Achieving Strong Positive Cooperativity through Activating Weak Non‐Covalent Interactions

Abstract

Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new molecular tubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. The X-ray single-crystal structure revealed that the strong positive cooperativity likely originates from eight C-H⋅⋅⋅O hydrogen bonds between the two head-to-head-arranged syn tube molecules. These relatively weak hydrogen bonds were not observed in the free hosts and only emerged in the complex. Furthermore, this complex was used as a basic motif to construct a robust [2+2] cyclic assembly, thus demonstrating its potential in molecular self-assembly.

Hydrogen Bonding versus H−H Interactions in Pillar[n]arenes

“…The ρ BCP parameters corresponding to cooperative hydrogen bonds in P5 and P7 macrocycles are reported in Table S5. These data along with the ∇ 2 ρ BCP values ascertain the presence of C−H−O hydrogen bonding . In other words, mutual orientation of adjacent hydroxyl group as noticed here triggers cooperative interactions from the aromatic hydrogen with neighbouring hydroxyl groups.…”

Directional Shuttling of a Stimuli‐Responsive Cone‐Like Macrocycle on a Single‐State Symmetric Dumbbell Axle

“…While the phenyl groups (protons f and g ) of the guest undergo much smaller shifts, indicating that the pentyl group is located in the center of the cavity. This is similar to the complex formed by the ether naphthotube . The binding stoichiometry is 1:1 as indicated by the mass spectrum (Supporting Information, Figure S11).…”

“…First, appropriate binding stations for 1 a and 1 a‐2H 2+ had to be determined. In analogy to its ether counterpart, we found 1 a binds guests with two quaternary ammonium moieties connected by a linear alkyl chain, for example, 2 2+ (Figure a). The binding is clearly indicated by the upfield shift of the NMR signals (0.2–−3.2 ppm) of the pentyl group (protons j , l , k , k ′, and l ′) of guest 2 2+ when mixed with 1 a (Figure ; Supporting Information, Figures S8–S10), suggesting that the guest is located inside the host cavity and experiences a shielding effect from the four naphthalene units.…”

Positive Allosteric Control of Guests Encapsulation by Metal Binding to Covalent Porphyrin Cages

“…Promising allostericm odulation of the receptora ctivity of multi-component 3D containers has been obtained using chemical, [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] redox, [49][50][51] or photoinducedr eactions. [52][53][54][55][56][57][58] Most of such structures are self-assembled through hydrogen or metal-ligand bonds, but covalent structures remaini nteresting for their high chemical stabilitya nd their ability to respond to variouss ignaling events.…”