluminescence, reaching 37% at room temperature quantum yields, being immobilized in a poly(methyl methacrylate) matrix. A photophysical study of these species in a CHCl solution, neat powder, and frozen (77 K) MeOCHOH-EtOH glass matrix─along with density-functional theory (DFT), ab initio methods, and spin-orbit coupling time-dependent DFT calculations─verified the effects of substitution in the imidoylamidinate ligands on the excited-state properties.

Computer Simulations of Deep Eutectic Solvents: Challenges, Solutions, and Perspectives.

Deep eutectic solvents (DESs) are one of the most rapidly evolving types of solvents, appearing in a broad range of applications, such as nanotechnology, electrochemistry, biomass transformation, pharmaceuticals, membrane technology, biocomposite development, modern 3D-printing, and many others. The range of their applicability continues to expand, which demands the development of new DESs with improved properties. To do so requires an understanding of the fundamental relationship between the structure and properties of DESs.

Stabilization of DNA by sodium and magnesium ions during the synthesis of DNA-bridged gold nanoparticles.

Nanostructures synthesized using DNA-conjugated gold nanoparticles have a wide range of applications in the field of biosensorics. The stability of the DNA duplex plays a critical role as it determines the final geometry of these nanostructures. The main way to control DNA stability is to maintain a high ionic strength of the buffer solution; at the same time, high salt concentrations lead to an aggregation of nanoparticles.

tRNA as a stabilizing matrix for fluorescent silver clusters: photophysical properties and IR study.

In this experimental study fluorescent silver clusters on a tRNA matrix were synthesized for the first time. Two types of fluorescent complexes emitting in the green (550 nm) and red (635 nm) regions of the visible spectrum were obtained. Using FTIR spectroscopy, we identified possible binding sites for the clusters, which appeared to be within the helical regions of tRNA.

Silver cluster-amino acid interactions: a quantum-chemical study.

Binding of silver ion (Ag) and two atomic neutral silver cluster (Ag) with a set of amino acids has been studied using Density Functional Theory (DFT) and ab initio MP2 method. We show that binding energy with Ag is higher for deprotonated anionic amino acids. Cysteine, aspartic acid, and tyrosine with deprotonated side chain exhibit the highest binding energy (G) values among all the amino acids: - 30.

Ultrafast fluorescence dynamics of DNA-based silver clusters.

Atomic-level understanding of the nature of the electronically excited states in ligand-stabilized metal nanoclusters (NCs) is a prerequisite for the design of new NCs with desired properties. In this study, we investigate the emission dynamics of a Ag-DNA complex using the fluorescence up-conversion technique. We show that most of the relaxation from the Franck-Condon state to the emissive state takes place in less than 100 fs, in spite of a relatively large Stokes shift of 4500 cm-1.

DNA as UV light-harvesting antenna.

The ordered structure of UV chromophores in DNA resembles photosynthetic light-harvesting complexes in which quantum coherence effects play a major role in highly efficient directional energy transfer. The possible role of coherent excitons in energy transport in DNA remains debated. Meanwhile, energy transport properties are greatly important for understanding the mechanisms of photochemical reactions in cellular DNA and for DNA-based artificial nanostructures.

DNA with Ionic, Atomic, and Clustered Silver: An XPS Study.

The rapidly developing field of bionanotechnology requires detailed knowledge of the mechanisms of interaction between inorganic matter and biomolecules. Under conditions different from those in an aqueous solution, however, the chemistry of these systems is elusive and may differ dramatically from their interactions in vitro and in vivo. Here, we report for the first time a photoemission study of a metal silver-DNA interface, formed in vacuo, in comparison with DNA-Ag and fluorescent DNA-Ag complexes formed in solution.

Ag-DNA Emitter: Metal Nanorod or Supramolecular Complex?

Ligand-stabilized luminescent metal clusters, in particular, DNA-based Ag clusters, are now employed in a host of applications such as sensing and bioimaging. Despite their utility, the nature of their excited states as well as detailed structures of the luminescent metal-ligand complexes remain poorly understood. We apply a new joint experimental and theoretical approach based on QM/MM-MD simulations of the fluorescence excitation spectra for three Ag clusters synthesized on a 12-mer DNA.

Noncanonical Stacking Geometries of Nucleobases as a Preferred Target for Solar Radiation.

Direct DNA absorption of UVB photons in a spectral range of 290-320 nm of terrestrial solar radiation is responsible for formation of cyclobutane pyrimidine dimers causing skin cancer. Formation of UVB-induced lesions is not random, and conformational features of their hot spots remain poorly understood. We calculated the electronic excitation spectra of thymine, cytosine, and adenine stacked dimers with ab initio methods in a wide range of conformations derived from PDB database and molecular dynamics trajectory of thymine-containing oligomer.

Fluorescent silver nanoclusters in condensed DNA.

We study the formation and fluorescent properties of silver nanoclusters encapsulated in condensed DNA nanoparticles. Fluorescent globular DNA nanoparticles are formed using a dsDNA-cluster complex and polyallylamine as condensing agents. The fluorescence emission spectrum of single DNA nanoparticles is obtained using tip-enhanced fluorescence microscopy.