Metal-Ligand Polyhedra

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<applet size='400' frame='true' align='right'
<applet size='400' frame='true' align='right'
scene='Metal-Ligand_Polyhedra/Polyhedron_main_chains/4' />
scene='Metal-Ligand_Polyhedra/Polyhedron_main_chains/4' />
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Metal ions with square planar coordination, when mixed with suitable ligands, can self-assemble into polyhedra of various sizes. Geometrical constraints limit the number of metal ions (vertices) to 6, 12, 24, 30, or 60 for entropically favored regular or semiregular polyhedra<ref>Coxeter, H. S. M., ''Regular Polytopes'', Dover Publications, New York, 3rd ed., 1973.</ref>. Shown at right (<scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/4'>restore initial scene</scene>) is the "main chain" of a crystallographic model for the largest such structure reported as of May, 2010<ref name="sun-fujita-2010" >PMID: 20430973</ref>. <scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/5'>24 palladium ions</scene> form the vertices of a 26-face polyhedron<ref>M24L48 forms a 26-faced ''rhombicubooctahedron'' with 18 square faces and 8 triangular faces. In this instance, the rectangular faces are very close to squares 13.35 &Aring;ngstroms on a side.</ref>. Three square faces and one triangular face meet at each vertex.
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Metal ions with square planar coordination, when mixed with bent bidentate ligands, can self-assemble into polyhedra of various sizes. Geometrical constraints limit the number of metal ions (vertices) to 6, 12, 24, 30, or 60 for entropically favored regular or semiregular polyhedra<ref>Coxeter, H. S. M., ''Regular Polytopes'', Dover Publications, New York, 3rd ed., 1973.</ref>. Shown at right (<scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/4'>restore initial scene</scene>) is the "main chain" of a crystallographic model for the largest such structure reported as of May, 2010<ref name="sun-fujita-2010" >PMID: 20430973</ref>. <scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/5'>24 palladium ions</scene> form the vertices of a 26-face polyhedron<ref>M24L48 forms a 26-faced ''rhombicubooctahedron'' with 18 square faces and 8 triangular faces. In this instance, the rectangular faces are very close to squares 13.35 &Aring;ngstroms on a side.</ref>. Three square faces and one triangular face meet at each vertex.
Each palladium ion is coordinated by <scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/6'>four nitrogens</scene>. The nitrogens are bridged by a <scene name='Metal-Ligand_Polyhedra/Single_main_chain_ligand/1'>dipyridylthiophene</scene> ("ligand"). There are two ligand molecules (L) per metal ion (M); hence, this structure is called '''M24L48'''.
Each palladium ion is coordinated by <scene name='Metal-Ligand_Polyhedra/Polyhedron_main_chains/6'>four nitrogens</scene>. The nitrogens are bridged by a <scene name='Metal-Ligand_Polyhedra/Single_main_chain_ligand/1'>dipyridylthiophene</scene> ("ligand"). There are two ligand molecules (L) per metal ion (M); hence, this structure is called '''M24L48'''.

Revision as of 23:40, 13 June 2010

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Contents

M24L48 Polyhedron (26 Faces)

Drag the structure with the mouse to rotate

Metal ions with square planar coordination, when mixed with bent bidentate ligands, can self-assemble into polyhedra of various sizes. Geometrical constraints limit the number of metal ions (vertices) to 6, 12, 24, 30, or 60 for entropically favored regular or semiregular polyhedra[1]. Shown at right () is the "main chain" of a crystallographic model for the largest such structure reported as of May, 2010[2]. form the vertices of a 26-face polyhedron[3]. Three square faces and one triangular face meet at each vertex.

Each palladium ion is coordinated by . The nitrogens are bridged by a ("ligand"). There are two ligand molecules (L) per metal ion (M); hence, this structure is called M24L48.

The models shown thus far are simplified, including only the "main chain". The actual M24L48 complex analyzed crystallographically contained a substituent of -OCH2CH2O- on each thiophene ring, PF6- counterions bound to the surface of the polyhedron, and hydrogen atoms. Here is the (but lacking the three additional nitrogens coordinating each palladium, and water, which was not resolved crystallographically). Here is the (but lacking PF6 and water).

Ligand Angle vs. Polyhedron Size

The dipyridylthiphene ligand pictured above, in the M24L48 polyhedron, has a bend angle of 149o[2]. A ligand with a sharper bend of 129o (dipyridylfuran[4]) forms a smaller polyhedron, M12L24[5]. A ligand with an even sharper bend of 90o forms M6L12[6].

Significance

To do:

  • improve final scene: sticks, custom colors.
  • color keys.
  • significance

References and Notes

  1. ↑ Coxeter, H. S. M., Regular Polytopes, Dover Publications, New York, 3rd ed., 1973.
  2. ↑ 2.0 2.1 Sun QF, Iwasa J, Ogawa D, Ishido Y, Sato S, Ozeki T, Sei Y, Yamaguchi K, Fujita M. Self-assembled M24L48 polyhedra and their sharp structural switch upon subtle ligand variation. Science. 2010 May 28;328(5982):1144-7. Epub 2010 Apr 29. PMID:20430973 doi:10.1126/science.1188605
  3. ↑ M24L48 forms a 26-faced rhombicubooctahedron with 18 square faces and 8 triangular faces. In this instance, the rectangular faces are very close to squares 13.35 Ångstroms on a side.
  4. ↑ Dipyridylfuran differs from dipyridylthiophene in that oxygen replaces the sulfur.
  5. ↑ Tominaga M, Suzuki K, Kawano M, Kusukawa T, Ozeki T, Sakamoto S, Yamaguchi K, Fujita M. Finite, spherical coordination networks that self-organize from 36 small components. Angew Chem Int Ed Engl. 2004 Oct 25;43(42):5621-5. PMID:15455450 doi:10.1002/anie.200461422
  6. ↑ Suzuki K, Tominaga M, Kawano M, Fujita M. Self-assembly of an M6L12 coordination cube. Chem Commun (Camb). 2009 Apr 7;(13):1638-40. Epub 2009 Feb 17. PMID:19294246 doi:10.1039/b822311d

Models

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