Self-assembled supramolecular structures of peptide derivatives often reflect a kinetically trapped state rather than the thermodynamically most favoured structure, which presents a challenge when trying to elucidate the molecular design rules for these systems. In this article we use thermodynamically controlled self-assembly, driven by enzymatic condensation of amino acid derivatives, to elucidate chemical composition/nanostructure relationships for four closely related Fmoc-dipeptide-methyl esters which form hydrogels; SF, SL, TF and TL. We demonstrate that each of the four systems self-assemble to form extended arrays of beta-sheets which interlock via pi-stacking of Fmoc-moieties, yet with subtle differences in molecular organisation as supported by rheology, fluorescence emission spectroscopy, infrared spectroscopy, X-ray diffraction analysis and molecular mechanics minimisation

Fluorination of the parent oxide, BaFeO 3-δ, with polyvinylidine fluoride gives rise to a cubic compound with a = 4.0603(4) Å at 298K. 57 Fe Mössbauer spectra confirmed that all the iron is present as Fe 3+. Neutron diffraction data showed complete occupancy of the anion sites indicating a composition BaFeO 2 F, with a large displacement of the Fe offsite. The magnetic ordering temperature was determined as T N = 645±5K. Neutron diffraction data at 4.2K established G-type anti-ferromagnetism with a magnetic moment per Fe 3+ ion of 3.95µ B . However, magnetisation measurements indicated the presence of a weak ferromagnetic moment, which is assigned to the canting of the antiferromagnetic structure. 57 Fe Mössbauer spectra in the temperature range 10 to 300K were fitted with a model of fluoride ion distribution that retains charge neutrality of the unit perovskite cell.

The emergent behavior of spin liquids that are born out of geometrical frustration makes them an intriguing state of matter. We show that in the quantum kagome antiferromagnet ZnCu3(OH)6SO4 several different correlated, yet fluctuating states exist. By combining complementary local-probe techniques with neutron scattering, we discover a crossover from a critical regime into a gapless spin-liquid phase with decreasing temperature. An additional unconventional instability of the latter phase leads to a second, distinct spin-liquid state that is stabilized at the lowest temperatures. We advance such complex behavior as a feature common to different frustrated quantum magnets.

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