Photoactivated Refractive Index Anisotropy in Fluorescent Thiophene Derivatives

The optical control of anisotropy in materials is highly advantageous for many technological applications, including the real-time modulation of another light signal in photonic switches and sensors. Here, we introduce three thiophene derivatives with a donor-acceptor structure, which feature different positions of an electron-acceptor nitrile group, and both photoalignment and luminescence properties. Quantum chemical calculations highlight the presence of trans-forms stable at room temperature and metastable cis-isomers. Besides photoluminescence peaked at 440-460 nm and 0.4 ns lifetime, the three nonlinear optical chromophores exhibit photoinduced anisotropy of the refractive index closely depending on the specific molecular structure, with higher values of birefringence at lower driving signal being obtained for ortho substitution of the nitrile group. All-optical modulation of an external light beam at rates of hundreds of hertz is demonstrated in the fluorescent systems. This finding opens an interesting route to multispectral photonic switches embedded in the active layers of light-emitting devices

TTF based donor-pi-acceptor dyads synthesized for NLO applications

Two new TTF-pi-acceptor dyads that contain p-nitrophenyl group as acceptor and bis-(styryl)benzene system as an efficient π−conjugated bridge have been synthesized by multistep synthetic procedure and their electrochemical behavior has been studied by cyclic voltammetry (CV). The occurrence of an intramolecular charge transfer (ICT) in these molecules has been evidenced by UV–Visible electronic absorption spectroscopy and these studies were completed by DFT calculations in both gas phase and in solution. The nonlinear optical parameters obtained via SHG and THG measurements are described and indicate that these materials are valuable candidates for the construction of optoelectronic and photonic devices. The Optical Kerr Effect measurements indicate that these materials exhibit a great potential in the field of optical switchers construction, where the material\u27s photoresponse time is a crucial parameter

Photo-Physical Transformations in Pyrazoline Derivative Based Systems

Discovery of <i>E</i>/<i>Z</i> or <i>trans</i>–<i>cis</i> photoisomerization in the azobenzenes and their derivatives had tremendous impact on the whole domain of photochromic materials including photochromic polymers and liquid crystals. Here we show similar configurational photoinduced transformation in a simple derivative of pyrazoline. The X-ray crystallographic investigations of (<i>E</i>)-3-(4-nitrostyryl)-1-phenyl-4,5-dihydro-1<i>H</i>-pyrazole (abbreviated as PY-pNO₂) in grown crystals show two different structures comprising of either <i>cis</i> or <i>trans</i> molecules. The performed quantum chemical calculations confirm the existence of both configurations of PY-pNO₂ at the room temperature. Photophysical properties of this compound derived from quantum chemical calculations predict possibility of <i>trans</i> to <i>cis</i> switching of PY-pNO₂ by light. Indeed, molecules of PY-pNO₂ embedded in PMMA polymeric matrix when illuminated with 532 nm linearly polarized laser light show the induced optical anisotropy, i.e., birefringence characteristic for photoisomerizable molecules similar to that in the group of the azobenzene derivatives

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