N. Chera¨ıti et al. / Journal of Organometallic Chemistry 575 (1999) 149–152
151
Scheme 2.
1
ESI-MS spectra (negative mode) and H-NMR further
confirmed the integrity of the two forms of the com-
plexes. In the case of compounds (10a) and (10b) the
ESI-MS spectra showed peaks at 577 (M–H)− and 590
(M–H)−, respectively, corresponding to salicylate
forms. In contrast, for the catecholate forms (9a) and
(9b), peaks at 575 (M–3K)− and 588 (M–3K)−, re-
spectively, were obtained.
1H-NMR spectra are only recorded for the non-para-
magnetic complexes (9b) and (10b).
Selected data for (2): lH (CDCl3) 0.90 (s, 3H), 3.90 (s,
6H), 7.56 (t, 6H), 7.68 (t, 3H), 7.81 (d, 6H); lC (CDCl3)
15.94 (s, CH3), 39.34 (s, C-quat), 69.69 (s, (CH2)2),
127.72 (s, C-aroma); 129.37 (s, C-aroma); 134.15 (s,
C-aroma); 134.72 (s, C-aroma); IC-MS (NH4+) m/z 558
((M+18)+, 100).
For (3): lH (CDCl3) 0.99 (s, 3H), 2.90 (d, 1/3 (2
CH3)), 3.82 (s, 6H),7.74 (m, 6H), 7.86 (m, 3H); lC
(CDCl3) 19.23 (s, CH3), 29 (s, C-quat), 44.81 (s,
(CH2)2), 123.40 (s, C-aroma), 131.85 (s, C-aroma),
134.12 (s, C-aroma), 168.91 (s, CꢀO); IC-MS (NH4+)
m/z 508 ((M+ +1)+, 100); 525 ((M+18)+, 35).
For (4): lH (D2O) 1.09 (s, 3H), 3.04 (s, 6H); lC (D2O)
(CDCl3 as reference) 17.20 (s, CH3); 35.61 (s, -C-quat);
43.00 (s, -CH2); ESI-MS (positive): m/z 118 (M+1)+.
For (7): lH (CDCl3) 0.98 (s, 3H, CH3), 3.02 (d, 6H,
2×-(CH2)-), 3.82 (s, 9H, 3×OCH3), 3.97 (s, 9H, 3×
OCH3), 7.21 (m, 6H), 7.55 (dd, 3H), 8.68 (t, 3H,
3×NH); lC (CDCl3) 18.71 (s, CH3), 42.06 (s, C-quat),
43.05 (s, -(CH2)-), 55.90 (s, OCH3), 61.41 (s, OCH3),
115.07 (s, 1C), 122.28 (s, 1C-aroma), 123.90 (s, 1C-
aroma), 127.08 (s, 1C-aroma), 147.5 (s, 1C-aroma),
152.57 (s, 1C-aroma), 166.41 (s, 1C-aroma), IC-MS
(NH4+) m/z 610 ((M+1)+, 74).
For (8): lH (DMSO-d6) 0.87 (s, 3H, CH3), 3.27 (d,
6H, CH2), 6.72–6.77 (t, 3H, H-aroma), 6.92–6.95 (d,
3H, H-aroma), 7.28–7.31 (d, 3H, H-aroma), 8.86 (t,
3H, 3×NH), 9.29 (s, 3H, 3×OH), 12.03 (s, 3H,
3×OH); lC (DMSO-d6) 19.09 (s, CH3), 42.07 (s, CH2),
42.98 (s, C-quat), 115.78 (s, C-aroma), 117.30 (s, C-
aroma), 146.27 (s, C-aroma), 148.77 (s, C-aroma),
169.75 (s, CꢀO); ESI-MS (positive): m/z 526 ((M+1)+,
32), 548 ((M+23)+, 100).
The synthesis of tris-catecholate ligands, based on the
reduction of conformational space, furnishes a new
type of siderophore models. With its low molecular-
weight, this type of molecule could provide a useful
biological probe; to elucidate and to reproduce specific
functions involved in microbial growth promotion and
hence in cell metabolism. Quantitative determination of
the formation constant and biological studies for ferric
ligand are in progress.
2. Materials and methods
All reagents were of the finest quality available com-
mercially. All solvents were distilled prior to use.
Ethylether was distilled and stored over sodium. DMF
was distilled and freshly used. The triethylamine was
stored over potassium hydroxide, dichloromethane was
distilled on CaCl2 and freshly used.
1H-NMR spectra were run on Bruker AM 250 and
AC 200 instruments at 250 and 200 MHz, 13C-NMR
were run on Bruker AC 200 instruments at 50 MHz.
Chemical shifts are reported in parts per million (l)
downfield from internal Me4Si. The abbreviations used
are: s, singlet; d, doublet; t, triplet; q, quadriplet; m,
multiplet. All compounds showed consistent NMR and
mass spectral data.CI-MS spectra were determined on
Nermag spectrometer using direct insertion probe, a
source pressure 10−1 torr and ammonia as the reactant
gas. Therefore (M+ +1) and (M+ +18) values are
reported. ESI-MS were recorded on a Finnigan spec-
trometer MAT 95.
For (9a): K3(FeL) ESI-MS (negative): m/z 575 (M–
3K)−.
For (9b): K3(GaL) lH (DMSO-d6) 0.92 (s, 3H, CH3),
3.15 (d, 6H, CH2), 6.35–6.42 (t, 3H, H-aroma), 6.59–
6.61 (d, 3H, H-aroma), 6.75–6.78 (d, 3H, H-aroma),
10.17 (t, 3H, 3×NH); ESI-MS (negative) m/z 588
(M–3K)−.