Synthesis, Spectral, and In Vitro Antibacterial Studies of Organosilicon(IV) Complexes with Schiff Bases Derived from Amino Acids

Table 3

¹H NMR spectral data^a of the ligands and their corresponding Me₃Si(IV) complexes.

Compounds	Chemical Shift (𝛿, ppm)
L^𝟏H	11.28 (s, 1H, COOH), 4.30 (s, 2H, N–CH2–), 8.02 (s, 1H, NH), H-aromatic: 7.58 (d, 𝐽=7.8, 1H), 7.28–7.48 (m, 2H,), and 7.80 (d, 𝐽=7.7, 1H).
Me3SiL^𝟏	4.32 (s, 2H, N–CH2–), 8.03 (s, 1H, NH), H-aromatic: 7.72 (d, 𝐽=7.6, 1H), 7.22–7.52 (m, 2H,), 7.98 (d, 𝐽=7.3, 1H), and 1.32 (s, 9H, Si–CH3)
L^𝟐H	11.25 (s, 1H, COOH), 4.72 (q, 1H, CH), 8.34 (s, 1H, sec. amide), 1.31 (d, 𝐽=6.8, 3H, CH3), H-aromatic: 7.61 (d, 𝐽=7.6, 1H), 7.21–7.41 (m, 2H,), and 7.82 (d, 𝐽=7.4, 1H).
Me3SiL^𝟐	4.70 (q, 1H, CH), 8.36 (s, 1H, sec. amide), 1.28 (d, 3H, CH3), H-aromatic: 7.66 (d, 𝐽=7.7, 1H), 7.20–7.46 (m, 2H,), 7.98 (d, 𝐽=7.6, 1H), and 1.25 (s, 9H, Si–CH3)
L^𝟑H	11.74 (s, 1H, COOH), 4.72 (d, 𝐽=6.8, 1H, CH), 8.05 (s, 1H, sec. amide), 2.30 (m, 2H, CH2), 2.04 (d, 𝐽=6.4, 3H, CH3), H-aromatic: 7.58 (d, 𝐽=8.1, 1H), 7.18–7.38 (m, 2H,), and 7.72 (d, 𝐽=7.6, 1H).
Me3SiL^𝟑	4.50 (d, 1H, CH), 8.01 (s, 1H, sec. amide), 2.22 (m, 2H, CH2), 2.06 (d, 3H, CH3), H-aromatic: 7.64 (d, 𝐽=7.9, 1H), 7.16–7.46 (m, 2H,), 7.88 (d, 𝐽=7.5, 1H), and 1.26 (s, 9H, Si–CH3)
L^𝟒H	11.50 (s, 1H, COOH), 4.25 (t, 1H, N–CH–CH2–), 3.08 (d, 𝐽=6.8, 2H, –CH2–Ph), 8.01 (s, 1H, NH), ), H-aromatic: 7.62 (d, 𝐽=8.1, 1H), 7.20–7.45 (m, 2H,), and 7.80 (d, 𝐽=7.8, 1H).
Me3SiL^𝟒	4.26 (t, 1H, N–CH–CH2–), 3.12 (d, 𝐽=6.9, 2H, –CH2–Ph), 8.08 (s, 1H, NH), H-aromatic: 7.70 (d, 𝐽=7.9, 1H), 7.20–7.45 (m, 2H,), 7.98 (d, 𝐽=7.8, 1H), and 1.30 (s, 9H, Si–CH3)
L^𝟓H	11.46 (s, 1H, COOH), 4.39 (d, 𝐽=8.3, 1H, CH), 8.12 (s, 1H, sec. amide), 10.15 (s, 1H, indole), 3.02 (m, 2H, CH2), H-aromatic: 7.65 (d, 𝐽=7.8, 1H), 7.15–7.30 (m, 2H,), and 7.84 (d, 𝐽=7.6, 1H).
Me3SiL^𝟓	3.16 (d, 1H, CH), 8.07 (s, 1H, sec. amide), 10.18 (s, 1H, indole), 2.98 (m, 2H, CH2), H-aromatic: 7.64 (d, 𝐽=7.7, 1H), 7.18–7.42 (m, 2H,), 8.01 (d, 𝐽=7.6, 1H), and 1.25 (s, 9H, Si–CH3)
L^𝟔H	12.55 (s, 1H, COOH), 4.61 (d, 𝐽=7.2, 1H, CH), 8.10 (s, 1H, sec. amide), 12.92 (s, 1H, imidazole), 3.15 (m, 2H, CH2), H-aromatic: 7.60 (d, 𝐽=7.9, 1H), 7.08–7.38 (m, 2H,), and 7.80 (d, 𝐽=7.7, 1H).
Me3SiL^𝟔	3.98 (d, 1H, CH), 8.03 (s, 1H, sec. amide), 12.79 (s, 1H, imidazole), 3.10 (m, 2H, CH2), 7.62 (d, 𝐽=7.8, 1H), 7.10–7.44 (m, 2H), 7.94 (d, 𝐽=7.7, 1H), and 1.28 (s, 9H, Si–CH3)
L^𝟕H	11.72 (s, 1H, COOH), 4.80 (d, 𝐽=6.9, 1H, CH), 8.15 (s, 1H, sec. amide), 2.30 (m, 2H, CH2), 2.10 (d, 𝐽=6.5, 3H, CH3), H-aromatic: 7.56 (d, 𝐽=7.7, 1H), 6.95–7.36 (m, 2H,), and 7.76 (d, 𝐽=7.8, 1H).
Me3SiL^𝟕	4.86 (d, 𝐽=6.9, 1H, CH), 3.10 (m, 1H, CH), 8.10 (s, 1H, sec. amide), 2.25 (m, 2H, CH2), 2.02 (d, 𝐽=6.3, 3H, CH3), H-aromatic: 7.66 (d, 𝐽=7.7, 1H), 7.12–7.48 (m, 2H,), 7.95 (d, 𝐽=7.9, 1H), and 1.20 (s, 9H, Si–CH3)
L^𝟖H	12.28 (s, 1H, COOH), 4.45 (t, 1H, –CH–), 3.28 (d, 𝐽=6.5, 2H, CH2), H-aromatic: 7.60 (d, 𝐽=7.8, 1H), 7.12–7.38 (m, 2H,), and 7.82 (d, 𝐽=7.7, 1H).
Me3SiL^𝟖	4.40 (t, 1H, –CH–), 3.25 (d, 𝐽=6.6, H, CH2), H-aromatic: 7.65 (d, 𝐽=7.8, 1H), 7.14–7.50 (m, 2H,), 7.92 (d, 𝐽=7.8, 1H), and 1.27 (s, 9H, Si–CH3)

aChemical shift (𝛿) in ppm: multiplicity is given as s: singlet, d: doublet, t: triplet, q: quartet, and m: complex pattern.