Dissertation

|3.4 Outlook, Exploratory Investigations and Perspectives|
(∠ edip
edip
N3,C5,C6
= 107.8(5)° > ∠N4,C6,C5 = 105.6(5)°). These effects are possibly due to the loss of double
bond character between C13 and N4 in comparison to eip and sterical or packing effects of the
alkyl moieties. Importantly, no significant changes at all were found between the equivalent bond
lengths and angles, comparing edip and bbip (e.g. ∠ bbip
edip
N3,C13,N4
= 110.9(6)° = ∠N3,C13,N4 = 110.8(5)° or
d bbip
edip
C13-N4
= 1.322(8) Å = dC13-N4 = 1.320(7) Å).
The packing in edip crystal is rather interesting. In the unit cell, four symmetry equivalent edip
molecules, 32 water molecules and four HCl molecules were found. Very prominent is the cisoidal
arrangement of the coplanar (∠ ip,ip = 9.4°) imidazophenanthroline moieties which is forced by
hydrogen bond formation between the two N-CH-N protons of the ligand and one bridging water
molecule. This preoriented bisdentate coordination sphere is very wide (d edip
C13-C26
= 5.991(8) Å) and
is therefore suitable for multicenter fragments (the corresponding C-C distance in the {Pd 2 Cl 4 }-
bridged complex by Hansen et al. was found to be equidistant, d Pd(NHC)
C-C
= 6.034 Å). The sterically
demanding durene moiety is twisted out of the plane of the two ip-moieties (∠ ip,durene = 81.8°)
and therefore out of the coordination site. Coordinated water is present in both phenanthroline
spheres, which is not uncommon and was observed previously in other cases as well (e.g. bbip).
The counter ions can be found embedded into a matrix of hydrogen bonded water molecules.
Significant π-stacking effect between neighboring aromatic systems are missing. Therefore, the
edip molecules are arranged in a superstructure of alternating molecules according to steric
effects.
For comparison reasons and to characterize the N,N-coordinating properties of the new ligands
eip and edip, the resulting ruthenium complexes were prepared (see figure 121). Furthermore, the
binuclear edip-bridged ruthenium complex represents the next step toward the target system.
The synthesis of the ruthenium complexes was performed in a similar manner as synthesis of
other ip-type complexes according to the protocol method C1 through stoichiometric reaction of
one equivalent of [Ru(tbbpy) 2 Cl 2 ] and one equivalent of ̂LL-ligand (eip, or edip) in a solvent
mixture of ethanol/water in a microwave reaction. After counter ion exchange with NH 4 PF 6 ,
the mononuclear complex [Ru(tbbpy) 2 (eip)][PF 6 ] 2 (Ru(eip)) and the binuclear edip-bridged
complex [{Ru(tbbpy) 2 } 2 (µ-edip)][PF 6 ] 6 (Ru 2 (edip)) were obtained in high yields, whereat in the
case of Ru 2 (edip) a longer reaction time of 5 hours had to be applied to force the reaction between
positively charged ruthenium center and positively charged ligand. Back and forth counter ion
exchange and reprecipitation with Bu 4 NCl and NH 4 PF 6 yielded both complexes, Ru(eip) and
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