First Synthesis and Structure of β-Ketoimine Calix[4]arenes: Complexation and Extraction Studies

Abstract

The synthesis of a new series of beta-ketoimine calix[4]arene derivatives is described. The reaction of calix[4]arene or p-tert-butylcalix[4]arene with bromoacetonitrile or bromobutyronitrile afforded di-, tri-, and tetranitrile calixarene derivatives (3-8, 3a), which were then reduced into the corresponding amine (9-13, 3b). The condensation of these aminocalixarenes with acetylacetone led to six beta-ketoimine calix[4]arene derivatives (14-18, 3c) as a class of selective receptors toward transition metals. Molecular structures of 4, 7, and 17 have been determined by X-ray diffraction. The packing of 17 revealed a network of intramolecular and intermolecular hydrogen bonds. The complexation properties of receptors 15, 17, and 3c toward different metal ions have been investigated by UV-vis titrations in organic media. The stoichiometries of complexes with 17 were determined by both the mole ratio method and Job plots. These novel receptors selectively complex Cu2+, Hg2+, and Ag+. Moreover, the extraction properties of 17 toward cations have been studied by liquid-liquid extraction and atomic absorption spectrometry. Compound 17 has good affinity and selectivity toward Pb2+.

Cooperative Recognition of a Copper Cation and Anion by a Calix[4]arene Substituted at the Lower Rim by a β‐Amino‐α,β‐Unsaturated Ketone

“…The formation of a new absorption band at 438 nm is reminiscent of a MLCT band between Cu I and the phenolic OH on the lower rim of ligand 2. [13,14] A similar broad absorption band for a Cu I tetrahedral complex has also been reported, which was ascribed to a MLCT band. [19] The autoreduction of Cu II to Cu I was reported in the copper ion complexation of a bisb-ketoimine-substituted calix[4]arene.…”

“…Model compounds 3 and 4 were synthesised by following the same synthetic strategy as calix[4]arenes 1 and 2, and they were obtained in 69 and 76 % yield, respectively. The structures of compounds 1-4 were confirmed by 1 H and 13 C NMR spectroscopy, mass spectrometry and HRMS. The structures of calix[4]arenes 1 and 2 were further confirmed by single-crystal X-ray analysis (Figure 1).…”

Tetrazoles and para‐Substituted Phenylazo‐Coupled Calix[4]arenes as Highly Sensitive Chromogenic Sensors for Ca2+

“…5,17-Bis[4- (4-substituted-phenyl)azo]-25,27-dioxyacetonitrilecalix[4]-arenes 2a (R = OMe) and 2b (R = NO 2 ) were synthesized starting from 25,27-dioxyacetonitrilecalix[4]arene 1 [12] by a diazo coupling reaction with the use of para-substituted aniline [1] in 87 and 63 % yield, respectively. The di-n-butyltin oxide mediated addition of trimethylsilyl azide (TMSN 3 ) with oxyacetonitrile calix[4]arenes 2a and 2b in toluene afforded the very polar 5,17-bis[4-(4-substituted-phenyl)azo]-25,27-bis[(oxymethyl)-2H-tetrazole]calix[4]arenes 3a and 3b in 89 and 67 % yield, respectively.…”

“…25,27-Dioxyacetonitrile-26,28-dihydroxycalix[4]arene (1) was synthesized according to a literature procedure. [12] General Procedure for the Synthesis of 2a and 2b: To an ice-cold solution of NaNO 2 (7.50 mmol) in 4  HCl (6.00 mL) was added a solution of para-substituted aniline (4.00 mmol) in acetone (8.00 mL), and the mixture was stirred for 1 min. The combined solution was added dropwise to another ice-cold solution of 25,27-dioxyacetonitrile-26,28-dihydroxycalix[4]arene (1; 1.00 mmol) in pyridine (12.00 mL) to produce an ox-blood-red solution.…”

Calixarene complexes with soft metal ions

“…Calixarenes 1-3 exist in a cone conformation in solution; with Cu 2+ , Ag + and Hg 2+ ions they yield the 1:1 complexes. 51 In the solid state "a polymeric linear chain" is formed as a result of intermolecular interactions between β-ketoimine groups.…”