Search Results (13)

2,2-Bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethanol (HL) is a heteroscorpionate ligand capable of coordinating metal ions through two nitrogen atoms and one oxygen atom. We report a base free synthetic route to metal complexes of L and explore the resulting structural diversity. Notably, complex composition varies substantially depending on the metal ion, including dinuclear molybdenum species and distinct coordination behavior with silicon and copper. The isolated compounds include the dinuclear, oxygen-bridged complexes (LMoO₂)₂O and (LMoO)(μ-O)₂, as well as the mononuclear complexes LTi(NMe₂)₃, LZrCl₃, LGeCl₃, LWO₂Cl, LCu(acetate)₂H, and LSiMe₂Cl. Single crystal X-ray diffraction reveals that the bulky complex structures generate cavities in the crystal lattice, frequently occupied by solvent molecules. The titanium, zirconium, molybdenum, tungsten, and germanium complexes exhibit octahedral coordination, while structural peculiarities are observed for copper and silicon. The copper(II) complex shows a distorted octahedral geometry with one elongated ligand bond; the silicon complex is pentacoordinated in the solid state. Additional characterization includes melting points, NMR, and IR spectroscopy. The developed synthetic strategy provides a straightforward and versatile route to heteroscorpionate metal complexes. Full article

Bis(pyrazol-1-yl)acetic acid (HC(pz)₂COOH) and bis(3,5-dimethyl-pyrazol-1-yl)acetic acid (HC(pz^Me2)₂COOH) were converted into the methyl ester derivatives 1 (L^OMe) and 2 (L^2OMe), respectively, and were used for the preparation of Cu(I) and Cu(II) complexes 3–10. The copper(II) complexes were prepared by the reaction of CuCl₂·2H₂O or CuBr₂ with ligands 1 and 2 in methanol solution. The copper(I) complexes were prepared by the reaction of Cu[(CH₃CN)₄]PF₆ and 1,3,5-triaza-7-phosphaadamantane (PTA) or triphenylphosphine with L^OMe and L^2OMe in acetonitrile solution. Synchrotron radiation-based complementary techniques (XPS, NEXAFS, and XAS) were used to investigate the electronic and molecular structures of the complexes and the local structure around copper ions in selected Cu(I) and Cu(II) coordination compounds. All Cu(I) and Cu(II) complexes showed a significant in vitro antitumor activity, proving to be more effective than the reference drug cisplatin in a panel of human cancer cell lines, and were able to overcome cisplatin resistance. Noticeably, Cu complexes appeared much more effective than cisplatin in 3D spheroid cultures. Mechanistic studies revealed that the antitumor potential did not correlate with cellular accumulation but was consistent with intracellular targeting of PDI, ER stress, and paraptotic cell death induction. Full article

The present article demonstrates selective cytotoxicity against cancer cells of the complexes [Co(L^D)₂]I₂∙CH₃OH (1), [CoL^D(NCS)₂] (2) and [VOL^D(NCS)₂]∙C₆H₅CH₃ (3) containing the dipodal tridentate ligand LD = N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)amine), formed in situ. All tested complexes expressed greater anticancer activities and were less toxic towards noncancerous cells than cisplatin. Cobalt complexes (1 and 2) combined high cytotoxicity with selectivity towards cancer cells and caused massive tumour cell death. The vanadium complex (3) induced apoptosis specifically in cancer cells and targeted proteins, controlling their invasive and metastatic properties. The presented experimental data and computational prediction of drug ability of coordination compounds may be helpful for designing novel and less toxic metal-based anticancer species with high specificities towards tumour cells. Full article

Two silver nitrate complexes with bisphosphines were obtained and characterized: [Ag(dcypm)]₂(NO₃)₂ (1; dcypm = bis(dicyclohexylphosphino)methane) and [Ag(dppm)]₂(Me₂Pz^H)_n(NO₃)₂ (n = 1, 2a; n = 2, 2b; dppm = bis(diphenylphosphino)methane, Me₂Pz^H = 3,5-dimethylpyrazole). The steric repulsions of bulky cyclohexyl substituents prevent additional ligand coordination to the silver atoms in 1. Compounds obtained feature the bimetallic eight-member cyclic core [AgPCP]₂. The intramolecular argenthophilic interaction (d(Ag···Ag) = 2.981 Å) was observed in complex 1. In contrast, the coordination of pyrazole led to the elongation of Ag···Ag distance to 3.218(1) Å in 2a and 3.520 Å in 2b. Complexes 1 and 2a possess phosphorescence both in the solution and solid state. Time-dependent density-functional theory (TD-DFT) calculations demonstrate the origin of their different emission profile. In the case of 1, upon excitation, the electron leaves the Ag–P bonding orbital and locates on the intramolecular Ag···Ag bond (metal-centered character). Complex 2a at room temperature exhibits a phosphorescence originating from the ³(M + L^P+N)L^PhCT state. At 77 K, the photoluminescence spectrum of complex 2a shows two bands of two different characters: ³(M + L^P+N)L^PhCT and ³LC^Ph transitions. The contribution of Ag atoms to the excited state in both complexes 2a and 2b decreased relative to 1 in agreement with the structural changes caused by pyrazole coordination. Full article

In the present article, copper(I) complexes of bis(pyrazol-1-yl) carboxylic acid (LH), bis(3,5-dimethylpyrazol-1-yl) carboxylic acid (L²H), and bis(pyrazol-1-yl) acetates conjugated with an N-methyl-d-aspartate (NMDA) receptor antagonist (L^NMDA or L^2NMDA) and phosphane ligands (triphenylphosphine or 1,3,5-triaza-7-phosphaadamantane) were synthesized. The selection of an NMDA antagonist for the coupling with LH and L²H was suggested by the observation that NMDA receptors are expressed and play a role in different types of cancer models. All the new complexes showed a significant antitumor activity on a panel of human tumor cell lines of different histology, with cisplatin-sensitive, cisplatin-resistant, or multi-drug-resistant phenotype. Their half maximal inhibitory concentration (IC₅₀) values were in the low- and sub-micromolar range and, in general, significantly lower than that of cisplatin. Interestingly, the fact that all the complexes proved to be significantly more active than cisplatin even in three-dimensional (3D) spheroids of H157 and BxPC3 cancer cells increased the relevance of the in vitro results. Finally, morphological analysis revealed that the most representative complex 8 induced a massive swelling of the endoplasmic reticulum (ER) membrane, which is a clear sign of ER stress. Full article

Copper(II) complexes of bis(pyrazol-1-yl)- and bis(triazol-1-yl)-acetate heteroscorpionate ligands have been synthesized. The copper(II) complexes [HC(COOH)(pz^Me2)₂]Cu[HC(COO)(pz^Me2)₂]·ClO₄, [HC(COOH)(pz)₂]₂Cu(ClO₄)₂ (pz^Me2 = 3,5-dimethylpyrazole; pz = pyrazole) were prepared by the reaction of Cu(ClO₄)₂·6H₂O with bis(3,5-dimethylpyrazol-1-yl)acetic acid (HC(COOH)(pz^Me2)₂) and bis(pyrazol-1-yl)acetic acid (HC(COOH)(pz)₂) ligands in ethanol solution. The copper(II) complex [HC(COOH)(tz)₂]₂Cu(ClO₄)₂·CH₃OH (tz = 1,2,4-triazole) was prepared by the reaction of Cu(ClO₄)₂·6H₂O with bis(1,2,4-triazol-1-yl)acetic acid (HC(COOH)(tz)₂) ligand in methanol solution. The synthesized Cu(II) complexes, as well as the corresponding uncoordinated ligands, were evaluated for their cytotoxic activity in monolayer and 3D spheroid cancer cell cultures with different Pt(II)-sensitivity. The results showed that [HC(COOH)(pz^Me2)₂]Cu[HC(COO)(pz^Me2)₂]·ClO₄ was active against cancer cell lines derived from solid tumors at low IC₅₀ and this effect was retained in the spheroid model. Structure and ultra-structure changes of treated cancer cells analyzed by Transmission Electron Microscopy (TEM) highlighted the induction of a cytoplasmic vacuolization, thus suggesting paraptotic-like cancer cell death triggering. Full article

Five of six new Zn(II) and Cu(II) complexes were active in the ring-opening polymerization (ROP) of ε-caprolactone (CL) under solvent-free conditions, producing polycaprolactones (PCLs) of high crystallinity with molecular weights between 22,900 and 38,700 g mol⁻¹ and decomposition temperatures above 260 °C. ¹H NMR analysis demonstrated that the PCLs obtained were mainly linear, having hydroxymethylene groups at the chain ends. The results obtained indicated a significant improvement in terms of the ratio of monomer:initiator compared to related Cu(II) and Zn(II) complexes. In addition, the structures of the complexes 1 and 4 were determined by single-crystal X-ray diffraction. The synthesis and full characterization of all complexes are described in this paper. Full article

Scorpionate ligands Tp* (hydrotris(3,5-dimethylpyrazol-1-yl)borate) and To^M (tris(4,4-dimethyloxazolin-2-yl)phenylborate) complexes of cobalt(II) with bidentate ligands were synthesized. Both Tp* and To^M coordinate to cobalt(II) in a tridentate fashion when the bidentate ligand is the less hindered acetylacetonate. In crystal structures, the geometry of cobalt(II) supported by the N₃O₂ donor set in the Tp* complex is a square-pyramid, whereas that in the To^M complex is close to a trigonal-bipyramid. Both Tp*- and To^M-acac complexes exhibit solvatochromic behavior, although the changing structural equilibria of these complexes in MeCN are quite different. In the bis(1-methylimidazol-2-yl)methylphenylborate (L^Ph) complexes, Tp* retains the tridentate (к³) mode, whereas To^M functions as the bidentate (к²) ligand, giving the tetrahedral cobalt(II) complex. The bowl-shaped cavity derived from the six methyl groups on To^M lead to susceptibility to the bulkiness of the opposite bidentate ligand. The entitled scorpionate compounds mediate hydrocarbon oxidation with organic peroxides. Allylic oxidation of cyclohexene occurs mainly on the reaction with tert-butyl hydroperoxide (TBHP), although the catalytic efficiency of the scorpionate ligand complexes is lower than that of Co(OAc)₂ and Co(acac)₂. On cyclohexane oxidation with meta-chloroperbenzoic acid (mCPBA), both To^M and Tp* complexes function as catalysts for hydroxylation. The higher electron-donating To^M complexes show faster initial reaction rates compared to the corresponding Tp* complexes. Full article

The solventless synthesis of tris(pyrazolyl)phenylmethane ligands of formula C₆H₅C(Pz^R2)₃ (R = H, Me), starting from PhCCl₃ and 3,5-dimethylpyrazole (Pz^Me2) or pyrazole (Pz) was performed. The sterically crowded C₆H₅C(Pz^Me2)₃ is thermally transformed into the bis(pyrazolyl)(p-pyrazolyl)phenylmethane ligand Pz^Me2-C₆H₄CH(Pz^Me2)₂. In this compound both Pz^Me2 rings are linked through the N-atom to the methine C-atom. At higher temperatures, the binding mode of Pz^Me2 changes from N1 to C4. All transformations occurred via quinonoid carbocation intermediates that undergo an aromatic electrophilic substitution on the 4-position of Pz^Me2. Reaction conditions were established to obtain five tris(pyrazolyl)phenylmethane ligands in moderate to good yields. ¹H- and ¹³C-NMR spectroscopy and X-ray diffraction of single crystals support the proposed structures. Full article

Formation of mixed-ligand Pd²⁺ complexes between canonical nucleoside 5'-monophosphates and five metal-ion-binding nucleoside analogs has been studied by ¹H-NMR spectroscopy to test the ability of these nucleoside surrogates to discriminate between unmodified nucleobases by Pd²⁺-mediated base pairing. The nucleoside analogs studied included 2,6-bis(3,5-dimethylpyrazol-1-yl)-, 2,6-bis(1-methylhydrazinyl)- and 6-(3,5-dimethylpyrazol-1-yl)-substituted 9-(β-d-ribofuranosyl)purines 1–3, and 2,4-bis(3,5-dimethylpyrazol-1-yl)- and 2,4-bis(1-methylhydrazinyl)-substituted 5-(β-d-ribofuranosyl)-pyrimidines 4–5. Among these, the purine derivatives 1-3 bound Pd²⁺ much more tightly than the pyrimidine derivatives 4, 5 despite apparently similar structures of the potential coordination sites. Compounds 1 and 2 formed markedly stable mixed-ligand Pd²⁺ complexes with UMP and GMP, UMP binding favored by 1 and GMP by 2. With 3, formation of mixed-ligand complexes was retarded by binding of two molecules of 3 to Pd²⁺. Full article

The tridentate ligand N,N-Bis(3,5-dimethylpyrazol-1-ylmethyl)-1-hydroxy-2-aminoethane (L) has been prepared in one step by condensation of two equivalents of 1-hydroxymethyl-3,5-dimethylpyrazole with one equivalent of 2-aminoethanol. This reaction is carried out under microwave irradiation (60 W) in the absence of solvent for 20 min [1]. Using this ligand L a new Cu(II) dinitrate complex has been prepared. The singlecrystal X-ray structure of the title compound, [N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)-1-hydroxy-2-aminoethane] (3,5-dimethylpyrazole)copper(II) dinitrate, revels that the copper (II) ion is coordinated to two pyrazole nitrogens, one tertiary amine nitrogen of the ligand L and 3,5-dimethylpyrazole, and in the apical position by an alcohol O atom. Full article