이 윤 원 , 김 유 진 , 정 덕 영 * Department of Chemistry - BK21, SungKyunKwan University

1. The Coordination Polymer of Co(II)–Glutarate: The 3-Dimensional Layered Structure and The Magnetic Property 이 윤 원, 김 유 진, 정 덕 영* Department of Chemistry - BK21, SungKyunKwan University

2. 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).

3. Experimental Procedure Teflon Vessel Metal ion source; CoCl2·6H2O 5 mmol Ligand; Glutaric acid 5 mmol aqueous KOH 1.5 M 5 mL ~pH 4.5 Heat in oven at 180 °C for 24 h under hydrothermal condition oven 180ºC Quench in cold water Dark purple crystals (Filter, wash with alcohol, yields in ~70%) Co-glutarate, Co[O2C(CH2)3CO2]

4. Inorganic layer Organic layer (Å) Inorganic layer Organic layer Inorganic layer MnDC-n Series Structure Even-Chain Odd-Chain d Magnetization Interlayer Distance

5. Mn-glutarate vs Co-glutarate MnO6 inorganic layer CoO4 inorganic layer anti-form (8.99 Å) Gauche-form (7.01 Å) anti-form (8.99 Å) anti-form (6.99 Å) Mn-glutarate Co-glutarate

6. 116.4 103.3 99.0 121.4 106.5 110.3 UV-Vis Spectrum Color : Dark purple Co2+(d7) in Td Strong field ground configuration : e4t23 Strong field ground term : 4A2 Peak Assignment 1302 nm (7680 cm-1) : 4A2g(F) 4T1g(F) 526 nm (12107cm-1) : 4A2g(F) 4T1g(P) Crystal Field Strength:Dt = 3612 cm-1 Racah parameter: Bt= 860 cm-1 *Dt = 4089 cm-1,Bt = 825 cm-1 for [Co(OH2)6]2+

7. Crystal Structure Data Asymmetric Unit Empirical formula CoC5H6O4 Formula weight 189.03 Crystal system monoclinic Space group P2/c Unit cell dimensions a = 14.002(3) Å b = 4.8064(10) Å c= 9.274(3) Å α= 90º β= 90.50(2)º γ= 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 C6 C5 C4 O1 O2 O4 Co O3 C1 C2 C3

8. Two Different Conformations of Glutarate Ligands 115.6º 115.6º 115.6º Gauche-form 115.2º 115.2º 109.8º Anti-form

9. b c a 2-D inorganic layer The 3-D Structure b 4.81 Å 6.99 Å 7.01 Å c 4.63 Å = Gauche-form = Anti-form c 90.5° a

10. Bridging mode of Carboxylate Gauche-form syn anti syn anti (syn-anti / syn-anti mode) Anti-form syn syn c 90.5° anti anti a (syn-anti / syn-anti mode)

11. Magnetization Co2+(in Td) ; 3d7 (S = 3/2) Lines-model fitting 1/c = T/C - Q/C (at T > 14 K) = 0.37 T + 9.50 C = 2.71 cm3K/mol Q = -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+ J = -2.42(1) g = 2.34(1) (5000 Oe, MPMS-SQUID magnetometer)

12. Hysteresis Loop

13. 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.