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Two covalent organic framework (COF) films supported by a glass substrate were obtained by solvothermal reaction of an electron donor with electron acceptor 1,3,5-triformylbenzene (TF) or 2,4,6-triformylphloroglucinol (TFP), respectively. The TFP-BD film exhibits a nonlinear absorption coefficient of −3.01 × 105 cm GW−1. The TFP-BD film can aggregate electrons around the connected monomer through the D–A effect due to its highly polar and electronegative carbonyl oxygen atoms, thereby modulating the electronic structure of the COFs. This work provides a novel approach for the structural modulation of optical materials with strong nonlinearity. [ABSTRACT FROM AUTHOR]

Abstract A series of quinazolinone derivatives have been designed and synthesized based to the structure of donor-π-acceptor-π-donor (D-π-A-π-D). In order to obtain materials with good third-order nonlinear optical response that we have introduced some electron-donating groups such as triarylamine, cumene, and N,N-dimethylaniline into the 8- or 2,8- position of the quinazolinone. Compared with the parent QZ-1 , the target compounds showed a significant red shift. Electrochemical data and theoretical calculation showed that the introduction of the donor group that extended the conjugation length of the molecule and reduced the HOMO/LOMO band gap which promoted the intramolecular charge transfer (ICT). Z-scan results demonstrated that as the electron-donating ability of the donor group increased, the synthetic materials exhibit stronger nonlinear optical response. Among them, QZB-1 incorporating with two triarylamine groups has a γ value of 34.616 × 10−32 esu, which is up to 38 times of the parent structure. The results of this study have guiding significance for the molecular design of nonlinear optical materials. Graphical abstract Image 1 Highlights • A series of Quinazolinone Derivatives were synthesized. • The introduction of electron-donating group can improve the HOMO energy level of molecule, thereby reducing the band gap. • The quinazolinone derivatives containing electron-donating groups have a large NLO responses. [ABSTRACT FROM AUTHOR]

In this work, five new quinacridone ( QA )-based dyes containing a N-donor moiety have been synthesized, defined as C12QA–F , C12QA–G , C12QA–H , C12QA–I and C12QA–J , for the application of third-order nonlinear optical (NLO) responses. A new design has been put forward with the first step of connecting a long alkyl chain on the planar structure of parent ring of QA , with the aim to increase the solubility of the compound and reduce its π-π intermolecular stacking and the second step of connecting N-donor groups to enhance the effect of molecule. Electrochemical measurement data indicated that the tuning of the HOMO and LUMO energy levels can be easily realized by introducing the N-donor moiety. The theoretical calculations showed a smaller dihedral angle between the QA moiety and the N-donor than the usual, implying an excellent planarity between the two groups, which is beneficial for the intramolecular charge transfer (ICT). NLO tested under similar Z-scan measurements conditions showed that, the second-order hyperpolarizability ( γ ) of the five synthesized compounds ranged from 2.136 × 10 −33 esu to 13.856 × 10 −33 esu, with the maximum of C12QA-H was more than 13 times higher than N,N-di(n-dodecane) quinacridone ( C12QA ) of 0.964 × 10 −33 esu. The results suggested that the designed QA -based compounds had good thermal stability and superior third-order NLO properties, very promising for integrated NLO devices. [ABSTRACT FROM AUTHOR]

A series of third-order nonlinear optical chromophores containing identical π -bridge and electron-donating groups, but with different electron-withdrawing groups have been designed and synthesized. The ultraviolet absorption, density functional theory calculations, and the third-order nonlinear optical (NLO) properties of these materials have been investigated and systematically studied. A theoretical study showed that the third-order NLO properties were enhanced by the increasing electron-withdrawing ability in accordance with the decreasing energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. The transferred charge to the substituent is increased and the affect on the electronic reallocation is reinforced with the increasing ability of the compounds to attract electrons. The third-order NLO susceptibilities, the second-order hyperpolarizabilities and response times of compounds were 2.829–6.034 × 10 −13 esu, 0.737–2.005 × 10 −31 esu, 41.92–68.71 fs Our results can be used to develop an efficient design strategy for NLO materials. [ABSTRACT FROM AUTHOR]

Herein we reported the preparation of a new type of ferrocene-based compounds with large conjugated system containing symmetrical aromatic vinyl and Schiff base moieties and the study of their third-order nonlinear optical (NLO) properties. Their third-order NLO properties were measured using femtosecond laser and degenerate four-wave mixing (DFWM) technique. The obtained χ (3) , n 2 and γ values of these molecules were found in the range of 0.998–1.429 × 10 −12 esu,1.847–2.646 × 10 −11 esu and 1.026–1.449 × 10 −30 esu, respectively. The response time ranged from 43.65 fs to 61.71 fs. The results indicate that these compounds have potential nonlinear optical applications. [ABSTRACT FROM AUTHOR]

The third-order nonlinear optical material with excellent performance is a molecule with a large π-conjugated structure for absorption structure and a high degree of delocalization. Nitrogen-sulfur derivatives have lone pairs of electrons in their N and S atoms, which makes them have a strong intramolecular charge transfer ability, which is conducive to the formation of donor-acceptor molecules. In this paper, phenothiazine is used as the matrix structure of the third-order nonlinear optical material, modified, and then metal coordination is performed to obtain [Zn(Py) 2 Cl 2 ] n and [Cd(Py) 2 Cl 2 ] n. Its structure is characterized by infrared spectroscopy, single crystal X-ray diffraction and powder X-ray diffraction. The morphology of the material was characterized by scanning electron microscopy. The photophysical properties, thermal properties and third-order nonlinear properties were tested, and the theoretical verification was carried out with the DFT calculation method, and the relationship between the structure and the third-order nonlinear properties was summarized. The experimental results show that phenothiazine has good electron donating ability, the two-photon absorption coefficient β is between 1.334–38.400 × 10−10 m/W, and the third-order nonlinear polarizability χ(3) is between 2.752–79.247 × 10−11 esu, The second-order hyperpolarizability γ of the ligand molecule is 5.213 × 10−34 esu. The χ(3) values of [Zn(Py) 2 Cl 2 ] n and [Cd(Py) 2 Cl 2 ] n are 4 orders of magnitude higher than ordinary α-quartz (χ(3) = 2.6 × 10−14 esu). [Display omitted] • Phenothiazine metal-organic framework materials were prepared. • The metal organic frame material formed by the D-A structure exhibits large third-order nonlinearity. • Proposed an efficient structure synthesis strategy for potential NLO materials. [ABSTRACT FROM AUTHOR]

Six symmetrical ferrocenyl Schiff base materials were synthesized and characterized by UV, 1 H NMR, mass spectrometry (MS) and elemental analysis. Their off-resonant third-order nonlinear optical properties were measured using femtosecond laser and degenerate four-wave mixing (DFWM) technique. The third-order nonlinear optical susceptibilities χ (3) were 1.961–6.363 × 10 −13 esu. The nonlinear refractive indexes n 2 were 3.609–11.716 × 10 −12 esu. The second-order hyperpolarizabilities γ of these molecules were 1.967–6.388 × 10 −31 esu. The response time were 45.759–73.079 fs. The results indicate that these materials have potential nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Acridone derivatives have much attracted attention due to their objective photoelectric properties. However, their applications in nonlinear optical (NLO) materials are rarely studied. In this work, we designed and synthesized four D-π-A-π-D acridone derivatives and one D-A-D type derivative as comparison. The effects of the structure on photophysics, electrochemistry and the third-order nonlinear optics were analyzed by UV spectrophotometer, fluorescence spectrophotometer, cyclic voltammetry and Z-scan technique. The results show that the introduction of acetylene group as a bridge is conducive to intramolecular charge transfer and can maintain the planarity of the molecule and enhances the third-order NLO properties. In the four target products, YA4 has the best third-order NLO properties, with its second-order hyperpolarizability γ (γ = 5.792 × 10−33 esu) 1.36 times that of YA1 (γ = 4.262 × 10−33 esu) and 6267 times that of urea (γ = 0.68 × 10−36 esu). The study showed that introducing an appropriate length of alkane chain into acridone derivatives can effectively reduce the intermolecular interference and improve their third-order NLO performance. [Display omitted] • A series of acridone derivatives were synthesized. • Introducing acetylene groups as π-bridge is beneficial to ICT and enhances the third-order NLO properties. • The acridone derivatives containing strong electron-donating groups have a large NLO responses. [ABSTRACT FROM AUTHOR]

Abstract In this work, four new quinazolinone (QZ)-based compounds containing triphenylamine (TPA) moiety have been synthesized, defined as QZC , QZC-1 , QZC-2 , QZC-3 , for the application of third-order nonlinear optical (NLO) responses. A new design of two-step synthesis has been put forward, the first step is Ullmann reaction with QZ , and the second is connecting QZ and the substituted triphenylamines (TPAs) through a Suzuki cross-coupling reaction to afford the target products. Electrochemical measurement data indicated that the tuning of the HOMO and LUMO energy levels can be easily achieved by introducing and modifying the donor moiety. The NLO properties were evaluated by the Z-scan technique which showed that introduction of a benzene ring as a π bridge could reduce the transmission energy of electrons from a ground state to an excited state, and the added methoxy in TPA moiety could promote the ICT, and improve the third-order NLO properties of molecules. Theoretical calculations matched well with the electrochemical information and NLO information. The results suggest that the materials based on QZ have potential applications in integrated NLO devices. Highlights • Four new quinazolinone (QZ)-based compounds containing TPA moiety have been synthesized. • Enlarged π-conjugation systems and additional ability of electron donating effectively improve the NLO properties. • Four QZ -based materials forming a push-pull system exhibit great potential applications in integrated NLO devices. [ABSTRACT FROM AUTHOR]