title: Inherently chiral uranyl-salophen macrocycles: computer-aided design and resolution.
abstract: [structure: see text] A flipping motion rapidly inverts the bent structure of uranyl-salophen compounds and, consequently, causes fast enantiomerization of nonsymmetrically substituted derivatives. This process has been previously slowed by introducing bulky substituents in the imine bond region. Since the resulting complexes dissociate upon chromatographic treatment, an alternative approach to the design and synthesis of robust, nonflipping uranyl-salophen compounds is here described. Such an approach is based on the idea that the flipping motion would be blocked by connecting the para positions with respect to the phenoxide oxygens by means of polymethylene bridges of suitable length. Analysis of a number of uranyl-salophen compounds by molecular mechanics, while showing that bulky substituents in the imine bond region cause severe distortions of the ligand backbone, suggested that the best chain lengths are those that fit the gap between the phenoxide rings without altering the natural geometry of the parent uranyl-salophen compound. Calculations showed that such chains are those composed of 12 and 13 methylene units. Accordingly, chiral uranyl-salophen macrocycles bridged with 12- and 13-methylene chains were synthesized in fairly good yields and resolved by chiral HPLC.
authors.affiliation: Dipartimento di Chimica and IMC-CNR Sezione Meccanismi di Reazione, Università La Sapienza, Box 34 Roma 62, 00185 Roma, Italy. antonella.dallacort@uniroma1.it
authors.forename: Antonella
authors.initials: A
authors.lastname: Dalla Cort
authors.forename: Luigi
authors.initials: L
authors.lastname: Mandolini
authors.forename: Chiara
authors.initials: C
authors.lastname: Pasquini
authors.forename: Luca
authors.initials: L
authors.lastname: Schiaffino
mesh_terms: D017076:Computer-Aided Design; D018360:Crystallography, X-Ray; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012459:Salicylates / Q000737:chemistry*; D013237:Stereoisomerism; D013997:Time Factors
chemical_list: D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D012459:Salicylates; C090416:salophen; C005460:uranyl acetate