Excess Electron Compounds Research Articles

Theoretically designed M@diaza[2.2.2]cryptand complexes: the role of non-covalent interactions in promoting NLO properties of organic electrides

ABSTRACT Organic excess electron compounds with significant nonlinear optical (NLO) properties are widely employed in optoelectronic applications. Herein, single-alkali metals with diaza[2.2.2] cryptand (M@crypt,M=Li, Na, and K) are investigated for optoelectronic and NLO properties by using the density functional theory. Thermodynamic and kinetic stabilities of present complexes are computed through interaction energy (Eint) and ab-initio molecular dynamic (AIMD) simulations. M@crypt complexes carry excess electrons and mimic molecular electrides. Quantum theory of atoms in molecules (QTAIM) analysis and reduced density gradient (RDG) spectra demonstrate the roles of the weak van der Waals (vdW) interactions between metal and complexant. The remarkable hyperpolarizability (βo) value up to 1.41 × 106 au may be credited to the presence of loosely bound excess electrons. The hyper Rayleigh scattering hyperpolarizability (βHRS) is recorded up to 1.31 × 106 au for the K@crypt. Furthermore, frequency-dependent first-order and second-order hyperpolarizability is more prominent at the applied frequency of ω = 0.042823 au. The electron localizing function (ELF) and localized orbital locator (LOL) analysis further disclose the nature of interaction between alkali metal and complexant. The TD-DFT method is adopted to get excited state parameters and absorbance properties. An electron density difference map (EDDM) is exploited to evaluate the orbital contributions in excited states. Hence, the studied electride may become a promising candidate for NLO materials. We anticipate that the present work will provide insight into further development of molecular electride for optoelectronic applications.

Rational Design, Stabilities and Nonlinear Optical Properties of Non-Conventional Transition Metalides; New Entry into Nonlinear Optical Materials.

Electronic and nonlinear optical properties of endohedral metallofullerenes are presented. The endohedral metallofullerenes contain transition metal encapsulated in inorganic fullerenes X12Y12 (X = B, Al & Y = N, P). The endohedral metallofullerenes (endo-TM@X12Y12) possess quite interesting geometric and electronic properties, which are the function of the nature of the atom and the size of fullerene. NBO charge and frontier molecular orbital analyses reveal that the transition metal encapsulated Al12N12 fullerenes (endo-TM@Al12N12) are true metalides when the transition metals are Ni, Cu and Zn. Endo-Cr@Al12N12 and endo-Co@Al12N12 are at the borderline between metalides and electrides with predominantly electride characteristics. The other members of the series are excess electron systems, which offer interesting electronic and nonlinear optical properties. The diversity of nature possessed by endo-TM@Al12N12 is not prevalent for other fullerenes. Endo-TM@Al12P12 are true metalides when the transition metals are (Cr-Zn). HOMO-LUMO gaps (EH-L) are reduced significantly for these endohedral metallofullerenes, with a maximum percent decrease in EH-L of up to 70%. Many complexes show odd-even oscillating behavior for EH-L and dipole moments. Odd electron species contain large dipole moments and small EH-L, whereas even electron systems have the opposite behavior. Despite the decrease in EH-L, these systems show high kinetic and thermodynamic stabilities. The encapsulation of transition metals is a highly exergonic process. These endo-TM@X12Y12 possess remarkable nonlinear optical response in which the first hyperpolarizability reaches up to 2.79 × 105 au for endo-V@Al12N12. This study helps in the comparative analysis of the potential nonlinear optical responses of electrides, metalides and other excess electron systems. In general, the potential nonlinear optical response of electrides is higher than metalides but lower than those of simple excess electron compounds. The higher non-linear optical response and interesting electronic characteristics of endo-TM@Al12N12 complexes may be promising contenders for potential NLO applications.

Designing Excess Electron Compounds by Substituting Alkali Metals to a Small and Versatile Tetracyclic Framework: A Theoretical Perspective.

Organic compound-based nonlinear optical (NLO) materials have sparked a lot of attention due to their multitude of applications and shorter optical response times than those of inorganic NLO materials. In the present investigation, we designed exo-exo-tetracyclo[6.2.1.13,6.02,7]dodecane (TCD) derivatives, which were obtained by replacing H atoms of methylene bridge carbon with alkali metals (Li, Na, and K). It was observed that upon the substitution of alkali metals at bridging CH2 carbon, absorption within the visible region occurred. Moving from 1 to 7 derivatives, the maximum absorption wavelength of the complexes exhibited a red shift. The designed molecules showed a high degree of intramolecular charge transfer (ICT) and excess electrons in nature, which were responsible for rapid optical response time and significant large molecular (hyper)polarizability. Calculated trends also inferred that the crucial transition energy decreased in order that also played a key role in the higher nonlinear optical response. Furthermore, to examine the effect of the structure/property relationship on the nonlinear optical properties of these investigated compounds (1-7), we calculated the density of state (DOS), transition density matrix (TDM), and frontier molecular orbitals (FMOs). The largest first static hyperpolarizability (βtot) of TCD derivative 7 was 72059 au, which was 43 times greater than that of the prototype p-nitroaniline (βtot = 1675 au).

Theoretical study of [36]adamanzane (36Adz) based alkalides with remarkable non-linear optical properties

Herein, a series of 36Adamanzane (stable C–N bond) based alkalides possessing alkaline Earth metal cation complexed by the 36Adz cage has been designed and studied with theoretical tools. All suggested complexes are within the range of effective NLO materials such as red-shifted λ max (1080–1241 nm), narrowed Eg (1.74 to 2.31 eV), lowered Eopt (0.9945–1.1485 eV), enhanced (5.3873–6.2544 au), ameliorated (454.20–1400.34 au) and (801301.48–819800.06 au) as compared to pure 36Adz (Eg = 10.2 eV, λ max = 179 nm, Eopt = 6.9217, = 241.64 and = 0.02 au). All of the aimed complexes have substantially large as well as values. NBO charges investigations reveal that one of the s-electrons has migrated from the inside metal atom to the outer one, resulting in not only alkalide characteristics but also significant NLO responses for the targeted compounds. This research is useful in the development of new types of excess electron compounds. The findings presented in this study may have implications for future research on high-performance NLO materials, as well as give important references for future research on various alkalides including non-alkali cations.

Transition metalides based on facially polarized all-cis-1,2,3,4,5,6-hexafluorocyclohexane - a new class of high performance second order nonlinear optical materials.

Continuous attempts are being made to discover new approaches to design materials with extraordinary nonlinear optical responses. Herein, for the first time, we report the geometric, electronic, and nonlinear optical properties of novel Janus transition metalides AM-J-TM (where AM = Li, Na and K, and TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) containing alkali metals as a source of excess electrons for transition metals to generate metalides. The Janus organic complexant used for the study is all cis 1,2,3,4,5,6-hexafluorocyclohexane F6C6H6 (J). These complexes contain the unique involvement of alkali metals (AM = Li, Na and K) as a source of excess electrons, which significantly affects the hyperpolarizability values of the resulting transition metalides. The NBO analysis reveals the charge transfer from alkali metals to the transition metals, thereby confirming the metalide behavior of the complexes. Moreover, the metalide nature of these complexes is validated through frontier molecular orbital (FMO) analysis. The values of interaction energies, vertical ionization potential (VIP) and vertical electron affinity (VEA) illustrate the stability of the metalide complexes. Ultimately, the hyperpolarizability values confirm the excellent nonlinear optical response of the designed transition metalides. The remarkable static first hyperpolarizability (β0) response up to 4 × 108 a.u. is observed for complexes of vanadium. Similarly, the complexes of AM-J-Mn and Li/Na-J-Sc show significantly high NLO response. These compounds besides providing a new entry into excess electron compounds will also pave the way for the design and synthesis of further novel NLO materials.

Alkali metal (Na and Li) doped C18 nanocluster with boosted electronic and nonlinear optical properties

To expand the uses of material in nonlinear optics, strategies for producing extraordinary nonlinear optical materials with excess electron compounds are widely known in the literature. In this study, cyclo18 (C18) nanocluster was doped with alkali metals (Na and Li) in such a way that the metal atom was placed inside the C18 surface to explore their nonlinear optical (NLO) properties by density functional theory (DFT) calculations. Alkali metals doping has lowered the band gap energy (4.64–4.55) when compared to the pure surface (6.76 eV). The alkali metals possess loosely bound excess electrons which can be easily excited, hence lowering the doped systems excitation energies, resulting a remarkable increase in the hyperpolarizabilities. The highest value of hyperpolarizability (17,975.051 C3 m3 J-2) has been explored by C18-Na. Moreover, isotropic and anisotropic polarizabilities (αiso and αaniso) were also computed for the alkali doped systems and outstanding outcomes were observed (αiso ranges from 45.69 to 53.07 C3 m3 J-2) and (αaniso ranges 49.91–61.07 C3 m3 J-2), when comparison was made between the doped and undoped surfaces. NCI analysis show that there exist van der Waals interactions among surface and the dopant. Absorption analyses were performed, and the results showed that these doped complexes having excess electrons absorbs at higher wavelength ranging from 675 to 683 nm. Furthermore, FMOs, TDM and NBO analysis revealed the outstanding electronic and charge transfer properties of these doped systems. As a result of our findings, alkali metal doped C18 may be a contender for efficient nonlinear optical characteristics

NLO properties and electride characteristics of superalkalis doped all-cis-1,2,3,4,5,6-hexafluorocyclohexane complexes

The designing and synthesis of efficient NLO materials is the demand of the century because of their importance in the development of photo-electronic devices. Herein, we studied the geometric, electronic, and nonlinear properties of superalkalis doped all-cis-1,2,3,4,5,6-hexafluorocyclohexane, Janus type complexes. These complexes have an unprecedented involvement of respective superalkalis as source of excess electrons, which resulted in the enhancement of nonlinear optical properties and electride characteristics. The interaction energies (−13.57 to −16.54 kcal mol−1) indicated the physisorption of superalkalis on C6H6F6. NBO charge analysis is used to predict the charge transfer during the complexation. The highest NLO response (1.68 ×106 au) is observed for Na2F@C6F6H6 complex. The enhancement in second hyperpolarizability (γo) values is seen at various frequencies. Further, to obtain NLO response from an experimental point of view, hyper Rayleigh scattering (βHRS) is also investigated. These complexes, in addition to being a new entry into excess electron compounds, will pave the way for the designing and synthesis of additional NLO materials. The remarkable static first hyperpolarizability (βo) and second hyperpolarizability (γo) responses make them ideal for future NLO materials.

The Alkaline-earthides based parallel-stacked dimer and trimer of Janus face C6H6F6 showing extremely large nonlinear optical responses

To research the aggregate effect on first hyperpolarizability (β0), we selected the dimer (2) and trimer (3) of all-cis 1,2,3,4,5,6-hexafluorocyclohexane C6H6F6 (1) in their parallel-stacked conformations as two ligands. And a series of excess electron compounds MA-2-MAE and MA-3-MAE (MA = Li, Na and K; MAE = Be, Mg and Ca) were successfully designed by doping alkali metal atom and alkaline-earth metal atom into the 2 or 3. In this work, we studied the geometric structures, electronic structures and NLO properties of MA-2-MAE and MA-3-MAE compounds by density functional theory (DFT). The HOMO orbitals analysis showed that MA-2-MAE and MA-3-MAE are alkaline-earthides. Among these alkaline-earthides, the largest β0 of the Li-3-Be is 1.46 × 107 au, which is almost 21 times larger than those values of M-C6H6F6 (M = Li, Na and K) (7.00 × 105 au). We sincerely hope this work will not only enrich the variety of excess electron compounds but also further reveal the impact of aggregate effect.

The electronic structures and nonlinear optical properties of Alkali and Alkali earth metal atoms doped C6H6Cl6: A density functional theoretical study

The all-cis 1,2,3,4,5,6-hexafluorocyclohexane C6H6F6 (1) is a well-known molecule which has an unusually large molecular dipole moment (6.2 Debye), and plentiful novel excess electron compounds have been successfully designed on the basis of it recently. Inspired by 1, in this study, we tried to replace all the F atoms in molecule C6H6F6 with Cl atoms and obtained the all-cis 1,2,3,4,5,6-hexachlorocyclohexane C6H6Cl6 (2). By introducing alkali metal atoms and alkaline earth metal atoms, a novel series of alkalides and excess electron compounds, namely MA*+-2-MA− (MA* = Na, K; MA = Li, Na and K) and MA*-2-MAE (MA* = Na, K; MAE = Be, Mg and Ca), were theoretically constructed and studied in this work. Our results exhibit the apparent charge transfer in MA*+-2-MA− systems by NBO analysis. And these compounds all show good stability from the values of VIE and Gap. Especially, Na+-2-Li− compound exhibit the largest first hyperpolarizability value (3.4 × 106 au). The calculated results indicate these novel proposed species possess significantly large nonlinear optical responses. We hope this work will attract more experimental interests and efforts to design and synthesize new excellent NLO materials.

Theoretical Study of Alkaline-Earth Metal (Be, Mg, and Ca)-Substituted Aluminum Nitride Nanocages With High Stability and Large Nonlinear Optical Responses.

By replacing one Al or N atom of aluminum nitride nanocage Al12N12 with an alkaline-earth metal atom, two series of compounds, namely, M@Al12N11 and M@Al11N12 (M = Be, Mg, and Ca), were constructed and investigated in theory. The substituted effect of alkaline-earth metal on the geometric structure and electronic properties of Al12N12 is studied in detail by density functional theory (DFT) methods. The calculated binding energies, HOMO–LUMO gaps, and VIE values of these compounds reveal that they possess high stability, though the NBO and HOMO analyses show that they are also excess electron compounds. Due to the existence of diffuse excess electrons, these alkaline-earth metal-substituted compounds exhibit larger first hyperpolarizabilities (β 0) than pure Al12N12 nanocage. In particular, these considered compounds exhibit satisfactory infrared (IR) (>1800 nm) and ultraviolet (UV) (˂ 250 nm) transparency. Therefore, these proposed excess electron compounds with high stability may be regarded as potential candidates for new UV and IR NLO molecules.

M@[12-crown-4] and M@[15-crown-5] where (M=Li, Na, and K); the very first examples of non-conventional one alkali metal-containing alkalides with remarkable static and dynamic NLO response

Excess electron compounds , such as alkalides, were shown to be promising nonlinear optical (NLO) materials with higher static and frequency-dependent nonlinearities. The intriguing alkalides are obtained after doping the alkali metals with crown ethers M@[12-crown-4] and M@[15-crown-5] (where M=Li, Na, and K). The studied complexes are thermodynamically stable and their interactions energies range from −66.51 to −3.51 kcal mol −1 . The geometric, electronic, and nonlinear optical properties are validated through density functional theory at the CAM-B3LYP/6-31+G(d,p) level of theory. The significant (negative) NBO charge present on alkali metals reveals their alkalide characteristics. Furthermore, reduced HOMO-LUMO gaps for the designed complexes show their excellent electronic and conductive properties. Being excess electron candidate the significant static first hyperpolarizability value increased up to 1.2 × 10 7 au where the β vec response recorded up to 1.1 × 10 7 au. The total hyperpolarizability nicely correlates with hyperpolarizability ( β tl ) which suggests their excellent NLO properties. Besides, the dynamic hyperpolarizability response for electro-optical pockel's effect β(-2ω;ω,0) increases up to 3.5 × 10 7 au at dispersion frequency of 1064 nm. The dynamic hyperpolarizability responses for SHG are much pronounced at the larger dispersion frequency. The dynamic second hyperpolarizability response for the dc-Kerr effect increases up to 6.4 × 10 9 au. The frequency-dependent NLO response of M@[12-crown-4] alkalides is slightly larger than those of M@[12-crown-4]. Moreover, the hyper Rayleigh scattering hyperpolarizability (β HRS ) value is calculated up to 3.4 × 10 6 au. • Single alkali metal based non-conventional alkalides are proposed as excess electron compounds. • These shows better thermodynamic stabilities and significant interactions energies for M@[15-crown-5] complexes. • The higher hyperpolarizability response for Li@[15-crown-5] rose up to 1.2 × 10 7 au. • The remarkable frequency-dependent NLO properties at ω = 1064 nm.

DFT study of alkali and alkaline earth metal-doped benzocryptand with remarkable NLO properties.

Strategies for designing remarkable nonlinear optical materials using excess electron compounds are well recognized in literature to enhance the applications of these compounds in nonlinear optics. In this study, density functional theory simulations are performed to study alkali and alkaline earth metal-doped benzocryptand using the B3LYP/6-31G+(d, p) level of theory. Vertical ionization energies (VIEs), reactivity parameters, interaction energies, and binding energies exposed the thermodynamic stability of these complexes. FMO analysis revealed that HOMO is located on alkali metals having polarized electrons, which are easy to excite. The doping strategy enhanced the charge transfer with low bandgap energy in the range of 0.68–2.23 eV, which is lower than that of the surface BC (5.50 eV). Also, the lower transition energies and higher oscillator strength indicate that these complexes exhibit excellent electronic and optical properties. Non-covalent interaction analysis suggested the presence of van der Waals interactions between dopants and surface. IR analysis provided information about the frequencies of stretching vibrations present in the complexes due to different bonds. UV-vis analysis revealed that all the newly designed excess electron complexes are transparent in the UV region and possessed maximum absorption in the visible and NIR region, ranging from 753.6 to 2150 nm, which is higher than the surface (244 nm). Thus, these complexes have a potential for high-performance NLO materials in the applications of optics. Natural bond orbital analysis (NBO), transition density matrix (TDM), electron density difference map (EDDM), and density of state (DOS) analyses were also performed to study the charge transfer properties. Moreover, these complexes possessed remarkable optoelectronic properties due to a significant increase in the isotropic linear polarizability (αiso) in the range of 629.59–1423.23 au. Further, these systems demonstrated an extraordinary large total first hyperpolarizability (βtl) in the range of 3695.55–910 706.43 au. The rationalization of hyperpolarizability by the two-level model reflected a noteworthy increase in βtl because of low transition energies (ΔE) and high transition dipole moment (Δμ). Thus, our results showed that alkali and alkaline earth metal-doped BC might be a competitor for efficient nonlinear optical properties with practical applications in the area of optoelectronics.

Germanium-based superatom clusters as excess electron compounds with significant static and dynamic NLO response; a DFT study.

Herein, the geometric, electronic, and nonlinear optical properties of excess electron zintl clusters Ge5AM3, Ge9AM5, and Ge10AM3 (AM = Li, Na, and K) are investigated. The clusters under consideration demonstrate considerable electronic stability as well as superalkali characteristics. The NBO charge is transferred from the alkali metal to the Ge-atoms. The FMO analysis shows fabulous conductive properties with a significant reduction in SOMO–LUMO gaps (0.79–4.04 eV) as compared with undoped systems. The designed clusters are completely transparent in the deep UV-region and show absorption in the visible and near-IR region. Being excess electron compounds these clusters exhibit remarkable hyperpolarizability response up to 8.99 × 10−26 esu, where a static second hyperpolarizability (γo) value of up to 2.15 × 10−30 esu was recorded for Ge9Na5 superatom clusters. The excitation energy is the main controlling factor for hyperpolarizability as revealed from the two-level model study. The electro-optical Pockel's effect and the second harmonic generation phenomenon (SHG) are used to investigate dynamic nonlinear optical features. At a lower applied frequency (=532 nm), the dynamic hyperpolarizability and second hyperpolarizability values are significantly higher for the studied clusters. Furthermore, for the Ge9K5 cluster, the hyper Rayleigh scattering (HRS) increases to 5.03 × 10−26 esu.

DFT studies of electronic and nonlinear optical properties of a novel class of excess electron compounds based on multi-alkali metal atoms-doped Janus face C13H10F12

Three-ring Janus face C13H10F12 has a larger surface than F6C6H6, which is useful to tune different types of excess electron compound by doping multi-alkali metal atoms.

Superalkali-based alkalides Li3O@[12-crown-4]M (where M= Li, Na, and K) with remarkable static and dynamic NLO properties; A DFT study

Exploring new nonlinear optical materials with excess electron character is extremely important for promoting the application of excess electron compounds in nonlinear optics. Herein, by using density functional theory (DFT) computations, new superalkali-based alkalides Li3O@[12-crown-4]M− are designed as excess electron compounds. QTAIM studies suggest that the complexant interacts with alkali and superalkali clusters through non-covalent interactions. These complexes are thermodynamically stable and their interaction energies range from −33.40 ∼ −44.23 kcal mol-1. The alkalide nature of these compounds is guaranteed by their HOMOs values and NBO charge analysis. Being excess electron compounds, these alkalides shows potential electronic properties. Their HOMO-LUMO gaps ranging from 0.17–0.27 eV. With excellent properties, these complexes show remarkable total hyperpolarizability (βo) response (9.30×104–5.26×106au). Interestingly, the hyperpolarizability response is dependent on the size of alkali metals. The βvec values are quite comparable to total hyperpolarizability at the same level of theory. Furthermore, the hyperpolarizability calculated through two-level model (βtl) values show a trend similar to hyperpolarizability. Additionally, the dynamic hyperpolarizability response for EOPE effects is much pronounced at the dispersion frequency of 532 nm. The second hyperpolarizability response for the dc-Kerr constant is increased up to 2.75 × 1012 au which is much higher than those of previously reported alkalides. Strikingly, the frequency-dependent NLO response shows dependence on alkalide character rather than the size of alkali metal (M). Moreover, the βHRS value is recorded up to 2.16 × 106 au. The significant dipolar contribution to hyperpolarizabilities Φβ(J = 1) are observed for these complexes.

Extremely large static and dynamic nonlinear optical response of small superalkali clusters NM3M’ (M, M’=Li, Na, K)

Exploring novel nonlinear optical (NLO) materials with excess electron properties is essential for advancing the use of excess electron compounds in optics. The studied superalkali clusters NM3M’ (M, M′ = Li, Na, K) are thermodynamically stable and their binding energies range from −27.10 to −53.84 kcal mol−1. The observed significant values for VIPs suggest their electronic stabilities. Being excess electron candidate these clusters show significant βo value (3.9 × 107 au), which nicely correlates the hyperpolarizability reported by a two-level model (βtl). Furthermore, these clusters exhibit a remarkable static second hyperpolarizability (γo) value of 1.1 × 1010 au for the NK4 superalkali cluster. The hyper Rayleigh scattering (βHRS) is also computed where the highest value of 2.9 × 107 is recorded for NNa3K superalkali. The obtained values of βvec values (projection of hyperpolarizability on dipole moment vector) also signify the excellent nonlinearity of clusters. Besides, the calculated electro-optica pockel's effect β(-ω; ω,0) and second harmonic generation β(-2ω; ω, ω) values are much pronounced at larger dispersion frequency ω = 1064 nm. Moreover, the frequency-dependent second hyperpolarizability γ(ω) with dc-Kerr effect γ(-ω; ω,0,0) and electric field induced second harmonic generation γ(-2ω; ω,ω,0) show larger values at ω = 1064 nm. Thus the highest value of the dc-Kerr constant increases up to 1.0 × 1011 au which also signifies the larger nonlinear refractive index of the studied cluster. We hope this work could open up new possibilities using superalkali clusters as NLO materials for optoelectronics, laser, second harmonic generation and as frequency doubler.

Design a novel type of excess electron compounds with large nonlinear optical responses using group 12 elements (Zn, Cd and Hg)

Based on the interesting Janus-type all-cis1,2,3,4,5,6-hexafluorocyclohexane (1) molecule, a novel type of excess electron compounds MF-1-MH (MF = Li, Na and K, MH = Zn, Cd and Hg) were designed theoretically. The geometric structures, electronic structures and nonlinear optical properties of MF-1-MH compounds were studied by density functional theory. Our results show that in Li-1-MH, the obvious charge transfer between Li and MH can be observed while in Na/K-1-MH, the charge transfer between Na/K and MH is negligible. Particularly, the MF-1-MH exhibit remarkable nonlinear optical (NLO) response and the first hyperpolarizability of the K-1-Zn almost achieve 1.0 × 106 au. We hope this work will further enrich the family of excess electron compounds, so that more experimental interests and efforts can be attracted to propose and synthesize new excellent NLO materials.

Oxacarbon superalkali C3X3Y3 (X = O, S and Y = Li, Na, K) clusters as excess electron compounds for remarkable static and dynamic NLO response

An intriguing class of excess electron oxacarbon superalkali clusters is explored for nonlinear optical response through density functional theory (DFT) methods at CAM-B3LYP/6–311++G(d,p). These superalkali clusters shows noticeable binding energies per atom (Eb) which reveals their thermodynamic stabilities (−86.45 ∼ −119.44 kcal mol−1). The obtained significant VIPs values also suggest the electronic stability of these clusters. The VIP values range from 2.06 eV to 3.42 eV. These clusters show remarkable electronic properties and their HOMO-LUMO gaps (EH-L) are significantly reduced. The lowest H-L gap of 0.96 eV is obtained for C3O3K3 while the highest H-L gap of 2.07 eV is calculated for C3S3Li3. The obtained PDOS spectra further provide evidence for the superior electronic properties of these clusters. The clusters show excellent nonlinear optical properties as revealed from remarkable values (1.6 × 106 au) of static first hyperpolarizability. The controlling factors for hyperpolarizability are also explored by using conventional two-level model. The calculated values of βo are correlated nicely with βtl. The crucial excitation energy is the key factor in controlling the first hyperpolarizability. In these excess electron clusters, the second hyperpolarizability (γo) response increases up to 4.3 × 109 au. Moreover, the calculated scattering hyperpolarizability (βHRS) values are quite significant in these clusters and the highest value of 1.3 × 106 au is calculated for C3S3K3. Additionally, these clusters also possess larger dynamic nonlinearities. The dynamic second hyperpolarizability with dc-Kerr effect increases up to 1.0 × 1011 au. The remarkable values for refractive index (n2) also suggest the excellent nonlinearity of these superalkali clusters.

Alkaline earth metals serving as source of excess electron for alkaline earth metals to impart large second and third order nonlinear optical response; a DFT study

Continuous strides are made to explore new strategies for the design of materials with remarkable nonlinear optical response. Herein, we report the geometric, electronic, and nonlinear optical properties of novel bis-alkaline earth metal doped complexes of Janus all-cis-1,2,3,4,5,6-hexafluorocyclohexane F6C6H6 (1). These complexes contain unprecedented involvement of alkaline earth metals as sources of excess electron for the 2nd alkaline earth metal atom in the complex. Geometric electronic and thermodynamic properties of studied complexes AE-1-AE (where AE = Be, Mg, Ca) are obtained at M06-2X/6-31+G(d,p) level of theory. The NBO analysis is performed to predict the charge transfer. Moreover, the excess electron nature of these complexes is validated through frontier molecular orbital (FMOs) analysis. The PDOS and TDOS analysis are also performed to further rationalize the electronic properties. The remarkable static first hyperpolarizability (β0) and second hyperpolarizability (γ0) response up to 2.91 × 104 au and 4.08 × 106 au, respectively, are recorded for these complexes. Furthermore, the two-level model is also employed to get a comprehensive picture of the controlling factors for hyperpolarizability. Moreover, to get nonlinearity response from the experimental point of view, hyper Rayleigh scattering (βHRS) has been calculated and the highest value of 7.38 × 103 au is noticed for the complex I (Ca-1-Ca). These compounds besides providing a new entry into excess electron compounds will also pave the path for designing and synthesis of further novel NLO materials.

Janus alkaline earthides with excellent NLO response from sodium and potassium as source of excess electrons; a first principles study

Alkaline earthide is a well-known class of the excess electron compounds with potential applications as NLO materials. In this study, all-cis-1,2,3,4,5,6-hexafluor-ocyclohexane C6H6F6 (1), a high polarized complexant having the largest dipole moment (6.2D) among all the known aliphatic hydrocarbons, is selected as a suitable molecule for designing a new series of excess electron molecules, alkaline-earthides. Geometric, thermodynamic and electronic properties of A-1-AE (A = Li, Na, K and AE = Be, Mg, Ca) are studied at M06-2X/6-31+G(d,p) level of theory. More specifically, alkaline-earthide nature is confirmed by distribution of densities in HOMOs, VIE values and NBO analysis. The alkaline earthide possess moderate complexation energies (−6.56 to −14.19 kcal/mol), which demonstrate their thermodynamic stability. These alkaline earthides possess very small excitation energies (0.54–1.64 eV) and very large first hyperpolarizabilities (up to 4.14 × 109 au). The higher hyperpolarizabilities values are attributed to the presence of excess electrons on alkaline earth metals which is confirmed through the partial density of states (PDOS) analysis. The hyperpolarizabilities are rationalized through two level model approach. Large hyperpolarizability values illustrate that the alkaline-earthides are a very promising entry into excess electron compounds.