Correlation between excited state orbital parentage and excited state acid-base behavior in transition metal complexes
Item
-
Title
-
Correlation between excited state orbital parentage and excited state acid-base behavior in transition metal complexes
-
Identifier
-
d_2009_2013:63e759974e25:12041
-
identifier
-
12746
-
Creator
-
Dimitrakopoulos, Jim,
-
Contributor
-
Harry D. Gafney
-
Date
-
2013
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Inorganic chemistry
-
Abstract
-
Chromium (III) polypyridyl and rhodium (III) polypyridyl complexes have been the subjects of considerable interest because of their extraordinary rich photophysical and photochemical properties. The following complexes were synthesized and studied: bis(2,2'-bipyridine) (2,3-bis (pyridyl)pyrazine) chromium(III) Hexafluorophosphate, tris(2,2'-bipyridine) chromium(III) Hexafluorophosphate, bis(1,10-phenanthroline) (2,3-bis(pyridyl)pyrazine) chromium(III) Hexafluorophosphate, bis(2,2'-bipyridine)(2,3-bis(pyridyl)pyrazine) rhodium(III) Nitrate, tris(2,2'-bipyridine) rhodium(III) Nitrate, and bis(2,2'-bipyridine)bis chloride rhodium(III)Hexafluorophosphate. All chromium polypyridyl complexes studied exhibit only metal-centered emissions (d-d); they display a fluorescence signal at approximately 695 nm ( 4A2g (c) 4T2g) and a phosphorescence signal at approximately 730 nm (4A2g(c) 2Eg). Quenching of both emissions occurs at high pH, while emission is enhanced at low pH. The [Rh(bpy)2dpp]3+ complex is found to display both metal-centered and ligand-centered emissions. The metal-centered emission (d-d) is the dominant luminescence feature at 77 K in ethanol-methanol glasses (4:1 v/v), but the ligand-centered (pi ¨ pi*) emission is enhanced relative to the metal-centered luminescence in fluid acetonitrile solutions. The bis complex, [Rh(bpy) 2C12]+, displays a dominant metal centered emission under all conditions that were studied. The [Rh(bpy)3] 3+ complex emits only from ligand-centered excited states at 77K. From this thesis, it became clear that the excited-state properties of a complex are related to the energy ordering of its low-energy excited states and, particularly, to the orbital nature of its lowest excited state. The energy positions of the MC, MLCT, and LC excited states depend on the ligand field strength, the redox properties of metal and ligands, and intrinsic properties of the ligands, respectively. Thus, in a series of complexes of the same metal ion, the energy ordering of the various excited states, and particularly the orbital nature of the lowest excited state, can be controlled by the choice of suitable ligands. It is therefore possible to design complexes having, at least to a certain degree, desired properties.
-
Type
-
dissertation
-
Source
-
2009_2013.csv
-
degree
-
Ph.D.
-
Program
-
Chemistry
