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Chemistry in Cages: Dinucleating Azacryptand Hosts and Their Cation and Anion Cryptates

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Raewyn M. Town

School of Chemistry, Queen''s University of Belfast, Belfast, BT9 5AG, Northern Ireland

Vickie McKee

Chemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK

Michael Arthurs

School of Natural and Environmental Sciences, Coventry University, Coventry, CV1 5FB, UK

Jane Nelson

Open University, Milton Keynes MK7 5AA UK

J. Chem. Educ., 2001, 78 (9), p 1269

DOI: 10.1021/ed078p1269

Publication Date (Web): September 1, 2001

Abstract

This experiment involves the synthesis of an iminocryptand ligand, the investigation of its fluxional NMR spectrum, and the generation of its aerobically stable dicopper(I) cryptate, whose NMR spectrum reflects the conformational change from divergent in the free cryptand to convergent in the cryptate. A μ-hydroxo dicopper(II) cryptate showing strong antiferromagnetic interaction can be made if the synthesis is carried out quickly enough to avert solvolytic ring-opening. Borohydride reduction of the ligand generates the aminocryptand host, which has the capacity to stabilize the +2 in preference to the +1 redox state of copper. The pseudohalide ion cyanate can be accommodated in cascade fashion between the Cu²⁺ ions in the aminocryptate. This markedly affects the infrared spectrum of the pseudohalide guest, but not the magnetic susceptibility of the Cu²⁺ paramagnets. Finally an anion cryptate is made. The cryptands and cryptates have been structurally characterized; their structures can be accessed online to assist understanding of their spectroscopic and magnetic properties. As an optional extension, an ion-selective electrode based on the aminocryptand can be made and tested for response to Cu²⁺ in the presence and absence of the competing cation Zn²⁺.