S. Sampath, S. Chandrasekaran et al.
FULL PAPER
4 Hz, 2 H), 6.97–6.95 (m, 2 H), 5.27 (s, 2 H), 5.26 (s, 2 H), 5.17 (s,
2 H), 5.11 (s, 2 H), 4.56 (dd, J1 = 13.6, J2 = 6 Hz, 1 H), 4.28–4.16
(m, 18 H), 3.02–2.96 (m, 2 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 171.1, 155.3, 142.9, 141.8, 135.3, 129.1, 128.4, 126.9, 123.2,
122.9, 80.7, 80.4, 69.1, 69.0, 68.9, 68.8 (2 C), 58.4, 58.3, 54.7, 50.0,
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49.9, 37.8 ppm. IR (neat): ν = 3420, 2926, 2248, 1722, 1515, 1049,
˜
732 cm–1. HRMS: m/z: calcd. for C38H37Fe2N7O4[M + Na+]:
790.1504; found 790.1565. [α]2D3 = 4 (c = 1.0, CHCl3).
[3]
General Procedure for the Synthesis of Trivalent Ferrocene Conju-
gates 12a, 13a: To a well-stirred solution of amino acid derived tris-
alkyne 12 (1 mmol) and ferrocenylmethyl azide
2 (0.795 g,
3.3 mmol) in tBuOH/H2O (1:1) (14 mL) CuSO4·5H2O (0.063 g,
0.25 mmol) was added followed by sodium ascorbate (0.099 g,
0.5 mmol). The reaction mixture was stirred for 24 h. Ethyl acetate
(50 mL) was added into the reaction mixture and was washed with
brine (25 mL) and filtered through anhydrous sodium sulfate. After
evaporation of ethyl acetate, the crude product was purified by
flash chromatography on silica gel.
[4]
[5]
Compound 12a: Yellow gum, yield 85% (1.001 g). 1H NMR
(400 MHz, CDCl3): δ = 7.59 (s, 1 H), 7.47 (s, 1 H), 7.39 (s, 1 H),
6.96 (d, J = 8.8 Hz, 2 H), 6.92 (d, J = 8.4 Hz, 2 H), 5.32 (s, 2 H),
5.29 (s, 2 H), 5.26 (s, 4 H), 5.17–5.11 (m, 4 H), 4.55 (dd, J1 = 13.5,
J2 = 5.7 Hz, 1 H), 4.28–4.16 (m, 27 H), 3.02–2.98 (m, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 170.9, 155.3, 153.4, 149.9, 142.8,
141.7, 141.4, 133.4, 130.3, 123.4 (2 C), 122.9, 120.9, 80.7, 80.5, 80.4,
69.1 (2 C), 69.0, 68.9 (2 C), 68.8 (2 C), 61.5, 58.5, 58.3, 54.6, 50.1,
[6]
[7]
50.0, 49.9, 37.2 ppm. IR (neat): ν = 3343, 2935, 1734, 1515, 1246,
˜
1048, 824, 731 cm–1. HRMS: m/z: calcd. for C53H51Fe3N10O7[M +
Na+]: 1129.1810; found 1129.1868. [α]2D3 = –2.0 (c = 2, CHCl3).
[8]
Electrochemical Measurements: Cyclic voltammetric experiments
were carried out using EG&G 273A (PAR USA) electrochemical
system. De-aerated CH3CN containing 0.2 Bu4NPF6 was used
as the electrolyte. The concentration of analytes was kept at 1 m.
The working electrode was gold disc, the counter electrode was a
large area Pt foil, and the reference electrode was Ag/AgCl/0.1
Bu4NPF6 in acetonitrile. The working electrode was carefully pol-
ished with basic Al2O3/water slurry, washed with methanol and
sonicated in H2O/MeOH-CH3CN (1:1):1 mixture for 15 min. The
working electrode was subsequently dipped into hot “piranha”
solution for a few seconds, washed well with doubly distilled water,
followed by electrochemical cycling in 0.5 H2SO4 between 0.2 V
and 1.5 V vs. SCE until reproducible voltammogramms were ob-
tained. The analytes were subsequently introduced and the voltam-
mogramms were recorded at 20 mV/s scan rate. The reference elec-
trode is calibrated against ferrocene/ferrocenium redox couple (Fc/
Fc+) in the same supporting electrolyte. The formal potential of
ferrocene/ferrocenium redox couple is 0.412 V (vs. Ag/AgCl/0.1
Bu4NPF6) in the solvent used for present studies (acetonitrile). Ac-
cordingly all the potential values in the voltammograms are given
with respect to ferrocene/ferrocenium couple.
[9]
[10]
[11]
Supporting Information (see also the footnote on the first page of
this article): Spectroscopic and analytical data of all the new com-
pounds.
Acknowledgments
[12]
[13]
a) A. Hess, O. Brosch, T. Weyhermuller, N. Metzler-Nolte, J.
Organomet. Chem. 1999, 589, 75–84; b) A. D. Ryabov, V. N.
Goral, L. Gorton, E. Csoregi, Chem. Eur. J. 1999, 5, 961–967.
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390, 142; b) Y. Katayama, S. Sakakihara, M. Maeda, Anal. Sci.
V. S. S. thanks the Council of Scientific and Industrial Research,
New Delhi for a senior research fellowship and S. C. N. thanks the
Department of Science and Technology, New Delhi for the JC Bose
National Fellowship.
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