Synthesis of some benzimidazole‐ and benzothiazole‐derived ligand systems and their precursory diacids

Abstract

Procedures are described for the preparation of various bidentate and linear tetradentate benzimidazoles and benzothiazoles incorporating units such as pyridyl and thioether, and for the preparation of certain thioether dicarboxylic acids precursory to them. Condensations of ortho‐functinal anilines with carboxylic acids were carried out in polyphosphoric acid or refluxing HCl solution. Syntheses are reported for: [HO2C(CH2)2S(CH2)2]2X (X = O, S), 1,9‐bis(benzimidazol‐2‐yl)‐2,5,8‐trithianonane, 1,11‐bis(N‐methylbenzimidazol‐2‐yl)‐3,6,9‐trithiaundecane, 1,11‐bis(2‐benzimidazol‐2‐yl)‐6‐oxo‐3,9‐dithiaundecane, 2‐(2‐pyridyl)benzothiazole, 2,6‐bis(benzothiazol‐2‐yl)pyridine, 2‐(2‐pyridyl)‐N‐methylbenzimidazole, 2‐(2‐pyridylmethyl)benzimidazole and 2‐(N‐methyl‐2‐piperidyl)benzimidazole. The compounds were characterized, where appropriate, by their mass, uv and 1H‐nmr spectra.

Spectroscopic differences between heterocyclic benzothiazoline, -thiazole and imine containing ligands and comparison of the Co and Cu pyridine benzothiazole and imine complexes

“…Although the mono- [13,18,21,22] and di-benzothiazoline [27][28][29] analogs in the current study have been previously reported, much of the spectroscopic characterization is incomplete and 1 H NMR data is mostly unavailable. The lack of data could be the result of oxidation products forming in tandem with the desired product complicating the analyses.…”

A novel paradigm for metal-induced ring flipping in the copper(II) complex of 1,2-bis( N -methylbenzimidazol-2 ′ -yl)benzene triflate

“…The ligand bmbz was obtained as a byproduct and in low yield in an earlier attempt to synthesize the compound [15]. We have prepared bmbz with increased yield and in one step by the adaptation of the published procedures for N -methylbenzimidazoles and 2-arylbenzimidazoles [16,17] Then, the copper complex was prepared by slowly adding a solution of copper(II) triflate (1.2 mmol) in methanol to a stirred solution of the ligand (0.41 g, 1.2 mmol) in methanol. The reaction mixture was further stirred for 0.5 h, and on slow evaporation of the solvent, the copper complex crystallized as dark brownish green microcrystals [19].…”

Tuning the spin crossover above room temperature: iron(II) complexes of substituted and deprotonated 2,6-bis(benzimidazol-2-yl)pyridine

“…The solid product was filtered off and recrystallized from acetone [Fe(bzimpy À1H ) 2 ] AE H 2 O (4). The ligand bzimpy was prepared by procedures described elsewhere [9]. The solution I: 0.31 g (1.0 mmol) of bzimpy, 20 cm 3 of ethanol, and 2 cm 3 of water.…”