Solution and Solid-State Photophysical Properties of Positional Isomeric Acrylonitrile Derivatives with Core Pyridine and Phenyl Moieties: Experimental and DFT Studies

The compounds I (Z)-2-(phenyl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile with one side (2,4,5-MeO-), one symmetrical (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(2,4,5-trimethoxyphenyl)acrylonitrile), II (both sides with (2,4,5-MeO-), and three positional isomers with pyridine (Z)-2-(pyridin-2- 3, or 4-yl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile, III–V were synthetized and characterized by UV-Vis, fluorescence, IR, H1-NMR, and EI mass spectrometry as well as single crystal X-ray diffraction (SCXRD). The optical properties were strongly influenced by the solvent (hyperchromic and hypochromic shift), which were compared with the solid state. According to the solvatochromism theory, the excited-state (μe) and ground-state (μg) dipole moments were calculated based on the variation of Stokes shift with the solvent’s relative permittivity, refractive index, and polarity parameters. SCXRD analyses revealed that the compounds I and II crystallized in the monoclinic system with the space group, P21/n and P21/c, respectively, and with Z = 4 and 2. III, IV, and V crystallized in space groups: orthorhombic, Pbca; triclinic, P-1; and monoclinic, P21 with Z = 1, 2, and 2, respectively. The intermolecular interactions for compounds I–V were investigated using the CCDC Mercury software and their energies were quantified using PIXEL. The density of states (DOS), molecular electrostatic potential surfaces (MEPS), and natural bond orbitals (NBO) of the compounds were determined to evaluate the photophysical properties.

Prediction of Solvatochromic Polarity Parameters for Aqueous Mixed-Solvent Systems

Solvent polarity is important data being used in solvent selections for preliminary engineering design of chemical processes. In this work, a predictive model is proposed for estimating the solvatochromic polarity of electronic transition energy (ET) of Reichardt indicator for aqueous mixtures. To validate the model, the ET values of eighteen aqueous mixtures collected from the literature were used. The predictive model provided a good estimation of ET values with an overall deviation of 2.1%, compared with an ideal model (5.1%) from the mole fraction average. The linear relationship of the contribution factor of hydrogen bond donor interactions (CFHBD) in the predictive model with Kamlet–Taft acidity was newly proposed in order to extend the model for other aqueous mixtures. The predictive model is applicable to many aqueous mixtures and simply requires three properties of pure components as: (i) ET values, (ii) gas-phase dipole moment and (iii) Kamlet–Taft acidity.

Complementary interpretation of ET(30) polarity parameters of ionic liquids

The ET(30) parameter of ionic liquids is determined by the hydrogen bond donating ability of the cation and the number of dipole ion pairs per volume.

Synthesis photophysical studies of some furfurylnitrones: high-ly selective chemosensors for Zn2+ and DFT studies

New aldonitrones(1-4) were synthesized and characterized by UV-vis, fluorescence, FT-IR, 1H and 13C NMR spectral analyses. The absorption and fluorescence sensing spectra of the compounds were precise in different polarity of solvent. The solvent polarity parameters have been used to propose a quantitative approach towards the reliable stability of the electronic ground and excited state species. Photochemical behaviors of the compounds were analyzed by applying multi-linear correlation methods. The characterized compounds 1-4 show a chemosensing detection of zinc ion in aqueous solution. Besides, the fluorescence spectroscopic responses were reversible when the Zn2+chelating reagentEDTANa2.The phenomenon proves that these compounds to show a sensitivity “on-off” sensor for Zn2+.Further, to recognize the molecular structure, electronic and optical properties and DFT calculations of the molecules were formed.

Validation of Instrument on Teaching Practices Among Lecturers at Community Colleges, Yemen

This study aims to explore a set of items measuring the lecturers’ teaching practice for developing a true scale of teaching practice. Rasch Model is applied to produce specific measurements on the lecturers’ teaching practice in order to generalize results and inferential studies. The items proved to measure a single dimension of lecturers’ teaching practice. The developed instrument termed LTP covers five dimensions. Construct validity was achieved through the Rasch Model Analysis using the dimensionality, item fit, and item polarity parameters. The reliability of the instrument was achieved by conducting person and item separation analysis, Cronbach alpha, and calculated person and item reliability estimates. The results of Rasch Model Analysis show that the items of LTP fit the model appropriately.