The gas-phase structure of 1-selena-closo-dodecaborane(11), 1-SeB11H11, determined by the concerted use of electron diffraction and computational methods

The molecular structure of 1-selena-closo-dodecaborane(11), 1-SeB11H11, has been determined by the concerted use of quantum chemical calculations and gas-phase electron diffraction. The structure has C(5v) symmetry and is distorted from a regular icosahedron mainly through the expansion of the pentagon of boron atoms adjacent to selenium, with r(a3,1)(B-B) = 192.2(2) pm. The Se-B bond length is extremely well determined [r(a3,1) (Se-B) = 212.9(2) pm] and this is reflected by a pronounced peak in the radial-distribution curve. The accuracy of the experimental structure, as well as that calculated at the MP2/962(d) level, has been gauged by comparison of the 11B chemical shifts (calculated at two different gauge-including atomic orbitals (GIAO) levels) with experimental NMR values. The inclusion of electron correlation in the magnetic property calculations (GIAO-MP2) gave superior results to those carried out using GIAO-Hartree-Fock.     

Bioaffinity magnetic reactor for peptide digestion followed by analysis using bottom-up shotgun proteomics strategy

We report an efficient and streamlined way to improve the analysis and identification of peptides and proteins in complex mixtures of soluble proteins, cell lysates, etc. By using the shotgun proteomics methodology combined with bioaffinity purification we can remove or minimize the interference contamination of a complex tryptic digest and so avoid the time-consuming separation steps before the final MS analysis. We have proved that by means of enzymatic fragmentation (endoproteinases with Arg-C or/and Lys-C specificity) connected with the isolation of specific peptides we can obtain a simplified peptide mixture for easier identification of the entire protein. A new bioaffinity sorbent was developed for this purpose. Anhydrotrypsin (AHT), an inactive form of trypsin with an affinity for peptides with arginine (Arg) or lysine (Lys) at the C-terminus, was immobilized onto micro/nanoparticles with superparamagnetic properties (silica magnetite particles (SiMAG)-Carboxyl, Chemicell, Germany). This AHT carrier with a determined binding capacity (26.8 nmol/mg of carrier) was tested with a model peptide, human neurotensin, and the resulting MS spectra confirmed the validity of this approach.     

Actinium coordination chemistry: A density functional theory study with monodentate and bidentate ligands

In the current study, the coordination chemistry of nine-coordinate Ac(III) complexes with 35 monodentate and bidentate ligands was investigated using density functional theory (DFT) in terms of their geometries, charges, reaction energies, and bonding interactions. The energy decomposition analysis with naturals orbitals for chemical valence (EDA-NOCV) and the quantum theory of atoms in molecules (QTAIM) were employed as analysis methods. Trivalent Ac exhibits the highest affinities toward hard acids (such as charged oxophilic donors, fluoride), so its classification as a hard acid is justified. Natural population analysis quantified the involvement of 5f orbitals on Ac to be about 30% of total valence electron natural configuration indicating that Ac is a member of the actinide series. Pearson correlation coefficients were used to study the pairwise correlations among the bond lengths, ΔG reaction energies, charges on Ac and donor atoms, and data from EDA-NOCV and QTAIM. Strong correlations and anticorrelations were found between Voronoi charges on donor atoms with ΔG, EDA-NOCV interaction energies and QTAIM bond critical point densities.     

Combination of Resonance and Non-Resonance Chiral Raman Scattering in a Cobalt(III) Complex

Resonance Raman optical activity (RROA) spectra with high sensitivity reveal details on molecular structure, chirality, and excited electronic properties. Despite the difficulty of the measurements, the recorded data for the Co(III) complex with S,S-N,N-ethylenediaminedisuccinic acid are of exceptional quality and, coupled with the theory, spectacularly document the molecular behavior in resonance. This includes a huge enhancement of the chiral scattering, contribution of the antisymmetric polarizabilities to the signal, and the Herzberg-Teller effect significantly shaping the spectra. The chiral component is by about one order of magnitude bigger than for an analogous aluminum complex. The band assignment and intensity profile were confirmed by simulations based on density functional and vibronic theories. The resonance was attributed to the S₀→S₃ transition, with the strongest signal enhancement of Raman and ROA spectral bands below about 800 cm⁻¹. For higher wavenumbers, other excited electronic states contribute to the scattering in a less resonant way. RROA spectroscopy thus appears as a unique tool to study the structure and electronic states of absorbing molecules in analytical chemistry, biology, and material science.     

Actinide-Actinide Bonding: Electron Delocalisation and σ-Aromaticity in the Tri-Thorium Cluster [{Th(η8-C8H8)(μ-Cl)2}3K2]

The tri-thorium cluster [{Th(η⁸-C₈H₈)(μ₃-Cl)₂}₃{K(THF)₂}₂]_∞ (Nature 2021, 598 , 72–75) was reported to feature intriguing σ-aromatic bonding between the thorium atoms, a mode of metal–metal bonding unique in the actinide series. However, the presence of this bonding motif has since been challenged by others. Here, we computationally explore electron delocalisation in a molecular cluster fragment of [{Th(η⁸-C₈H₈)(μ₃-Cl)₂}₃{K(THF)₂}₂]_∞ and examine its responses to an applied magnetic field using a variety of methods. We also discuss the importance of the choice of basis set for the Th atoms and issues regarding locating QTAIM bond critical points. When taken together, the computed data consistently suggest the presence of delocalised Th−Th bonding and Th₃ σ-aromaticity.     

Partially linearized, fully size-extensive, and reduced multireference coupled-cluster methods. I. Formalism and mutual relationship

We describe a fully size-extensive alternative of the reduced multireference (RMR) coupled-cluster (CC) method with singles (S) and doubles (D) that generates a subset of higher-than-pair cluster amplitudes, using linearized CC equations from the full CC chain, projected onto the corresponding higher-than-doubly excited configurations. This approach is referred to as partially linearized (pl) MR CCSD method and characterized by the acronym plMR CCSD. In contrast to a similar CCSDT-1 method [Y. S. Lee et al., J. Chem. Phys. 81, 5906 (1984)] this approach also considers higher than triples (currently up to hexuples), while focusing only on a small subset of such amplitudes, referred to as the primary ones. These amplitudes are selected using similar criteria as in RMR CCSD. An extension considering secondary triples via the standard (T)-type corrections, resulting in the plMR CCSD(T) method, is also considered. The relationship of RMR and plMR CCSD and CCSD(T) approaches is discussed, and their performance and characteristics are the subject of the subsequent Part II of this paper.     

Partially linearized, fully size-extensive, and reduced multireference coupled-cluster methods. II. Applications and performance

The partially linearized (pl), fully size-extensive multireference (MR) coupled-cluster (CC) method, fully accounting for singles (S) and doubles (D) and approximately for a subset of primary higher than doubles, referred to as plMR CCSD, as well as its plMR CCSD(T) version corrected for secondary triples, as described in Part I of this paper [X. Li and J. Paldus, J. Chem. Phys. 128, 144118 (2008)], are applied to the problem of bond breaking in the HF, F2, H2O, and N2 molecules, as well as to the H4 model, using basis sets of a DZ or a cc-pVDZ quality that enable a comparison with the full configuration interaction (FCI) exact energies for a given ab initio model. A comparison of the performance of the plMR CCSD/CCSD(T) approaches with those of the reduced MR (RMR) CCSD/CCSD(T) methods, as well as with the standard single reference (SR) CCSD and CCSD(T) methods, is made in each case. For the H4 model and N2 we also compare our results with the completely renormalized (CR) CC(2,3) method [P. Piecuch and M. W?och, J. Chem. Phys. 123, 224105 (2005)]. An important role of a proper choice of the model space for the MR-type methods is also addressed. The advantages and shortcomings of all these methods are pointed out and discussed, as well as their size-extensivity characteristics, in which case we distinguish supersystems involving noninteracting SR and MR subsystems from those involving only MR-type subsystems. Although the plMR-type approaches render fully size-extensive results, while the RMR CCSD may slightly violate this property, the latter method yields invariably superior results to the plMR CCSD ones and is more easy to apply in highly demanding cases, such as the triple-bond breaking in the nitrogen molecule.     

The reaction of (Sp)-2-(diphenylphosphino)ferrocenecarboxylic acid with carbodiimide reagents: Characterisation of the acid anhydride and urea products

Interaction of (S_p)-2-(diphenylphosphino)ferrocenecarboxylic acid [(S_p)-1] with N,N′-dicyclohexylcarbodiimide (DCC) and N-ethyl-N′-[3-(dimethylamino)propyl]carbodiimide (EDC) have been investigated in order to study the reacting system itself and to characterise side-products typically arising during the diimide-promoted condensation of acid (S_p)-1 with nucleophiles. The reaction between (S_p)-1 and DCC was found to give preferentially the respective urea derivative in the absence of a base, and (S_p)-2-(diphenylphosphino)ferrocenecarboxylic anhydride [(S_p,S_p)-3] when the same reaction was performed in the presence of 4-(dimethylamino)pyridine (DMAP). With EDC, the preference for a reaction pathway was less pronounced: whereas the reaction without the base afforded exclusively the corresponding urea, that in the presence of DMAP yielded a mixture of the urea and anhydride (S_p,S_p)-3.     

Electrostatic Filter Ash from Silane Production as Silicate Substitute in Zeolite Chemistry

This paper is a case study of complete substitution of sodium‐metasilicate in zeolite Na‐A synthesis by an electrostatic filter ash (FA) arising in high amounts during silane waste incineration process. The silicate abundant FA is a suitable material for reinsertion in zeolite chemistry. This is shown in the presented investigation by the development of a model reaction process at low temperatures (50–60 °C) and short times (1.5–4 h). The experiments were performed under addition of NaAlO₂ and variation of the alkalinity and the reaction period. Characterization and fine tuning of the process was mainly done by studying the kinetics of FA digestion and zeolite crystallization by XRD and chemical analyses (ICP‐OES) of solutions and solids. It could be shown that pure FA was mostly dissolved (98 %) in 8 M NaOH already after 1 h. Addition of NaAlO₂ and crystallization for further 60 min under optimized conditions at 50 °C yielded to a suitable product. It consists of zeolite Na‐A (92 % by mass) beside some hydrosodalite (8 % by mass). According to this low temperature short time process this study is a contribution for the development of energy efficient recycling solutions.