Carbohydrate and Trivalent Iron Ion Interactions in the Gas Phase and in Aqueous Solution - Metallic Systems: A Quantum Chemist's Perspective - page 97

(A) (B)

O6

O4

Fe l

O5

O3

O6 O2

C1

C7

O1

C7

O5

O1

C1

O4

O water 1

Fe ll

Fe l

O2

O3

O water 2

(C) (D)

FIGURE 3.5 Methyl-α-d-mannopyranoside. molecule. in. water. (A). obtained. from. CPMD.
simulations,.(B).obtained.from.CMD.simulations,.and.its.complexes.with.one.and.two.Fe 3+ .
ions,.and.(C,.D).obtained.from.CPMD.simulations,.with.conventional.numbering.of.speciic.
atoms.

To.study.the.coordination.of.more.than.one.Fe 3+ .ion.to.M,.we.performed.chemical.
reactivity.index.calculations.in.the.vicinity.of.Fe 3+ .and.water.molecules.and.simu-
lated.M.in.water.with.two.Fe 3+ .ions.(Figure.3.5)..The.chemical.reactivity.calcula-
tions.on.a.trajectory.of.M-Fe 3+ .with.the.irst.shell.of.water.molecules.obtained.from.
CPMD.simulations.show.that.the.heavy.atoms.of.the.carbohydrate.are.not.reactive.
toward.a.second.Fe 3+ .ion.(Table.3.2)..This.inding.is.consistent.with.the.experimental.
results..CPMD.simulations.show.that.the.irst.Fe 3+ .ion.is.still.coordinated.to.O3.and.
O4.atoms.in.the.presence.of.the.second.Fe 3+ .ion..However,.the.distances.between.the.
Fe 3+ .ion.and.O3.and.O4.atoms.are.slightly.larger.in.the.presence.of.the.second.Fe 3+ .
ion,.with.values.of.3.4.±.0.1.and.4.3.±.0.2.Å,.respectively.(Figure.3.5.and.Table.3.4)..
Furthermore,.the.simulations.with.a.single.Fe 3+ .ion.show.the.metal.ion.to.be.almost.