Zinc and cadmium halide compounds with the tridentate ligand 2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline showing yellow luminescence

Article abstract of DOI:10.1016/j.poly.2016.02.030

Five mononuclear complexes, i.e. ZnLCl₂ (1), [ZnLBr₂](CH₃CN) (2), ZnLBr₂ (3), CdLCl₂ (4), and CdLBr₂ (5), with L = 2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline, have been synthesiz

Full text of DOI:10.1016/j.poly.2016.02.030

Accepted Manuscript
Zinc and cadmium halide compounds with the tridentate ligand 2–(methylsul-
fanyl)-N-(pyridin-2-ylmethylidene)aniline showing yellow luminescence
Xue Liu, Adriana González-Castro, Ilpo Mutikainen, Andrej Pevec, Simon J.
Teat, Patrick Gamez, Jose Sanchez Costa, Elisabeth Bouwman, Jan Reedijk
PII:
S0277-5387(16)00124-8
DOI:
http://dx.doi.org/10.1016/j.poly.2016.02.030
POLY 11846
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
10 February 2016
20 February 2016
Please cite this article as: X. Liu, A. González-Castro, I. Mutikainen, A. Pevec, S.J. Teat, P. Gamez, J.S. Costa, E.
Bouwman, J. Reedijk, Zinc and cadmium halide compounds with the tridentate ligand 2–(methylsulfanyl)-N-
(pyridin-2-ylmethylidene)aniline showing yellow luminescence, Polyhedron (2016), doi: http://dx.doi.org/10.1016/
j.poly.2016.02.030
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

POLY-D-16-00134_R1_19feb16
Zinc and Cadmium Halide Compounds with the tridentate ligand
2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline showing yellow
luminescence.
Xue Liu,a Adriana González-Castro,a Ilpo Mutikainen,b Andrej Pevec,c Simon J. Teat,d
Patrick Gamez,a,e Jose Sanchez Costa,a,f Elisabeth Bouwman,a,* Jan Reedijka
a Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA
Leiden, The Netherlands; E-mail: bouwman@chem.leidenuniv.nl. Tel: +31 (0)71 527 4450.
b Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasenaukio 1), FI-00014,
Finland
c Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, Ljubljana,
Slovenia
d Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA,
94720, USA
e: Current address: Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís
Companys 23, 08010 Barcelona, Spain
f: Current address: IMDEA-Nanoscience c/Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
Abstract
Five mononuclear complexes, i.e. ZnLCl2 (1), [ZnLBr2](CH3CN) (2), ZnLBr2 (3), CdLCl2
(4), and CdLBr2 (5), with L= 2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline, have been
synthesized and characterized. For [ZnLBr2](CH3CN) only a few crystals were obtained from the
main batch of ZnLBr2.Their crystal structures and solid-state luminescence properties both at
room temperature and 77 K have been investigated. All compounds contain 5-coordinated Zn(II)
or Cd(II) ions in a square-pyramidal geometry, distorted towards trigonal bipyramidal. The phase
purity of all compounds has been evaluated by Powder XRD and IR. All five compounds show
photoluminescent properties both at room temperature and 77 K. In the solid state, the
compounds exhibit yellow luminescence with the maximum of emission at around 540 nm. By
cooling down to 77 K, the shape and position of the emission spectra of all these compounds
remains more or less constant.
1

Keywords:
Zinc(II); Cadmium(II); Schiff base; Chloride; Bromide; Luminescence
1. Introduction
Luminescent materials based on transition metals and lanthanoids have found wide
applications in lighting [1-3], luminescence sensing [4-6] and optical devices [7]. Among them,
d10 metal complexes comprising zinc(II) and cadmium(II) with a variety of ligands have drawn
extensive attention in the past decades due to their attractive luminescence properties [8-10].
Schiff bases have been widely employed in coordination chemistry due to their easy accessibility
and structural varieties [11]. Transition metal Schiff-base complexes show great importance in
catalysis [12], photochemistry [13], biochemistry [14] and materials science [15].
Selected zinc(II) and cadmium(II) Schiff-base complexes with excellent luminescence
properties have been reported in the literature[16, 17]. In this work, we have synthesized a series
of mononuclear zinc(II) and cadmium(II) coordination compounds using the tridentate
NNS-donor Schiff-base ligand 2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline
(abbreviated as L). The characterization and structure determination of the compounds have been
performed through NMR, IR, elemental analysis, X-ray crystallography and Powder XRD. The
photophysical properties have been studied by solid-state absorption spectra and further by solid-
state excitation and emission spectra. During the writing phase of the paper it was found that the
zinc bromide compound was studied in 1972, but only its crystal structure was reported [18]. This
structure appears to be isomorphous with our compound, ZnLBr2, but determined at room T and
reported with a higher R value.
2. Experimental part
2.1 Materials and general methods
2-(Methylthio)aniline and pyridine-2-carboxaldehyde were purchased from Sigma-
Aldrich. Pyridine-2-carboxaldehyde was distilled before use; the other chemicals and solvents
were used without further purification. 1H and 13C NMR spectra were recorded on a Bruker
DPX300 spectrometer. Elemental analysis for C, H, N was performed at the Microanalytical
laboratory Kolbe in Germany. FT-IR spectra were recorded on a Perkin-Elmer Paragon 1000
FTIR spectrophotometer equipped with a Golden Gate ATR device. X-ray powder diffraction
patterns were obtained on a Philips PW 1050 diffractometer using Cu Kα radiation (λ = 1.542 Å).
2

The room-temperature excitation and emission spectra were measured on a Shimadzu RF-
5301PC spectrofluoriphotometer. Solid-state absorption spectra were recorded with the Avantes
absorbance setup, using the Avantes AvaSpec-2048UA CCD spectrometer as detector, and the
AvaLight-DH-S Deuterium-Halogen light source. The low-temperature emission spectra (77 K)
were measured using a homemade sample holder with an irradiance calibrated CCD spectrometer
(Avantes AvaSpec-2048UA) as a detector. A 1000 W xenon lamp (LOT) and a Spex
monochromator were used as the excitation source. Photoluminescence quantum yields were
measured using the absolute method.[19] An integrating sphere (Avantes AvaSphere 30REFL)
and an CCD spectrometer (Avantes AvaSpec-2048UA) was used.
2.2. Ligand synthesis
The ligand 2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline (L) was synthesized
following a literature procedure [20]. A solution of 2-(methylthio)aniline (0.64 g, 4.6 mmol) and
fresh distilled pyridine-2-carboxaldehyde (0.50 g, 4.6 mmol) in toluene (50 mL) was refluxed for
24 h. The reaction mixture was then filtered and the solvent was evaporated under reduced
pressure. The crude product was recrystallized from toluene/hexane. Yellow crystals of pure
ligand were obtained. Yield: 0.83 g (75%). 1H NMR (300 MHz, CDCl3): δ =8.67 (d, 1H), 8.57 (s,
1H), 8.33(d,1H), 7.80 (t, 1H), 7.36 (t, 1H), 7.27 (m, 3H), 7.06 (d, 1H), 2.47 (s, 3H) ppm. 13C
NMR (300 MHz, CDCl3): δ =160.3, 154.7, 149.6, 147.9, 136.7, 134.8, 127.33, 125.3, 125.2,
124.6, 122.0, 117.5, 14.86 ppm. IR (v): 1620 (m), 1469 (s), 1433 (s), 1346 (w), 1266 (w), 1194
(w), 1068 (w), 1040 (w), 992 (m), 879 (s), 778 (vs), 749 (vs), 739 (vs), 726 (vs), 691 (s), 648 (m),
613 (s), 549 (s), 481 (vs) cm–1.
2.3 General procedure for synthesis of the compounds ZnLCl2 (1), ZnLBr2 (2) + (3), CdLCl2
(4), and CdLBr2 (5).
The ligand L (0.22 g, 1 mmol) was dissolved in 10 mL MeOH. To this solution, the metal
salt (1 mmol; ZnCl2, ZnBr2, CdCl2 and CdBr2, respectively) in MeOH (10 mL) was added
dropwise; the mixture was then stirred at 80 °C for 2 h. The precipitate was filtered and washed
with hot MeOH three times, then dried in air. The yellow compounds were finally recrystallized
from acetonitrile. ZnLCl2 (1), yield: 0.25 g (70%); ZnLBr2 (2+3), yield: 0.25 g (54%); CdLCl2 (4),
yield: 0.24 g (58%); CdLBr2 (5), yield: 0.27 mg (54%).
Basic spectroscopic data for each compound:
3

ZnLCl2 (1). 1H NMR (300 MHz, DMSO): δ =8.76 (d, J=4.7 Hz, 1H), 8.57 (s, 1H), 8.18 (d,
J=7.9 Hz, 1H), 8.02 (t, J=7.7 Hz, 1H), 7.59 (m, 1H), 7.30 (m, 2H), 7.24 (m, 2H), 2.44 (s, 3H)
ppm. 13C NMR (300 MHz, DMSO): δ =160.7, 150.3, 137.8, 128.0, 126.5, 125.6, 124.9, 122.1,
118.1, 14.3 ppm. Elemental analysis found (calc) for C13H12Cl2N2SZn: C, 42.92 (42.83); H, 3.31
(3.32); N, 7.83 (7.68); S, 8.66 (8.79). IR (v): 1627 (w), 1596 (s), 1563 (w), 1479 (w), 1441 (s),
1368 (m), 1298 (s), 1235 (m), 1203 (m), 1100 (m), 1044 (m), 1020 (s), 978 (s), 952 (m), 911 (m),
778 (vs), 744 (vs), 642 (s), 565 (s), 495 (s), 469 (s) cm–1.
ZnLBr2 (2+3). 1H NMR (300 MHz, DMSO): δ =8.76 (d, J=4.8 Hz, 1H), 8.56 (s, 1H), 8.19
(d, J=8.5 Hz, 1H), 8.02 (t, J=7.7 Hz, 1H), 7.59 (m, 1H), 7.31 (m, 2H), 7.24 (m, 2H), 2.45 (s, 3H)
ppm. 13C NMR (300 MHz, DMSO): δ =160.7, 150.3, 137.8, 127.9, 126.4, 125.6, 124.8, 122.0,
118.1, 14.3 ppm. Elemental analysis found (calc) for C13H12Br2N2SZn: C, 34.91 (34.43); H, 2.79
(2.67); N, 6.30 (6.18); S, 6.84 (7.07). IR (v): 1618 (w), 1588 (s), 1559 (w), 1474 (m), 1428 (s),
1369 (s), 1301 (s), 1238 (m), 1198 (m), 1150 (m), 1094 (m), 1044 (m), 1016 (s), 980 (s), 912 (m),
796 (vs), 767 (s), 761 (s), 744 (vs), 722 (s), 640 (s), 575 (s), 497 (s), 465 (w) cm–1. After
recrystallization from MeCN the sample showed visually distinguishable two kinds of crystals (in
an approximate ratio of 1:5); two different crystals (i.e. 2 and 3) were used for single-crystal
XRD studies.
CdLCl2 (4). 1H NMR (300 MHz, DMSO): δ =8.76 (d, J=3.9 Hz, 1H), 8.60 (s, 1H), 8.18 (d,
J=7.8 Hz, 1H), 8.04 (t, J=7.7 Hz, 1H), 7.68 (m, 1H), 7.32 (m, 2H), 7.25 (m, 2H), 2.44 (s, 3H)
ppm. 13C NMR (300 MHz, DMSO): δ =160.8, 150.3, 138.0, 128.0, 126.6, 125.7, 125.1, 122.7,
118.4, 14.5 ppm. Elemental analysis found (calc) for C13H12Cl2N2SCd: C, 38.40 (37.93); H, 2.91
(2.94); N, 6.94 (6.81); S, 7.26 (7.79). IR (v): 1624 (w), 1590 (s), 1563 (w), 1479 (w), 1438 (s),
1372 (m), 1304 (s), 1236 (m), 1199 (m), 1101 (m), 1014 (s), 979 (s), 965 (m), 910 (m), 776 (vs),
761 (vs), 741 (vs), 637 (s), 572 (s), 498 (s), 465 (s) cm–1.
CdLBr2 (5). 1H NMR (300 MHz, DMSO): δ =8.76 (d, J=4.7 Hz, 1H), 8.59 (s, 1H), 8.19 (d,
J=7.9 Hz, 1H), 8.05 (t, J=7.6 Hz, 1H), 7.60 (m, 1H), 7.32 (m, 2H), 7.26 (m, 2H), 2.45 (s, 3H)
ppm. 13C NMR (300 MHz, DMSO): δ =160.8, 150.3, 138.0, 128.0, 126.7, 125.7, 125.1, 122.7,
118.4, 14.5 ppm. Elemental analysis found (calc) for C13H12Br2N2SCd: C, 31.56 (31.20); H, 2.26
(2.42); N, 5.68 (5.60); S, 6.18 (6.41). IR (v): 1628 (w), 1590 (s), 1567 (w), 1475 (m), 1435 (m),
1373 (s), 1304 (m), 1232 (m), 1198 (m), 1097 (m), 1044 (m), 1011 (m), 984 (s), 903 (s), 780 (vs),
758 (vs), 743 (s), 637 (s), 571 (s), 492 (s), 460 (m) cm–1.
4

2.4: Single Crystal Structure Determinations
A single crystal of compound 1 was mounted at the diffractometer and measured both at
room temperature (293 K) and at 173 K by using a Nonius Kappa CCD area detector
diffractometer. A graphite monochromated MoKα radiation source (λ = 0.71073 Å) was
employed. Standard programs like SIR-92 [21], SHELXS–97 and SHELXL-97 [22] were used
for data structure solution and structure refinement. The structure was solved by direct methods
using and refined with a full-matrix least-squares procedure based on F2 using. All of the non-
hydrogen atoms were refined anisotropically. All other C-H hydrogen atoms (except C7-H7A)
were included in the model at geometrically calculated positions and refined using a riding model.
The hydrogen atom bonded to C7 was visible in the last stages of refinement and was refined
freely (distance C7-H7A = 0.93(2) Å). See Table 1 for more details.
Crystals of 2, 3 and 4 were selected for the X-ray measurements and mounted to nylon
loop using the oil-drop method [23] and data were collected using Bruker Kappa APEXII
diffractometer (Mo-Kα radiation, λ = 0.71073 Å) at 123 K. A crystal of 5 was mounted on a
MitGen loop in oil and data collected on Bruker APEX2 CCD diffractometer at beamline 11.3.1
of the Advanced Light Source (Synchrotron radiation, λ = 0.7749 Å) at 100 K. A total of 658
frames for CdLCl2, 1159 frames for [ZnLBr2](CH3CN), 718 frames for ZnLBr2 and 2880 frames
for CdLBr2 were collected. The frames were integrated with the Bruker SAINT software package
[24] using a narrow-frame algorithm and their intensities were corrected for Lorentz and
polarization effects. An absorption correction was applied using the Multi-Scan method
(SADABS) [24]. The programs SHELXS2014 [22], SHELXL2014 [25] were used for structure
solution and structure refinement. The non-hydrogen atoms were refined anisotropically. The H
atoms were situated at calculated positions and refined isotropically riding with the heavy atom
connected. More details are in Tables 1 and 2.
5

Table 1. Crystallographic data collection and refinement of (1), (2) and (3).
Compound
CCDC
(1)Low T: ZnLCl2
1445927
C13H12Cl2N2SZn
364.59
(1) Room T: ZnLCl2
1446902
C13H12Cl2N2SZn
364.59
(2) ZnLBr2(CH3CN)
1443691
C15H15Br2N3SZn
494.50
(3) ZnLBr2
1446921
C13H12Br2N2SZn
453.50
Chemical formula
Formula mass
Temperature (K)
Crystal system
Space group
a/Ǻ
173(2)
293(2)
123(2)
123(2)
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P21/n
triclinic
P-1
8.1510(10)
27.268(3)
6.9880(10)
90
8.2405(2)
27.6821(6)
7.09100(10)
90
8.1053(4)
24.6650(12)
9.0573(4)
90
8.0102(4)
9.3086(5)
10.9516(6)
76.836(2)
72.701(2)
76.094(2)
745.97(7)
2
b/Ǻ
c/Ǻ
α/◦
β/◦
113.640(10)
90
114.2888(1)
90
101.970(10)
90
γ/◦
V(Ǻ3)
1422.8(3)
4
1474.38(5)
4
1771.34(15)
4
Z
Radiation type
Density (calculated g/cm-3)
Absorption coefficient
(mm-1)
MoKα
MoKα
MoKα
MoKα
1.702
1.642
1.854
2.019
2.233
2.155
6.014
7.129
F (000)
736
736
968
440
Crystal size (mm3)
Goodness of fit on F2
R1, wR2 [I>2σ(I)]
R1, wR2 (all data)
0.30×0.30×0.15
1.110
0.2x0.08x0.08
1.049
0.40×0.35×0.35
1.151
0.30×0.12×0.12
1.109
0.0272, 0.0562
0.0311, 0.0576
0.0273,0.0625
0.0446, 0.0678
0.0200, 0.0441
0.0237, 0.0451
0.0189, 0.0440
0.0230, 0.0452
6

Table 2. Crystallographic data collection and refinement of (4) CdLBr2 (5).
Compound
(4) CdLCl2
1443712
C13H12Cl2N2SCd
411.61
(5) CdLBr2
1445920
CCDC
Chemical formula
C13H12Br2N2SCd
500.53
Formula mass
Temperature (K)
123(2)
100(2)
Crystal system
triclinic
triclinic
Space group
P-1
P-1
a/Ǻ
7.5791(3)
8.6549(4)
11.3533(5)
84.1060(10)
81.7830(10)
82.8210(10)
728.58(5)
2
7.6731(4)
8.9064(4)
11.5492(6)
84.129(2)
80.050(2)
81.189(2)
765.89(7)
2
b/Ǻ
c/Ǻ
α/◦
β/◦
γ/◦
V(Ǻ3)
Z
Radiation type
Density (calculated g/cm-3)
Absorption coefficient (mm-1)
F (000)
MoKα
Synchrotron; 0.77490 Ȧ
2.170
1.876
1.994
8.364
404
476
Crystal size (mm3)
Goodness of fit on F2
R1, wR2 [I>2σ(I)]
R1, wR2 (all data)
0.30×0.28×0.08
1.117
0.06 × 0.04 × 0.03
1.041
0.0161, 0.0404
0.0173, 0.0410
0.0258, 0.0630
0.0300, 0.0648
3. Results and discussion
3.1 Synthesis and characterization
The compounds ZnLCl2, CdLCl2 and CdLBr2 crystallized without any solvents and in
good phase purity, as discussed in the section Powder XRD and IR. The crystal structure of the
compound ZnLBr2 has been reported previously [18]. In our synthesis of ZnLBr2, two different
crystals were found and were isolated from the same batch; these two types of crystals were
impossible to obtain as separate batches. Very interestingly, it appeared that one type of crystals
crystallized with an acetonitrile molecule, namely [ZnLBr2](CH3CN), the other one without any
solvent, namely ZnLBr2. The elemental analysis of the bulk sample of ZnLBr2 is not fully in
agreement with the calculated values for the solvent-free complex. The slight deviation can be
fitted with partial inclusion of acetonitrile, suggesting that [ZnLBr2](CH3CN) is present for only
about 15% molar fraction in the powdered sample. However, the amount of [ZnLBr2](CH3CN)
7

present in the crystalline material may have been higher, as the powder was vacuum dried before
the elemental analysis was performed.
3.2 Crystal structure descriptions
ZnLCl2 (1), ZnLBr2 (2+3), CdLCl2 (4) and CdLBr2 (5) all appeared to have the same
molecular structure, and some of them are even isostructural with the same space group (see
Tables 1 and 2). For this paper only the structure of ZnLCl2 (1) at 173 K is discussed in detail, as
an example (see Figure 1a); the low-T and room-T structures differ only marginally due to lattice
contraction. The asymmetric unit contains only one molecule of ZnLCl2. The Zn(II) ion is five
coordinated by two N atoms and one S atom from the ligand, and two Cl- anions, with Zn-N
distances of 2.135(1) and 2.119(2) Å, a Zn-S distance of 2.698(1) Å, and Zn-Cl distances of
2.220(1) and 2.250(1) Å. The ligand is bound in a meridional fashion and the halide ions occupy
the remaining equatorial and the apical position of a square pyramid. The found bond lengths and
angles can be considered as normal [18, 26, 27]. The coordination sphere of Zn(II) is best
described as slightly distorted from square pyramidal towards trigonal bipyramidal, with τ (tau)
values [28] varying from 0.13-0.26 (see Table 3). One Cl– anion is relatively close to a hydrogen
from a C atom of a neighboring molecule, i.e. C(7)-H(7A)--Cl(2), which has a contact distance
C(7)--Cl(2) of 3.542(2) Å with a C(7)-H(7A)--Cl(2) angle of 159o(1). The structure is further
stabilized by intermolecular π-π stacking interactions. The distance between adjacent aromatic
rings are 3.8209(15) Å and 3.8166(13) Å (see Figure 1b).
Figure 1a. The molecular structure (asymmetric unit of the crystal structure) and used atomic
labelling of ZnLCl2 (1) at 173 K. Ellipsoids are plotted at 50% probability.
8

Figure 1b: An impression of the π-stacking interactions in ZnLCl2(1). Distances given are
between ring centers.
The asymmetric unit of [ZnLBr2](CH3CN) (2) contains one molecule of the complex and
one lattice solvent molecule (Figure S1). The Zn(II) ion in this case is also five-coordinated by
two N atoms and one S atom from the ligand and two Br- ions, in a geometry that is very similar
to that of the unsolvated molecule. The five-coordinate geometry is defined by a τ value [28] of
0.26. The π-π stacking interactions between adjacent aromatic rings have a centroid to centroid
distance of 3.8595(10) Å (see Figure S2). No significant hydrogen bonds can be found in the
structure. The acetonitrile molecule just fills void space in the lattice.
In CdLCl2 (4) and CdLBr2 (5) the distortion from square pyramidal towards trigonal
bipyramidal is larger than that in the case of the Zn(II) complexes, as seen from the τ values,
which are 0.36 and 0.37, respectively. These changes are ascribed to the larger ionic radius of
Cd(II). Relevant bond lengths, angles and τ values are also given in Table 3. In all structures the
methyl substituent at sulfur points in opposite direction of the apical halide.
9

Table 3. Selected bond lengths (Å) and bond angles (o) of ZnLCl2 (1), [ZnLBr2](CH3CN) (2), ZnLBr2 (3),
CdLCl2 (4) and CdLBr2 (5).
Distances
and angles
1: Low T
ZnLCl2
1: Room T
ZnLCl2
2: [ZnLBr2]-
(CH3CN)
2.132(2)
2.143(2)
2.639(1)
2.3745(3)
2.4233(3)
114.98(1)
97.51(1)
106.54(4)
111.18(4)
92.18(2)
94.79(4)
133.50(4)
149.16(4)
76.42(4)
77.04(6)
0.26
3: Low TR
ZnLBr2
Lit: Room T
ZnLBr2 [18]
2.1496
2.1215
2.6444
2.3669
2.3990
117.41
95.77
4: CdLCl2
5: CdLBr2
M-N1
2.1191(14)
2.1354(14)
2.6975(6)
2.2196(7)
2.2504(7)
112.29(2)
107.29(2)
111.58(5)
103.60(5)
87.49(2)
97.51(5)
143.02(5)
135.19(4)
73.29(4)
76.64(5)
0.131
2.1330(16)
2.1389(16)
2.7406(6)
2.2324(8)
2.2550(6)
113.01(3)
107.37(2)
111.75(5)
103.46(5)
87.33(2)
97.45(5)
142.32(5)
134.71(5)
72.64(4)
76.83(6)
0.127
2.149(2)
2.143(2)
2.6318(5)
2.3759(3)
2.4157(3)
116.49(1)
97.75(1)
107.80(4)
110.15(4)
91.87(1)
95.46(4)
132.76(4)
148.80(4)
76.09(4)
76.72(6)
0.25
2.355(1)
2.345(1)
2.7355(3)
2.4509(4)
2.4611(4)
106.03(1)
104.27(1)
98.01(3)
153.54(1)
100.23(1)
113.83(3)
100.43(3)
131.86(3)
70.17(3)
71.00(4)
0.36
2.351(2)
2.3431(19)
2.7269(7)
2.5686(3)
2.5829(3)
107.53(1)
102.04(2)
98.36(5)
152.63(5)
100.02(1)
115.80(6)
99.74(5)
130.63(6)
70.33(6)
71.02(7)
0.37
M-N8
M-S15
M-Cl1/Br1
M-Cl2/Br2
Cl1/Br1-M-Cl2/Br2
Cl1/Br1-M-S15
Cl1/Br1-M-N1
Cl1/Br1-M-N8
Cl2/Br2-M-S15
Cl2/Br2-M-N1
Cl2/Br2-M-N8
S15-M-N1
108.40
108.40
91.23
95.54
132.62
148.12
76.19
S15-M-N8
N1-M-N8
76.36
0.26
τ value [28]
10

3.3 Powder XRD and IR spectroscopy
The crystallographic phase purity of all compounds has been checked by powder XRD
and IR spectra. The ZnLCl2 (1), CdLCl2 (4) and CdLBr2 (5) samples show high purity and the
experimental Powder XRD patterns are highly similar to the simulated X-ray diffraction patterns
calculated from the single-crystal structures (Figure 2a, c, d). In agreement with the observation
that the compound ZnLBr2 (2+3) contains two types of crystals, the experimental pattern contains
all the main peaks from the two simulated patterns (Figure 2b). The IR spectra of all compounds
are highly similar, which further supports that all the compounds are isostructural and that
ZnLBr2 (3) is the main form present in the ZnLBr2 (2+3) bulk sample (Figure S3).
Figure 2. Experimental powder XRD patterns and simulated patterns from single-crystal
structures. a) ZnLCl2 (1). b) ZnLBr2 (2+3). c) CdLCl2 (4). d) CdLBr2 (5).
11

3.4 Photophysical properties.
The solid-state absorption spectra of the ligand and four complexes are shown in Figure
S4. The ligand exhibits a strong broad absorption band from 250 nm to 450 nm. The ZnLCl2 (1),
ZnLBr2 (2+3) and CdLCl2 (4) absorption bands are slightly narrower than that of the ligand in the
blue region, while the absorption spectrum of CdLBr2 (5) is similar to that of the ligand.
Room temperature excitation and emission spectra of ZnLCl2 (1), ZnLBr2 (2+3), CdLCl2
(4) and CdLBr2 (5) were recorded in the solid state, and are depicted in Figure 3. The compounds
ZnLCl2 (1) and CdLC2 (4) show a relatively intense yellow color emission, while ZnLBr2 (2+3),
CdLBr2 (5) exhibit a medium intense yellow color emission upon irradiation of 400 nm. The
emission spectra of all four compounds contain only one peak with a maximum at around 540 nm
(535 nm for the chloride compounds, 545 nm for the bromide compounds), which is assigned to
the ligand π-π* transition [29-34]. For ZnLCl2 (1), CdLCl2 (4) and CdLBr2 (5); although the
excitation spectra contain two peaks, varying the excitation wavelength did not make any
influence of the shape and position of emission spectra. The room temperature quantum yields of
ZnLCl2 (1) and CdLC2 (4) are 8% and 22%, respectively. The quantum yield of ZnLBr2 (2+3) and
CdLBr2 (5) cannot be determined by our setup and is estimated to be at most 5%.
Figure 3. Room temperature excitation (black) and emission (red and green) spectra of a) ZnLCl2
(1); b) ZnLBr2 (2+3); c) CdLCl2 (4); d) CdLBr2 (5).
12

The emission spectra of all four compounds have also been recorded at 77 K (see Figure
S5). The emission color changes at 290 K and 77 K have been calculated and are presented in the
so-called CIE (Commission International d’Elairage) chromaticity diagram (see Figure S6). The
CIE coordinates are listed in Table S1; although the coordinates at different temperatures are
significantly different, the color of emission remains largely the same. The emission spectra of all
samples at 77 K are almost identical to their room temperature emission spectra. Interestingly,
only the emission of the compound CdLBr2 seems to shift to a slightly more red color at lower
temperatures.
4. Concluding Remarks
In summary, a series of Zn(II) and Cd(II) halide complexes, all containing the
2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline ligand (L), has been successfully
synthesized and characterized. The compounds ZnLCl2 (1), ZnLBr2 (2+3), CdLCl2 (4) and
CdLBr2 (5) have the same molecular structure based on IR and X-ray diffraction data. For all
compounds the structures were solved by single-crystal X-ray diffraction. The compound ZnLBr2
was obtained as a mixture of two types of crystals, the pure ZnLBr2 (3) and the acetonitrile
solvate [ZnLBr2](CH3CN) (2); the unsolvated compound ZnLBr2 (3) appears to be the main
component. All five compounds show a bright yellow luminescence emission. Temperature
changes have negligible influence on the emission spectra.
Appendix A. Supplementary data
CCDC 1445927, 1446902, 1443691, 1446921, 1443712, and 1445920 contain the supplementary
crystallographic data for ZnLCl2 (1, 173 K), ZnLCl2 (1, 293 K), [ZnLBr2](CH3CN) (2), ZnLBr2
(3), CdLCl2 (4) and CdLBr2 (5), respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Spectroscopic details in the supplementary data include: Packing and stacking diagrams
for compounds 1 and 2. Infrared spectra and diffuse reflectance spectra of all new compounds.
Also the CIE (Commission International d’Elairage) chromaticity diagrams are presented, in
graphics and tabular form.
13

Acknowledgements:
X. Liu gratefully acknowledges a grant from the Chinese Scholarship Council (no.
201206250014). Andrej Pevec thanks the Slovenian Research Agency for support (grant P1-
0175). The Advanced Light Source is supported by the Director, Office of Science, Office of
Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-
05CH11231.
References
[1] P. Pust, V. Weiler, C. Hecht, A. Tücks, A.S. Wochnik, A.K. Henß, D. Wiechert, C. Scheu,
P.J. Schmidt, W. Schnick, Nat Mater, 13 (2014) 891-896.
[2] C.F. Zhu, S. Chaussedent, S.J. Liu, Y.F. Zhang, A. Monteil, N. Gaumer, Y.Z. Yue, J. Alloy.
Compd., 555 (2013) 232-236.
[3] X. Liu, S. Akerboom, S.H.C. Askes, I. Mutikainen, E. Bouwman, Inorg. Chem. Commun., 61
(2015) 60-63.
[4] H. Kim, G.R. You, G.J. Park, J.Y. Choi, I. Noh, Y. Kim, S.J. Kim, C. Kim, R.G. Harrison,
Dyes and Pigments, 113 (2015) 723-729.
[5] X.H. Qian, Z.C. Xu, Chem. Soc. Rev., 44 (2015) 4487-4493.
[6] X. Liu, S. Akerboom, M.d. Jong, I. Mutikainen, S. Tanase, A. Meijerink, E. Bouwman, Inorg.
Chem., 54 (2015) 11323-11329.
[7] M. de Torres, S. Semin, I. Razdolski, J.L. Xu, J.A.A.W. Elemans, T. Rasing, A.E. Rowan,
R.J.M. Nolte, Chem. Commun., 51 (2015) 2855-2858.
[8] R. Ghosh, S.H. Rahaman, C.N. Lin, T.H. Lu, B.K. Ghosh, Polyhedron, 25 (2006) 3104-3112.
[9] P. Suvanvapee, J. Boonmak, S. Youngme, Polyhedron, 102 (2015) 693-698.
[10] A.B. Pradhan, S.K. Mandal, S. Banerjee, A. Mukherjee, S. Das, A.R. Khuda Bukhsh, A.
Saha, Polyhedron, 94 (2015) 75-82.
[11] M. Shyamal, A. Panja, A. Saha, Polyhedron, 69 (2014) 141-148.
[12] K.C. Gupta, A.K. Sutar, Coord. Chem. Rev., 252 (2008) 1420-1450.
[13] N.K. Al Rasbi, J. Husband, J. Photochem. Photobiol., 314 (2016) 96-103.
[14] N. Raman, A. Kulandaisamy, C. Thangaraja, K. Jeyasubramanian, Transit. Metal Chem., 28
(2003) 29-36.
[15] Z.L. Liu, J. Zhang, T.F. Li, Z.N. Yu, S.X. Zhang, J. Fluor. Chem., 147 (2013) 36-39.
[16] Z. Zhang, W.X. Feng, P.Y. Su, X.Q. Lü, J.R. Song, D.D. Fan, W.K. Wong, R.A. Jones, C.Y.
Su, Inorg. Chem., 53 (2014) 5950-5960.
[17] M. Maiti, D. Sadhukhan, S. Thakurta, S. Roy, G. Pilet, R.J. Butcher, A. Nonat, L.J.
Charbonnière, S. Mitra, Inorg. Chem., 51 (2012) 12176-12187.
[18] A. Mangia, M. Nardelli, C. Palmieri, G. Pelizzi, J. Cryst. Mol. Struct., 2 (1972) 99-106.
[19] J.C.de Mello, H.F. Wittmann, R. Friend, Adv.Mater., 9 (1997) 230-232
[20] J.S. Costa, A.G. Castro, R. Pievo, O. Roubeau, B. Modec, B. Kozlevcar, S.J. Teat, P.
Gamez, J. Reedijk, CrystEngComm, 12 (2010) 3057-3064.
[21] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crystallogr., 27 (1994)
1045-1050.
14

[22] G.M. Sheldrick, Acta Crystallogr. Sect. A, 64 (2008) 112-122.
[23] T. Kottke, D. Stalke, J. Appl. Crystallogr., 26 (1993) 615-619.
[24] Bruker, APEX2, SAINT and SADABS, 2007 and 2009. , in, Bruker AXS Inc. , Madison,
Wisconsin, USA, 2009.
[25] G.M. Sheldrick, Acta Crystallogr. Sect. C Struct. Chem 71 (2015) 3-8.
[26] H.L. Gao, S.X. Jiang, Y.M. Hu, F.F. Li, Q.Q. Zhang, X.Y. Shi, J.Z. Cui, Inorg. Chem.
Commun., 44 (2014) 58-62.
[27] C. Bolm, K. Weickhardt, M. Zehnder, T. Ranff, Chem. Ber., 124 (1991) 1173-1180.
[28] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc., Dalton
Trans., (1984) 1349-1356.
[29] B. Dutta, P. Bag, U. Flörke, K. Nag, Inorg. Chem., 44 (2005) 147-157.
[30] S. Banthia, A. Samanta, J. Phys. Chem. B, 110 (2006) 6437-6440.
[31] W. Chen, Q. Peng, Y.D. Li, Cryst. Growth Des., 8 (2008) 564-567.
[32] Z. Li, A. Dellali, J. Malik, M. Motevalli, R.M. Nix, T. Olukoya, Y. Peng, H.Q. Ye, W.P.
Gillin, I. Hernández, P.B. Wyatt, Inorg. Chem., 52 (2013) 1379-1387.
[33] S. Majumder, L. Mandal, S. Mohanta, Inorg. Chem., 51 (2012) 8739-8749.
[34] P. Yang, X.X. Wu, J.Z. Huo, B. Ding, Y. Wang, X.G. Wang, CrystEngComm, 15 (2013)
8097-8109.
15

Zinc and Cadmium Halide Compounds with the tridentate ligand
2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline showing yellow
luminescence.
Xue Liu,a Adriana González-Castro,a Ilpo Mutikainen,b Andrej Pevec,c Simon J. Teat,d
Patrick Gamez,a,e Jose Sanchez Costa,a,f Elisabeth Bouwman,a,* Jan Reedijka
Graphical abstract
Five-coordinated zinc and cadmium complexes with the ligand 2-(methylsulfanyl)-N-
(pyridin-2-yl-methylidene)aniline have been synthesized, and characterized by NMR, IR,
elemental analysis, X-ray crystallography, Powder XRD and luminescence.
16

Zinc and Cadmium Halide Compounds with the tridentate ligand
2-(methylsulfanyl)-N-(pyridin-2-ylmethylidene)aniline showing
yellow luminescence.
Xue Liu,a Adriana González-Castro,a Ilpo Mutikainen,b Andrej Pevec,c Simon J. Teat,d
Patrick Gamez,a,e Jose Sanchez Costa,a,f Elisabeth Bouwman,a,* Jan Reedijka
Graphical abstract
Five-coordinated zinc and cadmium complexes with the ligand 2-(methylsulfanyl)-N-
(pyridin-2-yl-methylidene)aniline have been synthesized, and characterized by NMR, IR,
elemental analysis, X-ray crystallography, Powder XRD and luminescence.