Anion Complexation by Glycocluster Thioureamethyl Cavitands: Novel ESI‐MS‐Based Methods for the Determination of K_a Values

Abstract

A series of saccharide-thiourea functionalized cavitands was prepared in good yields (72-86 %) by reaction of a tetrakis(aminomethyl) cavitand with the thiocyanate derivatives of acetylated glucose, galactose, and cellobiose. The anion complexation behavior of the acetylated and deacetylated glycocluster thioureamethyl cavitands was studied with electrospray ionization mass spectrometry (ESI-MS) in acetonitrile and in a 1:1 acetonitrile/water mixture, respectively. All compounds show a preference for Cl(-). A linear relationship was found between the square root of the intensity and the concentration of the formed host-guest complex. Based on this relationship, novel methods have been developed to determine K(a) values, by means of direct titration and competition experiments.

The Underestimated Role of Counter Ions in Electrostatic Self‐Assembly:[1+1] Cavitand‐Calix[4]arene Capsules Based on Azinium–Sulfonate Interactions

“…In some cases, also signals of the capsule containing one or two solvent molecules are present (vide infra). Since no significant influence of suppression takes place at these concentrations, [20] it can be concluded that the absence of signals of the capsule components 1 and 2 is a strong indication of the almost complete association of the capsule at this low concentration (50 µ). The absence of signals of trimers, tetramers, etc.…”

Supramolekulare Chemie in Wasser

“…[134] Die ursprüng-lich entwickelten Cavitanden 53 (X = CH 2 , R 1 = Alkyl, R 2 = H, Alkyl) sind unlöslich in Wasser. Um die Löslichkeit in wässrigen Medien zu erhöhen, wurden am oberen oder unteren Rand geladene Gruppen, [135][136][137] Saccharidfunktionen [138,139] oder verzweigte Oxosubstituenten [136] …”

“…[135] Wir beschrieben die Cavitand-Anionenrezeptoren 53 (R = Me, R 1 = CH 2 NHCSNH-R 2 , R 2 = Glucose, Galactose oder Cellobiose; R = Me, R 1 = CH 2 S-Glucose) mit Thioharnstoff-Substituenten, die im Fall der Monosaccharidderivate eine Wasserlöslichkeit von 0.5-0.8 mm und im Fall der Cellobiosederivate > 300 mm erreichen. [138,139] Diese Rezeptoren binden anorganische Ionen (Br…”

Chemistry of Cavitands

“…Three tetrabenzamidazole cavitands (35)(36)(37) have been prepared and their binding properties with n-alkylammonium guests (38)(39)(40)(41)(42) have been studied [23]. The crystal of 35 obtained from CH 2 Cl 2 /EtOH has a vase conformation stabilized by four EtOH molecules which form hydrogen bonds with benzimidazole units.…”