Synthesis and crystal structures of three Schiff bases derived from 3-formylacetylacetone and o-, m- and p-aminobenzoic acid

Treatment of 3-formylacetylacetone with the isomeric o-, m- and p-aminobenzoic acids led to the formation of the corresponding Schiff bases, namely, 3-[(2-carboxyphenylamino)methylidene]pentane-2,4-dione, 1, 3-[(3-carboxyphenylamino)methylidene]pentane-2,4-dione, 2, and 3-[(4-carboxyphenylamino)methylidene]pentane-2,4-dione, 3, all C13H13NO4, that contain a planar amino-methylene-pentane-2,4-dione core with a strong intramolecular N—H...O hydrogen bridge. The carboxyphenyl groups attached to the nitrogen atom are almost coplanar to the central molecular fragment. Depending on the position of the carboxyl unit, different supramolecular structures with hydrogen-bonding networks are formed in the three title structures.

Quantum and Structural Molecular Fragment models used to predict anti-inflammatory activity

In this paper, we predict the anti-inflammatory activity of a series of 26 structures of N-arylanthranilic acid. So, Quantitatve Structure-Activity Relationship (QSAR) method remains the focus of many studies aimed at modeling and prediction of physicochemical properties or biological activities of molecule. Two models was used: quantum model and Structural Molecular Fragment (SMF) model. In the first model, semi-empirical (AM1) approach was used to calculate the quantum chemical descriptors using GAUSSIAN 09 package and the others chemical descriptors were calculated with chemaxon package. In the second model, Structural Molecular Fragment were generated by I.S.I.D.A (In Silico Design and Data Analysis). Our two models were built by using a Multiple Linear Regression Analysis (MLR).The concluded QSAR models reflected that the drugs activity was mainly attributed to quantum chemical descriptors with the statistical analysis of multiple R-squared equal to 0.9898 v.s 0.9077 for the Structural Molecular Fragment developed in I.S.I.D.A. Keywords: N-arylanthranilic acids, anti-inflammatory activity, quantum descriptors, Structural Molecular Fragment.

Two Tetranuclear Butterfly-Shaped Co(II) Complexes: Structure, Mass Spectrometric, and Magnetism

The organic ligand (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (HL) was used to react with CoX2·6H2O (X = Cl and Br) under solvothermal conditions to obtain the complex [Co4(L)6(X)2] (1, X = Cl; 2, X = Br). The butterfly-shaped structure of complex 1 and 2 suggest that Co(II) ions have two different coordinated modes, which are five coordination with O3NX environment and six coordination with O4N2 environment. In addition, the electrospray ionization mass spectrometry (ESI-MS) analysis indicated that the ion molecular fragment of highest intensity was [Co4(L)6]2+, and there existed a high nuclear fragment peak of [Co7(L)12]2+. Interestingly, it was basically completely transformed into [Co7(L)12]2+ two days later, so those two complexes were relatively stable in CH3OH. Magnetic characterization exhibited that complex 1 and 2 display field-induced single-molecule magnetic behavior, of which the energy hills Ueff/kB were 28 and 20 K under direct-current field of 0.1 T, respectively.

A Karplus Equation for the Conformational Analysis of Organic Molecular Crystals

In the liquid state, vicinal J couplings (3J) have been extensively used for conformational analysis of organic compounds, peptides and proteins through the use of empirical Karplus equations. Contrastingly, there are essentially no examples of the use of 3J for quantitative structural investigation of solids. With the support of DFT calculations, we show that 13C-13C 3J couplings measured on a series of 13C-enriched solids can be related to the dihedral angle of the corresponding molecular fragment by a simple Karplus relationship. We show that such function could be successfully used to deduce dihedral angles on a solid compound with known structure.

A Karplus Equation for the Conformational Analysis of Organic Molecular Crystals

In the liquid state, vicinal J couplings (3J) have been extensively used for conformational analysis of organic compounds, peptides and proteins through the use of empirical Karplus equations. Contrastingly, there are essentially no examples of the use of 3J for quantitative structural investigation of solids. With the support of DFT calculations, we show that 13C-13C 3J couplings measured on a series of 13C-enriched solids can be related to the dihedral angle of the corresponding molecular fragment by a simple Karplus relationship. We show that such function could be successfully used to deduce dihedral angles on a solid compound with known structure.

Probing the Dichotomy of Square Planar d¹⁰ Complexes: Geometric and Electronic Structure of Nickel π-Complexes

<div>Ni π-complexes are widely postulated as intermediates in organometallic chemistry. However, the nature of the bonding in such complexes has not been extensively studied. Herein, we probe the geometric and electronic structure of a series of nickel π-complexes using a combination of ³¹P NMR, Ni K-edge XAS, Ni K_β XES, and supporting density-functional computations. These complexes are best described as square planar d¹⁰ complexes with π-backbonding acting as the dominant factor in the M-L bond to the π ligand. The degree of backbonding correlates with both ²J_PP and the energy of the clearly observable Ni 1s→4p_z</div><div>pre-edge transition in the Ni K-edge XAS data. The degree of backbonding is determined by the energy of the π*_ip ligand acceptor orbital: unactivated olefinic ligands tend to be poor π-acids whereas ketones, aldehydes, and esters allow for greater backbonding. The strength of the backbonding from the neutral Ni(dtbpe) molecular fragment is dramatically increased via σ donation from the diphosphine ligands. In fact, in unactivated pi complexes, backbonding is dominated by charge donation from the phosphines, which allows for strong backdonation even though the metal centre retains a formal d¹⁰ electronic configuration. We describe this interaction as a formal 3-centre-4-electron (3c-4e) interaction where the nickel centre mediates charge transfer from the phosphine σ-donors to the π*_ip ligand acceptor orbital. The implications of this unusual bonding motif are described with respect to both geometric structure and reactivity.</div>

Influence of Local Environment on Inner Shell Excitation Spectra, Studied by Electron and X-ray Spectroscopy and Spectromicroscopy

Inner shell excitation spectroscopy is a local probe of the unoccupied electronic structure in the immediate vicinity of the core excited atom. As such, one might expect the inner shell spectrum of a given unit (a molecular fragment or a repeat unit of a solid) to be largely independent of where that unit is located. This is often an implicit assumption in spectral analysis and analytical applications. However, there are situations where inner shell excitation spectra exhibit significant sensitivity to their local environment. Here I categorize the ways in which inner shell spectra are affected by their local environment, and give examples from a career dedicated to developing a better understanding of inner shell excitation spectroscopy, its experimental techniques, and applications.