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1.
Chem Commun (Camb) ; 2020 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-32524101

RESUMO

The reaction of the bis(methoxy)-2-pyridyl-phosphine (MeO)2P(2-py) (1) with [Ni(MeCN)6](BF4)2 leads to the unexpected single-step reduction of NiII and the formation of a tetrahedral nickel(0) complex [{(MeO)2P(2-py-H)}2{(MeO)2P(2-py)}2Ni](BF4)2 (2). The redox activity is probably induced by the decomposition of the tetrafluoroborate anion; NMR spectroscopic studies point towards a fluoride-assisted oxidation of the 2-pyridyl-phosphine ligand, with associated reduction of the metal.

2.
Chempluschem ; 85(5): 958-962, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32412179

RESUMO

Reaction of the electrochemically in situ from elemental white phosphorus generated phosphine oxide H3 PO in a single electrochemical cell, supplied with lead cathode and aluminium anode, with cyclic ketones (cyclopentanone and cyclohexanone) results in formation of secondary phosphine oxides (bis(α-hydroxycyclopentyl)phosphine oxide 2 a, isolated yield 15 %, and bis(α-hydroxycyclohexyl)phosphine oxide 2 b, isolated yield 12 %) with two α-hydroxycycloalkyl substituents at the phosphorus atom. Bis(α-hydroxycyclopentyl)phosphine oxide reacts with [PdCl2 (COD)] (COD=1,5-cyclooctadiene) to give a new palladium complex trans-[PdCl2 {P(OH)(cyclo-C5 H8 -1-OH)2 }2 ] (3 a, isolated yield 11 %) bearing phosphinous acid as a ligand formed via tautomerization of the phosphine oxide. Finally, the cytotoxicity of the synthesized secondary phosphine oxides on tumor and healthy human cell lines was studied. It was found that at a concentration of 10-6 -10-4  M, phosphine oxides 2 a,b exhibit similar IC50 values for the M-Hela cell line (ca. 50 mM), but are non-toxic for MCF-7 cells. For human alveolar adenocarcinoma cells (A-549), only 2 a is active (ca. 35 mM), while 2 b is not toxic.

3.
Molecules ; 25(10)2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32429279

RESUMO

Ruthenium-based complexes have received much interest as potential metallodrugs. In this work, four RuII complexes bearing a dicarbollide moiety, a carbonyl ligand, and a phenanthroline-based ligand were synthesized and characterized, including single crystal diffraction analysis of compounds 2, 4, and 5 and an observed side product SP1. Complexes 2-5 are air and moisture stable under ambient conditions. They show excellent solubility in organic solvents, but low solubility in water.

4.
Inorg Chem ; 59(11): 7487-7503, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32314912

RESUMO

The octaphosphine {cyclo-(P4tBu3)}2 (1) possesses a multifaceted coordination chemistry. The predominant binding mode is a P,P-chelate, e.g., in the monometallic chelate complex [MLL'(1-κ2P2,P4')] in which the ligand 1 adopts a gauche conformation. Examples include square-planar (M = RhI, L = CO, L' = Cl (2), M = PdII, L = L' = Cl (3), M = PtII, L = L' = Cl (9)), tetrahedral (M = Co-I, L = NO, L' = CO (4)), and trigonal-planar complexes [ML(1-κ2P2,P4')] (M = Pd0, L = PPh3, (5), M = CuI, L = Br (6)). With 2 equiv of [CuBr(SMe2)], a dinuclear complex [(CuBr)2(1-κ2P2,P2',κ2P4,P4')] (7) was obtained which features a synperiplanar conformation of the octaphosphine. A second coordination mode was also observed in [PtCl2(1-κ2P1,P2')] (10) in which the bridge phosphorus atom in octaphosphine 1 is involved in the chelation, with the ligand in an antiperiplanar conformation. Thermolysis of selected complexes showed them to be suitable candidates for the generation of phosphorus-rich metal phosphides MPx (x > 1).

5.
Dalton Trans ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32242884

RESUMO

The coordination characteristics and donor/acceptor properties of a series of 2-pyridyl substituted phosphine ligands have been investigated using structural, spectroscopic and DFT calculational studies. A range of different coordination modes are observed in Mo and W carbonyl complexes of tris-2-pyridyl-phosphine ligands of the type P(2-py') (2-py' = substituted or unsubstituted 2-pyridyl group), including an unprecedented example exhibiting N,N',µ2-π coordination. DFT calculations were used to assess the relative donor/acceptor properties of a range of related 2-pyridyl-phosphine ligands with respect to PPh3 and PtBu3.

6.
Chemistry ; 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32291835

RESUMO

Invited for the cover of this issue is the group of Evamarie Hey-Hawkins at the University of Leipzig and colleagues at the University of Stuttgart and University of Regensburg. The image depicts the reported complexes as three similar flowers growing from one common branch representing the ligand. Read the full text of the article at 10.1002/chem.202000226.

7.
Sci Rep ; 10(1): 4827, 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-32179835

RESUMO

Owing to the involvement of cyclooxygenase-2 (COX-2) in carcinogenesis, COX-2-selective inhibitors are increasingly studied for their potential cytotoxic properties. Moreover, the incorporation of carboranes in structures of established anti-inflammatory drugs can improve the potency and metabolic stability of the inhibitors. Herein, we report the synthesis of carborane-containing derivatives of rofecoxib that display remarkable cytotoxic or cytostatic activity in the micromolar range with excellent selectivity for melanoma and colon cancer cell lines over normal cells. Furthermore, it was shown that the carborane-modified derivatives of rofecoxib showed different modes of action that were dependent on the cell type.

8.
Dalton Trans ; 49(15): 4817-4823, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32215416

RESUMO

A one-dimensional {[Zn(L)(DMF)2]}n (1) and a three-dimensional {[Cd(L)(DMF)]·DMF}n (2) coordination polymer based on the novel anthracene derivative H2L (H2L = 4,4'-(9,10-anthracenediyl)dicinnamic acid) were obtained by solvothermal synthesis and charaterised by single-crystal and powder X-ray diffraction, thermogravimetry, and infrared spectroscopy. The anthracene derivative H2L and coordination polymers 1 and 2 were used to modify a glassy carbon electrode and as such served as an active material for detection of H2O2. Cyclic voltammograms in the potential range from 0 to -0.5 V revealed concentration-dependent cathodic current in all three cases with a lower detection limit of 200 µM. The electrode modified with compound 2 showed the best performance towards hydrogen peroxide detection. The results suggest that the development of electrodes modified with inorganic polymers based on highly conjugated ligands can serve as potential electrocatalytic materials.

9.
Chemistry ; 26(26): 5765-5769, 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32048370

RESUMO

Tertiary phosphines are generally known to withstand inversion under moderate conditions. In this work, a remarkable racemization process of three P-chiral ferrocenyl phosphines is reported. Subjected to conventional column chromatography as highly enantioenriched compounds, they greatly experienced racemization when collected at the column outlet within minutes. Initially, attention was drawn to this unusual inversion behavior after observing that the superb enantiomeric excess of these ligands (>95 % ee in all cases) was almost lost in their corresponding ruthenium(II) complexes. Successively excluding possible racemization causes, these P-chiral ferrocenyl phosphines were found to undergo a significant, acid-catalyzed racemization process at room temperature within a few minutes. This process is mainly observed during standard column chromatography by using conventional silica or alumina, but can also be triggered deliberately by addition of certain acids. Therefore, the stereochemical preservation of P-chiral phosphines during their purification may per se not always be guaranteed, since column chromatography is the most frequently used technique for purifying such types of compounds.

10.
Chemistry ; 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32022973

RESUMO

2,4,6-Tris(1-diphenylphosphanyl-1'-ferrocenylene)-1,3,5-triazine (1) coordinates all three coinage metal(I) ions in a 1:1 tridentate coordination mode. The C3 -symmetric coordination in both solid state and solution is stabilised by an uncommon cation-π interaction between the triazine core and the metal cation. Intramolecular dynamic behaviour was observed by variable-temperature NMR spectroscopy. The borane adduct of 1, 1BH3 , displays four accessible oxidation states, suggesting complexes of 1 to be intriguing candidates for redox-switchable catalysis. Complexes 1Cu, 1Ag, and 1Au display a more complicated electrochemical behaviour, and the electrochemical mechanism was studied by temperature-resolved UV/Vis spectroelectrochemistry and chemical oxidation.

11.
Chemistry ; 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31916272

RESUMO

The design of porous materials for the recognition of multiple hydrocarbons is highly desirable for the energy-efficient separation and recognition of chemical feedstock. Herein, three new iso-structural porous discrete metal-organic cages of formula {[Pd3 (NiPr)3 PO]4 (R-AN)6 } (R-AN=anilate linkers) for the selective recognition of substituted aromatic hydrocarbons are reported. The tetrahedral cages 1, 2, and 3 containing anilate, chloranilate, and bromanilate linkers exhibited selective encapsulation of mesitylene, o-xylene, and p-xylene, respectively, over other analogous aromatic hydrocarbons. These selective encapsulations were driven by the variations in the portal diameters present at each of these cages and their interactions with the hydrocarbon guests. These observations are supported by mass spectrometry, NMR studies, and theoretical binding-energy calculations.

12.
J Inorg Biochem ; 203: 110903, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31683124

RESUMO

Three water-soluble tris-heteroleptic ruthenium(II) polypyridyl complexes [Ru(bpy)(phen)(bpg)]2+ (1), [Ru(bpy)(dppz)(bpg)]2+ (2), and [Ru(phen)(dppz)(bpg)]2+ (3) (where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2',3'-c] phenazine, bpg = 4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f] [1,10] phenanthroline-6,13-dione) have been synthesized and characterized. Molecular structures of complexes 1 and 3 are confirmed by single crystal X-ray structure determination. Interaction of complexes 1-3 with DNA is explored by various spectroscopic techniques. The complexes 1-3 show solvent dependent photophysical properties. Complexes 2 and 3 show extensive "molecular light switch" effect for DNA. The complexes 1-3 are low toxic towards HeLa (human cervical cancer) and HL-60 (human promyelocytic leukemia) cell lines. Further, the cellular uptake of complexes 2 and 3 by cells shows that complexes mainly localised on the nucleus of the cells.

13.
J Med Chem ; 63(5): 2358-2371, 2020 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-31589041

RESUMO

G-protein-coupled receptors like the human Y1 receptor (hY1R) are promising targets in cancer therapy due to their high overexpression on cancer cells and their ability to internalize together with the bound ligand. This mechanism was exploited to shuttle boron atoms into cancer cells for the application of boron neutron capture therapy (BNCT), a noninvasive approach to eliminate cancer cells. A maximized number of carboranes was introduced to the hY1R-preferring ligand [F7,P34]-NPY by solid phase peptide synthesis. Branched conjugates loaded with up to 80 boron atoms per peptide molecule exhibited a maintained receptor activation profile, and the selective uptake into hY1R-expressing cells was demonstrated by internalization studies. In order to ensure appropriate solubility in aqueous solution, we proved the need for eight hydroxyl groups per carborane. Thus, we suggest the utilization of bis-deoxygalactosyl-carborane building blocks in solid phase peptide synthesis to produce selective boron delivery agents for BNCT.

14.
J Org Chem ; 85(3): 1446-1457, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31813224

RESUMO

Boron neutron capture therapy (BNCT) allows the selective elimination of malignant tumor cells without affecting healthy tissue. Although this binary radiotherapy approach has been known for decades, BNCT failed to reach the daily clinics to date. One of the reasons is the lack of selective boron delivery agents. Using boron loaded peptide conjugates, which address G protein-coupled receptors overexpressed on tumor cells allow the intracellular accumulation of boron. The gastrin-releasing peptide receptor (GRPR) is a well-known target in cancer diagnosis and can potentially be used for BNCT. Here, we present the successful introduction of multiple bis-deoxygalactosyl-carborane building blocks to the GRPR-selective ligand [d-Phe6, ß-Ala11, Ala13, Nle14]Bn(6-14) (sBB2L) generating peptide conjugates with up to 80 boron atoms per molecule. Receptor activation was retained, metabolic stability was increased, and uptake into PC3 cells was proven without showing any intrinsic cytotoxicity. Furthermore, undesired uptake into liver cells was suppressed by using l-deoxygalactosyl modified carborane building blocks. Due to its high boron loading and excellent GRPR selectivity, this conjugate can be considered as a promising boron delivery agent for BNCT.

15.
Chemistry ; 26(5): 1008-1012, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31758612

RESUMO

Octaphosphane {cyclo-(P4 tBu3 )}2 (1) undergoes an unexpected isomerization reaction to the constitutional isomer 2,2',2'',2''',3,3'-hexa-tert-butyl-bicyclo[3.3.0]octaphosphane (2) in the presence of Lewis acidic metal salts. The mechanism of this reaction is discussed and elucidated with DFT calculations. The results underline the fascinating similarity between phosphorus-rich and isolobal carbon compounds. The new bicyclic octaphosphane 2 shows a dynamic behavior in solution and reacts with [AuCl(tht)] (tht=tetrahydrothiophene) to give a mono- ([AuCl(2-κP3 )], 3) and a dinuclear complex ([(AuCl)2 (2-κP3 ,κP3' )], 4). With cis-[PdCl2 (cod)] (cod=1,5-cyclooctadiene), the chelate complex ([PdCl2 (2-κ2 P2 ,P2' )], 5) with a different coordination mode of the ligand was obtained.

16.
Dalton Trans ; 49(1): 57-69, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31808482

RESUMO

Introduction of a bis(isopropylidene)-protected galactopyranosyl moiety in s-triazine-based boron-rich carboxylic acids and amines results in soluble and suitable coupling partners for tumour-selective biomolecules with applications as selective agents for boron neutron capture therapy (BNCT). Bearing either a carboxylic acid or primary amine as a functional group, these compounds are highly versatile and thus largely extend the possible coupling strategies with suitable biomolecules. Modification of the gastrin-releasing peptide receptor (GRPR) selective agonist [d-Phe6, ß-Ala11, Ala13, Nle14]Bn(6-14) with the carboxylic acid derivative yielded a bioconjugate with an optimal receptor activation and internalisation profile. This demonstrates the great potential of this approach for the development of novel boron delivery agents.

17.
ChemMedChem ; 14(24): 2061-2074, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31675152

RESUMO

The role of autophagy in cancer is often complex, ranging from tumor-promoting to -suppressing effects. In this study, two novel hybrid molecules were designed, containing a ruthenacarborane fragment conjugated with a known modulator of autophagy, namely a quinoline derivative. The complex closo-[3-(η6 -p-cymene)-1-(quinolin-8-yl-acetate)-3,1,2-RuC2 B9 H10 ] (4) showed a dual mode of action against the LN229 (human glioblastoma) cell line, where it inhibited tumor-promoting autophagy, and strongly inhibited cell proliferation, de facto blocking cellular division. These results, together with the tendency to spontaneously form nanoparticles in aqueous solution, make complex 4 a very promising drug candidate for further studies in vivo, for the treatment of autophagy-prone glioblastomas.

18.
ChemMedChem ; 14(24): 2075-2083, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31677361

RESUMO

Investigations on the antitumor activity of metallacarboranes are sparse in the literature and limited to a handful of ruthena- and molybdacarboranes. In this study, the molybdacarborane fragment [3-(CO)2 -closo-3,1,2-MoC2 B9 H11 ] was combined with a vector molecule, inspired by the well-known drug tamoxifen or 4,4'-dihydroxytamoxifen (TAM-diOH). The molybdacarborane derivative [3,3-{4-[1,1-bis(4-hydroxyphenyl)but-1-en-2-yl]-2,2'-bipyridine-κ2 N,N'}-3-(CO)2 -closo-3,1,2-MoC2 B9 H11 ] (10), as well as the ligand itself 4-[1,1-bis(4-hydroxyphenyl)but-1-en-2-yl]-2,2'-bipyridine (6) showed cytotoxic activities in the low micromolar range against breast adenocarcinoma (MDA-MB-231, MDA-MB-361 and MCF-7), human glioblastoma (LN-229) and human glioma (U-251) cell lines. In addition, compounds 6 and 10 were found to induce senescence and cytodestructive autophagy, lower ROS/RNS levels, but only the molybdacarborane 10 induced a strong increase of nitric oxide (NO) concentration in the MCF-7 cells.

19.
Dalton Trans ; 48(42): 15772-15777, 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31612881

RESUMO

Reaction of 1,2-bis(diphenylphosphino)-ortho-carborane (L) with [K(thf){(MesBIAN)Co(η4-cod)}] (1, MesBIAN = bis(mesityliminoace-naphthene)diimine, cod = 1,5-cyclooctadiene) affords an anionic 13-vertex closo-cobaltacarborane cluster (2) in one step. The mechanism of this transformation has been studied by experimental and quantum chemical techniques, which suggest that a series of outer-sphere electron transfer and isomerisation processes occurs. This work shows that low-valent metalate anions are promising reagents for the synthesis of anionic metallacarborane clusters.

20.
J Mater Chem B ; 7(43): 6810-6821, 2019 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-31608920

RESUMO

Drug delivery systems based on the zeolitic imidazolate framework ZIF-8 have recently attracted viable research interest owing to their capability of decomposing in acidic media and thus performing targeted drug delivery. In vivo realization of this mechanism faces a challenge of relatively slow decomposition rates, even at elevated acidic conditions that are barely achievable in diseased tissues. In this study we propose to combine drug delivery nanocomposites with a semiconductor photocatalytic agent that would be capable of inducing a local pH gradient in response to external electromagnetic radiation. In order to test this principle, a model drug-releasing nanocomposite comprising photocatalytic titania nanotubes, ZIF-8, and the antitumor drug doxorubicin has been investigated. This system was demonstrated to release the drug in a quantity sufficient for effectively suppressing IMR-32 neuroblastoma cells that were used as a model diseased tissue. With locally applied UV irradiation, this result was achieved within 40 minutes, which is a relatively short time compared to the release duration in systems without photocatalyst, typically taking from several hours to several days.

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