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Zinc(II) coordination architectures with two bulky anthracene-basedcarboxylic ligands: crystal structures and luminescent properties†‡

Jun-Jie Wang,a Chun-Sen Liu,a Tong-Liang Hu,a Ze Chang,a Cai-Yun Li,a Li-Fen Yan,a Pei-Quan Chen,c

Xian-He Bu,*a Qiang Wu,b Li-Juan Zhao,b Zhe Wangb and Xin-Zheng Zhangb

Received 5th July 2007, Accepted 3rd January 2008

First published as an Advance Article on the web 8th February 2008

DOI: 10.1039/b710209g

To systematically investigate the influence of ligands with a large conjugated p-system on the structures

and properties of their complexes, we synthesized seven ZnII complexes with two anthracene-based

carboxylic ligands, anthracene-9-carboxylic acid (HL1) and anthracene-9,10-dicarboxylic acid (H2L2),

and sometimes incorporating different auxiliary ligands, {[Zn(L1)2(H2O)2](H2O)}N (1), [Zn5(m3-

OH)2(L1)8(2,20-bipy)2] (2), Zn2(L1)4(phen)2(m-H2O) (3), {[Zn(L1)2(4,40-bipy)(CH3OH)2]}N (4),

{[Zn(L2)2](Hdmpy)2(H2O)2}N (5), {[Zn2(L2)(2,20-bipy)4](HL2)2}N (6) and

{[Zn2(L2)(pypz)2(Hpypz)2]}N (7) (2,20-bipy ¼ 2,20-bipyridine, phen ¼ 1,100-phenanthroline, Hpypz ¼3-(2-pyridyl)pyrazole, 4,40-bipy ¼ 4,40-bipyridine and Hdmpy ¼ protonated 2,6-dimethylpyridine),

which were characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. 1 has

a one-dimensional (1-D) chain structure, whereas 2 exhibits a new pentanuclear cluster structure

because of the introduction of a chelating 2,20-bipy ligand. 3 and 4 take dinuclear and 1-D structures,

respectively, by incorporating the auxiliary ligands phen and 4,40-bipy. 5 is a three-dimensional (3-D)

twofold interpenetrating diamondoid framework showing an open channel. 6 and 7 possess the

corresponding chain structures containing Zn2 units as nodes by introducing Hpypz and 4,40-bipy

auxiliary ligands, respectively. These results indicate that the nature of ligands and auxiliary ligands has

an important effect on the structural topologies of such complexes. Moreover, the luminescent

properties of the corresponding complexes and ligands have been briefly investigated.

Introduction

The chemistry of d10 metal–organic coordination architectures is

currently of great interest due to not only their intriguing struc-

tural diversity but also their potential applications as functional

materials.1,2 In this field, one of the great challenges is the ratio-

nal and controlled preparation of such complexes. One of the

effective approaches is the appropriate choice of organic ligands

as spacers, bridges or terminal groups with metal ions or metal

clusters as nodes, which, so far, has been at an evolutionary stage

with the current focus mainly on understanding the factors deter-

mining the crystal packing.1g,2 Among various ligands, the versa-

tile carboxylic acid ligands exhibiting diverse coordination

modes, especially for benzene-based and naphthalene-based

di- or multi-carboxylic acids, such as 1,4-benzenedicarboxylic

acid,3 1,4-naphthalenedicarboxylic acid4 and 1,3,5-benzenetri-

carboxylic acid,5 have been well used in the preparation of

aDepartment of Chemistry, Nankai University, Tianjin, 300071, China.E-mail: buxh@nankai.edu.cn; Fax: +86-22-23502458bPhotonics Center, TEDA Applied Physics School, The MOE Key Lab ofAdvanced Technique & Fabrication for Weak-Light Nonlinear PhotonicsMaterials, Tianjin, 300457, ChinacInstitute of Elemento-Organic Chemistry, Nankai University, Tianjin,300071, China

† CCDC reference numbers 617255–623316. For crystallographic data inCIF or other electronic format see DOI: 10.1039/b710209g

‡ Electronic supplementary information (ESI) available: Furtherstructural data (Fig. S1–S18, Scheme S1). See DOI: 10.1039/b710209g

This journal is ª The Royal Society of Chemistry 2008

various metal–organic complexes, which exhibit luminescent

properties.6

In comparison with the benzene- and naphthalene-based car-

boxylic acid ligands aforementioned, however, the investigation

of anthracene-based carboxylic acids has been less common,

such as anthracene-9-carboxylic acid (HL1)7 and anthracene-

9,10-dicarboxylic acid (H2L2) (Chart 1), especially for H2L

2

whose coordination chemistry of d10 transition metal has been

rarely investigated to date.8 Their larger conjugated p-systems

of anthracene ring (a representative fluorophore9 in fluorescence

signalling) are currently of interest in the development of fluores-

cent material and used as model compounds for electrolumines-

cence (EL),9a chemosensors9b and photoinduced electron transfer

(PET) sensors.9c–e Those characteristics mentioned above may

make HL1 and H2L1 show different coordination modes from

related benzene- and naphthalene-based carboxylic acids, and

may form interesting supramolecular structures with potential

properties. Besides, the skilful introduction of 2,20-bipyridyl-

like bidentate chelating1g or 4,40-bipyridyl-like linear bridging1a

molecules as spacers into the reaction systems involving various

carboxylic acid ligands, as auxiliary ligand, may generate some

interesting coordination architectures.

Considering the aspects stated above, our idea in this work is

to elaborately select the two kinds of ligands to construct d10

metal carboxylate complexes exhibiting rich photoluminescence

(see Chart 1): (1) two anthracene-based aromatic carboxylic

acids (HL1 and H2L2) as primary ligands by taking the advantage

of their carboxylate bridging coordination abilities together with

CrystEngComm, 2008, 10, 681–692 | 681

Chart 1 The ligands used in this work: carboxylic acid ligands (HL1 and

H2L2), chelating ligands (2,20-bidy, phen and Hpypz) and bridging

ligands (4,40-bidy).

Scheme 1 Coordination modes of HL1 and H2L2 in 1–7: (a) monoden-

tate; (b) h–O,O0–m–O,O chelating/bridging; (c) syn–syn bridging; (d)

m-O,O bridging; (e) bridging bis-monodentate; (f) bridging bis-bidentate.

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the steric bulk of their anthracene ring;(2) three 2,20-bipyridyl-

like chelating ligands (2,20-bipy, phen and Hpypz) as terminal

groups to reduce dimensionality of the networks formed; (3)

one bridging 4,40-bipy ligand as a good spacer in the construction

of metal carboxylate polymers. Herein, we report the syntheses,

crystal structures, and luminescent properties of seven ZnII

complexes with these ligands.

Results and discussion

Synthesis consideration and general characterizations

For a systematic investigation of the relationship between HL1 or

H2L2 and their ZnII complexes, our strategy was to obtain

crystals of their complexes suitable for X-ray diffraction, some-

times by changing systematically the auxiliary ligands including

bidentate chelating ligands (2,20-bipy, phen and Hpypz) as well

as linear bridging ligand (4,40-bipy). It should be pointed out

that the use of excess dmpy is the key point for the formation

of 2–7, which not only adjusts the pH values of the reaction

systems to weak basic conditions (pH ¼ ca. 7.2) but also some-

times acts as guest molecule included within the void cavities

of the 3-D open framework, such as the complex 5. In addition,

we have not obtained any complexes suitable for X-ray analysis

while using other basic compounds instead of dmpy, such as

NaOH or TMA.

Complexes 1–7 are all air stable. All general characterizations

were carried out with crystal samples. The elemental analyses

showed that the components of these complexes are well consis-

tent with the results of the structural analysis except those of 1

and 5, which may be due to the loss of the solvent H2O during

measurements. In general, the IR spectra show features

682 | CrystEngComm, 2008, 10, 681–692

attributable to each component of the complexes.10 The broad

band centered at ca. 3410�3450 cm�1 indicates the O–H stretch-

ing of the carboxylic group or water.11 For 1–4 (all including HL1

ligand), the characteristic bands of carboxylate groups appeared

in the usual region at 1647�1518 cm�1 for the antisymmetric

stretching vibrations and at 1442�1389 cm�1 for the symmetric

stretching vibrations. Furthermore, the Dn values [Dn ¼nas(COO�) � ns(COO�)] are 125, 99, and 83 cm�1 for 1, 205

and 189 cm�1 for 2, 219 and 142 cm�1 for 3 and 184 cm�1 for

4, respectively, in good agreement with their solid structural

features from the results of crystal structures.11a,b The IR spectra

of 5–7 (all including H2L2 ligand) also show characteristic

features attributable to the dicarboxylate stretching vibra-

tions.11c For 5 and 7, the differences (Dn) between the antisym-

metric stretching and symmetric stretching bands of the

dicarboxylate groups are 181 and 127 cm�1, respectively, attri-

butable to the bridging bis-monodentate coordination mode of

the dicarboxylate groups (Scheme 1e). For 6, the Dn values of

167 and 115 cm�1 assignable to the bridging bis-bidentate

coordination mode of the dicarboxylate groups were observed

(Scheme 1f). Therefore, the corresponding IR results are well

coincident with the crystallographic structural analyses.

Description of crystal structures

Complex 1. The structure of 1 consists of 1-D polymeric

coordination chains, {[Zn(L1)2(H2O)2](H2O)}N (Fig. 1a). The

This journal is ª The Royal Society of Chemistry 2008

Fig. 1 View of (a) the 1-D chain in 1 showing the O–H/O H-bonding;

(b) the coordination environment of ZnII in 2; (c) the coordination

environment of ZnII in 3 showing the O–H/O H-bonding and p/p

stacking; (d) the 1-D chain in 4 showing the O–H/O H-bonding (partial

H atoms, partial anthracene rings of HL1 and the free H2O omitted for

clarity).

This journal is ª The Royal Society of Chemistry 2008

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asymmetric unit of 1 is composed of one ZnII ion, two L1, two

coordinated H2O and a free H2O; namely, each ZnII ion is

coordinated to four carboxylate O atoms from three different

L1 ligands and two O atoms from two coordinated H2O mole-

cules, respectively (see ESI, Fig. S1a‡). The geometry around

each ZnII can be best described as a distorted octahedron in

which the ZnII ion deviates from the least-squares plane gener-

ated by O(2)–O(6)–O(2A)–O(1A) toward O(4) by only ca.

0.0151 A. The Zn–O bond distances lie in the range of

2.0222(2)�2.4783(1) A, and the bond angles around each ZnII

ranging from 55.88 to 179.67� (Table 1).13 Moreover, in the

coordination environment around each ZnII ion, the three L1

ligands adopt two different coordination modes: one monoden-

tate (Scheme 1a) and two h–O,O0–m–O,O chelating/bridging

(Scheme 1b) modes. In 1, there are intra-chain O–H/O H-bon-

ding interactions. The O(4A), O(1B) and O(3) atoms of three

distinct L1 ligands not only coordinate to ZnII ions (except

O(3) atom) but also act as the H-bonding acceptors to form

O–H/O H-bonding interactions with the O(5) and O(6) atoms

of the coordinated H2O molecules (see Table 2).

Complex 2. Different from 1, the structure of 2 (Fig. 1b) is

a neutral discrete pentanuclear [Zn5(m3-OH)2(L1)8(2,20-bipy)2]

complex with 2,20-bipy as a ‘‘terminal’’ chelating ligand, which

can often reduce structural dimensionality and lead to the forma-

tion of discrete polynuclear metal clusters.1g The pentanuclear

Zn–O core is further embedded within an outer open shell of

aromatic rings formed by the anthracene and pyridine of L1 and

2,20-bipy, respectively (ESI, Fig. S1b‡). The molecular structure

of 2 is centrosymmetric, having three independent ZnII ions

with three different coordination environments linked together

through the carboxylate groups of L1 and N donors of 2,20-

bipy. Each m3-OH interlinks three crystallographically unique

ZnII centers with the adjacent non-bonding Zn/Zn separations

of 3.326(3)��A for Zn(2)/Zn(3), 3.375(5)

��A for Zn(1)/Zn(2),

and 3.375(2)��A for Zn(1)/Zn(3), respectively (ESI, Fig. S4‡).

Zn(1) lies on a crystallographic inversion centre with a slightly

distorted octahedral coordination geometry and is coordinated

by two m3-OH groups [Zn(1)–O(1W) ¼ 2.077(4)��A] and four

carboxylate O atoms [Zn–O: 2.051(4)�2.186(4)��A] from four dif-

ferent L1 ligands lying on the equatorial plane and the axial posi-

tions of octahedral coordination geometry. Zn(2) is coordinated

by three carboxylate O atoms [Zn–O: 1.923(5)�1.928(7)��A]

from three L1 ligands and a m3-OH O atom [Zn(2)–O(1W) ¼1.991(5)

��A] to form a distorted tetrahedral coordination environ-

ment, whereas Zn(3) exists in an approximately tetragonal–pyra-

midal geometry, bounded by two N donors [Zn–N:

2.096(8)�2.134(6)��A] from a chelating 2,20-bipy ligand, two car-

boxylate O atoms [Zn–O: 2.038(5) and 2.066(5)��A] from two L1

ligands and a m3-OH O atom [Zn(3)–O(1W) ¼ 2.030(6)��A]. It

should be noted that the m3-OH group is not co-planar with

Zn(1), Zn(2) and Zn(3), and the O atom of the m3-OH group

deviates from the basal plane defined by Zn(1), Zn(2) and Zn(3)

by ca. 0.610��A; and all the Zn–O(hydroxo) distances here are

compatible to those documented in literature (Table 1).12 There-

fore, this pentanuclear Zn cluster includes 4, 5 and 6-coordinate

environments. Moreover, among the four independent carboxyl-

ate groups of each pentanuclear unit, three serve as a bidentate

ligand with a syn–syn bridging coordination mode (Scheme 1c)

CrystEngComm, 2008, 10, 681–692 | 683

Table 1 Selected bond distances (A) and angles (�) for 1–7a

1

Zn(1)–O(6) 2.0222(15) Zn(1)–O(2) 2.0244(11)Zn(1)–O(5) 2.0657(14) Zn(1)–O(4) 2.1004(11)Zn(1)–O(1)#1 2.1186(12) Zn(1)–O(2)#1 2.4783(12)O(6)–Zn(1)–O(2) 123.27(5) O(6)–Zn(1)–O(5) 90.81(7)O(2)–Zn(1)–O(5) 91.96(6) O(6)–Zn(1)–O(4) 89.15(6)O(2)–Zn(1)–O(4) 87.79(5) O(5)–Zn(1)–O(4) 179.67(6)O(6)–Zn(1)–O(1)#1 144.37(6) O(2)–Zn(1)–O(1)#1 92.12(4)O(5)–Zn(1)–O(1)#1 92.05(6) O(4)–Zn(1)–O(1)#1 88.17(5)O(6)–Zn(1)–O(2)#1 89.72(5) O(2)–Zn(1)–O(2)#1 146.42(2)O(5)–Zn(1)–O(2)#1 80.49(5) O(4)–Zn(1)–O(2)#1 99.83(4)O(1)#1–Zn(1)–O(2)#1 55.88(4)

2

Zn(1)–O(7)#1 2.051(4) Zn(1)–O(7) 2.051(4)Zn(1)–O(1WA)#1 2.077(4) Zn(1)–O(1WA) 2.077(4)Zn(1)–O(6)#1 2.186(4) Zn(1)–O(6) 2.186(4)Zn(2)–O(5) 1.922(4) Zn(2)–O(1) 1.927(5)Zn(2)–O(4) 1.955(4) Zn(2)–O(1WA) 1.991(4)Zn(3)–O(1WA) 2.030(4) Zn(3)–O(8) 2.037(4)Zn(3)–O(3) 2.066(4) Zn(3)–N(2) 2.095(5)Zn(3)–N(1) 2.135(5)O(7)#1–Zn(1)–O(7) 180.0(3) O(7)#1–Zn(1)–O(1WA)#1 94.47(17)O(7)–Zn(1)–O(1WA)#1 85.53(17) O(7)#1–Zn(1)–O(1WA) 85.53(17)O(7)–Zn(1)–O(1WA) 94.47(17) O(1WA)#1–Zn(1)–O(1WA) 180.0O(7)#1–Zn(1)–O(6)#1 87.89(16) O(7)–Zn(1)–O(6)#1 92.11(16)O(1WA)#1–Zn(1)–O(6)#1 98.91(16) O(1WA)–Zn(1)–O(6)#1 81.09(16)O(7)#1–Zn(1)–O(6) 92.11(16) O(7)–Zn(1)–O(6) 87.89(16)O(1WA)#1–Zn(1)–O(6) 81.09(16) O(1WA)–Zn(1)–O(6) 98.91(16)O(6)#1–Zn(1)–O(6) 180.0(2) O(5)–Zn(2)–O(1) 129.4(2)O(5)–Zn(2)–O(4) 99.74(18) O(1)–Zn(2)–O(4) 106.0(2)O(5)–Zn(2)–O(1WA) 112.97(18) O(1)–Zn(2)–O(1WA) 101.8(2)O(4)–Zn(2)–O(1WA) 104.49(18) O(1WA)–Zn(3)–O(8) 95.66(17)O(1WA)–Zn(3)–O(3) 103.58(17) O(8)–Zn(3)–O(3) 87.93(17)O(1WA)–Zn(3)–N(2) 152.46(19) O(8)–Zn(3)–N(2) 92.52(19)O(3)–Zn(3)–N(2) 102.95(19) O(1WA)–Zn(3)–N(1) 95.50(19)O(8)–Zn(3)–N(1) 168.83(19) O(3)–Zn(3)–N(1) 89.83(19)N(2)–Zn(3)–N(1) 77.3(2)

3

Zn(1)–O(3) 2.064(6) Zn(1)–O(1) 2.068(6)Zn(1)–N(2) 2.111(7) Zn(1)–N(1) 2.131(7)Zn(1)–O(1W) 2.187(6) Zn(1)–O(3)#1 2.288(6)Zn(1)–Zn(1)#1 3.095(3)O(3)–Zn(1)–O(1) 103.0(2) O(3)–Zn(1)–N(2) 105.5(3)O(1)–Zn(1)–N(2) 96.2(2) O(3)–Zn(1)–N(1) 163.3(2)O(1)–Zn(1)–N(1) 92.1(3) N(2)–Zn(1)–N(1) 79.5(3)O(3)–Zn(1)–O(1W) 78.7(2) O(1)–Zn(1)–O(1W) 88.1(2)N(2)–Zn(1)–O(1W) 173.08(19) N(1)–Zn(1)–O(1W) 95.0(2)O(3)–Zn(1)–O(3)#1 73.0(2) O(1)–Zn(1)–O(3)#1 162.2(2)N(2)–Zn(1)–O(3)#1 101.6(2) N(1)–Zn(1)–O(3)#1 90.4(2)O(1W)–Zn(1)–O(3)#1 74.07(19)

4

Zn(1)–O(1) 2.0534(13) Zn(1)–O(1)#1 2.0534(13)Zn(1)–O(3) 2.0909(14) Zn(1)–O(3)#1 2.0909(14)Zn(1)–N(2)#2 2.232(2) Zn(1)–N(1) 2.246(2)O(1)–Zn(1)–O(1)#1 177.08(8) O(1)–Zn(1)–O(3) 89.45(6)O(1)#1–Zn(1)–O(3) 90.59(6) O(1)–Zn(1)–O(3)#1 90.59(6)O(1)#1–Zn(1)–O(3)#1 89.45(6) O(3)–Zn(1)–O(3)#1 178.37(8)O(1)–Zn(1)–N(2)#2 88.54(4) O(1)#1–Zn(1)–N(2)#2 88.54(4)O(3)–Zn(1)–N(2)#2 90.81(4) O(3)#1–Zn(1)–N(2)#2 90.81(4)O(1)–Zn(1)–N(1) 91.46(4) O(1)#1–Zn(1)–N(1) 91.46(4)O(3)–Zn(1)–N(1) 89.19(4) O(3)#1–Zn(1)–N(1) 89.19(4)N(2)–Zn(1)–N(1) 180.000(1)

684 | CrystEngComm, 2008, 10, 681–692 This journal is ª The Royal Society of Chemistry 2008

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Table 1 (Contd. )

5

Zn(1)–O(7) 1.9371(14) Zn(1)–O(5) 1.9430(14)Zn(1)–O(1) 1.9540(15) Zn(1)–O(3)#1 1.9693(14)Zn(1)#2–O(3) 1.9692(14)O(7)–Zn(1)–O(5) 108.52(6) O(7)–Zn(1)–O(1) 114.61(6)O(5)–Zn(1)–O(1) 101.21(6) O(7)–Zn(1)–O(3)#1 98.21(6)O(5)–Zn(1)–O(3)#1 117.41(6) O(1)–Zn(1)–O(3)#1 117.27(6)

6

Zn(1)–N(3) 2.0976(17) Zn(1)–O(1) 2.1027(14)Zn(1)–N(1) 2.1097(17) Zn(1)–O(2)#1 2.1285(14)Zn(1)–N(2) 2.1977(18) Zn(1)–N(4) 2.2013(18)N(3)–Zn(1)–O(1) 98.60(6) N(3)–Zn(1)–N(1) 170.10(7)O(1)–Zn(1)–N(1) 88.64(6) N(3)–Zn(1)–O(2)#1 94.81(6)O(1)–Zn(1)–O(2)#1 96.00(5) N(1)–Zn(1)–O(2)#1 91.12(6)N(3)–Zn(1)–N(2) 97.46(7) O(1)–Zn(1)–N(2) 83.96(6)N(1)–Zn(1)–N(2) 76.48(7) O(2)#1–Zn(1)–N(2) 167.60(6)N(3)–Zn(1)–N(4) 76.47(7) O(1)–Zn(1)–N(4) 173.86(6)N(1)–Zn(1)–N(4) 95.84(7) O(2)#1–Zn(1)–N(4) 88.13(6)N(2)–Zn(1)–N(4) 92.98(7)

7

Zn(1)–N(1) 2.048(3) Zn(1)–N(2)#1 2.072(3)Zn(1)–O(1) 2.107(3) Zn(1)–N(5) 2.129(3)Zn(1)–N(3)#1 2.279(3) Zn(1)–N(6) 2.316(3)N(1)–Zn(1)–N(2)#1 100.56(12) N(1)–Zn(1)–O(1) 93.79(13)N(2)#1–Zn(1)–O(1) 93.59(12) N(1)–Zn(1)–N(5) 94.54(12)N(2)#1–Zn(1)–N(5) 161.26(12) O(1)–Zn(1)–N(5) 96.44(11)N(1)–Zn(1)–N(3)#1 176.32(11) N(2)#1–Zn(1)–N(3)#1 75.77(12)O(1)–Zn(1)–N(3)#1 86.42(12) N(5)–Zn(1)–N(3)#1 89.08(12)N(1)–Zn(1)–N(6) 91.81(13) N(2)#1–Zn(1)–N(6) 95.12(12)O(1)–Zn(1)–N(6) 168.61(12) N(5)–Zn(1)–N(6) 73.22(12)N(3)#1–Zn(1)–N(6) 88.63(12)

a Symmetry codes: for 1, #1: –x + 1, y + 1/2, –z + 3/2; for 2, #1: –x + 1, –y, –z + 1; for 3, #1: –x, y, –z + 1/2; for 4, #1: –x + 2, y, –z + 1/2; #2: x, y + 1, z;for 5, #1: x – 1/2, y, –z + 1/2; #2: x + 1/2, y, –z + 1/2; for 6, #1: �x + 1, �y + 1, �z + 2; for 7, #1: �x + 1, �y + 1, �z + 1.

Table 2 Hydrogen-Bonding Geometry (A, �) for 1 and 3–7a

D–H/A r(D–H) r(H/A) r(D/A) :D–H/A

1O(5)–H(5B)/O(4A) 0.787 1.987 2.773 175.05O(6)–H(6B)/O(1B) 0.695 2.144 2.784 153.90O(6)–H(6C)/O(3) 0.798 1.923 2.688 160.38

3O(1W)–H(1W)/O(2A) 0.842 1.769 2.579 160.40C(38)–H(38A)/O(3B) 0.950 2.521 3.284 137.42

4O(3)–H(3A)/O(2A) 0.808 1.860 2.626 157.93

5O(9)–H(9A)/O(2) 0.900 1.880 2.731 157.00O(9)–H(9B)/O(3A) 0.860 1.870 2.705 162.00O(10)–H(10A)/O(6) 0.880 1.950 2.821 170.00O(10)–H(10B)/O(8B) 0.900 1.930 2.795 161.00

6O(6)–H(6)/O(3A) 0.836 1.661 2.491 171.20C(7)–H(7A)/O(3A) 0.930 2.469 3.278 145.48

7N(4)–H(4B)/O(2) 0.860 1.886 2.676 152.20C(9)–H(9A)/O(2A) 0.930 2.576 3.339 139.60

a Symmetry codes: for 1, A): �x + 1, y + 1/2, �z + 3/2; B): x, y + 1, z; for3, A): �x, y, �z + 1/2; B): 0.5 � x, 0.5 � y, 1 � z; for 4, A): �x + 2, y, �z+ 1/2; for 5, A): x � 1/2, y, �z + 1/2; B): x � 1/2, �y + 1/2, �z + 1; for 6,A): �1 + x, y, z; for 7, A): �x + 1, �y + 2, �z + 2.

This journal is ª The Royal Society of Chemistry 2008

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and one as a monodentate terminal ligand (Scheme 1a). Each

pentanuclear metal cluster is surrounded by ten organic ligands,

namely, eight bridging L1 and two chelating 2,20-bipy ligands.

Complex 3. Using phen instead of 2,20-bipy under the same

conditions, the structure of 3 consists of a centrosymmetric dinu-

clear unit Zn2(L1)4(phen)2(m-H2O) with a ZnII ion six-coordi-

nated, if neglecting the Zn–Zn close contact, by two N donors

from one chelating phen ligand, three O atoms from three L1

ligands and one O atom from a m-H2O, respectively, in which

Zn(1) lies on a twofold axis (Fig. 1c and ESI, Fig. S1c‡). For

L1, there exist two kinds of carboxylic coordination modes

with ZnII; namely, monodentate (Scheme 1a) and m-O,O bridging

(Scheme 1d) coordination modes connect two ZnII ions to form

a four-membered ring composed of Zn(1), O(3), Zn(1A) and

O(3A) with the Zn–Zn contact distance being 3.095 A. As

such, each m-H2O also interlinks two crystallographically unique

ZnII centers that further stabilize the adopted dinuclear structure.

It is worth noting that the O(1W) atom of m-H2O presents

a strong intramolecular H-bonding interactions with the O(2A)

atom of L1 (Table 2). Then the adjacent dinuclear

Zn2(L1)4(phen)2(m-H2O) units are arranged into a 1-D chain by

the co-effects of the intermolecular p/p stacking and C–H/O

CrystEngComm, 2008, 10, 681–692 | 685

Fig. 2 (a) View of the coordination environment of ZnII in 5 showing the

p/p stacking; (b) single adamantanoid cages and a diagram illustrating

the twofold interpenetration in 5; (c) schematic representations of a single

diamondoid framework and the twofold interpenetrated diamondoid

network in 5; (d) space-filling diagram of the twofold interpenetrating

diamondoid network of 5 viewed down the a axis (partial H atoms

omitted for clarity).

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H-bonding (ESI, Fig. S6‡ and Table 2),15 and then to 2-D by the

inter-network C–H/p supramolecular interactions (ESI,

Fig. S7‡).14

Complex 4. Different from 2 and 3, when 4,40-bipy was used

instead of 2,20-bipy or phen, a new 1-D polymeric linear chain

of 4 is produced containing only one kind of ZnII ion coordina-

tion environment, in which Zn(1) and the 4,40-bipy ligand lie on

a twofold axis (Fig. 1d). The asymmetric unit of 4 is composed of

one ZnII ion, two anthracene-9-carboxylate (L1) groups, one 4,40-

bipy ligand and two free CH3OH molecules. The geometry

around each ZnII center can be best described as a distorted

octahedron formed by two carboxylate O atoms from two differ-

ent L1 ligands, two O atoms from two coordinated CH3OH

molecules and two N donors from two 4,40-bipy, respectively

(see ESI, Fig. S1-D‡). Moreover, in 4, L1 adopts a monodentate

coordination mode (Scheme 1a) and 4,40-bipy serves as a linear

bridging ligand [N(1)–Zn(1)–N(2) angle: 180.00�]. It should be

pointed out that in the chain structure of 4 there are intra-chain

O–H/O H-bonding interactions between O(3) atoms of

CH3OH molecules and O(2A) atoms of L1 (Table 2).

Complex 5. When we used 9,10-anthracene-dicarboxylic acid

(H2L2) instead of anthracene-9-carboxylic acid (HL1), a 3-D

twofold interpenetrating diamondoid network (5) is produced,

which crystallizes in the orthorhombic space group Pbca, and

in which one kind of Hdmpy ligand lies in a general position

and another two further Hdmpy ligands lie about independent

inversion centres in the large cavity (Fig. 2). As shown in

Fig. 2a, each asymmetric unit of 5 contains one Zn atom, two

L2 ligands (L2 ¼ 9,10-anthracene-dicarboxylate), two Hdmpy

ligands and two included aqua molecules (ESI, Fig. S1e‡).

Each ZnII is four-coordinated by four carboxylate O atoms

[Zn–O: 1.9371(1)�1.9693(1)��A] from four different L2 ligands

in a bridging bis-monodentate mode (Scheme 1e) to complete

a distorted tetrahedral coordination environment (Table 1). In

other words, the Zn(1) ion is connected to four adjacent ZnII

centers through the 9,10-anthracene-dicarboxylate (L2) bridges

to result in a 3-D polymeric network with a diamondoid struc-

ture. The first view of the structure displays a large cavity in

every diamondoid cage with the adjacent Zn/Zn separations

ranging from 10.894(1) to 11.051(1) A (Fig. 2b). A more careful

examination shows that such cavities are reduced by the other

identical interpenetrated diamondoid net. If the 9,10-anthracene-

dicarboxylate groups are omitted, the Zn/Zn/Zn angles in 5

range from 90.25 to 119.32� and deviate significantly from

109.45�, expected for an idealized diamondoid network.16

Thus, 5 adopts a distorted diamondoid structure, probably to

accommodate the inclusion of the free aqua and Hdmpy mole-

cules. As evidenced in Fig. 2c, a very large cavity exists within

a single diamondoid network. However, in order to minimize

the big void cavities in the diamondoid cages and stabilize the

whole framework, a twofold interpenetrating diamondoid

framework is generated. Moreover, the space-filling model

clearly shows that even after the twofold interpenetration, the

open space still exists within the coordination network of 5,

which is occupied by the Hdmpy and the free aqua molecules

(Fig. 2c,d). The free aqua molecules were included within the

void space left after the twofold interpenetration by O–H/O

686 | CrystEngComm, 2008, 10, 681–692

H-bonding interactions between aqua molecules and carboxylate

groups of L2 ligands (Table 2).

Complex 6. Similar to 5, the reaction of Zn(NO3)2$6 H2O and

L2 with 2,20-bipy gave rise to complex 6, {[Zn2(L2)(2,20-

bipy)4](HL2)2}N. As is shown in Fig. 3a, the structure of 6 is

a framework consisting of 1-D cationic chains {[Zn2(L2)(2,20-

bipy)4]2+}N, in which L2 ligand lies on an inversion centre,

containing dinuclear [Zn2(L2)(2,20-bipy)4]2+ units as nodes and

the partly deprotoned anionic chains {[(HL2)2]2-}N formed

through O–H/O H-bonding between carboxylate groups of

the free HL2 ligands (the non-bonding Zn/Zn separation is

4.764 A) (Table 2). In each asymmetric unit, the coordination

This journal is ª The Royal Society of Chemistry 2008

Fig. 3 View of (a) the 1-D chains in 6 showing the p/p stacking, the C–

H/O the C–H/p and by O–H/O H-bonding; (b) the 1-D chain in 7

showing the N–H/O H-bonding (partial H atoms omitted for clarity).

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geometry around ZnII is an octahedron and has a N4O2 coordi-

nation environment by four N donors of two chelating 2,20-bipy

ligands and two O atoms of two L2 ligands with bridging

bis-bidentate mode (ESI, Fig. S1f‡ and Scheme 1f). The ZnII

ion deviates from the least-squares plane generated by N(1)–

N(2)–N(3)–O(2A) toward O(1) by only ca. 0.0814 A. All the

Zn–N and Zn–O bond distances lie in the ranges of

2.0976(2)�2.2013(2) A and 2.1027(1)�2.1285(1) A, respectively,

with the bond angles around each ZnII center ranging from

76.47(7) to 173.86(6)�, being comparable with similar complexes

in the literature (Table 1).1g,13 For charge balance, each 1-D

cationic chain {[Zn2(L2)(2,20-bipy)4]2+}N was further surrounded

tightly by two partly deprotonated anionic chains {[(HL2)2]2�}N

via the co-effect of the C–H/O H-bonding interactions

(between the O atoms of the free HL2 ligands and H atoms of

pyridine rings in 2,20-bipy ligands) and the intermolecular

C–H/p interactions (Table 2 and Fig. 3a).15 In addition to

the obvious intra-chain p/p stacking with the centroid–cen-

troid separation, and the structure also contains numerous intra-

and inter-network C–H/p supramolecular interactions that

further link the 1-D chain entities into a 2-D sheet, and then to

a 3-D supramolecular network from the different crystallo-

graphic directions (ESI, Fig. S10, S11‡ and Fig. 3a).14

Complex 7. In comparison with 2,20-bipy, Hpypz is an

asymmetric 2,20-bipyridyl-like chelating ligand with an N–H

entity as a H-bonding donor whose coordination chemistry has

been well-documented.17 Therefore, when we use Hpypz instead

of 2,20-bipy as an auxiliary ligand under the same conditions,

another 1-D neutral chain structure {[Zn2(L2)(pypz)2(Hpy-

pz)2]}N (7) is produced containing centrosymmetric dinuclear

This journal is ª The Royal Society of Chemistry 2008

[Zn2(L2)(pypz)2(Hpypz)2]2+ units as nodes, in which the L2 ligand

lies on an inversion centre (Fig. 3b). The center ZnII ion is six-

coordinated by five N donors from three chelating Hpypz

ligands (two of them were deprotonated) and an O atom from

one L2 (ESI, Fig. S1 g‡). Hpypz and pypz all adopt the typical

chelating mode coordinating to the ZnII ion with the Zn–N

bond distances and N–Zn–N bond angles ranging from 2.048(3)

to 2.316(3) A and 73.22(12) to 176.32(11)�, respectively (see Table

1).13 It should be pointed out that the N(1) atoms of some Hpypz

ligands are deprotonated and coordinated to the ZnII ion via

bridging coordination mode and linked two ZnII ions to form

a six-membered ring which is composed of two pypz groups

and two ZnII ions [i.e., Zn(1) and Zn(1A)] with the non-bonding

Zn/Zn separation being 3.984 A. For Hpypz ligands, however,

the others are not deprotonated [i.e., N(4) and N(4A)], which

presents a strong intramolecular H-bonding interactions with

uncoordinated O(2) atom of L2 (Table 2). For L2, only one coor-

dination mode exists with the ZnII ion, namely, adopting the

bridging bis-monodentate mode (Scheme 1e) to link the dinuclear

units into a 1-D chain structure. Additionally, the adjacent 1-D

chains are linked together to form a 2-D network through the

inter-chain C–H/O H-bonding interactions between Hpypz

and L2 ligands (Table 2 and ESI, Fig. S12‡).15

From the above descriptions, it can be seen that the p/p

stacking or C–H/p supramolecular interactions in these

complexes play an important role in forming a 1-D chain, 2-D

sheet, even 3-D supramolecular network: for 1, the inter-chain

p/p stacking and the inter-network C–H/p supramolecular

interactions between the anthracene rings with an edge-to-face

orientation, see ESI, Fig. S2 and S3;‡ for 2, the intra- and

inter-network C–H/p supramolecular interactions through

the edge-to-face orientation between the anthracene and pyridine

rings of L1 and 2,20-bipy, see ESI, Fig. S5;‡ for 3, the intramolec-

ular face-to-face p/p stacking between anthracene and phenan-

throline rings of L1 and phen, the intermolecular p/p stacking

between the completely parallel phenanthroline rings from adja-

cent phen and the inter-network C–H/p supramolecular inter-

actions between the anthracene and phenanthroline rings with an

edge-to-face orientation, see ESI, Fig. S6, S7‡ and Fig. 1c; for 4,

the obvious inter-chain p/p stacking between the anthracene

rings of the L2 ligands and the obvious inter-network C–H/p

supramolecular interactions between the anthracene and 4,40-

bipyridine rings with an edge-to-face orientation, see ESI,

Fig. S8 and S9;‡ for 5, the p/p stacking interactions between

the anthracene and pyridine rings of L2 and Hdmpy, see

Fig. 2a; for 6, the intermolecular C–H/p interactions between

pyridine rings of the chelating 2,20-bipy ligands and anthracene

rings of the partly deprotonated HL2 carboxylate ligands with

an edge-to-face orientation and the intra- and inter-network

C–H/p supramolecular interactions between the anthracene

and pyridine rings with an edge-to-face orientation, see ESI,

Fig. S10, S11‡ and Fig. 3a).14,15

This work gives a good comparison between different anthra-

cene-based carboxylate complexes. The results indicate that the

steric bulk of the anthracene ring in HL1 and H2L2 plays an

important role in the formations of 1–7, and may offer effective

means of constructing unique coordination architectures (see

Table 3), which may play an important role in the luminescent

properties.

CrystEngComm, 2008, 10, 681–692 | 687

Table 3 Summary about structures for 1–7

Formula Dimension Coordination atoms Geometry of metal

1 C30H24O7Zn 1-D O6 Octahedron2 C140H90N4O18Zn5 Pentanuclear O6/O4/N2O3 Octahedron/

tetrahedron/tetragonalpyramid

3 C84H54N4O9Zn2 Dinuclear N2O4 Octahedron4 C42H34N2O6Zn 1-D N2O4 Octahedron5 C46H40N2O10Zn 3-D O4 Tetrahedron6 C88H58N8O12Zn2 1-D N4O2 Octahedron7 C48H34N12O4Zn2 1-D N5O Octahedron

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Luminescent properties

UV-vis spectra. All UV-vis absorption spectra of 1–7 (Fig. 4a)

and free ligands HL1, H2L2, 2,20-bipy, phen, Hpypz and 4,40-bipy

(ESI, Fig. S13‡) were recorded in the solid state at room temper-

ature. In the absorption spectra of HL1 and H2L2, there are two

characteristic absorption peaks (261 and 376 nm for HL1; 252

and 372 nm for H2L2), due to the K-band and B-band appeared

separately. Both of the K-band and the B-band correspond to

the p/p* transitions.18 For free 2,20-bipy, phen, Hpypz and

4,40-bipy, two characteristic K-band and B-band regions in their

absorption spectra were also observed (I: K-band region of ca.

Fig. 4 (a) Solid state UV-vis spectra for 1–7 at rt; (b) emission spectra of

1–7 in the solid state at rt (lex ¼ 422 nm for 1, 414 nm for 2, 420 nm for 3,

415 nm for 4, 389 nm for 5, 435 nm for 6, 389 nm for 7, respectively).

688 | CrystEngComm, 2008, 10, 681–692

210�265 nm; II: The B-band region of ca. 285�350 nm, see

ESI, Fig. S13‡). As such, the absorption bands profiles for 1–7

are very similar and the characteristic K-band (I: K-band region

of ca. 240�285 nm) and B-band (II: B-band region of ca.

380�415 nm) are still typical, which are further red-shifted as

compared to those absorption maxima of the corresponding

free ligands (Fig. 4a and ESI, Fig. S13‡). Therefore, the above

results show that the characteristic K-band and B-band

absorption in the UV-vis spectra of 1–7 should be mainly

assigned as p/p* transitions of HL1 (for 1–4) and H2L2 (for

5–7), respectively.

Emission properties. Luminescent compounds are currently of

great interest because of their potential applications in chemical

sensors, photochemistry, and electroluminescent (EL) displays.9

To examine the luminescent properties of the d10 metal

complexes, the luminescence of 1–7 (see Fig. 4b) as well as free

ligands HL1, H2L2, 2,20-bipy, phen, Hpypz and 4,40-bipy were

investigated at room temperature (ESI, Fig. S14 and S15‡). In

this work, meanwhile, the individual excitation/emission spectra

for each complex in 1–7 were separately shown in ESI, Fig. S16‡

for clarity. While the free ligands HL1 and H2L2 display moder-

ate luminescence in the solid state at lmax ¼ 510 and 524 nm

upon excitation at lEx ¼ 410 and 438 nm (ESI, Fig. S14‡), under

the same experimental conditions, 1–7 exhibit intense lumines-

cent emissions at lmax ¼ 465, 488, 468, 478, 430, 486, and

435 nm upon excitations at 422, 414, 420, 415, 389, 435, and

389 nm in the blue fluorescent regions, respectively (ESI,

Fig. S16‡). Therefore, for 1–7, the enhancements of lumines-

cence may be attributed to the chelating and/or bridging effects

of the ligands to the metal centers, which effectively increases

the rigidity of the ligands and reduces the loss of energy via

radiationless pathway.19

To better understand the luminescent properties from

a theoretical aspect, as representative examples, molecular

orbital (MO) calculations20 were applied to 2 and 3 (two discrete

molecules in this work) by DFT at the B3LYP level. Their fron-

tier molecular orbitals are depicted in Fig. 5. In 2, the highest

occupied molecular orbital (HOMO) is mainly associated with

the p-bonding orbitals from anthracene rings of HL1, whereas

the lowest unoccupied molecular orbital (LUMO) is on the p*-

antibonding orbitals of corresponding anthracene-based HL1

(Fig. 5a,b). In 3, the HOMO is also located in the p-bonding

orbitals from the anthracene rings of HL1, while the LUMO is

composed mainly of the p*-antibonding orbitals from the

phenanthroline rings of phen and also of the p*-antibonding

This journal is ª The Royal Society of Chemistry 2008

Fig. 5 The frontier molecular orbitals of 2 and 3: (a) HOMO for 2;

(b) LUMO for 2; (c) HOMO for 3; (d) LUMO for 3.

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orbitals from the anthracene rings of HL1 (Fig. 5c,d). Thus, the

origin of the emission of 2 and 3 might be mainly attributable to

the intraligand p*–p transitions, namely ligand-to-ligand charge

transfer (LLCT),19,20 since metal–ligand interactions usually

affect the emission wavelength of the organic components Table 4.

Although 1–7 have different coordination geometries and

sometimes have different auxiliary ligand environments, their

emission spectra, especially maximal main peak, resemble each

other in the peak profiles and are also similar to those of the

corresponding anthracene-based carboxylic acid ligands HL1 or

H2L2, such as the luminescent spectra of 1–4 (all including HL1

ligand). In addition, it should be pointed out that the auxiliary

ligands 2,20-bipy, phen, Hpypz and 4,40-bipy also show weak

fluorescence in their free solid state (ESI, Fig. S15‡).21 However,

by comparing the locations and profiles of their excitation/emis-

sion peaks with the corresponding complexes, we found that these

auxiliary ligands have almost no contribution to the fluorescent

emissions of the related complexes. As for 5, its emission spectra

Table 4 Summary for maximal emission (lEm) and excitation (lEx)Wavelength of the luminescent properties of HL1, H2L

2, 2,20-bipy,phen, Hpypz, 4,40-bipy and 1–7 in the solid state

Ligand lEx/lEm,/nm Complex lEx/lEm,/nm

HL1 410/510 1 422/465H2L

2 438/524 2 414/4882,20-bipy 318, 369/390, 414 3 420/468phen 310/361, 379 4 415/478Hpypz 370/410 5 389/4304,40-bipy 315/359 6 435/486

7 389/435

This journal is ª The Royal Society of Chemistry 2008

with another small peak (lmax ¼ 456 nm) is obviously different

from those of other complexes, which may be due to its unique

3-D twofold interpenetrating diamondoid framework in which

the Hdmpy ligands were asymmetrically included within the

void cavities through p/p stacking interactions between the

anthracene and pyridine rings of L2 and Hdmpy. Considering

the above-mentioned points together with the relevant analysis

results of solid UV-vis measurements and theoretical calcula-

tions, we believe that all the complexes in this work might absorb

the luminous energy and then emit fluorescence mainly through

their anthracene rings of HL1 and H2L2. The luminescent decay

curves of 1–7 were further obtained by femtosecond (fs) laser

system at room temperature (ESI, Fig. S17‡).

XRPD Results

To confirm whether the crystal structures are truly representative

of the bulk materials, X-ray powder diffraction (XRPD) experi-

ments have also been carried out for 1–7. The XRPD experimen-

tal and computer-simulated patterns of the corresponding

complexes are shown in ESI, Fig. S18.‡ Although the experimen-

tal patterns have a few unindexed diffraction lines and some are

slightly broadened in comparison with those simulated from the

single crystal models, it can still be considered favorably that the

bulk synthesized materials and the as-grown crystals are

homogeneous for 1–7.

Conclusion

In conclusion, we have successfully obtained a series of new ZnII

complexes having dinuclear, pentanuclear structures, 1-D and

3-D frameworks with two carboxylic ligands, HL1 and H2L2,

sometimes incorporating different auxiliary ligands (chelating

or bridging). The results reveal that the natures of HL1 and

H2L2 and auxiliary ligands, with kinds of intra- and/or inter-

molecular p/p stacking and C–H/p interactions, play an

important role in governing the structure and framework forma-

tion of 1–7. In addition, 1–7 display rich luminescent properties

at room temperature, mainly owing to their anthracene ring.

Experimental

Materials and general methods

Anthracene-9,10-dicarboxylic acid (H2L2) was synthesized

according to a reported literature procedure (ESI, Scheme

S1‡),8,22 and all the other reagents and solvents for synthesis

were commercially available and used as received or purified

by standard methods prior to use. Elemental analyses (C, H,

N) were performed on a Perkin-Elemer 240C analyzer. The IR

spectra were recorded in the range 4000�400 cm�1 on a Tensor

27 OPUS (Bruker) FT-IR spectrometer with KBr pellets. The

UV-Vis spectra were measured on Jasco V-550 Spectrometer

(JASCO Corp.).

Luminescent studies

The emission/excitation spectra were recorded on a JOBIN

YVON (HORIBA) FLUOROMAX-P spectrophotometer. The

luminescent lifetime was surveyed by a state-of-the-art gated/

CrystEngComm, 2008, 10, 681–692 | 689

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modulated intensified charge coupled device (ICCD) camera

system (ultrafast gate Picostar HR, Lavision Corp.) with the

femtosecond (fs) laser system (Spectra-Physics Corp.), and the

data were collected and recorded by a personal computer (PC).

The femtosecond (fs) laser system mainly contains a seed beam

generator, a pumping device and a parameter amplifier. The

seed beam pulses at 800 nm with pulse duration 80 fs and the

repetition rates about 82 MHz from the diode-pumped, mode-

locked Ti : sapphire laser (Mai Tai) were stretched and launched

into the Spectra-Physics Spitfire Ti: sapphire regenerative ampli-

fier (Spitfire) pumped by a diode-pumped, intra-cavity doubled

Nd : YLF laser (Evolution), which produces pulses at 523.5

nm with 1 KHz repetition rates. Thus the seed pulses were

amplified and compressed to duration of about 130 fs

(FWHM) at repetition rates of about 1 KHz. An ultrashort pulse

beam (400 nm, 130 fs, 1 KHz), which was generated from the

second harmonic generator (SHG), was further used for excita-

tion as well as the measurement of luminescent lifetime.

Calculation details

On the basis of crystal structures, the DFT calculations at the

B3LYP23 level were performed using the Gaussian 03 suite of

programs on a DeepComp 6800 supercomputer at the Virtual

Laboratory for Computational Chemistry and Supercomputing

Center of CNIC, Chinese Academy of Science and Nankai Stars

supercomputer at Nankai University.24 The ZnII ions in 2 and 3

were described with the LANL2DZ basis set, including effective

core potentials, while the 6–31 G basis set was used for C, N, O,

and H atoms.

Synthesis of complexes 1–7

{[Zn(L1)2(H2O)2](H2O)}N (1). 1 was obtained by the reaction

of Zn(NO3)2$6 H2O, HL1 and NaOH in a molar ratio of 1 : 1 : 1

mixed with 12 mL of water under hydrothermal conditions (at

160 �C for 3 d and cooled to room temperature with a 5 �C

h�1 rate). The yellow cubic crystals were washed with water,

ethanol and ether, and dried in air. Yield: �40%. Calcd (%)

for C30H24O7Zn (561.86): C, 64.13, H, 4.31; for C30H22O6Zn

(543.88, C30H24O7Zn–H2O): C, 66.25, H, 4.08; found (%): C,

66.07, H, 4.35. IR (KBr pellet, cm�1): 3444br, 3048w, 2360w,

1669w, 1625w, 1560s, 1534vs, 1518s, 1488m, 1435s, 1396w,

1321m, 1278w, 1017w, 952w, 886w, 845w, 796w, 763w, 729s,

670w, 598w, 559w, 522w.

[Zn5(m3-OH)2(L1)8(2,2

0-bipy)2] (2). A mixed solution of HL1

(0.05 mmol) and 2,20-bipy (0.05 mmol) in CH3OH (10 mL) in

the presence of excess dmpy (ca. 0.05 mL for adjusting the pH

value) was carefully layered on top of a H2O solution (15 mL)

of Zn(NO3)2$6 H2O (0.1 mmol) in a test tube. Yellow single

crystals suitable for X-ray analysis appeared at the boundary

between CH3OH and H2O after ca. one month at room

temperature. Yield: �50% based on HL1. Calcd. (found) for

C140H90N4O18Zn5 (2443.17): C, 68.83 (68.69), H, 3.71 (3.54),

N, 2.29 (2.41)%. IR (KBr pellet, cm�1): 3445br, 3046w, 1647s,

1631s, 1585vs, 1489w, 1442s, 1373m, 1323s, 1277m, 1155w,

1061w, 1025w, 1013w, 890w, 798w, 765m, 732s, 660m, 560m,

526w, 445w.

690 | CrystEngComm, 2008, 10, 681–692

Zn2(L1)4(phen)2(m-H2O) (3). The same procedure as that for 2

was used for this compound except for using phen instead of

2,20-bipy. Yield: �50% based on HL1. Calcd. (found) for

C84H54N4O9Zn2 (1394.05): C, 72.37 (72.59), H, 3.90 (4.12), N,

4.02 (3.91)%. IR (KBr pellet, cm�1) : 3414br, 2361w, 1792w,

1717w, 1699w, 1684w, 1653w, 1618s, 1541vs, 1518m, 1429w,

1399s, 1369w, 1321s, 1302m, 1268m, 1103w, 1012w, 886w,

843m, 730s, 659m, 557w, 425w.

{[Zn(L1)2(4,40-bipy)(CH3OH)2]}N (4). The same procedure as

that for 2 was used except for using 4,40-bipy instead of phen.

Yield: �70% based on HL1. Calcd. (found) for C42H34N2O6Zn

(728.08): C, 69.28 (69.39), H, 4.71 (4.52), N, 3.85 (3.63)%. IR

(KBr pellet, cm�1): 3441br, 2349w, 1573s, 1484w, 1441m,

1389s, 1319s, 1273m, 1217m, 1139w, 1069w, 1039m, 1004m,

885m, 862w, 841w, 820w, 733s, 664m, 626m, 599w, 560w,

523w, 417w.

{[Zn(L2)2](Hdmpy)2(H2O)2}N (5). A mixed solution of H2L2

(0.05 mmol) in C2H5OH (10 mL) in the presence of excess dmpy

(ca. 0.05 mL) was carefully layered on top of a H2O solution

(15 mL) of Zn(NO3)2$6 H2O (0.1 mmol) in a test tube. Yellow

single crystals suitable for X-ray analysis appeared at the boundary

between C2H5OH and H2O after ca. one month at room tempera-

ture. Yield: �40% based on H2L2. Calcd (%) for C46H40N2O10Zn

(846.17): C, 65.29, H, 4.76, N, 3.31; for C46H36N2O8Zn (810.18,

C46H40N2O10Zn �2H2O): C, 68.20, H, 4.48, N, 3.46; found (%):

C, 67.89, H, 4.39, N, 3.70. IR (KBr pellet, cm�1): 3441w, 3306br,

3034w, 2361w, 1636s, 1600vs, 1578s, 1519w, 1447m, 1419s,

1378w, 1316vs, 1278m, 1174w, 1058w, 1025w, 819m, 801m,

783m, 715w, 689s, 599w, 556w, 505w, 437w.

{[Zn2(L2)(2,20-bipy)4](HL2)2}N (6). The same procedure as that

for 5 was used for this compound except for the introduction of

auxiliary ligand 2,20-bipy (0.05 mmol). Yield: �60% based on

H2L2. Calcd. (found) for C88H58N8O12Zn2 (1550.16): C, 68.18

(68.06), H, 3.77 (3.91), N, 7.23 (7.04)%. IR (KBr pellet, cm�1):

3414m (br), 2361w, 1734w, 1699w, 1587vs, 1542s, 1491w,

1474w, 1446s, 1420m, 1320s, 1279m, 1158w, 1027w, 821w,

778w, 757m, 732w, 680s, 599w, 416w.

{[Zn2(L2)(pypz)2(Hpypz)2]}N (7). The same procedure as that

for 5 was used for this compound except for introducing the

auxiliary ligand Hpypz (0.05 mmol). Yield: �50% based on

H2L2. Calcd. (found) for C48H34N12O4Zn2 (973.62): C, 59.21

(59.37), H, 3.52 (3.45), N, 17.26 (16.98)%. IR (KBr pellet,

cm�1): 3440br, 3062w, 2361w, 1671w, 1605m, 1560vs, 1475w,

1458w, 1433s, 1363m, 1325s, 1280m, 1144m, 1096w, 1075w,

1050w, 1011w, 985w, 950w, 842m, 759s, 713w, 669w, 649w, 491w.

X-Ray powder diffraction

The X-ray powder diffraction patterns (XRPD) of 1–7 were

recorded on a Rigaku D/Max-2500 diffractometer, operated at

40 kV and 100 mA, using a Cu-target tube and a graphite mono-

chromator. The intensity data were recorded by a continuous

scan in a 2q/q mode from 3 to 80� with a step size of 0.02� and

a scan speed of 8� min�1. CCDC � 623311, 617255, and

623312 to 623316 (1, 2, and 3–7) contain the supplementary

This journal is ª The Royal Society of Chemistry 2008

Table 5 Crystal data and structure refinement summary for 1–7

1 2 3 4 5 6 7

Formula C30H24O7Zn C140H90N4O18Zn5 C84H54N4O9Zn2 C42H34N2O6Zn C46H40N2O10Zn C88H58N8O12Zn2 C48H34N12O4Zn2

FW 561.90 2443.17 1394.13 728.12 846.21 1550.23 973.64Space group P2(1)/c P-1 C2/c C2/c Pbca P2(1)/n P-1a/A 13.9951(2) 14.013(2) 22.62(2) 24.168(3) 16.442(2) 9.6712(2) 9.5311(19)b/A 7.70390(10) 15.329(3) 17.580(15) 11.5740(15) 17.697(3) 26.8053(4) 10.770(2)c/A 23.5124(3) 15.464(3) 18.070(17) 12.0378(16) 27.528(4) 13.5499(2) 12.445(2)a/� 90 67.147(2) 90 90 90 90 112.048(3)b/� 95.7870(10) 65.165(2) 115.734(13) 94.489(2) 90 92.7680(10) 95.725(3)g/� 90 83.999(3) 90 90 90 90 110.766(3)V/A3 2522.11(6) 2771.1(8) 6474(10) 3356.9(8) 8010(2) 3508.57(10) 1066.4(4)Z 4 1 4 4 8 4 2D/g cm�3 1.480 1.464 1.430 1.441 1.403 1.467 1.516m/mm�1 1.023 1.141 0.809 0.786 0.677 0.759 1.187Ra/wRb 0.0317/0.0828 0.0590/0.1744 0.1097/0.2340 0.0297/0.0784 0.0433/0.1164 0.0309/0.0840 0.0432/0.1204

a R ¼ SFo � Fc / SFo. b Rw ¼ [S[w(Fo2 � Fc

2)2] / Sw(Fo2)2]1/2.

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crystallographic data for this paper. These data can be obtained

from the Cambridge Crystallographic Data Centre, 12 Union

Road, Cambridge CB2 1EZ, UK; Fax: +44-1223-336033;

E-mail: deposit@ccdc.cam.ac.uk.‡

X-Ray data collection and structure determinations

X-Ray single-crystal diffraction data for 1–7 were collected on

a Bruker Smart 1000 CCD area-detector diffractometer at

293(2) K with Mo Ka radiation (l ¼ 0.71073 A) by u scan

mode. The program SAINT25 was used for integration of the

diffraction profiles. Semi-empirical absorption corrections were

applied using SADABS program.26 All the structures were

solved by direct methods using the SHELXS program of the

SHELXTL package and refined by full-matrix least-squares

methods with SHELXL (semi-empirical absorption corrections

were applied using SADABS program).27 ZnII ions in each com-

plex were located from the E-maps and the other non-hydrogen

atoms were located in successive difference Fourier syntheses

and refined with anisotropic thermal parameters on F2. The

hydrogen atoms, except for those of water, were generated

theoretically onto the specific atoms and refined with isotropic

thermal parameters riding on the parent atoms. The water

hydrogen atoms in 1, 3, and 5 were added by difference Fourier

E-maps and refined isotrolically. For 3, part of the anthracene

ring of the L1 ligand was refined in a disordered mode. Further

details for structural analysis are summarized in Table 5.

Acknowledgements

This work was supported by NSFC (Nos. 50673043 and

20531040) and the Natural Science Fund of Tianjin, China (07

JCZDJC00500). We gratefully thank Prof. Zhenyang Lin, The

Hongkong University of Science and Technology, for helpful

discussions and suggestions.

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This journal is ª The Royal Society of Chemistry 2008