The development of bimetallic catalysts for phosphorus ester hydrolysis and nanostructured chemical sensor materials based on liquid crystals.

摘要

The development of new methods for accelerating the hydrolysis of organophosphorus esters under mild conditions is an important area of industrial and academic research. Herein, several bimetallic complexes based on the binucleating ligand N,N,N',N'-tetrakis[(2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane (1L) have been developed and studied for the hydrolysis of the model organophosphorus ester p-nitrophenyl diphenylphosphate (PNPDPP). It was found that homobimetallic and heterobimetallic Cu(II), Zn(II), and Co(II) complexes of ligands 1L and its toluoyl ester derivative, 2L catalyze the hydrolysis of PNPDPP with relative rates, in many cases, that exceed those achieved by the most effective known transition-metal-based systems.; Systematic ligand modifications on certain elements of 1L (i.e., certain functional groups, bridging linker length) and changes to the metal-to-ligand ratio were investigated as avenues for improving the catalytic performance of its dizinc(II) complex for the hydrolysis of PNPDPP. Collectively, these studies showed that homobimetallic zinc(II) complexes made from 2L with two equivalents of ZnCl2 show the highest overall reactivity. Addition of a one- to four-fold excess of ZnCl2 to these systems (three to six total equivalents) led to an observed rate enhancement of nearly two orders of magnitude, making these systems the fastest known metal-based hydrolysis catalysts for phosphorus triesters currently known. The results obtained, in turn, were able to provide certain clues to the nature of the mechanism of action of these new bimetallic tetrabenzimidazole complexes.; This thesis also describes the design and study of chemical sensor materials based on liquid crystals. The ability to specifically detect the presence of certain chemical compounds at low concentrations is important on many levels including, but not limited to, healthcare, industrial process control, environmental testing, and military operations. Fluorescence-based chemical sensing is an important and promising means of doing this because it offers a quantitative, visual response with exceptional sensitivity for various analytes. To this end, the alcohol-appended 4-amino-1,8-naphthalimide based fluorescent photoinduced electron transfer (PET) chemosensor unit, 2-(2-hydroxy-ethyl)-6-(4-methyl-piperazin-1-yl)-benzo[de]isoquinoline-1,3-dione, has been developed. This molecule undergoes highly sensitive fluorescence enhancement when complexed to various transition metal and lanthanide cations. This chemosensor unit has been successfully linked through the alcohol moiety onto the lyotropic liquid crystalline monomer, 3,4,5-tris-(11-acryloyloxy-undecyloxy)-benzoic acid, with retention of activity.