Millennium Nucleus
Molecular Engineering for Catalysis and Biosensors

What we learned...


Theoretical and experimental characterization of a novel pyridine benzimidazole: Suitability for fluorescence staining in cells and antimicrobial properties
Alexander Carreño, Manuel Gacitua, Dayan Paez-Hernandez, Carmen Araneda, Ivonne Chavez, Marco Soto-Arriaza, Juan Manuel Manriquez, Wesley B. Swords, Ruben Polanco, Juan Fuentes, Guido Mora, Carolina Otero and Ramiro Arratia-Perez
New J. Chem., 2015, Accepted Manuscript [3.086, 2014]
DOI:   10.1039/C5NJ02772A
Benzimidazoles presenting intramolecular hydrogen bonding interactions have been normally used to better understand the role of H-bonding in biological processes. Here, we present an experimental and theoretical study of a new compound [2,4-di-tert-butyl-6-(3H-imidazo[4,5-c]pyridine-2-yl)phenol; (B2), a benzimidazole derivate, exhibiting an intramolecular hydrogen bond. B2 was synthesized and characterized by their 1H, HHCOSY, FT-IR and mass spectra (EI-MS 323 M+). The electronic and optical properties of B2 were studied with theoretical calculations using density functional theory (DFT) and time-dependent DFT (TDDFT). B2 showed luminescent emission at room temperature in different solvents, with a large Stokes shift (e.g.; λex= 335 nm; λem= 510 nm in acetonitrile). Also, the quantum yield (φ =0.21) and theoretical band emission are reported. We found that B2 exhibited a fluorescence emission around 500 nm in ethanol and in acetonitrile, that could be quenched by aqueous solutions of Hg(NO3)2 in the range of micro molar concentrations. Cyclic voltammetry in acetonitrile showed a strong anodic response due to a quasireversible process, with reduction and oxidation waves at -1.28 and -0.47 V vs SCE. Regarding the biological properties, we assessed the antimicrobial activity of B2 in Salmonella enterica (bacteria), Cryptococcus spp. (yeast), Candida albicans (yeast), Candida tropicalis (yeast) and Botrytis cinerea (mold). To this end, we determined the minimal inhibitory concentration (MIC) (for bacteria and yeasts), the growth inhibition halos (for yeasts), and the inhibition of mycelial growth (for the mold). We observed that B2 exerted an antifungal effect against Cryptococcus spp. and Botrytis cinerea. In addition, due to its fluorescence property, B2 has proven to be a suitable marker to observe bacteria (Salmonella enterica and an Escherichia coli derivative), yeasts (Candida albicans), and even human cells (SKOV-3 and HEK-293) by confocal microscopy.

Computational study of organo-cesium complexes and the possibility of lanthanide/actinide ions substitution
Walter A. Rabanal-León, Guillermo Martinez-Ariza, Sue A. Roberts, Christopher Hulme, Ramiro Arratia-Perez
Chem. Phys. Lett. 2015, 641, 181-186 [1.897, 2014]
DOI:   10.1016/j.cplett.2015.10.048
Relativistic DFT calculations suggest that two organo-cesium complexes studied herein afford large HOMO-LUMO gaps of around 2.4 eV with the PBE xc-functional, which accounts for their stability. Energy decomposition studies suggest these two complexes are largely ionic with about 20% covalency. However, when the Cs+ ions are substituted by the isoelectronic La3+ and Th4+, their predicted ionicity decreases significantly. The significant increase in covalence indicates that employing Ugi reaction cascades that afford tetramic acid-based organo-cesium complexes may be extended to La3+ and Th4+ organometallics.

The role of the [CpM(CO)2]- chromophore in the optical properties of the [Cp2ThMCp(CO)2]+ complexes, where M = Fe, Ru and Os. A theoretical view
Plinio Cantero-López, Laura Le Bras, Dayán Páez-Hernández and Ramiro Arratia-Pérez
Dalton Trans., 2015, Advance Article [4.197, 2014]
DOI:   10.1039/C5DT03121D
The chemical bond between actinide and the transition metal unsupported by bridging ligands is not well characterized. In this paper we study the electronic properties, bonding nature and optical spectra in a family of [Cp2ThMCp(CO)2]+ complexes where M = Fe, Ru, Os, based on the relativistic two component density functional theory calculations. The Morokuma-Ziegler energy decomposition analysis shows an important ionic contribution in the Th-M interaction with around 25% of covalent character. Clearly, charge transfer occurs on Th-M bond formation, however the orbital term most likely represents a strong charge rearrangement in the fragments due to the interaction. Finally the spin-orbit-ZORA calculation shows the possible NIR emission induced by the [FeCp(CO)2]- chromophore accomplishing the antenna effect that justifies the sensitization of the actinide complexes.

Role of the cation formal charge in cation–π interaction. A survey involving the [2.2.2]paracyclophane host from relativistic DFT calculations
Alexandre O. Ortolan, Giovanni F. Caramori, Gernot Frenking and Alvaro Muñoz-Castro
New J. Chem., 2015,39, 9963-9968 [3.086, 2014]
DOI:   10.1039/C5NJ02384J
The role of the metal formal charge in the cation–π interactions has been evaluated with relativistic DFT methods involving a versatile π-cryptating structure, namely [2.2.2]paracyclophane. Our study focuses on experimentally characterized [([2.2.2]pCp)M]n+ systems with M = Ag+ and Sn2+ and their Cd2+ and In+ counterparts, which exhibit 5s05p0 and 5s25p0 electron configurations. The acceptor capabilities increase when the metal charges go from 1+ to 2+, resulting in a large stabilization of the interaction. For the studied 5s05p0 cations Ag+ and Cd2+, the most stable conformation namely [(η222-[2.2.2]pCp)M]n+, the electrostatic contribution is more favorable by -9.3 kcal mol-1, whereas the ΔEOrb contribution increases by -151.6 kcal mol-1 towards a more favourable situation in the 2+ counterpart. Similarly in the 5s25p0 cationic group, the isoelectronic Sn2+ and In+ systems depict variation of the electrostatic and orbital terms, with a considerable decrease of the stabilizing ΔEOrb contribution, and in a lesser amount the ΔEElstat term. Thus, the variation of the interaction energy between the M+ and M2+ isoelectronic counterparts can be ascribed mainly to the variation of the ΔEOrb term, leading to a more covalent character of the interaction retaining a similar bonding scheme.

New Insights into Re3(μ-Cl)3Cl6 Aromaticity. Evidence of σ- and π-Diatropicity
Alejandro Vásquez-Espinal, Ricardo Pino-Rios, Luis Alvarez-Thon, Walter A. Rabanal-León, Juan J. Torres-Vega, Ramiro Arratia-Perez, and William Tiznado
J. Phys. Chem. Lett., 2015, 6, 4326-4330 [7.458, 2014]
DOI:   10.1021/acs.jpclett.5b01816
We have theoretically evaluated the behavior of the Re3(μ-Cl)3Cl6 cluster under magnetic perturbation, and it clearly shows that the magnetic response within the Re3(μ-Cl)3 plane is highly diatropic in nature. An analysis of both the magnetically induced current density (MICD) and induced magnetic field (Bind) allows us to classify this cluster as doubly σ- and also π-aromatic on the magnetic criterion. These findings contradict the classical Re-Re double bond representation and favor a chemical bonding pattern that involves delocalized bonds.

Theoretical study on interactions of fluorinated organomercurials with arene and gold fragments
Fernando Mendizabal, Sebastian Miranda-Rojas and Lorena Barrientos
Phys. Chem. Chem. Phys., 2015, 17, 26417-26428 [4.493, 2014]
DOI:   10.1039/C5CP04503G
The electronic structure and spectroscopic properties of [Hg(C6F5)2]2-{L}, [Hg3(o-C6F4)3]2·{L} (L = naphthalene, biphenyl, fluorene) and [Hg3(o-C6F4)3]{Au3(μ-C(OEt)[double bond, length as m-dash]NC6H4CH3)3}n (n = 1, 2) adducts were studied at the HF, MP2, SCS-MP2, DFT and DFT-D3 levels. The intermolecular interactions among the fragments were analyzed using the levels of calculations proposed. The energy decomposition analysis at the TPSS-D3 level was used to define the dominant components of the interaction. The van der Waals interactions between mercury and arene (Hg-arene) were found to be the main short-range stability contribution in the [Hg(C6F5)2]2-{L} and [Hg3(o-C6F4)3]2·{L} complexes. At the MP2, SCS-MP2 and DFT-D3 levels, equilibrium Hg-C distances are between 360 and 310 pm. The pair-wise energies were found to be between 18.0 and 6.0 kJ mol-1. In the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)[double bond, length as m-dash]NC6H4CH3)3}n (n = 1, 2) complexes the metallophilic intermolecular interaction is Hg-Au. Pair-wise energies of 85.7, 39.4, 78.1 and 57.9 kJ mol-1 were found at the MP2, SCS-MP2, TPSS-D3 and PBE-D3 levels using the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)[double bond, length as m-dash]NC6H4CH3)3} model. The same trend is maintained for the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)[double bond, length as m-dash]NC6H4CH3)3}2 model: 73.4, 29.3, 70.6 and 61.3 kJ mol-1 by MP2, SCS-MP2, TPSS-D3 and PBE-D3, respectively. The absorption spectra of these complexes were calculated using the single excitation time-dependent method at the TPSS-D3 level to validate the models against the experimental data.

Substituents role in zinc phthalocyanine derivatives used as dye-sensitized solar cells. A theoretical study using Density Functional Theory
Cristian Linares-Flores, Fernando Mendizabal, Ramiro Arratia-Pérez, Natalia Inostroza, Carlos Orellana
Chem. Phys. Lett. 2015, 639, 172-177 [1.897, 2014]
DOI:   10.1016/j.cplett.2015.09.025
A series of zinc phthalocyanine dyes with different electron-donating and electron-withdrawing substituents and using the COOH as the anchor group that interacts with the semiconductor (TiO2) surface, were studied employing DFT and TDDFT methodologies. Their HOMO and LUMO orbital energies and, the redox mediator position would facilitate the injection process toward the conduction band of TiO2. We tested the effect of some electron-donating or electron-withdrawing substituents over zinc phthalocyanine dyes in terms of the Hammett parameters (Σσ). We obtained a linear correlation between the substituents properties versus the free energy change of the electron-injection (ΔGinject) process.

Aromatic Lateral Substituents Influence the Excitation Energies of Hexa-aza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study
Walter Alfonso Rabanal-Leon, Juliana Andrea Murillo-Lopez, Dayan Paez Hernandez, and Ramiro Arratia-Perez
J. Phys. Chem. A 2015, 119, 9931-9940 [2.693, 2014]
DOI:   10.1021/acs.jpca.5b07202
The high interest on lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexa-aza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f-states, having small HOMO-LUMO energy gaps. The results obtained from the wave function theory calculations (SO-RASSI) put on evidence the multi-configurational character of their ground state and it is observed that the large spin-orbit coupling and the weak crystal-field produce a strong mix of the ground and the excited-states. The electron localization function (ELF) and the energy decomposition analysis (EDA) support the idea of a dative interaction between the macrocyclic ligand and the lanthanide center for all the studied systems; noting that, this interaction has a covalent character, where the d-orbital participation is evidenced from NBO analysis, leaving the f-shell completely non- interacting in the chemical bonding. From the optical part we observed in all cases the characteristic intra-ligand (IL) (π-π*) and ligand to metal charge transfer (LMCT) bands which are present in the ultraviolet and visible regions, and for the open-shell complexes we found the inherent f-f electronic transitions on the visible and near infra-red region. When the absorption spectra of the cerium hexa-aza macrocyclic complexes with aromatic and aliphatic lateral units (reported in a previous work) is compared, we observed a shift of the IL and LMCT bands to the visible region, whilst the f-f transitions increase their absorption intensities suggesting a more efficient population of the lanthanide excited-states; these facts allow us to suggest that lanthanide hexa-aza macrocyclic systems with aromatic lateral units may act as potential single antenna molecules.

The Synthesis of Stable, Complex Organocesium Tetramic Acids through the Ugi Reaction and Cesium-Carbonate-Promoted Cascades
Guillermo Martinez-Ariza, Muhammad Ayaz, Sue A. Roberts, Walter A. Rabanal-Leon, Ramiro Arratia-Perez, and Christopher Hulme
Angew. Chem. Int. Ed. 2015, 54, 1-6 [11.261, 2014]
DOI:   10.1002/anie.201504377
Two structurally unique organocesium carbanionic tetramic acids have been synthesized through expeditious and novel cascade reactions of strategically functionalized Ugi skeletons delivering products with two points of potential diversification. This is the first report of the use of multicomponent reactions and subsequent cascades to access complex, unprecedented organocesium architectures. Moreover, this article also highlights the first use of mild cesium carbonate as a cesium source for the construction of cesium organometallic scaffolds. Relativistic DFT calculations provide an insight into the electronic structure of the reported compounds.

Interaction of LD14 and TiO2 in dye-sensitized solar-cells (DSSC): A density functional theory study
Fernando Mendizabala, Alfredo Lopez, Ramiro Arratia-Perez, Gerald Zapata-Torres
Computational and Theoretical Chemistry, 2015, 1070, 117-125 [1.545, 2014]
DOI:   10.1016/j.comptc.2015.08.005
The interaction and electron injection processes of the LD14 dye on TiO2 cluster (anatase phase) in dye-sensitized solar cells (DSSCs) have been studied through calculations based on density functional theory (DFT) at the B3LYP, PBE and TPSS levels along with dispersion effects. The interaction of the LD14 dye with the TiO2 clusters was quantified using the DFT-D3 levels. The TDDFT calculations with the B3LYP-D3 in phase solvent (THF) in the LD14 and LD14-TiO2 models are the most suitable for describing the observed absorption energy bands. The free energy changes for electron injection support the better performance of LD14 on the TiO2 clusters.

Spectral, theoretical characterization and antifungal properties of two phenol derivatives Schiff base with an intramolecular hydrogen bond
Alexander Carreño, Manuel Gacitua, Dayan Paez-Hernandez, Ruben Polanco, Marcelo Preite, Juan Fuentes, Guido Mora, Ivonne Chavez and Ramiro Arratia-Perez
New J. Chem., 2015, Accepted Manuscript [3.086, 2014]
DOI:   10.1039/C5NJ01469G
Schiff bases show a wide variety of applications of great importance in medicinal research due to their range of biological activities, where some Schiff bases are known to be promising antifungal agents. In this article we describe the electronic structure, optical, redox and antifungal properties of (E)-2-[(2-amino-pyridin-3-ylimino)-methyl]-4,6-di-tert-butyl-phenol (L1) and (E)-2-[(4-amino-pyridin-3-ylimino)-methyl]-4,6-di-tert-butyl-phenol (L2), two isomers phenol derivatives Schiff bases exhibiting a strong intramolecular hydrogen bond (O-H•••N). These compounds were characterized by their 1H, HHCOSY, 13C-NMR, FT-IR spectra, and by cyclic voltammetry. All the experimental results were complemented with theoretical calculations using density functional theory (DFT) and time-dependent DFT (TDDFT). The antimicrobial activity of the compounds described herein was assessed by determining the minimal inhibitory concentration (MIC) and by a modification of the Kirby-Bauer method. We tested Salmonella enterica serovar Typhi (S. Typhi, Gram-negative bacteria), Cryptococcus spp. (yeast), and Candida albicans (yeast). We found that neither L1 nor L2 showed antimicrobial activity against S. Typhi or Candida albicans. On another hand, L2, in contrast to L1, exhibited antifungal activity against Cryptococcus spp. (MIC: 4.468 µg/mL) even better than commercial antifungal medicaments. We mentioned above that L1 and L2 are isomers, because the amino groups is in ortho-position in L1 and in para-position in L2, however no significant differences were detectable by UV-vis, FT-IR, oxidation potentials and TDDFT calculations, but the antifungal activity served in Cryptococcus spp clearly differentiated between both isomers.

Interaction of YD2 and TiO2 in dye-sensitized solar cells (DSSCs): a density functional theory study
Fernando Mendizabal, Alfredo Lopéz, Ramiro Arratia-Perez, Natalia Inostroza, Cristian Linares-Flores
J. Mol. Model. 2015, 21:226 [1.736, 2014]
DOI:   10.1007/s00894-015-2771-5
The interaction of the dye YD2 with a cluster of (anatase-phase) TiO2 (which is utilized in dye-sensitized solar cells, DSSCs) and electron injection by the dye into the cluster were studied by performing density functional theory (DFT) calculations at the B3LYP, PBE, and TPSS levels of theory, including dispersion effects. We studied and quantified the interaction of the metallomacrocycle with the TiO2 cluster and the electronic spectrum of the complex. TDDFT calculations using the B3LYP functional were found to be the most suitable for describing the observed absorption energy bands of YD2 and YD2-TiO2. Our calculations show that the diarylamino groups act as electron donors in the photon-induced injection that occurs in DSSCs. The free-energy changes that take place during electron injection support the good performance of YD2 on TiO2 clusters.

Imaging the Ultrafast Photoelectron Transfer Process in Alizarin-TiO2
Tatiana Gomez, Gunter Hermann, Ximena Zarate, Jhon Fredy Perez-Torres, and Jean Christophe Tremblay
Molecules 2015, 20(8), 13830-13853 [2.416, 2014]
DOI:   10.3390/molecules200813830
In this work, we adopt a quantum mechanical approach based on time-dependent density functional theory (TDDFT) to study the optical and electronic properties of alizarin supported on TiO2 nano-crystallites, as a prototypical dye-sensitized solar cell. To ensure proper alignment of the donor (alizarin) and acceptor (TiO2 nano-crystallite) levels, static optical excitation spectra are simulated using time-dependent density functional theory in response. The ultrafast photoelectron transfer from the dye to the cluster is simulated using an explicitly time-dependent, one-electron TDDFT ansatz. The model considers the ?-pulse excitation of a single active electron localized in the dye to the complete set of energetically accessible, delocalized molecular orbitals of the dye/nano-crystallite complex. A set of quantum mechanical tools derived from the transition electronic flux density is introduced to visualize and analyze the process in real time. The evolution of the created wave packet subject to absorbing boundary conditions at the borders of the cluster reveal that, while the electrons of the aromatic rings of alizarin are heavily involved in an ultrafast charge redistribution between the carbonyl groups of the dye molecule, they do not contribute positively to the electron injection and, overall, they delay the process.

Imaging the Ultrafast Photoelectron Transfer Process in Alizarin-TiO2
Tatiana Gomez, Gunter Hermann, Ximena Zarate, Jhon Fredy Pérez-Torres and Jean Christophe Tremblay
Molecules 2015, 20(8), 13830-13853 [2.465, 2015]
DOI:   10.3390/molecules200813830
In this work, we adopt a quantum mechanical approach based on time-dependent density functional theory (TDDFT) to study the optical and electronic properties of alizarin supported on TiO2 nano-crystallites, as a prototypical dye-sensitized solar cell. To ensure proper alignment of the donor (alizarin) and acceptor (TiO2 nano-crystallite) levels, static optical excitation spectra are simulated using time-dependent density functional theory in response. The ultrafast photoelectron transfer from the dye to the cluster is simulated using an explicitly time-dependent, one-electron TDDFT ansatz. The model considers the δ-pulse excitation of a single active electron localized in the dye to the complete set of energetically accessible, delocalized molecular orbitals of the dye/nano-crystallite complex. A set of quantum mechanical tools derived from the transition electronic flux density is introduced to visualize and analyze the process in real time. The evolution of the created wave packet subject to absorbing boundary conditions at the borders of the cluster reveal that, while the electrons of the aromatic rings of alizarin are heavily involved in an ultrafast charge redistribution between the carbonyl groups of the dye molecule, they do not contribute positively to the electron injection and, overall, they delay the process.

A theoretical study of substituted indeno[1,2-b]fluorene compounds and their possible applications in solar cells
Ivan Martinez, Ximena Zarate, Eduardo Schott, Cesar Morales-Verdejo, Francisco Castillo, Juan Manuel Manriquez, Ivonne Chavez
Chem. Phys. Lett. 2015, 636, 31-34 [1.897, 2014]
DOI:   10.1016/j.cplett.2015.06.085
This contribution mainly describes the theoretical computations based on density functional theory (DFT), of the anti-aromatic system indeno[1,2-b]fluorene with the aim of understanding the electronic effects of the substituting electron donating and electron withdrawing groups in the 6,12-positions, to investigate their potential role as sensitizers in solar cells devices. Ground state potential energy surfaces were obtained employing the B3LYP/6-31+G(d,p) theoretical level. The low energy electronic transitions were investigated through the TD-DFT method. It was possible to conclude that indeno[1,2-b]fluorine with NH2, NO2, CN substituents are the best candidates to act as light harvesting and sensitizers in solar cells.

Thermal Fluctuations on Förster Resonance Energy Transfer in Dyadic Solar Cell Sensitizers: A Combined Ab Initio Molecular Dynamics and TDDFT Investigation
Rodrigo A. Urzúa-Leiva, Sergio Rampino, Ramiro Arratia-Perez, Edoardo Mosconi, Mariachiara Pastore, and Filippo De Angelis
J. Phys. Chem. C, 2015, 119 (29), 16490-16499 [4.772, 2014]
DOI:   10.1021/acs.jpcc.5b04921
Förster resonance energy transfer (FRET) is a key process in dyadic dye-sensitized solar cells (DSSCs) where an "antenna" donor has the role of collecting photons and redirecting the captured energy to an adsorbed-dye acceptor unit. Despite its popularity in, e.g., biology, where FRET rates are used to derive structural information on fairly complex systems, relatively few studies have appeared in the DSSCs field. These were based, to the best of our knowledge, either on a static modeling of FRET or on the so called isotropic regime assuming an isotropic motion of the donor/acceptor units and uncorrelated donor/acceptor relative distance and orientation. In this paper we carry out a combined Car-Parrinello molecular dynamics and TDDFT investigation to unravel the impact of thermal fluctuations on FRET in two dyadic carbazole-phenothiazine dye sensitizers. Both isolated and full-packed adsorption conditions are considered, mimicking the dye adsorption topology on TiO2. Results are discussed in relation to the above mentioned models and rationalized in terms of the structural differences of the considered dyes. We find a considerable difference between the FRET rates calculated at zero temperature and the results obtained by including thermal fluctuations, highlighting an important role of the latter in determining FRET rates in dyadic donor-acceptor dye-sensitized solar cells.

Polyaniline nanostructure electrode: morphological control by a hybrid template
Carlos P. Silva, Mireya Santander-Nelli, Cristian Vera-Oyarce, Juan F. Silva, Alejandra Gómez, Lisa A. Muñoz, José H. Zagal, Miguel Gulppi, Jorge Pavez
Journal of Solid State Electrochemistry, July 2015 [2.668, 2014]
DOI:   10.1007/s10008-015-2944-2
We report here a novel approach to the template-assisted electrochemical synthesis of vertically aligned polyaniline (PANI) nanostructure surface arrays. When PANI is obtained by electropolymerization inside a custom-made anodic aluminum oxide (AAO) template, with an Au layer sputtered onto one side of the AAO acting as an anode, PANI nanotubes are obtained. In contrast, when the surface of this gold layer is modified with 4-aminothiophenol (4-ATP) as a self-assembled monolayer (SAM) film anchored to the gold layer via the thiol groups and on the opposite end having NH2 functionalities, we obtain a surface array of PANI nanowires. Cyclic voltammetry and SEM analysis show that the amino functionalities of Au/SAMs act as a nucleation site in the internal base of the AAO pore and determine both the morphology and structure of polyaniline and its electronic properties as well.

Metal containing cryptands as hosts for anions: evaluation of Cu(I)···X and π···X interactions in halide–tricopper(I) complexes through relativistic DFT calculations
Miguel Ponce-Vargas and Alvaro Muñoz-Castro
Phys. Chem. Chem. Phys., 2015, 17, 18677-18683 [4.493, 2014]
DOI:   10.1039/C5CP02737C
More selective than crown ethers, cryptands arise as suitable hosts for several ions, with the size of the cavity and the behavior of the atoms belonging to the structure being the main factors governing their selectivity. Similar to metallacrowns, inorganic counterparts of crown ethers, the presence of metal centers in cryptands can offer significant advantages in terms of ion recognition as they provide positively charged sites, which allow them to encapsulate anions. Here, through density functional methodologies, we evaluate the preference of a tricopper(I) cryptand host toward a series of halide ions ranging from the hard fluoride to the soft iodide, where the more intense interactions are established with the hardest one, and the electrostatic term is the more relevant contributor to total interaction energy. Upon exploration of this electrostatic contribution in more detail, it is observed that as the guest becomes softer, the increase of higher order Coulombic terms, such as dipole–dipole, dipole–quadrupole, and quadrupole–quadrupole, acquires more relevance on going from 9.22% to 41.25%, denoting the key role and variation of such forces in inclusion systems with metal-containing hosts.

Experimental and theoretical studies of the ancillary ligand (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol in the rhenium(I) core
Alexander Carreño, Manuel Gacitua, Eduardo Schott, Ximena Zarate, Juan Manuel Manriquez, Marcelo Preite, Sonia Ladeira, Annie Castel, Nancy Pizarro, Andres Vega, Ivonne Chavez, and Ramiro Arratia-Perez
New J. Chem., 2015, Advance Article [3.086, 2014]
DOI:   10.1039/C5NJ00772K
The fac-[Re(CO)3(deeb)L]+ complex (C2) where L is the (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol ancillary ligand, which presents an intramolecular hydrogen bond, has been synthesized and characterized using UV-vis, 1H-NMR, FT-IR, cyclic voltammetry and DFT calculations. The UV-vis absorption and emission properties have been studied at room temperature and the results were compared with TDDFT calculations including spin-orbit effects. We report an alternative synthesis route for the fac-Re(CO)3(deeb)Br (C1) complex where deeb = (4,4´-diethanoate)-2,2´-bpy. Besides, we have found that the C1 shows a red shift in the emission spectrum due to the nature of the ancillary electron donating ligand, while the C2 complex shows a blue shift in the emission spectrum suggesting that the ancillary ligand L has electron withdrawing ability and the importance of the intramolecular hydrogen bond. The calculations suggest that an experimental mixed absorption band at 361 nm could be assigned to MLCT and LLCT transitions. The electron withdrawing nature of the ancillary ligand in C2 explains the electrochemical behavior, which shows the oxidation of ReI at 1.83 V and the reduction of deeb at -0.77 V.

Exploring the nature of the excitation energies in [Re63-Q8)X6]4- clusters: a relativistic approach
Walter A. Rabanal-León, Juliana A. Murillo-López, Dayán Páez-Hernández, and Ramiro Arratia-Perez
Phys. Chem. Chem. Phys., 2015, Advance Article [4.493, 2014]
DOI:   10.1039/C5CP02003D
This contribution is a relativistic theoretical study to characterize systematically the main electronic transitions in a series of hexarhenium chalcogenide [Re63-Q8)X6]4- clusters with the aim of understanding: (i) the terminal ligand substitution effect, (ii) the substitution effect of the chalcogenide ion on the [Re63-Q8)]2+core, and finally (iii) the significance of the spin-orbit coupling (SOC) effect on the optical selection rules. In all the cases, we found characteristic bands at around 300-550 nm, where the band positions are directly determined by the terminal ligand. However, SCN-/NCS- presents a different nature of the orbitals involved in the electronic transitions, in comparison with the other studied terminal ligands, located in the near-infrared (NIR) region. All the bands are red-shifted as a consequence of the ligand contribution in the composition of the orbitals involved in the electronic excitations.

Axis-dependent magnetic behavior of C60 and C6010+. consequences of spherical aromatic character
A. Muñoz-Castro
Chem. Commun., 2015,51, 10287-10290 [6.834, 2014]
DOI:   10.1039/C5CC03352G
The magnetic response of C60 has been studied and compared to its spherical aromatic counterpart C6010+, focusing on the overall and local shielding tensors. A high axis dependence behavior at the outside region of the structure is characterized, unravelling a characteristic pattern of the local chemical shift anisotropy as a consequence of the spherical aromatic behavior.

Synthesis, reactivity, electrochemical behaviour, and molecular structure of crown ether cyrhetrene complexes
Fernando Godoy, Alejandra Gómez, Nicolas Agurto, Michelle Muñoz, Rodrigo Segura, Carlos P. Silva, Jorge Pavez, José H. Zagal, A. Hugo Klahn, M. Fuentealba, Andres Ibañez, Maria Teresa Garland
Journal of Organometallic Chemistry, 2015, 788, 42-48 [2.173, 2014]
DOI:   10.1016/j.jorganchem.2015.04.031
Cyrhetrenyl crown ether complexes [(η5-C5H4CHdouble bond; length as m-dashN-M)Re(CO)3] (where M = 4-benzo-15-crown-5 (3a), 4-benzo-18-crown-6 (3b), 2-methyl-15-crown-5 (3c), or 2-methyl-18-crown-6 (3d)) were synthesised from cyrhetrenylcarboxaldehyde (1) and the corresponding crown ether amines 2a-d. All the complexes were characterised by -IR spectroscopy, 1H and 13C NMR spectroscopies, and mass spectrometry. The stereochemistry for imine compounds 3a-d were determined using the 1H and 13C NMR spectroscopy data, which indicated that these complexes have the anti-(E) conformation. This was also confirmed by the X-ray crystal structures of 3b and 3c in the solid state. Additionally, the electrochemical behaviours of 1 and 3a-d were studied.

Building Nanoscale Molecular Wires Exploiting Electrocatalytic Interactions
Ingrid Ponce, Albert C. Aragonesa, Nadim Darwish, Pepita Pla-Vilanova, Ruben Oñate, Marcos Caroli Rezende, José H. Zagal, Zausto Sanza, Jorge Pavez, Ismael Díez-Pérez
Electrochimica Acta, in press. [4.504, 2014]
DOI:   10.1016/j.electacta.2015.03.150
Herein, we present a novel method to design nanoscale molecular wires by exploiting well-established electrocatalytic molecular platforms based on metallophthalocyanine blocks. Metallophthalocyanines exhibit high catalytic activity for a wide variety of electrochemical reactions of practical interests. To this aim, metallophthalocyanine molecules can be attached to an electrode surface via a conjugated mercaptopyridine axial ligand that provides (i) stable chemical binding to the metal surface through the thiol-anchoring group, and (ii) a good electrical communication between the metallophthalocyanine ring and the electrode surface. Our previous work demonstrates that long mercaptopyridinium blocks act as excellent linkers in such electrocatalytic platform, resulting in an optimal electrocatalytic activity of the metallophthalocyanine unit. Here we profit from this optimized electrocatalytic molecular platform to design new molecular wires that connect a metal nanoscale junction in a highly efficient and tunable way. To this aim, we use an STM break-junction approach to control the formation of a nanometric gap between two Au electrodes, both functionalized with mercaptopyridinium (bottom) and mercaptopyridine (top). When metallophthalocyanine is introduced into the functionalized metal nanojunction, stable molecular connections between the two electrodes are formed through axial coordination to the top and bottom pyridine moieties. We show that the highest conductance of the resulting nanoscale molecular wire corresponds to an Fe-phthalocyanine as compare to a Cu-phthalocyanine, which follows the electrocatalytic trend for such molecular systems. These results not only demonstrate a new strategy to design new families of highly conductive and tunable nanoscale molecular wires, but it also brings a new nanoscale electrical platform to help understanding some fundamental mechanistic aspects of molecular electrocatalysis.

A comparative study between post-Hartree-Fock methods and density functional theory in closed-shell aurophilic attraction
Fernando Mendizabal, Sebastián Miranda-Rojas, Lorena Barrientos-Poblete
Computational and Theoretical Chemistry 1057, 2015, 74-79 [1.545, 2014]
DOI:   10.1016/j.comptc.2015.01.021
The inter- and intramolecular aurophilic [ClAuPH3]2, [S(AuPH3)2] and [AuPH3]42+ interactions were studied using ab initio post-Hartree-Fock and DFT methodologies. The post-Hartree-Fock methods provide results closer to the experimental data than DFT-based methods. It is possible to highlight the results obtained by the SCS-MP2 and CCSD(T) methods. In the classic [ClAuPH3]2 dimer, the aurophilic interaction is driven by the induction and dispersion terms. When DFT is used, the best results of geometry and interaction energy are obtained with the PW91 level. We find -D3 Grimme correction, M06HF, M06L, M06 M062X, M052X, CAM-B3LYP and LC-?PBE provided results of similar accuracy as MP2.

Interaction in multilayer clusters: a theoretical survey of [Sn@Cu12@Sn20]12-, a three-layer matryoshka-like intermetalloid
Markus Rauhalahti and Alvaro Muñoz-Castro
RSC Adv. 5, 18782-18787, 2015 [3.840, 2014]
DOI:   10.1039/c4ra16660d
[Sn@Cu12@Sn20]12- represents an archetypal intermetalloid structure composed of several concentric polyhedral shells displaying a highly spherical shape. This feature paves the way to understanding the electronic structure of multilayered structures in terms of interacting superatomic shells. As a result, [Sn@Cu12@Sn20]12- can be regarded formally as [{Sn@Cu12}4-@{Sn20}8-], which ensures a favorable electronic configuration with a sizable HOMO-LUMO gap for the inner core [Sn@Cu12]4-. The interaction between the [Sn@Cu12]4- and [Sn20]8- layers involves a concentric bonding interaction of s-, p- and d-type. The approach employed here is suggested and demonstrated to be a useful strategy for rationalizing multilayer endohedral clusters, which can be extended to nanoparticles or even to less symmetrical systems.

[2.2.2]Paracyclophane, preference for η6 or η18 coordination mode including Ag(I) and Sn(II): a survey into the cation-π interaction nature through relativistic DFT calculations
Carolina Olea Ulloa, Miguel Ponce-Vargas, Rafael de Mattos Piccoli, Giovanni F. Caramori, Gernot Frenking, and Alvaro Muñoz-Castro
RSC Adv. 5, 7803-7811, 2015 [3.840, 2014]
DOI:   10.1039/c4ra12859a
[2.2.2]Paracyclophane is a versatile π-cryptating structure, which can exhibit η222 and η666 coordination with metal ions, involving two or six carbon atoms in each aromatic ring. According to the nature of the metallic cation, the interaction can occur at the centre of the cage or upper face of the structure, which is determined mainly by the ligand-to-metal charge transfer ruled by symmetry and energetic considerations, and thus by the nature of the cation-π interaction. For Ag(I), the 5s-Ag shell is close in energy to the frontier orbitals of paracyclophane, resulting in the formation of a bonding combination with the symmetric combination of the π2-type levels, which leads to a non-centered conformation. In contrast, the Sn(II) case exhibits a largely favourable bonding interaction with the π2 and π3 type levels, which involve the 5p-Sn shell and result in a centered conformation. The interaction between the metal and paracyclophane was studied via molecular orbitals diagram, energy decomposition analyses (EDA) and non-covalent indexes (NCI).