The interaction of BH2NH2 with HNZ (Z: O, S) in the gas phase: Theoretical study of the blue shift of N-H...H-B dihydrogen bonds and the red shift of N-H...O and N-H...S hydrogen bonds (original) (raw)
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Physical Chemistry Chemical Physics, 2008
Theoretical calculations at the MP2/6-311++G(2d,2p) level are used to analyze the interaction between HNZ (Z = O, S) and H 2 XNH 2 (X = B, Al). In the most stable conformation, the complexes are cyclic, the molecules being held together by conventional NHÁ Á ÁZ hydrogen bonds and by XHÁ Á ÁHN dihydrogen bonds. Binding energies including ZPE-and BSSE-corrections lie in the range 6.2-6.9 kJ mol À1 and there is little sensitivity to the nature of the X and Z atoms. In the XHÁ Á ÁHN dihydrogen bonds, the NH stretching vibrations are blue-shifted in the HNO complexes and red-shifted in the H 2 AlNH 2 -HNS complex. In the conventional NHÁ Á ÁZ hydrogen bonds, the NH stretching vibrations are red-shifted. The topological parameters at the bond critical point are in the usual range for hydrogen or dihydrogen bonds. A natural bond orbital analysis including the calculation of the atomic charges, hybridization, occupation of the antibonding orbitals and hyperconjugation energies shows that the shifts of the NH stretching vibrations in the conventional and dihydrogen bonds are mainly determined by the changes in occupation of the s*(NH) antibonding orbitals. The mechanism of intramolecular coupling is discussed and appears to be different for the HNO and HNS complexes. The analysis of all the theoretical data reveals that the NHÁ Á ÁZ bonds are stronger in the H 2 BNH 2 than in the H 2 AlNH 2 systems and that the XHÁ Á ÁHN dihydrogen bonds are stronger in the H 2 AlNH 2 than in the H 2 BNH 2 complexes. w Electronic supplementary information (ESI) available: Cartesian coordinates and energies including ZPE correction of monomers and complexes at the MP2/6-311++G(2d,2p) level of theory. See
Canadian Journal of Chemistry-revue Canadienne De Chimie, 2010
The hydrogen-bonded interactions in the simple (HNZ)2 dimers, with Z = O and S, were investigated using quantum chemical calculations with the second-order Møller-Plesset perturbation (MP2), coupled-cluster with single, double (CCSD), and triple excitations (CCSD(T)) methods in conjunction with the 6-311++G(2d,2p), aug-cc-pVDZ, and augcc-pVTZ basis sets. Six-membered cyclic structures were found to be stable complexes for the dimers (HNO)2, (HNS)2, and (HNO-HNS). The pair (HNS)2 has the largest complexation energy (-11 kJ/mol), and (HNO)2 the smallest one (-9 kJ/mol). A bond length contraction and a frequency blue shift of the N-H bond simultaneously occur upon hydrogen bond formation of the N-HÁÁÁS type, which has rarely been observed before. The stronger the intramolecular hyperconjugation and the lower the polarization of the X-H bond involved as proton donor in the hydrogen bond, the more predominant is the formation of a blue-shifting hydrogen bond.
Comparison between hydrogen and dihydrogen bonds among H3BNH3, H2BNH2, and NH3
The Journal of Chemical Physics, 2003
Several possible binary complexes among ammonia-borane, aminoborane, and ammonia, via hydrogen and/or dihydrogen bonds, have been investigated to understand the effect of different hybridization. Møller-Plesset second-order perturbation theory with aug-cc-pVDZ basis set was used. The interaction energy is corrected for basis set superposition error, and the Morokuma-Kitaura method was employed to decompose the total interaction energy. Like H 3 BNH 3 , the sp 2 hybridized H 2 BNH 2 also participates in Hand dihydrogen bond formation. However, such bonds are weaker than their sp 3 analogs. The contractions of BN bonds are associated with blueshift in vibrational frequency and stretches of BH and NH bonds with redshift. The polarization, charge transfer, correlation, and higher-order energy components are larger in dihydrogen bonded complexes, compared to classical H-bonded ammonia dimers.
2014
All calculations were performed at the high level of theory (MP2/6-311++G(d,p)). Five separate minima were identified on the potential energy surface of each complex pairing CH 3 X with HNO. In general, strength of complexes increases in going from F to Cl to Br, which is consistent with respective decrease of deprotonation enthalpy of the C-H bond respectively. All the C-H and N-H bonds are shortened upon complexation, corresponding to increase in their stretching frequencies. It is interesting that blue shift is observed in the N-H bonds; such a contraction in the N-H covalent bond is extremely rare. Linear correlation between change of stretching frequencies and change of the N-H and C-H bond lengths in all complexes has been reported in equation (1) and (2). Besides, the change of the N-H bond lengths and their stretching frequencies as a function of the change of occupation of σ*(N-H) orbitals and that of s-character of N hybrid orbitals were obtained as in expression (3) and (4).
Studying Complex Interaction of B2H4 with HOR(R = H, CH3) and Nhn(CH3)3-N (N = 0-3) Molecules
International Journal of Medical Nano Research
Borane complexes are extensively studied and have even been the subject of Nobel Prize by Brown [1]. Many scientific data exist that have shown that boron is an essential microelement in animal cells. With the knowledge that borate linkages function in cell-to-cell adhesion, it has been hypothesised that boronates target structural glycoproteins located along the cytoskeletonplasma membrane-cell wall assembly. On the other hand, boron-carrier molecules can be used as a therapeutic mean to fight cancers [2,3]. Also, they have been the subject of proton affinity experiments in chemical ionization mass spectrometry. Among non-covalent interactions which have been known in boron chemistry, both dihydrogen and hydrogen bonding patterns are particularly significant [4-9]. B 2 H 4 , designated as diborane (4), is probably the best known electron-deficient analogue of ethylene [10-13]. B 2 H 4 bears 10 valence electrons for chemical bonding. There are two standard two electron terminal B-H bonds, thus accounting for a total of four electrons. This leaves a total of six electrons to share between the two bridging H and the two B atoms. Consequently, there are two 3c-2e curved 'banana' B-H-B bridging bonds. According to the above illustrations, B 2 H 4 has two types of hydrogen atoms: terminal (H t-B) and bridging (B-H b-B) ones, which differ in nature and characteristics. The bridging hydrogens of B 2 H 4 participate in the electron deficient 'three-center,
Interaction of CHX3 (X = F, Cl, Br) with HNO induces remarkable blue shifts of both CH and NH bonds
Physical Chemistry Chemical Physics, 2009
The hydrogen-bonded complexes formed from interaction of trihalomethanes CHX 3 (X = F, Cl, Br) with nitrosyl hydride HNO were studied using ab initio MO calculations at the second-order perturbation theory (MP2/6-311++G(d,p)). Each interaction contains at least five separate equilibrium structures. Calculated binding energies range from 4 to 8 kJ mol À1 with both ZPE and BSSE corrections. While CHBr 3 leads to the most stable complexes with HNO, CHF 3 forms the least stable counterparts. The strength of complexes thus tends to increase from F to Cl to Br, which is consistent with a decrease of deprotonation enthalpy of the corresponding C-H bonds. It is remarkable that all the C-H and N-H bonds are shortened upon complexation, giving rise to an increase of their stretching frequencies. A blue shift is thus observed for the N-H bonds of the type N-HÁ Á ÁX (X = F, Cl, Br); such a contraction of the covalent N-H bond is extremely rare.
The Journal of Physical Chemistry A, 2002
The results of an ab initio study of complexes with X-H‚‚‚H-M dihydrogen bonds are presented. The proton donors include HCCH and its derivatives HCCF, HCCCl, and HCCCN; HCN and its derivatives HCNLi + and HCNNa + ; CNH, and H 2 O, and the proton acceptor is LiH. For comparison, selected complexes with NaH as the proton acceptor have also been investigated. The structures, binding energies and harmonic vibrational frequencies of all complexes were obtained at the MP2/aug′-cc-pVTZ level of theory. The most stable complexes with C-H groups as proton donors are the cationic complexes NaNCH + :HLi and LiNCH + : HLi. These complexes exhibit very short H‚‚‚‚H distances and are prototypical of dihydrogen-bonded complexes that may dissociate by eliminating H 2 . The calculated binding energies correlate with the H‚‚‚H distance, the elongation of the C-H donor bond, the amount of charge transfer into the H‚‚‚‚H bonding region, and the charge density at the H‚‚‚H bond critical point. As in conventional hydrogen-bonded complexes, the elongation of the proton donor C-H group correlates with the strength of the interaction, and with the red shift of the C-H stretching frequency. Although changes in the Li-H bond length do not follow a simple pattern, the Li-H stretching frequency is blue-shifted in the complexes.
Journal of Molecular Structure, 2006
Interaction of the salt (Ph 3 PaNaPPh 3 )BH 3 CN with the various OH and NH proton donors in low polar media was studied by variable temperature (200-290 K) IR spectroscopy and theoretically by DFT calculations. The formation of two types of complexes containing nonclassical dihydrogen bond to the hydride hydrogen (DHB) and classical hydrogen bond (HB) to nitrogen lone pair was shown in solution. The 1:1 complexes of both types (XH/H and XH/N) coexist in the presence of equimolar amount of proton donor. The addition of excess XH-acid leads to the increase of the classical HB content and appearance of the 1:2 complexes, where two basic sites work simultaneously. The structure, spectral characteristics, energy and electron redistribution were studied by DFT (B3LYP) method. The comparison DHB parameters of [BH 3 CN] K with those of the unsubstituted analogue [BH 4 ] K allowed analyzing the electronic effects of the CN group on the basic properties of boron hydride moiety. The electronic influence of the BH 3 group on CN K /HX hydrogen bond was also established by comparison with the corresponding classical HB to the CN K anion. q
Electronic Structure, Molecular Interaction, and Stability of the CH4−nH2O Complex, for n = 1−21
The Journal of Physical Chemistry A, 2008
Molecular calculations were carried out with four different methodologies to study the CH 4-nH 2 O complex, for n) 1-21. The HF and MP2 methods used considered the O atom with pseudopotential to freeze the 1s 2 shell. The other methodologies applied the Bhandhlyp and B3lyp exchange and correlation functionals. The optimized CH 4-nH 2 O structures are reported, specifying the number and type of H 2 O subunits (triangle, square, pentagon, etc.) that comprised the nH 2 O counterpart cluster or cage, that interacted with the CH 4 molecule, and, in the latter case, that provided its confinement. Results are focused to understand the stability of the CH 4-nH 2 O complex. The quality of the electron correlation effect, as well as the size of the nH 2 O cage to confine the guest molecule, and the number and type of H 2 O subunits comprising the nH 2 O cluster or cage are the most important factors to provide the stability of the complex and also dictate the particular n value at which the CH 4 molecule confinement occurs. This number was 14 for the HF, Bhandhlyp, and B3Lyp methods and 16 for the MP2 method. The reported hydrate structures for n < 20 could be predictive for future experiments.