Synthesis and functionalization of germanium triphenylcorrolate: The first example of a partially brominated corrole

Article abstract of DOI:10.1002/ejic.200700184

Ge complexes of 5,10,15-triphenylcorrole were prepared in refluxing dry DMF using GeCl₄ as the source of Ge. Chromatographic separation of the crude reaction mixture afforded the μ-oxo dimer 1 and the methoxy derivative 2a. The corresponding chloride 2b can be obtained by treatment of 1 or 2a with HCl. The reaction of 2a with Br₂ in CHCl₃/py afforded the hexabromo derivative 3 as the main product, giving the first indication of the regioselective substitution of pyrroles B and C on the corrole ring. The fully brominated open-chain tetrapyrrole 4 was also characterized as a reaction by-product. Different partially brominated Ge complexes 5 and 6 have been obtained by variation of reaction conditions, while the heptabromo derivative was obtained in a mixture with the corresponding fully brominated Ge corrole. Photophysical characterization of Ge corrolates confirmed the high fluorescence quantum yield of such complexes, and also led to the first observation of phosphorescence emissions from corrole complexes. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700184

FULL PAPER
DOI: 10.1002/ejic.200700184
Synthesis and Functionalization of Germanium Triphenylcorrolate: The First
Example of a Partially Brominated Corrole
Sara Nardis,[a] Federica Mandoj,[a] Roberto Paolesse,*[a] Frank R. Fronczek,[b]
Kevin M. Smith,[b] Luca Prodi,[c] Marco Montalti,[c] and Gionata Battistini[c]
Keywords: Corrole / Bromination / Regioselectivity / Porphyrinoids
Ge complexes of 5,10,15-triphenylcorrole were prepared in
tion by-product. Different partially brominated Ge com-
refluxing dry DMF using GeCl4 as the source of Ge. Chroma- plexes 5 and 6 have been obtained by variation of reaction
tographic separation of the crude reaction mixture afforded
the µ-oxo dimer 1 and the methoxy derivative 2a. The corre-
sponding chloride 2b can be obtained by treatment of 1 or
2a with HCl. The reaction of 2a with Br2 in CHCl3/py af-
forded the hexabromo derivative 3 as the main product, giv-
ing the first indication of the regioselective substitution of
pyrroles B and C on the corrole ring. The fully brominated
open-chain tetrapyrrole 4 was also characterized as a reac-
conditions, while the heptabromo derivative was obtained in
a mixture with the corresponding fully brominated Ge
corrole. Photophysical characterization of Ge corrolates con-
firmed the high fluorescence quantum yield of such com-
plexes, and also led to the first observation of phosphores-
cence emissions from corrole complexes.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
ferent synthetic routes[7] for the preparation of meso-aryl-
corroles from commercially available precursors has al-
lowed the functionalization of β-pyrrolic positions to be
studied. This constitutes the first step towards the prepara-
tion of more elaborate molecular architectures based on
corroles.
Introduction
In the last few years corrole has been the object of an
increasing number of studies, which have resulted in the ex-
ploitation of this macrocycle in different fields, such as ca-
talysis,[1] PDT[2] and chemical sensors.[3] The impetus for
this renewed interest is the intriguing behaviour shown by
corrole, which makes its chemistry unique in the porphy-
rinoid scenario. This intriguing character can be related to
the molecular structure; since it lacks the C20 meso bridge
(which confers a corrin-like skeleton) corrole retains an 18
π electron aromatic system, closely resembling porphyrins.
It is a trianionic ligand, a feature which, together with a
contracted porphyrinoid skeleton, leads to the stabilization
of formal high oxidation states[4,5] for coordinated metals,
and also to the pronounced non-innocent character of cor-
role as a ligand.[6] The coordination chemistry of this
macrocycle is therefore a challenging arena.
The β-functionalization of triphenylcorroles, however, in-
troduces the possible formation of different regioisomers
due to the lower symmetry of corrole compared with por-
phyrin, a further challenging feature that should be taken
into account. Many research groups have studied different
electrophilic reactions such as nitration, formylation, chlo-
rosulfonation or bromination;[8–13] it is worth mentioning
that the first three of these were shown to be regioselective,
leading to the isolation of partially substituted corroles. For
example, chlorosulfonation and nitration reactions[8] were
successfully carried out both on the free base and on the
gallium complex of tris-pentafluorophenylcorrole, using
chlorosulfonic acid and NaNO2/CH3CN respectively. The
interesting result of these synthetic approaches is that it has
been possible to isolate only a few isomers among the sev-
eral possible regioisomers. In the case of the chlorosul-
fonation reaction, purification of the 2,17- and the 3,17-
sulfonic acid derivatives has been reported, while the
NaNO2/CH3CN reaction afforded the mono-nitro, the
3,17-dinitro and the 2,3,7-trinitro derivative, depending on
the amount of the nitrating agent used.
Besides its coordination characteristics, another intri-
guing aspect of corrole chemistry is the reactivity of the
peripheral positions of corrole. The recent definition of dif-
[a] Dipartimento di Scienze e Tecnologie Chimiche, Università di
Roma,
“Tor Vergata” 00133 Rome, Italy
Fax: +39-0672594328
E-mail: roberto.paolesse@uniroma2.it
[b] Department of Chemistry, Louisiana State University,
Baton Rouge, LA 70803, USA
Also, in the case of the formylation[8,9] and carboxyla-
tion[13] reactions, mono and bis β-regiosubstituted corroles
have been obtained as the major products, even though the
novelty of these kinds of reactions is probably better deter-
[c] Dipartimento di Chimica “G. Ciamician”, Latemar Unit, Uni-
versità di Bologna,
Bologna, Italy
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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R. Paolesse et al.
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mined by the isolation of inner nitrogen substituted com- of the Ge–Cl bond, as observed in the case of previous Ge
pounds. A general feature of these functionalizations is the corrole derivatives. Column chromatography on alumina,
regioselectivity; 3 and 17 β-pyrrolic positions of the directly using CH2Cl2 as the eluent, afforded a dichroic green-
linked A and D pyrroles are the sites of the substitution, purple fraction followed by a second purple compound
in agreement with calculations of electron density at those which required a mixture of CHCl3/MeOH (95:5) for elu-
positions already reported in the literature.[8]
tion. The UV/Vis spectra of both fractions were in agree-
It is interesting to note that in the case of bromina- ment with the coordination of germanium to the corrole
tion,[10–12] attempts to isolate partially brominated corroles macrocycle, but with a significant blue shift of the ab-
have failed to date. Previous studies have demonstrated that sorbance bands of the first fraction with respect to the sec-
bromination reactions carried out on corroles mainly afford ond. This result, together with a high-field shift of the β-
1
the octabromo products both using the corrole free-base pyrrolic proton resonances in the H NMR spectrum sug-
and metal complexes, even in the presence of very small gested the formation of a µ-oxo dimer derivative (1), which
amounts of the brominating agent (either NBS and Br2).
was unambiguously characterized by X-ray crystallography.
Since brominated corroles have been shown to be useful To the best of our knowledge, this is the first example of
substrates for palladium(0) mediated cross-coupling reac- such a derivative in the corrole series, other than the iron
tions,[14] we have been keen to explore the possibility of pre- corrole complexes.[16]
paring partially brominated corroles. We have previously re-
Figure 1 shows one of the two Ge µ-oxo dimers in the
ported the bromination of the corrole free base,[10] while asymmetric unit. The Ge atoms have square-pyramidal co-
other groups studied the same reaction with metal com- ordination, lying 0.439 Å (average of four) from the N4
plexes, mainly copper[11] and manganese[12] derivatives. In plane. The Ge–N distances are in the range 1.881(9)–
these studies the major reaction product was always the β- 1.930(9) Å, with axial Ge–O distances in the range
octabromocorrole, in which all pyrrolic positions were sub- 1.718(11)–1.773(13) Å and Ge–O–Ge angles 147.3(5) and
stituted. No partially substituted derivatives have been iso- 149.0(4)°. Thus the N4 planes within each dimer are not
lated, although mixtures of different isomers were reported parallel, forming dihedral angles of 19.4(6) and 19.9(5)°.
when the stoichiometry of the brominating agent was re-
duced. Yields of reaction carried out with the corrole free
base, and either NBS or Br2 as brominating agent, are in
general quite low; this is probably due to the instability of
the macrocycle, which undergoes decomposition before the
substitution takes place if oxidizing reagents are present.
For this reason, we decided to investigate the reactivity of
germanium derivatives of corroles. We chose this metal
complex because it is diamagnetic, thereby allowing an eas-
ier characterization of the reaction products, and because
corrole stabilizes the coordinated metal in the +4 oxidation
state. We suspected that this would allow us to better con-
trol the substitution reaction and obtain partially bromi-
nated derivatives.
Figure 1. The X-ray structure of 1.
The characterization of the second fraction indicated the
Results and Discussion
formation of 2a, in which a methoxy group is present at the
The first phase of our study focused on the preparation axial position. The presence of the methoxy group is due to
of the Ge corrole complex. We have reported the prepara- the well know lability of the Ge–Cl bond toward oxygen
tion of germanium derivatives in the case of β-alkylcor- ligands and in this case to the solvent mixture used for the
roles,[15] and, to the best of our knowledge, in the tri- elution of the second chromatographic fraction. We also ex-
phenylcorrole series there is only one example of a Ge com- plored the possibility of modifying the nature of the axial
plex, the Ge(TPF5PC)OH reported by Gross.[16] We used ligand, as already observed in the case of β-alkylcorrole
the same metalation procedure, reacting triphenylcorrole complexes,[15] but found not to be possible in the case of
with GeCl4 in refluxing anhydrous DMF, and observed a TF5PC.[16] Treating a CHCl3 solution of 1 or 2a with a di-
prompt colour change of the solution from green to red- lute HCl solution afforded the complex GeTPCCl (2b): in
violet. The UV/Vis spectrum of the reaction mixture also the case of 2a the formation of the chloride complex was
indicated the formation of the complex, with the disappear- monitored by observing the disappearance of the 1H NMR
ance of the free base absorbance bands.
signal characteristic of the axial methoxy group which ap-
TLC of the crude mixture obtained after vacuum evapo- pears at around –1 ppm (Figure 2).
ration of the DMF showed the presence of two reaction
However it should be noted that, in some cases, the iso-
products. We decided to perform a chromatographic separa- lated complex was contaminated with variable amounts of
tion of the reaction mixture, despite the possible hydrolysis the corresponding hydroxy derivative, as demonstrated by
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The First Partially Brominated Corrole
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on pyrrole subunits B and C. In this case the reaction leads
to the substitution of the protons H8 and H12, closer to
the meso bridge, with the formation of only one of the three
possible regioisomers. This result confirms the behaviour
previously observed by Gross and Mahammed in the deu-
teration of the tris-(pentafluorophenyl)corrole, for which a
similar reactivity order, C3 Ͼ C2 ϾϾ C8 Ͼ C7, was re-
ported[19] (Figure 3).
Characterization of the material isolated from the second
fraction was more difficult. A Soret-like band was absent
from the UV/Vis spectrum, and we observed more reso-
nances than expected in the 1H NMR spectrum. In this
case, X-ray crystallography was necessary to characterize
compound 4: this derivative is a fully brominated open
chain tetrapyrrole (Figure 4).
There are several peculiar features of this compound to
be noted. An ethoxy group is added at the former 10-meth-
ine bridge of the corrole ring, with the formation of a meth-
ane bridge and the consequent interruption of the π conju-
gation. The ring is opened at the 5-methine bridge and the
Figure 2. Molecular structures of the germanium complexes 2a and
2b.
the 1H NMR signal for the –OH at –4.4 ppm, thus confirm- pyrrole-pyrrole direct link is retained in the tetrapyrrole.
ing the easy hydrolysis of the Ge–Cl bond under acidic con- The ring opening in this case is different from that observed
ditions (Figure 2). The bromination of complex 2a was car- previously with 10-phenyl-substituted corrole, which af-
ried out according to the previously reported pro- forded the corresponding biliverdin derivatives on reaction
cedure,[11,18] by using liquid bromine in CHCl3/py at room with molecular oxygen.[20] As a consequence of the ring
temperature. The reaction was initially carried out with an opening, a benzoyl group and a pyridinium substituent are
excess of Br2 in order to drive the reaction to the formation present at the terminal α-pyrrolic positions. While the ori-
of the fully substituted derivative. This protocol is usually gin of the benzoyl group can be confidently attributed to
adopted with other metal complexes[11,12] to avoid the po- the oxidation of the methine bridge, the presence of the
tential formation of a mixture of regioisomers. The progress pyridinium group is more surprising. Furthermore, the pos-
of the reaction was followed by spectrophotometry. A clear itive charge of this group is balanced by the presence of a
red shift of the Soret band was observed, consistent with central divalent ion, which consequently infers a zwitter-
the presence of halogen atoms in the metal complex struc- ionic character to the complex. While the identity of the
ture. However, also with a large excess of Br2, in the case central metal atom is not completely unambiguous, Zn ap-
of 2a TLC of the crude reaction mixture showed a number pears most consistent with all available information. Its co-
of products. Work up and purification with a silica plug ordination geometry is square planar, somewhat twisted
afforded two main fractions, eluted with CHCl3 and CHCl3/ from planarity by the spiral nature of the ligand. Thus N2
CH3OH (95:5) respectively. The first fraction contained lies 0.62(1) Å and N5 lies –0.43(1) Å out of the plane de-
some residual impurities and was further purified with a fined by the metal and the two central N atoms. Zn–N dis-
silica gel column and CHCl3 as eluent to give an analyti- tances vary 1.901(9)–2.016(1) Å.
cally pure product.
Further confirmation of the presence of Zn as coordi-
The UV/Vis spectrum of this fraction showed the pres- nated metal was given by MALDI mass spectrum, in which
ence of a Soret band, indicating the retention of the corrole a molecular peak at 1360 m/z was observed. In the FAB
macrocycle, but it was interesting to note the presence of a spectrum a peak was found at 1299 m/z, corresponding to
singlet in the β-pyrrolic proton region of the 1H NMR, also the free base derivative after loss of the Zn ion, probably
indicating incomplete peripheral substitution of the com- induced by the acidic matrix used in this technique. The
plex. The integration ratio corresponded to the presence of source of the coordinated Zn is probably the silica gel used
two pyrrolic protons, but the presence of a single resonance for the chromatographic separation. A similar Zn complex
indicated that substitution had occurred with good regiose- of a fully brominated open chain tetrapyrrole has recently
lectivity. This hypothesis was fully confirmed by the X-ray been reported in the literature and was obtained by bromi-
structure of crystals obtained from CHCl3/CH3OH.
nation induced ring-opening of tetraphenylporphyrin.[21]
To explore the possibility of achieving complete bromi-
The complex obtained was identified as 3, possessing six
bromine atoms on the peripheral positions. To the best of nation of 2a, the reaction was carried out at reflux for a
our knowledge this is the first example of an isolated and prolonged time (2 h); in this case we observed significant
characterized partially brominated corrole. The formation decomposition of the starting material, with the formation
of 3, not only confirms the higher reactivity of the pyrrolic of a mixture of three brominated products. A complete
positions on the two directly linked pyrroles A and D, but chromatographic separation was difficult to achieve from
1
also gives an indication of the substitution regioselectivity this mixture, although H NMR and MALDI-MS charac-
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R. Paolesse et al.
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Figure 3. Characterization of 3 by X-ray crystallography.
Figure 4. The X-ray structure of 4 (hydrogen atoms omitted).
terization indicated that the main component of the mixture by reducing the Br2:2a ratio. Initially we carried out the
was the heptabromo derivative, with the presence of the reactions reducing the reagent ratio in the range 70:1 to
fully brominated complex as a minor component. The third 10:1, obtaining the corresponding pentasubstituted com-
component of the mixture, although in a significantly lower plex as the reaction product. This complex can be reason-
amount, was easily identified as 3, by comparison of the ably assumed to be 5, considering that it is the necessary
spectroscopic data.
precursor of 3 (Figure 5).
Consequently, these results led us to explore the possibil-
The formation of 5 even with a slight excess of bromine
ity of obtaining other partially brominated Ge derivatives seems to indicate a pronounced reactivity of pyrrole sub-
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The First Partially Brominated Corrole
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units A and D, which are completely substituted, while the tives, considering that corroles present quantum yield val-
substitution of pyrroles B and C can be modulated by the ues higher[17] than those of the corresponding porphyrins
amount of reagent used.
and that the efficiency of the photophysical process can
When we further reduced the amount of Br2 to even be increased by the coordination of small metal ions
1.1 equiv., adding methanol as co-solvent, we observed the such as Gallium.[13]
formation of a tri-substituted derivative, which can be con-
fidently assumed to be (6). Significant decomposition of the dichloromethane are reported in Figure 6, with the most
starting material was observed in this case, however. relevant photophysical data reported in Table 1. As ex-
The absorption spectra of compounds 1, 2a and 3 in
The unprecedented formation of 1 led us to perform a pected, because of the already observed validity of the por-
photo-physical characterization of the Ge corrole deriva- phyrin four-orbital model for corroles, all three compounds
show a Soret band in the 380–440 nm region, and a set of
Q bands in the 540–620 nm region. The absorption spec-
trum of 2a [that of 2b is almost identical] is very similar to
the one described for Ge(TPF5PC)Cl. This is as expected
because the positions of the absorption maxima of corroles
are typically unaffected by the nature of the meso substitu-
ents.[22] For 1, relevant differences are observed instead: its
Soret band, while undergoing an expected almost doubling
in intensity, is shifted to a shorter wavelength by 13 nm. On
the other hand, the Q bands are much broader and shifted
to longer wavelengths. These findings clearly indicate a
strong interaction between the two macrocycles in the di-
mer. It is interesting to note that, at concentrations lower
than 10–6 , 1 is not stable, since its spectrum slowly
changes to become very similar to that of 2a. As already
mentioned, all the bands in 3 are red-shifted compared to
2a, indicating that the substituents on the β positions are
able to affect the photophysical properties of corroles, as
already observed for Ga complexes.[23] As far as the fluores-
cence spectra are concerned, the maximum of the fluores-
cence band of 2a (Figure 7) is close to that observed for
Ga(TPF5PC)Py (no fluorescence has been previously re-
ported for Ge corroles). In this case, the fluorescence quan-
tum yield, although higher than that of a metallated por-
phyrin, is lower than that reported for Ga(TPF5PC)Py,
probably because of a lower planarity of the macrocycle
(Table 2).
Figure 5. Molecular structures of 5 and 6.
Figure 6. UV/Vis spectra of germanium corrolates.
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Table 1. Most relevant absorption parameters of 1, 2a and 3 in maximum of this compound at 77 K is the only one that
CH2Cl2 solutions at room temperature and at 77 K.
shows a blue shift with respect to the maximum observed
εmax [–1 cm–1]
at room temperature, most probably because its excited
state shows a reduced dipole moment compared to the
ground state.[22b] The fluorescence spectrum of the dimer
1 is much broader and shifted even more towards longer
wavelengths in comparison to the monomer 2a, again indi-
cating a strong interaction between the two macrocycles.
The quantum yield (0.033), although reduced, is still in the
same range as those of two very well known metal com-
plexes, ZnTPP and Ru(bpy)32+. Again, the lifetime is very
short, indicating the occurrence of a relatively fast radiative
deactivation process also in this case.
Compound
λmax [nm]
1
399
528
567
598
412
5220
560
590
428
538
578
603
363000
13400
21300
24050
160000
7600
2a
3
9650
20600
248000
12050
25100
38000
Finally, we were able, for the first time, to observe the
phosphorescence coming from a corrole complex at 77 K
(Figure 8).
Figure 7. Fluorescence spectra of germanium corrolates.
Figure 8. Phosphorescence spectra of germanium corrolates.
Table 2. Most relevant luminescence parameters of 1, 2a and 3 in
CH2Cl2 solutions at room temperature and at 77 K.
All the phosphorescence bands observed were in the 760–
840 nm region, following the energetic order observed for
the fluorescence bands. It is worth noting that 1 and 2a
showed an excited state lifetime of around 30 ms, while 3
decayed ten times more quickly, indicating a much faster
inter-system crossing process, which confirms the presence
of the already invoked heavy atom effect in 3.
Room temperature
77 K
λmax
77 K
Compd. λmax
Φ
τ [ns]
τ
λmax
τ [ms]
[nm]
[nm]
[ns]
[nm]
1
2a
3
660
598
614
0.033 Ͻ 0.4
0.14 Ͻ 0.4
0.005 Ͻ 0.4
660
599
603
2.3
2.1
3.0
818
784
806
35.2
28.4
3.2
The very short excited state lifetime observed in this case
Conclusions
supports this hypothesis, indicating the presence of a very
fast (knr Ն2ϫ109 s–1) non radiative deactivation process. It
In conclusion, we have detailed here a useful, never pre-
is interesting to note, however, that the radiative rate con- viously reported route for the preparation of partially sub-
stant is also very high (kr Ն2ϫ108 s–1), especially if com- stituted corroles by bromination of the Ge triphenylcorrole
pared with other porphyrins and corroles.[22b] This finding complex, together with a further example of the peculiar
is clearly in line with the indication that corroles can be of reactivity of this macrocycle. Photophysical characteriza-
great interest for their photophysical properties, especially tion of Ge complexes also led to the first example of phos-
if it is possible to design new systems showing slower non phorescence emission from corrole derivatives.
radiative processes. Additionally, for 2a this latter process is
thermally activated as shown by the remarkable increase in
Experimental Section
the excited state lifetime at 77 K. The brominated com-
pound 3 shows a red shifted fluorescence spectrum in line
with its absorption spectrum, with a relatively low quantum
yield, most probably due to the heavy atom effect intro-
1
Physical Methods: H NMR spectra were recorded with a Bruker
AM400 (400 MHz) or Bruker Advance 300 (300 MHz) spectrome-
ter. Chemical shifts are given in ppm relative to tetramethylsilane
duced by the presence of bromine atoms. The fluorescence (TMS). Routine UV/Vis spectra were measured with a Varian Cary
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The First Partially Brominated Corrole
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50 Spectrophotometer, whereas more precise measurements were
performed with a Perkin–Elmer 18 Spectrophotometer equipped
with a temperature-controlled cell holder.
(1.2 mL, 24 mmol; d = 3.119) in 30 mL of CHCl3 was added drop-
wise during 15 min. The resulting mixture was stirred at room tem-
perature for one hour; after this period, pyridine (0.24 mL,
3.02 mmol; d = 0.978) dissolved in CHCl3 (30 mL) was added and
the mixture stirred for a further hour. The crude mixture was then
washed with an aqueous solution of Na2S2O5 (20% w/v). The or-
ganic phase was dried with anhydrous Na2SO4, the solvent was
evaporated and the crude mixture purified with silica gel (plug),
using CHCl3 as the eluent. A second fraction was eluted with a
mixture of CHCl3/MeOH (95:5). The first fraction was further
purified by column chromatography on silica gel, using CHCl3 as
the eluent. Recrystallization from CH2Cl2/MeOH (1:2) of both
fractions afforded respectively 3 (34%, 30 mg, 0.027 mmol) and 4
(5%, 5.3 mg, 0.004 mmol).
Materials: Silica gel 60 (70Ϯ230 mesh) was used for column
chromatography. Reagents and solvents (Aldrich, Merck or Fluka)
were of the highest grade available and were used without further
purification. CH2Cl2 used for the spectrophotometric measure-
ments was stored over activated molecular sieves.
Synthetic Methods: Triphenylcorrole was prepared as previously re-
ported in the literature.[7b]
Germanium 5,10,15-Triphenylcorrolates: In a 100 mL round-bot-
tomed flask equipped with a stirring bar, corrole (0.1 g; 0.2 mmol),
was dissolved in anhydrous DMF (20 mL). GeCl4 (96 µL;
0.8 mmol) was added under nitrogen and the mixture was refluxed
for about two hours, monitoring the progress of the reaction by
UV/Vis spectroscopy. After the absorption peaks of the starting
material had disappeared (the color of the solution changed from
green to deep purple), the solvent was evaporated and the product
purified by chromatography on silica gel, using CHCl3 as the elu-
ent. The first fraction eluted corresponded to the µ-oxo dimer (1),
while the second fraction, eluted with a mixture of CHCl3/MeOH
(95:5), was characterized as the monomeric germanium methoxide
(2a). GeTPC-Cl was obtained by treatment of fractions (1) and
(2a) with HCl (4 ). Recrystallization from CH2Cl2/hexane (1:2),
afforded GeTPC–Cl (2b) in 60% yield (76 mg, 0.12 mmol).
Spectroscopic Data for 3: 1H NMR (300 MHz, CDCl3): δ = 9.11
(s, 1 H, β-pyrrolic), 7.99 (m, 5 H, phenyl), 7.78 (m, 10 H, phenyl),
–0.78 (s, 3 H, -OCH3) ppm. MS (MALDI): m/z (%): 1101.6 (50)
[M+]. C38H20Br6GeN4O (1100.64): calcd. C 41.47, H 1.83, N 5.09;
found C 41.58, H 1.79, N 5.22.
Crystal Data for 3: Color: maroon, C38H20GeBr6N4O, Mr
=
1105.2, monoclinic space group P21/n, a = 13.330(2), b = 17.952(3),
c = 15.974(3) Å, β = 114.325(6)°, V = 3483.2(10) Å3, Z = 4, ρcalcd.
= 2.107 gcm–3, Mo-Kα radiation (λ = 0.71073 Å; µ = 7.87 mm–1),
T = 110 K, 48918 data points by Nonius KappaCCD, R = 0.051
(F2 Ͼ 2σ), Rw = 0.115 (all F2) for 10534 unique data points having
θ Ͻ 30.5° and 460 refined parameters. Residual electron density
peaks near C7 and C13 indicated the presence of small amounts of
heptabromo and/or octabromo compounds. Refinement of par-
tially populated Br atoms at these positions led to populations of
2.6%.
Spectroscopic Data for 1: 1H NMR (300 MHz, CDCl3): δ = 8.92
(d, 1J = 4.2 Hz, 4 H, β-pyrrolic), 8.62 (d, 1J = 4.2 Hz, 4 H, β-
pyrrolic), 8.55 (d, 1J = 4.8 Hz, 4 H, β-pyrrolic), 8.18 (d, 1J = 4.8 Hz,
4 H, β-pyrrolic), 7.67 (m, 30 H, phenyl) ppm. MS (FAB): m/z (%):
1208 (60) [M+]. C74H46Ge2N8O (1208.45): calcd. C 73.55, H 3.83,
N 9.27; found C 73.42, H 3.61, N 9.55.
1
Spectroscopic Data for 4: H NMR (300 MHz, CDCl3): δ = 7.78–
7.41 (m, 20 H), 3.77 (q, 2 H, -OCH2CH3), 1.25 (t, 3 H, -OCH2CH3)
ppm. UV/Vis (CH2Cl2): λmax (εϫ10–3) = 440 (9.3), 601 (3.7),
642 nm (2.4). MS (MALDI): m/z (%): 1360.2 (20) [M+].
C44H25Br8N5O2Zn (1360.33): calcd. C 38.85, H 1.85, N 5.15; found
C 38.90, H 1.83, N 5.24.
Crystal Data for 1: Color: dark purple, C74H46Ge2N8O·0.5CH2Cl2,
Mr = 1250.9, triclinic space group P-1, a = 14.6167(15), b =
19.802(3), c = 23.156(4) Å, α = 72.715(7), β = 85.464(8), γ =
68.930(6)°, V = 5968.8(15) Å3, Z = 4, ρcalcd. = 1.440 gcm–3, Mo-Kα
radiation (λ = 0.71073 Å; µ = 1.11 mm–1), T = 110 K, 31760 data
by Nonius KappaCCD, R = 0.098 (F2 Ͼ 2σ), Rw = 0.269 (all F2)
for 16529 unique data having θ Ͻ 23.2° and 759 refined parameters.
Two Ge oxo dimers were found in the asymmetric unit. Because of
the limited crystal quality, it was possible to refine only Ge, Cl and
O anisotropically. Further disordered solvent was modeled with
partially-populated C positions.
Crystal
Data
for
4:
Color:
dark
blue,
C44H25Br8N5O2Zn·CHCl3·C4H10O, Mr = 1457.1, monoclinic space
group P21/a, a = 15.599(10), b = 13.913(7), c = 24.280(17) Å, β =
90.87(2)°, V = 5269(6) Å3, Z = 4, ρcalcd. = 1.837 gcm–3, Mo-Kα
radiation (λ = 0.71073 Å; µ = 6.65 mm–1), T = 110 K, 22209 data
points by Nonius KappaCCD, R = 0.072 (F2 Ͼ 2σ), Rw = 0.154
(all F2) for 7321 unique data having θ Ͻ 23.5° and 352 refined
parameters. Because of limited crystal quality and disordered sol-
vent, it was possible to refine only Zn, Br, Cl and O anisotropically.
Refinement of the central metal as Ge led to unrealistically high
displacement parameters for this atom as well as significantly
higher R values.
1
Spectroscopic Data for 2a: H NMR (300 MHz, CDCl3): δ = 9.40
(d, 1J = 4.2 Hz, 2 H, β-pyrrolic), 9.21 (d, 1J = 4.8 Hz, 2 H, β-
pyrrolic), 9.08 (d, 1J = 4.2 Hz, 2 H, β-pyrrolic), 8.91 (d, 1J = 4.8 Hz,
2 H, β-pyrrolic), 8.44 (m, 2 H, phenyl), 8.35 (m, 1 H, phenyl), 8.21
(m, 2 H, phenyl), 8.09 (m, 1 H, phenyl), 7.81 (m, 9 H, phenyl),
–0.96 (s, 3 H, OCH3) ppm. MS (FAB): m/z (%): 627 (100) [M+].
C38H26GeN4O (627.26): calcd. C 72.76, H 4.18, N 8.93; found C
72.83, H 4.42, N 8.96.
Bromination of 2 (Br2:2 = 70:1): When the bromination is carried
out under the reaction conditions described above, with a reduced
amount of Br2 (0.3 mL, 5.8 mmol; d = 3.119), the subsequent chro-
matographic purification afforded
0.034 mmol).
5 in 43% yield (35 mg,
1
Spectroscopic Data for 2b: H NMR (300 MHz, CDCl3): δ = 9.45
(d, 1J = 4.3 Hz, 2 H, β-pyrrolic), 9.24 (d, 1J = 4.9 Hz, 2 H, β-
pyrrolic), 9.12 (d, 1J = 4.3 Hz, 2 H, β-pyrrolic), 8.94 (d, 1J = 4.9 Hz,
2 H, β-pyrrolic), 8.42 (m, 2 H, phenyl), 8.34 (m, 1 H, phenyl), 8.24
(m, 2 H, phenyl), 8.11 (m, 1 H, phenyl), 7.81 (m, 9 H, phenyl) ppm.
MS (FAB): m/z (%): 631 (100) [M+]. C37H23ClGeN4 (631.68): calcd.
C 70.35, H 3.67, N 8.87; found C 70.44, H 3.69, N 8.96.
Spectroscopic Data for 5: 1H NMR (300 MHz, CDCl3): δ = 9.07
(s, 1 H, β-pyrrolic), 8.91 (d, 1J = 4.98 Hz, 1 H, β-pyrrolic), 8.66 (d,
1J = 4.98 Hz, 1 H, β-pyrrolic), 7.85 (m, 15 H, phenyl), –0.78 (s, 3
H, OCH3) ppm. UV/Vis (CH2Cl2): λmax (εϫ10–3) = 423 (215), 533
(10.3), 575 (22), 596 nm (33) ppm. MS (FAB): m/z (%): 1022 (60)
[M+]. C38H21Br5GeN4O (1021.74): calcd. C 44.67, H 2.07, N 5.48;
found C 44.56, H 1.98, N 5.52.
Bromination of 2 (Br2:2 = 300:1): In a 250 mL round-bottomed
flask equipped with a dropping funnel, complex 2a (50 mg,
Bromination of 2 (Br2:2 = 1.1:1): When the bromination is carried
0.08 mmol) was dissolved in CHCl3 (80 mL) and a solution of Br2 out under the reaction conditions described above, with 2 (70 mg,
Eur. J. Inorg. Chem. 2007, 2345–2352
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2351

R. Paolesse et al.
FULL PAPER
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subsequent chromatographic purification afforded 6 in 49% yield
(47 mg, 0.054 mmol).
Spectroscopic Data for 6: 1H NMR (300 MHz, CDCl3): δ = 9.38
(s, 1 H, β-pyrrolic), 8.96 (d, 1J = 4.80 Hz, 2 H, β-pyrrolic), 8.81 (d,
1J = 4.80 Hz, 2 H, β-pyrrolic), 8.12 (m, 5 H, phenyl), 7.77 (m, 10
H, phenyl), –0.84 (s, 3 H, OCH3) ppm. UV/Vis (CH2Cl2): λmax
(εϫ10–3) = 414 (198), 525 (8.2), 565 (21.5), 589 nm (30.8) ppm. MS
(FAB): m/z (%): 864 (70) [M+]. C38H23Br3GeN4O (863.95): calcd. C
52.83, H 2.68, N 6.49; found C 52.71, H 2.73, N 6.34.
[9]
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CCDC631925 (for 1), -631926 (for 3) and -631927 (for 4) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from the Crystallographic Data Cen-
tre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
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Ricerca–Fondo per gli Investimenti della Ricerca di Base
(MIUR-FIRB) (projects RBNE01KZZM and LATEMAR) (see
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Received: January 11, 2007
Published Online: April 17, 2007
2352
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 2345–2352