Issue 45, 2013

Programmed multiple complexation for the creation of helical structures from acyclic phenol–bipyridine oligomer ligands

Abstract

Two new multidentate ligands, H3L1 and H4L2, possessing bipyridinephenol repetitive units were designed so that the multi-metal complexation could produce a single-helical structure in a pre-programmed fashion. The ligands were synthesized by successive palladium-catalyzed coupling reactions. The complexation of H3L1 with zinc(II) and nickel(II) acetate afforded [L1Zn2(OAc)] and [(L1)2Ni4](OAc)2, respectively. Each of the ligand moieties in these complexes formed a one-turn single helix. The zinc(II) complex [L1Zn2(OAc)] underwent a helix compression–extension motion in solution. The complexation of the H3L1 ligand with iron(III) chloride gave a dinuclear complex [(HL1)2Fe2Cl2] with a non-helical dimeric structure. The longer ligand H4L2 afforded a trinuclear complex [L2Zn3(OAc)2] with a 1.5-turn single-helical structure upon complexation with zinc(II) acetate. The reaction of the H4L2 ligand with cobalt(II) acetate under aerobic conditions gave a mixed valence complex [L2Co3(OAc)3(OMe)], which had two trivalent and one divalent cobalt ions. The structural features of the trinuclear complexes significantly depended on the metals; [L2Co3(OAc)3(OMe)] had a helical pitch of 7.6 Å, which was almost twice that of [L2Zn3(OAc)2] (4.0 Å).

Graphical abstract: Programmed multiple complexation for the creation of helical structures from acyclic phenol–bipyridine oligomer ligands

Supplementary files

Article information

Article type
Paper
Submitted
11 May 2013
Accepted
21 Jun 2013
First published
22 Jul 2013

Dalton Trans., 2013,42, 15974-15986

Programmed multiple complexation for the creation of helical structures from acyclic phenolbipyridine oligomer ligands

S. Akine, H. Nagumo and T. Nabeshima, Dalton Trans., 2013, 42, 15974 DOI: 10.1039/C3DT51240A

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