Molecular recognition and self-assembly special feature: Encapsulation and characterization of proton-bound amine homodimers in a water-soluble, self-assembled supramolecular host.
Cyclic amines can be encapsulated in a water-soluble self-assembled supramolecular host upon protonation. The hydrogen-bonding ability of the cyclic amines, as well as the reduced degrees of rotational freedom, allows for the formation of proton-bound homodimers inside of the assembly that are otherwise not observable in aqueous solution. The generality of homodimer formation was explored with small N-alkyl aziridines, azetidines, pyrrolidines, and piperidines. Proton-bound homodimer formation is observed for N-alkylaziridines (R = methyl, isopropyl, tert-butyl), N-alkylazetidines (R = isopropyl, tert-butyl), and N-methylpyrrolidine. At high concentration, formation of a proton-bound homotrimer is observed in the case of N-methylaziridine. The homodimers stay intact inside the assembly over a large concentration range, thereby suggesting cooperative encapsulation. Both G3(MP2)B3 and G3B3 calculations of the proton-bound homodimers were used to investigate the enthalpy of the hydrogen bond in the proton-bound homodimers and suggest that the enthalpic gain upon formation of the proton-bound homodimers may drive guest encapsulation.
Pluth
Michael D
MD
Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
Fiedler
Dorothea
D
Mugridge
Jeffrey S
JS
Bergman
Robert G
RG
Raymond
Kenneth N
KN
D000478:Alkylation; D000588:Amines / Q000737:chemistry*; D001384:Azetidines / Q000737:chemistry; D001388:Aziridines / Q000737:chemistry; D001665:Binding Sites; D019281:Dimerization; D006860:Hydrogen Bonding; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D010880:Piperidines / Q000737:chemistry; D011522:Protons; D011759:Pyrrolidines / Q000737:chemistry; D012995:Solubility; D014867:Water / Q000737:chemistry*
D000588:Amines; D001384:Azetidines; D001388:Aziridines; D010880:Piperidines; D011522:Protons; D011759:Pyrrolidines; D014867:Water; C054965:N-methylpyrrolidine