Abstract
CuBr(PPh3)2(4,6-dimethylpyrimidine-2-thione) (Cu-L) was synthesized by stirring CuBr(PPh3)3 and 4,6-dimethylpyrimidine-2-thione in dichloromethane. The crystal structure of Cu-L was obtained, and indicated that the complex adopts a distorted tetrahedral structure with several intramolecular hydrogen bonds. Moreover, a centrosymmetric dimer is formed by the intermolecular hydrogen bonding of the bromine acceptor created by symmetry operation 1−x, 1−y, 1−z to the methyl group (D3 = C42) of the pyrimidine–thione ligand. HSA-binding of Cu-L and its ligand were evaluated, revealing that Cu-L binds to HSA differently than its ligand. The HSA-bindings were modeled by molecular docking, which suggested that Cu-L binds to the II A domain while L binds between the I B and II A domains. Anticancer activities toward OVCAR-3 and HeLa cell lines were tested and indicated the significance of the copper center in enhancing the cytotoxic effect; negligible toxicities for L and Cu-L were observed towards a non-cancer cell line. The current study highlights the potential of copper(I)-phosphine complexes containing thione ligands as therapeutic agents.
Highlights
The coordination chemistry of N-heterocyclic-thiones with their tautomerization between the –NH–C(=S)– and –N=C(–SH)– forms was investigated with different transition metals, showing monomeric, dimeric, oligomeric, and polymeric complexes [1,2,3]
The crystal structure of the human serum albumin receptor was downloaded from the protein data bank (PDB: 1H9Z) [40]
Several intramolecular hydrogen bonds are established, while a centrosymmetric dimer is formed by the intermolecular hydrogen bonding of the bromine acceptor created by symmetry operation 1−x, 1−y, 1−z to the methyl group (D3 = C42) of the pyrimidine–thione ligand
Summary
The coordination chemistry of N-heterocyclic-thiones with their tautomerization between the –NH–C(=S)– and –N=C(–SH)– forms was investigated with different transition metals, showing monomeric, dimeric, oligomeric, and polymeric complexes [1,2,3]. Tri(p-tolyl)phosphine was employed with CuCl and 1,3-thiazolidine2-thione (equimolar ratio) for producing dimeric complexes with bridging thiones [8]. Increasing the cone angle of the phosphine by employing tri(m-tolyl)phosphine produced dimeric complexes with either thiones or halides bridging ligands [9]. A series of mixed-ligand mono- and dinuclear copper(I) halides with imidazolidine-2-thiones and triphenylphosphine were accessed by adopting a molar ratio of 1:2:1, producing three types of complexes: mononuclear tetrahedral [CuX(thione)(PPh3)2], halogen- and sulfur-bridged dimers, [Cu(μCl)(κ1-S-thione)(PPh3)]2 and [CuI(μ-S-thione)(PPh3)]2 [11]. Homoleptic and mixed-ligand copper(I) phosphine complexes have been intensively investigated as anticancer agents [17]. Utilizing polypyridyl ligands in synthesizing complexes of the general formula [Cu(PPh3)2(NN)]NO3 were achieved, highlighting IC50 values against several cancer cell lines in the range 0.32–5.25 μM. The cytotoxic effects of the complex against two cell lines are presented and compared to that of cisplatin
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