Ditopic Hexadentate Ligands with a Central Dihydrobenzo‐diimidazole Unit Forming a [2x2] Zn₄ Grid Complex

Abstract

A family of ditopic hexadentate ligands based on the parent compound 2,6-bis(6-(pyrazol-1-yl)pyridin-2-yl)-1,5-dihydrobenzo [1,2-d:4,5-d']diimidazole (L) was developed and synthesized by using a straightforward condensation reaction, which forms the interlinking central benzo [1,2-d:4,5-d']diimidazole bridge in the ligand backbone. The two secondary amine groups of the benzodiimidazole unit tautomerize and allow the formation of two tauto-conformers, which upon treatment with metal salts forms different isomeric coordination complexes. Here we report six new derivatives (1-6) that can tautomerize (varying the pyrazolylpyridine part) and 14 derivatives (7-13) with different alkyl and benzyl substitution on secondary amino groups (of L) that prevent the tautomerization. This way, it is possible to study the properties of isomeric coordination complexes and their intrinsic cooperativity by the example of [2x2] grid complexes in the future. A [2x2] Zn 4 complex of the ligand L was synthesized and structurally characterized.

Reversible pH‐Controlled Catenation of a Benzobisimidazole‐Based Tetranuclear Rectangle

“…For both metalla-macrocycles recorded in fresh solutions at C = 2 × 10 À 5 M, weaker emissions are observed at around 460 nm, which is consistent with the fluorescence of recently reported tetranuclear Zn-benzobisimidazoles grid complexes. [25] However, when decreasing the concentration to C = 10 À 6 M, the emission is blue-shifted to 430 nm and most likely corresponds to the free ligand in solution (Figure S35) as already observed by absorption spectrophotometry. [26] Complexation properties of Naph 2 BBI 2 were further investigated by UV-vis and fluorescence spectroscopy.…”

Chiral Resolution of Spin‐Crossover Active Iron(II) [2x2] Grid Complexes

“…By introducing chemical substitution at the secondary amine group on the parent ligand L to form the tertiary amine, tautomerization can be blocked. [28] Due to the difference in structural conformations, the cis‐ and trans‐type of ligands show different polarities, and this facilitates the separation of the cis‐ and trans‐ ligands by traditional column chromatography.…”