Synthesis and Structural Characterization of New Cu(I) Complexes with the Antithyroid Drug 6-n-Propyl-thiouracil. Study of the Cu(I)-Catalyzed Intermolecular Cycloaddition of Iodonium Ylides toward Benzo[b]furans with Pharmaceutical Implementations

Rational Coformer Selection in the Development of 6-Propyl-2-thiouracil Pharmaceutical Cocrystals

Pharmaceutical multicomponent solids have proved to efficiently modulate the physicochemical properties of active pharmaceutical ingredients. In this context, polyphenols are interesting coformers for designing pharmaceutical cocrystals due to their wide safety profile and interesting antioxidant properties. The novel 6-propyl-2-thiouracil multicomponent solids have been obtained by mechanochemical synthesis and fully characterized by powder and single-crystal X-ray diffraction methods. The analysis of supramolecular synthons has been further performed with computational methods, with both results revealing a robust supramolecular organization influenced by the different positions of the hydroxyl groups within the polyphenolic coformers. All novel 6-propyl-2-thiouracil cocrystals show an enhanced solubility profile, but unfortunately, their thermodynamic stability in aqueous media is limited to 24 h.

Coupling 6-chloro-3-methyluracil with copper: structural features, theoretical analysis, and biofunctional properties

As nucleobases in RNA and DNA, uracil and 5-methyluracil represent a recognized class of bioactive molecules and versatile ligands for coordination compounds with various biofunctional properties. In this study, 6-chloro-3-methyluracil (Hcmu) was used as an unexplored building block for the self-assembly generation of a new bioactive copper(II) complex, [Cu(cmu)₂(H₂O)₂]·4H₂O (1). This compound was isolated as a stable crystalline solid and fully characterized in solution and solid state by a variety of spectroscopic methods (UV-vis, EPR, fluorescence spectroscopy), cyclic voltammetry, X-ray diffraction, and DFT calculations. The structural, topological, H-bonding, and Hirshfeld surface features of 1 were also analyzed in detail. The compound 1 shows a distorted octahedral {CuN₂O₄} coordination environment with two trans cmu^- ligands adopting a bidentate N,O-coordination mode. The monocopper(II) molecular units participate in strong H-bonding interactions with water molecules of crystallization, leading to structural 0D → 3D extension into a 3D H-bonded network with a tfz-d topology. Molecular docking and ADME analysis as well as antibacterial and antioxidant activity studies were performed to assess the bioactivity of 1. In particular, this compound exhibits a prominent antibacterial effect against Gram negative (E. coli, P. aeruginosa) and positive (S. aureus, B. cereus) bacteria. The obtained copper(II) complex also represents the first structurally characterized coordination compound derived from 6-chloro-3-methyluracil, thus introducing this bioactive building block into a family of uracil metal complexes with notable biofunctional properties.

Structural, photolysis and biological studies of novel mixed metal Cu(I)-Sb(III) mixed ligand complexes

Direct reaction of copper(I) halides with triphenylstibine (tpSb) and 2-mercapto-thiazolidine (tzdtH) in 1:1:1 molar ratio, results in the formation of the [CuX(μ2-S)-tzdtH)(tpSb)]2 (X=Cl (1), Br (2) and I (3)) complexes. The complexes have been characterized by melting point, FT-IR, UV-vis, (1)H NMR spectroscopic data and X-ray crystallography. Complexes 1-3 are di-nuclear and they are the first examples of mixed metals (CuSb), mixed ligand (thioamide, stibine and halogen) containing complexes. Two μ2-S (1-3) atoms bridge the two copper(I) ions with tetrahedral geometry. The coordination sphere around copper atoms is completed by one Sb from tpSb and one halogen (chlorine, bromine or iodine) atom. Intermolecular via N-H⋯X (Cl (1) and Br (2)) interactions stabilized the assembly. The short coppercopper bond distances of 3.103 (1), 3.061 (2) and 3.110, 3.108 (3) Ǻ found in 1-3 indicates d(10)-d(10) interaction between metal centers. The complexes exhibit high photo-sensitivity to UVB light. The complexes 1-3 and the already known [Cu(μ2-I)(tpSb)2]2 (4) were tested for their in vitro cytotoxic activity against human cancer cell lines: MCF-7 (breast, estrogen receptor (ER) positive), MDA-MB-231 (breast, estrogen receptor (ER) negative) and MRC-5 (normal human fetal lung fibroblast cells) with sulforhodamine B (SRB) colorimetric assay. Since estrogen receptors (ERs) are located in MCF-7, in contrast to MDA-MB-231 cells, the estrogenic effect of 1-4 on MCF-7 cells was studied by the mean of methylene blue assay. Compound 4 exhibits the highest estrogenic effect. None of 1-4 exceeds the activity of cisplatin against MCF-7 cells, but they are more active than cisplatin towards MDA-MB-231 cells. UVB light increases the effectiveness of complexes on MCF-7 cells which in the case of 4 is up to 28% higher than the corresponding initial complex (without irradiation).

Luminescent mononuclear mixed ligand complexes of copper(I) with 5-phenyl-2,2'-bipyridine and triphenylphosphine

Reaction of 5-phenyl-2,2'-bipyridine (L) with a mixture of CuI or [Cu(CH3CN)4]BF4 and PPh3 leads to mononuclear heteroleptic complexes [CuL(PPh3)I] (1) and [CuL(PPh3)2]BF4 (2). According to X-ray diffraction, L crystallizes in the monoclinic space group P21/n, exhibiting a disorder over four orientations. Complexes 1 and 2 crystallize in the monoclinic space groups P21/c and P21, respectively. 1 comprises a discrete neutral molecule, while 2 has an ionic structure containing [CuL(PPh3)2](+) and BF4(-). Both structures reveal that each tetracoordinated copper(i) atom is linked to two nitrogen atoms of L, one iodide and one PPh3 in the structure of 1, or two PPh3 in the structure of 2 with the formation of a distorted tetrahedral coordination core. The structure of 2 is additionally stabilized by a weak intramolecular ππ stacking interaction formed between two adjacent phenyl rings of two PPh3 ligands. Hirshfeld surface analysis showed that the structures of both complexes are mainly characterized by HH and CH contacts as well as by IH in the structure of 1 and FH in the structure of 2. The 2D fingerprint plots of two different molecules in the structure of L showed that both molecules exhibit contacts for ππ stacking interactions. The factors important for the stability of 1 and 2 were further quantitatively and qualitatively characterized by the charge and energy decomposition method ETS-NOCV. According to diffuse reflectance spectroscopy in the solid state, free L exhibits bands exclusively in the UV region, while the spectra of 1 and 2 also contain bands in the visible range up to about 500 and 600 nm. All three compounds were found to be emissive in the solid state. DFT calculations have shown that, while emission of L is due to the ligand-centered π→π* transition, luminescence of 1 and 2 was assigned to a (M + X)LCT and MLCT excited states, respectively.

Mono- and binuclear copper(I) complexes of thionucleotide analogues and their catalytic activity on the synthesis of dihydrofurans

The reaction of copper(I) halides with 2-thiouracil (TUC), 6-methyl-2-thiouacil (MTUC), and 4-methyl-2-mercaptopyrimidine (MPMTH) in the presence of triphenylphosphine (tpp) in a 1:1:2 molar ratio results in a mixed-ligand copper(I) complex with the formulas [Cu2(tpp)4(TUC)Cl] (1), [Cu2(tpp)4(MTUC)Cl] (2), [Cu(tpp)2(MPMTH)Cl]·(1)/2CH3OH (3), [Cu(tpp)2(MTUC)Br] (4), and [Cu(tpp)2(MTUC)I]·(1)/2CH3CN (5). The complexes have been characterized by FT-IR, (1)H NMR, and UV-vis spectroscopic techniques and single-crystal X-ray crystallography. Complexes 1 and 2 are binuclear copper(I) complexes. Two phosphorus atoms from tpp ligands are coordinated to the copper(I) ions, forming two units that are linked to each other by a deprotonated TUC or MTUC chelating ligand through a sulfur bridge. A linear Cu-S-Cu moiety is formed. The tetrahedral geometry around the metal centers is completed by the nitrogen-donor atom from the TUC or MTUC ligand for the one unit, while for the other one, it is completed by the chloride anion. Two phosphorus atoms from two tpp ligands, one sulfur atom from MPMTH or MTUC ligand, and one halide anion (Cl, Br, and I) form a tetrahedron around the copper ion in 3-5 and two polymorphic forms of 4 (4a and 4b). In all of the complexes, either mono- or binuclear intramolecular O-H···X hydrogen bonds enhance the stability of the structures. On the other hand, in almost all cases of mononuclear complexes (with the exception of a symmetry-independent molecule in 4a), intermolecular NH···O hydrogen-bonding interactions lead to dimerization. Complexes 1-5 were studied for their catalytic activity for the intermolecular cycloaddition of iodonium ylides toward dihydrofuran formation by HPLC, (1)H NMR, and LC-HRMS spectroscopic techniques. The results show that the geometry and halogen and ligand types have a strong effect on the catalytic properties of the complexes. The highest yield of dihydrofurans was obtained when "linear" complexes 1 and 2 were used as the catalysts. The activity of the metal complexes on the copper(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide is rationalized through electronic structure calculation methods, and the results are compared with the experimental ones.