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Title
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Interactions of an asymmetric amine with a symmetric Cusalen complex : an EPR/ENDOR and HYSCORE investigation
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Author
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Abstract
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| Single enantiomers of R-/S-methylbenzylamine (MBA) were found to selectively form adducts with the chiral non-C2 symmetric Cusalen complex N-(3,5-di-tert-butylsalicylidene)-N′-(salicylidene)-cyclohexane-1,2-diamine copper(II), hereafter labelled [Cu(3)]. The g/A spin Hamiltonian parameters of this Cu(II) complex showed a decrease in symmetry from axial to rhombic upon formation of the [Cu(3)] + MBA adducts. The selectivity in enantiomeric discrimination was found to be only 59 ± 5% in favour of the heterochiral R,R′-[Cu(3)] + S-MBA and S,S′-[Cu(3)] + R-MBA adducts. This was directly evidenced by W-band EPR spectroscopy. The observed low selectivity for enantiomer discrimination is primarily attributed to the loss of the bulky tert-butyl groups from the 3,5 positions of [Cu(3)] compared to the parent N,N′-bis(3,5-di-tert-butylsalicylidene)-cyclohexane-1,2-diamine copper(II) ligand (labelled [Cu(1)]). The structure of the [Cu(3)] complex in the presence and absence of coordinating amine was further investigated by analysis of the ligand hyperfine interactions, as revealed through Q-band CW-ENDOR, X-band Davies ENDOR and HYSCORE. 1H couplings from the NH2 group of the amine, observed by ENDOR and HYSCORE, provided direct evidence of amine coordination. |
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Language
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English
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Source (journal)
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Physical chemistry, chemical physics / Royal Society of Chemistry [London] - Cambridge, 1999, currens
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Publication
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Cambridge
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The Royal Society of Chemistry
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2011
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ISSN
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1463-9076
[print]
1463-9084
[online]
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DOI
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10.1039/C1CP22522G
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Volume/pages
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13
:45
(2011)
, p. 20427-20434
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ISI
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000296871500049
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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