“Nindigo”: synthesis, coordination chemistry, and properties of indigo diimines as a new class of functional bridging ligands

Abstract

Reactions of indigo with anilines provide a simple route to indigo N,N'-diaryldiimines ("Nindigo"), a new binucleating ligand with two beta-diketiminate-type metal binding sites. Bis-palladium complexes have interesting ligand-centred properties such as redox activity and intense near infrared absorption.

Protoisomerization of indigo di- and monoimines

“…6,9 We recently reported the synthesis of indigo diimine ('Nindigo') derivatives. 10,11 . These more soluble indigo analogues have been shown by us 12 and others 13, 14 to possess a rich coordination chemistry.…”

“…(3) Indigo bis(aryl imines) (i.e. Nindigos) were originally reported over a century ago 16 (although the specific synthetic route has not been reproducible 10,17 ). Included in this original report were reactions of indigo bis(phenylimine) with strong acids (HCl, H2SO4, picric acid) which gave green solutions or crystalline materials.…”

Radical ligand-containing single-molecule magnets

“…Initial investigations of their coordination chemistry with Pd(hfac) 2 demonstrated rich redox activity and a near-IR absorption band centered at the ligand, suggesting a promising, tunable bridging ligand [207,208].…”

UncommoncisConfiguration of a Metal–Metal Bridging Noninnocent Nindigo Ligand

“…The metal precursors [Ru II (acac) 2 (CH 3 CN) 2 ], 22 cis-[Ru II (bpy) 2 Cl 2 ]·2H 2 O,23 and the ligand indigo-bis(N-phenylimine)24 …”