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The fluxional nature of halogen bonds (XBs) in small molecular clusters, supramolecules, and molecular crystals has received considerable attention in recent years. In this work, based on extensive density‐functional theory calculations and detailed electrostatic potential (ESP), natural bonding orbital (NBO), non‐covalent interactions‐reduced density gradient (NCI‐RDG), and quantum theory of atoms in molecules (QTAIM) analyses, we unveil the existence of fluxional halogen bonds (FXBs) in a series of linear (IC6F4I)m(OONC6H4NOO)n (m + n = 2–5) complexes of tetrafluorodiiodobenzene with dinitrobenzene which appear to be similar to the previously reported fluxional hydrogen bonds (FHBs) in small water clusters (H2O)n (n = 2–6). The obtained GS⇌TS⇌GS' fluxional mechanisms involve one FXB in the systems which fluctuates reversibly between two linear CI···O XBs in the ground states (GS and GS') via a bifurcated CI O2N van der Waals interaction in the transition state (TS). The cohesive energies (Ecoh) of these complexes with up to four XBs exhibit an almost perfect linear relationship with the numbers of XBs in the systems, with the average calculated halogen bond energy of Ecoh/XB = 3.48 kcal·mol−1 in the ground states which appears to be about 55% of the average calculated hydrogen bond energy (Ecoh/HB = 6.28 kcal·mol−1) in small water clusters. [ABSTRACT FROM AUTHOR]

Endohedral metallo-borospherenes M@B40 have received considerable attention since the discovery of B40 in 2014. However, the coordination bonding nature of most of actinide-doped endohedral An@B40 still remains in dispute or unexplored. Extensive and systematic first-principles theory calculations performed herein unveil the ground states of triplet U@B40 (1, C2v, 3A2), quartet U@B40− (2, C2v, 4B1), quintet Np@B40+ (3, C2v, 5A1), sextet Np@B40 (4, C2, 6A), septet Pu@B40 (5, C2v, 7A2), octet Am@B40 (6, C2v, 8A2), and octet Cm@B40+ (7, C2v, 8A2) at the coupled-cluster with triple excitations CCSD(T) level. Detailed principal interacting spin orbital (PISO) and adaptive natural density partitioning (AdNDP) analyses reveal their coordination bonding patterns and show that, with the numbers of unpaired α-electrons in parallel spins varying from nα = 2, 3, 4, 5, 6, 7, to 7 in these complexes, the percentage contribution of the An 5f-involved PISO pairs to overall coordination bonding interactions decreases monotonously from 41% to 1%, and the contribution of An 6d-involved PISO pairs increases monotonously from 47% to 72%, while the marginal contribution of An 7s-involved PISO pairs remains basically unchanged (4~7%). The IR, Raman, and photoelectron spectra of the most concerned species are computationally simulated to facilitate their characterizations in future experiments. [ABSTRACT FROM AUTHOR]

Environmentally friendly, high adsorption efficiency, and recyclable adsorbents meet the actual needs of organic dye wastewater treatment. Driven by noncovalent interactions between chitosan (CS) and 5,10,15,20‐tetra(4‐hydroxyphenyl) porphyrin sodium (THPPNa) under acidic conditions, a supramolecular polymer network is constructed. The supramolecular polymer network is applied as an excellent adsorbent for the removal of organic dyes from water with high efficiency. In addition, the supramolecular adsorbent shows excellent selectivity for the removal of organic anionic dyes from the mixtures of organic anionic and cationic dyes in water. Furthermore, the removal efficiency of anionic dyes of the network adsorbent keeps over 95% even after five adsorption–desorption cycles, indicating its reusability. This supramolecular polymer network shows its great potential as a low‐cost, effective, and selective adsorbent for removing organic dyes from water. [ABSTRACT FROM AUTHOR]

We show herein that 1,10‐dicyano substitution restricts the paragon fluxionality of bullvalene to just 14 isomers which isomerize along a single cycle. The restricted fluxionality of 1,10‐dicyanobullvalene (DCB) is investigated by means of: (i) Bonding analyses of the isomer structures using the adaptive natural density partitioning (AdNDP). (ii) Quantum dynamical simulations of the isomerizations along the cyclic intrinsic reaction coordinate of the potential energy surface (PES). The PES possesses 14 equivalent potential wells supporting 14 isomers which are separated by 14 equivalent potential barriers supporting 14 transition states. Accordingly, at low temperatures, DCB appears as a hindered molecular rotor, without any delocalization of the wavefunction in the 14 potential wells, without any nuclear spin isomers, and with completely negligible tunneling. These results are compared and found to differ from those for molecular boron rotors. (iii) Born‐Oppenheimer molecular dynamics (BOMD) simulations of thermally activated isomerizations. (iv) Calculations of the rate constants in the frame of transition state theory (TST) with reasonable agreement achieved with the BOMD results. (v) Simulations of the equilibration dynamics using rate equations for the isomerizations with TST rate coefficients. Accordingly, in the long‐time limit, isomerizations of the 14 isomers, each with Cs symmetry, approach the "14 Cs → C7v" thermally averaged structure. This is a superposition of the 14 equally populated isomer structures with an overall C7v symmetry. By extrapolation, the results for DCB yield working hypotheses for so far un‐explored properties e.g. for the equilibration dynamics of C10H10. [ABSTRACT FROM AUTHOR]

Among the known planar pentacoordinate atoms, chlorine is missing due to its large radius and high electronegativity. Herein, we report the first star-like superhalogen anion D5h Cl©Li5Cl5− (1), which contains a planar pentacoordinate chlorine (ppCl) at the center. Computer structural searches and high-level calculations reveal that 1 is a true global minimum (GM) on the potential energy surfaces. Molecular dynamics simulations indicate it is kinetically stable against isomerization or decomposition. Although detailed chemical bonding analyses reveal one delocalized 6c-2e σ bond over the Cl©Li5 central unit and five delocalized 3c-2e σ bonds along the periphery, while aromaticity has very little beneficial effect on stability, instead, ionic interaction dominates the stability of the system. More encouragingly, with the large HOMO–LUMO energy gap of 7.66 eV and vertical detachment energy of 7.87 eV, the highly chemically inert 1 can be viewed as a typical superhalogen anion and is possible to be synthesized and characterized in future experiments. [ABSTRACT FROM AUTHOR]

Using the experimentally known aromatic icosahedral superatoms Ih B12H122− and D5d 1,12-C2B10H12 as building blocks and based on extensive density functional theory calculations, we predict herein a series of core–shell superpolyhedral boranes and carboranes in a bottom-up approach, including the high-symmetry Th B12@B152H722− (2), C2h C2B10@B152H72 (3), D3d B12@B144H66 (4), Ih B12@C24B120H722− (6), and D5d C2B10@C24B120H72 (7). More interestingly, the superatom-assembled linear D2h B36H322− (8), close-packed planar D3dB84H602− (10), and nearly close-packed core–shell D3d B12@B144H66 (4) can be extended periodically to form the one-dimensional (1D) α-rhombohedral borane nanowire B12H10 (Pmmm) (9), two-dimensional (2D) α-rhombohedral monolayer borophane B12H6 (P 3 ¯ m 1 ) (11), and the experimentally known three-dimensional (3D) α-rhombohedral boron (R 3 ¯ m ) (12) which can be viewed as an assembly of the monolayer B12H6 (11) staggered in vertical direction, setting up a bottom-up strategy to form low-dimensional boron-based nanomaterials from their borane "seeds" via partial or complete dehydrogenations. Detailed bonding analyses indicate that the high stability of these nanostructures originates from the spherical aromaticity of their icosahedral B12 or C2B10 structural units which possess the universal skeleton electronic configuration of 1S21P61D101F8 following the Wade's n+1 rule. The infrared (IR) and Raman spectra of the most-concerned neutral B12@B144H66 (4) and C2B10@C24B120H72 (7) are computationally simulated to facilitate their experimental characterizations. [ABSTRACT FROM AUTHOR]

Based on extensive global minimum searches augmented with first-principles theory calculations, we predict herein the first boron-based perfect tetrahedral clusters Td B16P4 (2) and Td B16As4 (3) which, as aromatic non-metal analogs of the experimentally observed Td Au20 (2003, Science299, 864), all contain a truncated Td B16 (1) cage at the center effectively stabilized by four trivalent non-metal atoms (P, As) at the corners. Detailed natural bonding orbital (NBO) and adaptive natural density partitioning (AdNDP) bonding analyses indicate that the valences of all the trivalent component atoms in these tetrahedral clusters are fully satisfied, rendering spherical aromaticity and extra stability to the systems. The IR, Raman, and photoelectron spectra (PES) of the concerned species are theoretically simulated to facilitate their characterizations in future experiments. [ABSTRACT FROM AUTHOR]

Boron has been found to be able to form multiple bonds with lead. To probe Pb–B bonding, here we report an investigation of three Pb-doped boron clusters, PbB2−, PbB3O−, and PbB4O2−, which are produced by a laser ablation cluster source and characterized by photoelectron spectroscopy and ab initio calculations. The most stable structures of PbB2−, PbB3O−, and PbB4O2− are found to follow the formula, [PbB2(BO)n]− (n = 0–2), with zero, one, and two boronyl ligands coordinated to a triangular and aromatic PbB2 core, respectively. The PbB2− cluster contains a B＝B double bond and two Pb–B single bonds. The coordination of BO is observed to weaken Pb–B bonding but strengthen the B＝B bond in [PbB2(BO)n]− (n = 1, 2). The anionic [PbB2(BO)2]− and its corresponding neutral closed-shell [PbB2(BO)2] contain a B≡B triple bond. A low-lying Y-shaped isomer is also observed for PbB4O2−, consisting of a central sp2 hybridized B atom bonded to two boronyl ligands and a PbB unit. [ABSTRACT FROM AUTHOR]

Understanding the fluxional bonding nature of hydrogen bonds (HBs) and their networks in small water clusters and bulk water remains a huge challenge in both chemistry and physics. Detailed natural bonding orbital (NBO) and non-covalent interactions-reduced density gradient (NCI-RDG) analyses performed in this work at ab initio theoretical level unveil the existence of fluxional hydrogen bonds (FHBs) in small neutral water clusters (H2O)n (n = 2–6). The fluxional mechanisms of linear water dimer (H2O)2 and cyclic water trimer (H2O)3, tetramer (H2O)4, and pentamer (H2O)5 from their transition states (TSs) to ground states (GSs) mainly involve one 3c-2e FHB which fluctuates backward and forward through a weak 4c-2e van der Waals interaction in the TS, while that of the triangular prism water hexamer (H2O)6 involves two 3c-2e FHBs on two neighboring edges perpendicular to each other in a concerted mechanism. It is the FHBs that facilitate the structural fluxionalities of water clusters and their assemblies. [ABSTRACT FROM AUTHOR]