Metallacycles of Porphyrins as Building Blocks in the Construction of Higher Order Assemblies through Axial Coordination of Bridging Ligands: Solution- and Solid-State Characterization of Molecular Sa
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- 作者：Elisabetta Iengo ; Ennio Zangrando ; Romina Minatel ; and Enzo Alessio
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：February 13, 2002
- 年：2002
- 卷：124
- 期：6
- 页码：1003 - 1013
- 全文大小：188K
- 年卷期：v.124,no.6(February 13, 2002)
- ISSN：1520-5126
文摘
Treatment of the octahedral Ru(II)-dimethyl sulfoxide complexes trans-RuCl2(dmso-S)4 (1), trans-RuCl2(dmso-O)2(CO)2 (2), and trans-RuCl2(dmso)3(CO) (3) with a stoichiometric amount of 5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin (4'-cis-DPyP) yields, after chromatographic purification, the novel 2+2molecular squares of formula [trans,cis,cis-RuCl2(dmso-S)2(4'-cis-DPyP)]2 (4), [trans,cis,cis-RuCl2(CO)2(4'-cis-DPyP)]2 (5), and [trans,cis,cis-RuCl2(dmso-S)(CO)(4'-cis-DPyP)]2 (6), respectively. Compound 6 existsas an equimolar mixture of the isomeric metallacycles 6a and 6b, depending on whether the 4'-N(py) ringsof 4'-cis-DPyP's are trans to CO or to dmso-S. Compounds 4-6 were fully characterized by NMR and IRspectroscopy and by FAB mass spectrometry. Treatment of 5 with excess zinc acetate in chloroform/methanol mixtures led to the isolation of the corresponding zinc adduct [trans,cis,cis-RuCl2(CO)2(Zn·4'-cis-DPyP)]2 (5Zn). Treatment of 5Zn with 1 equiv of a trans ditopic N-donor ligand L (L = 4,4'-bipy, 5,15-bis(4'-pyridyl)-2,8,12,18-tetra-n-propyl-3,7,13,17-tetramethylporphyrin (4'-trans-DPyP-npm), or 5,15-bis(4'-pyridyl)-10,20-diphenylporphyrin (4'-trans-DPyP)) leads readily and selectively, according to 1H NMRspectroscopy, to the quantitative assemblying of 2:2 supramolecular adducts of stacked metallacycles offormula [(5Zn)2(
-L)2] (7-9), which were thoroughly characterized in solution by NMR spectroscopy. NMRfeatures indicate that, at ambient temperature, the equilibrium between 5Zn and L to yield [(5Zn)2(-L)2]has an intermediate to slow rate on the NMR time scale (relatively broad signals for L) and is totally shiftedtoward the 2:2 product (all or nothing process). Single-crystal X-ray investigations showed that, dependingon the nature of the bridging ligand, in the solid state these sandwich structures can either be maintainedor originate polymeric chains formulated as [(5Zn)(-L)]
. When L = 4'-trans-DPyP, both solution- andsolid-state data indicate that [(5Zn)2(-4'-trans-DPyP)2] (9) is a discrete supramolecular assembly of twomolecular squares of metalloporphyrins axially connected through other porphyrins. In this molecular box,the two bridging porphyrins are coplanar at a distance of about 11.4 Å. When L = 4,4'-bipy, thecorresponding adduct 7 has the anticipated sandwich-like discrete architecture [(5Zn)2(-4,4'-bipy)2] insolution, but it assumes a stairlike polymeric wire structure in the solid state. The polymer [(5Zn)(-4,4'-bipy)] is made by 5Zn squares bridged by 4,4'-bipy ligands which are axially coordinated alternatively onthe two opposite sides of each square. Our work clearly established that relatively simple supramolecularadducts of porphyrins, such as molecular squares, are suitable building blocks for the construction of moreelaborate assemblies of higher order by axial coordination of bridging ligands.
-L)2] (7-9), which were thoroughly characterized in solution by NMR spectroscopy. NMRfeatures indicate that, at ambient temperature, the equilibrium between 5Zn and L to yield [(5Zn)2(-L)2]has an intermediate to slow rate on the NMR time scale (relatively broad signals for L) and is totally shiftedtoward the 2:2 product (all or nothing process). Single-crystal X-ray investigations showed that, dependingon the nature of the bridging ligand, in the solid state these sandwich structures can either be maintainedor originate polymeric chains formulated as [(5Zn)(-L)]. When L = 4'-trans-DPyP, both solution- andsolid-state data indicate that [(5Zn)2(-4'-trans-DPyP)2] (9) is a discrete supramolecular assembly of twomolecular squares of metalloporphyrins axially connected through other porphyrins. In this molecular box,the two bridging porphyrins are coplanar at a distance of about 11.4 Å. When L = 4,4'-bipy, thecorresponding adduct 7 has the anticipated sandwich-like discrete architecture [(5Zn)2(-4,4'-bipy)2] insolution, but it assumes a stairlike polymeric wire structure in the solid state. The polymer [(5Zn)(-4,4'-bipy)] is made by 5Zn squares bridged by 4,4'-bipy ligands which are axially coordinated alternatively onthe two opposite sides of each square. Our work clearly established that relatively simple supramolecularadducts of porphyrins, such as molecular squares, are suitable building blocks for the construction of moreelaborate assemblies of higher order by axial coordination of bridging ligands.