Crystal Structure and Crystal Structure and Magnetic Property of Magnetic Property of

Cobalt Glutarate, Cobalt Glutarate, Co[OCo[O22C(CHC(CH22))33COCO22]]

이 윤 원 , 김 유 진 , 정 덕 영 **

Department of Chemistry - BK21,Department of Chemistry - BK21,SungKyunKwan University SungKyunKwan University

Introduction

A reasonable approach to build three-dimensional structures based on layered structural motifs is to control the packing of layers by organic pillars of changeable length and type. Pillared structures are potentially important for applications in catalysis, magneto material and etc. 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 conformation 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

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

Inorganic Layer

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

(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°

Crystal Structure View

c

(100)(100)

90°

b

a

(001)(001)

90°Gauche-form Anti-formAnti-form

b

Decomposition of Organic Chains

Rate = 10 °C/minUnder N2-gas Blowing

39%

Co[O2C(CH2)3CO2] CoO (39.6%) (~ 450 oC)

No hydrate water

C-O stretching

C-C stretch

No C=O stretch

IR and TG

4000 3500 3000 2500 2000 1500 1000 500

769.6531

1405.244

1534.484

2957

Tra

nsm

ittan

ce(%

)

Wavenumbers(cm -1)

IR TG

UV-Vis Spectrum

500 1000 15000.0

0.1

0.2

2300

2100

1568

1274

826

558

258

Ab

so

rba

nce

Wavelength(nm)

Color : Dark purple

Peak Assignment1274 nm (7849 cm-1): 4A2g(F) 4T1g(F)558 nm (179211cm-1): 4A2g(F) 4T1g(P)

Crystal Field Strength:t = 4418 cm-1

Racah parameter: Bt = 788 cm-1

106.5

99.0 103.3

110.3

116.4

121.4

Co2+(d7) in Td

Strong fieldground configuration

: e4t23

Strong fieldground term

: 4A2

Magnetization

0 50 100 150 200 250 3000

20

40

60

80

100

120

140

160

180

200

y = 0.57 x + 5.61

1/

M

Temperature(K)

1/M

Linear Fit

C = 0.18 cm3K/mol = -1.01 K eff = 3.69 B (at 300 K)

*eff (expt): 4.30-5.20 B for H.S.

1.73 B for L.S. state of Co2+

1/ = T/C - /C (at T > 50 K)= 0.57 T + 5.61

(100G, MPMS-SQUID magnetometer)

0 50 100 150 200 250 3000.00

0.01

0.02

0.03

0.04

0.05

M T

M(e

mu

/Co

)

Temperature(K)

0

1

2

Co2+(in Td) ; 3d7

Conclusion

All cobalt atoms were coordinated to four oxygen atoms (Td symmetry) by carboxylate groups to form an organic/inorganic hybrid compound in three-dimension. Interestingly, two different conformations of alkyl chain in glutarate ligands (anti-form and gauche-form) were observed in the crystal structure of the prepared Co-gluatarate compounds. Magnetic measurement showed long range with eff= 3.69 B (at 300 K).

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