Chemical bonding in Uranium-based materials: A local vibrational mode case study of Cs 2 UO 2 Cl 4 and UCl 4 crystals

The Local Vibrational Mode Analysis, initially applied to diverse molecular systems, was extended to periodic systems in 2019. This work introduces an enhanced version of the LModeA software, specifically designed for the comprehensive analysis of two and three-dimensional periodic structures. Notably, a novel interface with the Crystal package was established, enabling a seamless transition from molecules to periodic systems using a unified methodology. Two distinct sets of uranium-based systems were investigated: (i) the evolution of the Uranyl ion (UO  2 2 + ) traced from its molecular configurations to the solid state, exemplified by Cs  2 UO  2 Cl  4 and (ii) Uranium tetrachloride (UCl  4 ) in both its molecular and crystalline forms. The primary focus was on exploring the impact of crystal packing on key properties, including IR and Raman spectra, structural parameters, and an in-depth assessment of bond strength utilizing local mode perspectives. This work not only demonstrates the adaptability and versatility of LModeA for periodic systems but also highlights its potential for gaining insights into complex materials and aiding in the design of new materials through fine-tuning.

Classical versus Collective Interactions in Asymmetric Trigonal Bipyramidal Alkaline Metal‒Boron Halide Complexes

Collective interactions are a novel type of chemical bond formed between metals and electron-rich substituents around an electron-poor central atom. So far only a limited number of candidates for having collective interactions are reported. In this work, we extend the newly introduced concept of collective bonding to a series of neutral boron complexes with the general formula M2BX3 (M = Li, Na, and K; X = F, Cl, and Br). Our state-of-the-art ab initio computations suggest that these complexes form trigonal bipyramidal structures with a D3h to C3v distortion along the C3 axis of symmetry. The BX3 unit in the complexes distorts from planar to pyramidal akin to a sp3 hybridized atom. Interestingly, the interaction of the metals with the pyramidal side of BX3, where the lone pair in a hypothetical [BX3]2‒ should be located, is weaker than the interactions of metals with the inverted side, i.e., the middle of three halogen atoms. The origin of this stronger interaction can be explained by the formation of collective interactions between metals and halogen atoms as we explored via energy decomposition within the context of the theory of interacting quantum atoms, IQA.

Optically induced charge-transfer in donor-acceptor-substituted p- and m- C2B10H12 carboranes

Icosahedral carboranes, C2B10H12, have long been considered to be aromatic but the extent of conjugation between these clusters and their substituents is still being debated. m- and p-Carboranes are compared with m- and p-phenylenes as conjugated bridges in optical functional chromophores with a donor and an acceptor as substituents here. The absorption and fluorescence data for both carboranes from experimental techniques (including femtosecond transient absorption, time-resolved fluorescence and broadband fluorescence upconversion) show that the absorption and emission processes involve strong intramolecular charge transfer between the donor and acceptor substituents via the carborane cluster. From quantum chemical calculations on these carborane systems, the charge transfer process depends on the relative torsional angles of the donor and acceptor groups where an overlap between the two frontier orbitals exists in the bridging carborane cluster.

Chemical bonding dictates drastic critical temperature difference in two seemingly identical superconductors

Though YB6 and LaB6 share the same crystal structure, atomic valence electron configuration, and phonon modes, they exhibit drastically different phonon-mediated superconductivity. YB6 superconducts below 8.4 K, giving it the second-highest critical temperature of known borides, second only to MgB2. LaB6 does not superconduct until near-absolute zero temperatures (below 0.45 K), however. Though previous studies have quantified the canonical superconductivity descriptors of YB6's greater Fermi-level (Ef) density of states and higher electron-phonon coupling (EPC), the root of this difference has not been assessed with full detail of the electronic structure. Through chemical bonding, we determine low-lying, unoccupied 4f atomic orbitals in lanthanum to be the key difference between these superconductors. These orbitals, which are not accessible in YB6, hybridize with π B-B bonds and bring this π-system lower in energy than the σ B-B bonds otherwise at Ef. This inversion of bands is crucial: the optical phonon modes we show responsible for superconductivity cause the σ-orbitals of YB6 to change drastically in overlap, but couple weakly to the π-orbitals of LaB6. These phonons in YB6 even access a crossing of electronic states, indicating strong EPC. No such crossing in LaB6 is observed. Finally, a supercell (the M k-point) is shown to undergo Peierls-like effects in YB6, introducing additional EPC from both softened acoustic phonons and the same electron-coupled optical modes as in the unit cell. Overall, we find that LaB6 and YB6 have fundamentally different mechanisms of superconductivity, despite their otherwise near-identity.

The synthesis and characterization of an iron(VII) nitrido complex

Complexes of iron in high oxidation states are captivating research subjects due to their pivotal role as active intermediates in numerous catalytic processes. Structural and spectroscopic studies of well-defined model complexes often provide evidence of these intermediates. In addition to the fundamental molecular and electronic structure insights gained by these complexes, their reactivity also affects our understanding of catalytic reaction mechanisms for small molecule and bond-activation chemistry. Here, we report the synthesis, structural and spectroscopic characterization of a stable, octahedral Fe(VI) nitrido complex and an authenticated, unique Fe(VII) species, prepared by one-electron oxidation. The super-oxidized Fe(VII) nitride rearranges to an Fe(V) imide through an intramolecular amination mechanism and ligand exchange, which is characterized spectroscopically and computationally. This enables combined reactivity and stability studies on a single molecular system of a rare high-valent complex redox pair. Quantum chemical calculations complement the spectroscopic parameters and provide evidence for a diamagnetic (S = 0) d 2 Fe(VI) and a genuine S = 1/2, d 1 Fe(VII) configuration of these super-oxidized nitrido complexes.

A molecular extraction process for vanadium based on tandem selective complexation and precipitation

Recycling vanadium from alternative sources is essential due to its expanding demand, depletion in natural sources, and environmental issues with terrestrial mining. Here, we present a complexation-precipitation method to selectively recover pentavalent vanadium ions, V(V), from complex metal ion mixtures, using an acid-stable metal binding agent, the cyclic imidedioxime, naphthalimidedioxime (H2CIDIII). H2CIDIII showed high extraction capacity and fast binding towards V(V) with crystal structures showing a 1:1 M:L dimer, [V2(O)3(C12H6N3O2)2]2-, 1, and 1:2 M:L non-oxido, [V(C12H6N3O2)2] ̶ complex, 2. Complexation selectivity studies showed only 1 and 2 were anionic, allowing facile separation of the V(V) complexes by pH-controlled precipitation, removing the need for solid support. The tandem complexation-precipitation technique achieved high recovery selectivity for V(V) with a selectivity coefficient above 3 × 105 from synthetic mixed metal solutions and real oil sand tailings. Zebrafish toxicity assay confirmed the non-toxicity of 1 and 2, highlighting H2CIDIII's potential for practical and large-scale V(V) recovery.

Electronic structure of Li1,2,3 +,0,- and nature of the bonding in Li2,3 +,0,

The current study of the small lithium molecules Li2 +,0,- and Li3 +,0,- focuses on the nature of the bonding in these molecules as well as their structures and energetics (bond energies, ionization energies, and electron affinities). Valence CASSCF (2s,2p) calculations incorporate nondynamical electron correlation in the calculations, while the corresponding multireference configuration interaction and coupled cluster calculations incorporate dynamical electron correlation. Treatment of nondynamical correlation is critical for properly describing the Li2,3 +,0,- molecules as well as the Li- anion with dynamical correlation, in general, only fine-tuning the predictions. All lithium molecules and ions are bound, with the Li3 + and Li2 + ions being the most strongly bound, followed by Li3 - , Li2 , Li2 - and Li3 . The minimum energy structures of Li3 +,0,- are, respectively, an equilateral triangle, an isosceles triangle, and a linear structure. The results of SCGVB calculations are analyzed to obtain insights into the nature of the bonding in these molecules. An important finding of this work is that interstitial orbitals, a concept first put forward by McAdon and Goddard in 1985, play an essential role in the bonding of all lithium molecules considered here except for Li2 . The interstitial orbitals found in the Li3 +,0 molecules likely give rise to the non-nuclear attractors/maxima observed in these molecules.

Decoding energy decomposition analysis: Machine-learned Insights on the impact of the density functional on the bonding analysis

The concept of chemical bonding is a crucial aspect of chemistry that aids in understanding the complexity and reactivity of molecules and materials. However, the interpretation of chemical bonds can be hindered by the choice of the theoretical approach and the specific method utilized. This study aims to investigate the effect of choosing different density functionals on the interpretation of bonding achieved through energy decomposition analysis (EDA). To achieve this goal, a data set was created, representing four bonding groups and various combinations of functionals and dispersion correction schemes. The calculations showed significant variation among the different functionals for the EDA terms, with the dispersion correction terms exhibiting the highest variability. More information was extracted by using machine learning in combination with dimensionality reduction on the data set. Results indicate that, despite the differences in the EDA terms obtained from different functionals, the functional has the least significant impact, suggesting minimal influence on the bonding interpretation.

Dehydration kinetics of nanoconfined water in beryl probed by high temperature single crystal synchrotron X-ray diffraction

Understanding changes in material properties through external stimuli plays a key role in validating the expected performance of materials and engineering material properties in a controlled manner. Here, we introduce a fundamental protocol to deduce dehydration reactions kinetics of water confined in nanopore channels, with the cyclosilicate beryl as the scaffold of interest, using time-resolved synchrotron X-ray diffraction (SXRD), in the temperature interval of 298-1038 K. The temperature-dependent intensity ( I ) of the strongest reflection (112) was used as the crystallite variable. An estimation of an isobaric thermal crystallite coefficient, k , analogous with the isobaric thermal expansion coefficient, established the rate of relative crystallization as a function of temperature,∂ I ∂ T . A plot of lnk and 1 T gives rise to two kinetic steps, indicating a slow dehydration stage up to ~ 700 K and a fast dehydration stage up to the investigated temperature 1038 K. The crystal structure of beryl determined up to 1038 K, in temperature increment as small as 10 K, indicates the presence of channel ions Na and Fe and a gradual decrease of water upon heating.

Polar covalent apex-base bonding in borapyramidanes probed by solid-state NMR and DFT calculations

Pyramidane molecules have attracted chemists for many decades due to their regular shape, high symmetry and their correspondence in the macroscopic world. Recently, experimental access to a number of examples has been reported, in particular the rarely reported square pyramidal bora[4]pyramidanes. To describe the bonding situation of the nonclassical structure of pyramidanes, we present solid-state Nuclear Magnetic Resonance (NMR) as a versatile tool for deciphering such bonding properties for three now accessible bora[4]pyramidane and dibora[5]pyramidane molecules. 11 B solid-state NMR spectra indicate that the apical boron nuclei in these compounds are strongly shielded (around -50 ppm vs. BF3 -Et2 O complex) and possess quadrupolar coupling constants of less than 0.9 MHz pointing to a rather high local symmetry. 13 C-11 B spin-spin coupling constants have been explored as a measure of the bond covalency in the borapyramidanes. While the carbon-boron bond to the -B(C6 F5 )2 substituents of the base serves as an example for a classical covalent 2-center-2-electron (2c-2e) sp2 -carbon-sp2 -boron σ-bond with 1 J(13 C-11 B) coupling constants in the order of 75 Hz, those of the boron(apical)-carbon(basal) bonds in the pyramid are too small to measure. These results suggest that these bonds have a strongly ionic character, which is also supported by quantum-chemical calculations.

Rationally designed nanotrap structures for efficient separation of rare earth elements over a single step

Extracting rare earth elements (REEs) from wastewater is essential for the growth and an eco-friendly sustainable economy. However, it is a daunting challenge to separate individual rare earth elements by their subtle differences. To overcome this difficulty, we report a unique REE nanotrap that features dense uncoordinated carboxyl groups and triazole N atoms in a two-fold interpenetrated metal-organic framework (named NCU-1). Notably, the synergistic effect of suitable pore sizes and REE nanotraps in NCU-1 is highly responsive to the size variation of rare-earth ions and shows high selectivity toward light REE. As a proof of concept, Pr/Lu and Nd/Er are used as binary models, which give a high separation factor of SFPr/Lu = 796 and SFNd/Er = 273, demonstrating highly efficient separation over a single step. This ability achieves efficient and selective extraction and separation of REEs from mine tailings, establishing this platform as an important advance for sustainable obtaining high-purity REEs.

Assignment of individual structures from intermetalloid nickel gallium cluster ensembles

Poorly selective mixed-metal cluster synthesis and separation yield reaction solutions of inseparable intermetalloid cluster mixtures, which are often discarded. High-resolution mass spectrometry, however, can provide precise compositional data of such product mixtures. Structure assignments can be achieved by advanced computational screening and consideration of the complete structural space. Here, we experimentally verify structure and composition of a whole cluster ensemble by combining a set of spectroscopic techniques. Our study case are the very similar nickel/gallium clusters of M12, M13 and M14 core composition Ni6+xGa6+y (x + y ≤ 2). The rationalization of structure, bonding and reactivity is built upon the organometallic superatom cluster [Ni6Ga6](Cp*)6 = [Ga6](NiCp*)6 (1; Cp* = C5Me5). The structural conclusions are validated by reactivity tests using carbon monoxide, which selectively binds to Ni sites, whereas (triisopropylsilyl)acetylene selectively binds to Ga sites.

Coordination-induced O-H/N-H bond weakening by a redox non-innocent, aluminum-containing radical

Several renewable energy schemes aim to use the chemical bonds in abundant molecules like water and ammonia as energy reservoirs. Because the O-H and N-H bonds are quite strong (>100 kcal/mol), it is necessary to identify substances that dramatically weaken these bonds to facilitate proton-coupled electron transfer processes required for energy conversion. Usually this is accomplished through coordination-induced bond weakening by redox-active metals. However, coordination-induced bond weakening is difficult with earth's most abundant metal, aluminum, because of its redox inertness under mild conditions. Here, we report a system that uses aluminum with a redox non-innocent ligand to achieve significant levels of coordination-induced bond weakening of O-H and N-H bonds. The multisite proton-coupled electron transfer manifold described here points to redox non-innocent ligands as a design element to open coordination-induced bond weakening chemistry to more elements in the periodic table.

Defect passivation in methylammonium/bromine free inverted perovskite solar cells using charge-modulated molecular bonding

Molecular passivation is a prominent approach for improving the performance and operation stability of halide perovskite solar cells (HPSCs). Herein, we reveal discernible effects of diammonium molecules with either an aryl or alkyl core onto Methylammonium-free perovskites. Piperazine dihydriodide (PZDI), characterized by an alkyl core-electron cloud-rich-NH terminal, proves effective in mitigating surface and bulk defects and modifying surface chemistry or interfacial energy band, ultimately leading to improved carrier extraction. Benefiting from superior PZDI passivation, the device achieves an impressive efficiency of 23.17% (area ~1 cm2) (low open circuit voltage deficit ~0.327 V) along with superior operational stability. We achieve a certified efficiency of ~21.47% (area ~1.024 cm2) for inverted HPSC. PZDI strengthens adhesion to the perovskite via -NH2I and Mulliken charge distribution. Device analysis corroborates that stronger bonding interaction attenuates the defect densities and suppresses ion migration. This work underscores the crucial role of bifunctional molecules with stronger surface adsorption in defect mitigation, setting the stage for the design of charge-regulated molecular passivation to enhance the performance and stability of HPSC.

Synthesis, characterization, synergistic inhibition, and biological evaluation of novel Schiff base on 304 stainless steel in acid solution

A novel Schiff base [4-(morpholin-4-yl) benzylidenyl]thiosemicarbazide (MBT) was created by reaction condensation. The molecules of the products were verified by IR, 1HNMR, MS, and elemental techniques. The synergistic effect of KI with novel MBT on 304 stainless steel (SS) in acidic has been investigated experimentally and theoretically using DFT. The findings demonstrate that restriction efficacy on 304 SS improved with rising inhibitor concentrations, and this benefit was attributed to synergy when KI was injected. From EIS results, IE % increased with a higher concentration of MBT only and MBT + KI (from 100 to 600 ppm). MBT maximum IE % was 84.98%, at 600 ppm. MBT + KI, due to the I- ions synergistic effect, showed an IE% of about 95.48%, at 600 ppm. The adsorptions of MBT and MBT + KI on the surfaces of 304 SS are strongly fitted Langmuir adsorption isotherms. Thermodynamic parameters (Kads, ΔG0ads) were utilized. According to polarization findings, MBT behaves as a mixed-category antagonist. The Schiff base MBT was screened for its in vitro antimicrobial activities against some strains of bacteria and fungi. The result revealed that MBT proved to be an excellent candidate as a fungal agent being able to inhibit Aspergillus flavus.

A stabilization rule for metal carbido cluster bearing μ3-carbido single-atom-ligand encapsulated in carbon cage

Metal carbido complexes bearing single-carbon-atom ligand such as nitrogenase provide ideal models of adsorbed carbon atoms in heterogeneous catalysis. Trimetallic μ3-carbido clusterfullerenes found recently represent the simplest metal carbido complexes with the ligands being only carbon atoms, but only few are crystallographically characterized, and its formation prerequisite is unclear. Herein, we synthesize and isolate three vanadium-based μ3-CCFs featuring V = C double bonds and high valence state of V (+4), including VSc2C@Ih(7)-C80, VSc2C@D5h(6)-C80 and VSc2C@D3h(5)-C78. Based on a systematic theoretical study of all reported μ3-carbido clusterfullerenes, we further propose a supplemental Octet Rule, i.e., an eight-electron configuration of the μ3-carbido ligand is needed for stabilization of metal carbido clusters within μ3-carbido clusterfullerenes. Distinct from the classic Effective Atomic Number rule based on valence electron count of metal proposed in the 1920s, this rule counts the valence electrons of the single-carbon-atom ligand, and offers a general rule governing the stabilities of μ3-carbido clusterfullerenes.

Alkali metal reduction of alkali metal cations

Counter to synthetic convention and expectation provided by the relevant standard reduction potentials, the chloroberyllate, [{SiNDipp}BeClLi]2 [{SiNDipp} = {CH2SiMe2N(Dipp)}2; Dipp = 2,6-i-Pr2C6H3)], reacts with the group 1 elements (M = Na, K, Rb, Cs) to provide the respective heavier alkali metal analogues, [{SiNDipp}BeClM]2, through selective reduction of the Li+ cation. Whereas only [{SiNDipp}BeClRb]2 is amenable to reduction by potassium to its nearest lighter congener, these species may also be sequentially interconverted by treatment of [{SiNDipp}BeClM]2 by the successively heavier group 1 metal. A theoretical analysis combining density functional theory (DFT) with elemental thermochemistry is used to rationalise these observations, where consideration of the relevant enthalpies of atomisation of each alkali metal in its bulk metallic form proved crucial in accounting for experimental observations.

Crown-hydroxylamines are pH-dependent chelating N,O-ligands with a potential for aerobic oxidation catalysis

Despite the rich coordination chemistry, hydroxylamines are rarely used as ligands for transition metal coordination compounds. This is partially because of the instability of these complexes that undergo decomposition, disproportionation and oxidation processes involving the hydroxylamine motif. Here, we design macrocyclic poly-N-hydroxylamines (crown-hydroxylamines) that form complexes containing a d-metal ion (Cu(II), Ni(II), Mn(II), and Zn(II)) coordinated by multiple (up to six) hydroxylamine fragments. The stability of these complexes is likely to be due to a macrocycle effect and strong intramolecular H-bonding interactions between the N-OH groups. Crown-hydroxylamine complexes exhibit interesting pH-dependent behavior where the efficiency of metal binding increases upon deprotonation of the hydroxylamine groups. Copper complexes exhibit catalytic activity in aerobic oxidation reactions under ambient conditions, whereas the corresponding complexes with macrocyclic polyamines show poor or no activity. Our results show that crown-hydroxylamines display anomalous structural features and chemical behavior with respect to both organic hydroxylamines and polyaza-crowns.

A silylene-stabilized ditin(0) complex and its conversion to methylditin cation and distannavinylidene

Due to their intrinsic high reactivity, isolation of tin(0) complexes remains challenging. Herein, we report the synthesis of a silylene-stabilized ditin(0) complex (2) by reduction of a silylene-supported dibromostannylene (1) with 1 equivalent of magnesium (I) dimer in toluene. The structure of 2 was established by single crystal X-ray diffraction analysis. Density Functional Theory calculations revealed that complex 2 bears a Sn=Sn double bond and one lone pair of electrons on each of the Sn(0) atoms. Remarkably, complex 2 is readily methylated to give a mixed-valent methylditin cation (4), which undergoes topomerization in solution though a reversible 1,2-Me migration along a Sn=Sn bond. Computational studies showed that the three-coordinate Sn atom in 4 is the dominant electrophilic center, and allows for facile reaction with KHBBus3 furnishing an unprecedented N-heterocyclic silylenes-stabilized distannavinylidene (5). The synthesis of 2, 4 and 5 demonstrates the exceptional ability of N-heterocyclic silylenes to stabilize low valent tin complexes.

When Is a Bond Broken? The Polarizability Perspective

The question of when a chemical bond can be said to be broken is of fundamental chemical interest but has not been widely studied. Herein we propose that the maxima of static polarizability along bond dissociation coordinates naturally define cutoff points for bond rupture, as they represent the onset of localization of shared electron density into constituent fragments. Examples of computed polarizability maxima over the course of bond cleavage in main-group and transition metal compounds are provided, across covalent, dative and charge-shift bonds. The behavior along reaction paths is also considered. Overall, the static polarizability is found to be a sensitive reporter of electronic structure reorganization associated with bond stretching, and thus can serve as a metric for describing bond cleavage (or diagnose the absence of a chemical bond).

Threefold coordinated germanium in a GeO2 melt

The local structure around germanium is a fundamental issue in material science and geochemistry. In the prevailing viewpoint, germanium in GeO2 melt is coordinated by at least four oxygen atoms. However, the viewpoint has been debated for decades due to several unexplained bands present in the GeO2 melt Raman spectra. Using in situ Raman spectroscopy and density functional theory (DFT) computation, we have found a [GeOØ2]n (Ø = bridging oxygen) chain structure in a GeO2 melt. In this structure, the germanium atom is coordinated by three oxygen atoms and interacts weakly with two neighbouring non-bridging oxygen atoms. The bonding nature of the chain has been analyzed on the basis of the computational electronic structure. The results may settle down the longstanding debate on the GeO2 melt structure and modify our view on germanate chemistry.

Atomically precise ultrasmall copper cluster for room-temperature highly regioselective dehydrogenative coupling

Three-component dehydrogenative coupling reactions represent important and practical methodologies for forging new C-N bonds and C-C bonds. Achieving highly all-in-one dehydrogenative coupling functionalization by a single catalytic system remains a great challenge. Herein, we develop a rigid-flexible-coupled copper cluster [Cu3(NHC)3(PF6)3] (Cu3NC(NHC)) using a tridentate N-heterocyclic carbene ligand. The shell ligand endows Cu3NC(NHC) with dual attributes, including rigidity and flexibility, to improve activity and stability. The Cu3NC(NHC) is applied to catalyze both highly all-in-one dehydrogenative coupling transformations. Mechanistic studies and density functional theory illustrate that the improved regioselectivity is derived from the low energy of ion pair with copper acetylide and endo-iminium ions and the low transition state, which originates from the unique physicochemical properties of the Cu3NC(NHC) catalyst. This work highlights the importance of N-heterocyclic carbene in the modification of copper clusters, providing a new design rule to protect cluster catalytic centers and enhance catalysis.

Actinide-lanthanide single electron metal-metal bond formed in mixed-valence di-metallofullerenes

Understanding metal-metal bonding involving f-block elements has been a challenging goal in chemistry. Here we report a series of mixed-valence di-metallofullerenes, ThDy@C2n (2n = 72, 76, 78, and 80) and ThY@C2n (2n = 72 and 78), which feature single electron actinide-lanthanide metal-metal bonds, characterized by structural, spectroscopic and computational methods. Crystallographic characterization unambiguously confirmed that Th and Y or Dy are encapsulated inside variably sized fullerene carbon cages. The ESR study of ThY@D3h(5)-C78 shows a doublet as expected for an unpaired electron interacting with Y, and a SQUID magnetometric study of ThDy@D3h(5)-C78 reveals a high-spin ground state for the whole molecule. Theoretical studies further confirm the presence of a single-electron bonding interaction between Y or Dy and Th, due to a significant overlap between hybrid spd orbitals of the two metals.

Challenging an old paradigm by demonstrating transition metal-like chemistry at a neutral nonmetal center

We describe nonmetal adducts of the phosphorus center of terminal phosphinidene complexes using classical C- and N-ligands from metal coordination chemistry. The nature of the L-P bond has been analyzed by various theoretical methods including a refined method on the variation of the Laplacian of electron density ∇2ρ along the L-P bond path. Studies on thermal stability reveal stark differences between N-ligands such as N-methyl imidazole and C-ligands such as tert-butyl isocyanide, including ligand exchange reactions and a surprising formation of white phosphorus. A milestone is the transformation of a nonmetal-bound isocyanide into phosphaguanidine or an acyclic bisaminocarbene bound to phosphorus; the latter is analogous to the chemistry of transition metal-bound isocyanides, and the former reveals the differences. This example has been studied via cutting-edge DFT calculations leading to two pathways differently favored depending on variations in steric demand. This study reveals the emergence of organometallic from coordination chemistry of a neutral nonmetal center.

Dynamic and transformable Cu12 cluster-based C-H···π-stacked porous supramolecular frameworks

The assembly of cluster-based π-stacked porous supramolecular frameworks presents daunting challenges, including the design of suitable cluster building units, control of the sufficient C-H···π interactions, trade-off between structural dynamics and stability as well as understanding the resulting collective properties. Herein, we report a cluster-based C-H···π interaction-stacked porous supramolecular framework, namely, Cu12a-π, consisting of Cu12 nanocluster as a 6-connected node, which is further propagated to a dynamic porous supramolecular frameworks via dense intralayer C-H···π interactions, yielding permanent porosity. In addition, Cu12a-π can be transformed into cluster-based nonporous adaptive crystals (Cu12b-NACs) via ligand-exchange following a dissociation-reassembly mechanism. Moreover, Cu12a-π can efficiently remove 97.2% of iodine from saturated iodine aqueous solutions with a high uptake capacity of 2.96 g·g-1. These prospective results positioned at cluster-based porous supramolecular framework and enlighten follow-up researchers to design and synthesize such materials with better performance.

Synthesis of metalla-dual-azulenes with fluoride ion recognition properties

Azulene-based conjugated systems are of great interests due to their unusual structures and photophysical properties. Incorporation of a transition metal into azulene skeleton presents an intriguing opportunity to combine the dπ-pπ and pπ-pπ conjugated properties. No such metallaazulene skeleton however has been reported to date. Here, we describe our development of an efficient [5 + 2] annulation reaction to rapid construction of a unique metal-containing [5-5-7] scaffold, termed metalla-dual-azulene (MDA), which includes a metallaazulene and a metal-free organic azulene intertwined by sharing the tropylium motif. The two azulene motifs in MDA exhibit distinct reactivities. The azulene motif readily undergoes nucleophilic addition, leading to N-, O- and S-substituted cycloheptanetrienyl species. Demetalation of the metallaazulene moiety occurs when it reacts with nBu4NF, which enables highly selective recognition of fluoride anion and a noticeable color change. The practical [5 + 2] annulation methodology, facile functional-group modification, high and selective fluoride detection make this new π-conjugated polycyclic system very suitable for potential applications in photoelectric and sensing materials.

Coupled reaction equilibria enable the light-driven formation of metal-functionalized molecular vanadium oxides

The introduction of metal sites into molecular metal oxides, so-called polyoxometalates, is key for tuning their structure and reactivity. The complex mechanisms which govern metal-functionalization of polyoxometalates are still poorly understood. Here, we report a coupled set of light-dependent and light-independent reaction equilibria controlling the mono- and di-metal-functionalization of a prototype molecular vanadium oxide cluster. Comprehensive mechanistic analyses show that coordination of a Mg2+ ion to the species {(NMe2H2)2[VV12O32Cl]}3- results in formation of the mono-functionalized {(NMe2H2)[(MgCl)VV12O32Cl]}3- with simultaneous release of a NMe2H2+ placeholder cation. Irradiation of this species with visible light results in one-electron reduction of the vanadate, exchange of the second NMe2H2+ with Mg2+, and formation/crystallization of the di-metal-functionalized [(MgCl)2VIVVV11O32Cl]4-. Mechanistic studies show how stimuli such as light or competing cations affect the coupled equilibria. Transfer of this synthetic concept to other metal cations is also demonstrated, highlighting the versatility of the approach.

Synthesis and characterization of a formal 21-electron cobaltocene derivative

Metallocenes are highly versatile organometallic compounds. The versatility of the metallocenes stems from their ability to stabilize a wide range of formal electron counts. To date, d-block metallocenes with an electron count of up to 20 have been synthesized and utilized in catalysis, sensing, and other fields. However, d-block metallocenes with more than formal 20-electron counts have remained elusive. The synthesis and isolation of such complexes are challenging because the metal-carbon bonds in d-block metallocenes become weaker with increasing deviation from the stable 18-electron configuration. Here, we report the synthesis, isolation, and characterization of a 21-electron cobaltocene derivative. This discovery is based on the ligand design that allows the coordination of an electron pair donor to a 19-electron cobaltocene derivative while maintaining the cobalt-carbon bonds, a previously unexplored synthetic approach. Furthermore, we elucidate the origin of the stability, redox chemistry, and spin state of the 21-electron complex. This study reveals a synthetic method, structure, chemical bonding, and properties of the 21-electron metallocene derivative that expands our conceptual understanding of d-block metallocene chemistry. We expect that this report will open up previously unexplored synthetic possibilities in d-block transition metal chemistry, including the fields of catalysis and materials chemistry.

Two-dimensional graphitic metal carbides: structure, stability and electronic properties

Via first-principles computational modeling and calculations, we propose a new class of two-dimensional (2D) atomically thin crystals that contain metal-C3(MC3) moieties periodically distributed in a graphenic lattice, which we refer to as 2D graphitic metal carbides (g-MCs). Most g-MCs are dynamically stable as verified by the calculated phonon spectra. Our detailed chemical bonding analyzes reveal that the high stability of g-MCs can be attributed to a unique bonding feature, which manifests as the carbon-backbone-mediated metal-metal interactions. These analyzes provide new insights for understanding the stability of 2D materials. It is found that the calculated electronic band gaps and magnetic moments (per unit cell) of g-MCs can range from 0 to 1.30 eV and 0 to 4.40μB, respectively. Highly tunable electronic properties imply great potential of 2D g-MCs in various applications. As an example, we show that 2D g-MnC can be an excellent electrocatalyst towards CO2reductive reaction for the formation of formic acid with an exceptionally high loading of Mn atoms (∼43 wt%). We expect this work to simulate new experiments for fabrication and applications of g-MCs.

Doubly N-confused and ring-contracted [24]hexaphyrin Pd-complexes as stable antiaromatic N-confused expanded porphyrins

As isomers of the regular porphyrins, N-confused porphyrins have attracted extensive attention of chemists because of their unique chemical structures, chemical reactivities, and physical properties, which result in their promising applications in the fields of catalytic chemistry, biochemistry and material science. Typically, N-confused porphyrins are synthesized via acid catalyzed condensation and following oxidation during which lactams are often formed as the byproducts. Here we report doubly N-confused and ring-contracted [24]hexaphyrin(1.1.0.1.1.0) mono- and bis-Pd-complexes as stable antiaromatic N-confused expanded porphyrins, which are synthesized through Pd-catalyzed Suzuki-Miyaura coupling of 1,14-dibromotripyrrin. These macrocycles show a paratropic ring currents, an ill-defined Soret band, a red-shifted weak absorption tail, and a small HOMO-LUMO gap. NBS bromination of the bis Pd-complex give its mono- and dibromides regioselectively, which are effectively used to synthesize a [24]hexaphyrin dimer and a NiII porphyrin-[24]hexaphyrin-NiII porphyrin triad, respectively.

Polysilyne chains bridged with beryllium lead to flat 2D Dirac materials

Polysilyne with repeating disilyne units, a silicon analogue of polyacetylene, has a high potential for application to various novel silicon-based electronic devices because of the unique properties of Si=Si units with a smaller HOMO-LUMO energy gap than that of C=C units. However, one-dimensional (1D) polysilyne has not been synthesized yet. Here we propose a planar and air-stable two-dimensional (2D) silicon-based material with one-atom thickness consisting of beryllium-bridged 1D all-trans polysilyne, based on the first-principles calculations. The flat structure of 1D polysilyne, which is essential for the air stability of silicon π-electron conjugated systems, is realized by embedding polysilyne in a planar sheet. It was found that the 2D crystal optimized at the rhombus unit cell with the D2h group symmetry is a silicon-based Dirac semimetal with linear dispersion at the Fermi energy and hosts anisotropic Dirac fermions.

Understanding catalytic synergy in dinuclear polymerization catalysts for sustainable polymers

Understanding the chemistry underpinning intermetallic synergy and the discovery of generally applicable structure-performances relationships are major challenges in catalysis. Additionally, high-performance catalysts using earth-abundant, non-toxic and inexpensive elements must be prioritised. Here, a series of heterodinuclear catalysts of the form Co(III)M(I/II), where M(I/II) = Na(I), K(I), Ca(II), Sr(II), Ba(II) are evaluated for three different polymerizations, by assessment of rate constants, turn over frequencies, polymer selectivity and control. This allows for comparisons of performances both within and between catalysts containing Group I and II metals for CO2/propene oxide ring-opening copolymerization (ROCOP), propene oxide/phthalic anhydride ROCOP and lactide ring-opening polymerization (ROP). The data reveal new structure-performance correlations that apply across all the different polymerizations: catalysts featuring s-block metals of lower Lewis acidity show higher rates and selectivity. The epoxide/heterocumulene ROCOPs both show exponential activity increases (vs. Lewis acidity, measured by the pKa of [M(OH2)m]n+), whilst the lactide ROP activity and CO2/epoxide selectivity show linear increases. Such clear structure-activity/selectivity correlations are very unusual, yet are fully rationalised by the polymerization mechanisms and the chemistry of the catalytic intermediates. The general applicability across three different polymerizations is significant for future exploitation of catalytic synergy and provides a framework to improve other catalysts.

Accessing five oxidation states of uranium in a retained ligand framework

Understanding and exploiting the redox properties of uranium is of great importance because uranium has a wide range of possible oxidation states and holds great potential for small molecule activation and catalysis. However, it remains challenging to stabilise both low and high-valent uranium ions in a preserved ligand environment. Herein we report the synthesis and characterisation of a series of uranium(II-VI) complexes supported by a tripodal tris(amido)arene ligand. In addition, one- or two-electron redox transformations could be achieved with these compounds. Moreover, combined experimental and theoretical studies unveiled that the ambiphilic uranium-arene interactions are the key to balance the stabilisation of low and high-valent uranium, with the anchoring arene acting as a δ acceptor or a π donor. Our results reinforce the design strategy to incorporate metal-arene interactions in stabilising multiple oxidation states, and open up new avenues to explore the redox chemistry of uranium.

A new ternary derivative of the Laves phases in the Mg-Co-Ga system

Crystal structures of MgCoGa, Mg0.74CoGa0.52 and Mg0.49CoGa0.15 phases from the Mg-Co-Ga system were investigated using single-crystal diffraction. These structures belong to the family of so-called Laves phases. Hexagonal MgCoGa crystallizes as a disordered phase within the MgZn2 structure type. The orthorhombic structure of Mg0.74CoGa0.52 is a distortion variant of MgZn2 and URe2 structure type, and the structural relation is demonstrated in terms of a Bärnighausen formalism group-subgroup transformation scheme. The structure of trigonal phase Mg0.49CoGa0.15 is strongly disordered, as is shown by the presence of adjacent atomic sites which cannot be occupied simultaneously. In Mg0.49CoGa0.15, two subcells (A and B) were obtained in a ratio of 9:1. Subcell A is closely related to MgZn2-type.

Polymer Nanoantidotes

Intoxication is one of the most common causes of accidental death globally. Although some antidotes capable of neutralizing the toxicity of certain xenobiotics have become well established, the current reality is that clinicians primarily rely on nonspecific extracorporeal techniques to remove toxins. Nano-intervention strategies in which nanoantidotes neutralize toxicity in situ via physical interaction, chemical bonding, or biomimetic clearance have begun to show clinical potential. However, most nanoantidotes remain in the proof-of-concept stage, and the difficulty of constructing clinical relevance models and the unclear pharmacokinetics of nanoantidotes hinder their translation to clinic. This Concept reviews the detoxification mechanisms of polymer nanoantidotes and predicts the opportunities and challenges associated with their clinical application.

Boron-Based Inverse Sandwich V2B7- Cluster: Double π/σ Aromaticity, Metal-Metal Bonding, and Chemical Analogy to Planar Hypercoordinate Molecular Wheels

Inverse sandwich clusters composed of a monocyclic boron ring and two capping transition metal atoms are interesting alloy cluster systems, yet their chemical bonding nature has not been sufficiently elucidated to date. We report herein on the theoretical prediction of a new example of boron-based inverse sandwich alloy clusters, V₂B₇^-, through computational global-minimum structure searches and quantum chemical calculations. This alloy cluster has a heptatomic boron ring as well as a perpendicular V₂ dimer unit that penetrates through the ring. Chemical bonding analysis suggests that the inverse sandwich cluster is governed by globally delocalized 6π and 6σ frameworks, that is, double 6π/6σ aromaticity following the (4n + 2) Hückel rule. The skeleton B-B σ bonding in the cluster is shown not to be strictly Lewis-type two-center two-electron (2c-2e) σ bonds. Rather, these are quasi-Lewis-type, roof-like 4c-2e V-B₂-V σ bonds, which amount to seven in total and cover the whole surface of inverse sandwich in a truly three-dimensional manner. Theoretical evidence is revealed for a 2c-2e Lewis σ single bond within the V₂ dimer. Direct metal-metal bonding is scarce in inverse sandwich alloy clusters. The present inverse sandwich alloy cluster also offers a new type of electronic transmutation in physical chemistry, which helps establish an intriguing chemical analogy between inverse sandwich clusters and planar hypercoordinate molecular wheels.

The Myth of "Metavalency" in Phase-Change Materials

Phase-change memory materials (PCMs) have unusual properties and important applications, and recent efforts to find improved materials have focused on their bonding mechanisms. "Metavalent bonding" or "metavalency," intermediate between "metallic" and "covalent" bonding and comprising single-electron bonds, has been proposed as a fundamentally new mechanism that is relevant both here and for halide perovskite materials. However, it is shown that PCMs, which violate the octet rule, have two types of covalent bond: two-center, two-electron (2c-2e) bonds, and electron-rich, multicenter bonds (3c-4e bonds, hyperbonds) involving lone-pair electrons. The latter have bond orders less than one and are examples of the century-old concept of "partial" bonds.

Fundamental Aspects of Skin Cancer Drugs via Degree-Based Chemical Bonding Topological Descriptors

Due to significant advancements being made in the field of drug design, the use of topological descriptors remains the primary approach. When combined with QSPR models, descriptors illustrate a molecule's chemical properties numerically. Numbers relating to chemical composition topological indices are structures that link chemical composition to physical characteristics. This research concentrates on the analysis of curvilinear regression models and degree-based topological descriptors for thirteen skin cancer drugs. The physicochemical characteristics of the skin cancer drugs are examined while regression models are built for computed index values. An analysis is performed for several significant results based on the acquired data.

Less and Less Noble: Local Adsorption Properties of Supported Au, Ni, and Pt Nanoparticles

In this work, we studied the local adsorption properties of gold, nickel, and platinum nanoparticles. A correlation was established between the chemical properties of massive and nanosized particles of these metals. The formation of a stable adsorption complex M-A_ads on the nanoparticles' surface was described. It was shown that the difference in local adsorption properties is caused by specific contributions of nanoparticle charging, the deformation of its atomic lattice near the M-C interface, and the hybridization of the surface s- and p-states. The contribution of each factor to the formation of the M-A_ads chemical bond was described in terms of the Newns-Anderson chemisorption model.

Chemical Bonding and Dynamic Structural Fluxionality of a Boron-Based Na5B7 Sandwich Cluster

Doping alkali metals into boron clusters can effectively compensate for the intrinsic electron deficiency of boron and lead to interesting boron-based binary clusters, owing to the small electronegativity of the former elements. We report on the computational design of a three-layered sandwich cluster, Na5B7, on the basis of global-minimum (GM) searches and electronic structure calculations. It is shown that the Na5B7 cluster can be described as a charge-transfer complex: [Na4]2+[B7]3-[Na]+. In this sandwich cluster, the [B7]3- core assumes a molecular wheel in shape and features in-plane hexagonal coordination. The magic 6π/6σ double aromaticity underlies the stability of the [B7]3- molecular wheel, following the (4n + 2) Hückel rule. The tetrahedral Na4 ligand in the sandwich has a [Na4]2+ charge-state, which is the simplest example of three-dimensional aromaticity, spherical aromaticity, or superatom. Its 2σ electron counting renders σ aromaticity for the ligand. Overall, the sandwich cluster has three-fold 6π/6σ/2σ aromaticity. Molecular dynamics simulation shows that the sandwich cluster is dynamically fluxional even at room temperature, with a negligible energy barrier for intramolecular twisting between the B7 wheel and the Na4 ligand. The Na5B7 cluster offers a new example for dynamic structural fluxionality in molecular systems.

CAl4X4 (X = Te, Po): Double Aromatic Molecular Stars Containing Planar Tetracoordinate Carbon Atoms

Planar tetracoordinate carbon (ptC) species are scarce and exotic. Introducing four peripheral Te/Po auxiliary atoms is an effective strategy to flatten the tetrahedral structure of CAl₄ (T_d, ¹A₁). Neutral CAl₄X₄ (X = Te, Po) clusters possess quadrangular star structures containing perfect ptC centers. Unbiased density functional theory (DFT) searches and high-level CCSD(T) calculations suggest that these ptC species are the global minima on the potential energy surfaces. Bonding analyses indicate that 40 valence-electron (VE) is ideal for the ptC CAl₄X₄ (X = Te, Po): one delocalized π and three σ bonds for the CAl₄ core; four lone pairs (LPs) of four X atoms, eight localized Al-X σ bonds, and four delocalized Al-X-Al π bonds for the periphery. Thus, the ptC CAl₄X₄ (X = Te, Po) clusters possess the stable eight electron structures and 2π + 6σ double aromaticity. Born-Oppenheimer molecular dynamics (BOMD) simulations indicate that neutral ptC CAl₄X₄ (X = Te, Po) clusters are robust.

On the Nature of the Partial Covalent Bond between Noble Gas Elements and Noble Metal Atoms

This article provides a discussion on the nature of bonding between noble gases (Ng) and noble metals (M) from a quantum chemical perspective by investigating compounds such as NgMY (Y=CN, O, NO₃, SO₄, CO₃), [NgM-(bipy)]+, NgMCCH, and MCCNgH complexes, where M=Cu, Ag, Au and Ng=Kr-Rn, with some complexes containing the lighter noble gas atoms as well. Despite having very low chemical reactivity, noble gases have been observed to form weak bonds with noble metals such as copper, gold, and silver. In this study, we explore the factors that contribute to this unusual bonding behavior, including the electronic structure of the atoms involved and the geometric configuration of the concerned fragments. We also investigate the metastable nature of the resulting complexes by studying the energetics of their possible dissociation and internal isomerization channels. The noble gas-binding ability of the bare metal cyanides are higher than most of their bromide counterparts, with CuCN and AgCN showing higher affinity than their chloride analogues as well. In contrast, the oxides seem to have lower binding power than their corresponding halides. In the oxide and the bipyridyl complexes, the Ng-binding ability follows the order Au > Cu > Ag. The dissociation energies calculated, considering the zero-point energy correction for possible dissociation channels, increase as we move down the noble gas group. The bond between the noble gases and the noble metals in the complexes are found to have comparable weightage of orbital and electrostatic interactions, suggestive of a partial covalent nature. The same is validated from the topological analysis of electron density.

Elucidating the N-N and C-N Bond-breaking Mechanism in the Photoinduced Formation of Nitrile Imine

In this study, we revealed the significance of chemical bonding for the photochemically induced mechanism of 2-phenyl tetrazole derivatives generating nitrile imines. The correlated electron localization function shows that the formation of imine nitrile involves two key bond events: (i) the heterolytic C-N breakage taking place in the T₁ state and (ii) the homolytic N-N rupture occurring in the T₂ excited state. In particular, a cation-radical specie results from the C-N cleavage, whereas the N-N rupture creates a biradical resonant form of imine nitrile. Additionally, we noticed that the substantial pair delocalization of the C-C-N bonded structure could play a significant role in the conversion of the biradical imine nitrile into both the propargylic and allenic forms via the T₁ →S₀ deactivation.

Toward the High-Performance Lithium Primary Batteries by Chemically Modified Fluorinate Carbon with δ-MnO2

Li/CF_x battery is one of the most promising lithium primary batteries (LPBs) which yields the highest energy density but with poor rate capability. This Achilles'' heel hinders the large-scale applications of Li/CF_x batteries. This work first reports a facile chemical modification method of CF_x with δ-MnO₂ . Having benefited from the chemical bonding, the electrochemical performance at high-rate discharge is remarkably enhanced without compromising the specific capacity. The coin cells exhibit an energy density of 1.94 × 10³  Wh kg^-1 at 0.2 C, which is approaching the theoretical energy density of commercial fluorinated graphite (2.07 × 10³  Wh kg^-1 ). A power density of 5.49 × 10⁴  W kg^-1 at 40 C associated with an energy density of 4.39 × 10²  Wh kg^-1 , which is among the highest value of Li/CF_x batteries, are obtained. Besides, the punch batteries achieve an ultrahigh power density of 4.39 × 10⁴  W kg^-1 with an energy density of 7.60 × 10²  Wh kg^-1 at 30 C. The intrinsic reasons for this outstanding electrochemical performance, which are known as the fast Li⁺ diffusion kinetics guided by thin δ-MnO₂ flakes and the low formation energy barrier caused by chemical bonding, are explored by the galvanostatic intermittent titration technique (GITT) and theoretical calculations.

Computational investigation of functionalized carbenes on dinitrogen activation

Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal-based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal-free catalysts. One step toward metal-free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state-natural orbital for chemical valence (ETS-NOCV) calculations. Our results suggest that functional groups which introduce strong electron-withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back-bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation.

φ-Aromaticity in prismatic {Bi(6)}-based clusters

The occurrence of aromaticity in organic molecules is widely accepted, but its occurrence in purely metallic systems is less widespread. Molecules comprising only metal atoms (M) are known to be able to exhibit aromatic behaviour, sustaining ring currents inside an external magnetic field along M-M connection axes (σ-aromaticity) or above and below the plane (π-aromaticity) for cyclic or cage-type compounds. However, all-metal compounds provide an extension of the electrons' mobility also in other directions. Here, we show that regular {Bi₆} prisms exhibit a non-localizable molecular orbital of f-type symmetry and generate a strong ring current that leads to a behaviour referred to as φ-aromaticity. The experimentally observed heterometallic cluster [{CpRu}₃Bi₆]^-, based on a regular prismatic {Bi₆} unit, displays aromatic behaviour; according to quantum chemical calculations, the corresponding hypothetical Bi₆^2- prism shows a similar behaviour. By contrast, [{(cod)Ir}₃Bi₆] features a distorted Bi₆ moiety that inhibits φ-aromaticity.

Chemical interactions that govern the structures of metals

Most metals adopt simple structures such as body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP) structures in specific groupings across the periodic table, and many undergo transitions to surprisingly complex structures on compression, not expected from conventional free-electron-based theories of metals. First-principles calculations have been able to reproduce many observed structures and transitions, but a unified, predictive theory that underlies this behavior is not yet in hand. Discovered by analyzing the electronic properties of metals in various lattices over a broad range of sizes and geometries, a remarkably simple theory shows that the stability of metal structures is governed by electrons occupying local interstitial orbitals and their strong chemical interactions. The theory provides a basis for understanding and predicting structures in solid compounds and alloys over a broad range of conditions.

Bonding character of intermediates in on-surface Ullmann reactions revealed with energy decomposition analysis

On-surface synthesis has become a thriving topic in surface science. The Ullmann coupling reaction is the most applied synthetic route today, but the nature of the organometallic intermediate is still under discussion. We investigate the bonding nature of prototypical intermediate species (phenyl, naphthyl, anthracenyl, phenanthryl, and triphenylenyl) on the Cu(111) surface with a combination of plane wave and atomic orbital basis set methods using density functional theory calculations with periodic boundary conditions. The surface bonding is shown to be of covalent nature with a polarized shared-electron bond supported by π-back donation effects using energy decomposition analysis for extended systems (pEDA). The bond angle of the intermediates is determined by balancing dispersion attraction and Pauli repulsion between adsorbate and surface. The latter can be significantly reduced by adatoms on the surface. We furthermore investigate how to choose computational parameters for pEDA of organic adsorbates on metal surfaces efficiently and show that bonding interpretation requires consistent choice of the density functional.

σ-Aromatic MAl6S6 (M = Ni, Pd, Pt) Stars Containing Planar Hexacoordinate Transition Metals

Hypercoordinate transition-metal species are mainly dominated by the 18-valence-electron (18ve) counting. Herein, we report ternary MAl₆S₆ (M = Ni, Pd, Pt) clusters with the planar hexacoordinate metal (phM) centers, which feature 16ve counting instead of the classic 18ve rule. These global-minimum clusters are established via unbiased global searches, followed by PBE0 and single-point CCSD(T) calculations. The phM MAl₆ units are stabilized by six peripheral bridging S atoms in these star-like species. Chemical bonding analyses reveal that there are 10 delocalized electrons around the phM center, which can render the aromaticity according to the (4n + 2) Hückel rule. It is worth noting that adding an (or two) electron(s) to its π-type lowest unoccupied molecular orbital (LUMO) will make the system unstable.