Ian Rhys Morgan

Facile syntheses of dissymmetric ferrocene-functionalized Lewis acids and acid–base pairs

A facile synthetic approach is reported for the synthesis of dissymmetric 1,2-ferrocenediyl Lewis acids and mixed acid-base pairs including the first example of a 1-phosphino-2-borylferrocene; the use of non-racemic electrophiles allows for the isolation of single diastereomer products.

Structure–property relationships in metallosurfactants

The morphology of micelles formed by three sub-classes of metallosurfactants—those with macrocyclic, linear and gemini head groups—has been studied by small-angle neutron scattering (SANS) for a series of metal- and counter-ions. All the data may be described by a model that invokes a globular micelle morphology in which the dimensions of the micelle are consistent with the known chemical structure of the constituent groups within the metallosurfactant. For two macrocyclic head group metallosurfactants, viz. 1-(2-hydroxy-tetradecyl)-1,4,7-triazacyclonane that forms predominantly spherical micelles and 1-(2-hydroxy-tetradecyl)-1,4,7,10-tetraazacyclononane that forms disc-like micelles, the metal ion and its counter-ion have a negligible effect on the morphology of the micelle. Binary mixtures of surfactants with these two macrocyclic head groups (with homo- or hetero-metal ions/counter-ions) form mixed micelles whose morphology is an average of the two single component micelles. Further, as found for the single surfactant solutions, the metal and counter-ion had no effect on the morphology of the mixed surfactant micelle. Lastly, the micelle morphology of two gemini surfactants was also shown to be insensitive to the number and nature of the metal and counter-ions present, but sensitive to the structure of the head group. These observations considerably extend our understanding of the relationship between chemical structure and micelle morphology for these interesting molecules.

Self-Assembling Chiral Gelators for Fluorinated Media†

Formulations involving partially and fully fluorinated media represent a technological challenge given the lipophobic and hydrophobic nature of such liquids. The identification of self-associating materials with which to control the viscosity and solubilizing characteristics of fluorinated solvents is a particularly interesting area of research. It is shown here that the presence of the stereogenic centers inherent in a family of bis-(alpha,beta-dihydroxy ester)s is an essential requirement for the thermoreversible gelation of mixtures of partially fluorinated liquids 2H,3H-perfluoropentane (HPFP) and 1H,1H-heptafluorobutanol (HFB). Gelation is driven by hydrogen bonding, which induces a nonpreferred conformation around the bis-(alpha,beta-dihydroxy ester) structural motif. An analysis of the melting temperature yields an enthalpy of melting that is consistent with three to four hydrogen bonds, commensurate with the end-group structure of the gelator. Small-angle neutron scattering demonstrated the existence of the common fibrillar structures whose dimensions showed no obvious correlation with the molecular structure of the gelator.

Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

Summary Understanding the gelation of liquids by low molecular weight solutes at low concentrations gives an insight into many molecular recognition phenomena and also offers a simple route to modifying the physical properties of the liquid. Bis-(α,β-dihydroxy ester)s are shown here to gel thermoreversibly a wide range of solvents, raising interesting questions as to the mechanism of gelation. At gelator concentrations of 5–50 mg ml−1, gels were successfully formed in acetone, ethanol/water mixtures, toluene, cyclohexane and chloroform (the latter, albeit at a higher gelator concentration). A range of neutron techniques – in particular small-angle neutron scattering (SANS) – have been employed to probe the structure of a selection of these gels. The universality of gelation in a range of solvent types suggests the gelation mechanism is a feature of the bis-(α,β-dihydroxy ester) motif, with SANS demonstrating the presence of regular structures in the 30–40 Å range. A correlation between the apparent rodlike character of the structures formed and the polarity of the solvent is evident. Preliminary spin-echo neutron scattering studies (SESANS) indicated the absence of any larger scale structures. Inelastic neutron spectroscopy (INS) studies demonstrated that the solvent is largely unaffected by gelation, but does reveal insights into the thermal history of the samples. Further neutron studies of this kind (particularly SESANS and INS) are warranted, and it is hoped that this work will stimulate others to pursue this line of research.

Synthesis of bioorthogonal and crosslinking amino acids for use in peptide synthesis

The ability to incorporate non-canonical amino acids into proteins by genetic or chemical methods allows one to introduce novel chemical properties into a protein at a defined residue. Such a residue may then be modified using common organic transformations. In this way, the structure or function of the peptide may be altered without perturbing any of the other neighbouring amino acids in the peptide chain. Here, we describe the syntheses and potential applications of multiple para-substituted phenylalanine derivatives comprising an isothiocyanate, α-diazoketone, or nitrone functionality. In all, three novel amino acids were synthesized in good overall yields. These non-canonical amino acids permit the further development of in vitro and in vivo chemoselective and regioselective bioconjugate reactions not possible with other reagents.

CCDC 744802: Experimental Crystal Structure Determination

Related Article: A.E.J.Broomsgrove, D.A.Addy, A.Di Paolo, I.R.Morgan, C.Bresner, V.Chislett, I.A.Fallis, A.L.Thompson, D.Vidovic, S.Aldridge|2010|Inorg.Chem.|49|157|doi:10.1021/ic901673u