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Cryptands utilize inside CH or NH groups as hydrogen bond (H‐bond) donors to capture anions such as halides. In this work, the nature and selectivity of confined hydrogen bonds inside cryptands were computationally analyzed with the energy decomposition scheme based on the block‐localized wavefunction method (BLW‐ED), aiming at an elucidation of governing factors in the binding between cryptands and anions. It was revealed that the intrinsic strengths of inward hydrogen bonds are dominated by the electrostatic attraction, while the anion preferences (selectivity) of inner CH and NH hydrogen bonds are governed by the Pauli exchange repulsion and electrostatic interaction, respectively. Typical conformers of cages are classified into two groups, including theC_3(h)‐symmetrical conformers, in which all halide anions are located near the centroids of cages, and the “semi‐open” conformers, which exhibit shifted bonding sites for different halide anions. Accordingly, the difference in governing factors of selectivity is attributed to either the rigidity of cages or the binding site of anions for these two groups. In details, theC₃conformers of NH cryptands can be enlarged more remarkably than theC_3(h)‐symmetrical conformers of CH cryptands as the size of anion (ionic radius) increases, resulting in the relaxation of the Pauli repulsion and a dramatic reduction in electrostatic attraction, which eventually rules the selectivity of NH cryptands for halide anions. By contrary, the CH cryptands are more rigid and cannot effectively reduce the Pauli repulsion, which subsequently governs the anion preference. UnlikeC₃conformers whose rigidity determines the selectivity, semi‐open conformers exhibit different binding sites for different anions. From F⁻to I⁻, the bonding site shifts toward the outside end of the pocket inside the semi‐open NH cryptand, leading to the significant reduction of the electrostatic interaction that dominates the anion preference. Differently, binding sites are much less affected by the size of anion inside the semi‐open CH cryptand, in which the Pauli exchange repulsion remains the key factor for the selectivity of inner hydrogen bonds.

 

A unique thorium‐thorium bond was observed in the crystalline tri‐thorium cluster [{Th(η⁸‐C₈H₈)(μ₃‐Cl)₂}₃{K(THF)₂}₂]_∞, though the claim of σ‐aromaticity for Th₃bond has been questioned. Herein, a new type of core–shell syngenetic bonding model is proposed to describe the stability of this tri‐thorium cluster. The model involves a 3c–2e bond in the Th₃core and a multicentered (ThCl₂)₃charge‐shift bond with 12 electrons scattering along the outer shell. To differentiate the strengths of the 3c–2e bond and the charge‐shift bond, the block‐localized wavefunction (BLW) method which falls into the ab initio valence bond (VB) theory is employed to construct a strictly core/shell localized state and its contributing covalent resonance structure for the Th₃core bond. By comparing with the σ‐aromatic H₃⁺and nonaromatic Li₃⁺, the computed resonance energies and extra cyclic resonance energies confirm that this Th₃core bond is truly delocalized and σ‐aromatic.

 

A unique thorium‐thorium bond was observed in the crystalline tri‐thorium cluster [{Th(η⁸‐C₈H₈)(μ₃‐Cl)₂}₃{K(THF)₂}₂]_∞, though the claim of σ‐aromaticity for Th₃bond has been questioned. Herein, a new type of core–shell syngenetic bonding model is proposed to describe the stability of this tri‐thorium cluster. The model involves a 3c–2e bond in the Th₃core and a multicentered (ThCl₂)₃charge‐shift bond with 12 electrons scattering along the outer shell. To differentiate the strengths of the 3c–2e bond and the charge‐shift bond, the block‐localized wavefunction (BLW) method which falls into the ab initio valence bond (VB) theory is employed to construct a strictly core/shell localized state and its contributing covalent resonance structure for the Th₃core bond. By comparing with the σ‐aromatic H₃⁺and nonaromatic Li₃⁺, the computed resonance energies and extra cyclic resonance energies confirm that this Th₃core bond is truly delocalized and σ‐aromatic.

 

There have been remarkable advances in the syntheses and applications of groups 13 and 14 homonuclear ethene analogues. However, successes are largely limited to aryl‐ and/or silyl‐substituted species. Analogues bearing two or more heteroatoms are still scarce. In this work, the block‐localized wavefunction (BLW) method at the density functional theory (DFT) level was employed to study dialumene and disilene bearing two amino substituents whose optimal geometries exhibit significantly stretched central M=M (M=Al or Si) double bonds compared with aryl‐ and/or silyl‐substituted species. Computational analyses showed that the repulsion between the lone electron pairs of amino substituents and M=M π bond plays a critical role in the elongation of the M=M bonds. Evidently, replacing the substituent groups −NH₂with −BH₂can enhance the planarity and shorten the central double bonds due to the absence of lone pair electrons in BH₂.

 

Given the extraordinary versatility in chemical reactions and applications, boron compounds have gained increasing attentions in the past two decades. One of the remarkable advances is the unprecedented preparation of unsaturated boron species. Notably, Braunschweig et al. found that the cyclic (alkyl)(amino) carbenes (CAACs) stabilized diboron molecules (CAAC)₂B₂(SR)₂host unpaired electrons and exist in the 90°‐twisted diradical form, while other analogues, such as N‐heterocyclic carbenes (NHCs), stabilized diboron molecules prefer a conventional B=B double bond. Since previous studies recognized the differences in the steric effect between CAAC and NHC carbenes, here we focused on the role of thiol substituents in (CAAC)₂B₂(SR)₂by gradually localizing involved electrons. The co‐planarity of the thiol groups and the consequent captodative effect were found to be the culprit for the 90°‐twisted diradical form of (CAAC)₂B₂(SR)₂. Computational analyses identified two forces contributing to the π electron movements. One is the “push” effect of lone pairs on the sulfur atoms which boosts the π electron delocalization between the BB center and CAACs. The other is the π electron delocalization within each (CAAC)B(SR) fragment where the pull effect originates from the π electron withdrawal by CAACs. There are two such independent and orthogonal push‐pull channels which function mainly in individual (CAAC)B(SR) fragments. This enhanced π push‐pull effect in the triplet state facilitates the electronic excitation in (CAAC)₂B₂(SR)₂by reducing the singlet‐triplet gap.

 

Endohedral fullerenes, which can switch between distinct states with different geometries when triggered by external electric fields (EFs), can be used as logical devices at the molecular scale. However, the movement of electrons around fullerenes exerts an electrostatic shielding effect which alleviates the Coulomb force experienced by endohedral dopants, and thus must be properly evaluated for better elucidating the switching mechanism. Here we introduced new components to the energy decomposition scheme based on the block‐localized wavefunction method (i. e., BLW‐ED), to incorporate the shielding effect explicitly. We analyzed the external EF‐driven rotation of enclosed dipolar molecules inside C₇₀and evaluated the magnitudes of shielding in terms of the gradients of electrostatic potential and energy. In the absence of external EF, intrinsic rotational barriers are dominated by the Pauli exchange repulsion between enclosed molecules and C₇₀. When an external EF was applied, computations showed that only about 18% of external EFs can penetrate into the cage and interact with dipolar molecules. Thus, the shielding effect dramatically reduces the energy contribution originated from the interaction between endohedral dopants and external EFs. BLW‐ED analyses were further performed to inspect the effect of external EFs on the potential energy surfaces associated with the molecular rotation processes. Indeed, the interaction between penetrated EFs and enclosed molecules can still govern the orientational preferences of dipolar molecules and lower the rotational barrier for some dipolar molecules. But for other molecules, both the intrinsic electrostatic interaction and the Pauli repulsion respond to external EFs more sensitively and rule the changes of barrier heights and orientational preferences.

 

Recent work has produced theoretical evidence for two sites, colliding neutron stars and neutron-star–Wolf–Rayet binary systems, which might produce amino acids with the left-handed chirality preference found in meteorites. The Supernova Neutrino Amino Acid Processing (SNAAP) model uses electron antineutrinos and the magnetic field from source objects such as neutron stars to preferentially destroy one enantiomer over another. Large enantiomeric excesses are predicted for isovaline and alanine; although based on an earlier study, similar results are expected for the others. Isotopic abundances of 13 C and 15 O in meteorites provide a new test of the SNAAP model. This presents implications for the origins of life.