Atoms in Generalized Orbital Configurations: Towards Atom-Dedicated Density Functionals.

Deriving a practical formula for the atomic body with generalized shell occupations, we perform a detective analysis of the radial distribution in the exchange energy, hinting at ideas about new types of density functionals, dedicated to the specifics of the electronic structure of atoms, exploiting the intrinsic spherical symmetry.

Microwave Assisted Reactions of Fluorescent Pyrrolodiazine Building Blocks.

We report here the synthesis and optical spectral properties of several new pyrrolodiazine derivatives. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between N-alkylated pyridazine and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). The pyrrolopyridazine derivatives are blue emitters with moderate quantum yields (around 25%) in the case of pyrrolopyridazines and negligible yet measurable emission for pyrrolophthalazines.

On the Charge-Transfer Excitations in Azobenzene Maleimide Compounds: A Theoretical Study.

Photoswitchable systems with charge-transfer (CT) transitions have gained much attention during the recent years because of their many emerging applications. CT transitions themselves are of fundamental importance from physical, chemical, engineering, and molecular modeling points of view because they depend on the modified intramolecular electronic structure. CT transitions in azobenzene (AB) were observed when substituted with the maleimide (MI) functional group.

On The Density Functional Theory Treatment of Lanthanide Coordination Compounds: A Comparative Study in a Series of Cu-Ln (Ln = Gd, Tb, Lu) Binuclear Complexes.

The nontrivial aspects of electron structure in lanthanide complexes, considering ligand field (LF) and exchange coupling effects, have been investigated by means of density functional theory (DFT) calculations, taking as a prototypic case study a series of binuclear complexes [LCu(OCOMe)Ln(thd)], where L = N,N'-2,2-dimethyl-propylene-di(3-methoxy-salicylidene-iminato) and Ln = Tb, Lu, and Gd. Particular attention has been devoted to the Cu-Tb complex, which shows a quasi-degenerate nonrelativistic ground state. Challenging the limits of density functional theory (DFT), we devised a practical route to obtain different convergent solutions, permuting the starting guess orbitals in a manner resembling the run of the β electron formally originating from the f configuration of the Tb(III) over seven molecular orbitals (MOs) with predominant f-type character.

The Cycloaddition of the Benzimidazolium Ylides with Alkynes: New Mechanistic Insights.

New insights concerning the reaction mechanism in the cycloaddition reaction of benzimidazolium ylides to activated alkynes are presented. The proposed pathway leading both to 2-(1H-pyrrol-1-yl)anilines and to pyrrolo[1,2-a]quinoxalin-4(5H)-ones involves an opening of the imidazole ring from the cycloaddition product, followed by a nucleophilic attack of the aminic nitrogen to a proximal carbonyl group and the elimination of a leaving group. The mechanistic considerations are fully supported by experimental data, including the XRD resolved structure of the key reaction intermediate.

Quantum chemical study of a derivative of 3-substituted dithiocarbamic flavanone.

The aim of this work is to characterize a quite novel 3-dithiocarbamic flavonoid by vibrational spectroscopy in conjunction with Density Functional Theory (DFT) calculations. Quantum mechanics calculations of energies, geometries and vibrational wavenumbers in the ground state were carried out by using hybrid functional B3LYP with 6-311G(d,p) as basis set. The results indicate a remarkable agreement between the calculated molecular geometries, as well as vibrational frequencies, and the corresponding experimental data.

Conformational effects on the lowest excited states of benzoyl-pyrrolopyridazine: insights from PCM time-dependent DFT.

Time-dependent density functional theory (TD-DFT) computations and steady-state electronic spectroscopy measurements are performed on two recently synthesized pyrrolopyridazines to account for the detrimental effect of benzoyl substitution on the blue fluorescence emission. In the case of the highly fluorescent ester derivative, planar in ground state, we show that TD-DFT using the PBE0 and B3LYP hybrid functionals in the state-specific solvation approach provides an accurate description of absorption and emission properties. In benzoyl-pyrrolopyridazine, the (pretwisted) orientations of the benzoyl group and the solvent polarity are both found to modulate the nature of the lowest excited states.

Theoretical study on β-cyclodextrin inclusion complexes with propiconazole and protonated propiconazole.

The synthesis of the β-cyclodextrin/propiconazole nitrate inclusion complex and the advantages of the encapsulation of this drug were recently reported, but the experimental data only partially revealed the structure of the supramolecular complex due to the limitations in understanding the intermolecular association mechanism. The present work describes the equilibrium molecular geometries of β-cyclodextrin/propiconazole and β-cyclodextrin/protonated propiconazole, established by the AM1 and PM3 semi-empirical methods. The affinity between different parts of the guest molecule and the cyclodextrin cavity was studied considering that propiconazole possesses three residues able to be included into the host cavity through primary or secondary hydroxyl rims.