Bipyrazole-based palladium(II) complexes as DNA intercalator and artifcial metallonuclease
(E)-1-(3-bromothiophen-2-yl)-3-(5-chloro-3-methyl-1-phenyl-
1H-pyrazol-4-yl)prop-2-en-1-one (5 mmol) and phenyl hydra-
zine (5 mmol) after 3 h refux. Yield: 67%; yellow crystalline
solid; m.p.: >250 °C; 1H NMR (400 MHz, CDCl3): δ=2.22
(3H, s, –CH3), 3.55 (1H, dd, J=6.8 Hz, 8.0 Hz, 10.4 Hz, 4-Ha),
4.11 (1H, dd, J=12.8 Hz, 12.8 Hz, 4.8 Hz, 4-Hb), 5.41 (1H,
dd, J=7.2 Hz, 8.0 Hz, 5.6 Hz, 5-H), 6.82-7.58 (12H, m, 2′, 3′,
2″′-6″′, 2″′-6″′-H) ppm; 13C NMR (100 MHz, CDCl3): δ=13.2
(–CH3), 42.8 (–CH2 of pyrazoline), 55.7 (–CH of pyrazoline),
113.4, 113.5, 119.9, 124.8, 125.7, 126.2, 128.2, 129.0, 129.2,
129.3, 132.0 (aromatic CH), 113.9, 117.7, 121.8, 130.2, 138.2,
145.4, 149.0, 159.1 (aromatic C) ppm; IR (KBr): V =3020,
υ(C–H)ar, 1542, υ(C=N), 1396, υ(C=C), 1134, υ(C–N), 1041,
υ(C–Cl), 717, δ(C–H)ar, 833, υ(C–S–C)thiophene cm−1; MS: m/z
(%)=497.10 (100) [M+].
4-Hb), 5.38 (1H, dd, J=8.0 Hz, 8.0 Hz, 5.2 Hz, 5-H), 6.84-
7.57 (12H, m, 3′, 4′, 2″′-6″′, 2″′-6″′-H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 13.3 (–CH3), 41.1 (–CH2 of
pyrazoline), 56.0 (–CH of pyrazoline), 113.6, 113.7, 120.0,
124.8, 125.0, 126.3, 128.5, 129.4, 129.5, 129.6, 130.4 (aro-
matic CH), 114.2, 118.2, 121.1, 135.2, 139.1, 146.0, 149.0,
160.6 (aromatic C) ppm; IR (KBr): V = 3055, υ(C–H)ar,
1598, υ(C=N), 1380, υ(C=C), 1203, υ(C–N), 1118, υ(C–
Cl), 748, δ(C–H)ar, 871, υ(C–S–C)thiophene cm−1; MS: m/z
(%)=630.01 (100) [M+]; conductance: 12 Ω−1 cm2 mol−1;
UV–Vis: λmax (ε) = 280 (34,320), 415 (18,641) nm (M−1
cm−1).
Dichloro[5‑(5‑bromothiophen‑2‑yl)‑5′‑chloro‑3′‑methyl‑1′,2‑
diphenyl‑3,4‑dihydro‑1′H,2H‑3,4′‑bipyrazole]palladium(II)
(5c, C23H18BrCl3N4PdS) Prepared by the above method from
4c (5 mmol) and Na2PdCl4 (5 mmol). Yield: 64%; brownish
yellow solid; m.p.:>300 °C; 1H NMR (400 MHz, DMSO-
d6): δ=2.19 (3H, s, –CH3), 3.20 (1H, dd, J=8.4 Hz, 8.0 Hz,
10.0 Hz, 4-Ha), 3.79 (1H, dd, J=12.4 Hz, 12.0 Hz, 5.2 Hz,
4-Hb), 5.39 (1H, dd, J=8.0 Hz, 8.0 Hz, 5.2 Hz, 5-H), 6.82-
7.57 (12H, m, 3′, 4′, 2″′-6″′, 2″′-6″′-H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 13.8 –CH3), 41.5 (–CH2 of
pyrazoline), 55.9 (–CH of pyrazoline), 113.5, 113.6, 120.0,
125.3, 126.0, 128.8, 129.0, 129.5, 129.6, 130.6 (aromatic
CH), 114.1, 118.3, 124.1, 129.8, 138.2, 146.8, 149.6, 160.0
(aromatic C) ppm; IR (KBr): V = 3078, υ(C–H)ar, 1600,
υ(C=N), 1380, υ(C=C), 1180, υ(C–N), 1064, υ(C–Cl), 748,
δ(C–H)ar, 871, υ(C–S–C)thiophene cm−1; MS: m/z (%)=474.52
(100) [M+]; conductance: 11 Ω−1 cm2 mol−1; UV–Vis: λmax
(ε)=280 (36,471), 415 (18,113) nm (M−1 cm−1).
General synthesis of complexes 5a–5d
The square planar metal complexes 5a–5d of type [Pd(4n)
Cl2] were synthesized by the reactions of Na2PdCl4 with the
respective pyrazoline ligands 4a–4d in a 1: 1 molar ratio in
1: 1 methanol chloroform system. The reaction mixture was
refuxed for 30 min followed by stirring for 24 h at ambient
temperature.
Dichloro[5′‑chloro‑3′‑methyl‑1′,2‑diphenyl‑5‑(thiophen‑
2‑yl)‑3,4‑dihydro‑1′H,2H‑3,4′‑bipyrazole]palladium(II)
(5a, C23H19Cl3N4PdS) Prepared by the above method from
4a (5 mmol) and Na2PdCl4 (5 mmol). Yield: 65%; brownish
yellow solid; m.p.: >300 °C; 1H NMR (400 MHz, DMSO-
d6): δ=2.22 (3H, s, –CH3), 3.26 (1H, dd, J=8.4 Hz, 7.6 Hz,
10.0 Hz, 4-Ha), 3.85 (1H, dd, J=12.0 Hz, 12.0 Hz, 6.0 Hz,
4-Hb), 5.38 (1H, dd, J=8.0 Hz, 8.0 Hz, 4.0 Hz, 5-H), 6.86-
7.73 (13H, m, 2′, 3′, 4′, 2″′-6″′, 2″′-6″′-H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 13.9 (–CH3), 42.0 (–CH2 of
pyrazoline), 55.8 (–CH of pyrazoline), 112.8, 113.8, 120.0,
125.0, 126.0, 126.2, 127.1, 128.4, 129.4, 129.5, 129.5,
129.6 (aromatic CH), 114.0, 118.0, 120.2, 130.4, 138.2,
145.9, 149.0, 159.4 (aromatic C) ppm; IR (KBr): V =3062,
υ(C–H)ar, 1596, υ(C=N), 1380, υ(C=C), 1149, υ(C–N),
1072, υ(C–Cl), 748, δ(C–H)ar, 910, υ(C–S–C)thiophene cm−1;
MS: m/z (%)=595.98 (100) [M+]; conductance: 9 Ω−1 cm2
mol−1; UV–Vis: λmax (ε)=280 (32,641), 415 (14,924) nm
(M−1 cm−1).
Dichloro[5‑(3‑bromothiophen‑2‑yl)‑5′‑chloro‑3′‑methyl‑1′,2‑
diphenyl‑3,4‑dihydro‑1′H,2H‑3,4′‑bipyrazole]palladium(II)
(5d, C23H18BrCl3N4PdS) Prepared by the above method from
4d (5 mmol) and Na2PdCl4 (5 mmol). Yield: 62%; brownish
yellow solid; m.p.: >300 °C; 1H NMR (400 MHz, DMSO-
d6): δ=2.23 (3H, s, –CH3), 3.55 (1H, dd, J=7.6 Hz, 7.6 Hz,
10.0 Hz, 4-Ha), 4.11 (1H, dd, J=12.8 Hz, 12.8 Hz, 4.8 Hz,
4-Hb), 5.42 (1H, dd, J=8.0 Hz, 8.0 Hz, 4.8 Hz, 5-H), 6.82–
7.58 (12H, m, 2′, 3′, 2″′-6″′, 2″′-6″′-H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 13.6 (–CH3), 42.8 (–CH2 of
pyrazoline), 55.9 (–CH of pyrazoline), 113.8, 113.9, 120.1,
125.1, 126.1, 126.9, 128.7, 129.5, 129.6, 129.7, 132.2 (aro-
matic CH), 114.0, 117.9, 120.2, 130.4, 138.2, 145.9, 149.0,
159.4 (aromatic C) ppm; IR (KBr): V = 3078, υ(C–H)ar,
1600, υ(C=N), 1380, υ(C=C), 1180, υ(C–N), 1072, υ(C–
Cl), 748, δ(C–H)ar, 871, υ(C–S–C)thiophene cm−1; MS: m/z
(%)=674.79 (100) [M+]; Conductance: 8 Ω−1 cm2 mol−1;
UV–Vis: λmax (ε) = 280 (30,471), 415 (10,679) nm
(M−1 cm−1).
Dichloro[5′‑chloro‑5‑(5‑chlorothiophen‑2‑yl)‑3′‑methyl‑1′,2‑
diphenyl‑3,4‑dihydro‑1′H,2H‑3,4′‑bipyrazole]palladium(II)
(5b, C23H18Cl4N4PdS) Prepared by the above method from
4b (5 mmol) and Na2PdCl4 (5 mmol). Yield: 71%; brownish
yellow solid; m.p.:>300 °C; 1H NMR (400 MHz, DMSO-
d6): δ=2.20 (3H, s, –CH3), 3.20 (1H, dd, J=7.6 Hz, 8.0 Hz,
10.0 Hz, 4-Ha), 3.78 (1H, dd, J=12.4 Hz, 12.0 Hz, 5.2 Hz,
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