DIAMMINE-COPPER ION COMPLEXES: MICROENVIRONMENTAL FACTORS INFLUENCING THE GROUND AND EXCITED STATES (EXCIPLEXES)
Abstract
The physical properties of ground and excited state Cu(NN)(,2)('+) complexes are shown to be highly influenced by the environment in which these complexes are examined. A structural study, performed on an iso-electronic complex, bis(4,4',6,6'-tetramethylbipyridine) silver(I) tetrafluoroborate, indicates that the flattening distortion is Cu(NN)(,2)('+) systems is due to a packing effect rather than configurational mixing. This follows because the silver complex exhibits a greater flattening of the dihedral angle between the mean ligand planes (65.5(DEGREES) versus 68(DEGREES)). An examination of the extended structure reveals extensive slipped stacking of the aromatic ligands as the origin of this distortion. The structure and polarized absorption spectra copper(I)-doped crystals of bis(2,9-dimethylphenanthroline) silver(I) tetrafluoroborate have been obtained. This structure also reveals distortions from tetrahedral geometry which can be explained by stacking interactions. The polarized spectra reveal bands within the charge transfer manifold polarized both along and normal to the average metal-ligand axis. The major band in this region is polarized along the metal-ligand axis, as Mulliken's theory of charge transfer would predict. This band exhibits a vibrational splitting which is not found in the Raman spectrum of Cu(dmp)(,2)('+). This structure is explained by invocation of the MIME or missing mode effect. In the excited state, the environment produces a different effect. Both Lewis base solvents and anions have been shown to quench the emission (*Cu(dmp)(,2)('+). This quenching occurs by a static mechanism (anions) and both static and dynamic mechanism (solvents). The most important observation from these studies is that even a weak Lewis base, methylene chloride, will quench luminescence from *Cu(dmp)(,2)('+). This quenching is explained in terms of an inner-sphere coordination of the quencher to the copper center in the excited state.
Degree
Ph.D.
Subject Area
Chemistry
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