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Despite the chemistry of actinide-ligand bonding is continuing and of burgeoning interest, investigations of the chemical bonding of bimetallic complexes involving transuranics remain relatively less, and there are rarely studies on the bonding features between actinide and coinage metals (CM). We present a systematic research on the series of An@Au7 (An = Th to Cm), UCM7 (CM = Cu, Ag, Au), and WAu7 clusters to investigate the unique geometries, electronic structures, and chemical bonding between An 5f6d orbitals and CM ns orbitals, and to find their periodicity across the actinides and within the group of transition metals. A unique planar wheel-like structure for An@Au7 clusters with the help of actinide metals encapsulation via spin-orbit coupling, resulting in An(III). Instead, the transition-metal (TM) element W retains its usual six-gold-coordination structure in WAu7, thus forcing the seventh Au out of plane. The An-CM interactions, depending on the ion radii, become stronger with the increase of the atomic number of the actinide metals, as well as the CM. These results show that the presence of actinides in clusters can lead to unique electronic and geometrical structures.

Lanthanide oxo compounds are of vital importance in lanthanide chemistry, as well as in environmental and materials sciences. Praseodymium, as an exceptional element in lanthanides which can form a +V formal oxidation state (OSf) besides the dominant +III among the 4f-block element, displays the significant participation of the Pr 4f orbitals in bonding interactions which is commonly crucial in stabilizing the high oxidation state of Pr in PrO2+ and NPrO species. Here, we report a systematic theoretical study on the structures and stabilities of a series of XPrO (X: B, Al, C, Si, N, P, As, O, S, F, Cl) compounds along with [XPrO]+ cation (X: O, S) and [X3PrO] complexes (X: F and Cl). This work reveals that Pr is able to achieve the lowest and highest OSf and the OSf exhibits periodic variation from +I in BOPr and AlOPr to +II in SiOPr to +III in CPrO, FPrO, ClPrO and AsPrO to +IV in OPrO and SPrO and even to +V in NPrO, [OPrO]+, [SPrO]+, F3PrO and Cl3PrO. We found that the molecular structures are correlated to the Pr oxidation state due to the highly important 4f orbital in the chemical bonding of the high oxidation state compounds. Thus, not only the electronegativity of the ligand but also the quasi-degenerate Pr valence 4f orbitals, namely energetic covalency, control the oxidation state and play a fundamental role in affecting the electronic structural stability of Pr(v) compounds as well. This work demonstrates the structurally directing role of the f-orbital in the formation of the linear structure and is constructive for achieving the higher oxidation state of a given element by tuning the ligand.

As a group 12 element, mercury locating at the sixth row with a valent electronic configuration of 5 d 10 6 s 2 has been treated as a main group element featuring +I and +II oxidation states for a long time. C. K. Jorgensen conjectured the existences of HgF4 and HgF6 molecules in early 1960s, where HgF4 was first synthesized in 2007, but HgF6 as the Hg(+VI) compound was less known. In this paper we explored the electronic structure and decomposition paths of HgF6 by scalar (X1C) and 2-component relativistic (X2C) density functional calculations and more accurate multi-reference NEVPT2 calculations. It is found that the HgF6 molecule, where the mercury atom presents an extraordinary high oxidation state of +VI, is protected by a considerable barrier height of about 22 kcal/mol for the decomposition into HgF4 and two isolated fluorine atoms. The results propose that HgF6 is kinetically stable and may exist under exorbitant conditions.

Cadmium (Cd), a heavy metal toxic to humans, easily accumulates in rice grains. Rice with unacceptable Cd content has become a serious food safety problem in many rice production regions due to contaminations by industrialization and inappropriate waste management. The development of rice varieties with low grain Cd content is seen as an economic and long-term solution of this problem. The cation/H+ exchanger (CAX) family has been shown to play important roles in Cd uptake, transport and accumulation in plants. Here, we report the characterization of the rice CAX family. The six rice CAX genes all have homologous genes in Arabidopsis thaliana. Phylogenetic analysis identified two subfamilies with three rice and three Arabidopsis thaliana genes in both of them. All rice CAX genes have trans-member structures. OsCAX1a and OsCAX1c were localized in the vacuolar while OsCAX4 were localized in the plasma membrane in rice cell. The consequences of qRT-PCR analysis showed that all the six genes strongly expressed in the leaves under the different Cd treatments. Their expression in roots increased in a Cd dose-dependent manner. GUS staining assay showed that all the six rice CAX genes strongly expressed in roots, whereas OsCAX1c and OsCAX4 also strongly expressed in rice leaves. The yeast (Saccharomyces cerevisiae) cells expressing OsCAX1a, OsCAX1c and OsCAX4 grew better than those expressing the vector control on SD-Gal medium containing CdCl2. OsCAX1a and OsCAX1c enhanced while OsCAX4 reduced Cd accumulation in yeast. No auto-inhibition was found for all the rice CAX genes. Therefore, OsCAX1a, OsCAX1c and OsCAX4 are likely to involve in Cd uptake and translocation in rice, which need to be further validated.

Zn chlorin (Znchl) is easy to synthesize and has similar optical properties to those of bacteriochlorophyll c in the nature, which is expected to be used as a light-harvesting antenna system in artificial photosynthesis. In order to further explore the optical characteristics of Znchl, various sizes of a parallel layered Znchl-aggregate model and the THF-Znchl explicit solvent monomer model were constructed in this study, and their Qy excited state properties were simulated by using time-dependent density functional theory (TDDFT) and exciton theory. For the Znchl monomer, with a combination of the explicit solvent model and the implicit solvation model based on density (SMD), the calculated Qy excitation energy agreed very well with the experimental one. The Znchl aggregates may be simplified to a Zn36 model to reproduce the experimental Qy absorption spectrum by the Förster coupling theory. The proposed Znchl aggregate model provides a good foundation for the future exploration of other properties of Znchl and simulations of artificial light-harvesting antennas. The results also indicate that J-aggregrates along z-direction, due to intermolecular coordination bonds, are the dominant factor in extending the Qy band of Znchl into the near infrared region.

Zinc (Zn) is an essential trace element for the growth and development of both humans and plants. Increasing the accumulation of Zn in rice grains is important for the world&rsquo, s nutrition and health. In this study, we used a multiparent advanced generation intercross (MAGIC) population constructed using four parental lines and genotyped using a 55 K rice SNP array to identify QTLs related to Zn2+ concentrations in shoots at the seedling stage and grains at the mature stage. Five QTLs were detected as being associated with shoot Zn2+ concentration at the seedling stage, which explained 3.7&ndash, 5.7% of the phenotypic variation. Six QTLs were detected as associated with grain Zn2+ concentration at the mature stage, which explained 5.5&ndash, 8.9% of the phenotypic variation. Among the QTLs, qSZn2-1/qGZn2 and qSZn3/qGZn3 were identified as being associated with both the shoot and grain contents. Based on gene annotation and literature information, 16 candidate genes were chosen in the regions of qSZn1, qSZn2-1/qGZn2, qSZn3/qGZn3, qGZn7, and qGZn8. Analysis of candidate genes through qRT-PCR, complementation assay using the yeast Zn-uptake-deficient double-mutant ZHY3, and sequencing of the four parental lines suggested that LOC_Os02g06010 may play an important role in Zn2+ accumulation in indica rice.

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C&ndash, H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C&ndash, H bond strength change in excited states versus the ground state. For the first time, three excited states including &pi, y&prime, &rarr, 3s, &pi, 3py and &pi, 3pz were identified with stronger C=C ethylene double bonds than in the ground state.

11 aryl&ndash, lone pair and three aryl&ndash, anion &pi, &ndash, hole interactions are investigated, along with the argon&ndash, benzene dimer and water dimer as reference compounds, utilizing the local vibrational mode theory, originally introduced by Konkoli and Cremer, to quantify the strength of the &pi, hole interaction in terms of a new local vibrational mode stretching force constant between the two engaged monomers, which can be conveniently used to compare different &pi, hole systems. Several factors have emerged which influence strength of the &pi, hole interactions, including aryl substituent effects, the chemical nature of atoms composing the aryl rings/ &pi, hole acceptors, and secondary bonding interactions between donors/acceptors. Substituent effects indirectly affect the &pi, hole interaction strength, where electronegative aryl-substituents moderately increase &pi, hole interaction strength. N-aryl members significantly increase &pi, hole interaction strength, and anion acceptors bind more strongly with the &pi, hole compared to charge neutral acceptors (lone&ndash, pair donors). Secondary bonding interactions between the acceptor and the atoms in the aryl ring can increase &pi, hole interaction strength, while hydrogen bonding between the &pi, hole acceptor/donor can significantly increase or decrease strength of the &pi, hole interaction depending on the directionality of hydrogen bond donation. Work is in progress expanding this research on aryl &pi, hole interactions to a large number of systems, including halides, CO, and OCH3- as acceptors, in order to derive a general design protocol for new members of this interesting class of compounds.

Visualizing vibrational motions calculated with different ab initio packages requires dedicated post-processing tools. Here, we present a PyMOL plugin called PyVibMS for visualizing the vibrational motions for both molecular and solid systems calculated by mainstream quantum chemical computer programs including Gaussian, Q-Chem, VASP, and CRYSTAL. Benefiting from the continuing development of the PyMOL platform, PyVibMS provides powerful functionalities and user-friendly interface. PyVibMS was written in Python and its open-source nature makes it flexible and sustainable. As an example, the motions of the Konkoli-Cremer local vibrational modes are shown in this work for the first time. PyVibMS is freely available at https://github.com/smutao/PyVibMS . Graphical abstract In this work, a PyMOL plugin named PyVibMS is developed to visualize molecular and lattice vibrations.

The unified reaction valley approach (URVA) differs from mainstream mechanistic studies, as it describes a chemical reaction via the reaction path and the surrounding reaction valley on the potential energy surface from the van der Waals region to the transition state and far out into the exit channel, where the products are located. The key feature of URVA is the focus on the curving of the reaction path. Moving along the reaction path, any electronic structure change of the reacting molecules is registered by a change in their normal vibrational modes and their coupling with the path, which recovers the curvature of the reaction path. This leads to a unique curvature profile for each chemical reaction with curvature minima reflecting minimal change and curvature maxima, the location of important chemical events such as bond breaking/forming, charge polarization and transfer, rehybridization, etc. A unique decomposition of the path curvature into internal coordinate components provides comprehensive insights into the origins of the chemical changes taking place. After presenting the theoretical background of URVA, we discuss its application to four diverse catalytic processes: (i) the Rh catalyzed methanol carbonylation&mdash, the Monsanto process, (ii) the Sharpless epoxidation of allylic alcohols&mdash, transition to heterogenous catalysis, (iii) Au(I) assisted [3,3]-sigmatropic rearrangement of allyl acetate, and (iv) the Bacillus subtilis chorismate mutase catalyzed Claisen rearrangement&mdash, and show how URVA leads to a new protocol for fine-tuning of existing catalysts and the design of new efficient and eco-friendly catalysts. At the end of this article the pURVA software is introduced. The overall goal of this article is to introduce to the chemical community a new protocol for fine-tuning existing catalytic reactions while aiding in the design of modern and environmentally friendly catalysts.

The local vibrational mode analysis developed by Konkoli and Cremer has been successfully applied to characterize the intrinsic bond strength via local bond stretching force constants in molecular systems. A wealth of new insights into covalent bonding and weak chemical interactions ranging from hydrogen, halogen, pnicogen, and chalcogen to tetrel bonding has been obtained. In this work we extend the local vibrational mode analysis to periodic systems, i.e. crystals, allowing for the first time a quantitative in situ measure of bond strength in the extended systems of one, two, and three dimensions. We present the study of one-dimensional polyacetylene and hydrogen fluoride chains and two-dimensional layers of graphene, water, and melamine-cyanurate as well as three-dimensional ice I

The conformational properties of ring compounds such as cycloalkanes determine to a large extent their stability and reactivity. Therefore, the investigation of conformational processes such as ring inversion and/or ring pseudorotation has attracted a lot of attention over the past decades. An in-depth conformational analysis of ring compounds requires mapping the relevant parts of the conformational energy surface at stationary and also at non-stationary points. However, the latter is not feasible by a description of the ring with Cartesian or internal coordinates. We provide in this work, a solution to this problem by introducing a new coordinate system based on the Cremer–Pople puckering and deformation coordinates. Furthermore, analytic first- and second-order derivatives of puckering and deformation coordinates, i.e., B-matrices and D-tensors, were developed simplifying geometry optimization and frequency calculations. The new coordinate system is applied to map the potential energy surfaces and reaction paths of cycloheptane (C7H14), cyclooctane (C8H16), and cyclo[18]carbon (C18) at the quantum chemical level and to determine for the first time all stationary points of these ring compounds in a systematic way.

In this work a new curvilinear coordinate system is presented for the comprehensive description of polytopal rearrangements of N-coordinate compounds (N = 4-7) and systems containing an N-coordinate subunit. It is based on normal vibrational modes and a natural extension of the Cremer-Pople puckering coordinates ( J. Am. Chem. Soc. 1975, 97, 1354) together with the Zou-Izotov-Cremer deformation coordinates ( J. Phys. Chem. A 2011, 115, 8731) for ring structures to N-coordinate systems. We demonstrate that the new curvilinear coordinates are ideal reaction coordinates describing fluxional rearrangement pathways by revisiting the Berry pseudorotation and the lever mechanism in sulfur tetrafluoride, the Berry pseudorotation and two Muetterties' mechanisms in pentavalent compounds, the chimeric pseudorotation in iodine pentafluoride, Bailar and Ray-Dutt twists in hexacoordinate tris-chelates as well as the Bartell mechanism in iodine heptafluoride. The results of our study reveal that this dedicated curvilinear coordinate system can be applied to most coordination compounds opening new ways for the systematic modeling of fluxional processes.

Periodic local vibrational modes were calculated with the rev-vdW-DF2 density functional to quantify the intrinsic strength of the X-I⋯OA-type halogen bonding (X = I or Cl, OA: carbonyl, ether and N-oxide groups) in 32 model systems originating from 20 molecular crystals. We found that the halogen bonding between the donor dihalogen X-I and the wide collection of acceptor molecules OA features considerable variations of the local stretching force constants (0.1&ndash, 0.8 mdyn/&Aring, ) for I⋯O halogen bonds, demonstrating its powerful tunability in bond strength. Strong correlations between bond length and local stretching force constant were observed in crystals for both the donor X-I bonds and I⋯O halogen bonds, extending for the first time the generalized Badger&rsquo, s rule to crystals. It is demonstrated that the halogen atom X controlling the electrostatic attraction between the &sigma, hole on atom I and the acceptor atom O dominates the intrinsic strength of I⋯O halogen bonds. Different oxygen-containing acceptor molecules OA and even subtle changes induced by substituents can tweak the n &rarr, &sigma, &lowast, (X-I) charge transfer character, which is the second important factor determining the I⋯O bond strength. In addition, the presence of the second halogen bond with atom X of the donor X-I bond in crystals can substantially weaken the target I⋯O halogen bond. In summary, this study performing the in situ measurement of halogen bonding strength in crystalline structures demonstrates the vast potential of the periodic local vibrational mode theory for characterizing and understanding non-covalent interactions in materials.

Utilizing the analytic derivative formalism for the Mossbauer isomer shift in connection with the Dirac-exact two-component Normalized Elimination of the Small Component (2c-NESC) method a new appr...

Boranes and carboranes form non-classical H-bonds with the π-face of an arene provided entropic factors are excluded, for example via a suitably designed template. The self-assembled Ir-dithiolene phosphine complexes of the type [Cp∗Ir(PR3)S2C2B10H10] (R = C6H4X, X = H, F, OMe) provide such a template. Steric crowding causes that one of the B-H bonds of the carborane is positioned above the phenyl plane of R to form a non-classical B-H…π hydrogen bond. For the gas phase, this is predicted by quantum chemical calculations of the local B-H…π stretching force constants. The solid-state structures of six [Cp∗Ir(PR3)S2C2B10H10] complexes synthesized are in close agreement with the quantum chemical predictions thus suggesting the existence of B-H…π hydrogen bonds. The 1H[11B] NMR titration experiments reveal that non-covalent B-H…π bonds also exists in solution. Calculations show that the bond strength order of the B-H…π H-bond determined with the help of the local stretching force constant is 0.35, comparable to what is found for the H-bond in the water dimer. However, the B-H…π H-bond is electrostatic in nature as confirmed by the topological analysis of the electron density ρ(r). The role of this H-bond in carborane supramolecular chemistry is elucidated and discussed.

The electronic states of OsSi are calculated by multi-state N-electron valence state second order perturbation theory (MS-NEVPT2) with all-electron basis sets. The relativistic effects are considered comprehensively that allows us to identify the X3Σ0+– ground state. The theoretical equilibrium bond length 2.103 A is close to the experimental measurement of 2.1207 A while the vibrational frequency 466 cm–1 is smaller than the experimental value of 516 cm–1. Two excited states, namely 3Π1(I) and 3Π1(II), are located at 15568 and 18316 cm–1 above the ground state, respectively. The 3Π1(I) ← X3Σ0+– transition has been assigned to the experimental spectra at 15729 cm–1 and 3Π1(II) ← X3Σ0+– may produce the bands near 18469 cm–1. Although the latter transition energy is in accord with the experimental spectra, theoretical calculations give too small oscillator strength. Moreover, plenty of excited states with considerable oscillator strengths are located that could serve as reference data in future experiments....

By use of the theoretical method of density functional theory (DFT), we systemically investigate the chalcogen doped Cu4 metal clusters (Cu4O, Cu4S, and Cu4Se) as catalysts for the electrochemical CO2 reduction with toluene as solvent. These doped clusters have efficient catalytic properties which can reduce CO2 to CH4 and a small amount of CH3OH. In the case of CO2 hydrogenation to CH4, the reaction barrier of the Cu4O cluster and Cu4S cluster are reduced by 0.37 eV and 0.15 eV, respectively, compared with the pristine Cu4 cluster. The calculation results also show the overpotentials for the CO2 hydrogenation to CH4 in the order of Cu4S

Using catastrophe theory and the concept of a mutation path, an algorithm is developed that leads to the direct correlation of the normal vibrational modes of two structurally related molecules. The mutation path is defined by weighted incremental changes in mass and geometry of the molecules in question, which are successively applied to mutate a molecule into a structurally related molecule and thus continuously converting their normal vibrational spectra from one into the other. Correlation diagrams are generated that accurately relate the normal vibrational modes to each other by utilizing mode-mode overlap criteria and resolving allowed and avoided crossings of vibrational eigenstates. The limitations of normal mode correlation, however, foster the correlation of local vibrational modes, which offer a novel vibrational measure of similarity. It will be shown how this will open new avenues for chemical studies. © 2017 Wiley Periodicals, Inc.

Using the FPD composite approach of Peterson et. al. we calculate the permanent electric dipole moments of PtX (X = H, F, Cl, Br, and I) at the equilibrium geometries of their ground states. The dipole moment of PtF is estimated to be 3.421 Debye, being very close to the experimental value of 3.42(6) Debye. This research also suggests the ordering of dipole moments of PtX being proportional to the electronegativity of X.

Theoretical studies of hydrogen-bonding based on cluster models tend to overlook the peripheral monomers which are influential. By revisiting thirteen hydrogen-bonded complexes of H2O, HF and NH3, the “push-pull” effect is identified as a general mechanism that strengthens a hydrogen bond. Enhanced Lp ( X ) → σ ∗ ( X ′ - H ) charge transfer is proved to be the core of the “push-pull” effect. The charge transfer can convert an electrostatic hydrogen bond into a covalent hydrogen bond.

The algebraic exact two-component (X2C) relativistic Hamiltonian can be viewed as a matrix functional of the decoupling (X) and renormalization (R) matrices. It is precisely their responses to external perturbations that render X2C-based response theories different in form from the nonrelativistic counterparts. However, the situation is not really bad. Sticking to the energy gradients, it can be shown that the nuclear derivatives of X and R (Xμ and Rμ, respectively) can be transformed away to favor transformed, nucleus-independent density matrices, viz., the X2C energy gradients can be written in a form that does not depend explicitly on Xμ and Rμ. Further combined with the storage of quantities that are already available in the energy calculation, only 35 matrix multiplications are needed to construct the one-electron (relativistic) part of the X2C gradients, thereby rendering the gradient calculations very efficient. More efficiency can be gained by approximating the molecular X as the superposition of the atomic ones (denoted as X2C/AXR) and by further approximating the molecular R also as the superposition of the atomic ones (denoted as X2C/AU): The numbers of matrix multiplications required for constructing the one-electron (relativistic) parts of the X2C/AXR and X2C/AU gradients are reduced to 18 and 4, respectively. Similar approximations can also be applied to the X2C Hessian. It will be shown numerically that the X2C/AXR gradients and Hessians are extremely accurate (almost indistinguishable from the full X2C ones), whereas the X2C/AU ones do have discernible errors but which are tolerable in view of the dramatic gain in efficiency.

Cadmium (Cd), as a heavy metal, presents substantial biological toxicity and has harmful effects on human health. To lower the ingress levels of human Cd, it is necessary for Cd content in food crops to be reduced, which is of considerable significance for ensuring food safety. This review will summarize the genetic traits of Cd accumulation in rice and examine the mechanism of Cd uptake and translocation in rice. The status of genes related to Cd stress and Cd accumulation in rice in recent years will be summarized, and the genes related to Cd accumulation in rice will be classified according to their functions. In addition, an overview of quantitative trait loci (QTLs) mapping populations in rice will be introduced, aiming to provide a theoretical reference for the breeding of rice varieties with low Cd accumulation. Finally, existing problems and prospects will be put forward.

The laser-induced fluorescence (LIF) excitation spectra and single vibronic level (SVL) emission spectra of the jet-cooled molybdenum monoxide (MoO) molecule in the gas phase have been investigated in the range of 16,500–23,200 cm−1. Totally 11 rotationally resolved excitation spectra have been observed, and the rotational constants in 10 upper excited states and 4 lower spin-orbit components of the ground X 5Π state have been obtained. In addition, 10 spin-orbit components in the ground X 5Π state, the first and second excited states a 3Σ− and b 3∆, have been identified in the emission spectra. Ab initio calculations have been performed and used to identify the observed low-lying states.

The properties of liquid water are intimately related to the H-bond network among the individual water molecules. Utilizing vibrational spectroscopy and modeling water with DFT-optimized water clusters (6-mers and 50-mers), 16 out of a possible 36 different types of H-bonds are identified and ordered according to their intrinsic strength. The strongest H-bonds are obtained as a result of a concerted push–pull effect of four peripheral water molecules, which polarize the electron density in a way that supports charge transfer and partial covalent character of the targeted H-bond. For water molecules with tetra- and pentacoordinated O atoms, H-bonding is often associated with a geometrically unfavorable positioning of the acceptor lone pair and donor σ*(OH) orbitals so that electrostatic rather than covalent interactions increasingly dominate H-bonding. There is a striking linear dependence between the intrinsic strength of H-bonding as measured by the local H-bond stretching force constant and the delocali...

The low-lying electronic states of platinum ions (Pt(+)) and platinum monohalides (PtX; X = F, Cl, Br, and I) are calculated using the multireference configuration interaction method with relativistic effective core potentials. The spin-orbit coupling is taken into account through the perturbative state-interaction approach. For the Ω states of PtX below 35000 cm(-1), the potential energy curves and the corresponding spectroscopic constants are reported. It is found that the lowest Ω = 3/2 state is the ground one for the four species of PtX. Overall, the theoretical results are in reasonable agreement with the available experimental data.

The low-lying electronic states of the tungsten monosulfide (WS) molecule have been investigated using laser-induced fluorescence excitation spectra and high-level ab initio calculations. 29 vibronic bands in total are experimentally observed in the range of 13,100 – 21,500 cm−1 and grouped into 8 electronic transition systems. The spectroscopic constants including the vibrational frequency, rotational constant and radiative lifetime in the low-lying excited electronic state are obtained by analysis of the rovibrational-resolved spectra. Seven lowest Ω sub-states that belong to the lowest three Λ-S states considering the spin-orbit effect, i.e. the ground state 3Σ−, first and second excited states 5Π and 3Φ, are identified through single-vibrational-level emission spectra. In addition, seven Ω = 1 excited sub-states in the visible energy range are identified, which are consecutively consistent with the ab initio calculation results of the sixth to twelfth Ω = 1 sub-states. The experimental and theoretical results on WS molecule may provide a benchmark to study the electronic structure of those molecules with strong spin-orbit coupling and electron-electron correlation.

The (0,0) and (1,0) vibrational bands of the A Ω = 1 – X 3Σ‒0+ transition of PtS have been observed in high resolution absorption measurements recorded using intracavity laser spectroscopy with Fourier transform detection (ILS-FTS). Hyperfine structure in 195PtS lines was observed in the Q-branches only, due to the interaction of an unknown Ω = 0‒ state with the f levels of the A Ω = 1 state. The new (0,0) vibrational band has been rotationally analyzed and fit using PGOPHER. Results from the spectral analysis including deperturbation of the (0,0) band of the A Ω = 1 state are presented. Potential energy curves, spectroscopic constants, and transition dipole moments are presented for Λ-S and Ω electronic states with Te

The local vibrational mode analysis, originally introduced by Konkoli and Cremer, provides a physically sound platform for a comprehensive analysis of calculated or measured vibrational spectra and for providing detailed insights into chemical bonding and other structural features. In this work, we summarize the essentials of the local vibrational mode theory with a focus on local vibrational force constants and their relationship with compliance and relaxed force constants. Furthermore, we discuss how local vibrational force constants can be used (i) to assess the quality of empirically derived force constants, (ii) to disclose bonding features in large molecules, and (iii) to provide metal ligand force field parameters. Future applications will be suggested.

The relativistic Hamiltonian Normalised Elimination of the Small Component with atomic unitary transformation (NESCau) was used for the first time to calculate geometries and harmonic vibrational f...

Stable doublet radical molecules have recently emerged as a promising new type of emitters in organic light-emitting diodes (OLEDs), approaching 100% internal quantum efficiency. However, the detailed emission mechanism of these open-shell emitters remains elusive. Through theoretical model analysis and first-principles calculations, we unraveled the emission mechanism of a typical emitter, (4-N-carbazolyl-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl)methyl (TTM-1Cz). Our study showed that the electroluminescence arises from the first doublet excited state generated by injecting one electron into the singly occupied molecule orbital (SOMO) and one hole into the highest doubly occupied molecule orbital (HDMO). Because of the distinct charge-transfer rates in charge-injection processes, the puzzle of 100% formation ratio of the emissive doublet exciton in experiments is revealed. On the basis of this understanding, we propose simple molecular designs via substitutions that can tune the HDMO-SOMO gap and hence shift the emission wavelength to the region of yellow and green light.

Normal vibrational modes are generally delocalized over the molecular system, which makes it difficult to assign certain vibrations to specific fragments or functional groups. We introduce a new approach, the Generalized Subsystem Vibrational Analysis (GSVA), to extract the intrinsic fragmental vibrations of any fragment/subsystem from the whole system via the evaluation of the corresponding effective Hessian matrix. The retention of the curvature information with regard to the potential energy surface for the effective Hessian matrix endows our approach with a concrete physical basis and enables the normal vibrational modes of different molecular systems to be legitimately comparable. Furthermore, the intrinsic fragmental vibrations act as a new link between the Konkoli–Cremer local vibrational modes and the normal vibrational modes.

The unified reaction valley approach (URVA) used for a detailed mechanistic analysis of chemical reactions is improved in three different ways: (i) Direction and curvature of path are analyzed in terms of internal coordinate components that no longer depend on local vibrational modes. In this way, the path analysis is no longer sensitive to path instabilities associated with the occurrences of imaginary frequencies. (ii) The use of third order terms of the energy for a local description of the reaction valley allows an extension of the URVA analysis into the pre- and postchemical regions of the reaction path, which are typically characterized by flat energy regions. (iii) Configurational and conformational processes of the reaction complex are made transparent even in cases where these imply energy changes far less than a kcal/mol by exploiting the topology of the potential energy surface. As examples, the rhodium-catalyzed methanol carbonization, the Diels-Alder reaction between 1,3-butadiene and ethene, and the rearrangement of HCN to CNH are discussed.

Based on two-component relativistic atomic calculations, a free electron density function (EDF) library has been developed for nearly all the known ECPs of the elements Li (Z = 3) up to Ubn (Z = 120), which can be interfaced into modern quantum chemistry programs to save the .wfx wavefunction file. The applicability of this EDF library is demonstrated by the analyses of the quantum theory of atoms in molecules (QTAIM) and other real space functions on HeCuF, PtO42+, OgF4 , and TlCl3 (DMSO)2 . When a large-core ECP is used, it shows that the corrections by EDF may significantly improve the properties of some density-derived real space functions, but they are invalid for the wavefunction-depending real space functions. To classify different chemical bonds and especially some nonclassical interactions, a list of universal criteria has also been proposed. © 2018 Wiley Periodicals, Inc.

A novel approach is presented to assess chemical similarity based the local vibrational mode analysis developed by Konkoli and Cremer. The local mode frequency shifts are introduced as similarity descriptors that are sensitive to any electronic structure change. In this work, 59 different monosubstituted benzenes are compared. For a subset of 43 compounds, for which experimental data was available, the ortho-/para- and meta-directing effect in electrophilic aromatic substitution reactions could be correctly reproduced, proving the robustness of the new similarity index. For the remaining 16 compounds, the directing effect was predicted. The new approach is broadly applicable to all compounds for which either experimental or calculated vibrational frequency information is available.

Registration is a classical problem in the application of remote sensing images. The existing methods prefer to fit the relationship between target and source images with the same model on the whole. In fact, the geometrical relationship between two images is not always consistent, especially for the wide-field-viewed images of GaoFen-1 (GF-1) launched by the China Aerospace Science and Technology Corporation (CASC) in April 2013. Generally, The existing methods didn't take the local deformation into consideration. Towards this end, we solve the problem with three stages in this paper. Firstly, the coarse registration obtains the integral perspective transformation model of images. Secondly, the fine registration partitions image into many blocks and improves the relationship of every block with the inverse distance weighting (IDW) function. Finally, the coordinate transformation and resampling are the final step. Compared to other methods, the experiments demonstrate that the proposed algorithm is capable of generating satisfied results which are robust against deformation at local area.

Electronic transition spectrum of the tungsten monosulfide (WS) molecule in the near infrared region between 725 nm and 885 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The WS molecule was produced by reacting laser - ablated tungsten atoms with 1% CS2 seeded in argon. Fourteen vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into six electronic transition systems. Least-squares fit of the measured line positions yielded molecular constants for the electronic states observed. The ground state has been identified to be the X3Σ−(0+) state with bond length, ro, and vibrational frequency, ΔG1/2, determined to be 2.0676 A and 556.7 cm−1 respectively. Molecular constants and potential energy curves of low-lying Λ-S states and Ω sub-states of the WS molecule have been calculated at the MRCISD + Q level of theory with spin-orbit coupling. Calculated molecular properties of the ground and low-lying electronic states are generally in good agreement with experimental determinations. This work represents the first experimental investigation of the electronic transition spectrum of the WS molecule.

Potential energy curves of 65 and 147 low-lying Ω states of PtH and PtH+ are respectively constructed using the multireference configuration interaction with singles, doubles, and Davidson’s cluster corrections (MRCISD+Q), and the spin–orbit coupling effects are considered through the state-interaction approach with relativistic effective core potential spin–orbit operators. Spectroscopic constants fitted from these curves are reported and are compared with the available experimental or theoretical values. With the aid of the theoretical results including transition dipole moments, some experimentally reported electronic states and spectral bands of PtH are analyzed and reassigned. This work provides useful reference data for future experimental and theoretical studies of PtH and PtH+.

A new method for calculating nuclear magnetic resonance shielding constants of relativistic atoms based on the two-component (2c), spin-orbit coupling including Dirac-exact NESC (Normalized Elimination of the Small Component) approach is developed where each term of the diamagnetic and paramagnetic contribution to the isotropic shielding constant σiso is expressed in terms of analytical energy derivatives with regard to the magnetic field B and the nuclear magnetic moment 𝝁. The picture change caused by renormalization of the wave function is correctly described. 2c-NESC/HF (Hartree-Fock) results for the σiso values of 13 atoms with a closed shell ground state reveal a deviation from 4c-DHF (Dirac-HF) values by 0.01%–0.76%. Since the 2-electron part is effectively calculated using a modified screened nuclear shielding approach, the calculation is efficient and based on a series of matrix manipulations scaling with (2M)3 (M: number of basis functions).

The BDF (Beijing Density Functional) program package is in the first place a platform for theoretical and methodological developments, standing out particularly in relativistic quantum chemical methods for chemistry and physics of atoms, molecules, and periodic solids containing heavy elements. These include the whole spectrum of relativistic Hamiltonians and their combinations with density functional theory for the electronic structure of ground states as well as time-dependent and static density functional linear response theories for electronically excited states and electric/magnetic properties. However, not to be confused by its name, BDF nowadays comprises also of standard and novel wave function-based correlation methods for the ground and excited states of strongly correlated systems of electrons [e.g., multireference configuration interaction, static-dynamic-static configuration interaction, static-dynamic-static second-order perturbation theory, n-electron valence second-order perturbation theory, iterative configuration interaction (iCI), iCI with selection plus PT2, and equation-of-motion coupled-cluster]. Additional features of BDF include a maximum occupation method for finding excited states of Hartree-Fock/Kohn-Sham (HF/KS) equations, a very efficient localization of HF/KS and complete active space self-consistent field orbitals, and a unique solver for exterior and interior roots of large matrix eigenvalue problems.

In this work, we report the synthesis and emission behavior of two analogue compounds, 2-((E)-((9H-fluoren-2-yl)methylene)amino)-3-aminomaleonitrile (C1) and 2-amino-3-((E)-(4-(diphenylamino)benzylidene)amino)maleonitrile (C2). The two compounds exert both aggregation-induced emission (AIE) nature and intramolecular charge transfer (ICT) character. They show mechanochromic luminescence (MCL) in different ways: The C1 solid powder has strong green emission but would be quenched without color change after grinding. While C2 shows strong green emission in powder form but turns orange-red with a 30% loss in the quantum efficiency after grinding. The force-induced emission of both C1 and C2 can be changed back to the starting state by a simple immersion treatment in organic solvents, suggesting high fatigue resistance. Their MCL mechanisms were studied base on spectroscopic analysis combined with quantum chemical calculation. Powder x-ray diffraction (PXRD) diffractograms suggest a decrease in crystallinity rather than a full amorphization, excluding the phase transition mechanism that has been widely accepted for most of the MCL materials in prior reports. The photophysical process has been modeled according to the quantum chemical calculation using DFT-PBE0/6-311g (d,p), two stable isomers of C1 were detected, which exhibit structural relaxation with a conical intersection seam. The conical intersection of C1 can be accessed by mechanical stimuli but is unable to reach in the starting crystalline phase due to conformation rigidity. In contrast, such structural relaxation is less possible with C2 due to high emission in solution state. And the MCL mechanism mainly involves conformation planarizartion, which leads to bathochromic-shift with its emission. The new working mechanism with C1 is superior to other counterparts on account of its sensitivity and practicability. A new type of pressure sensor based on C1 film was developed, showing remarkable quenching effect with the pressure. A linear relation between pressure and emission intensity was obtained, offering a low detection limit down to 22.92 Mpa. This mechanochromic system succeeds in mechanical printing using MCL: Pressure up to 30 Mpa clearly imprints the cartoon patterns in detail with high contrast using the MCL materials, demonstrating a feasible prototype of printing technology.

The analytical energy gradient and Hessian of the two-component Normalized Elimination of the Small Component (2c-NESC) method with regard to the components of the electric field are derived and used to calculate spin-orbit coupling (SOC) corrected dipole moments and dipole polarizabilities of molecules, which contain elements with high atomic number. Calculated 2c-NESC dipole moments and isotropic polarizabilities agree well with the corresponding four-component-Dirac Hartree–Fock or density functional theory values. SOC corrections for the electrical properties are in general small, but become relevant for the accurate prediction of these properties when the molecules in question contain sixth and/or seventh period elements (e.g., the SO effect for At2 is about 10% of the 2c-NESC polarizability). The 2c-NESC changes in the electric molecular properties are rationalized in terms of spin-orbit splitting and SOC-induced mixing of frontier orbitals with the same j = l + s quantum numbers.

For the first time, nonclassical hydrogen (H)-bonding involving a B-H···π interaction is described utilizing both quantum chemical predictions and experimental realization. In the gas phase, a B-H···π H-bond is observed in either B2H6···benzene (ΔE = -5.07 kcal/mol) or carborane···benzene (ΔE = -3.94 kcal/mol) complex at reduced temperatures. Ir-dimercapto-carborane complexes [Cp*Ir(S2C2B10H10)] are designed to react with phosphines PR3 (R = C6H4X, X = H, F, OMe) to give [Cp*Ir(PR3)S2C2B10H10] for an investigation of B-H···π interactions at ambient temperatures. X-ray diffraction studies reveal that the interaction between the carborane BH bonds and the phosphine aryl substituents involves a BH···π H-bond (H···π distance: 2.40-2.76 Å). (1)H NMR experiments reveal that B-H···π interactions exist in solution according to measured (1)H{(11)B} signals at ambient temperatures in the range 0.0 ≤ δ ≤ 0.3 ppm. These are high-field shifted by more than 1.5 ppm relative to the (1)H{(11)B} signals obtained for the PMe3 analog without B-H···π bonding. Quantum chemical calculations suggest that the interaction is electrostatic and the local (B)H···ring stretching force constant is as large as the H-bond stretching force constant in the water dimer.

The intrinsic bond strength of C2 in its (1)Σg(+) ground state is determined from its stretching force constant utilizing MR-CISD+Q(8,8), MR-AQCC(8,8), and single-determinant coupled cluster calculations with triple and quadruple excitations. By referencing the CC stretching force constant to its local counterparts of ethane, ethylene, and acetylene, an intrinsic bond strength half way between that of a double bond and a triple bond is obtained. Diabatic MR-CISD+Q results do not change this. Confinement of C2 and suitable reference molecules in a noble gas cage leads to compression, polarization, and charge transfer effects, which are quantified by the local CC stretching force constants and differences of correlated electron densities. These results are in line with two π bonds and a partial σ bond. Bond orders and bond dissociation energies of small hydrocarbons do not support quadruple bonding in C2.