Ferrocene–Aspartate Dendrimers:
Conformational Analysis and
Electrochemical study
Anas Lataifeh, Heinz-Bernhard Kraatz*
Figure S1: A representative 13C NMR spectra of G2 (20 mM), FcG2 (20 mM) and
Fc[G2]2 (45 mM) in CDCl3. the spectra show the common set of signals for (i) the amide
and ester carbonyl (CO) at δ 173–156 range. (ii) The methyloxy CH3O at δ 53–50 range.
(iii) The alpha carbons in the range δ 49–48 and finally for the beta carbons span the
range of δ 37–35. The signal corresponding to the Boc (28 ppm) has disappeared from
the spectra of FcG2 and Fc[G2]2. The characteristic set of signals belongs to Fc group
has appeared at the chemical shift range δ 75–67 ppm.
S1
Figure S2: 1H NMR spectra of (a) FcG3, (b) FcG2 and (c) FcG1 (c = 5 mM, CDCl3). the plot
shows (i) a significant increase in the number and complexity of the peaks with the increase in
generation number. (ii) The Fc protons are not affected by the dendrimer environment upon
increasing generation number, the Fc protons overlaps with αCH protons at higher generation. *
Denotes the residual in CHCl3.
S2
Figure S3: 2D TOCSY of FcG1 (c = 5 mM, CDCl3). The βCH2 diastereotopic protons of
Asp exhibit a chemical shift difference (Δδ) of 0.23 ppm.
S3
Figure S4: 2D TOCSY of FcG2 (c = 5 mM, CDCl3). The core Asp has been identified
systematically by correlating the cross peaks of (i) the largest downfield chemical shift of
the αCH of the Asp proximal to Fc among the other alpha CH protons in the region δ
5.20–4.70, and (ii) the largest chemical shift difference (Δδ) of the diastereotopic βCH2.
In Fc-G2, The βCH2 diastereotopic protons of Asp proximal to Fc exhibit Δδ of 0.5,
while the Aspsurface exhibit Δδ = 0.20.
S4
Figure S5: 2D TOCSY of FcG3 (c = 5 mM, CDCl3). The βCH2 diastereotopic protons of
Aspsurface exhibit the smallest Δδ (0.08 ppm) among the other βCH2 protons (i.e. Aspcore
(Δδ = 0.2) and Aspbranch (Δδ = 0.1).
S5
Figure S6: A representative 2D HSQC spectra of (a) FcG2 (c = 20 mM, CDCl3) and (b)
Fc[G2]2 (45 mM, CDCl3). The meta-carbons are more deshielded δ 71, 70.9 than the
ortho- carbons δ 69.8, 69.5, in which there corresponding protons are shielded (CHm = δ
4.51, 4.42 and deshielded (CHo = δ 4.85, 4.82, respectively. This is due to the magnetic
anisotropy effect of the Fc proximal carbonyl (COFc) on the ortho protons (deshielding)
vs. the resonance effect (shielding) on the ortho carbons of the Cp ring. Such correlations
between the Cp carbons and there corresponding protons in mono- and disubstituted Fc
peptide conjugates were either poorly or mistakenly assigned, see References 5, 7 and 9–
24.
S6
(a)
Chemical Shift / ppm
8.60
Slope = -1.3 ppb/K
7.60
NH1
6.60
245
275
T /k
305
(b)
Chemical Shift / ppm
8.6
Slope = -4.2 ppb/K
7.6
NH1, NH1'
6.6
245
275
305 T / K
(C)
Chemical Shift / ppm
8.6
Slope = -1.0 ppb/K
NH2
7.6
Slope = -1.0 ppb/K
NH1
Slope = -1.6 ppb/K
6.6
245
NH3
275
305
T /K
(d)
Chemical Shift /ppm
8.6
Slope = -3.0 ppb/K NH2,
NH2'
Slope = -4.3 ppb/K NH3,
7.6
NH3'
Slope = -1.6ppb/K
6.6
245
275
305
NH1,
NH1'
T/K
Figure S8: VT-NMR of (a) FcG1, (b) Fc[G1]2, (c) FcG2, (d) Fc[G2]2.
S7
Figure S9: UV-visible spectra (a) and CD spectra (b) of FcG1 (––), FcG2 (---), FcG3
(….) in the range of 200–700 nm (c = 1 mM in CH3OH). The UV-vis spectra shows the
absorption of the Fc moiety (d-d transition) at ~ 444 nm (inset in Figure S8a) and a strong
absorption of the peptide fragment at ~ 350–200 nm range (marked with arrows for the
(ππ*) on the Cp rings at 350 and 315 nm, plateau at 270–230 nm for the amide
carbonyl (nπ*) proximal to Fc and strong absorption below 230 nm for the nπ* of
amide and ester carbonyl). The CD spectra show 3 minima (340 nm (Cp) and 260 nm
(Fc-CONH) and ~ 225 nm (CONH, COOCH3) in Asp) in which they correlate (i.e. position)
to the features resolved in the absorption spectra of the respective compounds.
S8