Second-order Nonlinear Optical Response Research Articles

Influence of the Nature of the Lipid Building Blocks on the Second-Order Nonlinear Optical Responses of an Embedded Di-8-ANEPPS Probe.

The extensive collection of lipids found in cell membranes is justified by the fact that each lipid contributes to their overall structure, dynamics, and properties and so to the biological processes taking place within them. It also showcases that, in order to deepen our understanding of membranes, we need to have a tool to differentiate lipid bilayers of varying composition. In this work, we investigate a suite of single-component saturated glycerophospholipids varying only in their headgroup structure by analyzing the second harmonic generation (SHG) nonlinear optical (NLO) response of a probe, di-8-ANEPPS, embedded into the membranes. The seven hydrophilic heads chosen (phosphatidylcholine (PC), phosphatidylethanolamine (PE), diaglycerol (GL), phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidyc acid (PA)) represent all the major headgroups that are part of mammalian plasma membranes and provide an assortment of neutral, zwiterrionic, and charged species. First, molecular dynamics simulations revealed that the lipidic arrangement is strongly sensitive to the nature of the hydrophilic head and less to the variety in the hydrophobic region. Membranes exhibiting drastically opposite structural properties can be pointed out: 1,2-dihexadecanoyl-rac-glycerol (DPGL) is the thickest and most ordered and aligned system, whereas 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) (DPPG) is thinnest and least ordered and aligned system. The structural analyses are then confronted with the molecular NLO responses, β, computed at the time-dependent density functional theory (TDDFT) level. As the orientation of the chromophore is impacted by the various degrees of order within the lipid bilayers, the diagonal component of the β tensor parallel to the bilayer normal, βZZZ, is as well. In the end, this computational approach provides insights into the link between lipid building blocks and the NLO responses of the embedded dye.

Open honeycomb frameworks of sulphides AHg4Ga5S12 (A = Rb, Cs) exhibiting infrared nonlinear optical properties.

A crystal structure with a diamond-like anionic framework belongs to a non-centrosymmetric macrostructure due to the aligned arrangement of tetrahedral units, meeting the premise of second-order nonlinear optical (NLO) materials. Herein, two new Hg-based sulphides, namely RbHg4Ga5S12 (1) and CsHg4Ga5S12 (2), which are isostructural and crystallise in the trigonal space group R3, are successfully isolated in sealed silica tubes by a solid-state reaction. The features of their three-dimensional open honeycomb frameworks are attributed to the parallel alignment of tetrahedral MS4 (M is disordered by 0.444 Hg and 0.555 Ga) building motifs, accompanied by Rb+ (or Cs+) reseating in the cavities. Notably, although the band gap values of 1 and 2 are 2.30 and 2.36 eV, separately, their thermal expansion anisotropies (0.15 and 0.41, respectively) are favourable for achieving laser-induced damage thresholds (5.6 and 5.8 times that of AgGaS2 for 1 and 2, respectively). In addition, the strong polarisability of tetrahedral MS4 building motifs in the diamond-like anionic structures is responsible for the promising second-harmonic generation (SHG) intensities (1.1 and 1.8 times that of AgGaS2 for 1 and 2, respectively) in the particle size range of 50-75 μm with non-phase-matchable behaviour at 1910 nm. Furthermore, theoretical investigation elaborates that electron transitions in compounds 1 and 2 mainly occur from valence band S-3p to conduction band Hg-6s and Ga-4s states, demonstrating that the linear and nonlinear optical properties originate primarily from the synergy of tetrahedral MS4 units.

Circularly polarized luminescence and nonlinear optical harmonic generation based on chiral zinc halides.

Chiral hybrid metal halides have grabbed extensive attention in linear and nonlinear chiroptics. Herein, 0D chiral zinc halides, (R-/S-2-MP)ZnCl4, have been fabricated, which demonstrate high efficiency second-order nonlinear optical responses. Incorporating Sb3+ into the chiral zinc halide matrix triggers the circularly polarized luminescence effectively with a balance between quantum yield and luminescence dissymmetry factor.

Investigation of first hyper-polarisability molecular switches between enol–keto equilibrium of phenyl benzodifurantrione: a DFT-based computational study

The contrast of the second-order nonlinear optical response between the enol (anti and syn) and keto tautomeric equilibrium of 7-Phenyl-7H-benzo[1,2-b;4,5-b’]difuran-2,3,6-trione (PBDT) with donor/acceptor substitution at the para position of phenyl group have been computed involving electron correlation, frequency dispersion, and solvent polarity effects. The Hyper Rayleigh Scattering (HRS) first-hyperpolarisability contrast between the enol and keto forms for PBDT and Nitro-substituted PBDT is 3.5 and 2.8, respectively. However, in NMe2-substituted PBDT, a large contrast (12 times) of HRS first hyper-polarisability between enol (anti and syn) and keto form is observed. Present study reveals that electron donor group (–NMe2) in PBDT plays a pivotal role for obtaining very high contrast in the first hyper-polarisability (β HRS and β vec) values between the enol and keto forms compare to the electron acceptor (–NO2) group substitution at the same position. The solvent effect also plays a significant role in further improving the first hyper-polarisability value and its switching behaviour between the enol and keto forms of NMe2-PBDT. NLO switching contrast between the enol and keto forms of donor/acceptor substituted PBDT is also explained using the electronic features including UV-Vis absorption spectra, HOMO–LUMO electron densities, optical energy gaps, charge transfer contribution etc.

Toward the design of inorganic–organic hybrid Ir(III) complexes containing borazine and benzene ligands with excellent second-order NLO responses: An appropriate substitution and π-conjugated extension

The high nonlinear optical (NLO) efficiency and good chemical stability render inorganic–organic hybrid materials widely applied in NLO filed. In this paper, we theoretically design a sequence of new cationic Ir(III) complexes based on parent complex Ir[(C^N)2(N^N)]+ (C^N = 2-phenylpyridine, N^N = 2,2′-bipyridine) through substituting pyridine by borazine ligands or extending borazine/benzene ligands on C^N/N^N position. The geometric and electronic structures, second-order NLO properties and absorption spectrum are evaluated by employing density functional theory (DFT) and time-dependent DFT methods. All designed complexes have smaller HOMO-LUMO energy gaps (0.74–1.82 eV) than parent complex (2.78 eV). N-5 (with borazine-benzene-borazine π-conjugated long chain on N^N ligands) has an unusually small Egap of 0.74 eV which may facilitate an easier electronic transition than other complexes. Interestingly, introducing borazine ligands on parent complex can increase first hyperpolarizability (βtot), but further addition of borazine not lead to positive effect on increasing βtot values. Hybridizing borazine and benzene ligands significantly improve the second-order NLO properties. Thereinto, the maximum βtot of N-5 is found to be 27,648 a.u. which is about 22 times larger than parent complex. The origin of largest βtot values can be reasonably explained by the two-level model due to low transition energy and high transition dipole moment. Further, the UV–Vis spectrum analysis is performed for all complexes, indicating that substituting or hybridizing inorganic and organic ligands are feasible way to make the maximum absorption wavelength red-shifted toward longer wavelength. Our proposed complexes may be used as efficient infrared (IR) NLO materials because of there is no obvious absorption detected in the IR region. This work may offer valuable guidelines for designing high-performance second-order NLO materials.

Effects of Encapsulating Tube and Encapsulated Molecular Chain Length on the Second-Order Nonlinear Optical Responses of Carbon Nanotubes Filled with Head-To-Tail Polar Molecules

Effects of Encapsulating Tube and Encapsulated Molecular Chain Length on the Second-Order Nonlinear Optical Responses of Carbon Nanotubes Filled with Head-To-Tail Polar Molecules

Hyperpolarizabilities of Push-Pull Chromophores in Solution: Interplay between Electronic and Vibrational Contributions.

Contemporary design of new organic non-linear optical (NLO) materials relies to a large extent on the understanding of molecular and electronic structure-property relationships revealed during the years by available computational approaches. The progress in theory-hand-in-hand with experiment-has enabled us to identify and analyze various physical aspects affecting the NLO responses, such as the environmental effects, molecular vibrations, frequency dispersion, and system dynamics. Although it is nowadays possible to reliably address these effects separately, the studies analyzing their mutual interplay are still very limited. Here, we employ density functional theory (DFT) methods in combination with an implicit solvent model to examine the solvent effects on the electronic and harmonic as well as anharmonic vibrational contributions to the static first hyperpolarizability of a series of push-pull α,ω-diphenylpolyene oligomers, which were experimentally shown to exhibit notable second-order NLO responses. We demonstrate that the magnitudes of both vibrational and electronic contributions being comparable in the gas phase significantly increase in solvents, and the enhancement can be, in some cases, as large as three- or even four-fold. The electrical and mechanical anharmonic contributions are not negligible but cancel each other out to a large extent. The computed dynamic solute NLO properties of the studied systems are shown to be in a fair agreement with those derived from experimentally measured electric-field-induced second-harmonic generation (EFISHG) signals. Our results substantiate the necessity to consider concomitantly both solvation and vibrational effects in modeling static NLO properties of solvated systems.

Predicting the Second-Order Nonlinear Optical Responses of Organic Materials: The Role of Dynamics.

The last 30 years have witnessed an ever-growing application of computational chemistry for rationalizing the nonlinear optical (NLO) responses of organic chromophores. More specifically, quantum chemical calculations proved highly helpful in gaining fundamental insights into the factors governing the magnitude and character of molecular first hyperpolarizabilities (β), be they either intrinsic to the chromophore molecular structure and arising from symmetry, chemical substitution, or π-electron delocalization, or induced by external contributions such as the laser probe or solvation and polarization effects. Most theoretical reports assumed a rigid picture of the investigated systems, the NLO responses being computed solely at the most stable geometry of the chromophores. Yet, recent developments combining classical molecular dynamics (MD) simulations and DFT calculations have evidenced the significant role of structural fluctuations, which may induce broad distributions of NLO responses, and even generate them in some instances.This Account presents recent case studies in which theoretical simulations have highlighted these effects. The discussion specifically focuses on the simulation of the second-order NLO properties that can be measured experimentally either from Hyper-Rayleigh Scattering (HRS) or Electric-Field Induced Second Harmonic Generation (EFISHG). More general but technical topics concerning several aspects of the calculations of hyperpolarizabilities are instead discussed in the Supporting Information.Selected examples include organic chromophores, photochromic systems, and ionic complexes in the liquid phase, for which the effects of explicit solvation, concentration, and chromophore aggregation are emphasized, as well as large flexible systems such as peptide chains and pyrimidine-based helical polymers, in which the relative variations of the responses were shown to be several times larger than their average values. The impact of geometrical fluctuations is also illustrated for supramolecular architectures with the examples of nanoparticles formed by organic dipolar dyes in water solution, whose soft nature allows for large shape variations translating into huge fluctuations in time of their NLO response, and of self-assembled monolayers (SAMs) based on indolino-oxazolidine or azobenzene switches, in which the geometrical distortions of the photochromic molecules, as well as their orientational and positional disorder within the SAMs, highly impact their NLO response and contrast upon switching. Finally, the effects of the rigidity and fluidity of the surrounding are evidenced for NLO dyes inserted in phospholipid bilayers.

Butterfly-Shaped Nanographenes with Excellent Second-Order Nonlinear Optical Properties: The Synergy of B/N and Azulene.

Azulene, a simple polar polycyclic aromatic hydrocarbon with connected electron donor and acceptor (DA), ignites the hope of designing second-order nonlinear optical (NLO) molecular materials from pure nonpolar carbon nanomaterials. In this work, a butterfly-shaped nanographene (π-DA-π) was designed by incorporating azulene between two coronenes. One more electron in a N atom or one electron fewer in a B atom with respect to a C atom can polarize charge distribution in carbon nanomaterials, and further doping of B and N in the designed butterfly-shaped nanographene changes the system from π-DA-π to D-π-A, leading to strong NLO responses. For example, the largest static first hyperpolarizability even reaches 173.89×10-30 esu per heavy atom. The synergetic role of B, N and azulene in the nanographene is scrutinized, and such a doping strategy is found to provide an effective means for the design of carbon-based functional materials. The strong second-order NLO responses of these butterfly-shaped carbon-based nanographenes under external fields, for example, sum frequency generation and difference frequency generation, could inspire future experimental exploration.

Chemical Reactivity, Topological Analysis, and Second-Order Nonlinear Optical Responses of M3O@Al12N12: A Quantum Chemical Study

Chemical Reactivity, Topological Analysis, and Second-Order Nonlinear Optical Responses of M3O@Al12N12: A Quantum Chemical Study

Structurally modulated D-π-D-A(Semiconductor) anchoring dyes to enhance the tunable NLO response: a DFT/TDDFT quest for new photovoltaic materials

In this paper, we designed new dyes (D-1 to D-5) with anchoring groups to test their stability for semiconductor surfaces with silyl unit as dye-sensitized solar cells (DSSCs). To investigate their photovoltaic efficiency, density functional theory (DFT) calculations were conducted with these novel D-π-D-A(Semiconductor) type structures using N,N-dimethylaniline and benzenesulfonate as electron donor (D) and a thiophene as π-conjugated spacers, with different semiconductor units as anchoring and electron acceptor units. A new dye structure as a reference (Ref-D) had been extended from methyl orange (MO) molecular structure with electron acceptor semiconducting units to improve the electronic transmission and increased maximum absorbance (λmax) to derive these new dyes (D-1 to D-5). The computed λmax of MO was obtained by testing DFT functional to benchmark it with its experimental λmax. Out of these functionals, the Coulomb-attenuating Becke, 3-parameter, Lee–Yang–Parr (CAM-B3LYP) functional having hybrid and long range correlation with 6-31G + (d,p) produced a nearly similar λmax (459 nm) as of its experimental one (464 nm). Their ionization potentials (I1) ranged between 2.65 and 5.31 eV which showed their good electron-donating nature. Their λmax values ranged between 532 and 565 nm which had a considerable red shift from Ref-D (465 nm). The highest second-order nonlinear optical (NLO) response of 134,532 Debye-Angstrom−1 was noted for dye D-2 which had the shortest bandgap. The charge tripping analysis of all the dyes miscible with the Ref-D showed an exclusive shift from highest occupied molecular orbital (HOMO) of reference to lowest unoccupied molecular orbital (LUMO) of dye. The density of states (DOS) calculations were performed with the dye D-5 to show that electronic transmission was from the dye towards the semiconductor in an efficient way. The inclusion of thiophene as π-conjugated spacer resulted in a significant increase in absorbance peak at around 80 nm. The DFT computed results offered an insight upon design of novel DSSCs with silyl anchoring groups for improved stability and efficiency. The present research is in a kind of prediction to develop new NLO materials with D-π-A design involving semiconductor as anchoring groups to attach with a DSSC surface.

A Hybrid Antiperovskite with Strong Linear and Second-Order Nonlinear Optical Responses.

Antiperovskites have been studied since the 1980s because of their rich physical and chemical properties, but their linear and second-order nonlinear optical responses remain largely unknown. Here we report a new polar crystal, Cs3 Cl(HC3 N3 S3 ) (I), which features a quasi-one-dimensional antiperovskite structure composed of ClCs6 polyhedra and A-site [HC3 N3 S3 ]2- rings. To our best knowledge, this kind of antiperovskite structure is reported for the first time. Remarkably, I exhibits a very strong nonlinear optical response up to 11.4 times that of the benchmark KH2 PO4 and exceptionally large birefringence of 0.52. The first-principles calculations and structural analyses reveal that [HC3 N3 S3 ]2- is the "material gene" while the antiperovskite structural feature making it in a favorable arrangement. This work provides a new structural platform for the rational design of integrated optoelectronic materials with linear and second-order nonlinear optical responses.

Second-order nonlinear optical response of tunable GaAs/AlηGa1−ηAs quantum dot with Hulthén-Hellmann potential

In this letter, the nonlinear optical properties of quantum dots (QDs) of GaAs/AlηGa1−ηAs material limited by Hulthén-Hellmann potential (HHP) are studied theoretically. We use the Nikiforov-Uvarov to obtain the energy level and wave function of the system and discuss the influence of various factors on the system. The results show that the radius of QDs, the depth of limiting potential and the effective mass of electrons have a significant effect on the second-harmonic generation (SHG) of QDs.

New N-pyrimidinyl stilbazolium crystals for second-order nonlinear optics

We report a new π-conjugated cationic chromophore based on phenolic N-pyrimidinyl stilbazolium and its corresponding non-centrosymmetric crystals. The new cationic chromophore, HPR (4-(4-hydroxy-3-methoxystyryl)-1-(pyrimidin-2-yl)pyridin-1-ium), consists of a strong electron donor, the 4-hydroxy-3-methoxyphenyl group based on two electron-donating groups, and a strong electron acceptor, the N-pyrimidinyl pyridinium group based on two electron-withdrawing groups. The HPR chromophore possesses large molecular optical nonlinearity with first hyperpolarizability of up to 264 × 10−30 esu, which is significantly larger than that of the benchmark stilbazolium chromophores. In solution, the HPR chromophore showed co-existence of phenol- and phenolate-like forms with two absorption bands (∼460 and ∼610 nm, respectively). In the crystalline state, all HPR-based derivatives with three different counter anions, N2S (naphthalene-2-sulfonate), VBS (4-vinylbenzenesulfonate), and NBS (3-nitrobenzenesulfonate), exhibit a macroscopic second-order nonlinear optical response. HPR-N2S crystals exhibit non-centrosymmetric monoclinic Pn space group symmetry and large off-diagonal effective macroscopic optical nonlinearity (94 × 10−30 esu), which is approximately four times higher than that of the benchmark stilbazolium crystals. Therefore, the newly developed HPR-based crystals are highly promising materials for second-order nonlinear optical applications.

Maximizing the linear and nonlinear optical responses of alkaline tricyanomelaminate

High-performance bi-functional materials are in urgent demand for the next-generation integrated optical devices. In this work, we successfully synthesized the first tricyanomelaminate with bi-functional optical responses, namely Cs3C6N9•H2O (I), from its analogue Na3C6N9•3H2O by a facile ion exchange method. In contrast to Na3C6N9•3H2O, I realizes an optimal arrangement of π-conjugated (C6N9)3− anion groups in its crystal structure. As a result, the second-order nonlinear optical (NLO) response is greatly enhanced from nearly zero of Na3C6N9•3H2O to ∼9.8 × KH2PO4 of I. Furthermore, I exhibits a giant linear optical anisotropic response (i.e. birefringence) of 0.52 at the wavelength of 550 nm. Both responses are almost the largest among the inorganic compounds of π-conjugated rings, which indicates that I has great potential as a bi-functional optical crystal. Structural and theoretical analyses reveal the microscopic origin of excellent optical properties. This work would attract a lot of interests to the persistently neglected potential of tricyanomelaminates as linear optical and NLO crystals.

High-Efficiency Second-Harmonic and Sum-Frequency Generation in a Silicon Nitride Microring Integrated with Few-Layer GaSe

Silicon nitride (SiN) photonics platform has attributes of ultra-low linear and nonlinear propagation losses and CMOS-compatible fabrication process, promising large-scale multifunctional photonic circuits. However, the centrosymmetric nature of SiN inhibits second-order nonlinear optical responses in its photonics platform, which is desirable for developing efficient nonlinear active devices. Here, we demonstrate high-efficiency second-order nonlinear processes in SiN photonics platform by integrating a few-layer GaSe flake on a SiN microring resonator. With the pump of microwatts continuous-wave lasers, second-harmonic generation and sum-frequency generation with the conversion efficiencies of 849%/W and 123%/W, respectively, are achieved, which benefit from the ultrahigh second-order nonlinear susceptibility of GaSe, resonance enhanced GaSe-light interaction, and phase-matching condition satisfied by the mode engineering. Combining with the easy integration, the GaSe-assisted high-efficiency second-order nonlinear processes offer a new route to enriching already strong functionality of SiN photonics platform in nonlinear optics.

Aggregation induced emission (AIE)-active ferrocene conjugated linear π−extended multi donor−π−acceptor (D-D′-π-A) chromophores: Synthesis, structural, theoretical, linear and nonlinear optical studies

A new series of ferrocene (D) and methoxyphenyl (D′) conjugated D-D′-π-A push-pull chromophores [Fc-(RPh)C=CH–CH=CN-R’{R, R’ = H, CN (1), OCH3, CN (2), H, C6H4NO2 (3), OCH3, C6H4NO2 (4)}] were synthesized and spectroscopically characterized. The structure of the chromophore 3 was confirmed by single crystal X-ray diffraction studies, and it was crystallized in triclinic crystal system with P-1 centrosymmetric space group. In the crystal packing, several non-covalent interactions (H-bonding and C–H·····π) were observed. The thermal behaviour of the chromophores 3 and 4 has been investigated using thermogravimetric analysis and was found to be stable up to 230 °C. The solvatochromic studies of the chromophores 1–4 showed a positive solvatochromism with red-shift from non-polar to polar solvents due to the high dipolar excited state in the presence of strong electron-donor and acceptor moieties. The electrochemical performance of the chromophores revealed the one-electron transfer from the ferrocene to ferrocenium ion Fe2+⇌Fe3+. The chromophores 1–4 exhibited low fluorescence intensity and quantum yield as a consequence of the quenching nature of ferrocene, it was further enhanced through the aggregation-induced emission (AIE) process in THF/H2O mixtures by the restriction of intramolecular rotation (RIR), and the chromophores 1–4 showed 2 times higher quantum yield in the aggregated state. The second-order nonlinear optical response was attained by Kurtz-Perry powder technique. The second harmonic generation (SHG) efficiencies of the chromophore 4 was close to the standard KDP, owing to the presence of multi-donor [Ferrocene (D) and methoxyphenyl (D′)] and acceptor groups with extended π-conjugation. In addition, the mesomeric effect (+M) of the methoxy group makes an effective charge transfer process. The optical and nonlinear optical properties of the chromophores were further analyzed by density functional theory (DFT) with different functionals (B3LYP, CAM-B3LYP and LC-BLYP). The hyperpolarizability values were underestimates in the B3LYP-hybrid functional because of the corrected long-range charge transfer between donor and acceptor in the D-π-A systems. The frontier molecular orbital (FMO) level helps for better understanding the charge transfer, nonlinear optical (NLO) properties, and the calculated HOMO-LUMO energy levels were in good agreement with the experimental results.

Unraveling the Symmetry Effects on the Second-Order Nonlinear Optical Responses of Molecular Switches: The Case of Ruthenium Complexes.

Owing to their odd order, second-order nonlinear optical (NLO) responses are very sensitive to symmetry. Therefore, within hyper-Rayleigh scattering (HRS) technique, the symmetry impacts the amplitude of the molecular responses, the HRS first hyperpolarizability (βHRS), and the depolarization ratio (DR). Starting from a challenging octupolar structure bearing six ruthenium(II) ammine centers π-conjugated via quaterpyridyl moieties to a tris-chelated zinc(II) core, together with its Λ shape and one-dimensional analogues built by replacing one or two Ru-quaterpyridyl moieties with bipyridine moieties, (time-dependent) density functional theory calculations have been enacted to unravel the symmetry-NLO response relationships as well as their RuII/III redox-triggered switching effects. The one-dimensional and Λ-shaped NLOphores present βHRS values ∼3 times larger than those of the octupolar system, for both Ru oxidation states. However, using the few-state valence bond-charge transfer models demonstrates that the βHRS response of the octupolar complex cation can become larger than those of its one-dimensional and Λ-shaped analogues provided stronger donor-acceptor groups are employed. In parallel, the DRs decrease from a strong dipolar character (DR ≈ 6) for the one-dimensional chromophore to a weaker dipolar character (DR ≈ 5) for the Λ-shaped one and to a clear octupolar character (DR ≈ 1.7) for the last one. In all cases, the β responses originate mostly from metal-to-ligand charge transfer excited states, as revealed using a new scheme for analyzing the variations in electron density upon excitation. The RuII/III oxidations lead to a strong decrease in the βHRS responses, which is attributed to the loss of the donor character of the Ru centers and therefore to the reduction of the push-pull π-conjugation. These results demonstrate that the NLO contrast and the NLO switching behavior of these Ru cations are maintained for the different molecular symmetries. Finally, the character of the β responses of the oxidized species, as revealed by the DR values, further evidences a clear evolution from dipolar to octupolar NLOphores.

Alkylated, naphthalimide-containing ionic compounds with rich thermotropic behaviour and nonlinear optical response

Alkylated, naphthalimide-containing ionic compounds show rich phase transitions governed by the type (branched or linear) and length of the aliphatic chains. In film state, these compounds exhibit both third- and second-order nonlinear optical responses.

Au with sp3 Hybridization in Li5AuP2.

The achievement of new bonding patterns of atoms in compounds is of great importance, which usually induces interesting physical and chemical properties. Rich oxidation states, diverse bonding types, and unique aurophilic attraction endow gold (Au) as a distinctive element. Here we report that a pressure-induced Li5AuP2, identified by a swarm intelligence-based structural prediction, becomes the first example of Au with sp3 hybridization. The most remarkable feature of Li5AuP2 is that it contains various frameworks made by AuP4, AuLi4, LiP4, and blende-like Li-P units, exhibiting noncentrosymmetry. The charge transfer from Li to Au makes Au 6p orbitals activate and hybridize with the 6s one. On the other hand, Li donating electrons to P and polar Au-P covalence make the constituent atoms satisfy the octet rule, rendering Li5AuP2 with a semiconducting character and a large second-order nonlinear optical response in the near-infrared region. Our work represents a significant step toward extending the understanding of gold chemistry.