Octahedral Arrangement of Porphyrin Moieties around Hexarhenium(III) Cluster Cores: Structure of (μ3-Selenido)hexa(5-(4-pyridyl)-10,15,20-tritolylporphyrin)hexarhenium(III) (2+)

Abstract

In memoriam Ai ItasakaHexanuclear rhenum(iii) cluster complexes are the subject of extensive current studies [1±17] because of their redox and photoluminescent properties as well as the versatility of the design of the coordination environment around the hexarhenium cores, Re 6 (m 3 -E) 8 (E S, Se). The cores may be regarded as a giant octahedral center, since the six terminal ligands are oriented in such a manner that each pair of neighboring ligands are arranged vertically to each other. It is possible to mimic the chemistry of simple octahedral metal complexes by using the hexarhenium cluster core, as ligand substitution at the six terminal sites of the core can be controlled with respect to the number and geometrical arrangements of the terminal ligands. Examples are the preparation of a series of pyridine (py) complexes, [Re 6 (m 3 -S) 8 Cl n (py) 6Àn ] (2Àn) (n 2 ± 4), which included the isolation of two isomers (cis and trans) for n 2, [4,13] and the bridge-chelate formation around the core by a long-chain bidentate ligand, (C 6 H 5 ) 2 P(CH 2 ) 6 P(C 6 H 5 ) 2 . [14] Another important aspect of using a giant octahedral center is to arrange as many as six sterically bulky ligands around the core, something that is difficult around a single metal center.In the past few years, we have been studying the preparation and properties of some oligomeric porphyrins that are constructed through coordination of pyridylporphyrins to metalloporphyrins. [18±26] Although the octahedral arrangement of the porphyrin ligands is interesting as an important structural motif and also as a building block of certain supramolecular complexes, it is too bulky to make stable six-coordinate mononuclear metal complexes. We now show that the octahedral arrangement of porphyrins is possible by using the hexarhenium cores. The new com-plexes 1 ± 4 (H 2 PyT 3 P 5-(4-pyridyl)-10,15,20-tritolylporphyrin) are reported herein.[Re 6 (m 3 -S) 8 (H 2 PyT 3 P) 6 ] 2 1[Re 6 (m 3 -S) 8 (ZnPyT 3 P) 6 ] 2 2[Re 6 (m 3 -Se) 8 (H 2 PyT 3 P) 6 ] 2 3[Re 6 (m 3 -Se) 8 (ZnPyT 3 P) 6 ] 2 4The complexes 1 and 3 containing free-base porphyrins were prepared by the substitution of 5-(4-pyridyl)-10,15,20tritolylporphyrin for the solvent molecules in [Re 6 (m 3 -S) 8 -(CH 3 CN) 6 ] 2 and [Re 6 (m 3 -Se) 8 (CH 3 CN) 6 ] 2 , respectively, in chlorobenzene. Zinc(ii) ions were introduced into the porphyrins in 1 and 3 by reacting them with zinc acetate in CH 2 Cl 2 to give 2 and 4, respectively.The structure of 3-(SbF 6 ) 2 was determined by single-crystal X-ray structure analysis. [27] Figure 1 shows the remarkable structure of 3. Six H 2 PyT 3 P groups coordinate to the [Re 6 Se 8 ] 2 core through the pyridyl group. The bond lengths and angles in the [Re 6 Se 8 ] 2 core reveal that the rhenium selenide cluster core has virtually O h symmetry as in other hexarhenium chalcogenide complexes. [3, 7±14, 28±34] The complex ion has a cystallographically imposed inversion center. In addition, six H 2 PyT 3 P groups are arranged essentially in a C 3 manner around the [R...

An Electrochemical and Photophysical Study of a Covalently Linked Inorganic–Organic Dyad

“…Similar to ruthenium(II) polypyridine complexes, hexanuclear rhenium(III) cluster complexes show unique redox and photoluminescent properties as well as the versatility of the coordination environment around the hexarhenium cores, [Re 6 (μ 3 ‐Q) 8 ] 2+ (Q=S, Se, Te) 9. Only a few precedents to [Re 6 (μ 3 ‐Q) 8 ] 2+ with peripherally attached porphyrin chromophores are known to date 10. However, the electronic interactions between [Re 6 (μ 3 ‐Q) 8 ] 2+ and porphyrin units have not yet been investigated in detail.…”

Distal protection of bifurcating vessels: A novel approach

“…These facts clearly reinforce the conclusion that the hexarhenium(III) core is able to mediate terminal ligand redox interaction. For the porphyrin‐coordinated complex 27 ,42 however, the ligand reduction process is observed as a single wave. It was argued that the perpendicular arrangement of the coordinated pyridyl group and the main porphyrin backbone would break the communication pathway from the one porphyrin ring to the other 42.…”

“…For the porphyrin‐coordinated complex 27 ,42 however, the ligand reduction process is observed as a single wave. It was argued that the perpendicular arrangement of the coordinated pyridyl group and the main porphyrin backbone would break the communication pathway from the one porphyrin ring to the other 42. Likewise, the smaller extent of mutual interactions of bpy ligands in 24 can be explained by possible perpendicular orientation of the two aromatic rings of bpy.…”

“…Further interesting phenomena are observed for the ligand redox response in the hexarhenium(III) complexes that have six identical redox‐active ligands at their six terminal sites 41. Figure 10 shows the DPV of [Re 6 (μ 3 ‐S) 8 (L) 6 ] 2+ , where L = bpy ( 24 ), bzpy ( 25 ), cpy ( 26 ), and 5‐(4‐pyridyl)‐10,15,20‐tritorylporphyrin ( 27 ).…”

Hydrogen-bonded supramolecular arrays of the [Re6(μ3-Se)8]2+core-containing clusters

“…The second series of complexes (4)(5)(6) were prepared according to Scheme 2. Owing to the poor solubility of the free PDCA in ordinary organic solvents, the ligand exchange was carried out by executing de-halogenation of the iodo-complexes 8a [Re 6 (µ 3 -Se) 8 (PEt 3 ) n I 6Ϫn ]I nϪ4 [n = 5, 4 (cis-and trans-)] using AgSbF 6 in the presence of excess PDCA in dichloromethane.…”