A surface-enhanced Raman scattering spectroscopic study of five p-amino substituted tetraphenyl porphyrins and NAD.
Item
-
Title
-
A surface-enhanced Raman scattering spectroscopic study of five p-amino substituted tetraphenyl porphyrins and NAD.
-
Identifier
-
AAI9130326
-
identifier
-
9130326
-
Creator
-
Hosten, Charles M.
-
Contributor
-
Advisers: R. Birke | J. Lombardi
-
Date
-
1991
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Chemistry, Analytical
-
Abstract
-
The technique of surface enhanced Raman spectroscopy is applied to the study of the orientation, conformation and structural characterization of five p-amino substituted tetraphenyl porphyrins and NAD adsorbed on silver and gold electrodes.;For a series of p-amino substituted tetraphenyl porphyrins dissolved in acetonitrile, the combination of SERS and cyclic voltammetry allowed for the identification of two types of adsorbates at {dollar}-{dollar}0.6V. The p-amino tetraphenyl porphyrin molecules were found to adsorb with their axes oriented parallel to the electrode surface resulting in maximum interaction between the amino nitrogens and the electrode surface. The SERS spectrum of meso-tetrakis(4-aminophenyl)porphine,(TAPP), obtained in the absence of solvent molecules indicates that rotation of the phenyl rings into near planarity with the porphyrin macrocycle occurs, resulting in an extension of the porphyrin aromatic system to include the phenyl groups.;TAPP was electropolymerized on a gold electrode from both non-aqueous and aqueous solutions. SERS was used to characterize the structural linkage between the monomers in the polymer. The linkage was identified as being identical to that found in nitrilo-2,5-cyclohexadiene-1-4diylidenenitrilo-1,4-phenylene which has been identified as one of the structural units found in polyaniline.;The relative SERS intensities of five different p-amino substituted TPP compounds were studied as a function of the number of amino groups on the molecule. A linear relationship was observed with the exception of the cis-disubstituted compound whose SERS intensity was approximately five times that of the trans disubstituted compound. This difference in intensity was related to differences in the orientation of the two molecules on the electrode surface.;The electrocatalytic activity of electropolymerized TAPP towards a number of biologically significant molecules, e.g. N-methyl nicotinamide, NAD and NADH, was investigated by cyclic voltammetry.;Finally the effect of electrode potential, solvent polarity and pH on the orientation and conformation of NAD adsorbed on a silver electrode was studied by SERS. At physiological pH, NAD adsorbs on the electrode surface in the folded conformation with interaction between the adsorbate and the sliver electrode occurring through the external amino group of the adenine ring. When NAD is adsorbed from a methanolic solution it adsorbs in the extended conformation with interaction occurring between the adenine, ribose and phosphate parts of the molecule. The nicotinamide group is oriented away from the surface. This conformation is similar to the conformation of NAD in biological systems.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
