Photoswitchable organoplatinum complexes containing an azobenzene derivative of 3,6-di(2-pyridyl)pyridazine

Article abstract of DOI:10.1139/cjc-2013-0588

The new, unsymmetrical azobenzene-tagged ligand 4-(4-azobenzene)-3,6-di(2- pyridyl)pyridazine, adpp, forms complexes with platinum(II) and platinum(IV), which exist as a mixture of geometrical isomers. The complexes are characterized primarily by their NMR spectra, while the structures of the ligand and its complexes [PtMe₂(adpp)], [PtBrMe₂(CH₂C ₆H₄-4-t-Bu)(adpp)], and [PtBrMe₂(CH ₂C₆H₃-3,5-t-Bu₂)(adpp)] have been structurally characterized. In solution, the compounds undergo easy photochemical trans-cis switching of the azobenzene group, with subsequent slow thermal isomerization back to the more stable trans-azobenzene isomer.

Full text of DOI:10.1139/cjc-2013-0588

7
06
ARTICLE
Photoswitchable organoplatinum complexes containing an
azobenzene derivative of 3,6-di(2-pyridyl)pyridazine
Mohamed E. Moustafa, Paul D. Boyle, and Richard J. Puddephatt
Abstract: The new, unsymmetrical azobenzene-tagged ligand 4-(4-azobenzene)-3,6-di(2-pyridyl)pyridazine, adpp, forms com-
plexes with platinum(II) and platinum(IV), which exist as a mixture of geometrical isomers. The complexes are characterized
primarily by their NMR spectra, while the structures of the ligand and its complexes [PtMe (adpp)], [PtBrMe (CH C H -4-t-Bu)(adpp)],
2
2
2 6 4
and [PtBrMe (CH C H -3,5-t-Bu )(adpp)] have been structurally characterized. In solution, the compounds undergo easy photo-
2
2
6
3
2
chemical trans−cis switching of the azobenzene group, with subsequent slow thermal isomerization back to the more stable
trans-azobenzene isomer.
Key words: platinum, azobenzene, photochemistry, organometallic.
Résumé : Le nouveau ligand marqué par l’azobenzène, la 4-(4-azobenzene)-3,6-di(2-pyridyl)pyridazine, ou adpp, forme des
complexes avec le platine(II) et le platine(IV), présents sous forme d’un mélange d’isomères géométriques. Les complexes sont
principalement caractérisés a` l’aide de leur spectre RMN et le ligand et ses complexes, [PtMe (adpp)], [PtBrMe (CH C H -4-t-Bu)(adpp)]
2
2
2 6 4
et [PtBrMe (CH C H -3,5-t-Bu )(adpp)] par leur structure chimique. En solution, les composés subissent facilement une transpo-
2
2
6
3
2
sition photochimique trans−cis du groupe azobenzène, qui redevient, par isomérisation thermique lente, l’isomère trans-
azobenzène, plus stable. [Traduit par la Rédaction]
Mots-clés : platine, azobenzéne, photochimie, organométallique.
Introduction
and its corresponding complexes with platinum(II) and platinu-
m(IV), in which the azobenzene group is further removed from
the platinum centre but in which ␲-conjugation is possible. The
There is continuing interest in the use of azobenzene deriva-
tives in artificial photochromic systems because the azobenzene
unit can be switched reversibly between trans and cis isomers,
ligand 3,6-di(2-pyridyl)pyridazine and its derivatives are known to
1
2
form stable complexes with transition metals, including copper,
1
,2
which have different electronic and structural properties. Typ-
ically, the more stable trans isomer can be converted to the cis
isomer by irradiation into its ␲−␲* band centred at about 340 nm,
while the cis isomer can be converted back to the trans isomer
either by mild heating or by irradiation into its ␲−␲* band centred
at about 450 nm (Scheme 1). The isomerization can be monitored
easily by taking advantage of the major differences in the UV-
13,14
15,16
17–19
silver,
ruthenium,
and platinum.
Pyridazines have also
been utilized in the framework for the synthesis of metal organic
20,21
frameworks.
Results and discussion
The synthesis of the new azobenzene-tagged ligand 4-(4-azobenzene)-
3,6-di(2-pyridyl)pyridazine, adpp, is shown in Scheme 3. The first
1
visible or H NMR spectra of the isomers, while the high stability
steps lead to the synthesis of the alkyne 4-ethynylazobenzene,
of azobenzene allows many switching cycles to be achieved with-
2
2,23
EAB, according to the published procedure,
while the second
out significant decomposition.1–4
step involves the reaction of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine with
There are still rather few photoswitchable organometallic
24
the alkyne with displacement of dinitrogen. This final reaction
complexes5 and the first photoswitchable organoplatinum com-
–9
is an inverse electron demand Diels−Alder reaction and has been
used to prepare several other derivatives of 3,6-di(2-pyridyl)pyrid-
plexes were reported only recently.1
0,11
Selected examples are
shown in Scheme 2. The azobenzene group has been incorporated
into a pyridyl-imine ligand in the platinum(II) complex A and into
an alkylplatinum group in the platinum(IV) complex B.
24
azine. As this reaction occurs, the purple colour of the tetrazine
is replaced by the orange colour of adpp.
The structure of the ligand adpp is shown in Fig. 1 and confirms
the expected trans stereochemistry of the azobenzene group. No-
tably, the ligand exhibits a conformation in which the neighbour-
ing pyridine and pyridazine nitrogen atoms mutually anti, which
is probably favoured by weak N··H hydrogen bonding interac-
tions. The two pyridyl rings are twisted out of the plane of the
pyridazine ring by 11° and 43° for the N(1) and N(4) rings, respec-
tively, while the azobenzene C H group is twisted out of the
In both A and B (Scheme 2), the azobenzene is only one atom
(nitrogen atom in A, carbon atom in B) removed from the plati-
num centre, but photoswitching was more efficient for B, in
which the azobenzene group is separated from platinum by a
saturated carbon centre, than for A, in which conjugation of the
␲
ble.
-systems of the azobenzene and platinum-imine groups is possi-
1
0,11
The present work describes the synthesis and photochem-
6
4
istry of an azobenzene-tagged 3,6-di(2-pyridyl)pyridazine ligand
plane of the pyridazine ring by 43°. The greater twists for the N(4)
Received 9 January 2014. Accepted 5 February 2014.
M.E. Moustafa. Department of Chemistry, University of Western Ontario, London, ON N6A 5B7, Canada; Department of Chemistry, Faculty of
Education, Suez Canal University, Arish, Egypt.
P.D. Boyle and R.J. Puddephatt. Department of Chemistry, University of Western Ontario, London, ON N6A 5B7, Canada.
Corresponding author: Richard J. Puddephatt (e-mail: pudd@uwo.ca).
This article is part of a Special Issue dedicated to Professor Barry Lever in recognition of his contributions to inorganic chemistry across Canada and beyond.
Can. J. Chem. 92: 706–715 (2014) dx.doi.org/10.1139/cjc-2013-0588
Published at www.nrcresearchpress.com/cjc on 25 February 2014.

Moustafa et al.
707
Scheme 1. Photoisomerization of azobenzene derivatives.
group to be roughly coplanar with the pyridazine group (twist
angle is 11° compared to 43° in the free ligand adpp) and this
increases steric effects with the azobenzene group when com-
pared to the free ligand adpp. The structure of 1a does, however,
allow CH··N hydrogen bonding of the free 2-pyridyl group to be
retained (N(3)··H(13) 2.52 Å, N(4)··H(10) 2.49 Å; twist angle of the
N(4) pyridyl group is 14° compared to 11° in free adpp). The chlo-
roform solvate molecule in 1a is hydrogen bonded to the electron-
rich dimethylplatinum(II) centre, with Pt(1)··H(1X) 2.65 Å, in the
2
6–28
range found for similar interactions.
The flat structure of the
di-2-pyridyl-pyridazine unit in 1a allows ␲-stacking between pairs
of molecules, as shown in Fig. 4. The isomers 1a and 1b do not
easily interconvert at room temperature.
Sb ci ph yer mi d ei n 2e .) . Photoswitchable organoplatinum complexes (NN = 2,2=-
The reaction of the ligand adpp with trans-[PtCl(Me)(SMe2)2]11 in
acetone afforded the complex [PtClMe(adpp)], 2, as depicted in
1
Scheme 5. The H NMR spectrum of 2 showed that it was formed as
a mixture of two isomers, with relative abundance of 65:35, iden-
2
6
3
tified as 2a (␦(MePt) 1.57, J = 84 Hz; ␦(H ) 9.62, J = 18 Hz) and
PtH
PtH
2
6
3
2
b (␦(MePt) 1.43, J
= 78 Hz; ␦(H ) 9.48, J
= 23), respectively.
PtH
PtH
For each isomer, the pyridyl nitrogen is trans to the methyl-
platinum group, as shown by the small value of the coupling
3
17
constant J
to the ortho proton. We were unable to separate
PtH
these complexes either by crystallization or by chromatography.
Oxidative addition reactions of complex [PtMe (adpp)], 2, to
2
give platinum(IV) derivatives
Complex 1 reacted with iodine or with alkyl halides by trans
oxidative addition to give the organoplatinum(IV) complexes il-
lustrated in Scheme 6. The complexes were formed as a mixture of
isomers, but since the platinum(IV) complexes are stable on a
silica column, it was possible to separate the isomers in some
cases by column chromatography.
1
The complexes were initially characterized by their H NMR and
mass spectra. The iodine adduct [PtI Me (adpp)], 3, was isolated as
2
2
a yellow solid and the isomers were successfully separated. The
1
H NMR spectrum of the major isomer 3a contained two methyl-
2
platinum resonances (␦(MePt) 2.50 and 2.83, each with J = 74 Hz)
with coupling constants JPtH characteristic for platinum(IV)
complexes. The H NMR spectrum of the major isomer of
PtH
2
1
1
1
[
PtIMe (adpp)], 4a, showed three equal intensity methylplatinum
3
2
resonances (␦ 0.83, JPtH = 74 Hz, assigned to the axial methyl
group, ␦ 1.64, J
2
2
= 71 Hz, and 1.93, J
= 72 Hz, assigned to the
PtH
PtH
equatorial methyl groups). An additional feature of complexes
pyridyl ring and the C H group are clearly to relieve steric con-
5–7 is that the CH protons of the ethyl or benzyl group are diaste-
reotopic and occur as an “AB” multiplet in the H NMR spectrum,
with further coupling to the methyl protons when X = Et
6
4
2
1
gestion between these groups, but it occurs at the expense of
-conjugation and hydrogen bonding (compare N(3)··H(11) 2.65 Å,
␲
N(2)··H(4) 2.52 Å, and N(1)··H(7) 2.45 Å). The azobenzene atoms are
close to being coplanar (twist between the two aryl groups is 7°).
(Scheme 6). For example, the CH Pt resonances of 6a were ob-
2
2
2
A
served at ␦ 2.98 (m, 1H, J
= 10 Hz, J
= 90 Hz, PtCH ).
= 91 Hz, PtCH ) and
HH
2
PtH
2
B
The complex [PtMe (adpp)], 1, was readily prepared by the reac-
␦ 3.05 (m, 1H, J = 10 Hz, J
2
HH
PtH
tion of the ligand adpp with the precursor [Pt Me (␮-SMe ) ] in
The structures of complexes 6a and 7b were determined and
are shown in Figs. 5 and 6, and each complex has the octahedral
stereochemistry at platinum(IV) expected for the product of trans
oxidative addition to isomer 1a or 1b, respectively. Because the
ligand adpp is unsymmetrical, the complexes are chiral and the
lattices contain both C and A enantiomers. In both complexes,
the benzyl group is directed towards the azobenzene group, per-
haps to optimize ␲-stacking attractions.
2
4
2 2
acetone,25 with displacement of the dimethyl sulfide ligands
1
(
Scheme 4), and was isolated as a red solid. The H NMR spectrum
of complex 1 showed that it was formed as a mixture of isomers 1a
and 1b in about an 85:15 ratio as determined by integration of
the methylplatinum resonances (Fig. 2). Complex 1a gave two
methylplatinum resonances (␦ 1.41 and 1.65, each with coupling
constant 2JPtH = 88 Hz), and a doublet resonance for the ortho
hydrogen atom of the coordinated pyridine ring was observed at
A summary of conformational parameters for the adpp ligand is
given in Table 1. In complex 7b, the 2-pyridyl group that is ortho to
the azobenzene group is not coordinated and its conformation,
measured by ⍜1, is similar to that in the free ligand adpp, whereas
the conformation of this 2-pyridyl group in 6a is similar to that in
1a. The 2-pyridyl group that is meta to the azobenzene group is
always roughly coplanar with the pyridazine ring, but flipped in
7b compared to the other compounds (Table 1). There is a large
variation in the twist of the aryl groups of the azobenzene unit,
⍜4, and this appears to arise from intermolecular packing forces.
Complex 6a gives the largest value of ⍜4, and there is intermolec-
3
␦
9.40, with coupling constant JPtH = 23 Hz, demonstrating chela-
tion of platinum(II) by the ligand adpp. Isomer 1b gave similar
2
2
6
parameters (␦(MePt)1.40, JPtH = 87 Hz; 1.62, JPtH = 87 Hz; ␦ (H )
3
8
.32, JPtH = 23 Hz).
It was not possible to separate the isomers of complex 1, but
single crystals of the major isomer 1a were obtained, as the chlo-
roform solvate, and its structure is shown in Figs. 3 and 4. It shows
that the 2-pyridyl group closer to the azobenzene coordinates to
platinum in forming the chelate complex. The reason for this
selectivity is not obvious, since chelation requires the N(1) pyridyl
Published by NRC Research Press

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Can. J. Chem. Vol. 92, 2014
Scheme 3. Synthesis of the azobenzene-tagged ligand adpp.
Fig. 1. Left: view of the structure of the ligand adpp; selected bond
lengths (Å): N(2)–N(3) 1.3365(9), N(5)–N(6) 1.2579(9). Right: favourable
hydrogen bond interactions. The twisting of the ortho 2-pyridyl
group weakens the hydrogen bond with the pyridazine nitrogen
atom.
The isomerization of the azobenzene group in the compounds
from the more stable trans to the less stable cis isomer was effected
by irradiation using ␭(irr) 365 nm, which excites primarily the
␲−␲* transition of the trans-azobenzene group, while the reverse
reaction occurred slowly and spontaneously at room tempera-
ture, as illustrated for the ligand adpp in Scheme 7. The reactions
1
1–11
were monitored by UV-visible and H NMR spectroscopy.
The changes in UV-visible spectra on photoisomerization of
adpp are illustrated in Fig. 8. The main feature is the decrease in
intensity of the ␲−␲* transition of the trans isomer at 340 nm,
while there is a small increase in the intensity of the n−␲* transi-
tion for the cis isomer at 441 nm. The quantum yield for photoi-
somerisation (⌽ = 0.12) (Table 2) was very similar to that for the
2
9–33
azobenzene standard (⌽ = 0.11).
The changes were fully re-
versed when the sample was stored in the dark, as slow thermal
isomerization back to the trans isomer occurred.
1
Changes in part of the H NMR spectrum upon photoisomeriza-
tion of adpp are shown in Fig. 9, emphasizing changes in selected
resonances of the di-2-pyridylpyridazine protons. Upon illumina-
ular ␲-stacking between phenyl groups of neighbouring mole-
cules.
tion of the free ligand trans-adpp in CD Cl with ␭(irr) 365 nm for
2
2
5
min, new peaks assigned to the cis isomer were observed. The
Photoisomerization studies
changes were reversed when the sample was stored in the dark.
The photoisomerization of the platinum complexes was studied
in a similar way. A typical series of UV-visible spectra is shown in
Fig. 10 for complex 6. During the course of irradiation with
365 nm light, a decrease in intensity of the ␲−␲* band of the trans
isomer at 320 nm was observed with the growth of a band at
437 nm attributed to the n−␲* band of the cis isomer. Keeping the
irradiated sample in the dark for 1 day led to recovery of the ␲−␲*
band of the trans isomer, confirming that the cis-to-trans isomer-
ization can be achieved thermally. Notably, the thermal isomer-
ization was slower than the analogous reaction for the free ligand
adpp. Figure 11 shows the recovery of intensity of the ␲−␲* band of
The UV-visible spectra of the compounds were measured in
dichloromethane solution (Table 2; Fig. 7) to investigate the effect
of metal on the electronic absorption spectrum of the azobenzene
unit. Both the precursor compound EAB and the free ligand adpp
contain a weak n−␲* band at 455 nm and a strong ␲−␲* band at
340–341 nm, while adpp gives an extra band at 290 nm associated
1–4,21, 28–32
with the dipyridylpyridazine (dppz) group.
In complex 1
(
largely isomer 1a), there is a strong band at 318 nm, assigned to
the dppz transition, with a broad shoulder at approximately
50 nm, assigned to the ␲−␲* transition, and two weak, broad
3
overlapping peaks at approximately 430 nm, assigned to the n−␲*
transition, and approximately 530 nm, assigned to a metal-to-
1
the trans isomer on warming the sample. As monitored by H NMR
ligand charge transfer transition originating from the filled 5d 2
spectroscopy, the irradiated sample solution contained about 25%
of the trans and 75% of the cis isomer at the photostationary state.
The other platinum complexes behaved similarly and data are
given in Table 2. It can be seen that the quantum yields for pho-
z
orbital of the electron-rich platinum(II) centre.3
3–37
This low-
energy band at approximately 530 nm in 1 was absent in the
platinum(IV) complexes.
Published by NRC Research Press

Moustafa et al.
709
Scheme 4. Synthesis of [PtMe (adpp)], 1.
2
Fig. 2. 1H NMR spectrum (400 MHz, chloroform-d) of complex 1 in
Fig. 4. The ␲-stacking between molecules of complex 1a.
195
the methylplatinum region. Pt satellite peaks of the major isomer
a are indicated by asterisks.
1
toisomerization are lower than for the ligand adpp or its precur-
sor EAB.
Fig. 3. View of the structure of the complex [PtMe (adpp)], 1a.
2
Thermal ellipsoids are at the 30% probability level and hydrogen
atoms are omitted for clarity. Selected bond lengths (Å): Pt(1)–C(1)
Conclusions
2
.038(2), Pt(1)–C(2) 2.045(3), Pt(1)–N(2) 2.076(2), Pt(1)–N(1) 2.084(19),
The ligand adpp is unsymmetrical and so it can give isomeric
platinum(II) complexes such as 1a and 1b (Scheme 4). Once
formed, the isomer ratio for the complexes in solution does not
change and the platinum(IV) complexes are sufficiently stable to
allow separation by column chromatography. Many platinum
complexes are kinetically inert, so the isomer ratio is likely to be
controlled mostly by kinetic factors. To gain further insight into
the thermodynamic stability of the isomers, DFT calculations
N(2)–N(3) 1.331(3), N(5)–N(6) 1.255(3). Hydrogen bond distance
Pt(1)··H(1X) 2.65 Å.
(
BLYP functional, double-zeta basis set, first-order scalar relativis-
tic corrections) were carried out for the isomers of the platinu-
m(II) complex 1 and the platinum(IV) complexes 6 and 7, for
which the structures of 1a, 6a, and 7b were known (Figs. 3, 5, and
6
). Typical calculated structures for 1a and 1b are shown in Fig. 12.
For all cases, the isomer 1a, 6a, or 7a was calculated to be 10–
−
1
1
1 kJ mol more stable than the corresponding isomer 1b, 6b, or
7
b, with no significant variation with oxidation state of platinum
or steric effects of substituents. The observed isomer ratio of 1a/1b
of approximately 6, if representing an equilibrium constant,
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Can. J. Chem. Vol. 92, 2014
Scheme 5. Synthesis of the complex [PtClMe(adpp)], 2.
Scheme 6. Oxidative addition reactions of complex 2.
Fig. 5. View of the structure of the complex [PtBrMe (CH C H -
2
2 6 4
4-t-Bu)(adpp)], 6a. Ellipsoids are at the 30% probability level and
hydrogen atoms were omitted for clarity. Selected bond lengths (Å):
Pt(1)–C(1) 2.051(2), Pt(1)–C(2) 2.044(2), Pt(1)–C(3) 2.074(2), Pt(1)–N(1)
2
.1669(17), Pt(1)–N(2) 2.1462(17), Pt(1)–Br(1) 2.6073(6), N(2)–N(3) 1.331(2),
N(5)–N(6) 1.260(3).
Fig. 6. View of the structure of the complex [PtBrMe (CH C H -
2
2 6 3
3
,5-t-Bu )(adpp)], 7b. Ellipsoids are at the 30% probability level and
2
hydrogen atoms were omitted for clarity. Selected bond lengths (Å):
Pt(1)–C(1) 2.044(5), Pt(1)–C(2) 2.034(5), Pt(1)–C(3) 2.091(5), Pt(1)–N(1)
2
.149(4), Pt(1)–N(2) 2.141(4), Pt(1)–Br(1) 2.6037(7), N(2)–N(3) 1.333(5),
N(5)–N(6) 1.175(7).
would require ⌬G for the equation of Fig. 12 at 298 K of
−
1
4
.5 kJ mol , in reasonable agreement with the calculation. We
conclude that both kinetic and thermodynamic factors favour the
formation of isomer 1a over 1b.
The DFT calculations for the cis-azobenzene isomers, formed by
−
1
photoisomerization, predict that they are about 50 kJ mol less
stable than the corresponding trans-azobenzene isomers. Similar
values were calculated for the platinum(II) and platinum(IV) com-
1
0,11
plexes studied previously as well as for the parent ligands.
Compared to the previous compounds, A and B (Scheme 2), the
complexes studied here are photoisomerized more easily than A
but less easily than B. This indicates that placing the azobenzene
Published by NRC Research Press

Moustafa et al.
711
Table 1. Conformation of adpp in the free ligand
and its complexes.
(CCDC 985642, 985643, 985645, and 985646) and unusual features
are described below.
The structure of the ligand adpp contained a disordered mole-
cule of acetone of solvation. The disorder was comprised of both
crystallographically imposed disorder and a general disorder, and
it was successfully modeled. The structure of complex 1a con-
adpp
1a
11
166
66
6a
13
175
58
41
7b
⌰
⌰
⌰
⌰
1a
137
169
43
7
146
5
43
21
a
2
3
4
a
b
tained a disordered molecule of CHCl of solvation that was mod-
3
22
eled successfully. The structure of 6a exhibited disorder of the
a
o
Twist angle ( ) with respect to the pyridazine ring: ⌰1,
t-butyl group over two sites and disorder of a molecule of CH Cl2
2
2
-pyridyl group ortho to azobenzene; ⌰2, 2-pyridyl group
meta to azobenzene; ⌰3, C H group.
4, twist angle between C H and C H groups of
6 5 6 4
azobenzene. The angles ⌰1 and ⌰2 are reported with re-
of solvation over two sites. For this structure, there was anoma-
lous electron density close to the platinum and bromine atoms,
perhaps resulting from deficiency in the absorption correction.
6
4
b
⌰
spect to the ideal chelate conformation.
4
-(4-Azobenzene)-3,6-di(2-pyridyl)pyridazine, adpp
To a solution of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (1 g, 4.24 mmol) in
group farther from the platinum centre, as in 1–7 compared to A,
leads to more efficient photochemistry but that the difference is
less marked than when an insulating saturated carbon centre is
dry toluene (40 mL) was added EAB (0.872 g, 4.24 mmol), and the
reaction mixture was heated under reflux for 48 h. The solvent
was removed under reduced pressure to afford the crude product
as a brown solid, which was purified by column chromatography,
using dichloromethane−hexane (15%:85%) as eluent, and was iso-
1
0,11
placed between the platinum and azobenzene units, as in B.
The lower quantum yields for the platinum complexes can thus be
correlated with the degree of mixing of the ␲−␲* excited state
with metal-based excited states, such as the MLCT excited states
for the platinum(II) complexes studied in this work.
lated as an orange powder. Yield 63% (1.1 g). NMR in CDCl , trans-
3
1
5C
5A
mD
adpp, ␦( H): 7.32 (m, 1H, H ), 7.46 (m, 3H, H , H ), 7.53 (m, 3H,
mE
pE
4C
3
oD
H
and H ), 7.85 (m, 1H, H ), 7.90 (d, 2H, J = 8 Hz, H ), 7.94
HH
4
A
oE
3
3C
(
m, 3H, H and H ), 8.04 (d, 1H, J
= 8 Hz, H ), 8.48 (d, 1H,
Experimental
HH
3
6C
5B
3
6A
JHH = 5 Hz, H ), 8.74 (s, 1H, H ), 8.75 (d, 1H, J = 5 Hz, H ), 8.84
1
HH
All reactions were performed under nitrogen atmosphere. H
3
3A
13
(
1
1
d, 1H, J = 8 Hz, H ); ␦( C): 158.0, 157.7, 155.5, 153.2, 152.5, 152.1,
1
3
HH
and C NMR spectra were recorded by using Varian Mercury 400,
Inova 400, and Inova 600 spectrometers, and data are reported
with respect to the labeling system of Chart 1. When mixtures of
isomers were present, assignments were confirmed by 2D COSY
49.5, 149.1, 139.71, 137.2, 136.7, 131.2, 129.7, 129.1, 125.5, 124.3,
+
23.5, 122.9, 121.9. HRMS (ESI) calcd. for C26H N [M] : 414.159;
18
6
found: 414.159. Single crystals of adpp were grown by slow diffu-
sion of n-pentane into a solution of the ligand dissolved in ace-
1
H NMR spectroscopy and, when possible, by comparison with the
1
tone. After photolysis, NMR in CDCl , cis-adpp, ␦( H): 6.81 (m, 2H,
3
NMR spectra of pure isomers. UV-visible spectra were measured
using a Varian Cary 300 Bio spectrophotometer. Mass spectra
were recorded using an electrospray PE-Sciex mass spectrometer
mE
3
mD
3
HH HH
oD
H
7
(
1
), 6.87 (d, 2H, J = 8 Hz, H ), 7.16 (d, 2H, J = 8 Hz, H ),
3
pE
5C
5A
.20 (t, 1H, J = 8 Hz, H ), 7.25 (m, 1H, H ), 7.46 (m, 1H, H ), 7.30
m, 2H, J = 8 Hz, H ), 7.82 (m, 1H, H ), 7.93 (m, 1H, H ), 7.96 (d,
H, J = 8 Hz, H ), 8.39 (d, 1H, J = 5 Hz, H ), 8.61 (s, 1H, H ),
.73 (d, 1H, J = 5 Hz, H ), 8.80 (d, 1H, J = 8 Hz, H ).
HH
3
oE
4C
4A
HH
(ESI-MS). DFT calculations were carried out by using the Amster-
3
3C
3
6C
5B
HH
HH
dam Density Functional program based on the BLYP functional,
with double-zeta basis set and first-order scalar relativistic correc-
3
6A
3
3A
8
HH
HH
3
8
tions.
[
PtMe (adpp)], 1
2
To a stirred solution of adpp (0.3 g, 0.724 mmol) in toluene
Photoswitching studies
(
20 mL) was added [Pt Me (␮-SMe ) ] (0.208 g, 0.362 mmol). The
2
4
2 2
For UV-visible monitoring, a sample of the complex was dis-
solved in dichloromethane and was irradiated in a quartz cuvette
with 1 cm width at room temperature with UV light at 365 nm
followed immediately by recording the absorption spectrum. For
solution colour rapidly changed from orange to red with precipi-
tation of a red solid. The reaction mixture was stirred for 1 h for
reaction completion. The solid complex was collected by filtra-
tion, washed with ether (3 × 2 mL) and pentane (3 × 2 mL), and
1
H NMR monitoring, a sample in CDCl or CD Cl in an NMR tube
3
2
2
dried under high vacuum. Yield 82% (0.38 g). NMR in CDCl , 1a,
3
was irradiated at room temperature at 365 nm followed by record-
ing the spectrum.
1
2
2
␦
( H): 1.41 (s, 3H, J
= 87 Hz, PtMe), 1.65 (s, 3H, J
= 87 Hz,
PtH
5
PtH
C
mE
5A
3C
PtMe), 7.26 (m, 3H, H , H ), 7.31 (m, 1H, H ), 7.47 (m, 8H, H
, H , H , H and H ), 7.66 (dt, 1H, J = 6 Hz, H ), 7.91 (d,
2H, JHH = 8 Hz, H ), 8.14 (s, 1H, H ), 8.21 (m, 1H, H ), 8.32 (d, 1H,
HH = 5 Hz, JPtH = 23 Hz, H ); 1b, ␦( H): 1.40 (s, 3H, JPtH = 88 Hz,
Pt-Me), 1.62 (s, 3H, JPtH = 88 Hz, Pt-Me), 7.17 (m, 1H, H ), 7.23 (m,
1H, H ), 7.59 (m, 5H, H , H and H ), 7.72 (m, 1H, H ), 7.97 (m,
,
4
A
oE
mD
4C
pE
3
6C
H
Quantum yield determinations
HH
3
oD
5B
3A
Asolutionofthetransisomerofeachcompoundindichlorometh-
ane was illuminated with UV light at 365 nm, and the absorbance
at the ␲−␲* band maximum was recorded every 30 s. The trans to
cis photoisomerization rate ␯ was obtained from the slope of the
graph of concentration of trans isomer against irradiation time
using azobenzene as a standard.
3
3
6A
1
2
J
2
5A
5
C
mD
mE
pE
4A
4
C
3A
oE
3
oD
1H, H ), 8.0 (m, 3H, H
H ), 8.10 (d, 2H, JHH = 8 Hz, H ), 8.74
(d, 1H, JHH = 6 Hz, H ), 8.90 (d, 1H, JHH = 8 Hz, H ), 8.99 (s, 1H,
,
3
6A
3
3C
5
B
3
3
6C
H
), 9.40 (d, 1H, J = 6 Hz, J
= 23 Hz, H ). Single crystals
HH
PtH
X-ray structure determinations
were grown by slow diffusion of n-pentane into a solution of the
In a typical experiment, a sample was mounted on a Mitegen
polyimide micromount with Paratone N oil. All X-ray measure-
ments were made using a Bruker Kappa Axis Apex2 diffractom-
eter at a temperature of 110 K. The frame integration was
performed using SAINT.3 The resulting raw data were scaled and
absorption corrected using a multiscan averaging of symmetry
compound dissolved in chloroform.
[PtClMe(adpp)], 2
To a stirred solution of the ligand (4-adppn) (0.1 g, 0.241 mmol)
in acetone (10 mL) was added trans [Pt ClMe(SMe ) ] (0.089 g,
9a
2
2 2
0.241 mmol). The solution colour immediately changed to red
with precipitation of a red solid. The reaction mixture was stirred
at room temperature for 1 h. The solid complex was collected by
filtration, washed with ether (3 × 2 mL) and pentane (3 × 2 mL), and
dried under high vacuum. Yield 89% (0.146 g). NMR in CD Cl , 2a,
39b
equivalent data using SADABS.
The structure was solved by
direct methods using the SIR2011 program.40 The hydrogen atoms
for the main molecule were introduced at idealized positions and
were allowed to refine isotropically. The structural model was fit
2
2
2
1
2
5C
to the data using full matrix least-squares based on F . The struc-
␦( H): 1.57 (s, 3H, J = 84 Hz, Pt-Me), 7.49 (m, 1H, H ), 7.54 (m, 6H,
H
PtH
5A
ture was refined using SHELXL-2013.41 Data are given in Table 3
mE
, H , H and H ), 7.71 (m, 1H, H ), 7.95 (m, 6H, H , H , H
mD
pE
4C
4A
3C
oD
Published by NRC Research Press

7
12
Can. J. Chem. Vol. 92, 2014
Table 2. Absorption maxima (nm) for the UV-visible bands associated primarily with the trans and cis azobenzene
group and quantum yields for photoisomerization of the trans to the cis isomer.
ABa
EABb
adpp
1
2
3
4
5
6
7
trans
−␲*
n−␲*
␲
320
450
340
455
341
455
6.0
3.0
318
448
6.8
3.1
318
445
9.9
6.1
319
446
2.2
1.1
318
448
7.8
4.2
318
429
320
448
9.7
3.7
319
447
9.7
4.0
−
−
5
5
␧(␲−␲*)c
␧(365)
1
1
0
0
d
cis
−␲*
␲
280
440
0.11
267
442
0.13
266
445
0.12
NRf
445
0.077
NRf
440
0.089
NRf
441
0.095
265
444
0.092
265
425
0.087
266
448
0.089
263
443
0.093
n−␲*
e
⌽
a
AB = azobenzene.
b
c
EAB = 4-ethynylazobenzene.
Extinction coefficient (M cm−1) at absorption maximum of the ␲−␲* transition.
−1
d
−1
−1
Extinction coefficient (M cm ) at irradiation wavelength of 365 nm.
e
Quantum yield for trans−cis isomerization with ␭(irr) 365 nm in dichloromethane.
f
Not resolved.
Fig. 7. UV-visible spectra of 4-ethynylazobenzene, EAB, free ligand
adpp, and complex 1 in dichloromethane.
Fig. 8. Change in the UV-visible spectrum upon photoisomerization
of the ligand adpp in dichloromethane with ␭(irr) 365 nm (a) before
irradiation and (b) after 2 min of irradiation.
Scheme 7. Photoisomerization of the azobenzene-tagged ligand.
Fig. 9. 1H NMR spectrum, in the region from ␦ 8.3 to 8.9, of the
ligand adpp (a) before irradiation (trans isomer only) and (b) after
photolysis for 5 min with ␭(irr) 365 nm (both trans and cis isomers
present).
oE
5B
6C
3
and H ), 8.20 (s, 1H, H ), 8.21 (m, 1H, H ), 8.41 (d, 1H, J = 6 Hz,
HH
3
A
3
3
6A
1
H
), 9.62 (d, 1H, J = 6 Hz, J
= 18 Hz, H ); 2b, ␦( H): 1.43 (s,
HH
PtH
2
5A
PtH HH
3
3
H
H, J
= 78 Hz, Pt-Me), 7.37 (m, 1H, H ), 7.25 (d, 2H, J = 8 Hz,
mD
5C
mE
pE
3
4A
), 7.60 (m, 4H, H , H and H ), 7.73 (dt, 1H, J = 8 Hz, H ),
HH
4
C
3A
oD
3
oE
8
1
9
.01 (m, 4H, H , H and H ), 8.12 (d, 2H, J = 8 Hz, H ), 8.70 (d,
HH
H, J = 6 Hz, H ), 8.75 (d, 1H, J = 8 Hz, H ), 9.05 (s, 1H, H5B),
3
6A
3
3C
HH HH
3
3
6C
.48 (d, 1H, J = 6 Hz, J
= 23 Hz, H ). HRMS (ESI) calcd. for
HH
PtH
+
C H N NaPt [M] : 682.1063; found: 682.1056.
2
7 21 6
[
PtI Me (adpp], 3
2 2
To a solution of complex 1 (0.05 g, 0.078 mmol) in acetone
(15 mL) was added excess iodine. After 10 min, the colour of the
solution had changed from red to yellow with precipitation of a
yellow solid. The mixture was stirred for 1 h and then the solid was
isolated by filtration, washed with ether (3 × 2 mL) and pentane
2
3
2
JPtH = 74 Hz, Pt-Me), 2.83 (s, 3H, J
= 74 Hz, Pt-Me), 7.48 (d, 2H,
PtH
mD
5C
mE
5A
JHH = 8 Hz, H ), 7.53 (m, 1H, H ), 7.59 (m, 3H, H and H ), 7.68
pE
3
oD
4C
(3 × 2 mL), and dried under vacuum. Yield 85% (0.06 g). The com-
(m, 1H, H ), 7.72 (d, 2H, J = 8 Hz, H ), 7.98 (m, 1H, H ), 8.02 (m,
2H, H and H ), 8.13 (d, 2H, J = 8 Hz, H ), 8.77 (d, 1H, J
6 Hz, H ), 8.84 (s, 1H, H ), 8.91(d, 1H, J = 8 Hz, H ), 9.12 (d, 1H,
HH
HH
3
C
4A
3
oE
3
plex was purified by column chromatography using acetone−
=
HH
HH
1
6C
5B
3
3A
hexanes (15%:85%) as eluent. NMR in CDCl , 3a, ␦( H): 2.51 (s, 3H,
3
Published by NRC Research Press

Moustafa et al.
713
8 Hz, HmD), 7.97 (m, 3H, H and HoD), 8.12 (d, 2H, J = 8 Hz, HoE),
3C
3
Fig. 10. UV-visible spectral changes upon photolysis of complex 6 at
HH
3
6C
5B
3
3
65 nm in dichloromethane.
8.76 (d, 1H, J = 8 Hz, H ), 8.84 (m, 1H, H ), 8.92 (d, 1H, J
=
HH
HH
7
Hz, H ), 9.10 (d, 1H, J = 6 Hz, J = 18 Hz, H6A), 4b, ␦( H): 0.77
3
A
3
3
1
HH PtH
2
2
(
s, 3H, J
= 74 Hz, Pt-Me), 1.51 (s, 3H, J
= 71 Hz, Pt-Me), 1.77 (s,
PtH
PtH
5A
PtH HH
2
3
3
H
H
2
1
H, J
= 71 Hz, Pt-Me), 7.37 (m, 1H, H ), 7.45 (d, 2H, J = 9 Hz,
mD
mE
pE
5C
4A
), 7.56 (m, 3H, H and H ), 7.77 (m, 1H, H ), 7.93 (m, 5H, H
,
oE
oD
4C
3
3A
and H ), 8.17 (m, 1H, H ), 8.22 (d, 1H, J = 8 Hz, H ), 8.41 (m,
HH
H, H3 and H ), 8.47 (s, 1H, H ), 9.07 (d, 1H, J = 6 Hz, J
C
6A
5B
3
3
=
HH
PtH
6
C
+
8 Hz, H ). HRMS (ESI) calcd. for C29H N NaPt[M] : 804.0887;
27 6
found: 804.0882.
[
PtIMe Et(adpp)], 5
This was prepared in a similar way but using EtI instead of MeI.
2
1
3
Yield 92%. (0.057 g). NMR in CDCl , 5a, ␦( H): 0.30 (t, 3H, J
5
0
1
1
(
H
7
=
3
PtH
2
2
A
9 Hz, J = 7 Hz, PtCH Me), 0.89 (m, 1H, J
= 69 Hz, Pt-CH ),
HH
2
PtH
2
2
B
.94 (m, 1H, J
= 68 Hz, Pt-CH ), 1.57 (s, 3H, J = 72 Hz, Pt-Me),
= 72 Hz, Pt-Me), 7.47 (m, 2H, H and H ), 7.53 (m,
PtH
PtH
5C
2
pE
.88 (s, 3H, J
PtH
5
A
4C
mE
4A
mD
H, H ), 7.72 (m, 3H, H and H ), 7.97 (m, 3H, H and H ), 8.02
oD
3
oE 3
HH HH
m, 2H, H ), 8.11 (d, 2H, J = 9 Hz, H ), 8.38 (dt, 1H, J = 8 Hz,
3
C
), 8.76 (d, 1H, J = 8 Hz, H ), 8.86 (s, 1H, H5B), 8.91 (d, 1H, J
3
6C
3
=
HH
HH
Fig. 11. Recovery of the trans ␲−␲* band at maximum absorbance
Hz, H ), 9.06 (d, 1H, J = 6 Hz, 3J = 19 Hz, H ); 5b, ␦( H): 0.21
3
A
3
6A
1
−1
HH
PtH
3
19 nm of complex 7 on heating at a rate of 2 °C min .
3
2
PtH HH 2 PtH
2
(
t, 3H, J = 59 Hz, J = 7 Hz, PtCH Me), 0.79 (m, 1H, J = 69 Hz,
A
2
B
2
Pt-CH ) 0.84 (m, 1H, J = 68 Hz, Pt-CH ), 1.55 (s, 3H, J = 72 Hz,
Pt-Me), 1.84 (s, 3H, J
2
7
PtH
PtH
5A
2
= 72 Hz, Pt-Me), 7.34 (m, 1H, H ), 7.43 (d,
PtH
3
mD
mE
pE
5C
H, J = 9 Hz, H ), 7.47 (m, 3H, H and H ), 7.77 (m, 1H, H ),
HH
oE
oD
4A
4C
.93 (m, 4H, H and H ), 7.80 (m, 1H, H ), 8.20 (m, 1H, H ), 8.22
3
3A
3
3C
(
d, 1H, J = 8 Hz, H ), 8.36 (d, 1H, J = 7 Hz, H ), 8.38 (d, 1H,
HH
HH
3
JHH = 7 Hz, H6A), 8.40 (s, 1H, H ), 9.12 (d, 1H, J = 6 Hz, J
5B
3
3
=
HH
PtH
6
C
+
1
8 Hz, H ). HRMS (ESI) calcd. for C30H29IN NaPt[M] : 818.1046;
6
found: 818.1038.
[
PtBrMe (CH C H -4-t-Bu) (4-adppn)], 6
To a solution of complex 1 (0.04 g, 0.063 mmol) in acetone
15 mL) was added 4-t-butylbenzyl bromide (0.014 g, 0.063 mmol).
2 2 6 4
(
The mixture was stirred at room temperature for 1 h and then the
precipitated yellow solid was collected by filtration and washed
with ether (3 × 2 mL) and pentane (3 × 2 mL) and dried under high
vacuum. Yield 82% (0.044 g). The product was purified by column
chromatography purification using acetone−hexanes (10%:90%) as
Fig. 12. Calculated structures of complexes 1a and 1b.
1
2
eluent. NMR in CDCl , 6a, ␦( H): 0.94 (s, 9H, t-Bu), 1.59 (s, 3H, J
=
=
3
PtH
2
2
7
1 Hz, Pt-Me), 1.97 (s, 3H, J
= 71 Hz, Pt-Me), 2.98 (m, 1H, J
PtH
HH
2
A
PtH HH PtH
2
2
10 Hz, J = 91 Hz, Pt-CH ), 3.05 (m, 1H, J = 10 Hz, J = 90 Hz,
B
3
o”
3
Pt-CH ), 6.48 (d, 2H, J = 3 Hz, Bn-H ), 6.66 (d, 2H, J = 8 Hz,
H
and H ), 7.95(t, 1H, J = 8 Hz, H ), 8.01 (m, 4H, H , H and
H
HH
HH
mE
mD
), 7.24 (dt, 2H, J = 3 Hz, Bn-H ), 7.59 (m, 5H, H , HpE, H
3
m”
5C
HH
3
5
A
4C
4A
oD
HH
3
C
3
oE
5B
3
), 8.10 (d, 2H, J = 7 Hz, H ), 8.62 (s, 1H, H ), 8.74 (d, 1H, J
=
HH
HH
6
C
3A
3
3
8
Hz, H ), 8.83 (m, 1H, H ), 8.88 (d, 1H, J = 6 Hz, J
= 18 Hz,
HH
PtH
6
A
+
H
). HRMS (ESI) calcd. for [C39H39BrN NaPt] : 888.1958; found:
6
8
88.1959. Single crystals of complex 6a were grown by slow diffu-
3JHH = 6 Hz, 3JPtH = 23 Hz, H ); 3b, ␦( H): 2.48 (s, 3H, J
6A
1
2
sion of n-pentane into a solution of the compound dissolved in
dichloromethane.
= 74 Hz,
PtH
5A
2
Pt-Me), ␦ 2.81 (s, 3H, J
= 74 Hz, Pt-Me), 7.37 (m, 1H, H ), 7.47 (d,
PtH
3
mD
mE
pE
2
7
H, J = 7 Hz, H ), 7.55 (m, 3H, Hm and H ), 7.82 (m, 1H, H5C),
HH
.98 (m, 5H, H HoE and H ), 8.16 (m, 1H, H ), 8.39 (m, 3H, H
4
C
oD
4C
3C
[PtBrMe (CH C H -3,5-t-Bu )(adpp)], 7
2 2 6 4 2
,
,
6
6
A
C
3A
5B
3
3
HH PtH
This was prepared in a similar way but using 3,5-di-t-butylbenzyl
bromide. Yield 80% (0.046 g). The product was purified by column
chromatography using dichloromethane−hexanes (20%:80%) as
H
H
and H ), 8.44 (s, 1H, H ), 9.10 (d, 1H, J = 6 Hz, J = 23 Hz,
). HRMS (ESI) calcd. for C28H24IN6 Pt[M-I] : 766.0755; found:
+
766.0955.
1
eluent. NMR in CD Cl , 7a, ␦( H): 0.96 (s, 18H, t-Bu), 1.58 (s, 3H,
2
2
2
2
[
PtIMe (adpp)], 4
To a solution of complex 1 (0.05 g, 0.078 mmol) in acetone
JPtH = 71 Hz, Pt-Me), 1.87 (s, 3H, JPtH = 71 Hz, Pt-Me), 2.99 (m, 1H,
3
2JHH = 11 Hz, JPtH = 91 Hz, Pt-CH ), 3.11 (m, 1H, JHH = 11 Hz, JPtH
2
A
2
2
=
B
4
o
4
HH HH
(15 mL) was added methyl iodide (0.02 mL). The mixture was
90 Hz, Pt-CH ), 6.35 (d, 2H, J = 3 Hz, Bn-H ), 6.89 (t, 1H, J
=
p
5C
5A
mE
stirred for 1 h and then the yellow precipitate of the product was
collected by filtration, washed with ether (3 × 2 mL) and pentane
3 Hz, Bn-H ), 7.47(m, 1H, H ), 7.53(m, 1H, H ), 7.55 (m, 3H, H
and H ), 7.58 (m, 3 H, H and H ), 7.99 (d, 2H, J = 8 Hz, HoD),
pE
mD
4C
3
HH
3C
4
A
oE
6C
(3 × 2 mL), and dried under high vacuum. Yield 94% (0.056 g). The
8.02 (m, 3 H, H and H ), 8.05 (m, 2H, H and H ), 8.76 (s, 1H,
H
18 Hz, H ); 7b, ␦( H): 1.03 (s, 18H, t-Bu), 1.55 (s, 3H, J
5
B
3
3A
3
3
complex was purified via column chromatography technique us-
), 8.77 (d, 1H, J = 7 Hz, H ), 8.91 (d, 1H, J = 6 Hz, J
=
HH
1
HH
PtH
6
A
2
ing dichloromethane−hexanes (10%:90%) as eluent. NMR in CDCl ,
= 71 Hz,
3
PtH
2
PtH HH
1
2
2
2
4
a, ␦( H): 0.83 (s, 3H, J
= 74 Hz, Pt-Me), 1.64 (s, 3H, J
= 71 Hz,
Pt-Me), 1.79 (s, 3H, J
= 71 Hz, Pt-Me), 3.02 (m, 1H, J = 11 Hz,
PtH
PtH
5C
2
2
A
2
2
HH PtH
B
Pt-Me), 1.93 (s, 3H, J
= 72 Hz, Pt-Me), 7.52 (m, 1H, H ), 7.57(m,
JPtH = 91 Hz, Pt-CH ), 3.10 (m, 1H, J = 11 Hz, J = 90 Hz, Pt-CH ),
PtH
mE
pE
4C
5A
4A
3
4
o
3
mD
5
H, H , H , H and H ), 7.69 (m, 1H, H ), 7.72 (d, 2H, J
=
6.33 (d, 2H, J = 2 Hz, Bn-H ), 7.23 (d, 2H, J = 8 Hz, H ), 7.43
HH HH
HH
Published by NRC Research Press

7
14
Can. J. Chem. Vol. 92, 2014
Chart 1. NMR labeling scheme for selected compounds.
Table 3. Crystal and refinement data.
Compound
adpp 0.5Me CO
1a CHCl3
6a CH Cl2
7b
2
2
Formula
C27.5H N O
C29H25Cl N Pt
C40H BrCl N Pt
C43H44BrN Pt
21
6
0.5
3
6
41
2
6
6
Formula weight (g/mol)
Colour/habit
Crystal system
Space group
T (K)
443.50
758.99
951.69
919.84
Orange prism
Monoclinic
C2/c
Red prism
Monoclinic
C2/c
Red prism
Monoclinic
P21/c
Orange prism
Triclinic
P1
110
110
110
110
a (Å)
b (Å)
c (Å)
31.968(9)
7.0483(19)
19.806(5)
90
94.121(5)
90
4451(2)
8
1.324
10.746(3)
15.813(3)
16.713(4)
90
94.986(8)
90
2829.3(11)
4
1.782
10.762(3)
12.997(3)
15.367(5)
70.860(6)
72.847(14)
73.649(7)
1899.3(9)
2
22.690(7)
15.654(5)
22.617(7)
90
103.919(7)
90
7797(4)
8
1.567
␣
␤
␥
(°)
(°)
(°)
3
V (Å )
Z
−1
␳
(calcd.) (g cm )
1.664
␭
␮
(Å) (MoK␣)
(cm )
0.71073
0.083
0.71073
5.274
0.71073
4.924
0.71073
4.662
−1
Reflections
Parameters
R1 (I > 2␴(I))
10860
430
0.0493
0.1483
20743
383
0.0453
0.0921
23463
509
0.0383
0.0774
11017
468
0.0455
0.1104
wR (all data)
2
3
mE
4
p
(
H
(
8
H
9
d, 2H, J = 8 Hz, H ), 7.49 (t, 1H, J = 2 Hz, Bn-H ), 7.55 (m, 3H,
(2) Bandara, H. M. D.; Burdette, S. C. Chem. Soc. Rev. 2012, 41, 1809. doi:10.1039/
HH
HH
pE 5A
5C
4A
4C
3A
c1cs15179g.
,H and H ), 7.95 (m, 1H, H ), 7.94 (m, 2H, H and H ), 7.97
(
3) Bohner, S. R.; Kruger, M.; Oesterhelt, D.; Moroder, L.; Nagele, T.;
Wachtveitl, J. J. Photochem. Photobiol. A 1997, 105, 235. doi:10.1016/S1010-
6030(96)04497-8.
3
oD
oE
3C
3
d, 2H, J = 8 Hz, H ), 8.01 (m, 3H, H and H ), 8.10 (d, 1H, J
=
HH
A
HH
6
5B
3
3
Hz, H ), 8.28 (s, 1H, H ), 8.87 (d, 1H, J = 6 Hz, J
= 18 Hz,
HH
PtH
6
C
+
). HRMS (ESI) calcd. for C43H47BrN NaPt[M] : 944.2578; found:
44.2582. Single crystals of complex 7b were grown by slow diffu-
sion of n-pentane into a solution of the compound dissolved in a
mixture of equal volumes of dichloromethane and chloroform.
(4) Fissi, A.; Pieroni, O.; Balestreri, E.; Amato, C. Macromolecules 1996, 29, 4680.
6
doi:10.1021/ma960280w.
(
(
5) Segorra-Maset, M. D.; van Leeuwen, P. W. N. M.; Freixa, Z. Eur. J. Inorg. Chem.
010, 2075. doi:10.1002/ejic.201000063.
6) Sakamoto, R.; Kume, S.; Sugimoto, M.; Nishihara, H. Chem. Eur. J. 2009, 15,
429. doi:10.1002/chem.200801593.
2
1
Supplementary material
Supplementary material is available with the article through
the journal Web site at http://nrcresearchpress.com/doi/suppl/
(7) Marchi, E.; Baroncini, M.; Bergamini, G.; van Heyst, J.; Vogtle, F.; Ceroni, P.
J. Am. Chem. Soc. 2012, 134, 15277. doi:10.1021/ja307522f.
8) Bardaji, M.; Barrio, M.; Espinet, P. Dalton Trans. 2011, 40, 2570. doi:10.1039/
c0dt01167c.
(
(
9) Tang, H.-S.; Zhu, N.; Yam, V. W.W. Organometallics 2007, 26, 22. doi:10.1021/
1
0.1139/cjc-2013-0588. Crystallographic data for the complexes
are available in CIF format (CCDC 985642, 985643, 985645, and
85646).
om0609719.
(
(
(
(
10) Moustafa, M. E.; McCready, M. S.; Puddephatt, R. J. Organometallics 2012, 31,
9
6262. doi:10.1021/om3005405.
11) Moustafa, M. E.; McCready, M. S.; Puddephatt, R. J. Organometallics 2013, 32,
2552. doi:10.1021/om4000314.
12) Mastropietro, T.F.; Marino, N.; Armentano, D.; De Munno, g.; Yuste, C.;
Lloret, F.; Julve, M. Cryst. Growth Des. 2013, 13, 270. doi:10.1021/cg301415p.
13) Baxter, P. N.W.; Lehn, J.-M; Kneisel, Fenske, B. O.D. Angew. Chem. Int. Ed. Engl.
Acknowledgement
We thank the NSERC (Canada) for financial support.
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