Preparation of Neutral trans - Cis [Ru(O2CR)2P2(NN)], Cationic [Ru(O2CR)P2(NN)](O2CR) and Pincer [Ru(O2CR)(CNN)P2] (P = PPh3, P2= diphosphine) Carboxylate Complexes and their Application in the Catalytic Carbonyl Compounds Reduction

The diacetate complexes trans-[Ru(\u3ba1-OAc)2(PPh3)2(NN)] (NN = ethylenediamine (en) (1), 2-(aminomethyl)pyridine (ampy) (2), 2-(aminomethyl)pyrimidine (ampyrim) (3)) have been isolated in 76-88% yield by reaction of [Ru(\u3ba2-OAc)2(PPh3)2] with the corresponding nitrogen ligands. The ampy-type derivatives 2 and 3 undergo isomerization to the thermodynamically most stable cationic complexes [Ru(\u3ba1-OAc)(PPh3)2(NN)]OAc (2a and 3a) and cis-[Ru(\u3ba1-OAc)2(PPh3)2(NN)] (2b and 3b) in methanol at RT. The trans-[Ru(\u3ba1-OAc)2(P2)2] (P2 = dppm (4), dppe (5)) compounds have been synthesized from [Ru(\u3ba2-OAc)2(PPh3)2] by reaction with the suitable diphosphine in toluene at 95 \ub0C. The complex cis-[Ru(\u3ba1-OAc)2(dppm)(ampy)](6) has been obtained from [Ru(\u3ba2-OAc)2(PPh3)2] and dppm in toluene at reflux and reaction with ampy. The derivatives trans-[Ru(\u3ba1-OAc)2P2(NN)] (7-16; NN = en, ampy, ampyrim, 8-aminoquinoline; P2 = dppp, dppb, dppf, (R)-BINAP) can be easily synthesized from [Ru(\u3ba2-OAc)2(PPh3)2] with a diphosphine and treatment with the NN ligands at RT. Alternatively these compounds have been prepared from trans-[Ru(OAc)2(PPh3)2(NN)] by reaction with the diphosphine in MEK at 50 \ub0C. The use of (R)-BINAP affords trans-[Ru(\u3ba1-OAc)2((R)-BINAP)(NN)] (NN = ampy (11), ampyrim (15)) isolated as single stereoisomers. Treatment of the ampy-type complexes 8-15 with methanol at RT leads to isomerization to the cationic derivatives [Ru(\u3ba2-OAc)P2(NN)]OAc (8a-15a; NN = ampy, ampyrim; P2 = dppp, dppb, dppf, (R)-BINAP). Similarly to 2, the dipivalate trans-[Ru(\u3ba1-OPiv)2(PPh3)2(ampy)] (18) is prepared from [Ru(\u3ba2-OPiv)2(PPh3)2] (17) and ampy in CHCl3. The pincer acetate [Ru(\u3ba1-OAc)(CNNOMe)(PPh3)2] (19) has been synthesized from [Ru(\u3ba2-OAc)2(PPh3)2] and HCNNOMe ligand in 2-propanol with NEt3 at reflux. In addition, the dppb pincer complexes [Ru(\u3ba1-OAc)(CNN)(dppb)] (CNN = AMTP (20), AMBQPh (21)) have been obtained from [Ru(\u3ba2-OAc)2(PPh3)2], dppb, and HAMTP or HAMBQPh with NEt3, respectively. The acetate NN and pincer complexes are active in transfer hydrogenation with 2-propanol and hydrogenation with H2 of carbonyl compounds at S/C values of up to 10000 and with TOF values of up to 160000 h-1

Exploring the Reactivity and Biological Effects of Heteroleptic N-Heterocyclic Carbene Gold(I)-Alkynyl Complexes

With the aim to explore the effects of different organometallic ligands on the reactivity and biological properties of a series of twelve heteroleptic AuI complexes, of general formula [Au(NHC)(alkynyl)] (NHC = benzimidazolylidene or 1,3-dihydroimidazolylidene) were synthesized and characterized by 1H and 13C NMR and elemental analysis, and in some cases also by X-ray diffraction. The compounds were all stable in H2O/DMSO as established by NMR spectroscopy, while they could react with model thiols (EtSH) in the presence of water to undergo ligand-substitution reactions. 1H NMR experiments showed that dissociation of the more labile alkynyl ligand was possible for all compounds, while in the case of the benzimidazolylidene series also dissociation of the NHC ligand could be observed. DFT calculations suggest that, depending on the steric hindrance exerted by both the NHC wingtip groups and the alkynyl substituents, the reaction can proceed either via a π-stabilized intermediate or with the alkynyl ligand remaining purely σ-coordinated to the AuI center until completely dissociated. The most stable compounds in PBS buffer (pH 7.4), as assessed by UV-Visible spectrophotometry, were further investigated for their ability to stabilize G4 DNA by FRET DNA melting assay, showing only moderate activity. Moreover, two derivatives were tested in vitro for their anticancer activities in three different human cancer cell lines and showed cytotoxicity in the low micromolar range

C−C Cross-Couplings from a Cyclometalated Au(III) C∧ N Complex: Mechanistic Insights and Synthetic Developments

In recent years, the reactivity of gold complexes was shown to extend well beyond π-activation and to hold promises to achieve selective cross-couplings in several C−C and C−E (E=heteroatom) bond forming reactions. Here, with the aim of exploiting new organometallic species for cross-coupling reactions, we report on the Au(III)-mediated C(sp2)−C(sp) occurring upon reaction of the cyclometalated complex [Au(CCH2N)Cl2] (1, CCH2N=2-benzylpyridine) with AgPhCC. The reaction progress has been monitored by NMR spectroscopy, demonstrating the involvement of a number of key intermediates, whose structures have been unambiguously ascertained through 1D and 2D NMR analyses (1H, 13C, 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC) as well as by HR-ESI-MS and X-ray diffraction studies. Furthermore, crystallographic studies have serendipitously resulted in the authentication of zwitterionic Au(I) complexes as side-products arising from cyclization of the coupling product in the coordination sphere of gold. The experimental work has been paralleled and complemented by DFT calculations of the reaction profiles, providing valuable insight into the structure and energetics of the key intermediates and transition states, as well as on the coordination sphere of gold along the whole process. Of note, the broader scope of the cross-coupling at the Au(III) CCH2N centre has also been demonstrated studying the reaction of 1 with C(sp2)-based nucleophiles, namely vinyl and heteroaryl tin and zinc reagents. These reactions stand as rare examples of C(sp2)−C(sp2) cross-couplings at Au(III)

Synthesis, Structural Characterization and Antiproliferative Activity of Gold(I) and Gold(III) Complexes Bearing Thioether-Functionalized N-Heterocyclic Carbenes

A series of gold(I) and gold(III) complexes with N-heterocyclic carbene ligands functionalized with a pendant thioether group (NHC-SR) was synthesized with straightforward procedures and characterized in solution with NMR spectroscopy and ESI-MS spectrometry, as well as in the solid state by means of single crystal X-ray diffraction analysis. Selected experimental aspects were rationalized through relativistic DFT calculations. The gold(I) and gold(III) complexes displayed moderate in vitro cytotoxicity towards breast cancer cells MCF7

Highly-fluorescent BODIPY-functionalised metallacages as drug delivery systems: synthesis, characterisation and cellular accumulation studies

With the aim of designing new metallosupramolecular architectures for drug delivery, research has focused on porous 3-dimensional (3D)-metallacages able to encapsulate cytotoxic agents protecting them from metabolism while targeting them to cancer sites. Here, two self-assembled [Pd2L4]4+ cages (CG1 and CG2) featuring 3,5-bis(3-ethynylpyridine)phenyl ligands (L) exo-functionalised with dipyrromethene (BODIPY) groups have been synthesised and characterised by different methods, including NMR spectroscopy and mass spectrometry. 1H NMR spectroscopy studies shows that the cages are able to encapsulate the anticancer drug cisplatin in their hydrophobic cavity, as evidenced by electrostatic potential (ESP) analysis based on XRD studies. The stability of the cages in an aqueous environment, and in the presence of the intracellular reducing agent glutathione, has been confirmed by UV-visible absorption spectroscopy. The luminescence properties of the cages enabled the investigation of their cellular uptake and intracellular localisation in human cancer cells by confocal laser scanning microscopy. In melanoma A375 cells, cage CG1 is taken up via active transport and endocytic trafficking studies show little evidence of transport through the early endosome while the cages accumulated in melanosomes rather than lysosomes. The antiproliferative activity of the lead cage was investigated in A375 together with two breast cancer cell lines, SK-BR-3 and MCF7. While the cage per se is non-cytotoxic, very different antiproliferative effects with respect to free cisplatin were evidenced for the [(cisplatin)2⊂CG1·BF4] complex in the various cell lines, which correlate with its different intracellular localisation profiles. The obtained preliminary results provide a new hypothesis on how the subcellular localisation of the cage affects the cisplatin intracellular release

Facile preparation of a cobalt diamine diketonate adduct as a potential vapor phase precursor for Co3O4films

Co3O4thin films and nanosystems are implemented in a broad range of functional systems, including gas sensors, (photo)catalysts, and electrochemical devices for energy applications. In this regard, chemical vapor deposition (CVD) is a promising route for the fabrication of high-quality films in which the precursor choice plays a key role in the process development. In this work, a heteroleptic cobalt complex bearing fluorinated diketonate ligands along with a diamine moiety [Co(tfa)2\ub7TMEDA; tfa = 1,1,1-trifluoro-2,4-pentanedionate and TMEDA =N,N,N\u2032,N\u2032-tetramethylethylenediamine] is investigated as a potential Co molecular precursor for the CVD of Co3O4systems. For the first time, the compound is characterized by crystal structure determination and comprehensive analytical studies, focusing also on its thermal properties and fragmentation patterns, important figures of merit for a CVD precursor. The outcomes of this investigation, accompanied by detailed theoretical studies, highlight its very favorable properties for CVD applications. In fact, growth experiments under oxygen atmospheres containing water vapor revealed the suitability of Co(tfa)2\ub7TMEDA for the fabrication of high-quality, phase-pure Co3O4thin films. The versatility of the proposed strategy in tailoring Co3O4structural/morphological features highlights its potential to obtain multi-functional films with controllable properties for a variety of eventual technological end-uses

A versatile Fe(II) diketonate diamine adduct: Preparation, characterization and validation in the chemical vapor deposition of iron oxide nanomaterials

Iron(III) oxide nanomaterials are extremely promising for the development of magnetic devices, gas sensors, photocatalysts, and photoelectrodes for solar water splitting. The fabrication of such systems by chemical vapor deposition (CVD) relies on the use of molecular sources joining shelf-stability, high volatility, and clean decomposition. Herein, we report for the first time on a versatile iron(II) precursor, namely Fe(tfa)2TMEDA (tfa = 1,1,1-trifluoro-2,4-pentanedionate; TMEDA = N,N,N\u2032,N\u2032-tetramethylethylenediamine), combining the above features with a simple molecular concept. A theoretical-experimental characterization confirmed the compound spectroscopic purity and monomeric nature, and enabled to elucidate its structural, vibrational and electronic properties, along with its fragmentation pathway and thermal behavior. The ideal Fe(tfa)2TMEDA characteristics for CVD applications were finally validated through the fabrication of high purity iron oxide nanomaterials. The latter, comprising the sole metastable \u3b2-Fe2O3 polymorph rather than the most stable rust (\u3b1-Fe2O3), were characterized by the occurrence of oxygen defects and a nano-organization tunable as a function of growth temperature and reaction atmosphere