Steric Effects on the Formation of Manganese Oxide Clusters and 2-Dimensional Ammonium Formate Architectures

摘要

It has been demonstrated by the Beatty group that altering the identity of the ortho-substituent of a dianiline counterion affects the assembly and dimensionality of a cadmium-chloride layer from 2-D to 0-D. This work seeks to extend this finding to metal oxide and organic hydrogen-bonded materials. By systematically increasing the ortho-substituent's size on the benzoate building block of reported manganese oxide clusters, of formula MnxOy(O2C-R)zL w (where R = Alkyl, L = neutral monodentate ligand), we aim to impact the self-assembly of these materials relative to their parent forms; establishing a structure/function relationship of each material through measurement of their magnetization. The formation of 2-dimensional hydrogen-bonded ammonium formate layers will be investigated in the same manner. By maintaining the formate anion, but altering the identity of the ammonium cation, typically a substituted benzylamine, a novel series of 2-D layered structures will be closely compared in order to determine the impact of substituents on the formation of these lamellar materials. With respect to the ammonium formate compounds, the size of the ortho-substituent is considered as well as the position of substituent around the ring. Additionally, these ammonium formate compounds will also be compared to analogous ammonium-3,5-pyrazoledicarboxylate structures (HPzDCA) to evaluate the impacts of the anion on the formation of these layered materials.;We have found that with metal oxides, solvothermal methods, in addition to a bulky ortho-phenyl substituted benzoate, were required to alter the crystal structure of the Mn12-type complex to a Mn13-supercubane-type structure. We also found that lowering the site-specific symmetry of distorted MnIII ions impacted the magnetization of the Mn12-type substituted compounds. With ammonium formates, we have found that, by modifying the substituent in a series of benzylamines, the shape and orientation of the layer sheets and the interlayer pillars are drastically altered as per hydrogen bonding, and CH/pi interactions. When compared to analogous HPzDCA compounds, the size of the anion (the mono-anion of 3,5-pyrazoledicarboxylic acid versus the formate ion) influences the shape of the layer. The smaller formate ion allows for enhanced flexibility in the hydrophilic sheet, as well as increased packing density of the ammonium cation.