New binuclear double-stranded manganese helicates as catalysts for alkene epoxidation

Abstract

New binuclear double-stranded helicates were formed between manganese(ii) perchlorate and chiral phenyl- and polyphenyl-bridged oligopyridines; they are active catalysts for alkene epoxidation.

Acid-induced formation of hydrogen-bonded double helix based on chiral polyphenyl-bridged bis(2,2′-bipyridine) ligands

“…The P-helical chirality of the [(L2) 2 H 2 ](FeCl 4 ) 2 is consistent with the rst positive CD signals observed in the CD spectra 52 which is similar to the spectra of the rigid Mn double-stranded helicates of L2 and L3. 35 The extensive p-p stacking of the aromatic rings of the strands of the double-stranded helical structure which lead to anisotropic effect also agree well with the upeld signals observed in the NMR spectra. Considering the observation and results obtained with L2, L3 and L4 in the experiments, we believe that the monoprotonated form of triphenyl-bridged L3 and tetraphenylbridged L4 also form double-stranded helical structure.…”

“…We have previously reported the synthesis of Mn double-stranded helicates with mono-to triphenyl-bridged bis(2,2 0 -bipyridine) L1-3 ligands. 35 Herein, together with a tetraphenyl-bridged bis(2,2 0 -bipyridine) L4, we report the synthesis of this series of ligands. Upon protonation, ligands L2-4 give intense CD signal in the presence of FeCl 4 À or ClO 4 À anion.…”

[Fe2L3]4+ Cylinders Derived from Bis(bidentate) 2-Pyridyl-1,2,3-triazole “Click” Ligands: Synthesis, Structures and Exploration of Biological Activity

“…With judicious choice of the metal ion and linker ligand cyclic-, doubly-, triply- or quadruply-stranded helicates can be generated. These systems display interesting electronic [7,8,9], optical [10,11,12,13], catalytic [14] and molecular recognition [15,16,17,18,19,20] properties. They have also been used as building blocks to generate novel mechanically interlocked systems [21].…”

Complementary double‐stranded helical oligomers bearing achiral bifunctional groups that catalyze asymmetric aldol reaction

“…Although a variety of optically active single-stranded helical polymers and supramolecular helical assemblies with specific functions, such as asymmetric catalysis and chiral recognition, 1,2 has been developed during the past three decades, those one-handed double helices reminiscent of the natural DNA double helix still remain a challenge regarding their synthesis, structures, and functions. [1][2][3][4][5][6][7][8][9] The chiral framework and space generated by such a double-helical structure have the potential for developing unique and conceptually new supramolecular asymmetric catalyses, 10,11 but successful examples are quite limited until now [12][13][14][15][16] except for the DNA-based catalysts. 17,18 Here, we show the invaluable role of a complementary double-helical framework with a controlled helicity for supramolecular bifunctional asymmetric organocatalysis.…”