Rotational Excitation Cross Sections for Chloronium Based on a New 5D Interaction Potential with Molecular Hydrogen.

Chloronium (HCl) is an important intermediate of Cl-chemistry in space. The accurate knowledge of its collisional properties allows a better interpretation of the corresponding observations in interstellar clouds and, therefore, a better estimation of its abundance in these environments. While the ro-vibrational spectroscopy of HCl is well-known, the studies of its collisional excitation are rather limited and these are available for the interaction with helium atoms only.

H2O-HCN complex: A new potential energy surface and intermolecular rovibrational states from rigorous quantum calculations.

In this work the H2O-HCN complex is quantitatively characterized in two ways. First, we report a new rigid-monomer 5D intermolecular potential energy surface (PES) for this complex, calculated using the symmetry-adapted perturbation theory based on density functional theory method. The PES is based on 2833 ab initio points computed employing the aug-cc-pVQZ basis set, utilizing the autoPES code, which provides a site-site analytical fit with the long-range region given by perturbation theory.

Solvent-induced polymorphism in dipodal N-donor ligands containing a biphenyl core.

Polymorph screenings for two related dipodal N-donor ligands containing a biphenyl core, namely 4,4'-bis(pyridin-4-ylmethyl)-1,1'-biphenyl (1) and 4,4'-bis(1-imidazol-1-ylmethyl)-1,1'-biphenyl (2) were performed, and the new phases were isolated and their crystal structures analysed. Profiling included methods such as PXRD and thermal analysis. Hirshfeld surface analyses, as well as crystal lattice energy calculations provided deeper insight in the interplay of the intermolecular forces and the stability of the isolated phases.

Towards the generation of potential energy surfaces of weakly bound medium-sized molecular systems: the case of benzonitrile-He complex.

Currently, the explicitly correlated coupled cluster method is used routinely to generate the multi-dimensional potential energy surfaces (mD-PESs) of van der Waals complexes of small molecular systems relevant for atmospheric, astrophysical and industrial applications. Although very accurate, this method is computationally prohibitive for medium and large molecules containing clusters. For instance, the recent detections of complex organic molecules (COMs) in the interstellar medium, such as benzonitrile, revealed the need to establish an accurate enough electronic structure approach to map the mD-PESs of these species interacting with the surrounding gases.

Electronic Structure and Spectroscopy of the AuO Cation.

The electronic structure and spectroscopy of the 29 lowest electronic states of the AuO cation were studied using multiconfigurational methods. These states correlate to the Au(S) + O(P) and Au(D) + O(P) dissociation limits. Their potentials were calculated along the Au-O internuclear distance.

Resolving the π-assisted U-N σ-bond formation using quantum information theory.

We model the potential energy profiles of the UO (NCO)Cl → NUOCl + CO reaction pathway [Y. Gong, V. Vallet, M.

Structure, energetics, and spectroscopy of the chromophores of HHe+n, HHe+n, and He+n clusters and their deuterated isotopologues.

The linear molecular ions HHe, HHe+2, and He+3 are the central units (chromophores) of certain He-solvated complexes of the HHe+n, HHe+n, and He+n families, respectively. These are complexes which do exist, according to mass-spectrometry studies, up to very high values. Apparently, for some of the HHe+n and He+n complexes, the linear symmetric tetratomic HHe+2 and the diatomic He+2 cations, respectively, may also be the central units.

Supramolecular Approach to Tuning the Photophysical Properties of Quadrupolar Squaraines.

In the present study, the influence of the hydrogen bonding for the one- and two-photon absorption of the prototypical squaraine dye is investigated with quantum chemistry tools. The central squaraine unit is bound by strong hydrogen bonds with 4-substituted N,N'-diphenylurea and, alternatively, N,N'-diphenylthiourea molecules, which affects to a high extend the properties of the squaraine electron accepting moiety, thus shifting its maximum absorption wavelength and enhancing the TPA cross section. The replacement of oxygen by sulfur atoms in the squaraine central ring, known to affect its photophysical behavior, is considered here as the way of modifying the strength and nature of the intermolecular contacts.

Buchwald-Hartwig Amination of Aryl Halides with Heterocyclic Amines in the Synthesis of Highly Fluorescent Benzodifuran-Based Star-Shaped Organic Semiconductors.

The study of palladium-catalyzed amination of bromobenzene with aromatic and heterocyclic amines, widely used in the synthesis of organic semiconductors, was performed. The best conditions for the coupling of aryl bromides with carbazole, diphenylamine, phenoxazine, phenothiazine, 9,9-dimethyl-9,10-dihydroacridine, and their derivatives have been developed. Based on the results, nine new star-shaped organic semiconductors, exhibiting up to 100% fluorescent quantum yield in the 400-550 nm range, have been synthesized in good yields.

Photochemical Properties and Stability of BODIPY Dyes.

The present study is devoted to the combined experimental and theoretical description of the photophysical properties and photodegradation of the new boron-dipyrromethene (BODIPY) derivatives obtained recently for biomedical applications, such as bacteria photoinactivation (Piskorz et al., Dyes and Pigments 2020, 178, 108322). Absorption and emission spectra for a wide group of solvents of different properties for the analyzed BODIPY derivatives were investigated in order to verify their suitability for photopharmacological applications.

Dataset of noncovalent intermolecular interaction energy curves for 24 small high-spin open-shell dimers.

We introduce a dataset of 24 interaction energy curves of open-shell noncovalent dimers, referred to as the O24 × 5 dataset. The dataset consists of high-spin dimers up to 11 atoms selected to assure diversity with respect to interaction types: dispersion, electrostatics, and induction. The benchmark interaction energies are obtained at the restricted open-shell CCSD(T) level of theory with complete basis set extrapolation (from aug-cc-pVQZ to aug-cc-pV5Z).

Nature of intermolecular interaction in squaraine dimers.

Squaraine dyes are known for their particular optical properties. They exhibit intense photochemically stable fluorescence in usually (near) infra red region that can be quenched by intermolecular interactions. Moreover, even the centrosymmetric dyes feature non-zero second harmonic generation upon aggregation.

Solvent-assisted structural conversion involving bimetallic complexes based on the tris(oxalato)ferrate(iii) unit with the green → blue → red crystal color sequence.

Three new complexes forming a dynamic system and given by the following formulae: [Cu(bpy)Fe(ox)]NO·HO 1, [Fe(bpy)][Fe(ox)]NO·10HO 2 and [Cu(bpy)][Fe(ox)]NO·10HO 3 (bpy - 2,2'-bipyridine, ox - oxalate), were synthesized from a methanol-water mixture or water, and characterized structurally, spectroscopically and magnetically. Compound 1 contains trinuclear [(bpy)Cu(μ-ox)Fe(ox)(μ-ox)Cu(bpy)] cations, while 2 and 3 can be classified as isomorphous ionic compounds, with alternately arranged hydrophobic and hydrophilic layers of mononuclear complex ions. The green crystals of 1 are perfectly stable in air, whereas in selected solvents they undergo irreversible solvent-assisted recrystallization towards red crystals of 2, which is also accompanied by the appearance of mononuclear blue copper complexes with oxalate, 2,2'-bipyridine and aqua ligands, already described in the literature.

Computational Study of the Influence of Nitrogen-Containing Unsaturated Heterocyclic Substituents on Electronic and Spectroscopic Properties of Squaraine Derivatives.

A comprehensive understanding of the influence of the different structural elements for the molecular properties is crucial for improving the material design procedures in the field of photosensitive dyes. The present study provides a detailed analysis of the influence of the number of heteroatoms (nitrogens) and the lengths of the π-electron skeleton on the one- and two-photon absorption of the symmetric squaraine dyes. Extended computational study covers the conventional vertical excitation calculations within the TD-DFT formalisms as well as several advanced single-reference methods including double excitations such as CIS(D), SAC-CI, and ADC(2).

Ab Initio Study of Chemical Reactions of Cold SrF and CaF Molecules with Alkali-Metal and Alkaline-Earth-Metal Atoms: The Implications for Sympathetic Cooling.

We investigate the energetics of the atom exchange reaction in the SrF + alkali-metal atom and CaF + alkali-metal atom systems. Such reactions are possible only for collisions of SrF and CaF with the lithium atoms, while they are energetically forbidden for other alkali-metal atoms. Specifically, we focus on SrF interacting with Li, Rb, and Sr atoms and use ab initio methods to demonstrate that the SrF + Li and SrF + Sr reactions are barrierless.

Orbit-orbit relativistic correction calculated with all-electron molecular explicitly correlated Gaussians.

An algorithm for calculating the first-order electronic orbit-orbit magnetic interaction correction for an electronic wave function expanded in terms of all-electron explicitly correlated molecular Gaussian (ECG) functions with shifted centers is derived and implemented. The algorithm is tested in calculations concerning the H molecule. It is also applied in calculations for LiH and H molecular systems.

Interaction-induced electric properties and cooperative effects in model systems.

A detailed analysis of the interaction-induced linear and non-linear axial static electric dipole properties and the interaction energy of the model HCHO(HF)(n) (n = 1, 2) complexes is carried out using the HF SCF, MP2, CCSD and CCSD(T) levels of approximation combined with a wide range of basis sets, namely the correlation-consistent basis sets of Dunning and co-workers, the polarization-consistent basis sets of Jensen, and the recently reported polarized LPol sets. The results of this study show that even the smallest among the LPol sets, the LPol-ds and LPol-dl sets, yield interaction induced axial static electric dipole properties of an accuracy comparable to that obtained with the aug-cc-pVQZ basis set. Using the LPol-ds, the LPol-dl, and the LPol-fl sets we have estimated the induced electric properties and the interaction energy of the HCHO(HF)(n) (n = 1-9) complexes, the cooperative effects in these systems, and the two-body effects.

Orbit-orbit relativistic corrections to the pure vibrational non-Born-Oppenheimer energies of H(2).

We report the derivation of the orbit-orbit relativistic correction for calculating pure vibrational states of diatomic molecular systems with sigma electrons within the framework that does not assume the Born-Oppenheimer (BO) approximation. The correction is calculated as the expectation value of the orbit-orbit interaction operator with the non-BO wave function expressed in terms of explicitly correlated Gaussian functions multiplied by even powers of the internuclear distance. With that we can now calculate the complete relativistic correction of the order of alpha(2) (where alpha=1/c).

Electron affinity of (7)Li calculated with the inclusion of nuclear motion and relativistic corrections.

Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of (7)Li and (7)Li(-). The nuclear motion has been explicitly included in the calculations (i.e.

Lowest excitation energy of 9Be.

Variational calculations employing explicitly correlated Gaussian functions and explicitly including the nuclear motion [i.e., without assuming the Born-Oppenheimer (BO) approximation] have been performed to determine the lowest singlet transition energy in the 9Be atom.

Relativistic corrections to the non-Born-Oppenheimer energies of the lowest singlet Rydberg states of 3He and 4He.

In this work the authors present an approach to calculate the leading-order relativistic corrections for ground and excited states of helium isotopomers. In the calculations they used variational wave functions expanded in terms of explicitly correlated Gaussians obtained without assuming the Born-Oppenheimer approximation.

Darwin and mass-velocity relativistic corrections in non-Born-Oppenheimer variational calculations.

The Pauli approach to account for the mass-velocity and Darwin relativistic corrections has been applied to the formalism for quantum mechanical molecular calculations that does not assume the Born-Oppenheimer (BO) approximation regarding separability of the electronic and nuclear motions in molecular systems. The corrections are determined using the first order perturbation theory and are derived for the non-BO wave function of a diatomic system expressed in terms of explicitly correlated Gaussian functions with premultipliers in the form of even powers of the internuclear distance. As a numerical example we used calculations of the transition energies for pure vibrational states of the HD(+) ion.

Darwin and mass-velocity relativistic corrections in the non-Born-Oppenheimer calculations of pure vibrational states of H2.

The Darwin and mass-velocity relativistic corrections have been calculated for all pure vibrational states of the H2 using the perturbation theory and very accurate variational wave functions obtained without assuming the Born-Oppenheimer (BO) approximation. Expansions in terms of explicitly correlated Gaussians with premultipliers in the form of even powers of the internuclear distance were used for the wave functions. With the inclusion of the two relativistic corrections to the non-BO energies the transition energies for the highest states agree more with the experimental results.

Convergence of experiment and theory on the pure vibrational spectrum of HeH(+).

Very accurate quantum mechanical calculations of the pure vibrational spectrum of the molecular ion are reported and compared with newly obtained pure vibrational transitions extracted from the available experimental data. The calculations are performed without assuming the Born-Oppenheimer approximation regarding separability of the nuclear and electronic motions and include the first order relativistic mass-velocity and Darwin corrections. For the two lowest transitions, whose experimental energies are established with the highest precision, the calculated and the experimental results show very good agreement.

Convergence of approximate two-component Hamiltonians: how far is the Dirac limit.

A systematic elimination of the off-diagonal parts of the Dirac Hamiltonian is carried out in the spirit of the Douglas-Kroll [Ann. Phys. 82, 87 1974] approach and the recently proposed infinite-order two-component method.