이 윤 원 , 김 유 진 , 정 덕 영 **

Department of Chemistry - BK21,Department of Chemistry - BK21,

SungKyunKwan University SungKyunKwan University

The Coordination Polymer of Co(II)–Glutarate: The 3-Dimensional Layered Structureand The Magnetic Property

Introduction

A reasonable approach to build three-dimensional structures based on layered structural motifs is to control the packing of layers by organic pillars with variable length.

A variety of layered structure with transition metal and dicarboxylate have been synthesized.

Single crystal of Co-glutarate, Co[O2C(CH2)3CO2], was synthesized as single crystal under hydrothermal condition, characterized by XRD, IR, TG, UV-vis, and SQUID. It is interesting to note that this structure represents the first example of carboxylate pillared structures containing only tetrahedral sites of cobalt(II) with two different conformations of glutarate ligands(anti/gauche-form).

Experimental Procedure

aqueousKOH 1.5 M 5 mL

Metal ion source; CoCl2·6H2O 5 mmol

Ligand;Glutaric acid 5 mmol

HO

O O

OH

oven

180ºC

Heat in oven at 180 °C for 24 h under

hydrothermal condition

Quench in cold water

Dark purple crystals(Filter, wash with alcohol, yields in ~70%) Co-glutarate,

Co[O2C(CH2)3CO2]

TeflonVessel

~pH 4.5

Inorganic layer

Inorganic layer

Inorganic layer

Organic layer

Organic layer

0 50 100 150 200 250 3000.00

0.02

0.04

0.06

0.08

0.10

0.12

MT

M(e

mu

/Mn

)

Temperature(K)

MnDC-3 MnDC-4 MnDC-5 MnDC-6 MnDC-7 MnDC-8

0

1

2

3

4

5

MagnetizationInterlayer Distance

0 1 2 3 4 5 6 7 8 9 10 11 12 130

2

4

6

8

10

12

14

16

18

20

22

24

Inte

rlay

er D

ista

nce

Number of CH2 groups

( Å )

Structure

d

MnDC-n Series

HO

O

HOOH

O

O

OH

O

n

nEven-Chain

Odd-Chain

Mn-glutarate vs Co-glutarate

Mn-glutarate

MnO6 inorganic layer

Gauche-form(7.01 Å)anti-form(6.99 Å)

Co-glutarate

CoO4 inorganic layer

anti-form(8.99 Å)

anti-form(8.99 Å)

500 1000 1500

0

20

40

60

80

2492236222821302826

526

404

572

% A

bs

orb

an

ce

Wavelength / nm

UV-Vis Spectrum

Color : Dark purple

Peak Assignment1302 nm (7680 cm-1) : 4A2g(F) 4T1g(F) 526 nm (12107cm-1) : 4A2g(F) 4T1g(P)

Crystal Field Strength:t = 3612 cm-1

Racah parameter: Bt = 860 cm-1

t = 4089 cm-1, Bt = 825 cm-1 for [Co(OH2)6]2+

106.5

99.0 103.3

110.3

116.4

121.4

Co2+(d7) in Td

Strong fieldground configuration

: e4t23

Strong fieldground term

: 4A2

Crystal Structure Data

Empirical formula CoC5H6O4

Formula weight 189.03 Crystal system monoclinicSpace group P2/cUnit cell dimensions a = 14.002(3) Å

b = 4.8064(10) Å c= 9.274(3) Åα= 90ºβ= 90.50(2)ºγ= 90º

Volume, Z 624.1(3) Å3, 4 Density (calculated) 2.012 mg/m3

Final R indices R1 = 0.0480

wR2 = 0.1316

R indices (all data) R1 = 0.0566

wR2 = 0.1601

Co

O1

O4

O3

O2

C4

C5

C6

C1

C2

C3

Asymmetric Unit

Gauche-form

Anti-form

Two Different Conformations of Glutarate Ligands

115.6º115.6º

115.6º

115.2º 115.2º109.8º

The 3-D Structure

b

c

c

a

b

a

c

4.81 Å

4.63 Å

7.01 Å

90.5°

6.99 Å

= Gauche-form

= Anti-form

2-D inorganic layer

(syn-anti / syn-anti mode)

syn syn

anti anti

(syn-anti / syn-anti mode)

syn

synanti

anti

Gauche-form

Anti-form

Bridging mode ofCarboxylate

c

a90.5°

Magnetization

1/ = T/C - /C (at T > 14 K) = 0.37 T + 9.50

C = 2.71 cm3K/mol = -25.75 K eff = 4.49 B (at 300 K)

*eff (expt): 4.30-5.20 B for H.S. 1.73 B for L.S. state of Co2+(5000 Oe, MPMS-SQUID magnetometer)

Co2+(in Td) ; 3d7 (S = 3/2)

0 50 100 150 200 250 3000

20

40

60

80

100

120

1/

M(C

o/e

mu

)Temperature(K)

0 50 100 150 200 250 3000.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

9 K

14 K

M(e

mu

/Co

)

Temperature/ K

0

1

2

T

/ cm3m

ol -1K

6

11

22

32 n

nn

M

B C

J

Ng

Lines-model fitting

J = -2.42(1) g = 2.34(1)

-30000 -20000 -10000 0 10000 20000 30000-2000

-1000

0

1000

2000

Mag

netiz

atio

n

Field(Oe)

4.2 K 2 K

Hysteresis Loop

-500 -250 0 250 500-100

-50

0

50

100

Mag

netiz

atio

n

Field(Oe)

4.2 K 2 K

Conclusion

All the cobalt atoms in the prepared Co-glutarate coordinate to four oxygen atoms (Td symmetry) of carboxylate groups to form an organic/inorganic hybrid compound in three-dimension. It is noted that two different conformations of alkyl chains of glutarate ligands (anti-form and gauche-form) were observed in the crystal structure of the prepared Co-gluatarate compound. Magnetic measurement showed antiferromagnetic long range ordering with J = 2.42 cm-1 fitted according to two-dimensional model system.

Acknowledgement We acknowledge financial support from the Electron Spin Science Center at POSTECH, established by KOSEF. The Korea Basic Science Institute provided us with SQUID magnetometer measurements for the present study.