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Buchwald-Hartwig amination of aryl halides with solvent-free condition was used for the preparation of electron donors with high density of electron cloud. Organic second order nonlinear optical chromophore ZML-c based on this electron donor was designed and synthesized. And chromophore ZML-ref without modified groups was also prepared as the contrast. Their delocalized energy levels were estimated by UV–Vis. spectra. Their thermal properties were studied by thermogravimetric analysis (TGA). Obviously, chromophore ZML-c showed lower delocalized energy levels and lower thermal decomposition temperature (just about 160 °C). The poled films showed the largest electro-optic (EO) coefficients of 23.5 pm/V and 10.6 pm/V respectively for chromophore ZML-c and ZML-ref. These results indicate that effective modification in indole ring may be a promising way to drastically change the electro-optical features of the titled compounds and show a direction of designing new electron donor in the field of nonlinear optical materials. [ABSTRACT FROM AUTHOR]

Organic electro-optic (EO) materials have been widely explored and used in the fabrication of microwave photonic devices. Their principal advantages are the follows: lower half-wave voltage, wider bandwidth, lower cost and more convenience of integration. Organic second order nonlinear optical (NLO) chromophores, as the core of the organic EO devices, define the key technological parameters: EO efficiency, long term stability, solubility and optical losses. In the present review article, the use of D–π–A chromophore molecules with polycyclic electron donors based on julolidinyl structure is reported and discussed. Significant improvement of electron donating ability and appropriate isolated effect are shown. Future perspectives of the application of such kind of NLO chromophores are considered. [ABSTRACT FROM AUTHOR]

Polymers based on N-phenyl maleimide, N-4-propargyl methoxy phenyl maleimide and methyl methacrylate was synthesized. High glass temperatures 183, 179, 159 °C respectively for P 1 , P 2 and P 3 were achieved. EO polymer P 3 –C 1 , P 3 –C 2 and P 3 –C 3 with about 30 wt% chromophore loading density were prepared by attaching Chromophore C 1 , C 2 and C 3 to polymer P 3 using copper-catalyzed Huisgen cycloaddition reactions in mild reaction conditions and high yield. Among the EO polymers, P 3 –C 3 showed us the best solubility in normal solvents and suitable glass temperature. EO films based on EO polymer P 3 –C 3 showed us large EO coefficient of 50 pm/V @1310 nm and good long-term stability, 85% EO activity was kept after annealing at 85 °C for 200 h. [ABSTRACT FROM AUTHOR]

Abstract: Two novel nonlinear optical (NLO) chromophores with 4-hydroxycarbazole as the electron donor were successfully designed and synthesized. The 4-hydroxycarbazole had two reaction sites where the isolated groups were introduced to the chromophores. The prepared chromophores were characterized by MS, 1H NMR and UV–vis spectra. Poled films of the chromophores doped in APC afforded the maximum electro-optic (EO) coefficient (r 33) of 40pm/V at 1310nm. This result was better than the similar chromophores reported using carbazole and aniline derivates as electron donor, which indicated that the introduction of isolated groups suppressed the dipole–dipole interaction between chromophores effectively and could aid the alignment of chromophores and improve the EO activity. This had been further demonstrated by the crystal structure analysis. [Copyright &y& Elsevier]

Three chromophores with tricyanofuran and tricyanopyrroline electron acceptors were synthesized and doped in high glass transition temperature ( T) polymer poly( N-(4-acetoxylphenyl)maleimide-co-styrene, NAPMI-co-ST). The electro-optic (EO), optical, and thermal properties of the doped poly(NAPMI-co-ST) were characterized and discussed. After being corona poled under 12 kV, this high T polymer material showed excellent EO activity and thermal stability. The highest EO coefficient ( r) reached 48.2 pm V (1,310 nm) and could remain 90 % of the original value for 100 h at 85 °C. The EO coefficient was relatively higher compared with other high T EO polymers. The thermal stability was also very good and the manufacture process was convenient and applicable for device fabrication. [ABSTRACT FROM AUTHOR]

A new nonlinear optical chromophore with strong electron-withdrawing acceptor and rigid-flexible dendron was synthesized. An electro-optic (EO) attenuated total reflectance modulator was prepared to measure the EO coefficient of the films. Modification of the tricyanopyrroline chromophore with rigid-flexible dendron group provided reduction of dipole-dipole interactions and improvement of its solubility. As the chromophore loading increased, there was a great improvement on the macroscopic EO response of the polymeric materials obtained by incorporating this chromophore as a guest in amorphous polycarbonate. The largest EO coefficient was 42 pm/V at 1310 nm. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

New tricyanopyrroline (TCP) chromophores with rigid-flexible dendron were prepared for second-order nonlinear optical (NLO) application. The chromophores were fully characterized using ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry. Thermal gravimetric analysis (TGA) revealed that the chromophores had excellent thermal stability. Large λ and high solvate chromic effects revealed that the chromophores had large second-order optical nonlinearity. The electro-optic coefficients ( r) were measured in the chromophores-doped poly(bisphenol A carbonate) films at the fundamental wavelength of 1310 nm, and the highest γ achieved was 217 pmV. Copyright © 2010 John Wiley & Sons, Ltd. Modification of the TCP chromophore with bulky groups provides reduction of dipole-dipole interactions, thus great improvement of the macroscopic electro-optic (EO) response was achieved by incorporating these chromophores as a guest into amorphous polycarbonate (APC). Furthermore, the modificated chromophore possesses good processability and exhibits high thermal decomposition temperature. [ABSTRACT FROM AUTHOR]

Organic electro-optic (EO) materials have been widely studied and used in microwave photonic devices, due to their advantages in half-wave voltage, bandwidth, low cost and ease of integration. Nonlinear optical (NLO) chromophores, as the core of organic EO materials, can directly decide the characters of organic EO materials, including large EO activity, long term stability, solubility and optical loss. Auxiliary donors have attracted great attentions in NLO chromophores for their strong electron donating ability and significant isolation effect. This feature article describes the application of auxiliary donor in NLO chromophores, including the EO activities, optical characters, stability, crystal structures and machinability. [ABSTRACT FROM AUTHOR]

Dual D-Pi-A nunchaku-like structure chromophore was designed and synthesized to improve electro-optic (EO) materials׳ EO coefficients ( r 33 ) and long term stability by a simple doping system. The r 33 values of poled APC/10% DIMER1 and APC/20% DIMER1 are 23 pm/V and 45 pm/V respectively. After annealed at 85 °C for 500 h, the poled film of APC/20% DIMER1 can retain more than 85% of its initial r 33 value. All these characters showed us superior prospects of application in EO devices. Chromophore DIMER1 also showed us good thermal stability; its decomposition temperature (Td) was higher than 280 °C, which is enough for its application in the EO devices. Also chromophore DIMER1 had good solubility in amorphous polycarbonate (APC); it could be dissolved in APC at high loading density (25%). [ABSTRACT FROM AUTHOR]

Compared with traditional inorganic second-order nonlinear optical (NLO) materials, organic second-order NLO materials have many advantages in bandwidth, dielectric constant, half-wave voltage, electro-optic (EO) coefficients, processability, and material cost. Due to their potential applications in telecommunications, computing, detection, terahertz generation, and construction of functional photonic crystals, organic NLO materials have been widely studied for several decades. Currently, the poling efficiency and long-term stability are the largest obstacles for the application of organic NLO materials. At the molecular level, these problems are mainly caused by the strong dipole–dipole intermolecular interactions between the NLO chromophores with D-π-A structures. In the molecular design of the polymer system, modification of the chromophores is considered to be an efficient pathway to solve this problem. Since 2009, many studies have been performed by our group to reduce the strong dipole–dipole intermolecular interactions between the chromophores. In this review, the development of organic NLO materials in recent years is summarized, including the following: 1) a brief introduction of organic second-order NLO materials, 2) the requirements of NLO materials for applications in devices, 3) optimization of the first-order hyperpolarizability of NLO chromophores, 4) the optimization of the chromophore loading parameters (N, ), and 5) improvements of the stabilities of organic NLO materials. • Organic second order NLO materials was briefly introduced. • Requirements of NLO materials for applications in devices were discussed. • Optimized method for first-order hyperpolarizability and loading parameters of chromophore were discussed. • Method for improving stability of organic NLO materials was included. [ABSTRACT FROM AUTHOR]

Abstract: Novel NLO chromophore with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group in electron bridge was prepared for investigating the NLO character. Chromophore FTC-wl was characterized using UV–Visible spectra, nuclear magnetic resonance, and mass spectrometry and showed us excellent thermal stability. EO films prepared by poly(bisphenol A carbonate) polymer doped with this chromophore at different content had been poled to afford the highest electro optic coefficients (r33) of 28pm/V. [Copyright &y& Elsevier]

Abstract: Novel organic second-order nonlinear optical (NLO) chromophore with a large flexible rigid isolated group was prepared. The NLO properties were measured in solution and PMMA polymer films. The first order hyperpolarizabilities were equal to 4×10−28 esu and 7×10−29 esu at 1064nm Nd:YAG laser wavelength in solvent and polymer, respectively and these results are in agreement with quantum chemical calculations. Moreover, this chromophore has high thermal stability when thermal decomposition temperature is 270°C. Electrostatic interactions of the chromophores were effectively reduced by isolated group. No apparent change of the shape of UV absorption spectra versus concentration was found. [Copyright &y& Elsevier]

Novel nonlinear optical (NLO) chromophore based on 6-(pyrrolidin-1-yl)-1H-indole as the electron donor group was designed and synthesized. The molecular structure of this chromophore was characterized by 1 H NMR spectra, 13 C NMR spectra, and MS spectra. The delocalized energy level was estimated by UV–Vis. spectra. The thermal property was studied by thermogravimetric analysis (TGA). The poled films containing chromophores ZML-1 with a loading density of 10 wt% in amorphous polycarbonate (APC) afford an average electro-optic (EO) coefficient ( r 33 ) of 19 pm/V at 1310 nm. Compared to the reported aniline-based chromophore ( r 33 = 12 pm/V) analogues, chromophore ZML-1 exhibits enhanced electro-optical activity. [ABSTRACT FROM AUTHOR]

Benchmark chromophore C1 and counterpart chromophore C2 with the same electron donor and acceptor was designed and synthesized to compare their different electro-optic coefficients and long term stability by doping system. The electro-optic coefficient of a poled film containing 25 wt% of C1 doped in amorphous polycarbonate (25 wt% C1 /APC) afforded a value of 22 pm/V at 1310 nm, while 25 wt% C2 /APC afforded a value of 60 pm/V. After annealing at 85 °C for 500 h, the poled film of 25 wt% C2 /APC could retain more than 85% of its initial r 33 value. In contrast, only 75% of the initial r 33 value of the poled film of 25 wt% C1 /APC was kept after 300 h. The excellent thermostability and its good temporal stability in APC made C2 a favorable candidate for practical application. [ABSTRACT FROM AUTHOR]

Abstract: A novel nunchaku-like organic second order nonlinear optical chromophore containing a D–π–A backbone and a rigid biphenylene unit was prepared. The UV–vis absorption spectra studies demonstrated that the large rigid structure could suppress dipole–dipole interactions effectively. The electro-optic coefficient of a poled film containing 20% wt of the new dye doped in amorphous polycarbonate afforded a value of 39 pm/V at 1310 nm. Compared with results obtained from a similar D–π–A chromophore without the rigid isolated group, the new dye gave better performance. Moreover, the electro-optic film prepared with the new dye gave greater temporal stability, compared to a similar D–π–A doped poled film that was reported previously. These results indicated that the introduction of a biphenylene group could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores. [Copyright &y& Elsevier]

Novel nonlinear optical (NLO) chromophore using benzo[b]furan moiety and trifluoromethyl-substituted tricyanofuran as the electron donor and acceptor respectively was designed and prepared. The structure of the novel chromophore was determined by NMR spectra, and the photophysical properties were studied via UV-vis spectra. The thermal decomposition temperature (T d)value of the obtained NLO chromophore reached to 212 °C, which endow the chromophore with good thermal stability during the materials processing. The nonlinearity of the chromophore was evaluated through theoretical calculation and electro-optic (EO) activity test, and the highest EO coefficient (r 33) was determined to 28 pm/V at the loading density of 25 wt% in polymethyl methacrylate. • Novel benzofuran-based nonlinear optical chromophore was designed and synthesized. • The acceptor was unexpected linked to the β -position of furan in the chromophore. • The present chromophore exhibited go0d thermal stability (T d reached to 212 °C). • The maximum EO coefficient of the reported chromophore reached to 28 p.m./V. [ABSTRACT FROM AUTHOR]

Abstract Novel nonlinear optical chromophores JC-TCF and JC-FTCF using tetramethyljulolidine-based coumarin as the electron-donor and tricyanofuran derivatives as the electron acceptors were designed, synthesized and investigated. The obtained chromophores own good solubility in common solvents, and good compatibility with host polymers. The chromophores also have good thermal stability, and the decomposition temperature exceed 200 °C. The UV–vis spectra indicated that JC-TCF and JC-FTCF possess good intramolecular charge transfer ability. Density functional theory (DFT) was used to study the energy gap and first-order hyperpolarizability(β). After contact poling, the guest-host polymer films of polymethyl methacrylate containing 20% wt JC-TCF and 20% wt JC-FTCF exhibited the highest electro-optic coefficient (r 33) up to 40 p.m./V and 76 p.m./V respectively, and the results indicated the chromophores' microscopic β value could be effectively translated to macroscopic EO activity, and the tetramethyljulolidine-based coumarin could be an useful candidate in the development of NLO materials. Highlights • Julolidine-based coumarin was used as electron-donor in design of NLO materials. • The coumarin's good electron-donation ability obviously enhanced the NLO properties. • The obtained materials exhibited better EO activity compared to the FTC chromophores. • The maximum EO activity of reported NLO chromophores reached to 76 p.m./V. • Coumarin could be an useful candidate in the development of NLO materials. [ABSTRACT FROM AUTHOR]

One novel chromophore C based on 4,4′-bis(diethylamino) benzophenone donor and CF 3 -Ph-TCF acceptor was synthesized. Alkoxy isolation group was introduced also. Cyclic voltammetry measurements showed that the new chromophore C had a much smaller energy gap (ΔE = 1.25 eV) than chromophore A and B. UV–Vis absorption indicated that obvious red shift (more than 100 nm) obtained for chromophore C. The doped film C containing CF 3 -Ph-TCF chromophore showed a r 33 value of 235 pm/V at the concentration of 25 wt% which is much higher than that of the TCF based chromophore A (149 pm/V) and B (163 pm/V). The thermal stability were high enough (>200 °C) to be further fabricated in devices and good EO property make application possible. [ABSTRACT FROM AUTHOR]

A series of high performance chromophores P1 P3, based on N -(4-dibutylaminophenyl) tetrahydroquinolinyl or julolidinyl donors, and phenyl-trifluoromethyl-tricyanofuran acceptors linked together via π-conjugation through thiophene or vinylene moieties as the bridges, have been designed and synthesized. Density functional theory (DFT) was used to calculate the HOMO-LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Chromophores P1 and P3 had good thermal stabilities with glass transition temperature higher than 110 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r 33 ) in poled polymers with rational chromophore designs. In electro-optic activities, the poled films of P1/APC, P2/APC and P3/APC afforded r 33 values of 223, 283 and 278 pmV −1 , respectively, at 1310 nm at the doping concentration of 25 wt%, which showed significant enhancement over the similar EO polymer systems previously reported. [ABSTRACT FROM AUTHOR]

Two series of highly efficient nonlinear optical chromophores A1-C1 and A2-C2 based on the julolidinyl donors and tricyanofuran or phenyl-trifluoromethyl-tricyanofuran acceptors (CF 3 -Ph-TCF) linked together via π-conjugation through thiophene or pyrrole or tetraene moieties as the bridges, have been synthesized and investigated. The ultraviolet absorption, solvatochromic, thermal stabilities and electro-optic activities of these chromophores were systematically studied to illustrate structure-performance relationships within the six chromophores. All the chromophores exhibited good thermal stabilities with the decomposition temperatures (T d ) higher than 200 °C. Appropriate combination of the π-conjugated bridge, electron-donor and electron-acceptor as well as the isolated group in the chromophores plays an important role in achieving larger electro-optic activities. Exemplified by the chromophore A2 with CF 3 -Ph-TCF acceptor, it gave a very large r 33 value of 223 pmV −1 at 1310 nm at the doping concentration of 25 wt%. [ABSTRACT FROM AUTHOR]

Nonconventional luminophores without long conjugated structures have received increasing attention due to their outstanding biocompatibility, easy preparation, environmental friendliness, and potential applications in sensing and imaging. The phenomena of aggregation emission, such as concentration-enhanced emission, aggregation-induced emission, excitation-dependent luminescence, and prevailing phosphorescence, are caused by molecular conformation and molecular packing. Herein, we briefly review the traditional luminophores represented by fused aromatic rings, and introduce the revolutionary concept of aggregation induced emission (AIE) in non-traditional luminescence and its applications in optics, biology, and other fields. The concept of the AIE can be applied to understand this phenomena in the field of non-traditional luminescence, in which non-aromatic systems contain electron-releasing and withdrawing parts, such as amine, amide, nitrile, imine, hydroxyl, carbonyl, etc. Moreover, we also address two mechanisms of cluster triggered emission (CTE) and crosslink-enhanced emission (CEE). Based on the reviewed data, we can conclude that the electron overlap caused by aggregation and through-space conjugation (TSC) have a profound impact on unconventional luminescence. We believe that this review would serve as a useful guide to design and application of unconventional luminophores, while the current challenges and future perspectives are also discussed. • The article introduced the revolutionary concept of aggregation induced emission (AIE) in non-traditional luminescence and its applications in optics, biology, and other fields. • Two mechanisms of cluster triggered emission (CTE) and crosslink-enhanced emission (CEE) were discussed in the field of non-aromatic luminescence systems. • In general, the three theories (AIE, CTE, CEE) are attributed to intramolecular motion restriction (RIM), electron overlap caused by aggregation and through-space conjugation (TSC). • We believe that this review would serve as a useful guide to design and application of unconventional luminophores, while the current challenges and future perspectives are also discussed. [ABSTRACT FROM AUTHOR]

Abstracts In this work, a series of novel second order nonlinear optical chromophores modified by heteroatom-groups in electron-donor has been synthesized and systematically investigated. The resulting nonlinear optical chromophores exhibited both good thermal stability and good solubility in common organic solvents. UV–Vis spectra and density functional theory calculations were carried out to investigate the influence of heteroatom-groups on the electro-optic activities. The results revealed that increasing the electron-donor strength will not always improve the nonlinear optical activity of chromophore. There is a best match for electron-donor and acceptor. As to electro-optic activities, the doped polymer film- d3 displayed the highest electro-optic coefficient value of 37 pm/v at the doping concentration of 25 wt%. These results indicated that the nonlinear optical activities could be enhanced by finding the best match for electron-donor and acceptor in chromophore design. [ABSTRACT FROM AUTHOR]

A novel chromophore based on N -(4-dibutylaminophenyl)tetrahydroquinolinyl donor group was synthesized to compare with traditional chromophores based on either diethylaminophenyl or triarylaminophenyl donor groups. Cyclic voltammetry measurements showed that the new chromophore had a much smaller energy gap than the structurally related chromophores. Density functional theory calculations suggested that the molecular quadratic hyperpolarizability (μβ) value of tetrahydroquinolinyl chromophore is 65% and 110% larger than that of either the diethylaminophenyl or triarylaminophenyl chromophores, respectively. The doped film containing the tetrahydroquinolinyl chromophore showed an r 33 value of 126 pm/V at the concentration of 25 wt% which is much higher than the electro-optic activity of the diethylaminophenyl derived chromophore (39 pm/V) and six times higher than that of the traditional triarylaminophenyl chromophore (19 pm/V). The tetrahydroquinolinyl chromophore possesses much higher thermal stability (with its onset decomposition temperature above 280 °C) than those of commonly used alkyl chromophores. [ABSTRACT FROM AUTHOR]

A series of second-order nonlinear optical chromophores containing an identical π-bridge and electron acceptor but different, aromatic amine electron-donating groups have been synthesized and systematically investigated. The donors studied here include traditional donors carbazole, triphenylamine and N , N -diethylaniline and novel donor phenothiazine, phenoxazine and N -(4-methoxyphenyl)phenoxazine. The ultraviolet absorption, solvatochromic, redox properties, density functional theory calculations, thermal stabilities and electro-optic activities of these chromophores were systematically studied to compare the strength of the donors and illustrate the structure–performance relationships within six chromophores. The results show that the new donors have stronger electron-donating ability than traditional donors. Moreover, they show reduced energy gap, much larger molecular quadratic hyperpolarizability (μβ) and r 33 value. Exemplified by the N -(4-methoxyphenyl)phenoxazine chromophore, it showed nearly three times higher μβ and more than four times higher r 33 value than that of the N -hexylcarbazole containing chromophore. [ABSTRACT FROM AUTHOR]

Two novel chromophores based on the phenoxazine (chromophore L1) or phenothiazine (chromophore L2) donor, and tricyanofuran acceptors linked together via thiophene as the bridges have been synthesized and systematically investigated. Cyclic voltammetry measurements showed that chromophore L1 had smaller energy gap than chromophore L2 due to the stronger electron-donating ability. Moreover, Density functional theory calculations suggested that the β value of chromophore L1 is 17% larger than that of chromophore L2. The doped film containing the chromophore L1 showed an r 33 value of 49 pm/V at the concentration of 25 wt% which is two times higher than the EO activity of the chromophore L2 (23 pm/V) and the traditional aryl chromophore (10–20 pm/V). High r 33 value, high thermal stability (onset decomposition temperatures higher than 220 °C) suggests the potential use of the new chromophore in nonlinear optical materials. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel second-order nonlinear optical chromophores containing additional heteroatoms in donor moieties has been synthesized and systematically characterized. The resulting nonlinear optical chromophores exhibited both good thermal stability (the decomposition temperature in the range of 249 °C–275 °C) and good solubility in common organic solvents such as chloroform, acetone and N, N-dimethyl formamide. In order to investigate the influence of additional heteroatom on the electro-optic activities, UV–Vis spectra and density functional theory calculations were carried out. The results revealed that the donor derived from m-phenylenediamine had higher electron density compared with other three donors. As to electro-optic activities, the doped polymer film-C displayed the highest electro-optic coefficient value of 31 pm/v at the doping concentration of 20 wt%. All these results indicated that the nonlinear optical activities could be enhanced by introducing suitable additional heteroatoms into donor moiety. [Copyright &y& Elsevier]

One novel second order nonlinear optical chromophore based on benzoxazin donor and tricyanovinyldihydrofuran acceptor linked together via thiophene bridge has been synthesized and characterized. According to cyclic voltammetry measurement, chromophore Z showed low energy gap. In addition, chromophore Z displayed good thermal stability with the onset decomposition temperature over 221 °C. The electro-optic coefficient of a poled film containing 25 wt% of chromophore Z doped in polymethylmethacrylate afforded a value of 64 pm/V at 1310 nm. The result showed that chromophore Z , which had good thermal stability and high r 33 values after poling in films, was a promising candidate for practical use. [ABSTRACT FROM AUTHOR]