Synthesis, conformational and host–guest properties of water-soluble pillar[5]arene

Abstract

Water-soluble pillar[5]arene was synthesized by the introduction of carboxylate anions at both upper and lower rims. When cationic viologen salt was mixed with the water-soluble pillar[5]arene in aqueous media, a very stable 1:1 host-guest complex was formed.

pH-Responsive Host–Guest Complexation in Pillar[6]arene-Containing Polyelectrolyte Multilayer Films

“…Since WP6 alone bears an absorbance maximum at 292 nm (see Supplementary Figure S1 in the supporting information), the new band might be the result of changed absorbance properties of the host due to the intermolecular interactions with the guest molecule. Additionally, a very weak charge transfer band is detected in the regime between 400 and 550 nm [22]. The latter was even more clearly identified by measuring the complex solution at an increased concentration (see Supplementary Figure S2), thus a charge transfer interaction between the electron-rich cavity and the electron-poor guest molecule is indicated.…”

“…MV was first titrated into a solution of WP6 at pH 7.8 and a binding constant of k a = (1.53 ± 0.39) 10 6 M −1 was extracted from a single site binding model (see Table 1 and Supplementary Figure S3 for raw data). The determined stoichiometry of n = 0.92 ± 0.07 further confirmed that a 1:1 complex was formed, as expected [22]. We then repeated the ITC experiments at pH 4.8 in order to figure out if acidic conditions are able to prevent the host-guest complexation due to the protonation of WP6.…”

“…The π-electron-rich cavity combined with the opportunity of structure-tailoring motivated scientists to investigate the potential of P[n]s in the field of host-guest chemistry. The molecular recognition of P[n = 5,6] towards a series of guest molecules has been reported, showing that cooperative host-guest-interactions such as electrostatics, hydrophobic interactions, charge transfer interactions, hydrogen bonding, and π-π-stacking are responsible for driving the complexation [22,23]. In addition, the introduction of stimuli-responsiveness on either the guest or the host enabled the fabrication of P[n]-guest based complexes, receptors, and drug delivery systems whose assembly could reversibly be switched by tuning either a single or multiple stimuli such as pH, light irradiation, or redox conditions [24][25][26][27][28][29][30][31].…”

Supramolecular FRET modulation by pseudorotaxane formation of a ditopic stilbazolium dye and carboxylato-pillar[5]arene

“…Especially, the discovery of water soluble derivatives (WPns) have further extended their applications in various biological systems. Mostly ionic (carboxylato [28][29][30], ammonium [31,32], imidazolium [33]) pillararenes, in particular carboxylato-Pns have been used in binding studies performed in aqueous medium. Carboxylato-pillar [5]arene (WP5), first synthesized by Ogoshi in 2010 [28] is an ideal host for ammonium-containing and electron-deficient guests [34][35][36].…”

“…Mostly ionic (carboxylato [28][29][30], ammonium [31,32], imidazolium [33]) pillararenes, in particular carboxylato-Pns have been used in binding studies performed in aqueous medium. Carboxylato-pillar [5]arene (WP5), first synthesized by Ogoshi in 2010 [28] is an ideal host for ammonium-containing and electron-deficient guests [34][35][36]. It is worth mentioning that only a few papers describe the complexation of fluorescent guests by WP5 [37,38] and the observation of FRET on sophisticated supramolecular systems containing pillararenes was reported only in two recent articles [39,40].…”