title: Dimeric self-assembly of pyridyl guanidinium carboxylates in polar solvents.
abstract: A series of pyridyl guanidinium-carboxylates has been prepared and the dimeric self-assembly of these studied in H(2)O/DMSO mixtures, principally using dilution isothermal calorimetry. Compounds 5 and 6, incorporating an aromatic ring in the "tethering" region between the guanidinium and carboxylate groups, demonstrate the strongest dimerisation in neat DMSO. X-ray crystal structures of 5 and 6 reveal two different dimerisation architectures in the solid-state, but both involve carboxylate-guanidinium salt bridges as anticipated, and π-π interactions. Compounds 10-16 incorporating peptidic fragments between the guanidinium and carboxylate groups, showed reduced dimerisation strength with increased amino acid content, but also sustained dimerisation under increasingly aqueous conditions, up to 50% H(2)O/DMSO in the case of 14 and 15. The extent of our study in H(2)O/DMSO mixtures was determined by substrate solubility of 10-16, and not the limit of self-assembly.
authors.affiliation: School of Chemistry, University of Southampton, Southampton, SO17 1BJ UK.
authors.forename: Muhammad Irfan
authors.initials: MI
authors.lastname: Ashiq
authors.forename: Biniam F
authors.initials: BF
authors.lastname: Tesfatsion
authors.forename: Francesca
authors.initials: F
authors.lastname: Gaggini
authors.forename: Sally
authors.initials: S
authors.lastname: Dixon
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Kilburn
mesh_terms: D002151:Calorimetry; D002264:Carboxylic Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide; D004952:Esters; D019791:Guanidine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013890:Thiourea / Q000138:chemical synthesis / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D004952:Esters; D011725:Pyridines; D012997:Solvents; D014867:Water; D013890:Thiourea; D019791:Guanidine; D004121:Dimethyl Sulfoxide