Thermal, optical, electrical and structural study of new symmetrical azomethine based on poly(1,4-butanediol)bis(4-aminobenzoate)

Crystal Structure Determination of 4-[(Di-p-tolyl-amino)-benzylidene]-(5-pyridin-4-yl-[1,3,4]thiadiazol-2-yl)-imine along with Selected Properties of Imine in Neutral and Protonated Form with Camforosulphonic Acid: Theoretical and Experimental Studies

The crystal structure was determined for the first time for 4-[(di-p-tolyl-amino)benzylidene]-(5-pyridin-4-yl-[1,3,4]thiadiazol-2-yl)-imine (trans-PPL9) by X-ray diffraction. The imine crystallized in the monoclinic P21/n space group with a = 18.9567(7) Å, b = 6.18597(17) Å, c = 22.5897(7) Å, and β = 114.009(4)°. Intermolecular interactions in the PPL9 crystal were only weak C-H⋯N hydrogen bonds investigated using the Hirshfeld surface. The electronic and geometric structure of the imine were investigated by the density functional theory and the time-dependent density-functional theory. The properties of the imine in neutral and protonated form with camforosulphonic acid (CSA) were investigated using cyclic voltammetry, UV-vis and 1H NMR spectroscopy. Theoretical and experimental studies showed that for the 1:1 molar ratio the protonation occured on nitrogen in pyridine in the PPL9 structure, as an effect of Brönsted acid-base interactions. Thermographic camera was used to defined defects in constructed simple devices with ITO/PPL9 (or PPL9:CSA)/Ag/ITO architecture. In conclusion, a thermally stable imine was synthesized in crystalline form and by CSA doping, a modification of absorption spectra together with reduction of overheating process was observed, suggesting its potential application in optoelectronics.

Synthesis and characterization of two new TiO2-containing benzothiazole-based imine composites for organic device applications

The effect of the presence of titanium dioxide in two new imines, (E,E)-(butane-1,4-diyl)bis(oxybutane-4,1-diyl) bis(4-{[(benzo[d][1,3]thiazol-2-yl)methylidene]amino}benzoate) (SP1) and (E)-N-[(benzo[d][1,3]thiazol-2-yl)methylidene]-4-dodecylaniline (SP2), on the properties and stability of imine:TiO₂ composites for organic device applications were examined. The investigated titanium dioxide (in anatase form, obtained via the sol-gel method) exhibited a surface area of 59.5 m²/g according to Brunauer-Emmett-Teller theory, and its structure is a combination of both meso- and microporous. The average pore diameter calculated by the Barrett-Joyner-Halenda method was 6.2 nm and the cumulative volume of pores was 0.117 m³/g. The imine SP1 exhibited columnar organization (Col), while SP2 revealed a hexagonal columnar crystalline phase (Col_hk). The imine:TiO₂ mixtures in various weight ratio (3:0, 3:1, 3:2, 3:3) showed a lower energy gap and HOMO-LUMO energy levels compared to pure TiO₂. This implies that TiO₂ provides not only a larger surface area for sensitizer adsorption and good electron collection, but also causes a shift of the imine energy levels resulting from intermolecular interaction. Also the temperature of the phase transition was slightly affected with the increase of TiO₂ concentration in imine-based composites. The changes observed in the Fourier transform middle-infrared absorption (FT-MIR) spectra confirmed the significant influence of TiO₂ on structural properties of both investigated imines. Similar interactions of oxygen vacancies existing on the TiO₂ surface with SP1 and SP2 were observed. The imine:TiO₂ mixtures showed good air stability and reusability, which demonstrates its potential for organic device applications.

Optical properties of unsymmetrical azomethines with one imine bonds

We have explored the photoluminescence (PL) and electronic properties, that is, orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT) of four unsymmetrical (UAz1-UAz4) azomethines. All of the investigated compounds exhibited mesomorphic behavior. The photoluminescence studies have shown that molecular structure of the imines influenced both the PL properties and HOMO-LUMO levels of azomethines. Azomethines emitted violet, blue or green light. The effect of excitation wavelength and concentration on the PL properties has been detected as well. Unsymmetrical imine UAz3 posses carbazole unit exhibited lower both HOMO and LUMO energies compare to others investigated azomethines. Additionally, azomethines were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Two unsymmetrical imines (UAz2 and UAz3) exhibited irreversible oxidation behavior. The HOMO level of the compound with ethylcarbazole (UAz2) moiety was observed at -5.22 eV, while for the UAz3 with phenoxybiphenyl unit was found at -5.64 eV. The data obtained by theoretical calculation using DFT method was very similar to the results obtained by electrochemical measurements.

Molecular structure and spectroscopic characterization of ethyl 4-aminobenzoate with experimental techniques and DFT quantum chemical calculations

The FT-IR and FT-Raman spectra of ethyl 4-aminobenzoate (EAB) in the solid phase were recorded. The fundamental vibrational wavenumbers, intensities of vibrational bands and the optimized geometrical parameters of the compound were evaluated using DFT (B3LYP) method with 6-311++G(d,p) basis set. The stable geometry of the compound was determined from the potential energy surface scan. Complete vibrational assignments and Natural Bond Orbital (NBO) analysis for the title compound were carried out. The assignments of the vibrational spectra were carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field (SQMFF) methodology. The molecule orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. UV-visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies were performed by time-dependent DFT (TD-DFT) approach. Mulliken population analysis on atomic charges were also calculated. Besides, molecular electrostatic potential (MEP) and thermodynamic properties were performed.