Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures

Abstract

A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert-butyl ester groups. Single-crystal X-ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy-substituted macrocycle undergoes a single-crystal-to-single-crystal transformation during which the molecular structure changes its conformation from 1,3-alternate (loaded with THF/water) to 1,2-alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles.

Main group metal lone-pair⋯π(arene) interactions: a new bonding mode for supramolecular associations

“…123. 124 These associate with translationally related molecules to generate a linear chain, motif 1_I, Fig. 18h.…”

Selenium-Functionalized Graphene Oxide That Can Modulate the Balance of Reactive Oxygen Species

“…Selenium is an essential trace element in living organisms and possesses unique chemical features due to its atomic structure. , Selenium atom has a larger atomic radius and smaller electronegativity compared with sulfur atom; the bond energy of diselenide bond was much lower in contrast to that of disulfide bond, at 172 and 240 kJ mol –1 , respectively . As a result, it has been proved that diselenide bond can respond to both redox condition and visible light irradiation in a highly sensitive manner. − The diselenide bond could be cleaved to form seleninic acid or selenol under redox conditions, and under visible light irradiation or under heating selenium radicals could be generated.…”

Dynamic Chemistry of Selenium: Se–N and Se–Se Dynamic Covalent Bonds in Polymeric Systems

“…In 1957, selenium was determined to be one of the necessary elements in the human body, after that, selenoproteins were also discovered, which prevent cell damage from free radicals. As free radicals are related to several chronic diseases, such as cancer and heart disease, various small antioxidant molecules containing selenium were synthesized and studied. − The previous applications of selenium in polymer chemistry, however, were mostly related to polyselenophenes by using their photovoltaic properties. − Selenium-containing macrocycles were also studied. , In our group, we have developed a series of selenium-containing polymers and used them in biosystems as responsive materials . In these studies, we took advantage of low bond energies of C–Se and Se–Se (C–Se, 244 kJ mol –1 ; Se–Se, 172 kJ mol –1 , while C–S, 272 kJ mol –1 ; S–S, 240 kJ mol –1 ), which makes the monoselenide and diselenide easy to be oxidized or reduced.…”

“…6−9 Selenium-containing macrocycles were also studied. 10,11 In our group, we have developed a series of selenium-containing polymers and used them in biosystems as responsive materials. 12 In these studies, we took advantage of low bond energies of C−Se and Se−Se (C−Se, 244 kJ mol −1 ; Se−Se, 172 kJ mol −1 , while C−S, 272 kJ mol −1 ; S−S, 240 kJ mol −1 ), 13 which makes the monoselenide and diselenide easy to be oxidized or reduced.…”