UVM Theses and Dissertations
Format:
Print
Author:
Manney, Matthew R.
Dept./Program:
Chemistry
Year:
2013
Degree:
MS
Abstract:
In this project, a series of mixed zirconium phenylbutyl methyl phosphonates, having the general formula Zr(O₃P(CH₂)₄C₆H₅)x(O₃PCH₃)₂-x, have been synthesized and studied. These materials have been produced in a series of stoichiometric ratios, and their structural and photophysical properties as this ratio was altered have been determined. After synthesis of each compound in the series, chemical characterizations were carried out using thermogravimetric analysis and infrared spectroscopy to confirm the pendant group ratio, and solid-state ³¹P NMR spectroscopy has been used to study the local phosphorus environments within the layered materials. A structural study of the series was undertaken using powder X-ray diffraction to study the interlayer spacing between plane's of zirconium atoms. The results of this study showed a novel structural dependence on pendant group stoichiometry, where a combination linear/stepwise behavior has been observed. There seem to be certain interlayer spacings which are favored, such that the solid materials will co-crystallize as two or more different systems, each with one of these spacings.
When uniform crystalline materials were obtained, it was found that in certain ranges of stoichiometric ratio there is a linear increase in interlayer spacing as the ratio is changed, and in other ranges there is a stepwise behavior, with one spacing being seen over a range of stoichiometric ratios. The second part of the study focused on the photophysical behavior of this series of materials. It was discovered that aggregation of the phenyl ring chromophores could be achieved in the layered materials, whereas it is very minor in the solution phase precursors. Chromophore aggregation was in the form of excimer formation, evidenced by featureless, red-shifted fluorescence emission bands, as opposed to ground-state dimerization. The fluorescence emission spectra showed almost exclusively excimer emission and little to no monomer emission at high ratios of phenylbutyl to methyl, with the degree of excimer formation decreasing as the amount of phenylbutyl in the material decreased. These materials served as a framework for inducing photophysical processes (i.e., excimer formation) upon chromophores for which these processes do not spontaneously occur in the solution phase.
When uniform crystalline materials were obtained, it was found that in certain ranges of stoichiometric ratio there is a linear increase in interlayer spacing as the ratio is changed, and in other ranges there is a stepwise behavior, with one spacing being seen over a range of stoichiometric ratios. The second part of the study focused on the photophysical behavior of this series of materials. It was discovered that aggregation of the phenyl ring chromophores could be achieved in the layered materials, whereas it is very minor in the solution phase precursors. Chromophore aggregation was in the form of excimer formation, evidenced by featureless, red-shifted fluorescence emission bands, as opposed to ground-state dimerization. The fluorescence emission spectra showed almost exclusively excimer emission and little to no monomer emission at high ratios of phenylbutyl to methyl, with the degree of excimer formation decreasing as the amount of phenylbutyl in the material decreased. These materials served as a framework for inducing photophysical processes (i.e., excimer formation) upon chromophores for which these processes do not spontaneously occur in the solution phase.