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To study the effect of polymeric structures on second‐order nonlinear optical properties, polysiloxanes materials based on azobenzene as chromophore have been designed and synthesized successfully. Herein, the siloxane monomer is directly bonded to azobenzene units by palladium catalysis, which avoids the influence of flexible chains on the photoelectric properties of azobenzene. According to the different positions of azobenzene units in the polymers, it is divided into side‐chain, main‐chain, and alternative‐type polymers. The chemical structures of obtained polysiloxanes are confirmed by nuclear magnetic resonance spectra and mass spectra. Three polymers present high thermal decomposition temperatures and the medium glass transition temperatures. The effects of polymeric structures on the second‐order nonlinear properties are compared. The main‐chain polysiloxane possesses the highest thermal stability because of its rigid architecture. The side‐chain polysiloxane shows the fastest isomerization transformation rate due to the large free volume. Besides, the alternative polysiloxane displays the best second‐order nonlinear performance with second harmonic generation coefficient (d33) value of 47.6 pm V−1, which is 3 times higher than the side‐chain one. [ABSTRACT FROM AUTHOR]

In the past few decades, many new infrared (IR) second‐order nonlinear optical (NLO) materials have been prepared by various synthetic methods to satisfy the growing market demand. However, few ones have the high potentials to be applicable since their comprehensive NLO properties cannot meet the standards, which include a series of indicators like large NLO effects, high laser‐induced damage thresholds (LIDTs), phase matchability, high thermal stability, good growth habit, and so on. Considering the available IR NLO materials' disadvantages and the market requirements, it is necessary to continuously explore new high‐performance ones. Hitherto, lots of chalcogenides, halides, and oxides have been explored as IR NLO materials. Recently, researchers have found that the combination of two or more structural units into one structure may achieve good NLO properties, as evidenced by the fact that diverse materials with multiple anions are receiving growing interest. Specifically, chalcohalides are highly promising as they may combine the advantages of chalcogenides and halides, viz. large NLO coefficients and wide IR transparency of the former, and large band gaps and high LIDTs of the latter. To address the status of chalcohalides, this review focuses on the newest progresses on this topic (mainly from the last five years), including ternary chalcohalides, quaternary chalcohalides, salt‐inclusion chalcohalides, and rare‐earth chalcohalides. Here we summarize and analyze their compositions, crystal structures, NLO properties, and discuss the structure‐property relationship. Finally, the development prospects for NLO chalcohalides are given. [ABSTRACT FROM AUTHOR]

Substitution of the diglyme ligand of [Eu(hfa)3(diglyme)] (where hfa is hexafluoroacetylacetonate) with a simple 1,10-phenanthroline leads to a six-fold increase of the product μβEFISH, as measured by the Electric-Field-Induced Second Harmonic generation (EFISH) technique. Similarly, [Eu(tta)3(1,10-phenanthroline)] (where Htta is 2-thenoyltrifluoroacetone) is characterized by a large second-order NLO response. Both 1,10-phenanthroline europium complexes have great potential as multifunctional materials for photonics. [ABSTRACT FROM AUTHOR]

Dendronized hyperbranched polymers (DHPs) can provide advantages for both hyperbranched polymers and dendrimers, making them a promising structure platform for high‐performance second‐order nonlinear optical (NLO) materials. Herein, a new A3+B2‐type DHP (HP2) is reported through facile and efficient [2+2] cycloaddition polymer postfunctionalization, in which tetracyanobutadienyl‐based moieties are introduced as the main chromophores while isophorone‐bridged moieties serve as the isolation chromophores. Benefiting from this unique hyperbranched structure design, the measured second‐harmonic generation coefficient of HP2 can reach up to 96.6 pm V−1 with high thermal stability, making it a good material candidate for second‐order NLO applications. [ABSTRACT FROM AUTHOR]

The chirality of metal-organic cages holds enormous potential for novel applications in diverse fields, while it is relatively rare to employ such asymmetric units for the construction of noncentrosymmetric materials. Herein, by self-assembling the 4,4',4''-nitrilotribenzoic acid (H3NBA) with bis(cyclopentadienyl)-zirconium dichloride (Cp2ZrCl2, Cp = η5-C5H5) in different solvent conditions, we have obtained three hierarchical packing modes of metallo-tetrahedra with distinct spatial symmetry groups (designated as Zr-α, Zr-β, and Zr-γ). Among them, Zr-α employs a simple cubic arrangement and is a common centrosymmetric superstructure, which consists of a pair of equimolar metallo-tetrahedra enantiomers in its unit cell. While Zr-β results in conglomerates with spontaneous resolution without using any resolving agents, giving rise to two enantiopure entities separately (Zr-β-P, Zr-β-M). More importantly, Zr-γ breaks the inversion center of symmetry and crystallizes into a racemic yet non-centrosymmetric superstructure with face-centered cubic packing mode. Based on the non-centrosymmetric nature, the hierarchical superstructure Zr-γ displayed good second harmonic generation activities. This work presents a successful instance wherein the reaction solvent induces the modulation of intermolecular packing mode to afford non-centrosymmetric solid materials, which can greatly promote the development of noncentrosymmetric solid (NCS) materials., (© 2024 Wiley‐VCH GmbH.)

Substitution of the diglyme ligand of [Eu(hfa)3(diglyme)] (where hfa is hexafluoroacetylacetonate) with a simple 1,10-phenanthroline leads to a six-fold increase of the product μβEFISH, as measured by the Electric-Field-Induced Second Harmonic generation (EFISH) technique. Similarly, [Eu(tta)3(1,10-phenanthroline)] (where Htta is 2-thenoyltrifluoroacetone) is characterized by a large second-order NLO response. Both 1,10-phenanthroline europium complexes have great potential as multifunctional materials for photonics.

A series of four V-shaped methylpyrimidinium salts bearing diphenylamino-electron-donating groups appended at various pyrimidine positions were designed. These chromophores were obtained by regioselective N(1) monomethylation by methyl methanesulfonate of the pyrimidine core. Linear optical properties were studied experimentally and electronic properties were further completed by (TD)-DFT calculations. The second-order nonlinear optical (NLO) properties were also studied using electric field induced second harmonic generation (EFISH) method in chloroform, and all pyrimidinium salts exhibited μβ0>1000×10-48 esu. The 2,4-disubstituted pyrimidinium core is preferred over 4,6-disubstitution as it enhances the NLO response and increases the dipole moment. (E,E)-2,4-Bis[4-(diphenylamino)styryl]-1-methylpyrimidin-1-ium methanesulfonate appears to be the best NLO-phore in chloroform in the series (μβ0=2500×10-48 esu) and a figure of merit μβ0/MW= 3.4 10-48 esumolg-1. [ABSTRACT FROM AUTHOR]

As a second-order nonlinear optical phenomenon, the bulk photovoltaic (BPV) effect is expected to break through the Shockley-Queisser limit of thermodynamic photoelectron conversion and improve the energy conversion efficiency of photovoltaic cells. Here, we have successfully induced a strong flexo-photovoltaic (FPV) effect, a form of BPV effect, in strained violet phosphorene nanosheets (VPNS) by utilizing strain engineering at the h-BN nanoedge, which was first observed in nontransition metal dichalcogenide (TMD) systems. This BPV effect was found to originate from the disruption of inversion symmetry induced by uniaxial strain applied to VPNS at the h-BN nanoedge. We have revealed the intricate relationship between the bulk photovoltaic effect and strain gradients in VPNS through thickness-dependent photovoltaic response experiments. A bulk photovoltaic coefficient of up to 1.3 × 10 -3 V -1 and a polarization extinction ratio of 21.6 have been achieved by systematically optimizing the height of the h-BN nanoedge and the thickness of VPNS, surpassing those of reported TMD materials (typically less than 3). Our results have revealed the fundamental relationship between the FPV effect and the strain gradients in low-dimensional materials and inspired further exploration of optoelectronic phenomena in strain-gradient engineered materials.

In this study, two new dendronized nonlinear optical (NLO) polymers were synthesized with high FTC chromophore loading density by introduction of high generation chromophore dendrons on the side chains. Due to their suitable molecular weights, both of them possessed good solubility in common solvents. They also inherited the advantages of dendrimers (large NLO coefficient), especially for PG2 whose NLO coefficient d33 value was as high as 282 pm·V-1. Also, PG2 had a good temporal stability with 80% of its maximum value being retained at the temperature as high as 129 °C. [ABSTRACT FROM AUTHOR]

With increasing research interests in the field of light-matter interactions, various methods have been developed for regulating nonlinear optical (NLO) materials. However, the design and synthesis of organic molecular materials for second-order nonlinear optics remain a great challenge because of the strict requirement of the materials to possess a noncentrosymmetric structure. In this work, two benzothiadiazole (BTD) derivatives referred to as BTD-H and BTD-F were synthesized, and their NLO properties in the crystalline states were studied. It was found that introducing fluorine into the BTD backbone effectively tuned the crystal packing styles of BTD derivatives to a noncentrosymmetric system for effective second-order NLO responses. Such a strategy to induce the noncentrosymmetric structure by introducing the fluorine atoms and halogen interactions may provide guidance for future engineering of organic NLO molecular materials. [ABSTRACT FROM AUTHOR]

The second-order nonlinear optical (NLO) properties of iridium(III) complexes having two cyclometalated 2-phenylpyridines and curcumin or tetrahydrocurcumin as ancillary ligand have been investigated both in solution and as guest in a polymeric organic matrix. In solution, these complexes are characterized by a significant second-order NLO response, as determined by the Electric Field Induced Second Harmonic (EFISH) technique, like the related complex with acetylacetonate. Whereas the low second-harmonic generation response of a composite film of [Ir(2-phenylpyridine)2(acetylacetonate)] in polymethyl methacrylate was not stable and fell down to zero upon turning off the electric field. A good and stable response was obtained with a film based on the iridium(III) complex bearing two cyclometalated 2-phenylpyridines and curcumin.

Whereas there is an increasing amount of reports on the second-order nonlinear optical (NLO) and luminescence properties of tetradentate [N2O2] Schiff base–zinc complexes, the study of zinc complexes having two bidentate [NO] Schiff-base ligands is relatively unexplored from an NLO point of view. This work puts in evidence that the known chiral bis{2-[(R)-(+)-1-phenylethyliminomethyl]phenolato-N,O}zinc(II) complex is a fascinating multifunctional molecular inorganic–organic hybrid material characterized by interesting second-order NLO and luminescent properties in solution. The emissive properties of the organic 2-(R)-(+)-1-phenylethyliminomethyl]phenol proligand are greatly enhanced upon coordination to the inorganic Zn(II) center.

Abstract: A simple adduct from tin tetraiodide SnI4 and octasulfur S8, SnI4⋅(S8)2 (1), is obtained employing a facile reaction. The combination of Sn4+ ions with d10 electron configuration, acentric SnI4 tetrahedra, and lone‐pair effects of S8, makes 1 a phase‐matchable infrared NLO crystal with a moderate second‐harmonic generation (SHG) response and a very high laser‐induced damage threshold (LIDT), which is well confirmed by the DFT calculations. [ABSTRACT FROM AUTHOR]

In order to explore the application of organic conjugated small molecules in bioimaging, a novel functional chromophore with A-π-D-π-A structure (Cr-3) was synthesized through Knoevenagel condensation reaction, consisting of carbazole unit as electron donor and cyanoacetic acid as electron acceptor groups. To improve the water solubility of this conjugated molecule, three carboxyl groups were introduced to chromophoreCr-3. Compared to the traditional D-π-A chromophores, chromophoreCr-3showed the great improvement in water with the solubility of 2000 ppm. Also, the thermal stability of chromophoreCr-3was also studied. The thermal decomposition temperature (Td) ofCr-3was approximately 180°C, which was attributed to the dehydration of the carboxyl groups. Though the second harmonic generation (SHG) effect was not very high, it is large enough for the detection of SHG signal in water solution (0.28 pm/V). [ABSTRACT FROM AUTHOR]

A novel cationic cyclometallated Ir(III) complex, namely [Ir(C^N-ppy-4-CH CHC 6 H 4 NEt 2 ) 2 (N^N-bpy-CH CHC 6 H 4 NEt 2 )][PF 6 ] (ppy = 2-phenylpyridine; bpy = 2,2′-bipyridine), was prepared and well characterized. Its good second-order NLO response, as determined in solution by the EFISH technique, and its interesting two-photon absorption activity, as measured by the Z-scan technique in the femtosecond case, make it a good candidate for application in photonics and biomedicine. [ABSTRACT FROM AUTHOR]

The effect on the second-order nonlinear optical properties of the nature of the π-delocalized moiety in the position 5 of a 1,3-di(2-pyridyl)benzene cyclometallated to a platinum(II) center was investigated. The influence of the substitution of a double bond with a triple bond as bridge between a triphenylamino group and the cyclometallated phenyl ring was studied and turned out to be negligible. Remarkably, the novel easily-prepared platinum(II) complex with a cyclometallated 5-styryl-1,3-di(2-pyridyl)benzene is characterized by a good second-order NLO response, as determined in solution by the EFISH technique; it is a good candidate for application in photonics. [ABSTRACT FROM AUTHOR]

The linear and second-order nonlinear optical (NLO) properties of two pyrene-pyridine chromophores, namely, 4-(pyren-1-yl)pyridine (L1) and 4-(2-(pyren-1-yl)ethyl)pyridine (L2), were investigated and modulated by performing protonation/deprotonation cycles or by complexation to d10 metal centers such as Zn(II) and Cu(I) to form the monomeric [Zn(CH3CO2)2(L1)2] complex and the [CuI(L2)]n coordination polymer, respectively. The structures of L1, L2, [Zn(CH3CO2)2(L1)2] and [CuI(L2)]n were determined by means of single-crystal X-ray diffraction studies. The NLO response, measured by the electric-field-induced second harmonic generation (EFISH) technique, was positive for both chromophores and showed an inversion of the sign after exposure to HCl vapors. This process was completely reversible and the original values were restored by simple exposure to NH3 vapors. Coordination of L1 to Zn(II) also resulted in a negative NLO response, although smaller in magnitude compared to the protonated form, due to the weak Lewis acidity of the “Zn(CH3CO2)2” fragment. The results were also interpreted on the basis of DFT/TDDFT calculations.

This short review outlines the main results obtained in the field of molecular materials based on zinc coordination compounds for second-order nonlinear optics. It presents an overview of the main classes of second-order nonlinear optical (NLO) active complexes bearing monodentate, bidentate, tridentate, or tetradentate π-delocalized ligands such as substituted stilbazoles, bipyridines, phenanthrolines, terpyridines, and Schiff bases. Macrocyclic ligands such as porphyrins and phthalocyanines are not covered. This paper shows how coordination to the Zn(II) center of π-delocalized nitrogen donor ligands produces a significant enhancement of their quadratic hyperpolarizability. Dipolar complexes are mainly presented, but octupolar zinc complexes are also presented. The coverage is mainly focused on NLO properties that are measured at the molecular level, working in solution, by means of the electric field-induced second harmonic generation (EFISH) or the hyper-Rayleigh scattering (HRS) techniques.

Dendrimers are considered as a promising family of organic second-order nonlinear optical (NLO) polymers because of their well-defined structures, easily modified peripheral functional groups, interior branches and central cores. In order to obtain NLO materials with high performance, dendrimer structures have been optimized in the past years, such as the 'branch only' and the 'root containing' type dendrimers. This feature article highlights the achievements in exploring the rational design of dendrimers, partially marked by their macroscopic NLO performance. [ABSTRACT FROM AUTHOR]

New electro optical chromophore with 4-(bis(2-hydroxyethyl)amino)-2,6-dipropoxybenzaldehyde as electron donor was synthesized and characterized by1H NMR spectra and mass spectra. Four hydroxyl groups were introduced to the electron donor, which could be easily reacting with carboxyl, isocyanate, anhydride, and so on, to afford us second-order nonlinear optical polymers. ChromophoreTshowed us good solubility in common solvents, thermal stability (above 200°C) and expected Uv-vis absorption. In this article, polymethyl methacrylate (PMMA) doped with chromophoreTat different loading density was prepared to second- order nonlinear optical films by spin coating. These films showed us large second-order nonlinear optical coefficients, 13.5, 19.7, 24.3, and 26.4 pm/V for the second-order nonlinear optical films with chromophore loading density of 10 wt%, 20 wt%, 30 wt%, and 40 wt%, respectively. [ABSTRACT FROM PUBLISHER]

Chiral metal halide perovskites with intrinsic asymmetric structures have drawn increased research interest for the application of second-order nonlinear optics (NLO). However, designing chiral perovskites with the features of a large NLO coefficient, high laser-induced damage thresholds (LDT), and environmental friendliness remains a major challenge. Herein, we have synthesized two chiral hybrid bismuth halides: (R/S-MBA) 4 Bi 2 Br 10 spiral structure microplates, templated by chiral (R/S)-methylbenzylamine (R/S-MBA). The as-grown chiral lead-free perovskite spiral microplates exhibit a recorded second harmonic generation (SHG) effect with a large effective second-order NLO coefficient ( d eff ) of 11.9 pm V -1 and a high LDT of up to 59.2 mJ cm -2 . More importantly, the twisted screw structures show competitive circular polarization sensitivity at 1200 nm with an anisotropy factor ( g SHG-CD ) of 0.58, which is about 3 times higher than that of reported Pb-based chiral perovskites. These findings provide a new platform to design multifunctional lead-free chiral perovskites for nonlinear photonic applications.

The synthesis of crystalline homochiral MOF materials is very important for their potential application in enantioselective processes and asymmetric catalysis. In this paper, four novel zinc based chiral boron imidazolate frameworks (BIFs), Zn 2 [BH(2-eim) 3 ](BA) 2 (OH) (BIF-132-BA , 2-eim ​= ​2-ethylimidazolate, BA ​= ​benzoate), Zn[HBH(2-ipim) 3 ](OHBA)(Ac) (BIF-133-OHBA , 2-ipim ​= ​2-isopropylimidazolate, OHBA ​= ​ o -hydroxybenzoate, Ac ​= ​acetate), Zn[HBH(2-ipim) 3 ](PHBA)(Ac) (BIF-133-PHBA , PHBA ​= ​ p -hydroxybenzoate), and Zn[HBH(2-ipim) 3 ](DHBA)(Ac) (BIF-133-DHBA , DHBA ​= ​2,4-dihydroxybenzoate) were prepared via solvothermal synthesis. Single-crystal X-ray diffraction demonstrated that the existence of hydrogen bonds between adjacent chains results in two different structure features of BIF-131 : a chiral ladder-like 1D chain (BIF-133-OHBA) and two supramolecular 2D layers (BIF-133-PHBA and BIF-133-DHBA). Then, the optical activities of as-synthesied crystals were preliminarily studied by circular dichroism (CD) spectroscopy. In addition, because they crystallized in noncentrosymmetric space groups, the powder second-harmonic generation (SHG) measurements were carried out and the SHG response of BIF-133-PHBA was almost comparable to potassium dihydrogen phosphate (KDP). Four novel zinc based chiral boron imidazolate frameworks (BIFs), were prepared from the potential chiral substrate of tridentate boron imidazoate ligands. The solid-state CD spectra indicate that the as-synthesized crystals of are optically active. Furthermore, due to their noncentrosymmetric space group, samples of BIF-133-PHBA were selected for the SHG measurements, which is the first example for BIFs used in NLO materials. [Display omitted] • Four novel zinc based chiral boron imidazolate frameworks (BIFs), were prepared from the potential chiral substrate of tridentate boron imidazoate ligands. • The solid-state CD spectra indicate that the as-synthesized crystals of are optically active. • The first examples for BIFs used in NLO materials. [ABSTRACT FROM AUTHOR]

Abstract: We studied the second-order NLO properties in solution of various Ir(III) acetylacetonate complexes bearing a substituted cyclometallated 4-styryl-2-phenylpyridine (ppy-4-styryl-R, with R = NEt2, OMe, H, NO2) with the EFISH technique. The dipole moments were evaluated by Density Functional Theory (DFT) calculations. We have also investigated the Second Harmonic Generation (SHG) of composite films based on the various cyclometallated Ir(III) complexes dispersed and oriented in a polymethylmethacrylate (PMMA) matrix. [Copyright &y& Elsevier]

[Display omitted] • Terthiophene with a pull Si-based group shows second-order NLO activity. • Si-based group impacts only on the nonlinear properties of the molecule. • Si-based pull unit ensures nonlinearity/transparency trade-off to terthiophene unit. In this paper we report an investigation on the linear and nonlinear properties of a non-classic push-pull molecule, based on the molecular design concept of a 'donor-free' chromophore. Herein a terthiophene unit acts both as a donor and a π-spacer group and a tris(trimethylsiloxy)silane substituent as an acceptor group. This latter can represent a model of a fragment of silica surface and it has been compared with a classic acceptor unit like the nitro group. The 'donor-free' chromophores have also been compared to more typical push-pull chromophores by replacing the terthiophene unit with the N,N-dimethylamino donor group. Despite the silane group only slightly impacts on the electronic and linear properties of the terthiophene, our results reveal high μβ EFISH values for silane-functionalized derivatives producing a NLO activity stronger than that of the nitro substituted. Finally, the investigated 'donor-free' NLO-phore exhibits interesting physical properties relevant in term of nonlinearity/transparency trade-off, a highly desired requirement for second-order NLO materials. [ABSTRACT FROM AUTHOR]

The enhancement of the vibrational sum‐frequency generation (SFG) signal from molecules adsorbed on metallic nanopillars excited at a resonance frequency matching their localized surface plasmons is reported. The nanopillars stand vertically on a metal surface and possess two plasmon modes that can be selectively excited by either the incident visible laser beam, or the generated SFG beam itself. This nanostructured platform increases the molecular SFG signal of a monolayer by two orders of magnitude. The localization and the geometry of the two plasmon modes enables to probe the molecules adsorbed onto the vertical nanopillar wall, or on the top of it, or on the flat surface between the pillars, selectively. In practice, this spatial selectivity is set by switching the polarization of the visible and SFG beams at resonance. Owing to the largely improved sensitivity combined with a specific spatial selectivity, plasmon‐enhanced SFG boosts the versatility of second‐order vibrational SFG spectroscopy or microscopy. This makes them promising platforms in the development of analytical molecular devices. [ABSTRACT FROM AUTHOR]

Abstract: The linear and nonlinear optical properties of MnHg(SCN)4 (MMTC) single crystal are studied by the Density Functional Theory (DFT) method. The optimized lattice constant can be compared with the experimental value. The DFT method is used to calculate the hyperpolarizability of MMTC single crystal and the second harmonic generation coefficient is studied by the ionic group theory. The obtained second harmonic generation coefficient is d 15=17.14–25.91pm/V, which is in agreement with the experimental result (19.8–28.8pm/V). It is found that the greatest contribution for the second harmonic generation of MMTC crystal is from HgS4 anionic group. [Copyright &y& Elsevier]

As DAST (1-methyl-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridinium p-toluenesulfonate) derivatives for improved crystal stability and inhibition of crystal water inclusion, 1-(2-hydroxyethyl)-4-(2-{4-[bis(2-hydroxyethyl)amino]phenyl}ethenyl)pyridinium salts 2 (2a-2l) and 1-(2-hydroxyethyl)-4-{2-[4-(diethylamino)phenyl]ethenyl}pyridinium salts 3 (3a-3l) were synthesized and their properties were investigated. Salts 3 were found to have no crystal water, and the cation with one hydroxyethyl group was effective to eliminate water inclusion in the crystals. Although the melting points of 2 were lower than those of the corresponding 3, decomposition temperatures of these chromophores were above 250°C indicating their good thermal stability. Crystals of m-nitrobenzenesulfonate salt 3f was obtained without crystal water and showed SHG activity. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis, linear and second-order nonlinear optical (NLO) properties of a series of ionic indoline and N,N-dimethylaniline based chromophores are described. In order to optimise the second-order NLO response of these compounds four basic variations to the molecules and/or their environments have been implemented and their effect studied. These consist of changes to the counter-anion (from iodide to p-toluenesulfonate to naphthalene-2-sulfonate), variation of the solvent polarity [dimethyl sulfoxide (DMSO) to methanol (MeOH) to chloroform (CHCl3)], annelation of the acceptor unit (pyridinium to quinolinium) and a change in the donor used (N,N-dimethylaniline to indoline). It is found that the strongest enhancements to the quadratic NLO response occur when the acceptor moiety is changed from pyridinium to quinolinium, while compounds with an indoline donor group are slightly superior to those containing dimethylaniline as donor. There is no real discernable change in the first hyperpolarizability on altering either the counter-anion or solvent used for the measurements. X-ray crystallographic data were obtained for two of the compounds, and they are found to pack in centrosymmetric fashion, and have a small degree of twisting between the donor and acceptor. From this data it is seen that there is a general agreement between the degree of bond-length alternation (BLA) and the NLO response of the chromophores, and that for charged chromophores such as these a BLA value of approximately 0.1Å is optimal. [ABSTRACT FROM AUTHOR]

Abstract: N,N′-(2-Hydroxy-propane-1,3-diyl)-bis(5-nitrosalicylaldiminato-N,O)-copper(II) has been synthesized. The crystal structure has been determined by X-ray diffraction analysis, and linear optical characterization has been determined by UV–vis spectroscopy. It was found that the molecule under investigation has solvatochromic behaviour in the UV region, implying non-zero microscopic first hyperpolarizability. To reveal the microscopic nonlinear optical (NLO) properties, the static first hyperpolarizabilities (β) and the electric dipole moments (μ) were evaluated by using the ab initio finite field (FF) method. According to the results of the FF calculations, the synthesized compound exhibits non-zero β values, and it might have microscopic NLO behaviour. [Copyright &y& Elsevier]

DAST (1-methyl-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridinium p-toluenesulfonate) is a promising crystalline material for electro-optic applications and THz-wave generation. DAST powder for crystal growth was prepared by two synthesis routes including the conventional one and we confirmed that purity of DAST powder became indistinguishable after proper recrystallization even using conventional synthesis process. The highest solubility of DAST was found for methanol-acetonitrile mixture, and DAST crystal growth in this mixture or methanol-ethanol mixture gave thicker crystals than those grown in methanol. Thus, morphological control of DAST single crystals was found to be possible by varying solvents. [ABSTRACT FROM AUTHOR]

A side-chain second-order nonlinear optical (NLO) poly(ester-imide) (PEI) possessing good organo-solubility, excellent film-forming property, high glass transition temperature (186 °C) and high thermal stability was synthesized. The NLO chromophore orientation in the polymer film achieved via corona poling showed high long-term stability at elevated temperatures up to 120 °C. A reflective electro-optic (EO) light modulator using this polymer as the EO material was fabricated and encoded electrical signals onto reflected light successfully. The EO coefficient γ33 of the PEI layer in the EO modulator was determined to be 11.5 pm/V at 650 nm by an improved attenuated-total-reflection method. [Copyright &y& Elsevier]

Five new square-pyramidal coordination compounds L · Zn(acac)2 (1–5) (acac=acetylacetonate; L is a variety of thiosemicarbazones: p-dimethylaminobenzaldehyde thiosemicarbazone (1), p-hydroxy-o-methoxybenzaldehyde thiosemicarbazone (2), p-methoxybenzaldehyde thiosemicarbazone (3), p-hydroxybenzaldehyde thiosemicarbazone (4), o-hydroxybenzaldehyde thiosemicarbazone (5)) have been synthesized and characterized by 1H NMR, IR, and elemental analysis. All of these compounds exhibit pretty wide transparent ranges in the visible region. Their electronic absorption spectra have been studied experimentally, and theoretically by ZINDO/S calculation. The latter has also been utilized to estimate the extent of intramolecular charge transfer. The MOPAC software package has been used to evaluate their first-order molecular hyperpolarizabilities (β). All β values of the five coordination compounds are larger than those of the corresponding thiosemicarbazones. And complex 1 shows the largest β0 (39.1×10−30 esu) in the series. [Copyright &y& Elsevier]

A new measurement technique has been developed to determine the magnitude of magnetic-dipole contributions to the second-order nonlinearity of oriented solutions of chiral molecules. The method is based on a modified electric-field induced second-harmonic generation technique. [Copyright &y& Elsevier]

The second-order nonlinear optical (NLO) properties of iridium(III) complexes having two cyclometalated 2-phenylpyridines and curcumin or tetrahydrocurcumin as ancillary ligand have been investigated both in solution and as guest in a polymeric organic matrix. In solution, these complexes are characterized by a significant second-order NLO response, as determined by the Electric Field Induced Second Harmonic (EFISH) technique, like the related complex with acetylacetonate. Whereas the low second-harmonic generation response of a composite film of [Ir(2-phenylpyridine)2(acetylacetonate)] in polymethyl methacrylate was not stable and fell down to zero upon turning off the electric field. A good and stable response was obtained with a film based on the iridium(III) complex bearing two cyclometalated 2-phenylpyridines and curcumin. [ABSTRACT FROM AUTHOR]

Whereas there is an increasing amount of reports on the second-order nonlinear optical (NLO) and luminescence properties of tetradentate [N2O2] Schiff base–zinc complexes, the study of zinc complexes having two bidentate [NO] Schiff-base ligands is relatively unexplored from an NLO point of view. This work puts in evidence that the known chiral bis{2-[(R)-(+)-1-phenylethyliminomethyl]phenolato-N,O}zinc(II) complex is a fascinating multifunctional molecular inorganic–organic hybrid material characterized by interesting second-order NLO and luminescent properties in solution. The emissive properties of the organic 2-(R)-(+)-1-phenylethyliminomethyl]phenol proligand are greatly enhanced upon coordination to the inorganic Zn(II) center. [ABSTRACT FROM AUTHOR]

In this work, we systematically designed and comparatively analyzed the geometric structures, electronic absorption spectra, polarizabilities, first hyperpolarizability (β tot) and dynamic hyper-Rayleigh scattering response of circular Pd(II)-nanohoop complexes with 2,2′-bipyridine-embedded CPPs ligand and curved complexes decorated with alkyl tether accompanied by linear counterparts via quantum chemical calculations. Correlating results demonstrated that in comparison to conventional linear species, nanohoop ligand coordinated with metal Pd(II) can achieve remarkably improved quadratic nonlinear optical (NLO) coefficient, whereas are not accompanied by a certain degree of bathochromic shift in the absorption band. This phenomenon effectively overcomes the trade-off between good transparency and high second-order NLO response. Intriguingly, alkyl tether modified curved complexes own the largest quadratic NLO responses in our case, even the conjugation is broken by alkyl chain modified. Noteworthily, further extending phenylene backbone will not yield any positive effect on the enhancement of their β tot values for circular and linear systems once the number of phenylene reaches a certain degree, suggesting that size-dependent effect can be deemed to an effective approach to obtain the desired NLO response. Additionally, the polarizable environment has a significant influence on second-order NLO behavior, especially an accelerated trend changing from gas phase to solid phase. Overall, we hope these results can enrich the cognition into the NLO structure-function correlations based on metal nanohoop complexes and provide new avenue toward coping with trade-off between good transparency and high NLO performance. Image 1 • Nanohoop ligand coordinated with metal Pd(II) can deal with trade-off between transparency and high NLO performance. • Maximum first hyperpolarizabilities have been obtained for curved complexes decorated with alkyl chain. • The linear and nonlinear optical coefficients of all studied complexes are size-dependent. [ABSTRACT FROM AUTHOR]