Soft templates in encapsulation complexes

Abstract

Template effects are an inevitable feature of supramolecular chemistry and were prominent in the discovery of crown ethers, carcerands and catenanes. Templates can act as guests or hosts, but in either role they must be structurally persistent - rigid or "hard" - on the timescale needed to form the final complexes. This report explores a peculiar effect encountered with self-assembled container molecules: soft templates. In these cases neither the guest nor the host has an independent existence, but they do coexist as complexes. The host and guest are prevented from collapsing into more familiar, stable structures by the forces that hold the complex together. The complexes represent emergent phenomena and offer a look at structures otherwise unknown in free solution.

Organic‐Inorganic Hybrid Materials: Multi‐Functional Solids for Multi‐Step Reaction Processes

“…The high structuralr obustness and stabilityo f the isolated actives ites detected in these solids,l argely im-prove the performances achieved by more traditional Class I hybrids wherein organic and inorganic counterparts are normally weakly connected by means of Vand er Waals, hydrogen bonding, or simple physico-chemical adsorption of soluble organocatalysts. [11] Therefore, the use of monomer precursors derived from functionalized silanes, in suitable synthesis conditions, allows the preparation of different families of organic-inorganic hybridm aterials with controllable structuration level and porous hierarchy.I nt his case, the induced morphologyo n the hybrids becomes decisive to define their physico-chemical properties andc onsequently their applicability. [12] In Figure 3 the main topologies which are formed starting from pre-designed siloxane precursors are presented.…”

Synthesis and Dimerization Studies of a Lipophilic Photoresponsive Aryl‐Extended Tetraurea‐Calix[4]pyrrole

“…The development of supramolecular systems [1][2][3][4][5][6][7] able to switch between two or more different states by the effect of external stimuli is an attractive goal of supramolecular chemistry. [8][9][10] Stimuli-controllable multi-functional supramolecular systems emerge when each state features different properties and/or functions such as morphology,a ggregation, and molecular recognition.…”

“…In host-guest chemistry,t he azobenzene unit has been installedi nto the frameworks of host molecules, such as crown ethers, [24] cyclodextrins, [25][26] dendrimers, [27][28] polymers, [29][30] calix [4]pyrroles, [31] resorcin [4]arenes, [32] and coordination cages, [33] as well as guest molecules. [34][35][36] In these examples, the isomerization of the azobenzene units allowed the modulation of the thermodynamics tabilities of the resulting complexes.…”

“…

We describe the syntheses of the lipophilic aryl-extended a,a,a,a-tetraurea-phenyl-calix [4]pyrrole 1,f eaturing four appended azo-phenyl groupsw ith two tert-butoxy carbonyl meta-substituents and itsp hoto-inactive counterpart 2.I nC D 2 Cl 2 solutions, both tetraurea-calix[4]pyrroles self-assemblei nto dimeric capsules by encapsulating one molecule of as uitable bis-N-oxide or two molecules of am ono-Noxide. The dimericc apsules are mainly stabilized by ac yclic array of sixteenh ydrogen bonds established between the eight unidirectionally oriented urea groups.

…”

Acyclic Cucurbit[n]uril‐Type Molecular Containers: Influence of Linker Length on Their Function as Solubilizing Agents

“…acetals) and thereby promote hydrolysis reactions under basic conditions, 4 to create chemical sensing ensembles, 5 and to contort alkanes into helical conformations. 6 The supramolecular chemistry of the cucurbit[n]uril (CB[n]) family of molecular containers (Figure 1) is particularly rich, in large part due to their high affinity, high selectivity, and stimuli responsive host•guest complexes. 7 For example, CB[n] compounds function as catalysts for cycloadditions reactions, 8 components of biomembrane and chemical sensing systems, 9 promotors of dimerization assembly for materials and biological applications, 10 and sorption materials for gas purification.…”