1. Introduction
Polypyridine ligands such as bipy (2,20-bipyridyl) and o-phen
(ortho-phenanthroline) are of great importance in the field of
photochemistry and photophysics of transition metal complexes
[1]. Depending on the metal and the substituents at the polypyridine
ligands MLCT (metal-to-ligand charge transfer) and IL (intraligand)
excited states dominate the photochemistry and
photophysics of these compounds. Rhenium(I) complexes are
rather interesting compounds of this type [1,2].The bidentate
ligand bipy(OH)2 can be deprotonated to its anion bipy(OH)(O).
This anion may be chelated to the metal either via the typical
N,N or N,O coordination [3,4] (Scheme 1).
The complex Re(I)[bipy(OH)2](CO)3Cl as the parent compound
contains two phenolic OH substituents at the bipy ligand [5]. However,
this complex is rather acidic and can be easily deprotonated.
Then the question arises if it is possible to observe the existence
and interconversion of both isomers of Scheme 1.