Figure 1.

Figure 2.
2 (Pd1) and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)](NO3)2 (Pd2) complexes.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/66e126ab7d402026d60a21cc/j_sjecr-2021-0030_fig_002.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251205%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251205T074554Z&X-Amz-Expires=3600&X-Amz-Signature=a8c885d9488cb2052f455852b604c8595d1bc0e80bd73334b0a40d3eda74dfa5&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 3.
![UV-Vis spectra of dinuclear [{Pd(en)Cl}2 (μ-1,5-nphe)]2+ and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)]2+ complexes and free 1,5-nphe ligand.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/66e126ab7d402026d60a21cc/j_sjecr-2021-0030_fig_003.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251205%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251205T074554Z&X-Amz-Expires=3600&X-Amz-Signature=4068e98dfa976b68ad073348fd4bc3c630ad7d2d36b725e2c8642719ae9d2dc5&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 4.

Figure 5.
![Absorption spectra of [{Pd(en)Cl}2(μ-1,5-nphe)]2+ and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)]2+ complexes in 0.01 M phosphate buffer before and after addition of CT-DNA. [Pd(II) complex] = 4.51 · 10−5 M, [DNA] = (0 – 2.00) · 10−4 M.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/66e126ab7d402026d60a21cc/j_sjecr-2021-0030_fig_005.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251205%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251205T074554Z&X-Amz-Expires=3600&X-Amz-Signature=1a2f223b1dc3910703b4c94b9aedd0397ed05f05132782f9e087801553dd7a68&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 6.
![EtBr/CT-DNA emission spectra in the presence of [{Pd(en)Cl}2(μ-1,5-nphe)]2+ and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)]2+ complex. [EtBr] = 1.28 · 10−5 M, [DNA] = 1.28 · 10−5 M, [Pd(II) complex] = (0 – 1.28) · 10−5 M. Inserted graph: Dependence of I0/I from concentration [Q].](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/66e126ab7d402026d60a21cc/j_sjecr-2021-0030_fig_006.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251205%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251205T074554Z&X-Amz-Expires=3600&X-Amz-Signature=5b39ea8ed3489b6495f4424af9f4ef55126c69f9880b1eb9929ad2937c871dbc&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 7.
![BSA emission spectra in the presence of [{Pd(en)Cl}2(μ-1,5-nphe)]2+ and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)]2+ complexes. [BSA] = 1.60 · 10−6 M, [Pd(II) complex] = (0 – 4.00) · 10−5 M; λex = 295 nm. Inserted graph: Dependence of Io/I from concentration [Q].](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/66e126ab7d402026d60a21cc/j_sjecr-2021-0030_fig_007.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251205%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251205T074554Z&X-Amz-Expires=3600&X-Amz-Signature=9779187eb0ae82edf8c539a71ecd90e85b055eeb4d2b2901c071dc60feef67f1&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Stern-Volmer constant (Ksv), quenching constant (kq), binding constant (Ka) and number of binding sites (n) for interactions between BSA and dinuclear Pd1 and Pd2 complexes_
| complex | Ksv · 105 (M−1) | kq · 1012 (M−1s−1) | Ka · 109 (M−1) | n |
|---|---|---|---|---|
| [{Pd(en)Cl}2 (μ-1,5-nphe)]2+ | (2.80 ± 0.03) | (28 ± 2) | (1.20 ± 0.05) | 1.8 |
| [{Pd(1,3-pd)Cl}2 (μ-1,5-nphe)]2+ | (3.90 ± 0.04) | (39 ± 1) | (1.20 ± 0.02) | 1.8 |
Stern-Volmer constant (Ksv), stability constant (Ka) and number of binding sites (n) of the investigated dinuclear palladium(II) complexes with CT-DNA
| complex | Ksv · 105 (M−1) | Ka · 105 (M−1) | n |
|---|---|---|---|
| [{Pd(en)Cl}2 (μ-1,5-nphe)]2+ | (4.50 ± 0.04) | (8.80 ± 0.02) | 1.7 |
| [{Pd(1,3-pd)Cl}2 (μ-1,5-nphe)]2+ | (2.80 ± 0.06) | (2.50 ± 0.05) | 1.1 |
1H and 13C NMR chemical shifts (δ, ppm) for 1,5-naphthyridine (1,5-nphe), ethylenediamine (en), 1,3-propylenediamine (1,3-pd) and the corresponding dinuclear palladium(II) complexes
| ligand/complex | NMR shifts | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1H | 13C | ||||||||
| H2, H6 | H4, H8 | H3, H7 | alifatic protons | C2, C6 | C4, C8 | C3, C7 | C4a, C8a | L | |
| 1,5-nphe | 8.57 dd | 7.89 d | 7.48 dd | 154 | 139 | 128 | 144 | ||
| en | 2.64 s (CH2) | 45 (CH2) | |||||||
| Pd1 | 10.21 d | 9.58 d | 8.14 m | 2.76 m (CH2) | 160 | 147 | 130 | 143 | 50 (CH2) |
| 1,3-pd | 1.60 m (H2, CH2) | 29 (C2, CH2) | |||||||
| Pd2 | 10.17 d | 9.55 d | 8.23 m | 1.85 m (H2,CH2) | 160 | 146 | 131 | 143 | 30 (C2, CH2) |
Internal binding constants (Kb), changes in Gibbs energy (ΔG) and hypochromism (H) of the investigated dinuclear palladium(II) complexes, Pd1 and Pd2, with CT-DNA
| complex | Kb · 104 (M−1) | ΔG (kJ/mol) | H |
|---|---|---|---|
| [{Pd(en)Cl}2 (μ-1,5-nphe)]2+ | (7.50 ± 0.05) | −28.93 | 22.42 |
| [{Pd(1,3-pd)Cl}2 (μ-1,5-nphe)]2+ | (4.00 ± 0.03) | −27.31 | 25.77 |