Abstract
This thesis focuses on the syntheses, structures, and properties of new cobalt phosphates and cobalt phosphites. According to their structure features and compositions, they can be categorized into three groups. (1) Layer Cobalt Phosphates (LCPO) We found that a stable cobalt phosphate layer, (H3O)Co2(OH)2(HPO4)(H2PO4), can be used as a basic structure unit for the construction of 3-D structures via either the self condensation or insertion of extra metal polyhedral units. Moreover, extra cobalt ions can be attached to the LCPO through sharing three oxygen corner and leave the forth corner as the active coordination sites for bifunction organic amine ligands such as DACH or APPIP, which interlink with LCPO to form a 3-D microporous structure. Replacing the bifunction amines by monofunctional amines such as CHA, a neutral 2-D structure is fabricated with a hydrophobic and expandable interlayer space, which finds application in intercalatioin and exfoliation. (2) Fluorinated Cobalt Phosphates In the system of CoO-P2O5-HF-Amine-H2O, five new compounds were acquired. Compound B1 and B2 belong to the organic-pillar type. These two compounds consist of the same inorganic layer of the fluorinated cobalt phosphates which are interlinked by the PYZ and BPE, respectively. Because the BPE molecule is long enough to eliminate the interlayered antiferromagnetic interaction, B2 become ferrimagnatic based on the faced-shared trimeric cobalt units below 20K. However, in the case of the shorter PYZ, the interlayered antiferromagnetic interaction is stronger. B1 show a metamagnetic behavior below 20K because of the competition between the ferrimagnetic and the antiferromagnetic interaction. B3 and B4 consist of similar D-4R units of fluorinated CPOs. However, the connections between the D-4R units are through strictly coner-sharing connection in B3 but coner- and edged-sharing connection in B4. B5 is a layered fluorinated cobalt vanadium phosphate. (3) Cobalt Phosphites In the system of CoO-P2O3- Amine-H2O, five new compounds were acquired. Among them, four are cobalt phosphites, and the other one is a cobalt pyrophosphate. The four cobalt phosphites are with zero-, one-, two- and three-dimensional structures, respectively. The imidazole is the coordination ligand of the zero-dimensional complex. The DACH is the organic cation of the one-dimensional chain structure. The ammonium is functioned as the interlayered cations of the two-dimensional layer structure. The three-dimensional cobalt phosphite is pillared with the PYZ ligand. The cobalt pyrophosphate belongs to a two-dimensional structure.