UC Santa Cruz

This dissertation will present three different variations of solvothermal methods for the obtainment of distinct classes of extended materials: the ionothermal synthesis of metal-doped nanoporous aluminophosphates, the hydrothermal synthesis of cationic coordination polymers, and the solvothermal synthesis for the crystallization of racemic polypeptide mixtures.Chapter 1 introduces the field of metal-doped nanoporous aluminophosphates, a class of zeolitic material commonly used as catalysts in the petrochemical industry. The history that led to the development of these materials, their unique chemistry, and their synthetic details are discussed. Ionothermal synthesis is presented as an alternative to the usual hydrothermal method, and its concepts and advantages are detailed. The last section of this chapter is a literature review presenting – to the best of our knowledge – all the current reports of MAPOs synthesized via the ionothermal route. Chapter 2 explores the ionothermal synthesis of AlPO4-5 molecular sieves and the doping of its inorganic framework with Mn2+ or Ni2+. The ionic liquids diisopropylimidazolium bromide (DIPI) and diisobutylimidazolium bromide (DIBU) were used as both the solvents and structure-directing agents, and HF was used as the mineralizer. Varying amounts of water, metal, and HF in the medium led to either AFI, cristobalite, or tridymite framework structures. The product’s phase(s) were determined by powder X-ray diffraction (PXRD). Further structural insights were obtained by studying the coordination of Al3+, P5+, and F- by solid-state nuclear magnetic resonance (SS-NMR) spectroscopy. Electron paragenetic resonance (EPR) spectroscopy and X-ray absorption spectroscopy (XAS) were used to investigate the metal incorporation in the framework. AlPO4-5 and MnAPO-5 phases were isolated. Although there was no evidence of NiAPO-5 formation, the presence of Ni2+ in the reaction medium affected the phase selectivity. Lastly, the thermal stability of the products was determined by thermogravimetric analysis (TGA). Chapter 3 describes the hydrothermal synthesis and single-crystal structure of the novel phase SLUG-53 [Ag(2,4'-bypiridine)NO3]. Close examination of PXRD and single-crystal X-ray diffraction (SCXRD) data reveals the material behaves as a soft-porous crystal, as temperature perturbations led to anisotropic distortions of the unit cell. SLUG-53 undergoes an anion exchange reaction, where the nitrate ions are replaced by perrhenate, a surrogate for the radioactive and hazardous ion pertechnetate. The structure of the resulting material, the novel SLUG-54 ([Ag(2,4'-bypiridine)ReO4]), was also elucidated by SCXRD and revealed that an 8-membered inorganic ring is formed between perrhenate ions and two adjacent chains of polymeric Ag-2,4'-bipyridine. Kinetics studies showed that the exchange reaction follows a pseudo-second-order mechanism. The data was fitted to the Langmuir model to reveal that SLUG-53 shows a superior adsorption capacity of 764 mg ReO4/g SLUG-53. Chapter 4 presents the first high-resolution crystal structure study on the rippled β-sheet formation predicted in 1953 by Pauling and Corey to occur in racemic polypeptide mixtures. While other predictions of these scientists have now become textbook knowledge, such as the pleated β-sheet, the then theorized rippled arrangement was yet to be deeply investigated. The study presented here describes the solvothermal obtainment of [FFF.fff], where L,L,L-tripenhylalanine and D,D,D-triphenylalanine polypeptides strands were found to form dimers in an antiparallel rippled configuration for the first time. Such dimeric units are then further arranged in a herringbone fashion. Ramachandran angles were investigated for [FFF.fff] and three other racemic proteins presenting rippled motifs, which were selected after extensive database mining. Chapter 5 presents a summary and describes future lines of investigation for each of the three projects discussed in this dissertation.