Synthesis, X-ray Structures, and Magnetic Properties of Copper(II) Pyridinecarboxylate Coordination Networks Mary E. Chapman, † Ponnaiyan Ayyappan, † Bruce M. Foxman, † Gordon T. Yee,* ,‡ and Wenbin Lin* ,† Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 Received October 17, 2000 ABSTRACT: The three-dimensional Cu(II) coordination polymers [Cu(isonicotinate) 2 ][EtOH] (1) and Cu(nicotinate) 2 (2) were synthesized by treating copper nitrate with isonicotinic acid and nicotinic acid under hydro(solvo)thermal conditions, respectively. X-ray single-crystal structure determinations reveal that the Cu(II) centers in 1 adopt a slightly distorted square pyramidal geometry, while the Cu(II) centers in 2 exhibit a coordination geometry intermediate between square pyramid and trigonal bipyramid. The Cu(II) centers in 1 and 2 coordinate to both the pyridyl and carboxylate functionalities of the isonicotinate and nicotinate bridging ligands, respectively, to result in complicated 3-D framework structures. Compound 1 exhibits rhombic open channels that are occupied by removable ethanol molecules. Magnetic measurements indicated that 1 is a simple paramagnet with only very weak antiferromagnetic interactions, while 2 exhibits more pronounced antiferromagnetic interactions with J/k )-6.4 K. Crystal data for 1: monoclinic, space group Cc, a ) 5.033(1) Å, b ) 24.855(5) Å, c ) 11.176(2) Å,  ) 99.35(3)°, and Z ) 4. Crystal data for 2: monoclinic, space group P2 1 /n, a ) 10.693(2) Å, b ) 9.589(2) Å, c ) 12.535(3) Å,  ) 112.09(3)°, and Z ) 4. Introduction Metal-directed self-assembly processes have recently provided a powerful tool for the synthesis of extended metal-organic coordination networks with diverse po- tential applications as zeolitic, catalytic, magnetic, and second-order nonlinear optical materials. 1 Most research effort in this area has so far been focused on coordina- tion polymers with either neutral donor ligands (e.g., 4,4′-bipyridine and polynitriles) 2,3 or strictly anionic groups (e.g., terephthalic acid and trimesic acid). 4 We have recently become interested in synthesizing coor- dination polymers with multifunctional ligands in which both neutral and anionic donor groups are present and can coordinate to metal centers, potentially to result in neutral polymeric structures. By introducing electronic asymmetry into the conjugated bridging ligands, we have demonstrated the rational synthesis of polar neutral coordination networks of transparent d 10 metals exhibiting interesting second-order nonlinear optical properties. 5 More recently, we have studied structure- magnetic property relationships of manganese(II) pyridinecarboxylate coordination networks that appear to be good examples of 1-D Heisenberg antiferromag- netic chains. 6 In this work, we examine the synthesis of Cu(II) coordination networks with both isonicotinate and nicotinate bridging ligands. We report here the synthesis, X-ray single-crystal structures, and magnetic properties of the two Cu(II) coordination polymers [Cu(isonicotinate) 2 ][EtOH] (1) and Cu(nicotinate) 2 (2). Experimental Section Materials and Methods. All chemicals were purchased from Aldrich and were used as received without further purification. The IR spectra were recorded as KBr pellets on a Paragon 1000 FT-IR spectrometer. Magnetic measurements were taken on a Quantum Design MPMS-7 SQUID magne- tometer at the National Institute of Standards and Technology in Boulder, CO. Synthesis of Bis(isonicotinato)copper(II)-Ethanol (1). Copper(II) nitrate hemipentahydrate (0.0581 g; 0.25 mmol) and isonicotinic acid (0.062 g, 0.5 mmol) were mixed in a heavy- walled Pyrex tube with ethanol (0.14 mL), acetonitrile (0.16 mL), and deionized water (0.50 mL). The tube was frozen with liquid nitrogen and sealed under vacuum. The tube was then heated at 75 °C for 24 h, at 110 °C for 72 h, and then at 130 °C for 24 h. After these different stages of heating, small bright blue crystals were obtained. The crystals were washed with 2 mL of ethanol and then twice with 2 mL of ethyl acetate. Yield: 0.050 g (57%). IR (cm -1 ): 1604 (s), 1550 (m), 1503 (w), 1416 (m), 1374 (s), 1231 (w), 1058 (m), 1032 (w), 882 (w), 849 (w), 775 (m), 706 (m). Synthesis of Bis(nicotinato)copper(II) (2). Copper ni- trate hemipentahydrate (0.0581 g, 0.25 mmol) and nicotinic acid (0.062 g, 0.5 mmol) were placed in a heavy-walled Pyrex tube with ethanol (0.10 mL), acetonitrile (0.20 mL), and deionized water (0.50 mL). The tube was frozen with liquid nitrogen and sealed under vacuum. The tube was then heated at 105 °C for 48 h and at 130 °C for 24 h. The blue product was washed three times with 2 mL of water and once with 2 mL of ethanol. Yield: 0.072 g (98%). IR (cm -1 ): 1654 (m), 1629 (s), 1570 (w), 1426 (m), 1385 (s), 1306 (w), 1189 (m), 1156 (w), 1092 (m), 1050 (m), 971 (w), 850 (m), 762 (m), 717 (w), 694 (m), 717 (w), 694 (m), 650 (w), 586 (w). Magnetic Data. The magnetic properties of 1 and 2 were investigated by SQUID magnetometry. The ∼20 mg samples were packed between two cotton plugs and placed into gelatin capsules. Two samples of each compound, from separate preparations, were measured, and the results were essentially the same for each pair. The applied field was 1000 G, and diamagnetic corrections were determined from Pascal’s con- stants and from the average gram susceptibilites of empty * To whom correspondence should be addressed. E-mail for W.L.: wlin@brandeis.edu. † Brandeis University. ‡ University of Colorado. CRYSTAL GROWTH & DESIGN 2001 VOL. 1, NO. 2 159 - 163 10.1021/cg005519l CCC: $20.00 © 2001 American Chemical Society Published on Web 01/19/2001