Interplay between molecular recognition and acid–base reactivity in tailored metal-based calix[6]arene receptors

Lepeintre, Martin; Višnjevac, Aleksandar; Jabin, Ivan; Colasson, Benoit (2025) Interplay between molecular recognition and acid–base reactivity in tailored metal-based calix[6]arene receptors. Organic & Biomolecular Chemistry, 23 (35). pp. 8012-8022. ISSN 1477-0520

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Abstract

This study explores the interplay between molecular recognition and acid–base reactivity in two novel Zn–calix[6]arene funnel complexes featuring phenol units in place of the anisole units present in the parent systems. The two complexes differ in the accessibility of their third coordination sphere. NMR and X-ray crystallography revealed that, like their anisole-based predecessors, these new complexes can encapsulate neutral guests such as acetonitrile. However, in contrast to the parent systems, which strongly bind primary amines, the new phenol-based systems undergo a base-induced structural reorganization upon addition of propylamine, triggered by a selective metal-assisted phenol deprotonation. Moreover, the presence of phenol groups enables intra–cavity binding of anions, provided their structure allows for simultaneous stabilization through hydrogen bonding. Finally, differences in the accessibility of the third coordination sphere between the two complexes influenced their affinity for long linear anions. These findings underscore a delicate balance between coordination–driven recognition, hydrogen bonding, and acid–base chemistry in such systems. The work expands the understanding of first, second and third coordination sphere effects in metallo–receptors and demonstrates how subtle structural modifications can modulate binding modes. It also suggests new directions for designing responsive host systems capable of switching behavior under mild stimuli.

Item Type:	Article
Uncontrolled Keywords:	molecular recognition; calix[6]arene; metal complexes; X-ray diffraction
Subjects:	NATURAL SCIENCES > Chemistry > Inorganic Chemistry
Divisions:	Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Biomimetički “funnel” i “bowl” supramolekularni sustavi za selektivno prepoznavanje DNA/RNA-CALIXDNA / CALIXDNA Aleksandar Višnjevac IP-2020-02-3786 HRZZ
Depositing User:	Ema Buhin Šaler
Date Deposited:	09 Mar 2026 12:05
URI:	http://fulir.irb.hr/id/eprint/11337
DOI:	10.1039/D5OB01099C

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