Single Helicates of Dipalladium(II) Hexapyrroles: Helicity Induction and Redox Tuning of Chiroptical Properties

Abstract

Hexapyrrole‐α,ω‐dialdehyde, which has eight donor atoms, afforded a dipalladium(II) single helicate (see picture; Pd pink, O red, N blue). A rapid interchange of the helical screw was slowed down by imine formation at the terminal aldehyde units with (R)‐(−)‐1‐cyclohexylethylamine, leading to an overwhelming excess of a P‐helical screw. This stable dinuclear single helicate has a redox‐driven reversible change in chiroptical properties.

Conformational Changes and Redox Properties of Bimetallic Single Helicates of Hexapyrrole‐α,ω‐dicarbaldehydes

“…Monometallic helical complexes, such as 10 Fe and 11 Co, were also prepared by oxidative metallation of the precursor ligands . As for bimetallic helicates, we have prepared the bisPd II complex 1 a Pd and the bisNi II complex 2 Ni of partially π‐conjugated hexapyrrolic ligands ,. The bisCu II hexapyrrolic helicate 3 Cu that is closely related to 1 a Pd but completely π conjugated was reported by Xie and co‐workers .…”

“…Although the solid‐state structures of the above‐mentioned single helicates were determined except that of 8 Zn, structures of the paramagnetic Fe, Co, and Cu helicates in solution have never been studied in detail. Our previous Communication showed that 1 a Pd was rapidly interchanging between P ‐ and M ‐helical conformations in solution . In order to give further insight into the stereochemistry in solution, we have investigated the Cu II , Ni II , and Pd II bimetallic complexes of hexapyrrole‐α,ω‐dicarbaldehydes and effects of the metal ions and alkyl substituents on their structures and properties will be described here.…”

Linear and circular helicates: A brief review

“…A hexapyrrole-α, ω-dialdehyde, H 4 L7 with terminal aldehyde groups (for the introduction of chirality) was reacted with [PdCl 2 (MeCN) 2 ] to give single-stranded helicate, [Pd 2 (L7)],7 8 ( Figure 5). The dipalladium(II) hexapyrroles was found to be dynamic and the rate of the conformational change was significantly slowed down by the conversion of the terminal formyl group into the imine group.…”

The Chain of Chirality Transfer as Determinant of Brain Functional Laterality. Breaking the Chirality Silence: Search for New Generation of Biomarkers; Relevance to Neurodegenerative Diseases, Cognitive Psychology, and Nutrition Science

“…The diversity of stereospecific (chiral) phenomena was observed in molecular structures including chirality recognition/sensing [95,96], chirality transfer [97], chirality/helicity induction [98][99][100][101], chirality amplification [102][103][104], chirality breaking [61,105], chirality conflict [106,107], helicity inversion [108][109][110], and chiral phase transitions XVII [111][112][113][114]116]. Progress in the studies of molecular chirality transformation is helpful in resolving three questions.…”