Different coordination environments of iron(III) and pseudopolymorphism in complexes with dipicolinic acid and 2-amino-6-picoline. The influence of molar ratio and solvent type
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- 作者：Masoumeh Tabatabaeea ; tabatabaee45@gmail.com ; Maryam Dadkhodaeea ; Boris-Marko Kukovecb
- 关键词：Pseudopolymorphism ; Co-crystal ; Dipicolinic acid ; Seven-coordinated iron(III) ; 2-Amino-6-picoline
- 刊名：Polyhedron
- 出版年：2013
- 出版时间：4 March, 2013
- 年：2013
- 卷：51
- 期：Complete
- 页码：316-322
- 全文大小：1014 K
文摘
Three iron(III) compounds of dipicolinic acid (dipicH2) and 2-amino-6-picoline (Hamp-6-pic), formulated as (Hamp-6-pic)[Fe(dipic)2][Fe(dipic)(NO3)(H2O)2]¡¤2H2O (1), (Hamp-6-pic)[Fe(dipic)2]¡¤H2O (2) and {(Hamp-6-pic)[Fe(dipic)2]}2¡¤H2O (3) (Hamp-6-pic+ = 2-amino-6-picolinium), were prepared and characterized by spectroscopic methods (IR and UV-Vis) and their molecular and crystal structures were determined by X-ray crystal structure analysis. Compound 1 was prepared by the reaction of Fe(NO3)3¡¤6H2O with dipicolinic acid and 2-amino-6-picoline in aqueous solution in a molar ratio of 1:1:1, while 2 was obtained by the same reaction but in a molar ratio of 2:2:1. Recrystallization of 2 in a mixture of methanol and ethanol led to the formation of 3. The neutral complex [Fe(dipic)(NO3)(H2O)2] is co-crystallized with (Hamp-6-pic)[Fe(dipic)2] in 1. Fe(III) ion is seven-coordinated (in a distorted pentagonal-bipyramidal geometry) by a tridentate dipicolinate and a bidentate nitrate ion and the coordination is completed by two water molecules in axial positions. Complexes 2 and 3 are examples of pseudopolymorphs which differ in the number of co-crystallized water molecules and in the crystal system (monoclinic (2) or triclinic (3)).