Synthesis, structural characterization, and cytotoxic evaluation of monofunctional cis-[Pt(NH3)2(N7-guanosine/2'-deoxyguanosine)X] (X = Cl, Br, I) complexes with anticancer potential

A series of new monofunctional platinum(II) complexes of the type cis-[Pt(NH3)2(N7-guanosine/2'-deoxyguanosine)X] (X = Cl, Br, I) were synthesized and characterized using NMR spectroscopy, mass spectrometry, and ICP-atomic emission spectroscopy. These complexes are designed to address the limitations of conventional bifunctional platinum-based drugs, such as cisplatin, which include issues with cytotoxicity and selectivity towards cancer cells. By incorporating guanosine or 2'-deoxyguanosine ligands and varying halido substituents, the study investigated how structural modifications influence the selectivity and cytotoxicity of the different analogues. To evaluate the anticancer potential of the newly synthesized platinum derivatives, various cancer cell lines were tested, including renal (Caki-1), uterine cervix (HeLa), breast (MCF-7), lymphoma (Raji), and mesothelioma (ZL-34). Additionally, selectivity against tumor cells was assessed by comparing their cytotoxic effects to those in the healthy, immortalized HK-2 cell line, a proximal tubular cell line derived from a normal human adult male kidney. Cytotoxicity analysis revealed that bromido-substituted Pt(II) complexes exhibited superior cytotoxicity across several cancer cell lines, particularly in HeLa and Raji cells, compared to their chlorido- and iodido-substituted counterparts. The iodido complexes exhibited higher efficacy against MCF-7 breast cancer cells, suggesting tumor-specific selectivity. Notably, these complexes demonstrated lower cytotoxicity in healthy cells compared to most of the tested cancer cell lines, as reflected by generally favorable selectivity indices (SI) relative to cisplatin.

First Attempts of the Use of 195Pt NMR of Phenylbenzothiazole Complexes as Spectroscopic Technique for the Cancer Diagnosis

Platinum complexes have been studied for cancer treatment for several decades. Furthermore, another important platinum characteristic is related to its chemical shifts, in which some studies have shown that the ¹⁹⁵Pt chemical shifts are very sensitive to the environment, coordination sphere, and oxidation state. Based on this relevant feature, Pt complexes can be proposed as potential probes for NMR spectroscopy, as the chemical shifts values will be different in different tissues (healthy and damaged) Therefore, in this paper, the main goal was to investigate the behavior of Pt chemical shifts in the different environments. Calculations were carried out in vacuum, implicit solvent, and inside the active site of P13K enzyme, which is related with breast cancer, using the density functional theory (DFT) method. Moreover, the investigation of platinum complexes with a selective moiety can contribute to early cancer diagnosis. Accordingly, the Pt complexes selected for this study presented a selective moiety, the 2-(4′aminophenyl)benzothiazole derivative. More specifically, two Pt complexes were used herein: One containing chlorine ligands and one containing water in place of chlorine. Some studies have shown that platinum complexes coordinated to chlorine atoms may suffer hydrolyses inside the cell due to the low chloride ion concentration. Thus, the same calculations were performed for both complexes. The results showed that both complexes presented different chemical shift values in the different proposed environments. Therefore, this paper shows that platinum complexes can be a potential probe in biological systems, and they should be studied not only for cancer treatment, but also for diagnosis.

Is hydrogen electronegativity higher than Pauling’s value? New clues from the13C and29Si NMR chemical shifts of [CHF3] and [SiHF3] molecules

We previously demonstrated that the δ NMR chemical shift of central NMR active atoms (A), in simple halido [AXn] (A=C, Si, Ge, Sn, Pb, Pt; Xn = combination of n halides, n = 4 or 6) derivatives, could be directly related to X radii overall sum, Σ(rL). Further correlation have also been observed for tetrahedral [AX4] (A=C, Si; X4 = combination of four halides) compounds where the X Pauling electronegativities sum,Σ(χLPau),$\Sigma (\chi _L^{{\rm{Pau}}}),$exceeds a specific value (≈12.4). In this work, we focused on these latter systems considering the H vs. X substitution. The analysis of the literature reported δ(13C) and δ(29Si) NMR chemical shift for the mono hydrogenated derivatives and in particular for [CHF3] and [SiHF3], characterized by the lowest Σ(rL) and the highestΣ(χLPau),$\Sigma (\chi _L^{{\rm{Pau}}}),$suggests a revised value for the H electronegativity ranking with respect to Pauling’s.

Insertion of terminal alkyne into Pt-N bond of the square planar [PtI2(Me2phen)] complex

The reactivity of [PtX₂(Me₂phen)] complexes (X = Cl, Br, I; Me₂phen = 2,9-dimethyl-1,10-phenanthroline) with terminal alkynes has been investigated. Although the dichlorido species [PtCl₂(Me₂phen)] exhibits negligible reactivity, the bromido and iodido derivatives lead in short time to the formation of five-coordinate Pt(ii) complexes of the type [PtX₂(Me₂phen)(η²-CH[triple bond, length as m-dash]CR)] (X = Br, I; R = Ph, n-Bu), in equilibrium with the starting reagents. Similar to analogous complexes with simple acetylene, the five coordinate species can also undergo dissociation of an halido ligand and formation of the transient square-planar cationic species [PtX(Me₂phen)(η²-CH[triple bond, length as m-dash]CR)]⁺. This latter can further evolve to give an unusual, sparingly soluble square planar product where the former terminal alkyne is converted into a :C[double bond, length as m-dash]C(H)(R) moiety with the α-carbon bridging the Pt(ii) core with one of the two N-donors of coordinated Me₂phen. The final product [PtX₂{κ²-N,C-(Z)-N[combining low line]1-N10-C[combining low line][double bond, length as m-dash]C(H)(R)}] (N1-N10 = 2,9-dimethyl-1,10-phenanthroline; X = Br, I) contains a Pt-N-C-C-N-C six-membered chelate ring in a square planar Pt(ii) coordination environment.

73Ge, 119Sn and 207Pb: general cooperative effects of single atom ligands on the NMR signals observed in tetrahedral [MXnY4-n] (M = Ge, Sn, Pb; 1 ≤ n ≤ 4; X, Y = Cl, Br, I) coordination compounds of heavier XIV group elements

An inverse linear relationship between ⁷³Ge, ¹¹⁹Sn and ²⁰⁷Pb NMR chemical shifts and the overall sum of ionic radii of coordinated halido ligands has been discovered in tetrahedral [MX_nY_4-n] (M = Ge, Sn, Pb; 1 ≤ n ≤ 4; X, Y = Cl, Br, I) coordination compounds. This finding is consistent with a previously reported correlation found in octahedral, pentacoordinate and square planar platinum complexes. The effect of the coordinated halido ligands acting on the metal as shielding conducting rings is therefore confirmed also by ⁷³Ge, ¹¹⁹Sn and ²⁰⁷Pb NMR spectroscopy.

NMR effective radius of hydrogen in XIV group hydrides evaluated by NMR spectroscopy

In the [ABr_nI_m] (A = C, Si, Ge, Sn; n + m = 4) compounds, with the heavier halido ligands bonded to the central IV group elements, the ¹³C, ²⁹Si, ⁷³Ge and ¹¹⁹Sn NMR chemical shifts were found to be linearly related to the bonded halides ionic radii overall sum, ∑(r_h). The ²⁰⁷Pb NMR chemical shift of the unstable [PbH₄] hydride could be calculated.

Halide Influence on Molecular and Supramolecular Arrangements of Iron Complexes with a 3,5-Bis(2-Pyridyl)-1,2,4,6-Thiatriazine Ligand

A series of iron centered complexes, namely, [Fe(Py2TTA)Cl2] (1), [Fe(Py2TTA)Br2] (2), and [Fe(μ-F)(Py2TTAO)F]∞ (3), were isolated via complexation of 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazine (Py2TTAH) with various ferric halides (e.g., FeF3, FeCl3, and FeBr3). Comparison of the optical and electrochemical spectroscopy, structural analysis, and magnetic studies reveal numerous similarities between the chlorido (1) and bromido (2) derivatives, which crystallize as discrete five-coordinate iron centered complexes with coordination geometries that are intermediate between trigonal bipyramidal and square base pyramid. Conversely, the fluorido derivative (3) results in a completely different structure due to oxidation of the ligand and the formation of a one-dimensional coordination polymer held together through a bridging fluoride ion. Consequently, the spectroscopic and magnetic behavior of 3 differs significantly compared with 1 and 2. Complexes 1 and 2 exhibit paramagnetic properties typical for a mononuclear S = 5/2 system with weak intermolecular antiferromagnetic interactions at low temperatures, whereas complex 3 demonstrates significant exchange couplings within the chain and weak antiferromagnetic interchain interactions, which stabilize a canted antiferromagnetic state below 4.2 K.