D3h Symmetry Research Articles

First-Principles Study of Stability and N2 Activation on the Octahedron RuRh Clusters

The geometric and electronic structures of different octahedron RuRh clusters are studied using density functional theory calculations. The binding energy, electronic structure, and energy gap of the clusters have been obtained to determine the possible stable structures. The results show that the Ru4Rh2 cluster is the most stable structure which has D4h symmetry with the largest ionization potential, smallest affinity energy and larger energy gap. Furthermore, the information on adsorption and dissociation of multiple nitrogen molecules and the density of state for the octahedral Ru4Rh2 cluster is analyzed. The dissociation barrier of three nitrogen molecules further decreases to 1.18 eV with an increase in the number of N2 molecules. The co-adsorption of multiple N2 molecules facilitates the dissociation of N2 on the Ru4Rh2 cluster. The strong interaction between the antibonding orbital of N2 and the d orbital of the Ru4Rh2 cluster is illustrated by calculating and analyzing the results of PDOS, which stretches the N−N bond length and reduces the activation energy to dissociation. The antibonding orbital of the nitrogen molecule shows distinct and unique catalytic activity for the dissociation of the adsorbed nitrogen molecule on the octahedral Ru4Rh2 cluster.

The Hyperporphyrin Concept: A Contemporary Perspective.

The Gouterman four-orbital model conceptualizes porphyrin UV–visible spectra as dominated by four frontier molecular orbitals—two nearly degenerate HOMOs and two exactly degenerate LUMOS under D4h symmetry. These are well separated from all the other molecular orbitals, and normal spectra involve transitions among these MOs. Unusual spectra occur when additional orbitals appear in this energy range, typically as a consequence of the central coordinated atom. For example, metals with empty d orbitals in a suitable energy range may lead to charge transfer from porphyrin (ligand) to metal, that is, so-called LMCT transitions. Metals with filled p or d orbitals may lead to charge transfer from metal to porphyrin, MLCT transitions. These cases lead to additional peaks and/or significant redshifts in the spectra and were classified as hyperporphyrins by Gouterman. Cases in which spectra are blueshifted were classified as hypsoporphyrins; they are common for relatively electronegative late transition metal porphyrins. Many of the same principles apply to porphyrin analogues, especially corroles. In this Perspective, we focus on two newer classes of hyperporphyrins: one reflecting substituent effects in protonated or deprotonated free-base tetraphenyporphyrins and the other reflecting “noninnocent” interactions between central metal ions and corroles. Hyperporphyrin effects on spectra can be dramatic, yet they can be generated by relatively simple changes and subtle structural variations, such as acid–base reactions or the selection of a central metal ion. These concepts suggest strategies for engineering porphyrin or porphyrinoid dyes for specific applications, especially those requiring far-red or near-infrared absorption or emission.

Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High-Valency Stereoscopic Molecular Nodes for Gas Separation.

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with Td , D3h , D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D4h ) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2 H2 /CO2 and C2 H2 /CH4 gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High‐Valency Stereoscopic Molecular Nodes for Gas Separation

AbstractThe structural diversity of three‐dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6‐connected stereoscopic nodes with Td, D3h, D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high‐valency quadrangular prism (D4h) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine‐linked COFs can be created. Low‐dose electron microscopy allows the direct visualization of their 2‐fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2H2/CO2 and C2H2/CH4 gas pairs. The introduction of high‐valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

A new simple route for synthesis of cadmium(II), zinc(II), cobalt(II), and manganese(II) carbonates using urea as a cheap precursor and theoretical investigation

ABSTRACT. The MnCO3.H2O, CoCO3.4H2O, ZnCO3, and CdCO3, respectively, were synthesized through a new precise, easy pathway for the reaction of MnI2, CoI2, ZnI2, or CdI2 aqueous solutions with a cheap precursor-urea for 10 h at ~ 70 oC. The IR spectra of reaction products designate the presence of characteristic bands of ionic carbonate, CO32– and absence of the individual bands of urea. The (CO3)2- ion is planar and therefore, it belongs to the D3h symmetry. It is expected to display four modes of vibrations. The stretching vibrations of the type; n(C-O) is observed in the range of (1376-1503) cm-1 while another stretching vibration n(C-O) is observed in the region 1060-1079 cm-1. The out of plane of vibration d(OCO) is observed in the range of (833-866) cm-1 while, the angle deformation bending vibration d(OCO) appear in the range of (708-732) cm-1. The infrared spectra of metal carbonate, show that, this product clearly has an uncoordinated water. The band related to the stretching vibration n(O-H) of uncoordinated H2O is observed as expected in the range of ~ 3000 cm-1. A general mechanism explaining the synthesis of carbonate compounds of cadmium(II), zinc(II), cobalt(II), and manganese(II), are described. Moreover, the DFT outcomes using B3LYP/LanL2DZ (basis set) agree with the experimental results.
 
 KEY WORDS: Carbonate, CoI2, Infrared spectra, Urea, DFT
 
 Bull. Chem. Soc. Ethiop. 2022, 36(2), 363-372. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i2.10

Revisiting the Three Vanadium Sandwich-Type Polyoxometalates: Structures, Solution Behavior, and Redox Properties.

It is well known that the trivacant anions α-B-[XW9O33]9- react with vanadyl ions to give the sandwich-type polyoxometalates [(VIVO)3(XW9O33)2]12- with X = AsIII or SbIII. Nevertheless, the oxidized derivatives have been obtained selectively by electrochemical oxidation from the fully reduced derivatives [(VIVO)3(XW9O33)2]12- allowing full characterization both in solution using UV-vis and multinuclear (17O, 51V, and 183W) NMR spectroscopies and in the solid state by single-crystal X-ray diffraction. Structural analysis of the oxidized [(VVO)3(XW9O33)2]9- polyanions is consistent with the idealized D3h symmetry, while solution studies reveal a fair hydrolytic stability in a wide pH range from 0 to 6. Besides, the D3h polyanions either as reduced or oxidized forms [(VO)3(AsW9O33)2]9/12- have been identified as the thermodynamic product that results from the conversion of the C2v polyanion [(H2O)(VO)3(AsW9O33)2]9/12- through moderate heating. Conversely, the SbIII-containing derivative gives exclusively the D3h polyanion, probably either due to the extended lone pair of the trigonal SbIII heterogroup that prevents the formation of the C2v arrangement or the lability of the oxo-metalate bonds that favor chemical exchange. The electrochemical studies of sandwich-type polyoxometalates revealed that each {V═O} group gives rise to a one-electron transfer process. At last, the redox properties appear strongly altered in the 0.3-5 pH range, consistent with proton-coupled electron transfers.

Computational Prediction of Graphdiyne-Supported Three-Atom Single-Cluster Catalysts

Computational Prediction of Graphdiyne-Supported Three-Atom Single-Cluster Catalysts

Cation distribution and site occupancy of nanoscale Cu2+-Er3+ substituted strontium hexaferrites via Raman and Mössbauer spectroscopy

In this research, we report on the cation distribution and site occupancy of Cu2+ and Er3+ ions in the hexagonal lattice of M-type strontium hexagonal ferrites with chemical composition Sr1-xCuxFe12-yEryO19 (x=0.0, 0.1, 0.2, and y=0.0, 0.4, 0.5) fabricated using sol-gel autocombustion technique. Raman analysis of the synthesized samples was conducted based on the group theory analysis of hexagonal ferrites based on the D6h symmetry. The Raman active modes based on the mode assignment and symmetry and were typical of M-type hexaferrite. Mössbauer spectroscopy shows the density of the s electron cloud at the 12k, 4f2, and 4f1 is affected by Cu2+-Er3+ substitution which indicate that all the five sexets originate from Fe3+ ion with high spin and that Er3+ ion (with d10 orbitals) occupies Fe3+ ion position at 12k, 4f2, 2a, and 2b sites in different proportion based on the Ligand theory.

Optical and photophysical properties of platinum benzoporphyrins with C2v and D2h symmetry

Platinum(II) mono- and di-benzoporphyrins carrying either ester or imide peripheral groups have been successfully synthesized. These benzoporphyrins possessing C[Formula: see text] and D[Formula: see text] symmetry were investigated using a range of techniques including UV-Vis and phosphorescence spectroscopy, differential pulse voltammetry, and transient absorption spectroscopy covering wide spatial and temporal ranges. Up to three oxidation and three reductions within the accessible potential window of dichlorobenzene were observed. Facile reductions for both mono- and dibenzoporphyrin derivatives, more so with imide peripheral substituents were witnessed. Computational studies were supportive of push-pull type interactions within these molecular systems. The formation of triplet excited states within 5 ps after laser excitation was confirmed by femtosecond transient absorption studies. Nanosecond transient absorption studies coupled with phosphorescence lifetime studies revealed relatively rapid relaxation of the triplet excited states as compared to a controlled platinum porphyrin suggesting push-pull type interactions on a slower time scale.

Controlling the magnetic properties of two-dimensional carbon-based Kagome polymers

With the help of first principles calculations, we have explored a promising route to control the magnetic properties of two-dimensional organic polymers based on all-carbon triangulene monomers. Similar to small triangulene nanostructures, the Kagome-organized triangulene polymer exhibits an antiferromagnetic ground state, but behaves as a Mott-insulator with relatively poor carrier mobilities. The doping of triangulenes with boron or nitrogen atoms contributes to switch the ground state of the polymer into a stable ferromagnetic phase, well separated in energy from the antiferromagnetic phase. The existence of a stable ferromagnetic phase is a direct consequence of electron confinement within B/N-rich triangulenes, where the D3h symmetry of the monomers in the Kagome pattern plays a major role on the resulting electronic structure properties. In addition, the two-dimensional Kagome lattice arrangement of B-rich triangulene polymer leads to highly dispersed spin-polarized semiconducting bands and high carrier mobilities that largely exceed known values for pure silicon. In contrast, the ferromagnetic phase of N-rich polymer shows half-metallic behaviour with lower mobilities than B-rich cases. Our results suggest that triangulene-based polymers could be used in diverse sectors from spin-based logic devices to quantum storage applications.

Luminescence spectroscopy of CaAl12O19:Eu3+ and SrAl12O19:Eu3+ nanoparticles

Development of red-emitting phosphors have gained enormous interest in recent year, due to their great potential for biological applications as well as display panels and solid-state lighting. Here, we present luminescence spectroscopy of deep-red-emitting CaAl12O19 (CA6) and SrAl12O19 (SA6) nanocrystals doped with Eu3+. CA6:Eu3+ and SA6:Eu3+ hexagonal nanoparticles (NPs) were prepared via a solvothermal reaction followed by a post-annealing process at 1150 °C. The luminescence spectra were obtained both at 298 and 5 K. Unaccustomed for Eu3+, the strongest emission was observed to originate from the 5D0→7F4 transition. Furthermore, emissions from the higher excited states (5D1-3) of the f-configuration of Eu3+ were also observed in these NP hosts at room temperature. In addition to the bands assigned to Eu3+ on the high symmetry D3h site, additional bands assigned to lower symmetry charge compensated sites have been identified. Crystal field (CF) parameters were obtained for the Eu3+ ion in SA6 compound, and the energy levels were estimated theoretically, which agreed well with the experimental values.

Effect of M site cation ordering on the lattice dynamical properties of the tetragonal Sr2MO4 (M=Cr, Fe, Co, Mo, and Sn) crystals

ABSTRACT Using normal coordinate analysis, the Raman and Infrared phonons are investigated for the tetragonal Ruddlesden-Popper series in phase I4/mmm and symmetry D4h 17. Three stretching and six bending force constants have been included for the calculations of the zone centre vibrational modes. Theoretical assignments for the Raman and infrared wavenumbers for Sr2CrO4, Sr2MoO4, and Sr2SnO4 compounds have been reported for the first time. As per our knowledge, no theoretical assignment has been done for the infrared frequencies for Sr2FeO4 and Sr2CoO4 compounds in I4/mmm phase so far. A strong correlation of the M site has been observed for the various frequencies giving insight into the structure of the studied compounds. The force constants involving the M-site atom show an expected set trend and also indicate the changes in values whenever the atomic orbit changes. Also, the frequencies which are completely dominated by the M atoms show a specific nature as the atomic number changes indicating the strong effect of the size of the M atom in the vibrational properties. In the tetragonal structure of the Ruddlesden-Popper phase of Sr2MO4 (M=Cr, Fe, Co, Mo, and Sn) crystals for each normal mode, the potential energy distributions have been analysed and the contributions of bending and stretching force constants towards different frequencies have been determined.

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

S K-edge XAS of CuII, CuI, and ZnII oxidized Dithiolene complexes: Covalent contributions to structure and the Jahn-Teller effect

Reduced dithiolene ligands are bound to high valent Mo centers in the active site of the oxotransferase family of enzymes. Related model complexes have been studied with great insight by Prof. Holm and his colleagues. This study focuses on the other limit of dithiolene chemistry: an investigation of the 2-electron oxidized dithiolene bound to low-valent late transition metal (TM) ions (ZnII, CuI, and CuII). The bonding descriptions of the oxidized dithiolene [N,N-dimethyl piperazine 2,3-dithione (Me2Dt0)] complexes are probed using S K-edge X-ray absorption spectroscopy (XAS) and the results are correlated to density functional theory (DFT) calculations. These experimentally supported calculations are then extended to explain the different geometric structures of the three complexes. The ZnII(Me2Dt0)2 complex has only ligand-ligand repulsion so it is stabilized at the D2d symmetry limit. The CuI(Me2Dt0)2 complex has additional weak backbonding thus distorts somewhat from D2d toward D2h symmetry. The CuII(Me2Dt0)2 complex has a strong σ donor bond that leads to both a large Jahn-Teller stabilization to D2h and an additional covalent contribution to the geometry. The combined strong stabilization results in the square planar, D2h structure. This study quantifies the competition between the ligand-ligand repulsion and the change in electronic structures in determining the final geometric structures of the oxidized dithiolene complexes, and provides quantitative insights into the Jahn-Teller stabilization energy and its origin.

A([18]crown‐6)]2[Pt(CO)3] ⋅ 10 NH3(A=K, Rb) – A crystal structure containing the long postulated [Pt(CO)3]2−

AbstractThe compound [A([18]crown‐6]2[Pt(CO)3] ⋅ 10 NH3(A=K, Rb, [18]crown‐ 6=1,4,7,10,13,16‐Hexaoxacyclooctadecane) containing the anion [Pt(CO)3]2−was the unexpected result of a reaction between K6Rb6Ge17, Pt(CO)2(PPh3)2, [18]crown‐6 and [2.2.2]‐crypt. This compound represents the first example of a mononuclear carbonyl platinate and expands the list of known group 10 carbonyl metallates. The central anion has a trigonal planar shape with an approximate D3hsymmetry. Theoretical investigations confirm the trigonal planar structure of the carbonylate and give insight into the electronic structure. The calculations reveal a strong charge density at the central platinum atom, while the HOMO shows a dispersion of the residual electrons under and over the carbonyl plane.

Investigating the predicted breathing-mode excitation of the Hoyle state

Knowledge of the low-lying monopole strength in C12—the Hoyle state in particular—is crucial for our understanding of both the astrophysically important 3α reaction and of α-particle clustering. Multiple theoretical models have predicted a breathing mode of the Hoyle State at Ex≈9 MeV, corresponding to a radial in-phase oscillation of the underlying α clusters. The C12(α,α′)C12 and C14(p,t)C12 reactions were employed to populate states in 12C in order to search for this predicted breathing mode. A self-consistent, simultaneous analysis of the inclusive spectra with R-matrix lineshapes, together with angular distributions of charged-particle decay, yielded clear evidence for excess monopole strength at Ex≈9 MeV which is highly collective. Reproduction of the experimentally observed inclusive yields using a fit, with consistent population ratios for the various broad states, required an additional source of monopole strength. The interpretation of this additional monopole resonance as the breathing-mode excitation of the Hoyle state would provide evidence supporting a D3h symmetry for the Hoyle state itself. The excess monopole strength may complicate analysis of the properties of the Hoyle state, modifying the temperature dependence of the 3α rate at T9≳2 and ultimately, the predicted nucleosynthesis in explosive stars.

Lattice vibrations of the Ruddlesden-Popper compounds barium orthorhodate, barium orthoiridate, barium orthoplumbate, and barium orthostannate in tetragonal phase

The investigation of the Raman and Infrared phonons has been done for the tetragonal Ruddlesden-Popper compounds Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate having phase I4/mmm and symmetry D4h 17 using normal coordinate analysis. With three stretching and six bending force constants, the zone center vibrational modes have been calculated. For the first time, the assignments for the Raman and infrared wavenumbers for the tetragonal compounds Barium Orthorhodate and Barium Orthoplumbate have been reported using Wilson’s GF-Matrix Method. The infrared wavenumbers for the compounds Barium Orthostannate and Barium Orthoiridate have been assigned theoretically in I4/mmm phase. A significant correlation of the cation Rhodium, Iridium, Tin, and Lead has been studied for the various vibrational modes providing insight into the structure of the investigated Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate compounds. The force constants containing the cation Rhodium, Iridium, Tin, and Lead follow a predictable pattern and also exhibit changes in values as the atomic orbit varies. Further, as the atomic number varies, the vibrational modes that are governed by the cation Rhodium, Iridium, Tin, and Lead take on a distinct nature demonstrating that the size of the cation has a significant impact on the vibrational properties. The potential energy distribution for each normal mode in the tetragonal structure of the Ruddlesden-Popper phase of Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate crystals have been analyzed and the contributions of stretching and bending force constants toward different vibrational modes have been calculated.

DFT Study of the Molecular and Electronic Structure of Metal-Free Tetrabenzoporphyrin and Its Metal Complexes with Zn, Cd, Al, Ga, In.

The electronic and molecular structures of metal-free tetrabenzoporphyrin (H2TBP) and its complexes with zinc, cadmium, aluminum, gallium and indium were investigated by density functional theory (DFT) calculations with a def2-TZVP basis set. A geometrical structure of ZnTBP and CdTBP was found to possess D4h symmetry; AlClTBP, GaClTBP and InClTBP were non-planar complexes with C4v symmetry. The molecular structure of H2TBP belonged to the point symmetry group of D2h. According to the results of the natural bond orbital (NBO) analysis, the M-N bonds had a substantial ionic character in the cases of the Zn(II) and Cd(II) complexes, with a noticeably increased covalent contribution for Al(III), Ga(III) and In(III) complexes with an axial –Cl ligand. The lowest excited states were computed with the use of time-dependent density functional theory (TDDFT) calculations. The model electronic absorption spectra indicated a weak influence of the nature of the metal on the Q-band position.

Expanded spherical trihedral metallo-borospherenes of transition-metal doped boron clusters: TM3B15q (TM = Zr, Hf; q = −1, 0, +1)

The discoveries of D3h Ln3B18– (Ln = La, Tb) , of which all the La or Tb and B atoms are integral parts of the cage surface, represent an unprecedented class of metallo-borospherenes. Based on particle swarm optimisation (PSO) algorithm and densityfunctionaltheory (DFT) calculations, a smaller spherical trihedral metallo-borospherene D3h TM3B15q (TM = Zr, Hf; q = -1, 0, +1) is designed, where the two B6 triangles of B18 framework in D3h Ln3B18– are remained but interconnected by three B atoms instead of three B2 units, resulting in each TM atom conjoined an equivalent η8–B8 ring. The high stability of proposed structure has been rationalized in terms of large average binding energy, low relative energy and geometric integrity at high temperature. Detailed orbital and bonding analysis of TM3B15 obtain that three localized 2c-2e B–B σ bonds and one delocalized 15c-2e B–B π bond are missing, and its HOMO is semi-occupied with the comparison of Ln3B18–. The most stable cationic and anionic isomers, formed from unoccupied or fully occupied HOMO of TM3B15, respectively, also have the D3h symmetry metallo-borospherene structures with similar molecular orbital shapes and bonding patterns. In addition, their IR and Raman spectra are simulated to facilitate the experiment characterizations in future.

Rigid Dysprosium(III) Single‐Molecule Magnets Exhibit Preserved Superparamagnetism in Solution

Comprehensive SummaryMolecules with long preserved magnetic moments are perceived as the smallest units for storing bytes, which could bring a new revolution for information technology. However, the rational design of such molecules remains challenging. Here two rigid adamantanol ligand based dysprosium(III) complexes ([Dy(1‐AdO)2(py)5]BPh4 ‐ 1 and [Dy(2‐AdO)2(py)5]BPh4 ‐ 2) with pentagonal‐bipyramidal coordination geometry and local D5h symmetry were successfully prepared, which display excellent single‐molecule magnet (SMM) behavior (Ueff ≈ 1835 K, TBZFC ≈ 24 K, TB100s ≈ 17 K and TBH = 23 K for 1; Ueff ≈ 1756 K, TBZFC ≈ 20 K, TB100s ≈ 16 K and TBH = 23 K for 2) due to the much weakened vibration in low energy regimes. Remarkably, the large energy barriers and high blocking temperatures for these two complexes in solid states are well preserved in solution. This is never observed in previous studies of SMMs, indicating that the adamantanol is rigid and can be introduced to make the composed molecules stable enough to maintain the solid state magnetic property in solution.