Synthesis of calix[4]arene derivatives with fluorescent subunits and study of their complexation with alkali-metal cation

Sintetizirano je sedam novih fluorescentnih derivata kaliks[4]arena s fenantridinskim (13) i difenilantracenskim (47) supstituentima na donjem obodu kaliksarenskog prstena. Spojevi su pripravljeni konvencionalnom organskom i mikrovalovima potpomognutom sintezom te su uspoređena reakcijska vremena i iskorištenja. Okarakterizirani su na temelju podataka dobivenih 1H i 13C NMR, FTIR spektroskopijom, elementnom analizom kao i spektrometrijom masa. Spektrofotometrijskim, fluorimetrijskim, potenciometrijskim i 1H NMR titracijama istraženo je kompleksiranje dobivenih liganada s alkalijskim kationima u smjesama otapala acetonitril/diklormetan i metanol/diklormetan ( fi= 0,5). Pri tome su određene konstante stabilnosti odgovarajućih kompleksa stehiometrije 1:1 (kation:ligand). Istraženo je i nastajanje ionskih parova u istim smjesama otapala, budući da ono također utječe na proces kompleksiranja. Kao što je očekivano s obzirom na izbor supstituenata, svi ligandi vežu alkalijske katione uz smanjenje afiniteta prema metalnim ionima s porastom njihova radiusa. Opaženo je da otapalo znatno utječe na stabilnost kompleksa, pri čemu je afinitet liganada prema kationima znatno veći u smjesi diklormetana s acetonitrilom nego onoj s metanolom. Može se zaključiti da bi pripravljeni kaliksarenski derivati mogli poslužiti kao osjetljivi fluorimetrijski senzori za alkalijske katione.In the framework of this work seven fluorescent calix[4]arene derivatives with phenanthridine (13) and diphenylanthracene (47) substituents at the lower calixarene rim were synthesized. Compounds were prepared by conventional organic synthesis as well as by microwave-assisted synthesis, and the reaction times and yields were compared. The compounds were characterized by means of FTIR, 1H and 13C NMR spectroscopies, elemental analysis as well as by mass spectrometry. The complexation of these ligands with alkali-metal cations was studied by spectrophotometric, fluorimetric, potentiometric, and NMR titrations in acetonitrile/dichloromethane and methanol/dichloromethane solvent mixtures ( phi= 0.5). The stability constants of the corresponding 1:1 (cation:ligand) complexes were determined. Ion association in these solvent mixtures was also investigated because this phenomenon can considerably affect the complexation process. The ligands were proven to bind the alkali-metal cations rather strongly with lowering of their binding abilities with the increase of the cation radius. It was found that solvent considerably affected the stability of the complexes, whereby the ligands showed significantly higher affinities for cations in acetonitrile than in methanol/dichloromethane mixture. It could be concluded that the prepared calixarene ligands could serve as sensitive fluorimetric sensors for alkali-metal cations

Photoinduced Autonomous Nonequilibrium Operation of a Molecular Shuttle by Combined Isomerization and Proton Transfer Through a Catalytic Pathway

We describe a [2]rotaxane whose recognition sites for the ring are a dibenzylammonium moiety, endowed with acidic and H-bonding donor properties, and an imidazolium center bearing a photoactive phenylazo substituent. Light irradiation of this compound triggers a network of E/Z isomerization and proton transfer reactions that enable autonomous and reversible ring shuttling away from equilibrium

Особенности планктонных сообществ Торейских озер (Забайкальский край) в маловодный год

Lakes Barun-Torey and Zun-Torey are the largest water bodies in Zabaikalsky Krai, and they are characterized by long-term cyclic changes in the water level. Samples of the planktonic community (algae and invertebrates) were collected from the Torey Lakes in June, August, and October in the dry 2016. Collection and processing of the samples was carried out using standard hydrobiological methods. The aim of the study was to investigate the planktonic communities in the Torey Lakes. The lakes were in different hydrological phases: Barun-Torey was in the initial filling phase (with isolated small lakes present on the dried bed), and Zun-Torey was in the shallowing phase. Considerable differences were observed between the compositions and structures of the planktonic communities, which were determined by the mineral content of the water. Diverse littoral plankton developed, consisting of 2-25 taxa of algae (total number of taxa – 46) and 2-15 species of invertebrates (total number of species – 29) in the oligohaline small lakes on the bottom of Lake Barun-Torey. The abundance and biomass of aquatic organisms varied within very wide limits: for phytoplankton – from 0.7 × 103 to 1260.0 × 103 cells / L and from 0.1 to 1271.0 mg / m3, and for zooplankton – from 9.2 × 103 to 19370.0 × 103 individuals / m3 and from 3.8 to 361.7 g / m3. Freshwater and euryhaline species were dominant. In polyhaline Lake Zun-Torey, the phytoplankton consisted of 3-12 taxa of algae (total number of taxa – 18), and the invertebrate fauna included only 3 species. The abundance of phytoplankton varied from 12.4 × 103 to 310.7 × 103 cells / L and a biomass from 1.0 to 14.7 mg / m3, and the abundance of zooplankton varied from 55.1 × 103 to 1656.0 × 103 individuals / m3 and a biomass from 1.1 to 85.5 g / m3. Euryhaline and halophilic species dominatedОзера Барун-Торей и Зун-Торей являются самыми крупными водоемами в Забайкальском крае, для них характерна хорошо выраженная цикличность, проявляющаяся в многолетних изменениях уровня воды. Материалом для работы послужили пробы, собранные на Торейских озерах в июне, августе, октябре в маловодный 2016 г. Сбор и обработка материалов проводилась согласно стандартным гидробиологическим методам. Целью работы стало изучение особенностей развития планктонных биоценозов Торейских озер, одновременно находящихся в разных гидрологических фазах: Барун-Торей – в начальной фазе наполнения, Зун-Торей – в фазе снижения уровня воды. В районе северной оконечности высохшего Барун-Торея в пределах дна его ложа отмечались мелкие водоемы, источником питания которых служила многолетняя мерзлота и разгрузка подземных вод по разлому, проходящему по западному берегу озера. В Зун-Торее продолжался процесс обмеления водоема, который закончился практически полным его высыханием осенью 2017 г. Состав и структура фитопланктона и зоопланктона в разные гидрологические периоды имели существенные различия, определяемые уровнем минерализации озерных вод. В олигогалинных водоемах котловины Барун-Торея развивался литоральный планктоценоз, состоящий из 46 таксонов водорослей (при колебаниях от 2 до 25) и 29 видов беспозвоночных (при колебаниях от 2 до 15). Значения численности и биомассы гидробионтов колебались в очень широких пределах: фитопланктон – от 0,7 до 1260,0 тыс. кл/л и от 0,1 до 1271,0 мг/м3, зоопланктон – от 9,2 до 19370,0 тыс. экз/м3 и от 3,8 до 361,7 г/м3. Доминировали пресноводные и эвригалинные виды. Альгофлора полигалинного оз. Зун-Торей состояла из 18 таксонов (при варьировании от 3 до 12), фауна беспозвоночных – из 3 видов. Количественные показатели варьировали от 12,4 до 310,7 тыс. кл/л и от 1,0 до 14,7 мг/м3 для фитопланктона, и от 55,1 до 1656,0 тыс. экз/м3 и от 1,1 до 85,5 г/м3 – для зоопланктона. Преобладали эвригалинные и галофильные вид

Complexation of Alkali Metal Cations by a Tertiary Amide Calix[4]Arene Derivative in Strongly Cation Solvating Solvents

The complexation of alkali-metal cations with calix[4]arene tertiary amide derivative (L) was studied in N-methylformamide (NMF), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) by means of microcalorimetric and UV spectrophotometric titrations. The Gibbs energies, enthalpies, and entropies for transfer of reactants and products from N-methylformamide to other solvents were determined. Favorable enthalpic contribution to overall stability was found to be the most important for all complexation reactions, especially in the case of NaL+ formation, resulting in an affinity peak of L for this cation. The complexation entropy changes were always unfavorable. The ligand dissolution was endothermic in all solvents, accompanied by positive solution entropy. The highest complex stability constants were determined in NMF, whereas in DMSO the affinity of L towards alkali metal cations was the lowest. An interesting interplay between the transfer enthalpies and entropies of the reactants and complexes was revealed and discussed in detail. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis of Fluorescent Diphenylanthracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

Two novel fluorescent calix[4]arenes comprising diphenylanthracene moiety at the lower rim were synthetized and their complexation with alkali metal cations in acetonitrile/dichloromethane and methanol/dichloromethane mixtures (φ = 0.5) was studied experimentally and by classical molecular dynamics and quantum chemical calculations. The monosubstituted calixarene derivative (L1) proved to be a poor cation receptor, whereas the ester-based macrocycle (L2) exhibited rather high affinity towards lithium, sodium and potassium cations, particularly in MeCN/CH2Cl2. All complexation reactions were enthalpically controlled, whereby the overall stability was the largest in the case of sodium complex. The computational investigations provided an additional insight into the complexation properties and structures of complex species. The molecular dynamics simulations indicated the occurrence of inclusion of solvent molecules in the calixarene hydrophobic cavity of the free and complexed ligand, which was found to significantly affect the complexation equilibria. This work is licensed under a Creative Commons Attribution 4.0 International License