Structures and solvatochromic phosphorescence of dicationic terpyridyl-platinum(II) complexes with foldable oligo(ortho-phenyleneethynylene) bridging ligands

Article abstract of DOI:10.1002/chem.200800394

A series of binuclear organoplatinum(II) complexes, [(tBu ₃tpy)Pt-(C≡C-1,2-C₆H₄) _n-C≡C-Pt(tBu₃tpy)]-[ClO₄]₂ (1-7, n = 1, 2, 3, 4, 5, 6, 8; tBu₃tpy = 4,4′,4″-tri- tert-butyl-2,2′:6′,2″-terpyridine) with foldable oligo(orthophenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 3·2.5 CH₃OH, 5·CH₃CN, and 6·4CH₃CN, each of the bridging orthophenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40%, the emission of complexes 3-7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho-phenyleneethynylene linkers in acetonitrile/water mixtures is postulated.

Full text of DOI:10.1002/chem.200800394

DOI: 10.1002/chem.200800394
Structures and Solvatochromic Phosphorescence ofDicationic Terpyridyl–
Platinum(II) Complexes with Foldable Oligo(ortho-phenyleneethynylene)
Bridging Ligands
Ming-Xin Zhu, Wei Lu, Nianyong Zhu, and Chi-Ming Che*[a]
Abstract: Aseries of binuclear organo-
tially folded conformation. In aerated
water/acetonitrile mixtures with water
percentages larger than 40%, the emis-
sion of complexes 3–7 are red-shifted
and enhanced when compared to those
recorded in acetonitrile. The red-shift
in emission energy and enhanced emis-
sion intensity can be attributed to the
inter- and/or intramolecular interac-
tions induced by the addition of water
to solutions of the platinum(II) com-
plexes in acetonitrile. Data from dy-
namic light scattering and transmission
electron microscopy studies revealed
that these binuclear platinum(II) com-
plexes aggregated into nanosized parti-
cles in acetonitrile/water mixtures. Hy-
drophobic folding of the ortho-phenyl-
ꢁ
platinum(II) complexes, [(tBu3tpy)Pt
ꢀ ꢁ ꢁ ꢀ ꢁ
(C C 1,2-C6H4)n C C Pt
ACHTREUNG
ACHTRE(UNG tBu3tpy)]-
tBu3tpy=4,4’,4’’-tri-tert-butyl-2,2’:6’,2’’-
terpyridine) with foldable oligo(ortho-
phenyleneethynylene) linkers were pre-
pared and characterized by spectro-
scopic methods and/or X-ray crystallo-
graphic analyses. In the crystal struc-
tures of 3·2.5CH3OH, 5·CH3CN, and
6·4CH3CN, each of the bridging ortho-
phenyleneethynylene ligands has a par-
Keywords: aggregation · hydropho-
bic effect · luminescence · phenyl-
eneethynylene · platinum
AHCTREUNG
Introduction
charge-transfer (LLCT) excited states.[4] Due to the square-
planar geometry of platinum(II) complexes, their emissive
triplet excited states are usually influenced by intra- and in-
termolecular interactions, including Pt···Pt and p–p interac-
tions, which are sensitive to solvent composition, complex
concentration and nucleophiles.[5] Subtle variations in the
coordination sphere and the microenvironment of the plati-
num(II) complexes could lead to remarkable fluctuations in
both their supramolecular structures and spectroscopic prop-
erties. Recent developments in phosphorescent organogela-
tors derived from terpyridyl–platinum(II)–acetylide com-
plexes are examples of the above perspective.[6]
Poly(phenyleneethynylene)s are a class of carbon-rich ma-
terials with extended p conjugations and have received con-
siderable attention in materials chemistry.[7] When compared
to the rigid linear oligo(para-phenyleneethynylene) (para-
PE) compounds, oligo(meta-phenyleneethynylene) (meta-
PE) and oligo(ortho-phenyleneethynylene) (ortho-PE) ana-
logues each have a flexible, angular configuration that
would allow the occurrence of a folded helical conformation
with the repeating unit of six and three aryl rings, respec-
tively.[8] It is anticipated that the folding of angular meta-
and ortho-PEs would be affected by solvent, temperature,
hydrogen bonding and metal-ion coordination.[9] Thus meta-
and ortho-PEs could be useful linkers to construct phosphor-
Phosphorescent transition-metal complexes are useful opto-
electronic[1] and chemosensory[2] materials. Of particular in-
terest are those metal complexes supported by alkynyl li-
gands that have received much attention in recent years.[3]
Alkynyl ligands are strong s-donors, destabilize the HOMO
of metal ions, and consequently suppress the nonradiative
d–d state deactivation, resulting in high emission quantum
yields and long emission lifetimes.[3c,d] In this regard, platin-
um(II)–terpyridyl complexes containing alkynyl ligands are
particularly attractive, since they possess rich photophysical
ꢀ
and spectroscopic properties, For example, the [(tpy)Pt
(C
CAr)]+ (tpy=2,2’:6’,2’’-terpyridine) complexes have been
demonstrated to have long-lived triplet metal-to-ligand
charge-transfer (MLCT) and/or triplet ligand-to-ligand
[a] M.-X. Zhu, Dr. W. Lu, Dr. N. Zhu, Prof. Dr. C.-M. Che
Department of Chemistry and
Open Laboratory of Chemical Biology of the
Institute of Molecular Technology for Drug Discovery and Synthesis
The University of Hong Kong, Pokfulam Road, Hong Kong (China)
Fax : (+852)2857-1586
E-mail: cmche@hku.hk
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200800394.
9736
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 9736 – 9746

FULL PAPER
escent metal–organic systems with folding properties arising
from p–p stacking and solvophobic interactions in solution.
Despite the extensive coordination chemistry of meta- and
para-PE ligands, metal complexes with ortho-PE ligands are
sparse in the literature.[10] Herein, we report the uniquely
red-shifted and enhanced phosphorescence of dicationic ter-
1–7, the molar ratios of [(tBu3tpy)PtCl]ClO4 to the
ꢀ ꢁ
ꢁ ꢀ ꢁ
AHCTRE[UGN ortho-PE(n)]H2 (ortho-PE(n)=C C 1,2-C6H4 (C C 1,2-
ꢁ ꢀ
C6H4)nꢁ1 C C, where n=1, 2, 3, 4, 5, 6, and 8, respectively)
are 2:1; whereas for the mononuclear complexes 8 and 9,
the molar ratios of ((tBu3tpy)PtCl]ClO4 to the alkynyl
ꢀ
ꢀ ꢁ
ꢀ
ligand [HC CC6H5 and H(C C 1,2-C6H4)2C CC6H5, re-
spectively) are 1:1. Purification over a neutral Al2O3 column
with CH2Cl2/acetone (volume ratio 4:1) followed by CH2Cl2/
CH3OH (volume ratio 4:1) as eluents gave 1–9 as an orange
or a red solid in moderate to high yields. The highest prod-
uct yield was 90% (8) and the lowest was 47% (5). These
complexes are air stable and soluble in CH2Cl2, CHCl3,
CH3CN, and acetone and slightly soluble in CH3OH. They
pyridyl–platinum(II) complexes
ꢀ ꢁ
containing
ortho-PE
ACHTRE(UNG tBu3tpy)]-
ꢁ
ꢁ ꢀ ꢁ
bridges, [(tBu3tpy)Pt (C C 1,2-C6H4)n C C Pt
ACHTREUNG[ClO4]2 (1–7, n=1, 2, 3, 4, 5, 6, 8; tBu3tpy=4,4’,4’’-tri-tert-
butyl-2,2’:6’,2’’-terpyridine), in aqueous medium. Two mono-
ꢁ ꢀ
nuclear complexes [(tBu3tpy)Pt C CC6H5]ClO4 (8) and
ꢁ
ꢀ
ꢀ
[(tBu3tpy)Pt (C C-1,2-C6H4)2-C CC6H5]ClO4 (9) were stud-
ied for comparison.
were characterized by H and 13C NMR spectroscopy, and
1
fast atom-bombardment (FAB) mass spectrometry (MS, see
1
Experimental Section). As revealed by the H NMR spectra
of these complexes, the 2 and 6’’ protons of the terpyridyl
ligand appear as a doublet with two Pt satellites (3JPtH
=
ꢂ40 Hz), which was previously reported for terpyridyl–plati-
num(II) systems.[4,5] The FAB mass spectra of 1–7 reveal
two major peaks corresponding to [MꢁClO4]+ and
[Mꢁ2ClO4]+, in which M represents the intact ion pair.
X-ray crystallography: Crystals of 3·2.5CH3OH, 5·CH3CN,
and 6·4CH3CN were obtained by slow diffusion of Et2O
into a solution of 3 in CH3OH or solutions of 5 and 6 in
CH3CN, and the crystal structures (Figure 1) were deter-
mined by X-ray crystal analysis. Crystallographic data col-
ꢁ
lection parameters are summarized in Table 1. The Pt C
ꢀ
ꢁ
(1.94–1.99 Š) and C C (1.14–1.22 Š) bond lengths and Pt
ꢀ
ꢁ ꢀ
C C (170.0–178.18) and C C C (172.4-178.98) angles are
comparable to those of reported platinum(II)–s-alkynyl
complexes containing terpyridyl and/or cyclometalated li-
gands.[4–5]
The crystal structure of 3 (Figure 1, left) shows that two
[(tBu3tpy)Pt] moieties adopt a distorted planar geometry
ꢁ
and are linked to each other by ortho-PE(3) through Pt C
bonds. The terpyridyl–platinum(II) planes and the phenyl
rings of the bridging ortho-PE(3) fold into a two-layered
helix as a result of the angular shape of the ortho-PE(3)
units and the p–p interactions between the [(tBu3tpy)Pt]
planes and their adjacent phenyl rings with interplanar dis-
tances of around 3.4 Š. Two [(tBu3tpy)Pt] planes in the
same molecule have a dihedral angle of 268. The view along
the folding axis of the ortho-PE(3) moiety is close to a regu-
lar triangle. Despite the bulky tert-butyl groups at the pe-
riphery of terpyridyl ligand, there is a close intermolecular
Pt···Pt contact (distance 3.24 Š) between two pairing cations
in a head-to-tail fashion. These cation pairs are packed into
infinite columns in the crystal structure. The intermolecular
and interplanar distance between two neighboring terpyridyl
planes is around 3.4 Š, which would allow for p–p interac-
tions.
Results
Synthesis and characterization: The series of terpyridyl–plat-
inum(II) complexes (1–8) and 9 were synthesized through
Sonogashira coupling reactions between [(tBu3tpy)PtCl]ClO4
and the corresponding ortho-PEs (Scheme 1). For complexes
Each of the cations in 5 (Figure 1, middle) and 6
(Figure 1, right) folds into a three-layered sandwichlike
structure with two terpyridyl–platinum(II) planes, one
serves as the first and the other one as the third layer, while
Scheme 1. Syntheses of complexes 1–7.
Chem. Eur. J. 2008, 14, 9736 – 9746
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9737

C.-M. Che et al.
Figure 1. Left: Perspective view (top) of the cation in 3·2.5CH3OH with hydrogen atoms, perchlorate ions and solvated molecules omitted for clarity.
The side view (bottom) of the cations is shown to emphasize the conformation of the ortho-PE(3) bridges and the intramolecular folding through intra-
molecular p-p interactions and intermolecular Pt···Pt contacts (as indicated with dashed lines). Middle: Perspective view (top) and side view (bottom) of
the cation in 5·CH3CN with hydrogen atoms, perchlorate ions and solvated molecules omitted for clarity. Right: Perspective view (top) and side view
(bottom) of the cation in 6·4CH3CN with hydrogen atoms, perchlorate ions and solvated molecules omitted for clarity.
for 6) are typical distances for
p–p interactions. There are two
antiparallel folding axes for the
ortho-PE(5) moiety in 5 and
ortho-PE(6) moiety in 6. Thus,
the view along the folding axis
of the helical structure in 5 and
6 could be described as a twist-
ed “figure eight”, and the fold-
ing direction for each loop of
the figure eight is opposite to
each other. No inter- or intra-
molecular Pt···Pt interactions
are found in the crystal struc-
tures of both 5 and 6. In 5, in-
termolecular separations be-
Table 1. Crystal data of complexes 3·2.5CH3OH, 5·CH3CN, and 6·4CH3CN.
3·2.5CH3OH
5·CH3CN
6·4CH3CN
formula
Mr
color
C
82.5H92Cl2N6O10.5Pt2
C98H93Cl2N7O8Pt2
1954.85
orange red
301
C112H106Cl2N10O8Pt2
2181.15
orange
1796.70
red
253
T [K]
253
crystal size [mm]
crystal system
space group
a [Š]
b [Š]
c [Š]
0.35”0.15”0.1
monoclinic
C2/c
28.180(6)
28.678(6)
19.779(4)
0.7”0.15”0.1
monoclinic
P21/c
17.777(4)
30.505(6)
20.462(4)
0.3”0.3”0.1
triclinic
¯
P1
17.444(4)
17.535(4)
19.790(4)
78.05(3)
69.92(3)
66.03(3)
5179(2)
2
a [8]
b [8]
90.10(3)
112.78(3)
g [8]
V [Š3]
Z
15984(6)
8
1.493
3.625
10231(4)
4
1.269
2.836
1calcd [gcmꢁ3
]
1.399
2.810
2204
m [mmꢁ1
(000)
]
tween
the
neighboring
F
A
7224
3924
[(tBu3tpy)Pt] planes are close
enough for p–p interactions
(3.50 Š), whereas for 6, the
[(tBu3tpy)Pt] planes between
the neighboring cations have a
dihedral angle of 24.08.
2qmax [8]
reflns
49.84
26040
8788 [Rint =0.070]
460
0.81
0.049
0.108
+1.158, ꢁ0.771
50.52
37975
12096 [Rint =0.056]
489
0.89
0.059
0.171
50.64
26382
13222 [Rint =0.068]
623
0.90
0.056
0.130
+1.124, ꢁ1.045
independent reflns
variables
GOF on F2
[a]
R1
[b]
wR2
ꢁ3
residual 1 [eŠ
]
+0.947, ꢁ1.299
1
2
2
2
2
=
2
[a] R1 =ꢀjjFo jꢁjFc jj/ꢀjFo j. [b] wR2 ={ꢀ[w(FoꢁFc)]/ꢀ[w(Fo) ]} .
Spectroscopic properties: The
photophysical properties of 1–9
are summarized in Table 2. The
the second layer is the central C6H4 ring of ortho-PE(5) for
electronic absorption spectra of 1–7 show an intense band at
312–365 nm (eꢂ4”104 dm3 molꢁ1 cmꢁ1) with vibronic struc-
tures and a less intense broad absorption band at 452–
ꢁ ꢀ ꢁ
5 and the central C6H4 C C C6H4 moiety of ortho-PE(6)
for 6. All the interlayer separations (ꢂ3.3 Š for 5, ꢂ3.4 Š
9738
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ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 9736 – 9746

Solvatochromic Platinum(II) Complexes
FULL PAPER
Table 2. Photophysical data of 1–9.
[a]
Complex
Medium
labs [nm] (emax [103 mꢁ1 cmꢁ1])
lem [nm] (tem [ms]) {fem}
1
CH2Cl2 (298 K)
CH3CN (298 K)
CH3OH (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[d]
solid (77 K)[d]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
CH2Cl2 (298 K)
CH3CN (298 K)
CH3OH (298 K)
solid (298 K)[d]
solid (77 K)[d]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[d]
solid (77 K)[d]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
CH2Cl2 (298 K)
solid (298 K)[b]
solid (77 K)[b]
glass (77 K)[c]
314 (45.0), 329 (36.2), 345 (34.3), 482 (11.6)
311 (35.0), 326 (30.9), 340 (30.4), 447 (sh, 8.8)
311 (33.1), 327 (29.2), 342 (29.7), 455 (sh, 8.4)
607 (0.4) {0.010}
604 (0.2) {0.003}
606 (0.1) {0.003}
647 (<0.1)
670 (1.1)
550 (17.3), 582 (sh)
650 (0.1) {0.005}
644 (<0.1)
2
3
4
5
312 (38.5), 325 (34.9), 341 (28.3), 453 (12.0)
313 (45.2), 325 (38.3), 339 (31.0), 473 (9.0)
314 (46.5), 325 (43.2), 340 (38.6), 362 (19.8), 452 (8.8)
664 (0.9)
545 (10.1), 623
591 (0.9) {0.004}
641 (0.2)
638 (3.6)
532, 611 (16.7)
605 (0.5) {0.006}
705 (0.3)
706 (0.8)
519 (25.1), 554
584 (0.6) {0.059}
567 (0.2) {0.004}
563 (0.1) {0.002}
663 (0.3)
547 (2.7), 592 (3.3), 707 (0.9)
523 (127.0), 564, 593
600 (2.3) {0.041}
314 (47.7), 325 (42.9), 340 (35.7), 365 (17.9), 467 (sh, 7.8)
313 (45.8), 326 (45.3), 339 (41.6), 364 (25.1), 434 (sh, 9.4)
314 (36.8), 326 (36.4), 340 (33.2), 366 (19.5), 435 (sh, 7.1)
6
7
8
9
314 (47.9), 325 (44.9), 340 (40.5), 364 (22.5), 461 (sh, 8.3)
316 (73.6), 325 (70.6), 339 (64.9), 364 (41.2), 457 (sh, 9.9)
315 (14.7), 340 (12.6), 413 (sh, 4.1)
659 (<0.1)
588 (4.9), 640 (sh, 1.9), 695 (1.2)
529 (21.6), 564, 595 (sh)
604 (0.6) {0.024}
662 (0.2)
586 (2.0), 705 (1.0)
526 (78.0), 561
593 (3.4) {0.111}
644 (<0.1)
643 (1.2)
518 (10.0), 547 (sh), 605 (sh)
580 (0.6) {0.087}
314 (28.3), 461 (sh, 4.1)
675 (0.2)
567 (sh), 672, 700 (1.0)
516 (23.9), 551 (sh, 17.0)
[a] Quantum yield for degassed solutions, using quinine sulfate in 0.1m H2SO4 (fem =0.546) as reference. [b] Microcrystalline solid. [c] CH3OH/
CH3CH2OH (v/v)=1:4 at 77 K. [d] Fine powder.
482 nm (eꢂ0.75–1.25”104 dm3 molꢁ1 cmꢁ1) in CH2Cl2 at
room temperature (Figure 2). When the bridging ortho-PE
ꢀ ꢁ
is extended from one to eight (C C 1,2-C6H4) repeating
units as in the case of 1–7, there is only a slight variation of
the low-energy absorption band maximum with no distinct
trend observed. For comparison, the spectroscopic data of
ꢀ
the two mononuclear complexes 8 and 9 containing the C
ꢀ ꢁ
ꢁ ꢀ
CC6H5 and (C C 1,2-C6H4)2 C CC6H5 ligand, respectively,
were studied. The absorption spectra of 8 and 9 (a high-
energy band at 314–340 nm and a low-energy band at 413–
461 nm) resemble that of the binuclear complexes 1–7. The
solvent effect on the absorption spectrum of 5 has been ex-
amined: the low-energy absorption band maximum blue-
shifts from 467 nm to ꢂ434 nm when the solvent changes
from CH2Cl2 to CH3CN and CH3OH (Figure 3). Similar
hypsochromism on the absorption spectrum of 1 has also
been observed (from 482 nm in CH2Cl2 to ꢂ450 nm in
CH3CN and CH3OH). The low-energy absorption band of 5
Figure 2. UV/Vis absorption spectra of 1–7 in CH2Cl2 at 298 K with the
inset showing the amplified 400–600 nm region.
Chem. Eur. J. 2008, 14, 9736 – 9746
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9739

C.-M. Che et al.
the emission maximum red-shifted from 583 to 699 nm
(2846 cmꢁ1) for 3, 598 to 657 nm (1502 cmꢁ1) for 4, 567 to
670 nm for (2711 cmꢁ1) 5, 584 to 657 nm (1903 cmꢁ1) for 6,
and 584 to 659 nm (1949 cmꢁ1) for 7; the corresponding
quantum yield increased by 3.6, 22.7, 8.4, 16.4 and 3.0-fold
for 3–7, respectively. The emission lifetimes showed slight
increments (from 0.1 to 0.6 ms). Most notably, the red-shifted
emission lmax upon addition of water is comparable in
energy to the corresponding room-temperature solid-state
emission (lmax =641, 705, 663, 659 and 662 nm for 3–7, re-
spectively). Under the same conditions, 1 and 2, which have
shorter ortho-PE(n) (n<3) ligands, showed red-shifted lmax
(611 to 633 nm (569 cmꢁ1) for 1, 645 to 721 nm (1634 cmꢁ1)
for 2), but less than a 0.2-fold enhancement in the emission
intensity was observed.
Figure 3. UV/Vis absorption and normalized emission (inset) spectra of 5
in CH2Cl2, CH3CN, and CH3OH (lex =350 nm) at 298 K.
ꢀ
The mononuclear complexes 8 with a C CC6H5 moiety
ꢀ ꢁ
ꢁ ꢀ
and 9 with a (C C 1,2-C6H4)2 C CC6H5 moiety in aerated
H2O/CH3CN mixtures were studied for comparison. For 9,
the emission lmax red-shifts from 571 to 655 nm (2246 cmꢁ1)
with a concomitant 19-fold enhancement in intensity when
the water percentage increases from 40 to 90%. In contrast,
8 has no angular ortho-PE ligand, and its emission in aerat-
ed H2O/CH3CN mixtures diminishes in intensity without a
red-shift in lmax upon increasing the water fraction from 0 to
0.9 (see Supporting Information).
obeys Beerꢁs law in the concentration range of 10ꢁ5–
10ꢁ4 moldmꢁ3 in CH3CN, suggesting no significant aggrega-
tion in this concentration range.
All these complexes are emissive in degassed solutions, in
solid state and in CH3OH/CH3CH2OH (v/v=1:4) glassy sol-
utions at 77 K. Emission lifetimes are in the microsecond
time region, and the emission quantum yields measured in
CH2Cl2 are in the range of 0.2–5.9% (the results are listed
in Table 2). The room-temperature emission lmax for 1–7 in
CH2Cl2 are 607, 650, 591, 605, 584, 600 and 604 nm, respec-
tively; while their corresponding solid-state emission
maxima are red-shifted (except for 2) to 647, 644, 641, 705,
663, 659 and 662 nm, respectively. For the mononuclear
complexes 8 and 9, their solid-state emissions are at lower
energies (644 nm for 8, 675 nm for 9) than in CH2Cl2
(593 nm for 8, 580 nm for 9). Complex 5 was chosen to illus-
trate the solvatochromic properties of this class of com-
plexes. Upon changing the solvent from CH2Cl2 to CH3CN
and CH3OH, its emission lmax (lifetime, quantum yield) is
blue-shifted from 584 (0.6 ms, 0.06) to 567 (0.2 ms, <0.01)
and 563 nm (0.1 ms, <0.01) (Figure 3). Increasing the coun-
terion concentration from 0.001m to 0.01m by adding a
LiClO4 salt to a solution of 5 in CH3OH at ꢂ1.0”
10ꢁ5 moldmꢁ3 did not change its electronic absorption and
emission spectra.
Complex 5 was chosen for further investigation. Upon in-
creasing the water content from 40 to 90%, the emission
lmax of 5 in aerated H2O/CH3CN mixtures red-shifted from
567 to 670 nm (2711 cmꢁ1) (the emission spectra are depict-
ed in Figure 4, top); the emission quantum yield increased
from <0.01 to 0.03, and the lifetime increased from 0.1 to
0.4 ms. The UV/Vis absorption spectra of 5 in aerated H2O/
CH3CN mixtures (Figure 4, middle) with increased water
percentage showed a sharp decrease in absorbance at l=
350 nm, together with a concomitant increase in the low-
energy absorption band at ꢂ500 nm. This is consistent with
the finding of an absorption peak maximum at 475 nm in
the excitation spectrum recorded with a solution of 5 in a
90:10 H2O/CH3CN mixture (monitored at emission wave-
length 674 nm) (Figure 4, bottom). The former is red-shifted
from the corresponding peak maximum at 458 nm when the
excitation spectrum was recorded in a 40:60 H2O/CH3CN
mixture (monitored at emission wavelength 568 nm;
Figure 4, bottom). The spectroscopic properties of 5 in aer-
ated Et2O/CH3CN mixtures were studied. Asolution of 5 in
an Et2O/CH3CN mixture containing 90% Et2O is not as
stable as in H2O/CH3CN mixtures. In the former, 5 precipi-
tated as a microcrystalline solid after standing for ꢂ24 h. In
contrast to the finding obtained with the H2O/CH3CN mix-
tures, upon gradually increasing the Et2O fraction from 40
to 90%, only slight changes in the UV/Vis absorption spec-
tra could be found, and the emission lmax remained at
Water-induced emission change: The emission properties of
1–7 in aerated H2O/CH3CN mixtures with increasing H2O
composition have been examined. The concentrations of the
platinum(II) complexes were fixed at 1.0”10ꢁ5 moldmꢁ3,
and all the absorption and emission spectra were measured
under aerated conditions. The solutions or dispersions used
for the spectroscopic measurements remained transparent
for at least 30 days, even when the water fraction was as
high as 90%. Ared-shift in emission energy and enhance-
ment of the emission intensity were found for 3–7 in aerated
H2O/CH3CN mixtures with a water composition of >40%
(v/v). Upon increasing the water fraction from 40 to 90%,
ꢂ570 nm with
a
fourfold enhancement in intensity
(Figure 5).
As 5 is insoluble in water but a solution (or dispersion) of
5 in H2O/CH3CN mixtures (volume ratio varying from 40:60
to 90:10) at a concentration of 1.0”10ꢁ5 moldmꢁ3 remained
9740
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Chem. Eur. J. 2008, 14, 9736 – 9746

Solvatochromic Platinum(II) Complexes
FULL PAPER
Figure 5. Emission traces (lex =350 nm) of complex 5 in Et2O/CH3CN
mixtures upon increasing the Et2O fraction.
ments showed that the average diameter of these spherical
aggregates was ꢂ33 nm (Figure 6, bottom). However, no
nanosized particles were observed by either DLS or TEM
studies in Et2O/CH3CN mixtures with volume ratio of 90:10.
Figure 4. Spectroscopic traces for 5 in aerated H2O/CH3CN mixtures
upon increasing the water fraction. Top: Emission traces (lex =350 nm)
with the inset showing the plot of emission intensity at 674 nm against
water fraction. Middle: UV/Vis absorption traces with the inset showing
the enlarged 400–600 nm region. Bottom: Excitation spectra monitored
at lem =568 (40% H2O) and 674 nm (90% H2O), respectively, with inset
showing the excitation spectra in 60% H2O/CH3CN mixture monitored
at lem =571 and 651 nm, respectively.
transparent, we envisage that 5 may exist as nanosized
spherical aggregates in these solution mixtures. Representa-
tive transmission electron micrograph (TEM) of the aggre-
gates formed by 5 in a 9:1 H2O/CH3CN mixture is depicted
in Figure 6 (top). Dynamic light scattering (DLS) measure-
Figure 6. Top: TEM image of 5 in H2O/CH3CN with a water fraction of
90%. Bottom: Histogram of particle size distribution of 5 in H2O/
CH3CN mixtures at 90% water fraction as determined by dynamic light
scattering.
Chem. Eur. J. 2008, 14, 9736 – 9746
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9741

C.-M. Che et al.
Similar submicron spherical structures were also found in a
9:1 H2O/CH3CN mixture of 6.
Discussion
Folded ortho-PE(n) moieties in crystal structures: Based on
the crystal structures of ortho-PEs or compounds containing
ortho-PE(n) bridges reported in literature, the ortho-PE
bridges can be summarized to adopt the following confor-
mations: I) transoid–transoid, II) transoid–cisoid, and III)
cisoid–cisoid (Figure 8). Grubbs and Kratz reported the
Variable-temperature NMR spectroscopy: In the literature,
1D and 2D (NOESY or ROESY) NMR have been utilized
to study the folding behavior of the ortho-PE(n) backbone
in polar solvents.[9f–h] In this work, a significant change in
the emission property of 5 was found in the aerated H2O/
CH3CN mixtures with a high water percentage. However,
under these conditions, the solubility of 5 is too low to allow
for a 2D (NOESY or ROESY) NMR study. An attempt to
replace the counterion of 5 from perchlorate to chloride by
using an anion-exchange resin (aiming to increase their
water solubility) was not successful. Instead, a variable-tem-
1
1
perature H NMR experiment was conducted, and a H–1H
COSY NMR measurement was also performed to assist in
the assignment of proton signals (see Supporting Informa-
tion for spectra). Again 5 was chosen for the study as its
1H NMR signals are well-resolved. Figure 7 displays the
NMR spectra of 5 in CD2Cl2 with a concentration of ꢂ5”
10ꢁ3 m at ꢁ60, ꢁ50, ꢁ40, ꢁ20, 0 and 208C. When the tem-
perature decreases from 20 to ꢁ608C, the NMR signals of
the terpyridyl protons H1 and H4 in the aromatic region are
shifted upfield; the chemical shifts of the terpyridyl H2 and
H3 remain unchanged, while the signals of two protons on
~
the central phenyl ring (marked as ) and other phenyl pro-
tons (except two protons) are shifted downfield. The NMR
signals of the terpyridyl protons H1, H2, H3 and H4 are
broadened upon decreasing temperature from 20 to ꢁ608C,
while the breadth of the other signal peaks remained almost
unchanged.
Figure 8. Partially folded conformations, I) transoid–transoid, II) tran-
soid–cisoid, III) cisoid–cisoid, of the ortho-PE(n) moieties revealed by
the crystal structures of a) 3·2.5CH3OH, b) 5·CH3CN, and c) 6·4CH3CN.
crystal structure of [ortho-PE(2)]Ph2 (Ph=phenyl) and
[ortho-PE(3)]Ph2, revealing a transoid–transoid and trans-
oid–cisoid helix, respectively.[8a] Youngs and co-workers re-
ported that [ortho-PE(4)]H2 and [ortho-PE(4)]ACHTREUNG(TMS)2
(TMS=trimethylsilane) adopt the transoid–transoid and
transoid–cisoid conformation, respectively, in the crystal
structures.[11] Substituted ortho-PE(2) and ortho-PE(3) with
pyridyl caps were reported by Bunz and co-workers to
adopt the transoid–transoid conformation in their crystal
structures.[9e] Two triethylphosphine–platinum complexes
containing a substituted ortho-PE(3) ligand and reported by
Haley and co-workers were regarded as a twisted transoid-
transoid conformation.[10e] In this work, the crystal structures
of 3, 5, and 6 revealed that each of the coordinated ortho-
PE(n) ligands of these complexes adopts a helical conforma-
tion. As depicted in Figure 8, 3 has a fully folded bridging
ortho-PE(3) ligand with cisoid–cisoid conformation; the
folding of ortho-PE(5) in 5 is considered to give rise to both
transoid–cisoid and cisoid–cisoid conformations; and the
folding of ortho-PE(6) in 6 has transoid–transoid and trans-
Figure 7. Variable-temperature 1H NMR spectra of 5 in CD2Cl2 solution
(ꢂ5”10ꢁ3 m) at ꢁ60, ꢁ50, ꢁ40, ꢁ20, 0 and 208C.
9742
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Chem. Eur. J. 2008, 14, 9736 – 9746

Solvatochromic Platinum(II) Complexes
FULL PAPER
oid–cisoid conformations. The biaxially helical conforma-
tions of the ortho-PE(n) moieties in 5 and 6 are in contrast
to the uniaxially helical structures reported for meta-PE(n)
compounds.[12] The coordinated ortho-PE(n) ligands of the
dicationic platinum(II) complexes described in this work are
partially folded in their crystal structures, because p–p inter-
actions could occur between the phenyleneethynylene moi-
eties of the ortho-PE(n) ligands and the capping terpyridyl–
platinum(II) moieties, all of which have a large p surface.
with increasing water percentage from 40 to 90%, a red-
shift of emission energy and enhancement in emission inten-
sity were observed for 3–7, and 9, the latter is a mononu-
clear PtII complex with the (C C 1,2-C6H4)2 C CC6H5
ligand. The emission energy of 3—7 and 9 in 9:1 H2O/
CH3CN mixtures are close to those recorded in solid state.
This may suggest the conformation of these complexes in
H2O/CH3CN mixtures with high H2O percentages could re-
semble the folded structures of the corresponding metal
complexes in the solid state. The red-shifts observed in the
UV/Vis absorption traces of these complexes in H2O/
CH3CN mixtures are in line with the aggregation and possi-
ble folding process upon increasing water contents. As de-
picted in Figure 4 (middle), the decrease in the absorbance
of a high-energy band of 5 (350 nm, assigned as IL p!p*
transitions) can be caused by an overlap of the pp orbitals of
the ortho-PE(5) moiety when the solvent polarity was in-
creased (hypochromicity),[8a] while the red-shift and increase
in the low-energy absorption (ꢂ500 nm, assigned as
ꢀ ꢁ
ꢁ ꢀ
Spectroscopic properties ofcomplexes 1–9 : The UV/Vis ab-
sorption spectra of 1–9 are similar to mononuclear [PtACHTRE(UNG tpy)-
ꢀ
A
plexes reported in the literature.[4] The corresponding free
ortho-PE ligands of 1–9 absorb strongly at 272–329 nm in
CH2Cl2 (see Supporting Information). With reference to
previous work, we assign the high-energy absorption band
of 1–9 at 313–365 nm to intra-ligand (IL) p!p*
ACHTREU(NG tBu3tpy)
ꢀ ꢁ
ꢀ
and p!p*[(C C 1,2-C6H4)nC C] transitions of the ortho-
PE bridge and the terpyridyl ligand, and the low-energy
dp(Pt)!p*
ACHTRE(UNG tBu3tpy) MLCT transitions) can be attributed to
band at 413–473 nm to a dp(Pt)!p*
A
Pt···Pt interactions and/or p–p interactions in solution. The
excitation peak maximum of 5 in a 90% H2O/CH3CN mix-
ture (monitored at lem =674 nm) red-shifted from that in
40% H2O/CH3CN mixture (monitored at lem =568 nm), re-
vealing that ground-state molecular interactions occurred in
the H2O/CH3CN solvent mixtures with high water percen-
tages (Figure 4, bottom). Nanoscale particles with an aver-
age diameter of ꢂ33 nm were found for 5 in a 9:1 H2O/
CH3CN mixture at a concentration of 1.0”10ꢁ5 moldmꢁ3.
In a dispersion of 5 in 9:1 Et2O/CH3CN mixture, although
nanosized particles were not detected in the TEM and DLS
observations, molecular aggregation is thought to occur be-
cause Et2O is a poor solvent for 5, and crystalline precipi-
tates were found after the mixture had stood for ꢂ24 h.
There was an enhancement in the emission intensity, but no
shift in the emission lmax upon increasing the Et2O content
from 40 to 90%, and the UV/Vis absorption spectra re-
mained almost unchanged. We suggest that, for 5 in Et2O/
CH3CN mixtures, aggregation leads to a diminished nonra-
diative decay of the emissive excited state as a consequence
of restricted motion of the molecules in the aggregates and
that this is the main reason for the enhanced emission inten-
sity. The intermolecular interactions resulting from aggrega-
tion may not significantly affect the emission energy. Similar
aggregation induced emissions have been observed in the lit-
erature.[13]
ligand charge transfer (MLCT) transition.[3c,4]
In solution, the emission lmax, lifetimes, and quantum
yields of 1–9 are close to those of the reported terpyridyl–
platinum(II) complexes.[4] The emission lmax blue-shifts
when the solvent polarity increases, indicating the ground
state is more polar than the excited states. This is consistent
with the MLCT assignment. With reference to previous
work, a 3[dp(Pt)!p*
ACHTRE(UNG tBu3tpy)] excited state mixed with
ACHTREUNG(ortho-PE)] is tentatively assigned to the emissions
A
of 1–9 recorded in anhydrous, organic solvents.[3c,4]
It is known that square-planar oligopyridyl–PtII complexes
usually absorb and emit at longer wavelengths in the solid
state and in solutions with high complex concentrations than
in diluted solutions. This is attributed to excimer/exciplex
formation through p–p interactions in the ground and/or ex-
cited states.[5] For example, the crystalline form of [Pt-
A
ACHTREUNG[CF3SO3] is orange-red, while a solution of this com-
AHCTREUNG
nol/DMF 5:5:1) at low temperatures displays red-shifted
MLCT and p–p excimer emission when compared with the
emission recorded with a diluted solution.[5a] The ortho-
PE(1) moiety in complex 1 is not long enough to be folded
into a helical conformation, thus the emission red-shift of 1
from lmax 604 nm in CH3CN to 647 nm in the solid state at
298 K could only be explained by intermolecular p–p inter-
actions and/or Pt···Pt interactions. In the cases of 3–7 with
the ortho-PE(n) (nꢃ3) moieties, they fold into a compact
structure as revealed by their X-ray crystal structures. Be-
sides intermolecular p–p interactions and/or Pt···Pt interac-
tions, the intramolecular p–p interactions between the
phenyl rings of the bridging ortho-PEs and the terminal ter-
pyridyl planes can be a prominent cause to the red-shift.
Considering the different polarity of H2O and Et2O, we
suggest that, in H2O/CH3CN solutions of 5, hydrophobic
folding is induced upon the addition of water. Intramolecu-
lar interactions between the [PtCAHTRE(UNG tBu3tpy)] planes and the
bridging ortho-PE(n) ligands account for the red-shifted
phosphorescence. This suggestion is further supported by
two experimental findings: 1) the emission energy (lem
=
674 nm) of 5 in the 9:1 H2O/CH3CN mixture resembles the
one (lem =663 nm) recorded in the crystalline solid state at
298 K, and the crystal structure of 5 revealed a partially
folded conformation of the ortho-PE(5) moiety; and 2) com-
Red-shifted and enhanced emission of complexes 3–7 and 9
in aerated H2O/CH3CN mixtures: In H2O/CH3CN mixtures
Chem. Eur. J. 2008, 14, 9736 – 9746
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9743

C.-M. Che et al.
ꢁ
ꢀ ꢁ
ꢁ ꢀ
1,2-C6H4 (C C 1,2-C6H4)nꢁ1 C CH, n=1, 2, 3, 4, 5, 6 and 8, respective-
plexes 3–7 and 9, which contain foldable ortho-PE(n) (nꢃ3)
moieties were found to exhibit red-shifted and enhanced
emissions in aerated H2O/CH3CN mixtures upon increasing
the water percentages, whereas these red-shifted and en-
hanced emissions were not observed for complexes 1, 2 and
8, which contain only shorter ortho-PE(n)s (n<3) moieties.
ꢀ ꢁ
ꢀ
ly), and H(C C 1,2-C6H4)2C CC6H5 were prepared according to litera-
ture methods.[8a,12,15] 1H and 13C NMR spectra were recorded on a Bruker
Avance 400 or DRX 300 FT-NMR spectrometer with TMS (1H and 13C)
as reference. Mass spectra (FAB) were obtained on a Finnigan MAT 95
mass spectrometer. Elemental analyses were performed by the Institute
of Chemistry, Chinese Academy of Sciences, Beijing. UV/Vis spectra
were recorded on a Perkin–Elmer Lambda 19 UV/Vis spectrophotome-
ter. The degassed solution samples for emission measurements underwent
at least four freeze-pump-thaw cycles. The aerated solution samples for
emission measurements were exposed to air. Emission spectra were ob-
tained on a SPEX Fluorolog-2 Model F111 fluorescence spectrophotom-
eter. Emission lifetime measurements were performed with a Quanta
Ray DCR-3 pulsed Nd:YAG laser system (pulse output 355 nm, 8 ns).
Luminescent quantum yields were referenced to quinine sulfate in 0.1m
H2SO4 solution (fem =0.546) with estimated error of ꢄ15%. The samples
for TEM observations were prepared by depositing a few drops of the
aqueous samples on the holey copper grid, which was then put into a des-
iccator. The TEM images were recorded on a Philips Tecnai 20 electron
microscope, with an accelerating voltage of 200 kV. The dynamic light
scattering (DLS) experiments were performed with a Malvern ZetaSizer
3000HSA. IR measurements were performed by using a Bio-Rad FT-IR
spectrometer.
1
The results of a variable-temperature H NMR study of 5
indicated that this complex may adopt an unfolded confor-
mation in CD2Cl2 at 298 K, but intermolecular p–p interac-
tions are possible at lower temperatures in this solvent
1
system. It has been reported that H signals are broadened
and shifted upfield as a result of p–p stacking interactions
due to self-association or aggregation of planar metal com-
plexes containing aryl p-conjugated organic ligands.[5f,14] In
this work, the terpyridyl protonsꢁ signals show broadening
and an upfield shift, presumably due to the intermolecular
p–p interactions of the terminal terpyridyl planes upon de-
crease in temperature. However, the signals of the protons
~
on the central phenyl ring (marked as ) are shifted down-
field and do not show peak broadening (Figure 7). 2D
NOESY signals, corresponding to interactions between ter-
pyridyl protons and two protons on the central phenyl ring,
as would be expected for helical conformation, were not ob-
Syntheses and characterization:
General procedure for the syntheses of complexes 1–9: Complexes 1–9
were synthesized by the overnight reaction of corresponding ortho-PEs
ꢁ
ꢀ ꢁ ꢀ
ꢁ ꢀ
(H (C C 1,2-C6H4)n C CH, n=1, 2, 3, 4, 5, 6, 8, respectively), HC
ꢁ
ꢀ ꢁ
ꢀ
CC6H5 or H (C C 1,2-C6H4)2C CC6H5 with [(tBu3tpy)PtCl]ClO4 (molar
ratio 1:2 for 1–7, 1:1 for 8 and 9) in argon-bubbled CH2Cl2/iPr2NH
(volume ratio 4:1) solvent mixture with a catalytic amount of CuI at
room temperature. Chromatography on neutral Al2O3 with CH2Cl2/ace-
tone (volume ratio 4:1) to CH2Cl2/CH3OH (volume ratio 4:1) as eluent
gave 1–9 as orange or red solids.
1
served in the variable-temperature H NMR spectra in solu-
tion. All these results exclude the possibility of 5 adopting a
folded helical conformation in CD2Cl2 upon decreasing tem-
perature from 20 to ꢁ608C. This is consistent with the spec-
troscopic studies on 5, in which the emission energies (lem
=
ꢁ ꢀ ꢁ
[(tBu3tpy)Pt 1,2-C6H4
ꢁ ꢀ ꢁ
C Pt
A
C
C
C
(tBu3tpy)]
G
(1):
Yield:
584 nm for CH2Cl2 solution at 298 K and lem =523 nm for a
glassy solution at 77 K) suggest a different conformation in
78%; 1H NMR (300 MHz, CD3CN, 258C): d=9.37 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 8.31 (s, 4H; terpyridyl H), 8.15 (d, 4J=
1.7 Hz, 4H; terpyridyl H), 7.74 (dd, 3J=6.0 Hz, 4H; terpyridyl H), 7.59
(m, 2H; phenyl H), 7.31 (m, 2H; phenyl H), 1.53 (s, 18H; tert-butyl H),
1.22 ppm (s, 36H; tert-butyl H); 13C{1H} NMR (100 MHz, CD3CN, 258C):
d=168.8, 167.5, 159.1 and 154.9 (quaternary C on terpyridyl), 156.1 (ter-
tiary C on terpyridyl), 132.6, 130.4 and 127.4 (C on phenyl ring), 127.1,
solution from the folded structure in the crystal form (lem
674 nm) of 5.
=
Conclusion
ꢁ ꢀ
124.1 and 122.5 (tertiary C on terpyridyl), 105.2 (Pt C C), 103.4 (Pt C
C), 38.2 and 37.0 (quaternary C on tert-butyl group), 30.6 and 30.1 ppm
(primary C on tert-butyl group); IR (KBr): n˜ =2122 cmꢁ1 (C C); FAB-
ꢀ
In conclusion, we prepared novel dicationic terpyridyl–plati-
num(II) complexes containing flexible ortho-PE(n) ligands
(PE=phenyleneethynylene), determined the helical confor-
mations of the ortho-PE(n) moieties in the crystal structures,
and demonstrated the uniquely red-shifted and enhanced
phosphorescence of these complexes in aerated H2O/
CH3CN solvent mixtures upon increasing the water percen-
tages. Intermolecular aggregation and intramolecular hydro-
phobic folding of the coordinated ortho-PE(n) (n=3) li-
gands are suggested as the main causes for these solvato-
chromic properties. These findings could benefit the molecu-
lar design of foldamers containing ortho-PE(n) moieties and
phosphorescent platinum(II) complexes with flexible struc-
tures and tunable emission properties.
MS (+ve): m/z: 1417 [MꢁClO4]+, 1317 [Mꢁ2ClO4]+, 659 [Mꢁ2ClO4]2+
;
elemental analysis calcd (%) for C64H74Cl2N6O8Pt2·H2O: C 50.10, H 4.99,
N 5.48; found: C 50.12, H 4.87, N 5.50.
ꢁ
ꢀ ꢁ
ꢁ ꢀ ꢁ
Pt
[(tBu3tpy)Pt (C
C
1,2-C6H4)2
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (2): Yield:
66%; 1H NMR (300 MHz, CD3CN, 258C): d=9.04 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 7.94 (d, 4J=1.7 Hz, 4H; terpyridyl H),
4
7.92 (s, 4H; terpyridyl H), 7.71 (dd, J=1.7 Hz, 2H; phenyl H), 7.46–7.35
3
(m, 6H; phenyl H), 7.28 (dd, J=8.4 Hz, 4H; terpyridyl H), 1.44 (s, 18H;
tert-butyl H), 1.39 ppm (s, 36H; tert-butyl H); 13C{1H} NMR (100 MHz,
CD3CN, 258C): d=168.9, 167.6, 158.6 and 154.8 (quaternary C on terpyr-
idyl), 156.2 (tertiary C on terpyridyl), 133.8, 133.6, 129.7 and 127.8 (C on
phenyl ring), 126.8 (tertiary C on terpyridyl), 126.5 (C on phenyl ring),
ꢁ ꢀ
123.7 and 121.5 (tertiary C on terpyridyl), 106.8 (Pt C C), 103.9 (Pt C
ꢀ
C), 93.4 (C C), 38.2 and 37.1 (quaternary C on tert-butyl group), 30.9
and 30.4 ppm (primary C on tert-butyl group); IR (KBr): n˜ =2120 cmꢁ1
+
+
ꢀ
(C C); FAB-MS (+ve): m/z: 1516 [MꢁClO4] , 1417 [Mꢁ2ClO4] , 708
[Mꢁ2ClO4]2+; elemental analysis calcd (%) for C72H78Cl2N6O8Pt2·H2O:
C 52.91, H 4.93, N 5.14; found: C 52.56, H 4.75, N 5.07.
ꢁ
ꢀ ꢁ
1,2-C6H4)3
ꢁ ꢀ ꢁ
Pt
[(tBu3tpy)Pt (C
C
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (3): Yield:
52%; 1H NMR (300 MHz, CD3CN, 258C): d=9.09 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 8.23 (s, 4H; terpyridyl H), 8.15 (d, 1.7J=
1.7 Hz, 4H; terpyridyl H), 7.35–7.27 (m, 4H; phenyl H), 7.22 (d, 3J=
6.0 Hz, 4H; terpyridyl H), 6.60 (t, 3J=8.0 Hz, 4H; phenyl H), 6.43 (t,
3J=8.0 Hz, 2H; phenyl H), 6.18 (t, 3J=8.4 Hz, 2H; phenyl H), 1.58 (s,
Experimental Section
General procedures: All starting materials were purchased from commer-
cial sources and used as received unless stated otherwise. The solvents
used for synthesis were of analytical grade. The ortho-PEs, (H (C C
ꢁ
ꢀ ꢁ
9744
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Chem. Eur. J. 2008, 14, 9736 – 9746

Solvatochromic Platinum(II) Complexes
FULL PAPER
18H; tert-butyl H), 1.36 ppm (s, 36H; tert-butyl H); 13C{1H} NMR
(100 MHz, CD3CN, 258C): d=167.8, 167.0, 159.3 and 154.9 (quaternary
C on terpyridyl), 154.6 (tertiary C on terpyridyl), 134.4, 132.5, 131.5,
131.3, 129.6, 128.6 and 127.5 (C on phenyl ring), 126.1 (tertiary C on ter-
pyridyl), 126.0 and 125.7 (C on phenyl ring), 123.9 and 122.2 (tertiary C
C104H94Cl2N6O8Pt2·0.5CH2Cl2: C 60.95, H 4.65, N 4.08; found: C 60.80, H
4.70, N 4.12.
ꢁ ꢀ ꢁ
[(tBu3tpy)Pt 1,2-C6H4)8
ꢁ ꢀ ꢁ
Pt
G
C
C
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (7): Yield:
57%; 1H NMR (300 MHz, CD3CN, 258C): d=8.68 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 7.88 (s, 4H; terpyridyl H), 7.85 (d, 4J=
1.7 Hz, 4H; terpyridyl H), 7.54 (d, 3J=8.2 Hz, 2H; phenyl H), 7.47 (d,
3J=8.1 Hz, 2H; phenyl H), 7.37–7.28 (m, 8H; phenyl H), 7.24–7.09 (m,
12H; phenyl H), 6.96 (m, 2H; phenyl H), 6.91 (dd, 3J=6.0 Hz, 4H; ter-
pyridyl H), 6.64 (td, 3J=8.0 Hz, 2H; phenyl H), 6.53 (d, 2H; phenyl H),
ꢁ ꢀ
ꢀ
ꢀ
on terpyridyl), 102.8 (Pt C C), 95.2 (C C), 91.9 (C C), 38.1 and 37.0
(quaternary C on tert-butyl group), 30.7 and 30.3 ppm (primary C on tert-
butyl group); IR (KBr)): n˜ =2120 cmꢁ1 (C C); FAB-MS (+ve): m/z:
ꢀ
1516 [Mꢁ2ClO4]+, 759 [Mꢁ2ClO4]2+; elemental analysis calcd (%) for
C80H82Cl2N6O8Pt2·2H2O: C 54.82, H 4.95, N 4.80; found: C 54.58, H 4.77,
N 4.85.
3
6.35 (td, J=8.1 Hz, 2H; phenyl H), 1.27 (s, 18H; tert-butyl H), 1.20 ppm
(s, 36H; tert-butyl H); 13C{1H} NMR (100 MHz, CD3CN, 258C): d=167.8,
166.6, 159.0 and 154.8 (quaternary C on terpyridyl), 154.5 (tertiary C on
terpyridyl), 134.7, 133.5, 133.1, 132.9, 132.7, 132.5, 132.1, 131.7, 130.5,
129.7, 129.6, 128.6, 128.4, 127.0, 126.7, 126.4, 126.3 and 126.2 (phenyl C),
125.9 (tertiary C on terpyridyl), 125.8 and 125.4 (phenyl C), 123.3 and
ꢁ
ꢀ ꢁ
1,2-C6H4)4
ꢁ ꢀ ꢁ
Pt
[(tBu3tpy)Pt (C
C
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (4): Yield:
51%; 1H NMR (300 MHz, CD3CN, 258C): d=8.88 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 8.16 (s, 4H; terpyridyl H), 8.01 (d, 4J=
1.7 Hz, 4H; terpyridyl H), 7.37–7.28(m, 8H; phenyl H), 7.23 (td, 3J=
8.4 Hz, 2H; phenyl H), 7.08 (m, 2H; phenyl H), 7.00 (dd, 3J=6.0, 4J=
1.7 Hz, 4H; terpyridyl H), 6.84 (m, 4H; phenyl H), 1.51 (s, 18H; tert-
butyl H), 1.21 ppm (s, 36H; tert-butyl H); 13C{1H} NMR (100 MHz,
CD3CN, 258C): d=168.1, 167.1, 159.2 and 154.8 (quaternary C on terpyr-
idyl), 154.7 (tertiary C on terpyridyl), 134.5, 132.9, 132.5, 130.3, 129.6,
129.2, 129.0,127.2 and 126.5 (C on phenyl ring), 126.2, 123.7 and 122.1
ꢁ ꢀ
ꢁ ꢀ
121.7 (tertiary C on terpyridyl), 106.6 (Pt C C), 101.8 (Pt C C), 95.0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(C C), 94.0 (C C), 93.2 (C C), 93.0 (C C), 92.2 (C C), 91.6 (C C), 37.8
and 36.7 (quaternary C on tert-butyl group), 30.5 and 30.1 ppm (primary
C on tert-butyl group); IR (KBr): n˜ =2119 cmꢁ1 (C C); FAB-MS (+ve):
ꢀ
m/z: 2116 [MꢁClO4]+, 2016 [Mꢁ2ClO4]+, 1008 [Mꢁ2ClO4]2+; elemental
analysis calcd (%) for C120H102Cl2N6O8Pt2·1.5CH2Cl2: C 62.24, H 4.51, N
3.58; found: C 62.18, H 4.46, N 3.38.
ꢁ ꢀ
ꢁ ꢀ
ꢀ
(tertiary C on terpyridyl), 106.2 (Pt C C), 102.6 (Pt C C), 94.7 (C C),
AHCTRE[UGN (tBu3tpy)Pt C
CC6H5]ClO4 (8): Yield: 90%; 1H NMR (400 MHz,
ꢁ ꢀ
ꢀ
ꢀ
93.4 (C C), 91.4 (C C), 38.0 and 36.8 (quaternary C on tert-butyl group),
30.6 and 30.1 ppm (primary
CD3CN, 258C): d=8.88 (d with Pt satellites, 3J=6.0 Hz, 2H; terpyridyl
H), 8.28 (s, 2H; terpyridyl H), 8.23 (d, 4J=1.8 Hz, 2H; terpyridyl H),
C on tert-butyl group); IR (KBr): n˜ =
2117 cmꢁ1 (C C); FAB-MS (+ve): m/z: 1716 [MꢁClO4]+, 1617
ꢀ
4
7.68 (dd, 3J=6.0, J=1.8 Hz, 2H; terpyridyl H), 7.43 (m, 2H; phenyl H),
[Mꢁ2ClO4]+, 808 [Mꢁ2ClO4]2+
; elemental analysis calcd (%) for
7.35 (t, 3J=8.4 Hz, 2H; phenyl H), 7.28 (m, 1H; phenyl H), 1.52 (s, 9H;
tert-butyl H), 1.43 ppm (s, 18H; tert-butyl H); 13C{1H} NMR (100 MHz,
CD3CN, 258C): d=168.5, 167.9, 159.8 and 155.1 (quaternary C on terpyr-
idyl), 154.7 (tertiary C on terpyridyl), 132.7, 129.3, 128.0 and 127.6 (C on
C88H86Cl2N6O8Pt2·H2O: C 57.61, H 4.83, N 4.58; found: C 57.66, H 4.83,
N 4.56.
ꢁ
ꢀ ꢁ
1,2-C6H4)5
ꢁ ꢀ ꢁ
Pt
[(tBu3tpy)Pt (C
C
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (5): Yield:
ꢁ
phenyl ring), 126.9, 124.1 and 122.3 (tertiary C on terpyridyl), 104.4 (Pt
ꢀ
ꢁ ꢀ
C C), 99.2 (Pt C C), 38.1 and 37.1 (quaternary C on tert-butyl group),
30.7 and 30.3 ppm (primary
C on tert-butyl group); IR (KBr): n˜ =
3J=7.8 Hz, 2H; phenyl H), 7.52 (td, J=8.0 Hz, 2H; phenyl H), 7.42 (dd,
ꢀ
3
2118 cmꢁ1 (C C); FAB-MS (+ve): m/z: 697 [MꢁClO4] ; elemental anal-
ysis calcd (%) for C35H40ClN3O4Pt: C 52.73, H 5.06, N 5.27; found: C
52.62, H 5.00, N 5.21.
+
3J=8.0 Hz, 2H; phenyl H), 7.38 (td, 3J=7.9 Hz, 2H; phenyl H), 7.32 (td,
3J=8.0 Hz, 2H; phenyl H), 7.26 (td, J=8.2 Hz, 2H; phenyl H), 7.07 (dd,
3
3J=6.0, 4J=1.7 Hz, 4H; terpyridyl H), 6.62 (m, 2H; phenyl H), 6.51 (d,
3J=7.9 Hz, 2H; phenyl H), 5.87 (m, 2H; phenyl H), 1.29 (s, 36H; tert-
butyl H), 1.26 ppm (s, 18H; tert-butyl H); 13C{1H} NMR (100 MHz,
CD3CN, 258C): d=168.1, 166.7, 159.2 and 154.9 (quaternary C on terpyr-
idyl), 154.5 (tertiary C on terpyridyl), 134.3, 134.2, 132.7, 132.2, 131.5,
130.7, 129.9, 129.8, 129.7, 127.5, 127.1, 126.9 and 126.6 (phenyl C), 126.1,
ꢁ
ꢀ ꢁ
ꢁ ꢀ
AHCRTEGNU[(tBu3tpy)Pt (C C 1,2-C6H4)2 C CC6H5]ClO4 (9): Yield, 83%;
1H NMR (400 MHz, CD3CN, 258C): d=8.91 (d with Pt satellites, 3J=
4
6.0 Hz, 2H; terpyridyl H), 8.15 (s, 2H; terpyridyl H), 8.07 (d, J=1.7 Hz,
2H; terpyridyl H), 7.65 (dd, 3J=8.2 Hz, 1H; phenyl H), 7.59 (dd, 3J=
3
7.9 Hz, 1H; phenyl H), 7.50 (dd, J=8.1 Hz, 1H; phenyl H),7.43–7.26 (m,
5H; phenyl H), 7.12 (m, 4H), 6.67 (m, 3H; phenyl H), 1.53 (s, 9H; tert-
butyl H), 1.33 ppm (s, 18H; tert-butyl H); 13C{1H} NMR (100 MHz,
CD3CN, 258C): d=168.1, 167.2, 159.2 and 155.0 (quaternary C on terpyr-
idyl), 154.7 (tertiary C on terpyridyl), 134.0, 133.4, 133.3, 133.2, 132.9,
130.3, 129.8, 129.7, 129.5, 129.0, 128.6, 127.3 and 126.5 (C on phenyl ring),
126.2 (tertiary C on terpyridyl), 126.1, 126.0 and 124.1 (C on phenyl
ꢁ ꢀ
ꢁ ꢀ
123.3 and 121.8 (tertiary C on terpyridyl), 106.8 (Pt C C), 101.5 (Pt C
ꢀ
ꢀ
ꢀ
ꢀ
C), 95.4 (C C), 93.8 (C C), 92.5 (C C), 91.6 (C C), 37.8 and 36.8 (qua-
ternary C on tert-butyl group), 30.4 and 30.3 ppm (primary C on tert-
butyl group); IR (KBr): n˜ =2119 cmꢁ1 (C C); FAB-MS (+ve): m/z: 1817
ꢀ
[MꢁClO4]+, 1718 [Mꢁ2ClO4]+, 859 [M-2ClO4]2+; elemental analysis
calcd (%) for C96H90Cl2N6O8Pt2·CH2Cl2: C 58.20, H 4.63, N 4.20; found:
C 58.52, H 4.78, N 4.52.
ꢁ ꢀ
ring), 123.8 and 122.1 (tertiary C on terpyridyl), 106.2 (Pt C C), 102.4
(Pt C C), 94.8 (C C), 91.9 (C C), 89.1 (C C), 38.1 and 36.9 (quaternary
ꢁ ꢀ
ꢀ
ꢀ
ꢀ
C on tert-butyl group), 30.7 and 30.3 ppm (primary C on tert-butyl
ꢁ
ꢀ ꢁ
C 1,2-C6H4)6
ꢁ ꢀ ꢁ
Pt
[(tBu3tpy)Pt (C
C
C
ACHTRUNEG(tBu3tpy)]AHCTRE[UGN ClO4]2 (6): Yield:
group); IR (KBr): n˜ =2117 cmꢁ1 (C C); FAB-MS (+ve): m/z: 897
ꢀ
65%; 1H NMR (400 MHz, CD3CN, 258C): d=8.80 (d with Pt satellites,
3J=6.0 Hz, 4H; terpyridyl H), 7.89 (s, 4H; terpyridyl H), 7.85 (d, 4J=
1.7 Hz, 4H; terpyridyl H), 7.73 (d, 3J=8.0 Hz, 2H; phenyl H), 7.57 (dd,
3J=8.0 Hz, 2H; phenyl H), 7.50 (td, 3J=7.9 Hz, 2H; phenyl H), 7.45 (d,
3J=7.8 Hz, 2H; phenyl H), 7.39–7.26 (m, 8H; phenyl H), 7.05 (td, 3J=
8.0 Hz, 2H; phenyl H), 7.00 (dd, 3J=6.0, 4J=1.7 Hz, 4H; terpyridyl H),
6.93 (d, 3J=8.2 Hz, 2H; phenyl H), 6.52 (td, 3J=8.4 Hz, 2H; phenyl H),
6.24 (d, 3J=8.2 Hz, 2H; phenyl H), 1.28 (s, 18H; tert-butyl H), 1.27 ppm
(s, 36H; tert-butyl H); 13C{1H} NMR (100 MHz, CD3CN, 258C): d=168.2,
166.9, 159.1 and 155.1 (quaternary C on terpyridyl), 154.7 (tertiary C on
terpyridyl), 135.4, 133.7, 132.8, 132.7, 132.0, 130.7, 130.5, 130.0, 129.8,
129.7, 129.1, 129.0, 127.3, 127.2, 127.1 126.6 and 126.2 (phenyl C), 126.1
(tertiary C on terpyridyl), 125.6 (phenyl C), 123.2 and 121.8 (tertiary C
[MꢁClO4]+; elemental analysis calcd (%) for C51H48ClN3O4Pt·H2O: C
60.32, H 4.96, N 4.14; found: C 60.10, H 4.98, N 4.10.
X-ray crystallography: Single crystals of 3·2.5CH3OH (slow diffusion of
Et2O into a solution of 3 in CH3OH), 5·CH3CN and 6·4CH3CN (slow dif-
fusion of Et2O into solutions of 5 or 6 in CH3CN) were obtained. X-ray
crystallographic data were collected on a MAR diffractometer with a
300 mm image plate detector using graphite-monochromated MoKa radia-
tion (l=0.71073 Š). The crystallographic data collection parameters are
summarized in Table 1. CCDC-288275 (3·2.5CH3OH), -288276
(5·CH3CN), and -288277 (6·4CH3CN) contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
ꢁ ꢀ
ꢁ ꢀ
ꢀ
ꢀ
on terpyridyl), 106.5 (Pt C C), 101.8 (Pt C C), 95.5 (C C), 94.8 (C C),
ꢀ
ꢀ
ꢀ
93.7 (C C), 92.6 (C C), 91.5 (C C), 38.0 and 36.9 (quaternary C on tert-
butyl group), 30.5 and 30.3 ppm (primary C on tert-butyl group); IR
(KBr): n˜ =2118 cmꢁ1 (C C); FAB-MS (+ve): m/z: 1818 [Mꢁ2ClO4] ,
+
ꢀ
909
[Mꢁ2ClO4]2+
;
elemental
analysis
calcd
(%)
for
Chem. Eur. J. 2008, 14, 9736 – 9746
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9745

C.-M. Che et al.
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Received: March 4, 2008
Revised: July 9, 2008
Published online: September 24, 2008
9746
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 9736 – 9746