Spectral data
C28H34N10O6Mg: colour, light brown; mp 280d; IR; 1620 b (C=O), 1734 m (C=O, ketone group), 2990 m (NH); 3400 m (OH stretch); 1H NMR; 1.27 (CH3, ethyl group), δ: 2.54 (CH2, ethyl group), 2.79 and 3.30 (2 CH2 of piperazinyl group), 3.88 (H, ring position 5), 8.87 (H, ring position 2), 9.51 (H, carboxylic group); C; H; N found: C 53.34; H 5.40; N 22.26; M 3.85.
C28H34N10O6Ca: colour, off white; mp 278d; IR; 1619 s (C=O), 1735 s (C=O, ketone group), 2995 m (NH), 3420 m (OH stretch); 1H NMR; δ: 1.34 (CH3, ethyl group), 2.47 (CH2, ethyl group), 2.84 and 3.32 (2 CH2 of piperazinyl group), 3.93 (H, ring position 5), 8.84 (H, ring position 2), 9.45 (H, carboxylic group); C; H; N found: C 52.05; H 5.26; N 21.73; M 6.21.
C28H34N10O6Cr: colour, greenish brown; mp 282d; IR; 1610 s (C=O), 1729 s (C=O, ketone group), 2985 m (NH), 3430 m (OH stretch); 1H NMR; δ: 1.29 (CH3, ethyl group), 2.58 (CH2, ethyl group), 2.87 and 3.27 (2 CH2 of piperazinyl group), 3.90 (H, ring position 5), 8.82 (H, ring position 2), 9.48 (H, carboxylic group); C; H; N found: C 51.11; H 5.23; N 21.35; M 7.88.
C28H34N10O6Mn: colour, light yellow; mp 274d; IR; 1612 b (C=O), 1732 sm (C=O, ketone group), 2983 m (NH), 3420 m (OH stretch); 1H NMR; δ: 1.31 (CH3, ethyl group), 2.56 (CH2, ethyl group), 2.81 and 3.28 (2 CH2 of piperazinyl group), 3.84 (H, ring position 5), 8.91 (H, ring position 2), 9.50 (H, carboxylic group); C; H; N found: C 50.79; H 5.22; N 21.21; M 8.31.
C28H34N10O6Fe: colour, orange; mp 220d; IR; 1605-1630 b (C=O), 1730 sm (C=O, ketone group), 2995 m (NH), 3440 m (OH stretch); 1H NMR; δ: 1.28 (CH3, ethyl group), 2.53 (CH2, ethyl group), 2.81 and 3.28 (2 CH2 of piperazinyl group), 3.84 (H, ring position 5), 8.91 (H, ring position 2), 9.50 (H, carboxylic group); C; H; N found: C 50.80; H 5.23; N 21.20; M 8.43.
C28H34N10O6Co: colour, light blue; mp 272d; IR; 1620 b (C=O), 1732 m (C=O, ketone group), 2983 m (NH), 3410 m (OH stretch); 1H NMR; δ: 1.33 (CH3, ethyl group), 2.48 (CH2, ethyl group), 2.82 and 3.31 (2 CH2 of piperazinyl group), 3.88 (H, ring position 5), 8.94 (H, ring position 2), 9.46 (H, carboxylic group); C; H; N found: C 50.50; H 5.20; N 21.06; M 8.88.
C28H34N10O6Ni: colour, greenish white; mp 288d; IR; 1613 s (C=O), 1725 m (C=O, ketone group), 2985 m (NH), 3390 m (OH stretch); 1H NMR; δ: 1.29 (CH3, ethyl group), 2.53 (CH2, ethyl group), 2.87 and 3.32 (2 CH2 of piperazinyl group), 3.89 (H, ring position 5), 8.90 (H, ring position 2), 9.49 (H, carboxylic group); C; H; N found: C 50.65; H 5.19; N 21.01; M 8.83.
C28H34N10O6Cu: colour, brown; mp 230; IR; 1605 m (C=O), 1724 m (C=O, ketone group), 2990 m (NH), 3380 m (OH stretch); 1H NMR; δ: 1.34 (CH3, ethyl group), 2.49 (CH2, ethyl group), 2.87 and 3.30 (2 CH2 of piperazinyl group), 4.0 (H, ring position 5), 8.96 (H, ring position 2), 9.56 (H, carboxylic group); C; H; N found: C 50.11; H 5.15; N 20.83; M 9.50.
C28H34N10O6Zn: colour, off white; mp 278d; IR; 1618 m (C=O), 1730 m (C=O, ketone group), 2985 m (NH), 3420 m (OH stretch); 1H NMR; δ: 1.36 (CH3, ethyl group), 2.57 (CH2, ethyl group), 2.85 and 3.26 (2 CH2 of piperazinyl group), 3.82 (H, ring position 5), 8.85 (H, ring position 2), 9.53 (H, carboxylic group); C; H; N found: C 50.10; H 5.12; N 20.90; M 9.72.
C28H34N10O6Cd: colour, white; mp 266; IR; 1600 b (C=O), 1720 m (C=O, ketone group), 2980 m (NH), 3440 b (OH stretch); 1H NMR; δ: 1.31 (CH3, ethyl group), 2.55 (CH2, ethyl group), 2.80 and 3.29 (2 CH2 of piperazinyl group), 3.92 (H, ring position 5), 8.89 (H, ring position 2), 9.59 (H, carboxylic group); C; H; N found: C 46.71; H 4.74; N 19.53; M 15.62.
Antibacterial studies
Antibacterial studies of pipemidic acid metal complexes against Gram-positive and Gram-negative organisms, such as Klebsiella Pneumoniae, Proteus mirabilis, Staphylococcus aureus, Corynebacterium hoffmanni, Klebsiella species, Shigella dysentery, Streptococcus faecalis, Corynebacterium diphtheria, Escherichia coli, Pseudomonas aeruginosa, Bacillus species, Citrobacter species, Salmonella typhi, and Streptococcus pyogenes were carried out by disk susceptibility technique. The diffusion technique, according to FDA, was followed used widely in clinical laboratories [15,16,17].