Anna Popczyk

In this paper we report the synthesis and photophysical properties of six novel thiophene derivatives (ThD) with D–π–A structure. The subject of this work is three nitrophenyls (1) BT-Th-NO₂ and three benzonitriles (2) BT-Th-CN, substituted at different positions of the aromatic ring ((a) ortho-, (b) meta- or (c) para-). Dyes were obtained using a simple three-step synthesis and their chemical structures were confirmed by ¹H and ¹³C NMR, IR and high resolution mass spectrometry. The influence of positional isomerism on the optical properties has been explored experimentally and theoretically. The photophysical properties were investigated using steady-state and time-resolved spectroscopy and the obtained results were supported by quantum-chemical calculations. TD-DFT calculations indicated that the charge-transfer strength can be correlated with the observed optical properties. In addition, the influence of the acceptor position on the photoluminescence spectra, fluorescence quantum yields and emission lifetimes was specified. We show that the ThD optical properties can be tuned in a wide spectral range by a change made in only a single step of the synthesis reaction.

In this paper, we present the third harmonic generation response of Znq₂ (Bis-(8-hydroxyquinolinato)zinc), Cuq₂ (8-Hydroxyquinoline copper(II)), and Alq₃ (Tris-(8-hydroxyquinoline)aluminum) organometallic compounds. An experiment was conducted for s and p polarizations of incident beam, using the Maker fringes technique. The third order nonlinear susceptibility χ⁽³⁾ was estimated using the Kubodera and Kobayashi comparative model, on the grounds that presented compounds exhibit high linear absorption of the generated third harmonic wavelength (355 nm). These complexes were deposited as thin films using the physical vapor deposition (PVD) method. Investigated complexes vary in terms of the coordination center and number of quinoline ligands, which visibly influence their nonlinear response. The global hybrid B3LYP functional with the basis set 6-31G(d) was used in computing the linear and non-linear optical properties. The computed γ_tot value (8765.36 × 10⁻³⁶ esu for Cuq₂) is superior to that of methylene blue (γ = 32.00 × 10⁻³⁶ esu). The calculated theoretical values were found to be in good agreement with the experimental results.