Supramolecular ruthenium complexes (Ru−PyPs) with
4-pyridyl/phenyl porphyrins (PyPs) have been designed
and characterized spectroscopically. Ruthenium−dimethyl
sulfoxide (Me2SO) complexes and their
carbonyl
derivatives were used as precursors to synthesize adducts with Ru:PyP
ratios of 1:1 and 1:2 (monomers), 2:1
(dimers), and 4:1 (tetramers). For example, treatment of
mono-(pyridyl)porphyrin MPyP
(5-(4-pyridyl)-10,15,20-triphenylporphyrin) with
cis,fac-RuCl2(Me2SO)3(CO)
yielded the 1:1 monomer
cis,cis,cis-RuCl2(Me2
SO)2(CO)(MPyP), while reaction with
trans-RuCl2(Me2
SO)4
or
trans,cis,cis-RuCl2(CO)2(Me2SO)2
(2:1 ratio) gave
the 1:2 monomers
trans,cis,cis-RuCl2(Me2
SO)2(MPyP)2
and
trans,cis,cis-RuCl2(CO)2(MPyP)2,
respectively.
Synthesis of the dimers,
(cis-DPyP)[cis,cis,cis-RuCl2(Me2
SO)2(CO)]2
and
(trans-DPyP)[cis,cis,cis-RuCl2(Me2
SO)2(CO)]2, was accomplished by reaction of the
bis-(pyridyl)porphyrins, cis-DPyP
(5,10-bis(4-pyridyl)-15,20-diphenylporphyrin) and trans-DPyP
(5,15-bis(4-pyridyl)-10,20-diphenylporphyrin),
respectively, with an excess
of
cis,fac-RuCl2(Me2SO)3(CO).
Similarly, treatment of
5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP)
with an
excess of
cis,fac-RuCl2(Me2SO)3(CO)
yielded the symmetric tetramer,
(TPyP)[cis,cis,cis-RuCl2(Me2
SO)2(CO)]4.
1H NMR spectroscopy proved particularly useful for
characterizing the Ru−PyPs. Coordination of Ru to
the
4-pyridyl groups affected mainly the resonances of the pyridyl
ring(s) of the PyPs, causing downfield shifts
(H2,6 signals from 0.3 to 0.9 ppm; H3,5 from 0.03 to 0.18 ppm).
The pyrrole proton resonances were particularly
informative about the geometry of the porphyrin. Treatment of
selected Ru−PyP adducts with an excess of zinc
acetate produced the corresponding zinc compounds, Ru−Zn·PyPs,
in good yield. Most of the Ru−PyPs and
Ru−Zn·PyPs are quite soluble in organic solvents like
CHCl3 and very robust in solution, where they
remain
intact for weeks. 1H NMR and electronic absorption
spectra provided evidence that only the Ru−Zn·PyPs
with
residual Me2
SO units self-assemble spontaneously
in solution. The observations are consistent with a
self-assembly
mode process occuring between the oxygen atom of a
Me2
SO ligand of one molecule and the zinc of
another
molecule.
