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  1. The Osme bond is defined as pairing a Group 8 metal atom as an electron acceptor in a noncovalent interaction with a nucleophile. DFT calculations with the ωB97XD functional consider MO4 (M = Ru, Os) as the Lewis acid, paired with a series of π electron donors C2H2, C2H4, C6H6, C4H5N, C4H4O, and C4H4S. The calculations establish interaction energies in the range between 9.5 and 26.4 kJ/mol. Os engages in stronger interactions than does Ru, and those involving more extensive π-systems within the aromatic rings form stronger bonds than do the smaller ethylene and acetylene. Extensive analysis questions the existence of a true Osme bond, as the bonding chiefly involves interactions with the three O atoms of MO4 that lie closest to the π-system, via π(C-C)→σ*(M-O) transfers. These interactions are supplemented by back donation from M-O bonds to the π*(CC) antibonding orbitals of the π-systems. Dispersion makes a large contribution to these interactions, higher than electrostatics and much greater than induction.

     
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  2. Both a long noncovalent C⋯N tetrel bond and a short covalent C–N bond between imidazole and F2CO represent minima of comparable energy, when the cooperativity of a H-bond is introduced into the system.

     
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  3. Steel, Karen P (Ed.)

    Age-related hearing loss (ARHL) is a common sensory impairment with complex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer hair cells, and a decreased phalloidin intensities of CP. Ultrastructural analysis revealed loss of the shortest row of stereocilia in the basal turn of the cochlea, and alterations in the cuticular plate surrounding stereocilia rootlets. Importantly, the hearing and HC phenotype in TG mice phenocopied that of the KO mice. These findings suggest that balanced expression of Fhod3 is critical for proper CP and stereocilia structure and function. Further investigation of Fhod3 related hearing impairment mechanisms may lend new insight towards the myriad mechanisms underlying ARHL, which in turn could facilitate the development of therapeutic strategies for ARHL.

     
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    Free, publicly-accessible full text available March 18, 2025
  4. The tetrel bond (TB) between 1,2-benzisothiazol-3-one-2-TF3-1,1-dioxide (T = C, Si) and the O atom of pyridine-1-oxide (PO) and its derivatives (PO-X, X = H, NO2, CN, F, CH3, OH, OCH3, NH2, and Li) is examined by quantum chemical means. The Si∙∙∙O TB is quite strong, with interaction energies approaching a maximum of nearly 70 kcal/mol, while the C∙∙∙O TB is an order of magnitude weaker, with interaction energies between 2.0 and 2.6 kcal/mol. An electron-withdrawing substituent on the Lewis base weakens this TB, while an electron-donating group has the opposite effect. The SiF3 group transfers roughly halfway between the N of the acid and the O of the base without the aid of cooperative effects from a third entity.

     
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  5. When attached to a tetrazole, a TtR 3 group (Tt = C, Si; R = H, F) engages in a Tt⋯N tetrel bond (TtB) with the Lewis base NCM (M = Li, Na). MP2/aug-cc-pVTZ calculations find that the Si⋯N TtB is rather strong, more than 20 kcal mol −1 for SiH 3 , and between 46 and 53 kcal mol −1 for SiF 3 . The C⋯N TtBs are relatively weaker, less than 8 kcal mol −1 . All of these bonds are intensified when a BH 3 or BF 3 molecule forms a triel bond to a N atom of the tetrazole ring, particularly for the C⋯N TtB, up to 11 kcal mol −1 . In these triads, the SiR 3 group displaces far enough along the line toward the base that it may be thought of as half transferred. 
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  6. The possibility that the intramolecular Tr⋯S triel bond is strengthened by resonance is examined by quantum chemical calculations within the planar five-membered ring of TrH 2 –CRCR–CRS (Tr = Al, Ga, In; R = NO 2 , CH 3 ). This internal bond is found to be rather short (2.4–2.7 Å) with a large bond energy between 12 and 21 kcal mol −1 . The pattern of bond length alternation and atomic charges within the ring is consistent with resonance involving the conjugated double bonds. This resonance enhances the triel bond strength by some 25%. The electron-withdrawing NO 2 group weakens the bond, but it is strengthened by the electron-donating CH 3 substituent. NICS analysis suggests the presence of a certain degree of aromaticity within the ring. 
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  7. The possibility of the transfer of the TH 3 group across a tetrel bond is considered by ab initio calculations. The TB is constructed by pairing PhTH 3 (Ph = phenyl; T = Si and Ge) with bases NH 3 , NHCH 2 , and the C 3 N 2 H 4 carbene. The TH 3 moves toward the base but only by a small amount in these dimers. However, when a Be 2+ or Mg 2+ dication is placed above the phenyl ring, the tetrel bond strength is greatly magnified reaching up to nearly 100 kcal mol −1 . This dication also induces a much higher degree of transfer which can be best categorized as half-transfer for the two N-bases and a near complete transfer for the carbene. 
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  8. The π-hole above the plane of the X 2 T′Y molecule (T′ = Si, Ge, Sn; X = F, Cl, H; Y = O, S) was allowed to interact with the TH hydride of TH(CH 3 ) 3 (T = Si, Ge, Sn). The resulting TH⋯T′ tetrel bond is quite strong, with interaction energies exceeding 30 kcal mol −1 . F 2 T′O engages in the strongest such bonds, as compared to F 2 T′S, Cl 2 T′O, or Cl 2 T′S. The bond weakens as T′ grows larger as in Si > Ge > Sn, despite the opposite trend in the depth of the π-hole. The reverse pattern of stronger tetrel bond with larger T is observed for the Lewis base TH(CH 3 ) 3 , even though the minimum in the electrostatic potential around the H is nearly independent of T. The TH⋯T′ arrangement is nonlinear which can be understood on the basis of the positions of the extrema in the molecular electrostatic potentials of the monomers. The tetrel bond is weakened when H 2 O forms an O⋯T′ tetrel bond with the second π-hole of F 2 T′O, and strengthened if H 2 O participates in an OH⋯O H-bond. 
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  9. Abstract

    The ability of B atoms on two different molecules to engage with one another in a noncovalent diboron bond is studied by ab initio calculations. Due to electron donation from its substituents, the trivalent B atom of BYZ2(Z=CO, N2, and CNH; Y=H and F) has the ability to in turn donate charge to the B of a BX3molecule (X=H, F, and CH3), thus forming a B⋅⋅⋅B diboron bond. These bonds are of two different strengths and character. BH(CO)2and BH(CNH)2, and their fluorosubstituted analogues BF(CO)2and BF(CNH)2, engage in a typical noncovalent bond with B(CH3)3and BF3, with interaction energies in the 3–8 kcal/mol range. Certain other combinations result in a much stronger diboron bond, in the 26–44 kcal/mol range, and with a high degree of covalent character. Bonds of this type occur when BH3is added to BH(CO)2, BH(CNH)2, BH(N2)2, and BF(CO)2, or in the complexes of BH(N2)2with B(CH3)3and BF3. The weaker noncovalent bonds are held together by roughly equal electrostatic and dispersion components, complemented by smaller polarization energy, while polarization is primarily responsible for the stronger ones.

     
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