A theoretical study of alkaline-earthides Li(NH3)4M (M = Be, Mg, Ca) with large first hyperpolarizability

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

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.

Superalkali-alkaline earthide ion pairs of δ+(AM-HMHC)-AM'δ- (AM = Li, Na and K; AM' = Be, Mg and Ca) possessing large NLO responses and excellent electronic stabilities and alkalide characteristics: a DFT study

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ+(AM-HMHC)-AM'δ- is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M+(calix[4]pyrrole)M'- (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ+(AM-HMHC)-AM'δ- are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response (βHRS). These alkaline earthides suggest prominently high βHRS up to 2.59 × 104 a.u. (boat forms of δ+(Na-HMHC)-Caδ-). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.

Theoretical study of the Tetraaminelithium and Tetraaminesodium molecules complexed with H-, Li- and Na- anions: static and dynamic NLO parameters

CONTEXT

This work focuses on the study of six molecules composed of the TetraAmineLithium (TALi+) and TetraAmineSodium (TANa+) structures linked with the anions H-, Li- and Na-. The NLO results obtained by these calculations showed significant values of static first hyperpolarizabilities (βtot) ranging from 8.74 * 10-30 to 691.99 * 10-30 esu. The two molecules TALi-Li and TALi-Na gave the highest values of static βtot equal to 563.20 and 691.99 * 10-30 esu respectively and static second hyperpolarizabilities (γav) of 680.02 and 779.05 * 10-35 esu. The highest dynamic first hyperpolarizabilities (β||) values are around 1474080.00 * 10-30 esu and 6,145,080.00 * 10-30 esu at 720 nm lasers and which are attributed to the two molecules TANa-Li and TANa-Na respectively. Four molecules have push-pull behavior where the anions are donor groups, the Li+-NH3 and Na+-NH3 groups are acceptor groups and a bridge composed by the three remaining NH3 ligands. The maximum wavelengths (λmax) in vacuum and in the presence of solvents for all molecules are in the range 240 to 870 nm.

METHOD

The software used in this study is Gaussian 16. The optimizations of the molecules were calculated by B3LYP-D3/6-31 +  + G(d,p). The static first hyperpolarizability (βtot) was calculated by different functionals: CAM-B3LYP, LC-wPBE, LC-BLYP, M11, wB97X, HSEh1PBE and M06-2X and the MP2 method, the basis-set used is 6-31 +  + G(d,p). Other calculations of static βtot were carried out by the CAM-B3LYP functional combined with several basis-sets: 6-31G(d,p), 6-31 +  + G(d,p), cc-pVDZ, AUG-cc- pVDZ, 6-311G(d,p), 6-311 +  + G(d,p), cc-pVTZ and AUG-cc-pVTZ. The calculations of the first (β||) and second (γ||) hyperpolarizabilities in second harmonic generation (SHG) were calculated by CAM-B3LYP/6-31 +  + G(d,p). The delocalization energies (E(2)) were determined by the NBO approach and calculated by the same functional and basis-set cited before. The solvation Gibbs energies (ΔGsolv) were calculated using the implicit SMD model. Maximum wavelengths (λmax) and oscillator strengths ([Formula: see text]) were calculated by TD-CAM-B3LYP/6-31 +  + G(d,p) in the presence of the implicit CPCM model.

Enhanced nonlinear optical response of alkalides based on stacked Janus all-cis-1,2,3,4,5,6-hexafluorocyclohexane

Significant efforts are continuously exerted by the scientific community to explore new strategies to design materials with high nonlinear optical responses. An effective approach is to design alkalides based on Janus molecules. Herein, we present a new approach to remarkably boost the NLO response of alkalides by stacking the Janus molecules. Alkalides based on stacked Janus molecule, M-n-M' (where n = 2 & 3 while M and M' are Li/Na/K) are studied for structural, energetic, electrical, and nonlinear optical properties. The thermodynamic stability of the designed complexes is confirmed by the energetic stabilities, which range between -14.07 and -28.77 kcal/mol. The alkalide character of alkali metals-doped complexes is confirmed by the NBO charge transfer and HOMO(s) densities. The HOMO densities are located on the doped alkali metal atoms, indicating their alkalide character. The absorptions in UV-Vis and near IR region confirm the deep ultraviolet transparency of the designed complexes. The maximum first static and dynamic hyperpolarizabilities of 5.13 × 107 and 6.6 × 106 au (at 1339 nm) confirm their high NLO response, especially for K-2-M' complexes. The NLO response of alkalides based on stacked Janus molecules is 1-2 orders of magnitude higher than the alkalide based on Janus monomer. The high values of dc-Kerr and electric field-induced response e.g., max ∼107 and 108 au, respectively have been obtained. These findings suggest that our designed complexes envision a new insight into the rational design of stable high NLO performance materials.

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.

Silver cluster doped graphyne (GY) with outstanding non-linear optical properties

This research study addresses the computational simulations of optical and nonlinear optical (NLO) characteristics of silver (Ag) cluster doped graphyne (GY) complexes. By precisely following DFT and TD-DFT hypothetical computations, in-depth characterization of GY@Agcenter, GY@Agside, GY@2Agperpendicular, GY@2Agabove, and GY@3Agcenter is accomplished using CAM-B3LYP/LANL2DZ while the CAM-B3LYP/mixed basis set is used for study of 2GY@Agcenter, 2GY@Agside, 2GY@2Agperpendicular, 2GY@2Agabove, and 2GY@3Agcenter. The effects of various graphyne surface based complexes on hyperpolarizabilities, frontier molecular orbitals (FMOs), density of states (DOS), absorption maximum (λ max), binding energy (E b), dipole moment (μ), electron density distribution map (EDDM), transition density matrix (TDM), electrostatic potential (ESP), vertical ionization energy (E VI) and electrical conductivity (σ) have been investigated. Infrared (IR), non-covalent interaction (NCI) analysis accompanied by isosurface are performed to study the vibrational frequencies and type of interaction. Doping strategies in all complexes impressively reformed charge transfer characteristics such as narrowing band gap (E g) in the range of 2.58-4.73 eV and enhanced λ max lying in the range of 368-536 nm as compared to pure GY with 5.78 eV E g and 265 nm λ max for (GY@Agcenter-GY@3Agcenter). In the case of (2GY@Agcenter-2GY@3Agcenter), when compared to 2GY with 5.58 eV E g and 275 nm absorption, maximum doping techniques have more effectively modified λ max in the region of 400-548 nm and E g, which is in the order of 2.55-4.62 eV. GY@3Agcenter and 2GY@3Agcenter reflected a noteworthy increment in linear polarizability α O (436.90 au) and (586 au) and the first hyperpolarizability β O (5048.77 au) and (17 270 au) because of their lowest excitation energy (ΔE) when studied in comparison with GY (α O = 281.54 and β O = 0.21 au) and 2GY surface (α O = 416 and β O = 0.06 au). Focusing on harmony between the tiny Ag clusters and graphyne surface as well as their influences on NLO properties, graphyne doping using its two-unit cells (2GY) is found to be expedient for the development of future nanoscale devices.