2-[2-(4-Acetyl­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

In the title compound, C23H18N2O3, the inter­planar angle between the benzoyl units is 80.51 (6)° while the dihedral angles between the hydrazinyl­idene and benzoyl groups are 43.43 (6) and 54.16 (6)°. In the crystal, a strong resonance-assisted intra­molecular N—H⋯O hydrogen bond is observed. The mol­ecules form an inversion dimer via a pair of weak C—H⋯O hydrogen bonds and a π–π inter­action [centroid–centroid distance of 3.5719 (10) Å]. These dimers are linked via weak C—H⋯O contacts, forming chains along the b axis

(Acetyl­acetonato)dibromido[2,2-diphenyl­hydrazin-1-ido(1−)][2,2-diphenyl­hydrazin-1-ido(2−)]molybdenum(VI)

In the title compound, [MoBr2(C12H11N2)(C12H10N2)(C5H7O2)], the MoVI atom is six-coordinated in a distorted octa­hedral geometry by two N atoms from the diphenyl­hydrazide(1−) and diphenyl­hydrazide(2−) ligands, two O atoms from a bidentate acetyl­acetonate ligand and two Br− ions. The mol­ecules form an inversion dimer via a pair of weak C—H⋯O hydrogen bonds and a π–π stacking inter­action with a centroid–centroid distance of 3.7401 (12) Å. Weak intra­molecular C—H⋯Br inter­actions and an intra­molecular π–π stacking inter­action with a centroid–centroid distance of 3.8118 (15) Å are also observed

2-[2-(4-Bromo­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

The conformation of the title mol­ecule, C21H15BrN2O2, is stabilized by a weak intra­molecular C—H⋯N hydrogen bond and a strong resonance-assisted N—H⋯O intra­molecular hydrogen bond. In the crystal, the mol­ecules are linked by weak inter­molecular C—H⋯O inter­actions, forming zigzag chains along the b axis

A second monoclinic polymorph of 2-[2-(4-meth­oxy­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

The title compound, C22H18N2O3 is the second monoclinic polymorph (P21/c) of the compound, the first being reported in space group P21 [Bertolasi et al. (1993 ▶). J. Chem. Soc. Perkin Trans. 2, pp. 2223–2228]. In the mol­ecular structure of the title compound, the inter­planar angle between the benzoyl units is 80.04 (5)°, while the corresponding angles between the phenyl­hydrazinyl­idene and benzoyl groups are 36.11 (5) and 55.77 (2)°. A strong resonance-assisted intra­molecular N—H⋯O hydrogen bond is found. In the crystal, the entire supra­molecular structure is constructed by weak inter­molecular C—H⋯O inter­actions and an inter-ring π–π inter­action [centroid–centroid distance = 3.6088 (8) Å]

2-[2-(3-Chloro­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

The mol­ecular structure of the title compound, C21H15ClN2O2, features one strong intra­molecular N—H⋯O resonance-assisted hydrogen bond (RAHB). In the crystal, mol­ecules form inversion-related dimers via pairs of weak inter­molecular N—H⋯O contacts. These dimers are further stabilized via three weak C—H⋯O contacts, developing the three-dimensional structure

(E)-3,5-Dimethyl-1-p-tolyl-4-(p-tolyl­diazen­yl)-1H-pyrazole

There are two independent mol­ecules, A and B, in the asymmetric unit of the title compound, C19H20N4, in each of which the N=N double bond has an E conformation. The dihedral angles between the pyrazole ring and the p-tolyl rings in the 1- and 4-positions are 22.54 (8) and 35.73 (7)°, respectively, in mol­ecule A. The corresponding dihedral angles in mol­ecule B are 28.13 (8) and 22.18 (8)°. In the crystal, the A and B mol­ecules are linked by weak C—H⋯π inter­actions, leading to inversion dimers in each case

Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication

International audienceno abstrac

High level relativistic calculations on transition metal complexes

Tesis (Doctor en Fisicoquímica Molecular)For calculating properties on molecules that contain heavy elements of the periodic table, only a theory that salves the four-component Dirac equation is suitable. In effect, scalar relativistic effects can stabilize s and p orbitals and destabilize d and f orbitals. In this context bond lengths and other spectroscopic constants can change drastically going from the non-relativistic to the relativistic framework. On the other hand, the spin-orbit effect could change completely the assignment of the ground state of a molecule. This thesis is a study of the Jahn-Teller effect in six heavy transition-metal complexes (RhF6 , WF6 , ReF6 , OsF6 , IrF6 , PtF6). In these complexes, the relativistic effects and electron correlation are large, therefore in order to obtain reliable results, all calculations have been carried out by solving the four-component Dirac equation. Dirac-Hartree-Fock (DHF) and correlated Density Functional Theory (DFT) methods were applied. The use of a four-component code involves a very demanding computational effort and nowadays it is considered a state-of-the-art method. The main results consisted in assigning the ground state and the geometry of the six complexes. Experimentally, the complex PtF6 is essentially diamagnetic ("singlet") and strictly octahedral, but previous theoretical studies had determined that it should distort due the J ahn-Teller effect and that its ground state should be a "triplet". The explanation of this contradiction is that the previous studies did not included the spin-orbit interaction. In contrast, the results in this thesis show unequivocally that PtF 6 is octahedral and that the J ahn-Teller effect is quenched by the spin-orbit effect. The other interesting case is IrF6 , since a non-relativistic or scalar relativistic description would show that this complex is not J ahn-Teller-distorted and must be octahedral, like its isoelectronic counterpart RhF6 . However, the results of this thesis indicate that IrF6 must distort, which is in complete agreement with experimental results. The results conclude that the J ahn-Teller must be studied including the spin-orbit interaction when the systems considered have heavy-metal nuclei. The spin-orbit effect could change the assignment of the ground state of the complexes studied, therefore if the J ahn-Teller effect is applicable in the non-relativistic framework, it could be canceled out in the relativistic one. In general, the criterion usually used to predict the existen ce of the J ahn-Teller effect in molecules with light atomic nuclei, is not valid anymore when the atomic nuclei are heavy.Para calcular propiedades de moléculas que contienen elementos pesados de la tabla periódica, sólo es adecuada una teoría que resuelva la ecuación de Dirac ele cuatro componentes. Los efectos escalares relativistas pueden estabilizar los orbitales s ancl p y desestabilizar los orbitales d and f. En este contexto, las longitudes ele enlace y otras constantes espectroscópicas pueden cambiar drásticamente al pasar desde el marco no-relativista al relativista. Además la interacción espín-órbita puede cambiar el estado fundamental ele una molécula. En esta tesis se ha estudiado el efecto J ahn-Teller en seis hexafiuoruros de atamos ele transición pesados (RhF6 , 'lvF6 , ReF6 , OsF6 , IrF6 , PtF6). En estos complejos, tanto los efectos relativistas como la correlación electrónica son considerables, por lo tanto para obtener resultados confiables se han efectuado cálculos que resuelven la ecuación de Dirac ele cuatro componentes. Se aplicó la teoría de Dirac-HartreeFock (DHF) y el método correlacionado Teoría del F\mcional ele la Densidad (DFT). El uso ele un programa de cuatro componentes implica un esfuerzo computacional enorme y hoy en día es considerado el método de cálculo más sofisticado existente. Los principales resultados consistieron en determinar el estado fundamental y la geometría de estos seis complejos. Experimentalmente, el complejo PtF6 es esencialmente diamagnético ("singlete") y estrictamente octahédrico, pero estudios teóricos previos habían determinado que éste debería distorsionar debido al efecto JahnTeller, además que su estado fundamental debería ser un "triplete". La explicación de esta contradicción está en que los estudios previos no consideraron la interacción espín-órbita. En contraste, los resultados de esta tesis determinaron inequívocamente una estructura octahédrica indicando que el efecto Jahn-Teller es cancelado debido al efecto espín-órbita. El otro caso interesante es IrF 6 , puesto que una descripción no-relativista o escalar relativista indicaría que este complejo no distorsiona por Jahn-Teller y debe ser octahédrico, tal como ocurre con RhF6 , el cual es iso-electrónico a IrF6 . Sin embargo, los resultados de esta tesis indican que IrF6 debe distorsionar, lo cual está de acuerdo con resultados experimentales. Los resultados concluyen que el efecto .J ahn-Teller debe ser estudiado con la inclusión de la interacción espín-órbita cuando los sistemas considerados contienen nucleos atómicos pesados. El efecto espín-órbita puede cambiar completamente el asignamiento del estado fundamental de los complejos estudiados, en consecuencia si el efecto .Jahn-teller es aplicable en el cuadro no-relativista, este efecto podría ser cancelado en el relativista. En general, el criterio usado normalmente para predecir la existencia del efecto .J ahn-Teller en moléculas con nucleos atómicos livianos, ya no es aplicable cuando los nucleos atómicos son pesados

Calculated geometry and paramagnetic hyperfine structure of the Cu7 cluster

All-electron spin polarized DFT calculations have been performed to optimize the pentagonal bipyramidal (D5h) geometry of the Cu7 cluster by using the B3LYP and the B3PW1 functionals with different basis sets. Dirac scattered-wave and its non-relativistic limit calculations are used to calculate the 63Cu hyperfine coupling constants using a first order perturbational procedure. Our calculations for the Cu7 cluster predict the 2 A2″ as its ground state. The calculated hyperfine coupling constants are in reasonable agreement with those experimentally determined for Cu7 in a matrix isolated ESR study by Van Zee and Weltner [J. Chem. Phys. 92 (1990) 6976]. © 2004 Elsevier B.V. All rights reserved

Quantification of molecular aromaticity as a predictive factor of astrophysical significance

Context. This study reports the index of aromaticity calculated by numerical integration of the magnetically-induced current density for cyclic hydrocarbon molecules both known to exist in astrophysical media as well as those proposed to exist. Aims. This study promotes the ring current strength (RCS) value for quantifying aromaticity as a means of predicting astrophysical detectability. Methods. Density functional theory (DFT) calculations at the B3LYP/aug-cc-pVTZ level provide optimized structures and the wave-functions needed to provide the RCS values for the molecules analyzed. Results. The known interstellar molecules examined c-C3H2, c-(O)C3H2, c-C3HC2H, o-benzyne, benzonitrile, 1-cyano and 2-cyanonaphthalene all have RCS values of 9.9 nA T−1 (nanoampere per Tesla) or above. The known antiaromatic species have RCS values of less than 0.0 nA T−1 as expected. Several proposed interstellar molecules likely will not persist if they form due to low RCS values including c-(C)C3H2. Other species such as p-benzyne and c-HCNN+ have high RCS values of 19.9 nAT−1 and 14.4nAT−1, respectively. Conclusions. Cyclic hydrocarbons previously observed in astrophysical media have high RCS values. Those with low or negative RCS values have yet to be observed implying that such a metric can indicate astrophysical significance