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"Ruthenium - chemistry"
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Synthesis, characterization, and biological activity of cationic ruthenium–arene complexes with sulfur ligands
Five cationic ruthenium–arene complexes with the generic formula [Ru(SAc)(S
2
C·NHC)(
p
-cymene)](PF
6
) (
5a–e
) were prepared in almost quantitative yields using a straightforward one-pot, two-step experimental procedure starting from [RuCl
2
(
p
-cymene)]
2
, an imidazol(in)ium-2-dithiocarboxylate (NHC·CS
2
) zwitterion, KSAc, and KPF
6
. These half-sandwich compounds were fully characterized by various analytical techniques and the molecular structures of two of them were solved by X-ray diffraction analysis, which revealed the existence of an intramolecular chalcogen bond between the oxygen atom of the thioacetate ligand and a proximal sulfur atom of the dithiocarboxylate unit. DFT calculations showed that the C=S
…
O charge transfer amounted to 2.4 kcal mol
−1
. The dissolution of [Ru(SAc)(S
2
C·IMes)(
p
-cymene)](PF
6
) (
5a
) in moist DMSO-
d
6
at room temperature did not cause the dissociation of its sulfur ligands. Instead,
p
-cymene was slowly released to afford the 12-electron [Ru(SAc)(S
2
C·IMes)]
+
cation that could be detected by mass spectrometry. Monitoring the solvolysis process by
1
H NMR spectroscopy showed that more than 22 days were needed to fully decompose the starting ruthenium–arene complex. Compounds
5a–e
exhibited a high antiproliferative activity against human glioma Hs683 and human lung carcinoma A549 cancer cells. In particular, the IMes derivative (
5a
) was the most potent compound of the series, achieving toxicities similar to those displayed by marketed platinum drugs.
Graphical abstract
Journal Article
Anticancer Ruthenium Complexes with HDAC Isoform Selectivity
The histone deacetylase (HDAC) enzymes have emerged as an important class of molecular targets in cancer therapy, with five inhibitors in clinical use. Recently, it has been shown that a lack of selectivity between the 11 Zn-dependent HDAC isoforms may lead to unwanted side-effects. In this paper, we show that piano stool Ru complexes can act as HDAC inhibitors, and variation in the capping arene leads to differences in HDAC isoform selectivity.
Journal Article
Recent developments in the nanostructured materials functionalized with ruthenium complexes for targeted drug delivery to tumors
In recent years, the field of metal-based drugs has been dominated by other existing precious metal drugs, and many researchers have focused their attention on the synthesis of various ruthenium (Ru) complexes due to their potential medical and pharmaceutical applications. The beneficial properties of Ru, which make it a highly promising therapeutic agent, include its variable oxidation states, low toxicity, high selectivity for diseased cells, ligand exchange properties, and the ability to mimic iron binding to biomolecules. In addition, Ru complexes have favorable adsorption properties, along with excellent photochemical and photophysical properties, which make them promising tools for photodynamic therapy. At present, nanostructured materials functionalized with Ru complexes have become an efficient way to administer Ru-based anticancer drugs for cancer treatment. In this review, the recent developments in the nanostructured materials functionalized with Ru complexes for targeted drug delivery to tumors are discussed. In addition, information on \"traditional\" (ie, non-nanostructured) Ru-based cancer therapies is included in a precise manner.
Journal Article
Ruthenium Complexes as Anticancer Agents: A Brief History and Perspectives
Platinum (Pt)-based anticancer drugs such as cisplatin have been used to treat various cancers. However, they have some limitations including poor selectivity and toxicity towards normal cells and increasing chemoresistance. Therefore, there is a need for novel metallo-anticancers, which has not been met for decades. Since the initial introduction of ruthenium (Ru) polypyridyl complex, a number of attempts at structural evolution have been conducted to improve efficacy. Among them, half-sandwich Ru-arene complexes have been the most prominent as an anticancer platform. Such complexes have clearly shown superior anticancer profiles such as increased selectivity toward cancer cells and ameliorating toxicity against normal cells compared to existing Pt-based anticancers. Currently, several Ru complexes are under human clinical trials. For improvement in selectivity and toxicity associated with chemotherapy, Ru complexes as photodynamic therapy (PDT), and photoactivated chemotherapy (PACT), which can selectively activate prodrug moieties in a specific region, have also been investigated. With all these studies on these interesting entities, new metallo-anticancer drugs to at least partially replace existing Pt-based anticancers are anticipated. This review covers a brief description of Ru-based anticancer complexes and perspectives.
Journal Article
A molecular ruthenium catalyst with water-oxidation activity comparable to that of photosystem II
Across chemical disciplines, an interest in developing artificial water splitting to O
2
and H
2
, driven by sunlight, has been motivated by the need for practical and environmentally friendly power generation without the consumption of fossil fuels. The central issue in light-driven water splitting is the efficiency of the water oxidation, which in the best-known catalysts falls short of the desired level by approximately two orders of magnitude. Here, we show that it is possible to close that ‘two orders of magnitude’ gap with a rationally designed molecular catalyst [Ru(bda)(isoq)
2
] (H
2
bda = 2,2′-bipyridine-6,6′-dicarboxylic acid; isoq = isoquinoline). This speeds up the water oxidation to an unprecedentedly high reaction rate with a turnover frequency of >300 s
−1
. This value is, for the first time, moderately comparable with the reaction rate of 100–400 s
−1
of the oxygen-evolving complex of photosystem II
in vivo
.
Increasing the efficiency and speed of the water-oxidation reaction is crucial to realizing light-driven water splitting. Now, a mononuclear ruthenium complex achieves fast water-oxidation catalysis with a high reaction rate of more than 300 turnovers per second, comparable to the activity of the oxygen-evolving complex in photosystem II.
Journal Article
Two-photon-absorbing ruthenium complexes enable near infrared light-driven photocatalysis
One-photon-absorbing photosensitizers are commonly used in homogeneous photocatalysis which require the absorption of ultraviolet (UV) /visible light to populate the desired excited states with adequate energy and lifetime. Nevertheless, the limited penetration depth and competing absorption by organic substrates of UV/visible light calls upon exploring the utilization of longer-wavelength irradiation, such as near-infrared light (λ
irr
> 700 nm). Despite being found applications in photodynamic therapy and bioimaging, two-photon absorption (TPA), the simultaneous absorption of two photons by one molecule, has been rarely explored in homogeneous photocatalysis. Herein, we report a group of ruthenium polypyridyl complexes possessing TPA capability that can drive a variety of organic transformations upon irradiation with 740 nm light. We demonstrate that these TPA ruthenium complexes can operate in an analogous manner as one-photon-absorbing photosensitizers for both energy-transfer and photoredox reactions, as well as function in concert with a transition metal co-catalyst for metallaphotoredox C–C coupling reactions.
The field of homogeneous metal- and photocatalysis typically uses one-photon-absorbing photosensitizers, which are highly functional, but require higher-energy light. Here the authors report a group of ruthenium polypyridyl complexes possessing two-photon-absorption capabilities, active with irradiation with lower-energy (740 nm) light.
Journal Article
Crystal structure of Δ-Ru(bpy)2dppz2+ bound to mismatched DNA reveals side-by-side metalloinsertion and intercalation
DNA mismatches represent a novel target in the development of diagnostics and therapeutics for cancer, because deficiencies in DNA mismatch repair are implicated in cancers, and cells that are repair-deficient show a high frequency of mismatches. Metal complexes with bulky intercalating ligands serve as probes for DNA mismatches. Here, we report the high-resolution (0.92 Å) crystal structure of the ruthenium ‘light switch’ complex Δ-[Ru(bpy)
2
dppz]
2+
(bpy = 2,2′-bipyridine and dppz = dipyridophenazine), which is known to show luminescence on binding to duplex DNA, bound to both mismatched and well-matched sites in the oligonucleotide 5′-(dCGGAAATTACCG)
2
-3′ (underline denotes AA mismatches). Two crystallographically independent views reveal that the complex binds mismatches through metalloinsertion, ejecting both mispaired adenosines. Additional ruthenium complexes are intercalated at well-matched sites, creating an array of complexes in the minor groove stabilized by stacking interactions between bpy ligands and extruded adenosines. This structure attests to the generality of metalloinsertion and metallointercalation as DNA binding modes.
A ‘light switch’ ruthenium complex is known to show enhanced luminescence in the presence of DNA mismatches — emerging targets for cancer diagnostics and therapeutics — but the way it interacts with DNA has remained unclear. Now, metalloinsertion into and metallointercalation at the minor groove of the double helix have been unambiguously observed in a high-resolution crystal structure.
Journal Article
Cyclometallated ruthenium catalyst enables late-stage directed arylation of pharmaceuticals
Biaryls are ubiquitous core structures in drugs, agrochemicals and organic materials that have profoundly improved many aspects of our society. Although traditional cross-couplings have made practical the synthesis of many biaryls, C–H arylation represents a more attractive and cost-effective strategy for building these structural motifs. Furthermore, the ability to install biaryl units in complex molecules via late-stage C–H arylation would allow access to valuable structural diversity, novel chemical space and intellectual property in only one step. However, known C–H arylation protocols are not suitable for substrates decorated with polar and delicate functionalities, which are commonly found in molecules that possess biological activity. Here we introduce a class of ruthenium catalysts that display a unique efficacy towards late-stage arylation of heavily functionalized substrates. The design and development of this class of catalysts was enabled by a mechanistic breakthrough on the Ru(ii)-catalysed C–H arylation of N–chelating substrates with aryl (pseudo)halides, which has remained poorly understood for nearly two decades.
Journal Article
Selective hydrogenolysis of catechyl lignin into propenylcatechol over an atomically dispersed ruthenium catalyst
C-lignin is a homo-biopolymer, being made up of caffeyl alcohol exclusively. There is significant interest in developing efficient and selective catalyst for depolymerization of C-lignin, as it represents an ideal feedstock for producing catechol derivatives. Here we report an atomically dispersed Ru catalyst, which can serve as an efficient catalyst for the hydrogenolysis of C-lignin via the cleavage of C−O bonds in benzodioxane linkages, giving catechols in high yields with TONs up to 345. A unique selectivity to propenylcatechol (77%) is obtained, which is otherwise hard to achieve, because this catalyst is capable of hydrogenolysis rather than hydrogenation. This catalyst also demonstrates good reusability in C-lignin depolymerization. Detailed investigations by model compounds concluded that the pathways involving dehydration and/or dehydrogenation reactions are incompatible routes; we deduced that caffeyl alcohol generated via concurrent C−O bonds cleavage of benzodioxane unit may act as an intermediate in the C-lignin hydrogenolysis. Current demonstration validates that atomically dispersed metals can not only catalyze small molecules reactions, but also drive the transformation of abundant and renewable biopolymer.
C-lignin represents an ideal feedstock for producing catechol derivatives. Here, the authors engineered an atomically dispersed Ru catalyst, which can cleave C−O bonds efficiently and circumvent C=C bonds hydrogenation selectively, thus leading to propenylcatechol in high yields with high TONs.
Journal Article