Heng-Qing Wu

After the electronic field: structure, bonding, and the first hyperpolarizability of HArF.

In this work, we add different strength of external electric field (Eext) along molecule axis (Z‐axis) to investigate the electric field induced effect on HArF structure. The H‐Ar bond is the shortest at Eext = −189 × 10−4 and the Ar‐F bond show shortest value at Eext = 185 × 10−4 au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H‐Ar shows downtrend (ranging from0.79 to 0.69) and ionic bond Ar‐F shows uptrend (ranging from 0.04 to 0.17). Interestingly, the natural bond orbital analyses show that the charges of F atom range from −0.961 to −0.771 and the charges of H atoms range from 0.402 to 0.246. Due to weakened charge transfer, the first hyperpolarizability (βtot) can be modulated from 4078 to 1087 au. On the other hand, make our results more useful to experimentalists, the frequency‐dependent first hyperpolarizabilities were investigated by the coupled perturbed Hartree‐Fork method. We hope that this work may offer a new idea for application of noble‐gas hydrides.

The encapsulated lithium effect of Li@C60Cl8 remarkably enhances the static first hyperpolarizability

Recently, C60Cl8 (C2v) has been experimentally synthesized (Y.-Z. Tan, et al., Nat. Mater., 2008, 7, 790) by the addition of eight chlorine atoms to C60 (C2v), which is associated with a Stone–Wales transformation of C60 (Ih). In this work, the first hyperpolarizabilities (βtot) of C60 (C2v) and C60Cl8 (C2v) are investigated. After the Stone–Wales transformation and chlorine addition reaction, the βtot values slightly increase from 0 for C60 (Ih) to 60 au for C60 (C2v) and 502 au for C60Cl8 (C2v), respectively. To further enhance the first hyperpolarizability, the endohedral fullerene derivative, Li@C60Cl8, formed by encapsulating a lithium (Li) atom inside the C60Cl8, has been designed. Interestingly, the electron transfer between Li and C60Cl8 leads to an extremely large βtot value of 25 569 au, which is considerably larger (51 times) than the 502 au of C60Cl8. It shows that the encapsulated Li effect plays an important role in enhancing the first hyperpolarizability, so the Li@C60Cl8 can be considered as a candidate for high-performance nonlinear optical materials.

Effect of dehydrogenation/hydrogenation on the linear and nonlinear optical properties of Li@porphyrins

AbstractIn the present work, Li@porphyrins and their derivatives were designed in order to explore the effect of dehydrogenation/hydrogenation on linear and nonlinear optical properties. Their stable structures were obtained by the M06-2X method. Moreover, the M06-2X method showed that dehydrogenation/hydrogenation has greatly influences polarizabilities (α0 values) and hyperpolarizabilities (βtot and γtot values): α0 values ranged from 331 to 389 au, βtot values from 0 to 2465 au, and γtot values from −21.2 × 104 to 21.4 × 104 au. This new knowledge of the effect of dehydrogenation/hydrogenation on nonlinear optical properties may prove beneficial to the design and development of high-performance porphyrin materials. FigureThe figure shows the Li@porphyrins 2a and 2b and their derivatives 0, 1 and 3 and 4, respectively, which were designed based on the effect of dehydrogenation/hydrogenation. Interestingly, dehydrogenation/hydrogenation greatly influences their βtot value, which ranges from 0 to 2465 au (according to the M06-2X method). The observed trend in the βtot values may suggest that high-performance NLO materials should be designed based on the effect of dehydrogenation/hydrogenation

Theoretical study on the transport properties of oligothiophene–diketopyrrolopyrrole derivatives: quinoidal versus aromatic

Abstract Density functional theory calculations were carried out to investigate the transport mechanism of three oligothiophene–diketopyrrolopyrrole (T-DPP) derivatives. The results show that quinoidal molecule 1 that has dicyanovinyl has lower the lowest unoccupied molecular orbital (LUMO) energy level and larger adiabatic electron affinity (EAa) comparing with quinoidal 2 that has monocyanovinyl as terminal groups, signifying that to increase the extent of quinoid could improve the stability of the molecules in the air. Moreover, quinoidal molecules 1 and 2 have lower LUMO energy level, larger EAa, and electron-transfer integral (Ve) comparing than aromatic molecule 3, which indicates that quinoidal T-DPP derivatives are more in favor of electron than hole transport compared with their aromatic ones. Thus, constructing quinoidal architecture was also an effective way to design n-type transport materials besides the conventional idea that introducing electron-withdrawing groups.

One lithium atom binding with P -nitroaniline: lithium salts or lithium electrides?

AbstractRecently, both lithium (Li) salts and Li electrides formed by one Li atom interacting with ligand complexes, have been widely investigated. An interesting question emerges: is the configuration of one Li atom interacting with ligand complexes a Li salt or electride? In the present work, four configurations n-Li-PNA (n = 1–4) were obtained by binding one Li atom with the p-nitroaniline (PNA) at different positions to explore this question. The results show that 1-Li-PNA and 2-Li-PNA are typical Li salts, and 4-Li-PNA is a typical Li electride. Significantly, 3-Li-PNA possesses both characteristics of Li salt and electride. At the same time, 3-Li-PNA has the largest first hyperpolarizability (2.9 × 106 au) by ROMP2 method compared with the other three configurations. Furthermore, the first hyperpolarizability of 3-Li-PNA is about 2600 times larger than that of PNA. Further, the vertical ionization potential (VIP) and interaction energy (Eint) indicate that 3-Li-PNA is less stable than 1-Li-PNA and 2-Li-PNA (Li salts), but is more stable than 4-Li-PNA (Li electrides). Graphical AbstractThe present work shows how to distinguish a compound with Li salt or Li electride characteristic and predicts a new compound with both Li salt and Li electride characteristic

The symmetric and asymmetric thiophene-fused benzocarborane: structures and first hyperpolarizabilities

AbstractThe unusual properties of thiophene-fused benzocarborane have attracted a lot of interest in recent years due to their wide applications in photonics and optoelectronics. In the present work, nine molecules [M, N] (M, N are labeled as the number of thiophene rings on the left and right part, respectively) on the basis of thiophene-fused benzocarborane were considered. The first hyperpolarizability (βtot) values of three synthesized symmetric molecules [1, 1], [2, 2], [3, 3] (M=N, Chem. Eur. J 2012. 18, 11251–11257) and six asymmetric molecules [1, 2], [1, 3], [1, 4], [1, 5], [2, 3], [2, 4] (M≠N) were investigated, βtot values of symmetric molecules show the order: 39 of [1, 1]< 800 of [2, 2]< 903 au of [3, 3], which indicate that βtot value increases with increasing the number of thiophene ring for symmetric molecules. The other order of βtot values can be observed: 39 of [1, 1]< 800 of [1, 2]< 3553 of [1, 3]< 7998 of [1, 4]< 13049 au of [1, 5] and 66 of [2, 2]< 3240 of [2, 3]< 8029 au of [2, 4]. Interestingly, when sum of M and N is constant, larger difference between M and N is, larger βtot value is: 800 au of [2, 2]< 3553 au of [1, 3]; 3240 au of [2, 3] < 7998 au of [1, 4]; 903 au of [3, 3]< 8029 au of [2, 4]< 13049 au of [1, 5]. Significantly, [1, 5] with six thiophene rings has the largest βtot value (13049 au) which is greatly larger than 903 au of [3, 3] with six thiophene rings. Furthermore, the natural bond orbital (NBO) charge populations, the nucleus-independent chemical shift (NICS), the bond length alternation (BLA) of the nine molecules and crucial transition were studied in our work. We hope that the present work will be beneficial for future theoretical and experimental studies on the electro-optical properties of thiophene-fused benzocarborane molecules. FigureIn the present work, nine molecules [M, N] (M, N are labeled as the number of thiophene rings on the left and right part, respectively) on the basis of thiophene-fused benzocarborane were considered. Interestingly, when sum of M and N is constant, larger difference between M and N is, larger βtot value is. Then, [1, 5] with six thiophene rings has the largest βtot value (13,049 au) which is greatly larger than 903 au of [3, 3] with six thiophene rings. Take the benzocarborane for a limb of a tree, increasing the number of thiophene rings, is like lengthing the branch.