Topological Evolution in Mercury(II) Schiff Base Complexes Tuned through Alkyl Substitution – Synthesis, Solid-State Structures, and Aggregation-Induced Emission Properties

Article abstract of DOI:10.1002/ejic.201600231

From two series of Schiff base ligands, (E)-N-(pyridine-2-yl)(CMe=NPhR) and (E)-N-(pyridine-2-yl)(CH=NPhR) [R = H, L1a, L1b; 2-CH₃, L2a, L2b; 4-CH₃, L3a, L3b; 2,6-(CH₃)₂, L4a, L4b; 2,6-(C₂H₅

Full text of DOI:10.1002/ejic.201600231

DOI: 10.1002/ejic.201600231
Full Paper
Luminescent Mercury Complexes
Topological Evolution in Mercury(II) Schiff Base Complexes
Tuned through Alkyl Substitution – Synthesis, Solid-State
Structures, and Aggregation-Induced Emission Properties
Yu-Wei Dong,[a] Rui-Qing Fan,*[a] Xin-Ming Wang,[a] Ping Wang,[a] Hui-Jie Zhang,[a]
Li-Guo Wei,[a] Yang Song,[a] Xi Du,[a] Wei Chen,[a] and Yu-Lin Yang*[a]
Abstract: From two series of Schiff base ligands, (E)-N-(pyrid- (PXRD). The crystal structures indicate that the position and
ine-2-yl)(CMe=NPhR) and (E)-N-(pyridine-2-yl)(CH=NPhR) [R = H, type of substituent can directly influence the formation of
L1a, L1b; 2-CH3, L2a, L2b; 4-CH3, L3a, L3b; 2,6-(CH3)2, L4a, L4b; 1D → 3D supramolecular metal–organic frameworks through
2,6-(C2H5)2, L5a, L5b; 2,6-(i-C3H7)2, L6a, L6b; 2,4,6-(CH3)3, L7a, C–H···Cl and π–π interactions. Complexes Hg1a–Hg7a and
L7b], fourteen mercury(II) complexes, namely, Hg1a–Hg7a and Hg1b–Hg7b display deep blue emissions at λ = 401–428 nm in
Hg1b–Hg7b were synthesized. Their structures were estab- acetonitrile solution and light blue emissions at λ = 443–
lished by single-crystal X-ray diffraction, and they were physi- 494 nm in the solid state. It is worth noting that Hg1a, Hg3a,
cally characterized by 1H and 13C NMR spectroscopy, ESI-MS, Hg1b, and Hg3b exhibit good aggregation-induced emission
FTIR spectroscopy, elemental analysis (EA), and powder XRD (AIE) properties in CH3CN/H2O solutions.
Introduction
rect crystal packing.[8] Hence, the major challenge in supramo-
lecular chemistry is the design and synthesis of organic ligands.
After almost a century since their discovery, Schiff base ligands
still play an important role in metal coordination chemistry, ow-
ing to their facile synthesis, remarkable versatility, and good
solubility in common solvents.[9] In general, compared with
rigid ligands, a metal-coordinated Schiff base ligand can more
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.
Supramolecular metal–organic frameworks (SMOFs)[1] have at-
tracted enormous attention because of their intriguing struc-
tures and wide potential applications in different areas such as
nonlinear optics, magnetism, photoluminescence, and electro-
chemistry.[2] SMOFs are the result of complementary interac-
tions between two or more components in a desired thermody-
namically favorable fashion through noncovalent interactions.
The type of noncovalent supramolecular interaction, such as
π–π stacking,[3] hydrogen bonding,[4] or secondary bonding in-
teractions (SBIs),[5] depends on the shape and functional groups
of the components that form the SMOF. Notably, appropriate
hydrogen-bonding and π–π stacking interactions can produce
the aggregation-induced emission (AIE) phenomenon, which
was first reported by Tang et al. in 2001.[6] Therefore, the real-
world applications of solid-state materials can be expanded sig-
nificantly if they exhibit aggregation-induced emission. These
functional materials are generally constructed from metal ions
and bridging organic ligands.[7] The ligand not only provides
capability for selective metal-ion coordination but also gener-
ates the desired noncovalent intermolecular interactions to di-
Owing to their applications in the paper industry, cosmetics,
paints, fluorescent lamps, sensors, and mercury batteries,[10]
mercury and its complexes are of immense importance in
chemistry and related disciplines. The spherical d10 configura-
tion of the mercury(II) ion is associated with a flexible coordina-
tion environment. Furthermore, owing to the lability of d10
metal complexes, the formation of coordination bonds is revers-
ible, and the metal ions and ligands can rearrange during the
supramolecular assembly to allow the formation of thermo-
dynamically more stable structures through the variation of the
coordination polyhedron and coordination number of the mer-
cury atom.[11]
Inspired by the above discussion, herein, two series of Schiff
base ligands, (E)-N-(pyridine-2-yl)(CMe=NPhR) and (E)-N-(pyr-
idine-2-yl)(CH=NPhR), which carry different alkyl substituents
on the phenyl rings (L1a–L7a and L1b–L7b, Scheme 1), have
been employed for the synthesis of mercury(II) complexes.
Fourteen mercury(II) complexes, namely, Hg1a–Hg7a and
Hg1b–Hg7b, were prepared through the reactions of the corre-
sponding ligands and HgCl2 in 1:1 molar ratios. Subsequently,
the structures of the ligands and mercury(II) complexes were
[a] MIIT Key Laboratory of Critical Materials Technology for New Energy
Conversion and Storage, School of Chemistry and Chemical Engineering,
Harbin Institute of Technology,
92, Xidazhi Street Nangang District, Harbin, 150001, P. R. China
E-mail: fanruiqing@hit.edu.cn
ylyang@hit.edu.cn
http://homepage.hit.edu.cn/pages/fanruiqing
http://homepage.hit.edu.cn/pages/yangyulin
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201600231.
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Scheme 1. Chemical structures and synthetic routes for Schiff base ligands (L1a–L7a and L1b–L7b) and mercury(II) complexes (Hg1a–Hg7a, Hg1b–Hg7b).
characterized through 1H and 13C NMR spectroscopy, ESI-MS, IR those of the corresponding ligands, and selected diagnostic
spectroscopy, elemental analysis (EA), and powder XRD (PXRD); bands are listed in the Exp. Section. In the IR spectra of ligands
ligands L3b and L6b and complexes Hg1a–Hg7a and Hg1b– L1a–L7a and L1b–L7b, the existence of C=N bonds is demon-
Hg7b were additionally characterized by single-crystal X-ray strated clearly by the presence of strong characteristic C=N
crystallography. Although the structure of Hg1b has been re- bands in the range ν = 1625–1669 cm–1. The negative shifts of
˜
ported by others recently, it is included herein for comprehen- these bands by 2–36 cm–1 in the spectra of the complexes may
sive comparison.[12] In this study, we investigated the effect of be attributed to the coordination of the nitrogen atom of the
related alkyl-substituted Schiff base ligands and intermolecular imine moiety to the metal ion.[13] This is further confirmed by
interactions (Hg···Cl secondary interactions, C–H···Cl hydrogen the presence of ν(M–N) vibrations in the region ν = 422–
˜
bonds, and π–π interactions) on the organization and stabiliza- 459 cm–1 in the spectra of all of the complexes.[14]
The 1H NMR spectra of the imine ligands L1a–L7a and L1b–
L7b as well as those of their mercury(II) complexes in CDCl3
were recorded at room temperature (Figures S3 and S4). In the
1H NMR spectra of the complexes, the chemical shifts are
slightly different from those observed for the non-coordinated
ligands. Of particular note are the Py-H6 resonances of Hg1a–
Hg7a and Hg1b–Hg7b, which are shifted downfield owing to
the coordination of the pyridine nitrogen atom to the mer-
cury(II) center. In the spectra of Hg1b–Hg7b, the resonance of
the imine proton is shifted downfield by at least 0.05 ppm.[15]
The position of the HC=N resonance is influenced by the alkyl
groups on the adjacent phenyl ring (Figure 1). For ligands L2b
and L4b–L7b in which the ring is substituted by one to three
methyl groups, 2,6-(C2H5)2, or 2,6-(iC3H7)2, the peak is generally
shifted upfield relative to that of L1b. Similarly, this peak is
shifted downfield for L3b with a 4-CH3 substituent on the
phenyl ring. This is most likely caused by the better electron-
donating ability and coplanarity in ligand L3b.
tion of SMOFs. Moreover, the influence of the substituent on
the photoluminescence of the compounds in CH3CN solution
and in the solid state are discussed. Complexes Hg1a, Hg3a,
Hg1b, and Hg3b exhibit AIE in CH3CN/H2O solutions.
Results and Discussion
Synthesis and Spectral Characterization
The fourteen imine ligands were prepared readily in one-step
procedures through the condensation of the pyridine aldehyde
derivative with the corresponding monamine in a 1:1 molar
ratio in anhydrous methanol/formic acid solution. Two pyridine
derivatives (2-acetylpyridine and 2-pyridinecarbaldehyde) and
seven different substituted anilines were investigated (see
Scheme 1). The recrystallization of L3b and L6b from n-hexane
provided yellow crystals suitable for X-ray analysis. The yields
of the fourteen imine ligands varied from 70 to 92 %. The com-
plexes (Hg1a–Hg7a and Hg1b–Hg7b) were prepared through
the reactions of HgCl2 and the corresponding imine ligands in
methanol or methanol/dichloromethane under reflux and ob-
tained as good-quality crystals in good yields. All of the com-
plexes in the solid state are stable upon extended exposure to
air. The complexes are soluble in common organic solvents,
such as chloroform, dimethyl sulfoxide, and acetonitrile.
In the 13C NMR spectra (Figures S5 and S6), the signals of
the C=N nuclei are observed at δ = 159.63–167.48 ppm. The
ESI-MS spectra (Figures S7 and S8) each exhibit an intense peak
at m/z = 183.09–552.74, which is assigned to [M + H]+. The
detailed data are listed in the Exp. Section. We performed pow-
der X-ray diffraction for Hg1a–Hg7a and Hg1b–Hg7b to check
the purity of the bulk products. In Figure S9, we can see that
The infrared spectra of Hg1a–Hg7a and Hg1b–Hg7b (see all major peak positions of the measured patterns are in good
Figures S1 and S2 in the Supporting Information) are similar to agreement with those simulated. Furthermore, the differences
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these complexes, single crystals were obtained and analyzed by
single-crystal X-ray diffraction.
Descriptions of the Structures
Structural Analysis of Hg1a–Hg7a
The coordination abilities of L1a–L7a were examined with mer-
cury dichloride. The crystallographic and structural determina-
tion data for complexes Hg1a–Hg7a are listed in Table S1. Se-
lected bond lengths and angles are summarized in Tables S2
and S3. The single-crystal X-ray diffraction analysis revealed that
complexes Hg1a–Hg7a have analogous structure units, as
shown in Figures 2 (a) and S10. In Hg1a–Hg7a, each asymmet-
ric unit consists of one crystallographically independent Hg2+
ion, one coordinated Schiff base ligand L1a–L7a, and two chlor-
ide ions. As the van der Waals radii of Hg and Cl are 1.70 and
1.80 Å,[16] respectively, any Hg···Cl distance less than 3.50 Å
and any Hg···Hg distance less than 3.4 Å may be considered
potentially significant. Therefore, we presume that Hg1a–Hg7a
form dimeric molecules through secondary Hg···Cl interactions
(the Hg···Cl distances are in the range 2.864–3.260 Å, Table 1);
no efficient d10···d10 weak interactions were observed (the
Hg···Hg distances are in the range 3.837–4.133 Å, Table 1). If the
secondary Hg···Cl interactions are included in the coordination
spheres of the mercury(II) ions, the five-coordinate geometry
indices, τ5, as defined by Addison and Reedijk,[17] are 0.020–
0.475 for Hg1a–Hg7a; therefore, the coordination geometries
are best described as pseudo-square-pyramidal (SQP).[18] In
Hg1a–Hg7a, the pyridyl and phenyl rings of the corresponding
ligands L1a–L7a are severely twisted, and the dihedral angles
are close to 90° (72.279–89.145°, Table 1).
For Hg1a, secondary Hg···Cl interactions with a distance of
2.888 Å and C–H···Cl (the H3A···Cl1 and H5A···Cl1 distances are
2.901 and 2.735 Å, respectively) hydrogen-bond interactions[19]
link the adjacent molecules to form 1D chains. These 1D chains
are further assembled into a 3D supramolecular network
through π–π stacking interactions (the centroid–centroid dis-
tances are 3.464 and 3.831 Å), as shown in Figure S11a. How-
ever, the mononuclear molecules of Hg3a are assembled into a
Figure 1. Change in chemical shift for the imine proton for (a) L1b–L7b and
(b) Hg1b–Hg7b.
in intensity may be due to the preferred orientation of the crys- 2D supramolecular layer through intermolecular H3A···Cl2,
tal products. These observations are consistent with the crystal H4A···Cl1, and H5A···Cl2 hydrogen bonds (see Table S4) as well
structures (see below). To further understand the structures of as secondary Hg···Cl interactions. Moreover, interlayer π–π
Figure 2. Molecular structures of (a) Hg1a and (b) Hg1b showing 50 % probability ellipsoids and the crystallographic numbering scheme.
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Table 1. Structural and geometrical parameters for Hg1a–Hg7a and Hg1b–Hg7b.
Complex
Coordination geometry
Addison parameter Hg···Cl bond length [Å] Hg···Hg bond length [Å] Dihedral angle [°][a] Dimensionality
(τ)
Hg1a
Hg2a
Hg3a
Hg4a
Hg5a
Hg6a
Hg7a
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
trigonal pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-square-pyramidal
pseudo-trigonal-bipyramidal
0.475
0.020
0.462
0.370
0.099
0.117
0.420
0.401
0.291
0.017
0.751
0.263
0.198
0.220
0.064
0.508
2.888(3)
3.032(2)
3.032(7)
2.997(6)
2.864(1)
3.070(1)
3.260(1)
3.146(1)
2.881(1)
3.098(8)
3.559(7)
3.458(7)
3.064(4)
3.199(5)
3.018(6)
3.078(5)
3.936(4)
3.837(3)
4.042(1)
4.101(9)
3.860(1)
4.133(2)
4.103(1)
4.048(2)
4.066(2)
4.178(1)
4.636(1)
–
78.786
77.250
72.279
78.034
89.145
83.512
80.044
78.999
11.760
47.736
7.152
3D
2D
3D
2D
2D
2D
1D
–
3D
1D
3D
–
Hg1b
Hg2b
Hg3b
7.860
Hg4b
Hg5b
Hg6b
Hg7b
4.065(9)
4.202(9)
4.052(9)
4.042(7)
75.501
69.377
88.005
83.483
1D
1D
1D
1D
[a] Between the pyridyl ring and phenyl ring.
stacking interactions with centroid–centroid distances of coordination bonds of the central ions (see Table S3) have small
3.690 Å between the two pyridine rings link the adjacent coor- differences. In Hg7a, the mercury(II) ions are pseudo-five-coor-
dination layers to form a 3D network (Figure S11b). In this case, dinate with distorted square-pyramidal coordination geometry
if the secondary Hg···Cl, C–H···Cl hydrogen-bond, and π–π in- and the trigonality indices τ = 0.420 (Hg1) and 0.401 (Hg2). The
teractions are regarded as the linkers, and each mononuclear dihedral angles between the pyridyl rings and the phenyl rings
unit is viewed as the node,[20] the simplified topological repre- in molecules I and II are 80.044 and 78.999°, respectively
sentations of Hg1a and Hg3a can be described as 3D diamond- (Table 1). Meanwhile, the steric arrangements in the crystal are
like architectures with point symbol 66, as shown in Fig- slightly different (Figure 4, c and d). In molecule I, long-distance
ures S11c and S11d, respectively.
interactions exist between each metal center and the chloride
ions of a neighboring [Hg(L7a)Cl2] unit, and the corresponding
Hg1···Cl2a (1 – x, 1 – y, 1 – z) distance is 3.260 Å, which is close
to the sum of the van der Waals radii of Hg and Cl (3.50 Å);
however, the Hg1···Hg1a distance of 4.103 Å yields inefficient
M···M interactions.[21] However, in molecule II, the Hg2···Cl4a
distance of 3.146 Å and the Hg2···Hg2a distance of 4.048 Å
indicate that the interactions between the [Hg(L7a)Cl2] units
are slightly stronger than those in I. The dimers of I and II are
assembled through intermolecular C2–H2A···Cl2 (2.712 Å), C5–
In contrast to Hg1a and Hg3a, owing to the bigger steric
hindrance of the 2-CH3, 2,6-(CH3)2, 2,6-(C2H5)2, and 2,6-(i-C3H7)2
substituents of the phenyl rings, the mononuclear molecules of
Hg2a and Hg4a–Hg6a are assembled into different 2D bilayers
(Figure 3) through noncovalent interactions (i.e., C–H···Cl
hydrogen bonds and π–π stacking) and secondary Hg···Cl inter-
actions only, and the 2D topological views are shown in Fig-
ure S12. Complex Hg7a displays two dimers (enantiomeric
forms I and II, see Figure 4, parts a and b) of identical composi-
tion in the crystal but with different behaviors. Each type is
composed of centrosymmetric [Hg(L7a)Cl2]2 dimers, which are
linked by a Hg–Cl2–Hg bridge. The lengths and angles of the
Figure 4. Molecular structure of Hg7a showing the crystallographic number-
ing schemes of (a) I and (b) II. The 1D arrangements of (c) I and (d) II type
molecules (different colors are used to distinguish I and II).
Figure 3. The 2D layer structures in (a) Hg2a, (b) Hg4a, (c) Hg5a, and (d)
Hg6a. The dotted lines represent the C–H···Cl and π–π interactions.
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H5A···Cl1 (2.709 Å), C18–H18A···Cl3 (2.815 Å), and C21–
The pyridyl and phenyl rings of the corresponding ligands in
H21A···Cl4 (2.669 Å) hydrogen bonds to form two different 1D Hg1b and Hg3b are arranged in a nearly parallel fashion
ladder-shaped chains, as shown in Figure 5 (c and d). As shown (11.760 vs. 7.152/7.860°). Nevertheless, in Hg2b and Hg4b–
in Figure S13, C–H···π interactions in Hg2a, Hg4a, and Hg6b Hg7b, the dihedral angles between the pyridyl and phenyl rings
provide further stabilization. The details of the C–H···Cl are in the range 47.736–88.005° (Table 1) and are severely
hydrogen-bond, π–π stacking, and C–H···π interactions for twisted compared with those in Hg1b and Hg3b. Supramolec-
Hg1a–Hg7a are summarized in Table S4.
ular structure analyses revealed that the mononuclear units of
Hg1b–Hg7b are further connected into 3D networks (in Hg1b
and Hg3b) and 1D chains (in Hg2b and Hg4b–Hg7b) through
noncovalent interactions, such as C–H···Cl/π–π and secondary
Hg···Cl interactions. Clearly, these results show that the substit-
uents play critical roles in directing the supramolecular assem-
blies of these complexes. The details of the C–H···Cl hydrogen
bonds and π–π stacking interactions for the complexes Hg1b–
Hg7b are summarized in Table S4. As shown in Figure 5 (a), the
mononuclear [HgL1bCl2] units are linked by intermolecular
C–H···Cl hydrogen-bond interactions (the H5A···Cl1, H5A···Cl2,
and H6A···Cl2 distances are 2.914, 2.893, and 2.900 Å, respec-
tively) and secondary Hg···Cl interactions with a distance of
2.881 Å to form a 2D layer structure. Then, the 2D layers further
extend into 3D five-connected bnn supramolecular structures
through π–π stacking interactions (3.951 Å). In Hg3b, in addi-
tion to π–π stacking interactions, intermolecular C–H···Cl and
secondary Hg···Cl interactions assemble the mononuclear mol-
ecules into a 3D supramolecular network (Figure 5, b). The over-
all topologies of Hg1b and Hg3b can be reduced to 3D archi-
tectures with point symbols (46·64) and (69·8), as illustrated in
Figure 5 (c and d), respectively. In contrast to Hg1b and Hg3b,
complexes Hg2b and Hg4b–Hg7b only form 1D chains (Fig-
ure S15) owing to the steric effects of the substituents. The
C–H···π interactions in Hg4b–Hg7b also provide further stabili-
zation (Figure S16).
Figure 5. The 3D network structures in (a) Hg1b and (b) Hg3b. The dotted
lines represent the C–H···Cl and π–π interactions. Topological views of the
3D network structures of (c) Hg1b and (d) Hg3b.
Structural Analysis of Hg1b–Hg7b
The structures of Hg2b–Hg7b were determined in the present
study and reveal a variety of structural motifs; the structure of
Hg1b was briefly reported previously but is included in the
discussion here for completeness. The crystallographic data for
Hg1b–Hg7b are listed in Table S1. Selected bond lengths and
angles are summarized in Tables S2 and S3. After recrystalliza-
tion from n-hexane, yellow block crystals of ligands L3b and
L6b were obtained. The N2–C6 bond lengths of 1.262(2) Å (L3b)
and 1.263(1) Å (L6b) indicate C=N double-bond character.[22]
The N1–C1–C6–N2 torsion angles of 12(3)/–4(3)° (Hg3b) and
–4.4(6)° (Hg6b) are twisted compared with those for the free
ligands L3b [–176.9(17)°] and L6b [–176.5(14)°], as shown in
Table S5. This can be explained by the stabilization of the struc-
ture through the coordination interaction. As shown in Fig-
ures 2 (b) and S14, secondary Hg···Cl interactions exist in all of
these structures except for Hg3b, and the corresponding Hg···Cl
distances are listed in Table 1. In Hg1b, Hg2b, and Hg4b–Hg6b,
the Hg cations are in pseudo-square-pyramidal coordination
environments with τ5 values in the range 0.017–0.291 (Table 1).
However, in Hg7b, the Hg cation is in a pseudo-trigonal-bi-
pyramidal environment (τ5 = 0.508) with atoms N1, Cl1, and Cl2
in the equatorial positions and the axial sites occupied by
atoms N2 and Cl1a. An interesting result was obtained for
Hg3b, namely, two independent [HgL3bCl2] molecules were
Photoluminescence Studies
Absorption and Solution Luminescence Properties of the
Mercury(II) Complexes in CH3CN
The UV/Vis absorption spectra of Hg1a–Hg7a and Hg1b–Hg7b
in CH3CN (10 μmol L–1) were recorded at room temperature
(Figure 6). As the molecules have similar structures, the UV/
Vis spectra are similar. All of the spectra exhibit two distinct
absorption bands in the range λ = 250 to 450 nm (ε = 2962–
45710
M
–1 cm–1). The maximum absorption wavelengths and
molar extinction coefficients (ε) are listed in Table 2. The high-
energy bands at λ ≈ 274–285 nm are assigned to the π–π*
transitions of the C=N chromophores, whereas the low-energy
bands at λ ≈ 330–360 nm are attributed to n–π* transitions,[24]
in accordance with previous studies of Schiff base complexes.
The introduction of electron-donating groups (–CH3 in the alde-
hyde or alkyl groups in the aniline) results in slight batho-
chromic shifts of the absorption bands.
Upon excitation in the UV domain (λ ≈ 340 nm), the fourteen
found. The Hg1···Cl4 distance of 3.559 Å is above the sum of the complexes give rise to blue luminescence. The excitation spec-
van der Waals radii (1.70 + 1.80 = 3.50 Å); thus, the coordination tra of Hg1a–Hg7a and Hg1b–Hg7b are dominated by two
geometries around the Hg1 and Hg2 atoms can be better de- intense bands centered at λ = 275 nm and λ ≈ 350–370 nm,
scribed as trigonal pyramidal (τ4 = 0.751)[23] and pseudo- respectively (Figure S17). Excitation at the maximum of the low-
square-pyramidal (τ5 = 0.263), respectively. The Hg···Hg distan- energy excitation band resulted in the observation of emission
ces of 4.042–4.636 Å show no weak d10···d10 interactions.
bands with maxima at λ = 413–428 and 401–425 nm for Hg1a–
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Table 2. Photophysical properties of Hg1a–Hg7a, Hg1b–Hg7b.
Complex Absorption[a]
Photoluminescence in acetonitrile
Photoluminescence in the solid state
–1 cm–1
)
λex [nm] λem [nm]
FWHM [nm]
τ [μs]
ΦPL
λex [nm]
λem [nm]
FWHM [nm]
τ [μs]
[b]
λabs [nm] (ε,
M
Hg1a
Hg2a
Hg3a
Hg4a
Hg5a
Hg6a
Hg7a
Hg1b
Hg2b
Hg3b
Hg4b
Hg5b
Hg6b
Hg7b
279 (22615), 346 (4436)
283 (23503), 354 (7516)
285 (33380), 356 (2962)
285 (42395), 356 (7845)
284 (26510), 360 (4410)
283 (45710), 356 (19490)
285 (33160), 360 (14440)
275 (15089), 330 (3067)
280 (29977), 336 (12742)
283 (32280), 331 (27135)
282 (14865), 346 (5505)
274 (27172), 340 (3697)
274 (32910), 340 (3922)
281 (29760), 345 (12757)
366
374
375
374
373
374
374
349
340
340
339
342
339
339
413
425
428
425
423
426
428
406
402
425
401
416
411
416
68.98
66.29
79.29
61.32
66.87
66.17
68.68
58.99
58.49
60.21
61.49
68.99
63.20
65.67
5.27
7.28
7.23
7.01
6.69
7.27
7.29
4.03
4.65
8.64
4.96
7.48
5.44
4.88
0.012
0.019
0.022
0.028
0.020
0.018
0.033
0.029
0.021
0.040
0.022
0.016
0.018
0.025
390
384
373
388
380
368
396
351
358
383
378
358
347
352
454
456
456
480
470
465
494
443
456
480
472
469
466
482
112.75
114.68
103.36
128.18
115.10
134.20
126.15
143.72
149.38
74.41
8.91
9.09
8.00
9.23
7.82
7.73
7.77
8.25
7.47
9.71
7.45
9.53
7.26
7.13
105.96
132.78
153.32
145.84
[a] Measured in CH3CN solution (ca. 1 × 10–5 ). [b] Quinine sulfate in 0.1 mol L–1 H2SO4 as reference (ΦPL = 0.546, λex = 350 nm).
M
(ΦF) are in the range 0.012–0.040 (Table 2), as measured with
quinine sulfate as a reference (ΦPL = 0.546 at λ = 350 nm); this
may be related to the heavy-atom effect.[25] However, Hg1b and
Hg3b exhibit moderately strong emission yields, which may be
derived from the better planarity of the Schiff base ligands in
these complexes (dihedral angles: 11.760° for Hg1b, 7.152 and
7.860° for Hg3b).
Figure 7. Emission spectra of (a) Hg1a–Hg7a and (b) Hg1b–Hg7b in aceto-
nitrile solution at 298 K. CIE chromaticity diagrams (1931 CIE standard) for (c)
Hg1a–Hg7a and (d) Hg1b–Hg7b.
Solid-State Luminescence Properties of the Mercury(II)
Complexes
Figure 6. UV/Vis absorption spectra of (a) Hg1a–Hg7a and (b) Hg1b–Hg7b
in acetonitrile solution at room temperature.
The emission data for Hg1a–Hg7a and Hg1b–Hg7b in the solid
state are summarized in Table 2. Upon excitation at λ ≈ 350 nm
Hg7a and Hg1b–Hg7b, respectively, (Figure 7, a and b). These (Figure S18), Hg1a–Hg7a display light blue emission with max-
bands exhibit blue luminescence, as shown in Figure 7, c and ima at λ = 454, 456, 456, 480, 470, 465, and 494 nm, respectively
d, and the Commission Internationale d'Eclairage (CIE) coordi- (Figures 8, a, and S19). These emission bands can be assigned
nates are summarized in Table S6. The effects of the ligand to the π*–π transitions of the corresponding Schiff base li-
structure on the luminescence properties will be discussed in gands.[26] The electron-donating ability of the substituents va-
detail below. In general, the complexes are weakly emissive in ries in the order H < i-C3H7 < C2H5 < CH3, and the emission
CH3CN solution, and their luminescence quantum yield values wavelength of the complexes varies in the order Hg1a
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(H) < Hg2a (2-CH3), Hg3a (4-CH3) < Hg4a [2,6-(CH3)2] < Hg7a Table S8. This emission spectra of frozen solutions (77 K) of the
[2,4,6-(CH3)3],
and
Hg6a
[2,6-(i-C3H7)2] < Hg5a
[2,6- complexes demonstrate that the luminescence of the com-
(C2H5)2] < Hg4a [2,6-(CH3)2], according to the classification of plexes is triplet-based.[31] A general trend is that the emission
the substituents. The electron-donating effect decreased the lifetime in the solid state (τ = 7.73–9.23 μs for Hg1a–Hg7a; τ =
energy difference between the highest occupied molecular or- 7.13–9.71 μs for Hg1b–Hg7b) is longer than that in CH3CN solu-
bital (HOMO) and the lowest unoccupied molecular orbital tion (τ = 5.27–7.29 μs for Hg1a–Hg7a; τ = 4.03–8.64 μs for
[27]
(LUMO) and led to redshifted λEm
.
The emission spectra of Hg1b–Hg7b); this might be explained by the occurrence of ad-
Hg1b–Hg7b also reveal this trend with maxima at λ = 443, 456, ditional nonradiative deactivation processes in CH3CN solu-
480, 472, 469, 466, and 482 nm, respectively (Figure 8, b). In tion.[32]
this study, we successfully synthesized two sets of complexes,
that is, those with “–CMe=N–” moieties and those with “–CH=
AIE Properties of Hg1a, Hg3a, Hg1b, and Hg3b
Among the fourteen complexes, Hg1a, Hg3a, Hg1b, and Hg3b
exhibit naked-eye-visible brilliant blue emission in the solid
state when irradiated with UV light (insets of Figure 8) but they
show very weak emission in CH3CN. These complexes are solu-
ble in common organic solvents such as chloroform, dimethyl
sulfoxide, and acetonitrile but insoluble in water. A different
amount of water (fw in the range 0–90 %) was titrated gradually
to the acetonitrile solutions of Hg1a, Hg3a, Hg1b, and Hg3b
with the overall concentration of the solution kept at
10 μmol L–1. Interestingly, the luminescence intensities of Hg1a,
Hg3a, Hg1b, and Hg3b were enhanced and exhibited spectral
shifts owing to their aggregated nature. Hence, we proceeded
to analyze the AIE further.
N–” moieties. We found that the former (Hg1a–Hg7a) have
longer emission wavelengths than the latter (Hg1b–Hg7b) ow-
ing to the introduction of a –CH3 group to the aldehyde. This
confirms that the different substituents have an influence on
the electronic structure and produce different optical proper-
ties. Interestingly, Hg3b emits bright blue-green luminescence
at λEm = 480 nm when irradiated at λ = 365 nm (inset of Fig-
ure 8, b). This phenomenon can be explained by the better
planarity of L3b in complex Hg3b.[28] In the solid state, the
maxima of the emission wavelengths for the mercury(II) com-
plexes are redshifted compared with those in acetonitrile solu-
tions; this may be caused by the formation of C–H···Cl hydrogen
bonds and π–π stacking interactions in the solid state, which
can effectively decrease the HOMO–LUMO energy gap and in-
As shown in Figure 9, upon the titration of water (fw from 0
fluence the ligand-centered π*–π transitions.[29] Meanwhile, the to 90 %) into acetonitrile solutions of Hg1a, Hg3a, Hg1b, and
full width at half-maximum (FWHM) values of the emission Hg3b, the luminescence peaks were gradually enhanced and
bands increase from the solid state to acetonitrile solution redshifted. Plots of the emission enhancement versus fw are
(Table 2).
depicted in the insets of Figure 9. The emission intensities in
the CH3CN/H2O mixtures with fw = 90 % are ca. 14.1, 13.2, 15.2,
and 38.9 times higher than those in pure CH3CN solution for
Hg1a, Hg3a, Hg1b, and Hg3b, respectively; therefore, these
complexes have AIE activity. Moreover, the increasing lumines-
cence intensity of these complexes with a redshift was caused
by the aggregation effect, and the luminescence band of Hg1a
shifted from λ = 413 to 423 nm (428→440 nm, Hg3a;
Figure 8. Emission spectra of (a) Hg1a–Hg7a and (b) Hg1b–Hg7b in the solid
state at 298 K.
In addition, the luminescence decay profiles of Hg1a–Hg7a
and Hg1b–Hg7b (Figures S20–S21) were investigated. The
emission lifetimes for Hg1a–Hg7a and Hg1b–Hg7b are in the
microsecond range (Table S7). These values indicate that the
heavy-atom effect (chlorine) on the molecular skeleton induces
a higher intersystem crossing (ISC) efficiency, which results in a
decrease of the emission from the singlet state owing to the
population of the triplet state.[30] Low-temperature measure-
ments of the emission spectra at 77 K were necessary to further
confirm this hypothesis. Compared with emission spectra at
298 K, the emission spectra at 77 K (Figures S22–S23) are red-
shifted by ca. 25–113 nm. The detailed data are listed in
Figure 9. Changes in emission intensities of (a) Hg1a, (b) Hg3a, (c) Hg1b, and
(d) Hg3b (10 μM) in CH3CN solutions titrated with water (0–90 % v/v) at room
temperature. Inset: Plot of I/I0–1 versus fw; I0 is the PL intensity in pure CH3CN
solution; photos of complexes in CH3CN/H2O mixtures (fw = 0 and 90 % v/v)
under UV illumination (365 nm).
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406→424 nm, Hg1b; 425→442 nm, Hg3b). Compared with the essential roles in the construction of 1D to 3D supramolecular
emission spectra of Hg1a, Hg3a, Hg1b, and Hg3b in CH3CN structures. This study clearly demonstrated that –H and 4-CH3
solution, the solid emission spectra show redshifted emission substituents in the phenyl ring can lead to 3D supramolecular
by 28–55 nm, and the solid-state emission intensities of these structures (Hg1a, Hg3a, Hg1b, and Hg3b), whereas large sub-
four complexes are at least ten times (11.3, Hg1a; 12.5, Hg3a; stituents such as 2-CH3, 2,6-(CH3)2, 2,6-(C2H5)2, 2,6-(i-C3H7)2, and
10.5, Hg1b; 25.9, Hg3b) higher than those in pure CH3CN solu- 2,4,6-(CH3)3 readily form 2D (Hg2a, Hg4a–Hg6a) or 1D (Hg7a,
tion (Figure S24).
Hg2b, Hg4b–Hg7b) SMOFs. Upon irradiation with UV light,
Hg1a–Hg7a and Hg1b–Hg7b display deep blue emission at λ =
401–428 nm in acetonitrile solution and light blue emissions
at λ = 443–494 nm in the solid state. The photoluminescence
properties of mercury(II) Schiff base complexes can be tuned
finely and predictably over a wide range of wavelengths
through small and readily implemented changes to the ligand
structure. By modifying the phenyl moiety with electron-donat-
ing substituents, the energy difference between the HOMO and
LUMO decreases, and the emissions are redshifted accordingly.
It is worth noting that Hg1a, Hg3a, Hg1b, and Hg3b exhibit
good aggregation-induced emission (AIE) properties in CH3CN/
H2O mixtures; in particular, the emission intensity of Hg3b with
fw = 90 % is ca. 39.9 times higher than that in pure CH3CN.
We performed another experiment in which the emission
spectra of Hg1a, Hg3a, Hg1b, and Hg3b at different concentra-
tions in CH3CN were recorded (Figure S25). It can be clearly
seen that the CH3CN solutions with low concentrations (c =
10–5
M) were almost nonemissive, and the fluorescence spectra
were nearly parallel to the abscissa. However, the fluorescence
intensities increased abruptly when the concentrations were
higher than 10–3
M M, the
. As the concentrations reached 10–1
emission intensities were approximately 8.4–18.9 times higher
than for the molecularly dispersed species in CH3CN for Hg1a,
Hg3a, Hg1b, and Hg3b. The emission maxima were redshifted
by 19–35 nm. These results indicate that these complexes are
indeed weak emitters in dilute solution and exhibit properties
close to those described for the aggregation-induced emission
concept.[33] As reported previously,[34] the AIE mechanism of
these complexes possibly arises from the restriction of intramo-
lecular rotation. In the CH3CN/H2O (10:90 v/v) mixture, most of
the molecules aggregate together rapidly through the inter-
molecular C–H···Cl hydrogen bonding and π–π stacking interac-
tions between adjacent pyridyl and phenyl rings, such that free
rotations are hindered and the rigidity of the molecules is in-
creased further to generate a more extended planar skeleton,
which might influence the luminescence.[35] However, our ob-
servations of AIE in the luminescence spectra of Hg1a, Hg3a,
Hg1b, and Hg3b suggests that both the enhancement and red-
shift caused by aggregation probably originate from the sup-
pression of twisted intramolecular charge transfer. The above
justification was also well supported by similar reports of AIE.[36]
As shown in Table 2, Hg1a and Hg3a have twisted conforma-
tions with larger torsion angles between the pyridyl and phenyl
rings (78.786 and 72.279°, respectively) than those of Hg1b and
Hg3b (11.760 and 7.152/7.860°, respectively). The distorted con-
formations decrease the planarity and conjugation of the whole
molecules and, thus, boost the energy level of the excited state.
As a result, Hg1a and Hg3a exhibit weaker AIE behavior than
Hg1b and Hg3b. Complexes with these AIE effects can be ap-
plied extensively as solid-state emission materials.
Experimental Section
Materials and Instrumentation: Caution! Compounds of mercury
are extremely toxic, and appropriate handling conditions should be
used for their generation and disposal. All reagents and solvents were
purchased from commercial sources and used without further puri-
fication. Elemental analyses were performed with a Perkin–Elmer
2400 automatic analyzer. The FTIR spectra (4000–400 cm–1) were
recorded with a Nicolet impact 410 FTIR spectrometer. The 1H NMR
spectra were obtained with a Bruker Avance 400 MHz spectrometer
with Si(CH3)4 as an internal standard. The 13C NMR (150 MHz) spec-
tra were recorded with a Bruker Avance-600 spectrometer. The MS
(ESI) spectra were recorded with a Bruker Esquire LC mass spec-
trometer. The PXRD patterns were recorded in the 2θ range 5–50°
with Cu-Kα radiation with a Shimadzu XRD-6000 X-ray diffractome-
ter. A Perkin–Elmer Lambda 35 spectrometer was used to record
the UV/Vis absorption spectra of the ligands and complexes. The
emission luminescence and lifetime properties were recorded with
an Edinburgh Instruments FLS 920 fluorescence spectrometer. Life-
time studies were performed with a 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 curves were fitted to a double exponential function:[37] I(t) =
A1 exp(–t/τ1) + A2 exp(–t/τ2), in which I is the luminescence inten-
sity, and τ1 and τ2 are the lifetimes for the exponential components.
The average lifetimes were calculated with Equation (1).
Conclusions
(1)
Two series of Schiff base ligands, (E)-N-(pyridine-2-yl)(CMe=
NPhR) and (E)-N-(pyridine-2-yl)(CH=NPhR), were used to synthe-
size fourteen mercury(II) complexes Hg1a–Hg7a and Hg1b–
Hg7b. These complexes are excellent models for investigating
the effects of the alkyl substituents [–H, 2-CH3, 4-CH3, 2,6-
(CH3)2, 2,6-(C2H5)2, 2,6-(i-C3H7)2, and 2,4,6-(CH3)3] on the supra-
molecular metal–organic frameworks (SMOFs) and their photo-
luminescence properties. The crystal structures of these com-
plexes indicate that intermolecular interactions, such as second-
Quinine sulfate in 0.1
M H2SO4 (quantum yield 0.54 at 350 nm) was
chosen as the standard.[38] The absolute values were calculated
from the fixed and known fluorescence quantum yield of the stan-
dard reference sample through Equation (2).
(2)
In Equation (2), Q is the quantum yield, I is the measured integrated
ary Hg···Cl, C–H···Cl hydrogen-bond, and π–π interactions, play emission intensity, n is the refractive index, and OD is the optical
Eur. J. Inorg. Chem. 2016, 3598–3610
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density. The subscript R refers to the reference fluorophore of
121.64, 118.47, 114.90, 17.82, 16.56 ppm. MS (ESI): m/z = 211.12
known quantum yield. To minimize reabsorption effects, absorben- [M + H]+.
cies in the 10 mm fluorescence cuvette were kept under 0.05 at the
(E)-4-Methyl-N-[(pyridin-2-yl)ethylidene]aniline (L3a): 2-Acetyl-
excitation wavelength (350 nm).
pyridine (1.57 mL, 14.00 mmol) and 4-methylaniline (1.56 mL,
14.00 mmol) afforded the product (2.25 g, yield 76 %). C14H14N2
(210.28): calcd. C 79.97, H 6.71, N 13.32; found C 79.94, H 6.75, N
X-ray Crystallography: Suitable crystals of L3b, L6b, Hg1a–Hg7a,
and Hg1b–Hg7b were selected, mounted, and studied with a Rig-
aku R-AXIS RAPID IP diffractometer. The diffraction data were col-
13.35. FTIR (KBr): ν = 3433 (w), 3054 (w), 2921 (w), 2862 (w), 1639
˜
lected with graphite-monochromated Mo-Kα radiation (λ
=
(s), 1584 (m), 1568 (m), 1517 (s), 1506 (s), 1466 (m), 1436 (m), 1358
(s), 1298 (m), 1282 (s), 1239 (m), 1219 (m), 1179 (w), 1149 (w), 1104
(s), 1044 (m), 1019 (w), 995 (m), 955 (m), 843 (m), 815 (m), 782 (m),
0.71073 Å). The structures were solved with direct methods[39] and
refined with full-matrix least-squares techniques on F2. All hydrogen
atoms were constrained in geometric positions to their parent at-
oms, and non-hydrogen atoms were refined anisotropically. The de-
tailed crystal structure refinement data are given in Table S1, and
selected bond lengths and angles are listed in Tables S2 and S3.
1
743 (w), 709 (w), 621 (w), 590 (m), 575 (w), 507 (m) cm–1. H NMR
(400 MHz, CDCl3): δ = 8.72 (d, 1 H, Py-H6), 8.08 (d, 1 H, Py-H3), 7.86
(m, 1 H, Py-H4), 7.50 (m, 1 H, Py-H5), 6.64–7.00 (m, 4 H, Ph-H2,3,5,6),
2.76 (s, 3 H, CH3), 2.26 (s, 3 H, Ph-CH3) ppm. 13C NMR (150 MHz,
CDCl3): δ = 162.47, 158.96, 149.91, 143.78, 137.67, 129.74, 127.79,
122.36, 119.66, 115.26, 20.45, 16.36 ppm. MS (ESI): m/z = 211.12
[M + H]+.
CCDC 1442117 (for Hg1a), 1442118 (for Hg2a), 1442119 (for Hg3a),
1442120 (for Hg4a), 1442121 (for Hg5a), 1442122 (for Hg6a),
1442123 (for Hg7a), 1442124 (for Hg2b), 1442125 (for Hg3b),
1442126 (for Hg4b), 1442127 (for Hg5b), 1442128 (for Hg6b),
1442129 (for Hg7b), 1442130 (for L3b), and 1442131 (for L6b) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre.
(E)-2,6-Dimethyl-N-[(pyridin-2-yl)ethylidene]aniline (L4a): 2-
Acetylpyridine (1.09 mL, 9.71 mmol) and 2,6-dimethylaniline
(1.20 mL, 9.73 mmol) afforded the product (1.76 g, yield 81 %).
C15H16N2 (224.31): calcd. C 80.32, H 7.19, N 12.49; found C 80.27, H
7.18, N 12.52. FTIR (KBr): ν = 3436 (w), 3053 (w), 2919 (w), 2855 (w),
˜
1650 (s), 1584 (w), 1569 (w), 1478 (m), 1437 (m), 1357 (m), 1297 (w),
1282 (m), 1239 (m), 1148 (w), 1100 (m), 1044 (w), 995 (w), 954 (w),
897 (w), 780 (m), 760 (m), 738 (w), 683 (w), 623 (w), 590 (m), 544
General Synthesis of Ligands: 2-Acetylpyridine in anhydrous
methanol (10 mL) and the respective aniline derivative (aniline,
2-methylaniline, 4-methylaniline, 2,6-dimethylaniline, 2,6-diethyl-
aniline, 2,6-diisopropylaniline, or 2,4,6-trimethylaniline; 1 equiv.) in
anhydrous methanol (10 mL) were mixed. The resultant solutions
were heated under reflux for ca. 8–12 h and subsequently concen-
trated under reduced pressure to obtain L1a–L7a as brown oil-like
crude products. The procedure for L1b–L7b was similar to that for
L1a–L7a, except that 2-pyridinecarbaldehyde was used instead of
2-acetylpyridine. Ligands L1b and L2b were yellow oils, and L3b–
L7b were yellow powders. Ligands L3b and L6b were recrystallized
from n-hexane/dichloromethane and n-hexane to afford yellow
crystals.
1
(w), 491 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.72 (d, 1 H, Py-
H6), 8.06 (d, 1 H, Py-H3), 7.85 (m, 1 H, Py-H4), 7.49 (m, 1 H, Py-H5),
6.67–6.98 (m, 3 H, Ph-H3,4,5), 2.77 (s, 3 H, CH3), 2.21 (s, 6 H, Ph-CH3)
ppm. 13C NMR (150 MHz, CDCl3): δ = 167.20, 153.46, 148.93, 142.77,
136.78, 128.19, 127.88, 127.06, 121.54, 117.84, 17.55, 16.61 ppm. MS
(ESI): m/z = 225.14 [M + H]+.
(E)-2,6-Diethyl-N-[(pyridin-2-yl)ethylidene]aniline (L5a): 2-Acet-
ylpyridine (1.44 mL, 12.86 mmol) and 2,6-diethylaniline (2.14 mL,
12.89 mmol) afforded the product (2.77 g, yield 85 %). C17H20N2
(252.36): calcd. C 80.91, H 7.99, N 11.10; found C 80.88, H 7.87, N
11.16. FTIR (KBr): ν = 3434 (w), 3056 (w), 2934 (w), 2873 (w), 1653
N-[(Pyridin-2-yl)ethylidene]aniline
(1.58 mL, 14.13 mmol) and aniline (1.29 mL, 14.15 mmol) afforded
the product (2.53 g, yield 91 %). C13H12N2 (196.25): calcd. C 79.56,
H 6.16, N 14.27; found C 79.61, H 6.15, N 14.23. FTIR (KBr): ν = 3434
(L1a):
2-Acetylpyridine
˜
(s), 1583 (m), 1569 (w), 1456 (s), 1357 (s), 1297 (m), 1282 (s), 1239
(m), 1149 (w), 1101 (m), 1059 (w), 1043 (w), 1020 (w), 996 (w), 954
(w), 901 (w), 780 (m), 744 (m), 622 (w), 590 (m), 539 (w), 474 (w)
˜
1
cm–1. H NMR (400 MHz, CDCl3): δ = 8.75 (d, 1 H, Py-H6), 8.12 (d, 1
(w), 3070 (w), 2962 (m), 2871 (w), 1625 (s), 1586 (m), 1567 (w), 1460
(s), 1438 (s), 1385 (m), 1297 (w), 1282 (m), 1265 (m), 1238 (m), 1146
(w), 1117 (w), 1101 (w), 1057 (w), 1044 (m), 995 (w), 956 (w), 885
H, Py-H3), 7.86 (m, 1 H, Py-H4), 7.50 (m, 1 H, Py-H5), 6.81–7.05 (m, 3
H, Ph-H3,4,5), 2.81 (s, 3 H, CH3), 2.61 (q, 4 H, Ph-CH2), 1.33 (t, 6 H, Ph-
CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.91, 156.37, 153.50,
148.93, 141.61, 136.73, 127.48, 125.95, 121.51, 118.18, 24.25, 16.96,
13.02 ppm. MS (ESI): m/z = 253.17 [M + H]+.
(w), 824 (w), 780 (m), 745 (m), 590 (w), 533 (w) cm–1 1H NMR
.
(400 MHz, CDCl3): δ = 8.72 (d, 1 H, Py-H6), 8.09 (d, 1 H, Py-H3), 7.86
(m, 1 H, Py-H4), 7.50 (m, 1 H, Py-H5), 6.84–7.19 (m, 5 H, Ph-H2,3,4,5,6),
2.77 (s, 3 H, CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 167.31,
153.45, 148.95, 146.53, 136.85, 129.22, 127.13, 121.60, 118.33,
115.03, 16.40 ppm. MS (ESI): m/z = 196.63 [M + H]+.
(E)-2,6-Diisopropyl-N-[(pyridin-2-yl)ethylidene]aniline (L6a): 2-
Acetylpyridine (0.96 mL, 8.58 mmol) and 2,6-diisopropylaniline
(1.61 mL, 8.56 mmol) afforded the product (1.95 g, yield 81 %).
C19H24N2 (280.41): calcd. C 81.38, H 8.63, N 9.99; found C 81.44, H
(E)-2-Methyl-N-[(pyridin-2-yl)ethylidene]aniline (L2a): 2-Acetyl-
pyridine (1.27 mL, 11.33 mmol) and 2-methylaniline (1.21 mL, 8.65, N 9.96. FTIR (KBr): ν = 3435 (w), 3072 (w), 2925 (w), 2863 (w),
˜
11.31 mmol) afforded the product (2.11 g, yield 89 %). C14H14N2
(210.28): calcd. C 79.97, H 6.71, N 13.32; found C 80.03, H 6.74, N
1655 (s), 1603 (s), 1586 (m), 1568 (m), 1500 (s), 1484 (w), 1467 (m),
1437 (m), 1421 (w), 1358 (m), 1298 (w), 1283 (m), 1239 (m), 1216
(w), 1174 (w), 1102 (m), 1075 (w), 1044 (m), 1028 (w), 995 (m), 955
(m), 906 (w), 879 (w), 780 (m), 754 (m), 694 (m), 623 (w), 591 (m),
13.29. FTIR (KBr): ν = 3433 (w), 3056 (w), 2918 (w), 2860 (w), 1643
˜
(s), 1624 (m), 1584 (m), 1568 (w), 1499 (m), 1468 (m), 1437 (m), 1358
(s), 1299 (m), 1282 (s), 1239 (m), 1222 (w), 1190 (w), 1148 (w), 1102
506 (m) cm–1 1H NMR (400 MHz, CDCl3): δ = 8.71 (d, 1 H, Py-H6),
.
(m), 1043 (m), 995 (w), 955 (w), 927 (w), 837 (w), 781 (s), 743 (s), 8.08 (d, 1 H, Py-H3), 7.85 (m, 1 H, Py-H4), 7.49 (m, 1 H, Py-H5), 6.78–
716 (w), 623 (w), 591 (m), 537 (w) cm–1. H NMR (400 MHz, CDCl3): 7.17 (m, 3 H, Ph-H3,4,5), 2.76 (s, 3 H, CH3), 2.25 (q, 2 H, Ph-CH), 1.28
1
δ = 8.71 (d, 1 H, Py-H6), 8.08 (d, 1 H, Py-H3), 7.84 (m, 1 H, Py-H4),
7.48 (m, 1 H, Py-H5), 6.68–7.08 (m, 4 H, Ph-H3,4,5,6), 2.77 (s, 3 H, CH3),
2.19 (s, 3 H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.89,
153.55, 149.02, 148.58, 144.80, 136.88, 130.44, 127.17, 126.98,
(d, 12 H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.95,
156.42, 148.57, 136.48, 135.77, 124.79, 123.58, 122.98, 122.75,
121.32, 28.24, 23.22, 22.90, 17.32 ppm. MS (ESI): m/z = 281.18
[M + H]+.
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(E)-2,4,6-Trimethyl-N-[(pyridin-2-yl)ethylidene]aniline (L7a): 2-
(E)-2,6-Dimethyl-N-[(pyridin-2-yl)methylene]aniline (L4b): 2-Pyr-
Acetylpyridine (1.43 mL, 12.73 mmol) and 2,4,6-trimethylaniline idinecarbaldehyde (1.50 mL, 15.77 mmol) and 2,6-dimethylaniline
(1.78 mL, 12.71 mmol) afforded the product (2.80 g, yield 92 %). (1.95 mL, 15.77 mmol) afforded the product (2.72 g, yield 82 %).
C16H18N2 (238.33): calcd. C 80.63, H 7.61, N 11.75; found C 80.68, H
C14H14N2 (210.27): calcd. C 79.97, H 6.71, N 13.32; found C 79.90, H
7.67, N 11.70. FTIR (KBr): ν = 3436 (w), 3053 (w), 2922 (w), 2861 (w),
1657 (s), 1608 (w), 1584 (w), 1568 (w), 1492 (s), 1467 (w), 1437 (m),
1378 (w), 1357 (s), 1297 (m), 1282 (m), 1239 (m), 1215 (w), 1157 (w),
6.67, N 13.42. FTIR (KBr): ν = 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),
˜
˜
1101 (m), 1043 (w), 1012 (w), 995 (w), 954 (w), 856 (m), 780 (s), 742 918 (w), 872 (m), 829 (w), 776 (s), 739 (w), 704 (w), 630 (w), 611 (w),
1
1
(w), 622 (w), 590 (m), 561 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 564 (w), 467 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.76 (d, 1 H,
8.72 (d, 1 H, Py-H6), 8.08 (d, 1 H, Py-H3), 7.85 (m, 1 H, Py-H4), 7.49
(m, 1 H, Py-H5), 6.80 (s, 2 H, Ph-H3,5), 2.77 (s, 3 H, CH3), 2.21 (t, 9 H,
Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 162.47, 158.96, 149.91,
Py-H6), 8.38 (s, 1 H, CH=N), 8.33 (d, 1 H, Py-H3), 7.88 (t, 1 H, Py-H4),
7.44 (t, 1 H, Py-H5), 7.01–7.12 (m, 3 H, Ph-H3,4,5), 2.20 (s, 6 H, Ph-
CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 163.44, 154.39, 150.29,
143.78, 137.67, 129.74, 127.79, 122.36, 119.66, 115.26, 20.45, 149.60, 136.67, 128.11, 126.79, 125.31, 124.05, 121.18, 18.28 ppm.
16.36 ppm. MS (ESI): m/z = 239.16 [M + H]+.
MS (ESI): m/z = 211.12 [M + H]+.
(E)-2,6-Diethyl-N-[(pyridin-2-yl)methylene]aniline (L5b): 2-Pyr-
idinecarbaldehyde (1.53 mL, 16.08 mmol) and 2,6-diethylaniline
(2.70 mL, 16.28 mmol) afforded the product (3.50 g, yield 91 %).
C16H18N2 (238.33): calcd. C 80.63, H 7.61, N 11.75; found C 80.58, H
N-[(Pyridin-2-yl)methylene]aniline (L1b): 2-Pyridinecarbaldehyde
(0.68 mL, 7.15 mmol) and aniline (0.65 mL, 7.13 mmol) afforded the
product (1.17 g, yield 90 %). C12H10N2 (182.22): calcd. C 79.10, H
5.53, N 15.37; found C 79.15, H 5.49, N 15.32. FTIR (KBr): ν = 3340
˜
7.63, N 11.72. FTIR (KBr): ν = 3425 (w), 3052 (w), 2964 (m), 2871 (w),
˜
(w), 3052 (w), 2960 (w), 2857 (w), 1650 (m), 1600 (s), 1570 (w), 1502
(m), 1471 (w), 1432 (m), 1319 (m), 1276 (w), 1251 (w), 1200 (w),
1178 (w), 1149 (w), 1087 (w), 1072 (w), 1045 (w), 1027 (w), 993 (m),
975 (w), 910 (w), 873 (w), 813 (w), 811 (w), 779 (m), 752 (s), 694 (m),
663 (w), 619 (w), 580 (w), 538 (w), 512 (w) cm–1. 1H NMR (400 MHz,
CDCl3): δ = 8.72 (d, 1 H, Py-H6), 8.61 (s, 1 H, CH=N), 8.22 (d, 1 H, Py-
H3), 7.81 (t, 1 H, Py-H4), 7.63 (t, 1 H, Py-H5), 6.61–7.42 (m, 5 H, Ph-
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) cm–1 1H NMR
.
(400 MHz, CDCl3): δ = 8.78 (d, 1 H, Py-H6), 8.38 (s, 1 H, CH=N), 8.32
(d, 1 H, Py-H3), 7.89 (t, 1 H, Py-H4), 7.45 (t, 1 H, Py-H5), 7.09–7.15 (m,
3 H, Ph-H3,4,5), 2.56 (q, 4 H, Ph-CH2), 1.18 (t, 6 H, Ph-CH3) ppm. 13C
NMR (150 MHz, CDCl3): δ = 163.03, 154.40, 149.64, 149.57, 136.74,
132.75, 126.29, 125.33, 124.30, 121.22, 24.66, 14.65 ppm. MS (ESI):
m/z = 239.16 [M + H]+.
H
2,3,4,5,6) ppm. 13C NMR (150 MHz, CDCl3): δ = 160.60, 154.51,
149.68, 136.70, 129.22, 126.72, 121.09, 117.54, 115.05, 113.01 ppm.
MS (ESI): m/z = 183.09 [M + H]+.
(E)-2-Methyl-N-[(pyridin-2-yl)methylene]aniline (L2b): 2-Pyr-
idinecarbaldehyde (1.44 mL, 15.14 mmol) and 2-methylaniline
(1.62 mL, 15.16 mmol) afforded the product (2.69 g, yield 91 %).
(E)-2,6-Diisopropyl-N-[(pyridin-2-yl)methylene]aniline (L6b): 2-
Pyridinecarbaldehyde (1.16 mL, 12.19 mmol) was heated under re-
flux (4 h) with 2,6-diisopropylaniline (2.35 mL, 12.46 mmol) in anhy-
drous methanol (25 mL). The solvent was removed under reduced
pressure, and the residue was purified by column chromatography
with ethyl acetate/petroleum ether (1:3 v/v) as the eluent. Recrystal-
lization from n-hexane gave yellow crystals, which were collected
by filtration and washed with cold n-hexane, yield 2.28 g (70 %).
C18H22N2 (266.38): calcd. C 81.16, H 8.32, N 10.52; found C 81.08, H
C13H12N2 (196.25): calcd. C 79.56, H 6.16, N 14.27; found C 79.52, H
6.20, N 14.23. FTIR (KBr): ν = 3349 (w), 3054 (m), 2948 (w), 2858 (w),
˜
1669 (m), 1587 (m), 1567 (m), 1486 (m), 1465 (m), 1436 (m), 1376
(w), 1344 (w), 1305 (w), 1278 (w), 1253 (w), 1211 (m), 1187 (m), 1147
(w), 1112 (m), 1089 (w), 1043 (m), 993 (m), 977 (w), 939 (w), 881
(m), 854 (w), 779 (s), 754 (m), 742 (m), 717 (m), 659 (w), 620 (w),
1
576 (w), 553 (w), 501 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.72
(d, 1 H, Py-H6), 8.52 (s, 1 H, CH=N), 8.27 (d, 1 H, Py-H3), 7.82 (t, 1 H,
Py-H4), 7.37 (t, 1 H, Py-H5), 7.00–7.24 (m, 4 H, Ph-H3,4,5,6), 2.39 (s, 3
H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 159.79, 154.74,
149.98, 149.50, 136.61, 132.23, 130.35, 126.79, 126.38, 125.02,
121.60, 117.51, 17.85 ppm. MS (ESI): m/z = 197.11 [M + H]+.
8.36, N 10.50. FTIR (KBr): ν = 3428 (w), 3072 (w), 2959 (vs), 2867 (m),
˜
16553 (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), 563 (w), 533 (w), 493 (w),
(E)-4-Methyl-N-[(pyridin-2-yl)methylene]aniline (L3b): 2-Pyr-
idinecarbaldehyde (1.52 mL, 15.98 mmol) and 4-methylaniline
(1.77 mL, 15.88 mmol) were dissolved in anhydrous methanol
(20 mL), and the resulting mixture was heated under reflux for 3 h.
The solvent was removed under reduced pressure, and the residue
was recrystallized from n-hexane/dichloromethane to give yellow
crystals, yield 2.79 g (90 %). C13H12N2 (196.25): calcd. C 79.56, H
459 (w) cm–1 1H NMR (400 MHz, CDCl3): δ = 8.77 (d, 1 H, Py-H6),
.
8.36 (s, 1 H, CH=N), 8.32 (d, 1 H, Py-H3), 7.92 (t, 1 H, Py-H4), 7.46 (t,
1 H, Py-H5), 6.83–7.20 (m, 3 H, Ph-H3,4,5), 3.00 (q, 2 H, Ph-CH), 1.21
(d, 12 H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 162.94,
154.31, 149.67, 148.36, 137.22, 136.77, 125.34, 124.48, 123.05,
121.34, 27.93, 23.46 ppm. MS (ESI): m/z = 267.19 [M + H]+.
6.16, N 14.27; found C 79.55, H 6.17, N 14.28. FTIR (KBr): ν = 3429
(E)-2,4,6-Trimethyl-N-[(pyridin-2-yl)methylene]aniline (L7b): 2-
Pyridinecarbaldehyde (1.50 mL, 15.75 mmol) and 2,4,6-trimethyl-
aniline (2.22 mL, 15.81 mmol) afforded the product (2.68 g, yield
76 %). C15H16N2 (224.30): calcd. C 80.32, H 7.19, N 12.49; found C
˜
(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),
80.28, H 7.18, N 12.45. FTIR (KBr): ν = 3432 (w), 3050 (w), 2911 (m),
˜
1
617 (m), 542 (m), 497 (w), 477 (w) cm–1. H NMR (400 MHz, CDCl3):
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), 993 (m), 982 (m), 955 (w),
934 (w), 897 (w), 876 (s), 863 (s), 791 (m), 770 (s), 739 (m), 643 (w),
δ = 8.74 (d, 1 H, Py-H6), 8.65 (s, 1 H, CH=N), 8.24 (d, 1 H, Py-H3), 7.84
(t, 1 H, Py-H4), 7.40 (t, 1 H, Py-H5), 6.63–7.29 (m, 4 H, Ph-H3,4,5,6), 2.41
(s, 3 H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 159.63, 154.68,
149.63, 148.31, 136.81, 136.71, 129.87, 125.01, 121.82, 121.12,
21.08 ppm. MS (ESI): m/z = 197.11 [M + H]+.
1
618 (w), 577 (w), 489 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.72
(d, 1 H, Py-H6), 8.33 (s, 1 H, CH=N), 8.29 (d, 1 H, Py-H3), 7.84 (t, 1 H,
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Py-H4), 7.40 (t, 1 H, Py-H5), 6.90 (s, 2 H, Ph-H3,5), 2.14–2.29 (m, 9 H,
Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 163.41, 154.52, 149.58,
Complex Hg5a: Yield 35.3 mg (67 %). C17H20Cl2HgN2 (523.85):
calcd. C 38.98, H 3.85, N 5.35; found C 38.89, H 3.91, N 5.40. FTIR
147.83, 136.68, 133.44, 128.81, 126.84, 125.23, 121.17, 20.75, (KBr): ν = 3427 (w), 3055 (w), 2958 (w), 2869 (w), 1644 (m), 1594
˜
18.24 ppm. MS (ESI): m/z = 225.14 [M + H]+.
(m), 1571 (w), 1440 (m), 1367 (m), 1315 (m), 1253 (m), 1195 (m),
1170 (m), 1124 (w), 1103 (w), 105 (w), 985 (w), 906 (w), 871 (w), 836
(w), 811 (w), 777 (s), 742 (w), 705 (w), 640 (w), 565 (w), 534 (w), 435
General Synthesis of Mercury(II) Complexes: The mercury(II)
complexes were synthesized by dissolving HgCl2 and the respective
Schiff base ligand (1 equiv.) in anhydrous solutions. Methanol was
used for Hg1a–Hg7a, whereas methanol/dichloromethane mixtures
were used for Hg1b–Hg7b, Scheme 1. The yellow solutions were
heated under reflux for 12 h and subsequently filtered. Quality sin-
gle crystals of the fourteen mercury(II) complexes were grown
through the slow evaporation of their solutions.
(w) cm–1 1H NMR (400 MHz, CDCl3): δ = 8.80 (d, 1 H, Py-H6), 8.13
.
(d, 1 H, Py-H3), 7.79 (m, 1 H, Py-H4), 7.49 (m, 1 H, Py-H5), 7.19–7.24
(m, 3 H, Ph-H3,4,5), 2.66 (s, 3 H, CH3), 2.37 (q, 4 H, Ph-CH2), 1.18 (t, 6
H, Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.82, 153.46,
149.98, 144.09, 139.94, 136.93, 132.93, 128.14, 126.04, 121.78, 23.83,
18.28, 13.68 ppm. MS (ESI): m/z = 524.65 [M + H]+, 253.17 [L + H]+.
Complex Hg1a: Yield 30.1 mg (64 %). C13H12Cl2HgN2 (467.75):
Complex Hg6a: Yield 33.9 mg (61 %). C19H24Cl2HgN2 (551.89):
calcd. C 33.38, H 2.59, N 5.99; found C 33.45, H 2.57, N 5.63. FTIR
calcd. C 41.35, H 4.38, N 5.08; found C 41.38, H 4.44, N 5.01. FTIR
(KBr): ν = 3434 (w), 3064 (w), 2962 (w), 2860 (w), 1620 (m), 1591 (KBr): ν = 3432 (w), 3069 (w), 2963 (w), 2868 (w), 1633 (m), 1591 (s),
˜
˜
(m), 1483 (m), 1439 (m), 1372 (m), 1312 (m), 1253 (m), 1212 (m),
1574 (w), 1482 (w), 1463 (m), 1443 (m), 1386 (m), 1370 (m), 1326
1169 (w), 1122 (w), 1102 (w), 1072 (w), 1052 (w), 1027 (w), 1010 (w), 1312 (m), 1256 (s), 1187 (m), 1164 (m), 1121 (m), 1104 (w), 1056
(m), 986 (w), 961 (w), 903 (w), 830 (m), 790 (s), 741 (m), 692 (m),
(m), 1045 (w), 1016 (s), 986 (w), 937 (w), 836 (w), 813 (m), 797 (m),
1
637 (w), 576 (w), 438 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.80 784 (s), 746 (w), 701 (w), 636 (w), 575 (w), 459 (w), 434 (w) cm–1. 1H
(d, 1 H, Py-H6), 8.15 (d, 1 H, Py-H3), 7.80 (m, 1 H, Py-H4), 7.55 (m, 1
H, Py-H5), 6.79–7.41 (m, 5 H, Ph-H2,3,4,5,6), 2.50 (s, 3 H, CH3) ppm. 13
NMR (150 MHz, CDCl3): δ = 165.18, 150.16, 148.77, 146.74, 140.09,
NMR (400 MHz, CDCl3): δ = 8.84 (d, 1 H, Py-H6), 8.16 (d, 1 H, Py-H3),
7.83 (m, 1 H, Py-H4), 7.55 (m, 1 H, Py-H5), 7.15–7.28 (m, 3 H, Ph-
C
H
3,4,5), 2.72 (s, 3 H, CH3), 2.40 (q, 2 H, Ph-CH), 1.10–1.32 (m, 12 H,
137.22, 129.70, 128.13, 125.84, 120.70, 18.16 ppm. MS (ESI): m/z = Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.93, 150.16, 149.06,
468.11 [M + H]+, 196.93 [L + H]+.
140.21, 138.45, 128.42, 126.90, 124.35, 123.35, 122.14, 28.27, 24.52,
22.83, 19.22 ppm. MS (ESI): m/z = 552.74 [M + H]+, 281.18 [L + H]+.
Complex Hg2a: Yield 28.2 mg (64 %). C14H14Cl2HgN2 (481.77):
calcd. C 34.90, H 2.93, N 5.81; found C 34.95, H 2.85, N 5.77. FTIR
Complex Hg7a: Yield 35.7 mg (70 %). C16H18Cl2HgN2 (509.83):
calcd. C 37.69, H 3.56, N 5.49; found C 37.73, H 3.60, N 5.51. FTIR
(KBr): ν = 3434 (w), 3050 (w), 2917 (w), 2852 (w), 1634 (m), 1591 (s),
˜
1572 (w), 1485 (m), 1456 (w), 1437 (m), 1371 (m), 1312 (m), 1254
(s), 1223 (m), 1191 (w), 1166 (w), 1126 (w), 1113 (w), 1102 (w), 1054
(w), 1045 (w), 1015 (m), 986 (w), 943 (w), 844 (w), 804 (m), 778 (s),
(KBr): ν = 3437 (w), 3060 (w), 2915 (w), 2855 (w), 1644 (m), 1593 (s),
˜
1572 (w), 1479 (m), 1439 (m), 1370 (m), 1315 (m), 1253 (s), 1213 (s),
1168 (w), 1155 (m), 1101 (w), 1053 (w), 1036 (w), 1013 (m), 987 (w),
955 (w), 900 (w), 857 (m), 810 (w), 786 (s), 746 (w), 635 (m), 602 (w),
755 (m), 717 (w), 639 (w), 576 (w), 539 (w), 441 (w) cm–1 1H NMR
.
(400 MHz, CDCl3): δ = 8.82 (d, 1 H, Py-H6), 8.11 (d, 1 H, Py-H3), 7.81
(m, 1 H, Py-H4), 7.52 (m, 1 H, Py-H5), 6.71–7.24 (m, 4 H, Ph-H3,4,5,6),
2.40 (s, 3 H, CH3), 2.21 (s, 3 H, Ph-CH3) ppm. 13C NMR (150 MHz,
CDCl3): δ = 165.86, 150.00, 149.02, 139.88, 136.96, 131.16, 130.47,
128.03, 127.22, 126.31, 125.65, 119.79, 18.02, 17.38 ppm. MS (ESI):
m/z = 482.60 [M + H]+, 211.12 [L + H]+.
1
561 (w), 506 (w), 435 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.83
(d, 1 H, Py-H6), 8.12 (d, 1 H, Py-H3), 7.82 (m, 1 H, Py-H4), 7.52 (m, 1
H, Py-H5), 6.96 (s, 2 H, Ph-H3,5), 2.36 (s, 3 H, CH3), 2.16–2.32 (m, 9 H,
Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.68, 150.19, 142.46,
140.19, 137.12, 129.46, 128.41, 127.41, 125.79, 122.10, 20.83, 18.35,
17.70 ppm. MS (ESI): m/z = 510.67 [M + H]+, 239.16 [L + H]+.
Complex Hg3a: Yield 29.0 mg (60 %). C14H14Cl2HgN2 (481.77):
calcd. C 34.90, H 2.93, N 5.81; found C 34.96, H 2.99, N 5.78. FTIR
Complex Hg1b: Yield 25.0 mg (55 %). C12H10Cl2HgN2 (453.71):
calcd. C 31.77, H 2.22, N 6.17; found C 31.80, H 2.23, N 6.10. FTIR
(KBr): ν = 3433 (w), 3068 (w), 2916 (w), 2859 (w), 1635 (m), 1591 (s),
˜
(KBr): ν = 3430 (w), 3062 (w), 2952 (w), 2870 (w), 1627 (w), 1590 (s),
˜
1574 (w), 1502 (s), 1477 (w), 1440 (m), 1366 (m), 1315 (m), 1254 (m),
1217 (m), 1171 (m), 1118 (w), 1105 (w), 1053 (w), 1011 (m), 988 (w),
940 (w), 850 (m), 830 (w), 788 (s), 748 (w), 707 (w), 634 (w), 575 (w),
1561 (w), 1492 (s), 1475 (m), 1455 (m), 1436 (s), 1418 (w), 1370 (m),
1338 (w), 1305 (m), 1288 (w), 1269 (w), 1240 (m), 1190 (w), 1153
(m), 1099 (m), 1079 (w), 1015 (m), 980 (s), 962 (m), 917 (m), 904 (s),
835 (w), 784 (s), 769 (s), 737 (m), 686 (m), 640 (m), 559 (w), 537 (m),
1
522 (w), 446 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.77 (d, 1 H,
Py-H6), 8.06 (d, 1 H, Py-H3), 7.85 (m, 1 H, Py-H4), 7.48 (m, 1 H, Py-
H5), 6.62–7.05 (m, 4 H, Ph-H2,3,5,6), 2.48 (s, 3 H, CH3), 2.38 (s, 3 H, Ph-
CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 164.88, 150.15, 144.08,
140.09, 136.62, 130.23, 128.06, 125.78, 120.79, 115.99, 21.06,
18.10 ppm. MS (ESI): m/z = 482.60 [M + H]+, 211.12 [L + H]+.
1
477 (w), 424 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.89 (d, 1 H,
Py-H6), 8.72 (s, 1 H, CH=N), 8.40 (d, 1 H, Py-H3), 8.06 (t, 1 H, Py-H4),
7.77 (t, 1 H, Py-H5), 6.60–7.51 (m, 5 H, Ph-H2,3,4,5,6) ppm. 13C NMR
(150 MHz, CDCl3): δ = 166.65, 150.48, 140.62, 139.55, 129.76, 127.51,
121.68, 118.24, 116.28, 115.16 ppm. MS (ESI): m/z = 454.58 [M +
H]+, 183.09 [L + H]+.
Complex Hg4a: Yield 29.4 mg (59 %). C15H16Cl2HgN2 (495.80):
calcd. C 36.34, H 3.25, N 5.65; found C 36.41, H 3.30, N 5.60. FTIR
(KBr): ν = 3435 (w), 3066 (w), 2917 (w), 2853 (w), 1642 (m), 1591 (s),
1574 (w), 1470 (w), 1437 (m), 1370 (w), 1311 (m), 1252 (m), 1202 calcd. C 32.14, H 2.90, N 5.77; found C 32.10, H 2.95, N 5.70. FTIR
Complex Hg2b: Yield 25.4 mg (52 %). C13H14Cl2HgN2O (485.75):
˜
(m), 1164 (w), 1120 (w), 1095 (w), 1052 (w), 1035 (w), 1013 (m), 982 (KBr): ν = 3433 (w), 3060 (w), 2950 (w), 2860 (w), 1633 (w), 1592
˜
(w), 923 (w), 893 (w), 836 (w), 795 (s), 777 (s), 739 (w), 703 (w), 640
(m), 1565 (w), 1489 (m), 1460 (w), 1439 (m), 1377 (w), 1314 (w),
1H 1265 (w), 1238 (w), 1210 (w), 1184 (w), 1159 (w), 1114 (w), 1050 (w),
1016 (m), 984 (w), 953 (w), 904 (w), 867 (w), 776 (s), 757 (m), 715
(w), 629 (w), 586 (w), 559 (w), 541 (w), 499 (w), 438 (w) cm–1
.
NMR (400 MHz, CDCl3): δ = 8.84 (d, 1 H, Py-H6), 8.14 (d, 1 H, Py-H3),
7.83 (m, 1 H, Py-H4), 7.52 (m, 1 H, Py-H5), 7.10–7.17 (m, 3 H, Ph-
(w), 638 (w), 583 (w), 561 (w), 503 (w), 477 (w), 453 (w) cm–1 1H
.
H
3,4,5), 2.36 (s, 3 H, CH3), 2.20 (s, 6 H, Ph-CH3) ppm. 13C NMR
NMR (400 MHz, CDCl3): δ = 8.79 (d, 1 H, Py-H6), 8.57 (s, 1 H, CH=N),
8.21 (d, 1 H, Py-H3), 8.06 (t, 1 H, Py-H4), 7.64 (t, 1 H, Py-H5), 7.13–
(150 MHz, CDCl3): δ = 166.48, 150.24, 149.10, 145.00, 140.23, 137.20,
128.84, 127.67, 126.13, 122.19, 18.46, 17.77 ppm. MS (ESI): m/z = 7.24 (m, 4 H, Ph-H3,4,5,6), 2.34 (s, 3 H, Ph-CH3) ppm. 13C NMR
496.95 [M + H]+, 225.14 [L + H]+.
(150 MHz, CDCl3): δ = 164.50, 158.68, 155.76, 151.81, 151.43, 142.03,
3608 © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2016, 3598–3610
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Full Paper
137.12, 133.29, 127.88, 125.34, 120.35, 119.83, 19.17 ppm. MS (ESI):
777 (s), 740 (w), 638 (m), 582 (w), 534 (w), 514 (w), 493 (w), 459 (w)
1
m/z = 486.55 [M + H]+, 197.11 [L + H]+.
cm–1. H NMR (400 MHz, CDCl3): δ = 8.84 (d, 1 H, Py-H6), 8.56 (s, 1
H, CH=N), 8.15 (d, 1 H, Py-H3), 7.81 (t, 1 H, Py-H4), 7.59 (t, 1 H, Py-
H5), 6.97 (s, 2 H, Ph-H3,5), 2.20–2.33 (m, 9 H, Ph-CH3) ppm. 13C NMR
(150 MHz, CDCl3): δ = 161.94, 150.40, 147.64, 145.10, 139.89, 136.15,
129.33, 129.09, 128.73, 128.36, 20.84, 18.65 ppm. MS (ESI): m/z =
496.55 [M + H]+, 225.14 [L + H]+.
Complex Hg3b: Yield 26.4 mg (57 %). C13H12Cl2HgN2 (467.74):
calcd. C 33.38, H 2.59, N 5.99; found C 33.40, H 2.57, N 5.92. FTIR
(KBr): ν = 3429 (w), 3060 (w), 2946 (w), 2856 (w), 1626 (w), 1591
˜
(m), 1562 (m), 1508 (m), 1476 (m), 1440 (m), 1414 (w), 1370 (w),
1320 (w), 1306 (m), 1271 (w), 1236 (w), 1192 (w), 1179 (w), 1154
(w), 1127 (w), 1103 (w), 1059 (w), 1038 (w), 1018 (m), 975 (m), 953
(w), 906 (m), 823 (s), 769 (m), 740 (w), 700 (w), 645 (w), 535 (m), 509
Acknowledgments
1
(w), 436 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.90 (d, 1 H, Py-
H6), 8.75 (s, 1 H, CH=N), 8.20 (d, 1 H, Py-H3), 7.97 (t, 1 H, Py-H4), 7.73
(t, 1 H, Py-H5), 7.32–7.45 (m, 4 H, Ph-H2,3,5,6), 2.37 (s, 3 H, Ph-CH3)
ppm. 13C NMR (150 MHz, CDCl3): δ = 162.49, 156.63, 150.97, 148.68,
141.08, 140.96, 130.53, 124.11, 121.84, 121.32, 22.36 ppm. MS (ESI):
m/z = 468.59 [M + H]+, 197.11 [L + H]+.
This work was supported by National Natural Science Founda-
tion of China (NSFC) (grant numbers 21371040, 21571042, and
21171044), the National key Basic Research Program of China
(973 Program, grant number 2013CB632900).
Complex Hg4b: Yield 31.3 mg (65 %). C14H14Cl2HgN2 (481.76):
calcd. C 34.90, H 2.93, N 5.81; found C 34.95, H 2.90, N 5.82. FTIR
Keywords: Metal–organic frameworks · Hydrogen bonding ·
Pi interactions · Luminescence · Aggregation-induced
emission · Mercury
(KBr): ν = 3431 (w), 3069 (w), 2965 (w), 2853 (w), 1644 (m), 1595
˜
(m), 1571 (w), 1469 (m), 1443 (m), 1386 (w), 1359 (w), 1311 (w),
1267 (w), 1224 (w), 1181 (m), 1158 (w), 1104 (w), 1091 (w), 1058
(w), 1043 (w), 1017 (m), 984 (w), 970 (w), 921 (w), 893 (m), 830 (w),
783 (s), 774 (s), 745 (w), 711 (w), 642 (w), 627 (w), 557 (w), 516 (w),
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480 (w), 422 (w) cm–1. H NMR (400 MHz, CDCl3): δ = 8.86 (d, 1 H,
Py-H6), 8.58 (s, 1 H, CH=N), 8.17 (d, 1 H, Py-H3), 7.86 (t, 1 H, Py-H4),
7.59 (t, 1 H, Py-H5), 7.10–7.17 (m, 3 H, Ph-H3,4,5), 2.31 (s, 6 H,
Ph-CH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.67, 153.97, 150.14,
142.68, 139.64, 137.11, 128.47, 128.23, 125.63, 121.47, 18.57 ppm.
MS (ESI): m/z = 482.52 [M + H]+, 211.12 [L + H]+.
Complex Hg5b: Yield 34.3 mg (67 %). C16H18Cl2HgN2 (509.81):
calcd. C 37.69, H 3.56, N 5.49; found C 37.62, H 3.55, N 5.45. FTIR
(KBr): ν = 3424 (w), 3057 (w), 2967 (w), 2875 (w), 1640 (m), 1591 (s),
˜
1569 (w), 1508 (w), 1476 (m), 1448 (s), 1373 (w), 1342 (w), 1328 (w),
1305 (m), 1268 (w), 1241 (w), 1218 (w), 1175 (m), 1158 (w), 1103
(m), 1053 (w), 1016 (m), 978 (w), 966 (w), 898 (m), 810 (m), 775 (s),
742 (w), 701 (w), 637 (w), 566 (w), 533 (m), 487 (w), 433 (w) cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.84 (d, 1 H, Py-H6), 8.53 (s, 1 H, CH=
N), 8.13 (d, 1 H, Py-H3), 7.82 (t, 1 H, Py-H4), 7.55 (t, 1 H, Py-H5), 7.16–
7.23 (m, 3 H, Ph-H3,4,5), 2.65 (q, 4 H, Ph-CH2), 1.18 (t, 6 H, Ph-CH3)
ppm. 13C NMR (150 MHz, CDCl3): δ = 161.94, 150.52, 147.52, 146.58,
139.93, 134.31, 129.12, 128.80, 126.68, 126.41, 24.33, 15.08 ppm. MS
(ESI): m/z = 510.61 [M + H]+, 239.16 [L + H]+.
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(KBr): ν = 3425 (w), 3062 (w), 2963 (m), 2866 (w), 1645 (m), 1592 (s),
˜
1566 (w), 1509 (m), 1477 (m), 1457 (m), 1440 (m), 1384 (w), 1363
(m), 1330 (w), 1307 (m), 1270 (w), 1256 (w), 1240 (w), 1223 (w), 1176
(m), 1155 (w), 1102 (m), 1057 (w), 1043 (w), 1013 (m), 996 (w), 977
(w), 956 (w), 933 (w), 900 (m), 823 (s), 805 (m), 772 (s), 761 (m), 742
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˜
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Eur. J. Inorg. Chem. 2016, 3598–3610
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© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Received: March 3, 2016
Published Online: July 4, 2016
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3610
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim