Living photolytic ring-opening polymerization of amino-functionalized [1]ferrocenophanes: Synthesis and layer-by-layer self-assembly of well-defined water-soluble polyferrocenylsilane polyelectrolytes

Article abstract of DOI:10.1002/chem.200700580

Facile synthetic routes have been developed that provide access to cationic and anionic water-soluble polyferrocenylsilane (PFS) polyelectrolytes with controlled molecular weight and narrow polydispersity. Living photolytic ring-opening polymerization of

Full text of DOI:10.1002/chem.200700580

DOI: 10.1002/chem.200700580
Living Photolytic Ring-Opening Polymerization of Amino-Functionalized
[1]Ferrocenophanes: Synthesis and Layer-by-Layer Self-Assembly of Well-
Defined Water-Soluble Polyferrocenylsilane Polyelectrolytes
[a]
Zhuo Wang,[a] GeorgetaMasson,
Ian Manners*[a, c]
Frank C. Peiris,[a, b] Geoffrey A. Ozin,*[a] and
Abstract: Facile synthetic routes have
been developed that provide access to
cationic and anionic water-soluble
controlled architectures. Further deri-
vatization of 5, 15,and 21 generated
water-soluble polyelectrolytes [(fcSiMe-
(LbL) self-assembly of electrostatic su-
perlattices. Our preliminary studies
have indicated that films made from
controlled low molecular-weight PFSs
possess a considerably thinner bilayer
thickness and higher refractive index
than those made from PFSs that have
an uncontrolled high molecular-weight.
These results suggest that the structure
and optical properties of LbL ultra-
thin films can be tuned by varying
polyelectrolyte chain length. The
water-soluble low molecular weight
PFSs are also useful materials for a
range of applications including LbL
self-assembly in highly confined spaces.
ꢀ
poly
A
{C CCH2N(CH2CH2CH2SO3Na)2})n]
ꢀ
lytes with controlled molecular weight
and narrow polydispersity. Living pho-
tolytic ring-opening polymerization of
(6),[{fcSiMe(C
CCH2NMe3OSO3-
[{fcSiMe(
A
(7),and
p-
A
amino-functionalized
[1]ferroceno-
spectively. The polyelectrolytes were
readily soluble in water and NaCl
aqueous solutions,with 6 and 22 exhib-
iting long-term stability in aqueous
media. The PFS materials 6 and 22,
have been utilized in the layer-by-layer
ꢀ
phane (fc) monomers [fcSiMe
G
CCH2N
CCH2N
ꢀ
N
ACHTREUNG
Me(C CCH2NMe2)] (14),and [fcSi-
Me(p-C6H4CH2NMe2)] (20) yielded the
corresponding
polyferrocenylsilanes
(SiMe2CH2)2})n](5),
(SiMe2CH2)2}2)n] (11),
ꢀ
[(fcSiMe
G
ACHTREUNG
Keywords: ferrocene · metallopoly-
mers · photolysis · polyelectrolytes ·
self-assembly
ꢀ
[(fcSi
A
ACHTREUNG
ꢀ
[{fcSiMe(C CCH2NMe2)}n] (15),and
[{fcSiMe(p-C6H4CH2NMe2)}n] (21) with
Introduction
blocks in the layer-by-layer (LbL) self-assembly of electro-
static superlattices,in which oppositely charged monolayers
are adsorbed sequentially from aqueous solutions onto a
substrate surface. The resulting multilayer thin films possess
a layer thickness on the nanometer scale and have been uti-
lized extensively in areas such as surface modification and
patterning,the manufacturing of thin film devices,and con-
trolled drug release.[2,3] Moreover,recent advances in poly-
mer synthesis have provided access to selected organic poly-
electrolytes that have controlled molecular weight and
narrow polymer size distribution. This has greatly facilitated
the development of new classes of polymeric materials such
as amphiphilic block copolymers,which possess hydrophilic
and hydrophobic blocks of controlled size and have been
used to prepare self-assembled micelles and vesicles that are
promising materials for various applications ranging from
controlled drug delivery to biomimetic membrane develop-
ment.[4] Despite extensive studies of organic polyelectrolytes,
Water-soluble polyelectrolytes are a class of polymers that
are of significant importance for industrial applications and
for the development of advanced materials.[1] These macro-
molecules have attracted much recent attention as building
[a] Z. Wang,G. Masson,Prof. F. C. Peiris,Prof. G. A. Ozin,
Prof. I. Manners
Department of Chemistry,University of Toronto
80 St. George Street,Toronto,Ontario M5S3H6 (Canada)
E-mail: gozin@chem.utoronto.ca
[b] Prof. F. C. Peiris
Physics Department,Kenyon College
Gambier,OH,43022 (USA)
[c] Prof. I. Manners
School of Chemistry,University of Bristol
Cantockꢀs Close,Bristol BS81TS (UK)
Fax : (+44)117-929-0509
E-mail: Ian.Manners@bristol.ac.uk
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FULL PAPER
however,reports on inorganic polyelectrolytes are rare,in
particular those with well-controlled architectures. This is es-
pecially the case for transition metal-containing polymers,
which would be expected to bring many attractive features,
such as conductive,optical,redox,and catalytic properties
to diverse advanced materials development and applica-
tions.[5–7]
Polyferrocenylsilanes (PFSs) 2 are a class of high molecu-
lar weight metal-containing macromolecules that were de-
veloped in the early 1990s through ring-opening polymeri-
not only facilitate the fundamental studies of these macro-
molecules and their multilayer films,but also help expand
the scope of their applications in materials science to in-
clude controlled LbL assembly and the development of am-
phiphilic metallo block copolymers and materials.
With these objectives in mind,we explored the synthesis
of well-defined PFS polyelectrolytes through anionic ROP
of strained ferrocenophanes,as molecular weight control
was difficult to achieve in thermal and transition metal-cata-
lyzed ROP.[24,26,27] However,the anionic route was found to
be unsatisfactory due to side reactions of the functional
groups in the monomers with the anionic n-butyllithium ini-
tiator and propagating chain ends. Recently,a new living
polymerization method,photolytic ring-opening polymeri-
zation (PROP),has been developed in the synthesis of
alkyl- and aryl-PFSs with good molecular weight con-
trol.[31–33] One of the attractive features of this method is the
mild reaction conditions,which we anticipated would be
more tolerant toward the functional groups that are unstable
in anionic polymerizations. In this paper we report full de-
tails of photolytic polymerization of functionalized ferroce-
nophane monomers,and the first synthesis of water-soluble
cationic and anionic PFS polyelectrolytes,which possess
well-controlled architectures with desired molecular weight
and narrow polydispersity. Our work on the LbL assembly
of these polyelectrolytes and preliminary study on the effect
of polymer molecular weight on the structure and property
of the resulting multilayer films is also discussed.
zation (ROP) of strained sila[1]ferrocenophanes
1
(Scheme 1).[5,8] These polymers possess a range of interest-
Scheme 1.
ing properties including reversible redox activity,semicon-
ductivity upon oxidation,and tunable magnetic properties
upon pyrolysis.[5,9–15] In addition,PFS block copolymers ob-
tained through anionic ROP have provided access to highly
ordered phase-separated domains in the solid state and self-
assembled micelles in solution.[16,17] Many other areas that
have potential PFS applications include microsphere tech-
nology,[18] radiation protective coatings,[19] photonic band
gap materials,[20,21] variable refractive index sensing materi-
als[22] and etch resists.[23]
Results and Discussion
The recent development of water-soluble PFSs has pro-
vided several of the first metallopolyelectrolytes that possess
transition metals in the main chain (shown here).[6,24–27]
To develop a general synthetic pathway that could provide
access to PFS polyelectrolytes with well-controlled architec-
tures,we examined ROP of a range of [1]ferrocenophanes
with various amino-functionalized substituents under photo-
lytic polymerization conditions. Further derivatization of the
resulting polymers was anticipated to afford the desired
macromolecules that have cationic and anionic water-soluble
groups along the polymer chain.
PROP of the silicon-bridged [1]ferrocenophane 3—synthe-
sis and characterization of protected aminopropynyl PFS 5:
The silicon-bridged [1]ferrocenophane 3,which has a pro-
tected amino group,was used in the photolytic ring-opening
polymerization as it had been demonstrated in our previous
work that the silyl protective group can be removed under
mild conditions.[26] It was anticipated that the resulting
amino PFS would serve as a precursor to both cationic and
anionic water-soluble PFSs.
PROP of [1]ferrocenophane 3 was carried out in the pres-
ence of 0.1 equivalents of anionic initiator sodium cyclopen-
tadienylide in THF and exposure to UV/Vis irradiation at
58C (Scheme 2). After 2 hours of stirring,the color of the
reaction solution turned from red to orange,indicating the
successful ring opening of the monomer. Precipitation of the
reaction mixture into degassed methanol afforded PFS 5 as
These polyelectrolytes have been used as building blocks in
the LbL assembly of organometallic–organic and all organo-
metallic electrostatic superlattices,which have found appli-
cations in materials science,such as redox-tunable capsules
and the tuning of optical properties of photonic crystals.[27–30]
Despite the recent advancement in the area of water-soluble
metallomacromolecules,polyelectrolytes which possess tran-
sition metals in the main chain have yet to be obtained with
controlled molecular weight and narrow molecular weight
distribution.[5,6] It is anticipated that the development of
metallopolyelectrolytes with controlled architectures will
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9373

G. A. Ozin,I. Manners et al.
tions based on the monomer/initiator ratio. The polymer
molecular weight from theoretical calculation and experi-
mental data is plotted against the monomer/initiator ratio in
Figure 1,which shows that excellent molecular-weight con-
Figure 1. Variation of molecular weight of polymer 5 with monomer/ini-
&
*
tiator ratio,[M]/[I],as calculated ( ) and obtained by GPC ( ).
Scheme 2.
trol can be achieved for polymers that have a Mn of up to
4.4”104 through PROP. At higher monomer/initiator ratios
of ꢁ200,however,polymer 5 was obtained with large poly-
dispersity and a molecular weight much lower than the cal-
culated theoretical value (Table 1,entry e). Moreover,bimo-
dal molecular weight distribution has been observed in
some instances. It is unclear as to what might have caused
such deviation in the polymer molecular weight at the high
monomer/initiator ratio,but the reaction of impurities with
propagating sites provides a possible explanation.
an orange-yellow gummy material. Gel permeation chroma-
tography (GPC) analysis of the product showed that the ma-
terial possessed a desired low molecular weight and narrow
polydispersity. In the numerous polymerization experiments
that we carried out,PFS 5 was obtained with a PDI general-
ly in the range of 1.10–1.20 and a molecular weight ranging
from Mn =3.9”103 to 6.3”103,which corresponds to approx-
imately 9–15 monomeric units. End-group analysis of the
polymer by 1H NMR spectroscopy indicated that the
number-average degree of polymerization (DPn) was usually
in the range of 8–14.
1
Polyferrocenylsilane 5 was characterized by using H, 13C,
and 29Si NMR spectroscopy and its structure was confirmed
by data comparison with high molecular-weight polymer
previously synthesized through transition metal-catalyzed
ring-opening polymerization.[26] Since we were able to
obtain 5 with desired short chain lengths,protons at the
chain ends can be clearly observed in the 1H NMR spec-
trum. For example,in the case of PFS 5 (DPn ꢁ10),the h5-
C5H5 protons at the ferrocenyl end of the polymer chain ex-
hibited a chemical shift at 4.21 ppm,slightly upfield from
the rest of the ferrocenyl protons in the main chain (4.23–
4.72 ppm). A similar trend was observed for the methylene
protons adjacent to the acetylene moiety on the chain ends
at 3.66 and 3.64 ppm,upfield from the principal peak of
those in the main chain at
By varying the monomer/initiator ratio,the protected
aminopropynyl polyferrocenylsilane can be obtained with
controlled architectures at higher molecular weight. Thus,
PFS 5 was prepared with 20,50,100 and 200 repeat units,
which corresponds to molecular weights in the range of Mn
ꢁ1.1”104–7.1”104. All polymers were characterized by
1
using H NMR spectroscopy and GPC,and the results are
summarized in Table 1. For a monomer/initiator ratio of up
to ꢁ100,polymer 5 can be obtained with relatively low
polydispersity. In addition,the molecular weights acquired
by using GPC were in good agreement with those obtained
from NMR end-group analysis and the theoretical calcula-
3.68 ppm. In addition,the
methyl protons in the cyclic di-
Table 1. Summary of data for polymer 5 synthesized by PROP.
[b]
[c]
Sample
[M]/[I][a]
DPn, NMR
Mn, calc
Mn, GPC
PDI[d]
t [h]
Yield of
PFS 5 [%]
Yield of
(À)PFS 6 [%]
A
as a slightly broadened single
peak at 0.27 ppm,and a small
signal at 0.25 ppm corresponds
to those at the Cp end of the
chain. The carbons of the cap-
ping Cp (h5-C5H5) on the ferro-
cenyl end of the polymer chain
a
b
c
d
e
10
20
50
100
200
8
25
55
115
–
4230
8460
21150
42300
84600
3900
11000
24100
43700
71100
1.14
1.24
2.5
4
4
5
6
70
48
59
65
90
91
83
85
80
88
1.32
1.08[e]
2.13[e]
1
[a] [M]/[I] denotes monomer:initiator ratio. [b] Values determined by H NMR integration of Cp polymer pro-
tons relative to the Cp end-group protons. [c] Cp end groups are not included. [d] Given by Mw/Mn from GPC
analysis. [e] Polymer was isolated by solvent removal under vacuum without being precipitated in methanol. were also clearly observed at
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Functionalized Ferrocenophanes
FULL PAPER
69.5 ppm in the 13C NMR spectrum,upfield from the ferro-
cenyl Cp ligands in the polymer main chain (d=69.8–
74.8 ppm). Notably,the h5-C5H5 protons at the ferrocenyl
of the silyl protective groups in PFS 5 followed by quaterni-
zation of the amino moieties afforded polyelectrolyte 7,
which was soluble in water and methanol. Although also
soluble in aqueous 0.1m NaCl solutions,the polyelectrolyte
remained stable only for a short period of time and precipi-
tated after two weeks.
1
end of the polymer chain can be detected in the H NMR
spectra of PFS 5 at a molecular weight of up to Mn =4.4”
104. This allows the estimation of the degree of polymeri-
zation (DPn,NMR) for polymers with repeat units of up to 100
by using end-group analysis through integration of the Cp
protons in the end group and the polymer main chain.
The proposed reaction pathway in PROP involves the ac-
The cationic PFS 7 was characterized by using 1H and
1
13C NMR spectroscopy. The H NMR spectrum obtained in
D2O indicated the successful removal of the protective
groups in polymer 5 by the absence of the methyl and meth-
ylene protons in the cyclic disilyl moiety (d=0.27 and
0.79 ppm,respectively). In addition,a single peak was ob-
served at d=3.22 ppm which corresponds to the methyl pro-
tons in the quaternary ammonium group. Furthermore,the
resonance of the methylene protons adjacent to the nitrogen
atom was shifted significantly downfield from d=3.68 ppm
in protected aminopropynyl PFS 5 to d=4.00 ppm in the
cationic polyelectrolyte 7,merging with the signals of the
ferrocenyl protons in the region of d=4.00–4.73 ppm. This
is consistent with our previous observation that the methyl-
ene protons adjacent to an amino group became less shield-
ed upon quaternization of the amino moiety.[25,26] The
13C NMR spectrum of 7 also supported the assigned struc-
ture. For example,the resonances of the methyl and methyl-
ene carbons in the protective groups of 5 were absent from
the spectrum of 7. And the methylene carbon adjacent to
5
À
tivation of the Fe
rocenophane
G
[(h5-C5H4)Fe
(h5-C5H4)SiMe
{C CCH2N-
(SiMe2CH2)2}] (3) with exposure to UV/Vis irradiation.[33] In
the presence of a cyclopentadienylide initiator such as Na-
[C5H5],the ring-strain in the monomer is relieved through
ACHTREUNG
the photoactivated replacement of a h5-C5H4 moiety by the
[C5H5]À anion in the initiator (Scheme 2).[31–33] The anionic
end group in the newly generated intermediate species Na+
ꢀ
A
(h5-C5H4)SiMe
U
U
U
(4) undergoes further propagation with other activated fer-
rocenophane monomers. Finally,termination of the poly-
merization by methanol quenching affords PFS 5 as the de-
sired product.
Synthesis and characterization of anionic PFS 6 and cationic
PFS 7 with controlled architectures: The synthesis of anionic
PFS 6 was achieved under mild conditions in a one-pot pro-
cedure in which the protected aminopropynyl PFS 5 was
used in a reaction with 1,3-propane sultone in the presence
of an excess amount of diisopropylethylamine in a mixture
of THF and methanol solvents (4:1 v/v) (Scheme 3).[26] The
polyelectrolyte 6 thus obtained was highly soluble and ex-
hibited long-term stability in water and aqueous NaCl solu-
tions. The structure of PFS 6 was confirmed by comparing
the nitrogen atom exhibited
a chemical shift of d=
56.8 ppm,a significant downfield shift from its resonance at
1
d=32.4 ppm in the protected aminopropynyl PFS 5. The H
and 13C NMR results confirmed that >96% of the amino
groups had been successfully quaternized.
PROP of the silicon-bridged [1]ferrocenophane 10—synthe-
sis and characterization of protected aminopropynyl PFS 11:
After the successful polymerization of the protected amino-
propynyl monomer 3,we next examined ferrocenophane 10
under the same photolytic ROP conditions with the aim to
obtain a controlled polyelectrolyte architecture which pos-
sesses two water-soluble ammonium groups in each repeat
unit. Monomer 10 was therefore synthesized from dichloro
sila [1]ferrocenophane 8[34] in a nucleophilic substitution re-
ꢀ
1
its H, 13C,and 29Si NMR data with that of the high molecu-
lar-weight analogue previously reported in the literature.[26]
The conversion of PFS 5 to cationic polyelectrolyte 7 was
carried out in a mixture of THF and methanol solvents (4:1,
v/v) in the presence of an excess amount of dimethyl sulfate
and diisopropylethylamine (Scheme 3). Therefore,removal
action with LiC CCH2N(SiMe2CH2)2 (9),which was gener-
R
ꢀ
ated in situ from protected propargylamine HC CCH2N-
[26]
(SiMe2CH2)2
and n-butyllithium at À788C (Scheme 4).
Recrystallization of the crude product in hexanes at À358C
afforded 10 as a red solid. Characterization by using 29Si,
13C,and 1H NMR spectroscopy as well as mass spectroscopy
Scheme 3.
Scheme 4.
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9375

G. A. Ozin,I. Manners et al.
afforded data that were consistent with the assigned struc-
ture.
does not require an extra deprotection step. This makes
monomer 14 an attractive precursor for the potentially
A
Polymerization of monomer 10 proceeded smoothly under
the aforementioned PROP conditions in the presence of 0.1
equivalents of NaCp (Scheme 5). PFS 11 was obtained as an
facile access to cationic PFS 7. Thus,monomer 14 was pre-
pared from the substitutionally labile sila[1]ferrocenophane
12[34] in a nucleophilic reaction with 3-dimethylamino-1-pro-
pynyl lithium (13) (Scheme 6). Recrystallization in hexanes
Scheme 6.
at À358C followed by vacuum sublimation (0.05 mmHg) of
the crude product at 70–758C afforded 14 as a dark red crys-
talline solid in moderate yield (63%). Monomer 14 was
characterized by using 29Si, 13C,and 1H NMR spectroscopy
and the data collected were in agreement with the assigned
structure.
In the presence of 0.1 equivalents of the anionic initiator
sodium cyclopentadienylide,PROP of monomer 14 in THF
proceeded smoothly with exposure to UV/Vis irradiation at
58C for 2.5 h (Scheme 7). Quenching of the reaction with
Scheme 5.
orange gummy material with a molecular weight of Mn =
4.9”103 and a PDI of 1.13 by using GPC analysis,corre-
sponding to ꢁ8 monomeric units. The polymer was charac-
terized by using 29Si, 13C,and 1H NMR spectroscopy and the
data were found to be in accordance with the assigned struc-
ture. Two signals were detected in the 29Si NMR spectrum at
d=14.9 and À45.8 ppm,corresponding to the silicon envi-
ronments in the protective group and the main chain of the
polymer,respectively. In the 13C NMR spectrum of 11,the
Cp ipso-carbon was detected at d=67.7 ppm,a significant
downfield shift from that in monomer 10 at d=31.9 ppm.
This was in agreement with our previous observations that
the release of ring-strain in ferrocenophane monomers
through ring-opening polymerization leads to a downfield
shift of the ipso-carbon signals.[26,34] As shown in the
13C NMR spectrum of PFS 5,the carbons of the capping cy-
clopentadienyl moiety (h5-C5H5) on the ferrocenyl end of
polymer 11 were clearly observed at d=69.9 ppm. In addi-
tion,two resonances characteristic of the acetylenic carbons
from the aminopropynyl substituents were detected at d=
1
82.8 and 109.9 ppm. The H NMR spectra was also consis-
tent with the assigned structure.
Deprotection and quaternization of the amino groups in
11 was carried out in a one-pot procedure as described in
the synthesis of PFS 7. However,the polymer formed cross-
linked material after several hours of stirring,which could
not be re-dissolved in commonly used solvents.
Scheme 7.
degassed ethanol,followed by precipitation of the crude
product into methanol,afforded dimethylaminopropynyl
PFS 15 as an orange gummy material in good yield
Synthesis and PROP of silicon-bridged dimethylaminopro-
pynyl[1]ferrocenophane 14—development of dimethylami-
nopropynyl PFS 15 and cationic PFS 7: The silicon-bridged
[1]ferrocenophane 14 presents an interesting monomer for
PROP studies as it possesses an unprotected tertiary amine
functionality,which may potentially interfere with the poly-
merization process. Meanwhile,in comparison to the pro-
tected amino groups in PFS 5,quaternization of the tertiary
amino group was expected to be more straight forward as it
A
vents such as benzene,THF and dichloromethane. GPC
analysis showed that it possessed a molecular weight of
Mn =3.4”103 and a narrow PDI of 1.08,which corresponds
to ꢁ11 repeat units in each chain.
Polymer 15 was characterized by using 29Si, 13C,and
1H NMR spectroscopy. The 29Si NMR signal was detected at
d=À24.7 ppm,analogous to that observed in the protected
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Chem. Eur. J. 2007, 13,9372 – 9383

Functionalized Ferrocenophanes
FULL PAPER
aminopropynyl PFS 5 (d=À24.8 ppm) and shifted downfield
from the bridging silicon atom in monomer 14 (d=
À28.7 ppm). In the 13C NMR spectrum of polymer 15,the
resonance of the ipso carbons (d=69.9 ppm) was shifted sig-
nificantly downfield from that in monomer 14 (d=
31.0 ppm),as a result of the release of ring strain in the fer-
rocenophane monomer.[26,34] As shown in the 13C NMR spec-
tra of PFSs 5 and 11,the carbons of the capping cyclopenta-
dienyl moiety (h5-C5H5) at the ferrocenyl end of polymer 15
therefore,hinder effective ring opening of the monomer.
This problem could be circumvented by using a monomer in
which the dimethylamino group is further removed from the
iron center. Therefore, p-(dimethylaminomethyl)phenyl si-
la[1]ferrocenophane 20 was synthesized as illustrated in
Scheme 8. Halogen-metal exchange between 4-bromoben-
1
were clearly observed at d=69.5 ppm. The H NMR spec-
troscopy data of 15 was also consistent with the assigned
structure.
The dimethylamino groups in polyferrocenylsilane 15
were converted to ammonium moieties in a reaction with di-
methyl sulfate in a mixed solvent of THF and methanol
(4:1,v/v) (Scheme 7). As the reaction proceeded,some of
the cationic polymer formed during the quaternization pre-
cipitated. To ensure all the amino groups were quaternized,
methanol was added to dissolve the precipitates and the re-
action mixture was allowed to stir overnight. Purification of
the crude product by precipitation in THF afforded the cat-
ionic polymer 7 as an orange powder,which was readily
soluble in methanol,water,and NaCl solutions. However,as
with the cationic polyelectrolyte obtained from the protect-
ed PFS 5,polymer 7 was unstable in 0.1m NaCl solutions
and precipitated after two weeks. The precipitate was not
soluble in common organic solvents and water,even at ele-
vated temperatures.
Scheme 8.
zyldimethylamine 18[36] and n-butyllithium yielded the
phenyl lithium species 19,[37] which was subsequently used in
the nucleophilic substitution reaction with chloro methyl[1]-
ferrocenophane 12 to afford monomer 20 as a dark red crys-
talline solid.
Ferrocenophane 20 was characterized by using 1H, 13C,
and 29Si NMR spectroscopy and the data were consistent
with the assigned structure. Most notable in the 1H NMR
spectrum were the phenyl proton resonances which were ob-
served as two doublets at d=7.48 and 7.96 ppm. This indi-
cated that the lithium–bromide exchange took place exclu-
sively at the para position of the phenyl ring,which was pre-
served in the subsequent reaction with the chloro ferroceno-
phane 12. The detection of four carbon signals in the phenyl
region of the 13C spectrum further confirmed that the di-
Synthesis and characterization of p-(dimethylaminomethyl)-
phenyl sila[1]ferrocenophane 20: A monomer that was of
significant interest to us was o-(dimethylaminomethyl)-
[35]
phenyl sila[1]ferrocenophane 16
as it had been previously
methylaminomethyl group was para to the silyl moiety on
the phenyl ring.
PROP of the silicon-bridged [1]ferrocenophane 20—synthe-
sis and characterization of PFS 21: Under exposure to UV/
Vis irradiation,the photolytic polymerization of monomer
20 proceeded smoothly in the presence of 0.1 equivalents of
NaCp (Scheme 9). After 3 hours of stirring,the color of the
reaction solution changed from dark red to orange,indicat-
ing that most of the monomer had been consumed. Precipi-
tation of the crude product in methanol gave polymer 21 as
an orange gummy material,which was soluble in common
organic solvents such as benzene,THF,and dichlorome-
thane. As the polymer adsorbed to the GPC column when
THF was used as an eluant,it was analyzed using a THF so-
lution containing 2.0% v/v of triethylamine. The GPC analy-
sis indicated that the polymer possessed a molecular weight
of Mn =4.6”103 and a PDI of 1.30,corresponding to ꢁ13
repeat units in each polymer chain. Notably,when a poly-
styrene (PS) standard (Mp =3600,PDI =1.04) was analyzed
on the same instrument by the same method,its molecular
weight and polydispersity index were Mn =4.5”103 and 1.18,
demonstrated that the thermal ROP of 16 affords a (di-
methylaminomethyl)phenyl PFS,which can be readily con-
ACHTREUNG
verted to the cationic phenyl polyferrocenylsilane 17.[24] This
polyelectrolyte is stable in NaCl solutions and has been used
extensively in the LbL assembly of PFS multilayers.[28,30]
However,although ferrocenophane 16 readily undergoes
thermal polymerization,ring opening of this monomer
under photolytic conditions was sluggish. A significant
amount of monomer 16 was detected in the reaction mixture
even after 5–7 hours of UV/Vis irradiation.
The sluggishness of the polymerization was probably a
result of the relatively close proximity of the dimethylamino
group and the iron center in the monomer,which may favor
intramolecular chelation between the two moieties and,
Chem. Eur. J. 2007, 13,9372 – 9383
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
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9377

G. A. Ozin,I. Manners et al.
Figure 2. Variation of molecular weight of polymer 21 with monomer/ini-
&
*
tiator ratio,[M]/[I],as calculated ( ) and obtained experimentally ( ).
Scheme 9.
respectively. The GPC result of the PS standard suggested
that the polydispersity of PFS 21 was likely to be much
smaller than 1.30. End-group analysis by using 1H NMR
spectroscopy indicated that the number of monomeric units
is approximately 13,which is comparable to that obtained
from the GPC analysis.
By varying the monomer/initiator ratio from 10 to 200,
polymer 21 have been obtained with molecular weight rang-
ing from 4.6”103 to 2.9”104 (Table 2). However,good mo-
lecular weight control and narrow polydispersity were only
achieved for polymers which possess up to 20 monomeric
units. At a higher monomer/initiator ratio (50:1),PFS 21
was obtained with large polydispersity and molecular
weights that deviate significantly from the theoretical values
(Figure 2).[38]
Figure 3. a) 1H (400 MHz) and b) 13C (100 MHz) NMR spectra of poly-
mer 21 in C6D6.
1
PFS 21 was characterized by using H, 13C,and 29Si NMR
spectroscopy (Figure 3). For polymers that have short chain
length,the 1H NMR spectrum showed a distinct chemical
shift at d=3.96 ppm,corresponding to the protons of the
capping h5-C5H5 group at the ferrocenyl end of the polymer
chain. This allows estimation of the number-average degree
of polymerization (DPn,NMR) for polymers that have repeat
units of up to 100 by using end-group analysis through inte-
gration of the Cp protons in the end group and in the main-
chain ferrocenyl moieties (d=4.00–4.28 ppm). In the
13C NMR spectrum,a downfield shift was detected for the
ipso-carbon from d=32.7 ppm in monomer 20 to d=
70.8 ppm in polymer 21 as a result of the release of ring-
strain in the monomer. The h5-C5H5 carbons at the ferrocen-
yl chain end were again clearly observed at d=69.2 ppm.
The 29Si NMR spectrum of 21 exhibited one signal at d=
À11.5 ppm,which was in ac-
cordance with the assigned
Table 2. Summary of data for polymer 21 synthesized by PROP.
structure.
[b]
[c]
Sample
[M]/[I][a]
DPn, NMR
Mn, calc
Mn, GPC
PDI[d]
t [h]
Yield of
Yield of
PFS 21 [%]
(+)PFS 22 [%]
Quaternization of 21—synthesis
and characterization of cationic
polyelectrolyte 22: In a proce-
dure analogous to the synthesis
of cationic PFS 7 from dime-
thylaminopropynyl PFS 15,the
dimethylamino groups in poly-
mer 21 were quaternized in the
a
b
c
d
e
10
20
50
100
200
13
20
60
80
–
3610
7220
18050
36100
72200
4600
6800
12200
22800
28800
1.30
1.20
1.45
1.65
2.61
3
4
4
5
6
70
62
58
48
52
93
70
90
82
77
1
[a] [M]/[I] denotes monomer:initiator ratio. [b] Values determined by H NMR integration of Cp polymer pro-
tons relative to the Cp end-group protons. [c] Cp end groups are not included. [d] Given by Mw/Mn from GPC
analysis.
9378
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Chem. Eur. J. 2007, 13,9372 – 9383

Functionalized Ferrocenophanes
FULL PAPER
presence of dimethyl sulfate to give the desired cationic PFS
22 as an orange powder (Scheme 9). This polyelectrolyte
was soluble in water,methanol,and aqueous NaCl solutions.
The solutions remained clear and stable over a long period
of time (i.e. more than half a year) under ambient condi-
tions.
electrolytes that have large uncontrolled molecular weights
can also complicate LbL assembly in highly confined spaces
with narrow openings such as micro- and nanochannels as
well as photonic crystals. In this work,we assembled LbL
films using polycation 22 and polyanion 6,which possess
controlled molecular weight and narrow polydispersity,and
our preliminary study indicated that the molecular weight of
these polyelectrolytes had a significant influence on the bi-
layer thickness and refractive index (RI) of these films.
The LbL assembly was carried out by sequentially dipping
a silicon substrate into the aqueous solutions of (+)PFS 22
The cationic PFS 22 in deuterated methanol was charac-
terized by using 1H, 13C,and
(Figure 4). In the H spectrum,the ammonium methyl pro-
29Si NMR spectroscopy
1
(DPn ꢁ13, Mn ꢁ6.4”103) and (À)PFS
6
(DPn ꢁ10, Mn
ꢁ4.4”103). The ionic strength of both solutions was main-
tained at a salt concentration of 0.1m NaCl. To minimize the
effect of molecular weight distribution,polyelectrolytes that
have a polydispersity index of less than 1.30 were used. Mul-
tilayer films of 5,10,20,30,and 40 bilayers of PFS polyelec-
trolytes were thus constructed,with each bilayer consisting
of one (+)PFS and one (À)PFS monolayer.
The thickness and refractive index of these well-defined
LbL films were examined by using ellipsometry measure-
ments. The linear relationship between film thickness and
bilayer number indicated a regular film growth in the LbL
assembly (Figure 5a),with the thickness of each bilayer esti-
mated to be ꢁ1.3 nm. The refractive index of each film was
measured in the visible-near IR region of l=400–1400 nm
(Figure 5b),with the RI value determined as 1.68 at l=
600 nm. This is comparable to the refractive indices of spin-
Figure 4. a) 1H (400 MHz) and b) 13C (100 MHz) NMR spectra of poly-
mer 22 in CD3OD.
tons exhibited a resonance at d=3.11 ppm,which was shift-
ed significantly downfield from the dimethyl protons in PFS
21 (d=2.12 ppm) as a result of the quaternization. The same
downfield shift was also observed for the methylene protons
adjacent to the nitrogen atom from d=3.33 ppm in 21 to
d=4.59 ppm in the cationic polymer. In addition,the ab-
1
sence of the dimethylamino proton signals in the H spec-
trum of 22 confirmed the successful quaternization of poly-
mer 21. The 13C and 29Si NMR of the polymer were also
consistent with the assigned structure.
Layer-by-layer self-assembly of PFSs 6 and 22—study of the
molecular-weight effect on the structure and optical proper-
ties of LbL films: The technique of LbL self-assembly has
been widely utilized as a practical method for surface modi-
fication and patterning as well as manufacturing of thin film
devices due to its simplicity and versatility.[2,3] While a wide
variety of polyelectrolytes have been successfully assembled
for many practical applications,the uncontrolled architec-
tures of these polymers pose a significant challenge to the
fundamental studies of the structure and property of the
multilayer films,as uncontrolled polymer molecular weight
and broad molecular-weight distributions can sometimes
make interpretation of experimental results difficult.[39] Poly-
Figure 5. a) Plot of LbL film thickness versus bilayer number. b) Disper-
sion of the index of refraction for the LbL structures.
Chem. Eur. J. 2007, 13,9372 – 9383
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
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9379

G. A. Ozin,I. Manners et al.
cast polymer films from PFSs with analogous structures.[40]
Our study also indicated that the index of refraction did not
change significantly with respect to the multilayer thickness.
The aforementioned results,are significantly different
from our previous work in which LbL films have been as-
sembled from PFS polyelectrolytes with uncontrolled high
molecular weight (Mw ꢁ105–106) and polydispersity (PDI>
1.8). For example,films assembled from ( +)PFS 17[41] and
ings,or gradients with defined dimensions and desired pho-
tonic properties. Further detailed investigation of multilayer
films as a function of PFS molecular weight,as well as LbL
self-assembly of water-soluble PFSs in confined spaces,will
be reported in the near future.
Experimental Section
5
(À)PFS 6,which have molecular weight in the order of 10 ,
have been found to exhibit a bilayer thickness of 4.8 nm,sig-
nificantly larger than that of the low molecular-weight
films.[42] In addition,the refractive index of these films was
determined to be 1.52 at l=600 nm,much lower than that
of the low molecular-weight LbL films or spin-cast films of
analogous structures.
Materials: All chemicals were purchased from Aldrich and used as re-
ꢀ
ceived unless otherwise specified. Compounds HC CCH2N-
A
[{fcSiMe(o-C6H4CH2NMe3OSO3Me)}n] (17)[24] (Mw ꢁ105) were synthe-
sized according to literature procedures. Solvents were dried according to
standard methods. Aqueous polyelectrolyte solutions were prepared by
using deionized water (18.2mWcm). Si
(111) substrates (2”1 cm2) were
H
The difference between the two groups of LbL films sug-
gests a more condensed multilayer structure in the well-de-
fined films assembled from low molecular-weight PFSs. LbL
assembly is generally considered as a multistep kinetic pro-
cess in which the coiled chains of polyelectrolytes first
adsorb onto a substrate surface and then relax to form more
extended chains.[2,3] In the case of low molecular-weight
PFSs,it may be difficult for the short polyelectrolyte chains
to adopt coiled conformations in aqueous solutions,owing
to steric restrictions of the bonds and electrostatic interac-
tions of the partially shielded ionic groups.[43] It is suspected
that PFS chains may deposit onto the substrate surface in
relatively extended conformations,which can lead to com-
pact multilayers with fewer loops and voids that contain air
and water,thus giving rise to thinner bilayer thickness and
higher refractive index. Further detailed study of the effect
of polymer molecular weight on the LbL assembly of multi-
layer films is currently underway and will be reported in the
near future.
cut from 3’’ polished wafers (International Wafer Service). Si substrates
were sputtered with a 100 Š Cr adhesion layer followed by a 1000 Š Au
layer.
Equipment: All manipulations of air-sensitive materials were performed
under nitrogen atmosphere either in an MBraun glovebox or by using
standard Schlenk line techniques. 1H, 13C NMR and 29Si spectra were re-
corded on Varian spectrometers (Unity 400,Gemini 300 or Mercury 300)
and referenced to residual protonated solvent (1H) or deuterated solvent
(13C) unless otherwise specified. Mass spectra were obtained with the use
of a VG 70–250S mass spectrometer operating in electron impact (EI)
mode. Molecular weights were estimated by using gel permeation chro-
matography (GPC) by using a Waters Associates 2690 separation module
equipped with a column heater,in-line degasser,a High Performance
Liquid Chromatography (HPLC) pump,and an autosampler. The separa-
tion module was equipped with a Waters 410 differential refractometer
as the concentration detector and,connected in parallel,a Viscotek
T60A dual detector consisting of a right-angle laser light scattering detec-
tor with a laser source of 670 nm and a four-capillary differential viscom-
eter. Software from Viscotek was used to analyze the data. Columns
from Polymer Laboratories with pore sizes of 5”102,1”10 4,and 1”
105 Š were used with THF as the eluant unless otherwise specified at a
flow rate of 1.0 mLminÀ1. Polystyrene standards purchased from Aldrich
and Viscotek were used for calibration.[44]
LbL assembly of PFS multilayers: The concentrations of the polyelectro-
lyte solutions were 10 mm PFS,based on the respective monomer repeat
units. Each solution was made in 0.1m NaCl and filtered through a
0.45 mm syringe filter prior to use. The substrates were alternately placed
in the PFS polyanion and polycation solutions for 10 min,rinsed with de-
ionized water through three immersions for 4 min each after each expo-
sure to polyelectrolyte,and finally dried with a gentle stream of com-
pressed air.
Conclusion
We have achieved the facile and reliable synthesis of the
first water-soluble metallopolyelectrolytes with transition
metals in the main chain,which possess controlled molecu-
lar weight and narrow polydispersity. These macromolecules
have been obtained through the photolytic ROP of amino-
functionalized [1]ferrocenophanes followed by further deri-
vatizations. The polyelectrolytes are readily soluble in water
and aqueous NaCl solutions,with 6 and 22 exhibiting stabili-
ty in aqueous NaCl solutions over a long period of time.
PFSs 6 and 22 have been utilized in the layer-by-layer self-
assembly of multilayer films,and their controlled structures
allow fundamental studies of LbL films in a more precise
fashion. Our preliminary results indicate that films made
from low molecular-weight PFSs are considerably thinner
and possess higher refractive index than those made from
high molecular-weight PFSs. This suggests that the structure
and optical properties of LbL thin films can be tuned by
varying polymer chain length,which may have significant
implications in the manufacturing of thin-film devices,coat-
Ellipsometry measurements: Ellipsometric measurements were obtained
by using a SOPRA GES-5 variable-angle spectroscopic ellipsometer. For
each sample,ellipsometry spectra were obtained at angles of incidence of
70 and 75 degrees. Using known values of the dielectric function of Au
substrate,and by varying film thickness and refractive index of the LbL
layer,the experimental data were fit to a model,which also included a
rough layer in the order of 1 nm. To improve fits,the LbL layer was mod-
eled as a film with 5–10% thickness-nonuniformity.
ꢀ
ꢀ
Synthesis of [(fcSiMe
(SiMe2CH2)2}2)n] (11), [{fcSiMe(C CCH2NMe2)}n] (15): In a typical pro-
cedure,Na [C5H5] (0.024 mL of 2.0m solution in THF,0.047 mmol) was
{C CCH2N
U
A
ꢀ
AHCTREUNG
AHCTREUNG
added in the absence of light to a solution of sila[1]ferrocenophane 3
(200 mg,0.472 mmol) in THF (2 mL). The solution was irradiated with
UV/Vis light and stirred for 2.5 h at 58C. The reaction was terminated
with a few drops of degassed ethanol,concentrated,precipitated into
methanol,and dried under high vacuum to afford polymer 5 as an orange
gummy solid (145 mg,0.342 mmol,73%). 1H NMR (300 MHz,C D6): d=
6
0.25,0.27 (12H; NSi
C
9380
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ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2007, 13,9372 – 9383

Functionalized Ferrocenophanes
FULL PAPER
Cp); 13C NMR (75 MHz,C D6): d=À0.09 (fcSiCH3),0.3 (NSi
C
night. Filtration of the reaction mixture followed by removal of the sol-
vents under high vacuum gave a dark red residue,which was dissolved in
hexanes and filtered again to remove any remaining lithium salt. Recrys-
tallization in hexanes at À358C followed by sublimation at 70–758C gave
6
ꢀ
ꢀ
73.22,74.6,74.8 (Cp),85.1 (Si C CCH2),109.7 ppm (Si C CCH2); GPC:
Mn =6.3”103,PDI =1.10.
14 as
a
red crystalline solid (1.86 g,6.01 mmol,63%).
1H NMR
G
U
(SiMe2CH2)2}2)n] (11): 1H NMR (400 MHz,C 6D6): d=
(CH3)2),0.79,0.81,0.82 (8H;
ꢀ
(400 MHz,C 6D6): d=0.57 (s,3H; fcSiC H3),2.20 (s,6H; NC H3),3.18 (s,
2H; NCH2),3.89,4.38,4.44,4.51 ppm (m,8H; Cp);
13C NMR (75 MHz,
0.22,0.25,0.27,0.28,0.29 (24H; NSi
ACHTREUNG
NSiCH2),3.67,3.66,3.68 (4H; NC H2),4.35 (s, h5-C5H5Fe),4.69,4.93 ppm
(s,8H; Cp); 13C NMR (100 MHz,C 6D6): d=0.29,0.37 (NSi
(CH3)2),8.8
(NSiCH2),32.4 (N CH2),67.7 ( ipso-Cp),69.9 ( h5-C5H5Fe),72.2,74.3,74.7,
C6D6): d=À2.6 (fcSiCH3),31.0 ( ipso-Cp),44.4 (N CH3),49.3 (N CH2),
AHCTREUNG
75.0,77.0,78.5,78.6 (Cp),85.6 (Si C CCH2),104.6 ppm (Si C CCH2); 29Si
ꢀ
ꢀ
75.3 (Cp),82.8 (SiC
CCH2),109.9 ppm (Si C CCH2); 29Si NMR
NMR (79 MHz,C D6): d=À28.7 ppm.
ꢀ
ꢀ
6
(79 MHz,C D6): d=À45.8,14.9 ppm; GPC: Mn =4.9”103,PDI =1.13.
Synthesis of [fcSiMe(p-C6H4CH2NMe2)] (20): 4-Bromobenzyldimethyl-
[{fcSiMe(C CCH2NMe2)}n] (15): 1H NMR (300 MHz,C 6D6): d=0.23 (s,
A
Dimethylamine (50 mL of 2.0m solution in THF,100 mmol) and diisopro-
pylethylamine (17.4 mL,100 mmol) were added dropwise to a solution of
4-bromobenzyl bromide (16.7 g,66.7 mmol) in benzene (100 mL) at 5 8C .
The white suspension was stirred for 1 h at 58C and then for 2 days at
258C. Filtration of the reaction mixture followed by thorough washing of
the white solid with benzene (30 mL”3) gave a combined organic solu-
tion which was concentrated on a rotavap. Further filtration of the resid-
ual white solid followed by vacuum distillation of the crude product af-
fcSiCH3
C
ꢀ
74.5,74.6,74.89,74.95 (Cp),88.6 (SiC
CCH2),103.9 ppm (Si C CCH2);
29Si NMR (79 MHz,C 6D6): d=À24.7 ppm; GPC: Mn =3.4”103,PDI =
1.08.
ꢀ
Synthesis of [{fcSiMe(C CCH2NMe3OSO3Me)}n] (7)
forded 4-bromobenzyldimethylamine (18) as
a clear colorless liquid
Procedure A: Diisopropylethylamine (1.03 mL,5.90 mmol) followed by
dimethyl sulfate (0.45 mL,4.72 mmol) were added to a solution of PFS
(7.68 g,35.9 mmol,54%) which was used in the following step. nBuLi
(9.31 mL of 1.6m solution in hexanes,14.9 mmol) was quickly added
(500 mg,1.18 mmol) in a mixture of THF (20 mL) and methanol (5 mL)
at 258C. As the reaction proceeded,additional methanol was added to
dissolve some of the cationic polymer which precipitated out of the solu-
tion. After seven days of reaction at room temperature,the solvents were
removed on a rotavap and the residue was dissolved in a small amount of
methanol prior to precipitation in THF. Suction filtration followed by
drying under high vacuum afforded the cationic polymer 7 as an orange
powder (270 mg,0.620 mmol,53%).
dropwise to
a solution of 4-bromobenzyldimethylamine (18) (3.25 g,
15.2 mmol) in diethyl ether (25 mL) at À788C. The yellow solution was
stirred for ꢁ2–3 min before a solution of chloromethylferrocenophane 12
(4.00 g,15.2 mmol) in diethyl ether (25 mL) was added dropwise quickly
through a canula. The reaction mixture was slowly warmed to 258C
during a three hour period. Removal of the solvents under high vacuum
gave a dark red residue,which was dissolved in hexanes (80 mL) and fil-
tered to remove the lithium chloride salt. Repeated recrystallization at
À558C gave 20 as a red crystalline solid (2.20 g,6.09 mmol,40%).
1H NMR (300 MHz,C 6D6): d=0.58 (s,3H; fcSiC H3),2.12 (s,6H;
NCH3),3.31 (s,2H; NC H2),4.03,4.06,4.39,4.44 (m,8H; Cp),7.48 (d,
Procedure B: Diisopropylethylamine (0.19 mL,1.09 mmol) followed by
dimethyl sulfate (0.10 mL,1.09 mmol) were added to a solution of PFS
15 (168 mg,0.543 mmol) in a mixture of THF (6 mL) and methanol
(1.5 mmol). The reaction mixture was stirred at 258C for 8 h. Removal of
the solvents on a rotavap followed by precipitation in THF afforded cat-
J=7.8 Hz,2H; Ph),7.96 ppm (d,
J=8.0 Hz,2H; Ph);
13C NMR
(75 MHz,C 6D6): d=À2.1 (fcSiCH3),32.7 ( ipso-Cp),45.9 (N CH3),64.9
ionic polymer
7 as an orange powder (154 mg,0.353 mmol,65%).
(NCH2),76.4,77.1,78.3,78.4 (Cp),129.5,134.5,134.9,142.7 ppm (Ph).
1H NMR (400 MHz,D 2O): d=0.77 (br,3H; fcSiC H3fc),3.22 (s,br,9H;
NCH3),3.74 (s,3H; OSO 3CH3),4.00–4.73 ppm (m,br,10H; Cp and
CH2N); 13C NMR (100 MHz,D 2O, dref(acetone) =30.2 ppm): d=0.2
(fcSiCH3),52.7 (N CH3),55.1 (OSO 3CH3),56.8 (N CH2),68.9 ( ipso-Cp),
29Si NMR (79 MHz,C D6): d=À8.2 ppm.
6
Synthesis of [{fcSiMe(p-C6H4CH2NMe2)}n] (21): Na[C5H5] (0.042 mL of
A
2.0m solution in THF,0.083 mmol) in the absence of light was added to a
solution of sila[1]ferrocenophane 20 (300 mg,0.830 mmol) in THF
(2 mL). The solution was irradiated with UV/Vis light and stirred for 3 h
at 58C. The reaction was terminated with a few drops of degassed etha-
nol,concentrated,precipitated into methanol,and dried under high
vacuum to afford polymer 21 as an orange gummy solid (210 mg,
0.581 mmol,70%). 1H NMR (400 MHz,C 6D6): d=0.79 (s,3H; fcSiC H3),
2.12 (s,6H; NC H3),3.33 (s,2H; NC H2),3.96 (s, h5-C5H5Fe),4.00–4.28
(m,8H; Cp),7.46 (d, J=8.0 Hz,2H; Ph),7.75 ppm (d, J=8.0 Hz,2H;
Ph); 13C NMR (100 MHz,C 6D6): d=À2.9, À2.4 (fcSiCH3),45.9 (N CH3),
64.9 (NCH2),69.2 ( h5-C5H5Fe),70.75,70.80 ( ipso-Cp),71.5,71.9,72.4,
ꢀ
ꢀ
72.9,73.9 (Cp),94.4 (SiC CCH2),96.0 ppm (Si C CCH2).
ꢀ
Synthesis of [fcSi
{C CCH2N
(SiMe2CH2)2}2] (10): nBuLi (8.84 mL of
1.6m solution in hexanes,14.1 mmol) was added dropwise to a solution of
[26]
ꢀ
protected
propargylamine
HC CCH2N
(SiMe2CH2)2
14.5 mmol) in diethyl ether (40 mL) at À788C. After 5 min of stirring,
the cold bath was removed and the reaction mixture was stirred for
ꢁ10 min before it was added slowly through a canula to a solution of di-
chloroferrocenophane 8 (2.0 g,7.07 mmol) in diethyl ether (50 mL) at
À788C. The reaction mixture was slowly warmed to 258C and stirred
overnight. Filtration of the reaction mixture followed by removal of the
solvents under high vacuum gave a dark red residue which was dissolved
in hexanes (50 mL) and filtered again to remove any remaining lithium
salt. Evaporation of hexanes (ꢁ25 mL) followed by recrystallization at
72.7,72.8,74.6,74.7,74.8 (Cp),129.0,135.0,137.8,141.2 ppm (Ph);
29Si
NMR (79 MHz,C 6D6): d=À11.5 ppm; GPC (2.0% v/v Et3N in THF as
eluant): Mn =4.6”103,PDI =1.30 (under the same condition,standard PS
with Mp =3600 and PDI=1.04 was detected with a molecular weight of
Mn =4.5”103 and PDI=1.18).
À358C gave 10 as a red solid (0.980 g,1.62 mmol,23%).
(400 MHz,C 6D6): d=0.21 (s,24H; NSi (CH3)2),0.75 (s,8H; NSiC H2),
3.53 (s,4H; NC H2),4.43,4.52 ppm (m,8H; Cp);
13C NMR (100 MHz,
(CH3)2),8.3 (NSi CH2),28.8 (N CH2),31.9 ( ipso-Cp),
AHCTREUNG
Synthesis of [{fcSiMe(p-C6H4CH2NMe3OSO3Me)}n] (22): Diisopropyl-
C6D6): d=À0.28 (NSi
ACHTREUNG
A
75.4,78.5 (Cp),79.4 (Si C CCH2),110.8 ppm (Si C CCH2); 29Si NMR
(79 MHz,C 6D6): d=À55.6,15.3 ppm; HRMS for C 28H44FeN2Si5 calcd:
604.1700; found: 604.1687.
ꢀ
ꢀ
1.25 mmol) were added to a solution of PFS 21 (180 mg,0.50 mmol) in
THF (2 mL) at 258C. Methanol (4 mL) was added to dissolve the precipi-
tate formed in the reaction mixture and the clear orange solution was
stirred for 2 h. After removal of the solvents on a rotavap,the residue
was dissolved in a small amount of methanol and precipitated in acetone.
The precipitate was redissolved in a small amount of methanol and pre-
cipitated in THF. Suction filtration followed by drying under high
vacuum afforded polymer 22 as an orange powder (225 mg,0.46 mmol,
93%). 1H NMR (400 MHz,CD 3OD): d=0.79 (s,3H; fcSiC H3),3.11 (s,
9H; NCH3),3.69 (s,3H; OSO 3CH3),3.90–4.21 (m,8H; Cp),4.59 (s,2H;
ꢀ
Synthesis of [fcSiMe(C CCH2NMe2)] (14): nBuLi (6.07 mL of 1.6m solu-
tion in hexanes,9.71 mmol) was added dropwise to a solution of 3-dime-
thylamino-1-propyne (1.08 mL,10.0 mmol) in diethyl ether (70 mL) at
À788C. After 5 min of stirring,the cold bath was removed and the white
suspension was stirred for ꢁ3 min before it was cooled again to À788C.
A solution of chloromethylferrocenophane 12 (2.50 g,9.52 mmol) in di-
ethyl ether (50 mL) through a canula was added slowly to this suspen-
sion. The reaction mixture was slowly warmed to 258C and stirred over-
NCH2),7.64 (d, J=7.2 Hz,2H; Ph),7.78 ppm (br,2H; Ph);
13C NMR
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G. A. Ozin,I. Manners et al.
(100 MHz,CD 3OD): d=À3.4 (fcSiCH3),53.4 (N CH3),55.3 (OSO 3CH3),
70.4–70.7 (NCH2, h5-C5H5Fe, ipso-Cp),73.1,73.5,75.0,75.4 (Cp),129.9,
133.4,136.2,143.7 ppm (Ph);
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Acknowledgements
We thank the Natural Science and Engineering Research Council
(NSERC) of Canada for funding and IM and GAO thank the Canadian
Government for Canada Research Chairs. IM also thanks the E.U. for a
Marie Curie Chair and the Royal Society of Chemistry for a Wolfson Re-
search Merit Award. We wish to thank Mr. Mingfeng Wang,Mr. Hai
Wang,Mr. David Rider and Mr. Lawrence Vanderark for GPC analysis,
and Ms. Suzanne Mamiche-Afara for preparing sputtered gold substrates.
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Functionalized Ferrocenophanes
FULL PAPER
[38] Although it is unclear as to what might have caused such deviation,
it is suspected that the dimethylamino groups in newly formed poly-
mers may interact with the metallomonomer in the polymerization
mixture,potentially leading to other reaction pathways.
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the phenyl moiety in 17 and para position in 22. This subtle differ-
ence is not anticipated to give rise to the significant difference ob-
served in the two groups of LbL films.
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Received: April 14,2007
Published online: October 8,2007
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9383