Chiral supramolecular frameworks based on chiral metallocycles: Crystal structures and photophysical properties

Article abstract of DOI:10.1002/ejic.201200100

Four purely chiral supramolecular frameworks were constructed from a new chiral terpyridyl ligand, (S)-2{4-[2,6-bis(pyridin-2-yl)pyridin-4-yl] benzylamino}propanoic acid (H₂ptpy). The resulting compounds 1-4, namely [Cd₂(Hptpy)₂(Ac)₂]?3CH ₃OH?H₂O (1) [Ni₂(Hptpy) ₂(CH₃OH)(H₂O)](ClO₄) ₂?CH₃OH?H₂O (2), [Ni ₂(Hptpy)₂(H₂O)₂](SCN)₂ (3), and [Cu₂(Hptpy)₂](dca)₂?4H ₂O (4) (Ac = acetate and dca = dicyanamide) all consist of those chiral metallocyclic units. As expected, those chiral nanometallocycles not only induced a chiral array or helicates but also amplified chirality through hydrogen-bonding interactions, and finally aggregated into complicated higher-dimensional chiral supramolecular architectures with chiral voids for further use. The formation of the metallocyclic units is easily monitored by UV/Vis spectra. Spectrophotometric titrations were performed by titrating Na(Hptpy) with a soltution of Cd(Ac)₂ in methanol, and the global stability constants of [Cd₂(Hptpy)₂]²⁺ (logβ = 17.60) were calculated. In combination with the structural analyses and UV/Vis and ES mass spectra, it is tentatively deduced that metallocycle units in 1-4 are the thermodynamically favored species in solution. Both the chiral H₂ptpy ligand and 1 in the solid state and in solution display purple emission. The bathochromic shift of 1 is mainly due to the bichelation and intrametallocyclic π-π interactions. By the self-assembly of the synthesized purely chiral terpyridyl ligand (S)-2{4-[2,6-bis(pyridin-2-yl) pyridin-4-yl]benzylamino}propanoic acid (H₂ptpy) with metal ions, a new class of purely chiral metal-organic frameworks built from the chiral metallocyclic subunits formed by two chiral (Hptpy)^- anions that bridge two metal ions in a head-to-tail style was prepared and characterized.

Full text of DOI:10.1002/ejic.201200100

FULL PAPER
DOI: 10.1002/ejic.201200100
Chiral Supramolecular Frameworks Based on Chiral Metallocycles: Crystal
Structures and Photophysical Properties
Jinxia Xu,[a] Ruiying Wang,[b] Yameng Li,[a] Zhiyang Gao,[a] Rui Yao,[a] Song Wang,[a] and
Benlai Wu*[a]
Keywords: Chirality / Metallocycles / Metal–organic frameworks / Supermolecular chemistry / Solution structure /
Fluorescence
Four purely chiral supramolecular frameworks were con-
structed from a new chiral terpyridyl ligand, (S)-2{4-[2,6-
tectures with chiral voids for further use. The formation of
the metallocyclic units is easily monitored by UV/Vis spectra.
Spectrophotometric titrations were performed by titrating
Na(Hptpy) with a soltution of Cd(Ac)2 in methanol, and the
global stability constants of [Cd2(Hptpy)2]2+ (logβ = 17.60)
were calculated. In combination with the structural analyses
and UV/Vis and ES mass spectra, it is tentatively deduced
that metallocycle units in 1–4 are the thermodynamically fa-
vored species in solution. Both the chiral H2ptpy ligand and
1 in the solid state and in solution display purple emission.
The bathochromic shift of 1 is mainly due to the bichelation
and intrametallocyclic π–π interactions.
bis(pyridin-2-yl)pyridin-4-yl]benzylamino}propanoic
acid
(H2ptpy). The resulting compounds 1–4, namely [Cd2(Hptpy)2-
(Ac)2]·3CH3OH·H2O (1) [Ni2(Hptpy)2(CH3OH)(H2O)](ClO4)2·
CH3OH·H2O (2), [Ni2(Hptpy)2(H2O)2](SCN)2 (3), and
[Cu2(Hptpy)2](dca)2·4H2O (4) (Ac = acetate and dca = dicyan-
amide) all consist of those chiral metallocyclic units. As ex-
pected, those chiral nanometallocycles not only induced a
chiral array or helicates but also amplified chirality through
hydrogen-bonding interactions, and finally aggregated into
complicated higher-dimensional chiral supramolecular archi-
Introduction
fluorescent sensor for enantioselective recognition of amino
acid derivatives.[5] Another representative work reported by
Lin et al. was a series of chiral hybrid metal–organic dendri-
mers constructed by chiral terpyridine–binaphthalene and
ruthenium.[6]
Terpyridine derivatives have special redox and photo-
physical properties that can be greatly tuned by the elec-
tronic characteristic of the substituents, conjugate systems,
or binding metal centers, and thus they have been widely
explored as multifunctional compounds and materials with
luminescence, information transport, and catalytic activity
in photo-, symmetric and asymmetric catalysis over the
years.[1,2] However, terpyridine-based chiral structures that
show promise in obtaining chiral functional materials have
rarely been reported. In 1993, Potts et al. prepared a chiral
crystal structure with septipydine, a new odd-numbered oli-
gopyridine, for the first time.[3] Subsequently, the synthesis
and utilization of optically pure terpyridyl-type ligands to
construct chiral compounds have been largely developed.
For example, chiral RhIII and RuIII complexes predeter-
mined with pineno-fused chiral terpyridyl ligands were syn-
thesized as chiral catalysts for enantioselective cyclopropan-
ation and hydrosilylation reactions.[4] By incorporating a
chiral 2,2Ј:6Ј,2ЈЈ-terpyridine into a crown ether, Kwong et
al. synthesized a novel chiral terpyridine macrocycle as a
Natural amino acids with biological activity, chirality,
and coordination variety are simple and practical chiral
precursors. Moreover, ligands that contain amino acid
groups are endowed with plentiful hydrogen-bonding inter-
actions that occur between nonbonded carboxylic oxygen
atoms and an amino proton directly or through water medi-
ation, which not only amplify chirality or induce a chiral
array of guests but also generate novel supramolecular
architectures that sometimes encapsulate interesting frame-
works of guests.[7] For example, by using thioether-bearing
amino acids, He et al. synthesized hydrogen-bonded well-
organized 1D infinite strands.[8] Rajalakshmi et al. reported
a series of bis(amino acidato)–metal(II) complexes with hy-
drogen-bonded 1–3D novel supramolecular networks.[9]
And Hong et al. synthesized a chiral CuII dinuclear com-
plex of N-salicylidenylhistidine in which the dinuclear units
assembled into a 3D hydrogen-bonded supramolecular
structure with left-handed helical water chains anchored in
the resultant 1D chiral channels.[10] In this context, we at-
tached an amino acid to terpyridyl according to Scheme 1.
The resulting (S)-2{4-[2,6-bis(pyridin-2-yl)pyridin-4-yl]-
benzylamino}propanoic acid (H2ptpy) ligand possesses a
[a] Department of Chemistry, Zhengzhou University,
Zhengzhou, Henan 450001, China
E-mail: wbl@zzu.edu.cn
[b] Henan Vocational College of Chemical Technology,
Zhengzhou, Henan 450042, China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201200100.
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Scheme 1. Schematic representation of the synthesis strategy for ligand (S)-2{4-[2,6-bis(pyridin-2-yl)pyridin-4-yl]benzylamino}propanoic
acid (H2ptpy).
large rigid structure, abundant photochemical and electro- lated with a good yield as reported in the literature.[11,12]
chemical characteristics that originate from terpyridine, and The reaction of l-α-alanine methyl ester hydrochloride and
chirality from attached l-α-alanine. On account of a combi- 2Ј resulted in oily 3Ј, which was hydrolyzed in a base-as-
nation of coordination, hydrogen-bonding interactions, and sisted reaction to produce ligand H2ptpy in a yield of 81%.
π–π interactions the multifunctional spacer H2ptpy should Complexes 1–4 were obtained through slow concentration
be suitable for the construction of metal-containing chiral or hydrothermal synthesis with quantitative NaOH used for
supramolecular frameworks that have attracted growing the deprotonation of the H2ptpy ligand in the reaction mix-
interest for their potential use in asymmetric catalysis, chiral tures. In the IR spectrum of 3Ј, the strong absorption cen-
separation, and sensing.[2–5] Herein we report the syntheses, tered at 1735 cm–1 is the typical vibration of esters, thus
structures, and photophysical properties of the chiral indicating that esterified l-α-alanine was attached to the
H2ptpy ligand and a series of chiral supramolecular frame- methyl group of 2,6-bis(pyridin-2-yl)-4-p-tolylpyridine. For
works based on chiral dinuclear metallocycles, namely H2ptpy, the strong peaks centered at 1603 and 1567 cm–1
[Cd2(Hptpy)2(Ac)2]·3CH3OH·H2O
(1),
[Ni2(Hptpy)2- are ascribed to the characteristic absorptions of the car-
(CH3OH)(H2O)](ClO4)2·CH3OH·H2O (2), [Ni2(Hptpy)2- boxyl group. The IR spectra of complexes 1–4 display the
(H2O)2](SCN)2 (3), and [Cu2(Hptpy)2](dca)2·4H2O (4) (Ac characteristic carboxylate bands in the ranges 1574–
= acetate and dca = dicyanamide).
1620 cm–1 for νas(CO2) and 1401–1410 cm–1 for νs(CO2).
The frequency difference between νas(CO2) and νs(CO2)
suggests a unidentate coordination mode of carboxylates
in each complex.[13] Notably, the very strong absorptions
centered at 1101 cm–1 for 2, 2057 cm–1 for 3, and 2235,
Results and Discussion
Syntheses and IR Spectra
–
2194, and 2137 cm–1 for 4 indicate the existence of ClO4
anions in 2, SCN– anions in 3, and (dca)– anions in 4, which
is fully consistent with their formulas.
The ligand H2ptpy was synthesized by four steps
(Scheme 1). The intermediate products 1Ј and 2Ј were iso-
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Chiral Supramolecular Frameworks Based on Chiral Metallocycles
Crystal Structures of 1–4: General Structure
Structural Features of [Cd2(Hptpy)2(Ac)2]·3CH3OH·H2O
(1)
Single-crystal X-ray analyses show that complexes 1–4 all
are chiral dinuclear metallocycles. The basic dinuclear units
are constructed by two chiral (Hptpy)– anions in a head-to-
tail bridge style to link with the same M atom (M = CdII,
NiII, and CuII). Regardless of the chirality that originates
from chiral (Hptpy)–, those [M2(Hptpy)2]2+ units are cen-
trosymmetric. Every deprotonated (Hptpy)– ion in 1–4
adopts a bichelating fashion of μ-κN,NЈ,NЈЈ:κO,NЈЈЈ. It
chelates two distinct metal ions with the three N atoms of
the terpyridyl and the N and O atoms of the amino acid
group, respectively, thereby allowing its terpyridyl group to
be almost coplanar with its phenyl group (dihedral angle
range of 4.3–8.8°). In the metallocycles of 1–4, two
(Hptpy)– ligands bridge two M atoms in an antiparallel
fashion, with the three N atoms of the terpyridyl and one
O atom of the amino acid group in the equatorial plane
and the N atom of the amino acid group occupying one
axial site. On the basis of the separation distances of the
two metal centers and of the two antiparallel 4-phenyl-2,6-
bis(pyridin-2-yl)pyridine groups [an average centroid-to-
centroid distance between the central pyridyl ring of one
(Hptpy)– ion and the phenyl ring of the other], the overall
dimensions of metallocycles of 1–4 are 11.123ϫ3.688,
11.328ϫ3.480, 11.312ϫ3.420, and 10.969ϫ3.607 Å,
respectively. In a sense, they all are compressed nanometallo-
cycles stabilized by stronger π–π interactions between the
antiparallel 4-phenyl-2,6-bis(pyridin-2-yl)pyridine groups.
In each metallocycle there are four asymmetric centers. The
permanent-chiral carbon atoms C2 and C27 possess (S)
configuration, whereas the labile-chiral nitrogen atoms N1
and N5, the chirality of which results from the coordination
Complex 1 crystallizes in the chiral space group P21, with
a Flack parameter value of –0.02(3). The asymmetric unit
consists of two CdII, two (Hptpy)–, two Ac–, three CH3OH,
and one H2O. As shown in Figure 1, the sixth coordination
site of each CdII atom is occupied by one O atom of acetate.
Cd–O and Cd–N bonds cover ranges of 2.216(7)–2.342(8)
and 2.361(9)–2.458(10) Å, respectively. The bonds of Cd–
Nterpyridyl are slightly longer than those observed in other
cadmium(II)–terpyridyl complexes.[14] The in-plane and
axis-transition angles for Cd1 [148.2(3), 133.3(3), and
148.5(2)°] and Cd2 [147.3(3), 137.7(3), and 143.6(2)°] indi-
cate that the octahedral coordination geometries sharply
deviate from an ideal octahedron on account of the bis-
(chelating) fashion of (Hptpy)– ligand. In every metallocy-
cle of 1, the labile-chiral N1 atom possesses (S) configura-
tion, whereas the N5 atom possesses (R) configuration. In
a sense, the chirality of the metallocycle originates in the
permanent-chiral carbon atoms, because the labile chirality
of the central N1 and N5 atoms is reversed. The chiral ex-
pansion along the a axis is achieved through double hydro-
gen-bonding connections between the chiral metallocycles
and lattice methanol molecules (see Figure 2). The resulting
1D chiral supramolecular networks pack to create chiral
crystals by means of a 21 operation along the b axis (Fig-
ure S1 in the Supporting Information).
Structure of [Ni2(Hptpy)2(CH3OH)(H2O)](ClO4)2·
CH3OH·H2O (2)
Complex 2 crystallizes in the chiral space group P1, with
recognition, possess (S) or (R) configuration. Similar nano- a Flack parameter value of 0.04(3). The asymmetric unit
metallocycles further aggregate into complicated chiral sup- consists of two NiII, two (Hptpy)–, two CH3OH, two H2O,
–
ramolecular architectures of 1–4 through the assistance of and two ClO4 . As shown in Figure 3, the sixth coordina-
different counteranions and solvents.
tion sites of Ni1 and Ni2 are occupied by O atoms from
Figure 1. View of the dinuclear metallocycle unit in 1, showing the sixth coordination sites of each CdII being occupied by one O atom
of acetate, the (S) configuration of permanent-chiral carbon atoms C2 and C27, and labile-chiral nitrogen atoms N1 with an (S) configura-
tion and N5 with an (R) configuration.
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Figure 2. View of the 1D chiral ladderlike network formed by double hydrogen-bonding connections between the chiral metallocycles
and lattice methanol molecules in 1 [O10···O3 2.607(11), N1A···O10 3.045(13), N5···O11 2.978(13), O11···O8A 2.724(10) Å; symmetry
operation: A: 1 + x, y, z].
one CH3OH and one H2O molecule, respectively. The Ni– are 176.1(4), 157.0(4), and 165.3(4)°, and for Ni2 they are
O and Ni–N bonds fall in the normal ranges of 1.953(9)– 173.4(4), 155.7(4), and 164.6(3), respectively, thus indicating
2.142(11) and 1.991(10)–2.183(10) Å, respectively. The Ni– an obvious deviation from an ideal octahedron on account
Nterpyridyl bond lengths are in accordance with the range of of the bis(chelating) fashion of the (Hptpy)– ligands. The
1.962–2.221 Å reported for other nickel(II)–terpyridyl com- labile-chiral N1 and N5 atoms possess (S) configuration in
plexes.[15] The in-plane and axis-transition angles for Ni1 each metallocycle of 2. Theoretically, the chirality of the N
Figure 3. View of the dinuclear metallocycle unit in 2, showing the sixth coordination sites of Ni1 and Ni2 occupied by O of CH3OH
and H2O, respectively, and permanent-chiral carbon atoms C2 and C27 and labile-chiral nitrogen atoms N1 and N5 all in an (S)
configuration.
Figure 4. View of the 1D double hydrogen-bonded chiral macrocycle chain in 2, showing double connections between the chiral metallo-
cycles and lattice molecules such as methanol and water [O3···O15 2.693(16), O15···O5A 2.569(16), O16···O2 2.789(17), O16···O6A
2.667(17) Å; symmetry operation: A: x – 1, y – 1, 1 + z].
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Chiral Supramolecular Frameworks Based on Chiral Metallocycles
atom in H2ptpy originates from one H atom of the amino 170.9(7), 156.4(6), and 166.4(5)°, respectively, and for Ni2
group in l-α-alanine being substituted by the 2,6-bis(pyr- they are 174.2(6), 154.4(7) and 167.1(5)°, respectively. These
idin-2-yl)-4-p-tolylpyridine group, and thus the resulting bond parameters are comparable with those found for 2.
chiral H2ptpy ligands are a mixture of (S)- and (R)-configu- As found for 1, the nitrogen atoms of the amino groups of
rational N atoms in a 1:1 ratio. In 2, all N atoms of the the two (Hptpy)– ions in each metallocycle of 3 possess (S)
amino groups of (Hptpy)– ligands possess (S) configura- and (R) configuration, respectively. As shown in Figure 5,
tion, thereby indicating a spontaneous resolution in each metallocycle acts as a four-connected supramolecular
crystallization or a configurational overturn of labile-chiral synthon through O–H···O hydrogen-bonding bridging four
nitrogen atoms during coordination. The chirality in 2 ex- adjacent metallocycles. Consequently, 2D chiral networks
tends along the a axis through double hydrogen-bonding extend along the b axis. Very interestingly, the chiral layer
connections between the chiral metallocycles and lattice contains rarely observed hydrogen-bonded heterochiral hel-
methanol and water molecules (see Figure 4). As shown in icates with the helical pitch given by one full rotation of
Figure S2 in the Supporting Information, the resultant hy- the twofold screw axis being 8.103 Å. The left-handed (M)
drogen-bonded chiral macrocycle chains pack through di- helicate only contains Ni1 nodes, whereas the right-handed
rect or perchlorate-mediated interchain C–H···O hydrogen (P) helicate only contains Ni2 nodes (Figure 5a and c).
bonds to form 3D chiral supermolecular crystals.
However, the alternate array of the (P) and (M) helicates
does not contribute additional chirality to the chiral layer.
Structure of [Ni2(Hptpy)2(H2O)2](SCN)2 (3)
Structure of [Cu2(Hptpy)2](dca)2·4H2O (4)
According to PLATON calculations, the space group of
complex 3 should have been assigned as P21/c. However,
Complex 4 crystallizes in the chiral space group P21, with
the use of enantiopure chiral H2ptpy ligands determines 3 a Flack parameter value of 0.012(13). The asymmetric unit
to crystallize in the chiral space group P21, with a Flack consists of two CuII, two (Hptpy)–, two (dca)–, and four
parameter value of 0.23(2) before a twin refinement. The H2O. As shown in Figure 6, two CuII centers in each metallo-
pseudosymmetry P21/c in the structural model can be due cycle of 4 are only coordinated by two (Hptpy)– ions in the
to the pseudotranslation symmetry of heavy Ni atoms.[16] same bis(chelating) fashion. The resultant square-pyrami-
The asymmetric unit of 3 consists of two NiII, two dal coordination geometry of each CuII atom is obviously
(Hptpy)–, two H2O, and two lattice SCN–. In 3, the sixth distorted due to the bis(chelating) fashion of the (Hptpy)–
coordination site of each NiII atom is occupied by O of ligands [Cu–O and Cu–N bond lengths are in the ranges
H2O with Ni–O and Ni–N bond lengths in the ranges of 1.921(4)–1.933(4) and 1.920(4)–2.243(4) Å, respectively; in-
1.926(13)–2.133(13) and 1.869(18)–2.173(12) Å, respec- plane angles are 167.27(16) and 154.61(16)° for Cu1,
tively; the in-plane and axis-transition angles for Ni1 are 167.03(17) and 154.99(17)° for Cu2]. As found in 1 and 3,
Figure 5. (b) View of the 2D chiral layer in 3 built from hydrogen-bonded helicates with each chiral metallocycle acting as a four-onnector,
(a) the simplified infinite right-handed (P) helicate only containing Ni2 nodes, and (c) the simplified infinite left-handed (M) helicate only
containing Ni1 nodes, with coordinating water, the carboxyl group of Hptpy, and Ni nodes in each helicate for clarity [O6···O5A 2.772(10),
O3···O2D 2.685(10) Å; symmetry operations: A: 2 – x, 1/2 + y, 2 – z; B: 2 – x, y – 1/2, 2 – z; C: –x, 1/2 + y, 1 – z; D: –x, y – 1/2, 1 – z].
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Figure 6. View of the coordination geometry around each CuII center in the metallocycle of 4, showing the (S) configuration of permanent-
chiral carbon atoms C2 and C27, and labile-chiral nitrogen atoms N1 with an (S) configuration and N5 with an (R) configuration.
Figure 7. View of the 2D chiral supramolecular layer formed by direct or water-mediated hydrogen-bonding connections of the chiral
metallocycles with the hydrogen-bonding ···(dca)–···(H2O)···(dca)–···(H2O)··· rings in 4. Hydrogen atoms attached to carbon atoms are
omitted for clarity.
the labile-chiral N1 and N5 atoms in each metallocycle of Electronic Spectra
4 possess (S) and (R) configuration, respectively. Notably,
two (dca)– anions are connected in a head-to-tail bridge
The electronic absorption spectra of Na(Hptpy) and
style by two H2O molecules through hydrogen-bonding in- complexes 1–4 were recorded in methanol (ca.
teractions, thereby forming a 16-membered ···(dca)–··· 1.0ϫ10–5 molL–1). As shown in Figure 8, they all are char-
(H2O)···(dca)–···(H2O)··· ring [O6···N9 2.949(14), O6···N12 acterized by intense absorptions between 200 and 400 nm,
2.886(11), O8···N11 2.747(14), O8···N14 3.004(9) Å], which ascribed to π Ǟ π* transitions associated with the aromatic
is further connected with four metallocycles through rings of the ligand. The free anion (Hptpy)– and all metal
direct or water-mediated hydrogen-bonding interactions complexes display intense absorption around 208 nm. The
[N5A···N14 3.119(7), N1C···N9 3.483(8), O5···O8 2.879(9), low-energy absorptions of (Hptpy)– appear at 251 and
O5···O4B 2.772(5), O7···O6 2.829(10), O7···O2 2.788(6) Å; 277 nm with a weaker protracting shoulder centered at
symmetry operations: A: 1 + x, y, z – 1; B: 2 + x, y, z – 1; 320 nm. For complexes 1–4, the low-energy absorptions
C: 1 + x, y, z]. Consequently, those chiral metallocycles are redshift to 289 nm with a slight shoulder centered at 233 nm
linked into chiral supramolecular layers, which pack to and a broad shoulder centered at 340 nm. The obvious red-
form chiral crystals of 4 (see Figure 7 and Figure S3 in the shift for all metal complexes is due to the metal-perturbed
Supporting Information).
energy increase of the lowest π-orbital and the higher conju-
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Chiral Supramolecular Frameworks Based on Chiral Metallocycles
gation of the π-system of the ligand as observed for com-
plexes of the terpyridyl-type ligands.[12,14a,17]
Figure 9. Selection of UV/Vis spectra from the spectrophotometric
titration of (Hptpy)– with Cd(Ac)2·6H2O in CH3OH. CdII/
(Hptpy)– ratio: free (Hptpy)– anion, 0.11, 0.22, 0.33, 0.44, 0.56,
0.67, 0.78, 0.89, 1.00, 1.11, 1.22, 1.33, 1.44, 1.67, 1.89, 2.11.
Figure 8. UV/Vis spectra of the free (Hptpy)– anion and complexes
1–4.
and 581.8, respectively. By careful comparison of the iso-
topic patterns between the observed peak and the theoreti-
cal simulation, the strongest peak at m/z = 521.0 (isotopic
peak spacings 0.5 Da) indicates a dication {i.e., metallocy-
cle [Cd2(Hptpy)2]2+}. The peak at m/z = 581.8 with about
half the intensity of the peak at m/z = 521.0 corresponds to
monomer [Cd(Hptpy)(Ac)]. The peaks for free H2ptpy li-
gand (m/z = 411.5) and [Cd2(Hptpy)2(Ac)]+ (m/z = 1099.6)
are minor. Unfortunately, the peak for neutral complex 1
{i.e., [Cd2(Hptpy)2(Ac)2]} in the methanol solution was not
observed. On the basis of the ESI-MS results, it can be in-
ferred that the metallocycle [Cd2(Hptpy)2]2+ is the domi-
nant species in the equilibrium system, which is consistent
with the results of the spectrophotometric titrations.
Solution Structure Study
As shown in Figure 8, the UV/Vis spectrum of free an-
ionic (Hptpy)– is apparently different from those of all
metallocycle complexes. As a representative example, the
formation of 1 in solution was explored by spectrophoto-
metric titrations. Through the addition of a prepared solu-
tion of Cd(Ac)2 (ca. 1.0ϫ10–3 molL–1) in methanol
(5 μL) to
a prepared solution of Na(Hptpy) (ca.
1.5ϫ10–5 molL–1) in methanol (3 mL), a series of sample
solutions with CdII/(Hptpy)– mol ratios of 0.00 up to 2.11
was prepared for spectrophotometric titrations. The UV/Vis
spectra of the resulting solutions were recorded one by one
over a wavelength range of 190–400 nm. As presented in
Figure 9, the nontypical absorption around 208 nm is grad-
ually strengthened, whereas the typical absorptions at 251
Stability Constant Determination
As shown in Figure 8, complex 1 has a moderate absorp-
and 277 nm for free anionic (Hptpy)– are notably weakened, tion between 340 and 350 nm, whereas the absorption in-
and the characteristic absorptions at 233, 289, and 340 nm tensity of free anionic (Hptpy)– in this area can be almost
for 1 are remarkably strengthened with the CdII/(Hptpy)– neglected. Therefore, the absorbance at 341 nm was re-
mol ratio increasing from 0.00 to 1.00. When the CdII/ corded for stability constant determination. Each recorded
(Hptpy)– mol ratio reached 1.00, the absorption peaks at sample was prepared by fixing the total amount of
251 and 277 nm almost disappeared, whereas the absorp- (Hptpy)– and CdII [Vtotal = VCdII + V(Hptpy)– = 3.0 mL, ntotal
+ n(Hptpy)– = 3.0ϫ 10–4 mmol] and changing the mol
CdII
tion peaks at 233 and 289 nm as well as the broad shoulder
=
absorption at 340 nm almost reached their extremes. As the fraction f (f = nCdII/ntotal) from 0.00 up to 1.00 by changing
mol ratio of CdII/(Hptpy)– was further increased from 1.00 the relative volumes of the methanol solutions of
to 2.11, the scanned curves overlapped without an obvious Cd(Ac)2 (ca. 1.0ϫ10–4 molL–1) and Na(Hptpy) (ca.
increase in the absorbance relative to that found in the sam- 1.0ϫ10–4 molL–1). The corresponding graph of absorbance
ple with the CdII/(Hptpy)– mol ratio of 1.00. These UV/Vis (A) at 341 nm versus f was plotted in Figure 10. Clearly, the
spectra indicate that the metallocycle [Cd2(Hptpy)2]2+ in 1 spectrophotometric data separate into two groups at f =
rapidly and quantitatively formed at a 1:1 ratio is the domi- 0.50, and each group can been linearly fitted with the Ori-
nant complex in solution.
gin program (Figure 11). The left group (f Յ 0.50) meets
Further ESI-MS studies on the behavior of complex 1 in the equation A = 0.07117 – 1.01015f, and the right group
solution were performed in methanol (ca. 10–5 molL–1), (f Ն 0.50) meets the equation A = 1.14207 – 1.14556f. The
and the obtained spectra (shown in Figure S4 in the Sup- experimental values of the highest point are f = 0.50 and A
porting Information) give two major peaks at m/z = 521.0 = 0.5668, and the fitting values of the highest point are f =
Eur. J. Inorg. Chem. 2012, 3349–3360
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3355

J. Xu, R. Wang, Y. Li, Z. Gao, R. Yao, S. Wang, B. Wu
FULL PAPER
0.4969 and AЈ = 0.5730. On the basis of α = (AЈ – A)/AЈ, 339 nm. As for 1, the Cotton effects around 276 and 313 nm
the dissociation degree α of [Cd2(Hptpy)2]2+ is calculated to mostly originate from the chiral H2ptpy ligands, but the for-
be 0.0108. Provided there is omplete dissociation of mation of the chiral structure of 1 has a considerable influ-
Cd(Ac)2 and only the formation of metallocycle ence on the direction (+ or –) of the CD signals except for
[Cd2(Hptpy)2]2+ in the equilibration system with f being an obvious shift of the absorption peak position. Addition-
0.50 (see above), the global stability constant (β) can be ally, a new positive Cotton effect around 362 nm may result
calculated by Equation (1). The result (logβ = 17.60) indi- from the formation of chiral metallocycles.
cates that the metallocycle structure of [Cd2(Hptpy)2]2+ is
very stable. In conjunction with the structural analyses of
complexes 1–4, namely, the strong bis(chelating) coordina-
tion and π–π interactions of (Hptpy)– in the metallocycles,
we may tentatively deduce that metallocycles [M2-
(Hptpy)2]2+ are the thermodynamically favored species in
solution.
Figure 11. Solid-state CD spectra of H2ptpy (solid line) and 1 (dot-
ted line) in KBr.
(1)
Photoluminescent Properties
The luminescence of 1 in solution and in the solid state
is shown in Figure 12. Complex 1 has an emission at λmax
= 404 nm in the solid state and at λmax = 361 nm in meth-
anol (ca. 1.0ϫ10–5 molL–1) upon excitation at 289 nm.
When excited at 277 nm, free H2ptpy ligand in the solid
state and free anionic (Hptpy)– in methanol (ca.
1.0ϫ10–5 molL–1) have emissions at λmax = 370 and
352 nm, respectively. The emission of free anionic (Hptpy)–
is very similar to that of a chiral terpyridine macrocycle.[5]
Clearly, the emissions of complex 1 in the solid state and in
solution undergo a bathochromic shift and quick decrease
in emission intensity relative to those of free H2ptpy ligand
in the solid state and free anionic (Hptpy)– in solution,
respectively. The emission of complex 1 is ascribed to the
metal-perturbed intraligand charge-transfer (ILCT) transi-
tion as reported for CdII or other d10 metal complexes with
N-donor ligands.[17,18] The enhancement of the emission
wavelengths of 1 in the solid state and in solution is mainly
due to the bis(chelation) and intrametallocyclic π–π interac-
tions, which impose a rather planar arrangement of the π-
delocalized chelating ligands. Perhaps the swift decrease of
Figure 10. Selection of UV/Vis spectra from the spectrophotomet-
ric titration of (Hptpy)– with Cd(Ac)2·6H2O in CH3OH. Mol frac-
II
tion f (f = nCd /ntotal): 0.00, 0.070, 0.13, 0.20, 0.27, 0.33, 0.40, 0.47,
0.50, 0.53, 0.60, 0.67, 0.73, 0.80, 0.87, 0.93, 1.00.
Solid-State Circular Dichroism (CD) Studies
To confirm the chiroptical activities, the circular dichro- the emission intensity of 1 owes itself to the effectively
ism (CD) spectra of free H2ptpy ligand and 1 were mea- metal-transferred energy release through the thermal vi-
sured in the solid state (Figure 11). The CD spectrum of 1 brations of terminal ligands (such as Ac– in solid or solvent
obviously indicates it has chirality. The homochiral H2ptpy in solution) and hydrogen atoms that ride on the coordinat-
molecule induced the stereoselective synthesis reaction of ing N atoms of the amino acid groups of (Hptpy)–. Notably,
the metallocycle 1, and the chirality was transferred from the emissions of 1 and the H2ptpy ligand in the solid state
the ligand to the metallocycle complex successfully. Chiral are bathochromic relative to those of 1 and anionic
H2ptpy ligands exhibit two Cotton effects around 299 and (Hptpy)– in methanol, respectively.
3356
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 3349–3360

Chiral Supramolecular Frameworks Based on Chiral Metallocycles
by similar chiral metallocyclic units, interestingly, the chiral
supramolecular architectures are sensitive to free solvents
and other terminal ligands, and therefore intentionally tun-
able.
Experimental Section
General Remarks: All reagents were purchased from commercial
sources and used as received. Compounds l-α-alanine ester, 2,6-
bis(pyridin-2-yl)-4-p-tolylpyridine, and 4-[4-(bromomethyl)phenyl]-
2,6-bis(pyridin-2-yl)pyridine were prepared according to literature
procedures.[11,12,19] Elemental analyses were performed with a
Carlo–Erba 1106 elemental analyzer. IR spectra were measured as
KBr pellets with a Nicolet NEXUS 470 FTIR spectrometer in the
range of 400–4000 cm–1. Electronic absorption spectra were re-
corded with a Unico-2102 UV/Vis spectrometer. 1H and 13C NMR
spectra were recorded with a Bruker DPX-300 spectrometer op-
erating at 300 MHz. Fluorescent spectra were determined with a
Hitachi F-4500 fluorophotometer in the solid state at room tem-
perature. Solid-state CD spectra were recorded with a MOS-450
spectrometer. Specific rotations were measured with a Perkin–El-
mer 341 with a wavelength of 589 nm in methanol solution at a
temperature of 20 °C. ESI-MS measurements were performed with
a DECAX-30000 LCQ Deca XP ion-trap mass spectrometer at a
concentration that ranged from 10–4 to 10–6 molL–1.
Synthesis of 2,6-Bis(pyridin-2-yl)-4-p-tolylpyridine (1Ј): 2-Acetylpyr-
idine (7.00 mL, 59.13 mmol), an aqueous solution of KOH (10 mL,
15%), and an aqueous solution of NH3 (100 mL, conc.) were added
to a mixture of 4-methylbenzaldehyde (13.27 mL, 118.27 mmol)
and EtOH (100 mL, 95%) in turn. The resulting mixture was
heated at reflux for 36 h, then cooled to room temperature. The
off-white solid was collected by filtration and washed with ice-cold
EtOH (10 mL, 95%). After recrystallization from EtOH, white
crystals (9.20 g) were obtained. Yield: 48%. M.p. 170 °C. IR (KBr):
ν = 3048 (w), 3013 (w), 2968 (w), 1602 (w), 1583 (s), 1565 (m),
˜
Figure 12. (a) Photoluminescent spectra of the free (Hptpy)– anion
and 1 in methanol, and (b) of free H2ptpy and 1 in the solid state.
1465 (m), 1385 (m), 1111 (w), 1073 (w), 1038 (w), 821 (m), 789 (s),
742 (w), 732 (s), 682 (m), 658 (m), 620 (m) cm–1. 1H NMR (CDCl3,
300 MHz): δ = 2.43 (s, 3 H), 7.31 (d, 2 H), 7.35 (t, 2 H), 7.83 (d, 2
H), 7.85–7.90 (m, 2 H), 8.67 (d, 2 H), 8.73 (s, 4 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 21.29, 118.58, 121.34, 123.75, 127.13,
Conclusion
We have designed and synthesized a new chiral terpyr- 129.64, 135.44, 136.81, 139.07, 149.10, 150.12, 155.84, 156.32 ppm.
idyl-type H2ptpy ligand derived from a chiral amino acid.
Synthesis of 4-[4-(Bromomethyl)phenyl]-2,6-bis(pyridin-2-yl)pyridine
Based on the self-assembly of this chiral ligand with metal
ions, a new class of purely chiral supramolecular frame-
works was prepared. These compounds all consist of
[M2(Hptpy)2]2+ chiral metallocyclic units formed by two
chiral (Hptpy)– ions bridging two metal ions in a head-to-
tail style and stabilized by the bis(chelation) and stronger
intrametallocyclic π–π-interactions. The formation of the
metallocyclic units is easily monitored by UV/Vis spec-
troscopy. Spectrophotometric titrations and ESI-MS data
reveal that these metallocyclic units are the thermodynami-
cally favored species in solution. As expected, these chiral
nanometallocycles not only induced a chiral array or hel-
icates but also amplified chirality through hydrogen-bond-
ing interactions, and finally aggregated into complicated
higher-dimensional chiral supramolecular architectures
with chiral voids for further use. The percent effective free
volumes in 1–4 calculated with PLATON are 17.8, 27.5,
(2Ј): Complex 1Ј (4.00 g, 12.37 mmol), N-bromosuccinimide (NBS;
2.42 g, 13.61 mmol), and a catalytic amount of benzoyl peroxide
(BPO) were dissolved in dry CCl4 (120 mL). The mixture was
heated to reflux under nitrogen for 8 h, cooled to room tempera-
ture, and filtered. The filtrate was washed with water and dried
with anhydrous magnesium sulfate. The solvent was removed in
vacuo to yield a precipitate. After recrystallization from an acetone/
EtOH mixture (1:2), a white powder (4.35 g) was obtained. Yield:
87%. M.p. 176 °C. IR (KBr): ν = 3050 (w), 3014 (w), 2923 (w),
˜
1602 (m), 1584 (s), 1565 (s), 1466 (s), 1387 (s), 1076 (w), 989 (m),
836 (m), 788 (s), 741 (m), 659 (m), 620 (m) cm–1. 1H NMR (CDCl3,
300 MHz): δ = 1.78 (s, 2 H), 6.72 (s, 2 H), 7.26–7.39 (m, 2 H), 7.54
(d, 2 H), 7.86 (s, 2 H), 7.89 (t, 2 H), 8.67 (d, 2 H), 8.73 (s, 4 H)
ppm. 13C NMR (CDCl3, 75 MHz): δ = 33.03, 118.79, 121.40,
123.93, 127.77, 129.66, 136.95, 138.55, 138.61, 149.14, 149.48,
155.97, 156.09 ppm.
Synthesis of
L-α-Alanine Methyl Ester Hydrochloride: A mixture of
l-α-alanine (5.00 g, 56.18 mmol) and anhydrous methanol (45 mL)
14.0, and 22.8%, respectively. Although mainly constructed was placed in a salt/ice bath to keep the temperature below –5 °C as
Eur. J. Inorg. Chem. 2012, 3349–3360
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3357

J. Xu, R. Wang, Y. Li, Z. Gao, R. Yao, S. Wang, B. Wu
FULL PAPER
SOCl2 (5.30 mL, 73.03 mmol) was added dropwise with continuous
stirring. The resulting mixture reacted with stirring in a tempera-
ture range from 0 to –5 °C for 1 h, and then was heated to reflux
for an additional 1 h. The solvent was removed in vacuo to give a
yellowish oil. With vigorous stirring, absolute diethyl ether (50 mL)
was added dropwise into the oil. After filtering and washing several
times with absolute diethyl ether, white crystals (5.53 g) were ob-
tained. Yield: 71%. 1H NMR (CDCl3, 300 MHz): δ = 1.73 (m, 3
H), 3.82 (s, 3 H), 4.33 (s, 1 H), 8.65 (s, 3 H) ppm.
(w), 2926 (w), 1609 (s), 1574 (s), 1478 (m), 1403 (s), 1327 (w), 1136
(w), 1010 (w), 795 (w), 690 (w), 660 (w) cm–1.
Synthesis of [Ni2(Hptpy)2(CH3OH)(H2O)](ClO4)2·CH3OH·H2O
(2): A mixture of Ni(ClO4)2·6H2O (36.6 mg, 0.1 mmol) and meth-
anol (8 mL) was added dropwise into a mixture of H2ptpy
(41.0 mg, 0.1 mmol), NaOH (4.0 mg, 0.1 mmol), and methanol
(8 mL). The resulting mixture was stirred for 30 min and filtered.
The filtrate was allowed to concentrate without any disturbance at
room temperature. About 1 week later, pale cyan block crystals
were obtained (25.8 mg, 42%). C52H54Cl2N8Ni2O16 (1235.37):
calcd. C 50.56, H 4.41, N 9.07; found C 50.82, H 4.33, N 9.24. IR
Synthesis
of
(S)-2{4-[2,6-Bis(pyridin-2-yl)pyridin-4-yl]benzyl-
amino}propanoic Acid (H2ptpy): A mixture of l-α-alanine methyl
ester hydrochloride (3.12 g, 22.44 mmol), anhydrous Na2CO3
(3.18 g, 30.00 mmol), and dry DMF (40 mL) was stirred at room
temperature for 1 h, and then a solution of 2Ј (3.00 g, 7.48 mmol)
and DMF (80 mL) was added dropwise. The resulting yellow solu-
tion was heated to 45 °C and kept at that temperature with con-
tinuous stirring for 18 h. All the above processes took place under
nitrogen. The red mixture was cooled to room temperature and
filtered to remove any solids. A red oil was obtained after removal
of the solvent in vacuo. The red oil was redissolved in dichloro-
methane and washed with distilled water several times. After evapo-
ration of the solvent, a pure red oil of 3Ј was obtained (2.58 g,
(KBr): ν = 3052 (w), 3015 (w), 1603 (s), 1556 (m), 1472 (m), 1426
˜
(m), 1404 (m), 1101 (s), 829 (m), 789 (s), 790 (m), 622 (m) cm–1.
Synthesis of [Ni2(Hptpy)2(H2O)2](SCN)2 (3): A mixture of H2ptpy
(41.0 mg, 0.1 mmol), NaOH (4.0 mg, 0.1 mmol), NiCl2·6H2O
(23.8 mg, 0.1 mmol), NH4SCN (15.2 mg, 0.2 mmol), and redistilled
water (8 mL) was sealed into a 25 mL Teflon-lined stainless steel
autoclave. The autoclave was heated in an oven at 150 °C for 3 d
and then gradually cooled to room temperature. After having been
filtered, prismatic cyan crystals were obtained (37.5 mg, 69%).
C52H46N10Ni2O6S2 (1088.54): calcd. C 57.38, H 4.26, N 12.87, S
5.89; found C 57.57, H 4.17, N 12.60, S 5.91. IR (KBr): ν = 3416
˜
81%). IR (KBr, selected values): ν = 3055 (w), 2987 (w), 1735 (s),
˜
(m), 3192 (w), 3062 (w), 2981 (w), 2057 (vs), 1604 (s), 1569 (w),
1471 (m), 1405 (s), 1382 (w), 1357 (w), 1015 (m), 884 (w), 730 (w),
639 (w) cm–1.
1584 (s), 1566 (m), 1546 (m), 1468 (m), 1388 (s), 1200 (m), 1150
(m), 791 (s), 742 (m), 620 (m) cm–1. A mixture of 3Ј (2.58 g,
6.08 mmol), methanol (40 mL), and an aqueous solution of NaOH
(10 mL, 5%) was heated at 40 °C with stirring for 48 h. As the pH
value of the reaction solution was adjusted to 6–7, a pale yellow
precipitate appeared. After having been filtered, washed with DMF,
and dried in air, a white powder (1.91 g) was obtained. Yield: 77%.
M.p. 264 °C. C25H21N4O2 (409.47): calcd. C 73.32, H 5.17, N
Synthesis of [Cu2(Hptpy)2](dca)2·4H2O (4): A mixture of H2L
(41.0 mg, 0.1 mmol), NaOH (4.0 mg, 0.1 mmol), CuCl2·2H2O
(17.0 mg, 0.1 mmol), Na(dca) (17.8 mg, 0.2 mmol), and H2O
(8 mL) was sealed into a 25 mL Teflon-lined stainless steel auto-
clave. The autoclavewas heated in an oven at 130 °C for 3 d, and
then gradually cooled to room temperature. After filtration, green
prismatic crystals were obtained (26.4 mg, 46%). C54H50Cu2N14O8
(1150.17): calcd. C 56.39, H 4.38, N 17.05; found C 56.61, H 4.29,
13.69; found C 72.86, H 5.24, N 13.55. IR (KBr): ν = 3425 (w),
˜
3049 (w), 2978 (w), 1603 (m), 1585 (s), 1567 (m), 1466 (m), 1391
(m), 1359 (m), 1297 (w), 1094 (w), 789 (m), 737 (w), 621 (w) cm–1.
[α]2D0 = +3.5 (c = 0.02, CH3OH) for Na(Hptpy).
N 17.30. IR (KBr): ν = 3420 (w), 3210 (m), 3070 (w), 2235 (s),
˜
2194 (m), 2137 (vs), 1620 (s), 1573 (m), 1556 (m), 1479 (m), 1410
(m), 1347 (m), 1319 (m), 1152 (w), 1021 (m), 790 (m), 692 (w), 657
(w) cm–1.
Synthesis of [Cd2(Hptpy)2(Ac)2]·3CH3OH·H2O (1): A mixture of
Cd(Ac)2·2H2O (6.6 mg, 0.025 mmol) and DMF (2 mL) was added
dropwise into a mixture of H2ptpy (10.3 mg, 0.025 mmol), NaOH
(1.0 mg, 0.025 mmol), and methanol (6 mL). The resulting mixture Spectrophotometric Measurements: All operations were performed
was stirred for 30 min and filtered. The filtrate was allowed to con-
centrate without any disturbance at room temperature. About
1 week later, colorless block crystals were obtained (9.9 mg, 62%).
at room temperature (ca. 24 °C) with the UV/Vis spectrometer
mentioned above. The solutions used to record the UV/Vis spectra
were prepared by completely dissolving a certain amount of
C57H62Cd2N8O12 (1275.96): calcd. C 53.65, H 4.90, N 8.78; found Na(Hptpy) and complexes 1–4 in methanol in volumetric flasks.
C 54.10, H 4.77, N 8.63. IR (KBr): ν = 3405 (m), 3229 (w), 3112 The reaction mixtures for the UV/Vis spectra were left to equili-
˜
Table 1. Crystal data and structure refinement for 1–4.
1
2
3
4
Empirical formula
T [K]
C57H62Cd2N8O12
293(2)
C52H54Cl2N8Ni2O16
293(2)
C52H46N10Ni2O6S2
293(2)
C54H50Cu2N14O8
293(2)
Crystal system
Space group
monoclinic
P21
triclinic
P1
monoclinic
P21
monoclinic
P21
a [Å]
b [Å]
c [Å]
α [°]
8.1935(4)
21.100(1)
17.232(1)
90
7.954(2)
10.735(2)
8.103(2)
28.881(6)
90
7.4346(2)
17.0866(4)
20.2306(4)
90
10.884(2)
18.153(4)
74.36(3)
β [°]
105.489(5)
90
2871.0(3)
2, 1.476
0.898
79.19(3)
76.20(3)
1457.0(5)
1, 1.408
1.050
108.86(2)
90
2377.4(8)
2, 1.521
0.799
94.977(2)
90
2560.24(10)
2, 1.492
γ [°]
V [Å3]
Z, ρcalcd. [gcm–3]
GoF
1.027
Flack parameter
R1, wR2 [IϾ2σ(I)]
Largest difference peak/hole
–0.02(3)
0.0373, 0.0774
0.747/–0.328
0.04(3)
0.0776, 0.1861
0.665/–0.434
0.00(0)
0.0783, 0.1484
0.011/–0.016
0.01(1)
0.0398, 0.0942
0.499/–0.331
3358
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Eur. J. Inorg. Chem. 2012, 3349–3360

Chiral Supramolecular Frameworks Based on Chiral Metallocycles
brate before recording the spectra (equilibration was very quick,
generally found to occur in 1 min).
Table 2. Selected bond lengths [Å] and angles [°] for 1–4.
1
X-ray Structure Determination: Crystallographic data for com-
pounds 1–4 were collected with an Oxford diffractometer by using
graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) at
288(2) K. Raw data collection and reduction were carried out by
using CrysAlisPro software. Empirical absorption correction was
carried out by using spherical harmonics, implemented in the
SCALE3 ABSPACK scaling algorithm. All structures were solved
by direct methods and expanded by using Fourier techniques. Non-
hydrogen atoms were refined with anisotropic displacement param-
eters during the final cycles. Hydrogen atoms were treated as ideal-
ized contributions, except for water molecules, the hydrogen atoms
of which were located from difference Fourier maps and included in
the final refinement by using geometrical restraints. All calculations
were performed by using SHELXTL.[20] Crystal data are summa-
rized in Table 1 and selected bond lengths and angles are listed in
Table 2. CCDC-860375 (for 1), -860376 (for 2), -860377 (for 3),
and -860378 (for 4) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
Cd1–O3
2.267(7)
2.385(8)
2.408(8)
2.216(7)
2.361(9)
2.442(8)
90.8(3)
Cd1–O1
2.342(8)
2.403(8)
2.427(10)
2.291(8)
2.362(8)
2.458(10)
148.5(2)
94.5(3)
Cd1–N1
Cd1–N7
Cd1–N6
Cd1–N8
Cd2–O8
Cd2–O5
Cd2–N3
Cd2–N5
Cd2–N2
Cd2–N4
O3–Cd1–O1
O1–Cd1–N1
O1–Cd1–N7
O3–Cd1–N6
N1–Cd1–N6
O3–Cd1–N8
N1–Cd1–N8
N6–Cd1–N8
O8–Cd2–N3
O8–Cd2–N5
N3–Cd2–N5
O5–Cd2–N2
N5–Cd2–N2
O5–Cd2–N4
N5–Cd2–N4
O3–Cd1–N1
O3–Cd1–N7
N1–Cd1–N7
O1–Cd1–N6
N7–Cd1–N6
O1–Cd1–N8
N7–Cd1–N8
O8–Cd2–O5
O5–Cd2–N3
O5–Cd2–N5
O8–Cd2–N2
N3–Cd2–N2
O8–Cd2–N4
N3–Cd2–N4
N2–Cd2–N4
71.8(3)
148.2(3)
96.0(3)
114.3(3)
81.6(3)
106.8(3)
89.0(3)
66.7(3)
144.8(2)
66.7(3)
90.8(3)
133.3(3)
96.7(3)
92.9(3)
147.3(3)
71.8(3)
143.6(2)
114.2(3)
78.5(3)
98.7(3)
69.1(3)
109.7(3)
143.3(2)
86.5(3)
87.5(3)
68.5(3)
137.7(3)
2
Ni1–O1
1.953(9)
2.093(12)
2.122(11)
1.991(10)
2.123(10)
2.135(11)
176.1(4)
79.2(4)
Ni1–N7
2.011(9)
2.148(11)
2.142(11)
2.030(8)
2.124(11)
2.183(10)
102.1(5)
81.8(4)
Ni1–N8
Ni1–N1
Ni1–N6
Ni1–O3
Ni2–N3
Ni2–O4
Ni2–O6
Ni2–N2
Ni2–N4
Ni2–N5
Supporting Information (see footnote on the first page of this arti-
cle): Figures S1–S4.
O1–Ni1–N7
N7–Ni1–N8
N7–Ni1–N1
O1–Ni1–N6
N8–Ni1–N6
O3–Ni1–O1
N8–Ni1–O3
O3–Ni1–N6
N3–Ni2–O6
N3–Ni2–N2
N2–Ni2–O6
O4–Ni2–N4
N2–Ni2–N4
O4–Ni2–N5
N2–Ni2–N5
O1–Ni1–N8
O1–Ni1–N1
N8–Ni1–N1
N7–Ni1–N6
N1–Ni1–N6
N7–Ni1–O3
N1–Ni1–O3
N3–Ni2–O4
O4–Ni2–O6
O4–Ni2–N2
N3–Ni2–N4
O6–Ni2–N4
N3–Ni2–N5
O6–Ni2–N5
N4–Ni2–N5
101.8(4)
100.8(4)
157.0(4)
83.6(4)
94.5(4)
77.8(4)
90.8(4)
Acknowledgments
92.8(4)
88.5(4)
165.3(4)
173.4(4)
84.4(4)
92.0(4)
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (20771094).
89.8(4)
78.5(4)
98.2(4)
89.5(4)
77.3(4)
106.0(4)
155.7(4)
80.1(4)
91.0(4)
105.6(4)
164.6(3)
93.4(4)
[1] a) S. Vaduvescu, P. G. Potvin, Eur. J. Inorg. Chem. 2004, 1763–
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92.5(4)
3
Ni1–N7
1.869(18)
2.115(17)
2.153(19)
1.926(13)
2.052(13)
2.142(17)
170.9(7)
94.3(5)
Ni1–O1
2.040(11)
2.116(12)
2.173(16)
2.050(19)
2.133(13)
2.173(12)
78.8(6)
Ni1–N6
Ni1–O3
Ni1–N8
Ni1–N1
Ni2–O4
Ni2–N2
Ni2–N3
Ni2–O6
Ni2–N4
Ni2–N5
N7–Ni1–O1
O1–Ni1–N6
O1–Ni1–O3
N7–Ni1–N8
N6–Ni1–N8
N7–Ni1–N1
N6–Ni1–N1
N1–Ni1–N8
O4–Ni2–N3
O4–Ni2–O6
N3–Ni2–O6
N2–Ni2–N4
N4–Ni2–O6
N2–Ni2–N5
O6–Ni2–N5
N7–Ni1–N6
N7–Ni1–O3
O3–Ni1–N6
O1–Ni1–N8
O3–Ni1–N8
O1–Ni1–N1
N1–Ni1–O3
N2–Ni2–O4
N2–Ni2–N3
O6–Ni2–N2
N4–Ni2–O4
N3–Ni2–N4
O4–Ni2–N5
N3–Ni2–N5
N5–Ni2–N4
88.2(7)
86.0(6)
91.3(6)
77.7(7)
109.0(7)
86.6(5)
156.4(6)
105.2(7)
93.2(7)
80.9(6)
166.4(5)
107.1(7)
76.6(7)
94.2(6)
174.2(6)
84.8(5)
87.2(6)
91.0(5)
98.0(6)
154.4(7)
90.1(5)
78.0(6)
82.4(5)
95.1(5)
101.9(5)
93.1(5)
167.1(5)
4
Cu1–O1
1.921(4)
Cu1–N7
1.938(4)
Cu1–N6
2.063(5)
Cu1–N8
2.066(4)
Cu1–N1
2.239(4)
Cu2–N3
1.920(4)
Cu2–O3
1.933(4)
Cu2–N2
2.042(5)
Cu2–N4
2.063(5)
Cu2–N5
2.243(4)
O1–Cu1–N7
N7–Cu1–N6
N7–Cu1–N8
O1–Cu1–N1
N6–Cu1–N1
N3–Cu2–O3
O3–Cu2–N2
O3–Cu2–N4
N3–Cu2–N5
N2–Cu2–N5
167.27(16)
79.56(17)
79.30(17)
80.82(16)
98.1(2)
O1–Cu1–N6
O1–Cu1–N8
N6–Cu1–N8
N7–Cu1–N1
N8–Cu1–N1
N3–Cu2–N2
N3–Cu2–N4
N2–Cu2–N4
O3–Cu2–N5
N4–Cu2–N5
102.26(17)
95.42(15)
154.61(16)
111.55(17)
102.6(2)
167.03(17)
95.01(17)
102.17(19)
110.76(15)
100.82(16)
79.54(18)
79.76(16)
154.99(17)
81.73(14)
99.54(16)
Eur. J. Inorg. Chem. 2012, 3349–3360
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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Received: February 1, 2012
Published Online: June 1, 2012
3360
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 3349–3360