Anion-Directed Synthesis of Metal-Organic Frameworks Based on 2-Picolinate Cu(II) Complexes: A Ferromagnetic Alternating Chain and Two Unprecedented Ferromagnetic Fish Backbone Chains
详细信息 查看全文
- 作者：Chaitali Biswas ; Pampa Mukherjee ; Michael G. B. Drew ; Carlos J. Gó ; mez-Garcí ; a ; Juan M. Clemente-Juan ; Ashutosh Ghosh
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：December 10, 2007
- 年：2007
- 卷：46
- 期：25
- 页码：10771 - 10780
- 全文大小：494K
- 年卷期：v.46,no.25(December 10, 2007)
- ISSN：1520-510X
文摘
Three new polynuclear copper(II) complexes of 2-picolinic acid (Hpic), {[Cu2(pic)3(H2O)]ClO4}n (1), {[Cu2(pic)3(H2O)]BF4}n (2), and [Cu2(pic)3(H2O)2(NO3)]n (3), have been synthesized by reaction of the "metalloligand" [Cu(pic)2] with the corresponding copper(II) salts. The compounds are characterized by single-crystal X-ray diffractionanalyses and variable-temperature magnetic measurements. Compounds 1 and 2 are isomorphous and crystallizein the triclinic system with space group P, while 3 crystallizes in the monoclinic system with space group P21/n.The structural analyses reveal that complexes 1 and 2 are constructed by "fish backbone" chains through syn-anti(equatorial-equatorial) carboxylate bridges, which are linked to one another by syn-anti (equatorial-axial) carboxylatebridges, giving rise to a rectangular grid-like two-dimensional net. Complex 3 is formed by alternating chains ofsyn-anti carboxylate-bridged copper(II) atoms, which are linked together by strong H bonds involving coordinatednitrate ions and water molecules and uncoordinated oxygen atoms from carboxylate groups. The different coordinationability of the anions along with their involvement in the H-bonding network seems to be responsible for the differencein the final polymeric structures. Variable-temperature (2-300 K) magnetic susceptibility measurement shows thepresence of weak ferromagnetic coupling for all three complexes that have been fitted with a fish backbone modeldeveloped for 1 and 2 (J = 1.74 and 0.99 cm-1; J' = 0.19 and 0.25 cm-1, respectively) and an alternating chainmodel for 3 (J = 1.19 cm-1 and J' = 1.19 cm-1).