Issue 37, 2020

Selective encapsulation and extraction of hydrogenphosphate by a hydrogen bond donor tripodal receptor

Abstract

Selective encapsulation of an anion by a hydrogen bond donor scaffold demands design and synthesis of suitable receptors which could discriminate between anions of identical size and shape or basicity. Here, we report the anion coordination chemistry of two second generation tripodal receptors (AUL and AAL) based on 1H-NMR and crystallization experiments. The tripodal urea-based receptor AUL can selectively encapsulate a hydrogenphosphate (HPO42−) dianion by six strong hydrogen bonds donated from the three urea groups. Theoretical calculations showed that AUL has the highest binding affinity for hydrogenphosphate when compared to other competitive anions (F, CN, CH3COO and HSO4). Because of its HPO42− selectivity, AUL has been successfully employed in the extraction of HPO42− from water in the presence of competitive anions (F/OH/CH3COO) by anion exchange between two immiscible phases. On the other hand, the tripodal amide-based receptor AAL when crystallized in the presence of F, CN, CH3COO, H2PO4 and HSO4 did not yield any hydrogen-bonded receptor–anion complex and instead crystalline AAL was precipitated in each case. 1H-NMR experiments showed significant broadening and/or downfield shift of –NH signals in AUL and AAL upon additions of F, Cl, CN, CH3COO and H2PO4 (supplied as tetraalkylammonium salts), indicative of strong hydrogen bonding interactions between –NH donors and anions in the solution-state.

Graphical abstract: Selective encapsulation and extraction of hydrogenphosphate by a hydrogen bond donor tripodal receptor

Supplementary files

Article information

Article type
Paper
Submitted
09 juin 2020
Accepted
06 août 2020
First published
07 août 2020

CrystEngComm, 2020,22, 6152-6160

Selective encapsulation and extraction of hydrogenphosphate by a hydrogen bond donor tripodal receptor

S. K. Dey, Archana, S. Pereira, S. S. Harmalkar, S. N. Mhaldar, V. V. Gobre and C. Janiak, CrystEngComm, 2020, 22, 6152 DOI: 10.1039/D0CE00834F

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