Characterization of [Zn(DNR)2] complex

3. Results and discussion
3.1 Characterization of [Zn(DNR)2] complex
The formation of [Zn(DNR)2] complex (Fig. 1) was confirmed by UV-visible and FT-IR spectroscopy, mass spectra and elemental analysis. The electronic spectra of the drug and the [Zn(DNR)2] complex were recorded in phosphate buffer at room temperature (Fig. 1S). In comparison with the free drug, the [Zn(DNR)2] complex spectrum reveals characteristic features. The electronic spectrum of the [Zn(DNR)2] complex exhibited bands at 230 nm, 250 nm and 290 nm correspond to -* transitions, where the band located at higher wavelength (490 nm) result from n-* transition [29].
To obtain information about the coordination mode of the ligand, FT-IR spectra of drug and [Zn(DNR)2] complex are characterized by some specific bands (Fig. 2S). In the FTIR spectra, the N-H band of the amino group of the sugar ring is unshifted in [Zn(DNR)2] complex compared to the free ligand (1716 cm-1). The IR spectrum of drug observed a wide, strong band coming from the stretching vibration of the hydroxyl group (OH) at 3397 cm-1. This band shifted to frequency (3384cm-1) in [Zn(DNR)2] complex which demonstrates that the substance was hydrated. The most prominent signals of quinone group seen at bands 960cm-1 and 907 cm-1 which corresponds to the carbonyl group and hydroxyl group the in the drug spectrum has been lost the in [Zn(DNR)2] complex spectrum, indicating coordination through the hydrogen atom of the hydroxyl group at C (23) and by the attaching to the oxygen atom of the carbonyl group C (26) (Fig. 1) [30]. Furthermore, 1413 cm1 band can be attributed to a ring C-C mode coupled to a C-OH mode [31]. This band shifted to frequency (1450 cm-1) in it [Zn(DNR)2] complex. Given the significant shifts in the C=O, C-C and OH bands, the results showed that coordination of the daunorubicin drug to metal was done through the binding of OH and C=O from the quinone group. The spectrum of [Zn(DNR)2] complex has exhibited new absorption bands at 414 cm-1 which was assigned for Zn-O stretching vibration [32].
Mass spectrum of the ligand shows the molecular ion peak at m/z 527.3. The [Zn(DNR)2] complex shows the molecular ion peak (M-2) at m/z 1117.3 (Fig. 3S). The data confirm the stoichiometry of the metal complex as being of the [Zn(DNR)2] type [33].

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