(E)-N-(Pyridine-2-ylmethylene)arylamine as an Assembling Ligand for Zn(II)/Cd(II) Complexes: Aryl Substitution and Anion Effects on the Dimensionality and Luminescence Properties of the Supramolecular Metal-Organic Frameworks

Article abstract of DOI:10.1021/acs.cgd.6b00347

Using five Schiff base ligands (E)-N-(pyridine-2-yl) (CH=NPhR) (where R = 4-CH₃, L¹; 2,6-(CH₃)₂, L²; 2,4,6-(CH₃)₃, L³; 2,6-(C₂H₅)₂, L⁴; 2,6-(i-C₃H₇)₂, L⁵), nine Zn(II)/Cd(II) complexes, namely, Zn1-Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5, have been successfully synthesized. The structures of the Zn(II)/Cd(II) complexes have been established by single crystal X-ray diffraction and further physically characterized by ¹H NMR, FT-IR, and elemental analysis. The crystal structures of these complexes indicate that the structures of ligand and anions can directly influence the formation of 1D → 3D supramolecular metal-organic frameworks (SMOFs) via C-H···O/C-H···Cl hydrogen bonds and π···π interactions. Upon irradiation with UV light, the nine Zn(II)/Cd(II) complexes display deep blue emissions of 401-436 nm in acetonitrile solution and light blue or bluish green emissions of 485-575 nm in the solid state, respectively. The photoluminescence properties of nine Zn(II)/Cd(II) complexes can be finely and predictably tuned over a wide range of wavelengths by small and easily implemented changes to ligand structure. It is worth noting that Zn1 and Cd1 exhibit obvious aggregation-induced emission enhancement (AIEE) properties in the CH₃CN-H₂O mixture solutions.

Full text of DOI:10.1021/acs.cgd.6b00347

Article
pubs.acs.org/crystal
(E)‑N‑(Pyridine-2-ylmethylene)arylamine as an Assembling Ligand for
Zn(II)/Cd(II) Complexes: Aryl Substitution and Anion Effects on the
Dimensionality and Luminescence Properties of the Supramolecular
Metal−Organic Frameworks
Yu-Wei Dong,† Rui-Qing Fan,*,† Xin-Ming Wang,† Ping Wang,† Hui-Jie Zhang,† Li-Guo Wei,†
Wei Chen,† and Yu-Lin Yang*,†
†MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical
Engineering, Harbin Institute of Technology, Harbin 150001, P. R. of China
S
* Supporting Information
ABSTRACT: Using five Schiff base ligands (E)-N-(pyridine-2-yl) (CH
NPhR) (where R = 4−CH3, L1; 2,6-(CH3)2, L2; 2,4,6-(CH3)3, L3; 2,6-(C2H5)2,
L4; 2,6-(i-C3H7)2, L5), nine Zn(II)/Cd(II) complexes, namely, Zn1−Zn3, Cd1,
Cd2, Cd3a, Cd3b, Cd4, and Cd5, have been successfully synthesized. The
structures of the Zn(II)/Cd(II) complexes have been established by single
1
crystal X-ray diffraction and further physically characterized by H NMR, FT−
IR, and elemental analysis. The crystal structures of these complexes indicate
that the structures of ligand and anions can directly influence the formation of
1D → 3D supramolecular metal−organic frameworks (SMOFs) via C−H···O/
C−H···Cl hydrogen bonds and π···π interactions. Upon irradiation with UV
light, the nine Zn(II)/Cd(II) complexes display deep blue emissions of 401−436 nm in acetonitrile solution and light blue or
bluish green emissions of 485−575 nm in the solid state, respectively. The photoluminescence properties of nine Zn(II)/Cd(II)
complexes can be finely and predictably tuned over a wide range of wavelengths by small and easily implemented changes to
ligand structure. It is worth noting that Zn1 and Cd1 exhibit obvious aggregation-induced emission enhancement (AIEE)
properties in the CH3CN−H2O mixture solutions.
coordination chemistry, even after almost a century since their
discovery, this is attributed to their facile synthesis, remarkable
versatility, and good solubility in common solvents.25−27 In
general, compared with rigid ligands, a metal-coordinated Schiff
base ligand can readily form intermolecular π···π or C−H···π
interactions in the aggregated or crystal state because of the
high flexibility of the imine unit.
The assembly process of the complex can be affected by
many factors; among them, the metal ions, anions, and ligands
are base-control factors.28,29 It is well-known that different
metal ions possess different properties and coordination modes,
which play key roles in the formation of both molecular
structures and packing structures of complexes. For example,
Zn(II) and Cd(II) ions often adopt different coordination
modes, such as four-, five-, six-, or seven-coordination modes
when they react with organic ligands.30−33 The introducing of
different small anions can also have a significant effect on the
structural construction of complexes and their properties. In
coordination chemistry, halogen, acetate, and nitrate ions have
been widely used as anions for the construction of the metal
coordination complexes because they can adjust the topologies
INTRODUCTION
■
Over the past decade, supramolecular chemistry of coordina-
tion compounds has attracted great interest due to their
intriguing structures and wide potential applications in different
areas, such as nonlinear optics, magnetism, photoluminescence,
and electrochemistry.1−8 These functional materials are
generally constructed by covalent and noncovalent interac-
tions.9,10 The type of noncovalent supramolecular interaction,
such as hydrogen bonding,11−14 and π···π stacking,15−19
depends on the shape and functional groups of the components
that form supramolecular metal−organic frameworks
(SMOFs). It is noteworthy that the appropriate hydrogen
bonding and π···π stacking interactions could produce the
aggregation-induced emission phenomenon, which was first
reported by Tang et al. in 2001.20 Therefore, this superiority in
the solid state materials significantly expands the real-world
applications if they possess aggregation-induced emission in the
solid or aggregated state. These functional materials are
generally constructed by metal ions and bridging organic
ligands.21 The ligand not only provides capability for selective
metal ion coordination but also generates desired noncovalent
intermolecular interactions to direct crystal packing.22−24
Hence, the major challenge of supramolecular chemistry lies
in the rewarding endeavors to design and synthesize organic
ligands. Schiff base ligands play an important role in metal
Received: March 3, 2016
Revised: May 3, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Scheme 1. Syntheses Routes of Five Ligands L1−L5 and Nine Corresponding Zn(II)/Cd(II) Complexes
of complexes through different covalent bonds or noncovalent
interactions.34,35
from the mixed solvent of n-hexane and dichloromethane. L3
and L5 were recrystallized from n-hexane to give yellow crystals.
Yields for the five imine ligands varied from 70 to 91%. Using a
self-assembled method, these ligands were reacted with Zn(II)/
Cd(II) salts to obtain a series of complexes, namely, Zn1−Zn3,
Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5. X-ray quality single
crystals of nine Zn(II)/Cd(II) complexes were grown from
slow evaporation of their solutions and were readily obtained in
good yields within the range 56−72%. The details of the
synthesis are given in the Experimental Section. We confirm
that all the complexes are stable in the solid state under
exposure to air. The complexes are soluble in common organic
solvents, such as chloroform, dimethyl sulfoxide, and
acetonitrile.
Inspired by the above discussion, herein, five Schiff base
ligands (E)-N-(pyridine-2-yl) (CHNPhR), L1−L5, Scheme 1,
carrying different alkyl substitutions in the phenyl ring have
been employed for the synthesis of Zn(II)/Cd(II) complexes.
Nine Zn(II)/Cd(II) complexes, namely Zn1−Zn3, Cd1, Cd2,
Cd3a, Cd3b, Cd4, and Cd5, were prepared by the reaction of
corresponding ligand and M(II) salts. Subsequently, the
structures of ligands and Zn(II)/Cd(II) complexes have been
1
characterized by means of H NMR, IR, and EA spectroscopic
studies, and for complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b,
Cd4, and Cd5 additionally by single-crystal X-ray crystallog-
raphy. The structure of complex Zn2 has been reported by
Zhao et al.,36 and there existed similar complexes in the
literature,37,38 but they simply show the structure of the unit
cell rather than intermolecular interactions. Herein, we
systematically investigated the effect of related alkyl substitution
Schiff base ligands and intermolecular interactions (C−H···O/
C−H···Cl hydrogen bonds and π···π interactions) in the
organization and stabilization of supramolecular metal−organic
frameworks (SMOFs). Moreover, the influence of the
substituent effect on the photoluminescence in CH3CN
solution and the solid state was discussed. Complexes Zn1
and Cd1 exhibit aggregation-induced emission enhancement
(AIEE) behavior in CH3CN/H2O solutions.
The infrared spectra of these nine Zn(II)/Cd(II) complexes
(see Figures S1−S5 in the Supporting Information) are similar
to that of the corresponding ligand, and the IR assignments of
selected diagnostic bands are given in the Experimental Section.
In the IR spectra of ligands L1−L5, the existence of CN
bonds is clearly demonstrated by the presence of strong
characteristic CN peaks in the range 1628−1668 cm−1.
These bands undergo negative shifts of 2−39 cm−1 in the
complexes, which may be attributed to the coordination of the
nitrogen atom of the imine to the metal ion.39,40 This is further
confirmed by the presence of a ν(M−N) vibration in the region
422−454 cm−1 in all the complexes.41 The 1H NMR spectra of
the imine ligands L1−L5 and its Zn(II)/Cd(II) complexes were
recorded in CDCl3 at room temperature (see Figures S6−S10
RESULTS AND DISCUSSION
■
1
in the Supporting Information). In the H NMR spectra, the
Synthesis and spectral characterization. The five imine
ligands (E)-N-(pyridine-2-yl)(CHNPhR) (where R = 4-
CH3, L1; 2,6-(CH3)2, L2; 2,4,6-(CH3)3, L3; 2,6-(C2H5)2, L4;
2,6-(i-C3H7)2, L5) were readily prepared in a one-step
procedure by condensation of 2-pyridinecarboxaldehyde with
the corresponding monamine in a 1:1 molar ratio in anhydrous
methanol/formic acid solution (see Scheme 1). Moreover, the
yellow bulk crystals of L1 were obtained by recrystallization
chemical shift values of the protons in the complexes are
slightly different from those observed for the noncoordinated
ligand. Of particular note is the HCN resonances of the nine
Zn(II)/Cd(II) complexes, which are moved downfield due to
coordination between the imine nitrogen and the M(II)
center.42 For the complexes, the imine proton is moved
downfield at most 0.10 ppm. Meanwhile, the resonance peaks
B
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 1. (a) Asymmetric unit cell of Zn1. The thermal ellipsoid is drawn at 50% probability. H atoms have been omitted for clarity. (b) Polyhedral
representation of the coordination sphere of the Zn(II) center in Zn1. (c) The 2D layer and (d) 3D network structure in Zn1. Dotted lines
represent the C−H···O interactions. (c) Topological view of the 3D network structure of Zn1.
at 1.82 (Zn1) and 2.04 (Cd1) ppm are assigned to −CH3COO
protons. To further understand the structures of these
complexes, single crystals were obtained and analyzed by single
crystal X-ray diffraction. The crystallographic data for these
nine Zn(II)/Cd(II) complexes are listed in Table S1,
Supporting Information.
as shown in Figure 1d. If the two separated trinuclear units are
viewed as two different nodes and the hydrogen bonds C−H···
O as the linkers, the resulting (6,6)-connected three-dimen-
sional supramolecular structure may be simplified by the
Schlafli symbol {412·63}, as depicted in Figure 1e.
̈
The asymmetric unit of complex [CdL1(OAc)2] (Cd1)
consists of one crystallographically independent Cd2+ cation,
one ligand L1, and two OAc− anions (Figure 2a). Every Cd2+
cation is seven-coordinated with slightly distorted pentagonal
bipyramid coordination geometry [CdN2O5], containing two N
atoms (N1 and N2) from L1, and five O atoms (O1, O2, O3,
O3A, and O4) from OAc− anions. Two equivalent [Cd(L1)]
moieties are linked via O3 and O3A atoms to form a binuclear
structure. The intermetallic Cd(1)···Cd(1A) distance is
3.821(6) Å. The distances of Cd1−N1 and Cd1−N2 are
2.327(2) and 2.416(2) Å, which are in agreement with the
values of a similar cadmium complex.43 The detailed bond
distances and angles for Cd1 are listed in Table S2, Supporting
Information. The adjacent binuclear molecules are intercon-
nected through C6−H6A···O4 and C8−H8A···O4 hydrogen
bond interactions to form a 1D chain (Figure 2b). The H6A···
O4 and H8A···O4 distances are 2.452 and 2.695 Å, respectively.
Two adjacent chains are interconnected via C3−H3A···O2
hydrogen bond interactions (dH3A···O2 = 2.533 Å) to construct a
2D layer. From the topological point of view, the binuclear unit
could be considered as the node, and hydrogen bonds C−H···
O could be considered as the linkers. Thus, the two-
dimensional net of Cd1 can be described as a 4-connected
Description of the structures. Structural analysis of Zn1
and Cd1. Complex [Zn3(L1)2(OAc)6] (Zn1) crystallized in the
triclinic space group P1. There exist two identical half
̅
molecules. As shown in Figure 1a, for a complete molecule,
two equivalent [Zn(L1)] moieties are bridged to the central
Zn2+ ion (Zn1) by two μ2-ηO :ηO OAc− anions and four μ2-
1
2
ηO :ηO OAc− anions, resulting in the formation of a trinuclear
structure. The two terminal Zn2+ ions, Zn4 and Zn4A, are six-
coordinated with one N atom (N4) from one chelating ligand
L1 and three O atoms (O7, O9, and O10) from the coordinated
OAc− anion to constitute the equatorial plane, and one N atom
(N3) and one O atom (O4) at the axial position, resulting in a
distorted octahedral geometry (Figure 1b). The central Zn2+
ion (Zn1) is six-coordinated with six O atoms (O8, O8A, O9,
O9A, O11, and O11A) from four OAc− anions. The
intermetallic Zn(1)···Zn(4) and Zn(2)···Zn(3) distances are
3.397(12) and 3.382(14) Å, respectively. The ligand (L1) is
approximately planar (the dihedral angles between the pyridyl
and phenyl rings: 6.053°/10.027°, Table 1) and coordinates to
the Zn via a bidentate N,N interaction. In complex Zn1, the
independent units are linked through C3−H3A···O10, C22−
H22A···O1, C23−H23A···O6, and C30−H30A···O5 hydrogen
bond interactions to generate a two-dimensional layer (Figure
1c). The H3A···O10, H22A···O1, H23A···O6, and H30A···O5
distances are 2.444, 2.478, 2.575, and 2.485 Å, respectively. The
two-dimensional layer further extends into the three-dimen-
sional supramolecular network through C6−H6A···O7, C21−
H21A···O1, and C25−H25A···O1 hydrogen bond interactions,
1
1
sql net with the Schlafli symbol {44.62} (Figure 2c).
̈
Structural analysis of Zn2 and Cd2. The N atoms of ligand
L2 are coordinated with ZnCl2/CdCl2 to form mononuclear
[ZnL2Cl2] (Zn2) and binuclear [CdL2Cl2]2 (Cd2), respec-
tively, as shown in Figure 3a and 3b. Using Addison’s
model,44,45 the coordination geometry around the zinc atom
C
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Table 1. Structural and Geometrical Parameters for Complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5
coordination
number
Addison
dihedral
D−H
H···A
D···A
D−H···A
a
Complex
coordination geometry parameter (τ) angle (deg)
D−H···A
(Å)
(Å)
(Å)
(deg)
dimension
3D
Zn1
6
octahedral
6.053, 10.027 C3−H3A···O10
C6−H6A···O7
0.930
0.930
0.930
0.930
0.930
0.930
0.930
2.444
2.630
2.550
2.478
2.575
2.494
2.485
3.176
3.447
3.326
3.314
3.432
3.277
3.343
3.952
3.330
3.365
3.440
3.633
3.703
3.642
3.610
3.839
3.889
3.650
3.572
3.684
3.701
3.715
3.820
3.558
3.420
3.636
3.518
3.397
3.276
3.348
3.395
3.735
3.593
3.657
3.474
3.593
135.585(2)
146.937(2)
141.171(4)
149.663(2)
153.259(4)
141.982(2)
153.536(2)
C21−H21A···O1
C22−H22A···O7
C23−H23A···O6
C25−H25A···O1
C30−H30A···O5
b
c
πCg1 ···πCg2
Cd1
Zn2
7
4
pentagonal bipyramid
tetrahedral
14.226
64.315
C3−H3A···O1
C6−H6A···O4
C8−H8A···O4
πCg1···πCg2
C2−H2A···Cl1
C5−H5A···Cl2
C6−H6A···Cl1
C10−H10A···Cl2
πCg1···πCg1
C2−H2A···Cl1
C4−H4A···Cl2
C2−H2A···Cl1
C6−H6A···Cl1
πCg1···πCg1
C4−H4A···Cl2
C5−H5A···Cl2
C6−H6A···Cl1
C15−H15B···Cl1
πCg1···πCg2
C2−H2A···O3
C6−H6A···O3
C11−H11A···O2
C13−H13C···O2
C2−H2A···Cl1
C4−H4A···Cl2
C6−H6A···Cl1
C5−H5A···Cl2
C6−H6A···Cl1
0.930
0.930
0.930
2.533
2.452
2.695
143.966(1)
167.071(1)
137.694(1)
2D
2D
0.831
0.930
0.930
0.930
0.930
2.888
2.898
2.781
2.946
147.170(1)
137.859(1)
149.051(1)
161.617(1)
Cd2
Zn3
5
4
trigonal bipyramidal
tetrahedral
0.543
0.848
85.649
73.266
0.930
0.930
0.930
0.930
2.919
2.927
2.860
2.889
136.452(5)
127.595(4)
148.410(3)
146.586(2)
2D
1D
Cd3a
Cd3b
4
6
tetrahedral
0.494
82.952
0.929
0.929
0.930
0.960
2.903
2.896
2.822
2.746
169.481(2)
129.263(1)
123.089(1)
154.669(1)
2D
3D
octahedral
tetrahedral
72.072
82.240
0.930
0.930
0.930
0.961
0.930
0.930
0.930
0.930
0.930
2.642
2.454
2.518
2.593
2.891
2.927
2.794
2.890
2.711
138.722(2)
147.361(1)
148.853(2)
141.156(2)
151.395(1)
129.647(1)
154.699(1)
121.964(1)
158.565(1)
Cd4
Cd5
4
4
0.760
0.737
2D
2D
tetrahedral
85.110
a
b
c
Between the pyridyl ring and phenyl ring. Cg1 = pyridyl ring. Cg2 = phenyl ring.
Figure 2. (a) Crystal structure of Cd1. The thermal ellipsoid is drawn at 50% probability. H atoms have been omitted for clarity. (b) The 1D chain
structure in Cd1. (c) The 2D layer structure and topological view in Cd1. Dotted lines represent the C−H···O interactions.
D
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 3. Crystal structures of (a) Zn2 and (b) Cd2. The thermal ellipsoid is drawn at 50% probability. H atoms have been omitted for clarity. The
2D layer structures of (c) Zn2 and (d) Cd2. Dotted lines represent the C−H···Cl interactions.
Figure 4. (a) Asymmetric unit cell of Cd3b. The thermal ellipsoid is drawn at 50% probability. H atoms have been omitted for clarity. (b)
Coordination geometry of cadmium(II) ions. (c) Depiction of the dihedral angle between the pyridine ring and the phenyl ring in Cd3b. (d) The
3D network structure of and (e) topological view in Cd3b. Dotted lines represent the C−H···O interactions.
in Zn2 (τ4 = 0.831) and the cadmium atom in Cd2 (τ5 =
0.543) can be better described as a tetrahedral and trigonal
bipyramidal, respectively. The X-ray single crystal structure of
Cd2 consists of half of the neutral binuclear molecule, with the
other half obtained by a center of inversion. The binuclear
moiety contains two Cd(II) atoms (Cd1 and Cd1A), which are
asymmetrically bridged by two chloride anions (Cl1 and Cl1A),
while the molecule of the bidentate L2 ligand is N-coordinated
to each cadmium atom. The separation of intramolecular Cd1···
Cd1A is 3.695(14) Å. The dihedral angles between the pyridine
E
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 5. Crystal structures of (a) Cd4 and (b) Cd5. The thermal ellipsoid is drawn at 50% probability. H atoms have been omitted for clarity. The
2D layer structures of (c) Cd4 and (d) Cd5. Dotted lines represent the C−H···Cl interactions.
ring and the phenyl ring are 64.315° (Zn2) and 85.649° (Cd2),
which is very twisted compared with the complexes of the
ligand L1. Likewise, the distances of M−N (imino) are
relatively shorter than M−N (pyridine). The average distances
of the M−N bonds are 2.068 Å (Zn2) and 2.354 Å (Cd2),
which is consistent with ionic radii. The selected bond lengths
and bond angles of complexes Zn2 and Cd2 are given in Table
S3, Supporting Information, respectively. Single crystal analysis
shows that complexes Zn2 and Cd2 are both two-dimensional
layer structures (Figures 3c and 3d, respectively) constructed
by the C−H···Cl (Table 1) hydrogen bond interactions.46
Significantly, additional intermolecular π···π interactions with
separations of about 3.889 Å (Figure 3c) also provide further
stabilization in complex Zn2. The resulting two-dimensional
nets may be simplified into a 2D 5-connected cem topology
1), and the resulting Cd3a two-dimensional nets may be
simplified into a 2D 5-connected {46·52·62} topology, as shown
in Figures S13a and S13b, respectively.
Single crystal analysis reveals that complex [Cd(L3)2(NO3)2]
(Cd3b) crystallizes in a monoclinic system, space group P21/n.
As shown in Figure 4a, the central metal Cd(II) ion is six
coordinated by two O atoms from two nitrate anions and by
four N atoms from two ligands, to form a distorted octahedral
geometry (Figure 4b). The bond angles around the Cd(II) ion
are in the range 72.84(7)−180.00(14) Å. The selected bond
distances and angles are shown in Table S4, Supporting
Information. The dihedral angles between the pyridine ring and
the phenyl ring in the Cd3b (72.072°) are approximately
perpendicular (Figure 4c). Similar to Zn1 and Cd1, C−H···O
hydrogen bond interactions based on the O atom of the
coordination anions are formed. As shown in Figure 4d, two
adjacent molecules are linked by the C2−H2A···O3, C6−
H6A···O3, and C11−H11A···O2 hydrogen bond interactions to
form a 3D SMOF. The H2A···O3, H6A···O3, and H11A···O2
distances are 2.642, 2.454, and 2.518 Å, respectively. In
addition, the hydrogen bonding interactions (C13−H13C···
O2) based on intramoleculers provide further stability to the
3D structure. The resulting three-dimensional supramolecular
structure may be simplified into a 3D 8-connected bcu topology
with the Schlafli symbol {33·44·53} for Zn2, and a 2D 3-
̈
connected hcb topology with the Schlafli symbol {63} for Cd2,
̈
as shown in Figures S11a and S11b, respectively.
Structural analysis of Zn3, Cd3a, and Cd3b. As shown in
Figures S12a and S12b, the complexes [ZnL3Cl2] (Zn3) and
[CdL3Cl2] (Cd3a) are isostructural, so we choose Cd3a to
represent the detailed structure. They all belong to the
monoclinic P21/c space group. In complex Cd3a, the Cd(II)
center adopts a distorted tetrahedral geometry (τ4 = 0.494,
Cd3a; 0.848, Zn3) coordinated by two nitrogen atoms of (E)-
2,4,6-trimethyl-N-((pyridin-2-yl)methylene)aniline (L3) and
two terminal chlorine ions. In particular, the Cd(II) cation
coordinates with nitrogen atoms from ligand L3 to form a five-
membered ring, which further extends system conjugation.
Complexes Zn3 and Cd3a have dihedral angles of 73.266° and
82.952°, respectively, between the pyridyl ring and the phenyl
ring (Table 1), which indicates that the ligand L3 is very twisted
in Zn3 and Cd3a. In addition, the mononuclear units of Zn3
and Cd3a are further assembled into a 1D chain and 2D net by
C−H···Cl hydrogen bond interactions (the detailed data of C−
H···Cl hydrogen bonds for Zn3 and Cd3a are listed in Table
with the Schlafli symbol {424·64} (Figure 4e).
̈
Structural analysis of Cd4 and Cd5. Both complexes Cd4
and Cd5 crystallize in the monoclinic P21/n space group. The
asymmetric unit of Cd4 consists of one independent Cd(II)
ion, one whole ligand L4, and two chlorine anions. The
coordination pattern of Cd5 is similar to that of Cd4, except for
L5 being used instead of L4. As shown in Figures 5a and 5b, the
Cd(II) ions in Cd4 and Cd5 are located in a distorted
tetrahedral coordination geometry with τ4 parameters 0.760
and 0.737, respectively. The Cd−N bond lengths in Cd4 vary
from 2.316(19) to 2.396(2) Å, and Cd−Cl bond lengths vary
from 2.423(10) to 2.524(12) Å, whereas these geometric
F
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
parameters vary from 2.316(2) to 2.402(2) Å and from
2.416(11) to 2.516(9) Å in Cd5, respectively (Table S5,
Supporting Information). The pyridyl and phenyl rings of
dihedral angles are 82.240° in Cd4 and 85.110° in Cd5,
respectively. Regarding the C−H···Cl hydrogen bond inter-
actions as linkers, and the mononuclear unit in Cd4 and Cd5 as
a 4-connected and a 3-connected node, respectively, Cd4
exhibits 2D sql topology with the Schlafli symbol {44·62}, and a
̈
2D hcb topology with the Schlafli symbol {63} for Cd5. The
̈
detailed data of C−H···Cl hydrogen bonds for Cd4 and Cd5
are listed in Table 1.
Effect of aryl substitution and anion on supramolecular
architecture. In this article, we have successfully synthesized a
series of Zn/Cd(II) SMOFs via the hydrogen bonding
interaction by the method of changing the aryl substitution
and anion.
Taking the structures into account, there exists a dramatic
influence of the aryl substitutions on the steric hindrance of the
complexes. With increased numbers of methyl substituents on
the ligands, the steric hindrance of the complexes gradually
increases [dihedral angles: 6.053° and 10.027°, Zn1 (2−CH3);
64.315°, Zn2 (2,6−(CH3)2); 73.266°, Zn3 (2,4,6−(CH3)3)],
which results in 3D → 1D supramolecular architectures. That is
to say, the complexes display better coplanarity with decreasing
numbers of methyl substituents. The larger steric hindrance of
ligands could hinder molecular assemblies and influence the
form of supramolecular architectures. In addition, the ligands
with 2,6-(CH3)2, 2,6-(C2H5)2, and 2,6-(i-C3H7)2 substituents in
the same position also augment the steric hindrance; however,
there seems to be little influence on constructing the
supramolecular architectures. With careful observation, we
find that most hydrogen bonding interactions concentrate on
the pyridine ring. Thus, the influence of different substituents in
the same position of the ligands is smaller than that of the
numbers of methyl substituents on the ligand.
Figure 6. UV−vis absorption spectra of the complexes Zn1−Zn3,
Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5 in acetonitrile solution at room
temperature.
Solid-state and solution luminescence properties of the
ligands and the complexes. The d10 metal complexes have
been reported to exhibit solid state emissions with easily
modulated intensities and wavelengths.49−51 Hence, the
luminescence properties of the ligands L1−L5 and the
corresponding nine Zn(II)/Cd(II) complexes were examined
in the solid state at room temperature. Selected data are
summarized in Table 2. The free ligands L1−L5 exhibit intense
emission bands centered at 474, 473, 494, 462, and 459 nm
(Figure S15, Supporting Information), respectively, which may
be attributed to the π*−π transitions.52,53 For the complexes
Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5, the
emission bands are observed at 486, 495, 509, 489, 503, 507,
575, 483, and 485 nm (Figure 7a), respectively. These bands
are red-shifted as compared to that of the corresponding ligand.
Due to the similarity of the emission bands with that of the
corresponding ligand, the emissions of these nine Zn(II)/
Cd(II) complexes may be attributed to the intraligand
transitions.54,55 A trend was observed in λem with Zn1 < Zn2
< Zn3 and Cd4 < Cd5 < Cd1 ≈ Cd2 < Cd3a, Cd3b, which is
On the other hand, although most of the complexes are made
by chloride as metal source, but through the hydrogen bonding
−
interaction, the complexes of NO3 anion and OAc− anion are
more likely to have a higher dimension. This gives us new ideas
for synthetic high dimensional complexes.
Photoluminescence Studies. Absorption properties of
the ligands and the complexes in CH3CN. The UV−vis
absorption spectra of the ligands L1−L5 and the corresponding
Zn(II)/Cd(II) complexes were recorded at room temperature
in CH3CN (10 μmol L−1). As the ligands have similar
structures, the UV−vis spectra are similar (Figure S14,
Supporting Information). As shown in Figure 6, the absorption
bands of the Zn(II)/Cd(II) complexes are similar to the
corresponding ligands; thus, these absorption bands can be
assigned to the transitions of the corresponding ligands. The
UV−vis absorption spectra of these nine Zn(II)/Cd(II)
complexes exhibit two distinct absorption bands in the range
250 to 500 nm (ε = 2235−42213 M−1 cm−1). The numerical
values of the maximum absorption wavelength and molar
extinction coefficients (ε) are listed in Table 2. The high energy
bands at ca. 274−289 nm are assigned to the π−π* transition of
the CN chromophore, whereas the low energy bands at ca.
333−359 nm are due to n−π* transitions,47,48 which are in
accordance with previous studies of Schiff base complexes. After
complexation, these bands were shifted to a lower wavelength
(hypsochromic shift) region, thus suggesting the coordination
of the pyridine nitrogen and imine nitrogen with the Zn(II)/
Cd(II) ions.
consistent with the electron-donating ability (−i-C3H7
<
−C2H5 < −CH3) of substituents of these ligands L1−L5. The
electron-donating effect decreased the energy difference
between the HOMO and LUMO, leading to a λem red-shift.56
Although complexes Cd3a and Cd3b have the same metal ions,
their emission wavelengths and intensities differ greatly, which
may be ascribed to the difference in the coordinated anions,
because luminescent behavior is closely related to the local
environments around the metal ions.57,58 It is also noteworthy
that the luminescence intensities for Zn1 and Cd1 are stronger
than that for the others, which may be related to the better
planarity and the C−H···O and π···π stacking interactions for
assembled supramolecular structures in the solid state
complex.59
In acetonitrile solution, the emission bands are observed at
382−418 nm and 401−436 nm, respectively, for ligands L1−L5
(Figure S16, Supporting Information) and the nine complexes
(Figure 7b). These bands exhibit deep blue luminescence
G
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Table 2. Photophysical Properties of Ligands L1−L5 and Complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5
a
absorption
photoluminescence in acetonitrile
photoluminescence in the solid state
b
complex
λabs/nm (ε/M−1 cm−1
)
λem/nm
FWHM/nm
τ/μs
ΦPL
CIE(x, y)
λem/nm
FWHW/nm
τ/μs
CIE(x, y)
L1
283(26774), 323(21417)
283(32794), 333(38129)
289(22247), 349(33605)
274(17947), 347(4190)
283(34368), 347(5199)
283(33402), 349(4573)
274(17800), 348(3725)
283(42213), 359(7023)
274(19935), 348(7570)
283(25086), 355(5556)
274(16505), 342(2090)
274(11390), 346(2235)
274(19935), 343(2590)
286(4940), 351(8235)
410
417
425
412
434
433
418
435
430
435
399
404
382
401
84.18
74.41
77.60
90.58
69.79
78.75
101.15
62.99
66.48
77.63
64.73
60.08
74.12
65.21
5.58
7.72
7.26
4.25
7.99
8.17
5.20
6.31
8.05
8.10
4.84
5.94
5.41
6.16
0.017
0.118
0.112
0.027
0.254
0.210
0.035
0.287
0.190
0.246
0.017
0.138
0.015
0.125
0.16, 0.07
0.17, 0.12
0.15, 0.08
0.21, 0.20
0.17, 0.11
0.18, 0.15
0.22, 0.21
0.17, 0.11
0.18, 0.14
0.18, 0.15
0.23, 0.17
0.20, 0.16
0.23, 0.22
0.21, 0.18
474
486
489
473
495
503
494
509
507
575
462
483
459
485
101.71
82.53
7.71
9.92
9.12
6.86
8.25
8.57
6.02
7.86
8.79
9.52
5.74
8.35
5.50
7.08
0.18, 0.24
0.20, 0.39
0.21, 0.33
0.17, 0.23
0.26, 0.37
0.18, 0.40
0.28, 0.36
0.31, 0.50
0.27, 0.41
0.47, 0.52
0.15, 0.21
0.24, 0.34
0.20, 0.25
0.20, 0.29
Zn1
Cd1
L2
95.05
127.50
96.08
Zn2
Cd2
L3
93.88
159.34
108.64
138.67
128.31
146.61
113.37
147.13
116.56
Zn3
Cd3a
Cd3b
L4
Cd4
L5
Cd5
a
b
Measured in CH3CN solutions (∼1 × 10−5 M). Take quinine sulfate in 0.1 mol L−1 H2SO4 as reference (ΦPL = 0.546).
Figure 7. Emission spectra of the complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5 in (a) the solid state and (b) acetonitrile solution.
emission, and the Commission Internationale d’Eclairage (CIE)
coordinates are summarized in Table 2. In acetonitrile solution,
the maximum emission peaks are blue-shifted 61−140 nm
compared with those in the solid state. These phenomenons
can be explained by the formation of hydrogen bonds and π···π
stacking interactions in the solid state, which can effectively
decrease the HOMO−LUMO energy gap, and influence the
ligand-centered π*−π transitions.60 Meanwhile, the full width
at half-maximum (fwhm) of the emission band decreases from
acetonitrile solution to the solid state (Table 2). All
luminescence quantum yields of these nine Zn(II)/Cd(II)
complexes in solution were measured by the optical dilute
method of Demas and Crosby61 with a standard of quinine
sulfate (Φr = 0.546) and are listed in Table 2. The
luminescence quantum yields of Zn1−Zn3, Cd1, Cd2, Cd3a,
Cd3b, Cd4, and Cd5 in CH3CN are 0.118, 0.254, 0.287, 0.112,
0.210, 0.190, 0.246, 0.138, and 0.125, respectively, which are
higher than that of the corresponding ligand. Particularly, the
quantum yield of Zn2 (ΦF = 0.254) is 9.41-fold compared to L2
(ΦF = 0.027). This is because the coordination of the ligands to
the M(II) ions increases the rigidity of the molecular edifice
and reduces the loss of energy by radiationless thermal
vibrations.62 In addition, the quantum yields of Zn1 and Cd1
are apparently weaker than that of the other complexes in
acetonitrile solution; on the contrary, they exhibit excellent
luminescence emission in the solid state.
The luminescence decay profiles of ligands L1−L5 and the
nine Zn(II)/Cd(II) complexes were measured at their optimal
excitation wavelengths in the solid state and acetonitrile
solution at 298 K. The detailed data are listed in Table S6,
Supporting Information. A general trend is that the
luminescence lifetimes for M(II) (M = Zn and Cd) complexes
either in the solid state or acetonitrile solution at 298 K are
mostly longer than that of the corresponding ligands L1−L5.
The most obvious observation is that the lifetime of Cd2 (τ =
8.17 μs) is 1.92-fold compared to the corresponding ligand L2
(τ = 4.25 μs) in acetonitrile solution. This is attributed to the
more stable structure and interaction upon coordination.63
Meanwhile, the luminescence lifetimes of the ligand and
corresponding complexes in the solid state (τ = 5.50−7.71 μs
for L1−L5; τ = 7.08−9.92 μs for Zn(II)/Cd(II) complexes) are
longer than those in acetonitrile solution (τ = 4.25−5.58 μs for
H
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 8. Emission spectra of complexes (a) Zn1 and (b) Cd1 (10 μM) in CH3CN−H2O mixtures with different water fractions (0−90% v/v) at
room temperature. Inset: Plot of luminescence intensity of complexes Zn1 and Cd1 in CH3CN−H2O mixtures with different amounts of water.
Luminescence intensities of complexes (c) Zn1 and (d) Cd1 in CH3CN at different concentrations.
L1−L5; τ = 5.94−8.17 μs for Zn(II)/Cd(II) complexes), which
might be explained by the fact that there is a less polar nature in
the solid-state environment.64
However, a significant enhancement of luminescence is
observed when the water fraction reaches 50%. The emission
intensity in the CH3CN−H2O mixture with fw = 90% is about
5.59 and 6.45 times higher than that in pure CH3CN solution
for Zn1 and Cd1, respectively, which indicates that the
complexes Zn1 and Cd1 have AIEE activity. The inset depicts
the changes of luminescence intensity with different water
fractions. Compared with the emission spectrum of Zn1 in pure
CH3CN solution, the solid emission spectrum shows a 69 nm
(64 nm for Cd1) red-shifted emission, and the solid state
emission intensity of Zn1 becomes 10.4-fold (10.6 for Cd1)
higher than that in pure CH3CN solution (Figure S17,
Supporting Information).
We performed another experiment: the emission spectra of
Zn1 and Cd1 in different concentrations of CH3CN were
recorded (Figures 8c and 8d). It can be clearly seen that the
CH3CN solution with a low concentration (c = 10−5 M) was a
weak emission and the luminescence spectrum were nearly
parallel to the abscissa. However, the luminescence intensities
abruptly increased when the concentration was >10−3 M. As the
concentration reached 10−1 M, the emission intensity was
approximately 7.7 and 8.7 times higher than the molecularly
dispersed species in CH3CN for Zn1 and Cd1, respectively.
The emission maxima were 53 nm (Zn1) and 50 nm (Cd1)
red-shifted. These results indicate that these complexes are
indeed a weak emitter in dilute solution, which is close to the
properties described by the aggregation-induced emission
concept.65 As reported by previous literature,66−68 the AIEE
mechanism of these complexes possibly arose from the
restriction of intramolecular rotation. In the mixture of
CH3CN/H2O (10/90 v/v), most of the Zn1 and Cd1
molecules aggregated together rapidly by the intermolecular
C−H···O hydrogen bonding and π···π stacking interactions
between adjacent pyridyl rings and phenyl rings. Such free
rotations are hindered and further increase the rigidity of the
Effect of aryl substitution and anion on luminescence
properties in the solid state. In this article, we mainly talk
about photoluminescence properties from two aspects: for one
thing, the electron-donating ability of the alkyl substitution
could regulate and control the maximum emission wavelength,
and then realize the control of luminescence color. For
instance, a trend was observed in λem with Zn1 (486 nm) <
Zn2 (495 nm) < Zn3 (509 nm) in the solid state, which is
consistent with the electron-donating ability (2,4,6-(CH3)3 >
2,6-(CH3)2 > 2-CH3) of substituents of ligands. As shown in
Table 2, the Cd(II) complexes also have analogous regular
−
pattern. For another, the anions (Cl−, NO3 , OAc−) mainly
influence the intensity of emission. The emission intensities of
Cl− anion complexes are generally lower than those of NO3
−
and OAc− anion complexes. This phenomenon indicates that
the presence of chlorine on the complex skeleton induces a
noticeable decrease of the intensity. Such behavior could be
assigned to the heavy atom effect and suggest that they might
have a higher intersystem crossing (ISC) efficiency, resulting in
a decrease of the emission.
Aggregation-induced emission enhancement (AIEE) prop-
erties of complexes Zn1 and Cd1. The emission behaviors of
Zn1 and Cd1 have been further investigated through a classical
AIE experiment. We added different amounts of water, a poor
solvent for the luminophors, to the pure CH3CN solutions to
obtain water fractions (fw) of 0−90% and then monitored the
photoluminescence changes. The concentration was main-
tained at 10 μmol L−1. As shown in Figures 8a and 8b, there is a
clear trend that Zn1 and Cd1 are weakly emissive in
acetonitrile solution, but the emission dramatically increased
after adding a large amount of water. The emission intensity is
very weak, and changes little as fw increases from 0% to 40%.
I
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
n2
nR2
molecules to generate a more extended planar skeleton; thus,
this might influence the luminescence.69−71 Simultaneously, the
complexes Zn1 and Cd1 have a planar conformation with
minor torsion angles between the pyridyl ring and phenyl ring
(6.053°/10.027° for Zn1; 14.226° for Cd1), which is beneficial
for luminescence emission.72 Complexes with these AIEE
effects can be extensively applied as solid state emission
materials.
ODR
I
Q = Q
R IR OD
(2)
.
In eq 2, Q is the quantum yield, I is the measured integrated
emission intensity, n is the refractive index, and OD is the optical
density. The subscript R refers to the reference fluorophore of known
quantum yield. In order to minimize reabsorption effects, absorbencies
in the 10 mm fluorescence cuvette were kept under 0.05 at the
excitation wavelength (350 nm).
CONCLUSIONS
X-ray crystallography. Suitable crystals of nine zinc(II)/
cadmium(II) complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4,
and Cd5 were selected and mounted on a Rigaku R−AXIS RAPID IP
diffractometer. Diffraction data were collected using graphite-
monochromatized Mo·Kα radiation (λ = 0.71073 Å). The structures
were solved with direct methods76 and refined with full−matrix least−
squares on F2. All the hydrogen atoms were constrained in geometric
positions to their parent atoms and non-hydrogen atoms were refined
anisotropically. The detailed crystal structure refinement data are given
in Table S1 (the Supporting Information), selected bond lengths and
angles are listed in Tables S2−S5 (the Supporting Information). The
CCDC numbers are 1449214−1449222 for Zn1, Cd1, Zn2, Cd2,
Zn3, Cd3a, Cd3b, Cd4, and Cd5, respectively.
■
In summary, five Schiff base ligands (E)-N-(pyridine-2-
yl)(CHNPhR) (where R = 4-CH3, L1; 2,6-(CH3)2, L2;
2,4,6-(CH3)3, L3; 2,6-(C2H5)2, L4; 2,6-(i-C3H7)2, L5) and nine
Zn(II)/Cd(II) complexes Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b,
Cd4, and Cd5 have been successfully synthesized. They are
excellent models for investigating the alkyl substitution effect
on the supramolecular metal−organic frameworks (SMOFs)
and photoluminescence properties. The crystal structures of
these complexes indicate that intermolecular interactions, such
as C−H···O/C−H···Cl hydrogen bonds and π···π interactions,
play essential roles in constructing 1D → 3D supramolecular
architectures. Upon irradiation with UV light, the nine Zn(II)/
Cd(II) complexes display deep blue emissions of 401−436 nm
in acetonitrile solution and light blue, bluish green emissions of
485−575 nm in the solid state, respectively. The photo-
luminescence properties of nine Zn(II)/Cd(II) complexes can
be finely and predictably tuned over a wide range of
wavelengths by small and easily implemented changes to ligand
structure. By modifying the phenyl moiety with electron-
donating substituents, the energy difference between HOMO
and LUMO decreases, and the emissions red-shift accordingly.
It is worth noting that Zn1 and Cd1 exhibit obvious
aggregation-induced emission enhancement (AIEE) properties
in the CH3CN−H2O mixture solutions.
General synthesis of ligand. The Schiff base ligands L1−L5 were
synthesized by dissolving 2-pyridinecarboxaldehyde in anhydrous
methanol (10 mL) and 1 molar equivalence of the respective aniline
derivates (4-methylaniline, 2,6-dimethylaniline, 2,4,6-trimethylaniline
2,6-diethylaniline, and 2,6-diisopropylaniline) in anhydrous methanol
(10 mL) and mixing the two. The resultant solutions were set at reflux
for ca. 8−12 h and subsequently concentrated under reduced pressure
to obtain the crude products. L1 was recrystallized from the mixed
solvent of n-hexane and dichloromethane to give yellow crystal. L3 and
L5 were recrystallized from n-hexane to give yellow crystals.
(E)-4-Methyl-N-((pyridin-2-yl)methylene)aniline (L1). 2-Pyridine-
carboxaldehyde (1.52 mL, 15.98 mmol) and 4-methylaniline (1.77
mL, 15.88 mmol) were dissolved in 20 mL of anhydrous methanol and
the resulting mixture was heated at reflux temperature for 3 h. The
solvent was removed under reduced pressure and the residue was
recrystallized from the mixed solvent of n-hexane and dichloromethane
to give yellow crystals. Yield: 2.79 g (90%). Anal. Calcd (%) for
C13H12N2 (M = 196.25 g mol−1): C, 79.56; H, 6.16; N, 14.27. Found:
C, 79.55; H, 6.17; N, 14.28. FT-IR (KBr, cm−1): 3429(w), 3050(w),
2917(w), 2861(w), 1628(m), 1582(m), 1566(m), 1506(s), 1463(m),
1434(m), 1347(w), 1291(w), 1256(w), 1234(w), 1213(w), 1198(w),
1140(w), 1111(w), 1085(w), 1038(w), 992(m), 969(w), 947(w),
880(m), 822(s), 774(w), 738(m), 706(w), 646(w), 617(m), 542(m),
497(w), 477(w). 1H NMR (400 MHz, CDCl3): δ 8.74 (d, 1H, Py-H6),
8.65 (s, 1H, CHN), 8.24 (d, 1H, Py-H3), 7.84 (t, 1H, Py-H4), 7.40
(t, 1H, Py-H5), 6.63−7.29 (m, 4H, Ph-H3,4,5,6), 2.41 (s, 3H, Ph−CH3)
ppm.
EXPERIMENTAL SECTION
■
Materials and instrumentation. All reagents and solvents were
purchased from commercial sources and were used without further
purification. Elemental analyses were carried out on a Perkin−Elmer
2400 automatic analyzer. FT−IR spectra data (4000−400 cm−1) were
1
collected by a Nicolet impact 410 FT−IR spectrometer. H NMR
spectra were obtained using a Bruker Avance−400 MHz spectrometer
with Si(CH3)4 as internal standard. A Perkin−Elmer Lambda 35
spectrometer was used to measure the UV−vis absorption spectra of
ligands and complexes. The emission luminescence and lifetime
properties were recorded with Edinburgh FLS 920 fluorescence
spectrometer. Lifetime studies were performed using photon-counting
system with a microsecond pulse lamp as the excitation source. The
emission decays were analyzed by the sum of exponential functions.
The decay curve is well fitted into a double exponential function:73 I(t)
= A1 exp(−t/τ1) + A2 exp(−t/τ2), where I is the luminescence
intensity, and τ1 and τ2 are the lifetimes for the exponential
components. The average lifetime was calculated according to the
following equation:
(E)-2,6-Dimethyl-N-((pyridin-2-yl)methylene)aniline (L2). 2-Pyridi-
necarboxaldehyde (1.50 mL, 15.77 mmol) and 2,6-dimethylaniline
(1.95 mL, 15.77 mmol) gave 2.72 g of product (yield: 82%). Anal.
Calcd (%) for C14H14N2 (M = 210.27 g mol−1): C, 79.97; H, 6.71; N,
13.32. Found: C, 79.90; H, 6.67; N, 13.42. FT-IR (KBr, cm−1):
3434(w), 3045(w), 2916(m), 2852(w), 1652(s), 1585(m), 1568(m),
1469(s), 1436(m), 1374(w), 1348(w), 1289(w), 1252(w), 1190(s),
1146(m), 1088(m), 1041(m), 990(m), 918(w), 872(m), 829(w),
1
776(s), 739(w), 704(w), 630(w), 611(w), 564(w), 467(w). H NMR
τ12A1% + τ22A2%
(400 MHz, CDCl3): δ 8.76 (d, 1H, Py-H6), 8.38 (s, 1H, CHN),
8.33 (d, 1H, Py-H3), 7.88 (t, 1H, Py-H4), 7.44 (t, 1H, Py-H5), 7.01−
7.12 (m, 3H, Ph-H3,4,5), 2.20 (s, 6H, Ph−CH3) ppm.
τ1A1% + τ2A2%
(1)
.
(E)-2,4,6-Trimethyl-N-((pyridin-2-yl)methylene)aniline (L3). 2-Pyr-
idinecarboxaldehyde (1.50 mL, 15.75 mmol) and 2,4,6-trimethylani-
line (2.22 mL, 15.81 mmol) gave 2.68 g of product (yield: 76%). Anal.
Calcd (%) for C15H16N2 (M = 224.30 g mol−1): C, 80.32; H, 7.19; N,
12.49. Found: C, 80.28; H, 7.18; N, 12.45. FT-IR (KBr, cm−1):
3432(w), 3050(w), 2911(m), 2854(w), 1668(vs), 1586(m), 1567(m),
1482(s), 1468(s), 1436(m), 1400(w), 1386(w), 1376(w), 1347(w),
1288(w), 1259(w), 1202(s), 1144(m), 1088(w), 1041(w), 1015(w),
Reference for quantum yield measurements: Lakowicz, J. R.
Principles of Fluorescence Spectroscopy, 2nd ed.; Kluwer Academic/
Plenum Publishers: New York, 1999. Quinine sulfate in 0.1 M H2SO4
(quantum yield 0.546 at 350 nm) was chosen as a standard.74,75
Absolute values are calculated using the standard reference sample that
has a fixed and known fluorescence quantum yield value, according to
the following equation:
J
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
993(m), 982(m), 955(w), 934(w), 897(w), 876(s), 863(s), 791(m),
770(s), 739(m), 643(w), 618(w), 577(w), 489(w). H NMR (400
MHz, CDCl3): δ 8.72 (d, 1H, Py-H6), 8.33 (s, 1H, CHN), 8.29 (d,
1H, Py-H3), 7.84 (t, 1H, Py-H4), 7.40 (t, 1H, Py-H5), 6.90 (s, 2H, Ph-
H3,5), 2.14−2.29 (m, 9H, Ph−CH3) ppm.
was allowed to stand at room temperature in air. Yellow bulk crystals
of Zn2 were obtained by slow evaporation after 1 day. Yield: 46.9 g
(68%). Anal. Calcd (%) for C14H14Cl2N2Zn (M = 346.54 g mol−1): C,
48.52; H, 4.07; N, 8.08. Found: C, 48.55; H, 4.02; N, 8.15. FT-IR
(KBr, cm−1): 3434(w), 3067(w), 2955(w), 2853(w), 1631(w),
1597(s), 1569(w), 1479(m), 1444(m), 1385(w), 1359(w), 1302(m),
1275(w), 1225(w), 1184(m), 1160(w), 1106(m), 1093(w), 1071(w),
1048(w), 1024(m), 988(w), 929(w), 907(w), 788(s), 778(s), 741(w),
1
(E)-2,6-Diethyl-N-((pyridin-2-yl)methylene)aniline (L4). 2-Pyridine-
carboxaldehyde (1.53 mL, 16.08 mmol) and 2,6-diethylaniline (2.70
mL, 16.28 mmol) gave 3.50 g of product (yield: 91%). Anal. Calcd (%)
for C16H18N2 (M = 238.33 g mol−1): C, 80.63; H, 7.61; N, 11.75.
Found: C, 80.58; H, 7.63; N, 11.72. FT-IR (KBr, cm−1): 3425(w),
3052(w), 2964(m), 2871(w), 1643(s), 1584(m), 1565(m), 1468(s),
1435(m), 1374(m), 1355(w), 1319(w), 1292(w), 1256(w), 1228(w),
1189(m), 1164(w), 1147(m), 1099(m), 1088(w), 1060(w), 1041(w),
1006(w), 992(m), 964(w), 875(s), 835(w), 797(w), 775(s), 753(s),
704(w), 635(w), 618(w), 593(w), 563(w), 525(w), 499(w), 471(w).
1H NMR (400 MHz, CDCl3): δ 8.78 (d, 1H, Py-H6), 8.38 (s, 1H,
CHN), 8.32 (d, 1H, Py-H3), 7.89 (t, 1H, Py-H4), 7.45 (t, 1H, Py-
H5), 7.09−7.15 (m, 3H, Ph-H3,4,5), 2.56 (q, 4H, Ph−CH2-), 1.18 (t,
6H, Ph−CH3) ppm.
1
715(w), 648(w), 648(w), 524(w), 488(w), 435(w). H NMR (400
MHz, CDCl3): δ 8.98 (d, 1H, Py-H6), 8.46 (s, 1H, CHN), 8.32 (t,
1H, Py-H3), 7.96 (d, 1H, Py-H4), 7.54 (t, 1H, Py-H5), 7.02−7.17 (m,
3H, Ph-H3,4,5), 2.28 (s, 6H, Ph−CH3) ppm.
[CdL2Cl2]2 (Cd2). The procedure was similar to that of Zn2, except
that CdCl2 (45.6 mg, 0.2 mmol) and CH3CN (25 mL) were used
instead of ZnCl2 and CH3OH, respectively. Colorless crystals of Cd2
were obtained by slow evaporation after 1 day. Yield: 43.6 g (56%).
Anal. Calcd (%) for C28H28Cl4N4Cd2 (M = 787.16 g mol−1): C, 42.72;
H, 3.59; N, 7.12. Found: C, 42.68; H, 3.63; N, 7.15. FT-IR (KBr,
cm−1): 3432(w), 3061(w), 2940(w), 2855(w), 1642(s), 1593(s),
1573(w), 1473(m), 1445(m), 1381(w), 1361(w), 1304(m), 1275(w),
1258(w), 1224(w), 1186(s), 1164(w), 1105(w), 1090(w), 1051(w),
1034(w), 1016(m), 984(w), 908(m), 796(s), 771(s), 741(w), 715(w),
640(w), 628(w), 520(w), 476(w), 432(w). 1H NMR (400 MHz,
CDCl3): δ 8.83 (d, 1H, Py-H6), 8.41 (s, 1H, CHN), 8.00 (d, 1H,
Py-H3), 7.91 (t, 1H, Py-H4), 7.54 (t, 1H, Py-H5), 6.75−7.00 (m, 3H,
Ph-H3,4,5), 2.26 (s, 6H, Ph−CH3) ppm.
(E)-2,6-Diisopropyl-N-((pyridin-2-yl)methylene)aniline (L5). 2-Pyr-
idinecarboxaldehyde (1.16 mL, 12.19 mmol) was refluxed (4 h) with
2,6-diisopropylaniline (2.35 mL, 12.46 mmol) in 25 mL of anhydrous
methanol. The solvent was removed under reduced pressure and the
residue was purified by column chromatograph using a mixture of
ethyl acetate and aether petrolei (1:3, v/v) as eluent.
Recrystallization from n-hexane gave yellow crystals, which were
filtered and washed with cold n-hexane. Yield: 2.28 g (70%). Anal.
Calcd (%) for C18H22N2 (M = 266.38 g mol−1): C, 81.16; H, 8.32; N,
10.52. Found: C, 81.08; H, 8.36; N, 10.50. FT-IR (KBr, cm−1):
3428(w), 3072(w), 2959(vs), 2867(m), 1653(s), 1587(m), 1567(m),
1471(s), 1440(m), 1385(m), 1363(m), 1347(w), 1324(m), 1308(w),
1295(m), 1254(m), 1226(w), 1179(m), 1150(m), 1107(w), 1091(w),
1054(m), 1045(m), 1011(w), 996(m), 970(w), 933(m), 879(m),
827(w), 808(w), 796(m), 779(m), 755(s), 701(w), 640(w), 620(w),
[ZnL3Cl2] (Zn3). The procedure was similar to that of Zn2, except
that L3 (44.5 mg, 0.2 mmol) was used instead of L2. Pale yellow bulk
crystals of Zn3 were obtained by slow evaporation after 3 days. Yield:
44.2 g (62%). Anal. Calcd (%) for C15H16Cl2N2Zn (M = 360.57 g
mol−1): C, 49.96; H, 4.47; N, 7.77. Found: C, 49.88; H, 4.45; N, 7.76.
FT-IR (KBr, cm−1): 3438(w), 3064(w), 2920(w), 2858(w), 1629(m),
1595(s), 1568(w), 1481(s), 1444(m), 1424(w), 1383(w), 1360(m),
1301(m), 1274(w), 1227(w), 1199(m), 1161(w), 1142(w), 1106(w),
1052(w), 1025(m), 987(w), 959(w), 936(w), 908(w), 848(m),
778(s), 747(w), 731(w), 643(m), 581(w), 507(w), 497(w), 475(w),
454(w). 1H NMR (400 MHz, CDCl3): δ 8.97 (d, 1H, Py-H6), 8.43 (s,
1H, CHN), 8.30 (t, 1H, Py-H3), 7.93−7.96 (m, 2H, Py-H4,5), 6.97
(s, 2H, Ph-H3,5), 2.26−2.33 (m, 9H, Ph−CH3) ppm.
1
563(w), 533(w), 493(w), 459(w). H NMR (400 MHz, CDCl3): δ
8.77 (d, 1H, Py-H6), 8.36 (s, 1H, CHN), 8.32 (d, 1H, Py-H3), 7.92
(t, 1H, Py-H4), 7.46 (t, 1H, Py-H5), 6.83−7.20 (m, 3H, Ph-H3,4,5), 3.00
(q, 2H, Ph−CH-), 1.21 (d, 12H, Ph−CH3) ppm.
[Zn3(L1)2(OAc)6] (Zn1). A mixture of Zn(OAc)2·2H2O (21.9 mg, 0.1
mmol) and L1 (19.1 mg, 0.1 mmol) was dissolved in CH3CN (8 mL)
and stirred for 30 min, then heated in a sealed vial at 80 °C for 1 day.
Colorless rectangular block crystals of Zn1 were obtained. Yield: 30.0
g (65%). Anal. Calcd (%) for C38H42O12N4Zn3 (M = 942.87 g mol−1):
C, 48.41; H, 4.49; N, 5.94. Found: C, 48.47; H, 4.52; N, 5.92. FT-IR
(KBr, cm−1): 3433(w), 3029(w), 2923(w), 2870(w), 1616(m),
1509(m), 1481(m), 1424(s), 1385(m), 1322(m), 1272(w),
1243(w), 1200(w), 1178(w), 1160(w), 1104(w), 1051(m),
1019(m), 964(w), 933(w), 914(w), 838(m), 829(m), 776(m),
[CdL3Cl2]2 (Cd3a). The procedure was similar to that of Zn3, except
that CdCl2 (45.6 mg, 0.2 mmol) and CH3OH (5 mL)/CH2Cl2 (25
mL) were used instead of ZnCl2 and CH3OH, respectively. Yellow
bulk crystals of Cd3 were obtained by slow evaporation after 2 days.
Yield: 52.1 g (64%). Anal. Calcd (%) for C30H32Cl4N4Cd2 (M =
815.20 g mol−1): C, 44.20; H, 3.96; N, 6.87. Found: C, 44.25; H, 4.03;
N, 6.85. FT-IR (KBr, cm−1): 3443(m), 3066(w), 2916(w), 2860(w),
1645(s), 1594(s), 1572(w), 1484(m), 1445(m), 1383(w), 1367(w),
1311(m), 1269(w), 1229(w), 1201(w), 1162(w), 1143(m), 1104(w),
1054(w), 1040(w), 1018(m), 982(w), 969(w), 935(w), 902(m),
869(w), 853(w), 780(s), 742(w), 639(m), 584(w), 495(w), 422(w).
1H NMR (400 MHz, CDCl3): δ 8.84 (d, 1H, Py-H6), 8.39 (s, 1H,
CHN), 8.12 (t, 1H, Py-H3), 7.92 (t, 1H, Py-H4), 7.56 (t, 1H, Py-
H5), 6.91 (s, 2H, Ph-H3,5), 2.23−2.27 (m, 9H, Ph−CH3) ppm.
[Cd(L3)2(NO3)2] (Cd3b). A mixture of Cd(NO3)2·4H2O (32.0 mg,
0.1 mmol) and L3 (65.0 mg, 0.3 mmol) with a molar ration of 1:3 was
dissolved in CH3CN (8.0 mL). After stirring for 30 min in air, it was
transferred into a 15 mL Teflon−lined stainless steel autoclave and
heated at 120 °C for 4.5 days. Colorless crystals of Cd3b were
obtained by slow evaporation after 6 days. Yield: 46.4 g (65%). Anal.
Calcd (%) for C30H32N6O6Cd (M = 685.02 g mol−1): C, 52.60; H,
4.71; N, 12.27. Found: C, 52.59; H, 4.75; N, 12.30. FT-IR (KBr,
cm−1): 3473(w), 3079(w), 2937(w), 2848(w), 2395(m), 2291(w),
1633(m), 1589(m), 1467(m), 1419(m), 1307(s), 1197(w), 1139(w),
1022(w), 904(w), 860(w), 777(w), 628(w), 590(w), 493(w), 460(w).
1H NMR (400 MHz, CDCl3): δ 8.85 (d, 1H, Py-H6), 8.40 (s, 1H,
CHN), 8.01 (d, 1H, Py-H3), 7.93 (t, 1H, Py-H4), 7.57 (t, 1H, Py-
H5), 7.12 (s, 2H, Ph-H3,5), 2.48−2.72 (m, 9H, Ph−CH3) ppm.
[CdL4Cl2] (Cd4). The procedure was similar to that of Cd3, except
that L4 (23.5 mg, 0.1 mmol) was used instead of L3. Yellow bulk
crystals of Cd3 were obtained by slow evaporation after 8 days. Yield:
1
750(w), 681(m), 666(m), 614(m), 541(m), 426(w). H NMR (400
MHz, CDCl3): δ 8.73 (d, 1H, Py-H6), 8.67 (s, 1H, CHN), 8.16 (d,
1H, Py-H3), 8.00 (t, 1H, Py-H4), 7.57 (t, 1H, Py-H5), 7.25−7.32 (m,
4H, Ph-H3,4,5,6), 2.34 (s, 3H, Ph−CH3), 1.82 (s, 9H, −CH3COO)
ppm.
[CdL1(OAc)2] (Cd1). The preparation of Cd1 was similar to that of
Zn1, except for Cd(OAc)2·2H2O (26.7 mg, 0.1 mmol) was used
instead of Zn(OAc)2·2H2O. Yield: 30.8 g (72%). Anal. Calcd (%) for
C17H18N2O4Cd (M = 426.74 g mol−1): C, 47.85; H, 4.25; N, 6.56.
Found: C, 47.78; H, 4.30; N, 6.49. FT-IR (KBr, cm−1): 3403(w),
3063(w), 2981(w), 2867(w), 1626(m), 1592(s), 1563(s), 1511(m),
1481(m), 1440(m), 1414(s), 1337(m), 1312(w), 1270(w), 1239(w),
1198(w), 1158(w), 1102(w), 1051(w), 1015(m), 939(w), 910(w),
829(m), 814(m), 781(m), 747(w), 705(w), 671(s), 653(m), 635(w),
1
619(w), 537(m), 506(w), 485(w), 462(w), 427(w). H NMR (400
MHz, CDCl3): δ 8.98 (d, 1H, Py-H6), 8.69 (s, 1H, CHN), 8.10 (t,
1H, Py-H3), 7.82 (d, 1H, Py-H4), 7.72 (t, 1H, Py-H5), 7.30−7.56 (m,
4H, Ph-H3,4,5,6), 2.41 (s, 3H, Ph−CH3), 2.04 (s, 6H, −CH3COO)
ppm.
[ZnL2Cl2] (Zn2). L2 (41.5 mg, 0.2 mmol) and ZnCl2 (27.3 mg, 0.2
mmol) were refluxed in 25 mL of anhydrous methanol for 2.5 h. The
mixture was then cooled to room temperature and filtered. The filtrate
K
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
29.2 g (70%). Anal. Calcd (%) for C16H18Cl2N2Cd (M = 421.62 g
mol−1): C, 45.58; H, 4.30; N, 6.64. Found: C, 45.61; H, 4.25; N, 6.63.
FT-IR (KBr, cm−1): 3432(w), 3061(w), 2971(m), 2869(w), 1639(m),
1593(s), 1571(w), 1481(w), 1457(m), 1441(w), 1369(w), 1307(m),
1270(w), 1224(w), 1176(m), 1158(w), 1103(m), 1056(w), 1034(w),
1017(m), 987(w), 910(m), 869(w), 835(w), 808(m), 779(s), 761(w),
(4) Han, L. L.; Hu, T. P.; Mei, K.; Guo, Z. M.; Yin, C.; Wang, Y. X.;
Zheng, J.; Wang, X. P.; Sun, D. Dalton Trans. 2015, 44, 6052−6061.
(5) Banerjee, R.; Phan, A.; Wang, B.; Knobler, C.; Furukawa, H.;
O’Keeffe, M.; Yaghi, O. M. Science 2008, 319, 939−943.
(6) Lin, J. B.; Zhang, J. P.; Chen, X. M. J. Am. Chem. Soc. 2010, 132,
6654−6656.
1
712(w), 640(w), 589(w), 573(w), 503(w), 439(w). H NMR (400
(7) Yuan, S.; Deng, Y. K.; Sun, D. Chem. - Eur. J. 2014, 20, 10093−
10098.
MHz, CDCl3): δ 8.76 (d, 1H, Py-H6), 8.40 (s, 1H, CHN), 8.21 (d,
1H, Py-H3), 8.06 (t, 1H, Py-H4), 7.64 (t, 1H, Py-H5), 7.03−7.12 (m,
3H, Ph-H3,4,5), 2.46 (q, 4H, Ph−CH2-), 1.14 (t, 6H, Ph−CH3) ppm.
[CdL5Cl2] (Cd5). The procedure was similar to that of Cd4, except
that L5 (26.6 mg, 0.1 mmol) was used instead of L4. Yellow bulk
crystals of Cd5 were obtained by slow evaporation after 6 days. Yield:
32.5 g (72%). Anal. Calcd (%) for C18H22Cl2N2Cd (M = 449.68 g
mol−1): C, 48.08; H, 4.93; N, 6.23. Found: C, 48.13; H, 4.90; N, 6.25.
FT-IR (KBr, cm−1): 3448(w), 3070(w), 2965(m), 2868(w), 1640(m),
1595(s), 1572(w), 1482(m), 1458(m), 1444(m), 1384(w), 1371(w),
1330(w), 1308(w), 1270(w), 1257(w), 1223(w), 1176(m), 1158(w),
1103(m), 1058(w), 1018(m), 961(w), 933(w), 906(w), 806(s),
776(s), 761(s), 706(w), 638(w), 568(w), 539(w), 500(w), 471(w),
431(w). 1H NMR (400 MHz, CDCl3): δ 8.77 (d, 1H, Py-H6), 8.39 (s,
1H, CHN), 8.23 (d, 1H, Py-H3), 8.04 (t, 1H, Py-H4), 7.63 (t, 1H,
Py-H5), 7.11−7.20 (m, 3H, Ph-H3,4,5), 2.89 (q, 2H, Ph−CH-), 1.14 (d,
12H, Ph−CH3) ppm.
(8) Guo, Z. Q.; Yiu, S. M.; Chan, M. C. W. Chem. - Eur. J. 2013, 19,
8937−8947.
(9) Zhou, H. C.; Long, J. R.; Yaghi, O. M. Chem. Rev. 2012, 112,
673−674.
(10) Lu, W. G.; Wei, Z. W.; Gu, Z. Y.; Liu, T. F.; Park, J.; Park, J.;
Tian, J.; Zhang, M. W.; Zhang, Q.; Gentle, T., III; Bosch, M.; Zhou, H.
C. Chem. Soc. Rev. 2014, 43, 5561−5593.
(11) Ali, A.; Hundal, G.; Gupta, R. Cryst. Growth Des. 2012, 12,
1308−1319.
(12) Duong, A.; Maris, T.; Wuest, J. D. Inorg. Chem. 2011, 50, 5605−
5618.
(13) Natale, D.; Mareque-Rivas, J. C. Chem. Commun. 2008, 425−
437.
(14) Nishio, M. CrystEngComm 2004, 6, 130−158.
(15) Janssen, F. F. B. J.; Gelder, R.; Rowan, A. E. Cryst. Growth Des.
2011, 11, 4326−4333.
(16) Field, J. S.; Munro, O. Q.; Waldron, B. P. Dalton Trans. 2012,
41, 5486−5496.
(17) Lin, J. M.; Qiu, Y. X.; Chen, W. B.; Yang, M.; Zhou, A. J.; Dong,
W.; Tian, C. E. CrystEngComm 2012, 14, 2779−2786.
(18) He, L.; Ma, D.; Duan, L.; Wei, Y.; Qiao, J.; Zhang, D.; Dong, G.;
Wang, L.; Qiu, Y. Inorg. Chem. 2012, 51, 4502−4510.
(19) Semeniuc, R. F.; Reamer, T. J.; Smith, M. D. New J. Chem. 2010,
34, 439−452.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.cgd.6b00347.
Structural information for Zn1−Zn3, Cd1, Cd2, Cd3a,
1
Cd3b, Cd4, and Cd5, FT−IR spectra, H NMR spectra,
luminescent data, and selected bond lengths and angles
for Zn1−Zn3, Cd1, Cd2, Cd3a, Cd3b, Cd4, and Cd5
(PDF)
(20) Luo, J.; Xie, Z.; Lam, J. W.; Cheng, L.; Chen, H.; Qiu, C.; Kwok,
H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001,
1740−1741.
(21) Bhattacharya, B.; Haldar, R.; Maity, D. K.; Maji, T. K.; Ghoshal,
D. CrystEngComm 2015, 17, 3478−3486.
Accession Codes
CCDC 1449214−1449222 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(22) Papaefstathiou, G. S.; MacGillivray, L. R. Coord. Chem. Rev.
2003, 246, 169−184.
(23) Kuzu, I.; Krummenacher, I.; Meyer, J.; Armbruster, F.; Breher,
F. Dalton Trans. 2008, 5836−5865.
(24) Khavasi, H. R.; Salimi, A. R.; Eshtiagh-Hosseini, H.; Amini, M.
M. CrystEngComm 2011, 13, 3710−3717.
(25) Li, G. F.; Ren, X. Y.; Shan, G. G.; Che, W. L.; Zhu, D. X.; Yan, L.
K.; Su, Z. M.; Bryce, M. R. Chem. Commun. 2015, 51, 13036−13039.
(26) Nath, M.; Saini, P. K. Dalton Trans. 2011, 40, 7077−7121.
(27) Lo, W. K.; Wong, W. K.; Wong, W. Y.; Guo, J. P. Eur. J. Inorg.
Chem. 2005, 2005, 3950−3954.
AUTHOR INFORMATION
■
Corresponding Authors
*(Rui-Qing Fan) Fax: +86-451-86413710. E-mail: fanruiqing@
hit.edu.cn.
*(Yu-Lin Yang) Fax: +86-451-86413710. E-mail: ylyang@hit.
edu.cn.
(28) Bassanetti, I.; Mezzadri, F.; Comotti, A.; Sozzani, P.; Gennari,
M.; Calestani, G.; Marchio,
9145.
̀
L. J. Am. Chem. Soc. 2012, 134, 9142−
Notes
(29) Song, L. S.; Wang, H. M.; Niu, Y. Y.; Hou, H. W.; Zhu, Y.
CrystEngComm 2012, 14, 4927−4938.
The authors declare no competing financial interest.
(30) Li, S. M.; Zheng, X. J.; Yuan, D. Q.; Ablet, A.; Jin, L. P. Inorg.
Chem. 2012, 51, 1201−1203.
ACKNOWLEDGMENTS
■
(31) Tanabe, K. K.; Allen, C. A.; Cohen, S. M. Angew. Chem., Int. Ed.
2010, 49, 9730−9733.
This work was supported by National Natural Science
Foundation of China (Grant 21371040, 21571042, and
21171044) and the National Key Basic Research Program of
China (973 Program, No. 2013CB632900).
(32) Feng, R.; Jiang, F. L.; Chen, L.; Yan, C. F.; Wu, M. Y.; Hong, M.
C. Chem. Commun. 2009, 5296−5298.
(33) Wang, H. L.; Qi, D. D.; Xie, Z.; Cao, W.; Wang, K.; Shang, H.;
Jiang, J. Z. Chem. Commun. 2013, 49, 889−891.
(34) Machura, B.; Nawrot, I.; Michalik, K. Polyhedron 2011, 30,
2619−2626.
REFERENCES
■
(1) Hiratani, K.; Albrecht, M. Chem. Soc. Rev. 2008, 37, 2413−2421.
(2) Pluth, M. D.; Bergman, R. G.; Raymond, K. N. Acc. Chem. Res.
2009, 42, 1650−1659.
(3) Barnett, S. A.; Champness, N. R. Coord. Chem. Rev. 2003, 246,
145−168.
(35) Ma, Q.; Zhu, M. L.; Yuan, C. X.; Feng, S. S.; Lu, L. P.; Wang, Q.
M. Cryst. Growth Des. 2010, 10, 1706−1714.
(36) Liu, X. H.; Zhao, L. M.; Liu, F. S. Acta Crystallogr., Sect. E: Struct.
Rep. Online 2012, E68, m311.
L
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
(37) Basu Baul, T. S.; Kundu, S.; Linden, A.; Raviprakash, N.;
Mannac, S. K.; da Silva, M. F. C. G. Dalton Trans. 2014, 43, 1191−
1202.
(38) Roy, A. S.; Saha, P.; Mitra, P.; Maity, S. S.; Ghoshc, S.; Ghosh, P.
Dalton Trans. 2011, 40, 7375−7384.
(39) Baran, P.; Boca, R.; Breza, M.; Elias, H.; Fuess, H.; Jorik, V.;
Klement, R.; Svoboda, I. Polyhedron 2002, 21, 1561−1571.
(40) Gong, X.; Ge, Y. Y.; Fang, M.; Gu, Z. G.; Zheng, S. R.; Li, W. S.;
Hu, S. J.; Li, S. B.; Cai, Y. P. CrystEngComm 2011, 13, 6911−6915.
(41) Shakir, M.; Azam, M.; Azim, Y.; Parveen, S.; Khan, A. U.
Polyhedron 2007, 26, 5513−5518.
(42) Kumar, J.; Sarma, M. J.; Phukan, P.; Das, D. K. Dalton Trans.
2015, 44, 4576−4581.
(43) Dong, Y. W.; Fan, R. Q.; Wang, P.; Wei, L. G.; Wang, X. M.;
Zhang, H. J.; Gao, S.; Yang, Y. L.; Wang, Y. L. Dalton Trans. 2015, 44,
5306−5322.
(68) Yang, X. D.; Chen, X. L.; Lu, X. D.; Yan, C. G.; Xu, Y. K.; Hang,
X. D.; Qu, J. Q.; Liu, R. Y. J. Mater. Chem. C 2016, 4, 383−390.
(69) Zhou, T. L.; Li, F.; Fan, Y.; Song, W. F.; Mu, X. Y.; Zhang, H.
Y.; Wang, Y. Chem. Commun. 2009, 3199−3201.
(70) Wurthner, F.; Kaiser, T. E.; Saha-Moller, C. R. Angew. Chem.,
̈
̈
Int. Ed. 2011, 50, 3376−3410.
(71) Wong, W. Y.; Liu, L.; Shi, J. X. Angew. Chem., Int. Ed. 2003, 42,
4064−4068.
(72) Yang, M. D.; Xu, D. L.; Xi, W. G.; Wang, L. K.; Zheng, J.;
Huang, J.; Zhang, J. Y.; Zhou, H. P.; Wu, J. Y.; Tian, Y. P. J. Org. Chem.
2013, 78, 10344−10359.
(73) Chen, S.; Wu, Y. K.; Zhao, Y.; Fang, D. N. RSC Adv. 2015, 5,
72009−72018.
(74) Lakowicz, R. Z. Principles of fluorescence spectroscopy, 2nd ed.;
Klumer Academic/Plenum Publisher: New York, 1999.
(75) Liu, H.; Ye, T.; Mao, C. Angew. Chem., Int. Ed. 2007, 46, 6473−
6475.
(76) Sheldrick, G. M. SHELXTL NT Crystal Structure Analysis
Package, Version 5.10; Bruker AXS,: Analytical X-ray System, Madison,
WI, 1999.
(44) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor,
G. C. J. Chem. Soc., Dalton Trans. 1984, 1349−1356.
(45) Yang, L.; Powell, D. R.; Houser, R. P. Dalton Trans. 2007, 955−
964.
(46) Dong, Y. W.; Fan, R. Q.; Wang, P.; Wei, L. G.; Wang, X. M.;
Gao, S.; Zhang, H. J.; Yang, Y. L.; Wang, Y. L. Inorg. Chem. 2015, 54,
7742−7752.
(47) Dey, D.; Kaur, G.; Ranjani, A.; Gayathri, L.; Chakraborty, P.;
Adhikary, J.; Pasan, J.; Dhanasekaran, D.; Choudhury, A. R.; Akbarsha,
M. A.; Kole, N.; Biswas, B. Eur. J. Inorg. Chem. 2014, 2014, 3350−
3358.
(48) Maiti, M.; Sadhukhan, D.; Thakurta, S.; Roy, S.; Pilet, G.;
Butcher, R. J.; Nonat, A.; Charbonnier
2012, 51, 12176−12187.
(49) Wu, G.; Wang, X. F.; Okamura, T.; Sun, W. Y.; Ueyama, N.
Inorg. Chem. 2006, 45, 8523−8532.
̀
e, L. J.; Mitra, S. Inorg. Chem.
(50) Ciurtin, D. M.; Pschirer, N. G.; Smith, M. D.; Bunz, U. H. F.;
zur Loye, H. C. Chem. Mater. 2001, 13, 2743−2745.
(51) Dong, Y. B.; Wang, P.; Huang, R. Q.; Smith, M. D. Inorg. Chem.
2004, 43, 4727−4739.
(52) Ding, C. X.; Rui, X.; Wang, C.; Xie, Y. S. CrystEngComm 2014,
16, 1010−1019.
(53) Shi, X.; Zhu, G. S.; Fang, Q. R.; Wu, G.; Tian, G.; Wang, R. W.;
Zhang, D. L.; Xue, M.; S. Qiu, L. Eur. J. Inorg. Chem. 2004, 2004, 185−
191.
(54) Xu, C. Y.; Guo, Q. Q.; Wang, X. J.; Hou, H. W.; Fan, Y. T. Cryst.
Growth Des. 2011, 11, 1869−1879.
(55) Dong, B. X.; Xu, Q. Cryst. Growth Des. 2009, 9, 2776−2782.
(56) Wu, Y. H.; Chen, L.; Yu, J.; Tong, S. L.; Yan, Y. Dyes Pigm.
2013, 97, 423−428.
(57) Wen, L. L.; Dang, D. B.; Duan, C. Y.; Li, Y. Z.; Tian, Z. F.;
Meng, Q. J. Inorg. Chem. 2005, 44, 7161−7170.
(58) Zhang, Y. N.; Liu, P.; Wang, Y. Y.; Wu, L. Y.; Pang, L. Y.; Shi, Q.
Z. Cryst. Growth Des. 2011, 11, 1531−1541.
(59) Jin, F.; Wang, H. Z.; Zhang, Y.; Wang, Y.; Zhang, J.; Kong, L.;
Hao, F. Y.; Yang, J. X.; Wu, J. Y.; Tian, Y. P.; Zhou, H. P.
CrystEngComm 2013, 15, 3687−3695.
(60) Stylianou, K. C.; Heck, R.; Chong, S. Y.; Bacsa, J.; Jones, J. T. A.;
Khimyak, Y. Z.; Bradshaw, D.; Rosseinsky, M. J. J. Am. Chem. Soc.
2010, 132, 4119−4130.
(61) Crosby, G. A.; Demas, J. N. J. Phys. Chem. 1971, 75, 991−1024.
(62) Maxim, C.; Tuna, F.; Madalan, A. M.; Avarvari, N.; Andruh, M.
Cryst. Growth Des. 2012, 12, 1654−1665.
(63) Mandal, H.; Chakrabartty, S.; Ray, D. RSC Adv. 2014, 4,
65044−65055.
(64) Durai Murugan, K.; Natarajan, P. Eur. Polym. J. 2011, 47, 1664−
1675.
(65) Wang, X. M.; Wang, P.; Fan, R. Q.; Xu, M. Y.; Qiang, L. S.; Wei,
L. G.; Yang, Y. L.; Wang, Y. L. Dalton Trans. 2015, 44, 5179−5190.
(66) Hong, Y. N.; Lam, J. W. Y.; Tang, B. Z. Chem. Commun. 2009,
4332−4353.
(67) Shellaiah, M.; Wu, Y. H.; Singh, A.; Raju, M. V. R.; Lin, H. C. J.
Mater. Chem. A 2013, 1, 1310−1318.
M
DOI: 10.1021/acs.cgd.6b00347
Cryst. Growth Des. XXXX, XXX, XXX−XXX