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A density functional theory (DFT) study is performedto determine the stability of the complexes formed between eitherthe N or O site of 3-methyl-4-pyrimidone and 1-methyl-2-pyrimidonemolecules and different ligands. The studied ligands are boron andalkali Lewis acids, namely, B(CH3)3, HB(CH3)2, H2B(CH3), BH3, H2BF, HBF2, BF3, Li+, Na+, and K+. The acids are divided into twogroups according to their hardness. The reactivity predictions, accordingto the molecular electrostatic potential (MEP) map and the naturalbond orbital (NBO) analysis, are in agreement with the calculatedrelative stabilities. Our findings reveal a strong regioselectivitywith borane and its derivatives preferring the nitrogen site in bothpyrimidone isomers, while a preference for oxygen is observed forthe alkali acids in the 3-methyl-4-pyrimidone molecule. The complexationof 1-methyl-2-pyrimidone with these hard alkali acids does not showany discrimination between the two sites due to the presence of acontinuous delocalized density region between the nitrogen and theoxygen atoms. The preference of boron Lewis acids toward the N siteis due to the stronger B–N bond as compared to the B–Obond. The influence of fluorine or methyl substitution on the boronatom is discussed through natural orbital analysis (NBO) concentratingon the overlap of the boron empty p-orbital with the F lone pairsand methyl hyperconjugation, respectively. The electrophilicity ofthe boron acids gives a good overall picture of the interaction capabilitieswith the Lewis base. [ABSTRACT FROM AUTHOR]

Density functional theory calculations at the B3LYP/SVP and B3LYP/6-31lG(d) levels were carried out for a series of XH3B80 complexes with X = {N, P, As, B, Al}. To probe the regioselectivity of B80, the electronic Fukui function, the molecular electrostatic potential (MEP), and the natural bond orbital (NBO) were determined. These indices were shown to provide reliable guides to predict the relative reactivities of the boron buckyball sites. Thermodynamic stabilities of the complexes formed by the reaction of B80 with nucleophiles (NH3, PH3, AsH3) and electrophiles (BH3, A1H3) are in good agreement with the prediction of regioselectivity indicated on the basis of Fukui and MEP indices. The qualitative results suggest the boron buckyball to be an amphoteric and hard molecule. It has two distinct reactive sites localized on caps and frame, which act as acids and bases, respectively. Most of the complexes are stable with formation energies comparable to that of the analogous complexes of the borane molecule, BH3BH3, BH3NH3, and BH3A1H3. The B-H-B bond characteristics of diborane are recovered in B80BH3. Exohedral complexes are more stable than endohedral complexes. The most stable complexes are those with NH3 on the caps and BH3 on the pentagonal ring of B80. [ABSTRACT FROM AUTHOR]

A combined computational and interpretational DFT study is performed to investigate the regioselectivity of B 18 and B 30 leapfrog boron sheets upon reaction with XH 3 -type electrophiles and nucleophiles (X = N, P, As, B, Al). The M062X, B3LYP, and B3LYP-D3 functionals are used combined with the 6-31+G(d,p) basis. The molecular electrostatic potential (MEP), Fukui functions, and the dual descriptor are employed to predict the local reactivity of B 18 and B 30 . Our results reveal that both clusters are hard and prefer to react with hard bases and acids, such as NH 3 and BH 3 . Further, these leapfrog B 6n clusters can play the role of catalysts as they break B-H and Al-H bonds of BH 3 and AlH 3 in s -BH 3 -B 6n and s -AlH 3 -B 6 n complexes, respectively. Leapfrog B 6 n -XH 3 complexes (X = B and Al) can be considered as an interaction between two electron-deficient systems. Therefore, the chemical reactivity between these systems cannot be interpreted in terms of the Hard-Soft-Acid-Base principle.

Theoretical calculations were performed to investigate the interplay between σ-hole, anion-HC and cation-π interactions in the complexes of dibromo[2,2]paracyclophane (DBr[2,2]PCP) with alkali (Li + , Na + , K + ), alkaline earth metal cations (Be 2+ , Mg 2+ , and Ca 2+ ), and halogen anions (F - , Cl - , and Br - ) using the wave function (MP2) and density functional theory (M06-2X and B3LYP) methods with the 6-311++G(d,p) basis set. The study reveals that DBr[2,2]PCP behaves as amphoteric molecule with a predominance of basic character. It prefers to interact with hard cations and hard anions such as Be 2+ and F - through cation-π and anion···HC interactions, respectively. Substitution of Br by F and Cl atoms in DBr[2,2]PCP decreases slightly the interaction energies of DX[2,2]PCP-halogen complexes (X = F, Cl, and Br) by 2.0 and 0.3 kcal/mol (M06-2X), respectively. The anion-HC interactions in DBr[2,2]PCP complexes are ∼10 kcal/mol stronger (B3LYP; ∼15 kcal/mol at M06-2X and 7 kcal/mol at MP2) than the σ-hole interactions.

The electronic structure of Eu 2+ compounds results from a complex combination of strongly correlated electrons and relativistic effects as well as weak ligand-field interaction. There is tremendous interest in calculating the electronic structure as nowadays the Eu 2+ ion is becoming more and more crucial, for instance, in lighting technologies. Recently, interest in semiempirical methods to qualitatively evaluate the electronic structure and to model the optical spectra has gained popularity, although the theoretical methods strongly rely upon empirical inputs, hindering their prediction capabilities. Besides, ab initio multireference models are computationally heavy and demand very elaborative theoretical background. Herein, application of the ligand-field density functional theory (LFDFT) method that is recently available in the Amsterdam Modeling Suite is shown: (i) to elucidate the electronic structure properties on the basis of the multiplet energy levels of Eu configurations 4f 7 and 4f 6 5d 1 and (ii) to model the optical spectra quite accurately if compared to the conventional time-dependent density functional theory tool. We present a theoretical study of the molecular Eu(η 9 -C 9 H 9 ) 2 complex and its underlying photoluminescence properties with respect to the Eu 4f-5d electron transitions. We model the excitation and emission spectra with good agreement with the experiments, opening up the possibility of modeling lanthanides in complex environment like nanomaterials by means of LFDFT at much-reduced computational resources and cost.

Density functional theory calculations at the B3LYP/SVP and B3LYP/6-311G(d) levels were carried out for a series of XH(3)B(80) complexes with X = {N, P, As, B, Al}. To probe the regioselectivity of B(80), the electronic Fukui function, the molecular electrostatic potential (MEP), and the natural bond orbital (NBO) were determined. These indices were shown to provide reliable guides to predict the relative reactivities of the boron buckyball sites. Thermodynamic stabilities of the complexes formed by the reaction of B(80) with nucleophiles (NH(3), PH(3), AsH(3)) and electrophiles (BH(3), AlH(3)) are in good agreement with the prediction of regioselectivity indicated on the basis of Fukui and MEP indices. The qualitative results suggest the boron buckyball to be an amphoteric and hard molecule. It has two distinct reactive sites localized on caps and frame, which act as acids and bases, respectively. Most of the complexes are stable with formation energies comparable to that of the analogous complexes of the borane molecule, BH(3)BH(3), BH(3)NH(3), and BH(3)AlH(3). The B-H-B bond characteristics of diborane are recovered in B(80)BH(3). Exohedral complexes are more stable than endohedral complexes. The most stable complexes are those with NH(3) on the caps and BH(3) on the pentagonal ring of B(80)., (© 2011 American Chemical Society)

A density functional theory study of small base molecules and tetrahedral and cubane-like group V clusters encapsulated in B(80) shows that the boron buckyball is a hard acid and prefers hard bases like NH(3) or N(2)H(4) to form stable off-centered complexes. In contrast, tetrahedral and cubane-like clusters of this family are metastable in the cage. The most favorable clusters are the mixed tetrahedral and cubane clusters formed by nitrogen and phosphorus atoms such as P(2)N(2)@B(80), P(3)N@B(80), and P(4)N(4)@B(80). The boron cap atoms are electrophilic centers, and prefer mainly to react with electron rich nucleophilic sites. The stability of the complexes will be governed by the size and electron donating character of the encapsulated clusters. B(80) forms stable complexes with hard materials where a bidentate interaction of the encapsulated molecule with two boron cap atoms is preferred over a single direct complex toward a single endohedral boron.