title: Self-complementary recognition of supramolecular urea-aminotriazines in solution and on surfaces.
abstract: The recognition of self-complementary quadruple urea-aminotriazine (UAT)-based hydrogen-bonded arrays was investigated in solution and at surfaces. For this purpose, an UAT-based donor-acceptor-donor-acceptor (DADA) array and complementary receptors were synthesized. Two-dimensional proton nuclear magnetic resonance ((1)H NMR) measurements in CDCl(3) pointed at an intramolecular hydrogen-bond stabilization of the UAT, which promotes a planar molecular geometry and, thereby, results in a significant stabilization of the dimeric complex. The bond strength of the UAT dimers at surfaces was determined by atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS) in hexadecane. The UAT receptor was immobilized on gold surfaces using an ultrathin layer of ethylene glycol terminated lipoic acid and isocyanate chemistry. The layers obtained and the reversible self-complementary recognition were thoroughly characterized with contact angle measurements, grazing angle Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and AFM. Loading rate-dependent SMFS measurements yielded a barrier width x(β) and a bond lifetime at zero force t(off)(0) of 0.29 ± 0.02 nm and 100 ± 80 ms, respectively. The value of the corresponding off-rate constant k(off) suggests a substantially larger value of the dimerization constant compared to theoretical predictions, which is fully in line with the additional intramolecular hydrogen-bond stabilization detected in solution by (1)H NMR spectroscopy.
authors.affiliation: Department of Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, Post Office Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Anika
authors.initials: A
authors.lastname: Embrechts
authors.forename: Aldrik H
authors.initials: AH
authors.lastname: Velders
authors.forename: Holger
authors.initials: H
authors.lastname: Schönherr
authors.forename: G Julius
authors.initials: GJ
authors.lastname: Vancso
mesh_terms: D006860:Hydrogen Bonding; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D012996:Solutions; D013499:Surface Properties; D014227:Triazines / Q000737:chemistry*; D014508:Urea / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D012996:Solutions; D014227:Triazines; D014508:Urea