Perpendicularly Arranged Ruthenium Porphyrin Dimers and Trimers

Article abstract of DOI:10.1021/ic961154b

A series of ruthenium(II) porphyrin dimers and trimers (carbonyl dimers, 1-4; carbonyl trimers, 5-7, bis(pyridyl) trimers, 8-10), having axial or bridging porphyrin ligands, were synthesized and characterized by ¹H NMR and IR spectroscopy and mass spectrometry. An X-ray structural determination of Ru^II(OEP)(CO)(H₂PyP₃P) (1) (OEP = octaethylporphyrinato dianion, H₂PyP₃P = 5-pyridyl-10,15,20-triphenylporphyrinato dianion) was carried out. The axial porphyrin ligand is coordinated to the ruthenium porphyrin subunit obliquely. The Ru-N(Py) bond length is 2.237(4) ?, and the angle between the ruthenium porphyrin macrocycle and the pyridyl ring is 63.23(35)°. Crystallographic data for 1 are as follows: chemical formula C₈₀H₇₃N₉ORu·CH₂Cl ₂, triclinic, P1, a = 14.954(5) ?, b = 25.792(5) ?, c = 10.124(3) ?, α = 90.21(2)°, β = 108.43(2)°, γ = 73.39(2)°, Z = 2, R(F) = 0.0674. ¹H NMR signals of 2,6- and 3,5-pyridyl protons of the axial ligand porphyrins of the oligomers 1-10 showed significant upfield shifts, indicating that the axial porphyrin subunits are coordinated to the ruthenium porphyrin subunits through the pyridyl group in solution. UV-vis spectra revealed the presence of excitonic interaction between two axial ligand porphyrin subunits in the trimers 8-10. The MLCT bands from the central ruthenium(II) ions to the octaethylporphyrin rings were observed around 450 nm in 8 and 9. Cyclic voltammograms of the carbonyl dimers and trimers showed no redox waves of the ruthenium(II) ions, because the ruthenium(II) oxidation state of these complexes was significantly stabilized by the coordination of the axial CO ligands. On the other hand, bis(pyridyl) trimers exhibit the Ru(III/II) waves in the region of -0.12 to +0.15 V vs Ag/Ag⁺ reference electrode.

Full text of DOI:10.1021/ic961154b

Inorg. Chem. 1997, 36, 1625-1635
1625
Perpendicularly Arranged Ruthenium Porphyrin Dimers and Trimers
Kenji Funatsu,† Akira Kimura,† Taira Imamura,*,† Akio Ichimura,‡ and Yoichi Sasaki†
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060, Japan, and
Department of Chemistry, Faculty of Science, Osaka City University, Osaka 558, Japan
ReceiVed September 18, 1996X
A series of ruthenium(II) porphyrin dimers and trimers (carbonyl dimers, 1-4; carbonyl trimers, 5-7, bis(pyridyl)
trimers, 8-10), having axial or bridging porphyrin ligands, were synthesized and characterized by 1H NMR and
IR spectroscopy and mass spectrometry. An X-ray structural determination of RuII(OEP)(CO)(H2PyP3P) (1) (OEP
) octaethylporphyrinato dianion, H2PyP3P ) 5-pyridyl-10,15,20-triphenylporphyrinato dianion) was carried out.
The axial porphyrin ligand is coordinated to the ruthenium porphyrin subunit obliquely. The Ru-N(Py) bond
length is 2.237(4) Å, and the angle between the ruthenium porphyrin macrocycle and the pyridyl ring is 63.23(35)°.
Crystallographic data for 1 are as follows: chemical formula C80H73N9ORu‚CH2Cl2, triclinic, P1h, a ) 14.954(5)
Å, b ) 25.792(5) Å, c ) 10.124(3) Å, R ) 90.21(2)°, â ) 108.43(2)°, γ ) 73.39(2)°, Z ) 2, R(F) ) 0.0674. 1H
NMR signals of 2,6- and 3,5-pyridyl protons of the axial ligand porphyrins of the oligomers 1-10 showed significant
upfield shifts, indicating that the axial porphyrin subunits are coordinated to the ruthenium porphyrin subunits
through the pyridyl group in solution. UV-vis spectra revealed the presence of excitonic interaction between
two axial ligand porphyrin subunits in the trimers 8-10. The MLCT bands from the central ruthenium(II) ions
to the octaethylporphyrin rings were observed around 450 nm in 8 and 9. Cyclic voltammograms of the carbonyl
dimers and trimers showed no redox waves of the ruthenium(II) ions, because the ruthenium(II) oxidation state
of these complexes was significantly stabilized by the coordination of the axial CO ligands. On the other hand,
bis(pyridyl) trimers exhibit the Ru(III/II) waves in the region of -0.12 to +0.15 V vs Ag/Ag+ reference electrode.
Introduction
Sanders et al. achieved the construction of a cyclic zinc
porphyrin trimer linked by 1,4-biphenylbutadiyne spacers, which
Many flat- and gable-porphyrin oligomers linked by organic
spacers have been synthesized as models for photosynthetic
reaction centers to clarify effective factors such as inter-
porphyrin distance and orientation as well as the number of
porphyrin pigments on the photoinduced long-distance electron
or energy transfer reaction processes.1 Porphyrin oligomers
having more than three porphyrin pigments have also been noted
as synthetic molecular devices and models of light-harvesting
systems.2 The ruthenium dimer with a biphenylene organic
spacer showed the unusual properties of taking a variety of small
nitrogen molecules such as N2 and N2H2 between the cofacially
arranged porphyrin subunits and demonstrated the probability
of molecular electrode catalysts for the reduction of N2.3 Similar
cofacial cobalt(II) porphyrin dimers have also been examined
as catalysts of electrochemical reduction of oxygen to water.4
Thus, porphyrin oligomers have revealed fascinating photo-
chemical and catalytic properties.
catalyzed Diels-Alder reactions stereoselectively.5 In the
process of preparation, a new synthetic strategy using stereo-
selective template reactions was used; i.e., the zinc trimer was
synthesized by a proper template reaction of tripyridyltriazine.6
Other approaches to construct porphyrin oligomers include
a ligation method of meso-pyridylporphyrins, e.g., a stable
(2) (a) Harriman, J. D. A.; Milgram, L. R. Chem. Phys. Lett. 1987, 136,
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† Hokkaido University.
‡ Osaka City University.
X Abstract published in AdVance ACS Abstracts, March 1, 1997.
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K. R.; Vicente, M. G. H.; Forsyth, T. P.; Smith, K. M. Angew. Chem.,
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S0020-1669(96)01154-8 CCC: $14.00 © 1997 American Chemical Society

1626 Inorganic Chemistry, Vol. 36, No. 8, 1997
Funatsu et al.
Figure 1. Ruthenium porphyrin oligomers.
porphyrin dimer and tetramer were synthesized by the ligation
of mono(pyridyl)porphyrins or that of zinc complexes to square
planer Pt(II) and Pd(II) arrays.7 Fleischer and Shachater also
reported some oligomers as a result of the treatment of meso-
pyridylporphyrins with zinc tetraphenylporphyrin complexes.8
The X-ray crystal structural determination for a tetramer clarified
that the pyridyl substituents were bound to the zinc ions with
an unusual tilt. 1H NMR mesurements indicated that Zn(TPP)-
(H2PyP3P), [Zn(TPP)]2(cis-H2Py2P2P), and [Zn(TPP)]2(trans-
H2Py2P2P) were present in solution.8,9 A novel cyclic ruthenium
porphyrin tetramer [Ru(PyP3P)(CO)]4 was also synthesized.10
The ruthenium tetramer was successfully isolated, because of
the stability of the Ru-N(Py) bond unlike the zinc porphyrin
oligomers. Furthermore, a ruthenium porphyrin pentamer
[Ru(TPP)(CO)]4{Zn(Py4P)} was recently prepared by the liga-
tion of four pyridyl substituents of tetrapyridylporphyrin to four
ruthenium tetraarylporphyrin monomers.11 A series of similar
osmium(II) porphyrin oligomers, Os(OEP)(CO)(H2PyP3P),
[Os(OEP)(CO)]2(trans-H2Py2P2P), [Os(OEP)(CO)]2(cis-H2Py2P2P),
[Os(OEP)(CO)]3(H2Py3PP), and [Os(OEP)(CO)]4(H2Py4P), were
also independently prepared and characterized.12 These zinc,
ruthenium, and osmium porphyrin oligomers have a character-
istic perpendicular geometry between zinc, ruthenium, or
osmium porphyrin subunits and axial porphyrin subunits. In
addition, there are a few reports outlining the synthesis and
photophysical properties of “axial-bonding type” phosphorus(V)
porphyrin dimers and trimers13 and of a porphyrin and sapphyrin
pair bound electrostatically.14 Thus, perpendicularly linking
porphyrin oligomers have recently gained a lot of attention,
because the synthesis, structure, properties, and probabilities as
a functional molecule are of great interest.
Herein, we report the synthesis and characterization of a series
of perpendicularly linking ruthenium porphyrin oligomers (1-
4, carbonyl dimers; 5-7, carbonyl trimers; 8-10, bis(pyridyl)
trimers) (Figure 1). The X-ray crystal structure of 1 is also
reported. The structure of the oligomers in solution was
discussed on the basis of NMR ring current shifts of pyridyl
protons in comparison with those of corresponding monomers
Ru(OEP)(CO)(Py), Ru(TPP)(CO)(Py), and Ru(OEP)(Py)2. In-
teractions between porphyrin subunits in a molecule were also
discussed on UV-vis spectroscopic and electrochemical proper-
ties of the oligomers 1-10, in which 1, 2, 5, and 8 were
previously reported in a preliminary account (Figure 1).15
Experimental Section
Materials. H2TPP was obtained as a byproduct of meso-pyridylpor-
phyrin ligands described below. H2OEP and H2TTP were prepared
according to the methods described in the literature.16 Triruthenium(0)
dodecacarbonyl, Ru3(CO)12, was purchased from Aldrich. Silica gel
(Wakogel C-300, 200) and alumina (Wolem, neutral, activity II) were
used for column chromatography. RuII(TPP)(CO)(MeOH) and
RuII(OEP)(CO)(MeOH) were prepared as described in the literature.17
RuII(TTP)(CO)(MeOH) was prepared by a method analogous to that
used for RuII(TPP)(CO)(MeOH). 1H NMR, UV-vis, and IR spectro-
scopic data for these complexes agreed well with the reported values,
and the elemental analyses were also satisfactory.17 These data are
given below for comparison to the new oligomers as follows.
(7) Yuan, H.; Thomas, L.; Woo, K. Inorg. Chem. 1996, 35, 2808.
(8) Fleischer, E. B.; Shachter, A. M. Inorg. Chem. 1991, 30, 3763.
(9) Abbreviations: TPP ) 5,10,15,20-tetraphenylporphyrinato dianion;
OEP ) 2,3,7,8,12,13,17,18-octaethylporphyrinato dianion; TTP )
5,10,15,20-tetratolylporphyrinato dianion; H2PyP3P ) 5-pyridyl-
10,15,20-triphenylporphyrin; cis-H2Py2P2P ) 5,10-dipyridyl-15,20-
RuII(OEP)(CO)(MeOH). Anal. Calcd for C38H48N4O2Ru: C,
65.77; H, 6.97; N, 8.08. Found: C, 66.00; H, 7.01; N, 7.93. UV-vis
(CH2Cl2): λmax/nm 392 (Soret), 517, 548. IR (KBr): νCO 1950, 1923
diphenylporphyrin; trans-H2Py2P2P
)
5,15-dipyridyl-10,20-di-
(13) (a) Susumu, K.; Segawa, H.; Shimidzu, T. Chem. Lett. 1995, 929. (b)
Rao, T. A.; Maiya, B. G. J. Chem. Soc., Chem. Commun. 1995, 939.
(14) Kral, V.; Springs, S. L.; Sessler, J. L. J. Am. Chem. Soc. 1995, 117,
8881.
(15) Kimura, A.; Funatsu, K.; Imamura, T.; Kido, H.; Sasaki, Y. Chem.
Lett. 1995, 207.
(16) Paine, J. P., III; Kirshner, W. B.; Moskowitz, D. W. J. Org. Chem.
1976, 41, 3857.
(17) Collman, J. P.; Barnes, C. E.; Brothers, P. J.; Collins, T. J.; Ozawa,
T.; Gallucci, J. C.; Ibers, J. A. J. Am. Chem. Soc. 1984, 106, 5151.
phenylporphyrin; H2Py3PP ) 5,10,15-tripyridyl-20-phenylporphyrin;
H2Py4P ) 5,10,15,20-tetrapyridylporphyrin; Py ) pyridine; (TBA)-
PF6 ) n-tetrabutylammonium hexafluorophosphate; Por ) por-
phyrinato dianion unspecified.
(10) Funatsu, K.; Kimura, A.; Imamura, T.; Sasaki, Y. Chem. Lett. 1996,
765.
(11) Alessio, E.; Macchi, M.; Heath, S.; Marzill, L. G. J. Chem. Soc., Chem.
Commun. 1996, 1411.
(12) Kariya, N.; Imamura, T.; Sasaki, Y. Inorg. Chem. 1997, 36, 833.

Ruthenium Porphyrin Dimers and Trimers
cm-1 1H NMR (CD2Cl2, 270 MHz) (δ/ppm): Hmeso 9.95 (s); CH3CH2
Inorganic Chemistry, Vol. 36, No. 8, 1997 1627
.
use. The solution was refluxed for 1 h under argon atmosphere, cooled
to room temperature, and evaporated to dryness. The reddish-purple
solid was dissolved in a small amount of dichloromethane purified
immediately before use. The solution was loaded on a silica gel column
and eluted with dichloromethane as an eluent. A red eluate was dried
to give a product. The product was recrystallized from toluene-hexane
and dried at 100 °C in vacuo for 5 h (yield: 34 mg, 88.3%).
4.11 (q, 7.56 Hz); CH3CH2 1.94 (t, 7.56 Hz).
RuII(TPP)(CO)(MeOH). Anal. Calcd for C46H32N4O2Ru: C,
71.34; H, 4.17; N, 7.24. Found: C, 71.42; H, 4.36; N, 7.11. UV-vis
(CH2Cl2): λmax/nm 413 (Soret), 532, 569 (sh). IR (KBr): νCO 1944
cm-1 1H NMR (CD2Cl2, 270 MHz) (δ/ppm): Hâ 8.67 (s); Ho 8.25
.
(d), 8.07 (d); Hm,p 7.69 (m).
RuII(TTP)(CO)(MeOH). Anal. Calcd for C50H40N4O2Ru: C,
72.35; H, 4.86; N, 6.75. Found: C, 71.96; H, 4.70; N, 6.88. UV-vis
(CH2Cl2): λmax/nm 417 (Soret), 530, 569 (sh). IR (KBr): νCO 1945
Anal. Calcd for C80H71N9ORuZn: C, 71.65; H, 5.34; N, 9.40.
Found: C, 71.62; H, 5.32; N, 9.37. 1H NMR (CD2Cl2, 270 MHz):
Hmeso 10.04 (s, 4H); CH3CH2 4.09 (q, 8H); CH3CH2 2.02 (t, 12H); Ho
7.97 (m, 2H), 7.85 (m, 4H); Hm,p 7.45 (m, 9H); Hâ 8.76 (d, 2H), 8.72
(d, 2H), 8.45 (d, 2H), 7.24 (d, 2H); H3,5-Py 5.79 (d, 2H); H2,6-Py 1.26 (d,
2H) ppm. UV-vis (CH2Cl2) (log ꢀ): λmax/nm 395 (5.45), 419 (5.71),
516 (4.18), 548 (4.63), 586 (3.64). IR (KBr): νCO 1941 cm-1. FAB-
MS (NBA) shows a sharp parent peak at 1340 (m/z+).
RuII(TPP)(CO)(H2PyP3P) (3). Ru(TPP)(CO)(EtOH) (50 mg, 6.3
× 10-5 mol) and H2PyP3P (50 mg, 8.1 × 10-5 mol) were dissolved in
2-methoxyethanol (CH3OCH2CH2OH) (70 mL), which was bubbled
with argon for 20 min before use. The solution was refluxed for 1 h,
cooled to room temperature, and filtered through a sintered glass before
addition of water (50 mL). A red colored precipitate thus obtained
was filtered off, washed with water, dissolved in CH2Cl2, and finally
purified by column chromatography using a silica gel column. The
first red eluate was dried up. The solid material was recrystallized
from dichloromethane-methanol. The reddish-purple product was
dried at 100 °C in vacuo for 3 h (yield: 78 mg, 71%).
Anal. Calcd as C88H57N9ORu: C, 77.85; H, 4.23; N, 9.29. Found:
C, 77.85; H, 4.84; N, 9.16. 1H NMR (CD2Cl2, 270 MHz): Ho 8.32
(m, 4H), 8.19 (m, 4H), 8.08 (m, 2H), 8.00 (m, 4H); Hm,p 7.7-7.5 (m,
21H); Hâ 8.75 (10H), 8.70 (d, 2H), 8.46 (d, 2H), 7.30 (d, 2H); H3,5-Py
6.10 (d, 2H); H2,6-Py 1.92 (d, 2H); HNH -3.33 (s, 2H) ppm. UV-vis
(CH2Cl2) (log ꢀ): λmax/nm 419 (5.84), 519 (4.44), 530 (sh), 550 (sh),
588 (3.79), 645 (3.60). IR (KBr): νCO 1968, 1953 cm-1. FAB-MS
(NBA) shows a sharp parent peak at 1358 (m/z+).
RuII(TTP)(CO)(H2PyP3P) (4). RuII(TTP)(CO)(H2PyP3P) was syn-
thesized by a method similar to that of RuII(OEP)(CO)(H2PyP3P) using
RuII(TTP)(CO)(MeOH) instead of RuII(OEP)(CO)(MeOH). RuII-
(TTP)(CO)(MeOH) (100 mg, 1.2 × 10-4 mol) and H2PyP3P (75 mg,
1.2 × 10-4 mol) were dissolved in a spectral grade of toluene which
was bubbled with argon before use. The solution was refluxed for 1
h under argon, cooled to room temperature, and evaporated to dryness.
The solid material was dissolved in a small amount of dichloromethane.
The solution was loaded on a silica gel column and eluted with
dichloromethane. A red eluate was evaporated to dryness. The product
was recrystallized from dichloromethane-methanol. The red product
was dried at 110 °C in vacuo for 3 h (yield: 130 mg, 77%).
Anal. Calcd for C92H65N9ORu: C, 78.16; H, 4.63; N, 8.92.
Found: C, 78.73; H, 4.98: N, 9.03. 1H NMR (CD2Cl2, 270 MHz):
Ho 8.19 (m, 4H), 8.07 (m, 6H), 8.01 (m, 4H); Hm,p 7.7-7.5 (m, 17H);
Hâ 8.75 (10H), 8.72 (d, 2H), 8.46 (d, 2H), 7.30 (d, 2H); H-CH3 2.67
(s, 12H); H3,5-Py 6.06 (d, 2H); H2,6-Py 1.91 (d, 2H); HNH -3.32 (s, 2H)
ppm. UV-vis (CH2Cl2) (log ꢀ): λmax/nm 417 (5.86), 519 (4.45), 530
(sh), 550 (sh), 589 (3.85), 647 (3.73). IR (KBr): νCO 1952 cm-1. FAB-
MS (NBA) shows a sharp parent peak at 1413 (m/z+).
[RuII(OEP)(CO)]2(trans-H2Py2P2P) (5). RuII(OEP)(CO)(MeOH)
(40 mg, 5.8 × 10-5 mol) and trans-H2Py2P2P (18 mg, 2.9 × 10-5 mol)
were dissolved in toluene which was bubbled with argon before use.
The solution was refluxed for 5 h with mixing and cooled to room
temperature followed by evaporation to dryness. The resulting solid
was dissolved in a small amount of toluene and chromatographed using
an alumina column. A red band was collected using toluene as an
eluent and evaporated to dryness (yield: 25 mg, 45%).
cm-1 1H NMR (CD2Cl2, 270 MHz) (δ/ppm): Hâ 8.69 (s); Ho 8.07
.
(d), 7.99 (d); Hm,p 7.53 (m); H-CH3 2.66 (s).
Synthesis of Axial Porphyrin Ligands. Porphyrins containing
pyridyl groups, H2PyP3P and trans-H2Py2P2P, were synthesized ac-
cording to the literature and separated using silica gel columns.8,18 When
benzaldehyde (15 mL), isonicotinaldehyde (5 mL), and pyrrole (14 mL)
were used for the preparation of these porphyrin ligands, the amounts
of H2PyP3P and trans-H2Py2P2P were 1.44 g and 27.5 mg, respectively,
which correspond to 29 and 0.56% yields of the total amount of the
products obtained by chromatography. The porphyrins purified were
identified by thin-layer chromatography, elemental analysis, visible
1
spectroscopy, and H NMR measurements. These data agreed well
with the reported results.8 1H NMR for H2PyP3P (CD2Cl2, 400 MHz):
HNH -2.88 (s, 2H), Hâ 8.85 (m, 8H), Ho 8.20 (m, 6H), Hm,p 7.77 (m,
9H), H2,6-Py 8.98 (dd, 2H), H3,5-Py 8.15 (dd, 2H) ppm. 1H NMR for
trans-H2Py2P2P: HNH -2.92 (s, 2H), Hâ 8.87 (m, 8H), Ho 8.19 (m,
4H), Hm,p 7.77 (m, 6H), H2,6-Py 8.99 (dd, 4H), H3,5-Py 8.15 (dd, 4H)
ppm.
Zn(PyP3P). The zinc porphyrin, Zn(PyP3P), was prepared according
to the method described in the literature.8 A mixed solution of toluene
(40 mL) and 2,6-lutidine (10 mL) was added to the acetone solution
(40 mL) containing ZnCl2 (270 mg). To the solution, H2PyP3P (200
mg) was added and stirred for 4 h at room temperature until the
absorption around 650 nm from the free ligand had disappeared. After
the addition of distilled water (100 mL), the solution was left to stand
for several hours. The organic layer was concentrated by evaporation
and diluted with ethanol (150 mL) and left to stand for 1 night. The
solid product thus obtained was filtered out and dissolved in dichlo-
romethane. The solution was loaded on a silica gel column followed
by elution with dichloromethane. The crude product obtained by
evaporation was recrystallized using toluene-hexane. The absorption
spectrum of the complex having bands at 424, 554, and 594 nm was
similar to the reported one.8
RuII(OEP)(CO)(H2PyP3P) (1). RuII(OEP)(CO)(MeOH) (48 mg, 6.9
× 10-5 mol) and H2PyP3P (48 mg, 7.8 × 10-5 mol) were dissolved in
a spectral grade of toluene which was bubbled with argon before use.
The solution was refluxed for 30 min under argon, cooled to room
temperature, and evaporated to dryness. The solid material was
dissolved in a small amount of dichloromethane which was purified
immediately before use. The solution was loaded on a silica gel column
and eluted with dichloromethane. The first red fraction was collected
and dried to give a product. The red product was recrystallized from
toluene-hexane and dried at 110 °C in vacuo for 5 h (yield: 60 mg,
67.5%). Planar single crystals suitable for X-ray crystallography were
obtained from dichloromethane-methanol.
Anal. Calcd for C80H73N9ORu: C, 75.21; H, 5.76; N, 9.87.
Found: C, 75.37; H, 5.92; N, 10.00. 1H NMR (CD2Cl2, 270 MHz):
Hmeso 10.01 (s, 4H); CH3CH2 4.08 (q, 8H); CH3CH2 1.96 (t, 12H); Ho
8.04 (m, 2H), 7.95 (m, 4H); Hm,p 7.68 (m, 9H); Hâ 8.69 (d, 2H), 8.65
(d, 2H), 8.36 (d, 2H), 7.16 (d, 2H); H3,5-Py 5.77 (d, 2H); H2,6-Py 1.23 (d,
2H); HNH -3.41 (s, 2H) ppm. UV-vis (CH2Cl2) (log ꢀ): λmax/nm 395
(5.48), 418 (5.60), 514 (4.50), 550 (4.47), 590 (3.73), 646 (3.60). IR
(KBr): νCO 1945 cm-1. FAB-MS (matrix: 3-nitrobenzyl alcohol )
NBA) shows a sharp parent peak at 1277 (m/z+).
Anal. Calcd for C116H116N14O2Ru2: C, 71.80; H, 6.03; N, 10.01.
Found: C, 72.05; H, 6.19; N, 10.12. 1H NMR (CD2Cl2, 270 MHz):
RuII(OEP)(CO){Zn(PyP3P)} (2). RuII(OEP)(CO){Zn(PyP3P)} was
synthesized by a method similar to that of RuII(OEP)(CO)(H2PyP3P)
using Zn(PyP3P) in place of H2PyP3P. RuII(OEP)(CO)(MeOH) (20 mg,
2.9 × 10-5 mol) and Zn(PyP3P) (20 mg, 2.9 × 10-5 mol) were dissolved
in a spectral grade of toluene which was bubbled with argon before
H
meso 9.97 (s, 8H); CH3CH2 4.03 (q, 16H); CH3CH2 1.90 (t, 24H); Ho
7.7 (m, 4H); Hm,p 7.7-7.5 (m, 6H); Hâ 8.19 (d, 4H), 7.01 (d, 4H);
3,5-Py 5.62 (d, 4H); H2,6-Py 1.15 (d, 4H); HNH -3.98 (s, 2H) ppm. UV-
vis (CH2Cl2) (log ꢀ): λmax/nm 395 (5.71), 421 (5.59), 515 (4.67), 550
H
(4.80), 591 (3.72), 648 (3.57). IR (KBr): νCO 1942 cm-1
.
[RuII(TPP)(CO)]2(trans-H2Py2P2P) (6). RuII(TPP)(CO)(MeOH)
(130 mg, 1.6 × 10-4 mol) and trans-H2Py2P2P (50 mg, 8.1 × 10-5
mol) were dissolved in toluene which was bubbled with argon before
(18) Alder, A. D.; Longo, F. R.; Finarelli, J. D.; Goldmacher, J.; Assour,
J.; Korsalioff, L. J. Org. Chem. 1967, 32, 476.

1628 Inorganic Chemistry, Vol. 36, No. 8, 1997
Funatsu et al.
use. The solution was refluxed for 2 h under argon, cooled to room
temperature, and evaporated to dryness. The solid material was
dissolved in a small amount of dichloromethane. The solution was
loaded on a silica gel column and eluted with dichloromethane. A red
eluate was evaporated to dryness. The product was recrystallized from
dichloromethane-methanol and dried at 80 °C in vacuo for 3 h (yield:
30 mg, 17%).
Table 1. Crystallographic Data for 1
formula
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
C80H73N9ORu‚CH2Cl2
triclinic
P1h
14.954(5)
25.793(5)
10.125(3)
90.12(2)
108.43(2)
73.39(2)
3534.0(2)
2
Anal. Calcd for C132H84N14O2Ru2: C, 75.48; H, 4.03; N, 9.34.
Found: C, 75.56; H, 4.26; N, 9.20. 1H NMR (CD2Cl2, 270 MHz): Ho
8.30-8.00 (m, 20H); Hm,p 7.7-7.4 (m, 30H); Hâ 8.69 (s, 16H), 8.20
(d, 4H), 7.19 (d, 4H); H3,5-Py 5.95 (d, 4H); H2,6-Py 1.85 (d, 4H); HNH
-3.80 (s, 2H) ppm. UV-vis (CH2Cl2) (log ꢀ): λmax/nm 414 (5.95),
520 (sh), 530 (4.65), 565 (sh), 589 (3.91), 646 (3.67). IR (KBr): νCO
Z
d
calcd/g cm-3
1.282
cryst size/mm
scan mode
0.50 × 0.70 × 0.30
1974, 1952 cm-1
.
ω-2θ
[RuII(TTP)(CO)]2(trans-H2Py2P2P) (7). [RuII(TTP)(CO)]2(trans-
H2Py2P2P) was synthesized by a method similar to [RuII(OEP)-
(CO)]2(trans-H2Py2P2P) using RuII(TTP)(CO)(MeOH). RuII(TTP)(CO)-
(MeOH) (55 mg, 6.6 × 10-5 mol) and trans-H2Py2P2P (20 mg, 3.3 ×
10-5 mol) were dissolved in toluene which was bubbled with argon
before use. The solution was refluxed for 2 h under argon, cooled to
room temperature, and evaporated to dryness. The solid material was
dissolved in a small amount of dichloromethane. The solution was
loaded on a silica gel column and eluted with dichloromethane. A red
eluate was evaporated to dryness. The red product was recrystallized
from dichloromethane-hexane and dried at 110 °C in vacuo for 3h
(yield: 41 mg, 55%).
scan speed/deg min-1
2θmax/deg
6
55
h,k,l range
(20,(34,+14
17 766
9316, Fo > 6σ(Fo)
0.0674
0.0816
no. of unique reflns
no. of obsd reflns
Ra
a
Rw
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) (∑w(|Fo| - |Fc|)2/∑w|Fo| )1/2
Table 2. Selected Bond Distances of 1 (Å)a
.
2
Ru-N1
2.050(4) CR-Câ (av for OEP)
2.042(5) Câ-Câ (av for OEP)
2.046(4) CR-Cm (av for OEP)
2.066(5) N-CR (av for H2PyP3P) 1.377(8)
2.237(4) CR-Câ (av for H2PyP3P) 1.451(9)
1.801(6) Câ-Câ (av for H2PyP3P) 1.378(9)
1.165(7) CR-Cm (av for H2PyP3P) 1.394(8)
1.459(9)
1.363(10)
1.390(9)
Ru-N2
Anal. Calcd for C140H100N14O2Ru2: C, 76.00; H, 4.56; N, 8.87.
Found: C, 75.70; H, 4.71; N, 8.86. 1H NMR (CD2Cl2, 270 MHz): Ho
8.29 (m, 8H), 8.15 (m, 8H), 7.99 (m, 4H); Hm,p 7.8-7.5 (m, 22H); Hâ
8.71 (s, 16H), 8.14 (d, 4H), 7.17 (d, 4H); H3,5-Py 5.93 (d, 4H); H2,6-Py
Ru-N3
Ru-N4
Ru-N(Py)
Ru-C(CO)
C(CO)-O(CO)
1.83 (d, 4H); HNH -3.82 (s, 2H) ppm. UV-vis (CH2Cl2) (log ꢀ): λmax
nm 414 (5.96), 520 (sh), 532 (4.66), 565 (sh), 586 (3.91), 646 (3.67).
IR (KBr): νCO 1958 cm-1
/
N-CR (av for OEP) 1.375(8)
.
a CR, R-pyrrole carbon; Câ, â-pyrrole carbon; Cm, methine carbon.
Ru(OEP)(H2PyP3P)2 (8). Dry toluene solution (700 mL) containing
Ru(OEP)(CO)(MeOH) (60 mg, 8.6 × 10-5 mol) and H2PyP3P (106
mg, 1.7 × 10-4 mol) was photoirradiated with a 100 W medium-
pressure mercury-vapor lamp for 8 h during vigorous stirring with Ar
bubbling. The solution was concentrated to load on an alumina column.
A brown fraction eluted with toluene was collected. The eluate was
evaporated to dryness. The deep-purple solid was recrystallized from
toluene-hexane and dried at 110 °C in vacuo for 3 h (yield: 100 mg,
63%).
grade toluene solution (700 mL) containing Ru(TTP)(CO)(MeOH) (60
mg, 7.2 × 10-5 mol) and H2PyP3P (90 mg, 1.4 × 10-4 mol) was
photoirradiated with a 100 W medium-pressure mercury-vapor lamp
for 6 h during vigorous stirring under Ar. The solution was concen-
trated to load on an alumina column. A brown band eluted with toluene
was collected. The eluate was evaporated to dryness. The deep-purple
solid material was recrystallized from toluene-hexane and dried at 110
°C in vacuo for 3 h (yield: 52 mg, 36%).
Anal. Calcd as C122H102N14Ru: C, 78.56; H, 5.51; N, 10.52.
Found: C, 77.37; H, 5.60; N, 10.33. 1H NMR (C6D6, 270 MHz): Hmeso
10.06 (s, 4H); CH3CH2 4.09 (q, 8H); CH3CH2 2.08 (t, 12H); Ho 8.01
(m, 8H), 7.91 (m, 4H); Hm,p -7.5 (m, 18H); Hâ 8.79 (d, 4H), 8.77 (d,
4H), 8.25 (d, 4H), 6.93 (d, 4H); H3,5-Py 5.31 (d, 4H); H2,6-Py 2.82 (d,
4H); HNH -2.81 (s, 4H) ppm. UV-vis (C6H5CH3) (log ꢀ): λmax/nm
399 (sh), 419 (5.73), 456 (4.70), 516 (4.80), 546 (2.73), 588 (1.33),
652 (1.09), 650-750 (broad band). FAB-MS (NBA) shows a sharp
parent peak at 1865 (m/z+).
Ru(OEP){Zn(PyP3P)}2 (9). RuII(OEP)(H2PyP3P)2 (50 mg, 2.7 ×
10-5 mol) and Zn(CH3COO)2 (50 mg, 2.7 × 10-4 mol) were dissolved
in a mixed solvent of toluene (35 mL) and ethanol (15 mL). The
solution was vigorously stirred for 5 h at room temperature until the
absorption around 650 nm due to the axial porphyrin of H2PyP3P had
completely disappeared. The solution was evaporated to dryness. The
solid material was dissolved in a small amount of toluene. The solution
was loaded on an alumina column and eluted with toluene. A brown
eluate was collected and evaporated to dryness. The product was
recrystallized from toluene-hexane. The deep-purple product was dried
at 110 °C in vacuo for 3 h (yield: 20 mg, 40%).
Anal. Calcd for C134H94N14Ru: C, 80.41; H, 4.73; N, 9.81.
Found: C, 71.55; H, 4.64; N, 9.69. 1H NMR (C6D6, 270 MHz): Ho
8.48 (m, 8H), 8.06 (m, 4H), 7.95 (m, 8H); Hm,p ∼7.5 (m, 18H); Hâ
9.01 (s, 8H), 8.84 (d, 4H), 8.82 (d, 4H), 8.55 (d, 4H), 7.55 (d, 4H);
H3,5-Py 5.61 (d, 4H); H2,6-Py 3.49 (d, 4H); H-CH3 2.46 (s, 12H) ppm.
UV-vis (C6H5CH3) (log ꢀ): λmax/nm 418 (5.83), 511 (4.77), 547 (4.26),
592 (4.17), 652 (4.13), 650-750 (broad band).
X-ray Structural Determinations. X-ray data for 1 were collected
with graphite-monochromated Mo KR radiation on a Rigaku AFC-5R
diffractometer at 23 °C. Unit cell parameters were obtained by least-
squares refinement of 25 reflections (25° e 2θ e 30°). The intensities
of three standard reflections monitored, every 150 reflections, showed
no appreciable decay during the data collection.
The crystal structure was solved by standard heavy-atom procedures.
The positional and thermal parameters were refined by the block-
diagonal-matrix least-squares method. The minimized function was
-1
∑w(|Fo| - |Fc|)2, where w
) σ(|Fo|) + (0.015|Fo|)2. No attempt
was made to locate hydrogen atoms in the structure analysis. Com-
putational work was carried out by using standard programs in UNICS
III19 and ORTEP.20 Crystallographic data are given in Table 1.
Selected bond distances, angles, and dihedral angles are summarized
in Tables 2-4. Listings of non-hydrogen atom coordinates and
isotropic thermal parameters are given in Table S1. Anisotropic thermal
parameters (Table S2) and full listings of bond distances (Table S3)
and angles (Table S4) are also provided as Supporting Information.
Anal. Calcd for C122H98N14RuZn2: C, 73.55; H, 4.23; N, 9.29.
Found: C, 73.38; H, 5.04; N, 9.66. 1H NMR (C6D6, 270 MHz): Hmeso
10.10 (s, 4H); CH3CH2 4.11 (q, 8H); CH3CH2 2.07 (t, 12H); Ho ∼8.11
(m, 12H); Hm,p ∼7.5 (m, 18H); Hâ 8.96 (d, 4H), 8.92 (d, 4H), 8.40 (d,
4H), 7.11 (d, 4H); H3,5-Py 5.54 (d, 4H); H2,6-Py 2.96 (d, 4H) ppm. UV-
vis (C6H5CH3) (log ꢀ): λmax/nm 395 (5.23), 423 (5.82), 450 (sh), 523
(4.61), 547 (4.66), 594 (3.96), 653 (3.95). FAB-MS (NBA) shows a
sharp parent peak at 1913 (m/z+).
(19) Sakurai, T.; Kobayashi, K. Rikagaku Kenkyuusho Hokoku (Rep. Inst.
Phys. Chem. Res.) 1979, 55, 69.
(20) Jonson, C. K. ORTEP II; Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976.
Ru(TTP)(H2PyP3P)2 (10). RuII(TTP)(H2PyP3P)2 was synthesized
by a method similar to that for RuII(OEP)(H2PyP3P)2 (8). A spectral

Ruthenium Porphyrin Dimers and Trimers
Inorganic Chemistry, Vol. 36, No. 8, 1997 1629
Table 3. Selected Bond Angles of 1 (deg)
N-Ru-N (trans)
173.9(2)-176.2(2)
N-Ru-N (cis)
89.7(2)-90.2(2)
C(CO)-Ru-N(Py)
Ru-C(CO)-O(CO)
175.0(2)
179.7(6)
CR-N-CR (av for OEP)
N-CR-Câ (av for OEP)
N-CR-Cm (av for OEP)
CR-Câ-Câ (av for OEP)
Câ-Cm-Câ (av for OEP)
CR-N-Cµ (av for H2PyP3P)
N-CR-Câ (av for H2PyP3P)
N-CR-Cm (av for H2PyP3P)
CR-Câ-Câ (av for H2PyP3P)
Câ-Cm-Câ (av for H2PyP3P)
106.7(5)-108.2(5)
108.2(6)-109.9(5)
125.0(6)-126.4(5)
106.3(5)-107.9(7)
126.0(4)-126.6(7)
106.7(5)-107.9(5)
108.7(6)-109.8(5)
125.3(5)-126.6(5)
105.5(5)-108.0(6)
124.0(5)-126.6(5)
Table 4. Selected Dihedral Angles of 1 (deg)a
(OEP)p-(H2PyP3P)p
(OEP)p-(Py)p
(H2PyP3P)p-(Py)p
(OEP)p-(N(Py)-C23)v
(Py)p-(Ru-N(Py))v
(OEP)p-(Ru-N(Py))v
80.78(8)
63.23(35)
68.92(49)
63.20(14)
160.48(18)
82.72(10)
a p, plane; v, vector.
Electrochemical Measurements. Cyclic voltammetry and steady-
state voltammetry were performed with a Fuso microelectrode poten-
tiostat HECS 972 and a Fuso potential sweep unit HECS 321B. The
data were recorded on a Graphtec WVX-2400 X-Y recorder or were
digitized and stored in an NEC PC-9800 personal computer through a
Riken Denshi TCDC-12-8000 transient recorder. Locally written
software was employed for data collection and analysis. The working
and the counter electrodes used in cyclic voltammetry measurements
were a platinum disk electrode (i.d. ) 1.6 mm) and a platinum wire,
respectively. Cyclic voltammograms were recorded at a scan rate of
100 mV/s at 10 °C. The sample solutions in 0.1 M (TBA)PF6-CH2Cl2
((TBA)PF6 ) tetrabutylammonium hexafluorophosphate) were deoxy-
genated with a stream of argon. The reference electrode was Ag/0.01
M [Ag(CH3CN)2]PF6, 0.1 M (TBA)PF6 (acetonitrile), and the half-
wave potential of the ferrocenium/ferrocene couple was +0.352 V. The
working electrode used in steady state voltammetry measurements was
a platinum microdisk electrode (i.d. ) 30 µm). The counter and
reference electrodes were the same as the cyclic voltammetry measure-
ments. Steady-state voltammograms were recorded at a scan rate of
10 mV/s at 10 °C.
Figure 2. Molecular structure and atom labeling of Ru(OEP)(CO)-
(H2PyP3P) (1). Thermal ellipsoids are drawn to illustrate 50% prob-
ability surface.
Other Measurements. 1H NMR spectra were recorded on a JEOL-
EX 270 spectrometer. IR spectra (KBr disk) were obtained with a
Hitachi 270-50 infrared spectrophotometer. UV-vis spectra were
recorded on a Shimadzu U best-30 or a Hitachi U-3410 spectropho-
tometer.
Results and Discussion
Crystal Structure of 1. The molecular geometry and
labeling scheme of 1 is shown in Figure 2. For the sake of
clarity, the ethyl substituents of the octaethylporphyrin core have
been omitted. Crystallographic data are given in Table 1.
Selected bond distances, angles, and dihedral angles are listed
in Tables 2-4, respectively.
The crystal structure consists of two Ru(OEP)(CO)(H2PyP3P)
molecules and two dichloromethane molecules in a unit cell.
The bond distances of Ru-N(OEP) span the range 2.042(5)-
2.066(5) Å (average 2.051 Å) as shown in Table 2. The average
distance is almost the same as that of Ru(TPP)(CO)(EtOH)
(2.049 Å)21 and Ru(TPP)(CO)(Py) (2.052 Å).22a Other bond
distances of the ruthenium porphyrin ring and axial porphyrin
Figure 3. Brief illustrations of tilt and tipping angles to the axial
porphyrin plane of 1.
ring are similar to those of general porphyrin structures. The
carbonyl ligand is coordinated to the ruthenium ion linearly with
the 179.7(6)° angle of Ru-C(CO)-O(CO), which is similar to
that of Ru(TPP)(CO)(Py).22a The bond length Ru-C(CO) of
1 (1.801 Å) is intermediate between those of Ru(TPP)(CO)-
(EtOH) (1.77 Å)21 and Ru(TPP)(CO)(Py) (1.838 Å).22a The
bond length Ru-N(Py) (2.237 Å) is longer than that of
Ru(TPP)(CO)(Py) (2.193 Å).22a Some dihedral angles of 1,
illustrated and summarized in Figure 3 and Table 4, respectively,
are also characteristic; i.e., the dihedral angle between the
pyridyl ring and the octaethylporphyrin ring is 63.20° and the
Ru-N(Py) bond is tilted by ca. 7.3° from the perpendicular to
the octaethylporphyrin plane, though, in the corresponding
(21) Bonnet, J. J.; Eaton, S. S.; Eaton, G. R.; Holm, R. H.; Ibers, J. A. J.
Am. Chem. Soc. 1973, 95, 2141.
(22) (a) Little, R. G.; Ibers, J. A. J. Am. Chem. Soc. 1973, 95, 8583. (b)
Hopf, F. R.; O’Brien, T. P.; Scheidt, W. R.; Whitten, D. G. J. Am.
Chem. Soc. 1975, 97, 277.

1630 Inorganic Chemistry, Vol. 36, No. 8, 1997
Funatsu et al.
Figure 4. Diagram to illustrate the nonplanarity of the porphyrin
skeleton of the ruthenium porphyrin ring. The numbers indicate the
perpendicular displacement of an atom (in units of 0.001 Å) from the
mean plane of the 24-atom core of the porphyrin. The Ru atom was
not included in the plane calculation.
Figure 6. Packing description of 1: Top view with respect to axial
porphyrin macrocycles.
octaethylporphyrin subunits are aligned by interposing carbonyl
ligands with a 3.34 Å layer distance. The octaethylporphryin
macrocycles are not overlapping with each other. And in the
other, the subunits are facing 18.25 Å apart, sandwiching the
axial porphyrin ligands. The shortest distance between two
carbons of the ethyl substituents of adjacent octaethylporphyrins
is 3.899 Å. The axial porphyrin ligands are aligned horizontally.
The axial porphyrin planes are superimposed alternately on
adjacent axial porphyrin ligands. The mean-plane separation
between the overlapped two porphyrin ligands is 4.24 Å. The
shortest intermolecular atomic distances between the axial
porphyrin ligands and between the axial porphyrin core atoms
are found to be 3.726 Å for C37(â-pyrrole carbon)-C59(phenyl
carbon) and 4.125 Å for N7-C34, respectively. In addition,
the shortest distance between no overlapped adjacent axial
porphyrins is 4.644 Å of C40-C42 and the mean-plane
separation was 4.54 Å. Then, these mean-plane separations and
shortest atomic distances between the adjacent axial porphyrin
cores are too long to affirm the existence of π-π interac-
tions.24,25 Hence, we think that the tilt of the pyridyl ring of 1,
discussed above, cannot be attributed to a strain between axial
porphyrin subunits but mainly to crystal-packing effects.
1H NMR Spectra. For the measurements of 1H NMR
spectra, carbonyl dimers and trimers 1-7 and bis(pyridyl)
trimers 8-10 were dissolved in CD2Cl2 and C6D6, respectively.26
Figure 5. Diagram to illustrate the nonplanarity of the porphyrin
skeleton of the axial porphyrin ring. The numbers indicate the
perpendicular displacement of an atom (in units of 0.001 Å) from the
mean plane of the 24-atom core of the porphyrin.
monomer complexes such as Ru(TPP)(CO)(Py)22a and Ru(OEP)-
(Py)2,22b the pyridyl rings and the ruthenium porphyrin rings
are essentially perpendicular. The pyridyl ring is also tipped
by ca. 19.5° (tipping angle: 160.48°) from the Ru-N(Py) bond
toward the octaethyporphyrin plane. These features are char-
acteristic of the porphyrin oligomers linked perpendicularly; i.e.,
the tilted and tipping angles for the Zn(PyP3P) polymer were
also observed to be 10 and 155.6(8)°, respectively.8 This
extensive tilt of bound pyridine of the Zn(PyP3P) polymer was
explained by the strain induced by polymerization besides
crystal-packing effects.8 However, we imagine that the tilt of
the pyridyl ring of 1 is the result of crystal-packing effects as
discussed later.
The ruthenium octaethylporphyrin macrocycle of 1 is not
completely planar as shown in Figure 4. The ruthenium ion
lies 0.119(1) Å out of the mean plane of the 24-atom core toward
CO. This displacement is still larger than that of a monomeric
analogue of Ru(TPP)(CO)(Py) with a corresponding value of
0.079 Å.22a The maximum displacement among the atoms of
the ruthenium porphyrin macrocycle is 0.207 Å of C2 (â-pyrrole
carbon), which is larger than that of Ru(TPP)(CO)(Py) by more
than three times. The axial porphyrin macrocycle is also
distorted significantly as shown in Figure 5. Displacements of
several pyrrole carbon atoms from the mean plane of 24-atom
core are more than 0.2 Å, which is also significantly larger than
in free H2TPP.23
1
All the Ru(II) porphyrin oligomers showed sharp H NMR
signals which indicated that these oligomers were all dia-
magnetic. The chemical shifts of the oligomers are listed in
Table 5.
The spectrum of 1 revealed that the oligomer took on the
dimeric structure even in solution. Integral intensities of the
signals agreed well with the composition of 1:1 for OEP and
(23) (a) Silvers, S. J.; Tulinsky, A. J. Am. Chem. Soc. 1967, 89, 3331. (b)
Chen, B. M. L.; Tulinsky, A. J. Am. Chem. Soc. 1972, 94, 4144. (c)
Codding, P. W.; Tulinsky, A. J. Am. Chem. Soc. 1972, 94, 4151.
(24) (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112,
5525. (b) Blach, A. L.; Latos-Grazynski, L.; Noll, B. C.; Szterenberg,
L.; Zovinka, E. P. J. Am. Chem. Soc. 1993, 113, 11846.
(25) Scheidt, W. R.; Lee, Y. J., Struct. Bonding (Berlin) 1987, 64, 1.
(26) Deuterated benzene C6D6 was used for the bis(pyridyl) complexes of
8-10 as a solvent, because the analogous complex of RuII(OEP)(Py)2
was slowly oxidized in chloroform to generate the corresponding
ruthenium(III) complexes which caused paramagnetic shifts and
broadening in the NMR spectra.22b
The crystal of 1 has a layer structure of octaethylporphyrin
rings as shown in Figure 6. The layer structure is composed
of two kinds of layers; i.e., in the one layer, the ruthenium(II)

Ruthenium Porphyrin Dimers and Trimers
Inorganic Chemistry, Vol. 36, No. 8, 1997 1631
Table 5. 1H NMR Data for Ruthenium(II) Porphyrin Oligomers (CD2Cl2)
Ru porphyrin subunit
(Ru(OEP), Ru(TPP), Ru(TTP))
axial ligand porphyrin subunit
(H2PyP3P or trans-H2Py2P2)
phenyl (axial ligand or Ru(Por))
meso CH2 CH3
(OEP) (OEP) (OEP) (TPP, TTP) (TTP)
â-pyrrole CH3
ligand or complex
NH 2,6-Py 3,5-Py
â-pyrrole
o
m,p
H2PyP3P
-2.88 8.98
-2.92 8.99
8.15 8.85
8.15 8.87
8.20
8.19
7.77
7.77
trans-H2Py2P2P
Ru(OEP)(CO)(ROH)a
9.95 4.11 1.94
8.67
Ru(TPP)(CO)(ROH)a
8.25, 8.04
2.66 8.07, 7.99
8.04, 7.95
7.69
7.53
7.68
7.45
7.67
Ru(TTP)(CO)(ROH)a
8.69
1
-3.41 1.23
-2.90 1.82
1.26
-3.33 1.92
-3.32 1.91
-3.98 1.15
-3.80 1.85
-3.82 1.83
-2.81 2.82
2.96
5.77 8.69, 8.65, 8.36, 7.16 10.01 4.08 1.96
5.20 8.76, 8.72, 8.18, 6.62 10.37 4.09 2.02
5.79 8.78, 8.75, 8.45, 7.24 10.04 4.15 1.96
6.10 8.75, 8.70, 8.46, 7.30
1b
2
7.97, 7.85
8.04, 7.94
3
4
5
6
7
8
9
10
8.75
8.75
8.32, 8.19, 8.08,8.00 7.7-7.5
6.06 8.75, 8.72, 8.46, 7.30
2.67 8.19, 8.07, 8.01
7.7-7.5
7.7-7.5
7.7-7.4
7.8-7.5
5.62 8.19, 7.01
5.95 8.20, 7.19
5.93 8.14, 7.17
5.31 8.79, 8.77, 8.25, 6.93 10.06 4.09 2.08
5.54 8.96, 8.92, 8.40, 7.11 10.10 4.11 2.07
5.61 8.84, 8.82, 8.55, 7.55
9.97 4.03 1.90
7.7
8.69
8.71
8.29, 8.15, 7.97
2.65 8.15, 7.99, 7.80
8.01, 7.91
∼7.5
∼8.11
∼7.5
∼7.5
-2.59 3.49
9.01
2.46 8.48, 8.06, 7.95
a In CDCl3. b In C6D6.
H2PyP3P porphyrins. The signals for the 2,6- and 3,5-protons
of the pyridyl group of the axial porphyrin ligand were observed
as doublets at the fields of 1.23 and 5.77 ppm, which were
significantly higher than the corresponding resonance shifts of
free H2PyP3P, at 8.98 and 8.15 ppm, respectively, as shown in
Figure 7a. Similar upfield shifts have been observed for the
pyridyl groups in an aggregated Zn(PyP3P) polymer and in
Ru(OEP)(CO)(Py).8,27 The results clearly indicate the coordina-
tion of H2PyP3P to the central ruthenium ion of the Ru(OEP)-
(CO) core through the pyridyl group even in solution. The
signals of â-pyrrole protons of the H2PyP3P part also indicate
the coordination of this to Ru(OEP)(CO). The four signals
observed at high-field regions at 7.16, 8.36, 8.65, and 8.69 ppm
should be assigned to the protons located near the Ru(OEP)-
(CO) core as shown in Figure 7b. The chemical shifts of the
OEP ring protons were not so different from those of Ru(OEP)-
(CO)(Py).27 The inner NH proton signal was observed at -3.41
ppm.
Figure 7. 1H NMR spectrum of 1 in CD2Cl2: (a) In the region of -4
to 10 ppm; (b) in the region 7.0-8.8 ppm. The symbol “×” denotes
solvent and solvent impurity peaks.
from the difference in shielding effects of the ruthenium
porphyrin rings.
1
Similar H NMR results to 1, i.e., upfield shifts of pyridyl
The signal intensities of the carbonyl trimers 5-7 revealed
that the complexes consisted of two ruthenium porphyrin
subunits and one bridging ligand of trans-H2Py2P2P. Significant
high-field shifts of the 2,6- and 3,5-pyridyl protons of trans-
H2Py2P2P indicated that each trimer had a sandwich structure
with a bridging trans-H2Py2P2P. The resonances due to the
protons of ruthenium porphyrin cores occurred around the
magnetic fields similar to the corresponding carbonyl monomers
of Ru(Por)(CO)(Py) and carbonyl dimers of 1, 3, and 4.
However, the two signals of the â-pyrrole protons of the
bridging porphyrin ligands appeared at 7.0-7.2 and 8.2 ppm,
though the carbonyl dimers showed four signals. The splitting
patterns reflect each structure of these oligomers. In addition,
the pyridyl protons and the inner NH protons appeared at higher
fields than the dimers. The difference in chemical shifts of the
inner NH proton resonances between the carbonyl trimers and
the corresponding carbonyl dimers was ca. 0.5 ppm, and that
between the carbonyl dimers and free H2PyP3P was again ca.
0.5 ppm. These results suggest that the ring currents of each
ruthenium porphyrin in a molecule influence equally the inner
NH protons located in the center of a bridging porphyrin ligand.
Similar results were reported for [Ru(TPP)(CO)]4(ZnPy4P)11 and
a series of osmium(II) porphryin oligomers.12
protons, were also observed in the carbonyl dimers 2-4 except
for the following. In the case of 2, the absence of any signals
around -3 ppm showed the substitution of the inner NH protons
by a Zn(II) ion. The phenyl or tolyl proton signals of the
ruthenium porphyrin rings of 3 or 4 could not be explicitly
assigned, because of the overlapping of the signals with those
of axial porphyrins. Nevertheless, the high-field shifts of the
pyridyl and â-pyrrole protons of 3 and 4 indicated the formation
of porphyrin dimers.
Table 6 shows the extent of upfield shifts (∆δ) of 2,6- and
3,5-pyridyl protons of the porphyrin oligomers from the
corresponding signals of the pyridyl group of free H2PyP3P.
The respective ∆δ values of -7.75 and -2.38 ppm for 1 in
CD2Cl2 are very similar to those of Ru(OEP)(CO)(Py) (in
CDCl3). 3 also has comparable values. The similitude of ∆δ
values between the carbonyl dimers and the corresponding
monomers and the sharpness of the pyridyl and four â-pyrrole
proton signals indicate that the axial porphyrins are coordinated
vertically to the Ru(II) ion with almost the same Ru-N(Py)
distances as those of the corresponding monomers unlike the
crystal structure of 1. The ∆δ values of 1 and Ru(OEP)(CO)-
(Py) are comparable even in C6D6. The ∆δ values of 3 are
smaller than those of 1. The difference should mainly come
All 1H NMR signals of the bis(pyridyl) trimers 8-10 in C6D6
were listed in Table 5. The signal intensities revealed that the
complexes consisted of 1:2 fractions of ruthenium porphyrin
(27) Antipas, A.; Buchler, J. W.; Gouterman, M.; Smith, P. D. J. Am. Chem.
Soc. 1978, 100, 3015.

1632 Inorganic Chemistry, Vol. 36, No. 8, 1997
Funatsu et al.
Table 6. Chemical Shifts of Pyridyl Protons and Ruthenium Porphyrin Ring Protons and Chemical Shift Difference (∆δ) from Free Pyridine
(or H2PyP3P) or Corresponding Ruthenium Porphyrin Monomersa
compd
solv
2,6-Py
3,5-Py
4-Py
meso
-CH2-
-CH3
Ru(OEP)(CO)(Py)
CDCl3
C6D6
CD2Cl2
C6D6
CDCl3
CD2Cl2
C6D6
C6D6
CDCl3
C6D6
0.88 (-7.72)
1.26 (-7.30)
1.23 (-7.75)
1.82 (-7.23)
1.55 (-7.05)
1.92 (-7.06)
2.16 (-6.40)
2.82 (-6.23)
8.6 (0)
4.89 (-2.31)
4.05 (-2.66)
5.77 (-2.38)
5.20 (-2.76)
5.21 (-1.99)
6.10 (-2.05)
4.08 (-2.63)
5.31 (-2.64)
7.2 (0)
5.81 (-1.79)
4.56 (-2.47)
9.79 (0)
10.18 (0)
10.01 (0.22)
10.37 (0.19)
3.97 (0)
3.97 (0)
4.08 (0.11)
4.09 (0.12)
1.89 (0)
1.92 (0)
1.96 (0.07)
2.02 (0.10)
1
Ru(TPP)(CO)(Py)
3
Ru(OEP)(Py)2
8
Py
Py
6.09
4.63 (-2.40)
9.65 (0)
10.06 (0.41)
3.88 (0)
4.09 (0.21)
1.92 (0)
2.08 (0.14)
7.6
7.03
8.56 (0)
6.71 (0)
H2PyP3P
H2PyP3P
CD2Cl2
C6D6
8.98 (0)
9.05 (0)
8.15 (0)
7.95 (0)
a Values vs TMS. The values in parentheses show the chemical shift differences (- for the upfield shift) (2,6-Py, 3,5-Py) relative to free
pyridine or H2PyP3P and the chemical shift differences (+ for the downfield shift) (meso, -CH2-, -CH3) relative to the corresponding ruthenium
porphyrin monomers.
Table 7. UV-Vis Data for Ruthenium Porphyrin Oligomers
λ
max/nm (ꢀ/104 M-1 cm-1
)
Soret band
extra band
complex
solv
Q band
1
2
3
4
5
6
7
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
395 (30.4) 418 (40.1) 514 (3.16), 550 (2.98), 5.90 (0.54), 646 (0.40)
395 (28.2) 419 (51.3) 516 (1.52), 548 (4.22), 586 (0.44)
419 (69.0) 519 (2.75), 530 (sh), 550 (sh), 588 (0.61), 645 (0.40)
417 (71.9) 519 (2.80), 530 (sh), 550 (sh), 589 (0.70), 647 (0.54)
395 (51.3) 421 (38.7) 515 (4.69), 550 (6.30), 591 (0.53), 648 (0.37)
414 (88.6) 520 (sh), 530 (4.51), 565 (sh), 589 (0.76), 646 (0.47)
414 (92.0) 520 (sh), 532 (4.53), 565 (sh), 586 (0.81), 646 (0.47)
8
9
10
C6H5CH3 399 (sh)
C6H5CH3 395 (17.1) 423 (66.7) 523 (4.07), 547 (4.57), 594 (0.91)
419 (53.6) 516 (6.38), 546 (2.73), 588 (1.33), 652 (1.09)
456 (5.0)
450 (sh)
650-750
653 (0.897)
650-750
C6H5CH3
CH2Cl2
418 (67.2) 511 (5.87), 547 (1.81), 592 (1.47), 652 (1.36)
417 (44.9) 514 (2.0), 549 (0.78), 589 (0.61), 645 (0.40)
518 (1.59), 549 (2.45)
H2PyP3P
Ru(OEP)(CO)(Py)a CH2Cl2
396 (23.4)
395 (10.2)
Ru(TPP)(CO)(Py)b
CHCl3
C6H6
413 (28.2) 495 (sh), 532 (1.78), 566 (0.37)
495 (1.48), 521 (3.80)
a
Ru(OEP)(Py)2
450 (1.58)
a Reference 27. b Reference 21.
cores and axial porphyrin subunits. The axial porphyrin ligands
also exhibited high-field shifts and the same splitting pattern
with the corresponding carbonyl dimers, 1, 2, and 4. These
results apparently indicate that the complexes 8-10 are the
trimers having two axial porphyrins. The ring current shifts of
the pyridyl groups in 8 are comparable to those in Ru(OEP)-
(Py)2; i.e., the two axial porphyrins of 8 are coordinated
perpendicularly to the ruthenium porphyrin core with the Ru-
N(Py) distance similar to Ru-N(Py) in Ru(OEP)(Py)2 in which
the ruthenium ion is on the plane of the porphyrin ring.22b
The ring current of axial porphyrins in these oligomers caused
only very slight downfield shifts on the resonances of ruthenium
porphyrin ring protons. In comparison to the chemical shifts
of the OEP ring protons of Ru(OEP)(CO)(Py), all shifts of the
OEP rings of 1 were observed at lower field regions to a small
extent. A maximal downfield shift was observed in the meso-
protons which was the nearest to the axial porphyrins. The
degree of the downfield shifts of 1 was not so sensitive to the
difference in solvents such as CD2Cl2 and C6D6. Similar trends
in the downfield shifts of OEP rings were observed in 8, the
magnitude of downfield shifts of 8 being nearly twice of 1.
Therefore, it is obvious that the extent of the downfield shift of
OEP rings is proportional to the number of the axial porphyrins,
suggesting that the sum of ring currents of two axial porphyrins
determines the resonance shifts of protons of the ruthenium
porphyrin ring.
complexes. The ∆δ values of the 2,6- and 3,5-pyridyl protons
of the Zn(PyP3P) polymer, Zn(TPP)(H2PyP3P), and Zn(TPP)-
(Py) were reported as -6.4 and -1.9, -4.3 and -1.3, and -5.9
and -1.8 ppm, respectively.8 The difference in the ∆δ values
between the Zn(PyP3P) polymer and Zn(TPP)(Py) was attributed
to the change in tilt angle of the pyridine rings by the simulations
of ring current effects. The estimated tilt angles of the
Zn(PyP3P) polymer and Zn(TPP)(Py) were ca. 25 and ca. 0°,
respectively. Although the tilt of pyridine ring of Zn(PyP3P)
tetramer was actually demonstrated by X-ray crystallographic
determination, the X-ray result cannot explain the large deviation
1
of the ∆δ values of Zn(TPP)(H2PyP3P). Judging from the H
NMR data of the ruthenium porphyrin oligomers, it is supposed
that the disagreement in the ∆δ values of Zn porphyrin
complexes is caused by the dissociation of axial ligands from
these Zn porphyrin cores, which results in the difference in
downfield shifts of the pyridyl proton signals.28
UV-Visible Spectra of Ruthenium Carbonyl Complexes.
The data for the absorption spectra of the carbonyl complexes
(1-7) in dichloromethane and for the complexes with no
carbonyl ligands (8-10) in toluene are tabulated in Table 7.
Absorption spectra of the ruthenium carbonyl complexes were
essentially the sum of those of ruthenium porphyrin subunits
and free H2PyP3P porphyrins. The complexes 1, 2, and 5
showed two Soret bands of constituent porphyrin subunits. The
absorptions at 395 and around 420 nm were ascribed to the
bands of ruthenium OEP subunits and axial or bridging
As described above, comparable ring current shifts of pyridyl
protons were observed between the carbonyl dimers (1 and 3)
or the bis(pyridyl) trimer 8 and the corresponding ruthenium
porphyrin monomers. This is in contrast to Zn porphyrin
(28) Anderson, H. L.; Hunter, C. A.; Meah, M. N.; Sanders, J. K. M. J.
Am. Chem. Soc. 1990, 112, 5780.

Ruthenium Porphyrin Dimers and Trimers
Inorganic Chemistry, Vol. 36, No. 8, 1997 1633
porphyrin ligands, respectively. There are no large changes in
the wavelengths of the absorption bands from the bands of the
parent compounds of Ru(OEP)(CO)(Py)27 and free axial por-
phyrin ligands. Complex 5 in dichloromethane has absorption
bands at 395 and 421 nm with higher intensity and a relatively
small intensity, respectively, reflecting the formula composed
from a 2:1 ratio for ruthenium porphyrin subunits and bridging
porphyrin subunits. In fact, the molar absorptivity at 395 nm
with 51.3 × 104 M-1 cm-1 is nearly equivalent to twice that of
the molar absorptivity of Ru(OEP)(CO)(Py). In addition, the
Soret absorption maximum of OEP part of 5 is not different
from those of 1, 2, and Ru(OEP)(CO)(Py). These results are
in sharp contrast to the fact that many porphyrin oligomers
having face-to-face conformation show blue shifts of the Soret
bands relative to the parent monomers.3i,j,28,29 The absorption
properties of these face-to-face porphyrin oligomers are under-
stood as the excitonic interactions between the porphyrin rings,
as described by the Kasha model;1b,3d,30 i.e., the degree of a
Soret blue shift depends on the distance between porphyrin
rings.1b,30 It may be that in the complex 5 the distance between
the two ruthenium porphyrin cores is too large to allow
interaction.
Figure 8. UV-vis spectral change of 8 (CH2Cl2 solution) by the
addition of the CH3CN solution of (NH4)2Ce(NO3)6.
Further, for 8-10, one more extra broad band was observed
in the region of 650-750 nm with molar absorptivities of about
8000 M-1 cm-1. The band was also decreased in intensity by
the stoichiometric oxidation of RuII(OEP)(H2PyP3P)2 (8) with
(NH4)2Ce(NO3)6 to form [RuIII(OEP)(H2PyP3P)2]+ as shown in
Figure 8. The peak maximum was at the wavelength around
675 nm for 9 and was at 725 nm for 8. Ru(OEP)(Py)2 exhibits
very weak near-IR bands around ∼645 (sh) and ∼715 (sh) nm,
which are assigned to forbidden CT d-eg(π*) transitions.27 The
near-IR bands of 8-10 are too intense to assign to the forbidden
CT transitions and are tentatively assigned to CT bands between
two axial porphyrins via ruthenium(II) ions.
The Soret bands of three complexes are also not simple
overlaps of the corresponding bands of the ruthenium porphyrin
subunits and the axial porphyrin subunits. The complex 8
exhibits a broad Soret band with a peak maximum at 419 nm
and a shoulder around 400 nm. The Soret band is seemingly
composed of overlaps of those of the ruthenium porphyrin
subunit (399 nm) and the axial porphyrin subunits (417 nm).
However, the molar absorptivity at 419 nm (53.9 × 104 M-1
cm-1) is much smaller than the expected value for two H2PyP3P
(ca. 90 × 104 M-1 cm-1). While the molar absorptivity of an
axial porphyrin of the carbonyl complex 1 is smaller than that
of the free H2PyP3P (ca. 45 × 104 M-1 cm-1),35 the extent of
the decrease for 8 is much more. Furthermore, in the spectral
change of 8 by the reaction with pyridine to generate
RuII(OEP)(Py)2 and two free H2PyP3P, the Soret band at 419
nm of axial porphyrins shifted to 417 nm and increased in
intensity significantly. These characteristic features of the
In the cases of complexes 3, 4, 6, and 7 having ruthenium
tetraarylporphyrin moieties, the Soret bands were observed as
an apparent one intense band because of the similar Soret band
energies between ruthenium porphyrin subunits and axial
porphyrin subunits.21 The molar absorptivity of the Soret band
for each dimer and trimer complex is essentially equal to the
sum of molar absorptivities of its components. In the Q band
region from 515 to 565 nm, absorption spectra of all carbonyl
complexes are also regarded as overlap of those of both core
and ligand porphyrin subunits. The bands around 590 and 645
nm are essentially the absorptions of axial porphyrins.
UV-Visible Spectra of Ruthenium Bis(pyridyl) Com-
plexes. Unlike carbonyl complexes, the ternary porphyrins,
8-10, with no carbonyl ligands have extra bands besides the
corresponding bands of the parent porphyrin subunits. For
instance, the complexes 8 and 9 showed an intense extra band
around 450 nm, which can be assigned to dπ(RuII)-π*(OEP)
MLCT, similarly to Ru(OEP)(Py)2.27 The significant large
molar absorptivity of the band of 8 (5 × 104 M-1 cm-1) as
compared with that of Ru(OEP)(Py)2 (1.58 × 104 M-1cm-1
)
might raise some doubts about the assignment of the band.
However, the following facts support the proposed assign-
ment: The bands of the two complexes were decreased in
intensity by the stoichiometric oxidation of Ru(II) to Ru(III)
using (NH4)2Ce(NO3)6 as shown in Figure 8.31 Furthermore,
the band shifted remarkably to a longer wavelength in more
polar solvents, while the bands originated from Ru(OEP) and
H2PyP3P gave essentially no shifts. For example, the charac-
teristic band of 8 shifted from 456 nm in toluene (dielectric
constant: 2.4)32 to 466 nm in tetrahydrofuran (7.4) and 475
nm in dichloromethane (8.9). The observed solvent effect is
typical of the metal to ligand charge transfer band. Thus the
bands should be assigned to MLCT from the ruthenium ion to
the horizontal porphyrin ring.33 The characteristic absorption
band was also observed for the complex 9 around 450 nm but
not observed for the TTP complex 10 as well as Ru(TPP)(Py)2.34
(31) Metalloporphyrins can be oxidized either at the metal center or at the
porphyrin rings to generate π-cation radicals. The bis(pyridyl) complex
8 can be oxidized at the three parts, i.e., the metal center, the ruthenium
porphyrin ring, and the axial porphyrin rings. If a π-cation radical
was generated, the absorption spectrum should cause a significant
change, i.e., relative broad bands should appear in the region 500-
700 nm and the Soret band should be broadened. However, no broad
band was observed in the region in the oxidation process of 8. In
addition, the shoulder around 400 nm, which can be assigned to the
Soret band of OEP, is blue-shifted. These spectral changes fitted well
the change in the oxidation process of RuII(OEP)(Py)2 to generate
[RuIII(OEP)(Py)2]+; i.e., the oxidations of 8 occurred at the metal center
to form [RuIII(OEP)(H2PyP3P)2]+ and π-cation radicals were not
generated on either the metalloporphyrin ring or the axial porphyrin
rings. This observation is consistent with the results of electrochemical
studies described below in the text.
(29) (a) Tran-Thi, T. H.; Lipskier, J. F.; Maillard, P.; Momenteau, M.;
Lopez-Gastillo, J.-M.; Jay-Grein, J.-P. J. Phys. Chem. 1992, 96, 1073.
(b) Hunter, C. A.; Meah, M. N.; Sanders, J. K. M. J. Am. Chem. Soc.
1990, 112, 5773.
(30) (a) Kasha, M.; Rawls, H. L.; El-Bayoumi, M. A. Pure Appl. Chem.
1965, 11, 371. (b) Kasha, M. Radiat. Res. 1963, 20, 55. (c) Hunter,
C. A.; Sanders, J. K. M.; Stone, A. J. Chem. Phys. 1989, 133, 395.
(32) Wollmann, H. Pharmazie 1974, 29, 708.
(33) Marvaud, V.; Launay, J. P. Inorg. Chem. 1993, 32, 1376.
(34) Brown, G. M.; Hopf, F. R.; Ferguson, J. A.; Meyer, T. J.; Whitten,
D. G. J. Am. Chem. Soc. 1973, 95, 5939.
(35) The molar absorptivity of the axial porphyrin subunit of 1 is 43.9 ×
104 M-1 cm-1 in toluene, which is larger than that in dichloromethane
(40.1 × 104 M-1 cm-1).

1634 Inorganic Chemistry, Vol. 36, No. 8, 1997
Funatsu et al.
Scheme 1
absorption spectra were also observed in the complexes 9 and
10. Although the distinct split of the Soret bands, which was
direct evidence of excitonic interaction as reported for various
gable and flat porphyrin dimers linked covalently,1b,i,3d,g,28,30,36
was not observed, those results clearly suggest the presence of
excitonic interactions between two axial porphyrin ligands.
Electrochemical Studies. The electrochemical properties of
ruthenium porphyrin oligomers in dichloromethane were studied
by cyclic voltammetry and steady-state voltammetry. The
results are schematically shown in Scheme 1, and the data are
listed in Table 8.
The free porphyrin of H2PyP3P showed a reversible oxidation
wave at 0.94 V and two reversible reduction waves at -1.30
and -1.63 V vs Ag/Ag+ in 0.1 M (TBA)PF6-CH2Cl2 solution
as shown in Figure 9a. The corresponding three redox waves
were also observed for H2TPP. Thus, these redox processes
should be ascribed to the formation of a monocation radical, a
monoanion radical, and a dianion, respectively.34,37 Beside these
peaks, a small cathodic peak was observed around 0.6 V for
the free H2PyP3P when scanned to 1.0 V. The peak became
more distinct when scanned to 1.5 V. This redox behavior was
not observed for H2TPP. However, the H2TPP solution
containing nucleophilic pyridine or 4,4′-bipyridine exhibits a
very similar redox profile with a cathodic peak around 0.6 V
(vs SCE).38 Under the conditions, the cathodic peak was
ascribed to the chemical reaction to generate a â-substituted
porphyrin after the oxidation of H2TPP ring.38 Therefore, certain
chemical reactions such as dimerization or polymerization of
H2PyP3P must also take place in the case of H2PyP3P, though
the characterization of the products was not performed. In
addition, the cathodic peak was not observed in the ruthenium
porphyrin oligomer of 8 as shown in Figure 9d, because of the
ligation of the pyridyl substituents to the ruthenium(II) ion.
The ruthenium carbonyl dimer of 1 exhibited a reversible
one-electron oxidation wave at 0.53 V as shown in Figure 9b.
The oxidation was assigned to the formation process of π-cation
radicals on the ruthenium porphyrin ring, because the oxidation
waves of Ru(OEP+)(CO)(L)/Ru(OEP)(CO)(L) (L ) Py or
Figure 9. Cyclic voltammograms of H2PyP3P, 1, 5, and 8 in 0.1 M
(TBA)PF6-CH2Cl2 at 10 °C.
vacant site) couples were observed around 0.65-0.70 V (vs
SCE).34,39 Other carbonyl dimers, 3 and 4, showed the oxidation
waves of ruthenium porphyrin rings at 0.74 and 0.68 V,
respectively. In the region higher than 1.0 V, the oxidation
waves at 1.01 V were overlapped with the one at 1.09 V for 1
and around 1.20-1.25 V for 3 and 4, respectively. The
comparison of the heights of the overlapped waves to those of
the first oxidation waves corresponding to the reversible one-
electron oxidation of the ruthenium porphyrin ring revealed that
the overlapped wave (>1.0 V) is an overall two-electron process.
The former one in the two oxidation waves should be assigned
to the first oxidation processes of an axial ligand porphyrin ring
and the latter one the second oxidation processes of ruthenium
porphyrin rings in comparison of redox profiles between 1, 3,
and 4. The ruthenium(II) porphyrin complexes having carbonyl
ligands show no Ru(II) oxidation processes.34,39 In carbonyl
dimers (1, 3, and 4) and trimers (5 and 7), oxidation occurred
at the porphyrin rings rather than the ruthenium center.
The dimers, 1, 3, and 4, also exhibited two one-electron
reduction waves in the potential region lower than -1.0 V, while
the corresponding ruthenium(II) porphyrin monomer analogues
showed no reduction waves.34,39a,b These waves were at the
potentials close to the free H2PyP3P. Hence those waves can
be assigned to the reduction of the axial ligand porphyrins. The
redox potentials of axial ligand porphyrins slightly shifted to a
(36) (a) Won, Y.; Friesner, R. A.; Johnson, M. R.; Sessler, J. L. Photosynth.
Res. 1989, 201. (b) Anderson, H. L. Inorg. Chem. 1994, 33, 972.
(37) (a) Felton, R. H.; Linschitz, L. J. Am. Chem. Soc. 1966, 88, 113. (b)
Heiling, G. P.; Wilson, G. S. Anal. Chem. 1971, 43, 545.
(38) Giraudeau, A.; Ruhlmann, L.; El Kahef, L.; Gross, M. J. Am. Chem.
Soc. 1996, 118, 2969.
(39) (a) Felton, R. H. In The Porphyrins; Dolphin, D., Ed.; Academic
Press: New York, 1979; Vol. 5, Chapter 3. (b) Brown, G. M.; Hopf,
F. R.; Meyer, T. J.; Whitten, D. G. J. Am. Chem. Soc. 1975, 97, 5385.
(c) Pacheco, G. M.; James, B. R.; Rettig, S. J. Inorg. Chem. 1995, 34,
3477.

Ruthenium Porphyrin Dimers and Trimers
Inorganic Chemistry, Vol. 36, No. 8, 1997 1635
Table 8. Electrochemical Data for Selected Porphyrin Oligomersa
Ru(Por+)/
Ru(Por)
axial
ligand (oxdn)
Ru(Por2+)/
Ru(Por+)
axial ligand (redn)
complex
Ru(III/II)
H2PyP3P
-1.63 (56) [1]
-1.610 (57) [1]
-1.600 (53) [1]
-1.575 [1]
-1.301 (57) [1]
-1.274 (60) [1]
-1.263 (73) [1]
-1.268 (83) [1]
-1.225 (84) [1]
-1.213 (76) [1]
0.943 (51) [1]
1.01 [1]
1.012 (60) [1]
1.010 (50) [1]
Ru(OEP)(CO)(H2PyP3P) (1)
Ru(TPP)(CO)(H2PyP3P) (3)
Ru(TTP)(CO)(H2PyP3P) (4)
[Ru(OEP)(CO)]2(H2Py2P2P) (5) -1.650 (88) [1]
[Ru(TTP)(CO)]2(H2Py2P2P) (7) -1.587 [1]
0.532 (57) [1]
0.735 (56) [1]
0.680 (51) [1]
1.09 [1]
1.259 (48) [1]
1.207 (52) [1]
0.538 (57) [1 × 2] 1.107 (58) [1]b
1.107 (58) [1 × 2]b
1.20 (81) [1 × 2]b
0.701 (62) [1 × 2] 1.20 (81) [1]b
Ru(OEP)(H2PyP3P)2 (8)
Ru(TTP)(H2PyP3P)2 (10)
-1.658 (72) [1 × 2] -1.292 (68) [1 × 2] -0.114 (57) [1] 1.02 [1]
1.02 [1 × 2]
-1.680 [1 × 2] -1.281 (65) [1 × 2]
0.137 (63) [1] 1.125 (50c) [1]
1.03 (60)c [1 × 2]
a Half-wave potentials (E1/2) were obtained from the steady-state voltammograms with a platinum microelectrode. The numbers in parentheses
are log-plot slope values in mV for the steady-state voltammograms. The numerals in brackets are the numbers of electrons transferred which are
evaluated from the wave heights and the log-plot slopes. 1 × 2 means that two reversible one-electron processes occur at almost the same potential.
b An overlapped wave. c Peak separation from CV.
positive direction as compared with those of free porphyrin
ligands. This may result from the coordination of the axial
porphyrin ligands at the site trans to the carbonyl ligands which
have very strong π-acceptor properties.
Conclusion
Ruthenium(II) porphyrin dimers and trimers, 1-10, with axial
or bridging porphyrin ligands were synthesized and characterized
by spectroscopic measurements.
The ruthenium carbonyl trimers, 5 and 7, showed character-
istic redox properties similar to the dimers of 1 and 4. The
two one-electron oxidation waves of two ruthenium porphyrin
rings were observed at 0.54 V for 5 (Figure 9c) and 0.70 V for
7 as a perfectly overlapped reversible wave with the log plot
slope of ca. 60 mV similar to those of dimers of 1 and 4. These
results indicated that the ruthenium porphyrin rings in a molecule
were oxidized almost independently at the same potentials. In
the potential region higher than 1 V, three-electron processes,
composed of the first oxidation step of bridging porphyrins and
the second oxidation step of two ruthenium porphyrin rings,
were observed. Similarly, the two one-electron reduction waves
of the bridging ligands, observed in the negative region lower
than -1.0 V, appeared at potentials higher than those for 1 and
4. This is because the two pyridyl substituents of the bridging
porphyrins coordinate to the sites trans to carbonyl ligands.
In contrast to the ruthenium carbonyl complexes, the bis-
(pyridyl) trimers 8 and 10 afforded the characteristic one-
electron oxidation waves of the Ru(III)/Ru(II) couples at -0.11
(Figure 9d) and 0.13 V, respectively. The different potentials
reflect electron-donor abilities of the two different ruthenium
porphyrin rings, similarly to the relation between Ru(OEP)-
(Py)2 (0.08 V vs SCE) and Ru(TPP)(Py)2 (0.21 V vs SCE).34,39
Other anodic waves were also observed at 0.99 V for 8 and
1.05 V for 10, though the electron number of these processes
could not be exactly confirmed by steady-state voltammetry
since presumably the complexes were adsorbed on the electrode
as [RuIII(Por)(H2PyP3P)2]PF6. The processes should be three-
electron processes composed of the first oxidation of two axial
porphyrin rings and the first oxidation of a ruthenium porphyrin
ring, because all the three porphyrins species, H2PyP3P, [RuIII-
(OEP)(Py)2]+, and [RuIII(TPP)(Py)2]+, gave the first oxidation
waves of porphyrin rings to generate π-cation radicals at the
potentials around 0.8-1.0 V vs SCE.34,39a
The X-ray crystallographic structure analysis was performed
on a carbonyl dimer of 1. The axial porphyrin ligand is
coordinated obliquely to the ruthenium porphyrin subunit
through a pyridyl group. The ruthenium ion is displaced toward
the CO ligand from the 24-atom mean plane by 0.119 Å. The
ruthenium porphyrin plane and the axial porphyrin plane are
significantly ruffled. An axial porphyrin macrocycle is facing
another one in the neighboring molecule. The mean-plane
separation of the porphyrin pair is 4.24 Å, which is still longer
than that of π - π interacting porphyrins.
1H NMR spectra of 1 in solution reflected the dimer structure,
i.e., the pyridine signals of the axial ligand porphyrin shifted to
higher field dramatically by the shielding effect of the ruthenium
porphyrin ring. The proton signals of the ruthenium porphyrin
subunit were observed at chemical shifts similar to those of
corresponding free monomer. The result confirmed that the
coordination of the axial ligand porphyrin to the ruthenium
porphyrin subunit through the pyridyl group was retained in
solution. Other dimers and trimers, 2-10, are also stable in
solutions.
UV-visible spectra of the carbonyl dimers and trimers, 1-7,
were essentially composed of the spectra of the parent ruthenium
porphyrins and axial or bridging porphyrins. The bis(pyridyl)
trimers 8-10 suggested the presence of excitonic interactions
between the two axial ligand porphyrins as revealed by the
decrease in intensity accompanied by the broadening of the Soret
bands. The complexes 8 and 9 exhibited characteristic MLCT
bands around 450 nm.
Electrochemical analyses revealed that each porphyrin subunit
comprising the porphyrin oligomers of 1-10 was reduced or
oxidized separately; i.e., there is little interaction between the
porphyrin subunits at least under the electrochemical conditions.
Two reduction waves of the axial ligand porphyrins of 8 were
observed at -1.29 and -1.66 V and those of 10 at -1.28 and
-1.68 V as an overlapped two-electron process, respectively.
The potential values are very similar to the values of free
porphyrins. As no separation of the waves was observed, it is
clear that two axial porphyrins were reduced independently at
the same potential. In addition, these results suggest that the
coordination of axial porphyrins through the pyridyl groups to
ruthenium ions essentially causes no change in redox potentials
on the axial porphyrin rings. Therefore, the positive shifts in
redox potentials of the axial porphyrins in the carbonyl
oligomers must be caused by the trans influence of carbonyl
ligands.
Acknowledgment. This work was supported by a Grant-
in-aid for Scientific Research from the Ministry of Education,
Science, and Culture of Japan (Nos. 08454206 and 06804034),
by the 1994 Kawasaki Steel 21st Century Foundation, and in
part by the 1993 Suhara Memorial Foundation.
Supporting Information Available: Tables of fractional coordi-
nates and isotropic thermal parameters, anisotropic thermal parameters,
bond lengths, and bond angles (Tables S1-S4) (9 pages). Ordering
information is given on any current masthead page.
IC961154B