Synthesis and characterization of dendritic platinum bisferrocenylacetylide complexes

Article abstract of DOI:10.1139/v11-159

A series of new dendritic platinum bisferrocenylacetylide complexes have been synthesized utilizing the coupling reaction of trans-Pt complexes with C-H bonds in alkynes as key steps. These new bimetallic dendrimers were fully characterized by multinuclea

Full text of DOI:10.1139/v11-159

278
Synthesis and characterization of dendritic
platinum bisferrocenylacetylide complexes
Qing Han, Li-Jun Chen, Hai-Bo Yang, Quan-Jie Li, Jiuming He, Hongwei Tan,
Zeper Abliz, and Cui-Hong Wang
Abstract: A series of new dendritic platinum bisferrocenylacetylide complexes have been synthesized utilizing the coupling
reaction of trans-Pt complexes with C–H bonds in alkynes as key steps. These new bimetallic dendrimers were fully charac-
terized by multinuclear NMR (1H, 13C, and 31P) and mass spectrometry (MALDI-TOF-MS and CSI-TOF-MS). Electrochem-
ical studies of these complexes were carried out and revealed that all of the redox moieties are stable, independent, and
electrochemically active. In addition, all metallodendrimers show one-electron reaction responses, and the increased sizes of
these complexes did not exhibit a dramatic influence on the diffusion coefficient.
Key words: metallodendrimer, platinum biferrocenylacetylide complex, electrochemistry.
Résumé : On a réalisé la synthèse d’une série de nouveaux complexes dendritiques du bisferrocénylacétylure de platine en
utilisant comme étapes clés une réaction de couplage de complexes trans du platine avec les liaisons C–H d’alcynes. Ces
nouveaux dendrimères bimétalliques ont été complètement caractérisés par RMN multinucléaire (1H, 13C et 31P) et par spec-
trométrie de masse en temps de vol (SM-TDV) avec ionisation par désorption au laser d’une matrice (« MALDI ») ou avec
ionisation par nébulisation à froid (INF). On a effectué des études électrochimiques de ces complexes qui révèlent que toutes
les portions redox sont stables, indépendantes et électrochimiquement actives. De plus, tous les métallodendrimères donnent
des réponses avec des réactions un électron et l’augmentation de la taille de ces complexes n’influence pas d’une façon dra-
matique le coefficient de diffusion.
Mots‐clés : métallodendrimère, complexe de bisferrocénylacétylure de platine, électrochimie.
[Traduit par la Rédaction]
ple, we reported the fabrication of a new family of metallo-
dendrimers possessing well-defined and controllable cavities
as cores via coordination-driven self-assembly.12 Recently,
our research interests have turned to the fabrication of het-
erometallic dendrimers connected by unsaturated carbon-rich
bridges.
The carbon-rich organometallic complexes containing rigid
p-conjugated chains have attracted considerable attention in
the past few decades.13 By taking advantage of the linear ge-
ometry of the alkynyl unit and its p-unsaturated character,
the metal alkynyls have been extensively explored to prepare
molecular wires and polymeric organometallic materials,
which may possess interesting properties such as optical non-
linearity, luminescence, liquid crystallinity, and electrical
conductivity.14 In particular, the complexes with mixed-
valence bimetallic skeletons have evolved to be important
design targets for investigations into molecular electronic
devices and chemical-sensing applications because of the
possible charge delocalization along the entire conjugated
backbone.15,16
Introduction
Dendrimers1 are globular, highly branched macromolecules
with a “well-defined” three-dimensional shape, size, and mo-
lecular weight. Usually, these branched macromolecules are
comprised of several dendritic wedges extending outward
from an internal core via interactive or stepwise procedures.
In the past two decades, the design and synthesis of diverse
dendrimers has received increasing attention,2 not only be-
cause of their aesthetically pleasing structures but also as a
result of their various applications in host–guest chemistry,3
material science,4 and membrane chemistry.5 Since the pio-
neering work by Newkome et al.6 and Balzani and co-workers7
in the early 1990s, metallodendrimers8,9 have evolved to be
one of the most attractive fields within supramolecular
chemistry. The incorporation of metal ions to the dendritic
framework usually gives rise to new properties for the cor-
responding metallodendritic architectures, such as novel
physical, optical, electrochemical, photochemical, biological,
and catalytic properties.10,11 Thus, numerous efforts have
been taken to construct new metallodendrimers. For exam-
Received 30 August 2011. Accepted 19 October 2011. Published at www.nrcresearchpress.com/cjc on 8 February 2012.
Q. Han, L.-J. Chen, H.-B. Yang, and C.-H. Wang. Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department
of Chemistry, East China Normal University, Shanghai 200062, P.R. China.
Q.-J. Li and H. Tan. Department of Chemistry, Beijing Normal University, Beijing 100875, P.R. China.
J. He and Z. Abliz. Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing
100050, P.R. China.
Corresponding author: Cui-Hong Wang (e-mail: chwang@chem.ecnu.edu.cn)
Can. J. Chem. 90: 278–289 (2012)
doi:10.1139/V11-159
Published by NRC Research Press

Han et al.
279
Ferrocene, as a stable and readily oxidizable organometal-
7a–7c, by using similar procedures to those reported in pre-
vious studies.22d,23d Subsequent coupling reactions of 7a–7c
with ferrocenylacetylene resulted in the target Pt–Fe bimetal-
lic dendrimers with a 60° orientation. Another series of 120°
dendritic platinum–bisferrocenylacetylide complexes were ob-
tained through similar procedures from known dendritic diio-
dometal complexes 8a–8c12d as outlined in Scheme 2. In all
cases, the desired complexes were purified by column chro-
matography on silica gel using dichloromethane as eluent
and were obtained as yellow glassy solids with high purities.
They exhibited good solubility in common organic solvents
such as CH2Cl2 and CHCl3. Moreover, these newly designed
metallodendrimers are air- and humidity-stable at room tem-
perature.
lic complex, has been widely utilized in multifunctional
compounds because of its potential to be used in electrolumi-
nescence, information storage, and photochemical devices.17,18
With their importance to material chemistry, there is in-
creasing interest in the construction of novel ferrocenyl bi-
metallic oligomers or polymers.19 For example, in the early
1990s, the synthesis and oxidation of Pt(II)–, Ru(II)–, Os
(II)–, and Mn(I)–ferrocenylacetylide complexes were re-
ported by the groups of Sato, Werner, Wong,20 and Wolf.21
After that the possibility of nonlinear optical response and
the important role of the mixed-valence states in these com-
plexes have been extensively investigated. For instance,
Wolf and co-workers21 synthesized a series of novel ruthe-
nium(II) bisferrocenylacetylide complexes and investigated
the effect of ancillaryl ligands on electronic delocalization.
In the past decade, the design and construction of plati-
num–acetylide dendrimers has attracted a great deal of atten-
tion because of their potential to provide new nano-sized
organometallic materials.18 For instance, Takahashi and co-
workers22a reported the preparation of a new family of platinum–
acetylide dendrimers possessing a porphyrin core. These
novel dendrimers exhibited intramolecular energy transfer
from platinum–acetylide moieties to the porphyrin core. In-
spired in part by our successful results on the synthesis of
platinum–acetylide building blocks,12d,23b–23e we envisioned
that the synthesis of new platinum–bisferrocenylacetylide
dendrimers with different spatial orientations would be real-
ized by the proper choice of precursors with predefined an-
gles and symmetry. It is noted that bimetallic
metallodendrimers are of interest because of a variety of
materials and synthetic applications.22a,22b,23g In addition,
the possibility of fine-tuning the size and spatial orientation
of the metallodendrimers would help provide enhanced
understanding of the geometrical influence on the photo-
and electro-chemical properties. Herein, we designed and
synthesized two series of platinum–bisferrocenylacetylide
dendrimers with different spatial orientations (60° and
120°) (Chart 1). The structures of all complexes were char-
acterized by multinuclear NMR (1H, 13C, and 31P) and mass
spectrometry (MALDI-TOF-MS and CSI-TOF-MS), and
their electrochemical behavior was investigated.
Structure characterization
Multinuclear NMR (1H, 13C, and 31P) analysis of all bimet-
allic acetylide complexes revealed the formation of discrete
highly symmetric species. The room-temperature 31P NMR
spectra of dendritic complexes 1a–1c and 2a–2c displayed a
sharp singlet (ca. d = 11.5 ppm) accompanied by platinum
satellites (ca. J
= 2380 Hz), which is consistent with the
Pt-P
trans configuration around the Pt(II) atom. It should be noted
that the singlet in the 31P NMR spectra of 1a–1c and 2a–2c
exhibited a small downfield shift from the diiodometal pre-
cursors by ~2.3 ppm (Fig. 1). This change, as well as the in-
crease in coupling of the flanking 195Pt satellites (ca.
DJ = +60 Hz), might be caused by the electron-withdrawing
effect of the large p-conjugate bridges. Moreover, with the
increase in the generation of dendrimers, 31P NMR spectra
1
of complexes do not display obvious changes. The H NMR
spectra of 1a–1c exhibited characteristic phenanthrene proton
resonances in the aromatic area, one singlet and two dou-
1
blets. Compared with the diPt(II) precursors 7a–7c, the H
NMR spectra of 1a–1c show that some proton resonances in
the phenanthrene ring displayed slight downfield shifts owing
to the electron-withdrawing effect of the large p-conjugate
bridges. For example, the singlet (d 8.51 ppm) of 1c showed
an ~0.03 ppm downfield shift from 8.48 ppm in the spectrum
1
of 7c. Likewise, the analysis of the H NMR spectra of 2a–
2c agrees well with the characterization of 120° bimetallic
acetylide dendrimers.
Usually MALDI-TOF-MS studies allow the complexes to
remain intact during the analysis process and provide the
high resolution required for the unambiguous determination
of their absolute molecular weight and molecularity.
MALDI-TOF-MS investigation of bimetallic acytelide den-
drimers 1a–1c and 2a–2c were carried out first. Because of
high molecular weights and complex isotope splitting of
such multimetallic dendrimers, it is difficult to get strong
mass signals even under the MALDI-TOF-MS conditions.
With considerable effort, satisfactory high-resolution
MALDI-TOF-MS results of 1a and 2a and 2b were found,
confirming the structure of such bimetallic complexes. To ob-
tain the higher resolution of mass spectrometric studies for
the other complexes, CSI-TOF-MS studies of 1b, 1c, and 2c
were performed. In the CSI-TOF-MS spectrum of 1b, the
peak at m/z = 2124.0, corresponding to the charge state
[M + H]+, was observed, and its isotopic resolution is in ex-
cellent agreement with the theoretical distribution (see Sup-
plementary data). Moreover, the peaks at m/z = 1495.2 for
Results and discussion
Synthesis of dendritic platinum–bisferrocenylacetylide
complexes
The acidity of C–H bonds in alkynes induced by transition
metals has received considerable attention in organometallic
chemistry.23 Herein, we utilized the coupling reaction of
trans-Pt complexes with C–H bonds in alkynes as key steps
to the synthesis of all dendritic bimetallic complexes. Com-
plexes 1a–1c were easily prepared in five steps as indicated
in Scheme 1. Fréchet-type dendrons were introduced by an
etherification reaction of 3 with corresponding dendritic bro-
mides. From dendritic 3,6-dibromophenanthrene derivatives
4a–4c, dendritic 3,6-diethynylphenanthrenes 6a–6c were ob-
tained by the coupling reaction with (trimethylsilyl)acetylene,
followed by deprotection with K2CO3 in a mixture of metha-
nol and THF. Compounds 6a–6c were then reacted with
4 equiv of trans-PtI2(PEt3)2 to give diiodometal complexes
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280
Can. J. Chem. Vol. 90, 2012
Chart 1.
1c and m/z = 1505.3 for 2c were found in the CSI-TOF-MS
spectra of [G-3] bimetallic acetylide dendrimers, which corre-
sponds to the [M + 2H]2+ charge state. These peaks were
isotopically resolved and agree well with their theoretical dis-
tribution (Fig. 2).
spectrum of each compound, the approximate mirror symme-
try with the respect to the lowest energy absorption bands
was observed, which indicated that the same optical transi-
tion was involved in both absorption and emission processes.
In addition, a small Stokes shift was found in each fluores-
cence spectrum, indicating that the emission emanates from
the lowest singlet state. It should be noted that the emission
bands are only slightly influenced by the increase of dendritic
generations.
Simulated molecular models
Flexible high-generation dendrimers often prove difficult
to crystallize. All attempts to grow X-ray quality single crys-
tals of dendritic bimetallic complexes 1a–1c and 2a–2c have
proven to be unsuccessful to date. Thus, PM6 semiempirical
molecular orbital method was employed to optimize the ge-
ometry of all dendritic platinum–bisferrocenylacetylide com-
plexes. In the optimized structures of all bimetallic
complexes, the ferrocene moieties and phenyl acetylides are
s-bonded to platinum in a trans configuration with 60° and
120° spatial orientations, respectively, whereas the dendrons
position on the other side. Coordination around the platinum
atoms is square-planar, with slight tetrahedral distortions.
Moreover, the distance between two Fe atoms is about
1.7 nm for 1a–1c and 2.4 nm for 2a–2c (Fig. 3; also see Sup-
plementary data).
Electrochemistry properties
The electrochemical behavior of these platinum–acetylide
biferrocenyl dendrimers has been investigated via cyclic vol-
tammetry (CV) (Table 2). The study was performed in a di-
chloromethane solution of 1a–1c and 2a–2c containing
0.2 mol/L n-Bu4NPF6 as the supporting electrolyte at a
~7.0 mm2 glassy carbon electrode. The cyclic voltammo-
grams corresponding to the one-electron oxidation of the fer-
rocene groups yielded anodic to cathodic peak current ratios
of ia/ic ≈ 1 (Fig. 4; also see Supplementary data). Moreover,
it was found that the oxidation of the ferrocene moieties in
each complex was reversible, which was indicated by the
nearly identical cathodic and anodic peak currents, as well
as nearly scan-rate-independent peak potentials. The differ-
ence between the anodic and cathodic peak potentials (DEp)
measured at different scan rates was found to be larger than
the theoretical value of 59 mV expected for a reversible one-
electron redox reaction, a consequence of the solution ohmic
resistance.
With the aim of obtaining the effects of dendron subunits
in the electrochemical properties of ferrocenes, the further cy-
clic voltammetry of these complexes was carried out to gain
the diffusion coefficients (D). Different from our previous re-
ports,12 the D values did not change dramatically with an in-
crease in the molecular weight and molecular size in this
study. These results indicate that the dendron moieties are lo-
cated far from the electrochemical active centers and do not
influence the electrochemical activity of ferrocenyl groups,
which has been supported by the optimized structures.
Absorption and emission properties
The absorption and emission properties of this series of
platinum–acetylide biferrocenyl dendrimers were studied in
dilute dichloromethane solution (ca. 10–5 mol/L) and the
data are collected in Table 1. The electronic absorption spec-
tra of metallodedrimers 1a–1c displayed absorption bands in
the range of 264–336 and 357–381 nm. Likewise, the ab-
sorption spectra of 2a–2c were dominated by intense rela-
tively broad bands in the near-UV region with strong
transitions at higher energy. The dominant absorption band
was described as metal-to-ligand charge transfer (MLCT)
transitions according to a similar previous report.24 Upon
photo excitation, all metallodendrimers show weak lumines-
cence in dichloromethane solution at room temperature. For
example, upon being excited at 362 nm, 1a–1c feature a
band with a maximum at 406–409 nm in dilute dichlorome-
thane solution (ca. 10–5 mol/L). Furthermore, in the emission
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Han et al.
281
Scheme 1. Synthetic route of complexes 1a–1c.
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282
Can. J. Chem. Vol. 90, 2012
Scheme 2. Synthetic route of complexes 2a–2c.
Fig. 1. Partial 31P NMR (400 MHz, CDCl3, 298 K) spectra of 7c
(A) and 1c (B).
vents (CDCl3) and all other reagents were purchased and
used without further purification.
Physical measurements and instrumentation
1H, 13C, and 31P NMR spectra were recorded on a Bruker
300 MHz spectrometer (1H: 300 MHz; 13C: 75 MHz; and
31P: 121.4 MHz) at 298 K or a 400 MHz spectrometer (1H:
400 MHz; 13C: 100 MHz; and 31P: 162 MHz) at 298 K. The
1H and 13C NMR chemical shifts are reported relative to re-
sidual solvent signals, and 31P NMR resonances are refer-
enced to an internal standard sample of 85% H3PO4 (d 0.0).
Coupling constants (J) are in Hz and chemical shifts (d) are
in ppm. Multiplicities are denoted as follows: s = singlet,
d = doublet, m = multiplet, and t = triplet. ESI-MS and EI -MS
were recorded on an Agilent 5973N mass spectrometer using
electrospray or electron ionization. MALDI-HRMS was re-
corded on a Waters GCT Premier mass spectrometer. CSI-
TOF-MS was recorded on a JMS-T100LC mass spectrome-
ter using electrospray ionization.
Spectroscopic measurements
UV–vis spectra were recorded on a Cary 50 Bio UV–vis
spectrophotometer. Emission spectra were measured on a
Cary Eclipse luminescence spectrometer. Samples for absorp-
tion and emission measurements were contained in 1 cm
quartz cuvettes. CV was performed using a three-electrode
cell and a RST electrochemical work station. The working
electrode was a glassy carbon disk with a surface area of
~7.0 mm2. A SCE electrode was used as reference electrode
and a Pt wire as the counter electrode.
Experimental section
General comments
Materials and reagents
Synthesis of 4a–4c
Under an atmosphere of nitrogen, 3 (772 mg, 2.10 mmol),
[G-n]-Br (for G0, 0.59 mL, 4.83 mmol; for G1, 1.85 g,
Toluene and THF was distilled from sodium and diethyl-
amine was dried over potassium hydroxide. All solvents
were degassed under N2 for 30 min before use. NMR sol-
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Han et al.
283
Fig. 2. Calculated (top trace) and experimental (bottom trace) CSI-TOF-MS spectra of [G-3] bimetallic dendrimers 1c (A) and 2c (B).
Fig. 3. Simulated molecular model of [G-3] complexes 1c (A) and 2c (B) optimized with the PM6 semiempirical molecular orbital method.
Table 1. UV–vis absorption and emission data for complexes 1a–1c and 2a–2c.
No.
1
2
3
4
Complex
Absorbance (lmax, nm)
264, 335, 359, 378
264, 336, 358, 381
265, 335, 357, 380
264, 288, 334
30 ((mol/L)–1 cm–1)
Emission (lmax, nm)
406, 420
409
1a
1b
1c
2a
2b
2c
56007, 42191, 40964, 37052
54739, 40499, 39590, 35607
54247, 37567, 35417, 30815
45204, 39842, 41519
47075, 42130, 41216
43241, 51956, 42752
408
405, 424
403, 422
409
5
6
265, 286, 335
268, 285, 334
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Can. J. Chem. Vol. 90, 2012
Table 2. Cyclic voltammetry data for complexes 1a–1c and
2a–2c (CH2Cl2 with 0.2 mol/L n-Bu4NPF6, 298 K).
Synthesis of 5a–5c
To a 50 mL round-bottomed Schlenk flask were added
4a–4c (4a, 200 mg, 0.36 mmol; 4b, 250 mg, 0.26 mmol;
and 4c, 300 mg, 0.16 mmol), trimethylsilylethyne (for G1,
0.41 mL, 2.88 mmol; for G2, 0.30 mL, 2.08 mmol; and for
G3, 0.19 mL, 1.28 mmol), Pd(PPh3)4 (for G1, 42 mg; for
G2, 30 mg; and for G3, 19 mg), and CuI (for G1, 7.0 mg;
for G2, 5.0 mg; and for G3, 3.0 mg). Then a mixture of tet-
rahydrofuran (for G1, 4.0 mL; for G2, 3.0 mL; and for G3,
2.0 mL) and dry diethylamine (for G1, 4.0 mL; for G2,
3.0 mL; and for G3, 2.0 mL) was added under nitrogen. The
solution was stirred at 66 °C for 24 h. The solvent was re-
moved under vacuum and the resulting yellow residue was
purified via column chromatography on silica gel (dichloro-
methane / petroleum ether, ~1:2) to provide compounds 5a–
5c (yields: G1, 91%; G2, 90%; and G3, 78%).
N-
o.
1
2
3
4
5
6
Complex
E1/2 (V vs SCE)
0.339 0.002
0.332 0.003
0.323 0.002
0.348 0.001
0.340 0.001
0.323 0.003
105 D (cm2 s–1)
1.19 0.02
1.09 0.02
1.07 0.02
1.04 0.01
1.04 0.01
0.97 0.01
1a
1b
1c
2a
2b
2c
Note: E1/2, half-wave potential; D, diffusion coefficient.
4.83 mmol; for G2, 3.9 g, 4.83 mmol), and K2CO3 (2.9 g,
21.0 mmol) were dissolved in DMF (25 mL). The mixture
was heated at reflux for 18 h and then cooled to room tem-
perature. Solvent was distilled and the resulting mixture was
poured into water and extracted with methylene chloride (3 ×
15 mL). The methylene chloride solution was washed with
water, dried over anhydrous magnesium sulfate, and filtered.
The crude products were purified by column chromatography
on silica gel (dichloromethane / petroleum ether, ~1:1) to give
compounds 4a–4c.
Synthesis of 6a–6c
Desilylation of 5a–5c (5a, 105 mg, 0.18 mmol; 5b,
182 mg, 0.18 mmol; and 5c, 335 mg, 0.18 mmol) was
achieved by stirring the compounds in a K2CO3 suspending
solution of methanol–THF (100 mg in 20 mL methanol and
20 mL THF) for 4 h. The solution was carefully diluted with
30 mL of water and organic product was extracted with di-
ethyl ether. Drying the ether phase over magnesium sulfate
and subsequent filtration resulted in slightly yellow oil after
removal of the solvent. Compounds 6a–6c were obtained by
column chromatography on silica gel (dichloromethane /
petroleum ether, ~1:1).
4a
Yield (white solid): 0.58 g, 65%; mp 192 °C. Rf 0.74 (di-
chloromethane / petroleum ether, 1;1). 1H NMR (CDCl3,
300 MHz) d: 8.66 (s, H1, 2H), 8.10 (d, H2, J = 8.7 Hz, 2H),
7.69 (d, H3, J = 6.3 Hz, 2H), 7.52–7.49 (m, PhH, 4H), 7.43–
7.36 (m, PhH, 6H), 5.27 (s, PhCH2O, 4H). 13C NMR
(CDCl3, 75 MHz) d: 143.2, 136.9, 130.6, 129.0, 128.6,
128.4, 125.4, 124.3, 120.6, 75.5. MALDI-HRMS for 4a m/z
calcd for C28H20Br2O2Na ([M + Na]+): 568.97; found:
569.00.
6a
Yield (pale yellow solid): 92 mg, 88%; mp 138 °C. Rf 0.31
(dichloromethane / petroleum ether, 1:3). 1H NMR (CDCl3,
400 MHz) d: 8.76 (s, H1, 2H), 8.19 (d, H2, J = 8.0 Hz, 2H),
7.68 (d, H3, J = 8.8 Hz, 2H), 7.53–7.51 (m, H3 and PhH,
4H), 7.41–7.39 (m, PhH, 6H), 5.28 (s, PhCH2O, 4H), 3.22
(s, C≡CH, 2H). 13C NMR (CDCl3, 100 MHz) d: 144.0,
137.1, 130.2, 129.5, 128.6, 128.4, 128.3, 127.8, 126.9,
122.7 119.8, 84.0, 77.9, 75.6. EI HRMS of 6a m/z calcd for
C32H22O2: 438.1620 (M+); found: 438.1623.
4b
Yield (white glassy solid): 0.92 g, 45%; mp 152 °C. Rf
0.50 (dichloromethane / petroleum ether, 3:1). 1H NMR
(CDCl3, 300 MHz) d: 8.67 (d, H1, J = 1.5 Hz, 2H), 8.08 (d,
H2, J = 8.7 Hz, 2H), 7.69 (d, H3, J = 9.0 Hz, 2H), 7.37–7.29
(m, PhH, 20H), 6.74 (d, PhH, J = 2.1 Hz, 4H), 6.57 (t, PhH,
J = 2.1 Hz, 2H), 5.18 (s, PhCH2O, 4H), 4.93 (s, PhCH2O,
8H). 13C NMR (CDCl3, 75 MHz) d: 160.1, 143.1, 139.3,
136.7, 130.7, 129.1, 128.6, 128.3, 128.0, 127.5, 125.5,
124.3, 120.7, 106.9, 101.9, 75.3, 70.1. MALDI-HRMS of
4b m/z calcd for C56H44Br2O6Na ([M + Na]+): 993.14;
found: 993.20.
6b
Yield (pale yellow solid): 160 mg, 88%; mp 104 °C. Rf
0.31 (dichloromethane / petroleum ether, 1:1). 1H NMR
(CDCl3, 400 MHz) d: 8.77 (s, H1, 2H), 8.17 (d, H2, J =
8.4 Hz, 2H), 7.68 (d, H3, J = 8.4 Hz, 2H), 7.36–7.33 (m,
PhH, 20H), 6.76 (s, PhH, 4H), 6.56 (s, PhH, 2H), 5.20 (s,
PhCH2O, 4H), 4.92 (s, PhCH2O, 8H), 3.23 (s, C≡CH, 2H).
13C NMR (CDCl3, 100 MHz) d: 160.1, 143.9, 139.4, 136.7,
130.3, 129.4, 128.6, 128.0, 127.5, 127.0, 122.6, 119.9, 106.9,
101.9, 84.0, 78.0, 75.3, 70.1. ESI HRMS of 6b m/z calcd for
C60H46NaO6 ([M + Na]+): 885.3187; found: 885.3175.
4c
Yield (white glassy solid): 1.45 g, 38%; mp: 46 °C. Rf
0.36 (dichloromethane / petroleum ether, 4:1). 1H NMR
(CDCl3, 400 MHz) d: 8.65 (s, H1, 2H), 8.09 (d, H2, J =
8.8 Hz, 2H), 7.69 (d, H3, J = 6.3 Hz, 2H), 7.34–7.28 (m,
PhH, 40H), 6.72 (s, PhH, 4H), 6.62 (s, PhH, 8H), 6.51 (s,
PhH, 6H), 5.15 (s, PhCH2O, 4H), 4.93 (s, PhCH2O, 16H),
4.82 (s, PhCH2O, 8H). 13C NMR (CDCl3, 100 MHz) d:
160.1, 160.0, 143.2, 139.4, 139.2, 136.7, 130.7, 129.1,
128.5, 128.3, 127.9, 127.5, 124.3, 120.8, 106.8, 106.4,
102.0, 101.6, 70.0, 69.9. MALDI-HRMS of 4c m/z calcd for
C112H92Br2O14Na ([M + Na]+): 1841.48; found: 1841.60.
6c
Yield (pale yellow solid): 241 mg, 72%; mp 42 °C. Rf 0.38
(dichloromethane / petroleum ether, 3:1). 1H NMR (CDCl3,
400 MHz) d: 8.76 (s, H1, 2H), 8.19 (d, H2, J = 6.8 Hz, 2H),
7.69 (d, H3, J = 6.4 Hz, 2H), 7.34–7.30 (m, PhH, 40H), 6.73
(s, PhH, 4H), 6.63 (s, PhH, 8H), 6.51 (s, PhH, 6H), 5.17 (s,
PhCH2O, 4H), 4.93 (s, PhCH2O, 16H), 4.82 (s, PhCH2O,
8H), 3.20 (s, C≡CH, 2H). 13C NMR (CDCl3, 100 MHz) d:
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Han et al.
285
Fig. 4. Cyclic voltammograms of 1c (A) and 2c (C) at a scan rate of 25–250 mV/s and plot of the experimental ratio i vs v1/2 at a scan rate of
25–250 mV/s (B for 1c and D for 2c). i, intensity of electric current; v, voltage.
160.1, 160.0, 143.9, 139.5, 139.2, 136.8, 130.3, 129.4, 128.5,
128.4, 127.9, 127.5, 127.0, 122.6, 120.0, 106.8, 106.4, 102.0,
101.6, 84.0, 78.1, 70.0, 69.9. MALDI-HRMS for 13C NMR
(CDCl3, 100 MHz) d: 160.1, 160.0, 143.9, 139.5, 139.2,
136.8, 130.3, 129.4, 128.5, 128.4, 127.9, 127.5, 127.0,
122.6, 120.0, 106.8, 106.4, 102.0, 101.6, 84.0, 78.1, 75.3,
70.0, 69.9. ESI HRMS of 6c m/z calcd for C116H94NaO14
([M + Na]+): 1733.6541; found: 1733.6473.
8.8 Hz, 2H), 7.55–7.49 (m, H3 and PhH, 6H), 7.43–7.36 (m,
PhH, 6H), 5.24 (s, PhCH2O, 4H), 2.28–2.27 (m, PhCH2CH3,
24H), 1.25–1.18 (m, PhCH2CH3, 36H). 13C NMR (CDCl3,
100 MHz) d: 143.2, 137.6, 129.7, 128.5, 128.3, 128.1,
127.1, 125.9, 124.2, 122.1, 75.4, 16.9, 16.7, 16.6, 8.5, 8.4,
1
8.2. 31P NMR (CDCl3, 161.9 Hz) d: 9.18 (s, JPt–P
=
2323.3 Hz). MALDI-HRMS of 7a m/z calcd for
C56H81I2O2P4Pt2 ([M + H]+): 1553.26; found: 1552.90.
7b
Synthesis of 7a–7c
Yield (yellow solid): 107 mg, 60%; mp 55 °C. Rf 0.57 (di-
chloromethane / petroleum ether, 3:1). 1H NMR (CDCl3,
400 MHz) d: 8.47 (s, H1, 2H), 8.09 (d, H2, J = 8.8 Hz, 2H),
7.51 (d, H3, J = 8.0 Hz, 2H), 7.38–7.32 (m, PhH, 20H), 6.80
(s, PhH, 4H), 6.56 (s, PhH, 2H), 5.19 (s, PhCH2O, 4H), 4.93
(s, PhCH2O, 8H), 2.28 (br, PhCH2CH3, 24H), 1.26–1.19 (m,
PhCH2CH3, 36H). 13C NMR (CDCl3, 100 MHz) d: 160.1,
143.0, 139.9, 136.8, 129.8, 128.5, 128.0, 127.6, 126.0,
To a solution of CuI (4 mg, 0.02 mmol) and Pt(PEt3)2I2
(254 mg, 0.37 mmol) in 12 mL THF and 5 mL diethylamine
was added dropwise to a solution of compound 6a, 6b, or 6c
(6a, 40 mg, 0.09 mmol; 6b, 78 mg, 0.09 mmol; or 6c,
154 mg, 0.09 mmol)) in THF (3 mL) under an atmosphere
of nitrogen. The mixture was stirred at room temperature for
3 h. The solvent was removed in vacuo and the residue was
purified via column column chromatography with dichloro-
methane as eluent afforded the products 7a–7c as a yellow
solid.
124.2, 122.1, 106.9, 101.8, 90.9, 75.1, 70.1, 16.9, 16.7,
1
16.6, 8.4. 31P NMR (CDCl3, 161.9 Hz) d: 9.17 (s, JPt–P
=
2323.3 Hz).
7a
7c
Yield (pale yellow solid): 78 mg, 56%; mp 180 °C. Rf =
0.45 (dichloromethane / petroleum ether, 1:1). 1H NMR
(CDCl3, 400 MHz) d: 8.46 (s, H1, 2H), 8.11 (d, H2, J =
Yield (yellow solid): 150 mg, 49%; mp 49 °C. Rf 0.54 (di-
chloromethane / petroleum ether, 6:1). 1H NMR (CDCl3,
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286
Can. J. Chem. Vol. 90, 2012
400 MHz) d: 8.48 (s, H1, 2H), 8.12 (d, H2, J = 8.4 Hz, 2H),
7.53 (d, H3, J = 7.6 Hz, 2H), 7.34–7.29 (m, PhH, 40H), 6.78
(s, PhH, 4H), 6.63 (s, PhH, 8H), 6.51 (s, PhH, 6H), 5.16 (s,
PhCH2O, 4H), 4.93 (s, PhCH2O, 16H), 4.82 (s, PhCH2O,
8H), 2.27 (br, PhCH2CH3, 24H), 1.26–1.17 (m, PhCH2CH3,
36H). 13C NMR (CDCl3, 100 MHz) d: 160.1, 143.1, 140.0,
139.2, 136.8, 129.9, 128.5, 128.3, 127.9, 127.5, 127.0,
122.0, 106.7, 106.5, 101.8, 101.6, 75.2, 70.0, 69.9, 16.9,
8H), 4.26 (s, Fc–H, 4H), 4.16 (s, Fc–H, 10H), 4.08 (s, Fc–
H, 4H), 2.35–2.33 (m, PhCH2CH3, 24H), 1.39–1.27 (m,
PhCH2CH3, 36H). 13C NMR (CDCl3, 100 MHz) d: 160.1,
160.0, 140.1, 139.2, 136.8, 128.5, 127.9, 127.5, 106.7,
106.5, 101.6, 70.3, 70.0, 69.9, 69.4, 67.0, 16.6, 16.4, 16.3,
1
8.5. 31P NMR (CDCl3, 161.9 Hz) d: 11.4 (s, JPt–P
=
2379.9 Hz). CSI-TOF-MS of 1c m/z calcd for
C164H172Fe2O14P4Pt2 ([M + 2H]2+): 1495.00; found: 1495.20.
16.8, 16.6, 8.4. 31P NMR (CDCl3, 161.9 Hz) d: 9.24 (s, 1JPt–P
=
2321.6 Hz).
Synthesis of 2a–2c
The synthetic procedure of 2a–2c was similar to that for
1a–1c except that 120° [G-1]–[G-3] dendritic precursors 8a–
8c were used and the brownish yellow glassy solids were ob-
tained as desired products with moderate yields (G1, 76%;
G2, 68%; and G3, 66%).
Synthesis of 1a–1c
One of complexes 7a–7c (7a, 93 mg, 0.06 mmol; 7b,
119 mg, 0.06 mmol; or 7c, 170 mg, 0.06 mmol) and ethynyl-
ferrocene (50 mg, 0.24 mmol) were dissolved in a mixture of
THF (10 mL) and diethylamine (5 mL). CuI (2.0 mg) was
added to this reaction mixture as a catalyst. The yellowish
brown mixture was then stirred at room temperature for
12 h, and the solvent was removed under reduced pressure.
The greenish yellow gummy residue was then purified by
column chromatography on silica gel with dichloromethane
as the eluent to afford a brownish yellow glassy solid of ei-
ther 1a, 1b, or 1c.
2a
Yield (brownish yellow glassy solid): 101 mg, 76%; mp:
1
49 °C. Rf 0.23 (dichloromethane / petroleum ether, 3:1). H
NMR (CDCl3, 400 MHz) d: 7.46–7.35 (m, PhH, 12H), 7.12
(s, H1, 1H), 6.87–6.85 (m, H2 and PhH, 3H), 5.11 (s,
PhCH2O, 4H), 4.23 (s, Fc–H, 4H), 4.14 (s, Fc–H, 10H),
4.06 (s, Fc–H, 4H), 2.17–2.18 (m, PhCH2CH3, 24H), 1.27–
1.21 (m, PhCH2CH3, 36H). 13C NMR (CDCl3, 100 MHz) d:
164.7, 159.9, 150.3, 136.4, 131.8, 131.2, 129.6, 128.6, 128.1,
127.5, 120.6, 109.0, 108.7, 108.5, 107.7, 105.1, 102.3, 72.8,
70.4, 70.2, 69.3, 66.9, 16.6, 16.4, 16.2, 14.1, 8.4. 31P NMR
1a
Yield (brownish yellow glassy solid): 39 mg, 42%; mp
47 °C. Rf 0.58 (dichloromethane). 1H NMR (CDCl3,
400 MHz) d: 8.48 (s, H1, 2H), 8.08 (d, H2, J = 8.0 Hz, 2H),
7.56–7.50 (m, PhH, 6H), 7.41–7.36 (m, PhH, 6H), 5.23 (s,
PhCH2O, 4H), 4.25 (s, Fc–H, 4H), 4.15 (s, Fc–H, 10H),
4.07 (s, Fc–H, 4H), 2.25–2.23 (m, PhCH2CH3, 24H), 1.33–
1.27 (m, PhCH2CH3, 36H). 13C NMR (CDCl3, 100 MHz) d:
167.7, 143.0, 137.6, 132.3, 130.9, 130.0, 128.8, 128.5, 128.3,
128.0, 126.8, 124.4, 121.8, 75.4, 70.3, 70.0, 69.4, 67.0, 65.5,
16.6, 16.5, 16.3, 8.5. 31P NMR (CDCl3, 161.9 Hz) d: 11.5 (s,
1
(CDCl3, 162 Hz) d: 11.4 (s, JPt–P = 2386.4 Hz). MALDI-
HRMS of 2a m/z calcd for C79H99Fe2O4P4Pt2 ([M + H]+):
1737.45; found: 1736.50.
2b
Yield (brownish yellow glassy solid): 86 mg, 68%; mp
53 °C. Rf 0.67 (dichloromethane / ethyl acetate, 1:20). 1H
NMR (CDCl3, 400 MHz) d: 7.43–7.30 (m, PhH, 22H), 7.11
(s, H1, 1H), 6.84–6.82 (m, H2 and PhH, 3H), 6.69 (s, PhH,
4H), 6.58 (s, PhH, 2H), 5.04 (s, PhCH2O, 12H), 4.22 (s, Fc–
H, 4H), 4.18 (s, Fc–H, 10H), 4.05 (s, Fc–H, 4H), 2.16 (br,
PhCH2CH3, 24H), 1.24–1.18 (m, PhCH2CH3, 36H). 13C
NMR (CDCl3, 100 MHz) d: 160.2, 159.8, 138.8, 136.8,
128.6, 128.0, 127.5, 109.0, 106.4, 101.8, 70.2, 69.4, 67.0,
16.6, 16.4, 16.2, 8.4. 31P NMR (CDCl3, 161.9 Hz) d: 11.5
1JPt–P = 2381.5 Hz). MALDI-HRMS of 1a m/z calcd for
C80H99Fe2O2P4Pt2 ([M + H]+): 1717.46; found: 1721.60.
1b
Yield (brownish yellow glassy solid): 48 mg, 37%; mp
49 °C. Rf 0.51 (dichloromethane). 1H NMR (CDCl3,
400 MHz) d: 8.51 (s, H1, 2H), 8.09 (d, H2, J = 7.6 Hz, 2H),
7.54 (d, H3, J = 8.0 Hz, 2H), 7.39–7.32 (m, PhH, 20H), 6.82
(s, PhH, 4H), 6.58 (s, PhH, 2H), 5.20 (s, PhCH2O, 4H), 4.94
(s, PhCH2O, 8H), 4.27 (s, Fc–H, 4H), 4.17 (s, Fc–H, 10H),
4.09 (s, Fc–H, 4H), 2.27–2.26 (m, PhCH2CH3, 24H), 1.40–
1.29 (m, PhCH2CH3, 36H). 13C NMR (CDCl3, 100 MHz) d:
160.1, 140.1, 136.8, 130.2, 128.5, 128.4, 127.9, 127.6, 124.4,
1
(s, JPt–P = 2379.9 Hz). MALDI-HRMS of 2b m/z calcd for
C107H123Fe2O8P4Pt2 ([M + H]+): 2161.62; found: 2161.60.
2c
Yield (brownish yellow glassy solid): 117 mg, 66%; mp
55 °C. Rf 0.67 (dichloromethane). 1H NMR (CDCl3,
400 MHz) d: 7.44 (s, PhH, 1H), 7.40–7.30 (m, PhH, 42H),
7.10 (s, H1, 1H), 6.84 (s, H2 and PhH, 3H), 6.67 (s, PhH,
12H), 6.56 (s, PhH, 6H), 5.01–4.95 (m, PhCH2O, 28), 4.22
(s, Fc–H, 4H), 4.13 (s, Fc–H, 10H), 4.05 (s, Fc–H, 4H),
2.14 (br, Fc–H, 24H), 1.28–1.17 (m, Fc–H, 36H). 13C NMR
(CDCl3, 100 MHz) d: 160.2, 160.1, 159.8, 139.2, 136.8,
128.6, 128.0, 127.5, 106.5, 106.4, 106.7, 70.2, 70.1, 70.0,
69.4, 66.9, 16.6, 16.4, 16.2, 8.4. 31P NMR (CDCl3, 162 Hz)
121.8, 106.8, 101.8, 75.1, 70.3, 69.4, 67.0, 16.6, 16.5, 16.3,
8.5. 31P NMR (CDCl3, 161.9 Hz) d: 11.5 (s, JPt–P
=
1
2379.9 Hz). CSI-TOF-MS of 1b m/z calcd for
C108H123Fe2O6P4Pt2 ([M + H]+): 2141.63; found: 2142.00.
1c
Yield (brownish yellow glassy solid): 56 mg, 33%; mp:
50 °C. Rf 0.45(dichloromethane). 1H NMR (CDCl3,
400 MHz) d: 8.51 (s, H1, 2H), 8.11 (d, H2, J = 8.4 Hz, 2H),
7.55 (d, H3, J = 8.0 Hz, 2H), 7.35–7.30 (m, PhH, 40H), 6.80
(s, PhH, 4H), 6.65 (s, PhH, 8H), 6.52 (s, PhH, 6H), 5.17 (s,
PhCH2O, 4H), 4.94 (s, PhCH2O, 16H), 4.82 (s, PhCH2O,
1
d: 11.4 (s, JPt–P = 2379.9 Hz). CSI-TOF-MS of 2c m/z calcd
for C163H172Fe2O16P4Pt2 ([M + 2H]2+): 1505.00; found:
1505.30.
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Han et al.
287
Sci. 2005, 30 (3–4), 294. doi:10.1016/j.progpolymsci.2005.01.
007.
Conclusion
By employing the coupling reaction of trans-Pt complexes
with C–H bonds in alkynes as key steps, we have success-
fully prepared a new family of dendritic platinum–bisferroce-
nylacetylide complexes from simple starting materials in
satisfactory yields. Multinuclear NMR (1H, 13C, and 31P)
analysis of all metallodendrimers displayed very similar char-
acteristics that are indicative of the generation of the desired
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species. The sharp NMR signals in both 31P {1H} and H
1
NMR spectra, along with the solubility of these species,
ruled out the formation of oligomers. Moreover, mass spec-
trometric studies, including MALDI-TOF-MS and CSI-TOF-
MS, provided further evidence for the unambiguous determi-
nation of their absolute molecular weight and molecularity.
All bimetallic metallodendrimers exhibit remarkable solubil-
ity in common organic solvents, such as dichloromethane
and chloroform. Furthermore, these newly designed metallo-
dendrimers are air- and humidity-stable at room temperature.
Electrochemical studies reveal that all of the redox moieties
are stable, independent, and electrochemically active. In addi-
tion, all metallodendrimers show one-electron reaction re-
sponses and the increased size of the assemblies do not
influence D. To the best of our knowledge, this is the first
report on the synthesis of platinum–bisferrocenylacetylide
dendrimers, which obviously enriches the library of hetero-
metallic dendrimers connected by unsaturated carbon-rich
bridges.
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Supplementary data
Supplementary data are available with the article through
the journal Web site http://nrcresearchpress.com/doi/suppl/
10.1130/v11-159.
Acknowledgments
(6) Newkome, G. R.; Moorefield, C. N.; Baker, G. R.; Johnson, A.
L.; Behara, R. K. Angew. Chem. Int. Ed. Engl. 1991, 30 (9),
1176. doi:10.1002/anie.199111761.
Professor C.-H. Wang thanks East China Normal Univer-
sity for financial support.
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