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ABSTRACT: Quantum chemical calculations have been performed to study the complex of MCN-LiCN-XCCH (M = H, Li, and Na; X = Cl, Br, and I). The aim is to study the cooperative effect between halogen bond and lithium bond. The alkali metal has an enhancing effect on the lithium bond, making it increased by 77 and 94% for the Li and Na, respectively. There is the cooperativity between the lithium bond and halogen bond. The former has a larger enhancing effect on the latter, being in a range of 11.7-29.4%. The effect of cooperativity on the halogen bond is dependent on the type of metal and halogen atoms. The enhancing mechanism has been analyzed in views with the orbital interaction, charge transfer, dipole moment, polarizability, atom charges, and electrostatic potentials. The results show that the electrostatic interaction plays an important role in the enhancement of halogen bond.
Journal of Computational Chemistry 11/2011; 32(15):3296-303. · 4.58 Impact Factor
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ABSTRACT: A novel method was developed using molecular imprinting technology (MIT) coupled with flow-injection chemiluminescence (FI-CL) for highly sensitive detection of phenformin hydrochloride (PH). The phenformin imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Newly synthesized molecularly imprinted polymer (MIP) particles were packed into a column as a selective recognition element for determination of PH. A CL method for the determination of PH was developed based on the CL reaction of PH with N-bromosuccinimide sensitized by eosin Y in basic media. The optimization of detection conditions was investigated. The CL intensity responded linearly to the concentration of PH in the range 0.09-2.0 µg/mL, with a correlation coefficient of 0.9920. The detection limit was 0.031 µg/mL. The relative standard deviation for the determination of 1.0 µg/mL PH solution was 1.0% (n = 11). The method was applied to the determination of PH in urine samples, with satisfactory results.
Luminescence 10/2011; 27(4):297-301. · 1.73 Impact Factor
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The Journal of Physical Chemistry A 08/2011; 115(30):8586-7. · 2.95 Impact Factor
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ABSTRACT: We designed M(1)⋅⋅⋅C(6)H(5)X⋅⋅⋅HM(2) (M(1) =Li(+), Na(+); X=Cl, Br; M(2) =Li, Na, BeH, MgH) complexes to enhance halogen-hydride halogen bonding with a cation-π interaction. The interaction strength has been estimated mainly in terms of the binding distance and the interaction energy. The results show that halogen-hydride halogen bonding is strengthened greatly by a cation-π interaction. The interaction energy in the triads is two to six times as much as that in the dyads. The largest interaction energy is -8.31 kcal mol(-1) for the halogen bond in the Li(+)⋅⋅⋅C(6)H(5)Br⋅⋅⋅HNa complex. The nature of the cation, the halogen donor, and the metal hydride influence the nature of the halogen bond. The enhancement effect of Li(+) on the halogen bond is larger than that of Na(+). The halogen bond in the Cl donor has a greater enhancement than that in the Br one. The metal hydride imposes its effect in the order HBeH<HMgH<HNa<HLi for the Cl complex and HBeH<HMgH<HLi<HNa for the Br complex. The large cooperative energy indicates that there is a strong interplay between the halogen-hydride halogen bonding and the cation-π interaction. Natural bond orbital and energy decomposition analyses indicate that the electrostatic interaction plays a dominate role in enhancing halogen bonding by a cation-π interaction.
ChemPhysChem 06/2011; 12(12):2289-95. · 3.41 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed to study the hybridization effect in H(2)O-AuCH(2)CH(3), H(2)O-AuCHCH(2), and H(2)O-AuCCH dimers, and the cooperativity between the hydrogen bond and Au bonding in three trimers (T1, T2, and T3) composed of one AuCCH and two H(2)O molecules. With regard to the organic Au compounds, sp-hybridized AuCCH forms the strongest Au bonding, followed by sp(2) and then sp(3). The C-Au bond is elongated, and its elongation becomes larger with the increase of the s character in hybrid orbitals, whereas the corresponding stretch vibration displays a small blue shift. The positive cooperativity is present for the hydrogen bond and Au bonding in T1 and T2 trimers, whereas the negative cooperativity is found in T3 trimer. The results show that the hybridization effect and cooperative interaction in Au bonding are similar to those in hydrogen bonds. Additionally, an OH···Au hydrogen bond is suggested in T1 trimer.
The Journal of Physical Chemistry A 03/2011; 115(13):2853-8. · 2.95 Impact Factor
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Journal of Computational Chemistry. 01/2011; 32:3296-3303.
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ABSTRACT: Quantum chemical calculations have been performed on the complexes formed between HArF and dihalogen molecules (XY=ClCl, ClF, BrCl, and BrF) at the MP2/6-311++G(2d,2p) level. For each complex, two minima were found, which correspond to one hydrogen-bonded complex and one halogen-bonded complex. The halogen-bonded complex with the F atom of HArF is more stable than the hydrogen-bonded complex with the H atom of HArF. A large blue shift of the H-Ar stretching frequency was observed in the hydrogen-bonded complex. However, in the halogen-bonded complex, in which the H-Ar bond is not involved in the interaction, a much large blue shift was observed for the same bond. The natural bond orbital and atoms in molecules analyses have been performed for these complexes. The energy decomposition analysis indicated that the electrostatic interaction plays a main contribution in formation of both complexes although the contribution from the charge-transfer interaction is also important.
Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 10/2010; 77(2):506-11. · 2.10 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed for the MCCBr−NCM′ (M and M′ = H, Li, Na, F, NH2, and CH3) halogen-bonded complexes at the MP2/aug-cc-pVTZ level. The binding energy is in a range of 1.34−23.42 kJ/mol. The results show that the alkali metal has a prominent effect on the strength of halogen bond, and this effect is different for the alkali metal in the halogen and electron donors. The alkali atom in the halogen donor makes it weaken greatly, whereas that in the electron donor causes it to enhance greatly. Natural bond orbital analysis shows that the alkali atom is electron-withdrawing in the halogen donor and electron-donating in the electron donor. In formation of the halogen bond, the former is a negative contribution, whereas the latter is a positive one. A similar charge transfer is also found for the H atom in the halogen and electron donors. These complexes have also been analyzed with the atoms in molecules theory.
The Journal of Physical Chemistry A 09/2010; 114(37):10320-5. · 2.95 Impact Factor
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ABSTRACT: The role of methyl group in H(2)O⋯XF and H(2)S⋯XF (X=Cl and Br) halogen-bonded complexes has been investigated with quantum chemical calculations. The halogen bond in the H(2)O⋯XF complexes is stronger than that in the H(2)S⋯XF complexes. However, the S⋯X halogen bond is stronger than the O⋯X one with the increase of methyl number. The result shows that the methyl group in the halogen acceptor has a positive contribution to the formation of halogen bond and there is a positive nonadditivity of methyl groups. Surprisingly, the methyl groups in dimethyl sulfide causes an increase of 150% for the interaction energy of S⋯Cl halogen bond. The natural bond orbital analyses have been performed to unveil the mechanism of the methyl group in the halogen bonding formation.
The Journal of chemical physics 09/2010; 133(11):114303. · 3.09 Impact Factor
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ABSTRACT: An ab initio study of the complexes formed between MH (M=O and S) and HXY (XY=CN and NC) was carried out at the UQCISD/6-311++G(2df,2p) level. For comparison, the corresponding H2M–HXY complexes were also studied. Two minima were found for each molecular pair. The results show the necessity of electron correlation and larger basis sets in the study of open-shell hydrogen-bonded complexes. As the proton donor and acceptor, the OH radical is favourable for the formation of a hydrogen bond with HXY than is the SH radical. The MH radical is more likely to donate a proton than H2M, whereas H2M is more likely to accept a proton than the MH radical. Natural bond orbital and atoms in molecules analyses were performed for these systems. It is shown that the complexes are held together mainly by electrostatic interactions.
Molecular Physics 06/2010; 108(12):1655-1664. · 1.82 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed on six halogen–hydride halogen bonded complexes with F3CCl or F3CBr as the halogen donor and metal hydride (HLi, HBeH and HMgH) as the halogen acceptor. At the MP2/6-311++G(d,p) level, the interaction strength spans from 2.62 to 17.68 kJ mol–1. The C–Cl and C–Br bonds are contracted. However, no evident blue shift accompanies this contraction. The H–Li bond is also contracted, but the H–He and H–Mg bonds are lengthened. However, a blue shift occurs for all these bond-stretching vibrations. These properties were analysed using the theory of natural bond orbital (NBO) and atoms in molecules (AIM). A symmetry-adapted perturbation theory (SAPT) analysis was also carried out to unveil the nature of this novel interaction. It is demonstrated that the electrostatic interaction plays a main role in the interaction, although induction and dispersion interactions are also important.
Molecular Physics. 03/2010; 108(5):611-617.
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ABSTRACT: The complexes H(2)C-LiX (X = H, OH, F, Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)) have been studied with quantum chemical calculations at the MP2/6-311++G(d,p) level. A new type of lithium bond was proposed, in which the carbene acts as the electron donor. This new type of lithium bond was characterized in view of the geometrical, spectral and energetic parameters. The Li-X bond elongates in all lithium bonded complexes. The Li-X stretch vibration has a red shift in the complexes H(2)C-LiX (X = H, OH, F); however, it exhibits a blue shift in the complexes H(2)C-LiX (X = Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)). The binding energies are in a range of 16.88-21.13 kcal/mol, indicating that the carbene is a good electron donor in the interaction. The energy decomposition analyses show that the electrostatic contribution is largest, polarization counterpart is followed, and charge transfer is smallest. The effect of substitution and hybridization on this type of lithium bond has also been investigated.
The Journal of Physical Chemistry A 12/2009; 113(51):14156-60. · 2.95 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed to study the structure and properties of the pi hydrogen-bonded complex formed between acetylene and HArCCF at the MP2/6-311++G(2d,2p) level. The C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes were also studied for comparison with the C(2)H(2)...HArCCF complex. The basis set superposition errors (BSSE)-counterpoise corrected potential-energy surface (PES) has a larger influence on the structure and properties of the C(2)H(2)...HArCCF complex than those of the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes. The C(2)H(2)...HArCCF complex exhibits a very large harmonic vibrational frequency blue shift of 574 cm(-1) for the H-Ar stretch, whereas the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes exhibit a small red shift of 35 and 47 cm(-1) for the H-C stretch, respectively; upon complexation the IR intensity decreases in the former, whereas it increases in the latter. The origin of the frequency shift and nature of the hydrogen bond in these complexes have been unveiled with the natural bond orbital analysis and energy decomposition.
The Journal of Physical Chemistry A 05/2009; 113(17):5235-9. · 2.95 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed for 1:1 and 1:2 systems of SCS and HF at the MP2/aug-cc-pVTZ level. There are two isomers for SCS–HF dimer. One is combined through a hydrogen bond with SCS as the electron donor; the other is formed by a σ-hole bond with SCS as the electron acceptor. Although the σ-hole bond is weaker than the hydrogen bond, the former is still competitive with the latter in this system. For comparison, the OCO–HF, SeCSe–HF, and SCS–HCl systems have also been analyzed. The most stable structure is the trimer where there are a FH⋯S hydrogen bond and a direct HF–HF contact simultaneously. It is shown that there is a cooperative effect between the hydrogen bond and the σ-hole bond. The band of 3843 cm−1 is assigned to the H–F stretch vibration in the σ-hole-bonded dimer. The natural bond orbital (NBO) and atoms in molecules (AIM) analyses have been performed for a better understanding the interactions.
Journal of Molecular Structure THEOCHEM 952:90-95. · 1.44 Impact Factor
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ABSTRACT: In this work, ab initio calculations have been performed to investigate the interaction between FnH3−nCBr (n = 0, 1, 2, 3) and HMgH at the MP2/aug-cc-pVTZ level. The results obtained from these calculations reveal the weak non-covalent Br⋯H interactions in all complexes. The calculated interaction energies for the complexes span from −2.17 to −8.98 kJ/mol. Upon complexation, the C–Br and H–Mg bonds are both elongated. Most C–Br stretches have a small red shift, whereas the H–Mg stretch exhibits a blue shift. These complexes are stabilized by the electrostatic interaction, charge transfer interaction and polarization interaction. The halogen-bonding nature of the Br⋯H interactions has been identified in terms of the bond critical point analysis within the theory of atoms in molecules.
Journal of Molecular Structure THEOCHEM 942:145-148. · 1.44 Impact Factor
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ABSTRACT: An ab initio computational study of the properties of π hydrogen-bonded complex of HArF and C2H4 has been carried out at the MP2/6-311++G(2d,2p) level of theory. For comparison, the C2H4···HF complex was also studied. The T-shape complex of C2H4···HArF was found to have a larger red shift of the H–Ar stretching frequency, accompanied by a decrease in the infrared intensity of the stretching mode and larger elongation of the H–Ar bond. The insertion of an Ar atom into the HF molecule causes an increase of about 47% in the interaction energy at the QCISD theory. The charge transfer within the HAF molecule upon complexation was examined with the natural bond orbital analyses. The minima on the basis set superposition errors (BSSE)-counterpoise-corrected potential-energy surface (PES) have been determined and the results were compared with those obtained from the uncorrected PES.
Journal of Molecular Structure THEOCHEM 897:69-72. · 1.44 Impact Factor
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Chemical Physics Letters 469:48-51. · 2.34 Impact Factor
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ABSTRACT: Quantum chemical calculations have been performed to study lithium-bonded complexes of XMgH–LiCY3 (X = H, F, CH3; Y = H, F) at the MP2/6-311++G(d,p) level. The geometrical, spectral and energetic parameters have been analyzed. Upon complexation, the Mg–H and Li–C bonds are lengthened, whereas their stretch vibrations have a blue shift. The interaction energies are in a range of 9.71–15.97 kcal/mol. The methyl group in CH3MgH enhances this interaction, whereas that in LiCH3 weakens it. The F atom in FMgH weakens this interaction, whereas that in LiCF3 enhances it. The calculations of natural bond orbital (NBO) and atoms in molecules (AIM) have also been carried out for these complexes. The electrostatic interaction is mainly responsible for the stability of these lithium-bonded complexes.
Journal of Molecular Structure THEOCHEM 916:28-32. · 1.44 Impact Factor
