Solid-State NMR Study of Paramagnetic Bis(alaninato-κ(2)N,O)copper(II) and Bis(1-amino(cyclo)alkane-1-carboxylato-κ(2)N,O)copper(II) Complexes: Reflection of Stereoisomerism and Molecular Mobility in (13)C and (2)H Fast Magic Angle Spinning Spectra.
Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.
†Department of Chemistry, Faculty of Engineering, University of Pannonia, Egyetem utca 10, H-8201 Veszprém, Hungary.
Gábor
G
Szalontai
†Department of Chemistry, Faculty of Engineering, University of Pannonia, Egyetem utca 10, H-8201 Veszprém, Hungary.
Róbert
R
Csonka
†Department of Chemistry, Faculty of Engineering, University of Pannonia, Egyetem utca 10, H-8201 Veszprém, Hungary.
Gábor
G
Speier
†Department of Chemistry, Faculty of Engineering, University of Pannonia, Egyetem utca 10, H-8201 Veszprém, Hungary.
József
J
Kaizer
‡Institute for Medical Research and Occupational Health, Ksaverska cesta 2, P.O. Box 291, HR-10001 Zagreb, Croatia.
Jasmina
J
Sabolović
D000409:Alanine / Q000737:chemistry*; D000599:Amino Acids, Diamino / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003903:Deuterium / Q000737:chemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism
D000599:Amino Acids, Diamino; D002264:Carboxylic Acids; D056831:Coordination Complexes; D009942:Organometallic Compounds; C062116:methylaminoalanine-copper(II); D003300:Copper; D003903:Deuterium; D000409:Alanine