Isolation of the Au145(SR)60X compound (R = n-butyl, n-pentyl; X = Br, Cl): novel gold nanoclusters that exhibit properties subtly distinct from the ubiquitous icosahedral Au144(SR)60 compound.

We report the identification and quantitative isolation of Au145(SR)60X (R = n-butyl, n-pentyl; X = halide) along with elucidation of key properties as compared to the corresponding ubiquitous chiral-icosahedral Au144(SR)60 cluster known to have a central vacancy. The stoichiometries were assessed by electrospray mass spectrometry (ESI-MS) at isotopic resolution, and induced dissociation patterns indicate the 'extra' (Au,Br) atoms are strongly bound components of these structures. Voltammetric and spectroscopic characterization reveals Au145(SR)60X behaviors that are qualitatively similar to yet fascinatingly distinct from those of Au144(SR)60. (1H,13C)-NMR spectra clearly show how both Au145(SR)60X and Au144(SR)60 are capped by 12 distinct ligand types of 5-fold equivalence, as was recently established for Au144(SR)60 capped by shorter ligands, demonstrating that this novel cluster shares the same chiral-icosahedral motif. Intriguingly, Au145(SR)60X is strongly near-IR luminescent, whereas under comparable conditions Au144(SR)60 barely emits. The photoluminescence pattern of Au145(SR)60X is very similar to that observed for Au25(SR)18, which contains the Au13 core. The combined results are interpreted as consistent with neutral Au145(SR)60X as a diamagnetic species, electronically and structurally similar to the corresponding Au144(SR)60 compounds.

Synthesis, Characterization and Biological Activity of Novel Cu(II) Complexes of 6-Methyl-2-Oxo-1,2-Dihydroquinoline-3-Carbaldehyde-4n-Substituted Thiosemicarbazones.

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

Metal Doping of Au25(SR)18- Clusters: Insights and Hindsights.

The study of the structures and properties of atomically precise gold nanoclusters is the object of active research worldwide. Recently, research has been also focusing on the doping of metal nanoclusters through introduction of noble metals, such as platinum, and less noble metals, such as cadmium and mercury. Previous studies, which relied extensively on the use of mass spectrometry and single-crystal X-ray crystallography, led to the assignment of the location of each of these foreign-metal atoms. Our study provides new insights into this topic and, particularly, compelling evidence about the actual position of the selected metal atoms M = Pt, Pd, Hg, and Cd in the structure of Au24M(SR)180. To make sure that the results were not dependent on the thiolate, for SR we used both butanethiolate and phenylethanethiolate. The clusters were prepared according to different literature procedures that were supposed to lead to different doping positions. Use of NMR spectroscopy and isotope effects, with the support of mass spectrometry, electrochemistry, and single-crystal X-ray crystallography, led us to confirm that noble metals indeed dope the cluster at its central position, whereas no matter how the doping reaction is conducted and the nature of the ligand, the position of both Cd and Hg is always on the icosahedron shell, rather than at the central or staple position, as often reported. Our results not only provide a reassessment of previous conclusions, but also highlight the importance of NMR spectroscopy studies and cast doubts on drawing conclusions mostly based on single-crystal X-ray crystallography.

Nuclear and Electron Magnetic Resonance Spectroscopies of Atomically Precise Gold Nanoclusters.

Atomically precise gold nanoclusters display properties that are unseen in larger nanoparticles. When the number of gold atoms is sufficiently small, the clusters exhibit molecular properties. Their study requires extensive use of classic molecular physical chemistry and, thus, methods such as vibrational spectroscopies, electrochemistry, density functional theory and molecular dynamics calculations, and of course nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies. NMR and EPR studies have been mostly carried out on the benchmark, stable molecules Au25(SR)18, Au38(SR)24, Au102(SR)44, and Au144(SR)60 (where SR = thiolate). In this Account, we showcase examples primarily taken from our previous and ongoing NMR and EPR studies, which we hope will trigger further interest in the use of these sensitive, though often underutilized, techniques. Indeed, 1D and 2D NMR spectra of pure, atomically precise clusters can be very detailed and informative. Molecular clusters are molecules and, thus, have discrete energy levels and undergo stepwise oxidation or reduction. The effect of the charge state on the chemical shifts and line shapes is a function of the ligand type (ligands differ due to specific bonds with different Au atom types) and the position of the chemical group along the ligand backbone: for groups near the Au core, they can be very dramatic. Ligand-protected gold clusters are hard-soft molecules where a hard metal core is surrounded by a dynamic molecular layer. The latter provides a nanoenvironment that interfaces the cluster core with the surrounding environment and can be permeated by molecules and ions. NMR spectroscopy is especially useful to assess its structure. For example, the data show that whereas long alkanethiolates form bundles, shorter chains exhibit more conformational freedom and are quite folded. NMR spectroscopy allows studying diastereotopic effects and provides information on possible hydrogen bonds of ligands with sulfur or surface gold atoms. EPR spectroscopy is a very precise technique to check and characterize the magnetic state of gold clusters or clusters doped with foreign-metal atoms. Electron nuclear double resonance (ENDOR) provides a powerful tool to assess the interaction of an unpaired electron with nuclei, as we showed for 197Au and 1H. It can be used as a sensitive probe of the spin-density distribution in nanoclusters: for example, it showed that the singly occupied molecular orbital may span outside the Au core by nearly 6 Å. Solid-state EPR spectroscopy has provided compelling evidence that the specific ligands and the crystallinity degree are very important factors in determining the interactions between clusters in the solid state. Depending on the condition, paramagnetic, superparamagnetic, ferromagnetic, or antiferromagnetic behavior can be observed. Time-resolved EPR was successfully tested to determine the efficiency of singlet-oxygen generation via sensitization of Au25 clusters. This Account thus demonstrates some of the remarkable insights that can be gained into the properties of atomically precise clusters through detailed NMR and EPR studies.

Gold Fusion: From Au25(SR)18 to Au38(SR)24, the Most Unexpected Transformation of a Very Stable Nanocluster.

The study of the molecular cluster Au25(SR)18 has provided a wealth of fundamental insights into the properties of clusters protected by thiolated ligands (SR). This is also because this cluster has been particularly stable under a number of experimental conditions. Very unexpectedly, we found that paramagnetic Au25(SR)180 undergoes a spontaneous bimolecular fusion to form another benchmark gold nanocluster, Au38(SR)24. We tested this reaction with a series of Au25 clusters. The fusion was confirmed and characterized by UV-vis absorption spectroscopy, ESI mass spectrometry, 1H and 13C NMR spectroscopy, and electrochemistry. NMR evidences the presence of four types of ligand and, for the same proton type, double signals caused by the diastereotopicity arising from the chirality of the capping shell. This effect propagates up to the third carbon atom along the ligand chain. Electrochemistry provides a particularly convenient way to study the evolution process and determine the fusion rate constant, which decreases as the ligand length increases. No reaction is observed for the anionic clusters, whereas the radical nature of Au25(SR)180 appears to play an important role. This transformation of a stable cluster into a larger stable cluster without addition of any co-reagent also features the bottom-up assembly of the Au13 building block in solution. This very unexpected result could modify our view of the relative stability of molecular gold nanoclusters.

Synthesis, characterization and cytotoxic activity of novel copper(II) complexes with aroylhydrazone derivatives of 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde.

Three new 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde terminal substituted aroylhydrazone ligands (2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H2L1, 1, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H2L2, 2, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H2L3, 3) and the corresponding novel copper(II) complexes [Cu(L)(CH3OH)(NO3)](L = HL1 (4), HL2 (5), HL3 (6-6+), have been synthesized to compare their coordination behaviour and biological activity with respect to the presence of an OH group in different positions of the phenyl ring in the hydrazone moieties. The new ligands and their copper complexes were characterized by elemental analysis and spectroscopic techniques. The molecular structures of the new complexes 4 and 6-6+ were determined by single crystal X-ray diffraction. The interactions of the free ligands and their copper complexes with calf thymus DNA were tested by absorption measurements and ethidium bromide competitive studies which revealed that all compounds may interact with calf thymus DNA through intercalation. Furthermore, a comparative analysis of the cytotoxic effect of the compounds on a panel of human cancer cell lines showed that the copper complexes exhibited in vitro antitumor activity significantly higher than that of the free ligands and also of cisplatin.

A SERRS/MRI multimodal contrast agent based on naked Au nanoparticles functionalized with a Gd(iii) loaded PEG polymer for tumor imaging and localized hyperthermia.

Multimodal contrast agents offer new interesting diagnostic possibilities, summing the benefits of multiple imaging techniques. Magnetic resonance and optical imaging are complementary techniques. The first allows total body screening, even though it suffers from low spatial resolution and needs high loadings, whereas the second shows lower penetration, but bright signals, and a higher spatial resolution and needs lower loadings. We present a plasmonic nanosystem as a MRI (magnetic resonance imaging) and SERRS (surface enhanced resonance Raman scattering) multimodal contrast agent. Naked gold nanoparticles, obtained by laser ablation synthesis in solution, are organized as a highly efficient SERRS substrate with a naphthalocyanine reporter and functionalized with a MRI contrast agent with a newly synthesized 3DOTA-PEG polymer, with a high GdIII loading. As a proof of concept, in vivo and ex vivo MRI and SERRS experiments are also performed. The plasmonic property of the nanosystem is then exploited to show its usefulness for localized hyperthermia.

Atomically precise Au144(SR)60 nanoclusters (R = Et, Pr) are capped by 12 distinct ligand types of 5-fold equivalence and display gigantic diastereotopic effects.

For two decades, Au144(SR)60 has been one of the most studied and used thiolate (SR) protected gold nanoclusters. In many ways, however, it proved to be a challenging and elusive case, also because of the difficulties in solving its structure by single-crystal X-ray crystallography. We used very short thiols and could prepare Au144(SC2H5)60 and Au144(SC3H7)60 in a very pure form, which was confirmed by UV-vis absorption spectroscopy and very regular electrochemistry patterns. Inductively coupled plasma and electrospray ionization mass spectrometries gave definite proof of the Au144(SR)60 stoichiometry. High-resolution 1D and 2D NMR spectroscopy in the solution phase provided the result of assessing the presence of 12 ligand types in exactly the same amount (5-fold equivalence). Equally important, we found that the two protons belonging to each methylene group along the thiolate chain are diastereotopic. For the α-CH2 protons, the diastereotopic effect can be indeed gigantic, as it reaches chemical-shift differences of 2.9 ppm. DFT calculations provided insights into the relationship between structure and NMR results. In particular, the 12 ligand types and corresponding diastereotopic effects may be explained by considering the presence of C-H···S hydrogen bonds. These results thus provide fundamental insights into the structure of the thiolate layer capping this long-studied gold nanocluster.

Ion Pair Formation between Tertiary Aliphatic Amines and Perchlorate in the Biphasic Water/Dichloromethane System.

The ability of aliphatic amines (AAs), namely, tripropylamine (TPrA), trisobutylamine (TisoBuA), and tributylamine (TBuA), to form ion pairs with perchlorate anion (ClO4-) in biphasic aqueous/dichloromethane (CH2Cl2) mixtures containing ClO4- 0.1 M has been demonstrated by GC with flame ionization (FID) and mass detectors (MS) and by NMR measurements. The extraction efficiency of the AAs to the organic phase was modeled by equations that were used to fit the experimental GC data, allowing us to determine values for KP (partition constant of the free AA), KIP (formation constant of the ion pair), and KPIP (partition constant of the ion pair) for TPrA, TisoBuA, and TBuA at 25 °C. Ion pairs were shown to form in CH2Cl2 also when ClO4- is replaced by other inorganic anions, like NO3-, ClO3-, Cl-, H2PO4-, and IO3-. No ion pairs formed when CH2Cl2 was replaced by n-hexane, suggesting that aliphatic amine ion pairs can form in polar organic solvents but not in nonpolar ones.

Atom Transfer Radical Polymerization of Methacrylic Acid: A Won Challenge.

Polymerization of acidic monomers is one of the biggest challenges for atom transfer radical polymerization (ATRP). An intramolecular cyclization reaction leading to the loss of the C-X chain-end functionality was found to be the main reason for the partial termination of the growing polymer chains. Three approaches were used to overcome this problem: using Cl as the chain-end halogen, lowering the pH (to 0.9), and increasing polymerization rate. Methacrylic acid (MAA) was polymerized by both electrochemically mediated ATRP and supplemental activator and reducing agent ATRP up to high conversion (>90%), in t ≤ 4 h at 25 °C, using inexpensive and nontoxic reagents (NaCl, diluted HCl, water). Control over molecular weight (MW) dispersity was satisfactory, and MWs were in agreement with theoretical values. The "livingness" of the process was confirmed by an electrochemical switch, used to repeatedly and periodically deactivate/reactivate growing chains.

A magnetic look into the protecting layer of Au25 clusters.

The field of molecular metal clusters protected by organothiolates is experiencing a very rapid growth. So far, however, a clear understanding of the fine interactions between the cluster core and the capping monolayer has remained elusive, despite the importance of the latter in interfacing the former to the surrounding medium. Here, we describe a very sensitive methodology that enables comprehensive assessment of these interactions. Pulse electron nuclear double resonance (ENDOR) was employed to study the interaction of the unpaired electron with the protons of the alkanethiolate ligands in four structurally related paramagnetic Au25(SR)018 clusters (R = ethyl, propyl, butyl, 2-methylpropyl). Whereas some of these structures were known, we present the first structural description of the highly symmetric Au25(SPr)018 cluster. Through knowledge of the structural data, the ENDOR signals could be successfully related to the types of ligand and the distance of the relevant protons from the central gold core. We found that orbital distribution affects atoms that can be as far as 6 Å from the icosahedral core. Simulations of the spectra provided the values of the hyperfine coupling constants. The resulting information was compared with that provided by 1H NMR spectroscopy, and molecular dynamics calculations provided useful hints to understanding differences between the ENDOR and NMR results. It is shown that the unpaired electron can be used as a very precise probe of the main structural features of the interface between the metal core and the capping ligands.

Smart and Covalently Cross-Linked: Hybrid Shape Memory Materials Reinforced through Covalent Bonds by Zirconium Oxoclusters.

The first examples of organic-inorganic hybrid materials reinforced by transition-metal oxoclusters that exhibit shape memory properties, based on the covalent incorporation of zirconium-based inorganic building blocks, are reported. Methacrylate-functionalized zirconium oxoclusters Zr4 O2 (OMc)12 and [Zr6 O4 (OH)4 (OOCCH2 CH3 )3 {OOCC(CH3 )=CH2 }9 ]2 , with the covalent incorporation in a butyl acrylate (BA)/polycaprolactone dimethacrylate (PCLDMA) copolymer and the noncovalent incorporation of [Zr6 O4 (OH)4 (OOCCH2 CH3 )12 ]2 are focused upon herein. Shape recovery and fixity rates are studied to observe if the shape memory properties are preserved upon going from a simple copolymer to noncovalent or covalent-based hybrids. These rates display values higher than 90 %, which provides evidence that the oxocluster does not hinder the shape memory properties in the hybrid materials. The introduction of an inorganic phase and the progressively more stable interactions between organic and inorganic parts lead to an enhancement of the thermomechanical properties. The materials are characterized through FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and swelling tests. Dynamic-mechanical analyses are used to investigate whether the hybrid materials display thermally activated shape memory properties. The stability of the hybrid materials are evaluated by a combined spectroscopic approach based on FTIR, solid-state NMR, and X-ray absorption spectroscopy.

Gold nanowired: a linear (Au25)(n) polymer from Au25 molecular clusters.

Au25(SR)18 has provided fundamental insights into the properties of clusters protected by monolayers of thiolated ligands (SR). Because of its ultrasmall core, 1 nm, Au25(SR)18 displays molecular behavior. We prepared a Au25 cluster capped by n-butanethiolates (SBu), obtained its structure by single-crystal X-ray crystallography, and studied its properties both experimentally and theoretically. Whereas in solution Au25(SBu)18(0) is a paramagnetic molecule, in the crystal it becomes a linear polymer of Au25 clusters connected via single Au-Au bonds and stabilized by proper orientation of clusters and interdigitation of ligands. At low temperature, [Au25(SBu)18(0)]n has a nonmagnetic ground state and can be described as a one-dimensional antiferromagnetic system. These findings provide a breakthrough into the properties and possible solid-state applications of molecular gold nanowires.

Au25(SEt)18, a nearly naked thiolate-protected Au25 cluster: structural analysis by single crystal X-ray crystallography and electron nuclear double resonance.

X-ray crystallography has been fundamental in discovering fine structural features of ultrasmall gold clusters capped by thiolated ligands. For still unknown structures, however, new tools capable of providing relevant structural information are sought. We prepared a 25-gold atom nanocluster protected by the smallest ligand ever used, ethanethiol. This cluster displays the electrochemistry, mass spectrometry, and UV-vis absorption spectroscopy features of similar Au25 clusters protected by 18 thiolated ligands. The anionic and the neutral form of Au25(SEt)18 were fully characterized by (1)H and (13)C NMR spectroscopy, which confirmed the monolayer's properties and the paramagnetism of neutral Au25(SEt)18(0). X-ray crystallography analysis of the latter provided the first known structure of a gold cluster protected by a simple, linear alkanethiolate. Here, we also report the direct observation by electron nuclear double resonance (ENDOR) of hyperfine interactions between a surface-delocalized unpaired electron and the gold atoms of a nanocluster. The advantages of knowing the exact molecular structure and having used such a small ligand allowed us to compare the experimental values of hyperfine couplings with DFT calculations unaffected by structure's approximations or omissions.

Electron transfer through 3D monolayers on Au25 clusters.

The monolayer protecting small gold nanoparticles (monolayer-protected clusters, MPCs) is generally represented as the 3D equivalent of 2D self-assembled monolayers (SAMs) on extended gold surfaces. However, despite the growing relevance of MPCs in important applied areas, such as catalysis and nanomedicine, our knowledge of the structure of 3D SAMs in solution is still extremely limited. We prepared a large series of monodisperse Au25(SCnH2n+1)18 clusters (n=2, 4, 6, 8, 10, 12, 14, 16, 18) and studied how electrons tunnel through these monolayers. Electron transfer results, nicely supported by 1H NMR spectroscopy, IR absorption spectroscopy, and molecular dynamics results, show that there is a critical ligand length marking the transition between short ligands, which form a quite fluid monolayer structure, and longer alkyl chains, which self-organize into bundles. At variance with the truly protecting 2D SAMs, efficient electronic communication of the Au25 core with the outer environment is thus possible even for long alkyl chains. These conclusions provide a different picture of how an ultrasmall gold core talks with the environment through/with its protecting but not-so-shielding monolayer.

Characterization and quantification of N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine biocide by NMR, HPLC/MS and titration techniques.

The present paper reports the determination of the tri-amine N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (TA) present in a raw material called LONZABAC used to formulate various, widely used commercial biocides. The active principle, TA, is present in LONZABAC together with other molecules at lower concentration levels. Three independent analytical approaches, namely solution NMR spectroscopy, liquid chromatography coupled to high resolution mass spectrometry (LC/HRMS) and acid-base titration in mixed solvent, were used to overcome the problem of the non-availability of the active principle as high purity standard. NMR analysis of raw material, using a suitable internal standard, evidenced in all analyzed lots the presence of the active principle, the N-dodecyl-1,3-propanediamine (DA) and the n-dodecylamine (MA) and the absence of non-organic, NMR-inactive species. NMR peak integration led to a rough composition of the MA:DA:TA as 1:9:90. The LC/HRMS analysis allowed the accurate determination of DA and MA and confirmed in all samples the presence of the TA, which was estimated by difference: MA=1.4±0.3%, DA=11.1±0.7%, TA=87.5±1.3%. The obtained results were used to setup an easy, rapid and cheap acid-base titration method able to furnish a sufficiently accurate evaluation of the active principle both in the raw material and in diluted commercial products. For the raw material the results were: TA+MA=91.1±0.8% and DA-MA=8.9±0.8%, statistically coherent with LC/MS ones. The LC/MS approach demonstrated also its great potentialities to recognize trace of the biocide components both in environmental samples and in the formulated commercial products.

ß-Fe2O3 nanomaterials from an iron(II) diketonate-diamine complex: a study from molecular precursor to growth process.

Iron oxide is a key multi-functional material in many different fields of modern technology. The ß-Fe(2)O(3) cubic phase, one of the least studied Fe-O systems, was obtained by Chemical Vapor Deposition (CVD) using for the first time a Fe(II) ß-diketonate diamine complex, Fe(hfa)(2)·TMEDA, as the molecular source (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N',N'-tetramethylethylenediamine). The strong visible light absorption of ß-Fe(2)O(3) deposits highlights their possible functional application in photocatalytic hydrogen production under solar light. A comprehensive investigation on the Fe(ii) complex, performed by a joint experimental-theoretical approach, explains the molecular origin of its excellent thermal behaviour and reveals why this species is a successful precursor for the CVD of iron oxide nanostructures.

Effect of the charge state (z = -1, 0, +1) on the nuclear magnetic resonance of monodisperse Au25[S(CH2)2Ph]18(z) clusters.

Monodisperse Au(25)L(18)(0) (L = S(CH(2))(2)Ph) and [n-Oct(4)N(+)][Au(25)L(18)(-)] clusters were synthesized in tetrahydrofuran. An original strategy was then devised to oxidize them: in the presence of bis(pentafluorobenzoyl) peroxide, the neutral or the negatively charged clusters react as efficient electron donors in a dissociative electron-transfer (ET) process, in the former case yielding [Au(25)L(18)(+)][C(6)F(5)CO(2)(-)]. As opposed to other reported redox methods, this dissociative ET approach is irreversible, easily controllable, and clean, particularly for NMR purposes, as no hydrogen atoms are introduced. By using this approach, the -1, 0, and +1 charge states of Au(25)L(18) could be fully characterized by (1)H and (13)C NMR spectroscopy, using one- and two-dimensional techniques, in various solvents, and as a function of temperature. For all charge states, the NMR results and analysis nicely match recent structural findings about the presence of two different ligand populations in the capping monolayer, each resonance of the two ligand families displaying distinct NMR patterns. The radical nature of Au(25)L(18)(0) is particularly evident in the (1)H and (13)C NMR patterns of the inner ligands. The NMR behavior of radical Au(25)L(18)(0) was also simulated by DFT calculations, and the interplay between theory and experiments revealed a fundamental paramagnetic contribution coming from Fermi contact shifts. Interestingly, the NMR patterns of Au(25)L(18)(-) and Au(25)L(18)(+) were found to be quite similar, pointing to the latter cluster form as a diamagnetic species.

Platinum(II) chloride indenyl complexes: electrochemical and biological evaluation.

Four platinum(II) complexes of general formula [PtCl(η(1)-C(9)H(7))L(2)] [where L(2) is 1,2-bis(diphenylphosphino)ethane (dppe) 1 or cycloocta-1,5-diene (cod) 3] and [PtCl(2)L(2)] (where L(2) is dppe 2 or cod 4) were studied. Inhibition growth assays on human tumor cell lines evidenced for 1 and 3 an antiproliferative effect and, interestingly, the cytotoxic effect exerted by 1 is similar to that of cisplatin. Electrochemical and NMR measurements allowed us to determine the structural and redox properties. Investigation of the mechanism of action responsible for the cytotoxicity demonstrated a weak capacity of interacting with DNA. Some experiments performed on rat liver mitochondria indicate that 1 acts as an inducer of the mitochondrial permeability transition, thus leading to the release of proapoptotic factors, such as cytochrome c and apoptosis-inducing factor.

From thioxo cluster to dithio cluster: exploring the chemistry of polynuclear zirconium complexes with S,O and S,S ligands.

Three different zirconium thio and oxothio clusters, characterized by different coordination modes of dithioacetate and/or monothioacetate ligands, were obtained by the reaction of monothioacetic acid with zirconium n-butoxide, Zr(O(n)Bu)4, in different experimental conditions. In particular, we isolated the three polynuclear Zr3(µ3-SSSCCH3)2(SSCCH3)6·2(n)BuOH (Zr3), Zr4(µ3-O)2(µ-η(1)-SOCCH3)2(SOCCH3)8(O(n)Bu)2 (Zr4), and Zr6(µ3-O)5(µ-SOCCH3)2(µ-OOCCH3)(SOCCH3)11((n)BuOH) (Zr6) derivatives, presenting some peculiar characteristics. Zr6 has an unusual star-shaped structure. Only sulfur-based ligands, viz., chelating dithioacetate monoanions and an unusual ethane-1,1,1-trithiolate group µ3 coordinating the Zr ions, were observed in the case of Zr3. 1D and 2D NMR analyses confirmed the presence of differently coordinated ligands. Raman spectroscopy was further used to characterize the new polynuclear complexes. Time-resolved extended X-ray absorption fine structure measurements, devoted to unraveling the cluster formation mechanisms, evidenced a fast coordination of sulfur ligands and subsequent relatively rapid rearrangements.