2024-05-08 星期三
Hao-Ling Sun,† Song Gao,*,† Bao-Qing Ma,† Gang Su,‡ and Stuart R. Batten§
College of Chemistry and Molecular Engineering, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory on Rare Earth Materials and Bioinorganic Chemistry, Peking University, Beijing 100871, China, Department of Physics, The Graduate School of the Chinese Academy of Sciences, P. O. Box 3908, Beijing 100039, China, and School of Chemistry, P. O. Box 23, Monash University, Clayton, Victoria 3800, Australia
Received November 18, 2003; Revised Manuscript Received April 20, 2004
The reaction of MnCl2·4H2O and 2,5-dimethylpyrazine-dioxide (2,5-dmpdo) with various anions in H2O affords different complexes, the solid structures of which are controlled by the choice of counteranions. Reaction of MnCl2·4H2O and 2,5-dmpdo with NH4NCS yields [Mn(NCS)2(2,5-dmpdo)1.5(H2O)2]·0.5(2,5-dmpdo)·H2O (1), which contains Mn(II) dimers bridged by 2,5-dmpdo. However, with the replacement of NH4NCS with NaN3 or sodium dicyanamide (Na(dca)) in the above reaction, Mn(N3)2(2,5-dmpdo)(H2O)2 (2) or Mn(dca)2(2,5-dmpdo) (3) was isolated. Compound 2 consists of a one-dimensional zigzag chain constructed by 2,5-dmpdo bridging ligands. Compound 3 is comprised of two-dimensional layers constructed by bridging 2,5-dmpdo and dca ligands. These results unequivocally indicate that the nature of the counteranions, which play different roles in each complex, is the key factor governing the structural topologies of them. While using 2,3-dimethylpyrazine-dioxide (2,3-dmpdo) instead of 2,5-dmpdo, [Mn(dca)2(2,3-dmpdo)]·H2O (4) was obtained, which contains a CdSO4-like three-dimensional open framework constructed by 2,3-dmpdo and dca, indicating a minor change of the bridging ligand can have great effect on the topology of the crystal structure. Magnetic studies reveal that the four complexes exhibit spin-flop transitions below 2.12 K for 1, 6.14 K for 2, 6.23 K for 3, and 5.37 K for 4, respectively.