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Composite polymer materials doped with original push–pull chromophores with the quinoxaline core in the conjugated bridge have been developed. Chromophores with various substituents in the aniline donor moiety and tricyanofuran acceptor are characterized by high thermal stability and predicted values of first hyperpolarizability (up to 1000 × 10−30 esu). Nonlinear optical (NLO) coefficient d33 of corona-poled polymer films achieved 75 pm V−1 for materials doped with chromophore with N,N-dibutylamino-3-ethylbenzene donor at 25 wt% content, while doping with a similar chromophore with an additional bulky cyclohexylphenyl group in the acceptor leads to maximum d33 value 97 pm V−1 for 40 wt% chromophore content and 65 pm V−1 for neat chromophore material. The temporal and thermal stabilities of the NLO response at room temperature and heating to 50 °C during 100 hours is shown to be high: for some polymer materials the value of d33 remained almost constant for 24 months at room temperature and at least 94% of the response preserved after heating. [ABSTRACT FROM AUTHOR]

Impact of π-deficient heterocyclic core (A′) in conjugated bridge of D-π-A′-π-A chromophores (D = N,N- dihexylaniline, A = tricyanofuran derivative) on optical and thermal properties has been investigated. Three new chromophores with vinyl-hetaryl-vinyl bridges containing π-deficient benzoazine moiety (quinoxaline, quinoxalinone and quinoline) have been synthesized along with new chromophores with vinyl-thiophene-vinyl bridge containing π-excessive heterocycle and short vinylene bridge, and their properties are compared to reveal the role of π-deficient hetaryl moiety. Their linear optical properties were systematically investigated by UV–Vis spectroscopy and molecular nonlinear optical (NLO) characteristics were predicted by DFT calculations. As the aromaticity of the heterocycle in the bridge increases, a hypochromicity and hypsochromic shift of the absorption maximum manifest themselves in the UV–Vis spectra, the origin of electron transitions was studied by TD-DFT with CAM-B3LYP and PBE0 density functionals. The calculated first hyperpolarizability, β tot , for A′ = quinoxaline, quinoline and thiophene, was shown to be almost independent on the type of the π-bridge core, being in a narrow interval 800–831⋅10−30 esu, while for A′ = quinoxalinone β tot is essentially higher (996⋅10−30 esu). All chromophores exhibit good thermal stability (T d > 192 °C). Thin films of composite polymer materials with PMMA matrix and studied chromophores as guests as well as of some molecular glasses were spin-cast and corona-poled, and their quadratic NLO activity was measured by two different techniques. For materials with guest chromophores containing quinoxalinone, quinoxaline and thiophene moieties in the bridges NLO coefficients d 33 were found to be rather close and reached 76 pm/V, what is almost 3 times higher than that for polymer film with quinoline-based chromophore. Rather high values of NLO coefficients for molecular glasses based on chromophores with quinoline, thiophene and quinoxalinone cores were obtained: 52, 124 and 132 pm/V, respectively, which notably exceed the values for composite materials with these chromophores as guests. [Display omitted] • First representative of a new class of NLO chromophores with divinylquinoline bridge was synthesized. • UV–vis spectra of quino(xa)line chromophores have high-intensity line in higher energy region. • Polymer composites with quinoxalin(on)e and thiophene chromophores have close d 33 values. • Quinoxalinone chromophore molecular glass exhibits high NLO coefficient value of 132 p.m./V. [ABSTRACT FROM AUTHOR]