Carbohydrate and Trivalent Iron Ion Interactions in the Gas Phase and in Aqueous Solution - Metallic Systems: A Quantum Chemist's Perspective - page 92

the.calculated.FF.indices.and.the.NPA.values.(see.Tables.3.1.and.3.2)..The.distances.
between.the.Fe 3+ .ion.and.the.O2,.O3,.and.O4.atoms.vary.between.2.7.and.3.8.Å,.and.
the.average.O2-Fe 3+ -O4.angle.is.such.that.the.transition.metal.ion.is.symmetrically.
located.between.the.O2.and.O4.atoms.(see.Table.3.3)..In.contrast,.CMD.simulations.
yield.different.results.regarding.the.coordination.chemistry.of.the.Fe 3+ .ion.and.M.in.
the.gas.phase..Based.on.the.CMD.simulations,.the.Fe 3+ .ion.is.more.mobile.and.less.
coordinated;.its.distance.to.all.hydroxyl.group.oxygen.atoms.of.M.varies.between.
5. and. 11. Å.. This. might. be. due. to. the. neglect. of. the. partial. charge. differences. of.

TABLE 3.2
Calculated Average Natural Partial Charges (NPA) for the
Fe Ion and Carbohydrate in the Gas Phase and in Water at
the BLYP/6-311+G(2d,p) Level of Theory

M M-Fe 3+

Atom Gas Phase In Water Gas Phase In Water

O1 −0.59.±.0.06 −0.58.±.0.04 −0.72.±.0.03 −0.57.±.0.03

O2 −0.73.±.0.04 −0.79.±.0.02 −0.62.±.0.05 −0.78.±.0.02

O3 −0.75.±.0.04 −0.77.±.0.02 −0.63.±.0.04 −0.73.±.0.01

O4 −0.76.±.0.05 −0.75.±.0.04 −0.61.±.0.06 −0.79.±.0.02

O5 −0.59.±.0.04 −0.56.±.0.02 −0.52.±.0.03 −0.62.±.0.05

O6 −0.75.±.0.03 −0.79.±.0.03 −0.54.±.0.07 −0.79.±.0.02

Fe I III 1.77.±.0.08 0.72.±.0.03

TABLE 3.3
Speciic Bond Lengths and Bond Angles of M and Its Complexes with Fe in
the Gas Phase Calculated via CPMD and CMD Simulations

M M-Fe 3+ M-Fe 2 3+

CPMD MD CPMD MD CPMD MD

O3-H2/Å 2.0.±.0.3 2.3.±.0.5 2.3.±.0.2 2.5.±.0.4 2.7.±.0.2 2.9.±.0.4

O4-H3/Å 2.4.±.0.4 2.7.±.0.5 2.5.±.0.2 2.7.±.0.3 2.4.±.0.3 2.9.±.0.2

O6-H4/Å 2.1.±.0.3 2.9.±.0.4 2.5.±.0.2 2.7.±.0.2 2.4.±.0.3 3.2.±.0.4

θ(O2H2O3)/(deg) 146.±.19 107.±.23 109.±.17 116.±.38 106.±.18 108.±.39

θ(O3H3O4)/(deg) 112.±.28 101.±.21 103.±.13 101.±.25 106.±.10 98.±.19

θ(O4H4O6)/(deg) 120.±.27 115.±.38 100.±.22 129.±.28 105.±.14 117.±.31

Fe I -O2/Å 3.3.±.0.2 8.4.±.3.2 3.3.±.0.2 8.7.±.2.9

Fe I -O3/Å 3.0.±.0.3 7.9.±.2.2 3.9.±.0.2 8.8.±.3.1

Fe I -O4/Å 3.5.±.0.3 7.7.±.3.5 4.1.±.0.5 8.2.±.3.6

69.±.4 68.±.3

θ(O2FeO4)/(deg)

Fe II -O1/Å 5.1.±.1.9 7.3.±.3.2

Fe II -O2/Å 4.9.±.1.4 9.8.±.2.1