BH Molecule Research Articles

Calculations of Positron Scattering from Boron, BH, BF, BF2, and BF3

The single-center convergent close-coupling (CCC) method is applied to calculate positron scattering from boron. A model potential approach is utilized to extract the positronium formation, direct ionization, and values between the positronium formation and ionization thresholds. We present results for total, electron loss, elastic, momentum transfer, total bound state excitation, positronium formation, direct ionization, stopping power, and mean excitation energy from 10−5 eV to 5000 eV. For boron, there is only one other set of theoretical positron calculations for elastic and momentum transfer above 500 eV, which is in excellent agreement with the current CCC results. Using the current results for boron atoms and previous CCC calculations for hydrogen and fluorine atoms, positron scattering from BF, BF2, BF3, and BH molecules is calculated for energies between 0.1 eV and 5000 eV with a modified independent atom approach.

Semiempirical Methods for Molecular Systems in Strong Magnetic Fields.

A general scheme is presented to extend semiempirical methods to include the effects of arbitrary strength magnetic fields, while maintaining computational efficiency. The approach utilizes three main modifications; a London atomic orbital (LAO) basis set is introduced, field-dependent kinetic energy corrections are added to the model Hamiltonian, and spin-Zeeman interaction energy terms are included. The approach is applied to the widely available density-functional tight-binding method GFN1-xTB. Considering the basis set requirements for the kinetic energy corrections in a magnetic field leads to two variants: a single-basis approach GFN1-xTB-M0 and a dual-basis approach GFN1-xTB-M1. The LAO basis in the latter includes the appropriate nodal structure for an accurate representation of the kinetic energy corrections. The variants are assessed by benchmarking magnetizabilities and nuclear magnetic resonance shielding constants calculated using weak magnetic fields. Remarkably, the GFN1-xTB-M1 approach also exhibits excellent performance for strong fields, || ≤ 0.2B0 (B0 = 2.3505 × 105 T), recovering exotic features such as the para- to dia-magnetic transition in the BH molecule and the preferred electronic configuration, molecular conformation, and orientation of benzene. At stronger field strengths, || > 0.2B0, a degradation in the quality of the results is observed. The utility of GFN1-xTB-M1 is demonstrated by performing conformer searches in a range of field strengths for the cyclooctatetraene molecule, with GFN1-xTB-M1 capturing the transition from tub to planar conformations at high field, consistent with much more computationally demanding current-density functional theory calculations. Magnetically induced currents are also shown to be well described for the benzene and infinitene molecules, the latter demonstrating the flexibility and computational efficiency of the approach. The GFN1-xTB-M1 approach is a useful tool for the study of structure, conformation, and dynamics of large systems in magnetic fields at the semiempirical level as well as for preoptimization of molecular structure in ab initio calculations, enabling more efficient exploration of complex potential energy surfaces and reactivity in the presence of external fields.

New Insights into Adsorption Properties of the Tubular Au26 from AIMD Simulations and Electronic Interactions

Recently, we revealed the electronic nature of the tubular Au26 based on spherical aromaticity. The peculiar structure of the Au26 could be an ideal catalyst model for studying the adsorptions of the Au nanotubes. However, through Google Scholar, we found that no one has reported connections between the structure and reactivity properties of Au26. Here, three kinds of molecules are selected to study the fundamental adsorption behaviors that occur on the surface of Au26. When one CO molecule is adsorbed on the Au26, the σ-hole adsorption structure is quickly identified as belonging to a ground state energy, and it still maintains integrity at a temperature of 500 K, where σ donations and π-back donations take place; however, two CO molecules make the structure of Au26 appear with distortions or collapse. When one H2 is adsorbed on the Au26, the H-H bond length is slightly elongated due to charge transfers to the anti-bonding σ* orbital of H2. The Au26-H2 can maintain integrity within 100 fs at 300 K and the H2 molecule starts moving away from the Au26 after 200 fs. Moreover, the Au26 can act as a Lewis base to stabilize the electron-deficient BH3 molecule, and frontier molecular orbitals overlap between the Au26 and BH3.

Reactivity of triphosphinoboranes towards H3B·SMe2: access to derivatives of boraphosphacycloalkanes with diverse substituents.

Triphosphinoboranes activated the B-H bond in the BH3 molecule without any catalysts at room temperature. Hydroboration reactions led to boraphosphacyloalkanes with diverse structures. The outcomes of reactions depend on the size of the phosphanyl substituent on the boron atom of the parent triphosphinoborane, where derivatives of boraphosphacyclobutane and boraphosphacyclohexane were obtained. Furthermore, the precursor of triphosphinoboranes, namely bromodiphosphinoborane, also exhibited high reactivity towards H3B·SMe2, yielding bromo-substituted boraphosphacyclobutane. The obtained products were characterized by heteronuclear NMR spectroscopy, single crystal X-ray diffraction, and elemental analysis.

Dual Reactivity of a Geometrically Constrained Phosphenium Cation.

A geometrically constrained phosphenium cation in bis(pyrrolyl)pyridine based NNN pincer type ligand (1+ ) was synthesized, isolated and its preliminary reactivity was studied with small molecules. 1+ reacts with MeOH and Et2NH, activating the O−H and N−H bonds via a P‐center/ligand assisted path. The reaction of 1+ with one equiv. of H3NBH3 leads to its dehydrogenation producing 5. Interestingly, reaction of 1+ with an excess H3NBH3 leads to phosphinidene (PI) species coordinating to two BH3 molecules (6). In contrast, [1+ ][OTf] reacts with Et3SiH by hydride abstraction yielding 1‐H and Et3SiOTf, while [1+ ][B(C6F5)4] reacts with Et3SiH via an oxidative addition type reaction of Si−H bond to P‐center, affording a new PV compound (8). However, 8 is not stable over time and degrades to a complex mixture of compounds in matter of minutes. Despite this, the ability of [1+ ][B(C6F5)4] to activate Si−H bond could still be tested in catalytic hydrosilylation of benzaldehyde, where 1+ closely mimics transition metal behaviour.

Dual Reactivity of a Geometrically Constrained Phosphenium Cation

A geometrically constrained phosphenium cation in bis(pyrrolyl)pyridine based NNN pincer type ligand (1+) was synthesized, isolated and its preliminary reactivity was studied with small molecules. 1+ reacts with MeOH and Et2NH, activating the O−H and N−H bonds via a P-center/ligand assisted path. The reaction of 1+ with one equiv. of H3NBH3 leads to its dehydrogenation producing 5. Interestingly, reaction of 1+ with an excess H3NBH3 leads to phosphinidene (PI) species coordinating to two BH3 molecules (6). In contrast, [1+][OTf] reacts with Et3SiH by hydride abstraction yielding 1-H and Et3SiOTf, while [1+][B(C6F5)4] reacts with Et3SiH via an oxidative addition type reaction of Si−H bond to P-center, affording a new PV compound (8). However, 8 is not stable over time and degrades to a complex mixture of compounds in matter of minutes. Despite this, the ability of [1+][B(C6F5)4] to activate Si−H bond could still be tested in catalytic hydrosilylation of benzaldehyde, where 1+ closely mimics transition metal behaviour.

Theoretical study on spectroscopic properties of 8 Λ-S and 23 Ω states for BH molecule

In this work, the potential energy curves of eight low electronic states (X<sup>1</sup>Σ<sup>+</sup>, a<sup>3</sup>Π, A<sup>1</sup>Π, b<sup>3</sup>Σ<sup>-</sup>, 2<sup>3</sup>Π, 1<sup>3</sup>Σ<sup>+</sup>, 1<sup>5</sup>Σ<sup>-</sup>, and 1<sup>5</sup>Π) and twenty-three Ω states of BH molecule, and the transition dipole moments among the <inline-formula><tex-math id="M10">\begin{document}$ {\text{X}}{}^{\text{1}}{\Sigma}_{{{\text{0}}^ + }}^ + $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M10.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M11">\begin{document}$ {{\text{a}}^{\text{3}}}{\Pi_{{{\text{0}}^ + }}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M11.png"/></alternatives></inline-formula>, a<sup>3</sup>Π<sub>1</sub>, a<sup>3</sup>Π<sub>2</sub>, and A<sup>1</sup>Π<sub>1</sub> states are calculated by using the internally contracted multireference configuration interaction (icMRCI) method. In order to obtain the accurate potential energy curve, the errors caused by single and double electron excitation, core-valence correlation effects, relativistic effects and basis set truncation are corrected. The spectral and transition data of BH molecule are in good agreement with the available theoretical and experimental data. The calculation results show that the A<sup>1</sup>Π<sub>1</sub>(<i>υ′</i> = 0-2, <i>J′</i> = 1, +) →<inline-formula><tex-math id="M12">\begin{document}$ {\text{X}}{}^{\text{1}}{\Sigma}_{{{\text{0}}^ + }}^ + $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M12.png"/></alternatives></inline-formula>(<i>υ′′</i> = 0-2, <i>J′′</i> = 1, –) transition has large Einstein <i>A</i>-coefficient, weighted absorption oscillator strength, and highly diagonal vibrational branching ratio<i> R</i><sub><i>υ′υ′′</i></sub>, and the excited state A<sup>1</sup>Π<sub>1</sub>(<i>υ′</i> = 0, 1) have short spontaneous radiation lifetimes. Moreover, the effects of <inline-formula><tex-math id="M13">\begin{document}$ {{\text{a}}^{\text{3}}}{\Pi_{{{\text{0}}^ + }}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M13.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M13.png"/></alternatives></inline-formula>and a<sup>3</sup>Π<sub>1</sub> states on A<sup>1</sup>Π<sub>1</sub>(<i>υ′</i> = 0) ↔ <inline-formula><tex-math id="M14">\begin{document}$ {\text{X}}{}^{\text{1}}{\Sigma}_{{{\text{0}}^ + }}^ + $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M14.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M14.png"/></alternatives></inline-formula>(<i>υ′′</i> = 0) cycle transition can be ignored. Therefore, according to the A<sup>1</sup>Π<sub>1</sub>(<i>υ′</i><sub> </sub>= 0-1, <i>J′</i> = 1, +) ↔ <inline-formula><tex-math id="M15">\begin{document}$ {\text{X}}{}^{\text{1}}{\Sigma}_{{{\text{0}}^ + }}^ + $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M15.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220038_M15.png"/></alternatives></inline-formula>(<i>υ′′</i><sub> </sub>= 0-3, <i>J</i>′′ = 1, –) cycle transition, we propose to apply one main cooling laser (<i>λ</i><sub>00</sub> = 432.45 nm) and two repumping lasers (<i>λ</i><sub>10</sub> = 479.67 nm and <i>λ</i><sub>21</sub> = 481.40 nm) to laser cooling BH molecules, and evaluation of the cooling effect.

Fabrication of novel three-dimensional Fe3O4-based particles electrodes with enhanced electrocatalytic activity for Berberine removal

Reasonable design of three-dimensional (3D) catalytic particle electrodes (CPEs) is crucial for achieving efficient electrocatalytic oxidation of organic pollutants. Herein, the novel Fe3O4/SnO2/GO (FO/SO/GO) particle electrode has been developed and serviced to the 3D electrocatalytic berberine hydrochloride oxidation system with DSA (RuO2–IrO2–SnO2/Ti) electrode as anode and GDE (gas diffusion electrode) electrode as the cathode. Compared with 2D systems and other CPEs, FO/SO/GO electrode shows excellent electrocatalytic activity and remarkable stability for BH removal, that is, the removal rate of BH is 94.8% within 90 min, and the rate constant is 0.03095 min−1. More importantly, after five cycles, the ternary composite still maintains a strong ability to oxidize pollutants. The structural characterization and electrochemical measurement further uncover that the electron transfer ability and electrocatalytic oxidation efficiency are highly dependent on the surface structure regulation of CPEs. Furthermore, the quenching experiments show that hydroxyl radicals are the main active species in the 3D electro-Fenton (EF) system, which can oxidize BH molecules adsorbed on the surface of GO to CO2, H2O, or other products. The results could potentially provide new insights for designing and fabricating more stable and efficient 3D CPEs electrocatalytic removal of organic pollutants in the future.

A cautionary tale: Problems in the valence-CASSCF description of the ground state (X1Σ+) of BF.

In the full optimized reaction space and valence-complete active space self-consistent field (vCAS) methods, a set of active orbitals is defined as the union of the valence orbitals on the atoms, all possible configurations involving the active orbitals are generated, and the orbitals and configuration coefficients are self-consistently optimized. Such wave functions have tremendous flexibility, which makes these methods incredibly powerful but can also lead to inconsistencies in the description of the electronic structure of molecules. In this paper, the problems that can arise in vCAS calculations are illustrated by calculations on the BH and BF molecules. BH is well described by the full vCAS wave function, which accounts for molecular dissociation and 2s-2p near-degeneracy in the boron atom. The same is not true for the full vCAS wave function for BF. There is mixing of core and active orbitals at short internuclear distances and swapping of core and active orbitals at large internuclear distances. In addition, the virtual 2π orbitals, which were included in the active space to account for the 2s-2p near degeneracy effect, are used instead to describe radial correlation of the electrons in the F2pπ-like pairs. Although the above changes lead to lower vCAS energies, they lead to higher vCAS+1+2 energies as well as irregularities and/or discontinuities in the potential energy curves. All of the above problems can be addressed by using the spin-coupled generalized valence bond-inspired vCAS wave function for BF, which includes only a subset of the atomic valence orbitals in the active space.

Influence of Multisite Metal-Ligand Cooperativity on the Redox Activity of Noninnocent N2S2 Ligands.

Metal-ligand cooperativity (MLC) relies on chemically reactive ligands to assist metals with small-molecule binding and activation, and it has facilitated unprecedented examples of catalysis with metal complexes. Despite growing interest in combining ligand-centered chemical and redox reactions for chemical transformations, there are few studies demonstrating how chemically engaging redox active ligands in MLC affects their electrochemical properties when bound to metals. Here we report stepwise changes in the redox activity of model Ru complexes as zero, one, and two BH3 molecules undergo MLC binding with a triaryl noninnocent N2S2 ligand derived from o-phenylenediamine (L1). A similar series of Ru complexes with a diaryl N2S2 ligand with ethylene substituted in place of phenylene (L2) is also described to evaluate the influence of the o-phenylenediamine subunit on redox activity and MLC. Cyclic voltammetry (CV) studies and density functional theory (DFT) calculations show that MLC attenuates ligand-centered redox activity in both series of complexes, but electron transfer is still achieved when only one of the two redox-active sites on the ligands is chemically engaged. The results demonstrate how incorporating more than one multifunctional reactive site could be an effective strategy for maintaining redox noninnocence in ligands that are also chemically reactive and competent for MLC.

Analyzing Magnetically Induced Currents in Molecular Systems Using Current-Density-Functional Theory

A suite of tools for the analysis of magnetically induced currents is introduced. These are applicable to both the weak-field regime, well described by linear response perturbation theory, and to the high-field regime, which is inaccessible to such methods. A disc-based quadrature scheme is proposed for the analysis of magnetically induced current susceptibilities, providing quadratures that are consistently defined between different molecular systems and applicable to both planar 2D and general 3D molecular systems in a black-box manner. The applicability of the approach is demonstrated for a range of planar ring systems, the ground and excited states of the benzene molecule and the ring, bowl and cage isomers of the C_20 molecule in the presence of a weak magnetic field. In the presence of a strong magnetic field, the para- to dia-magnetic transition of the BH molecule is studied, demonstrating that magnetically induced currents present a visual interpretation of this phenomenon, providing insight beyond that accessible using linear-response methods.

Performance of the NOF-MP2 method in hydrogen abstraction reactions

The recently proposed natural orbital functional second-order M{\o}ller-Plesset (NOF-MP2) method is capableof achieving both dynamic and static correlation even for those systems with significant multiconfigurational character. We test its reliability to describe the electron correlation in radical formation reactions, namely, in the homolytic X-H bond cleavage of LiH, BH, CH4, NH3, H2O and HF molecules. Our results are compared with CASSCF and CASPT2 wavefunction calculations and the experimental data. For a dataset of 20 organic molecules, the thermodynamics of C-H homolytic bond cleavage, in which the C-H bond is broken in the presence of different chemical environments, is presented. The radical stabilization energies obtained for such general dataset are compared with the experimental data. It is observed that NOF-MP2 is able to give a quantitative agreement for dissociation energies, with a performance comparable to that of the accurate CASPT2 method.

Theoretical Modeling of the Structure and Stability of Complexes of the Icosahedral Al−13 Ion with Borane and Alane Molecules

The structures, energies, and spectroscopic characteristics of the \({\rm{A}}{{\rm{l}}_{13}}({\rm{B}}{{\rm{H}}_3})_n^-\) and \({\rm{A}}{{\rm{l}}_{13}}({\rm{Al}}{{\rm{H}}_3})_n^-\) complexes with the centered icosahedral aluminum cluster \({\rm{Al}}_{13}^-\) successively “solvated” with borane and alane molecules with n = 1–16 sequentially “solvated” with borane, alane, diborane, and dialane molecules (L = BH3, AlH3, B2H6, and Al2H6) have been calculated by the density functional theory (DFT) method. According to calculations, in the first half of the borane series \({\rm{A}}{{\rm{l}}_{13}}({\rm{B}}{{\rm{H}}_3})_n^-\), the BH3 molecules are coordinated to edges of the Al13 cage through two B–Al bonds and the B–Hb–Al hydrogen bridge. With increasing number of ligands n, B–Hb–B′ bridges between the ligands and binuclear B2Hm moieties with m = 3–5 appear in the surface region of the complexes. The calculations predicted the stability of borane complexes to decomposition with elimination of a diborane molecule and the possibility of their existence in the isolated state. In the early members of the alane series \({\rm{A}}{{\rm{l}}_{13}}({\rm{Al}}{{\rm{H}}_3})_n^-\), the ligands are also bound to the cage through two Al–Al′ bonds and a hydrogen bridge; with increasing n, they are even more prone than boranes to form H-bridges between the ligands and binuclear surface moieties Al2Hm. At n > 10, the internal cage is severely distorted and opened. At the end of the series, the cage changes its composition due to transfer of several Al atoms to the surface region. The alane complexes are less stable than their borane analogues; however, for the systems of the second half of the \({\rm{A}}{{\rm{l}}_{13}}({\rm{Al}}{{\rm{H}}_3})_n^-\) series, the calculations predict noticeable stability to decomposition with elimination of the dialane molecule. Trends in structural characteristics and energies of the complexes with increasing n are traced. The results can be of interest for modeling the structure and stability of more complicated nanosized aluminoborohydrides and aluminohydrides with high hydrogen content.

Fully numerical Hartree‐Fock and density functional calculations. II. Diatomic molecules

AbstractWe present the implementation of a variational finite element solver in the HelFEM program for benchmark calculations on diatomic systems. A basis set of the form is used, where (μ, ν, φ) are transformed prolate spheroidal coordinates, B n(μ) are finite element shape functions, and are spherical harmonics. The basis set allows for an arbitrary level of accuracy in calculations on diatomic molecules, which can be performed at present with either nonrelativistic Hartree‐Fock (HF) or density functional (DF) theory. Hundreds of DFs at the local spin density approximation (LDA), generalized gradient approximation (GGA), and the meta‐GGA level can be used through an interface with the Libxc library; meta‐GGA and hybrid DFs are not available in other fully numerical diatomic program packages. Finite electric fields are also supported in HelFEM, enabling access to electric properties. We introduce a powerful tool for adaptively choosing the basis set by using the core Hamiltonian as a proxy for its completeness. HelFEM and the novel basis set procedure are demonstrated by reproducing the restricted open‐shell HF limit energies of 68 diatomic molecules from the first to the fourth period with excellent agreement with literature values, despite requiring orders of magnitude fewer parameters for the wave function. Then, the electric properties of the BH and N2 molecules under finite field are studied, again yielding excellent agreement with previous HF limit values for energies, dipole moments, and dipole polarizabilities, again with much more compact wave functions than what were needed for the literature references. Finally, HF, LDA, GGA, and meta‐GGA calculations of the atomization energy of N2 are performed, demonstrating the superb accuracy of the present approach.

Theoretical Modeling of the Structure of Complexes of the Dodecaalane Anion Al12H2−12 with Borane, Alane, Diborane, and Dialane Molecules

The structures, energies, and spectroscopic characteristics of Al12 H12 (L) 2− complexes with the icosahedral Al12 H 12 2− , dianion sequentially “solvated” with borane, alane, diborane, and dialane molecules (L = BH3, AlH3, B2H6, and Al2H6) have been calculated by the density functional theory method. It has been shown that upon the coordination to the dianion, the BH3 and B2H6 molecules change their configuration and coordinate as bidentate BH4 and B2H7 ligands, while their alane analogues coordinate as monodentate AlH4 and Al2H7 groups to form tetrahydroboranate and tetrahydroalanate complexes like Al12 H12-n (BH4) 2− and Al12 H12-n (AlH4) 2− , respectively. The hydroboranate complexes are stable to decomposition with elimination of a diborane molecule within ∼15−17 kcal/mol for all n values, n = 1−12. Their alanate analogues Al12 H12-n (AlH4) 2− are less stable, but the first members of the series (with n = 2−4) also exhibit noticeable stability to elimination of a dialane molecule within ∼7−10 kcal/mol. Calculations have predicted a possibility of the existence of the most stable of the considered complexes in an isolated state or under matrix isolation conditions. The results can be useful in quantum-chemical modeling of the structure and stability of nanoscale aluminoborohydride compounds with high hydrogen content.

Carbonyl compounds of Tc, Re, and Bh: Electronic structure, bonding, and volatility

Calculations of molecular properties of M(CO)5 and MH(CO)5, where M = Tc, Re, and Bh, and of the products of their decomposition, M(CO)4 and MH(CO)4, were performed using density functional theory and coupled-cluster methods implemented in the relativistic program suits such as ADF, DIRAC, and ReSpect. The calculated first M-CO bond dissociation energies (FBDEs) of Bh(CO)5 and BhH(CO)5 turned out to be significantly weaker than those of the corresponding Re homologs. The reason for that is the relativistic destabilization and expansion of the 6d AOs, responsible for weaker σ-forth and π-back donations in the Bh compounds. The relativistic FBDEs of M(CO)5 have, therefore, a Λ-shape behavior in the row Tc-Re-Bh, while the non-relativistic values increase toward Bh. Using the results of the molecular calculations and a molecule-slab interaction model, adsorption enthalpies, ΔH ads, of group-7 carbonyl hydrides on quartz and Teflon were estimated for future gas-phase chromatography experiments. It was found that BhH(CO)5 should be almost as volatile as the homologs, although its interaction with the surfaces should be somewhat stronger than that of MH(CO)5 (M = Tc and Re), while the M(CO)4 (M = Tc, Re, and Bh) molecules should be non-volatile. It will, therefore, be difficult to distinguish between the group-7 MH(CO)5 species by measuring their ΔH ads on surfaces of Teflon and quartz with an error bar of ±4 kJ/mol. The trends in properties and ΔH ads of group-7 carbonyl hydrides are similar to those of group-8 carbonyls of Ru, Os, and Hs.

Where and How Does an Organic Molecule Having a C–X Bond Release X– Anion Like an Inorganic Compound? A Theoretical Study

In this research, at first, a comparative DFT study on hydride or fluoride release from a number of known orthoamides, their fluorine derivative having a central C-F bond and some simple organic compounds, is reported. The obtained data show that orthoamides release hydride or fluoride anions much easier than do other known organic compounds studied here. Interestingly, three simulated orthoamides having a central C-F bond, spontaneously and like an inorganic compound, release fluoride anion upon dissolving in polar solvents. The calculations confirmed that hyperconjugation interactions in the initial orthoamides facilitate the anion release from these compounds. However, the data clearly show that the proper overlap of an empty p orbital of the central carbon atom with adjacent lone-pair orbitals of nitrogen atoms ( lpN → lp*C or, in other words, the pπ-pπ interaction) in the resulting carbocations is a more important factor that must be taken into consideration when designing the hydride, fluoride, or other anion releasing agents. In addition, for the first time, a mechanism of hydride and fluoride removal from the orthoamides either through their reaction with BH3 and BF3 molecules, respectively, or upon their protonation is provided. To continue and for generalization of results to other groups attached to the central carbon atom of orthoamides, the reactions of H+ with orthoamides having the CH3, OH, CN, NH2, or C5H5 substituents were studied. The results showed that in all cases and in both gas and solution phases the above substituents easily leave the carbon atom as an anion and bond to H+. Thus, we have to conclude that upon the reaction of orthoamides with usual Lewis acids, many types of substituents on their central carbon atom can leave these compounds as anions.

Developments in molecular electronic structure evaluation based on the self-frictional field with Slater-type orbitals

Molecular electronic structure evaluations are investigated here using complete orthonormal sets of Guseinov $$\psi^{\left( \alpha \right)}$$ exponential-type orbitals ( $$\psi^{\left( \alpha \right)}$$ ETOs), where $$\alpha = 1,0, - 1, - 2, \ldots$$ is the self-friction quantum number. Using two-center overlap integrals over Slater-type orbitals (STOs) with same screening constants, all the one- and two-electron multicenter integrals are reformulated with the help of the Lowdin alpha radial function. The proposed formula yields useful definitions that enable us to evaluate the multicenter integrals and related combined Hartree–Fock–Roothaan equations over STOs. In terms of the self-frictional field effect, the effectiveness of the method is demonstrated using the BH3 molecule as an example application. The results of the calculation are validated using existing methods.

Unitary coupled-cluster based self-consistent polarization propagator theory: A third-order formulation and pilot applications.

In this article, the development of a third-order self-consistent polarization propagator method based on unitary coupled-cluster (UCC) parametrization of the ground-state wavefunction and the excitation manifold comprising unitary-transformed excitation operators, hereafter referred to as UCC3, is reported. The UCC3 method is designed to provide excitation energies correct up to the third order for excited states dominated by single excitations. An expansion for the UCC transformed Hamiltonian involving Bernoulli numbers as expansion coefficients is adopted in the derivation of UCC3 working equations. Interestingly, UCC-based polarization propagator theory offers an alternative derivation for the strict version of the third-order algebraic diagrammatic construction [ADC(3)-s] method. The UCC3 results for the excitation energies of excited states in H2O, HF, N2, Ne, CH2, BH, and C2 molecules are compared with benchmark full configuration interaction values as well as ADC(3) and equation-of-motion coupled-cluster singles and doubles results to demonstrate the accuracy of the UCC3 method. UCC-based self-consistent polarization propagator theory appears to be a promising framework for developing non-perturbative hermitian formulations for treating electronically excited states.

On the Computational Characterization of Charge-Transfer Effects in Noncovalently Bound Molecular Complexes.

Charge-transfer (CT) is an important binding force in the formation of intermolecular complexes, and there have been a variety of theoretical models proposed to quantify this effect. These approaches, which typically rely on a definition of a "CT-free" state based on a partition of the system, sometimes yield significantly different results for a given intermolecular complex. Two widely used definitions of the "CT-free" state, the absolutely localized molecular orbitals (ALMO) method (where only on-fragment orbital mixings are permitted) and the constrained density functional theory (CDFT) approach (where fragment electron populations are fixed), are carefully examined in this work. Natural bond orbital (NBO) and the regularized symmetry-adapted perturbation theory (SAPT) are also briefly considered. Results for the ALMO and CDFT definitions of CT are compared on a broad range of model systems, including hydrogen-bonding systems, borane complexes, metal-carbonyl complexes, and complexes formed by water and metal cations. For most of these systems, CDFT yields a much smaller equilibrium CT energy compared to that given by the ALMO-based definition. This is mainly because the CDFT population constraint does not fully inhibit CT, which means that the CDFT "CT-free" state is in fact CT-contaminated. Examples of this contamination include (i) matching forward and backward donation (e.g., formic acid dimer) and (ii) unidirectional CT without changing fragment populations. The magnitude of the latter effect is quantified in systems such as the water dimer by employing a 3-space density constraint in addition to the orbital constraint. Furthermore, by means of the adiabatic EDA, it is shown that several observable effects of CT, such as the "pyramidalization" of the planar BH3 molecule upon the complexation with Lewis bases, already appear on the "CT-free" CDFT surface. These results reveal the essential distinctions between the ALMO and CDFT definitions of CT and suggest that the former is more consistent with accepted understanding of the role of CT in intermolecular binding.