Poly(dimethylsiloxane)-Substituted 2,2[prime]:6,2[Prime ...

1666 

Poly(dimethylsiloxane)-Substituted 2,2 0 :6,2 00 - 

Terpyridines: Synthesis and Characterization 

of New Amphiphilic Supramolecular 

Diblock Copolymers 

Steve Landsmann, Andreas Winter, Manuela Chiper, Charles-André Fustin, 

Stephanie Hoeppener, Daan Wouters, Jean-François Gohy, 

Ulrich S. Schubert* 

S. Landsmann, A. Winter, M. Chiper, S. Hoeppener, D. Wouters, 

U. S. Schubert 

Laboratory of Macromolecular Chemistry and Nanoscience 

(SMN), Eindhoven University of Technology, P.O. Box 513, 5600 

MB Eindhoven, The Netherlands 

Fax: (þ31) (0)40 2474186; E-mail: u.s.schubert@tue.nl 

S. Landsmann, U. S. Schubert 

Laboratory of Organic and Macromolecular Chemistry, 

Friedrich-Schiller-University Jena, Humboldtstr. 10, 07743 Jena, 

Germany 

C.-A. Fustin, J.-F. Gohy 

Unité CMAT and CERMIN, Université catholique de Louvain, Place 

L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium 

Introduction 

Full Paper 

Terpyridine-modified hydrophobic poly(dimethylsiloxane) and hydrophilic poly(ethylene 

oxide) were combined to new metallo-supramolecular AB-diblock copolymers by utilizing 

Ru(II) ions. The polymers were synthesized by hydrosilylation of heteroleptic allyloxy-functionalized 

Ru(II) complexes. The amphiphilic AB-diblock 

copolymers were used to prepare micelles in an aqueous 

environment, which were subsequently characterized 

by dynamic light scattering and cryogenic 

transmission electron microscopy. 

In recent years, polysiloxanes have found many applications 

due to the fact that their unique properties can 

hardly be realized by polymers with organic backbones. 

Low glass-transition temperatures, high thermal stability, 

biocompatibility, hydrophobicity, high gas permeability, 

oxidative resistance and a low surface energy are among 

the properties resulting from the polar siloxane backbone. 

[1] In particular, poly(dimethylsiloxane) (PDMS) has 

successfully been introduced as a new (hybrid) material for 

coatings, membranes, microfluids, biomedical applications 

Macromol. Chem. Phys. 2008, 209, 1666–1672 

ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/macp.200800219

Poly(dimethylsiloxane)-Substituted 2,2 0 :6,2 00 -Terpyridines: Synthesis ... 

and as stamps for soft nanolithography. [1] On the other 

hand, only very few examples are known from the 

literature where polysiloxanes have been used to form 

supramolecular assemblies. [2] 

Among others, 2,20 :60 ,200-terpyridines are important 

building blocks in supramolecular chemistry. [3,4] Due to 

their strong chelating behavior, they form stable complexes 

with most transition metal ions, including Ru(II), 

Fe(II), Ir(III), Os(III), Pt(II) and Zn(II). The introduction of 

these complexes into polymeric structures results in novel 

functional metallo-supramolecular materials combining 

the properties of both worlds. The attractive photochemical 

and electrochemical properties of such materials have 

found a variety of applications, for instance in the fields of 

photocatalysis, as active materials in self-assembled 

molecular devices, photoactive molecular wires, and 

luminescent sensors in molecular biology and medical 

diagnostics. [4,5] 

The first step towards the synthesis of metallo-supramolecular 

polymers is the attachment of the terpyridine 

ligand to a polymer. The synthetic strategies towards 

terpyridine-functionalized polymers reported in the 

literature so far include: end-group functionalization, 

the use of terpyridine-functionalized initiators, terpyridine-bearing 

monomers and terpyridine-containing 

terminating agents. [4,6] The second step consists of the 

self-assembly of the terpyridine-functionalized polymers 

into metallo-supramolecular materials. We are currently 

particularly interested in the synthesis of (amphiphilic) 

A-[M]-B metallo-supramolecular diblock copolymers in 

which A-[ and B-[ stand for two different terpyridine endfunctionalized 

polymer blocks and M represents the 

transition metal ion. The synthesis of such structures 

requires the formation of heteroleptic complexes. This 

means that the reaction between A-[, B-[ and M should lead 

selectively to the formation of A-[M]-B complexes and that 

the formation of the homoleptic complexes should be 

avoided. Indeed, the synthesis of A-[Ru II ]-B metallosupramolecular 

block copolymers can be selectively 

achieved in a two-step procedure by, first, creating the 

A-[Ru III 

(or B-[Ru III ) mono-complex, which is further 

reacted under the appropriate reducing conditions with 

B-[(or A-[) to form the desired A-[Ru II ]-B complex. [6d] 

Here, we have used this approach to self-assemble 

new terpyridine-functionalized PDMS-systems and 

terpyridine-bearing poly(ethylene oxide) compounds, 

yielding amphiphilic block copolymers. These structures 

could represent promising new functional materials, as 

they combine the properties of classical organic polymers 

with those of polysiloxanes mentioned above and the 

(supramolecular) chemistry of terpyridines. Both the 

synthesis of these amphiphilic metallo-supramolecular 

block copolymers and their use to form micelles in water 

are discussed in the present contribution. 

Experimental Part 

All solvents (Biosolve) and reagents were used without further 

purification. The hydrogen-terminated poly(dimethylsiloxane) (5, 

PDMS, Mn ¼ 4 380 Da) a was obtained from Gelest Inc., RuCl3 H2O 

and NH 4PF 6 were acquired from Aldrich. The Karstedt’s catalyst 

was purchased from ABCR. Terpyridine-functionalized poly- 

(ethylene oxide) (3) was prepared according to a literature 

procedure. [6a,b] For preparative size exclusion chromatography, 

Bio-Rad SX-1 beads swollen in THF were used. 

Gel permeation chromatography measurements (GPC) were 

performed on a Waters GPC system, consisting of an isocratic 

pump, a solvent degasser, a column oven, a 2996 photodiode array 

detector (PDA), a 2414 refractive-index (RI) detector, a 717 Plus 

autosampler and a Styragel HT 4 GPC column with a precolumn 

installed. A solution of 5 10 3 M NH 4PF 6 in DMF was used as an 

eluent at a flow rate of 0.5 mL min 1 and a column temperature 

of 50 8C. Molecular weights were calculated against poly(ethylene 

oxide) standards. 

Infrared (IR) spectra were measured in ATR mode on a Perkin 

Elmer 1600 FT-IR spectrometer. 1 H and 13 C nuclear magnetic 

resonance (NMR) spectra were recorded at room temperature on a 

Varian Gemini 400 spectrometer, using deuterated chloroform, 

dichloromethane and acetonitrile as solvents (Cambridge Isotopes 

Laboratories). 29 Si NMR spectra were measured on a Bruker AV500 

instrument in deuterated acetone (Deutero GmbH). All chemical 

shifts are reported in ppm (d) downfield from tetramethylsilane; 

coupling constants (J values) are reported in Hz. 

Matrix-assisted laser desorption/ionization time-of-flight mass 

spectrometry (MALDI-TOF MS) was performed on a Voyager DE 

PRO biospectrometry workstation (Applied Biosystems) time-offlight 

mass spectrometer with dithranol as the matrix, and NaI as 

the ionization agent. Ultraviolet (UV) spectra were measured on 

a PerkinElmer Lamda-45 spectrometer (1 cm cuvettes, 10 5 M in 

CH2Cl2). 

Elemental analyses were carried out on a EuroVector EuroEA300 

elemental analyzer for CHNS-O. Dynamic light scattering (DLS) 

experiments were performed on a Malvern CGS-3 equipped with a 

He-Ne laser (633 nm). The measurements were performed at an 

angle of 908 and at a temperature of 25 8C. The results were 

analyzed by the CONTIN method, which is based on an inverse- 

Laplace transformation of the data and which gives access to a size 

distribution histogram for the analyzed micellar solutions. 

Cryogenic transmission electron microscopy (cryo-TEM) measurements 

were performed on a FEI Tecnai 20, type Sphera TEM 

operating at 200 kV (LaB6 filament). Images were recorded with a 

bottom mounted 1k 1k Gatan CCD camera. A Gatan cryo-holder 

operating at 170 8C was used for the cryo-TEM measurements. 

R2/2 Quantifoil Jena grids were purchased from SPI. Cryo-TEM 

specimens were prepared by applying 3 mL aliquots to the grids 

within the environmental chamber (22 8C, relative humidity 

100%) of an automated vitrification robot (FEI Vitrobot Mark III). 

Excess liquid was blotted away ( 2 mm offset, 2.5 s) with filter 

paper within the environmental chamber of the Vitrobot. The 

a The number average molecular weight (Mn) and the molecular 

weight distribution (PDI) of 5 were determined by GPC (toluene 

with 0.02 M diethanolamine) using a poly(dimethylsiloxane) calibration. 


ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.mcp-journal.de 1667

1668 

grids were subsequently shot through a shutter into melting ethane 

placed just outside the environmental chamber. Vitrified specimens 

were stored under liquid nitrogen before imaging. Prior to blotting, 

the grids were made hydrophilic by surface plasma treatment using 

a Cressington 208 carbon coater operating at 5 mA for 40 s. 

General Procedure for the Synthesis of 4(-Substituted 

2,2(:6(,2 00 -Terpyridines (1) 

2-Acetylpyridine (5 g, 42 mmol), aqueous ammonia (25%, 50 mL) 

and KOH (2.35 g, 42 mmol) were added to a solution of the 

corresponding aromatic aldehyde (21 mmol) in EtOH (100 mL). 

After stirring at room temperature for 6 h, the crude product was 

isolated by filtration and washed with cold EtOH (10 mL) and 

dried. Further purification was achieved by recrystallization from 

EtOH. [7] 

4 0 -(4-Allyloxyphenyl)-2,2 0 :6 0 ,2 00 -Terpyridine (1a) 

Yield: 32%, pale orange needles. 

1 H NMR (CDCl3): d ¼ 8.73 (d, 3 J ¼ 4.8 Hz, 2 H), 8.71 (s, 2 H), 8.67 (d, 

3 J ¼ 7.6 Hz, 2 H), 7.90–7.84 (m, 4 H), 7.35 (ddd, 3 J ¼ 7.0 Hz, 

3 J ¼ 4.4 Hz, 4 J ¼ 1.6 Hz, 2 H), 7.05 (d, 3 J ¼ 8.8 Hz, 2 H), 6.09 (mc, 1 H), 

5.46 (m c, 1 H), 5.33 (m c, 1 H), 4.62 (td, 3 J ¼ 5.2 Hz, 4 J ¼ 1.6 Hz, 2 H). 

13 C NMR (CDCl3): d ¼ 159.5, 156.4, 155.8, 149.7, 149.1, 136.8, 

133.0, 130.9, 128.5, 123.7, 121.3, 118.3, 117.9, 115.1, 68.9. 

UV/vis (CHCl 3): l (e) ¼ 256 (22 118), 289 (37 446). 

IR (ATR): 3 064, 3 016, 2 918, 2 891, 2 853, 1 608, 1 584, 1 566, 

1 513, 1 466, 1 440, 1 419, 1 390, 1 296, 1 260, 1 247, 1 228, 1 181, 

989, 925, 834, 789, 732. 

MALDI-TOF MS: m/z ¼ 366 [MþH] þ . 

C24H19N3O (365.44): calcd. C 78.88, H 5.24, N 11.50; found C 

79.02, H 5.25, N 11.31. 

4 0 -(3,4-Bis(Allyloxy)Phenyl)-2,2 0 :6 0 ,2 00 -Terpyridine (1b) 

Yield: 35%, yellow needles. 

1 H NMR (CDCl3): d ¼ 8.72 (d, 3 J ¼ 4.0 Hz, 2 H), 8.67 (s, 2 H), 8.65 (d, 

3 J ¼ 8.0 Hz, 2 H), 7.88 (dt, 3 J ¼ 8.0 Hz, 3 J ¼ 7.2 Hz, 4 J ¼ 1.6 Hz, 2 H), 

7.48 (dd, 3 J ¼ 8.8 Hz, 4 J ¼ 2.4 Hz, 1 H), 7.44 (d, 4 J ¼ 2.4 Hz, 1 H), 7.35 

(ddd, 3 J ¼ 7.0 Hz, 3 J ¼ 4.4 Hz, 4 J ¼ 1.2 Hz, 2 H), 7.01 (d, 3 J ¼ 7.0 Hz, 

1 H), 6.14 (m c, 2 H), 5.48 (m c, 2 H), 5.32 (m c, 2 H), 4.74 (td, 3 J ¼ 5.2 Hz, 

4 J ¼ 1.6 Hz, 2 H), 4.68 (td, 3 J ¼ 5.2 Hz, 4 J ¼ 1.6 Hz, 2 H). 

13 C NMR (CDCl3): d ¼ 156.2, 155.7, 149.9, 149.5, 149.0, 148.7, 

136.7, 133.2, 133.1, 131.5, 123.7, 121.2, 120.5, 118.4, 117.8, 117.7, 

114.0, 113.2. 

UV/vis (CHCl3): l (e) ¼ 243 (29 040), 289 (31 604). 

IR (ATR): 3 050, 3 016, 2 990, 2 918, 2 894, 2 856, 1 602, 1 583, 

1 567, 1 519, 1 468, 1 443, 1 410, 1 391, 1 360, 1 321, 1 266, 1 252, 1 243, 

1 198, 1 151, 1 126, 1 026, 1 003, 989, 919, 894, 841, 789, 781, 745. 

MALDI-TOF MS: m/z ¼ 422 [MþH] þ . 

C 27H 23N 3O 2 (421.50): calcd. C 76.94, H 5.50, N 9.97; found C 

76.91, H 5.65, N 9.78. 

General Procedure for the Synthesis of Ru(III) 

Mono-Terpyridine Complexes [(1)RuCl 3] (2) 

A solution of RuCl3 H2O (154 mg, 0.75 mmol) and the 

corresponding terpyridine 1 (0.74 mmol) in MeOH (40 mL) was 

heated under reflux for 12 h. After cooling to 0 8C, the precipitate 

was isolated by vacuum filtration. The product was subsequently 

washed with water (20 mL), MeOH (20 mL) and diethyl ether 

(20 mL) and dried in a vacuum oven at 40 8C. [5] 

[4 0 -(4-Allyloxyphenyl)-2,2 0 :6 0 ,2 00 -Terpyridine] 

Ruthenium(III)-Chloride (2a) 

Yield: 55%, olive-colored powder. 

MALDI-TOF MS: m/z ¼ 537 [M–Cl] þ . 

C 24H 19Cl 3N 3ORu (572.86): calcd. C 50.32, H 3.34, N 7.34; found C 

50.21, H 3.41, N 7.51. 

[4 0 -(3,4-Bis(Allyloxy)Phenyl)-2,2 0 :6 0 ,2 00 -Terpyridine] 

Ruthenium(III)-Chloride (2b) 

Yield: 72%, dark green powder. 

MALDI-TOF MS: m/z ¼ 594 [M–Cl] þ , 596.86 [M–ClþH] þ . 

C27H23Cl3N3O2Ru (628.92): calcd. C 51.56, H 3.69, N 6.68; found C 

51.33, H 3.48, N 6.52. 

General Procedure for the Synthesis of Ru(II) Bis- 

Terpyridine Complexes [(4(-PEO70-tpy)Ru(2)](PF6)2 (4) 

A suspension of [(tpy)RuCl3] 2 (0.12 mmol) and (4 0 -PEO70)- 

2,2 0 :6 0 ,2 00 -terpyridine 3 (410 mg, 0.12 mmol, Mn ¼ 3 330 Da) in 

MeOH (35 mL) containing N-ethylmorpholine (NEM, 10 drops) was 

heated under reflux for 12 h. After cooling to room temperature, a 

solution of NH4PF6 (120 mg) in MeOH (5 mL) was added and 

stirring was continued at this temperature for 6 h. The solvent was 

evaporated and the residue was dissolved in CH2Cl2 (20 mL) and 

washed with water (2 5 mL). Drying over MgSO4 and evaporation 

of the solvent yielded the crude product, which was further 

purified by preparative size exclusion chromatography (Bio-Rad S- 

X1 beads, THF as eluent). [6d] 

[(4 0 -PEO70-tpy)Ru(2a)](PF 6) 2 (4a) 

Yield: 95%, red solid. 

1 H NMR (CD2Cl2): d ¼ 8.82 (s, 2 H), 8.54 (d, 3 J ¼ 8.0 Hz, 2 H), 8.43 

(d, 3 J ¼ 8.0 Hz, 2 H), 8.34 (s, 2 H), 8.10 (d, 3 J ¼ 8.8 Hz, 2 H), 7.94 (dt, 

3 J ¼ 8.0 Hz, 4 J ¼ 1.6 Hz, 2 H), 7.91 (dt, 3 J ¼ 8.0 Hz, 4 J ¼ 1.6 Hz, 2 H), 

7.41 (d, 3 J ¼ 5.6 Hz, 2 H), 7.36 (d, 3 J ¼ 5.6 Hz, 2 H), 7.29–7.23 (m, 4 H), 

7.19 (mc, 2 H), 6.17 (mc, 1 H), 5.53 (mc, 1 H), 5.39 (mc, 1 H), 4.78–4.73 

(m, 4 H), 4.11 (m c, 2 H), 3.85–3.42 (m, H PEG), 3.35 (s, 3 H). 

13 C NMR (CD2Cl2): d ¼ 166.1, 160.5, 157.6, 157.4, 155.3, 155.1, 

151.7, 151.6, 149.2, 137.6, 137.5, 132.5, 128.6, 128.4, 127.4, 124.0, 

123.9, 120.4, 117.3, 115.5, 110.8, 71.5, 70.1 (C PEG), 68.6, 58.2. 

UV/vis (CHCl3): lmax (e) ¼ 275 (47 208), 285 (41 992), 308 

(63 813), 493 (22 099). 

MALDI-TOF MS: Mn ¼ 3 370 Da. 

C 182H 316N 6O 73F 12P 2Ru (4147.49): calcd. C 52.71, H 7.68, N 2.03; 

found C 52.45, H 7.89, N 1.86. 

[(4 0 -PEO70-tpy)Ru(2b)](PF6)2 (4b) 

S. Landsmann et al. 

Yield: 84%, dark red solid. 

1 H NMR (CD2Cl2): d ¼ 8.78 (s, 2 H), 8.55 (d, 3 J ¼ 8.0 Hz, 2 H), 8.42 

(d, 3 J ¼ 8.8 Hz, 2 H), 8.35 (s, 2 H), 7.96–7.88 (m, 4 H), 7.70 (dd, 

3 J ¼ 8.0 Hz, 4 J ¼ 2.4 Hz, 1 H), 7.66 (d, 4 J ¼ 2.4 Hz, 1 H), 7.41–7.36 (m, 




4 H), 7.27–7.17 (m, 5 H), 6.20 (m c, 2 H), 5.55 (m c, 2 H), 5.38 (m c, 2 H), 

4.85 (td, 3 J ¼ 5.2 Hz, 4 J ¼ 1.6 Hz, 4 H), 4.78–4.74 (mc, 4 H), 4.11 (mc,2 

H), 3.85–3.42 (m, HPEG), 3.35 (s, 3 H). 

13 C NMR (CD2Cl 2): d ¼ 166.1, 157.7, 157.4, 155.3, 155.0, 151.9, 

151.5, 150.5, 149.0, 148.1, 137.6, 137.5, 133.0, 132.6, 129.0, 127.4, 

127.4, 124.0, 120.7, 120.6, 117.4, 117.2, 113.8, 112.8, 110.8, 71.4, 

70.4, 70.1 (C PEG), 69.9, 69.4, 58.2. 

UV/vis (CHCl 3): l max (e) ¼ 275 (49 827), 286 (46 374), 308 

(65 791), 493 (23 628). 


C 185H 320N 6O 74F 12P 2Ru (4 203.557): calcd. C 52.86, H 7.67, N 2.00; 

found C 53.35, H 7.93, N 2.04. 

General Procedure for the Hydrosilylation Reaction 

The reaction was realized in oven-dried glassware and under an 

argon atmosphere. To a degassed solution of the hydrogenterminated 

PDMS 5 (7 equivalents per allyl-group) and Karstedt’s 

catalyst (2 mL, 3 to 3.5% Pt in vinyl-terminated PDMS) in CH 2Cl 2 

(50 mL) was added the heteroleptic bis-terpyridine complex 4 

(0.2 mmol). The reaction mixture was stirred under reflux for 48 h. 

After purification by preparative size exclusion chromatography 

the PDMS-containing polymer was dried in a vacuum oven at 

40 8C. [2d] 

[(4 0 -PEG70-tpy)Ru(2a-PDMS)](PF6)2 (6a) 

1 

H NMR (CD2Cl2): d ¼ 8.82 (s, 2 H), 8.54 (d, 3 J ¼ 7.2 Hz, 2 H), 8.44 (d, 

3 3 

J ¼ 8.0 Hz, 2 H), 8.35 (s, 2 H), 8.10 (d, J ¼ 8.8 Hz, 2 H), 7.97–7.89 (m, 

4 H), 7.42 (d, 3 J ¼ 5.2 Hz, 2 H), 7.36 (d, 3 J ¼ 4.8 Hz, 2 H), 7.29–7.18 (m, 

6 H), 4.78 (mc, 2 H), 4.15–4.10 (m, 4 H), 3.85–3.43 (m, HPEG), 3.35 (s, 3 

H), 1.93 (mc, 2 H), 0.25–( )0.05 (m, HPDMS). 

29 

Si NMR (d6-acetone): d ¼ 22.53. 


UV/vis (CHCl3): l (e) ¼ 275 (23 785), 285 (21 798), 308 (29 701), 

493 (10 088). 

[(4 0 -PEG70-tpy)Ru(2b-PDMS)](PF6)2 (6b) 

1 

H NMR (CD2Cl2): d ¼ 8.79 (s, 2 H), 8.55 (mc, 2 H), 8.45 (d, 3 J ¼ 8.0 Hz, 

2 H), 8.36 (s, 2 H), 7.97–7.89 (m, 4 H), 7.74–7.63 (m, 2 H), 7.44–7.37 

(m, 4 H), 7.28–7.18 (m, 5 H), 4.78 (mc, 2 H), 4.22 (mc, 2 H), 4.15–4.10 

(mc, 4 H), 3.86–3.43 (m, HPEG), 3.36 (s, 3 H), 2.02–1.93 (m, 4 H), 0.25– 

( )0.04 (m, HPDMS). 

29 

Si NMR (d6-acetone): d ¼ 22.56. 


UV/vis (CHCl3): l (e) ¼ 276 (28 988), 285 (27 670), 308 (32 533), 

494 (11 483). 

Preparation of the Micelles 

The copolymers were dissolved in acetone (1 g L 1 ). A water 

volume equal to half the acetone volume was added by steps of 

50 mL, then the same water volume was added in one shot. The 

solution was then dialyzed against water to remove the acetone. 

The final concentration of the copolymers in pure water was about 

0.3 g L 1 . The solutions were filtered through 1 mm filters before 

measurements. 

Results and Discussion 

In an extension to previous work on metallosupramolecular 

copolymers, we chose poly(dimethylsiloxane) 

as a non-organic, hydrophobic polymer for the 

construction of new amphiphilic block copolymers. The 

transition metal-catalyzed hydrosilylation of carboncarbon 

double bonds is a highly versatile tool in modern 

organo-silicon chemistry. [1] Using the optimized, highly 

efficient one-pot procedure, we synthesized two allyloxyfunctionalized 

2,2 0 :6 0 ,2 00 -terpyridines (1) as suitable building 

blocks for the subsequent attachment of the polysiloxane 

backbone to the terpyridine moieties. [7] In order 

to avoid the possible deactivation of the labile Pt-based 

Karstedt’s catalyst by the strongly coordinating terpyridine 

ligand, all hydrosilylation reactions were carried out 

using stable transition metal complexes derived from the 

corresponding terpyridines (1). Furthermore, the special 

complexation chemistry of the Ru(III)/Ru(II) couple 

allowed the highly selective synthesis of heteroleptic 

Ru(II) bis-terpyridine complexes. This synthetic approach, 

as depicted in Scheme 1, involved the synthesis of the 

Ru(III) mono-terpyridine complexes (2) in medium to high 

yields (2a: 55%; 2b: 72%). A second terpyridine ligand (3), 

bearing the hydrophilic poly(ethylene oxide) substituent, 

was then coordinated under reducing conditions. The 

characteristic color change of the reaction mixture clearly 

indicated the formation of the red heteroleptic Ru(II) 

complexes (4). [6] 

The purified products 4a and b were fully characterized 

by GPC, 1 H NMR, UV/vis and IR. Furthermore, the existence 

and purity were confirmed by MALDI-TOF MS and 

elemental analysis for both cases. In comparison to the 

uncomplexed PEO70-macroligand 3, a significant shift of 

the signals towards higher molar mass was observed in the 

GPC curves. The GPC traces (see Figure 1 for 4b), as recorded 

with a photo diode array detector (PDA), additionally 

revealed the characteristic MLCT bands for Ru(II) bisterpyridine 

complexes at around 495 nm. The 1 H NMR 

spectrum of 4b clearly showed the signals of the two 

different terpyridine ligands in the aromatic region 

(Figure 1). Upon complexation, distinct shifts for the 

protons of the terpyridine units were monitored. 

The synthesis of the Ru(II)-containing AB-block copolymers 

(6) involved the hydrosilylation reaction of the 

allyloxy-functionalized complexes 4a and b with PDMS 5 

(Mn ¼ 4 380 Da) in the presence of the Pt(0)-based 

Karstedt’s catalyst (Scheme 1). A ten-fold excess of 5 

was used in these reactions to avoid bis-functionalization 

of the a,v-hydrogen-terminated PDMS. [2a] The hydrosilylation 

reactions were found to be quantitative and the 

isolated red metallo-polymers were characterized by UV/ 

vis, 1 H NMR and 29 Si NMR spectroscopy, as well as GPC 

after purification by preparative size exclusion chromato- 



1670 

graphy using Bio-Rad beads. Full conversion was proven by 

NMR spectroscopy. No olefinic protons could be detected in 

the 1 H NMR spectra after the reaction and the signal of the 

former allylic methylene group for 6a and b, respectively, 

b The assignment of the signals in the 29 Si NMR spectra was 

supported by NMR experiments applying decoupling methods 

(INEPT). 


Scheme 1. Schematic representation of the synthesis of the amphiphilic block copolymers A-[Ru]-B (6) by hydrosilylation reaction of the 

corresponding heteroleptic Ru(II) bis-terpyridine complexes (4). 

Figure 1. Left: GPC trace (photo diode array detector) of 4b (recorded with DMF containing 5 10 3 M NH 4PF 6). Right: 1 H NMR spectrum of 4b 

(400 MHz, CD 2Cl 2,258C). 

had shifted to higher field due to the absence of the double 

bond. Strong signals for both polymeric backbones around 

3.6 (for PEO) and 0.1 ppm (for PDMS) were observed. The 

intense signal at 22.56 ppm in the 29 Si NMR spectrum 

was assigned to the PDMS-backbone structure. b The 

characteristic MLCT band for Ru(II) bis-terpyridine complexes 

present in both the UV/vis spectra and the GPC 

chromatograms (photo diode array detector) of 6a and b 




Figure 2. Left: GPC trace (photo diode array detector) of 6b (recorded with DMF containing 5 10 3 M NH 4PF 6). Right: Normalized absorption 

spectra of 1b (dashed line), 4b (dotted line) and 6b (solid line); for all absorption spectra: 10 5 M in CHCl 3. 

gave further evidence of the formation of the hydrosilylated 

products (see Figure 2 for 6b). 

So far, studies on the formation of (supramolecular) 

micelles containing polysiloxanes as hydrophobic blocks 

in water are very rare. [8] In a continuation of our work on 

supramolecular amphiphilic materials, we also investigated 

the micellization behavior of the two synthesized 

metallo-supramolecular copolymers 6a and b in water. [9] 

Since these samples were not readily soluble in water, 

they were initially dissolved in a non-selective solvent, 

acetone, to which water was gradually added. Acetone was 

removed by dialysis and the micellar aqueous solutions 

were subsequently investigated by dynamic light scattering 

(DLS). No dependence of the DLS data on the concentration 

of the micellar solution was observed. The results 

were analyzed by the CONTIN method, which provides 

access to a size distribution histogram of the micelles. [10] A 

typical CONTIN histogram observed for sample 6b is 

shown in Figure 3. The results are in good agreement with 

the formation of well-defined micelles with a moderate 

size polydispersity and a R h of 58 nm, as measured from 

the maximum of the size histogram. 

The morphology of the micelles was further investigated 

by cryogenic transmission electron microscopy 

(cryo-TEM). A typical TEM micrograph of the micelles 

formed by 6b is shown in Figure 3. In comparison to 

the DLS data, the aggregates visualized by this technique 

are much smaller and show a broad size distribution. The 

aggregates are displayed as dark circular objects with a 

diameter between 10 and 20 nm on a lighter background. 

These micelles consist of a core, which is composed of the 

hydrophobic poly(dimethylsiloxane) block, and the corona, 

which is composed of the solvated poly(ethylene oxide) 

chains. Because of the differences in density of the micellecore 

and the surrounding solvated corona chains, as well as 

a higher scattering probability inside the core due to the 

presence of comparably heavier Si atoms and the heavy 

metal-based complexes, the cryo-TEM technique only 

images the core of the micelles. The average radius of 

the micelles was determined to be 6.46 for a set of over 70 

micelles and a standard deviation of 1.64 nm was observed 

with maximum and minimum micelle diameters of 8 and 

28 nm, respectively. However, the average size of 6.5 nm 

seems reasonable, considering the scaling predictions for 

Figure 3. CONTIN size distribution histogram obtained from aqueous micelles formed by 6b (left) and cryo-TEM image of the same micelles 

in the vitrified state (right). 



1672 

hairy-type micelles [Equation (1)], [11] in which RC denotes 

the radius of the micellar core, NB the degree of polymerization 

for the non-soluble block and a represents a 

scaling factor correlating to the size of the monomer unit. 

RC / a N 3 = 5 

B 

Substituting the observed micellar radius from cryo- 

TEM and the degree of polymerization into the equation 

gives a value of about 0.58 nm for the scaling factor a. 

Although this value cannot be directly interpreted as a size 

of the dimethylsiloxane monomer unit, its value seems 

reasonable and indicates the formation of well-defined 

hairy-type micelles. [12] 

In conclusion, these results confirm that stable spherical 

micelles can be obtained from the amphiphilic block 

copolymers investigated in this study. 

Conclusion 

We have reported the first synthesis of two new metallosupramolecular 

A-[M]-B diblock copolymers, consisting of 

a hydrophilic poly(ethylene oxide) block A and a hydrophobic 

poly(dimethylsiloxane) block B linked together by a 

Ru(II) bis-terpyridine complex. In order to circumvent the 

possible deactivation of the labile Pt(0)-catalyst by the 

strongly chelating terpyridine moieties, the synthesis was 

performed by a straightforward Pt(0)-catalyzed hydrosilylation 

of allyloxy-functionalized Ru(II)-precursor complexes. 

Additionally, well-defined micelles of the amphiphilic 

supramolecular materials, showing a moderate size 

polydispersity, were observed in aqueous medium applying 

dynamic light scattering (DLS) and cryogenic transmission 

electron microscopy (cryo-TEM). 

Acknowledgements: The authors would like to thank the Nederlands 

Organisatie voor Wetenschappelijk Onderzoek (VICI award 

for U. S. Schubert) and the Fonds der Chemischen Industrie for 

financial support of this research. We also acknowledge PSS 

Polymer Standards Service GmbH, Mainz/Germany, for performing 

gel permeation chromatography of PDMSs, as well as 

H. Marsmann and H. Egold, both from Paderborn University, 

Germany, for the 29 Si NMR measurements. TEM imaging was 

carried out with the support of the cryo-TEM research unit, 

Eindhoven University of Technology. CAF and JFG thank the 

STIPOMAT ESF Programme and the ‘‘Politique Scientifique 

Fédérale’’ for financial support in the frame of the ‘‘Interuniversity 

Attraction Poles Programme (PAI VI/27): Functional Supramolecular 

Systems’’. CAF is Research Associate of the FRS-FNRS. 

Received: April 26, 2008; Accepted: May 15, 2008; DOI: 10.1002/ 

macp.200800219 

(1) 


Keywords: metallo-supramolecular copolymers; micelles; poly- 

(dimethylsiloxane); supramolecular structures; terpyridines 

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