Quadruply Hydrogen Bonded Cytosine Modules for Supramolecular Applications

Abstract

In view of the range of properties required from supramolecular materials, there is clearly a need for new strong quadruple hydrogen bonded modules, which can be used in polymer or copolymer synthesis via the self- or hetero-association of complimentary units. A cytosine-based module has been prepared for supramolecular applications using a straightforward synthetic approach. The cytosine module was designed such that it does not undergo tautomeric changes observed with ureidopyrimidinones. The cytosine module was capable of forming quadruple hydrogen bonded assemblies both in solution and in the solid state, and the structure of the dimeric self-assembled unit was confirmed by single-crystal X-ray and solution NMR techniques. The dimerization constant was estimated to be greater than 9 × 106 M-1 in deuterated benzene. The capacity of the cytosine-based module to strongly hetero-associate with the ureidopyrimidinone module was demonstrated, and a supramolecular polymer of a bifunctional unit incorporating the cytosine module and PEG-based linker was described.

Competitive Intramolecular Hydrogen Bonding in Oligo(ethylene oxide) Substituted Quadruple Hydrogen Bonded Systems

“…Taking all of the results into account, two mechanisms can be thought to be responsible for the reduction of K dim in oligoEO substituted 2-ureido-pyrimidinones: (1) 2 ), it can be easily recognized that an increase in the stability of the 6[1H] tautomer leads to a rapid decrease in the observed K dim (Figure 6a) due to a decrease in K taut . As was explained previously, the stabilizing effect of intramolecular hydrogen bonding of the oligoEO chain on the 6[1H] monomer will be lower for longer spacers (increasing m) as a result of entropic effects, whereas it will increase with the number of possible interactions (n).…”

Bindungsmechanismen in supramolekularen Komplexen

“…[360] Solche D-AArrays eignen sich besonders für die nichtkovalente Verbindung von Fullerenen zu Elektronendonoreinheiten in redoxoder photoaktivierbaren Systemen. [361] Derivate von Cytosin [362] oder Guanidin [363] wie 25 und 26 sind teilweise frei von ungünstigen tautomeren Formen und dimerisieren in Chloroform mit K > 10 7 m À1 . Mit der DAADKombination aus 1,8-Naphthyridinen und Guanosin lässt sich das Problem einer unerwünschten Selbstassoziation einer Komponente umgehen.…”

Oligo(p‐phenylene‐ethynylene)s with Backbone Conformation Controlled by Competitive Intramolecular Hydrogen Bonds

“…Hence, hydrogen bonds and OEG side chains have frequently been implemented simultaneously in supramolecular architectures. [3][4][5][6][7][8][9][10] However, caution ought to be used in designing such systems because the oxygen atoms in OEGs are potential hydrogen-bond acceptors and may interfere with the designed hydrogen-bonding motifs. Recently, "back-folding" of OEG side chains driven by intramolecular hydrogen-bond formation with hydrogen-bond donors in the core structure was observed and investigated in a number of systems.…”