Nonlinear optical properties of conjugated platinum(II) acetylides with multibranched donor-acceptor structures

Article abstract of DOI:10.1002/ejic.201402043

Six conjugated platinum(II) acetylides with multibranched donor-acceptor structures (1-6) were synthesized. The absorption maxima of triazine-centered complexes 1-3 are red-shifted by 36-43 nm compared with those of triphenylamine-centered complexes 4-6.

Full text of DOI:10.1002/ejic.201402043

FULL PAPER
DOI:10.1002/ejic.201402043
Nonlinear Optical Properties of Conjugated Platinum(II)
Acetylides with Multibranched Donor–Acceptor Structures
Puhui Xie,*[a] Lingyu Wang,[b] Zhaohui Huang,[b] Fengqi Guo,*[b]
and Qiu Jin[a]
Keywords: Donor-acceptor systems / Nonlinear optics / Platinum / Density functional calculations
Six conjugated platinum(II) acetylides with multibranched
donor-acceptor structures (1–6) were synthesized. The ab-
sorption maxima of triazine-centered complexes 1–3 are red-
shifted by 36–43 nm compared with those of triphenylamine-
centered complexes 4–6. The luminescence spectra of 4–6 in
air-saturated chloroform showed one fluorescence peak and
one phosphorescence peak. However, only one fluorescence
peak was detected for 1–3 in air-saturated chloroform. The
transient absorption spectra of the compounds indicate the
effective intersystem crossing from S1 to T1. The nonlinear
optical properties of 1–6 in N,N-dimethylformamide were
studied using open Z-scan method. The results indicate that
complexes 1 and 6 exhibit good nonlinear optical perform-
ance. The ratios of the effective nonlinear absorption cross
section to ground-state absorption cross section σeff/σ0 of
complexes 1–6 are in the range of 4–22.
from the visible to infrared spectroscopic region because of
the spin-orbit coupling interaction between the d orbital of
the heavy PtII ion and the π orbitals of the ligands. Conse-
quently, the reverse saturable absorption properties of some
platinum(II) complexes have been studied extensively. How-
ever, the pioneering work done so far has mainly focused
on the linear heavy metal atoms containing acetylides, and
the relationship between the molecular structure and the
nonlinear optical properties, especially the effect of the do-
nor-acceptor structure on the nonlinear optical properties
was not discussed.[12,17–22] In recent years, the two-photon
absorption phenomenon and the enhanced nonlinear ab-
sorption based on the absorption from both the singlet and
triplet states of several platinum acetylides with linear di-
polar geometry have been reported.[23–26] In addition, it has
been reported that the molecules with multipolar geome-
tries could overcome the nonlinear optical efficiency/optical
transparency trade-off and disfavor the centrosymmetric
packing in the solid state, both of which have hampered the
efficiency of quadratic nonlinear optical materials. Thus,
lots of multibranched organic molecules were synthesized
and their third-order nonlinear optical properties, especially
the TPA properties, studied in recent years.[27–33] The Hum-
phrey group have synthesized a series of Ru-containing or
multimetal-containing hyperbranched acetylide dendrimers,
and testified that the dendritic alkynylruthenium complexes
have a larger TPA cross-section than the corresponding lin-
ear model complexes, and that the nonlinear optical effect
increases with an increase in the number of metal valence
electrons.[30] Although some multibranched platinum(II)-
containing acetylides have been synthesized and studied,
their nonlinear optical properties, especially the reverse sat-
urable absorption properties, are seldom reported.[33–35] The
Introduction
Nonlinear optical materials have attracted significant
interest because of their potential applications in electronic
and optoelectronic areas such as optical data storage, op-
tical limiting, photovoltaic devices, 3D microfabrication,
microscopy and photodynamic therapy.[1–10] Two significant
conclusions from previous work can be made: (1) Molecules
with donor-acceptor structures such as D–A, D–A–D,
D–π–A, D–π–D, and multibranched structures generally ex-
hibit excellent two-photon absorption properties, and the
two-photon absorption cross sections can be increased by
extending the molecular conjugated system or incorporat-
ing multidipole chromophores into the molecular struc-
ture.[11–14] (2) Molecules containing heavy metal ions and
rigid structures always exhibit large reverse saturable ab-
sorption due to the enhancement of the intersystem cross-
ing from the first singlet excited state to the first triplet
excited state.[15,16] These conclusions can provide helpful
guidelines for designing materials with large overall nonlin-
ear optical properties.
Platinum(II) acetylide oligomers and polymers exhibit
high, linear transmission over the visible region and strong
reverse saturable absorption of the first triplet excited state
[a] College of Sciences, Henan Agricultural University,
Zhengzhou, Henan 450002, P. R. China
E-mail: phxie2013@163.com
http://www.henau.edu.cn
[b] College of Chemistry and Molecular Engineering, Zhengzhou
University,
Zhengzhou 450001, P. R. China
E-mail: fqguo@zzu.edu.cn
http://www.zzu.edu.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402043.
Eur. J. Inorg. Chem. 2014, 2544–2551
2544
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Figure 1. Structures of the multibranched conjugated trinuclear platinum(II) acetylide complexes.
detailed relationship between the structure and the two- lated using density functional theory (DFT) at the 6-31G(d)
photon absorption, as well as the excited state absorption, level for C, H, N, O and P, and at the Lanl2DZ level for
have still not been discussed clearly. Furthermore, how the the Pt atoms. All the butyl groups in the molecules were
two-photon absorption and the excited state absorption af- replaced with the methyl groups in order to simplify the
fect each other based on the structure of the complexes have calculation process. The calculations were performed with
also not been clearly discussed.
the Gaussian 03 software package.[36] The calculated elec-
In order to address these questions, six multibranched tronic distribution situation is shown in Figure 2.
platinum(II) acetylide complexes with donor-acceptor
structures 1–6, as shown in Figure 1, were designed and
synthesized. The design of the complexes is based on the
well-known A–π–A, D–π–A and D–π–D motifs yielding
materials with significant two-photon absorption. The in-
sertion of the heavy metal atom into an organic molecule
often results in materials with strong excited state absorp-
tion from the triplet state.[16,32] Multibranched molecules
consisting of a strong 1,3,5-triazine electron-accepting cen-
ter or a strong triphenylamine electron-donating center
have been shown to be excellent TPA materials, and the
linked electron-donating or electron-accepting end groups,
such as alkyl, nitro and nitrile, can enhance the extent of the
electron delocalization of the molecules.[29] The synthesized
platinum acetylide complexes combine the donor-acceptor
structure, multibranched structure and heavy metal in one
molecule and this makes it possible to study the interaction
between the two-photon absorption and the reverse satura-
ble absorption based on the structure of the complexes.
This paper will report the synthetic process, the photophysi-
cal properties and the nonlinear optical properties of the
designed molecules for nanosecond lasers. The more de-
tailed nonlinear optical properties for picosecond lasers and
the relationship between the structure and nonlinear optical
properties, as well as the interaction between two-photon
absorption and reverse saturable absorption from the triplet
state will be discussed in the future.
Results and Discussion
Quantum Calculations
Figure 2. Electronic density distribution of the HOMO and LUMO
The geometries of the platinum acetylides 2, 3, 4 and 6
orbitals of the platinum acetylides with multibranched donor-ac-
were optimized. The HOMO and the LUMO were calcu- ceptor structures.
Eur. J. Inorg. Chem. 2014, 2544–2551
2545
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
As shown in Figure 2, the electronic density of the sorption maxima greatly, and the molar extinction coeffi-
HOMO of the triazine-centered complex 2 with the elec- cients increase with the increasing electron-withdrawing
tron-pushing end is localized on the three branched chains ability of the substituents. However, for the triphenylamine-
with a clear contribution from PtII, whereas the electronic centered complexes 4–6, the electron-withdrawing group
density of the LUMO of 2 is mostly located at the center NO2 makes the absorption maxima of 6 red-shifted by 5 nm
of the molecule. The ligand-to-ligand (LLCT) and metal- compared with that of 4. All the complexes showed weak
to-ligand charge transfer (MLCT) clearly occur when the absorption above 450 nm, which provides a wide observa-
molecule is excited and the contribution of the metal dπ tion window for the application in optical limiters.
orbital to the LUMO is negligible compared with that in
the HOMO. The electronic density of the HOMO of the
triazine-centered complex 3 with the electron-withdrawing
end is mostly localized on the arylacetyl groups between the
triazine and the metal ion on the three branched chains
with a slight contribution from PtII and the triazine group,
whereas the electronic density of the LUMO of 3 is mostly
located at the three electron-withdrawing arylacetyl groups
on the end. The ligand-to-ligand (LLCT) charge transfer
clearly occurs when the molecule is excited, and the contri-
bution of the metal dπ orbital and the triazine centre to
the LUMO is negligible compare with that in HOMO. The
electronic density of the HOMO of 4 with a triarylamine
center and electron-pushing ends on the three branched
chains is located at the center with a clear contribution of
Figure 3. Electronic absorption spectra of compounds 1–6 in
the metal dπ orbital, whereas the electronic density of the
LUMO is mostly located at the three metal ions. An obvi-
ous ligand-to-metal charge transfer (LMCT) happens when
the molecule is excited. The electronic density of the
HOMO of 6 with a triarylamine center and electron-with-
drawing ends on the three branched chains is also located
at the center with clear contribution of the metal dπ orbital,
whereas the electronic density of the LUMO is mostly lo-
cated at the three electron-withdrawing arylacetyl ending
groups. The LLCT and metal-to-ligand charge transfer
(MLCT) occur when the molecule is excited and the contri-
bution of the metal dπ orbital to the LUMO is negligible.
All the molecules exhibit conjugated systems after the inser-
tion of PtII ions into the skeletons of them and the electron
transfer process could occur by passing through the metal
ions. In addition, the charge transfer behavior of these com-
plexes should be dominated by the structures of the molecu-
lar skeletons. So it is possible to study the effect of heavy
metal ions on the two photon absorption of the organic
molecules with multibranched donor-accepter structures.
chloroform at 1.0ϫ10–5 molLϪ1 in a 1 cm cuvette.
Table 1. Photophysical properties of 1–6.
λAbs
/nm
λF
λP
Stokes-shift
/nm
ΔES
/eV
τem
/ns
τTA
/μs
/nm /nm
1
2
3
4
418
418
420
377
509
510
474
411 501
420 547
475 585
–
–
–
91
92
54
24
2.74
2.71
2.79
3.12
1.60[a]
3.73
3.67
3.01
1.50
1.51[a]
1.44[a]
1.26[a]
410 (69%)[b]
2761 (28%)[b]
1.28[a]
5
6
382
382
38
93
3.07
3.02
0.72
545 (58%)[b]
3140 (38%)[b]
1.34[a]
479 (78%)[b]
3700 (20%)[b]
[a] Lifetime of fluorescence. [b] Lifetime of phosphorescence.
Figure 4 shows the excitation and luminescence spectra
of complexes 1–6 in air-saturated chloroform. For the tri-
azine-centered complexes 1–3, the luminescence maxima
are located at 510 nm, 509 nm and 474 nm, respectively, val-
ues which do not change in air-free chloroform solution
and the responsible emissive lifetimes are in the range of
1.4–1.6 ns. These emissions can be attributed to the fluores-
Electronic Absorption Spectra and Photoluminescence
Spectra
The electronic absorption spectra of 1–6 in chloroform cence from their first singlet excited states. The fluorescence
at 1 ϫ10–5 molLϪ1 are shown in Figure 3 and the photo- maximum of 3 is blue-shifted by 35 nm compared with
physical data are presented in Table 1. All the complexes those of 1 and 2 because of the electron-withdrawing prop-
exhibit absorption maxima in the range of 350–450 nm, erties of the triazine and the NO2 group. The low fluores-
attributed to the π–π* transitions. The absorption maxima cence quantum yields of 0.058, 0.058 and 0.0049 for 1, 2
of 1–3 are red-shifted by 36–43 nm when compared with and 3, respectively, indicate that the molecular population
those of 4–6 because of the larger conjugated systems of 1– in the S1 state relaxes mainly by means of intersystem cross-
3 relative to those in 4–6. For the triazine-centered com- ing to the T1 state or internal conversion to the ground
plexes 1–3, the electronic push-pull properties of the para state. However, the phosphorescence bands of 1–3 at room
substituent on the phenyl acetylide do not affect their ab- temperature were not observed in air-free chloroform. The
Eur. J. Inorg. Chem. 2014, 2544–2551
2546
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
phosphorescence of some platinum acetylide complexes has acetylide make both the fluorescence and phosphorescence
only been observed at low temperature.[37] In addition, the maxima of 5 and 6 red-shifted compared with that in 4
larger conjugated system of 1–3 relative to that in 4–6 de- with an electron-donating group at the end of the phenyl
creased the coupling interaction between the ligands and acetylide. The detectable room temperature phosphores-
the d orbital of PtII, and finally decreased the phosphores- cence spectra of 4–6 indicate that the heavy atom effect in-
cence quantum yields of 1–3. This is consistent with the creases the intersystem crossing quantum yield. So it is pos-
reported results.[38]
sible for these molecules to possess great triplet excited state
Figure 4. Normalized absorption and photoluminescence spectra
in air-saturated chloroform solution of 1–3 (a) and 4–6 (b).
From the calculated results, the contribution of the metal
dπ orbital in the LUMO of 1–3 is negligible and this also
indicates the weak spin-orbital coupling effect.
The luminescence spectra of complexes 4–6 in air-satu-
rated chloroform exhibit two main peaks (Figure 4, b and
Figure 5). As shown in Figure 5, for each complex, the peak
with the shorter wavelength, which becomes weak in the
air-free solution and has a lifetime in the range of 1.26–
1.34 ns, can be attributed to the fluorescence, and the peak
with the longer wavelength, which becomes strong in air-
free solution and has a lifetime in the range of 410–3700 ns,
can be attributed to the phosphorescence. The detailed data
are also listed in Table 1. The conjugated systems in 4–6
which are smaller than in 1–3 increase the coupling interac-
tion between the ligands and the PtII d orbital and this
makes the phosphorescence of 4–6 detectable at room tem-
perature. For the triphenylamine-centered complexes 4–6,
Figure 5. Photoluminescence spectra in air-saturated and air-free
the electron-withdrawing groups at the end of the phenyl chloroform solutions of 4 (a), 5 (b) and 6 (c).
Eur. J. Inorg. Chem. 2014, 2544–2551
2547
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
absorption. This is consistent with the reported results[32]
and the calculated results that the contribution of the metal
dπ to the LUMO of 4–6 is effective. The phosphorescence
bands of the synthesized complexes are significantly over-
lapping with the corresponding fluorescence bands so we
did not calculate the quantum yields of the phosphores-
cence for complexes 4–6.
Transient Absorption (TA) Spectroscopy
The time resolved transient absorption spectra are illus-
trated in Figure 6 for complexes 1–5. Transient absorption
of complex 6 was too weak to be observed. The TA spectra
of 1, 2 and 3 show a similar strong absorption throughout
the visible region with the maximum at around 610 nm and
extending into the near-IR region. The τTA values of 1, 2
and 3, as listed in Table 1, do not coincide with their τem
values, which have been attributed to fluorescence lifetimes,
indicating that the transient absorption arises from the trip-
let excited state. The strong transient absorption of 1, 2 and
3 shows that the intersystem crossing from S1 to the T1
state is effective and is consistent with the low fluorescent
quantum yields of them. The TA spectra of 4 and 5 show
a moderately intense narrow absorption band around
460 nm and a strong absorption band above 550 nm ex-
tending to the near-IR region. In addition, the τTA values
coincide with τem values of the phosphorescence, indicating
that the transient absorption arises from the same excited
triplet state. In view of the calculated results and the similar
appearance of the TA spectra to the other TA absorption
of platinum(II) acetylide complexes, the transient absorp-
tion of the title complexes maybe represent the 3MLCT and
3π,π* excited states.[18,39]
Nonlinear Absorption Properties
The nonlinear absorption behaviors of 1–6 in DMF were
investigated using the open aperture Z-scan technique. As
shown in Figure 3, 1–6 show very weak linear absorption
at 532 nm, which provides a high transmittance at low inci-
dent laser energy. However, the weak linear absorption of
the complexes at 532 nm makes the direct ground state to
triplet state absorption possible, which may also contribute
to the nonlinear optical absorption.[40] In view of the fact
that the S0ǞT1 transition is forbidden by normal spectro-
scopic selection rules, so the direct ground state to triplet
state absorption is always insufficiently strong to build up
the electron population of the T1 state to a high level even
if the spin selection rule can be broken. In addition, there
should be a bleach signal in the wavelength region of
532 nm in the transient absorption spectrum if the direct
ground state to triplet state absorption is the main mecha-
nism to induce the nonlinear optical absorption of the T1
state. However, there is no bleach in the transient absorp-
tion spectra (Figure 6). Thus, the nonlinear absorption
properties should be attributed to the two-photon absorp-
Figure 6. Transient absorption difference spectra of the title com-
plexes 1 (a), 2 (b), 3 (c), 4 (d) and 5 (e) in nitrogen-degassed DMF
solution at room temperature following 355 nm excitation. The ar-
tion from the ground state and the excited state absorption rows indicate the direction of the time decay.
Eur. J. Inorg. Chem. 2014, 2544–2551
2548
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
from the first triplet excited state, which was induced by the creased to minimum. The open Z-scan data for 1–3 and 4–
two-photon absorption. The mechanism can be depicted by 6 at a concentration of 5.0ϫ10–4 molLϪ1 in DMF solution
a simple five energy-level model as shown in Figure 7. The are listed in Figure 8 (a and b), respectively, and the solid
chromophore undergoes two-photon excitation from the curve is the theoretical fitting. These results indicate that
ground state (S0) to the first singlet excited state (S1) or all of the complexes exhibit obvious nonlinear absorption
higher singlet excited state (Sn). The S1 state can decay by properties. The ground state cross-sections, σ0, of complexes
means of the emissive path (F) or internal conversion (IC) 1–6 are estimated at the magnitude of 10–18 cm2 based on ε
to the ground state, or intersystem crossing (ISC) to the = 4.34ϫ10–4σ0N0,[42] in which ε is the molar absorption
first triplet excited state (T1). The T1 state also can be ex- coefficient, N0 is Avogadro’s constant and σ0 is the ground
cited to the higher excited triplet state, such as T2 by ab- state absorption cross section. The effective nonlinear ab-
sorbing another photon, or decay to the ground state by sorption cross-sections (σeff) of the complexes were calcu-
phosphorescence (P) or internal conversion (IC).
lated by fitting the experimental data using Equation (1).
The effective nonlinear absorption cross-sections and
ground-state absorption cross-sections data of 1–6 are listed
in Table 2. The magnitudes of the ground-state absorption
cross-sections of 1–6 are of the order of 10–18 cm2, whereas
the excited-state absorption cross-sections are of the order
of 10–17 cm2 at 532 nm. It is quite obvious that the efficient
nonlinear absorption cross-sections are much larger than
those of the ground state.
Figure 7. Five energy-level diagram for depicting the two-photon
absorption from the first singlet excited state and the excited state
absorption from the first triplet excited state induced by the two-
photon absorption.
In order to compare the overall nonlinear optical proper-
ties of 1–6 but neglecting the detailed mechanism, the nor-
malized transmittance data of the open aperture Z-scan
were fitted according to the nonlinear absorption. In
theory, it can be described by the following rate; see Equa-
tions (1), (2) and (3).[41]
q0
q0
T = ln(1 +
)/(
1 + x2 1 + x2
)
(1)
σ
effα0F0Leff
q0 =
(2)
2hν
1 – e–α L
0
Leff
=
(3)
α0
2
T is the normalized transmittance, F0 = E/(πω0 /2) is the
on-axis laser fluency at the focus, E is the incident pulse
energy, x = z/z0, where z is the distance of sample from the
2
focus and z0 is the diffraction length of the beam, z0 = πω0 /
λ where ω0 is the beam waist at the focus; h is Planck’s
constant; Leff is the effective sample thickness and L is the
real sample thickness. The results from the Z-scan experi-
ments are shown in Figure 8 in which the solid lines are
theoretical fitting curves from Equation (1). As the sample
was moved away from the focus point, the transmittances
of all the complexes tended to an almost flat line which
displayed the linear absorption under weak light irradia-
tion. As the samples were moved close to the focus point,
the transmittances decreased as the laser irradiance in-
Figure 8. Open Z-scan data for 1–3 (a) and 4–6 (b) at a concentra-
tion of 5.0ϫ10–4 molLϪ1 in DMF solution. The solid curve is the
theoretical fitting.
The ratio of σeff/σ0 can be used to describe the overall
creased. At the focus point (x = 0) where the laser irradi- nonlinear optical properties. For the triazine-centered com-
ance reached maximum, the normalized transmittance de- plexes 1–3, the value of σeff/σ0 increased with the electron
Eur. J. Inorg. Chem. 2014, 2544–2551
2549
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Methods: 1H NMR spectra were recorded on a DRX-400 spec-
trometer and the chemical shifts are reported in ppm relative to
TMS. MALDI-TOF mass spectra were measured on an AXIMA-
CRF system. Elemental analyses were performed on a Flash EA
1112 analyzer. UV/Vis absorption spectra were measured on a TU-
1901 spectrophotometer. The luminescence spectra were measured
with a Cary Eclipse fluorescence spectrometer. The fluorescence
quantum yields, Φf, were determined relative to quinine sulfate as
the standard (Φf = 0.55 in 0.5 n H2SO4).[43] The emission lifetimes
were measured on a FM-4P-TCSPC time-resolved fluorescence
spectrometer. Transient absorption spectroscopy and transient ab-
sorption lifetimes were measured on an Edinburgh LP920 laser
flash photolysis spectrometer. The samples were excited by the
third-harmonic output (355 nm) of a Nd:YAG laser.
Table 2. The effective nonlinear absorption cross-sections of 1–6 in
DMF.
σ0 /10–18cm2
σeff /10–17cm2
σeff/σ0
1
2
3
4
5
6
3.72
3.94
7.96
2.43
5.74
2.93
8.21
1.61
2.52
1.34
2.19
4.85
22
4.1
3.2
5.5
3.8
16.6
pushing ability of the substitutes on the arylacetylide, and
the value of σeff/σ0 of 1 arrived at 22. Amongst the tri-
phenylamine-centered complexes 4–6, compound 6 with the
strong electron-withdrawing –NO2 substituent on the aryl-
acetylide has the biggest σeff/σ0 value of 16.6. However, 5
with a –CN electron-withdrawing substituent on the aryla-
cetylide only had a similar σeff/σ0 value to complex 4 with
the electron pushing –CH3 substituent on the arylacetylide,
probably because the conjugation effect of –CN reduced the
electron pulling effect of itself. From this result we can see
that the multibranched conjugated platinum(II) acetylide
complexes with a donor-acceptor structure have good over-
all nonlinear optical properties.
The open-aperture Z-scan measurements were performed with a
diode-pumped pulse laser (Valiant 4ω-100), which provides linearly
polarized 16 ns optical pulses at 532 nm wavelength with a repeti-
tion of 100 Hz. The input laser beam was split into two beams by
a beam splitter (Newport). One beam was employed as a reference
to monitor the incident laser energy and the other was focused into
the center of a 2 mm path-length sample cell by a 15 cm focal-
length lens. The incident and transmitted laser pulses were moni-
tored by two energy detectors, D1 and D2 (PE9-F and PE50 energy
probes, Laser Precision), as reported.[44] The measured diameter of
the light spot at the focus was 50 μm. The concentrations of all the
samples were 5.0ϫ10–4 molLϪ1 in DMF and samples were placed
in a 2 mm path-length quartz cell.
Conclusions
Supporting Information (see footnote on the first page of this arti-
cle): Details on the syntheses and characterization of the complexes
1–6.
Three triazine-centered and three triphenylamine-cen-
tered multibranched conjugated platinum(II) acetylide com-
plexes were synthesized. Their geometries were optimized
and the HOMOs and LUMOs were calculated using DFT.
The calculations show that all the molecules keep the conju-
gated system after the insertion of PtII ions into the skel-
etons and the electron transfer process could occur by pass-
ing through the metal ions. The charge transfer behaviors
of these complexes should be dominated by the structures
of the molecular skeletons. The low fluorescence quantum
yields, detectable phosphorescence at room temperature
and the time resolved transient absorption properties of
them indicate that the intersystem crossing is effective. It is
possible for the molecules to possess great triplet excited
state absorption. The multibranched conjugated plati-
num(II) complexes exhibit good nonlinear optical perform-
ance and the overall nonlinear optical properties increase
with an increase in the difference between the electronic
pull-push ability between the center and the branch chro-
mophores. More detailed research on how the two-photon
absorption and the excited state absorption affect each
other related to the structure of the complexes is going on
in our lab and will be discussed in the future.
Acknowledgments
The authors thank the National Natural Science Foundation of
China (NSFC) (grant number 21102037) and the Education De-
partment of Henan Province (grant number 2010GGJS-048) for the
financial support.
[1] D. A. Parthenopoulos, P. M. Rentzepis, Science 1989, 245, 843–
845.
[2] A. S. Dvornikov, P. M. Rentzepis, Opt. Commun. 1995, 119,
341–346.
[3] S. S. Chavan, B. G. Bharate, Inorg. Chim. Acta 2013, 394, 598–
604.
[4] R. Westlund, E. Malmstrom, C. Lopes, J. Ohgren, T. Rodgers,
Y. Saito, S. Kawata, E. Glimsdal, M. Lindgren, Adv. Funct.
Mater. 2008, 18, 1939–1948.
[5] F. Dai, H. Zhan, Q. Liu, Y. Fu, J. Li, Q. Wang, Z. Xie, L.
Wang, F. Yan, W.-Y. Wong, Chem. Eur. J. 2012, 18, 1502–1511.
[6] F. Guo, Y. G. Kim, J. R. Reynolds, K. S. Schanze, Chem. Com-
mun. 2006, 1887–1889.
[7] S. Achelle, P. Couleaud, P. Baldeck, M. P. Teulade-Fichou, P.
Maillard, Eur. J. Org. Chem. 2011, 76, 1271–1279.
[8] S. Kawata, H. B. Sun, T. Tanaka, K. Takada, Nature 2001, 412,
697–698.
[9] W. Denk, J. H. Strickler, W. W. Webb, Science 1990, 248, 73–
76.
Experimental Section
[10] J. D. Bhawalkar, N. D. Kumar, C. F. Zhao, P. N. Prasad, J. Clin.
Laser Med. Surg. 1997, 15, 201–204.
[11] H. Kim, B. Cho, Chem. Commun. 2009, 153–164.
[12] T. Lin, Y. Huang, Y. Chen, C. Hu, Tetrahedron 2010, 66, 1375–
1382.
Materials: All the starting materials from commercially available
sources were used without any purification. All the solvents were
dried and distilled by the standard methods. The details of the syn-
theses of the complexes 1–6 are given in the Supporting Infor-
mation.
[13] G. Zhou, W.-Y. Wong, C. Ye, Z. Lin, Adv. Funct. Mater. 2007,
17, 963–975.
Eur. J. Inorg. Chem. 2014, 2544–2551
2550
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[14]
[33] K. Onitsuka, M. Fujimoto, N. Ohshiro, S. Takahashi, Angew.
Chem. Int. Ed. 1999, 38, 689–692; Angew. Chem. 1999, 111,
751.
X. Su, H. Xu, Q. Guo, G. Shi, J. Yang, Y. Song, X. Li, J.
Polym. Sci., Part A J. Polym. Sci. A: Polym. Chem. 2008, 46,
4529–4541.
[34] C. E. Powell, M. P. Cifuentes, M. G. Humphrey, A. C. Willis,
J. P. Morrall, M. Samoc, Polyhedron 2007, 26, 284–289.
[35] S. Ghosh, P. S. Mukherjee, Organometallics 2008, 27, 316–319.
[36] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. W.
Pomelli, J. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth,
P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03, revision B.05,
Gaussian, Inc., Pittsburgh, PA, USA, 2003.
[15]
[16]
[17]
Y. Chen, L. Gao, N. He, J. Wang, Y. Araki, W. Blau, O. Ito,
Mini-Rev. Org. Chem. 2009, 6, 55–65.
J. Zhao, W. Wu, J. Sun, S. Guo, Chem. Soc. Rev. 2013, 42,
5323–5351.
R. Zieba, C. Desroches, F. Chaput, M. Carlsson, B. Eliasson,
C. Lopes, M. Lindgren, S. Parola, Adv. Funct. Mater. 2009, 19,
235–241.
F. Guo, W. Sun, Y. Liu, K. Schanze, Inorg. Chem. 2005, 44,
4055–4065.
J. E. McGarrah, R. Eisenberg, Inorg. Chem. 2003, 42, 4355–
4365.
W. J. Blau, H. J. Byrne, D. J. Cardin, A. P. Davey, J. Mater.
Chem. 1991, 1, 245–249.
A. P. Davey, H. J. Byrne, H. Page, W. Blau, D. J. Cardin, Synth.
Met. 1993, 58, 161–172.
H. Page, W. Blau, A. P. Davey, X. Lou, D. J. Cardin, Synth.
Met. 1994, 63, 179–182.
[18]
[19]
[20]
[21]
[22]
[23] J. E. Rogers, T. M. Cooper, P. A. Fleitz, D. J. Glass, D. G.
McLean, J. Phys. Chem. A 2002, 106, 10108–10115.
[24] E. Glimsdal, M. Carlsson, B. Eliasson, B. Minaev, M.
Lindgren, J. Phys. Chem. A 2007, 111, 244–250.
[25] L. Liu, D. Huang, S. M. Draper, X. Yi, W. Wu, J. Zhao, Dalton
Trans. 2013, 42, 10694–10706.
[37] L. Chen, A. H. Shelton, K.-Y. Kim, K. S. Schanze, ACS Appl.
Mater. Interfaces 2011, 3, 3225–3238.
[26] W. Wu, J. Zhao, J. Sun, L. Huang, X. Yi, J. Mater. Chem. C
2013, 1, 705–716.
[38] J. E. Rogers, J. E. Slagle, D. M. Krein, A. R. Burke, B. C. Hall,
A. Fratini, D. G. McLean, P. A. Fleitz, T. M. Cooper, M. Dro-
bizhev, N. S. Makarov, A. Rebane, K.-Y. Kim, R. Farley, K. S.
Schanze, Inorg. Chem. 2007, 46, 6483–6494.
[39] C. E. Whittle, J. A. Weinstein, M. W. George, K. S. Schance,
Inorg. Chem. 2001, 40, 4053–4062.
[27] S. K. Hurst, N. T. Lucas, M. G. Humphrey, T. Isoshima, K.
Wostyn, I. Asselberghs, K. Clays, A. Persoons, M. Samoc, B.
Luther-Davies, Inorg. Chim. Acta 2003, 350, 62–76.
[28] C. E. Powell, J. P. Morrall, S. A. Ward, M. P. Cifuentes,
E. G. A. Notaras, M. Samoc, M. G. Humphrey, J. Am. Chem.
Soc. 2004, 126, 12234–12235.
[40] T. J. McKay, J. A. Bolger, J. Staromlynska, J. R. Davy, J. Chem.
Phys. 1998, 108, 5537–5541.
[29] Y. Jiang, Y. Wang, B. Wang, J. Yang, N. He, S. Qian, J. Hua, [41] G. L. Wood, M. J. Miller, A. G. Mott, Opt. Lett. 1995, 20, 973–
Chem. Asian J. 2011, 6, 157–165.
975.
[30] A. M. McDonagh, C. E. Powell, J. P. Morrall, M. P. Cifuentes,
M. G. Humphrey, Organometallics 2003, 22, 1402–1413.
[31] K. Onitsuka, A. Iuchi, M. Fujimoto, S. Takahashi, Chem.
Commun. 2001, 741–742.
[32] A. M. McDonagh, M. G. Humphrey, M. Samoc, B. Luther-
Davies, S. Houbrechts, T. Wada, H. Sasabe, A. Persoons, J.
Am. Chem. Soc. 1999, 121, 1405–1406.
[42] T. Xia, D. J. Hagan, A. Dogariu, A. A. Said, E. W. Van Stry-
land, Appl. Opt. 1997, 36, 4110–4122.
[43] G. A. Crosby, J. N. Demas, J. Phys. Chem. 1971, 75, 991–1024.
[44] M. Sheik-Bahae, A. A. Said, E. W. Stryland, Opt. Lett. 1989,
14, 955–957.
Received: February 11, 2014
Published Online: April 28, 2014
Eur. J. Inorg. Chem. 2014, 2544–2551
2551
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim