The effects of external electric field: creating non-zero first hyperpolarizability for centrosymmetric benzene and strongly enhancing first hyperpolarizability for non-centrosymmetric edge-modified graphene ribbon H2N-(3,3)ZGNR-NO2.

How to generate a non-zero first hyperpolarizability for a centrosymmetric molecule is a challenging question. In this paper, an external (pump) electric field is used to make a centrosymmetric benzene molecule generate a non-zero value of the electric field induced first hyperpolarizability (ß (F) ). This comes from the centrosymmetry breaking of electron cloud. Two interesting rules are exhibited. (1) ß (F) is anisotropic for different directional fields (F i, i = X, Y, Z). (2) The field dependence of ß (F) is a non-monotonic function, and an optimum external electric field causes the maximum value of ß (F) . The largest first hyperpolarizability ß (F) reaches the considerable level of 3.9 × 10(5) a.u. under F Y = 330 × 10(-4) a.u. for benzene. The external electric field effects on non-centrosymmetric edge-modified graphene ribbon H2N-(3,3)ZGNR-NO2 was also studied in this work. The first hyperpolarizability reaches as much as 2.1 × 10(7) a.u. under F X = 600 × 10(-4) a.u. for H2N-(3,3)ZGNR-NO2. We show that the external electric field can not only create a non-zero first hyperpolarizability for centrosymmetric molecule, but also remarkably enhance the first hyperpolarizability for a non-centrosymmetric molecule.

New acceptor-bridge-donor strategy for enhancing NLO response with long-range excess electron transfer from the NH2...M/M3O donor (M = Li, Na, K) to inside the electron hole cage C20F19 acceptor through the unusual σ chain bridge (CH2)4.

Using the strong electron hole cage C20F19 acceptor, the NH2...M/M3O (M = Li, Na, and K) complicated donors with excess electron, and the unusual σ chain (CH2)4 bridge, we construct a new kind of electride molecular salt e(-)@C20F19-(CH2)4-NH2...M(+)/M3O(+) (M = Li, Na, and K) with excess electron anion inside the hole cage (to be encapsulated excess electron-hole pair) serving as a new A-B-D strategy for enhancing nonlinear optical (NLO) response. An interesting push-pull mechanism of excess electron generation and its long-range transfer is exhibited. The excess electron is pushed out from the (super)alkali atom M/M3O by the lone pair of NH2 in the donor and further pulled inside the hole cage C20F19 acceptor through the efficient long σ chain (CH2)4 bridge. Owing to the long-range electron transfer, the new designed electride molecular salts with the excess electron-hole pair exhibit large NLO response. For the e(-)@C20F19-(CH2)4-NH2...Na(+), its large first hyperpolarizability (ß0) reaches up to 9.5 × 10(6) au, which is about 2.4 × 10(4) times the 400 au for the relative e(-)@C20F20...Na(+) without the extended chain (CH2)4-NH2. It is shown that the new strategy is considerably efficient in enhancing the NLO response for the salts. In addition, the effects of different bridges and alkali atomic number on ß0 are also exhibited. Further, three modulating factors are found for enhancing NLO response. They are the σ chain bridge, bridge-end group with lone pair, and (super)alkali atom. The new knowledge may be significant for designing new NLO materials and electronic devices with electrons inside the cages. They may also be the basis of establishing potential organic chemistry with electron-hole pair.

Influence of C-terminal tail deletion on structure and stability of hyperthermophile Sulfolobus tokodaii RNase HI.

The C-terminus tail (G144-T149) of the hyperthermophile Sulfolobus tokodaii (Sto-RNase HI) plays an important role in this protein's hyperstabilization and may therefore be a good protein stability tag. Detailed understanding of the structural and dynamic effects of C-terminus tail deletion is required for gaining insights into the thermal stability mechanism of Sto-RNase HI. Focused on Sulfolobus tokodaii RNase HI (Sto-RNase HI) and its derivative lacking the C-terminal tail (ΔC6 Sto-RNase HI) (PDB codes: 2EHG and 3ALY), we applied molecular dynamics (MD) simulations at four different temperatures (300, 375, 475, and 500 K) to examine the effect of the C-terminal tail on the hyperstabilization of Sto-RNase HI and to investigate the unfolding process of Sto-RNase HI and ΔC6 Sto-RNase HI. The simulations suggest that the C-terminal tail has significant impact in hyperstabilization of Sto-RNase HI and the unfolding of these two proteins evolves along dissimilar pathways. Essential dynamics analysis indicates that the essential subspaces of the two proteins at different temperatures are non-overlapping within the trajectories and they exhibit different directions of motion. Our work can give important information to understand the three-state folding mechanism of Sto-RNase HI and to offer alternative strategies to improve the protein stability.

Direct ab initio study on the rate constants of radical C2(A 3Π(u)) + C3H8 reaction.

The mechanism and kinetics of the radical (3)C(2) + C(3)H(8) reaction have been investigated theoretically by direct ab initio kinetics over a wide temperature range. The potential energy surfaces have been constructed at the CCSD(T)/B3//UMP2/B1 levels of theory. The electron transfer was also analyzed by quasi-restricted orbital (QRO) in detail. It was shown that all these channels proceed exclusively via hydrogen abstraction. The overall ICVT/SCT rate constants are in agreement with the available experimental results. The prediction shows that the secondary hydrogen of C(3)H(8) abstraction by (3)C(2) radical is the major pathway at low temperatures (below 700 K), while as the temperature increases, the primary hydrogen of C(3)H(8) abstraction becomes more important and more favorable. A negative temperature dependence of the rate constants for the reaction of (3)C(2) + C(3)H(8) was observed. The three-(k (3)) and four-parameter (k (4)) rate-temperature expressions were also provided within 243-2000 K to facilitate future experimental studies.

Structural and dynamic basis of human cytochrome P450 7B1: a survey of substrate selectivity and major active site access channels.

Cytochrome P450 (CYP) 7B1 is a steroid cytochrome P450 7α-hydroxylase that has been linked directly with bile salt synthesis and hereditary spastic paraplegia type 5 (SPG5). The enzyme provides the primary metabolic route for neurosteroids dehydroepiandrosterone (DHEA), cholesterol derivatives 25-hydroxycholesterol (25-HOChol), and other steroids such as 5α-androstane-3ß,17ß-diol (anediol), and 5α-androstene-3ß,17ß-diol (enediol). A series of investigations including homology modeling, molecular dynamics (MD), and automatic docking, combined with the results of previous experimental site-directed mutagenesis studies and access channels analysis, have identified the structural features relevant to the substrate selectivity of CYP7B1. The results clearly identify the dominant access channels and critical residues responsible for ligand binding. Both binding free energy analysis and total interaction energy analysis are consistent with the experimental conclusion that 25-HOChol is the best substrate. According to 20 ns MD simulations, the Phe cluster residues that lie above the active site, particularly Phe489, are proposed to merge the active site with the adjacent channel to the surface and accommodate substrate binding in a reasonable orientation. The investigation of CYP7B1-substrate binding modes provides detailed insights into the poorly understood structural features of human CYP7B1 at the atomic level, and will be valuable information for drug development and protein engineering.

Influence of hyperthermophilic protein Cren7 on the stability and conformation of DNA: insights from molecular dynamics simulation and free energy analysis.

Cren7, a novel chromatin protein highly conserved among crenarchaea, plays an important role in genome packaging and gene regulation. However, the detail dynamical structural characteristic of the Cren7-DNA complex and the detail study of the DNA in the complex have not been done. Focused on two specific Cren7-DNA complexes (PDB codes 3LWH and 3LWI ), we applied molecular dynamics (MD) simulations at four different temperatures (300, 350, 400, and 450 K) and the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) free energy calculation at 300 and 350 K to examine the role of Cren7 protein in enhancing the stability of DNA duplexes via protein-DNA interactions, and to study the structural transition in DNA. The simulation results indicate that Cren7 stabilizes DNA duplex in a certain temperature range in the binary complex compared with the unbound DNA molecules. At the same time, DNA molecules were found to undergo B-like to A-like form transitions with increased temperature. The results of statistical analyses of the H-bond and hydrophobic contacts show that some residues have significant influence on the structure of DNA molecules. Our work can give important information to understand the interactions of proteins with nucleic acids and other ligands.

Insights into the thermal stabilization and conformational transitions of DNA by hyperthermophile protein Sso7d: molecular dynamics simulations and MM-PBSA analysis.

In the assembly of DNA-protein complex, the DNA kinking plays an important role in nucleoprotein structures and gene regulation. Molecular dynamics (MD) simulations were performed on specific protein-DNA complexes in this study to investigate the stability and structural transitions of DNA depending on temperature. Furthermore, we introduced the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) approach to analyze the interactions between DNA and protein in hyperthermophile. Focused on two specific Sso7d-DNA complexes (PDB codes: 1BNZ and 1BF4), we performed MD simulations at four temperatures (300, 360, 420, and 480 K) and MM-PBSA at 300 and 360 K to illustrate detailed information on the changes of DNA. Our results show that Sso7d stabilizes DNA duplex over a certain temperature range and DNA molecules undergo B-like to A-like form transitions in the binary complex with the temperature increasing, which are consistent with the experimental data. Our work will contribute to a better understanding of protein-DNA interaction.

Mechanism insights of ethane C-H bond activations by bare [Fe(III)═O]+: explicit electronic structure analysis.

Alkane C-H bond activation by various catalysts and enzymes has attracted considerable attention recently, but many issues are still unanswered. The conversion of ethane to ethanol and ethene by bare [Fe(III)═O](+) has been explored using density functional theory and coupled-cluster method comprehensively. Two possible reaction mechanisms are available for the entire reaction, the direct H-abstraction mechanism and the concerted mechanism. First, in the direct H-abstraction mechanism, a direct H-abstraction is encountered in the initial step, going through a collinear transition state C···H···O-Fe and then leading to the generation of an intermediate Fe-OH bound to the alkyl radical weakly. The final product of the direct H-abstraction mechanism is ethanol, which is produced by the hydroxyl group back transfer to the carbon radical. Second, in the concerted reaction mechanism, the H-abstraction process is characterized via overcoming four/five-centered transition states (6/4)TSH_c5 or (4)TSH_c4. The second step of the concerted mechanism can lead to either product ethanol or ethene. Moreover, the major product ethene can be obtained through two different pathways, the one-step pathway and the stepwise pathway. It is the first report that the former pathway starting from (6/4)IM_c to the product can be better described as a proton-coupled electron transfer (PCET). It plays an important role in the product ethene generation according to the CCSD(T) results. The spin-orbital coupling (SOC) calculations demonstrate that the title reaction should proceed via a two-state reactivity (TSR) pattern and that the spin-forbidden transition could slightly lower the rate-determining energy barrier height. This thorough theoretical study, especially the explicit electronic structure analysis, may provide important clues for understanding and studying the C-H bond activation promoted by iron-based artificial catalysts.

Ab initio investigation on ion-associated species and association process in aqueous Na2SO4 and Na2SO4/MgSO4 solutions.

In the present paper, the possible ion associated species in pure Na(2)SO(4) and mixed Na(2)SO(4)/MgSO(4) aqueous solutions are investigated via the ab initio method at the HF/6-31+G∗ level. The vibrational v(1)-SO(4)(2-) band is analyzed. For the unhydrated species, when the number of metal ions around the SO(4)(2-) ion is less than 3, the dominating effect to the v(1)-SO(4)(2-) band is the polarization of the cations, while the M-O bonding will be dominating as the number is equal to or more than 3. For the hydrated species, the coordinated structures of the Na(+) ion in all ion pairs are not stable due to the strong effect of the SO(4)(2-) ion but relatively stable in the triple ion (TI) clusters since there are fewer vacant hydration sites around the SO(4)(2-). The v(1)-SO(4)(2-) frequencies are close to that of the hydrated SO(4)(2-) ion in the ion pairs and larger in both Na(2)SO(4) and Na(2)SO(4)/MgSO(4) TI clusters. On the basis of our calculated results, the evolvement of Raman spectra in the Na(2)SO(4)/MgSO(4) droplet with the molar ratio of 1:1 is explained.

Evolution of lone pair of excess electrons inside molecular cages with the deformation of the cage in e2@C60F60 systems.

For unusual e(2)@C(60)F(60)(I(h), D(6h), and D(5d)) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C(60)F(60) cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e(2)@C(60)F(60)(I(h)) and triplet states for short capsular shaped e(2)@C(60)F(60)(D(6h)) and long capsular shaped e(2)@C(60)F(60)(D(5d)), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720-2.283 eV and VDEs (II) of 3.959-5.288 eV), which shows their stabilities and suggests that the large C(60)F(60) cage is the efficient container of excess electrons.

Alkali metal atom-aromatic ring: a novel interaction mode realizes large first hyperpolarizabilities of M@AR (M=Li, Na, and K, AR=pyrrole, indole, thiophene, and benzene).

Several new electride compounds M@pyrrole (M = Li, Na, and K), Li@AR (AR = indole, thiophene, and benzene), Li@tryptophan and Li@serotonin were designed and investigated, which exhibit considerably large first hyperpolarizabilities (ß(0)) (6705, 1116, 11399, 5781, 4808, 1536, 8106, and 9389 au, respectively) by comparison with their corresponding sole molecules pyrrole (ß(0) = 30 au), indole (104 au), thiophene (6 au), benzene (0 au), tryptophan (159 au) and serotonin (151 au), respectively. The computational results revealed that the interaction of the alkali metal atom with π-conjugated aromatic ring (AR) is one effectively new approach to produce diffuse excess electron to get a large ß(0) value, which is advantageous for the design of the novel high-performance NLO materials with π-conjugated AR: alkali metal atoms doped nanomaterials and biomolecules.

Theoretical mechanistic study of the reaction of the methylidyne radical with methylacetylene.

A detailed doublet potential energy surface for the reaction of CH with CH(3)CCH is investigated at the B3LYP/6-311G(d,p) and G3B3 (single-point) levels. Various possible reaction pathways are probed. It is shown that the reaction is initiated by the addition of CH to the terminal C atom of CH(3)CCH, forming CH(3)CCHCH 1 (1a,1b). Starting from 1 (1a,1b), the most feasible pathway is the ring closure of 1a to CH(3)-cCCHCH 2 followed by dissociation to P ( 3 )(CH(3)-cCCCH+H), or a 2,3 H shift in 1a to form CH(3)CHCCH 3 followed by C-H bond cleavage to form P ( 5 )(CH(2)CHCCH+H), or a 1,2 H-shift in 1 (1a, 1b) to form CH(3)CCCH(2) 4 followed by C-H bond fission to form P ( 6 )(CH(2)CCCH(2)+H). Much less competitively, 1 (1a,1b) can undergo 3,4 H shift to form CH(2)CHCHCH 5. Subsequently, 5 can undergo either C-H bond cleavage to form P ( 5 ) (CH(2)CHCCH+H) or C-C bond cleavage to generate P ( 7 ) (C(2)H(2)+C(2)H(3)). Our calculated results may represent the first mechanistic study of the CH + CH(3)CCH reaction, and may thus lead to a deeper understanding of the title reaction.

Direct ab initio dynamics study of radical C4H (X̃2Σ+) + CH4 reaction.

The methane (CH(4)) hydrogen abstraction reaction by linear butadiynyl radical C(4)H (CCCCH) has been investigated by direct ab initio dynamics over a wide temperature range of 100-3000 K, theoretically. The potential energy surfaces (PESs) have been constructed at the CCSD(T)/aug-cc-pVTZ//BB1K/6-311G(d,p) levels of theory. Two different hydrogen abstraction channels by C(1) and C(4) of C(4)H (C(1)C(2)C(3)C(4)H) have been considered. The results indicate that the C(1) position of C(4)H is a more reactive site. The electron transfer behaviors of two possible channels are also analyzed by quasi-restricted orbital (QRO) in detail. The rate constants calculated by canonical variational transition-state theory (CVT) with the small-curvature tunneling correction (SCT) are in excellent agreement with available experimental values. The normal and three-parameter expressions of Arrhenius rate constants are also provided within 100-3000 K. It is expected to be helpful for further studies on the reaction dynamics behaviors over a wide temperature range where no experimental data is available so far.

Exceptionally large second-order nonlinear optical response in donor-graphene nanoribbon-acceptor systems.

Graphene nanoribbon (GNR) has been used, for the first time, as an excellent conjugated bridge in a donor-conjugated bridge-acceptor (D-B-A) framework to design high-performance second-order nonlinear optical materials. Owing to the unique diradical planar conjugated bridge of GNR, D(NH(2))-GNR-A(NO(2)) exhibits exceptionally large static first hyperpolarizability (ß(0)) up to 2.5×10(6) a.u. (22000×10(-30) esu) for H(2)N-(7,3)ZGNR-NO(2) (ZGNR=zigzag-edged GNR), which is about 15 times larger than the recorded value of ß(0) (1470×10(-30) esu) for the D-A polyene reported by Blanchard-Desce et al. [Chem. Eur. J. 1997, 3, 1091]. Interestingly, we have found that the size effect of GNR plays a key role in increasing ß(0) for the H(2)N-GNR-NO(2) system, in which the width effect of GNR perpendicular to the D-A direction is superior to the length effect along the D-A direction.

Electric field-driven acid-base chemistry: proton transfer from acid (HCl) to base (NH3/H2O).

It is well-known that single H3N-HCl and H2O-HCl acid-base pairs do not react to form the ion pairs, H4N(+)Cl(-) and H3O(+)Cl(-), in isolation. On the basis of ab initio method, we propose a physical method of external electric field (Eext) to drive the proton transfer from acid (HCl) to base (NH3/H2O). Our results show that when Eext along the proton-transfer direction achieves or exceeds the critical electric field (Ec), the proton transfer occurs, such as, the Ec values of proton transfer for H3N-HCl and H2O-HCl are 54 × 10(-4) and 210 × 10(-4) au, respectively. And the degree of the proton transfer can be controlled by modulating the strength of Eext. Furthermore, we estimate the inductive strength of an excess electron (Ee) equivalent to the Eext = 125 × 10(-4) au, which is greater than the Ec (54 × 10(-4) au) of NH3-HCl but less than the Ec (210 × 10(-4) au) of H2O-HCl. This explains well the anion photoelectron spectroscopy [Eustis et al. Science 2008, 319, 936] that an excess electron can trigger the proton transfer for H3N-HCl but not for H2O-HCl. On the basis of the above estimation, we also predict that two excess electrons can induce H2O-HCl to undergo the proton transfer and form the ion pair H3O(+)Cl(-).

Beryllium and boron decoration forms planar tetracoordinate carbon strips at the edge of graphene nanoribbons.

Graphene has been viewed as one of the most promising materials in many fields. Recently, it has been found that by using Cu-decoration at the edge of zigzag graphene nanoribbons (ZGNR), a novel kind of planar tetracoordinate carbon (ptC) strip can be formed. In this paper, we investigate the edge-decoration of armchair graphene nanoribbons (AGNR) by various atom types and find that two new kinds of ptC strip can be effectively formed by using Be or B decoration. For the Be-decorated AGNR, the edge Be atoms take the form of a "zigzag-like" chain, and all the edge C atoms have a ptC nature. However, for the B-decorated AGNR, the edge B atoms form an infinite yet "fractured" chain consisting of separate B(4)-subunits, which results in only 50% of the edge C atoms being ptCs, in contrast with Be-decorated AGNR and Cu-decorated ZGNR. The high thermal stability of both types of ptC-based AGNR is indicated by isomeric sampling and molecular dynamics simulations.

Theoretical investigation of the interaction between carbon monoxide and carbon nanotubes with single-vacancy defects.

Density functional theory calculations are used to study the healing process of a defective CNT (i.e. (8,0) CNT) by CO molecules. The healing undergoes three evolutionary steps: 1) the chemisorption of the first CO molecule, 2) the incorporation of the C atom of CO into the CNT, accompanied by the adsorption of the leaving O atom on the CNT surface, 3) the removal of the adsorbed O atom from the CNT surface by a second CO molecule to form CO(2) and the perfect CNT. Overall, adsorption of the first CO reveals a barrier of 2.99 kcal mol(-1) and is strongly exothermal by 109.11 kcal mol(-1), while adsorption of a second CO has an intrinsic barrier of 32.37 kcal mol(-1)and is exothermal by 62.34 kcal mol(-1). In light of the unique conditions of CNT synthesis, that is, high temperatures in a closed container, the healing of the defective CNT could be effective in the presence of CO molecules. Therefore, we propose that among the available CNT synthesis procedures, the good performance of chemical vapor decomposition of CO on metal nanoparticles might be ascribed to the dual role of CO, that is, CO acts both as a carbon source and a defect healer. The present results are expected to help a deeper understanding of CNT growth.

How does a double-cage single molecule confine an excess electron? Unusual intercage excess electron transfer transition.

To realize the chemistry of a multicage organic molecule with excess electron, as a model, by confining an excess electron inside a double-cage single molecule, the structures of e⁻@C24F22(NH)2C20F18 (e⁻@AB) and e⁻@C20F18(NH)2C20F18 (e⁻@BB') are obtained at the B3LYP/6-31G(d) + 4s4p theory level. It is confirmed that the excess electron is mainly confined inside one cage with larger interior electronic attractive potential (A for e⁻@AB and B for e⁻@BB') in the ground state, while the electron is localized in the other one in the first excited state. Owing to such excess electron localizations, an interesting intercage excess electron transfer transition takes places. This intercage excess electron transfer transition exhibits five characteristics: (1) the excess electron transfer from one cage to another (A → B for e⁻@AB and B → B' for e⁻@BB''); (2) the transition is between the ground and first excited state; (3) the wavelength and strength are the largest; (4) the transition accompanies a significant charge transfer (Δq > 0.8) and molecular dipole moment change (Δµ > 20 D); (5) the transition corresponds to SOMO → LUMO. For the transition, the oscillator strength is larger and the wavelength is shorter for the asymmetric structure (e⁻@AB) than for the symmetric one (e⁻@BB'), which indicates that the intercage excess electron transfer transition may be regulated by changing the size of cage. This work is useful for the designs of organic electronic sponges (porous organic electrides), organic conductor with excess electrons, and photoelectric and nanoelectronic devices.

Reaction mechanism of CH + C(3)H(6): a theoretical study.

A detailed theoretical study is performed at the B3LYP/6-311G(d,p) and G3B3 (single-point) levels as an attempt to explore the reaction mechanism of CH with C(3)H(6). It is shown that the barrierless association of CH with C(3)H(6) forms two energy-rich isomers CH(3)-cCHCHCH(2) (1), and CH(2)CH(2)CHCH(2) (4). Isomers 1 and 4 are predicted to undergo subsequent isomerization and dissociation steps leading to ten dissociation products P(1) (CH(3)-cCHCHCH + H), P(2) (CH(3)-cCCHCH(2) + H), P(3) (cCHCHCH(2) + CH(3)), P(4) (CH(3)CHCCH(2) + H), P(5) (cis-CH(2)CHCHCH(2) + H), P(6) (trans-CH(2)CHCHCH(2) + H), P(7) (C(2)H(4) + C(2)H(3)), P(8) (CH(3)CCH + CH(3)), P(9) (CH(3)CCCH(3) + H) and P(12) (CH(2)CCH(2) + CH(3)), which are thermodynamically and kinetically possible. Among these products, P(5), P(6), and P(7) may be the most favorable products with comparable yields; P(1), P(2), and P(3) may be the much less competitive products, followed by the almost negligible P(4), P(8), P(9), and P(12). Since the isomers and transition states involved in the CH + C(3)H(6) reaction all lie lower than the reactant, the title reaction is expected to be fast, which is consistent with the measured large rate constant in experiment. The present study may lead us to a deep understanding of the CH radical chemistry.

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.