Studies of delocalized electron bonding

Valence Bond calculations are made using the methane-type models, CH ₂, CH ₃, and CH ₄. The calculated proton spin-spin coupling constants are found to depend on the complexity of the model. These coupling constants are related to the exchange order and bond order, which are useful as explicit measures of the extent of delocalized electron bonding.

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Zusammenfassung An den Modellen vom Methantyp: CH ₂, CH ₃, und CH ₄ werden Valenzstrukturrechnungen ausgeführt. Es ergibt sich, daß die errechneten Spin-Spin-Kopplungskonstanten der Protonen vom Umfang des Modells abhängen. Diese Kopplungskonstanten werden mit Austausch- und Bindungsordnung verknüpft, die als explizites Maß für die delokalisierte Elektronenbindung von Nutzen sind.

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Résumé Des calculs sur les modèles du type méthane: CH ₂, CH ₃, et CH ₄ sont faits dans le cadre de la méthode de la mésomérie. On trouve que les constantes de couplage spin-spin protonique dépendent de la complexité du modèle. Ces constantes de couplage sont liées aux indices d'échange et de liaison, quantités qui peuvent servir de mesures explicites de la délocalisation de la liaison électronique.

     

Studies of delocalized electron bonding

A calculation of the ethane barrier is made using a six-electron model in which all single exchange interactions are included. A barrier of 0.6 Kcal. per mole favoring the staggered configuration is calculated. The wave function is used to calculate the NMR proton spin-spin coupling constants, which are found to be at variance with the experimental values. The factors which influence these calculated results are discussed.

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Zusammenfassung Die Potentialschwelle für die innere Rotation des Äthans wird mit einem Sechselektronen-modell unter Einschluß aller Austauschintegrale berechnet. Man erhält eine Schwelle von 0,6 kcal/Mol zugunsten der trans-Konfiguration. Die mit der Eigenfunktion berechneten magnetischen Spin-Spin-Kopplungskonstanten der Protonen weichen von den experimentellen Werten ab. Die die berechneten Werte beeinflussenden Faktoren werden diskutiert.

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Résumé La barrière de potentiel de la rotation intramoléculaire de léthane est calculée à l'aide d'un modèle à 6 électrons et tenant compte de toutes les interactions d'échange. On la calcule à 0,6 kcal/mole en faveur de la configuration trans. Avec la fonction d'onde sont calculées les constantes de couplage magnétique des spins protoniques; elles sont en désaccord avec les valeurs expérimentales. Les facteurs influençant ces résultats sont discutés.

     

Studies on water bonding in potassium paradodecatungstate

Investigations of crystalline potassium paratungstate B by means of IR and NMR spectroscopy indicate that 2 water molecules and 2 OH groups are coordinated in the anion and the formula of the polytungstate is: K₁₀[W₁₂/OH/₂/H₂O/₂O₄₀]·6H₂O.     

Employing halogen-halogen interaction to construct high-temperature hybrid perovskite phase transition materials

Organic-inorganic hybrid perovskites (OIHPs) materials with high phase transition temperature (T_p) have been widely studied in the field of molecular switches, solar energy and electric power. At present, the OIHPs with high T_p are generally constructed through molecular design, which can be applied to a wide temperature range. Here, three one-dimensional (1D) OIHPs [R-ClEQ]PbCl₃ (T_p = 442 K), [R-ClEQ]PbBr₃ (T_p= 499 K) and [R-ClEQ]PbI₃ (T_p above m.p.) (R-ClEQ = (R)-N-chloroethyl-3-quinuclidinol) with different T_p are obtained by regulating the halogen-halogen interaction and hydrogen bonding in the system. Especially in [R-ClEQ]PbX₃ (X = Cl, Br and I) crystal system, all the halogen bonds tend to form at approximately 180°angles and the strength of halogen bonding is found to be increased from 1.59 × 10^–3 Hartree to 2.35 × 10^–3 Hartree with increased atom number from Cl to I. The synergistic effect of halogen bonding and hydrogen bonding provide a useful strategy for the design OIHPs phase transition materials with high T_p.     

硼烷分子中化学键性质的研究III. 锥型分子B3H6X的结构与成键特征

用MP2/6-31G方法, 对三角锥型分子B3H6X(X=B^2^-, C^-,N, O^+, BH^-, CH和NH^+)及其碎片B3H6和X的结构进行了abinitio研究。结果表明, 当X=NH^+, O^+和N时, B3H6基环上的端氢(Ht)朝着帽基X方向, 而当X=CH, BH^-, B^2^-和C^-时, Ht却转向帽基X的方向。这种特征可用配位原子的电负性和配位原子轨道的弥散性给以说明。我们还进一步研究了B3H6X系列化合物的结合能和稳定性。     

Utilizing hydrogen bonds and halogen-halogen interactions in the design of uranyl hybrid materials

Reactions of the uranyl cation (UO(2)(2+)) with 4-halopyridinium ions (X = Cl, Br, I) in high halide media (X' = Cl, Br) have produced six novel compounds, the structures of which have been determined by single crystal X-ray diffraction (XRD). The compounds can be divided into two categories based on the different modes of hydrogen bonding and halogen-halogen interactions present in the crystal structures, with one group showing approximately Type I halogen-halogen interactions and the second showing Type II. Presented is a discussion of the relative strengths of the interactions as a function of halogen size.     

Studies of intramolecular hydrogen bonding in protonated and non-protonated hexahydropyridinobenzodioxins

The conformational stability of hexahydropyridobenzodioxin and related derivatives in both protonated and non-protonated forms have been investigated by means of ab initio molecular orbital methods as well as semi-empirical AM1 and PM3 methods. One of the cis conformers (cis2e) has been found to be most stable due to the formation of an intramolecular hydrogen bond, other conformers including the trans isomer cannot form this interaction but are of different stability because of the orientation of the polar oxygens and the nitrogen. The effect of the intramolecular hydrogen bonding on the stability of hexahydropyridobenzodioxin and its methylated derivatives has been examined using various basis sets levels. In protonated form, both the semi-empirical and ab initio calculations give excellent agreement in energetic order; however, different orderings of conformer stabilities are observed by different computational methods in non-protonated form. The results provide insight into the intramolecular hydrogen bonding in computational studies of biologically important molecules.     

Studies in hydrogen bonding: Association in ammonia using an empirical potential

The empirical potential EPEN /2 has been used to establish the structures of isolated hydrogen-bonding ammonia clusters. The most stable forms of the dimer have a linear or near-linear structure. The trimer has a closed structure with zero dipole moment. Two stable tetramer forms were found: one with a closed structure and zero dipole moment in agreement with experimental findings, and one with a pyramidal structure with nonzero dipole moment which may be an artifact of the EPEN /2 potential. The relation of the dimer structures to the limited available experimental information is discussed.     

Studies in hydrogen bonding: Association in methanol using an empirical potential

The empirical potential, EPEN , has been used to establish the structures of isolated hydrogen-bonded clusters in methanol. The most stable configuration of the dimer is found to have a trans near-linear form, whereas the most stable forms of the trimer and tetramer are cyclic. Charge interactions in the tetramer make it the most stable, in terms of energy per hydrogen bond, of these three species. These results are in conformity with various types of experiment. Other species of dimer, trimer, and tetramer, corresponding to local energy minima, have also been identified.     

Chlorinated derivatives of c78-fullerene isomers with unusually short intermolecular halogen-halogen contacts

The chlorinated fullerenes C78(2)Cl18 and C78(3)Cl18 were synthesized by highly selective chlorination of the individual isomers. They were crystallized as C78(2)Cl18 x Br2 x TiCl4 and solvent free C78(3)Cl18. The carbon connectivities of both isomers have been confirmed through X-ray single-crystal analysis. Studious investigation of both crystal packings together with the crystal structure of C78(4)Cl18 has revealed the presence of unusually short intermolecular halogen-halogen contacts, which provide evidence for attractive intermolecular interactions, the nature of which is discussed.     

Solvent-controlled assembling by hydrogen bridges and halogen-halogen interactions of novel organotin oxo clusters

The crystal structure of the novel methylene-bridged tetraorganodistannoxane ([Ph(HO)SnCH2Sn(I)Ph]O)4 (1) depends on the solvent it is crystallised from and is controlled by hydrogen bridges and interhalogen interactions.     

Studies on the hydrogen bonding of aniline's derivatives by FT-IR

The hydrogen bonding of 23 aniline's derivatives in various solvents and in solid states are studied by Fourier transform infrared spectroscopy. The Infrared absorption of their amino group is greatly influenced by solvents. Compared with those data determined in hexane, the symmetric stretching frequency (nu(s)) and asymmetric stretching frequency (nu(as)) of amino group have an obvious bathochromic shift in benzene, but a relatively smaller shift in CCl4. It is also found that the concentration of these compounds has very little effect on the frequencies, the band shapes and relative absorption intensities of amino group. This indicates that the intermolecular hydrogen bonds are very weak between the aniline's derivatives in the solution. The substituent of methyl (-CH3) has different electronic effects in organic solvents with various polarities. Methyl group behaves as an electron-donating functional group in hexane, however, it shows an electron-withdrawing effect in benzene. When methoxyl (CH3O-) is ortho-substituted, v(as) of amino group increases and nu(s) almost does not change. While methoxyl (CH3O-) is meta-substituted, v(as) of amino group increases, but nu(s) decreases. The groups of chloro- (Cl-) and nitro- (-NO2) cause a hyposochromic shift of the nu(as) and nu(s) of amino group, while substituent of -NH2 makes a bathochromic shift. The solvents influence the relative intensities of nu(as) and nu(s) of amino group more greatly than the substituents do. In solid states, the amino group of aniline's derivatives has more than two absorption bands because of forming the inter- or intra-molecular hydrogen bonds.     

Studies of hydrophobic bonding in aqueous alcohols: Enthalpy measurements and model calculations

The coefficients which measure the contribution of a pair of solute molecules to the excess enthalpy have been measured in water at 25°C for all pairs of alcohols which can be formed from the series methyl to n-butyl plus t-butyl as well as for ethanol with some of the higher alcohols and with the n-alkyl sulfonates through octyl. The methylene-group contribution to these coefficients is readily identifiable in suitable cases. These data and the corresponding free-energy and volume coefficients, where they are known, are analyzed in terms of amodel which specifies the core repulsion and solvation-layer overlap terms in the potential for the interaction of two solute molecules. The latter term has an adjustable parameter, the so-called Gurney free-energy parameter which is adjusted for each solute pair to fit the free-energy data. Its temperature and pressure derivatives are adjusted to fit the enthalpy and volume data, respectively. These parameters are compared with the corresponding thermodynamic coefficients of solvation as far as possible.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.A portion of the talk presented at the H. S. Frank Symposium has been published else-where. The discussion section at the end of this paper pertains mainly to that portion.     

Dinitrogen and carbon monoxide hydrogen bonding in protonic zeolites: Studies from variable-temperature infrared spectroscopy

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-Y results in hydrogen bonding of the adsorbed N₂ molecules with the zeolite Si(OH)Al Brønsted-acid groups. This hydrogen-bonding interaction leads to activation, in the infrared, of the fundamental N–N stretching mode, which appears at 2334 cm⁻¹. From infrared spectra taken over a temperature range, the standard enthalpy of formation of the OH···N₂ complex was found to be ΔH⁰ = −15.7(±1) kJ mol⁻¹. Similarly, variable-temperature infrared spectroscopy was used to determine the standard enthalpy change involved in formation of H-bonded CO complexes for CO adsorbed on the zeolites H-ZSM-5 and H-FER; the corresponding values of ΔH⁰ were found to be −29.4(±1) and −28.4(±1) kJ mol⁻¹, respectively. The whole set of results was analysed in the context of other relevant data available in the literature.     

Novel self-protective phosphorescence from crystalline nanoparticles assembled by 3-bromo- and 3-iodo-carbazoles based on halogen-halogen interaction in suspension solutions

The crystalline nanoparticles can be assembled by 3-bromo- and 3-iodo-carbazole (3-BrC and 3-IC) based on the halogen-halogen interaction in suspension aqueous solutions. As the colloid-like suspension was dropped onto film the particles further aggregate as rod-like structures with size of 3 μm in length and 1 μm in width. The halogen-halogen interaction are well proved by single crystal X-ray data, and the data reveal that each bromine atom interacts with the neighboring two, and each iodine atom interacts with the neighboring five and I-I interaction is stronger than that of Br-Br. Both 3-BrC and 3-IC can emit novel self-protective room temperature phosphorescence (RTP) in the range of 480 to near 800 nm at the excitation of 338 nm, and 3-BrC shows additionally the delayed fluorescence emission from 350 to 480 nm, both possessing the charge-transfer character caused by halogenations. RTP decay possesses the bi-exponential property and RTP lifetimes are 3.37, 31.16 ms (with ethanol) and 1.52, 30.83 ms (with THF) for 3-BrC or 3.53, 14.95 ms (with ethanol) and 1.68 ms, 13.74 ms (with THF) for 3-IC, showing “ heavier atom ”, I, makes intersystem crossing rate k_ISC from both S₁ to T₁ and T₁ to S₀ faster. For the results, the detection limits of 3-BrC and 3-IC can reach 2.4 × 10⁻⁷ and 9.0 × 10⁻⁸ mol L⁻¹, respectively, with wider linear range and higher precision compared with other systems.     

Halogen bonding and chalcogen bonding mediated sensing

Sigma–hole interactions, in particular halogen bonding (XB) and chalcogen bonding (ChB), have become indispensable tools in supramolecular chemistry, with wide-ranging applications in crystal engineering, catalysis and materials chemistry as well as anion recognition, transport and sensing. The latter has very rapidly developed in recent years and is becoming a mature research area in its own right. This can be attributed to the numerous advantages sigma–hole interactions imbue in sensor design, in particular high degrees of selectivity, sensitivity and the capability for sensing in aqueous media. Herein, we provide the first detailed overview of all developments in the field of XB and ChB mediated sensing, in particular the detection of anions but also neutral (gaseous) Lewis bases. This includes a wide range of optical colorimetric and luminescent sensors as well as an array of electrochemical sensors, most notably redox-active host systems. In addition, we discuss a range of other sensor designs, including capacitive sensors and chemiresistors, and provide a detailed overview and outlook for future fundamental developments in the field. Importantly the sensing concepts and methodologies described herein for the XB and ChB mediated sensing of anions, are generically applicable for the development of supramolecular receptors and sensors in general, including those for cations and neutral molecules employing a wide array of non-covalent interactions. As such we believe this review to be a useful guide to both the supramolecular and general chemistry community with interests in the fields of host–guest recognition and small molecule sensing. Moreover, we also highlight the need for a broader integration of supramolecular chemistry, analytical chemistry, synthetic chemistry and materials science in the development of the next generation of potent sensors.

Sigma–hole mediated detection of anions is rapidly emerging as a new paradigm in supramolecular sensor chemistry. Herein, we provide an overview of this field including halogen bonding and chalcogen bonding optical, electrochemical and other sensors.     

Halogen bonding in solution

Halogen bonding is the electron density donation based weak interaction of halogens with Lewis bases. Its applicability for molecular recognition processes long remained unappreciated and has so far mostly been studied in silico and in solid state. As most physiological processes and chemical reactions take place in solution, investigations in solutions are of highest relevance for its use in the pharmaceutical and material scientific toolboxes. Following a short discussion of the phenomenon of halogen bonding, this tutorial review presents an overview of the methods hitherto applied for gaining an improved understanding of its behaviour in solutions and summarizes the gained knowledge in order to indicate the scope of the techniques and to facilitate exciting future developments.     

开壳层元素簇合物BCHe^2+的几何构型和成键性质研究

本文用ab initio方法研究了开壳层元素簇合物BCHe^2^+基态的三种几何构型, 即线形BC-He^2^+, CB-He^2^+和T形(He在B-C键中点上方)的稳定性半讨论了其成健性质。计算了势能曲线。计算是在6-31G^*, 6-311G^*^*, 6-311+G^*^*,6-311++G^*^*, 6-311G^*^*(2df)和6-311G(3df,2p)基组下, 用UHF, MP2, PMP2,MP4(SDTQ), CISD和ST4CCD方法完成的。结果表明, He与B和C之间有弱键存在。三种构型之间的能量差别不大, 其结构都是非刚性的。在我们所查阅文献范围内, 本工作尚属首次。