Synthesis and cytotoxicity studies of Cu(I) and Ag(I) complexes based on sterically hindered β-diketonates with different degrees of fluorination

Design, synthesis, and in vitro antitumor properties of Cu(I) and Ag(I) phosphane complexes supported by the anions of sterically hindered β-diketone ligands, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3) featuring trifluoromethyl or methyl groups on the phenyl moieties have been reported. In order to compare the biological effects of substituents on the phenyl moieties, the analogous copper(I) and silver(I) complexes of the anion of the parent 1,3-diphenylpropane-1,3-dione (HLPh) ligand were also synthesized and included in the study. In the syntheses of the Cu(I) and Ag(I) complexes, the phosphane coligands triphenylphosphine (PPh3) and 1,3,5-triaza-7-phosphaadamantane (PTA) were used to stabilize silver and copper in the +1 oxidation state, preventing the metal ion reduction to Ag(0) or oxidation to Cu(II), respectively. X-ray crystal structures of HLCF3 and the metal adducts [Cu(LCF3)(PPh3)2] and [Ag(LPh)(PPh3)2] are also presented. The antitumor properties of both classes of metal complexes were evaluated against a series of human tumor cell lines derived from different solid tumors, by means of both 2D and 3D cell viability studies. They display noteworthy antitumor properties and are more potent than cisplatin in inhibiting cancer cell growth.

Novel Silver Complexes Based on Phosphanes and Ester Derivatives of Bis(pyrazol-1-yl)acetate Ligands Targeting TrxR: New Promising Chemotherapeutic Tools Relevant to SCLC Management

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 silver(I) complexes 3-5. The Ag(I) complexes were prepared by the reaction of AgNO₃ and 1,3,5-triaza-7-phosphaadamantane (PTA) or triphenylphosphine (PPh₃) with L^OMe and L^2OMe in methanol solution. All Ag(I) complexes showed a significant in vitro antitumor activity, proving to be more effective than the reference drug cisplatin in the in-house human cancer cell line panel containing examples of different solid tumors. Compounds were particularly effective against the highly aggressive and intrinsically resistant human small-cell lung carcinoma (SCLC) cells, either in 2D and 3D cancer cell models. Mechanistic studies revealed their ability to accumulate into cancer cells and to selectively target Thioredoxin (TrxR), thus leading to redox homeostasis unbalance and ultimately inducing cancer cell death through apoptosis.

Rare Earth Complexes of Europium(II) and Substituted Bis(pyrazolyl)borates with High Photoluminescence Efficiency

Rare earth europium(II) complexes based on d-f transition luminescence have characteristics of broad emission spectra, tunable emission colors and short excited state lifetimes, showing great potential in display, lighting and other fields. In this work, four complexes of Eu(II) and bis(pyrazolyl)borate ligands, where pyrazolyl stands for pyrazolyl, 3-methylpyrazolyl, 3,5-dimethylpyrazolyl or 3-trifluoromethylpyrazole, were designed and synthesized. Due to the varied steric hindrance of the ligands, different numbers of solvent molecules (tetrahydrofuran) are participated to saturate the coordination structure. These complexes showed blue-green to yellow emissions with maximum wavelength in the range of 490-560 nm, and short excited state lifetimes of 30-540 ns. Among them, the highest photoluminescence quantum yield can reach 100%. In addition, when the complexes were heated under vacuum or nitrogen atmosphere, they finally transformed into the complexes of Eu(II) and corresponding tri(pyrazolyl)borate ligands and sublimated away.

Comparison of Functionalized Lithium Dihydrobis(azolyl)borates with Their Corresponding Azolates as Environmentally Friendly Red Pyrotechnic Coloring Agents

The recent awareness of the impact of strontium on health has stimulated research efforts on lithium-based red pyrotechnic colorants. We have previously shown lithium dihydrobis(azolyl)borates to be promising candidates due to their favorable adjustment to a reductive and low-temperature flame atmosphere. These compounds are assumed to be sufficiently stable only if the pK_a values of the heterocycles are between 5 and 20. Apart from their acidities, functionalization of 1H-tetrazole and 1H-pyrazole with nitro or amino groups, respectively, tailors the oxygen balances of the resulting Lewis acid base adducts to enhance the fuel-rich flame environment or to make them oxidizing agents. This work determines whether the lithium salts of dihydrobis(3-nitropyrazol-1-yl)borate and dihydrobis(5-aminotetrazol-1-yl)borate are suitable replacements for strontium-containing color imparters. Furthermore, the influence of potentially green-light-producing boron is evaluated by comparing the emissions of the lithium borates and the corresponding lithium azolates.

Scorpionate complexes of aza-18-crown-6 containing fluoronitrophenyl substituents as studied by electrospray ionization mass spectrometry

RATIONALE

Coordination of a metal cation by a nitro group is rare and the interaction between them is usually weak. Examples of complexes in which such an interaction takes place are metal complexes of cyclams containing nitrophenyl or nitrobenzyl substituents. It seemed to be interesting to check if in the complexes of the respective crown ether conjugates the interaction can also take place.

METHODS

We synthesized the respective conjugates of aza-18-crown-6, namely fluoro-substituted N-nitrophenylaza-18C6 conjugates. Their complexes with alkali and alkali earth metal cations were generated in the gas phase by electrospray ionization mass spectrometry (ESI-MS). Both collision-induced dissociation 'in-source' and collision-induced dissociation tandem mass spectrometry (ESI-CID-'in-source' and ESI-CID-MS/MS) were used to study the gas-phase stabilities of the generated complexes.

RESULTS

The gas-phase decomposition of the studied complexes indicated that the complexes formed by the conjugates containing a nitro group at the ortho position are more stable than those formed by the conjugates with a nitro group at the para position.

CONCLUSIONS

This indicates that a metal cation complexed by crown ether ring is additionally coordinated by a nitro group in the scorpionate mode. To the best of our knowledge, our finding provide the first example of a complex in which a metal cation complexed by a crown ether ring is additionally coordinated by a nitro group.

Bis(acetylacetonato)bis(pyrazolato)ruthenate(iii) as a redox-active scorpionate ligand

The potential of a new anionic octahedral metal complex [Ru(III)(acac)2(pz)2](-) ((-)) (pzH = pyrazole) as a ligand with a scorpionate coordination behaviour like tris(pyrazolyl)borate (tp) and reversible redox activity is presented. Trinuclear metal complexes, [Ru(III)2Zn(II)(acac)4(pz)4] () and [Ru(II)Ru(III)2(acac)4(pz)4] (), were each synthesized by the reaction of ZnCl2 or Ru3(CO)12 with [Ru(III)(acac)2(pz)(pzH)] (H) that is in situ deprotonated and acts as a precursor of (-). Single-crystal X-ray diffraction studies clarified that (-) acts as a scorpionate ligand; two (-) units in and one unit in function as bidentate ligands with two pyrazolates as pincers, while another (-) unit in functions as a tridentate ligand with one oxygen atom as a tail in addition to the two pyrazolate pincers. Moreover, and showed reversible multi-stage redox behaviours based on the Ru(II)/Ru(III) and Ru(III)/Ru(IV) couples of the (-) units in the cyclic voltammetry (CV) measurements. Based on the X-ray, IR, and CV measurements and the comparison with other Ru(ii) complexes with tp derivatives, the (-) unit was found to act as a redox-active scorpionate with electron withdrawing properties compared to the tp.

Silver(I) and copper(I) complexes supported by fully fluorinated 1,3,5-triazapentadienyl ligands

Synthesis of the perfluorinated 1,3,5-triazapentadiene [N{(CF(3))C(C(6)F(5))N}(2)]H and the use of its conjugate base as a supporting ligand for the isolation of silver(i) and copper(i) complexes are reported. Some of the related chemistry involving [N{(C(3)F(7))C(C(6)F(5))N}(2)](-) (that has bulkier -C(3)F(7) groups on the 1,3,5-triazapentadienyl ligand backbone) is also presented. X-ray crystallographic data show a wide variety of structures ranging from intermolecular, hydrogen-bonded chain structure for [N{(CF(3))C(C(6)F(5))N}(2)]H with a twisted W-shaped N(3)C(2) core, monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Ag(CN(t)Bu)(2) and [N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(CN(t)Bu)(2) where the κ(1)-bonded triazapentadienyl ligand bonding to the metal fragment via the central nitrogen atom, monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Ag(PPh(3))(2) and [N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(PPh(3))(2) that feature κ(1)-bonded triazapentadienyl ligand bonding to the metal fragment via one of the terminal nitrogen atoms, to that of the monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Cu(CN(t)Bu)(2) containing a κ(2)-bonded triazapentadienyl ligand and a U-shaped NCNCN ligand backbone. The isocyanide adducts show relatively high ν(CN) values in the IR spectra.