Optical Nature and Binding Energetics of Fluorescent Fluoride Sensor Bis(bora)calixarene and Design Strategies of Its Homologues
JOURNAL OF PHYSICAL CHEMISTRY C
Authors: Jin, Jaehyeok; Park, Ji Young; Lee, Yoon Sup
We report a theoretical assessment on F- sensing with bis(bora)-calixarene, a known fluorescent sensor. Geometries of bis(bora)calixarene and its fluoride-binding complex are optimized at the ONIOM(B3LYP/6-31+G(d):B3LYP/3-21G) level of theory in both the gas phase and the CH2Cl2 solution by using the Polarizable Continuum Model (PCM). Decreases in UV absorption and fluorescence of bis(bora)calixarene upon F- binding are explained by Time-Dependent Density Functional Theory (TD-DFT) calculation. The theoretical calculations indicate that the fluorescence quenching behavior when F- binds with bis(bora)calixarene is the result of cooperative endo- and exo-bindings, which contradicts the previously reported experiment that suggested only the endo-binding. Furthermore, the observed fluorescence can be understood as an emission from the second and higher excited states via prompt fluorescence. This sensor-anion binding is predicted only with fluoride, but not with chloride or bromide anions. The substitution of boron atoms with group 13 and 15 atoms is also explored for the design of effective fluoride sensors. To predict the binding affinity, we calculate the binding energy of chemosensors with F-. Some of the substituted homologues studied here are expected to be potential fluoride sensors. In this regard, degrees of pyramidality and parallelity act as useful indicators to predict the binding affinity as well as the structure of both homonuclear and heteronuclear motifs.
Regional climatic anomalies of air temperature of the Southern Coast of Crimea and their relation with global atmospheric processes
25TH INTERNATIONAL SYMPOSIUM ON ATMOSPHERIC AND OCEAN OPTICS: ATMOSPHERIC PHYSICS
Authors: Kazakov, S. I.; Metik-Diyunova, V. V.; Simonova, Yu. V.; Mayboroda, S. A.; Boguslaysky, A. S.
According to long-term hydrometeorological data obtained at the Black Sea Hydrophysical Proving Ground (BSHPG) located on the Southern Coast of Crimea, the analysis of annual, monthly and daily average anomalies of surface air temperature for the period 2012-2016 is performed. The correlations of the of the surface air temperature anomalies with the North Atlantic Oscillation (NAO) and Southern Oscillation (SOI) indices are considered, and an increase in the absolute value of air temperature anomalies in the summer period has been revealed. The negative air temperature anomalies during the winter period, their connection with the regional factor of climate variability (Bora) and atmospheric processes in the European region are considered. A general increase in surface air temperature over South Coast of Crimea during the study period is observed.