Kinetics and Energetics of Thermal Cis-Trans Isomerization of a Resonance-Activated Azobenzene in BMIM-Based Ionic Liquids for PF₆-/Tf₂N- Comparison

First thermal studies on visible-light-switchable negative T-type photochromes of a nitrile-rich series

Representatives of visible-light-switchable nitrile-rich negative T-type photochromes (NRP) were synthesized. The temperature effect on the thermal relaxation of the photoinduced form of NRP was studied for the first time. It was found that regardless the temperature the reverse thermal reaction in ethanol and 1,4-dioxane proceeded according to a first-order kinetic equation, while an unusual pseudo-zero order of the dark reaction was observed in acetonitrile. Using the obtained experimental data, the activation energy as well as the activation parameters, such as entropy and enthalpy of activation, were calculated for the first time for thermal relaxation of NRP photochromes. It was also shown that an initial form of NRP photochromes bearing a tricyanofuran acceptor was more temperature resistant than the initial form of photochromes with a tricyanopyrrole acceptor.

The temperature effect on the thermal stability of both the initial and photoinduced forms of nitrile-rich T-type photochromes was studied for the first time.

Molecular Design of Microcapsule Shells for Visible Light-Triggered Release

The development of photo-responsive capsules to tune and control the sustained-release of encapsulated actives is a fascinating and challenging route to improve the performances and effectiveness of a wide range of delivery applications. In this work, we report the preparation of visible light-responsive capsules obtained via oil-in-water interfacial polycondensation between modified diacyl-chloride azobenzene moiety and diamine flexible spacer in the presence of cross-linkers with different structures and functionalities. The effect on the release profile of the encapsulated perfume oil was investigated using three flexible spacers with different lengths (1,8-diaminooctane; 1,6-diaminohexane and 1,4-diaminobutane) and two types of cross-linkers (1,3,5-benzenetricarbonyl trichloride and melamine). We analyzed how the properties of microcapsules can be tailored changing the design of the shell structure. Fine tuning of the perfume release profiles was obtained. The changes in capsules size and morphology due to visible light irradiation were monitored via light scattering, optical microscopy and atomic force microscopy. Perfume release was 50% faster in the systems prepared with melamine as the cross-linker. Modelling studies were carried out to support the discussion of the experimental results.

The structural and electronic properties of 3,3′-azothiophene photo-switching systems

3,3′-Azothiophenes demonstrate effective photo-induced isomerization in solution. Activation energies and entropies confirm the thermal stability of cis conformations at 20 °C.

Learning organic chemistry day by day: The best choice of the best pharmacy students

BACKGROUND AND PURPOSE

During over ten years of experience in teaching organic chemistry at the Department of Pharmacy we have tried to answer the following question: why do most students tend to take the exam one, two, or more years after the end of the course they have attended? Several reasons could justify this delay, but three seem to be the most common drawbacks for our students: a) time needed for the comprehension of the arguments; b) the number of mandatory exams to pass before organic chemistry; c) lack of a self-evaluation method.

EDUCATIONAL ACTIVITY AND SETTING

To increase the number of students in the exam sessions of the semester just after the course we have proposed two strategies: 1) a systematic, but stressless, approach by which homework and everyday life examples concerning organic chemistry are used to increase the sense of responsibility in studying; 2) the modification of the number of mandatory exams required for organic chemistry.

FINDINGS

The rate of successful students in the exam sessions at the end of the course increased from 38.3 up to 61.3%. Interestingly, the highest scores tend to be obtained by students in the first session available just after the conclusion of the course.

DISCUSSION AND SUMMARY

The combined effect of Strategy 1 and Strategy 2 seems to be effective in promoting the learning of organic chemistry and points out that the best performances tend to be associated with students which follow organized studying.