D_3h‐Symmetric Porphyrin‐Based Rigid Macrocyclic Ligands for Multicofacial Multinuclear Complexes in a One‐Nanometer‐Sized Cavity

Abstract

The one-step synthesis of D3h -symmetric cyclic porphyrin trimers 1 composed of three 2,2'-[4,4'-bis(methoxycarbonyl)]bipyridyl moieties and three porphyrinatozinc moieties was achieved from a nickel-mediated reductive coupling of meso-5,15-bis(6-chloro-4-methoxycarbonylpyrid-2-yl)porphyrinatozinc. Although cyclic trimers 1 were obtained as a mixture that included other cyclic and acyclic porphyrin oligomers, an extremely specific separation was observed only for cyclic trimers 1 when using columns of silica gel modified with pyrenylethyl, cyanopropyl, and other groups. Structural analysis of cyclic trimers 1 was carried out by means of NMR spectroscopy and X-ray crystallography. Treatment of an η(3) -allylpalladium complex with a cyclic trimer gave a tris(palladium) complex containing three η(3) -allylpalladium groups inside the space, which indicated that the bipyridyl moieties inside the ring could work as bidentate metalloligands.

Synthesis of Double-Bridged Cofacial Nickel Porphyrin Dimers with 2,2′-Bipyridyl Pillars and Their Restricted Coordination Space

“…Preparation of Cyclic Dimers and Chromatographic Behaviors. The treatment of free-base porphyrin 54 with nickel acetate gave the corresponding Ni porphyrin dimethyl ester 1 Me . To examine the effect of alkyl chains in the ester groups on both the coupling reaction and the chromatography, corresponding butyl and octyl esters, 1 Bu and 1 Oc , were also prepared by transesterification of 1 Me with n-butanol and n-octanol, respectively, in the presence of a tin catalyst.…”

“…28−53 However, cyclic arrays connected alternately with 2,2′-bipyridyl moieties and porphyrins are limited, except for our cyclic trimer Zn-3 Me (Figure 1) connected through 2,2′-bipyridyl moieties and Zn porphyrins. 54 Because the coordination sites on the 2,2′bipyridyl moieties are directed to the center of the cyclic trimer Zn-3 Me , the compound was applied as a functional ligand for multi-cofacial and multinuclear complexes. 55−61 The compound Zn-3 Me -(allylPd) 3 (Figure 1), in which three cationic η 3 -allylpalladium species were incorporated as bipyridyl complexes, has been previously reported as a demonstration of the coordination ability of Zn-3 Me .…”

“…55−61 The compound Zn-3 Me -(allylPd) 3 (Figure 1), in which three cationic η 3 -allylpalladium species were incorporated as bipyridyl complexes, has been previously reported as a demonstration of the coordination ability of Zn-3 Me . 54 The cyclic compound Zn-3 Me was prepared by the reductive homocoupling reaction of bis(chloropyridyl)porphyrinatozinc molecules, followed by efficient separation from the mixture including the target compound and other acyclic oligomers on a cyanopropyl-modified silica gel column. In the case of the Zn porphyrin derivative, a cyclic trimer was afforded as the dominant component.…”

Metal-templated synthesis of rigid and conformationally restricted cyclic bisporphyrins: specific retention times on a cyanopropyl-modified silica gel column

“…Unexpectedly, the order does not follow the distances between the two zinc porphyrins in Zn 2 -CP2 o, Zn 2 -CP2 m , and Zn 2 -CP2 p . From the comparison of cyclic zinc porphyrin trimers 32 and cyclic nickel porphyrin dimers 14 , we expected that a shorter distance between the two zinc porphyrins would be advantageous for longer retention. However, the order of Zn 2 -CP2 m and Zn 2 -CP2 p was inverted, and the retention time of Zn 2 -CP2 p was significantly longer.…”

Thieme Chemistry Journals Awardees – Where Are They Now? Synthesis of a Dinuclear Copper NHC Complex Bearing a Rigid π-Conjugated Cyclic Framework

“…of the ring and ensures that the distance between them is fixed. So far, the reported rigid cyclic dinuclear complexes with multiple metals in the ring contained either pyridyl [10][11][12][13][14] or Schiff base type 15,16 coordination sites, making the synthesis described herein unprecedented. To enhance the solubility of the complex, four 3,5-di-tert-butylbenzene units were introduced in the meta-junction part distant from the catalyst center.…”