C–H···π Hydrogen Bonding between Electron-Rich Benzene Rings and Polarized C–H Bonds: Selectivity in the Complexation of Highly Hydrophilic Guest Molecules with Calix[4]resorcarene Hosts in Water

Abstract

Tetrasulfonate derivatives of calix[4]resorcarene (calix[4]arene derived from resorcinol) (1) form 1 : 1 complexes with highly hydrophilic guest molecules, such as ethers, alcohols, ketones, and sulfoxides, in water. The affinities of three types of the guests increase in the order CH3–X–CH3 < (–CH2CH2–X–)2 < CH3–X–CH2CH2–X–CH3 (X = O, CH(OH), C=O, or S=O), reflecting the importance of multiple host-guest interactions. The binding constants (K) with respect to X increase in the order O < CH(OH) < C=O < S=O or CH(OH) < O < C=O < S=O. As for the effects of substituents Y on 2-C of the benzene rings of the host, both 1b (Y = CH3) and 1c (Y = OH) exhibit higher binding capabilities than does the parent host 1a (Y = H). Thus, the present complexation is promoted by electron-withdrawing residue (X) in the guests and electron-donating substituents (Y) in the host. The binding of CH3–X–CH3 (X = C=O or S=O) to hosts 1a—c is characterized by favorable enthalpy changes and unfavorable entropy changes. These results, coupled with NMR data, indicate that the driving force of the present complexation is a C–H···π interaction between C–H bonds of a guest as soft acids and benzene rings of the host as soft bases.

Receptor properties of calix[4]resorcinarenes toward tetramethylammonium and choline cations in micellar solutions of sodium dodecyl sulfate

“…The hydrophobic effect, being a moving force of formation of "host-guest" complexes based on cyclodextrins, plays no noticeable role in similar compounds of calixarenes. 26 Intermolecular interactions between the negatively charged rim of the solubilized [H 4 L] 4-anion and sulfate groups of SDS should not either be expected. Therefore, mixed micellar aggregates [H 4 L] 4--SDS should have good inclusion properties to ward organic cations.…”

Photophysical and electrochemical properties of the outer-sphere associate of [Ru(bipy)3]2+ with p-sulfonatothiacalix[4]arene

“…Being more electropositive, the Co 3+ ion withdraws the electron density from the bipyridyl frag ments more strongly than does Ru 2+ . In the context of Kobayashi´s theory, 30 [Co(bipy) 3 ] 3+ is a stronger CH acid than [Ru(bipy) 3 ] 2+ , which in turn can account for the more efficient CH-π interactions and the more efficient shield ing of bipyridyl protons.…”

(π)C—H···S, (allyl)C—H···C(π) and π···π intermolecular interactions: synthesis, characterization, and crystal structure of 2,2′-bipyridine bis(diallyldithiocarbamato)zinc(II)

“…On the other hand, short C-H···aryl [35][36][37] were observed in the stabilisation of inclusion complexes. They have in fact the structural and spectroscopic properties of weak hydrogen bonds [38][39][40][41], very similar to O-H···π and N-H···π interactions.…”