Maltol‐Derived Ruthenium–Cymene Complexes with Tumor Inhibiting Properties: The Impact of Ligand–Metal Bond Stability on Anticancer Activity In Vitro

Organometallic ruthenium–arene compounds bearing a maltol ligand have been shown to be nearly inactive in in vitro anticancer assays, presumably due to the formation of dimeric Ru^II species in aqueous solutions. In an attempt to stabilize such complexes, [Ru(η⁶‐p‐cymene)(XY)Cl] (XY=pyrones or thiopyrones) complexes with different substitution pattern of the (thio)pyrone ligands have been synthesized, their structures characterized spectroscopically, and their aquation behavior investigated as well as their tumor‐inhibiting potency. The aquation behavior of pyrone systems with electron‐donating substituents and of thiopyrone complexes was found to be significantly different from that of the maltol‐type complex reported previously. However, the formation of the dimer can be excluded as the primary reason for the inactivity of the complex because some of the stable compounds are not active in cancer cell lines either. In contrast, studies of their reactivity towards amino acids demonstrate different reactivities of the pyrone and thiopyrone complexes, and the higher stability of the latter probably renders them active against human tumor cells.     

Ruthenium–Arene–β‐Carboline Complexes as Potent Inhibitors of Cyclin‐Dependent Kinase 1: Synthesis,Characterization and Anticancer Mechanism Studies

A series of Ru^II–arene complexes ( 1 – 6 ) of the general formula [(η⁶‐arene)Ru(L)Cl]PF₆ (arene=benzene or p‐cymene; L=bidentate β‐carboline derivative, an indole alkaloid with potential cyclin‐dependent kinases (CDKs) inhibitory activities) is reported. All the complexes were fully characterized by classical analytical methods, and three were characterized by X‐ray crystallography. Hydrolytic studies show that β‐carboline ligands play a vital role in their aqueous behaviour. These complexes are highly active in vitro, with the most active complex 6 displaying a 3‐ to 12‐fold higher anticancer activity than cisplatin against several cancer cell lines. Interestingly, the complexes are able to overcome cross‐resistance to cisplatin, and show much lower cytotoxicity against normal cells. Complexes 1 – 6 may directly target CDK1, because they can block cells in the G2M phase, down‐regulate the expression of CDK1 and cyclin B1, and inhibit CDK1/cyclin B in vitro. Further mechanism studies show that the complexes can effectively induce apoptosis through mitochondrial‐related pathways and intracellular reactive oxygen species (ROS) elevation.     

Ligand Bridged Heterodinuclear Transition Metal Complexes – Syntheses,Structures and Electrochemical Investigations

The syntheses of the homo‐ and hererobimetallic compounds [L_n¹M(η⁵‐C₅H₄)CMe₂(η⁵‐C₉H₆)²ML_n] ( 2a‐5d ), [(C₉H₇)CMe₂(η⁵‐C₅H₄)Fe(η⁵‐C₅H₄)CMe₂(η⁵‐C₉H₆)²ML_n] ( 6a‐c ), and [(η⁵‐C₅H₄)CMe₂(η⁵‐C₉H₆)²ML_n]₂Fe ( 7a‐b ) are reported with ¹ML_n = Rh(cod) 2 , Ir(cod) 3 , Mn(CO)₃ 4 and FeCp 5 , ²ML_n = Rh(cod) a , Ir(cod) b , Mn(CO)₃ c and FeCp d , respectively. Crystal structures of 3a, 3b and 5c are described showing two different ligand conformations in form of two rotamers. The energetic difference between these both rotamers is insignificant small in the gas phase according to DFT calculations. The rotation barrier for the species has been determined to 23 kJ/mol. According to the absence of intermolecular interactions in the solid state, the preference for one of the conformers is deduced from packing effects. All complexes are investigated by cyclic voltammetry. The shift of the redox potentials with respect to the mononuclear reference systems is a suitable tool to determine intermetallic electronic interaction. For some compounds, the normal behaviour with an increasing separation of the redox potentials is observed. A second group of complexes shows the opposite behaviour with a decreasing in the potential differences. A mechanism of intramolecular catalytic oxidation is supposed for that species.     

四个对苯酚四唑硫酮金属(II)配合物的合成和晶体结构

四唑酸(–CN4H)与羧酸(–COOH)具有相似的酸性。对苯酚四唑硫酮(H2L)可以作为单齿(–S或–N)或双齿(–N, N或–N, S)配体与金属离子配位形成配位化合物。合成了4个以H2L为配体的金属(II)配合物：Co(HL)2(Py)2(H2O)2 (1), [Mn(HL)2(H2O)4]·2H2O (2), Mn(HL)2(Phen)2 (3), and [Zn(HL)2(Phen)2]·0.5H2O·1.5CH3OH (4),并用X−射线单晶衍射法测定了晶体结构。晶体结构分析表明,在这些配合物中所有的中心金属原子均呈现六配位的八面体构型。在配合物1和2中,HL–配体以氧原子与中心金属原子配位,而在配合物3和4中HL–配体则以硫原子与中心金属原子配位。     

Regioselective Synthesis and Characterization of Multinuclear Convex‐Bound Ruthenium‐[n]Cycloparaphenylene (n=5 and 6) Complexes

Mono‐ and multinuclear complexes of ruthenium and [n]cycloparaphenylene (CPP, n=5 and 6) were synthesized in excellent yields through ligand exchange of the cationic complex [(Cp)Ru(CH₃CN)₃](PF₆) with CPP. In the multinuclear complexes, ruthenium selectively coordinated to alternate paraphenylene units to give bis‐ and tris‐coordinated Ru complexes for [5] and [6]CPPs, respectively. Single‐crystal X‐ray analysis revealed the Ru was coordinated with η⁶‐hapticity on the convex surface of CPP.     

Crystal Structures of Ln（NO3）3（Ln=La,Yb）Complexes with 12—crown—4

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Synthesis,Charactarization and Crystal Structures of Lanthanide Phenoxyacetate Complexes with1,10—Phenanthroline

Three new lanthanide phenoxyacetate complexes with 1,10‐phenanthroline. [Nd(POA)₃ (phen)]₂ · 2C₂H₅OH (1), [Eu(POA)₃‐ (phen)]₂ · 2C₂H₅OH (2) and [Sm(POA)₂(DMSO)(phen)]₂‐ (ClO₄)₂ (3) (POA= phenoxyacetate, phen = 1,10‐phenanthroline, DMSO = dimethyl sulfoxide), were synthesized and characterized by elemental analyses, IR, UV‐vis and FAB‐MS spectra. Their structures were determined by single crystal X‐ray diffraction analysis. In complexes 1 and 2, the carboxylate groups are bonded to Ln³⁺ ion in three modes: the chelating bidentate, the bridging bidentate and the bridging tridentate. In complex 3, the carboxylate groups are bonded to Sm³⁺ ion only involved in one mode: the bridging bidentate. The luminescence behavior of complex 2 was also studied by means of emission spectra.     

Synthesis,Crystal Structures,and Anti‐cervical Cancer Activity Evaluation of Three Trinuclear Transition Metal(II) Complexes with N,O‐Donor Schiff Base Ligand

A new bi‐nucleating Schiff base ligand, 2‐(((3‐(dimethylamino)propyl)imino)methyl)‐6‐methoxyphenol (HL₁) was prepared by a one‐pot condensation reaction, which was further used in the construction of three trinuclear Schiff base transition metal(II) complexes [Cu₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 1 ), [Co₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 2 ), and [Cu₃(L1)₂(N₃)₄] ( 3 ). Furthermore, a green hand grinding technique was implemented to reduce the particle size of the coordination complexes to generate the nanoscale compounds. The SEM studies reveal the formation of square and spherical particles for nano 1 and 2 , and nanorod for nano 3 . In addition, the anti‐proliferation activity of nano 1 – 3 was detected on the human cervical cancer Hela cells with CCK‐8 assay. The cell viability curves and IC₅₀ values indicated that only nano 1 has anti‐proliferation activity on Hela cells. To further investigate the mechanism of nano 1 induced Hela cell death, the Annexin V‐FITC/PI double staining assay, western blot assay, and ROS level detection was conducted.     

镧系元素(La、Tb、Dy)的喹啉氧基乙酰胺配合物的结构及荧光性质

合成并通过单晶衍射表征了3个稀土配合物[LaL₂(NO₃)₃]·CH₃CN(1),[Ln(L)(NO₃)₃(H₂O)](Ln=Tb(2),Dy(3),L=N-苯基-2-(5-氯-8-喹啉氧基)乙酰胺)。在配合物1中,十二配位的La(Ⅲ)离子采取扭曲的二十面体配位构型,分别与来自2个酰胺配体L的4个氧原子和2个氮原子,及3个双齿配位硝酸根配位。配合物2和3的结构与拥有相同有机配体的Pr、Nd、Sm、Eu、Gd和Er配合物同构。在每个配合物中,十配位的稀土离子与来自1个配体L的2个氧原子和1个氮原子,3个双齿配位硝酸根和1个水分子配位,拥有扭曲的双帽四方反棱柱配位构型。固态配合物2和3在可见区发射强荧光。     

镧系元素(La、Tb、Dy)的喹啉氧基乙酰胺配合物的结构及荧光性质

合成并通过单晶衍射表征了3个稀土配合物[LaL₂(NO₃)₃]·CH₃CN(1),[Ln(L)(NO₃)₃(H₂O)](Ln=Tb (2), Dy (3), L=N-苯基-2-(5-氯-8-喹啉氧基)乙酰胺)。在配合物1中,十二配位的La(Ⅲ)离子采取扭曲的二十面体配位构型,分别与来自2个酰胺配体L的4个氧原子和2个氮原子,及3个双齿配位硝酸根配位。配合物2和3的结构与拥有相同有机配体的Pr、Nd、Sm、Eu、Gd和Er配合物同构。在每个配合物中,十配位的稀土离子与来自1个配体L的2个氧原子和1个氮原子,3个双齿配位硝酸根和1个水分子配位,拥有扭曲的双帽四方反棱柱配位构型。固态配合物2和3在可见区发射强荧光。     

Platinum(II)–Gadolinium(III) Complexes as Potential Single‐Molecular Theranostic Agents for Cancer Treatment

Theranostic agents are emerging multifunctional molecules capable of simultaneous therapy and diagnosis of diseases. We found that platinum(II)–gadolinium(III) complexes with the formula [{Pt(NH₃)₂Cl}₂GdL](NO₃)₂ possess such properties. The Gd center is stable in solution and the cytoplasm, whereas the Pt centers undergo ligand substitution in cancer cells. The Pt units interact with DNA and significantly promote the cellular uptake of Gd complexes. The cytotoxicity of the Pt–Gd complexes is comparable to that of cisplatin at high concentrations (≥0.1 mM ), and their proton relaxivity is higher than that of the commercial magnetic resonance imaging (MRI) contrast agent Gd–DTPA. T₁‐weighted MRI on B6 mice demonstrated that these complexes can reveal the accumulation of platinum drugs in vivo. Their cytotoxicity and imaging capabilities make the Pt–Gd complexes promising theranostic agents for cancer treatment.     

Alkali Metal and Alkaline Earth Metal Complexes with the Bis(borane‐diphenylphosphanyl)amido Ligand – Synthesis,Structures, and Catalysis for Ring‐Opening Polymerization of ϵ‐Caprolactone

The syntheses of lithium and alkaline earth metal complexes with the bis(borane‐diphenylphosphanyl)amido ligand ( 1 ‐ H ) of molecular formulas [{κ²‐N(PPh₂(BH₃))₂}Li(THF)₂] ( 2 ) and [{κ³‐N(PPh₂(BH₃))₂}₂M(THF)₂] [(M = Ca ( 3 ), Sr ( 4 ), Ba ( 5 )] are reported. The lithium complex 2 was obtained by treatment of bis(borane‐diphenylphosphanyl)amine ( 1 ‐ H ) with lithium bis(trimethylsilyl)amide in a 1:1 molar ratio via the silylamine elimination method. The corresponding homoleptic alkaline earth metal complexes 3 – 5 were prepared by two synthetic routes – first, the treatment of metal bis(trimethylsilyl)amide and protio ligand 1 ‐ H via the elimination of silylamine, and second, through salt metathesis reaction involving respective metal diiodides and lithium salt 2 . The molecular structures of lithium complex 2 and barium complex 5 were established by single‐crystal X‐ray diffraction analysis. In the solid‐state structure of 2 , the lithium ion is ligated by amido nitrogen atoms and hydrogen atoms of the BH₃ group in κ²‐coordination of the ligand 1 resulting in a distorted tetrahedral geometry around the lithium ion. However, in complex 5 , κ³‐coordination of the ligand 1 was observed, and the barium ion adopted a distorted octahedral arrangement. The metal complex 5 was tested as catalyst for the ring opening polymerization of ?‐caprolactone. High activity for the barium complex 5 towards ring opening polymerization (ROP) of ?‐caprolactone with a narrow polydispersity index was observed. Additionally, first‐principle calculations to investigate the structure and coordination properties of alkaline earth metal complexes 3 – 5 as a comparative study between the experimental and theoretical findings were described.     

基于2,5-噻吩二羧酸的稀土配合物的合成和表征

以2,5-噻吩二甲酸和稀土盐为原料,通过水热反应,合成了3个稀土金属配位聚合物{[La（OH）（SO₄）]}_n（1）,{[La₂（TDC）₂（SUC）]}_n（2）和{[Gd₂（TDC）₂（ox）（H₂O）₄]·2H₂O}_n（3）（H₂TDC=2,5-噻吩二甲酸,SUC=丁二酸,ox=草酸）,分别用X射线单晶衍射、元素分析、红外光谱对配合物2和3进行了表征。实验结果表明：配合物2和3均呈现三维网络结构,其中配合物2属于正交晶系,空间群为Pbca,a=1.372 8（4）nm,b=0.704 0（2）nm,c=2.136 2（6）nm,Z=8;配合物3属于单斜晶系,空间群为C2/c,a=1.934 3（4）nm,b=0.990 5（2）nm,c=1.252 8（3）nm,β=107.463（4）°,Z=4。     

Potent Anticancer Activity and Possible Low Toxicity of Platinum(II) Complexes with Functionalized 1,1‐Cyclobutanedicarboxylate as a Leaving Ligand

Two platinum(II) complexes, DN603 and DN604, were designed and prepared by using 3‐oxocyclobutane‐1,1‐dicarboxylate as a ligand. The compounds were prepared according to the concept that incorporation of a functionalized moiety in the leaving ligand that did not affect its coordination bonding to the metal atom would play a key role in the anticancer activity of the resulting platinum complex. The newly prepared compounds were found to show potent in vitro anticancer activity comparable to cisplatin and oxaliplatin; especially DN604, which exhibited low acute toxicity similar to carboplatin, and presented acceptable solubility and stability in water. Chemical and biological results indicated that the functionalized moiety, uncoordinated, led to potent anticancer activity and low apparent toxicity of the platinum complexes by affecting the kinetic properties of the compounds.     

Biotransformations of Anticancer Ruthenium(III) Complexes: An X‐Ray Absorption Spectroscopic Study

An anti‐metastatic drug, NAMI‐A ((ImH)[Ru^IIICl₄(Im)(dmso)]; Im=imidazole, dmso=S‐bound dimethylsulfoxide), and a cytotoxic drug, KP1019 ((IndH)[Ru^IIICl₄(Ind)₂]; Ind=indazole), are two Ru‐based anticancer drugs in human clinical trials. Their reactivities under biologically relevant conditions, including aqueous buffers, protein solutions or gels (e.g, albumin, transferrin and collagen), undiluted blood serum, cell‐culture medium and human liver (HepG2) cancer cells, were studied by Ru K‐edge X‐ray absorption spectroscopy (XAS). These XAS data were fitted from linear combinations of spectra of well‐characterised Ru compounds. The absence of XAS data from the parent drugs in these fits points to profound changes in the coordination environments of Ru^III. The fits point to the presence of Ru^IV/III clusters and binding of Ru^III to S‐donor groups, amine/imine and carboxylato groups of proteins. Cellular uptake of KP1019 is approximately 20‐fold higher than that of NAMI‐A under the same conditions, but it diminishes drastically after the decomposition of KP1019 in cell‐culture media, which indicate that the parent complex is taken in by cells through passive diffusion.     

Synthesis,Characterization and Catalytic Application of Pyridine‐Bridged N‐Heterocyclic Carbene–Ruthenium Complexes in the Hydrogenation of Carbonates

A series of bulky pyridine‐bridged NHC–Ru complexes have been rationally designed and synthesized; these exhibited very high catalytic activity in the hydrogenation of cyclic and linear carbonates under mild reaction conditions. In the presence of catalytic amounts of a weak base, a broad range of substrates with different ring size and steric bulk were well tolerated, providing methanol and the corresponding diols in excellent yields with a catalyst loading as low as 0.5 mol %.     

Thiomaltol‐Based Organometallic Complexes with 1‐Methylimidazole as Leaving Group: Synthesis,Stability, and Biological Behavior

Thiomaltol, a potential S,O‐coordinating molecule, has been utilized for the complexation of four different organometallic fragments, yielding the desired Ru^II, Os^II, Rh^III, and Ir^III complexes having a “piano‐stool” configuration. In addition to the synthesis of these compounds with a chlorido leaving group, the analogous 1‐methylimidazole derivatives have been prepared, giving rise to thiomaltol‐based organometallics with enhanced stability under physiological conditions. The organometallic compounds have been characterized by NMR spectroscopy, elemental analysis, and X‐ray diffraction analysis. Their behavior in aqueous solution and their interactions with certain amino acids have been studied by ESI mass spectrometry. Their pH‐dependent stability has been investigated by ¹H NMR in aqueous solution, and their cytotoxicity against three different cancer cell lines has been investigated. Furthermore, their capacity as topoisomerase IIα inhibitors as well as their effect on the cell cycle distribution and reactive oxygen species (ROS) generation have been elucidated.