TY - JOUR
T1 - Chiral metal complexes. 5. Sources of chiral discrimination in aqueous solutions of the complexes Δ,Λ-[Ru(diimine)2(L-aspartate)]° and their conjugate acids
AU - Goodwin, Terence J.
AU - A. Williams, Peter
AU - Vagg, Robert S.
PY - 1982
Y1 - 1982
N2 - The complex ternary species Δ,Λ-[Ru(phen)2(L-asp)]°, Δ,Λ-[Ru(phen)2(L-aspH)]+ and their bipy analogues (L-aspH2 = L-aspartic acid, phen = 1,10-phenanthroline, bipy = 2,2′-bipyridyl) have been synthesised and characterized, and the various diastereoisomers separated using cation exchange chromatography. Equilibrium constants in H2O solution for the reaction Δ-[Ru(diimine)2(L-aa)]n+
qa ⇌Λ-[Ru(diimine)2(L-aa)]n+
(aq), L-aa being either [L- asp]2- or ([L-aspH]-, are 1.00(1), 1.39(1), 0.88(1) and 1.22(1), respectively at 298.2 K. In D2O, the corresponding values are 1.52(10), 1.50(4), 1.09(3) and 1.21(9). High resolution 1H nmr studies indicate that a strong intramolecular hydrogen bond between the uncoordinated carboxyl group and an amine hydrogen atom of the amino acid exists when the species are deprotonated, and that this effects the relative thermodynamic stabilities of the diastereoisomers. Equilibration differences in H2O and D2O suggest the possibility of hydrophobic bonding being a source of chiral discriminations in complexes of this type. Such discriminations, although small in magnitude, arising from the above interactions and steric effects are discussed.
AB - The complex ternary species Δ,Λ-[Ru(phen)2(L-asp)]°, Δ,Λ-[Ru(phen)2(L-aspH)]+ and their bipy analogues (L-aspH2 = L-aspartic acid, phen = 1,10-phenanthroline, bipy = 2,2′-bipyridyl) have been synthesised and characterized, and the various diastereoisomers separated using cation exchange chromatography. Equilibrium constants in H2O solution for the reaction Δ-[Ru(diimine)2(L-aa)]n+
qa ⇌Λ-[Ru(diimine)2(L-aa)]n+
(aq), L-aa being either [L- asp]2- or ([L-aspH]-, are 1.00(1), 1.39(1), 0.88(1) and 1.22(1), respectively at 298.2 K. In D2O, the corresponding values are 1.52(10), 1.50(4), 1.09(3) and 1.21(9). High resolution 1H nmr studies indicate that a strong intramolecular hydrogen bond between the uncoordinated carboxyl group and an amine hydrogen atom of the amino acid exists when the species are deprotonated, and that this effects the relative thermodynamic stabilities of the diastereoisomers. Equilibration differences in H2O and D2O suggest the possibility of hydrophobic bonding being a source of chiral discriminations in complexes of this type. Such discriminations, although small in magnitude, arising from the above interactions and steric effects are discussed.
UR - http://www.scopus.com/inward/record.url?scp=0001187731&partnerID=8YFLogxK
U2 - 10.1016/S0020-1693(00)81904-0
DO - 10.1016/S0020-1693(00)81904-0
M3 - Article
AN - SCOPUS:0001187731
SN - 0020-1693
VL - 63
SP - 133
EP - 140
JO - Inorganica Chimica Acta
JF - Inorganica Chimica Acta
IS - C
ER -