Enhanced Nonlinear Optical Activity of Molecules Containing Two D−π−A Chromophores Locked Parallel to Each Other

Abstract

A series of H-shaped second-order nonlinear optical (NLO) chromophores with two parallel and nonconjugated D-π-A units have been synthesized, in which a 9,10-dihydroanthracene is employed as molecular backbone. The measurement results of hyper-Rayleigh scattering (HRS) and UV-vis spectra show that the first molecular hyperpolarizability (β) values of H-shaped chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds (the enhancements per azo D-π-A unit from 1.2 to 3.0 are observed), without causing a large shift of the absorption band to longer wavelength. Therefore, it gives an available way of solving the trade-off between nonlinearity and transparency in designing NLO chromophores. Furthermore, some main-chain fluoro-containing polyimides embedded with the H-shaped chromophores have also been prepared. The elemental investigation results show that the polyimides exhibit a higher macroscopic nonlinear optical coefficient (d 33 ) 35.0 to ∼70.2 pm/V), good thermal stability (T g 198 to ∼210 °C, T d 240 to ∼245 °C), and optical transparency (λ max < 400 nm).

Theoretical Study of Effect of the Number of N,N-dimethyl-4-nitroaniline Units in Novel “Parallel Connection” Chromophores on Its Nonlinear Optical Properties

“…Therefore, there is always a tradeoff between nonlinearity and transparency [14][15][16][17][18][19][20][21][22][23]. To resolve this problem, we had designed and synthesized a series of H-typed chromophores with two parallel and nonconjugated D-π-A units [24][25][26][27]. The results of hyper-Rayleigh scattering (HRS) and UV-vis spectra show that the first hyperpolarizability (β) values of H-typed chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds without causing a large shift of the absorption band to longer wavelength [24][25][26][27].…”

“…To resolve this problem, we had designed and synthesized a series of H-typed chromophores with two parallel and nonconjugated D-π-A units [24][25][26][27]. The results of hyper-Rayleigh scattering (HRS) and UV-vis spectra show that the first hyperpolarizability (β) values of H-typed chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds without causing a large shift of the absorption band to longer wavelength [24][25][26][27]. It suggests an available way of solving the tradeoff between nonlinearity and transparency in designing NLO chromophores, that is, design of chromophore with parallel and non-conjugated multi-D-π-A units.…”

Tuning the absorption spectra and nonlinear optical properties of D‐π‐A azobenzene derivatives by changing the dipole moment and conjugation length: a theoretical study

“…One promising strategy is to assemble the linear D‐ π ‐A dipolar units into some novel oligomers with various topologies, such as H‐shape, X‐shape, Y‐shape, U‐shape, Λ‐shape, and so on 11–15. Among them, the H‐shaped dimers and polymers have gained an increased attention 16–20. In 2006, Liu's group synthesized two series of NLO polymers, which combine two chromophores via an isolation spacer 16.…”

Theoretical study on the nonlinear optical properties of donor/acceptor-functionalized trigonal dehydrobenzoannulenes

“…2DCT chromophores which possess multiple donor-acceptor substituents, such as ''K-shaped" [9], ''X-shaped" [10], ''Y-shaped" [11], ''U-shaped" [12], ''H-shaped" [13], have a 2D b tensor character, where the off-diagonal components become significant. This is different from the typical 1D system, where b is solely dominated by diagonal terms [14].…”