Polymorphism and weak antiferromagnetic interactions in dibromo[(−)-sparteine-N,N]copper(II) |
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Authors: | Sung Kwon Kang Young-Inn Kim Karl Seff |
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Institution: | a Department of Chemistry, Chungnam National University, Daejeon 305-764, Republic of Korea b Department of Chemistry, Chemistry Institute for Functional Materials, Pusan National University, Changjeon-Dong, Kumjeong-Ku, Pusan 609-735, Republic of Korea c Department of Chemistry Education, Pusan National University, Pusan 609-735, Republic of Korea d Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822, USA |
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Abstract: | Two polymorphic crystal structures of the title compound, dibromo(−)-sparteine-N,N′]copper(II), 1, were determined. The structures of two isomorphs of 1, 1a orthorhombic, P212121, a=11.0463(9) Å, b=11.9839(15) Å and c=12.7835(19) Å] and 1b orthorhombic, P212121, a=7.6779(9) Å, b=12.0927(14) Å and c=18.090(2) Å], are composed of the same basic structural unit, Cu(C15H26N2)Br2. The bond distances in the molecular structures of 1a and 1b are identical to each other within the esds. However, there are slight differences in the bond angles around the Cu(II) center and considerable differences in their packing structure. Crystal 1a exhibits weak anti-ferromagnetism (J=−1.89 cm−1) as opposed to the magnetically isolated paramagnetism observed for the analogous dichloro(−)-sparteine]copper(II), 2. The results of a magneto-structural investigation of 1a and 2, and other supporting evidence, suggest that the pathway for the weak antiferromagnetic super-exchange in 1a might be through a Cu-Br ? Br-Cu contact. |
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Keywords: | Polymorphism Halide-halide contact Antiferromagnetism (&minus )-Sparteine Copper(II) |
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