Tetrel Bond between 6-OTX3-Fulvene and NH3: Substituents and Aromaticity.

Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the ⁻OCH3 group at the exocyclic carbon of fulvene can form a moderate carbon bond with NH3 with an interaction energy of about -10 kJ/mol. The ⁻OSiH3 group engages in a stronger tetrel bond than does the ⁻OGeH3 group, while a reverse result is found for both ⁻OSiF3 and ⁻OGeF3 groups. The abnormal order in the former is mainly due to the stronger orbital interaction in the ⁻OSiH3 complex, which has a larger deformation energy. The cyano groups adjoined to the fulvene ring not only cause a change in the interaction type, from vdW interactions in the unsubstituted system of ⁻OCF3 to carbon bonding, but also greatly strengthen tetrel bonding. The formation of tetrel bonding has an enhancing effect on the aromaticity of the fulvene ring.

Protic vs Aprotic Solvent Effect on Proton Transfer in 3-Hydroxyisoquinoline: A Theoretical Study.

In this work, the structures, energetics, and tautomerizations in 3-hydroxyisoquinoline (3HIQ) in both the ground state and the excited state have been theoretically investigated by the MP2, TDDFT, and CASPT2 methods, respectively. The solvent effect including the implicit solvent and explicit solvent on the structures, energetics, and tautomeizations are revealed. We found that the explicit solvent plays a more important role in the structures, energetics, and tautomerizations in 3HIQ than implicit solvent in both the ground state and the excited state. The proton transfer is more facilitated in explicit solvent (water or methanol) compared to that in the gas phase and in the implicit solvent in the excited state, and the reactive role of the molecular solvent is found to be related with the two linear hydrogen bonds.

Tetrel-hydride interaction between XH3F (X = C, Si, Ge, Sn) and HM (M = Li, Na, BeH, MgH).

A tetrel-hydride interaction was predicted and characterized in the complexes of XH3F···HM (X = C, Si, Ge, Sn; M = Li, Na, BeH, MgH) at the MP2/aug-cc-pVTZ level, where XH3F and HM are treated as the Lewis acid and base, respectively. This new interaction was analyzed in terms of geometrical parameters, interaction energies, and spectroscopic characteristics of the complexes. The strength of the interaction is essentially related to the nature of X and M groups, with both the larger atomic number of X and the increased reactivity of M giving rise to a stronger tetrel-hydride interaction. The tetrel-hydride interaction exhibits similar substituent effects to that of dihydrogen bonds, where the electron-donating CH3 and Li groups in the metal hydride strengthen the binding interactions. NBO analyses demonstrate that both BD(H-M) → BD*(X-F) and BD(H-M) → BD*(X-H) orbital interactions play the stabilizing role in the formation of the complex XH3F···HM (X = C, Si, Ge, and Sn; M = Li, Na, BeH, and MgH). The major contribution to the total interaction energy is electrostatic energy for all of the complexes, even though the dispersion/polarization parts are nonnegligible for the weak/strong tetrel-hydride interaction, respectively.

Risk factors of postoperative recurrences in patients with clinical stage I NSCLC.

BACKGROUND: Despite advances in radiation therapy, chemotherapy, and newly developed molecular targeting therapies, long-term survival after resection for patients with NSCLC remains less than 50%. We investigated factors predicting postoperative locoregional recurrences and distant metastases in patients with clinical stage I non-small-cell lung cancer (NSCLC) after surgical resection. METHODS: All patients with clinical stage I NSCLC, who underwent surgical resection between January 2002 and June 2006, were reviewed retrospectively. Multiple logistic regression analyses were used to identify independent risk factors for patients with locoregional recurrences and distant metastases. RESULTS: A total of 261 patients were eligible. Overall survival was significant related to locoregional recurrences (P = 0.03) and distant metastases (P <0.001). There were significant differences of locoregional recurrence in tumor differentiation (P = 0.032) and advanced pathological stage (P = 0.002). In the group of distant metastases, there were significant differences in tumor differentiation (P = 0.035), lymphovascular space invasion (P = 0.031). Among the relationship between pattern of distant metastasis and clinicopathologic variables in patients with clinical stage I NSCLC, SUVmax (P = 0.02) and tumor size (P = 0.001) had significant differences. According to multiple logistic regression analysis, tumor differentiation is the only risk factor of postoperative outcome for locoregional recurrence and serum CEA (>3.5 ng/mL) is the predictor of distant metastasis. CONCLUSIONS: Tumor differentiation and serum CEA were predictors of postoperative relapse for clinical stage I NSCLC after surgical resection. Risk factors of postoperative recurrence in patients with clinical stage I NSCLC may enable us to optimize the patient selection for postoperative adjuvant therapies or neoadjuvant treatment before surgery.

Concerted interaction between pnicogen and halogen bonds in XCl-FH2P-NH3 (X=F, OH, CN, NC, and FCC).

We analyze the interplay between pnicogen-bonding and halogen-bonding interactions in the XCl-FH(2)P-NH(3) (X=F, OH, CN, NC, and FCC) complex at the MP2/aug-cc-pVTZ level. Synergetic effects are observed when pnicogen and halogen bonds coexist in the same complex. These effects are studied in terms of geometric and energetic features of the complexes. Natural bond orbital theory and Bader's theory of "atoms in molecules" are used to characterize the interactions and analyze their enhancement with varying electron density at critical points and orbital interactions. The physical nature of the interactions and the mechanism of the synergetic effects are studied using symmetry-adapted perturbation theory. By taking advantage of all the aforementioned computational methods, the present study examines how both interactions mutually influence each other.

Enhancement of iodine-hydride interaction by substitution and cooperative effects in NCX-NCI-HMY complexes.

The NCX-NCI-HMY (X=H, Cl, Br, I, Li; M=Be, Mg; Y=H, Li, Na) trimers are investigated to find ways to enhance the iodine-hydride interaction. The interaction energy in the NCI-HMH dimer is -2.87 and -5.87 kcal mol(-1) for M=Be and Mg, respectively. When the free H atom in the NCI-HMH dimer is replaced with an alkali atom, the interaction energy is enhanced greatly. When NCX is added into this dimer, the interaction energy of the iodine-hydride interaction is increased by 9-45 % and its increased percentage follows the order X=Cl

Prediction and characterization of a chalcogen-hydride interaction with metal hybrids as an electron donor in F2CS-HM and F2CSe-HM (M = Li, Na, BeH, MgH, MgCH3) complexes.

A novel type of σ-hole bonding has been predicted and characterized in F(2)CS-HM and F(2)CSe-HM (M = Li, Na, BeH, MgH) complexes at the MP2/aug-cc-pVTZ level. This interaction, termed a chalcogen-hydride interaction, was analyzed in terms of geometric, energetic and spectroscopic features of the complexes. It exhibits similar properties to hydrogen bonding and halogen bonding. The methyl group in metal hydrides makes a positive contribution to the formation of chalcogen-hydride bonded complexes. In the F(2)CSe-HLi-OH(2) complex, the chalcogen-hydride bonding shows synergetic effects with lithium bonding. These complexes have been analyzed with the atoms in molecules (AIM) theory and symmetry adapted perturbation theory (SAPT) method. The results show that the chalcogen-hydride bonding is dominated with an electrostatic interaction.

Pnicogen-hydride interaction between FH2X (X = P and As) and HM (M = ZnH, BeH, MgH, Li, and Na).

A pnicogen-hydride interaction has been predicted and characterized in FH(2)P-HM and FH(2)As-HM (M = ZnH, BeH, MgH, Li, and Na) complexes at the MP2/aug-cc-pVTZ level. For the complexes analyzed here, P(As) and HM are treated as a Lewis acid and a Lewis base, respectively. This interaction is moderate or strong since, for the strongest interaction of the FH(2)As-HNa complex, the interaction energy amounts to -24.79 kcal/mol, and the binding distance is equal to about 1.7 Å, much less than the sum of the corresponding van der Waals radii. By comparison with some related systems, it is concluded that the pnicogen-hydride interactions are stronger than dihydrogen bonds and lithium-hydride interactions. This interaction has been analyzed with natural bond orbitals, atoms in molecules, electron localization function, and symmetry adapted perturbation theory methods.

The role of nitro group on the excited-state relaxation mechanism of P-Z base pair.

DNAs' photostability is significant to the normal function of organisms. P-Z is a hydrogen bonded artificial DNA base pair, where P and Z represent 2-amino-imidazo[1,2-a]-1,3,5-triazin-4(8H)one and 6-amino-5nitro-2(1H)-pyridone, respectively. The excited-state relaxation mechanism of P-Z pair is investigated using static TDDFT calculations combined with the non-adiabatic dynamic simulations at TDDFT level. The roles of nitro rotation, nitro out-of-plane deformation, and single proton transfer (SPT) along hydrogen bond are revealed. The results of potential energy profile calculations demonstrate that the SPT processes along the hydrogen bonds are unfavorable to occur statically, which is in great contrast to the natural base pair. The non-adiabatic dynamic simulations show that the excited-state nitro rotation and nitro out-of-plane deformation are the two important relaxation channels which lead to the fast internal conversion to S0 state. The SPT from Z to P is also observed, followed by distortion on P, inducing the fast internal conversion to S0 state. However, this channel (decay via SPT process) plays minor roles on the excited-state relaxation mechanism statistically. This work shows the great differences of the excited-state relaxation mechanism between the natural base pairs and artificial base pair, also sheds new light into the role of hydrogen bond and nitro group in P-Z base pair.

The structure, properties, and nature of HArF-HOX (X = F, Cl, Br) complex: an ab initio study and an unusual short hydrogen bond.

The structure and properties (geometric, energetic, electronic, spectroscopic, and thermodynamic properties) of HArF-HOX (X = F, Cl, Br) complex have been investigated at the MP2/aug-cc-pVTZ level. Three types of complexes are formed through a hydrogen bond or a halogen bond. The HArF-HOX complex is the most stable, followed by the FArH-OHX complex, and the HArF-XOH complex is the most unstable. The binding distance in FArH-OHX complex is very short (1.1-1.7 Å) and is smaller than that in HArF-HOX complex. However, the interaction strength in the former is weaker than that in the latter. Thus, an unusual short hydrogen bond is present in FArH-OHX complex. The associated H-Ar bond exhibits a red shift, whereas the distant one gives a blue shift. A similar result is also found for the O-H and O-X bonds. The isotropic chemical shift is negative for the associated hydrogen atom but is positive for the associated halogen atom. However, a reverse result is found for the anisotropic chemical shift. The analyses of natural bond orbital and atoms in molecules have been performed for these complexes to understand the nature and properties of hydrogen and halogen bonds.

Some measures for making halogen bonds stronger than hydrogen bonds in H2CS-HOX (X = F, Cl, and Br) complexes.

The properties and applications of halogen bonds are dependent greatly on their strength. In this paper, we suggested some measures for enhancing the strength of the halogen bond relative to the hydrogen bond in the H(2)CS-HOX (X = F, Cl, and Br) system by means of quantum chemical calculations. It has been shown that with comparison to H(2)CO, the S electron donor in H(2)CS results in a smaller difference in strength for the Cl halogen bond and the corresponding hydrogen bond, and the Br halogen bond is even stronger than the hydrogen bond. The Li atom in LiHCS and methyl group in MeHCS cause an increase in the strength of halogen bonding and hydrogen bonding, but the former makes the halogen bond stronger and the latter makes the hydrogen bond stronger. In solvents, the halogen bond in the Br system is strong enough to compete with the hydrogen bond. The interaction nature and properties in these complexes have been analyzed with the natural bond orbital theory.

Theoretical study on HBO+ and HOB+ cations using multiconfiguration second-order perturbation theory.

The HBO(+) and HOB(+) cations have been reinvestigated using the CASSCF and CASPT2 methods in conjunction with the contracted atomic natural orbital (ANO) basis sets. The geometries of all stationary points in the potential energy surfaces were optimized at the CASSCF/ANO and CASPT2/ANO levels. The ground and the first excited states of HBO(+) are predicted to be X(2)Pi and A(2)Sigma(+) states, respectively. It was predicted that the ground state of HOB(+) is X(2)Sigma(+) state. The A(2)Pi state of HOB(+) has unique imaginary frequency. A bending local minimum M1 was found for the first time along the 1(2)A'' potential energy surface and the A(2)Pi state of HOB(+) should be the transition state of the isomerization reactions for M1<--> M1. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions were calculated as functions of the HBO bond angle. Many of the CASSCF and CASPT2 calculated results were different from the previously published QCISD(T) results.

A new unconventional halogen bond C-X...H-M between HCCX (X = Cl and Br) and HMH (M = Be and Mg): an ab initio study.

In this article, a new type of halogen-bonded complex YCCX...HMY (X = Cl, Br; M = Be, Mg; Y = H, F, CH(3)) has been predicted and characterized at the MP2/aug-cc-pVTZ level. We named it as halogen-hydride halogen bonding. In each YCCX...HMY complex, a halogen bond is formed between the positively charged X atom and the negatively charged H atom. This new kind of halogen bond has similar characteristics to the conventional halogen bond, such as the elongation of the C-X bond and the red shift of the C-X stretch frequency upon complexation. The interaction strength of this type of halogen bond is in a range of 3.34-10.52 kJ/mol, which is smaller than that of dihydrogen bond and conventional halogen bond. The nature of the electrostatic interaction in this type of halogen bond has also been unveiled by means of the natural bond orbital, atoms in molecules, and energy decomposition analyses.

Push-pull electron effects of the complexant in a Li atom doped molecule with electride character: a new strategy to enhance the first hyperpolarizability.

Differing from the reported strategy of push or pull electron effects of the complexant, a new strategy of the combination effects of both push and pull electrons of the complexant to enhance the first hyperpolarizability is performed with two Li atom doped complexants with a pair of difluorophenyl subunit rings. Large variance of the static first hyperpolarizabilities (beta(0)) are exhibited at the MP2/6-311++G(d,p) level. The order of the beta(0) values is 2.9 x10(2) (complexant UD) << 5.9 x 10(3) (LL) < 1.9 x 10(4) (H-L) < 2.3 x 10(4) (H(F)-L) < 3.2 x 10(4) (L-L) < 7.8 x 10(5) a.u. (H(F)-L(F)). It is found that H(F)-L(F) with the edge-type push-pull electronic effect of the complexant has the largest beta(0). The edge-type push-pull electronic effect brings a 2700 times increase in the beta(0) from the UD to H(F)-L(F) structure. It shows that the push-pull electronic effect is a highly effective strategy to enhance the beta(0) value. The beta(0) (7.8 x 10(5) a.u.) of the H(F)-L(F) is considerable, due to the small DeltaE and the very large Delta mu (18.085 a.u.), which comes from the corresponding long-range charge transfer transition. It is interesting that a pair of subunit rings of the complexant may have different electronic effects. In H-L and H(F)-L(F), the left ring with a longer distance between Li and the subunit ring exhibits a push electronic effect, while the right ring with the shorter distance exhibits a pull electronic effect. This work may contribute to the development of potential high-performance nonlinear optical materials.

[Theoretical study of geometrical structures and properties of several replaced mercapto molecules].

The geometrical structures of several Raman probe molecules were optimized using density functional theory (DFT) of the hybrid density functional B3LYP method and 6-311+ + G** basis set. Their energy gap, nucleus independent chemical shift (NICS), polarizability and vibration spectrum were studied. The theoretical results showed that: 4-MPY, MBA and PATP had planar structures, the angle of BDT between S-H and benzene ring plane was 20. 2 degrees, and the 4-MBT was 39. 6 degrees; they all have a strong aroma and a large value of polarization. The order of the average of molecular hyperpolarizability tensor was BDT > 4-MBT > 4-MBA > 4-MPY > PATP, and the trends of polarizability anisotropy invariant were 4-MBA > 4-MBT > BDT > PATP > 4-MPY.

Cooperativity between the dihydrogen bond and the NHC hydrogen bond in LiH-(HCN)n Complexes.

The cooperativity between the dihydrogen bond and the NHC hydrogen bond in LiH-(HCN)(n) (n=2 and 3) complexes is investigated at the MP2 level of theory. The bond lengths, dipole moments, and energies are analyzed. It is demonstrated that synergetic effects are present in the complexes. The cooperativity contribution of the dihydrogen bond is smaller than that of the NHC hydrogen bond. The three-body energy in systems involving different types of hydrogen bonds is larger than that in the same hydrogen-bonded systems. NBO analyses indicate that orbital interaction, charge transfer, and bond polarization are mainly responsible for the cooperativity between the two types of hydrogen bonds.

[Density functional theory studies on structure and spectrum of Cu3 Ti cluster].

Bulk intermetallic Ti-Cu compounds have been found to possess special properties, including increased hardness, as well as displaying enhanced sound absorption and e shape memory. Since only one Raman progression is observed, there is not sufficient information to determine the structure of TiCu3. The different structures and vibrational frequencies of the Cu3 Ti cluster were studied by means of the density functional theory with SVWN5, B3LYP and BPW91 methods at basis sets of lanl2dz, 6-31g, 6-311g, 6-311g(d), 6-311 +/- g(2df) and 6-311 +/- g(3d2f). The calculated results show that the ground state of the Cu3 Ti cluster is a e-type structure with the C2v point group symmetry, and the bond lengths and vibrational frequencies of Cu3 T are considerably dependent on the variation of basis sets. We observed only a single Raman progression in approximately 300 cm(-1). This progression is most likely the totally symmetric stretch. The computed and observed Raman spectra were also compared with each other.

Nonlinear optical properties of aluminum nitride nanotubes doped by excess electron: a first principle study.

Aluminum nitride nanotubes (AlNNTs) doped by the excess electron, e@AlNNT and M@N-AlNNT (M = Li, Na, K), have been designed and their geometrical, electronic, and nonlinear optical (NLO) properties have been explored theoretically. The results showed that the excess electron narrows the energy gap between HOMO and LUMO values (EH-L) of the doped systems in the range of 3.42-5.37 eV, which is due to a new energy level HOMO formed for the doped excess electron, with higher energy than the original HOMO of AlNNT. Importantly, the doped excess electron considerably increases the first hyperpolarizability (ß0) from 130 a.u. of the undoped AlNNT to 646 a.u. for e@AlNNT, 2606 a.u. for Li@N-AlNNT, while 1.14 × 105 a.u. for Na@N-AlNNT, and 1.37 × 106 a.u. for K@N-AlNNT. The enormous ß0 values for Na@N-AlNNT and K@N-AlNNT are attributed to the low transition energy. These results demonstrate that AlNNTs are a promising material in high-performance NLO nanomaterials for electronic devices.

Carbon Excess C3N: A Potential Candidate as Li-Ion Battery Material.

Xu et al.'s recent experimental work ( Adv. Mater. 2017, 29, 1702007) suggested that C3N is a potential candidate as Li-ion battery with unusual electrochemical characteristics. However, the obvious capacity loss (from 787.3 to 383.3 mA h·g-1) occurs after several cycles, which restricts its high performance. To understand and further solve this issue, in the present study, we have studied the intercalation processes of Li ions into C3N via first-principle simulations. The results reveal that the Li-ion theoretical capacity in pure C3N is only 133.94 mA h·g-1, the value is obviously lower than experimental one. After examining the experimental results in detail, it is found that the chemical component of the as-generated C xN structure is actually C2.67N with N excess. In this case, the calculated theoretical capacity is 837.06 mA h·g-1, while part of Li ions are irreversibly trapped in C2.67N, resulting in the capacity loss. This phenomenon is consistent with the experimental results. Accordingly, we suggest that N excess C3N, but not pure C3N, is the proposed Li-ion battery material in Xu et al.'s experiment. To solve the capacity loss issue and maintain the excellent performance of C3N-based anode material, the C3N with slightly excess C (C3.33N), which has been successfully fabricated in the experiment, is considered in view of its relatively low chemical activity as compared with N excess C3N. Our results reveal that the C excess C3N is a potential Li-ion battery material, which exhibits the low open circle voltage (0.12 V), high reversible capacity (840.35 mA h·g-1), fast charging/discharging rate, and good electronic conductivity.

[Study of spectral property of Er3+-doped TiO2].

Spectral property of Er3+-doped TiO2 prepared with gel method using absolute alcohol, glacial acetic acid and tetrabutyl titanate was studied. The Stokes emission spectra at 488 nm and upconversion emission spectra at 980 nm of the material were measured. In the visible range, green and red light was observed with green light corresponding to 2H(11/2), 4S(3/2)-->4I(15/2) transition of Er3+, and red light corresponding to 4F(9/2)-->4I(15/2) transition of Er3+. The green and red light are both two-phonon process from the curve of In Ivis-ln Iin, as the light intensity is directly proportional to the square of pump power. Elementary studies of the upconversion process were conducted.