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This study identifies and characterizes a second polymorph (Poly‐II) of quinoline‐4‐carbaldoxime (HQ), isolated from an acetone‐acetonitrile mixture. Poly‐II was compared to the previously known Poly‐I using PXRD, DSC, IR, and Raman spectroscopy. Poly‐I forms a 1D supramolecular assembly, whereas Poly‐II exhibits a 2D assembly with additional hydrogen bonds. Hirshfeld surface analysis reveals the presence of different non‐covalent interactions in Poly‐I and Poly‐II, and atom‐in‐molecule (AIM) analysis identifies their strength. AIM analysis, along with Espinosa's relation, was used to calculate the strength of O─H···N and C─H···N interactions in Poly‐I and Poly‐II. The values are −30.0 and −6.17 kJ/mol for Poly‐I, whereas the values for Poly‐II are −36.18 and −3.66 kJ/mol. The plane wave periodic DFT calculations determined the lattice energies of Poly‐I and Poly‐II to be −1.52 and −1.53 eV, respectively, indicating that both polymorphs have comparable stability. The crystal parameters of Poly‐I and Poly‐II obtained from theoretical simulations and the experiment are comparable, indicating the similar stability of Poly‐I and Poly‐II. Computational simulations confirmed experimental data, showing both polymorphs have similar stability and melting points despite different unit cell volumes. [ABSTRACT FROM AUTHOR]

The interaction between pyridines and the π‐hole of BeH2 leads to the formation of strong beryllium‐bonded complexes. Theoretical investigations demonstrate that the Be−N bonding interaction can effectively regulate the electronic current through a molecular junction. The electronic conductance exhibits distinct switching behavior depending on the substituent groups at the para position of pyridine, highlighting the role of Be−N interaction as a potent chemical gate in the proposed device. The complexes exhibit short intermolecular distances ranging from 1.724 to 1.752 Å, emphasizing their strong binding. Detailed analysis of electronic rearrangements and geometric perturbations upon complex formation provides insights into the underlying reasons for the formation of such strong Be−N bonds, with bond strengths varying from −116.25 to −92.96 kJ/mol. Moreover, the influence of chemical substituents on the local electronic transmission of the beryllium‐bonded complex offers valuable insights for the implementation of a secondary chemical gate in single‐molecule devices. This study paves the way for the development of chemically gateable, functional single‐molecule transistors, advancing the design and fabrication of multifunctional single‐molecule devices in the nanoscale regime. [ABSTRACT FROM AUTHOR]

A theoretical study has been carried out on the π‐hole based chalcogen bonding interaction between SO3 and various pyridines (XC5H4N), at the MP2=full/aug‐cc‐pVTZ level, to obtain a better insight into the nature and strength of N…S bond. Our calculations predict two different types of chalcogen bonded complexes: (1) Type‐A complex is formed via lone pair‐ π‐hole (N…S) interaction, and (2) Type‐B complex is stabilized through π‐hole‐π‐electron interaction. The binding energy of the Type‐A complexes varies between −109.78 and ‐81.56 kJ/mol whereas it ranges between −28.93 and −17.82 kJ/mol for Type‐B complexes. The nature of the N…S bond and the changes in its properties on the influence of electron donating and electron withdrawing substituents have been discussed with the help of various computational tools like AIM, NCI, SAPT and NBO analysis. The binding energy of the Type‐A complexes are found to correlate with the basicity parameters such as PA and Vs,min of the substituted pyridines. The binding energies of the pyridine complexes with SF2, SO2, CS2 and OCS are also computed for finding the effect of variation of Vs,max value of the S‐atom on the binding energy. The 2nd order hyperconjugation interaction energy between LP(N) and σ*(S−O)/LP*(S) is well correlated to the binding energy as: −ΔE=0.11E(2) −20.08. The variation in the bond distances and their corresponding vibrational frequencies of both the interacting partners (XC5H4N and SO3) are discussed in detail.A theoretical study has been carried out on the π‐hole chalcogen bonded complexes between SO3 and substituted pyridines. The strength and nature of the π‐hole based N…S bonded complexes are compared with the σ‐hole based N…S chalcogen bonded complexes employing various computational tools like NBO, AIM, NCI and SAPT. Hyperconjugation interaction between the two units plays an important role in stabilizing the complex. [ABSTRACT FROM AUTHOR]

Abstract: Theoretical studies have been carried out on the halogen bonding interaction between para substituted chlorobenzene (YC6H4Cl, Y = H, NH2, CH3, F, CN, NO2) and N(CH3)3 using ab initio MP2/aug‐cc‐pVDZ and DFT based wB97XD/6‐311++G(d,p) methods. The positive electrostatic potential (VS,max) on the Cl atom and the heterolytic bond breaking enthalpy of the CCl bond have been calculated and their role on halogen bonding is discussed. The heterolytic bond breaking enthalpy of the CCl bond is proposed as a measure of the strength of the σ‐hole on Cl atom. The binding strength of the complexes ranging between −6.13 kJ mol−1 and −9.29 kJ mol−1 are linearly related to the VS,max of the Cl atom and the bond breaking enthalpy of the CCl bond. In addition, energy decomposition analysis was performed on the halogen bonded complexes via symmetry adapted perturbation theory (SAPT) to predict the dominant energy component and the nature of the N···Cl interaction. [ABSTRACT FROM AUTHOR]