Nonlinear Optical Properties of Tri-nuclear Transition Metal Clusters M-(μ-S)s-M''''(M=Mo, W; M''''=Cu, Ag, Au)

Some of the transition metal cluster compounds show promising nonlinear optical (NLO) responsibilities1, which may apply in optical absorption, self-focusing, refraction and optical limiting effects. However, the traditional trial-and-error method is insufficient to achieve satisfactory novel material research. Theoretical investigations provide detailed understanding of the structure-property relationship and are helpful to the design and simulations of novel NLO materials. In this paper…     

Solvent induced enhancement of nonlinear optical response of graphdiyne

Flat and crystalline materials with exceptional nonlinear optical(NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices.Graphdiyne(GD),a new twodimensional(2 D) carbon allotrope,has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials.Here,we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents(alcohols) using a femtosecond Z-scan technique.The measured nonlinear optical refractive index is in the order of ~10^-8 cm²/W,which is approximately one order of magnitude higher than that of most 2 D materials.In particular,we find that different NLO responses can be observed from GD when dispersed in different solvents,with the strongest NLO response when dispersed in 1-propanol.It is proposed that some intrinsic properties of the solvents,such as the polarity and viscosity,could influence the NLO response of GD materials.Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.     

Synthesis and Study of Second-order Nonlinear Optical Properties of 3-Substituted-6- (substituted-phenylazo) coumarins

It has attracted a lot of attentions to synthesize and investigate the behaviors of organic second-order nonlinear optical (NLO) materials. [1,2] We have ever reported that acridine derivatives ,[3] 4-substituted-benzylideneoxazol-5(4H)-one[4] and 4,4′-di-styryl-biphenyl derivatives[5] possess good second-order NLO properties. Coumarin derivatives are good organic optical materials and azobenzene derivatives possess a higher second-order nonlinear polarization values, however, there are few reports about the study on the synthetic method, optical behavior, especially,second-order NLO properties of 3-substitued-6-(substituted-phenylazo) coumarin derivatives. Therefore, a series of the following compounds were prepared in order to investigate their NLO behavior.     

Second-order Nonlinear Optical Properties of a Series of Benzothiazole Derivatives

The second-order nonlinear optical (NLO) properties of a series of benzothiazole derivatives were studied by use of the ZINDO-SOS method.These chromophores are formed by a donor- π- bridge-acceptor system,based on a nitro group connected with benzothiazole as the acceptor and a hydroxyl-functional amino group as the donor.For the purpose of comparison,we also designed molecules in which nitrobenzene is an acceptor,The calculation results indicate that benzothiazole derivatives exhibit larger second-odrder polarizabilities than nitrobenzene derivatives.In order to clarify the origin of the NLO response of these chromophores,their electron properties were investigated as well.The benzothiazole derivatives are good candidates for application in electro-optical device due to their high optical nonlinearities,good thermal and photonic stability.     

Molecular and Crystal Structure of Trans -2- [p-N- methyl-N-(2'-hydroxyethyl)amino)phenyl-nitroethene?

1 INTRODUCTIONOver the past two decades, nonlinear optics is drawing steady attention because of its wide application proposed in the photonics-based technologies of optical signal processing, optical switching, optical sensing etc. A wide variety of materials including inorganic and organic crystals, thin films, and organic polymers and polymeric composites possess nonlinear optical (NLO) properties[1~3]. Among them, the polymer materials processed into thin films are expected to play a…     

Theoretical Investigation of Nonlinear Optical Properties of Organic and Transition Metal Hybrid Azobenzene Dendrimers

In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, second and third generation （G1, G2 and G3, respectively） are investigated by semi-empirical methods. The calculated results show that the nonlinear optical （NLO） properties of these organic dendrimers are mainly determined by the azobenzene chromospheres. Additionally, the values oft and y increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers （core-hybrid and branch-end hybrid according to the sites combined with transition metals） are simulated and discussed in detail in the framework of time-dependent density functional theory （TDDFT）. The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.     

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores

The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using the second-order MФller-Plesset （MP2） and density functional theory （DFT） methods with the basis set of 6-31＋G（d）. According to the calculated results, the relationship between the molecular static first hyperpolarizability （βμ） and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories： type Ⅰ with negative βμ and type Ⅱ bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between Ⅰ and Ⅱ chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.     

Bioapplications Manipulated by AIEgens with Nonlinear Optical Effect

The modern medicine requires precise diagnostic techniques while the fluorescent imaging shows great potential in such applications due to its excellent sensitivity and high resolution.However,conducting fluorescent imaging in deep-tissue is not so easy because most luminogens show short-wavelength excitation,which may undergo severe light scattering by the bio-tissue.The marriage of fluorescent imaging with nonlinear optical(NLO)effect can alleviate such adverse effects by utilizing NIR laser to reduce light scattering.On the other hand,scientists are enthusiastic in pursuing luminescent materials,which can match well with NLO application.Aggregation-induced emission(AIE)materials exhibit huge advantages in such aspect not only because of its high luminescent efficiency in aggregate state but also due to its excellent photo-stability(a key factor to meet laser application because of its ultrahigh energy density).Inspired by this,many interesting and meaningful works have sprung up based on AIE luminogens with NLO effect in recent years,and for such reason,it motivates us to summarize them to give a systematic presentation.Here,we first give a brief introduction of the principle of NLO effect.Secondly,the strategies for improving the NLO effect of AIE materials,such as increasing molecular conjugation,introduction of donor-acceptor effect,induction of centrally asymmetric array of AIE molecules in crystals and introduction of intermolecular interactions are clarified.In the final part,we also present the multiple applications of AIEgens with NLO effect in cell imaging,deep-tissue tumor and brain blood vessel imaging and photodynamic therapy.We believe,with this review,the topic will attract more attention from the scientists in multi-science field to accelerate the development of AIE materials in biomedical applications.     

Recent Advances in Nonlinear Optical Phosphate Materials

In recent years, motivated by the discovery of deep-UV(wavelengths below 200 nm) nonlinear optical(NLO) phosphates, Ba_3P_3O_(10)X(Cl, Br), phosphates have entered into a passionate research era. In this review, recently discovered phosphate materials containing different anionic groups, i.e., isolated [PO_4], [P_2O_7] dimer, [P_3O_(10)] trimer, and [PO_3]∞ chain, are summarized, including their syntheses, structures, NLO performances and properties. Especially phosphates with short absorption edges in the deep-UV region and good SHG efficiency are introduced in detail. We hope that this work will present a clear view of the crystal chemistry of phosphates and promote the discovery of new high-performing second-order NLO materials to meet the urgent needs in laser science.     

PREPARATION AND SECOND-ORDER OPTICAL NONLINEARITY OF NOVEL PHENOXYSILICON NETWORKS BY SOL-GEL PROCESS**

 Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H₂O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d₃₃) of 10-?～10-8 esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120℃) indicated that these films exhibit high d33 stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.     

噻唑类生色分子的电子光谱和非线性光学性质

在B3LYP/6-31+G*水平上对八种噻唑类生色分子的电子光谱与二阶非线性光学性质茁进行计算研究. 结果表明, 含羟乙基、烷氧乙基、氟乙基和氨乙基活性基团的噻唑类分子具有大的β值, 为1.6×10-28 esu左右, 与实验结果基本一致. 气相中的最大吸收波长λmax位于480-488 nm范围内. 含羟乙基活性基团的噻唑分子, 随溶剂极性增大, λmax有红移趋势.     

Switchable Nonlinear Optical Properties of η(5)-Monocyclopentadienylmetal Complexes: A DFT Approach

Density functional theory (DFT) calculations have been carried out to investigate the switching of the second-order nonlinear optical (NLO) properties of η(5)-monocyclopentadienyliron(II) and ruthenium(II) model complexes presenting 5-(3-(thiophen-2-yl)benzo[c]thiophen-1-yl)thiophene-2-carbonitrile as a ligand. The switching properties were induced by redox means. Both oxidation and reduction stimulus have been considered, and calculations have been performed both for the complexes and for the free benzo[c]thiophene derivative ligand in order to elucidate the role played by the organometallic fragment on the second-order NLO properties of these complexes. B3LYP, CAM-B3LYP, and M06 functionals were used for our calculations. The results show some important structural changes upon oxidation/reduction that are accompanied by significant differences on the corresponding second-order NLO properties. TD-DFT calculations show that these differences on the second-order NLO response upon oxidation/reduction are due to a change in the charge transfer pattern, in which the organometallic iron and ruthenium moieties play an important role. The calculated static hyperpolarizabilities were found to be strongly functional dependent. CAM-B3LYP, however, seems to predict more reliable structural and optical data as well as hyperpolarizabilities when compared to experimental data. The use of this functional predicts that the studied complexes can be viewed as acting as redox second-order NLO switches, in particular using oxidation stimulus. The β(tot) value of one-electron oxidized species is at least ～8.3 times (for Ru complex) and ～5.5 times (for Fe complex) as large as that of its nonoxidized counterparts.     

Theoretical study on the second-order nonlinear optical properties of asymmetric spirosilabifluorene derivatives

The equilibrium geometries of four asymmetric spirosilabifluorene derivatives are optimized by means of the DFT/B3LYP method with the 6-31G* basis sets in this paper. On the basis of the optimized structures, the electronic structure and second-order nonlinear optical properties are calculated by using time-dependent density-functional theory (TDDFT) based on the 6-31G* level combined with the sum-over-states (SOS) method. The results show that these compounds possess remarkably larger molecular second-order polarizabilities than typical organometallic and organic compounds, and replacement of a carbon atom with nitrogen within the conjugated substituent has a great influence on the second-order nonlinear optical properties. Analysis of the main contributions to the second-order polarizability suggests that charge transfer from the z-axis directions plays a key role in the nonlinear optical response. These compounds have a possibility to be excellent second-order nonlinear optical (NLO) materials from the standpoint of large beta values, small dipole moment, high transparency, and small dispersion behaviors.     

Systematic study of the structure-property relationship of a series of ferrocenyl nonlinear optical chromophores

A series of novel nonlinear optical (NLO) chromophores 1-4 incorporating the ferrocenyl (Fc) group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran (TCF) derivatives as electron acceptors are presented. The use of a constant Fc donor and varied acceptors and bridges makes it possible to systematically determine the contribution of the conjugated bridge and the acceptor strength to chromophore nonlinear optical activity. The X-ray crystal structures of all four chromophores allow for the systematic investigation of the structure-property relationship for this class of molecules. For example, the crystal structures reveal that both cyclopentadienyl groups in the ferrocenyl donor contribute to the electron donating ability. The first-order hyperpolarizabilities beta of these chromophores, measured by hyper-Rayleigh scattering (HRS) relative to p-nitroaniline are reported. These beta values are compared to those calculated by density functional theory (DFT). The excellent agreement between the theoretical and experimental beta values demonstrates that a linear relation exists between the hyperpolarizability and the bond length alternation. An electrooptic coefficient, r(33), of approximately 25 pm/V at 1300 nm, for compound 4, incorporated into a polymer matrix, is competitive with organic chromophores. Moreover, this r(33) is more than 30 times larger than the previously reported value for an organometallic chromophore in a poled polymer matrix. This work not only underscores the potential for Fc donor moieties, which have been underutilized, but also demonstrates that experimental characterization and theoretical simulations are now congruent, viable methods for assessing potential performance of NLO materials.     

Palladium Catalyzed Synthesis of Fluorine-containing 3-Biaryl-1-ferrocenyl-2-propene-1-one

In the last two decades, molecular-based second-order nonlinear optical (NLO) chromo-phores1, have attracted much interest because of their potential applications in emerging 2opto-electronic technologies. These efforts have mainly focused on organic systems.More recently, organometallic molecules have been investigated as well. In comparisonto common organic molecules, they offer a large variety of novel structures3, . The 4possibility of high environmental stability, and divers…     

2H NMR calculations on polynuclear transition metal complexes: on the influence of local symmetry and other factors

It is now well-known that (2)H solid-state NMR techniques can bring a better understanding of the interaction of deuterium with metal atoms in organometallic mononuclear complexes, clusters or nanoparticles. In that context, we have recently obtained experimental quadrupolar coupling constants and asymmetry parameters characteristic of deuterium atoms involved in various bonding situations in ruthenium clusters, namely D(4)Ru(4)(CO)(12), D(2)Ru(6)(CO)(18) and other related compounds [Gutmann et al., J. Am. Chem. Soc., 2010, 132, 11759], which are model compounds for edge-bridging (μ-H) and face-capping (μ(3)-H) coordination types on ruthenium surfaces. The present work is in line with density functional theory (DFT) calculations of the electric field gradient (EFG) tensors in deuterated organometallic ruthenium complexes. The comparison of quadrupolar coupling constants shows an excellent agreement between calculated and observed values. This confirms that DFT is a method of choice for the analysis of deuterium NMR spectra. Such calculations are achieved on a large number of ruthenium clusters in order to obtain quadrupolar coupling constants characteristic of a given coordination type: terminal-D, η(2)-D(2), μ-D, μ(3)-D as well as μ(4)-D and μ(6)-D (i.e. interstitial deuterides). Given the dependence of such NMR parameters mainly on local symmetry, these results are expected to remain valid for large assemblies of ruthenium atoms, such as organometallic ruthenium nanoparticles.     

13顶点金属碳硼烷结构和非线性光学性质的DFT研究

采用量子化学密度泛函理论(DFT)B3LYP/6-31G(d)方法,对4,1,6-MC2B10H1213顶点金属碳硼烷几何构型进行优化,结合有限场(FF)方法计算了它们的极化率和二阶非线性光学(NLO)系数.结果表明,十个13顶点金属碳硼烷分子中1a～6a的二阶NLO系数与其构型纵向扩张呈现相同的规律.分子的前线分子轨道能级差越小,其二阶NLO系数越大.对于不同自旋态的同种金属碳硼烷分子,其偶极矩值为高自旋态大于相应的低自旋态,极化率和二阶NLO系数与自旋多重度没有一致的对应规律,自旋多重度对NLO性质影响不大.     

Au(I)...Ag(I) metallophilic interactions between anionic units: theoretical studies on a AuAg4 square pyramidal arrangement

We have studied theoretically the organometallic compound (NBu4)2[Au(3,5-C6F3Cl2)2Ag4(CF3CO2)5], whose dianionic part displays a AuAg4 square pyramidal arrangement based on closed-shell Au(I)...Ag(I) interactions between two monoanionic fragments. DFT/B3LYP, ab initio Hartree-Fock (HF), and second-order M?ller Plesset perturbation theory (MP2) calculations have been carried out for simplified model systems. Model system [AuPh2]-...[Ag4(CO2H)5]- (C1) has been chosen from DFT results as an appropriate model for the study of the interactions. The four Au(I)...Ag(I) interactions and two additional C...Ag(I) interactions are observed when dispersion-type interactions are considered in the level of theory (MP2) displaying a metallophilic attraction between two anionic units. The study of model C2 (similar to C1 but with minimized C...Ag(I) interactions) permits the study of the Au(I)...Ag(I) interactions separately, which confirms the existence of stabilizing Au(I)...Ag(I) interactions around 13 kJ.mol(-1) each.     

Mechanism Insights into Second-Order Nonlinear Optical Responses of Anionic Metal Clusters

We present the first-principle calculations on the electronic excitations and second-order properties in solution phase of two typical inorganic trinuclear anionic clusters, [MoCu₂S₄(SPh)₂]²⁻ and [Mo₂CuS₄]¹⁻(edt)₂(PPh₃) (edt=1,2-ethanedithiolato) in the framework of density functional theory (DFT). The computed excitation energies are in good agreement with the outcome of the measurements. The predicted values of the molecular quadratic hyperpolarizabilities are of the comparable order of those of the typical organometallic chromophores. We demonstrate the significant contributions to the second-order responses from the charge transfers between the metal centers (MMCT) which are ascribed to the direct metal–metal bonding interactions in these two charged clusters. This meaningful ligand-independent mechanism for the second-order response largely relates to metal–metal bonding strength, and the understanding will benefit to the future design of the new-generation molecular based nonlinear optical materials and optoelectronic devices by means of the conscious tuning of metal–metal interactions and metal-core structures of inorganic polynuclear clusters.