Synthesis of photo-luminescent Zn(II) Schiff base complexes and its derivative containing Pd(II) moiety

Article abstract of DOI:10.1039/b316281h

An efficient method was developed for the preparation of a series of zinc Schiff base complexes. Introduction of a pyridyl group as a bridging unit as well as incorporation of ethynyl and electron-donating groups into the salicylidene moiety of these comp

Full text of DOI:10.1039/b316281h

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F U L L P A P E R
Synthesis of photo-luminescent Zn(II) Schiff base complexes and its
derivative containing Pd(II) moiety
Ku-Hsien Chang, Chiung-Cheng Huang, Yi-Hung Liu, Ya-Hui Hu, Pi-Tai Chou and
Ying-Chih Lin*
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106.
E-mail: yclin@ntu.edu.tw; Fax: +(886)-2-23636359
Received 12th December 2003, Accepted 2nd April 2004
First published as an Advance Article on the web 26th April 2004
An efficient method was developed for the preparation of a series of zinc Schiff base complexes. Introduction of a pyridyl
group as a bridging unit as well as incorporation of ethynyl and electron-donating groups into the salicylidene moiety of
these complexes moderately enhances the photoluminescence intensity and quantum yield. Electron-rich palladium groups
possibly influence the photophysical character through the bridging CC bond. The crystal structure of the pyridine
adduct of a salen Zn complex is determined by X-ray diffraction analysis.
four coordinated ones, by single crystal X-ray diffraction analysis
Introduction
unfortunately failed to yield positive results. Alternatively, by ad-
There have been numerous reports of transition metal complexes
dition of pyridine to one of these complexes, we are able to grow
containing salen ligands1 with two oxygen and two nitrogen donor
single crystals and the structure of this complex is confirmed by
atoms as well as other similar ligands2 but only a few reports of
X-ray diffraction analysis.
complexes containing related ligands in which one or both aryl rings
are alkynylated.3,4 Gothelf and co-workers have recently described
the synthesis of phenylacetylene linked porphyrin molecules4 using
Sonogashira coupling for the immobilisation of chiral Mn–salen
complexes on gold electrodes and surfaces. As the growth of in-
terest in the use of chiral zinc and other metal salen complexes in
asymmetric Lewis acid-catalyzed reactions becomes more signifi-
cant,1,5 we are interested to see if the aryl alkynylated salen metal
complexes could be readily prepared and how the chemical reactiv-
ity of these complexes varies relative to their parent complexes. In
addition, as some of these complexes show luminescent properties,
it is interesting to explore how this feature could be modified by
the presence of the alkynyl group. Recently, luminescent materials
have attracted much attention due to their significant expansibility
in commercial applications such as organic light emitting devices
(OLEDs).6 In contrast to organic dyes and polymers,7 few efficient
materials based on chelated metal complexes using Schiff bases
such as three-ligand complexes (Alq3 (q = 8-hydroxyquinoline)
and its analogue),8 two-ligand complexes,9 and other chelated de-
rivatives10 have been investigated. A series of intramolecular azo-
methine Zn Schiff base complexes11 were reported to be effective
emitters having good electron transport capability in a two-layer
cell structure. Due to facile quenching of fluorescence by decay of
the excited electron via dense inner-shell d orbitals, it was generally
believed that systems containing transition metal complexes would
not display intense luminescence properties. Recently, incorpora-
tion of acetylide into metal complexes12 was found to destabilize
non-radiative d–d transitions and maintain strict structural integrity
thus displaying reasonable luminescence properties. We therefore
developed a synthetic method to prepare a series of Zn(II) Schiff
base complexes containing alkynyl groups and studied their cor-
responding photophysical properties. One such complex was also
modified by the incorporation of two palladium phosphine groups
via the alkynyl group. Preliminary absorption and emission data of
these mononuclear and trinuclear complexes in solution indicated
that the luminescence efficiency was indeed improved by introduc-
tion of the CC triple bond and electron-donating alkyl groups.
Recently, several research groups13 have focused on the issue of
coordination mode of the Zn complexes containing Schiff base li-
gands. It is generally believed that four coordinated Zn Schiff base
complexes are reluctant to form single crystals, while the structures
of many five coordinated complexes are known in the literature.
Our attempts to structurally characterize new complexes, possibly
Results and discussion
Synthesis of ethynylsalophen
Treatment of 5-bromo-salicylaldehyde with trimethylsilylacety-
lene in the presence of Pd(PPh3)2Cl2 and CuI in Et3N at 80 °C af-
fords 5-trimethylsilylacetylene-salicylaldehyde (1a) in 92% yield
(Scheme 1). Hydrolysis of the trimethylsilyl group is achieved in
methanol solution of K2CO3 generating 5-ethynylsalicylaldehyde
(1) in moderate yield (60%). Two other alkynyl substituted salicyl-
aldehyde, 2 and 3 (see Scheme 1), are similarly synthesized by the
Sonogashira coupling reaction in 71% and 60% yield, respectively.
Previously only a few salicylaldehydes bearing alkynyl substituent
were reported.14
In the 1H NMR spectrum of 1, resonance of the hydroxyl proton
is observed at  11.11. It has been reported that OH of 2-hydroxy-
acetophenone, which has a carbonyl group at the ortho-position to
the hydroxy group, is at  12.05, further downfield than that of the
phenol proton at  7.54.15 This deshielding shift is attributable to
the formation of intramolecular hydrogen bonding. The resonance
at  9.85 is assigned to the aldehyde group. Three well-resolved
resonances at  7.70 (d, 4JH–H = 2.02 Hz), 7.60 (dd, 3JH–H = 8.60 Hz,
4JH–H = 2.02 Hz) and 6.94 (d, 3JH–H = 8.60 Hz) are assigned to pro-
tons on the phenyl group. Resonance of the ethynyl proton is found
at  3.02. In the 13C NMR spectrum, the resonance at  195.9 is
assigned to the carbonyl carbon. Resonances at  81.9 and 76.8 are
assigned to two alkynyl carbons. The EI mass spectrum showing the
parent peak at m/z 146 (M+) and elemental analysis are consistent
with the proposed formula of 1. Spectroscopic data of 2 and 3 are
also consistent with the proposed structures.
Treatment of 1 with o-phenylenediamine in ethanol at 50 °C led
to the formation of an orange solid identified as H2(5-ethynylsalo-
phen) (4), see Scheme 1, in 90% yield. The new ethynylsalophen
is air-stable and soluble in common organic solvents. The 1H NMR
spectrum of 4 shows a resonance at  13.32 assignable to the phenol
proton that is even further downfield than that of 1 possibly due to
hydrogen bonding between the phenol proton and the imine nitro-
gen. The singlet resonance at  8.58 is assigned to the proton of the
imine NCH group and the resonance at  2.99 is assigned to the
terminal ethynyl proton. In the 13C NMR spectrum, the resonance
at  162.8 is assigned to the imine carbon. Two resonances at  82.9
and 77.2 are assigned to the ethynyl carbons.
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8
1 7 3 1

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Scheme 1
Synthesis of Zn Schiff base complexes
lated zinc analogue, the four coordinated arrangement of the Schiff
base ligands seems most likely.13 However, we can not rule out that
this complex might be a five coordinated structure.
In previous studies,11,16 metal-Schiff base complexes were generally
obtained by a direct reaction of metal salt with Schiff base, which
is often prepared by condensation of amines and hydroxyaldehydes
at elevated temperature in alcoholic solvent followed by recrystal-
lization. However, an alternative preparation for these Schiff base
complexes is the treatment of metal salt with salicylaldehyde to
generate a bis(salicylaldehydato) metal complex followed by treat-
ing this intermediate with amine to give the desired product. In our
study, the later one-pot strategy is utilized for ease of handling and
purification.
Synthesis of ethynyl-substituted Zn(II) Schiff base complexes
For the preparation of ethynyl-substituted complex 6, 1 is treated
with zinc acetate in methanol and, after filtration, o-phenylenedi-
amine was added to the filtrate to give the yellow product 6 in 88%
yield, Scheme 2. Complex 6 is soluble in DMSO but is only slightly
soluble in other organic solvent. Yellow-green fluorescence was ob-
served in solution under UV illumination of 6. In the 1H NMR spec-
trum of 6, the resonance at  9.02 is assigned to the imine (NCH)
proton and the resonance at  3.89 is assigned to the ethynyl proton.
In the 13C NMR spectrum the resonance at  162.6 is assigned to the
CN carbon. Characterization was also achieved by FAB-MS, and
elemental analysis.
Complex 7 is similarly prepared from 1, zinc acetate and 2,3-di-
aminopyridine in methanol. Complex 7 is air-stable, and is soluble
only in THF and DMSO. Yellow fluorescence is observed in both
solution and solid state. Due to the asymmetrical pyridine group,
the 1H NMR spectrum in DMSO displays two resonances at  9.43
and 9.10 assignable to the two imine NCH protons. Three sets of
1H resonances of three aromatic groups are all well resolved. One
set at  8.44, 8.35 and 7.49 is assigned to the pyridyl group. The
second set appears at  7.70, 7.35, and 6.76 along with the third set
at  7.63, 7.32 and 6.72. However, only one signal is found at  3.90
for the two ethynyl protons since these two terminal ethynyl protons
are far away from the asymmetrical pyridyl group. In the 13C NMR
spectrum resonances of the imine carbons are found at  163.8 and
162.9, and that of four ethynyl carbons are observed at  84.2, 84.1,
77.7, and 77.6.
To prepare the zinc Schiff base complex, zinc acetate is first
treated with salicylaldehyde, and the mixture stirred in methanol
for 30 min at room temperature. To the resulting solution was sub-
sequently added o-phenylenediamine, and the formed precipitation
was collected and washed with methanol. Complex 5a is prepared
by using this method and the yield is almost quantitative. Compared
with the reported method,11,16 our procedure required only mild re-
action conditions (room temperature) and with no additional work
necessary for the synthesis of the free Schiff base. Complex 5a is
air-stable and soluble in THF and DMSO. In the 1H NMR spectrum
of 5a the resonance of the imine NCH proton is found at  9.02.
The Schiff base 2,3-bis(salicylideneamino)pyridine17 has been
applied for the determination of Cu2+ by fluorescence quench-
ing and there was only one example of Zn complex with pyridyl
salen-type ligand in the literature.18 Due to the high fluorescent
intensity of free pyridine-bridging Schiff base, the corresponding
Zn complex is assumed to show improved photophysical properties
than that with a phenylene-bridging unit. Complex 5b is therefore
synthesized by the reaction of salicylaldehyde with zinc acetate fol-
lowed by treating the mixture with 2,3-diaminopyridine in methanol
at room temperature. The resulting yellow product 5b was isolated
in 77% yield. Due to the asymmetrical structure of 5b, the 1H NMR
spectrum shows two signals at 9.57 and 8.98 attributed to two
non-equivalent imine NCH protons. In the FAB mass spectrum
the parent peak is found at m/z 380.1 (M+ + 1). Complexes 5a and
5b have been characterized by elemental analysis and by mass and
NMR spectroscopic techniques, and in analogy to the recently iso-
To explore the influence of substituents on the bridging phenyl-
ene group, derivatives of 6 and 7 with different functional groups
were synthesized. Complex 8 having an additional electron-donat-
ing methyl group is obtained as a yellow powder by the same proce-
dure as that of 6 in 73%. Complex 9 having an electron-withdrawing
nitro group on the bridging phenylene ring is obtained as a peachy
red powder in 76% yield. Unlike 6–8, complex 9 does not show
1 7 3 2
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8

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Scheme 2
apparent fluorescence either in solution or the solid state under UV
was dried under vacuum, and the residue was redissolved in a small
irradiation. Complex 10 is prepared by addition of 3,4-diaminopyri-
dine to a mixture of 1 and zinc acetate in MeOH affording a red
powder 10 in 48% yield, which is lower than that of its 2,3-isomer 7.
The 1H NMR data shows two absorptions at  9.16 and 9.14, which
are assigned to imine protons. Resonances of the ethynyl protons
are found at  3.92 and 3.90. Other spectral data of 10 are similar
to those of 7.
amount of THF. The mixture was subsequently added into a stirring
solution of petroleum ether affording a yellow powder in 83% yield.
For 15 and 16, the products were obtained as orange powders both
in ca. 30% yield. The low yield could be due to the presence of the
bulky tert-butyl group at the 3-position thus obstructing condensa-
tion of diamine with the bis(salicylaldehydato) zinc intermediate.
1
In general, two H absorptions of non-equivalent imine NCH
protons are observed for these complexes.
1
The H chemical shifts of the imine (NCH) groups of com-
plexes 6–10 can be briefly accounted for by electronic property
of imino substituents. Complexes 7 and 10 having heteroatomic
bridging units show downfield resonances of imine protons relative
to that of 6. With an electron-withdrawing nitro group, the same
tendency is also observed for 9. The 1H chemical shifts of the ethy-
nyl protons also reveal a similar tendency, but are not obvious due
to distal separation between them and the imino groups. The 13C
resonances of imine carbons are located at around  164, and the C
and C of ethynyl groups are found at around  84 and 77.
Recently,19 the rac-1,2-cyclohexanediamino-N,N′-bis(3,5-di-tert-
butylsalicyl- aldehyde) zinc(II) and chiral pure (R,R)-isomer have
been synthesized by the reaction of Schiff base with highly reactive
Et2Zn in hexane. The Schiff base was generated by the reaction of
diamine and 3,5-di-tert-butylsalicylaldehyde in refluxing ethanol.
Structure determination of the pyridine adduct of 16
Most of four coordinated Zn complexes possess tetrahedron geom-
etry, and a few of them have been reported recently in the literature.
Attempts to obtain single crystals of Zn salen complexes, however,
failed to yield a suitable solid sample for structure determination. It
is known that five-coordinated Zn(salen)(L) complexes form single
crystals much more easily. We thus added pyridine to induce forma-
tion of single crystals of adduct, 16a. The structure of 16a has been
determined by X-ray diffraction analysis. An ORTEP drawing is
shown in Fig. 1 and selective bond distances and angles are listed
in Table 1. The molecular structure of 16a features the zinc atom in
a five coordinate square pyramidal geometry. The salophen ligand
occupies the basal plane while the pyridine ligand occupies the api-
cal position. The Zn center lies 0.41(1) Å above the N2O2 coordina-
tion plane. The Zn–N(1)(pyridine) distance (2.127(2) Å), similar
to that observed in other complexes,19a,b is slightly longer than the
Zn–N(salen ligand) (2.068(2) 2.118(2) Å) distances.
Synthesis of other alkynyl-substituted Zn(II) Schiff base
complexes
Compound 7 containing a pyridiyl bridge displays excellent lumi-
nescent character, we therefore prepared derivatives with different
substituent groups on the phenyl ring. Complex 11 is synthesized
from the reaction of 1a with zinc acetate and 2,3-diaminopyridine in
83% yield, Scheme 1. The solubility of 11, having two terminal tri-
methylsilyl groups, is better than that of 7 in common polar organic
solvents. The reaction of 2 with zinc acetate and 2,3-diaminopyri-
dine gave the orange product 12 in 93% yield. In comparison with
other complexes, complex 12 with a bridging pyridyl group shows
lower solubility in organic solvents even in DMSO. Complex 13,
with two additional OCH3 groups in the salicylidene fragment, is
also obtained as an orange powder in 49% isolated yield.
Several tert-butyl-substituted salicylaldehydes are commercially
available for the synthesis of the corresponding Zn complexes
14–16. Although complexes of other metals1 are widely utilized
in asymmetric catalysis, the zinc analogue has not been reported.
Complexes 14–16 are readily prepared by the method mentioned
above. Due to its high solubility complex 14 could not form a solid
precipitation during the preparation. Therefore, the reaction mixture
Synthesis of trinuclear palladium–zinc complexes
Preparation of trinuclear heterometallic complex 17 is achieved
by the reaction of 6 with trans-Pd(PnBu3)2Cl2 in the presence of
catalytic amounts of CuI in Et2NH at room temperature. Complex
17 decomposes in silica gel. Purification of 17 was through filtra-
tion to separate the solid state side-products of the reaction from the
mixture followed by addition of hexane to the solution affording the
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8
1 7 3 3

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Table 1 Selected bond distance (Å) and angle (degree) of 16a
Table 2 Photophysical data for 5–18 in THF
Zn(1)–O(1)
Zn(1)–N(1)
Zn(1)–N(3)
1.960(2)
2.127(2)
2.068(2)
Zn(1)–O(2)
Zn(1)–N(2)
1.971(2)
2.118(2)
Quantum
yield
em
Absorption

Emission
Compound
max/nm (10−3 /M−1 cm−1)

max/nm
N(3)–Zn(1)–N(2)
O(1)–Zn(1)–N(2)
O(2)–Zn(1)–N(2)
N(2)–Zn(1)–N(1)
O(1)–Zn(1)–N(3)
78.50(7)
87.09(7)
160.36(8)
102.08(8)
148.73(8)
O(2)–Zn(1)–N(3)
N(3)–Zn(1)–N(1)
O(1)–Zn(1)–O(2)
O(2)–Zn(1)–N(1)
O(1)–Zn(1)–N(1)
88.74(7)
111.38(8)
96.63(7)
96.43(8)
98.64(8)
5a
5b
6
7
8
405 (8.38)
417 (13.77)
412 (11.65)
426 (12.58)
417 (17.47)
444 (11.68)
430 (13.39)
431 (10.19)
506
508
519
524
513
0.03
0.17
0.09
0.52
0.09
9
512, 571
531
6.2 × 10−3
0.21
10
11
12
13
14
15
16
17
18
527
0.67
0.74
0.05
0.28
0.39
0.40
0.11
0.12
442 (16.06), 472 (14.16)
445 (20.00)
543a
555
430 (14.90)
423 (16.97)
433 (12.25)
458 (13.25)
525
518
534
563
454 (9.85)
558
a ex = 442 nm.
Fig. 1 ORTEP drawing of complex 16a (30% probability ellipsoids).
orange-yellow complex 17. CuCl could also be utilized in the prepa-
ration of 17, but was less efficient. Interestingly, polymerization
caused by CuI as a catalyst was not observed.20 Complex 17 is
stable in air, and is soluble in common organic solvents. Orange
fluorescence is observed in solution, whereas yellow fluorescence
1
is observed in the solid state under UV irradiation. The H NMR
spectrum of 17 shows an expected pattern for the proposed struc-
ture. The signal of the NCH proton of the imine group is found
at  8.23. The 13C NMR spectrum reveals two alkynyl carbons at 
105.2 and 93.2, the later with 2JC–P = 16.8 Hz.
Fig. 2 Emission spectra of complexes 6, 12, and 17 in THF.
Replacement of terminal chloride with cyanide at the Pd moiety
in 17 is achieved by addition of AgCN in THF generating the bright
orange complex 18 in moderate yield. Complex 18 is reasonably
soluble in polar organic solvents and shows orange fluorescence
both in solution and in the solid state. In the 1H NMR spectrum of
similar emission peak wavelength at ~507 nm, the quantum yield
of 0.17 for 5b with a pyridyl bridge is about five times as much
as that of 5a (em ~ 0.03) with a phenylene bridge. A similar trend
is also observed for 6 (em ~ 0.09) and 7 (em ~ 0.52) tailored by
phenylene and pyridyl bridges, respectively. With addition of two
ethynyl groups, the absorption and emission peaks of 6 and 7 are
slightly red shifted relative to that of 5a and 5b. Furthermore, the
quantum yields of the ethynyl-substituted 6 and 7 are higher than
that of the ethynyl-free 5a and 5b, respectively, by approximately 3
fold. With an electron-donating methyl group added on the bridging
phenylene unit, complex 8 exhibits similar photophysical properties
with those of 6. The nitro group on complex 9 offers an extra conju-
gated backbone, resulting in a bathochromic shift in both absorption
(444 nm) and emission (571 nm) spectra relative to 6. However, the
fluorescence intensity is significantly quenched by the presence of
the nitro group. The effects of the methyl and nitro groups are simi-
lar to those described in the literature.16 In comparison to 7, complex
10 bearing a 3,4-diaminopyridyl bridge displays a slight red shift in
both absorption and emission spectra as well as a lower quantum
yield. When the alkynyl proton of 7 is replaced by a Si(CH3)3 group,
forming 11, both absorption and emission peaks are found to be red-
shifted in comparison with those of 7, accompanied by an increase
of the fluorescence quantum yield up to 0.67. For 12, the conjugated
backbone is largely elongated by the presence of two 4-pentylphenyl
groups on the alkynyl terminus. Accordingly, both absorption and
emission spectra of 12 are significantly red shifted relative to those
of 7, and the quantum efficiency has been improved to 0.74. Con-
versely, complex 13 bearing an electron donating methoxy group
near the metal center exhibits bathochromic spectral features with
respect to 11. The exceedingly low quantum yield of 0.05 for 13
indicates that the methoxy group acts as a good quencher, of which
the deactivation process possibly involves torsional motions.
18, the resonance at  8.52 is assigned to the NCH group. The 31
P
NMR spectrum displays a singlet resonance at  12.61. Two-dimen-
sional 1H–13C HMQC and HMBC NMR methods are employed to
gain information on the structure of 18. Nine 13C signals of phenyl
carbon are expected and eight peaks are found. The HMQC spectrum
reveals that two resonances overlap at  137.7 as indicated by cor-
relating the two protons at  7.11 and 7.08. The resonance at  110.7
and 99.8 are assigned to C and C of the ethynyl group, respectively,
based on the HMQC and HMBC NMR data. The coupling reactions
of complexes 7–10 with trans-Pd(PnBu3)2Cl2 have also been carried
out. The 31P NMR and FAB mass data indicate formation of the tri-
nuclear complexes, and the red-shift of fluorescence induced by UV
illumination was observed in all cases. However, due to instability,
these trinuclear complexes were not isolated as pure products.
Photophysical studies of Schiff base complexes
Table 2 summarizes the photophysical data of complexes 5–18,
of which the emission spectra were obtained by excitation at their
longest peak wavelength. Fig. 2 gives emission spectra of three
complexes 6, 12, and 17. The wavelength at the intersection point
of the absorption spectra between the sample and the reference
was taken as the excitation wavelength in determining the quan-
tum yield. Quantum yields were determined while the absorbance
was kept in the range of 0.1–0.2 to avoid the interference of
reabsorption.
In general, replacing phenylene with the pyridyl bridge in the
Schiff base of the titled zinc salen complexes significantly increases
the emission quantum yield (see Table 2). For example, albeit a
1 7 3 4
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8

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For 14–16, the photophysical data clearly reveal that the supple-
mentary electron-donating tert-butyl groups indeed enhance the
quantum efficiency as well as bathochromically shift both absorp-
tion and emission peaks relative to that of 5. Furthermore, the 3-
substituted derivative (15) exhibits less spectral shifts but larger
enhancement in quantum efficiency than that of the 5-substituted
one (14). Accordingly, it is reasonable to expect that the fluores-
cence yield of 16, bearing tert-butyl groups at both 3 and 5 posi-
tions, lies in between that of 14 and 15. Finally, the introduction
of two electron-rich palladium groups, forming 17 and 18, causes
significant red-shifting (>30 nm) for both absorption and emission
peaks relative to e.g. 6. Spectral features of 18 are found to be in
hypsochromically shifted with respect to 17, possibly due to the
stronger electron-withdrawing ability of the cyano group (18) than
that of the chloride group (17). Incorporating the palladium moiety
only slightly improves the emission efficiency, as indicated by the
quantum yields of 0.11 and 0.12 for 17 and 18, respectively, which
are only slightly higher than the quantum yield of 0.09 in 6.
In view of future electrooptical applications, complex 12, of
which the quantum yield is the highest among 5–18, was further
examined to gain detailed insights into the relaxation dynamics in
solution as well as in pure solid. The lifetime of 12 was measured to
be 2.01 ns in THF. Giving the observed lifetime of 0.74 ns a radia-
tive lifetime as short as 2.72 ns is deduced in THF. In the solid, the
emission peak wavelength for 12 is slightly red shifted to 575 nm,
with a similar spectral profile as that observed in THF. The fluores-
cence quantum yield was measured to be as high as of 0.21 with a
lifetime of 0.53 ns in the solid. The results lead us to conclude that
complex 12 bearing a long alkyl-chain side arm is subject to negli-
gible  stacking in the solid and thus is suited to future applications
in e.g. OLEDs.
ses were carried on a Perkin-Elmer 2400 CHN elemental analyzer
in National Taiwan University.
Absorption spectra were obtained using an HP 8453 diode array
spectrophotometer. Emission spectra were taken using an Hitachi
F-4500 luminescence spectrometer. Luminescence quantum yields
(em) were calculated relative to [RuII(bipy)3]Cl2 in air-equilibrated
aqueous solution (em = 0.028).21 A configuration of front-face
excitation was used to measure the emission of the solid sample, in
which the cell was made by assembling two edge-polished quartz
plates with various Teflon spacers.Acombination of appropriate fil-
ters was used to avoid the interference from the scattering light. An
integrated sphere was applied to measure the quantum yield in the
solid state, in which the solid sample film was prepared via either
the spin coating or vapor deposition method and was excited by a
457 nm Ar+ laser line. The resulting luminescence was acquired by
an intensified charge-coupled detector for subsequent analyses.
Lifetime studies were performed using an Edinburgh FL 900
photon-counting system with a hydrogen-filled/or a nitrogen lamp
as the excitation source. Data were analyzed using the nonlinear
least squares procedure in combination with an iterative convolu-
tion method. The emission decays were analyzed by the sum of ex-
ponential functions, which allows partial removal of the instrument
time broadening and consequently renders a temporal resolution
of ~200 ps.
Preparation of 5-ethynylsalicylaldehyde (1). To a mixture
of 5-bromosalicyl- aldehyde (5.00 g, 24.87 mmol), Pd(PPh3)2Cl2
(0.52 g, 0.74 mmol), and CuI (0.15 g, 0.75 mmol) in 80 mL of
Et3N, trimethylsilylacetylene (5.5 mL, 38.72 mmol) was added.
The mixture was stirred for 3 h at 80 °C. After cooling, the result-
ing ammonium salt was filtered off, and the residue was purified
by chromatography on silica gel with THF/hexane (1:2) as eluent.
Removal of solvent under vacuum afforded a yellow powder, and
the product was identified as 5-trimethylsilylethynylsalicylalde-
hyde (1a) (4.99 g, 92%). 1H NMR (CDCl3):  11.09 (b, 1 H, OH);
9.83 (s, 1 H, OCH); 7.68 (d, 1 H, Ph, 4JH–H = 1.9 Hz); 7.58 (dd, 1
H, Ph, 3JH–H = 8.7 Hz, 4JH–H = 1.9 Hz); 6.92 (d, 1 H, Ph, 3JH–H = 8.7
Hz); 0.23 (s, 9 H, CH3). 13C NMR (CDCl3): 196.0 (CO); 161.5,
140.1, 137.5, 120.3, 117.9, 115.1 (Ph); 103.1 (CCSi(CH3)3); 93.8
(CCSi(CH3)3); −0.1 (CH3). MS (EI): m/z 218 (M+).
Concluding remarks
We have demonstrated that a series of novel luminescent Zn(II)
Schiff base complexes could be readily synthesized. Preparation
of zinc Schiff base complexes 5–16 (see Scheme 1) was readily
achieved by treatment of the corresponding salicylaldehyde with
zinc acetate followed by addition of diamine in methanol. The
desired solid state Zn(II) complexes formed from the reaction
solution were readily collected via filtration. Terminal alkynyl
groups in complex 6 could be efficiently used for the preparation
of hetero-trinuclear palladium derivatives. Preparation of the het-
erometallic trinuclear complex 17 is achieved by the reaction of
trans-Pd(PnBu3)2Cl2 with 6 at the alkynyl terminus in the presence
of CuI in Et2NH. Replacement of two chlorides by cyanides at the
Pd moiety in 17 could be achieved by the reaction with AgCN gen-
erating the bright orange complex 18.
The photoluminescence of the pyridyl-containing Schiff base
complexes 5b and 7 is more efficient than that of 5a and 6. Ad-
dition of two ethynyl groups in the backbone of 6 and 7 enhances
the fluorescence efficiency by a large margin relative to 5a and 5b,
respectively. The tert-butyl groups in 14–16 are not as advantageous
as the ethynyl ones. The nitro and methoxy groups containing lone-
pair electrons quench the photoluminescence. The heterometallic
complexes 17 and 18 vary in the color (wavelength alteration) of
the fluorescence and give slightly higher quantum yield compared
with those of the mononuclear complex 6.
A methanol solution (40 mL) containing 1a (2.0 g, 9.17 mmol)
and K2CO3 (2.0 g, 14.5 mmol) was stirred for 12 h at room
temperature. The resulting precipitate was filtered off, and the
filtrate was dried. To the residue was added a mixture of H2O
(50 mL) and CH2Cl2 (50 mL) to afford a two-phase solution. The
aqueous layer was further extracted with CH2Cl2 (2 × 50 mL),
and the combined CH2Cl2 solution was dried over MgSO4.
The solution was filtered through Celite and the filtrate dried
under vacuum. The crude product was eluted with THF/hexane
(1:2) on a silica gel column. Removal of solvent afforded an
orange–yellow powder identified as 5-ethynyl-salicylaldehyde
(1) (0.81 g, 60%). 1H NMR (CDCl3):  11.11 (s, 1H, OH); 9.85 (s,
4
1H, OCH); 7.70 (d, 1H, Ph, JH–H = 2.0 Hz); 7.60 (dd, 1H, Ph,
4
3
3JH–H = 8.6 Hz, JH–H = 2.0 Hz); 6.94 (d, 1H, Ph, JH–H = 8.6 Hz);
3.02 (s, 1H, HC). 13C NMR (CDCl3): 195.9 (CO); 161.7, 140.2,
137.5, 120.4, 118.1, 113.9 (Ph); 81.9 (CCH); 76.8 (CCH). MS
(EI): m/z 146 (M+). Anal. Calcd for C9H6O2: C, 73.97; H, 4.14.
Found: C, 73.78; H, 3.97.
Experimental
Synthesis of 5-(p-pentylphenylethynyl)salicylaldehyde (2).
To a mixture of 5-bromo-salicylaldehyde (0.97 g, 4.8 mmol),
Pd(PPh3)2Cl2 (44 mg, 63 mol), PPh3 (88 mg, 0.336 mmol) and CuI
(44 mg, 0.22 mmol) in Et3N (30 mL), was added 1-ethynyl-4-pen-
tylbenzene (1.69 mL, 8.7 mmol). The mixture was stirred for 10 h at
60 °C. Ammonium salt thus formed was filtered off, and the amine
solution was dried in vacuum. The residue was eluted with THF/
hexane (1:3) as eluent on a SiO2 column. The first band having blue
fluorescence was excluded, and the second band was collected. The
solvent was removed and the residue washed with hexane affording
off-white powder, identified as 2 (1.0 g, 71%). 1H NMR (CDCl3):
General procedures
All manipulations were performed under nitrogen using a vacuum-
line, dry box, and standard Schlenk techniques. CH2Cl2 was distilled
from CaH2 and diethyl ether and THF from Na/ketyl. All other sol-
vents and reagents were of reagent grade and were used without
purification. NMR spectra were recorded on Bruker DMX-500,
AM-300 and AC-200WB FT-NMR spectrometers at room tem-
perature (unless states otherwise) and were reported in units of 
with residual protons in the solvent as standard (CDCl3,  7.24;
d6-methyl sulfoxide,  2.50; CD2Cl2,  5.32). FAB mass spectra
were recorded on a JEOL SX-102A spectrometer. Elemental analy-
 11.09 (s, 1H, OH); 9.87 (s, 1H, OCH); 7.73 (d, 1H, Ph, 4JH–H
=
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8
1 7 3 5

View Article Online
4
3
1.98 Hz); 7.64 (dd, 1H, Ph, JH–H = 1.98 Hz, JH–H = 8.7 Hz); 7.41
(d, 2H, Ph, 3JH–H = 8.1 Hz); 7.15 (d, 2H, Ph, 3JH–H = 8.1 Hz); 6.97 (d,
2H, Ph, 3JH–H = 8.7 Hz); 2.60 (t, 2H, CH2, 3JH–H = 7.50 Hz); 1.60 (m,
The mixture was stirred for 3 h, and the resulting yellow precipitate
was collected by filtration and washed with methanol. The yellow
1
product was identified as complex 6 (0.12 g, 82%). H NMR (d6-
2H, CH2); 1.31 (m, 4H, CH2); 0.87 (t, 3H, CH3, 3JH–H = 6.60 Hz). 13
C
DMSO):  9.02 (s, 2H, NCH); 7.88 (m, 2H, Ph); 7.52 (d, 2H,
4
3
NMR (CDCl3): 196.1 (CO); 161.3, 143.7, 139.8, 136.8, 131.4,
128.5, 120.5, 120.0, 118.1, 115.5 (Ph); 89.1, 86.9 (CC); 35.9, 31.4,
30.9, 22.5 (CH2), 14.0 (CH3). MS (EI): m/z 292 (M+). Anal. Calcd
for C20H20O2: C, 82.16; H, 6.89. Found: C, 81.98; H, 6.56.
Ph, JH–H = 2.25 Hz); 7.42 (m, 2H, Ph); 7.30 (dd, 2H, Ph, JH–H =
4
3
8.82 Hz, JH–H = 2.25 Hz); 6.69 (d, 2H, Ph, JH–H = 8.82 Hz); 3.89
(s, 2H, HCC). 13C NMR (d6-DMSO): 172.4 (Ph); 162.6 (CN);
140.4; 139.3, 137.0, 127.9, 123.8, 119.5, 116.7, 105.7 (Ph); 84.4
(CCH); 77.6 (CCH). MS (FAB): m/z 427.0 (M+ + 1). Anal.
Calcd for C24H14N2O2Zn: C, 67.39; H, 3.30; N, 6.55. Found: C,
67.18; H, 3.18; N, 6.42.
Synthesis of 5-trimethylsilylethynyl-3-methoxysalicylalde-
hyde (3). To a mixture of 5-bromo-3-methoxysalicylaldehyde
(3.00 g, 12.98 mmol), Pd(PPh3)2Cl2 (0.27 g, 0.39 mmol) and CuI
(78 mg, 0.39 mmol) in Et3N (80 mL), was added trimethylsi-
lylacetylene (4.6 mL, 32.45 mmol). The mixture was stirred for 4
h at 80 °C. Ammonium salt was filtered off, and the residue was
purified by chromatography on silica gel with THF/hexane (1:2) as
eluent. Removal of solvent afforded a yellow oil, which became a
colloidal solid after standing overnight in a fume hood. The product
was identified as compound 3 (1.91 g, 59.2%). 1H NMR (CDCl3):
Preparation of complex 7. Complex 7 was prepared from 1
(73 mg, 0.5 mmol) Zn(OAc)2·2H2O (50 mg, 0.23 mmol) and 2,3-
diaminopyridine (25.3 mg, 0.23 mmol) in methanol (10 mL) using
similar procedures. The yellow product 7 was isolated in 66% yield
1
(65.1 mg). H NMR (d6-DMSO):  9.43 (s, 1H, NCH); 9.10 (s,
3
1H, NCH); 8.44 (d, 1H, Py, JH–H = 4.54 Hz); 8.35 (d, 1H, Py,
3JH–H = 8.26 Hz); 7.70 (d, 1H, Ph, 4JH–H = 2.24 Hz); 7.63 (d, 1H, Ph,
4JH–H = 2.19 Hz); 7.49 (dd, 1H, Py, 3JH–H = 8.26 Hz, 3JH–H = 4.54 Hz);
7.35 (dd, 1H, Ph, 3JH–H = 8.93 Hz, 4JH–H = 2.24 Hz); 7.32 (dd, 1H, Ph,
3JH–H = 8.90 Hz, 4JH–H = 2.19 Hz); 6.76 (d, 1H, Ph, 3JH–H = 8.93 Hz);
 11.21 (s, 1H, OH); 9.84 (s, 1H, OCH); 7.32 (d, 1H, Ph, 4JH–H
=
4
1.47 Hz); 7.13 (d, 1H, Ph, JH–H = 1.47 Hz); 3.90 (s, 3H, OCH3),
0.23 (s, 9H, Si(CH3)3). 13C NMR (CDCl3): 196.0 (CO); 152.1,
148.1, 128.5, 120.4, 120.3, 114.7 (Ph); 103.5 (CCSi(CH3)3); 93.6
(CCSi(CH3)3); −0.1 (CH3). MS (EI): m/z 248 (M+).
3
6.72 (d, 1H, Ph, JH–H = 8.90 Hz); 3.90 (s, 1H, HCC); 3.89 (s,
1H, HCC). 13C NMR (d6-DMSO): 173.4, 172.6 (Ph); 163.8,
162.9 (CN); 149.4, 146.6, 141.1, 140.3, 137.7, 137.1, 134.3,
125.0, 124.1, 123.9, 123.3, 119.3, 118.9, 106.1, 105.8 (Ph); 84.2,
84.1(CCH); 77.7, 77.6 (CCH). MS (FAB): m/z 428.1 (M+ + 1).
Anal. Calcd for C23H13N3O2Zn: C, 64.43; H, 3.06; N, 9.80. Found:
C, 64.45; H, 2.94; N, 9.55.
Preparation of H2(5-ethynylsalophen) (4). An ethanol solution
(40 mL) of 1 (0.9 g, 6.16 mmol) and o-phenylenediamine (0.3 g,
2.77 mmol) was stirred at 50 ºC for 4 h. The resulting orange pre-
cipitate was filtered and washed with ethanol, and was identified as
4 (0.9 g, 90%). 1H NMR (CD2Cl2):  13.32 (s, 2H, OH); 8.621 (s,
4
Preparation of complexes 8, 9, and 10. Complex 8 was simi-
larly prepared from 1 (0.1 g, 0.68 mmol), Zn(OAc)2·2H2O (75.1 mg,
0.34 mmol) and 3,4-diaminotoluene (41.5 mg, 0.34 mmol) in 73%
yield (0.11g). 1H NMR (d6-DMSO):  9.02 (s, 1H, NCH); 8.99 (s,
1H, Ph, NCH); 7.79 (d, 1H, Ph, 3JH–H = 8.38 Hz); 7.73 (s, 1H, Ph);
7.64 (d, 2H, Ph, 3JH–H = 6.40 Hz); 7.30 (d, 2H, Ph, 3JH–H = 8.82 Hz);
7.24 (d, 1H, Ph, 3JH–H = 8.32 Hz); 6.68 (d, 2H, Ph, 3JH–H = 8.84 Hz);
3.87 (s, 2H, HCC); 2.41 (s, 3H, CH3). 13C NMR (d6-DMSO):
172.3, 172.2 (Ph); 162.3, 161.6 (CN); 140.3, 140.2, 138.9, 137.5,
136.8, 136.6, 128.5, 123.62, 123.56, 119.4, 116.9, 116.4, 105.6,
105.5 (Ph); 84.4, 84.3 (CCH); 77.5 (CCH); 21.1 (CH3). MS
(FAB): m/z 441.1 (M+ + 1). Anal. Calcd for C25H16N3O4Zn: C,
67.97; H, 3.65; N, 6.34. Found: C, 67.64; H, 3.35; N, 6.11.
2H, NCH); 7.59 (d, 2H, Ph, JH–H = 1.77 Hz); 7.50 (dd, 2H, Ph,
3JH–H = 8.31 Hz, JH–H = 1.77 Hz); 7.39 (m, 2H, Ph); 7.28 (m, 2H,
4
Ph); 6.98 (d, 2H, Ph, JH–H = 8.31 Hz); 3.07 (s, 2H, CCH). 13C
3
NMR (CDCl3):  162.8 (CN); 161.8, 142.2, 137.0, 136.2, 128.2,
119.6, 119.0, 118.0, 112.8 (Ph); 82.9 (CCH); 77.2 (CH). MS
(EI): m/z 364 (M+). Anal. Calcd for C24H16N2O2: C, 79.11; H, 4.43;
N, 7.69. Found: C, 79.48; H, 4.33; N, 7.46.
Preparation of complex 5a. The salicylaldehyde (0.2 mL, 1.9
mmol) in methanol (20 mL) was first treated with Zn(OAc)2·2H2O
(0.21 g, 0.95 mmol) and the mixture was stirred for 30 min at room
temperature. Then o-phenylenediamine (0.103 g, 0.95 mmol) was
added into the solution. The mixture was stirred for 4 h, and the re-
sulting yellow precipitation was collected by filtration and washed
with methanol and was identified as 5a (0.35 g, 97%). 1H NMR (d6-
DMSO):  9.02 (s, 2H, NCH); 7.91 (m, 2H, Ph); 7.41 (m, 4H, Ph);
7.24 (m, 2H, Ph); 6.71 (d, 2H, Ph, 3JH–H = 8.41 Hz); 6.52 (t, 2H, Ph,
3JH–H = 7.09 Hz). 13C NMR (d6-DMSO): 172.2 (Ph); 162.8 (CN);
139.4, 136.2, 134.3, 127.2, 123.1, 119.4, 116.4, 112.9 (Ph). MS
(FAB, Zn = 64): m/z 379.0 (M+ + 1). Anal. Calcd for C20H14N2O2Zn:
C, 63.26; H, 3.72; N, 7.38. Found: C, 62.99; H, 3.75; N, 7.39.
Complex 9 was prepared from 1 (74 mg, 0.51 mmol),
Zn(OAc)2·2H2O (51 mg, 0.23 mmol) and 4-nitro-1,2-phenylene-
diamine (35.5 mg, 0.23 mmol) in 76% yield (82 mg). 1H NMR
(d6-DMSO):  9.21 (s, 1H, NCH); 9.13 (s, 1H, NCH); 8.78 (d,
1H, Ph, 4JH–H = 2.33 Hz); 8.25 (dd, 1H, Ph, 3JH–H = 9.07 Hz, 4JH–H
2.33 Hz); 8.10 (d, 1H, Ph, 3JH–H = 9.07 Hz); 7.75 (d, 1H, Ph, 4JH–H
2.36 Hz); 7.68 (d, 1H, Ph, 4JH–H = 2.26 Hz); 7.35 (dd,1H, Ph, 3JH–H
8.87 Hz, 4JH–H = 2.36 Hz); 7.32 (dd,1H, Ph, 3JH–H = 8.90 Hz, 4JH–H
2.26 Hz); 6.71 (d, 1H, Ph, 3JH–H = 8.87 Hz); 6.70 (d, 1H, Ph, 3JH–H
=
=
=
=
=
8.90 Hz); 3.90 (s, 1H, HCC); 3.89 (s, 1H, HCC). 13C NMR
(d6-DMSO): 173.3, 172.8 (Ph); 165.3, 164.6 (CN); 145.9, 144.8,
140.9, 139.7, 137.8, 137.4, 124.1, 123.8, 122.1, 119.22, 119.17,
117.9, 112.4, 106.1, 105.9 (Ph); 84.1, 84.0 (CCH); 77.8, 77.5
(CCH). Anal. Calcd for C24H13N3O4Zn: C, 60.97; H, 2.77; N,
8.89. Found: C, 60.62; H, 2.65; N, 8.58.
Preparation of complex 5b. Complex 5b was similarly pre-
pared from salicylaldehyde (0.2 mL, 1.9 mmol), Zn(OAc)2·2H2O
(0.21 g, 0.95 mmol) in methanol (20 mL) and 2,3-diamino-
pyridine (0.103 g, 0.95 mmol). The yellow product 5b was iso-
1
lated in 77% yield (0.28 g). H NMR (d8-THF):  9.57 (s, 1H,
NCH); 8.98 (s, 1H, NCH); 8.33 (m, 1H, Ar); 8.19 (dd, 1H, Ar,
3JH–H = 8.23 Hz, 4JH–H = 1.38 Hz); 7.34–7.14 (m, 5H, Ar); 6.85 (d,
2H, Ar, 3JH–H = 8.62 Hz); 6.48 (m, 2H, Ar). 13C NMR (d6-DMSO): 
173.6, 172.6 (Ph); 164.2, 163.2 (CN); 149.6, 146.1, 137.0, 136.2,
135.3, 134.7, 134.4, 124.6, 123.5, 123.3, 122.9, 119.5, 119.0,
113.5.1, 113.2 (Ph). MS (FAB, Zn = 64): m/z 380.1 (M+ + 1). Anal.
Calcd for C19H13N3O2Zn: C, 59.94; H, 3.44; N, 11.04. Found: C,
59.85; H, 3.35; N, 10.87.
Complex 10 was similarly prepared from 1 (0.2 g, 1.37 mmol),
Zn(OAc)2·2H2O (0.15 mg, 0.68 mmol) and 3,4-diaminopyridine
(74.6 mg, 0.68 mmol) in 48% yield (0.14 g). 1H NMR (d6-DMSO):
 9.16 (s, 1H, NCH); 9.14 (s, 1H, NCH); 9.12 (s, 1H, Ar); 8.54
(d, 1H, Ar, 3JH–H = 5.52 Hz); 7.84 (d, 1H, Ar, 3JH–H = 5.52 Hz); 7.66
(d, 1H, Ph, 4JH–H = 2.24 Hz); 7.63 (d, 1H, Ph, 4JH–H = 2.21 Hz); 7.34
3
4
(dd, 1H, Ph, JH–H = 8.67 Hz, JH–H = 2.23 Hz); 7.32 (dd, 1H, Ph,
3JH–H = 8.75 Hz, 4JH–H = 2.38 Hz); 6.71 (d, 1H, Ph, 3JH–H = 8.75 Hz);
6.70 (d, 1H, Ph, 3JH–H = 8.67 Hz); 3.92 (s, 1H, HCC); 3.90 (s, 1H,
HCC). 13C NMR (d6-DMSO): 173.4, 172.5 (Ph); 165.3, 163.4
(CN); 148.2, 145.0, 140.9, 140.4, 139.7, 137.8, 137.1, 134.8,
124.2, 123.9, 119.4, 119.0, 110.6, 106.0, 105.7 (Ph); 84.2, 84.0
(CCH); 77.8, 77.6 (CCH). MS (FAB): m/z 428.0 (M+ + 1).
Preparation of complex 6. Compound 1 (0.1 g, 0.68 mmol)
in methanol (10 mL) was treated with Zn(OAc)2·2H2O (75.1 mg,
0.34 mmol) and the mixture was stirred for 30 min at room tem-
perature. The resulting precipitate was filtered off, and to the filtrate
was sequentially added o-phenylenediamine (37 mg, 0.34 mmol).
1 7 3 6
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8

View Article Online
Anal. Calcd for C23H13N3O2Zn: C, 64.43; H, 3.06; N, 9.80. Found:
C, 64.16; H, 2.98; N, 9.55.
Complex 16 was similarly prepared from 3,5-di-tert-
butylsalicylaldehyde (1.0 g, 4.27 mmol), Zn(OAc)2·2H2O (0.47 g,
2.14 mmol) and 2,3-diaminopyridine (0.233 g, 2.14 mmol) in 30%
yield (0.38 g). 1H NMR (d6-DMSO):  9.45 (s, 1H, NCH); 9.12
(s, 1H, NCH); 8.35 (d, 2H, Ar); 7.36 (d, 3H, Ar); 7.24 (m, 2H,
Ar); 1.50 (s, 18H, CH3); 1.28 (s, 18H, CH3). 13C NMR (d6-DMSO):
171.8, 170.7 (Ph); 164.0, 163.0 (CN); 150.0, 145.4, 141.3, 141.0,
134.5, 133.8, 133.5, 129.9, 129.4, 128.8, 123.9, 122.2, 118.3, 117.8
(Ph); 35.2 (C(CH3)3); 33.5 (C(CH3)3); 31.3 (CH3); 29.5 (CH3). MS
(FAB): m/z 604.4 (M+ + 1).Anal. Calcd for C35H45N3O2Zn: C, 69.47;
H, 7.50; N, 6.94. Found: C, 69.25; H, 7.38; N, 6.83. The pyridine
adduct 16a was obtained by addition of pyridine to the THF solu-
tion of 16 then carefully spread over the surface of the mixture with
ethanol to yield orange single crystals for structure determination.
Preparation of complexes 11–16. Compound 1a (0.5 g,
2.28 mmol) in methanol (30 mL) was treated with Zn(OAc)2·2H2O
(0.25 g, 1.14 mmol) and the mixture stirred for 30 min at room
temperature. The resulting solution was added 2,3-diaminopyridine
(0.124 g, 1.14 mmol), and the mixture was stirred for 3 h. The re-
sulting yellow precipitate was collected by filtration and washed
with methanol. The yellow product was identified as complex 11
(0.54 g, 83%). 1H NMR (d6-DMSO):  9.41 (s, 1H, NCH); 9.10
(s, 1H, NCH); 8.44 (d, 1 H, Py, 3JH–H = 4.74 Hz); 8.31 (d, 1H, Py,
3JH–H = 8.44 Hz); 7.69 (d, 1H, Ph, 4JH–H = 2.23 Hz); 7.63 (d, 1H, Ph,
4JH–H = 2.15 Hz); 7.49 (dd,1H, Py, 3JH–H = 8.44 Hz, 3JH–H = 4.74 Hz);
3
7.30 (m, 2H, Ph); 6.76 (d, 1H, Ph, JH–H = 8.86 Hz); 6.72 (d, 1H,
3
Ph, JH–H = 8.80 Hz); 0.21 (s, 18H, CH3). 13C NMR (d6-DMSO):
Preparation of complex 17. To a mixture of 6 (0.1 g, 0.23
mmol), trans-Pd- (PnBu3)2Cl2 (0.27 g, 0.46 mmol), and CuI (4 mg,
10 mol) was added Et2NH (15 mL). The mixture was stirred for
3 h at room temperature. The resulting ammonium salt was filtered
off, and solvent of the filtrate was evaporated under reduced pres-
sure. The residue was extracted using 3 × 3 mL of diethyl ether, and
then the solution was concentrated, and was added into a hexane
solution leading to formation of orange–yellow powder which was
collected by filtration and washed with hexane. The product was
identified as complex 17 (0.12 g, 34%). 1H NMR (CD2Cl2):  8.23
(s, 2H, NCH); 7.28 (s, 2H, Ph,); 7.13 (4H, Ph, 3JH–H = 7.84 Hz);
6.96 (s, 2H, Ph); 6.65 (d, 2H, Ph, 3JH–H = 7.84 Hz); 1.92 (m, 24H,
CH2); 1.57 (m, 24H, CH2); 1.46 (m, 24H, CH2); 0.95 (t, 36H, CH3,
3JH–H = 7.11 Hz). 31P NMR (CDCl3):  10.3. 13C NMR (CD2Cl2):
173.6, 172.8 (Ph); 163.9, 163.0 (CN); 149.5, 146.8, 141.2, 140.7,
137.7, 137.0, 134.4, 125.0, 124.2, 124.0, 123.5, 119.5, 119.0,
106.7, 106.43 (Ph); 106.37, 106.35 (CCSi(CH3)3); 90.9, 90.7
(CCSi(CH3)3); 0.2 (CH3). MS (FAB): m/z 573.0 (M+ + 1). Anal.
Calcd for C29H29N3O2Si2Zn: C, 60.77; H, 5.10; N, 7.33. Found: C,
60.55; H, 5.02; N, 7.16.
Complex 12 was similarly prepared from 2 (0.30 g, 1.03 mmol),
Zn(OAc)2·2H2O (0.113 g, 0.515 mmol) and 2,3-diaminopyridine
(56 mg, 0.514 mmol) in 93% yield (0.35 g). 1H NMR (d6-DMSO): 
9.46 (s, 1H, NCH); 9.14 (s, 1H, NCH); 8.45 (d, 1H, Py, 3JH–H
=
4.70 Hz); 8.35 (d, 1H, Py, 3JH–H = 8.22 Hz); 7.76 (s, 1H, Ph); 7.70
(s, 1H, Ph); 7.50 (dd,1H, Py, 3JH–H = 8.22 Hz, 3JH–H = 4.70 Hz); 7.40
(d, 6H, Ph, 3JH–H = 7.78 Hz); 7.22 (d, 4H, Ph, 3JH–H = 7.78 Hz); 6.77
(d, 2H, Ph, 3JH–H = 9.04 Hz); 2.59 (t, 4H, CH2, 3JH–H = 7.76 Hz); 1.57
(m, 4H, CH2); 1.30 (br, 8H, CH2); 0.87 (t, 6H, CH3, 3JH–H = 6.73 Hz).
MS (FAB): m/z 720.2 (M+ + 1). Anal. Calcd for C45H41N3O2Zn: C,
74.94; H, 5.73; N, 5.83. Found: C, 74.78; H, 5.62; N, 5.67.
168.6 (Ph); 162.4(CN); 140.3, 138.0, 137.2, 128.3, 124.0, 120.6,
2
117.1, 116.4 (Ph); 105.2 (CC–Pd); 93.2 (t, CC–Pd, JC–P
=
2
16.8 Hz); 27.0 (CH2); 24.4 (CH2, JC–P = 6.6 Hz); 23.7 (t, CH2,
1JC–P = 13.4 Hz); 14.2 (CH3). MS (FAB, Zn = 64, Pd = 106, Cl =
35): m/z 1517.3 (M+ + 3); 1481.4 (M+ + 2-Cl); 1279.3 (M+ + 2-Cl,
PnBu3). Anal. Calcd for C72H120Cl2N2O2P4Pd2Zn: C, 56.94; H, 7.96;
N, 1.84. Found: C, 56.66; H, 7.77; N, 1.78.
Complex 13 was similarly prepared from 3 (0.5 g, 2.0 mmol),
Zn(OAc)2·2H2O (0.22 g, 1.0 mmol) and 2,3-diaminopyridine
1
(0.11 g, 1.0 mmol) in 49% yield (0.31 g). H NMR (d6-DMSO):
 9.41 (s, 1H, NCH); 9.09 (s, 1H, NCH); 8.41 (d, 1H, Py,
3
3JH–H = 4.58 Hz); 8.31 (d, 1H, Py, JH–H = 8.24 Hz); 7.46 (dd, 1H,
Preparation of complex 18. To a mixture of 17 (40 mg,
26.4 mol) and AgCN (7.8 mg, 58 mol) was added THF (10 mL).
The mixture was stirred for 2 h, and the resulting AgCl salt was
filtered off. The clear THF solution was concentrated, and added
into a stirring hexane solution generating an orange powder which
was collected by filtration and washed with hexane. The product
was identified as complex 18 (25 mg, 63.3%). 1H NMR (CD2Cl2):
 8.52 (s, 2H, NCH); 7.52 (br, 2H, Ph); 7.32 (br, 2H, Ph); 7.11 (d,
Py, 3JH–H = 8.24 Hz, 3JH–H = 4.58 Hz); 7.30 (d, 2H, Ph, 4JH–H = 1.85
Hz); 6.83 (d, 2H, Ph, 4JH–H = 1.85 Hz); 3.79 (s, 6H, OCH3); 0.22 (s,
18H, Si(CH3)3). 13C NMR (d6-DMSO): 165.5, 164.6 (Ph); 163.8,
162.8 (CN); 152.5, 152.4, 149.4, 146.5, 134.3, 132.7, 132.4,
124.7, 123.2, 119.0, 118.4, 117.9, 115.3, 114.9, 106.9 (Ph); 105.3,
105.0 (CCSi(CH3)3); 90.3, 90.1 (CCSi(CH3)3); 55.2 (OCH3);
0.2 (Si(CH3)3). MS (FAB): m/z 632.2 (M+ + 1). Anal. Calcd for
C31H33N3O4Si2Zn: C, 58.80; H, 5.25; N, 6.64. Found: C, 58.64; H,
5.12; N, 6.56.
Complex 14 was similarly prepared from 5-tert-
butylsalicylaldehyde (0.2 mL, 1.17 mmol), Zn(OAc)2·2H2O
(0.125 g, 0.58 mmol) and 2,3-diaminopyridine (63.5 mg,
0.58 mmol) in 83% yield (0.54 g). H NMR (CDCl3):  9.40 (s,
1H, NCH); 8.70 (s, 1H, NCH); 8.40 (d, 1H, Py, JH–H = 3.94
2H, Ph, 3JH–H = 8.74 Hz); 7.08 (s, 2H, Ph); 6.69 (br, 2H, Ph, 3JH–H
=
8.74 Hz); 1.88 (br 24H, CH2); 1.45 (br, 24H, CH2); 1.38 (br, 24H,
CH2); 0.88 (br, 36H, CH3). 31P NMR (C6D6):  12.61. 13C NMR
(CD2Cl2): 172.5 (Ph); 161.4 (CN); 140.8; 137.7 (two carbons);
127.6; 124.4; 119.4; 116.2; 113.0; 110.7 (CC–Pd); 99.8 (br,
1
1
CC–Pd); 27.1 (CH2); 25.2 (t, CH2, JC–P = 14.2 Hz); 24.9 (CH2,
2JC–P = 6.6 Hz); 14.1 (CH3).Anal. Calcd for C74H120N4O2P4Pd2Zn: C,
3
3
Hz); 7.96 (d, 1H, Py, JH–H = 7.13 Hz); 7.31 (br, 3H, Py and Ph);
67.97; H, 3.65; N, 6.34. Found: C, 56.72; H, 3.55; N, 6.28.
7.16 (br, 4H, Ph); 1.21 (s, 18H, CH3). 13C NMR (d6-DMSO): 172.0,
170.9 (Ph); 164.3, 163.3 (CN); 149.8, 145.9, 135.2, 134.9, 134.5,
133.6, 132.9, 132.0, 131.3, 124.4, 123.2, 123.1, 122.6, 118.2, 117.7
(Ph); 33.4 (C(CH3)3); 31.1 (CH3). MS (FAB): m/z 492.2 (M+ + 1).
Anal. Calcd for C27H29N3O2Zn: C, 65.79; H, 5.93; N, 8.53. Found:
C, 65.65; H, 5.84; N, 8.44.
Single crystal X-ray diffraction analysis of 16a. Single crys-
tals of 16a suitable for an X-ray diffraction study were grown as
mentioned above. A single crystal of dimensions 0.25 × 0.20 ×
0.15 mm3 was glued to a glass fiber and mounted on a Nonius Kap-
paCCD diffractometer. The diffraction data were collected using 3
kW sealed-tube molybdenum K radiation (T = 295 K). Exposure
time was 5 s per frame.22 SADABS (Siemens area detector absorp-
tion) absorption correction23 was applied, and decay was negligible.
Data were processed and the structure was solved and refined by the
SHELXTL program. The structure was solved using direct methods
and confirmed by Patterson methods refining on intensities of all
data to give R1 = 0.0477 and wR2 = 0.1143 for 8652 unique ob-
served reflections (I > 2(I)).24 Hydrogen atoms were placed geo-
metrically using the riding model with thermal parameters set to 1.2
times that for the atoms to which the hydrogen is attached and 1.5
times that for the methyl hydrogens.
Complex 15 was similarly prepared from 3-tert-
butylsalicylaldehyde (0.5 mL, 2.92 mmol), Zn(OAc)2·2H2O
(0.32 g, 1.46 mmol) and 2,3-diaminopyridine (0.16 g, 1.47 mmol)
in 32% yield (0.23). 1H NMR (CDCl3):  9.44 (s, 1H, NCH); 9.10
(s, 1H, NCH); 8.35 (m, 2H, ArH); 7.40 (m, 1H, ArH); 7.28 (m,
4H, ArH); 6.47 (t, 2H, Ph, 3JH–H = 7.25 Hz); 1.48 (s, 18H, CH3). 13
C
NMR (d6-DMSO): 173.4, 172.4 (Ph); 163.9, 163.0 (CN); 149.8,
145.9, 141.9, 141.7, 135.2, 134.4, 131.2, 130.7, 124.1, 122.5, 119.5,
119.0, 112.8, 112.5 (Ph); 35.1 (C(CH3)3); 29.4 (CH3). MS (FAB):
m/z 492.2 (M+ + 1). Anal. Calcd for C27H29N3O2Zn: C, 65.79; H,
5.93; N, 8.53. Found: C, 65.66; H, 5.79; N, 8.46.
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8
1 7 3 7

View Article Online
Chem., 2000, 10, 1471; (d) A. Kraft, A. C. Grimsdale and A. B. Holmes,
Angew. Chem. Int. Ed., 1998, 37, 402; (e) Y. Z. Wang and A. J. Epstein,
Acc. Chem. Res., 1999, 32, 217.
Crystal data for 16a: C40H50N4O2Zn, M = 684.21, mono-
clinic, space group P21/c, a = 12.9630(2), b = 15.4880(3), c =
18.8460(3) Å,  = 92.831(1), V = 3779.11(11) Å3, Z = 4, reflections
measured 25763, reflections unique 8652 with Rint = 0.0481, T =
295(2) K, Final R indices {I > 2(I)}; R1 = 0.0477, wR2 = 0.1143
and for all data R1 = 0.0888, wR2 = 0.1417.
CCDC reference number 226734.
See http://www.rsc.org/suppdata/dt/b3/b316281h/ for crystallo-
graphic data in CIF or other electronic format.
8 S. A. Van Slyke, patent application, US 5,151,629, 1992.
9 Y. Hamada, T. Sano, K. Shibata and K. Kuroki, Jpn. J. Appl. Phys., 1995,
34, L824.
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J. Appl. Phys., 1995, 34, 1883.
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Appl. Phys., 1993, 32, L511.
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1999, 578, 3.
13 (a) S. Mizukami, H. Houjou, Y. Nagawa and M. Kanesato, Chem.
Commun., 2003, 1148; (b) J. Reglinski, S. Morris and D. E. Stevenson,
Polyhedron, 2002, 21, 2175; (c) J. S. Sanmartin, M. R. Bermejo,
A. M. Garcia-Deibe andA. L. Llamas-Saiz, Chem. Commun., 2000, 795;
(d) C. Arici and M. Aksu, Anal. Sci., 2002, 18, 727; (e) D. Hall and F. H.
Moore, J. Chem. Soc. A, 1966, 1822.
14 (a) Y. J. Cho, K. Y. Rho, S. H. Kim, S. R. Keum and C. M. Yoon,
Dyes Pigm. 1999, 44, 19; (b) M. Pal, K. Parasuraman, S. Gupta and
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Acknowledgement
Financial support provided by the National Science Council of
Taiwan is grateful acknowledged. Funding for the Instrumen-
tation Facility of the Department of Chemistry of NTU has
also been provided in part by the National Science Council of
Taiwan.
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25 GOF = [Σ[w(F2o − F2 )2]/(n − p)]1/2, where n and p denote the number
c
of data and parameters. R1 = (Σ||Fo| − |Fc||)/|Fo|, wR2 = [Σ−[w(F2
−
o
F2 )2]/Σ[w(F2 )2]]1/2 where w = 1/[2(F2 ) + (aP)2 + bP] and P = [(max;
c
o
o
0, F2 ) + 2F2 ]/3.
o
c
1 7 3 8
D a l t o n T r a n s . , 2 0 0 4 , 1 7 3 1 – 1 7 3 8