P.P. Utthra et al. / Journal of Photochemistry & Photobiology, B: Biology 158 (2016) 136–144
137
Zn(II) metal ions. The results showed promise in designing and
developing newer and effective antimicrobial agents as well as novel
DNA probes.
[Co(L1)2] (2) Yield: 75%, Anal. calc. for C18H14CoN8O2: C, 49.9; H, 3.2;
N, 25.8; Cu, 13.6%; Found C, 49.7; H, 3.1; N, 25.6; Co, 13.4%. IR data (KBr,
cm−1); 1603 ν(C_N), 3172 (\\NH triazole ring), 427 ν(M\\N), 554
ν(M\\O). MS m/z (%): 433 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) = 15.3.
λ
max (cm−1) in DMF, 10,800, 10,941, 27,648. μeff (BM): 4.85.
2. Experimental Protocol
[Ni(L1)2] (3) Yield: 76%, Anal. calc. for C18H14N8NiO2: C, 49.9; H,
3.2; N, 25.8; Ni, 13.5%; Found C, 49.8; H, 3.0; N, 25.4; Ni, 13.3%. IR
data (KBr, cm−1); 1605 ν(C_N), 3172 (\\NH triazole ring), 431
ν(M\\N), 561 ν(M\\O). MS m/z (%): 432 [M+]. ΛM 10−3
(Ω−1 cm2 mol−1) = 15.6. λmax (cm−1) in DMF, 10,940, 10,100,
27,413. μeff (BM): 3.15.
The materials and methods, DNA binding, cleavage and antimicrobi-
al procedures are given in the Supplementary file (S1).
2.1. Synthesis of Schiff Bases (L1–L3)
[Zn(L1)2] (4) Yield: 73%, Anal. calc. for C18H14N8O2Zn: C, 49.1; H, 3.2;
N, 25.4; Zn, 14.8%; Found C, 49.0; H, 3.1; N, 25.2; Zn, 14.7%. IR data (KBr,
cm−1); 1608 ν(C_N), 3172 (\\NH triazole ring), 428 ν(M\\N), 572
ν(M\\O). MS m/z (%): 438 [M+]. 1H NMR (δ, ppm): 7.01–7.66 (aromat-
ic) (m); 8.6 (CH) (s), 8.3 (CH) (s), 13.5 (\\NH) (s). 13C NMR (δ, ppm):
116.2–157.8 (C1 to C6), 157.8 (C7), 157.5 (C8), 145.7 (C9). ΛM 10−3
(Ω−1 cm2 mol−1) = 14.7. λmax (cm−1) in DMF, 39,589, 27,489. μeff
(BM): diamagnetic.
The Schiff bases (L1–L3) were prepared by condensing of 3-amino-
1,2,4-triazole (10 mmol) dissolved in hot ethanol (15 mL) to a
magnetically stirred hot solution of salicylaldehyde and its derivatives
(where L1 — salicylaldehyde derived Schiff base, L2 — nitro substituted
salicylaldehyde derived Schiff base, L3
— methoxy substituted
salicylaldehyde derived Schiff base) (10 mmol) in hot ethanol
(15 mL). The condensed mixture was then refluxed for 2 h and the yel-
low solid precipitated on cooling was washed with hot ethanol first,
then pet-ether and dried. Further, it was recrystallized in a hot solution
of ethanol–methanol (1:1) and dried in vacuo. The same method was
applied for the preparation of all other ligands L2 and L3.
[CuL1L2] (5) Yield: 77%, Anal. calc. for C18H13CuN9O4: C, 44.7; H, 2.7;
N, 26.1; Cu, 13.1%; Found C, 44.5; H, 2.4; N, 26.0; Cu, 13.0%. IR data (KBr,
cm−1); 1610 ν(C_N), 3196 (\\NH triazole ring), 434 ν(M\\N), 592
ν(M\\O). MS m/z (%): 482 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) =
19.5.λmax (cm−1) in DMF, 15,890, 14,435, 15,726. μeff (BM): 1.86.
[CoL1L2] (6) Yield: 72%, Anal. calc. for C18H13CoN9O4: C, 45.2; H, 2.7;
N, 26.3; Co, 12.3%; Found C, 45.0; H, 2.6; N, 26.1; Co, 12.1%. IR data (KBr,
cm−1); 1606 ν(C_N), 3196 (\\NH triazole ring), 421 ν(M\\N), 587
ν(M\\O). MS m/z (%): 478 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) =
17.2.λmax (cm−1) in DMF, 10,118,11,341,24,930. μeff (BM): 4.88
[NiL1L2] (7) Yield: 79%, Anal. calc. for C18H13N9NiO4: C, 45.2; H, 2.7;
N, 26.3; Ni, 12.2%; Found C, 45.1; H, 2.5; N, 26.1; Ni, 12.1%. IR data
(KBr, cm−1); 1603 ν(C_N), 3196 (\\NH triazole ring), 433 ν(M\\N),
575 ν(M\\O). MS m/z (%): 477 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) =
18.5. λmax (cm−1) in DMF, 11,411,10,040, 25,113. μeff (BM):3.10.
[ZnL1L2] (8) Yield: 75%, Anal. calc. for C18H13N9O4Zn: C, 44.6; H, 2.7;
N, 26.0; Zn, 13.4%; Found C, 44.5; H, 2.6; N, 25.9; Zn, 13.2%. IR data (KBr,
cm−1); 1609 ν(C_N), 3196 (\\NH triazole ring), 429 ν(M\\N), 562
ν(M\\O). MS m/z (%): 483 [M+]. 1H NMR (δ): 7.04–7.58 (aromatic)
(m); 8.5 (CH) (s), 8.3 (CH) (s), 13.5 (\\NH) (s). 13C NMR (δ, ppm):
115.8–157.9 (C1 to C6), 157.2 (C7), 157.3 (C8), 145.2 (C9). ΛM 10−3
(Ω−1 cm2 mol−1) = 16.9.λmax (cm−1) in DMF, 35,668, 28,972. μeff
(BM): diamagnetic.
[L1], Yield: 72%. Anal. calc. for C9H8N4O: C, 57.4; H, 4.2; N, 29.7%;
Found C, 57.3; H, 4.1; N, 29.5%. IR data (KBr, cm−1); 1645 ν(C_N),
3172 (\\NH triazole ring), 3363 (H-bonded OH), 1575–1400 (C_C ar-
omatic stretching), 1047 (N\\N bond of triazole). 1H NMR (δ, ppm):
7.02–7.63 (aromatic) (m); 8.5 (CH) (s), 8.2 (CH) (s), 5.3 (OH) (s), 13.5
(\\NH) (s). 13C NMR (δ, ppm): 120.5–132.1 (C1 to C6), 160.0 (C7),
158.1 (C8), 146.6 (C9). UV–vis, (DMF, cm−1); 35,998, 27,361. MS m/z
(%): 188 [M+].
[L2], Yield: 74%. Anal. calc. for C9H7N5O3: C, 46.3; H, 3.0; N, 30.0%;
Found C, 46.2; H, 2.9; N, 29.8%. IR data (KBr, cm−1); 1643 ν(C_N),
3196 (\\NH triazole ring), 3298 (H-bonded OH), 1575–1400 (C_C ar-
omatic stretching), 1047 (N\\N bond of triazole), 1473, 1312, 833
ν(\\C\\N str;\\NO2). 1H NMR (δ, ppm): 7.28–8.35 (aromatic) (m);
8.3 (CH) (s), 8.2 (CH) (s), 5.3 (OH) (s), 13.5 (\\NH) (s). 13C NMR (δ,
ppm): 118.0–140.6 (C1 to C6), 160.0 (C7), 158.1 (C8), 146.6 (C9). UV–
vis, (DMF, cm−1); 35,985, 28,601. MS m/z (%): 233 [M+].
[L3], Yield: 70%. Anal. calc. for C10H10N4O2: C, 55.0; H, 4.6; N, 25.6%;
Found C, 54.9; H, 4.5; N, 25.4%. IR data (KBr, cm−1); 1638ν(C_N),
3187 (\\NH triazole ring), 3324 (H-bonded OH), 1575–1400 (C_C ar-
omatic stretching), 1047 (N\\N bond of triazole). 1H NMR (δ, ppm):
6.91–7.33 (aromatic) (m); 8.3 (CH) (s), 8.2 (CH) (s), 5.3 (OH) (s), 13.5
(\\NH) (s); 3.8 (\\OCH3) (s). 13C NMR (δ, ppm): 113.5–153.3(C1 to
C6), 160.0 (C7), 158.1 (C8), 146.6 (C9), 55.8 (C10). UV–vis, (DMF,
cm−1); 39,651, 29,149. MS m/z (%): 218 [M+].
[CuL1L3] (9) Yield: 71%, Anal. calc. for C19H16CuN8O3: C, 48.7; H, 3.4;
N, 23.9; Cu, 13.5%; Found C, 48.5; H, 3.3; N, 23.7; Cu, 13.4%. IR data (KBr,
cm−1); 1611 ν(C_N), 3187 (\\NH triazole ring), 436 ν(M\\N), 595
ν(M\\O). MS m/z (%): 467 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) = 14.2.
λ
max (cm−1) in DMF, 15,637, 14,741,15,878. μeff (BM): 1.89.
[CoL1L3] (10) Yield: 70%, Anal. calc. for C19H16CoN8O3: C, 49.2; H,
2.2. Synthesis of Metal Complexes
3.4; N, 24.1; Co, 12.7%; Found C, 49.1; H, 3.3; N, 24.0; Co, 12.6%. IR
data (KBr, cm−1); 1607 ν(C_N), 3187 (\\NH triazole ring), 426
ν(M\\N), 567 ν(M\\O). MS m/z (%): 463 [M+]. ΛM 10−3
(Ω−1 cm2 mol−1) = 15.8. λmax (cm−1) in DMF, 10,451, 11,427,
26,348. μeff (BM): 4.82
The metal complexes of the types [M(L1)2], [ML1L2] and [ML1L3]
were synthesized using the following procedure. The synthesized ligand
L1 (20 mmol) was dissolved in a hot ethanolic solution and condensed
with the appropriate metal chloride salts (Cu, Co, Ni, Zn) (10 mmol).
On cooling the product obtained was washed with hot ethanol, pet-
ether and then dried in vacuo. The obtained metal complexes [M(L1)2]
were in 1:2 ratio (metal: L1). Similar procedure was followed for the
preparation of other metal complexes, where the metal ratios were
the same while the ratios of ligands were varied. Accordingly, com-
plexes 5–8 were of type [ML1L2] with (L1:M:L2) ratio and complexes
9–12 were of type [ML1L3] with the ratio (L1:M:L3).
[NiL1L3] (11) Yield: 68%, Anal. calc. for C19H16N8NiO3: C, 49.2; H, 3.4;
N, 24.2; Ni, 12.6%; Found C, 49.1; H, 3.3; N, 24.1; Ni, 12.5%. IR data (KBr,
cm−1); 1604 ν(C_N), 3187 (\\NH triazole ring), 435 ν(M\\N), 592
ν(M\\O). MS m/z (%): 462 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) = 18.7.
λ
max (cm−1) in DMF, 11,910, 10,163, 25,715. μeff (BM): 3.17.
[ZnL1L3] (12) Yield: 73%, Anal. calc. for C19H16N8O3Zn: C, 48.5; H, 3.4;
N, 23.8; Zn, 13.5%; Found C, 48.3; H, 3.3; N, 23.7; Zn, 13.5%. IR data (KBr,
cm−1); 1605 ν(C_N), 3187 (\\NH triazole ring), 423 ν(M\\N), 587
ν(M\\O). MS m/z (%): 468 [M+]. 1H NMR (δ): 7.1–7.9 (aromatic)
(m); 8.4 (CH) (s), 8.3 (CH) (s), 13.5 (\\NH) (s). 13C NMR (δ, ppm):
116.0–158.9 (C1 to C6), 157.6 (C7), 158.9 (C8), 146.2 (C9), 55.8 (C10).
ΛM 10−3 (Ω−1 cm2 mol−1) = 16.2. λmax (cm−1) in DMF, 35,425,
28,943. μeff (BM): diamagnetic.
[Cu(L1)2] (1), Yield: 78%, Anal. calc. for C18H14CuN8O2: C, 49.3; H, 3.2;
N, 25.5; Cu, 14.5%; Found C, 49.1; H, 3.1; N, 25.3; Cu, 14.2%. IR data (KBr,
cm−1); 1607 ν(C_N), 3413 (\\NH triazole ring), 425 ν(M\\N), 574
ν(M\\O). MS m/z (%): 437 [M+]. ΛM 10−3 (Ω−1 cm2 mol−1) =
14.6.λmax (cm−1) in DMF, 15,997,14,861,15,345. μeff (BM): 1.84.