Long-Range Charge Transfer Driven by External Electric Field

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C: Plasmonics; Optical, Magnetic, and Hybrid Materials

Long-Range Charge Transfer Driven by External Electric Field in Alkalides M-LCaL- M (M = Li or Na, L = All-Cis 1,2,3,4,5,6-Hexafluorocyclohexane): Facially Polarized Janustype Second Order Nonlinear Molecular Optical Switches Yin-Feng Wang, Jia Li, Jiangen Huang, Tian Qin, Yun-Meng Liu, Fan Zhong, Wen Zhang, and Zhi-Ru Li J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 03 Sep 2019 Downloaded from pubs.acs.org on September 3, 2019

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The Journal of Physical Chemistry

Long-range Charge Transfer Driven by External Electric Field in Alkalides MLCaL-M (M = Li or Na, L = all-cis 1,2,3,4,5,6-Hexafluorocyclohexane): Facially Polarized Janus-type Second Order Nonlinear Molecular Optical Switches Yin-Feng Wang,a Jia Li,a Jiangen Huang,a Tian Qin,a Yun-Meng Liu,a Fan Zhong,a Wen Zhanga Jiangxi Province Key Laboratory of Coordination Chemistry, Institute of Applied Chemistry, School of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an, Jiangxi 343009 (P.R. China). E-mail: [email protected] Zhi-Ru Li* State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry Jilin University, Changchun, 130023, China, E-mail: [email protected]

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Abstract: Alkalides with large nonlinear optical (NLO) responses exhibit broad applications in electro-optical devices field. In present work, based on alkali (Li and Na) in conjunction with alkaline-earth (Ca) atoms doped into facially polarized all-cis1,2,3,4,5,6-Hexafluorocyclohexan (C6F6H6), we firstly reported two facially polarized Janus-type alkalides as an external electric field (EEF) induced second order nonlinear optical switches M-LCaL-M (M = Li or Na, L = C6F6H6). The two 4s electrons of Ca atom are, respectively, pushed out by the negative fluorocarbon face of one L and each of them concentrate on one alkali atom and combine with the s electron of the later to form excess electron pair. Owing to the two excess electron pairs (HOMO and HOMO-1), the novel alkalides M--LCa2+L-M- is formed. Interestingly, with continuous increasing of EEF magnitude, the centrosymmetric M--LCa2+L-M- bearing two excess electron pairs is obviously broken and a long-range charge transfer is exhibited gradually from one end alkali atom through the middle LCaL to the other end one. Meanwhile, the EEF driving brings a large static electronic first hyperpolarizability from 0 (EEF = 0, Off form) to 59826 (M = Li, EEF = 19 × 10-4 au, On form) or 64231 au (M = Na, EEF = 12 × 10-4 au, On form). They also own largest vibrational first hyperpolarizabilities (On form). These results show alkalide M--LCa2+L-M- have potential application for NLO materials as well as exhibit high sensitive, fast and reversible switching advantage.

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Introduction Since Coe et al.1 discovered the first redox-stimulated nonlinear optical (NLO) molecular switch in 1999, the investigation on the switching NLO materials has been a fast-growing activity research field and attracted considerable researcher’s interests because they hold wide potential technological applications in photonic and electro-optical devices.2-4 NLO molecular switches are often made up of special molecules, polymers, nanosystems, supramolecules, functional surfaces, etc. They can be stimulated by the outside world to convert between two or more chemical forms (including structures) to show significant differences in nonlinear optical properties. To our knowledge, the types of stimulus used to trigger the commutation of NLO molecular switches studied mainly include light irradiation (photoisomerization),5-13 redox reaction,1,14-18 pH variation,19,20 temperature,21 ion recognition,2,4,22-24 and induction of external electric field.25-29 Interestingly, Li et al. have exhibited that a high external electric field (EEF) can make a centrosymmetric benzene molecule without NLO response generates a large first hyperpolarizability (β0) due to a centrosymmetry breaking of the electron cloud.26

The electride NLO switch induced by EEF can exhitbit large β0 values of 3.15 × 106 au for

e@K(1)@calyx[4]pyrrole@K(2)@e,27 2.2 × 106 au for e-+Ca2+(Ni@Pb12)2- Ca2++e-,28 and 5.0 × 106 au for Be6Li14. 29 Based on the fact that introducing excess electron(s) into a molecule can dramatically increase its static first hyperpolarizability (β0),30,31 in recently years, a new research field about excess electron chemistry, has been built30-36 and an amount of NLO molecules with excess electron are continuously reported.30,31,34,38-47 Alkalide32-34 with anion sites occupied by alkali anion and electride35-38 bearing excess electron anion are typical representations of excess electron molecules. In particularly, alkalides have attracted more and more attentions.34,40-47 For instance, the calculated β0 values cup-like alkalide molecules Li+(calix[4]pyrrole)K- and K+(en)3K- are 2.4 ×104,34 and 1.8 ×105 au,44 respectively. Furthermore, alkaline-earth based alkalides had been confirmed by Dye’s group from experimental viewpoint and the first alkaline-earth based alkalide Ba2+(H5Azacryptand[2.2.2]-)Na-·2MeNH2 were synthesized.33 At the same time, previous theoretical prediction studies have pointed out alkaline-earth atoms dope into a suited ligand can also form alkaline-earth based alkalide with considerable NLO response.40-43 Our results show that the alkaline-earth based alkalide Be(NH3)nBe exhibits large β0 value of 1.26 ×105 au.41 Rcently, O’Hagan and co-workers reported48-49 that all-cis 1,2,3,4,5,6-Hexafluorocyclohexane (C6F6H6) is a stable and facially polarized Janus-type molecule bearing a positive hydrocarbon and negative fluorocarbon faces. Ziegler et al., confirmed that positive and negative face of C6F6H6 present remarkable bind trend with cation Na+ and anion Cl- from experiment and theoretical stimulation.50 Wu et al46 have also proven that a series of alkalide-based alkalides M+·1·M’(M, M’ = Li, Na and K, 1 = C6F6H6) exhibit considerable NLO response. Obviously, design of novel NLO switch with loosely bound excess electron is necessary in order to accelerate the 3



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applications of excess electron compounds in NLO field. It is worth to noticing that all of the EEF induced second order NLO switches with excess electron reported by Li et al.26-39 are electride molecules, and the EEF induced alkalide as second order NLO switch has not been reported yet. Motivated by above, in current work, we theoretically constructed two new organic alkalide M--LCa2+L-M- (M = Li or Na, L = C6F6H6) as NLO switch molecules by doped alkali (Li and Na) in conjunction with alkaline-earth (Ca) atoms into C6F6H6 (see Figure 1) and investigated their NLO properties under different EEFs as well as exhibited long-range excess charge transfer. Our computational results demonstrate that the static first hyperpolarizabilities of two new alkalide molecules are dramatically enhanced under inducing of EEFs and may be regard as potential second order NLO switches. We hope this work can provide a theoretical reference for development molecular switch devices.

Computational Details In this work, all quantum chemistry calculations, including geometrical optimization, frequency calculation, single point, natural population analysis (NPA),51 interaction energy (Eint), and β0 were done by using Gaussian16 (Version A.03) program.52 Electron localization function (ELF) diagrams were obtained by free and open source Multiwfn program (Version 3.4).53 Popular and novel hybrid meta exchange-correction function M06-2X54 in combination with 6311++G(2d,2p) basis set were utilized for above tasks. Geometrical structures of these studied systems under different EEFs were fully optimized and the frequency calculations confirmed these geometrical structures lies on their minima of potential energy surfaces of ground states since frequency calculations display no imaginary. M06-2X not only exhibits good performance for calculating electronic structures, but also broadly used to calculate electric properties,55-56 i.e. dipole moment, polarizability, hyper-polarizabilities. In order to certify the reliability of M062X for calculating electronic contribution of the hyperpolarizabilities (β0), Gu’s results47 displays that the difference of β0 values between MP2 and M06-2X is within 1.8% for C6F6H6 (L), and therefore, M06-2X/6-311++G(2d,2p) was chosen to calculate the β0 values of alkalide L-M-L-M’ and superalkalide L-M-L-M’3O (M = Li and K, M’ = Li and Na). Because MP2 calculation of β0 is expensive for large system, we also choose M06-2X to calculate static and dynamic first hyperpolarizability. On the other hand, Oscillator strength, transition energy, the difference of dipole moment between ground state and crucial transition state were obtained at TD-M06-2X/6-311++G(2d,2p) level. The definition of interaction energy (Eint) obeys the following equation by using counterpoise procedure in order to basis set superposition error (BSSE):57 Eint = Etot -2E(M - C6F6H6) - E(Ca)

(1)

where Etot, E(M-C6F6H6), and E(Ca) denote total energies corresponding to M-LCaL-M, M-C6F6H6 as well as Ca. 4


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What’s more, M-C6F6H6 and Ca kept the same geometries with M-LCaL-M (M = Li or Na, L = C6F6H6). The vertical ionization potentials (VIPs) of these molecules under EEFs were obtained at the same level. The VIP is defined as follows: VIP(I) = E[M - LCaL - M] + - E[M - LCaL - M] VIP(II) = E[M - LCaL - M]𝟐 + - E[M - LCaL - M] +

(2) (3)

where the energies E[M-LCaL-M], E[M-LCaL-M]+ and E[M-LCaL-M]2+ were calculated at the optimum geometry of the neutral molecule. We used unrestricted orbitals for the [M-LCaL-M]+ and restricted orbitals for the M-LCaL-M and [M-LCaL-M]+. The static electronic first hyperpolarizability (β0) is noted as follows: βe0 = (β2x + β2y + β2z)

1/2

(4)

where βi = (βiii + βijj + βikk), i,j,k = x,y,z

(5)

The vibrational contribution to first hyperpolarizability was evaluated by using Bishop-Hasan-Kirtman (BHK) approach and this method is a numerical approach, more detail information for BHK method, readers are recommended to read previous lecture.58 The vibrational contribution static first hyperpolarizability βzzznr is written follow equations: βzzz,tot(0,0,0) = 𝛽𝑧𝑧𝑧𝑒(0,0,0) + βnr zzz(0,0,0) βzzz,tot =

[∆μ1,z(RF,Fz,1)] + 2∆μz(RFw,Fwz) + [∆μ2,z(RF,Fz,2)] ∆F2

∆μz(RF,Fz) = μz(RF,Fz) - μz(RFw,Fwz)

(6) (7) (8)

where βzzz,tot(0,0,0), βzzz(0,0,0) and βzzznr(0,0,0) represent total static first hyperpolarizability, electronic and vibrational contribution to the static first hyperpolarizability tensor, respectively; Δμz(RF,Fz) is the difference of dipole moment between dipole moment of test external electric field μz(RF,Fz) and that of work external electric field μz(RFw,Fw); RF denotes equilibrium molecular geometry under an external electric field.

Results and Discussion A. Geometrical Characteristics In present work, the range of imposed EEF along with dipole moment direction (z-axis) for M-LCaL-M (M = Li or Na, L = C6F6H6) is 0 ~ 20×10-4 au (1 au =51.422V/Å). That’s due to a larger EEF (≥21×10-4 au ) will destroy their geometrical structure. Thus, EEF =20 ×10-4 au is critical value (EEFc). To measure the effect of EEF on geometrical structure, we have collected some important geometrical parameters (L, R1, R2, R3 and R4) of M-LCaL-M and they are listed at Table

5



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S1-S2. The point groups of optimized geometrical structures without and with EEFs (See Table S1-S2) for M-LCaL-M are, respectively, C2h and C3v at M06-2X/6-311++G(2d,2p) level. In order to well visualize the variable relationship of geometrical parameters with the increasing of the EEF, the dependences of geometrical parameters on different EEFs are plotted in Figure 2. Interesting, it can be found that both of two alkali atoms (Li or Na) slightly move toward the direction of the positive pole of the EEF under the effect of the EFF due to the negative charge of them. Still, the molecular size almost does not change. For Li-LCaL-Li, the bond length Li1H1 (R1 with variable range of 0 ~ 0.15 Å) and F1-Ca (R2 with variable range of 0 ~ 0.04 Å) increases with the increasing of EEF. On the contrary, the bond length Li2-H2 (R4 with variable range of 0 ~ 0.12 Å) and F2-Ca (R3 with variable range of 0 ~ 0.03 Å) decreases with increasing EEF. Interesting, the rising amplitude of R1 and descending one of R4 are almost equal. Also, the similar situation happens to the variable magnitudes of R2 and R3. As a results, the distance L (variable range of 0 ~ 0.06Å) between two end Li atoms (Li1 and Li2) almost don’t change. The geometrical parameters of NaLCaL-Na possess the same variation trends in respect to that of Li-LCaL-Li. To be specific, both the effects of an EEF on geometrical structures of Li-LCaL-Li and Na-LCaL-Na are small. The variations of these geometrical parameters indicate that geometrical structures of M-LCaL-M (M = Li or Na) exhibit integrity and reversible switching advantage, which is beneficial to developing molecular NLO switch.

B. Molecular stabilities For these facially polarized Janus-type alkalide molecules, the electronic stability is important in view of the existences of loosely bound excess electron pairs. From Table 1, the small relative energies indicate that the energy differences among the structures with and without EEFs are small. That is to say, the existence of the external electric field has little effect on the stability of the molecule. The electronic stability of a molecule may be characterized by its vertical ionization potential (VIP) values. From Table 1, the field-free VIP(I) and VIP(II) values of Li-LCaL-Li (4.18 and 7.52 eV) are slightly larger than that of Na-LCaL-Na (3.98 and 7.49 eV), respectively. Still, the VIP(I) values are very close to that of the reported alkalide Mg(NH3)6Na2 (3.96 eV).43 The VIP(II) values are smaller than the large value (7.78 eV) of the electride molecule with the excess electron protected inside the C36F36 cage.39 Therefore, these alkalides M-LCaL-M (M = Li or Na, L = C6F6H6) exhibit moderate electronic stability among investigated alkalide and electride molecules. Both VIP(I) and VIP(II) values of these alkalides M-LCaL-M (M = Li or Na, L = C6F6H6) only slightly vary with the increasing of EEF, which also suggests that the effect of external electric field on electronic stability is small. we also calculate the interaction energy (Eint) between Ca and M-C6F6H6 (M=Li and Na) under different EEF 6


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magnitudes, these Eint values are also given in Table 1. Eint values clearly suggest that it has large interaction between Ca and M-C6F6H6 (M = Li and Na). In addition, Eint value increases with increasing the magnitude of EEF. Electron localization function59 (ELF) is a useful tool to study on electronic structural character because ELF can intuitively exhibit localization degree of electron for different position of real three-dimension space. From ELF diagrams (See Figure 3), it can be seen that part electron focuses on the position between alkali atoms and C6F6H6, which indicates that large interaction presents between alkali atoms and C6F6H6. Because the energy difference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), i.e., HOMO-LUMO gap (EHL) is another useful quantity for examining the molecular chemical stability. The larger HOMO-LUMO gap, the higher chemical stability. Table 1 shows the EHL value is in the ranges of 2.24 ~ 2.47 eV and 2.10 ~ 2.32 eV for Li-LCaL-Li and Na-LCaL-Na under different EEF magnitudes, respectively. These EHL values are smaller than that of the reported alkalide Mg(NH3)6Na2 (2.98 eV),43 but obviously larger than that of the reported electrides

e−···K(1)+···calix[4]pyrrole···K(2)+···e−

(1.315

~

1.719

eV

eV)27

and

all-metal

electride,

e−+M2+(Ni@Pb12)2−M2++e− (1.40 ~ 1.45 eV eV)28 under different EEF magnitudes. The latter two are EEF manipulated second-order NLO switch of electride molecules. Therefore, it is more stable for our EEF manipulated second-order NLO switch of alkalide M-LCaL-M (M = Li or Na, L = C6F6H6) than the reported two electride switches.

C. Location of excess electron pairs and charge transfer To investigate excess electron distribution of M-LCaL-M (M = Li or Na, L = C6F6H6) under different EEFs, the natural population analysis (NPA)51 charges on alkali and Ca atoms are given in Table 2. From Table 2 knows, the NBO charges of Ca atom are 1.431 and 1.421 for Li-LCaL-Li and Na-LCaL-Na with fieldfree, respectively. Under the effect of EEFs, its charges still cover the ranges of 1.420 ~ 1.431 and 1.407 ~ 1.431, respectively. These results shows that the Ca atom loses the two 4s electrons and the valence of it is +2 in both Li-LCaLLi and Na-LCaL-Na without and with EEFs. So, where are the two 2s electrons? It is worth to noticing that the NBO charges of alkali atoms are negative. The NBO charges of alkali atoms are -0.140 and -0.216 for Li-LCaL-Li and Na-LCaL-Na with field-free, respectively. From the Figure 4 knows, both the electron clouds of HOMO and HOMO-1 for Li-LCaL-Li mainly concentrate on two opposite end alkali atoms to form two hemispherical orbital lobes and the lobes are centrosymmetry. The similar situation occurs in Na-LCaL-Na. Also, from Table 1, the small energy difference between HOMO and HOMO-1 for both Li-LCaL-Li and Na-LCaL-Na indicates that they may be degenerate orbitals. Then, the two 4s electrons of Ca atom should be polarized and pushed out by the negative fluorocarbon face of L to concentrates on the alkali atom. 7



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To confirm this, the models of Li-L···L-Li and LCaL are constructed. We take the two models from equilibrium geometry of Li-LCaL-Li by removing the rest Ca or Li atoms simply. Triplet structure of Li-L···L-Li were used because it is -25.12 kcal/mol of energy lower for triplet Li-L···L-Li than for singlet one. From Figure 4a, both the electron clouds of the single occupied molecular orbitals (SOMOs) of model Li-L···L-Li also mainly concentrate on two opposite end Li atoms to form two hemispherical orbital lobes. SOMO1 and SOMO2 are degenerate. These situations are similar to that of HOMO and HOMO-1 of Li-LCaL-Li. However, the electron clouds of the HOMO of LCaL mainly concentrate on Ca atom itself, which is just similar to that of the lowest unoccupied molecular orbital (LUMO) Li-LCaL-Li. Then, SOMOs of model Li-L···L-Li contribute to the HOMO and HOMO-1 of Li-LCaL-Li, while HOMO of model LCaL contribute to lowest unoccupied MO (LUMO) of Li-LCaL-Li. The NBO charges of both Li atoms in Li-L···L-Li are 0.068, while that of Ca atom in model LCaL is 0.540 due to the electron-withdrawing effect of negative fluorocarbon face of L. Therefore, it can be confirmed that, for both Li-LCaL-Li and Na-LCaL-Na, the two 4s electrons of Ca atom are, respectively, pushed out by the negative fluorocarbon face of one L and each of them concentrates on one alkali atom (M) and combines with the s electron of the later to form excess electron pairs (see Figure

4b). The M-LCaL-M (M = Li or Na, L = C6F6H6) has

salt-like electronic structure M--LCa2+L-M-. As a result, the novel alkalides M--LCa2+L-M- (M = Li or Na, L = C6F6H6) is formed. Interestingly, with continuous increasing of the EEF magnitude, the centrosymmetric M--LCa2+L-M- bearing two excess electron pairs is obviously broken and half of excess electron clouds (one hemispherical orbital lobe) is gradually transferred from one end alkali atom through the middle LCaL to the other end alkali atom. From Figure 5, within an EEF, the lower lobe is partly transferred to the upper one for HOMO and the upper lobe is partly transferred to the lower one for HOMO-1. As the EEF further strengthens, the lower lobe tends to totally merge into the upper one for HOMO and upper lobe tends to totally merge into the lower one for HOMO-1. Subsequently, when the EEF magnitude increases, the orbital energy HOMO monotonically increases while that of HOMO-1 monotonically decreases (see Table 1). HOMO and HOMO-1 are not degenerate due to the existence of the EEF. In particularly, when EEF = 12 × 10-4 au for Na-LCaL-Na, the transfer processes are completed. For the opposite transfer processes between HOMO and HOMO-1, as a result, the NBO charge of the alkali atoms (see Table 2) demonstrate that a long-range charge transfer is exhibited gradually from upper alkali atom (Li2 or Na2) through the middle LCaL to the lower alkali atom (Li1 or Na1, see Figure

2). With continuous increasing of the EEF magnitude,

the negative NBO charge of Li1 in Li-LCaL-Li or Na1 in Na-LCaL-Na monotonically decreases to a large negative value while that of Li2 or Na monotonically increases to a positive one (see Table 1). Finally, the alkalide M--LCa2+L-M- bearing two excess electron pairs is changed into alkalide M(1-)--LCa2+L-M(1+)-. 8


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The most important thing is that obvious charge transfer is occurred under EEF driven, which may bring considerable NLO response.

D. Second order NLO properties The centrosymmetric structure with loosely bound excess electron can be broken easily with a small EEF which drives long-range charge transfer and then may bring large NLO response. Consequently, a second order NLO switch of a novel alkalide molecule driven by an external electric field is expected.26-28 The selected static electronic first hyperpolarizabilities (β0e) of M-LCaL-M (M = Li or Na, L = C6F6H6) under different EEFs using M06-2X/6-311++G(2d,2p) level are shown in Table 3. The variable relationship of β0e values for M-LCaL-M with respect to EEF magnitude is shown in Figure 6. All the β0e values of M-LCaL-M (M = Li or Na, L = C6F6H6) from EEF = 0 to 20 × 10-4 au were listed in Table S3. From Table 3, the β0e values of alkalides of both Li-LCaL-Li and Na-LCaL-Na with EEF = 0 are zero due to the centrosymmetric electronic strucutres of them, which suggests it is the off form for Li-LCaL-Li and Na-LCaL-Na with EEF = 0. When an EEF is applied, the centrosymmetric electronic structure is broken and a high β0e value may be existent. For Li-LCaL-Li, from Figure 6a, it is found that the β0e value monotonically increases from 0 to 59826 au with continuous increasing of the EEF magnitude in the range of 0 ~ 19 × 10-4 au. From EEF = 19 × 10-4 to 20 × 10-4 au (EEFc), β0e value decreases. So, the maximum β0e value of 59826 au with EEF of 19 × 10-4 au corresponds to on form. In Figure 5a, it is also exhibited that the field dependent transfer processes of both HOMO and HOMO-1 (in shape and lobe size) of Li-LCaL-Li shows a clear correlation with the β0e value under stimulation of EEF in the range of 0 ~ 19 × 10-4 au. Both HOMO and HOMO-1 have a very small lobe and a large lobe as EEF = 19 × 10-4 au. For Na-LCaL-Na, from Figure 6b, the maximum β0e value of 64231 au corresponds to EEF = 12 × 10-4 au. In Figure 5b, the small lobe vanishes at EEF = 12 × 10-4 au for both HOMO and HOMO-1. Thun, the maximum β0e value of 64231 au with EEF of 12 × 10-4 au corresponds to on form. These results suggest that second order NLO switches of alkalides M-LCaL-M have advantages with high sensitive and fast switching under EEF stimulation. In this work, the field-induced NLO responses for the M-LCaL-M (M = Li or Na, L = C6F6H6) cannot be explained with the aid of a simple two-level model60 involving electron transition properties (see Table 3). This may because there exist two excited states with excess electron transitions involve both excess electron pairs. Excess electron transition of HOMO  LUMO (one excess electron pair) contributes to the first excited state with large percentage of transition coefficient, while that of HOMO-1  LUMO (another

excess electron pair) contributes to second excited state with large 9



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percentage of transition coefficient. Nevertheless, some correlations between Li-LCaL-Li and Na-LCaL-Na are exhibited. For the first excited state under an EEF, the transition energy (E) of the former is larger than the corresponding one of the later. The similar situation occurs for the second excited state. These may be the reason why the β0e value of Li-LCaL-Li under an EEF is larger than the corresponding one of the later. Also, the second excited state (HOMO-1  LUMO) with large percentage of transition coefficient may mainly contribute to the large β0e values of M-LCaL-M (M = Li or Na, L = C6F6H6) under an EEF due to the absence of it with field-free for each of M-LCaL-M. Luis and co-workers have analyzed vibrational NLO properties of a series excess electron compounds, which shows that the impact of vibrational hyperpolarizability is also quite significant and even it may be larger than electronic hyperpolarizability.61-62 Thus, in order to study on the behavior of vibrational hyperpolarizability, we also further calculated the vibrational first hyperpolarizability tensor βzzznr of M-LCaL-M (M = Li or Na, L = C6F6H6) with EEF = 12 × 10-4 au, by using Bishop-Hasan-Kirtman approach.58 These values were listed in Table 4. It is crucial to use a desirable step size when using numerical method, because unconscionable step size will bring large numerical error. Our test results found that step size 0.0005 is reasonable for M-LCaL-M. From Table 4, the ration η(βzzznr/βzzz) between βzzznr and electronic first hyperpolarizability βzzze is 3.39 and 2.03 for M= Li and M = Na, respectively, which demonstrates that vibrational contribution plays a key role for NLO properties of alkalides M-LCaL-M (M = Li or Na, L = C6F6H6). To make our theoretical calculation work become meaningful compared with experimental measures, we further calculated frequency dependent values second harmonic generation β(-2ω,ω,ω) and electro-optical Pockels effect β(-ω,ω,0) by Couple-Perturbtion-Hartree-Fock method. Selected β(-2ω,ω,ω) and β(-ω,ω,0) values of M-LCaL-M (M = Li or Na, L = C6F6H6) were listed in Table S4&5. As shown in Figure 7, these frequency dependence values of M-LCaL-M (M = Li or Na, L = C6F6H6) under different external electric field have same variable relationship with β0e. Still, the maximum β(2ω,ω,ω) and β(-ω,ω,0) values with EEF of 19 × 10-4 au

corresponds to On form for M = Li and that with EEF of 12 ×

10-4 au corresponds to On form for M = Na. All the β(-2ω,ω,ω) and β(-ω,ω,0) values increase with increasing external field frequency ω.

Conclusion In present work, we selected alkali atoms (Li and Na) in combine with alkaline-earth atom (Ca) doped into facility polarized molecule all-cis1,2,3,4,5,6-Hexafluorocyclohexan(C6F6H6) for constructing second order alkalide NLO switch, which is triggered by imposed an EEF (range from 0 to 20×10-4 a.u.) along with dipole moment direction (z-axis). We found that the two 4s electrons of Ca atom are, respectively, pushed out by the negative fluorocarbon face of one L and each of them concentrate on one alkali atom (M) and combine with the s electron of the later to form excess electron pair. As a result, the novel alkalides M--LCa2+L-M- is formed. 10


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The EEF effect on geometrical structure is small. The centrosymmetric structure with two loosely bound excess electron pairs is easily broken under EEF stimulation and EEF can drive a long-range charge transfer gradually from one end alkali atom through the middle LCaL to the other end alkali atom (M(1-)--LCa2+L-M(1+)-). The EEF driving brings a large static first hyperpolarizability from 0 (EEF = 0, Off form) to 59826 (M = Li, EEF = 19 × 10-4 au, On form) or 64231 au (M = Na, EEF = 12 × 10-4 au, On form). They also possess maximum vibrational first hyperpolarizabilities (on form). These results show alkalide M--LCa2+L-M- have potential application for NLO materials as well as exhibit high sensitive, fast and reversible switching advantage. This work expands the research field of EEF induced second order NLO switch with excess electron(s).

Conflicts of interest There are no conflicts to declare.

Acknowledgment. This work was supported by the National Natural Science Foundation of China (Nos. 21662018, 21362015). This work was also supported the financial support of the Science and Technology Project of Jiangxi Provincial Department of Education (Nos. GJJ170623, GJJ14557).

Supporting Information Available: Additional Tables showing that dipole moment, polarizability, static and dynamic first hyperpolarizability, Point group, distance L between alkali atoms, bond length R1, R2, R3, R4, natural population analysis charges on alkali atoms These materials are available free of charge via the Internet at http://pubs.acs.org.

11



Page 12 of 31

References (1) Coe, B. J.; Houbrechts, S.; Asselberghs, I.; Persoons, A. Efficient, Reversible Redox‐Switching of Molecular First Hyperpolarizabilities in Ruthenium(II) Complexes Possessing Large Quadratic Optical Nonlinearities. Angew. Chem. Int. Ed. 1999, 38, 366-369. (2) Champagne, B.; Plaquet, A.; Pozzo, J. L.; Rodriguez,V.; Castet, F. Nonlinear Optical Molecular Switches as Selective Cation Sensors. J. Am. Chem. Soc. 2012, 134, 8101-8103. (3) Ray, P. C. Size and Shape Dependent Second Order Nonlinear Optical Properties of Nanomaterials and Their Application in Biological and Chemical Sensing. Chem. Rev. 2010, 110, 5332-5365. (4) Castet, F.; Rodriguez, V.; Pozzo, J. L.; Ducasse, L.; Plaquet, A.; Champagne, B. Design and Characterization of Molecular Nonlinear Optical Switches. Acc. Chem. Res. 2013, 46, 2656-2665. (5) Bondu, F.; Quertinmont, J.; Rodriguez, V.; Pozzo, J.-L.; Plaquet, A.; Champagne, B.; F. Castet, Second ‐ Order Nonlinear Optical Properties of a Dithienylethene–Indolinooxazolidine Hybrid: A Joint Experimental and Theoretical Investigation. Chem. Eur. J. 2015, 21, 18749-18757. (6) Chen, K. J.; Laurent, A. D.; D. Jacquemin, Strategies for Designing Diarylethenes as Efficient Nonlinear Optical Switches. J. Phys. Chem. C. 2014, 118, 4334-4345. (7) Song, P.; Gao, A. H.; Zhou, P. W.; Chu, T. S. Theoretical Study on Photoisomerization Effect with a Reversible Nonlinear Optical Switch for Dithiazolylarylene. J. Phys. Chem. A. 2012, 116, 5392-5397. (8) Zhang, M.-Y.; Wang, C.-H.; Wang, W.-Y.; Ma, N.-N.; Sun, S.-L.; Qiu, Y.-Q. Strategy for Enhancing Second-Order Nonlinear Optical Properties of the Pt(II) Dithienylethene Complexes: Substituent Effect, π-Conjugated Influence, and Photoisomerization Switch. J. Phys. Chem. A. 2013, 117, 12497-12510. (9) Boixel, J.; Guerchais, V.; Le Bozec, H.; Jacquemin, D.; Amar, A.; Boucekkine, A.; Colombo, A.; Dragonetti, C.; Marinotto, D.; Roberto, D.; Righetto, S.; De Angelis, R. Second-Order NLO Switches from Molecules to Polymer Films Based on Photochromic Cyclometalated Platinum (II) Complexes J. Am. Chem. Soc. 2014, 136, 5367-5375. (10) Lin, J.; Zhang, M.-X. A Study On the New Designing Scheme Of Dithienylethene Containing Nonlinear Optical Switching Molecules. J. Atomic. Mol. Phys. 2016, 33, 194-200. (11) Zhang, L.-H.; Wang, Y.; Ma, F.; Liu, C.-G. Theoretical Studies on Photo-Triggered Second-Order Nonlinear Optical Switches in a Series of Polyoxometalate-Spiropyran Compounds. J. Organometallic Chem. 2012, 716, 245-251. (12) Yu, H.-L.; Hong, B.; Zhao, H.-Y. Nonlinear Optical Properties of Rhenium(I) Complexes: Influence of the Extended π-Conjugated Connectors and Proton Abstraction. J. Mol. Graph. Model. 2015, 61, 196-203. (13) Schulze, M.; Utecht, M.; Hebert, A.; Rück-Braun, K.; Saalfrank, P.; Tegeder, P. Reversible Photoswitching of the 12


Page 13 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Interfacial Nonlinear Optical Response. J. Phys. Chem. Lett. 2015, 6, 505-509. (14) Coe, B. J.; Foxon, S. P.; Pilkington, R. A.; Sánchez, S.; Whittaker, D.; Clays, K.; Depotter, G.; Brunschwig, B. S. Nonlinear Optical Chromophores with Two Ferrocenyl, Octamethylferrocenyl, or 4-(Diphenylamino)phenyl Groups Attached to Rhenium(I) or Zinc(II) Centers. Organometallics. 2015, 34, 1701-1715. (15) Liu C.-G.; Guan, X.-H. Redox and Photoisomerization Switching of the Second-Order Optical Nonlinearity of a Tetrathiafulvalene Derivative of Spiropyran Across Five States: a DFT Study. Phys. Chem. Chem. Phys. 2012, 14, 5297-5306. (16) Wang, J.-P.; Yang, G-C.; Yan, L.-K.; Guan, W.; Wen, S.-Z.; Su, Z.-M. TDDFT Studies On Chiral Organophosphonate Substituted Divacant Keggin-Type Polyoxotungstate: Diplex Multistep-Redox-Triggered Chiroptical and NLO Switch. Dalton. Trans. 2012, 41, 10097-10104. (17) Green, K. A.; Cifuentes,; Samoc, M.; Humphrey, M. G. Metal Alkynyl Complexes as Switchable NLO Systems. Coord. Chem. Rev. 2011, 255, 2530-2541. (18) Samoc, M.; Gauthier, N.; Cifuentes, M. P.; Paul, F.; Lapinte ,C.; Humphrey, M. G. Electrochemical Switching of the Cubic Nonlinear Optical Properties of an Aryldiethynyl-Linked Heterobimetallic Complex between Three Distinct States. Angew. Chem., Int. Ed. 2006, 45, 7376-7379. (19) Plaquet, A.; Champagne, B.; Kulhanek, J.; Bures,F.; Bogdan, E.; Castet, F.; Ducasse, L.; Rodriguez, V. Effects of the Nature and Length of the π-Conjugated Bridge on the Second-Order Nonlinear Optical Responses of Push-Pull Molecules Including 4,5-Dicyanoimidazole and Their Protonated Forms. ChemPhysChem. 2011, 12, 3245-3252. (20) Asselberghs, I.; Zhao, Y.; Clays, K.; Persoons, A.; Comito, A.; Rubin, Y. Reversible Switching of Molecular SecondOrder Nonlinear Optical Polarizability through Proton-Transfer. Chem. Phys. Lett. 2002, 364, 279-283. (21) Lia, W.-Q.; Ye, H.-Y.;. Fu, D.-W; Li, P.-F.; Chen, L.-Z.; Zhang, Y. Temperature-Triggered Reversible Dielectric and Nonlinear Optical Switch Based on the One-Dimensional Organic-Inorganic Hybrid Phase Transition Compound [C6H11NH3]2CdCl4. Inorg. Chem. 2014, 53, 11146-11151. (22) Ye, J.-T.; Wang, L.; Wang, H.-Q.; Chen, Z.-Z.; Qiu , Y.-Q.; Xie, H.-M. Spirooxazine Molecular Switches With Nonlinear Optical Responses As Selective Cation Sensors. RSC. Adv. 2017, 7, 642-650. (23) Samoc, M.; Gauthier, N.; Cifuentes, M. P.; Paul, F.; Lapinte, C.; umphrey, M. G. Electrochemical Switching of the Cubic Nonlinear Optical Properties of an Aryldiethynyl-Linked Heterobimetallic Complex between Three Distinct States. Angew. Chem., Int. Ed. 2006, 45, 7376-7379. (24) Li, P. X.; Wang, M. S.; Zhang, M. J.; Lin, C. S.; Cai, L. Z.; Guo, S. P.; Guo, G. C. Electron-Transfer Photochromism To Switch Bulk Second‐Order Nonlinear Optical Properties with High Contrast. Angew. Chem., Int. Ed. 2014, 53, 13



Page 14 of 31

11529-11531. (25) Lamere, J. F.; Lacroix, P. G.; Farfan, N.; Rivera, J. M.; Santillan, R.; Nakatani, K. Synthesis, Characterization and Nonlinear Optical (NLO) Properties of a Push-Pull Bisboronate Chromophore With a Potential Electric Field Induced NLO switch. J. Mater. Chem. 2006, 16, 2913-2920. (26) Bai, Y.; Zhou, Z. J.; Wang, J. J.; Li, Y.; Wu, D.; Chen, W.; Li, Z.-R.; Sun, C. C. 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. J. Mol. Model. 2013, 19, 3983-3991. (27) Wang, J.-J.; Zhou, Z.-J.; He, H.-M.; Wu, D.; Li, Y.; Li, Z.-R.; Zhang, H.-X. An External Electric Field Manipulated Second-Order Nonlinear Optical Switch of an Electride Molecule: A Long-Range Electron Transfer Forms a Lone Excess Electron Pair and Quenches Singlet Diradical. J. Phys. Chem. C. 2016, 120, 13656-13666. (28) He, H.-M.; Li, Y.; Yang, H.; Yu, D.; Li, S.-Y.; Wu, D.; Hou, J.-H.; Zhong, R.-L.; Zhou, Z.-J.; Gu, F.-L.; Luis, J. M.; Li, Z.-R. Efficient External Electric Field Manipulated Nonlinear Optical Switches of All-Metal Electride Molecules with Infrared Transparency: Nonbonding Electron Transfer Forms an Excess Electron Lone Pair. J. Phys. Chem. C. 2017, 121, 958-968. (29) Hou, J.; Liu, Y.; Zhang, X.; Duan, Q.; Jiang, D.; Qin, J.; Zhao, R. Electric-Field-Induced Nonlinear Optical Switches of All-Metal Spherical Aromatic Molecules With Infrared Transparency: A Theoretical Study. New. J. Chem. 2018, 42, 1031-1036. (30) Zhong, R. L.; Xu, H. L.; Li, Z. R.; Su, Z. M. Role of Excess Electrons in Nonlinear Optical Response. J. Phys. Chem. Lett. 2015, 6, 612-619. (31) Yu, G.; Huang, X.; Li, S.; Chen, W. Theoretical Insights and Design Of Intriguing Nonlinear Optical Species Involving the Excess Electron. Int. J. Quantum Chem. 2015, 115, 671-679. (32) Kim, J.; Ichimura, A. S.; Huang, R. H.; Redko, M.; Phillips, R. C.; Jackson, J. E.; Dye, Crystalline Salts of Na- and K(Alkalides) that Are Stable at Room Temperature. J. L. J. Am. Chem. Soc. 1999, 121, 10666-10667. (33) Rekko, M. Y.; Vlassa, M.; Jackson, J. E.; Harrison, A. W.; Dye, J. L. Barium Azacryptand Sodide, the First Alkalide with an Alkaline Earth Cation, Also Contains a Novel Dimer, (Na2)2-. J. Am. Chem. Soc. 2003, 125, 2259-2263. (34) Chen, W.; Li, Z. R.; Wu, D.; Li, Y.; Sun, C. C.; Gu, F. L.; Aoki, Y. Nonlinear Optical Properties of Alkalides Li+(calix[4]pyrrole)M- (M = Li, Na, and K): Alkali Anion Atomic Number Dependence. J. Am. Chem. Soc. 2006, 128, 1072-1073. (35) Dye, J. L. Electrons as Anions. Science 2003, 301, 607-608. 14


Page 15 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(36) Matsuishi, S.; Toda, Y.; Miyakawa, M.; Hayashi, K.; Kamiya, T.; Hirano, M.; Tanaka, I.; Hosono, H. High-Density Electron Anions in a Nanoporous Single Crystal: [Ca24Al28O64]4+(4e-). Science 2003, 301,626-629. (37) Ye, T. N.; Lu, Y. F.; Li, J.; Nakao, T.; Yang, H. S.; Tada, T.; Kitano, M.; Hosono, H. Copper-Based Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions. J. Am. Chem. Soc. 2017, 139, 17089-17097. (38) Xu, H. L.; Li, Z.-R.; Wu, D.; Wang, B. Q.; Li, Y.; Gu, F. L.; Aoki, Y. Structures and Large NLO Responses of New Electrides: Li-Doped Fluorocarbon Chain. J. Am. Chem. Soc. 2007, 129, 2967-2970. (39) Wang, J. J.; Zhou, Z.-J.; Bai, Y.; He, H.-M.; Wu, D.; Li, Y.; Li, Z.- R.; Zhang, H.-X. A new Strategy for Simultaneously Enhancing Nonlinear Optical Response and Electron Stability in Novel Cup-Saucer+-Cage--Shaped Sandwich Electride Molecules with an Excess Electron Protected Inside the Cage. Dalton. Trans. 2015, 44, 4207-4214. (40) Wang, Y.-F.; Huang, J.; Zhou, G. Coordination Number Effect of Nitrogen Atom on the Structures and NLO Responses: Alkaline Earth-Based Alkalides. Struct. Chem. 2013, 24,1545-1553. (41) Wang, Y.-F.; Li, B.; Huang, J.; Li, J.; Li, Z.-R. Effect of Alkaline Earth Metal Atom on the Large Static First Hyperpolarizabilities of Alkaline Earth-Based Alkalides Be(NH3)nM (M = Be and Ca) in Comparison with Alkalides Li(NH3)nNa (n = 1-3) Comput. Theor. Chem. 2015, 1051, 10-16. (42) Fan, L. T.; Li, Y.; Wu, D.; Li, Z. R.; Sun, C. C. Structural Characteristics and Large Non-Linear Optical Responses of New Alkaline Earth-Based Alkalides. Aust. J. Chem. 2012, 65, 138-144. (43) Sun, W. M.; Wu, D.; Li, Y.; Liu, J. Y.; He, H. M.; Li, Z. R. A theoretical Study on Novel Alkaline Earth-Based Excess Electron Compounds: Unique Alkalides With Considerable Nonlinear Optical Responses. Phys. Chem. Chem. Phys. 2015,17, 4524-4532. (44) Mai, J.; Gong, S.; Li, N.; Luo, Q.; Li, Z. A Novel Class of Compounds-Superalkalides: M+(en)3M3’O- (M, M’ = Li, Na, and K; en = ethylenediamine)-with Excellent Nonlinear Optical Properties and High Stabilities. Phys. Chem. Chem. Phys. 2015,17, 28754-28764. (45) Hou, J.; Zhu, L.; Jiang, D.; Qin J.; Duan. Q. Alkaline-earthide: A New Class Of Excess Electron Compounds LiC6H6F6-M (M = Be, Mg and Ca) with Extremely Large Nonlinear Optical Responses. Chem. Phys. Lett. 2018, 711, 55-59. (46) Sun, W. M.; Ni, B. L.; Wu, D.; Lan, J. M.; Li, C. Y.; Li, Y.; Li, Z. R. Designing Alkalides with Considerable Nonlinear Optical

Responses

and

High

Stability

Based

on

the

Facially

Polarized

Janus

all-cis-1,2,3,4,5,6-

Hexaﬂuorocyclohexane Organometallics. 2017, 36, 3352-3359. (47) Li, B.; Peng, D.; Gu, F. l.; Zhu, C. Facially Polarized Molecule for Alkalides and Superalkalides with Considerable Nonlinear Optical Response. ChemistrySelect. 2018, 3,12782-12790. 15



Page 16 of 31

(48) Keddie, N. S.; Slawin, A. M. Z.; Lebl, T.; Philp, D.; O’Hagan, D. All-cis 1,2,3,4,5,6-hexafluorocyclohexane is a Facially Polarized Cyclohexane Nat. Chem. 2015, 7, 483-488. (49) Santschi, N.; Gilmour, R. A. A Janus Cyclohexane Ring. Nat. Chem. 2015, 7, 467-468. (50) Ziegler, B. E.; Lecours, M.; Marta, R. A.; Featherstone, J.; Fillion, E.; Hopkins, W. S.; Steinmetz, V.; Keddie, N. S.; O’Hagan D.; McMahon, T. B. Janus Face Aspect of All-cis 1,2,3,4,5,6-Hexafluorocyclohexane Dictates Remarkable Anion and Cation Interactions In the Gas Phase. J. Am. Chem. Soc. 2016, 138, 7460-7463. (51) Glendening, E.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J. E.; Bohmann, J. A.; Morales, C. M.; Weinhold, F. NBO 3.0 program. University of Wisconsin, Madison, 2001. (52) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian 09, Revision A.02; Gaussian, Inc., Wallingford CT, 2009. (53) Lu, T.; Chen, F. W. Multiwfn: A multifunctional wavefunction analyser. J. Comput. Chem. 2012, 33, 580-592. (54) Zhao, Y.; Truhlar, D. G. The M06 Suite of Density Functionals for Main Group Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States, and Transition Elements: Two New Functionals And Systematic Testing Of Four M06-Class Functionals and 12 other Functionals. Theor. Chem. Acc. 2008, 120, 215-241. (55) Zhong, R. L.; Xu, H. L.; Sun, S. L.; Qiu. Y. Q.; Su, Z. M. The Excess Electron in a Boron Nitride Nanotube: Pyramidal NBO Charge Distribution and Remarkable First Hyperpolarizability. Chem. Eur. J. 2012, 18, 11350-11355. (56) Gao, F. W.; Xu H. L.; Su, Z. M. Tuning the Inter-Molecular Charge Transfer, Second-Order Nonlinear Optical and Absorption Spectra Properties of A π-Dimer Under an External Electric Field. Phys. Chem. Chem. Phys. 2017, 19, 31958-31964. (57) Sasagane, K.; Aiga, F.; Itoh, R. Higher-order Response Theory Based on the Quasienergy Derivatives: the Derivation of the Frequency-dependent Polarizabilities and Hyperpolarizabilities. J. Chem. Phys. 1993, 99,3738-3778. (58) Bishop, D. M.; Hasan, M.; Kirtman, B. A Simple Method for Determining Approximate Static and Dynamic Vibrational Hyperpolarizabilities. J. Chem. Phys. 1995, 103, 4157-4159. (59) Lu, T.; F; Chen, W. Meaning and Functional Form of the Electron Localization Function. Acta Phys. -Chim. Sin. 2011, 27, 2786-2792. (60) Kanis, D. R.; Ratner, M. A.; Marks, T. J. Design and Construction of Molecular Assemblies with Large Second-Order Optical Nonlinearities. Quantum Chemical Aspects. Chem. Rev. 1994, 94, 195-242. (61) Torrent-Sucarrat, M.; Anglada, J. M.; Luis, J. M. Evaluation of the Nonlinear Optical Properties for Annulenes with Hückel and Möbius Topologies. J. Chem. Theory. Comput. 2011, 7, 3935-3943. (62) Garcia-Borràs, M.; Solà, M.; Luis, J. M.; Kirtman, B. Electronic and Vibrational Nonlinear Optical Properties of Five 16


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Representative Electrides. J. Chem. Theory. Comput. 2012, 8, 2688-2697.

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Table Captions

Table 1. Total energies (Etot, au), relative energies (Erel, kcal/mol), vertical ionization potentials (VIPI& II, eV), interaction energies (Eint, kcal/mol), HOMO (EH, eV), HOMO-1 (EH-1, eV), and HOMO-LUMO gap (EHL, eV) of M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric fields (EEFs, × 10-4, au). Table 2. Natural population analysis charges on Li, Na and Ca atoms for M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric fields (EEFs, × 10-4, au). Table 3. Effect of selected external electric fields (EEFs, × 10-4, au) on static electronic first hyperpolarizability (β0e, au), Oscillator strength (f0), and transition energy (E, eV) for M-LCaL-M (M = Li or Na, L = C6F6H6). Table 4. Electronic first hyperpolarizability tensor βzzz0, vibrational first hyperpolarizability tensor βzzznr, and ratio η of βzzznr/βzzz0 for M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric field (EEF, × 10-4, au).

18


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Figure Legends Figure 1. Optimized geometry structures (with and without external electric field (EEF) in direction z-axis) of M--LCa2+LM- (M = Li or Na, L = C6F6H6) at M06-2X/6-311++G(2d,2p) level. Figure 2. Evolution of distance (L, Å) between alkali atoms (M), bond length R1, R2, R3 and R4 (Å) for M-LCaL-M (M = Li or Na, L = C6F6H6) with increasing external electric field (EEF). Figure 3. Evolution of ELF for (a) Li-LCaL-Li and (b) Na-LCaL-Na (L = C6F6H6) with increasing external electric field (EEF). Figure 4. Formation of two excess electron pairs in Li-LCaL-Li, and (b) excess electron orbital energy diagram. Figure 5. Evolution of excess electron orbitals (HOMO and HOMO-1 with isovalue = 0.02) for (a) Li-LCaL-Li and (b) Na-LCaL-Na (L = C6F6H6) with increasing external electric field (EEF). Figure 6. Relationship between static electronic first hyperpolarizability β0e and external electric field (EEF). Figure 7. Selected frequency-dependent first hyperpolarizability β(-2ω,ω, ω) and β(-ω,ω,0) of M-LCaL-M (M = Li or Na, L = C6F6H6) with increasing external electric field (EEF). a) β(-ω,ω,0) and c) β(-2ω,ω, ω) for M = Li; b) β(-ω,ω,0) and d) β(-2ω,ω, ω) for M = Na.

Graphical abstract. Under an external electric field (EEF), facially polarized Janus-type alkalides M--LCa2+L-M- with two excess electron pairs concentrate on end alkali atoms (EEF = 0, Off form) exhibits long-range charge transfer from one end alkali atom through the middle LCaL to the other end one and large static electronic first hyperpolarizabilities of 59826 (M = Li, EEF = 19 × 10-4 au, On form) and 64231 au (M = Na, EEF = 12 × 10-4 au, On form).

19


The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

Page 20 of 31

Table 1. Total energies (Etot, au), relative energies (Erel, kcal/mol), vertical ionization potentials (VIPI& II, eV), interaction energies (Eint, kcal/mol), HOMO (EH, eV), HOMO-1 (EH-1, eV), and HOMO-LUMO gap (EHL, eV) of M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric fields (EEFs, × 10-4, au). EEF

Li-LCaL-Li

4

8

12

16

19

20

Etot -2355.11118707 -2355.11142797 -2355.11128690 -2355.11106214 -2355.11077070 -2355.11051476 -2355.11042208 Erel 0.00 -0.15 -0.06 0.08 0.26 0.42 0.48 VIP(I) 4.18 4.21 4.19 4.17 4.14 4.12 4.11 VIP(II) 7.52 7.50 7.52 7.54 7.57 7.60 7.61 Eint -56.53 -55.65 -56.42 -57.64 -59.30 -60.88 -61.48 EHL 2.47 2.45 2.38 2.32 2.25 2.20 2.24 EH -3.73 -3.70 -3.64 -3.58 -3.52 -3.48 -2.87 EH-1 -3.84 -3.88 -3.95 -4.03 -4.10 -4.16 -3.64 Etot

Na-LCaL-Na

0

-2664.62906034 -2664.62879782 -2664.62871407 -2664.62858327 -2664.62856767 -2664.62844790 -2664.62840466

Erel

0.00

0.16

0.22

0.30

0.31

0.38

0.41

VIP(I)

3.98

4.00

4.13

4.04

4.08

4.11

4.18

7.49 -48.77 2.32 -3.68 -3.78

7.49 -49.15 2.30 -3.65 -3.81

7.38 -49.72 2.26 -3.61 -3.86

7.49 -50.67 2.20 -3.56 -3.92

7.50 -51.95 2.15 -3.52 -3.98

7.50 -53.12 2.11 -3.49 -4.02

7.44 -53.55 2.10 -3.48 -4.04

VIP(II) Eint EHL EH EH-1

20


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Table 2. Natural population analysis charges on Li, Na and Ca atoms for M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric fields (EEFs, × 10-4, au). EEF qLi1 Li-LCaL-Li

Na-LCaL-Na

0

4

8

12

16

19

20

qCa

-0.140 -0.140 1.431

-0.206 -0.077 1.428

-0.270 -0.015 1.427

-0.341 0.044 1.425

-0.400 0.102 1.423

-0.447 0.145 1.421

-0.463 0.160 1.420

qNa1

-0.216

-0.276

-0.342

-0.400

-0.460

-0.504

-0.517

qNa2

-0.216 1.421

-0.155 1.421

-0.097 1.419

-0.042 1.416

0.011 1.412

0.049 1.408

0.062 1.407

qLi2

qCa

21



Table 3. Effect of selected external electric fields (EEFs, × 10-4, au) on static electronic first hyperpolarizability (β0e, au), Oscillator strength (f0), and transition energy (E, eV) for M-LCaL-M (M = Li or Na, L = C6F6H6). EEF

0

Li-LCaL-Li

e

β0 0 e βzzz 0 Excited State 1 f0 0.7924 1.3991 E transiti H  L (95.13%) a on Excited State 2 f0 E transiti on

Na-LCaL-Na

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

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β0e 0 e βzzz 0 Excited State 1 f0 0.7199 1.2829 E transiti H  L (95.99%) a on Excited State 2 f0 E transiti on

apercentage

4

8

12

16

19

20

15649 12743

29889 24181

43215 34896

55988 45294

59826 47650

59156 46574

0.7105 1.3927

0.5990 1.3592

0.5094 1.3176

0.4418 1.2729

0.4012 1.2389

0.3888 1.2273

H  L (90.87%) H-1 L (4.06%)

H  L (91.52%) H-1 L (3.18%)

H  L (92.30%) H-1 L (2.03%)

H  L (92.51%)

H  L (92.44%)

H  L (92.38%)

0.0717 1.6231

0.1954 1.6607

0.3054 1.7056

0.4045 1.7518

0.4799 1.7858

0.4890 1.7957

H-1  L (92.71%) H-1  L (93.29%) H-1  L (93.97%) H-1  L (93.58%) H-1  L (95.13%) H-1  L (82.40%) H  L (4.31%) H  L (3.51%) H  L (2.41%) H  L (2.01%) 24740 49124 64231 53572 47492 50454 24051 48796 65690 56590 49209 51201 0.6748 1.2780

0.5862 1.2516

0.5098 1.2179

0.4526 1.1853

0.4178 1.1585

0.4076 1.1496

H  L (93.06%) H-1 L (2.93%)

H  L (93.06%) H-1 L (2.88%)

H  L (93.80%) H-1 L (2.01%)

H  L (94.11%)

H  L (94.22%)

H  L (94.23%)

0.0496 1.4872

0.1429 1.5145

0.2273 1.5488

0.2987 1.589

0.3450 1.6164

0.3594 1.6253

H-1  L (94.28%) H-1  L (94.13%) H-1  L (94.78%) H-1  L (95.07%) H-1  L (95.01%) H-1  L (94.93%) H  L (3.07%) H  L (3.08%) H  L (2.23%)

of transition coefficient in parentheses.

22


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Table 4. Electronic first hyperpolarizability tensor βzzz0, vibrational first hyperpolarizability tensor βzzznr, and ratio η of βzzznr/βzzz0 for M-LCaL-M (M = Li or Na, L = C6F6H6) under selected external electric field (EEF, × 10-4, au). EEF 12

Li-LCaL-Li βzzz0

βzzznr

34896

118304

Na-LCaL-Na η

βzzz0

βzzznr

η

3.39

65690

133508

2.03

23



Figure 1. Optimized geometry structures (with and without external electric field (EEF) in direction z-axis) of M--LCa2+L-M- (M = Li or Na, L = C6F6H6) at M06-2X/6-311++G(2d,2p) level.


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Figure 2. Evolution of distance (L, Å) between alkali atoms (M), bond length R1, R2, R3, and R4 (Å) for MLCaL-M (M = Li or Na, L = C6F6H6) with increasing external electric field (EEF).



Figure 3. Evolution of ELF for (a) Li-LCaL-Li and (b) Na-LCaL-Na (L = C6F6H6) with increasing external electric field (EEF).


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Figure 4. Formation of two excess electron pairs in Li-LCaL-Li, and (b) excess electron orbital energy diagram.



Figure 5. Evolution of excess electron orbitals (HOMO and HOMO-1 with isovalue = 0.02) for (a) Li-LCaL-Li and (b) Na-LCaL-Na (L = C6F6H6) with increasing external electric field (EEF).


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Figure 6. Relationship between static electronic first hyperpolarizability β0e and external electric field (EEF).



Figure 7. Selected frequency-dependent first hyperpolarizability β(-2ω,ω, ω) and β(-ω,ω,0) of M-LCaL-M (M = Li or Na, L = C6F6H6) with increasing external electric field (EEF). a) β(-ω,ω,0) and c)β(-2ω,ω, ω) for M = Li; b) β(-ω,ω,0) and d) β(-2ω,ω, ω) for M = Na.


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Graphical abstract. Under an external electric field (EEF), facially polarized Janus-type alkalides M--LCa2+LM- with two excess electron pairs concentrate on end alkali atoms (EEF = 0, Off form) exhibits long-range charge transfer from one end alkali atom through the middle LCaL to the other end one and large static electronic first hyperpolarizabilities of 59826 (M = Li, EEF = 19 × 10-4 au, On form) and 64231 au (M = Na, EEF = 12 × 10-4 au, On form).


Long-Range Charge Transfer Driven by External Electric Field

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