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Despite advances in Ir(III) and Ru(II) photosensitizers (PSs), their lack of selectivity for cancer cells has hindered their use in photodynamic therapy (PDT). We disclose the synthesis and characterization of two pairs of Ir(III) and Ru(II) polypyridyl complexes bearing two β-carboline ligands (N^N') functionalized with -COOMe ( L1 ) or -COOH ( L2 ), resulting in PSs of formulas [Ir(C^N) 2 (N^N')]Cl ( Ir-Me: C^N = ppy, N^N' = L1 ; Ir-H: C^N = ppy, N^N' = L2 ) and [Ru(N^N) 2 (N^N')](Cl) 2 ( Ru-Me: N^N = bpy, N^N' = L1; Ru-H: N^N = bpy, N^N' = L2 ). To enhance their selectivity toward cancer cells, Ir-H and Ru-H were coupled to a bombesin derivative ( BN3 ), resulting in the metallopeptides Ir-BN and Ru-BN . Ir(III) complexes showed higher anticancer activity than their Ru(II) counterparts, particularly upon blue light irradiation, but lacked cancer cell selectivity. In contrast, Ir-BN and Ru-BN exhibited selective photocytoxicity against prostate cancer cells, with a lower effect against nonmalignant fibroblasts. All compounds generated ROS and induced severe mitochondrial toxicity upon photoactivation, leading to apoptosis. Additionally, the ability of Ir-Me to oxidize NADH was demonstrated, suggesting a mechanism for mitochondrial damage. Our findings indicated that the conjugation of metal PSs with BN3 creates efficient PDT agents, achieving selectivity through targeting bombesin receptors and local photoactivation.

Ir(III) and Ru(II) polypyridyl complexes are promising photosensitizers (PSs) for photodynamic therapy (PDT) due to their outstanding photophysical properties. Herein, one series of cyclometallated Ir(III) complexes and two series of Ru(II) polypyridyl derivatives bearing three different thiazolyl-β-carboline N^N' ligands have been synthesized, aiming to evaluate the impact of the different metal fragments ([Ir(C^N) 2 ] + or [Ru(N^N) 2 ] 2+ ) and N^N' ligands on the photophysical and biological properties. All the compounds exhibit remarkable photostability under blue-light irradiation and are emissive (605 < λ em  < 720 nm), with the Ru(II) derivatives displaying higher photoluminescence quantum yields and longer excited state lifetimes. The Ir PSs display pK a values between 5.9 and 7.9, whereas their Ru counterparts are less acidic (pK a > 9.3). The presence of the deprotonated form in the Ir-PSs favours the generation of reactive oxygen species (ROS) since, according to theoretical calculations, it features a low-lying ligand-centered triplet excited state (T 1  =  3 LC) with a long lifetime. All compounds have demonstrated anticancer activity. Ir(III) complexes 1-3 exhibit the highest cytotoxicity in dark conditions, comparable to cisplatin. Their activity is notably enhanced by blue-light irradiation, resulting in nanomolar IC 50 values and phototoxicity indexes (PIs) between 70 and 201 in different cancer cell lines. The Ir(III) PSs are also activated by green (with PI between 16 and 19.2) and red light in the case of complex 3 (PI = 8.5). Their antitumor efficacy is confirmed by clonogenic assays and using spheroid models. The Ir(III) complexes rapidly enter cells, accumulating in mitochondria and lysosomes. Upon photoactivation, they generate ROS, leading to mitochondrial dysfunction and lysosomal damage and ultimately cell apoptosis. Additionally, they inhibit cancer cell migration, a crucial step in metastasis. In contrast, Ru(II) complex 6 exhibits moderate mitochondrial activity. Overall, Ir(III) complexes 1-3 show potential for selective light-controlled cancer treatment, providing an alternative mechanism to chemotherapy and the ability to inhibit lethal cancer cell dissemination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The synthesis and characterization of two half-sandwich complexes of Ru(II) and Ir(III) with thiabendazole as ancillary ligand and their DNA binding ability were investigated using experimental and computational methods. 1 H NMR and acid-base studies have shown that aquo-complexes are the reactive species. Kinetic studies show that both complexes bind covalently to DNA through the metal site and non covalently through the ancillary ligand. Thermal stability studies, viscosity, circular dichroism measurements and quantum chemical calculations have shown that the covalent binding causes breaking of the H-bonding between base pairs, bringing about DNA denaturation and compaction. Additionally, molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) calculations shed light into the binding features of the Ru(II) and Ir(III) complexes and their respective enantiomers toward double-helical DNA, highlighting the important role played by the NˆN ancillary ligand once the complexes are covalently linked to DNA. Moreover, metal quantification in the nucleus of SW480 colon adenocarcinoma cells were carried out by inductively coupled plasma-mass spectrometry (ICP-MS), both complexes are more internalized than cisplatin after 4 h of exposition. However, in spite of the dramatic changes in the helicity of the DNA secondary structure induced by these complexes and their nuclear localization, antiproliferative studies have revealed that both, Ru(II) and Ir(III) complexes, cannot be considered cytotoxic. This unexpected behavior can be justified by the fast formation of aquo-complexes, which may react with components of the cell culture medium or the cytoplasm compartment in such a way that they may become deactivated before reaching DNA.

A new family of neutral ruthenium(II) arene complexes of the type [Ru(η 6 -arene)X(κ 2 - O, N-L)] (η 6 -arene = p-cym, bz; X = Cl - , SCN - ; HL1 = 2-(2'-hydroxyphenyl)benzimidazole, HL2 = 2-(2'-hydroxyphenyl)benzothiazole) has been synthesized and characterized. The cytotoxic activity of the Ru(II) complexes was evaluated in several tumor cell lines (A549, HepG2 and SW480) both in the dark and after soft irradiation with UV and blue light. None of the complexes bearing benzimidazole (HL1) as a ligand displayed phototoxicity, whereas the complexes with a benzothiazole ligand (HL2) exhibited photoactivation; the sensitivity observed for UV was higher than for blue light irradiation. The interesting results displayed by HL2 and [Ru(η 6 - p-cym)(NCS)(κ 2 - O, N-L2)], [3a], in terms of photo cytotoxicity prompted us to analyze their interaction with DNA, both in the dark and under irradiation conditions, in an effort to shed some light on their mechanism of action. The results of this study revealed that HL2 interacts with DNA by groove binding, whereas [3a] interacts by a dual mode of binding, an external groove binding, and covalent binding of the metal center to the guanine moiety. Interestingly, both HL2 and [3a] display a clear preference for AT base pairs, and this causes fluorescence enhancement. Additionally, cleavage of the pUC18 plasmid DNA by the complex is observed upon irradiation. The study of the irradiated form demonstrates that the arene ligand is released to yield species such as [Ru(κ 2 - O, N-L2)(κ 1 - S-DMSO) 2 (μ-SCN)] 2 [3c] and [Ru(κ 2 - O, N-L2)(κ 1 - S-DMSO) 3 (SCN)] [3d]. Such photo dissociation occurs even in the absence of oxygen and leads to cytotoxicity enhancement, an effect attributed to the presence of [3d], thus revealing the potential of [3a] as a pro-drug for photoactivated anticancer chemotherapy (PACT).

The synthesis and characterization of Pt(II) (1 and 2) and Ru(II) arene (3 and 4) or polypyridine (5 and 6) complexes is described. With the aim of having a functional group to form bioconjugates, one uncoordinated carboxyl group has been introduced in all complexes. Some of the complexes were selected for their potential in photodynamic therapy (PDT). The molecular structures of complexes 2 and 5, as well as that of the sodium salt of the 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine ligand (cptpy), were determined by X-ray diffraction. Different techniques were used to evaluate the binding capacity to model DNA molecules, and MTT cytotoxicity assays were performed against four cell lines. Compounds 3, 4, and 5 showed little tendency to bind to DNA and exhibited poor biological activity. Compound 2 behaves as bonded to DNA probably through a covalent interaction, although its cytotoxicity was very low. Compound 1 and possibly 6, both of which contain a cptpy ligand, were able to intercalate with DNA, but toxicity was not observed for 6. However, compound 1 was active in all cell lines tested. Clonogenic assays and apoptosis induction studies were also performed on the PC-3 line for 1. The photodynamic behavior for complexes 1, 5, and 6 indicated that their nuclease activity was enhanced after irradiation at λ = 447 nm. The cell viability was significantly reduced only in the case of 5. The different behavior in the absence or presence of light makes complex 5 a potential prodrug of interest in PDT. Molecular docking studies followed by molecular dynamics simulations for 1 and the counterpart without the carboxyl group confirmed the experimental data that pointed to an intercalation mechanism. The cytotoxicity of 1 and the potential of 5 in PDT make them good candidates for subsequent conjugation, through the carboxyl group, to "selected peptides" which could facilitate the selective vectorization of the complex toward receptors that are overexpressed in neoplastic cell lines.

In this work, we report experimental and computational evidence for the intercalation into the DNA base-pairs of the free quinones quinizarin (Q) and naphthazarin (N) and the interstrand covalent binding of their p-cymene di-ruthenium(ii) complexes (Cl 2 Ru 2 X, with X = N, Q bridging ligands). The intercalation extent for the N complex was larger than that for Q, which is in good agreement with the higher relative contour length and melting temperature for the same C X /C DNA ratio and with the computational mean stacking distances between the ligand and the nearest base-pair (3.34 Å and 3.19 Å) for N and Q, respectively. However, the apparent binding constant of Q/DNA, two orders higher than that of N/DNA, indicates that the thermal stability of the X/DNA complex is more related to the degree of intercalation than to the magnitude of the binding constant. Cl 2 Ru 2 X complexes undergo aquation, forming the aqua-derivatives [(H 2 O) 2 Ru 2 X] 2+ . These can further bind covalently to DNA via interstrand crosslinking, through both Ru centres and two N7 sites of consecutive guanines, to give (DNA 1,2 )Ru 2 X complexes, by a mechanism similar to that of cisplatin. To the best of our knowledge, this type of interaction with dinuclear Ru(ii) complexes has not been reported hitherto. The experimental and computational results reveal that the number of rings of the aromatic moiety and the covalent binding to DNA play a key role in the behaviour of the quinones and their Ru(ii) derivatives. The cytotoxicity of the ligands and the corresponding Ru(ii) complexes was evaluated in MCF-7, A2780, A2780cis tumour cells and in the healthy cell line MRC-5. The cytotoxic activity was notable for N and negligible for Q. The IC 50 values and the resistance (RF) and selectivity (SF) factors show that the Cl 2 Ru 2 N complex is the most promising among the four studied anticancer drugs.

The ligands 2-pyridin-2-yl-1H-benzimidazole (HL(1)), 1-methyl-2-pyridin-2-ylbenzimidazole (HL(2)), and 2-(1H-imidazol-2-yl)pyridine (HL(3)) and the proligand 2-phenyl-1H-benzimidazole (HL(4)) have been used to prepare five different types of new ruthenium(II) arene compounds: (i) monocationic complexes with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL)]Y [HL = HL(1), HL(2), or HL(3); Y = Cl or BF4; arene = 2-phenoxyethanol (phoxet), benzene (bz), or p-cymene (p-cym)]; (ii) dicationic aqua complexes of the formula [(η(6)-arene)Ru(OH2)(κ(2)-N,N-HL(1))](Y)2 (Y = Cl or TfO; arene = phoxet, bz, or p-cym); (iii) the nucleobase derivative [(η(6)-arene)Ru(9-MeG)(κ(2)-N,N-HL(1))](PF6)2 (9-MeG = 9-methylguanine); (iv) neutral complexes consistent with the formulation [(η(6)-arene)RuCl(κ(2)-N,N-L(1))] (arene = bz or p-cym); (v) the neutral cyclometalated complex [(η(6)-p-cym)RuCl(κ(2)-N,C-L(4))]. The cytototoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (MCR-5, MCF-7, A2780, and A2780cis) in order to establish structure-activity relationships. Three of the compounds with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL(1))]Cl differing in the arene moiety have been studied in depth in terms of thermodynamic dissociation constants, aquation kinetic constants, and DNA binding measurements. The biologically most active compound is the p-cym derivative, which strongly destabilizes the DNA double helix, whereas those with bz and phoxet have only a small effect on the stability of the DNA double helix. Moreover, the inhibitory activity of several compounds toward CDK1 has also been evaluated. The DNA binding ability of some of the studied compounds and their CDK1 inhibitory effect suggest a multitarget mechanism for their biological activity.

New cationic, half-sandwich Ru(II) arene compounds of general formula [(η(6)-arene)RuCl(κ(2)-N,N-L)]X (where L are functionalized phenanthrolines such as 1,10-phenanthroline-5-amine (aphen); 5,6-epoxy-5,6-dihydro-[1,10]phenanthroline (ephen); or 4,7-dihydroxy-1,10-phenanthroline (dhphen)) have been prepared to study their anticancer potential. All the isolated complexes have been fully characterized by spectroscopic and analytical techniques. The structure of endo-[(η(6)-p-cymene)RuCl(κ(2)-N,N-ephen)]BF4, [2a](BF4), has been determined by X-ray crystallography. The in vitro cytotoxicity of the aphen and ephen phenanthrolines and their Ru derivatives [(η(6)-p-cymene)RuCl(κ(2)-N,N-L)]Cl ([1a]Cl and [2a]Cl, respectively) assessed in tumour cell lines has shown that the free ligands are more active than the organometallic products, with aphen being the most potent specimen. Furthermore, the binding interaction of both [1a]Cl and aphen with calf thymus DNA (CT-DNA) has been investigated using a variety of thermodynamic and kinetic techniques. The aphen free ligand intercalates into DNA at low ligand content, whereas [1a]Cl forms with DNA a bifunctional partially intercalated-covalent complex, in which the intercalation constant is nearly three orders of magnitude lower than that of aphen. This finding demonstrates that the covalent binding noticeably weakens the intercalation, a feature presumably related to the higher cytotoxic activity of aphen relative to that of [1a]Cl.

The synthesis and full characterization of the new aqua-complex [(η(6)-p-cymene)Ru(OH2)(κ(2)-N,N-2-pydaT)](BF4)2, [2](BF4)2, and the nucleobase derivative [(η(6)-p-cymene)Ru(9-MeG)(κ(2)-N,N-2-pydaT)](BF4)2, [4](PF6)2, where 2-pydaT = 2,4-diamino-6-(2-pyridyl)-1,3,5-triazine and 9-MeG = 9-methylguanine, are reported here. The crystal structures of both [4](PF6)2 and the chloro complex [(η(6)-p-cymene)RuCl(κ(2)-N,N-2-pydaT)](PF6), [1](PF6), have been elucidated by X-ray diffraction. The former provided relevant information regarding the interaction of the metallic fragment [(η(6)-p-cymene)Ru(κ(2)-N,N-2-pydaT)](2+) and a simple model of DNA. NMR and kinetic absorbance studies have proven that the aqua-complex [2](BF4)2 binds to the N7 site of guanine in nucleobases, nucleotides, or DNA. A stable bifunctional interaction (covalent and partially intercalated) between the [(η(6)-p-cymene)Ru(κ(2)-N,N-2-pydaT)](2+) fragment and CT-DNA has been corroborated by kinetic, circular dichroism, viscometry, and thermal denaturation experiments. The reaction mechanism entails the very fast formation of the Ru-O-(PO3) linkage prior to the fast intercalation of the 2-pydaT fragment. Then, a Ru-N7-(G) covalent bond is formed at the expense of the Ru-O-(PO3) bond, yielding a bifunctional complex. The dissociation rate of the intercalated fragment is slow, and this confers additional interest to [2](BF4)2 in view of the likely correlation between slow dissociation and biological activity, on the assumption that DNA is the only biotarget. Furthermore, [2](BF4)2 displays notable pH-dependent cytotoxic activity in human ovarian carcinoma cells (A2780, IC50 = 11.0 μM at pH = 7.4; IC50 = 6.58 μM at pH = 6.5). What is more, complex [2](BF4)2 is not cross-resistant with cisplatin, exhibiting a resistance factor, RF(A2780cis), of 0.28, and it shows moderate selectivity toward the cancer cell lines, in particular, A2780cis (IC50 = 3.0 5 ± 0.08 μM), relative to human lung fibroblast cells (MRC-5; IC50 = 24 μM), the model for healthy cells.

Aminophosphines 2-(diphenylphosphino)-1-methylimidazole (dpim) and diphenyl-2-pyridylphosphine (PPh(2)py) have been used to prepare two series of Ru(II) arene complexes of formulae [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-dpim)]Y (series a: 1a·Y-3a·Y) and [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-PPh(2)py)]Y (series b: 1b·Y-3b·Y) (where X=acac, acetylacetonate; bzac, benzoyl acetonate; dbzm, dibenzoyl methanoate; Y=BF(4), BPh(4)). The structures of 1a·BF(4), 1a·BPh(4), 3a·BF(4), 1b·BPh(4) and 3b·BPh(4) were determined by X-ray diffraction. The tetrafluoroborate derivatives are more soluble in organic solvents than their tetraphenylborate counterparts. Five BF(4)(-) derivatives (all except the unstable 1b·BF(4)) were selected to evaluate the cytotoxic behavior in vitro against the human cancer cell lines MCF-7 (breast cancer) and CAPAN-1 (pancreatic cancer). 2b·BF(4) and 3b·BF(4) exhibited IC(50) values similar to those of cisplatin. Electrophoresis and AFM studies showed good correspondence between the biological activity levels of 2b·BF(4) and 3b·BF(4) and their ability to modify the DNA structure. Hydrolytic studies indicate that aquation could be involved in the activation mechanism of these complexes and confirm that the hydrolysis rate of 3b·BF(4) is higher than that of 3a·BF(4). Thus, the cytotoxic activity trends are explained in terms of the higher reactivity of derivatives from series b, which in turn is rationalized as being the result of the electronic features of dpim and PPh(2)py established by cyclic voltammetry measurements., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The reactions of two diaminotriazine ligands 2,4-diamino-6-(2-pyridyl)-1,3,5-triazine (2-pydaT) and 6-phenyl-2,4-diamino-1,3,5-triazine (PhdaT) with ruthenium-arene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(η(6)-arene)Ru(κ(2)-N,N-2-pydaT)Cl]X (X=BF(4), TsO; arene=p-cymene: 1·BF(4), 1·TsO; arene=benzene: 2·BF(4), 2·TsO). The neutral cyclometalated complex [(η(6)-p-cymene)Ru(κ(2)-C,N-PhdaT*)Cl] (3) was also isolated. The structures of complexes 2·BF(4) and 3·H(2)O were determined by X-ray diffraction. Complex 1·BF(4) underwent a partial reversible-aquation process in water. UV/Vis and NMR spectroscopic measurements showed that the reaction was hindered by the addition of NaCl and was pH-controlled in acidic solution. At pH 7.0 (sodium cacodylate) Ru-Cl complex 1·BF(4) was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1·BF(4) underwent basic hydrolysis to afford a Ru-OH complex (5). Fluorimetric studies revealed that the interaction of complex 1·BF(4) with DNA was not straightforward; instead, its main features were closely linked to ionic strength and to the [DNA]/complex ratio. The bifunctional complex 1·BF(4) was capable of interacting concurrently through both its p-cymene and 2-pydaT groups. Cytotoxicity and genotoxicity studies showed that, contrary to the expected behavior, the complex species was biologically inactive; the formation of a Ru-OH complex could be responsible for such behavior., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Deuterium labeling is an interesting process that leads to compounds of use in different fields. We describe the transfer hydrogenation of aldehydes and the selective C1 deuteration of the obtained alcohols in D2O, as the only deuterium source. Different aromatic, alkylic and α,β-unsaturated aldehydes were reduced in the presence of [RuCl(p-cymene)(dmbpy)]BF4, (dmbpy=4,4'-dimethyl-2,2'-bipyridine) as the pre-catalyst and HCO2Na/HCO2H as the hydrogen source. Moreover, furfural and glucose, were selectively reduced to the valuable alcohols, furfuryl alcohol and sorbitol. The processes were carried out in neat water or in a biphasic water/toluene system. The biphasic system allowed easy recycling, higher yields, and higher selective D incorporation (using D2O/toluene). The deuteration took place due to an efficient effective M-H/D+ exchange from D2O that allows the inversion of polarity of D+ (umpolung). DFT calculations that explain the catalytic behavior in water are also included. [ABSTRACT FROM AUTHOR]

The transfer hydrogenation (TH) of several aldimines has been studied using [RuCl(p‐cymene)(dmbpy)]BF4, 1, (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine) as a precatalyst. Both neat water and a biphasic water/toluene mixture (w/t) have been successfully used as solvents. In the w/t medium the corresponding precursors, amine and aldehyde, were also used as substrates for a transfer hydrogenative reductive amination. Selective deuterium labeling of the resulting alkylated amines was the main goal of this work. On using D2O the D‐content in the amine was negligible but a high level of D‐incorporation was achieved in D2O/toluene. According to calculations, this is due to the effect of the relative rates of the hydride transfer and that of the RuH/D+ exchange. The incorporation of deuterium increases with time as a consequence of the reduction in the hydride transfer rate as the substrate concentration diminishes. The recyclability assays performed reflect the importance of pH in the selectivity of the TH towards the imine or the aldehyde resulting from imine hydrolysis. And now for something a little different: The use of a biphasic medium D2O/toluene allows the selective deuterium incorporation in alkylated amines obtained from transfer hydrogenation from aldimines. This incorporation, which takes place by a RuH/D+ exchange, is negligible in neat D2O. [ABSTRACT FROM AUTHOR]

New cationic, half-sandwich Ru(II) arene compounds of general formula [(η6-arene)RuCl(κ2-N,N-L)]X (where L are functionalized phenanthrolines such as 1,10-phenanthroline-5-amine (aphen); 5,6-epoxy- 5,6-dihydro-[1,10]phenanthroline (ephen); or 4,7-dihydroxy-1,10-phenanthroline (dhphen)) have been prepared to study their anticancer potential. All the isolated complexes have been fully characterized by spectroscopic and analytical techniques. The structure of endo-[(η6-p-cymene)RuCl(κ2-N,N-ephen)]BF4, [2a](BF4), has been determined by X-ray crystallography. The in vitro cytotoxicity of the aphen and ephen phenanthrolines and their Ru derivatives [(η6-p-cymene)RuCl(κ2-N,N-L)]Cl ([1a]Cl and [2a]Cl, respectively) assessed in tumour cell lines has shown that the free ligands are more active than the organometallic products, with aphen being the most potent specimen. Furthermore, the binding interaction of both [1a]Cl and aphen with calf thymus DNA (CT-DNA) has been investigated using a variety of thermodynamic and kinetic techniques. The aphen free ligand intercalates into DNA at low ligand content, whereas [1a]Cl forms with DNA a bifunctional partially intercalated-covalent complex, in which the intercalation constant is nearly three orders of magnitude lower than that of aphen. This finding demonstrates that the covalent binding noticeably weakens the intercalation, a feature presumably related to the higher cytotoxic activity of aphen relative to that of [1a]Cl. [ABSTRACT FROM AUTHOR]

An important challenge in the field of anticancer chemotherapy is the search for new species to overcome the resistance of standard drugs. An interesting approach is to link bioactive ligands to metal fragments. In this work, we have synthesized a set of p-cymene-Ru or cyclopentadienyl-M (M = Rh, Ir) complexes with four chrysin-derived pro-ligands with different -OR substituents at position 7 of ring A. The introduction of a piperidine ring on chrysin led to the highly cytotoxic pro-ligand HL4 and its metal complexes L4-M (SW480 and A549 cell lines, cytotoxic order: L4-Ir > L4-Ru ≈ L4-Rh). HL4 and its complexes induce apoptosis and can overcome cis-platinum resistance. However, HL4 turns out to be more cytotoxic in healthy than in tumor cells in contrast to its metal complexes which displayed higher selectivity than cisplatin towards cancer cells. All L4-M complexes interact with double stranded DNA. Nonetheless, the influence of the metal is clear because only complex L4-Ir causes DNA cleavage, through the generation of highly reactive oxygen species (1O2). This result supports the hypothesis of a potential dual mechanism consisting of two different chemical pathways: DNA binding and ROS generation. This behavior provides this complex with a great effectivity in terms of cytotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: A novel ruthenium bisbipyridine complex, [Ru(bpy)2(hpzb)](PF6)2 (1) (hpzb=hexakis(pyrazol-1-yl)benzene) was obtained in the reaction between [Ru(bpy)2Cl2], the tritopic ligand hpzb and NH4PF6. A high selectivity has been found in the reaction and when the hpzb ligand was made to react with more than one ruthenium fragment, it coordinated selectively only to the first metallic fragment, and it was not possible to introduce two or three ruthenium centres. A similar complex with a deuterated bipyridine has also been obtained. The reaction with the methylated ligand hexakis(3,5-dimethylpyrazol-1-yl)benzene does not take place. A complete assignment of all the proton and carbon NMR signals of 1 was carried out. The orientation of the free pyrazolyl groups is also discussed. The redox properties and the anticancer activity of complex 1 have been studied. [Copyright &y& Elsevier]

The complex [RuH(κ3-bpzmPhO)(cod)] (1) was synthesized by the reaction of [RuH(cod)(NH2NMe2)3][BPh4] with the potassium salt of 2-phenoxy-bis(pyrazol-1-yl)methane (bpzmPhOK). This ligand adopts a κ3-N,N,O coordination on the metal center that is reminiscent of the situation usually observed in trispyrazolylborate complexes. Complex 1 exists in solution as a mixture of two diastereoisomers that are in equilibrium. The reaction of 1 with different phosphines (PMe3, PMe2Ph, PMePh2 and PPh3) has been studied. The reaction product depends not only on the nature of the phosphine but also on the complex:L ratio and the temperature. Diphosphine derivatives of stoichiometries [RuH(κ1-O-bpzmPhO)(cod)L2] (L=PMe3, PMe2Ph) and [RuH(κ3-bpzmPhO)L2] (L=PMe3, PMe2Ph, PMePh2, PPh3) were prepared. Similarly, tetraphosphine derivatives of formula [cis-O,H-RuH(κ1-O-bpzmPhO)L4] (L=PMe3, PMe2Ph) were obtained. The complex with PMe2Ph can be transformed into the respective trans isomer by heating the solution. The reaction of 1 with five equivalents of PMe3 gives rise to a pentaphosphine derivative with complete decoordination of the anionic bpzmPhO ligand. This ligand exhibits hemilabile behavior that involve a reversible coordination of the pyrazole fragments. Proton transfer reactions from HBF4 to 1 have also been studied both in acetone-d6 and in methanol-d4. In all of these processes the proton is selectively transferred to the oxygen of the bpzmPhO ligand, which remains coordinated through at least the N-donor centers. Three hydride derivatives are formed in these reactions and they differ either in the relative orientation of the ligands or in the coordination of the OH group of the ligand. [Copyright &y& Elsevier]

The complex [(η6-p-cymene)Ru(OH2)(κ2-N,N-HL1)](OTf)2(HL1= 2-pyridin-2-yl-1H-benzimidazole), [2c](OTf)2, undergoes easy deprotonationof the N–H group at physiologicalpH, producing [(η6-p-cymene)Ru(OH2)(κ2-N,N-L1)]+, [2c′]+, prone to dimerization both in solution and in thesolid state. X-ray measurements on [2c′]BF4have shown that dimer units are formed in thesolid state by a combination of π–π stacking contactsbetween the aromatic rings of [L1]−andhydrogen bonding involving the water molecules coordinated to themetal center and the deprotonated imidazolyl N atom. The T-jump kineticcurves of the 2D ↔ D2equilibrium recorded in themicrosecond time scale have allowed us to determine the parametersof the dimerization process. The dimer content diminishes as the ionicstrength drops. The different kinetic and thermodynamic techniqueshave all shown that the monomer reacts with DNA, producing the bifunctionalintercalated (through the benzimidazole ligand)-covalent (Ru/N7G)[(η6-p-cymene)Ru(κ2-N,N-L1)]/DNA complex. The cytotoxic activity of [2c′]+was evaluated against human lung carcinoma cells(A549) by the MTT cell viability assay. Interestingly, the percentageof surviving cells as a function of the [2c′]+content displayed biphasic behavior, interpretedas a result of the rise in the dimer content of [2c′]+. As only the monomer can react with DNA,a reasonable correlation between cytotoxic activity and formationof the [(η6-p-cymene)Ru(κ2-N,N-L1)]/DNA complex is established. [ABSTRACT FROM AUTHOR]

Diastereomerically pure complexes of formula CpRuCl(PP*) and CpRUH(pp*) with chiral ferrocenyl diphosphines were prepared and the selectivity of proton-transfer processes over the monohydride compounds with different acids was studied. With 1 equiv of HBF4 the cis-dihydrogen and trans-dihydride complexes were formed while with 3 equiv of CF3CO2H the trans-dihydride derivative was the only product. However, the use of 1 equiv of CF3CO2H led to a dihydrogen bonded complex with an extremely short RUH…HO2CF3 interaction that exhibits proton-hydride exchange. Using the labeled acid CF3CO2D, a stereoselective transference of the deuteron was demonstrated that implies the previous epimerization of the monohydride and the subsequent attack of the acid in the position previously occupied by the hydride. [ABSTRACT FROM AUTHOR]