BioMed Research International
Volume 2019 (2019), Article ID 9835745, 14 pages
https://doi.org/10.1155/2019/9835745

Research Article

New Platinum(IV) and Palladium(II) Transition Metal Complexes of s-Triazine Derivative: Synthesis, Spectral, and Anticancer Agents Studies

Fatima A. I. Al-Khodir, Hana M. A. Abumelha, Tarfah Al-Warhi, and S. A. Al-Issa

Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Saudi Arabia

Correspondence should be addressed to Fatima A. I. Al-Khodir; fatimaalkhodir@yahoo.com

Received 25 October 2018; Revised 1 January 2019; Accepted 31 January 2019; Published 17 February 2019

Academic Editor: Jinsong Ren

Copyright © 2019 Fatima A. I. Al-Khodir et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

New Pd(II) and Pt(IV) triazine complexes [Pt₃(L¹)₂(Cl)₉(H₂O)₃].3Cl.3H₂O (1), [Pt₃(L²)₂(Cl)₉(H₂O)₃].3Cl (2), [Pt₃(L³)₂(Cl)₉(H₂O)₃].3Cl (3), [Pt₂(L⁴)₂(Cl)₆(H₂O)₂] .2Cl.4H₂O (4), [Pd₃(L¹)₂(H₂O)₆] .3Cl₂ (5), [Pd₃(L²)₂(H₂O)₆].3Cl₂ (6), [Pd₃(L³)₂(H₂O)₆].3Cl₂ (7), and [Pd₂(L⁴)₂(H₂O)₄].2Cl₂ (8) were synthesized and well characterized using elemental analyses, molar conductance, IR, UV-Vis, magnetic susceptibility, ¹H, ¹³C-NMR spectra, and thermal analyses. These analyses deduced that the L¹, L², and L³ ligands act as tridentate forming octahedral geometry with Pt(IV) metal ions and square planar geometry in case of Pd(II) complexes but the L⁴ ligand acts as bidentate chelate. The molar conductance values refer to the fact that all the prepared s-triazine complexes have electrolyte properties which are investigated in DMSO solvent. Surface morphology behaviors of prepared complexes have been scanned using TEM. The crystalline behavior of triazine complexes has been checked based on X-ray powder diffraction patterns. The antimicrobial activity of the free ligands and their platinum(IV) and palladium(II) complexes against the species Staphylococcus aureus (G+), Escherichia coli (G−), Aspergillus flavus, and Candida albicans has been carried out and compared with the standard one. The coordination of ligands towards metal ions makes them stronger bacteriostatic agents, thus inhibiting the growth of bacteria and fungi more than the free ligands. The cytotoxic assessment IC₅₀ of the free ligands and its platinum(IV) complexes in vitro against human colon and lung cancer cell lines introduced a promising efficiency.

1. Introduction

The s-triazine and its derivatives have a wide range of pharmaceutical benefits: antiviral, antimalarial, antibacterial, anti-inflammatory, antileukemia, anticancer, and anti-HIV activities [1–4]. Many triazine analogues are utilized as a building block for the construction of multisite ligand systems [5, 6]. A number of triazine analogues were tested for ion extraction of metal ions which have been reviewed [7, 8]. Some triazine derivatives with pyrazole, functioning at the least conventional habiliments, are screened and identified as potential inhibitors of photosynthetic electron transport [9]. In literature survey, it was refereed that the organic s-triazine’s derivative compounds and transition metal complexes have been found to be effective in the field of nonlinear optical activity (NLO) [10–12] that can act as an auxiliary acceptor in NLO chromophores. Further advantages in considering the s-triazine as central moiety are its symmetric nature by which it will be possible to chemically tune its NLO nature by mono- or disubstitution [13, 14]. 1,3,5-Triazine is considered to be a remarkable in supramolecular chemistry since it can take part in all types of interactions, namely, coordination, hydrogen bonds, electrostatic and charge-transfer attractions, and aromatic-stacking interactions [15]. Triazine derivatives have been widely used in several fields such as herbicide [16, 17]. In materials chemistry 1,3,5-triazine derivatives have been used as acceptors in star-shaped systems [18], liquid crystals [19], redox active chromophores [20], photovoltaic devices [21], and blue phosphorescent [22]. Also, it was used as functional materials [23], catalysts [24], absorption of surfactants [25], nanoporous membranes for desalination [26], and cathodes for lithium batteries [27, 28].

In connection of our previously work [29], this article aimed to synthesized new platinum(IV) and palladium(II) complexes with four triazine ligands (Figure 1) and checked the biological property and anticancer significance.

Figure 1: Structures of prepared triazine ligands [29]. L¹= N²-(4-chlorophenyl)-N⁴,N⁶-di(pyrimidin-2-yl)-1,3,5-triazine-2,4,6-triamine. L²= N²-(4-chlorophenyl)-N⁴,N⁶-di(pyrimidin-2-yl)-1,3,5-triazine-2,4,6-triamine. L³=6-chloro-N²-(pyrimidin-2-yl)-N⁴-(1H-1,2,4-triazol-3-yl)-1,3,5-triazine-2,4-diamine. L⁴= 6-chloro-N²-(4-chlorophenyl)-N⁴-(pyrimidin-2-yl)-1,3,5-triazine-2,4-diamine).

2. Materials and Methods

2.1. Chemicals

The PtCl₄ and PdCl₂ salts were received from Sigma-Aldrich Chemical Corporation, St. Louis, Mo, USA.

2.2. Synthesis of Trisubstituted s-Triazine Derivative Ligands

Synthesis of N²,N⁴,N⁶-triaryl-1,3,5-triazine-2,4,6-triamine primary nucleus (Figure 2) was carried out as described in literature [30, 31]. The synthesis of L¹, L², L³, and L⁴ triazine ligands was carried out according to our previously work [29], L¹ prepared by stirring the mixtures of 2-aminopyrimidine with 6-chloro-N²-(4-chlorophenyl)-N⁴-di(pyrimidin-2-yl)-1,3,5-triazine-2,4-diamine in dioxane at refluxed temperature; L² prepared by stirring the mixtures of 2-aminothiazole with 6-chloro-N²-(4-chlorophenyl)-N⁴-(pyrimidin-2-yl)-1,3,5-triazine-2,4-diamine in dioxane at refluxed temperature; L³ prepared by stirring the mixtures of 2-aminopyrimidine with 4,6-dichloro-N²-(1H-1,2,4-triazol-3-yl)-1,3,5-triazin-2-amine in dioxane 50°C; L⁴ prepared by stirring the mixtures of 2-aminopyrimidine with 4,6-dichloro-N-( 4-chlorophenyl)-1,3,5-triazin-2-amine in dioxane 50°C.

Figure 2: Synthesis of trisubstituted triazine derivatives.

2.3. Synthesis of Pt(IV) and Pd(II) Complexes

A hot methanolic solution of the metal chloride (Pt(IV) and Pd(II)) (1 mM) was added to the hot methanolic solution of ligands (L¹, L², L³, or L⁴) (1 mM). The mixed solutions were stirred and refluxed at 70°C for 6 hrs. The colored precipitates thus separated out were washed with methanol and dried in vacuo.

2.4. Instrumentals

No. | Type of analysis | Model of the instruments
(i) | Elemental analyses | Perkin Elmer CHN 2400 (USA)
(ii) | Metal ions | gravimetrically
(iii) | Melting point | MPS10–120
(iv) | Molar conductivities | Jenway 4010 conductivity meter
(v) | Infrared spectra | Bruker Alpha FTIR Spectrophotometer
(vi) | UV-Vis absorption spectra | UV2 Unicam UV/Vis Spectrophotometer
(vii) | Magnetic moments | Magnetic Susceptibility Balance, Sherwood Scientific, Cambridge Science Park, Cambridge, England
(viii) | ,-NMR spectra | Oxford YH-300 NMR spectrometer
(ix) | Mass spectra | 70 eV using AEI MS 30 mass spectrometer
(x) | Thermal studies TG/DTG | Mettler Toledo AG thermogravimetric analyzer
(xi) | SEM | Quanta FEG 250 equipment
(xii) | XRD | X 'Pert PRO PANanalytical X-ray powder diffraction
(xiii) | TEM | JEOL 100s microscopy

2.5. Antimicrobial Study

Antimicrobial evaluations of the investigated samples were assessed by a modified Kirby-Bauer disc diffusion method [32, 33].

2.6. Anticancer Study

All tested samples were checked against human colon and lung cancer cell line by using neutral red (NR) technique [34].

3. Results and Discussion

3.1. Microanalytical and Physical Data

All the platinum(IV) and palladium(II) s-triazine derivative complexes were obtained as colored solids by the reaction of ligands (L¹, L², L³, and L⁴) with anhydrous metal chloride salts (PtCl₄ and PdCl₂). The experimental of elemental analyses of the ligands and their metal complexes (Table 1) are in good agreement with the calculated data. The ligands and their metal (IV/II) complexes are stable at room temperature and soluble in common organic solvents such as (DMSO and DMF). According to the elemental analysis and spectroscopic assignments, the chelating sites and geometry have been suggested and are displayed in Figure 3. The molar conductance of both free s-triazine derivative ligands and their Pt(IV) and Pd(II) complexes in 10⁻³ M of DMSO solution is in the range of 64.7–139.3 μS, which reveals the electrolytic behavior of the complexes [35]. Melting points of all complexes have values more than >300°C due to thermal stability properties.

Table 1: Microanalytical and physicochemical data of ligands and their complexes.

Compounds
Color
Λ(μS)
Elemental analyses found(Calc.)
Yield, %

%C
%H
%N
%M

1
Yellow
126.8
(21.44)
(2.01)
(14.71)
(30.73)
77

21.32
1.96
14.57
30.66

2
Brown
70.6
(20.66)
(1.63)
(13.55)
(31.46)
72

20.54
1.54
13.50
31.32

3
Green
64.7
(13.13)
(1.22)
(17.02)
(35.55)
71

13.09
1.18
17.00
35.50

4
Pale yellow
95.6
(22.64)
(2.19)
(14.22)
(28.29)
69

22.56
2.13
14.16
28.11

5
Dark brown
139.3
(28.64)
(2.69)
(19.65)
(22.39)
75

28.56
2.57
19.54
22.31

6
Red brown
82
(26.77)
(2.53)
(17.56)
(22.24)
70

26.71
2.51
17.49
22.19

7
Brownish green
106.7
(17.70)
(2.15)
(22.94)
(26.14)
74

17.65
2.09
22.90
26.11

8
Brown
122.3
(30.49)
(2.56)
(19.15)
(20.78)
71

30.41
2.49
19.12
20.69

[Pt₃(L¹)₂(Cl)₉(H₂O)₃].3Cl.3H₂O (1), [Pt₃(L²)₂(Cl)₉(H₂O)₃].3Cl (2), [Pt₃(L³)₂(Cl)₉(H₂O)₃].3Cl (3), [Pt₂(L⁴)₂(Cl)₆(H₂O)₂] .2Cl.4H₂O (4), [Pd₃(L¹)₂(H₂O)₆].3Cl₂ (5), [Pd₃(L²)₂(H₂O)₆].3Cl₂ (6), [Pd₃(L³)₂(H₂O)₆] .3Cl₂ (7) and [Pd₂(L⁴)₂(H₂O)₄].2Cl₂ (8).

Figure 3: Suggested structures of Pt(IV) and Pd(II) complexes.

3.2. FT-IR Spectra

Peaks at 1620, 1560, 1485, 740, and 627 cm⁻¹ present in L¹, L², L³, and L⁴ s-triazine derivatives ligands can be assigned for the C=, C=C, C=N, C–S, and C–Cl stretching vibrations. The FT-IR spectra of the ligands show a strong-to-medium strong bands at 1488 cm⁻¹ (L¹), 1485 cm⁻¹ (L²), 1510 cm⁻¹ (L³), and 1484 cm⁻¹ (L⁴) which are assigned to ν(C=N) group of triazine [36]. Infrared spectral data of the 1–8 complexes (Table 2; Figure 4) usually a lot of valuable information is provided about the coordination mechanism. The free ligands which exhibit a band at 1623 cm⁻¹ (L¹), 1619 cm⁻¹ (L²), 1621 cm⁻¹ (L³), and 1619 cm⁻¹ (L⁴) are assigned to ν(C=N) of pyrimidine and triazole rings. In case of complexes, this band is shifted to 1698–1667 cm⁻¹ region attributed to nitrogen atom of (C=N) coordination to metal ion. The ligands shows a medium strong band at 1510–1484 cm⁻¹, which is characteristic of the ν(C=N) group in s-triazine [37, 38]. This band shifted to lower frequency of 1396–1382 cm⁻¹ upon complexation which indicates that triazine ring nitrogen is one of the coordinating atoms in the ligand [38]. The ν(N–H) stretching frequency of pyrimidine/triazole rings exhibited at 3260–3112 cm⁻¹ was shifted to lower wavenumbers after complexation due to the reduction of lone pair repulsive forces on the nitrogen atoms [39]. In the FT-IR spectra of complexes, the medium-weak bands appeared at 570–440 cm⁻¹ regions which can be assigned to ν(M–N) [40] and confirm the interaction between metal and ligand.

Table 2: FT-IR spectral band assignments of L¹, L², L³, and L⁴ ligands and their complexes.

Compounds
FTIR spectral assignments (cm⁻¹)

ν(N–H)
ν(C=N
ν(C=C
ν(C=N
ν(M–N)

L¹
3249-3112
1623
1559
1488
-

L²
3260-3142
1619
1555
1485
-

L³
3251-3156
1621
1586
1510
-

L⁴
3244-3150
1619
1574
1484
-

1
3200
1679
1560
1385
545, 447

2
-
1667
1537
1383
536, 441

3
-
1698
1585
1382
570, 470

4
-
1695
1567
1390
530, 469

5
-
1689
1530
1394
537, 440

6
-
1695
1557
1396
540, 463

7
-
1698
1550
1391
537, 467

8
-
1691
1537
1393
537, 463

(a)

(b)

Figure 4: FT-IR spectra of (a) [Pt₂(L⁴)₂(Cl)₆(H₂O)₂].2Cl.4H₂O (4) and (b) [Pd₃(L²)₂ (H₂O)₆].3Cl₂ (6).

3.3. Electronic and Magnetic Studies

The electronic spectra of [Pt₃(L¹)₂(Cl)₉(H₂O)₃].3Cl.3H₂O (1), [Pt₃(L²)₂(Cl)₉(H₂O)₃].3Cl (2), [Pt₃(L³)₂(Cl)₉(H₂O)₃].3Cl (3), and [Pt₂(L⁴)₂(Cl)₆(H₂O)₂] .2Cl.4H₂O (4) complexes which displayed charge-transfer transitions may interfere and prevent the observation of all the expected bands [41, 42].The distinct bands at 300–311 and 337–396 cm⁻¹ are attributed to a combination of metal ligand charge transfer (M→) and d–d transition band. The other weak band at 429–437 cm⁻¹ is attributed to combination of N→Pt(IV) metal charge transfer (Lπ→) and d–d transition bands. The Pt(IV) complexes are found to be diamagnetic character, so the Pt(IV) complexes must be octahedral geometry. The Pt(IV) is d⁶ system and four bands are expected due to ¹A1g→  ³T1g, ¹A1g→  ³T2g, ¹A1g→  ¹T1g, and ¹A1g→  ¹T2g transitions. The shift to lower frequency after complexation is due to the binding between Pt(IV) ion nitrogen atom of triazine, pyrimidine, thiazole, and triazole rings. Palladium(II) complexes have diamagnetic properties. The electronic absorption spectra of palladium(II) complexes have distinguished bands at (300 nm), (312 and 352 nm), (309, 334 and 391 nm), and (296, and 339 nm) for L¹, L², L³, and L⁴ ligands, respectively, due to Pd- charge-transfer transitions.

3.4. ¹H, ¹³C-NMR Spectra

Complex 1. ¹H-NMR (DMSO-d₆): δ = 7.26 (t, H, J = 4.5 Hz, pyrimidine C₅H), 7.30 (t, H, J = 4.5 Hz, pyrimidine C₅H), 7.34 (d, 2H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.39 (d, 2H, J = 9.9 Hz, p-Chloroaniline C₂H), 8.81 (d, 2H, J = 4.5 Hz, pyrimidine C4,6H), 8.91 (d, 2H, J = 4.5 Hz, pyrimidine C4,6H), 9.82 (s, 1H, NH), 11.19 (s, 1H, NH), 12.06 (s, 1H, NH). ¹³C-NMR (DMSO-d₆): δ = 111.4, 113.8, 117.9, 123.9, 130.7, 140.1, 144.1, 147.5, 153.1, 157.1, 159.2, 163.4, 163.9, 166.2, and 169.7 (Ar-C, C=C, C=N).

Complex 2. ¹H-NMR (DMSO-d₆): δ = 7.34 (d, 2H, J = 7.2 Hz, thiazole C₅H), 7.38 (t, 4H, J = 4.5 Hz, pyrimidine C₅H), 7.44 (d, 4H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.77 (d, 4H, J = 9.9 Hz, p-Chloroaniline C₂H), 7.86 (d, 2H, J = 6.3 Hz, thiazole C₄H), 8.09 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 9.51 (s, 2H, NH), 11.18 (s, 2H, NH), 12.08 (s, 2H, NH). ¹³C-NMR (DMSO-d₆): δ = 112.5, 114.0, 114.9, 123.2, 132.5, 145.2, 151.4, 152.9, 155.4, 157.0, 158.8, 162.0, 163.5, and 172.2 (Ar-C, C=C, C=N, C-S).

Complex 3. ¹H-NMR (DMSO-d₆): δ = 7.23 (t, 2H, J = 4.5 Hz, pyrimidine C₅H), 7.32 (s, 2H, triazole C₅H), 8.45 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 8.91 (s, 2H, NH), 11.22 (s, 2H, NH), 11.46 (s, 1H, NH). ¹³C-NMR (DMSO-d₆): δ = 115.8, 142.8, 146.5, 155.0, 156.2, 159.2, 163.8, 163.9, and 167.1 (Ar-C, C=C, C=N, C-Cl).

Complex 4. ¹H-NMR (DMSO-d₆): δ = 7.35 (t, 4H, J = 4.5 Hz, pyrimidine C₅H), 7.39 (d, 4H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.44 (d, 4H, J = 9.9 Hz, p-Chloroaniline C₂H), 7.76 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 9.50 (s, 2H, NH), 11.19 (s, 2H, NH). ¹³C-NMR (DMSO-d₆): δ = 111.9, 118.0, 123.1, 132.4, 144.4, 147.9, 153.5, 156.8, 161.8, 166.6, and 172.1 (Ar-C, C=C, C=N, C-Cl).

Complex 5. ¹H-NMR (DMSO-d₆): δ = 7.32 (t, 2H, J = 4.5 Hz, pyrimidine C₅H), 7.35 (t, 2H, J = 4.5 z, pyrimidine C₅H), 7.41 (d, 4H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.46 (d, 4H, J = 9.9 Hz, p-Chloroaniline C₂H), 8.57 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 7.79 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 9.55 (s, 2H, NH), 11.19 (s, 2H, NH), 11.20 (s, 2H, NH). ¹³C-NMR (DMSO-d₆): δ = 113.1, 115.1, 120.1, 123.8, 129.4, 141.7, 147.0, 149.8, 152.4, 157.7, 159.6, 163.1, 163.9, 165.8, and 171.1 (Ar-C, C=C, C=N).

Complex 6. ¹H-NMR (DMSO-d₆): δ = 7.33 (d, 2H, J = 7.2 Hz, thiazole C₅H), 7.36 (t, 4H, J = 4.5 Hz, pyrimidine C₅H), 7.45 (d, 4H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.78 (d, 4H, J = 9.9 Hz, p-Chloroaniline C₂H), 7.81 (d, 2H, J = 6.3 Hz, thiazole C₄H), 8.12 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 9.55 (s, 2H, NH), 11.20 (s, 2H, NH), 12.02 (s, 2H, NH). ¹³C-NMR (DMSO-d₆): δ = 110.2, 113.1, 115.8, 123.8, 131.8, 146.1, 150.3, 152.1, 155.0, 156.6, 158.1, 161.2, 163.1, and 173.4 (Ar-C, C=C, C=N, C-S).

Complex 7. ¹H-NMR (DMSO-d₆): δ = 7.21 (t, 2H, J = 4.5 Hz, pyrimidine C₅H), 7.39 (s, 2H, triazole C₅H), 8.46 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 8.92 (s, 2H, NH), 11.20 (s, 2H, NH), 11.48 (s, 1H, NH). ¹³C-NMR (DMSO-d₆): δ = 116.5, 141.9, 147.4, 154.4, 155.9, 159.8, 163.1, 164.5, and 168.8 (Ar-C, C=C, C=N, C-Cl).

Complex 8. ¹H-NMR (DMSO-d₆): δ = 7.33 (t, 4H, J = 4.5 Hz, pyrimidine C₅H), 7.36 (d, 4H, J = 4.5 Hz, p-Chloroaniline C₃H), 7.46 (d, 4H, J = 9.9 Hz, p-Chloroaniline C₂H), 7.81 (d, 4H, J = 4.5 Hz, pyrimidine C4,6H), 9.55 (s, 2H, NH), 11.20 (s, 2H, NH). ¹³C-NMR (DMSO-d₆): δ = 113.5, 119.2, 122.9, 130.5, 145.5, 149.4, 153.1, 157.4, 162.7, 165.6, and 171.8 (Ar-C, C=C, C=N, C-Cl).

The ¹H-NMR spectral data of the synthesized Pt(IV) and Pd(II) complexes have been shifted to downfield because of formation metal chelating through the nitrogen atoms of triazine, pyrimidine, thiazole, and triazole rings.

3.5. Thermogravimetric Studies

Thermal analyses (TG-DTG) were performed under N₂ atmosphere. The thermogravimetric and differential thermogravimetric curves of the synthesized Pt(IV) (1–4) and Pd(II) (5–8) complexes are shown in Figures 5 and 6. Table 3 refereed to the thermal decomposition assignments of all complexes from room temperature till 1000°C.

Table 3: Thermo gravimetric data of Pt(IV) and Pd(II) triazine complexes.

Complexes

Total weight loss
Total residual

Weight loss, %
Assignments
Residue, %
Assignments

1
100
74
3H₂O uncoord
26
PtO₂ + Few carbons

300, 380, 600
2L¹+6Cl₂

2
100
70
3H₂O coord
30
PtO₂ + Few carbons

310, 380, 580
2L²+6Cl₂

3
100
68
3H₂O coord
32
PtO₂ + Few carbons

370, 580, 700
2L³+6Cl₂

4
100
72
4H₂O uncoord
28
PtO₂ + Few carbons

280, 380, 700
2L⁴+4Cl₂+2H₂O

5
230, 360, 620
75
2L¹+3Cl₂+6H₂O
25
PdO + Few carbons

6
360, 420, 800
75
2L²+3Cl₂+6H₂O
25
PdO + Few carbons

7
300, 360, 650
78
2L³+3Cl₂+6H₂O
22
PdO + Few carbons

8
380, 620, 800
82
2L⁴+2Cl₂+4H₂O
18
PdO + Few carbons

(a) Complex 1

(b) Complex 2

(c) Complex 3

(d) Complex 4

Figure 5: TGA-DTG curves of Pt(IV) complexes 1–4.

(a) Complex 5

(b) Complex 6

(c) Complex 7

(d) Complex 8

Figure 6: TGA-DTG curves of Pd(II) complexes 5–8.

3.6. X-Ray Diffraction Spectra

XRD diffraction patterns of the solid Pt(IV) and Pd(III) triazine complexes have been displayed in Figure 7. The diffraction patterns of new Pt(IV) and Pd(II) complexes at 2θ values are (11.094, 13.585, 15.041, 15.840, 19.929, 22.276, 23.198, 30.360, 33.693, 39.780, 47.720°), (5.082, 12.894, 19.845, 29.786°), (12.861, 16.426, 17.438, 19.695, 22.031, 26.390, 35.265°), (13.078, 19.773, 29.893, 35.342, 45.307°), (16.712, 27.173, 28.562, 31756, 37.958, 45.472, 56.157, 57.440, 59.071°), (4.948, 10.051, 13.820, 16.705, 17.357, 19.608, 20.512, 24.738, 26.567, 27.247, 29.786, 37.806, 56.168, 57.332, 59.199°), (5.527, 11.110, 16.704, 18.605, 27.263, 28.547, 29.090, 33.708, 37.678, 51.690, 56.690, 56.193, 57.367, 59.096, 79.472°), and (16.839, 27.384, 28.680, 37.851, 48.826, 50.279, 56.287, 57.573, 59.194°) for the complexes 1–8, respectively. The particle size was estimated using Scherrer’s equation [43]. The XRD patterns due to metallic platinum are agreement with JCPDS PDF card no. 04-0802 standard card [44] with (111), (200), (220) planes, respectively. Powder XRD patterns of Pd(II) complexes are shown in Figure 7. These spectra included distinguish patterns at 2θ = 37.678, 51.690, 59.096, and 79.472° assigned to (111), (200), (220), and (311) of Pd metal with fcc structure matching with JCPDS file no. 87-0638 [45]. This result confirms the presence of metallic Pd with fcc structure. The grain sizes of platinum(IV) and palladium(II) complexes are existed within 42–50 and nm according to highest distinguish peaks.

(a) XRD patterns of [Pt₃(L¹)₂(Cl)₉(H₂O)₃].3Cl.3H₂O (1) complex

(b) XRD patterns of [Pd₃(L³)₂(H₂O)₆] .3Cl₂ (7) complex

Figure 7

3.7. Scanning and Transmission Electron Microscopes

The SEM photos of Pt(IV) and Pd(II) complexes 1–8 are shown in Figure 8. These images reveal that the surface of all complexes is homogeneous with various morphological view because of the role of Pt(IV) and Pd(II) metal ions in the rearrangement of grains.

Figure 8: SEM photos of Pt(IV) and Pd(II) complexes 1–8.

According to the TEM technique (Figure 9), the average of particle size of platinum(IV) complexes existed within 15–92 nm.

Figure 9: TEM photos of Pt(IV) complexes 1–4.

3.8. Biological Studies

3.8.1. Antibacterial Assessments

Table 4 refers to the antibacterial activity of the free triazine ligands (L¹, L², L³, and L⁴) comparable with its platinum(IV) and palladium(II) complexes (1–8) against Staphylococcus aureus (G+), Escherichia coli (G−), and fungi (Aspergillus flavus and Candida albicans). All complexes beside the four free ligands which have not any significant inhibitory against both respected fungi except for complexes of 1, 3, 5, 7, and 8 have moderate inhibitory against Aspergillus flavus. All complexes have a moderate bacterial inhibitory in comparison with ampicillin standard drug. The variation in the activity of different metal complexes against different microorganisms depends on either the impermeability of the cells of the microbes or the differences in ribosomes in microbial cells [46, 47].

Table 4: Inhibition zone diameter of free ligands and its Pt(IV) and Pd(II) complexes.

Sample
Inhibition zone diameter (mm/mg Sample)

Bacteria
Fungi

Escherichia coli 
(G⁻)
Staphylococcus aureus 
(G⁺)
Aspergillus flavus 
(Fungus)
Candida albicans 
(Fungus)

Standard
Ampicillin: Antibacterial agent
30
24
--
--

Amphotericin B: Antifungal agent
--
--
16
21

Control: DMSO
0.0
0.0
0.0
0.0

L¹
11
10
10
0.0

L²
0.0
0.0
0.0
0.0

L³
0.0
0.0
0.0
0.0

L⁴
15
10
0.0
0.0

1
19
18
16
0.0

2
12
11
0.0
0.0

3
24
23
12
0.0

4
14
12
0.0
0.0

5
14
15
15
0.0

6
11
11
0.0
0.0

7
16
17
12
0.0

8
14
15
11
0.0

Ampicillin and amphotericin B are standards of antibacterial and antifungal agents.

3.8.2. Anticancer Assessments

Table 5 and Figure 10 refer to the IC₅₀ results of the free triazine ligands and its Pt(IV) complexes. From these data, it is clearly deduced that the [Pt₃(L³)₂(Cl)₉(H₂O)₃].3Cl (3) complex has an efficiency against human colon and human lung cancer A549 cell lines rather than its corresponding free L³ ligand.

Table 5: IC₅₀ activity of the free ligands and its Pt(IV) complexes.

Against human colon cancer cell lines

Concentration (μg/mL)
Viability (%)

L¹
1
L²
2
L³
3
L⁴
4

100
65
66
61
72.7
55.3
6.4
35.5
44.6

50
70
67.8
64.4
81.7
60
31.8
41.4
56.6

10
72
70
69.3
82.5
65
62.9
66.8
71.5

IC₅₀
170
461
277
259
162.8
27
50.7
79

Against human lung cancer A549 cell lines

Concentration (μg/mL)
Viability (%)

L¹
1
L²
2
L³
3
L⁴
4

150
82.4
100
96
100
100
44.6
100
77.7

100
83.4
100
98.7
100
100
61.7
100
100

50
86
100
100
100
100
66.5
100
100

10
98.7
100
100
100
100
100
100
100

IC₅₀
431.4
-
1305.7
-
-
128
-
212

(a) Images of the neutral red cytotoxicity test of the free L¹, L², L³, and L⁴ ligands and their Pt(IV) complexes (1–4) against human colon cancer cell lines

(b) Images of the neutral red cytotoxicity test of the free L¹, L², L³, and L⁴ ligands and their Pt(IV) complexes (1–4) against human lung cancer A549 cell lines

Figure 10

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University. The authors would like to thank Professor Dr. Ibrahim A. Alsarra for his scientific guidance; also they would like to thank the Assistant Researcher Mrs. Lina Almaliky for her participation in the preparation of experimental work in lab.

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