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πAromatic circuits involving 198 electrons.

The experimentally characterized hexamethylbenzene dication C6(CH3)62+ shows a pentagonal-pyramidal structure involving a carbon-capped five-membered ring. The structural characterization of this hypercoordination (or hypervalency) gives rise if the aromatic behavior remains in the resulting pentagon ring. Here, we investigated the induced magnetic field of C6(CH3)62+ to gain a deeper understanding of the resulting non-classical structural situation in a representative pentagonal-pyramidal structure. Our results support the view of a C5(CH3)5−/CCH33+ structure, depicting a π-aromatic pentamethylcyclopentadienyl anion with a 6π-electron kernel, with a capped carbon which does not decrease the characteristic shielding cone property of the aromatic ring. Hence, carbon-capped rings are suggested to retain the aromatic behavior from the former aromatic ring. We expect that the analysis of both the overall magnetic response and NMR chemical shifts may be informative to unravel the characteristic patterns in the formation of hypervalent carbon atoms involving non-classical chemical environments.

International audience; The iconic W@Au(12) icosahedral bare cluster reaches the favorable closed-shell superatomic electron configuration 1S(2) 1P(6) 1D(10), making it an 18-cluster electron (18-ce) superatom. Here, we pursue the evaluation of a ligand-protected counterpart based on the construction of a fully phosphine-protected [W@Au(12)(dppm)(6)] cluster strongly related to the characterized [Au(13)(dppm)(6)](5+) homometallic counterpart. The later cluster has the same total number of valence electrons as the former but is considered an 8-ce superatom with 1S(2) 1P(6) configuration. The fundamental differences between 8- and 18-ce species are investigated. The character of the frontier orbitals varies from 1P/1D in the 8-ce case to a 1D/ligand for 18-ce species, enabling an efficient charge transfer toward the ligands upon irradiation, being interesting for electron injection in optoelectronic devices and black absorbers applications. Excited-state properties are also revisited, showing different geometrical and electronic structure variations between 8- and 18-ce species. Moreover, the continuum between the 8- and 18-ce limits has been explored by varying the nature of the encapsulated dopant between group 6 and group 11. The transition between the 8- and 18-ce counts can be formally situated between Pt (8-ce) and Ir (18-ce). Thus, 18-ce derivatives obtained as doped counterparts of homometallic gold clusters can introduce useful alternatives to achieve different properties in related structural motifs, which can be further explored owing to their extension of the well-established versatility of current gold nanoclusters.

Relevant virulence traits in Candida are associated with the dimorphic change and biofilm formation, which became an important target to reduce the antifungal resistance. In this work, Co(II) complexes containing a benzotriazole derivative ligand showed a promising capacity of reduce these virulence traits. These complexes exhibited higher antifungal activities than the free ligands against all the Candida albicans and non-albicans strains tested, where compounds 2 and 4 showed minimum inhibitory concentration values between 15.62 and 125 µg mL− 1. Moreover, four complexes (2–5) of Co(II) and Cu(II) with benzotriazole ligand were synthesized. These compounds were obtained as air-stable solids and characterized by melting point, thermogravimetric analysis, infrared, Raman and ultraviolet/visible spectroscopy. The analysis of the characterization data allowed to identify that all the complexes had 1:1 (M:L) stoichiometries. Additionally, Density Functional Theory calculations were carried out for 2 and 3 to propose a probable geometry of both compounds. The conformer Da of 2 was the most stable conformer according to the Energy Decomposition Analysis; while the conformers of 3 have a fluxional behavior in this analysis that didn’t allow to recognize the most probable conformer. These results provide an important platform for the design of new compounds with antifungal activities and capacity of attack other target of relevance to reduce the antimicrobial resistance.

Cyclo-para-phenylene (CPP) nanobelt structures with curved π-surfaces are of relevance in the development of desirable building units for materials science. Dimeric [10]CPP motifs have been reported ([10]SCPP), extending the individual features to fused nanobelts sharing structural components. Our results indicate a local-aromatic behavior of the neutral dimeric motif, leading to a switched-on character upon di- and tetra-oxidation resulting in the formation of two long-ranged shielding regions at the center of each [10]CPP fused unit. This evaluation shows the ability to enable two global aromatic circuits to compromise the overall carbon backbone, instead of being located exclusively at each phenylene ring. Thus, fused nanobelt structures are able to sustain a dual global aromatic behavior, which can be switched-on

With the advancement of combinatorial chemistry and big data, drug repositioning has boomed. In this sense, machine learning and artificial intelligence techniques offer a priori information to identify the most promising candidates. In this study, we combine QSAR and docking methodologies to identify compounds with potential inhibitory activity of vasoactive metalloproteases for the treatment of cardiovascular diseases. To develop this study, we used a database of 191 thermolysin inhibitor compounds, which is the largest as far as we know. First, we use Dragon's molecular descriptors (0-3D) to develop classification models using Bayesian networks (Naive Bayes) and artificial neural networks (Multilayer Perceptron). The obtained models are used for virtual screening of small molecules in the international DrugBank database. Second, docking experiments are carried out for all three enzymes using the Autodock Vina program, to identify possible interactions with the active site of human metalloproteases. As a result, high-performance artificial intelligence QSAR models are obtained for training and prediction sets. These allowed the identification of 18 compounds with potential inhibitory activity and an adequate oral bioavailability profile, which were evaluated using docking. Four of them showed high binding energies for the three enzymes, and we propose them as potential dual ACE/NEP inhibitors for the control of blood pressure. In summary, the in silico strategies used here constitute an important tool for the early identification of new antihypertensive drug candidates, with substantial savings in time and money.

We show the synthesis and characterization of four heterobimetallic compounds derived from s-indacene of general formula [{(CO)3Mn}-s-Ic-{MCp*}]q with M = Fe, Co, Ni, and Ru; q = 0, 1+. The complexes reported here were characterized by 1H and 13C NMR, elemental analysis and FT-IR. Additionally, the X-ray crystal structure of [(CO)3Mn-s-Ic-FeCp*] (1) and Mossbauer spectra are reported. The heterobimetallic compounds exhibit higher quasireversible redox potentials compared with ferrocene and catocene under the same reaction conditions. The complexes were tested as catalysts on the thermal decomposition of ammonium perchlorate examined by a differential scanning calorimetry technique to study their catalytic behavior. Compound (1) causes a decrease of ammonium perchlorate's decomposition temperature to 315 °C, consequently increasing the heat release by 138 J·g-1. Conversely, [{(CO)3Mn}-s-Ic'-{CoCp*}] (2) presents a higher heat release (2462 J·g-1), comparable to catocene.

Recently, P. V. Nhat et al., have discussed and commented on our article (DOI: 10.1039/D0CP04018E) for the case of the most stable structure of Ag15. They have found a new most stable structure (labeled as 15-1) in comparison to the putative global minimum reported by us, which is a four layered 1-4-6-4 stacking structure with a C2v point group (15-2). In this reply, we have performed a larger structure search which allowed us to confirm the results of Nhat et al. The results show the existence of multiple isoenergetic isomers with similar structure motifs for the Ag15 system, increasing the problem complexity to locate the global minimum. The results in regard to the structure and electronic properties of the new lowest energy structure are discussed.

In the present work, the lowest energy structures and electronic properties of Agn clusters up to n = 16 are investigated using a successive growth algorithm coupled with density functional theory calculations (DFT). In the literature, a number of putative global minimum structures for silver clusters have been reported by using different approaches, but a comparative study for n = 15-16 has not been undertaken so far. Here, we perform a comparative study using the PW91/cc-pVDZ-PP level to more precisely determine the optimal configuration. For Ag15, the most stable configuration is a four layered 1-4-6-4 stacking structure with C2v symmetry. For Ag16 a new most stable form is found with a 1-4-2-5-1-3 stacking structure in the singlet state, slightly more stable than the putative global minimum reported. By means of the electrostatic potential, the new putative global minimum has been found to be more reactive, and the active sites of the clusters were identified and confirmed with the interaction energy. The electronic and vibrational properties are found to be in good agreement with the available experimental data. Theoretical data on the infrared spectra of the clusters is also provided.

Gold clusters are useful templates for nanosized species retaining a distinctive size-dependent behavior. Usually, a ligand-protected shell passivates such clusters, where their properties can be p...

Different theoretical methodologies were applied to a series of substituted benzenes C6X6 (with X = H, F, Cl, Br and I) to pursue the property of aromaticity. HOMA (as structural criterion), NICS (FIPC-NICS, isotropic and ZZ employed as magnetic criteria) as well as the indexes ASE, MCI, PDI and FLU, interestingly provided controversial data respect to the magnetically induced current density plots and chemical intuition, which is extensively discussed in the herein work. Furthermore, EDA-NOCV was used to complement the rational explanation of the observed results.

Recently, P. V. Nhat et al., have discussed and commented on our article (DOI: 10.1039/D0CP04018E) for the case of the most stable structure of Ag15. They have found a new most stable structure (labeled as 15-1) in comparison to the putative global minimum reported by us, which is a four layered 1-4-6-4 stacking structure with a C2v point group (15-2). In this reply, we have performed a larger structure search which allowed us to confirm the results of Nhat et al. The results show the existence of multiple isoenergetic isomers with similar structure motifs for the Ag15 system, increasing the problem complexity to locate the global minimum. The results in regard to the structure and electronic properties of the new lowest energy structure are discussed.

The search for new antibacterial agents that could decrease bacterial resistance is a subject in continuous development. Gram-negative and Gram-positive bacteria possess a group of metalloproteins belonging to the MEROPS peptidase (M4) family, which is the main virulence factor of these bacteria. In this work, we used the previous results of a computational biochemistry protocol of a series of ligands designed in silico using thermolysin as a model for the search of antihypertensive agents. Here, thermolysin from Bacillus thermoproteolyticus, a metalloprotein of the M4 family, was used to determine the most promising candidate as an antibacterial agent. Our results from docking, molecular dynamics simulation, molecular mechanics Poisson&ndash, Boltzmann (MM-PBSA) method, ligand efficiency, and ADME-Tox properties (Absorption, Distribution, Metabolism, Excretion, and Toxicity) indicate that the designed ligands were adequately oriented in the thermolysin active site. The Lig783, Lig2177, and Lig3444 compounds showed the best dynamic behavior, however, from the ADME-Tox calculated properties, Lig783 was selected as the unique antibacterial agent candidate amongst the designed ligands.

The search for new antibacterial agents that could decrease bacterial resistance is a subject that is continuously developing. The Gram-negative and Gram-positive bacteria have a metalloproteins group belonging to the M4 family. That is the main virulence factor of these bacteria. In this work, we have used a computational protocol based on the comprehensive analysis of the results of docking, molecular dynamics simulation, MM-PBSA, ligand efficiency, and ADME-Tox properties of ligand designed in silico in the previous manuscript using the Thermolysin from Bacillus thermoproteolyticus, a metalloprotein of the M4 family as a target. The principal results obtained were the designed ligands were adequately oriented in the thermolysin active center. The Lig783, Lig2177, and Lig3444 compounds were those with better dynamic behavior, however, when analyzing the results extracted from the ADME-Tox properties, only Lig783 was the best antibacterial agent candidate.

In the present work, the lowest energy structures and electronic properties of Agn clusters up to n = 16 are investigated using a successive growth algorithm coupled with density functional theory calculations (DFT). In the literature, a number of putative global minimum structures for silver clusters have been reported by using different approaches, but a comparative study for n = 15-16 has not been undertaken so far. Here, we perform a comparative study using the PW91/cc-pVDZ-PP level to more precisely determine the optimal configuration. For Ag15, the most stable configuration is a four layered 1-4-6-4 stacking structure with C2v symmetry. For Ag16 a new most stable form is found with a 1-4-2-5-1-3 stacking structure in the singlet state, slightly more stable than the putative global minimum reported. By means of the electrostatic potential, the new putative global minimum has been found to be more reactive, and the active sites of the clusters were identified and confirmed with the interaction energy. The electronic and vibrational properties are found to be in good agreement with the available experimental data. Theoretical data on the infrared spectra of the clusters is also provided.

Flagellin is the major component of the flagellum, and a ligand for Toll-like receptor 5. As reported, recombinant flagellin (rFLA) from Vibrio anguillarum and its D1 domain (rND1) are able to promote in vitro an upregulation of pro-inflammatory genes in gilthead seabream (Sparus aurata) and rainbow trout (Oncorhynchus mykiss) macrophages. This study evaluated the in vitro and in vivo stimulatory/adjuvant effect for rFLA and rND1 during P. salmonis vaccination in Atlantic salmon (Salmo salar). We demonstrated that rFLA and rND1 are molecules able to generate an acute upregulation of pro-inflammatory cytokines (IL-1β, IL-8, IL-12β), allowing the expression of genes associated with T-cell activation (IL-2, CD4, CD8β), and differentiation (IFNγ, IL-4/13, T-bet, Eomes, GATA3), in a differential manner, tissue/time dependent way. Altogether, our results suggest that rFLA and rND1 are valid candidates to be used as an immuno-stimulant or adjuvants with existing vaccines in farmed salmon.

La ciencia nos rodea y esta en todas las cosas que hacemos a diario, solo que a veces pensamos que es mas compleja… ipero no lo es! Junto a investigadores e investigadoras del Instituto de Ciencias Quimicas Aplicadas de la Universidad Autonoma de Chile, Con las manos en la ciencia te invita a descubrir algunos fenomenos cientificos sin necesidad de estar en un laboratorio ni salir de tu casa.

The high yield synthesis, characterization and biological trials of a family of compounds containing the pyrazole core (E)-3,5-dimethyl-1-(4-R-phenyl)-4-(phenyldiazenyl)-1H-pyrazoles (with R = 4-CH3O (1), 4-CH3 (2), 4-H (3), 4-F (4), 4-Cl (5), 4-CF3 (6), 4-CN (7), 4-NO2 (8), 3-Cl (9), 3-NO2 (10), 2-Cl (11) and C6F5 (12)) are reported. Hammett correlations were found for the experimental and theoretical computed data, showing the dependence of all the obtained results on the donor or acceptor nature of the R substituent. In this sense, the absorption wavelength does decrease as the electron-withdrawing character of the substituent increases. Furthermore, the wavelength intensity does follow a Hammett correlation with the sigma donor character of the substituents. The compounds were characterized using MP, EA, UV–vis, FT-IR, 1H NMR, 13C NMR including bidimensional NMR experiments (HMBC and HMQC). The structures of 4, 5 and 8 were successfully elucidated by means of X-Ray diffraction. Pyrazole based dyes are known in pharmacological areas. Therefore, biological activity of all these structures were tested against cancer cell lines over a wide library of cell lines (60), including leukemia, colon and brain cancer, showing that the compounds have anticancer activity, which expands the knowledge of this kind of dyes as targets for this critical application. Finally, quantum calculations were carried out in order to give a rational explanation to the observed UV–vis absorption bands and FT-IR signals. As shown, it is possible to tune the molecular/electronic structure of the synthesized dyes by means of changing the R substituent in the structure.

In this letter, we discussed the plausible formation of [Au11Re] as a superatom with an electronic structure accounted by the 1S21P61D10 shell order, denoting similar stability to [W@Au12]. The possible hollow or endohedral structures show a variable HOMO-LUMO gap according to the given structure (from 0.33 to 1.30 eV, at the PBE/ZORA level). Our results show that the energy minimum is an endohedral arrangement, where Re is encapsulated in a D3h-Au11 cage, retaining a higher gold-dopant stoichiometric ratio. This approach is useful for further rationalization and design of novel superatoms expanding the libraries of endohedral clusters.

Spatial race under low oxygen conditions requires solid mild propellants to be used. Therefore, we study the catalytic effect of the previously reported [trans-Cu(μ-OH)(μ-dmpz)]6 complex on the thermal decomposition of ammonium perchlorate by a differential scanning calorimetry (DSC) technique. The copper compound causes a decrease of ammonium perchlorate’s decomposition temperature to 372.5 °C, consequently increasing the heat release by 576 J·g−1, when used in a 5 wt% as burning rate (BR) catalyst. It must be remarked that, the [trans-Cu(μ-OH)(μ-dmpz)]6 complex presents a superior performance as BR catalyst when compared to nano-metallic oxides. This Cu(II) compound modifies the decomposition mechanism of ammonium perchlorate, providing the necessary O2 to accelerate the overall burning process paving the way to the study of copper pyrazolate complexes as BR catalysts.

We present a study of the magnetically induced current density, calculated using London atomic orbitals, for the cis and trans isomers of dihydroindeno-[1,2-b]-fluorene (IF) and a set of 12 substituted macrocycles (where R = H, NH2, O-tBu, CH3, Si(CH3)3, OH, OCH3, F, Cl, Br, CN and NO2). Qualitative and quantitative analyses were done at Hartree–Fock and density functional theory (DFT) levels. The DFT results are not very sensitive to the choice of the density functional (BLYP and B3LYP). We found a linear correlation between the integrated magnetic susceptibilities values (χtotal) and Hammett parameters (σp) of the substituent group bonded directly to the outer six-member rings of the macrocycle structure. Our results suggest that the aromaticity of IF is not extensively modified by the presence of acceptor and donor substituent groups. The effect is rather local, and only strong π donor ligands lead to an aromaticity decrease of the outer six-member rings of the macrocycle directly attached to the substituent. Therefore, this series of indenofluorene derivatives correspond to a set of alternant aromatic and antiaromatic ring moieties, rather than a completely delocalized system. The effect of IF derivatives on the local aromaticity could not be reproduced using the nucleus independent chemical shift (NICS) calculations, which seem insensitive to the change of ligands.

The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu2(μ − I)2(μ − L)2]n, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.

In this article, we employed density functional theory calculation methods to determine the relationship between the chemical hardness (η), intermolecular chemical hardness (η DA), and nucleophilicity (N) chemical reactivity descriptors, as well as the energy of the occupied frontier orbitals (E a1g), and the electrocatalytic activity of different metallophthalocyanines [MPc’s with M=Cr(II), Mn(II), Fe(II), Co(I), Ni(II), and Cu(II)] for the oxygen reduction reaction. Our results suggest that η DA, N, and E a1g are appropriate parameters to estimate the electrocatalytic activity. On the other hand, the type of the metallic center determines the strength of the oxygen-binding energy, where a strong electronic interaction promotes the efficient electro-reduction of the dioxygen molecule, which is observed experimentally as a high catalytic activity.

The search for new therapies for the treatment of Arterial hypertension is a major concern in the scientific community. Here, we employ a computational biochemistry protocol to evaluate the performance of six compounds (Lig783, Lig1022, Lig1392, Lig2177, Lig3444 and Lig6199) to act as antihypertensive agents. This protocol consists of Docking experiments, efficiency calculations of ligands, molecular dynamics simulations, free energy, pharmacological and toxicological properties predictions (ADME-Tox) of the six ligands against Thermolysin. Our results show that the docked structures had an adequate orientation in the pocket of the Thermolysin enzymes, reproducing the X-ray crystal structure of Inhibitor-Thermolysin complexes in an acceptable way. The most promising candidates to act as antihypertensive agents among the series are Lig2177 and Lig3444. These compounds form the most stable ligand-Thermolysin complexes according to their binding free energy values obtained in the docking experiments as well as MM-GBSA decomposition analysis calculations. They present the lowest values of Ki, indicating that these ligands bind strongly to Thermolysin. Lig2177 was oriented in the pocket of Thermolysin in such a way that both OH of the dihydroxyl-amino groups to establish hydrogen bond interactions with Glu146 and Glu166. In the same way, Lig3444 interacts with Asp150, Glu143 and Tyr157. Additionally, Lig2177 and Lig3444 fulfill all the requirements established by Lipinski Veber and Pfizer 3/75 rules, indicating that these compounds could be safe compounds to be used as antihypertensive agents. We are confident that our computational biochemistry protocol can be used to evaluate and predict the behavior of a broad range of compounds designed in silicoagainst a protein target.

Context. Formaldehyde H2CO was the first organic polyatomic molecule discovered in the interstellar medium to have been detected in a variety of sources. However, pathways to synthesize this molecule under interstellar conditions have yet to be discussed. Aims. We carried out a systematic study to analyze the chemical processes that can explain the H2CO formation mechanism toward a decamer of methanol (CH3OH)10 as target material to mimic an ice mantle bombarded by an OH+ cation. Methods. We performed Born-Oppenheimer (ab initio) molecular dynamics simulations to obtain the formation mechanisms of complex organic molecules (COMs) such as formaldehyde H2CO and its HCOH isomer. Results. We found that CH2OH+ and CH2(OH)2 are the main precursors to form H2CO and HCOH. We discuss its formation mechanisms and the astrophysical implications in star-forming regions. These processes are likely relevant to the production of COMs.

The use of different N-heterocyclic carbene (NHC) as dative ligands benefits from their capabilities ranging from strong to weak σ-donor according to the Tolman electronic parameter (TEP), well spread in the formation of monometallic complexes, and recently extended to metallic nanocluster and surfaces. Here, we set to explore the role of relativistic effects in determining the stabilization of the dative carbon–metal bond on coinage metal complexes given by NHC-MCl species (M = Cu, Ag, Au), by quantifying their contribution to the different terms related to the bond formation by comparing scalar relativistic and non-relativistic DFT calculations. Our results show a strong contribution to the stabilization of the NHC-M bond, increasing along with the group, from the lighter Cu atom (7.9%) to Ag (15.3%), and most notoriously for the heavier member, Au (39.9%). This observation is similar along the different stabilizing terms related to the C-M bond, where the acceptor character of the metal center is affected, resulting in a stronger σ-donor interaction from the involved ligand. Thus, the theoretical evaluation of carbon–metal bonds requires the equal footing treatment of relativistic effects along with the group, which is beneficial for the theoretical evaluation of ligand capabilities prior to the engaging exploration of the efficient formation of related complexes involving lighter to heavy metallic centers.

We report the molecular and electronic structure, and the calculated electronic excitation energies, using the time dependent density functional methodologies (TD-DFT), and the induced magnetic field (Bi) of a series of Cu(I) dithiolato and diselenolato species of formula [Cu8(L)6]. They are composed by eight copper atoms forming a Cu8 cube and six bidentate ligands (L), where twelve chalcogen atoms (Q) bridging the edges of the copper cube, in such a way that chalcogen atoms describe an icosahedron, enclosing a cubic [Cu8( μ -Q12)]4− core of Th symmetry. The Q…Q bite distance is similar in all clusters, without being influenced by the Cu-Cu distance, suggesting the existence of metallophilic interactions that stabilize the cluster structure. Despite of the structural similarities, the electronic structure of these clusters present some differences which are magnified on their optical properties. Excitation energies and their composition depend on the nature of each different ligand in these clusters, according to CT λ ( M ) index to determine the ligand to metal (LM) or metal to ligand charge transfer (MLCT) character of each calculated electronic transition. The magnetic properties calculations show the importance to separate the magnetic response into their individual components (Bi with i = x, y, z, iso), and diamagnetic and paramagnetic contributions to understand the differences according to the type of ligand on the cluster structure.

In this article, a serie of density functional theory (DFT) calculations were carried out on Keggin heteropolyanions [ XM 12 O 40 ] n - (X = Sn(IV), Sb(V) and Te(VI); M = Mo and W; n = 2,3,4) to analyze their molecular structure, vibrational spectra and electronic structure. The energy and composition of the frontier orbitals resemble those containing internal heteroatoms of preceding periods. We found that the diameter of the encapsulated internal { XO 4 } subunit varies as X does, while { M 12 O 36 } size and distances remain almost constant along the series. Vibrational modes calculations show that exist a dependency of the frequency and the anionic charge, nature of the heteroatom X and calculation methodology. Energy decomposition analysis of the { XO 4 } – { M 12 O 36 } interaction shows a predominant ionic character due to the high charge of the { XO 4 } anionic subunit. COSMO solvation model enabled us to compare heteropolyanions with different total charges. Our results suggest the possibility that these Keggin anions should be stable, being a new challenge for synthetic inorganic chemists.

Gold–graphene interaction at the interface is evaluated through different polyaromatic hydrocarbons (PAH), accounted by C6H6, C24H12, C54H16, and C96H18, focusing into different energetic terms related to the overall interaction. Our results characterize the neutral gold–PAH interaction nature with 45% of dispersion character, 35% of electrostatic, and 20% of covalent character, suggesting that moderate van der Waals character is mostly involved in the interaction, which increases according to the size of the respective PAH. The resulting surface charge distribution in the graphene model is a relevant parameter to take into account, since the ability of the surface charge to be reorganized over the polycyclic structure in both contact and surrounding regions is important in order to evaluate interactions and different interacting conformations. Our results suggest that for a Au12 contact surface of radius 4.13 A, the covalent, electrostatic and dispersion character of the interaction are effectively accou...

A new structure for spherical fullerene is evaluated involving sixty phenylene rings, replacing every C-vertex from C60, which is based on the isolated-pentagon-rule (IPR) motif based on a cyclo‐meta‐phenylene derivatives reported by Isobe group, resulting in superstructures mimicking C60 (1). Density functional theory calculation shows its stability and properties, also predicting a related C70 counterpart (2), and nano-onions incorporating C60 and C70 inside 1 and 2. These species are attractive targets of 0D-covalent organic frameworks (0D-COF) related to hollow fullerenes, which can be extended to other sp (Taylor et al., 1990) [2]-based species. The obtained structures show increased redox potentials in a larger π-surface area in comparison to C60 and C70, which are of relevance for photovoltaic applications.

In this article, we simulated the collisions of an OH• projectile impacting on a methanol cluster formed by ten units of methanol to mimic an ice mantle (CH3OH)10. The chemical processes occurring after the impact were studied through Born-Oppenheimer (ab-initio) molecular dynamics. We focus on collisions with initial kinetic impact energy of 10–22 eV, where the richest chemistry happens. We report the formation mechanisms of stable complex organic molecules (COMs) such as methoxymethanol CH3OCH2OH, formic acid HCOOH, formyl radical HCO, formaldehyde H2CO and its elusive HCOH isomer. We show that CH2(OH)2, •CH2OH or +CH2OH are key intermediates to generate H2CO and other COMs. We compare the outcomes using OH• with those using OH− projectiles. These processes are likely relevant to the production of COMs in astrophysical environments. We discuss its formation mechanism and the astrophysical implications of these chemical pathways in star-forming regions.

Here we discussed the plausible formation of the Cu10Ru cluster as a superatomic specie accounted for its 1S21P61D10 shell order. By stochastic structure search on Cu10Ru clusters, we found six low-lying cluster isomers with ΔE values from 0.0 to 4.7 kcal∙mol above the ground state denoting an endohedral motif with the Ru dopant inside the Cu10 cage. By using molecular dynamics simulations we found a clear trend of encapsulation of the Ru atom at low temperatures. These results are useful for further rationalization and design of novel spherical superatoms expanding the libraries of stable endohedral clusters.

[Sn@Cu12@Sn20]12− and [As@Ni12@As20]3− structures display highly spherical shapes according to A@B12@A20. Their analysis denote similar features in the electronic structure construction, however the resulting charge distribution exhibits large differences accounting for the different electronic requirements of such concentric structures. This leads to different electronic distribution in the overall system, where the composition of relevant electronic shells and charge distribution in the whole cluster is an important point to take into account in addition to well developed electron count rules.

New fluorescent crosslinked aromatic polyamides containing phenylen, thiophene and furane groups in the main chain were synthesized by self-condensation from 3-(5-aminothiophen-2-yl)propenoic acid, 3-(5-aminofuran-2-yl)propenoic acid and 3-(4-((5-aminothiophen-2-yl)methyleneamino)phenyl)propenoic acid using the phosphorylation method and triphenylphosphite as initiator. The amino compounds were obtained from 3-(5-nitrothiophen-2-yl)propenoic acid, 3-(5-nitrofuran-2-yl)propenoic acid and 3-(4-((5-nitrothiophen-2-yl)methyleneamino)phenyl)propenoic by selective reduction of each nitro group and was confirmed by 1H-NMR and FT-IR spectroscopy. Crosslinking of polyamides ocurr by mechanism between vinyl side groups reacts with the vinyl carbon of another chain, giving rise to interchain linear crosslinking. Depending on the structure the polymers have higher degree of crosslinking. Some vinyl groups react by thermal treatmentat 200 oC. Partially crosslinked polyamides with high emission fluorescence were obtained. Consequently amide bond formation, crosslinking and conjugation are the main factors that influence the fluorescence process. While polymers have several factors that affect the fluorescence, we believe that the most significant is the crosslinking of vinyl bonds. Subsequent thermal treatment of polyamides provoked crosslinking increase and fluorescence loss. The effect of the chemical structure was correlated with the thermal decomposition. Polyamides were characterized by UV-visible, FT-IR and 1H-NMR spectroscopy, inherent viscosity and thermogravimetric analysis (TGA). The synthesized polyamides exhibited potential for heat sensitive devices application since the fluorescence can be activated or quenched according to a heating process.

The complexation of metal cations into a host-guest situation is particularly well exemplified by [2.2.2]paracyclophane and Ag(I), which leads to a strong cation-π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation-π interaction in a host-guest scenario. From an analysis of certain components of the induced magnetic field and the (13)C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host-guest pairs involving both inorganic and organic hosts.

Several poly(thiophene) derivatives containing triphenylamine (TPA) as electron-donor were synthesized by chemical homopolymerization in CHCl3 media using FeCl3 as oxidizing agent. Monomers containing TPA bonded by imine groups to terminal thiophene, bithiophene, terthiophene units allows polymerization to be performed in conditions similar to thiophene. TPA units are regularly spaced in 2, 4, 6 and 8 thiophenyl units in the main chain. TPA electron-donor effect on the polymers chains, as compared to poly(thiophene) was studied. Polymers, labeled as poly(TPA-Th), poly(TPA-biTh) and poly(TPA-Terth) were characterized by 1H-NMR, FT-IR and UV–visible spectroscopy, elemental analysis, thermal stability (TGA) intrinsic viscosity, differential scanning calorimetry (DSC) and electrochemically using cyclic voltammetry (CV). The characterizations are consistent with the proposed structures. The polymers exhibited different optical absorption. They exhibited low intrinsic viscosity, a different effective conjugation and high thermal stability. Moreover, the polymers displayed two redox processes with a redox potential lower than that of poly(thiophene). Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO) and optical band gap (Eg) were measured and the obtained values were compared with those of poly(thiophene). The effect of the presence of TPA units in the thiophenyl chains on HOMO, LUMO, band gap, redox potential and on TGA is reported. To complete the series, HOMO/LUMO levels and band gap of a polymer containing TPA with 8 thiophenyl units in the chain were determined using theoretical calculations. The results proved that, with respect to poly(thiophene), it is possible to decrease HOMO and LUMO without changing the band gap, projecting itself as a potential polymer to be studied in organic photocells.

This work deals about the synthesis and characterization of compounds containing the pyrazole core belonging to the family of (E)-4-((3,5-dimethyl-1-(4-R-phenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile, with possible application as ligands in inorganic chemistry. These compounds were obtained by reaction of a substituted arylhydrazine, R C6H4 NHNH2, R: 4-OCH3, 4-CH3, 4-F, 4-H, 4-Cl, 4-CF3, 4-CN, 3-Cl, 3-NO2, 2-Cl and perfluorophenylhydrazine, C6F5-NH2NH; with a β-diketohydrazone precursor of formula (CH3CO)2C N NH C6H4 4-CN. Analytical techniques (MP and EA) and spectroscopic methods such as UV–Vis, IR, 1H NMR, 13C NMR were employed to characterize the prepared systems. One of the synthesized compounds yielded in ethanol single crystals suitable for X-ray diffraction study. In order to model all the studied compounds and the molecular orbitals involved in the transitions, DFT and TDDFT calculations were performed. The non-variability of the bond distances suggests the robustness of the conjugated structure formed by the R C6H4 pyrazole N N benzonitrile rings, which is poorly affected by the change of the substituents over the phenyl ring.

Two related families of molybdenum complexes of the form [MoBr 2 L(NNR 1 R 2 ) 2 ], where L = 2,2′-bipyridine (bipy) or ortho -phenanthroline ( o -phen) and NNR 1 R 2 = N,N substituted hydrazido(2−) ligands where R 1 and R 2 correspond to methyl and/or phenyl groups. The derivatives have been fully theoretically characterized, carrying on the geometrical characterization of molecular structure, energy decomposition analysis (EDA) and calculation of the absorption spectra using TD-DFT. The study has been performed using Density Functional Theory (DFT), using LDA and GGA(PW91 and BP86) functionals, with the TZP slater type basis set. We found that the complexes are isostructural, have a very similar orbital composition and also show very similar energy values for the frontier molecular orbitals (FMO), except in case of the LUMO+1 which exhibit a special behaviour. The calculated excitations energies are in agreement with the previously reported experimental data. Due to the good agreement between the experimental and theoretical report, a proposal of not yet synthesized complexes was performed.

A theoretical study of the electronic and molecular structure of [Cu(binap) 2 ] + ( 1 ) and [Pd(binap) 2 ] ( 2 ) complexes (binap = 2,20-bis(diphenylphosphino)-1,10-binaphthyl) was performed. We examined the ground states and the lowest excited states (S 1 and T 1 ) in order to get insights about the luminescence processes of these systems. Geometry optimizations were performed at density functional theory DFT (PW91 functional) employing Slater type orbitals (STO) including two polarization functions (TZ2P) and scalar relativistic corrections via the ZORA Hamiltonian. The UV–Vis absorption spectra were simulated employing time-dependent density functional theory (TD-DFT) and solvent effects were estimated using the COSMO model. The calculated excitation energies are in good agreement with experimental data, which is reflected by the calculated UV–Vis spectra. The results suggest that the lowest-energy excited state in each compound corresponds to a ML-LCT (metal–ligand to ligand charge transfer) state. We constructed Jablonsky diagrams for the luminescence phenom. In ( 1 ), this process consists of flourescence originated from the S 1 state and the phosphorescence from the T 1 state. In ( 2 ) the emission energy only results in phosphorescence. We found mainly differences in the geometrical parameters that envolve the Pd metal. The structural changes observed in the calculated geometries of the first excited states respect to those of the ground state have significative relevance in the values of the calculated Stokes shifts showed by the complexes in their UV–Vis/emission spectra.