The search for prebiotic chemical pathways to biologically relevant molecules and their precursors has been a longstanding puzzle. On the basis of our previous experimental study, a general scheme for prebiotic reaction routes from formamide to different precursors and pyrimidine bases, namely, cytosine, uracil, 5-methylcytosine, thymine, isocytosine, and 2,4-diaminopyrimidine, is proposed. All required precursors, such as hydrogen cyanide, ammonia, water, formic acid, isocyanic acid, formyl cyanide, cyanamide, urea, 2-aminoacetonitrile, guanidine, formaldehyde, cyanovinylalcohol, and cyanoacetaldehyde, needed in the reactions are obtained by decomposition of the starting compound, namely, formamide. In these reactions, formamide and its tautomer, formimidic acid, as well as formic acid, play the role of a proton-carrying catalyst. A diverse reactivity landscape was revealed within just a few steps of those of these simple molecules. Reaction pathways to cytosine and uracil were discovered, involving lower activation energies and fewer reaction steps compared with those of proposed alternatives. Accounting for formamide-catalyzed reactions qualitatively affects the interpretation of the reaction kinetics.

Two series of cationic monoalkynyl Pt(II) complexes [Pt(terpy)(C2-L-P(O)Ph2)][X] with different counterions and alkynylphosphine oxide ligands (L = no linker, 0[X]; phenylene, 1[X]; biphenylene, 2[X]; naphthylene, 3 [X]; terpy = 2,2 ':6 ',2 ''-terpyridine; X = Cl-, BArF-tetrakis-((bis-(trifluoromethyl)phenyl)borate)) have been synthesized and characterized by spectroscopic methods. Optical and photophysical data show that in solution emission origin and energy are controlled by the structure of it-conjugated linker. In contrast, in the solid state, the anion size is the main factor which determines luminescence properties and stimuli-responsive behavior. Complexes with small Cl-counterion show red to NIR 3MMLCT emission that can be altered by mechanical treatment or exposure under MeOH/H2O vapor. Metathesis to bulky BArF-anion results in significant hypsochromic shift and less pronounced luminescence response to external stimuli. In addition, both series of complexes demonstrate different response to addition of polyfluoroarenes (C6F6, C6F5I, 1,4-C6F4I2). As a result, the combination of different responses allows for the realization of multi-color luminescence in a wide range of wavelengths for a single complex. TDDFT calculations are consistent with the experimental results and assign mixed 3ILCT and 3MLCT emission character for individual molecule. Comparison of the contributions to NTO between the 1[X]-3[X] and previously reported monoalkynylphosphonium complexes showed that the structure of alkynyl ligand substituent (-P(O)Ph2/-P+MePh2) has a significant effect on the electronic structure of excited states.

Among six hydrazones derived from pyridoxal 5 '-phosphate and hydrazides of isonicotinic (PLP-INH), nicotinic (PLP-NH), picolinic (PLP-PH), pyrazinoic (PLP-PRZ), 2-furoic (PLP-F2H), and thienyl-2-carboxylic (PLP-T2H) acids, the two first ones differ from other four as they show no fluorescent while irradiated by light with lambda ex = 365 nm despite sharing the similar structure with others. To understand the reason of such different behavior of the structural analogs, we delved into photophysical study of the hydrazones registering their excitation and emission spectra in crystalline phase and amorphous powder at room temperature and 77 K. The quantum yield and lifetimes of the excited stated were also measured allowing for deriving the rate constants of radiative and non-radiative decay of the excited states. Unusual dual-band character of the emission spectra was observed for five of six hydrazones (save PLP-INH), which was explained by the coexistence of two different conformers in the solid phase. Quantum chemical calculations were performed to test such a hypothesis. The conformers most preferred energetically as well as the unstable ones were selected and shown (using TD DFT) to have different fluorescent electron transitions. The stable structures possessing red-shifted emission bands are suggested to populate the amorphous phase, while the unstable species emitting within the shorter wavelength range belong in crystal phase. For PLP-INH, the exceptional relationship between the vertical electron transitions of stable and unstable conformers was noted.

Two series of heteroleptic monoalkynylphosphonium Pt(II) complexes decorated with 2,2':6',2''-terpyridine (terpy, N series) and 6-phenyl-2,2'-bipyridine (phbpy, C series) ligands, were prepared and characterized by spectroscopic methods. The complexes obtained exhibit triplet emission in solution, and the characteristics inside the series depend on the nature of the alkynylphosphonium ligand. The description of electronic transitions responsible for energy absorption and emission in discrete Pt(II) complexes was made on the basis of a detailed analysis of the results of DFT calculations, and has shown to involve MLCT, ILCT, and LLCT transitions. The complexes of both series exhibit triplet solid-state luminescence with parameters that also depend on the composition of the complexes, and the analysis of the experimental data indicates the realization of LC, MLCT, MMLCT, and MC transitions due to Pt & ctdot;Pt metallophilic interactions and matrix rigidity. It was shown that the anion variation leads to a significant difference in the photophysical characteristics of the N complexes, which exhibit a smooth dependence of the luminescent properties on the anion size. Using quantum chemical modeling, it is demonstrated how the anion size influences the Pt & ctdot;Pt distance in the solid state.

Herein, the detailed mechanism of intramolecular proton transfer in molecular switches, constructed from 7-hydroxy quinoline substituted in the eight-position C-C single axle, connected to three different proton cranes (morpholine, piperidine, and 1,3,5-dioxazine), was investigated by means of theoretical chemistry. The theoretical interpretation of the rotational mechanism and its stable structures were proposed for the well-known Varma's proton crane, based on morpholine molecule. The reliability of the theoretical simulations was confirmed by the available literature data from time-dependent IR measurements.

New proton cranes based on 7-hydroxy-quinoline and 3-hydroxypyridine.

The tautomeric properties of favipiravir were investigated experimentally for the first time by using molecular spectroscopy (UV–Vis absorption, fluorescence and NMR), as well as DFT quantum–chemical calculations. According to the obtained results, the enol tautomer is substantially more stable in most of the organic solvents. In the presence of water, a keto form appears to be favored due to the specific solute–solvent interactions. Upon the addition of alkaline-earth-metal ions, deprotonation and complexation occurred simultaneously, giving the formation of 2 : 1 ligand : metal complexes. According to the theoretical simulations, the metal ion is captured between the carbonyl groups as a result of the size–fit effect.

A series of heteroleptic bis-alkynyl-diimine mononuclear Pt(II) complexes with alkynylphosphonium and di-tert-butyl-2,2'-bipyridine (dtbpy) ligands have been prepared and characterized by spectroscopic methods and single-crystal XRD. The Pt(II) complexes obtained in the present study demonstrate triplet emission in solution, which originates from 3MLCT/3LC states where the nature of the π-conjugated linker in the alkynylphosphonium ligand manages the contributions of each transition, and this conclusion is supported by DFT calculations. Additionally, the presence of the phosphonium group connected to alkynyl through the π-conjugated linker enhances nonlinear optical properties of the Pt(II) complexes increasing two-photon absorption cross section up to 400 GM. In the solid state, the Pt(II) complexes demonstrate emission that is attributed to 3MMLCT transitions due to the presence of Pt-Pt metallophilic interactions, and the reversible assembly and disassembly of these interactions by grinding and solvent treatment are responsible for the mechanochromic luminescence. It has been experimentally shown that stimuli-responsive emission of the Pt(II) complexes is the result of a "monomer/dimer" transformation; this conclusion is confirmed by DFT calculations for discrete complexes and different dimers with or without Pt-Pt interactions.

In this work we show, using the example of a series of [Cu(Xantphos)(N^N)]+ complexes (N^N being substituted 5-phenyl-bipyridine) with different peripheral N^N ligands, that substituents distant from the main action zone can have a significant effect on the physicochemical properties of the system. By using the C≡C bond on the periphery of the coordination environment, three hybrid molecular systems with −Si(CH3)3, −Au(PR3), and −C2HN3(CH2)C10H7 fragments were produced. The Cu(I) complexes thus obtained demonstrate complicated emission behaviour, which was investigated by spectroscopic, electrochemical, and computational methods in order to understand the mechanism of energy transfer. It was found that the −Si(CH3)3 fragment connected to the peripheral C≡C bond changes luminescence to long-lived intra-ligand phosphorescence, in contrast to MLCT phosphorescence or TADF. The obtained results can be used for the design of new materials based on Cu(I) complexes with controlled optoelectronic properties on the molecular level, as well as for the production of hybrid systems.

We report herein a family of polynuclear complexes, [Au@Ag4(Py3P)4]X5 and [Au@Cu4(Py3P)4]X5 [X = NO3, ClO4, OTf, BF4, SbF6], containing unprecedented Au-centered Ag4 and Cu4 tetrahedral cores supported by tris(2-pyridyl)phosphine (Py3P) ligands. The [Au@Ag4]5+ clusters are synthesized via controlled substitution of the central Ag(I) ion in all-silver [Ag@Ag4]5+ precursors by the reaction with Au(tht)Cl, while the [Au@Cu4]5+ cluster is assembled through the treatment of a pre-organized [Au(Py3P)4]+ metallo-ligand with 4 equiv of a Cu(I) source. The structure of the Au@M4 clusters has been experimentally and theoretically investigated to reveal very weak intermolecular Au-M metallophilic interactions. At ambient temperature, the designed compounds emit a modest turquoise-to-yellow luminescence with microsecond lifetimes. Based on the temperature-dependent photophysical experiments and DFT/TD-DFT computations, the emission observed has been assigned to an MLCT or LLCT type depending on composition of the cluster core.

Reaction pathway of prebiotic reactions for formation of the pteridines: pterin, xanthopterine, isoxanthopterine and leucopterine, as well as the purine nucleobase guanine from pure formamide are presented. In these reactions, formamide or its tautomer, formimidic acid, play the role of proton-carrying catalyst. All required raw materials, such as hydrogen cyanide, ammonia, water, formic acid, urea, 2-aminomalononitrile, glyoxal, glyoxylic acid and oxalic acid needed in the self-catalyzed reactions are obtained by partial decomposition of formamide. We show that the prebiotic formation of nucleobases and pterins is closely linked and they probably coexisted at the beginning of chemical evolution.

Mechanisms of reactions for formylation of urea, leading toN,N '-diformylurea, and for the dehydration of glycinamide andN,N '-diformylurea, yielding hypoxanthine, are suggested. It is shown that these reactions are self-catalyzed. The first is catalyzed by formic acid, while the second is catalyzed byN,N '-diformylurea. The suggested reaction mechanism shows that the N3 and N9 atoms of hypoxanthine originate from urea in agreement with available(1)H NMR experimental data by Lagoja and Herdewijn (Lagoja & Herdewijn,Chem. Biodiv.2004, 1, 106). A complete reaction pathway of prebiotic reactions for formation of the hypoxanthine from urea, formic acid, and glycinamide in formamide, where formamide/formimidic acid plays the role of a proton-carrying catalyst, is also suggested.

A series of organometallic complexes containing an alkynylphosphinegold(I) fragment and a phenylene-terpyridine moiety connected together by flexible linker have been prepared using the specially designed terpyridine ligands. The compounds were studied crystallographically to reveal that all of them contain a linearly coordinated Au(I) atom and a free terpyridine moiety. The different orientations of the molecules relative to each other in the solid state determine the multiple noncovalent interactions such as antiparallel ππ stacking, CH-π, and CH-Au, but no aurophilic interactions are realized. The organometallic Au(I) complexes obtained show fluorescence in the solution and dual singlet-triplet emission in the solid state. This means that their photophysical behavior is determined by both intermolecular lattice-defined interactions and Au(I) atom introduction. Density functional theory computational analysis supported the assignment of emission to intraligand electronic transitions only inside the phenylene-terpyridine part with no Au(I) involved. In addition, a study of the nature of the excited states for the "dimer" with an antiparallel orientation of the terpyridine fragment showed that this orientation leads to the generation of abstracted singlet and triplet states, lowering their energy in comparison with the monomer complex. Thus, the complexes obtained can be qualified as examples of Au(I)-containing organometallic aggregation-induced-emission luminogens.

Molecular dynamics simulations were carried out for a finite sample of NaA zeolite in contact with bulk carbon dioxide in a wide range of temperatures and CO2 contents. Density and diffusion profiles were obtained to estimate the depth at which the external surfaces of the zeolite affect CO2 diffusion in porous space. The approximate depth of surface effects for NaA zeolite was estimated as ca. 2 nm, though this figure may vary depending on temperature and adsorbed gas density. Diffusion coefficients and diffusion activation energies were calculated for CO2 and Na+ in the bulk-like region of the zeolite. Diffusion activation energy for carbon dioxide demonstrated a non-monotonic dependence on the amount of adsorbed gas.

Complete reaction pathway of prebiotic reactions for formation of the purine nucleobases adenine, hypoxanthine, guanine, isoguanine, 2,6-diaminopurine, and xanthine from pure formamide are presented. All reactants (hydrogen cyanide, ammonia, water, formic acid, urea) and catalysts (formamide and formimidic add) needed in the self-catalyzed reactions are available from a starting compound, formamide. The required raw materials are obtained by partial decomposition of formamide.

Abiotic synthesis of nucleobases and amino acids is of critical importance as it sheds light on potential prebiotic chemical reactions. During thermal decomposition of formamide in vacuum conditions, purine, cytosine, adenine, hypoxanthine, uracil, pterin, urea, urocanic acid, glycine, alanine and norvaline were detected. The compounds were obtained without catalyst by heating at 100-180 °C or microwave heating of formamide. Reaction network of self-catalyzed chemical reactions is suggested, showing how from only one parent molecule, nucleobases, urea and the amino acid glycine can be produced. The reaction pathways are theoretically determined using SCS-MP2 calculations.Communicated by Ramaswamy H. Sarma.

Chromophore-containing phosphines produce highly solvatochromic gold(i) fluorophores. Their combination with red-emitting Eu centers offers a facile approach to dual emissive complexes with widely tunable luminescence characteristics.

A substituted pyridazine acts as a sensitizer in mononuclear heteroleptic Ln(iii) complexes.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.