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Ligating properties of a tripodal, potentially tetradentate aminetris(phenol) ligand, tris(2-hydroxy-3,5-di-tert-butylbenzyl)amine, H3L, containing [N,O,O,O] donor atoms toward the vanadium ions in +iiiand ivoxidation states have been studied. The structures of complexes 1[LVIII(CH3OH)]0, 2[LVIV(OCH3)]0and 3[LVIV(acac)]0were determined by X-ray diffraction methods as having five-coordinate V(iii), 1, five-coordinate non-oxo-vanadium(iv), 2, and six-coordinate non-oxo-vanadium(iv) 3, respectively. Compounds 1–3were also studied with electrochemical methods, variable-temperature (2–295 K) magnetic susceptibility measurements and X-band electron paramagnetic resonance (EPR) spectroscopy. The electrochemical results of 2and 3suggest metal-centered oxidation, i.e.the generation of a VV-phenolate species. EPR investigations indicate a (dxy)1ground state showing a considerable increase in the in-plane π-bonding, as is expected for a phenolate ligand. [ABSTRACT FROM AUTHOR]

2-Aminomethylaniline was converted into the N,N′-bis(pivaloyl) (1) or -bis(trimethylsilyl) (2) derivative, using 2 ButC(O)Cl or 2 Me3SiCl ( RCl), respectively, with 2 NEt3, or for 2from successively using 2 LiBunand 2 RCl. N,N′-Bis(neopentyl)-2-(aminomethyl)aniline (3) was prepared by LiAlH4reduction of 1. From 2or 3and 2 LiBun, the appropriate dilitiodiamide {2-[{N(Li)R}C6H4{CH2N(Li)R}(L)]2(L absent, 4a; or L = THF, 4b) or the N,N′-bis(neopentyl) analogue (5) of 4awas prepared. Treatment of 4awith 2 ButNC, 2 (2,6-Me2C6H3NC) or 2 ButCN ( L′) furnished the corresponding adduct [2-N{Li(L′)R}C6H4{CH2N(Li)R}] (4c, 4dor 4e, respectively), whereas 4bwith 2 PhCN afforded [2-{N(Li)R}C6H4{CH2C(Ph) = NLi(NCPh)}] (6). The dimeric bis(amido)stannylene [Sn{N(R)C6H4(CH2NR)-1,2}]2(7) was obtained from 4aand [Sn(μ-Cl)NR2]2, while the N,N′-bis(neopentyl) analogue 8of 7was similarly derived from [Sn(μ-Cl)NR2]2and 5. Reaction of two equivalents of the diamine 2with Pb(NR2)2yielded 9, the lead homologue of 7. Oxidative addition of sulfur to 7led to the dimeric bis(diamido)tin sulfide 10. Treatment of 2successively with ‘MgBu2’ in C5H12and THF gave [Mg{N(R)C6H4(CH2NR)}(THF)]2(11a), which by displacement of its THF by an equivalent portion of ButCN or PhCN produced [Mg{N(R)C6H4(CH2NR)}(CNR')n] [R′ = But, n= 1 (11b); R′ = Ph, n= 2 (11c)]. The Ca (12), Sr (13) or Ba (14) analogues of the Mg compound 11awere isolated from 2and either the appropriate compound M(NR2)2(M = Ca, Sr, Ba), or successively 2 LiBunand 2 M(OTos)2. The new compounds 1–14were characterized by microanalysis (C, H, N; not for 1, 2, 3, 5), solution NMR spectra, νmax(CN) (IR for 4c, 4d, 4e, 6, 11b, 11c), selected EI-MS peaks (for 1, 2, 3, 7, 8, 9, 10), and single crystal X-ray diffraction (for 4a, 4b, 11a). [ABSTRACT FROM AUTHOR]

Ligand–metal cooperation in iridium and platinum complexes bearing tricyclic dibenzobarrelene-based PC(sp3)P pincer ligands is discussed. We demonstrated that the carbon–metal bond in these complexes may be efficiently cleaved and regenerated via1,2-addition/elimination reactions. [ABSTRACT FROM AUTHOR]

The synthesis of novel heterobimetallic derivatives of general formula [RuClCp(PPh3)-μ-dmoPTA-1κP:2κ2N,N′-M(acac-κ2O,O′)2] (M = Ni (3), Zn (4); dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) is described. The preparations of the ruthenium–cobalt analogue (M = Co (2)) and the starting compound [RuClCp(HdmoPTA-κP)(PPh3)](CF3SO3) have been revised and their yield improved. Similar to 2, the solid state structures of 3and 4show that the dmoPTA-P and the dmoPTA-NCH3atoms are involved in the coordination to the {RuCpCl(PPh3)} and {M(acac)2} moieties, respectively. The size of the diffusing units is almost the same for the three binuclear complexes, indicating that they exhibit similar solution structures. The diamagnetic ruthenium–zinc derivative was fully characterized in solution at 193 K by NMR as two diastereomeric pairs of enantiomers (R-Ru, Δ-Zn; R-Ru, Λ-Zn; S-Ru, Δ-Zn; S-Ru, Λ-Zn). Finally, the electrochemical properties of the complexes have been investigated by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Trialkyl imido niobium and tantalum complexes [MR3(NtBu)] (M = Nb, R = Me 2, CH2CMe33, CH2CMe2Ph 4, CH2SiMe35; M = Ta, R = Me 6, CH2CMe2Ph 7, CH2SiMe38) have been prepared by treatment of solutions containing [MCl3(NtBu)py2] (M = Nb 1a, Ta 1b) with three equivalents of magnesium reagent. By an unexpected hydrolysis reaction of the tris-trimethylsilylmethyl imido tantalum compound 8a, a μ-oxo derivative [(Me3SiCH2O)(Me3SiCH2)3Ta(μ-O)Ta(CH2SiMe3)2(NtBu)] (8a) was formed and its structure was studied by X-ray diffraction methods. Reactions of trialkyl imido compounds with two equivalents of isocyanide 2,6-Me2C6H3NC result in the migration of two alkyl groups, leading to the formation of a series of alkyl imido bisiminoacyl derivatives [MR(NtBu){C(R)NAr}2] (Ar = 2,6-Me2C6H3; M = Nb, R = Me 9, CH2CMe310, CH2CMe2Ph 11, CH2SiMe312, CH2Ph 13; M = Ta, R = CH2CMe314, CH2CMe2Ph 15, CH2SiMe316). All compounds were studied by IR and NMR (1H, 13C and 15N) spectroscopy. [ABSTRACT FROM AUTHOR]

Twelve Pt(ii) complexes with cis-PtP2S2pharmacophores (where P2refers to two monodentate or one bidentate phosphane ligand and S2is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(ii)complexes. On the whole, the cis-PtP2S2compounds displayed significant antiproliferative properties while the cis-PtP2Cl2(cis-dichloro bisphosphane Pt(ii)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(ii) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP2Cl2compounds, whereas cis-PtP2S2compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure–activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP2S2compounds strongly suggests that these compounds will undergo specific activation within the cellular environment. [ABSTRACT FROM AUTHOR]

Pseudooctahedral complexes [MCl3(NtBu)L2] (M = Nb, L = py 1, ½ tmeda 3; M = Ta, L = py 2, ½ tmeda 4) have been studied by spectroscopic methods. By a VT 1H NMR experiment a mutual exchange process between the pyaxand pyfreein the complexes 1–2was observed, whereas 13C and 15N NMR studies showed in the complexes 3–4a tmeda ligand with an axial/equatorial coordination mode. The reaction of 2with 3 equiv of Grignard reagent produces the methathesis products [TaR3(NtBu)] (R = CH2CMeCH25, CH2CHCHCH36) in which 2-methylallyl and 2-butenyl groups appear with a η3- and σ-coordination mode, respectively. When, toluene solutions of the compounds 5–6were treated with 2 equiv of 2,6-dimethylphenylisocyanide the imido bisiminoacyl compounds [TaR(NtBu){C(R)NAr-κ1C}2] (Ar = 2,6-Me2C6H3; R = CH2CMeCH27, CH2CHCHCH38) can be isolated, viaan imido iminoacyl intermediate [TaR2(NtBu){C(R)NAr-κ1C}] (Ar = 2,6-Me2C6H3; R = CH2CMeCH29) as we have observed in the treatment of 5with 1 equiv of isocyanide; however, the analogous reaction between 5and COPh2leads to the formation of the trisalkoxo imido compound [Ta(OCPh2R)3(NtBu)] (R = CH2CMeCH210). All new complexes were studied by IR and multinuclear NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Two {Co3+–Zn2+} heterobimetallic coordination networks have been synthesized utilizing Co3+complex as the building blocks. The structural studies reveal 2D sheet-like networks where the Co3+containing building blocks are connected through Zn2+ions. Two different building blocks generate two unique networks as evidenced by the crystallographic studies and other properties. These networks are shown to catalyze Lewis metal ion assisted Strecker reaction in heterogeneous manner. [ABSTRACT FROM AUTHOR]

The structures and magnetic properties of a family of new octanuclear heterometallic 3d-4fcomplexes [MnIII4LnIII4(μ3-OH)4(μ2,η1-X)4(O2CBut)8(t-bdea)4]·solv, where X = N3−, Ln = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6); X = OCN−, Ln = Dy (7); X = NO3−, Ln = Gd (8), Tb (9), Dy (10), Ho (11), Er (12); solv = MeCN or toluene, are reported. The metal topology in the aggregates can be described as consisting of a “Ln4-square inscribed in a Mn4-square”. Complexes 1-7are prepared by the reactions of t-butyldiethanolamine (t-bdeaH2) with a preformed hexanuclear manganese pivalate complex [Mn6], the respective lanthanide salt and either NaN3or NaNCO, while 8-12are obtained from the direct reaction of Mn(OAc)2, Ln(NO3)3·xH2O and t-butyldiethanolamine. The magnetic properties of all the complexes were investigated using variable temperature magnetic susceptibility and magnetisation measurements. Similar magnetic behaviour was observed for compounds containing the same lanthanide, indicating that changing the bridging ligand X does not have a significant effect on the magnetic behaviour. The TbIIIand DyIIIcompounds 4, 5, 7, 9and 10all show frequency-dependent acsusceptibilities indicative of a slow relaxation of magnetisation and are therefore considered as Single-Molecule Magnets. [ABSTRACT FROM AUTHOR]

The role of the NH3ligands in the highly successful antitumour agents cisplatin and carboplatin is not fully understood. Suggestions that the ammonia ligands are involved in target recognition through hydrogen bond formation, e.g.with guanine-O6, have been questioned. Here, we review the roles and functions of NH3ligands of cis-PtCl2(NH3)2and likewise of its trans-isomer in complexes with model nucleobases as well as other N-heterocyclic ligands. Specifically, their roles in hydrogen bonding interactions with nucleobases as well as anions, the influence on acid–base properties of co-ligands, their involvement in condensation reactions, as well as a variety of displacement reactions will be examined. As a result, it can be stated that the ammonia ligands in cis- and trans-PtII(NH3)2entities display additional features to those generally discussed in the last four decades since the discovery of the antitumour activity of cisplatin. [ABSTRACT FROM AUTHOR]

An electrospray ionization mass spectrometer equipped with a quadrupole ion trap as the mass analyzer provided a powerful tool for the investigation of metal ligand affinities of catalysts for atom transfer radical polymerization. It allowed, in particular, (i) the identification, in a library of ligands, of the most stable, and thus active, copper catalysts; (ii) the assessment of the effects of the reaction medium on the relative stabilities of the catalyst complexes; and (iii) the evaluation of the influence of the nature of the ligand on both the complex halogenophilicity and the metal–ligand stabilities in the gas-phase. [ABSTRACT FROM AUTHOR]

The loading of pre-treated amorphous silica with platinum or palladium was carried out by using the molecular precursors Pt2(μ-Cl)2Cl2(CO)2, or Pd2(μ-Cl)2Cl2(CO)2, respectively, which contain the required amount of coordinated CO to carry out the formation of the metal particles upon contact with moisture. The reactivity of the well-soluble mononuclear platinum complex cis-PtCl2(CO)2with stoichiometric amounts of water was investigated either under N2or CO. The metal nanoparticles produced on the silica matrix have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalytic performance of the silica-supported metals thus produced was evaluated in the hydrogenation of cyclohexene. [ABSTRACT FROM AUTHOR]

The combination of a [1111]metacyclophane blocked in 1,3-alternate conformation and bearing four imidazole units with MX2(M = Co, Cu, Zn and Hg; X = Cl or Br) complexes leads to the formation of a series of analogous neutral metallamacrotricycles. In all cases, the structure of the binuclear complexes has been studied by X-ray diffraction methods on single crystals. [ABSTRACT FROM AUTHOR]

Isostructural CoII2CoIII4LnIII4(Ln = Y (1), Gd (2) and Dy (3)) coordination clusters formed using the ligand Tris are the first examples of 3d-4f complexes involving this ligand and show weak ferromagnetic coupling between the CoIIions and slow relaxation (SMM) behaviour for 3. [ABSTRACT FROM AUTHOR]

Copper complexes have long been considered as a promising class of anticancer or antibacterial therapeutics. In this paper, two novel copper(II) complexes containing a β-carboline derivative and amino acids, namely [Cu(1-Im-βc)(L -Val)]ClO4·0.5H2O (Cu1) and [Cu(1-Im-βc)(L -Phe)]ClO4·0.5H2O (Cu2), where 1-Im-βc = 1-(2-imidazolyl)-β-carboline, L -Val = L -valine, and L -Phe = L -phenylalanine, were designed and synthesized. The complexes were characterized by elemental analysis, infrared spectroscopy, molar conductivity measurements, and mass spectrometry to determine their spatial structures and compositions. Both complexes bind to DNA by insertion. The complexes also show a good affinity for human serum albumin (HSA). In addition, the antitumor activity of the two complexes against lung cancer cells (A549), cervical cancer cells (HeLa), and breast cancer cells (MBA-MD-231) is significantly superior to that of the traditional antitumor drug, cisplatin. Finally, the anticancer mechanism results show that the complexes can induce apoptosis in HeLa cells, which is associated with mitochondrial damage, oxidative stress caused by reactive oxygen species (ROS) production, and activation of the caspase protein family. This study demonstrates that the introduction of aromatic heterocyclic alkaloid ligands with a broad spectrum of biological activities and water-soluble amino acid ligands into copper complexes can regulate their amphiphilic properties and biological activity, so as to obtain highly efficient copper-based therapeutics. [ABSTRACT FROM AUTHOR]

This paper describes the recognition process of tetrahedral [CuII(tnz)2X2] (X = Cl, Br) complexes by a DNA chain, analyzing the specific interaction between the DNA bases and backbone with the metal and the tinidazole (tnz) ligand. We identified the coordination of the copper metal center with one or two phosphates as the first recognition site for the tinidazole copper(II) complexes, while the ligands present partial intercalation into the minor groove. Also, we discuss a novel trigonal copper(I) tnz bromide complex, obtained by reducing the previously reported [Cu(tnz)2Br2]. This complex sheds light on the mechanism of action of tnz metal complexes as one of the most stable DNA-complex adducts depicts a trigonal geometry around the copper ion. [ABSTRACT FROM AUTHOR]

This paper demonstrates the metal ion effects on the quercetin 2,4-dioxygenase (2,4-QD)-like reactivity. For this purpose, a series of five metal(II)–acetato complexes [MII(L)(OAc)] {M = Mn (1OAc), Co (2OAc), Ni (3OAc), Cu (4OAc), Zn (5OAc); OAc = acetate} supported with a newly designed N3O-donor carboxylato ligand L− {L− = 2-((benzyl((6′-methyl-[2,2′-bipyridin]-6-yl)methyl)amino)methyl)benzoate} has been synthesised as models for the active sites of MII-substituted 2,4-QDs. The enzyme–substrate (ES) model complexes [MII(L)(fla)] {M = Mn (1fla), Co (2fla), Ni (3fla), Cu (4fla), Zn (5fla); flaH = flavonol} have been synthesised by reacting flaH with their corresponding acetate-bound complexes in basic conditions. Detailed physicochemical properties of all the compounds are reported. Furthermore, single-crystal X-ray diffractions have been done to determine the structures of the compounds 2OAc·2H2O, 3OAc, 4OAc·CH2Cl2·2H2O, 5OAc·2H2O and 2fla·MeOH. The enzymatic reactivities of complexes 1OAc–5OAc towards the dioxygenation of flavonol have been explored in detail. All the complexes effectively catalyse the oxygenative degradation of flavonol in N,N-dimethylformamide (DMF) medium at 70 °C under multiple-turnover conditions and produce enzyme-type products. Kinetic investigations were performed to see the metal ions' effects on reactivity. The reaction rates vary with the metal ions, showing the order Co > Ni > Zn > Mn > Cu. The studies reveal that the reactivities of the [MII(L)(OAc)] complexes are governed primarily by three factors viz the ES adduct formation constant (Kf), the redox potential (Epa) of the bound fla−/fla˙ couple, and the degree of delocalisation of the fla˙ radical with the metal electrons, which are drastically influenced by the M2+ ions. In the mechanistic interpretation, a single-electron transfer (SET) from the bound-flavonolate to dioxygen has been proposed to generate the catalytically important "M(II)–fla˙" radical and superoxide ion, which react further to bring about the dioxygenation reaction. The identification of the metal(II)-bound flavonoxy radical intermediate for the case of cobalt using EPR spectroscopy and the detection of superoxide ion by NBT2+ test and EPR spin-trapping experiment (DMPO test) are remarkable in envisaging the reaction pathway. [ABSTRACT FROM AUTHOR]

Transition metal isocyanide complexes have attracted increasing attention owing to their versatile applications in catalytic organic transformations. Compared with metal complexes with neutral isocyanide ligands, those featuring anionic isocyanide groups are relatively rare and poorly understood. So far, there has been no report on structurally characterized metal anionic isocyanopentafluorophosphate complexes that may have potential for the development of some unique polymerization reactions. In this paper, we adopt a dicationic thiolate-bridged diiron complex as the reaction platform for the coordination activation and functionalization of cyanide. When treating with KCN, a facile salt metathesis with hexafluorophosphate anions occurred to generate monocyanide or dicyanide species. However, using trimethylsilyl cyanide as the substrate, an unsymmetrical diiron complex bearing a terminal [CNSiMe3] ligand and an anionic [NCPF5]− group derived from the activation of one non-coordinating anion PF6− was obtained in a high yield. Interestingly, due to the lability of the N–Si bond in the [CNSiMe3] ligand, it can play the role of an active site for the interaction with counter anions in the outer sphere. On one hand, this labile ligand can facilitate the activation of the P–F bond in PF6− and the C–B bond in BPh4− to afford structurally characterized thiolate-bridged diiron anionic isocyanopentafluorophosphate and isocyanotriphenylborate complexes, respectively. On the other hand, it can also interact with Lut·HCl to convert into a cyanide ligand stabilized by a hydrogen bonding interaction. This work represents a new synthetic pathway to furnish metal anionic isocyanide complexes. [ABSTRACT FROM AUTHOR]

This paper reports firstly the syntheses, crystal structures, and thermal and magnetic properties of spin crossover salts of formulae [Fe(bpp)2]3[Cr(CN)6]2·13H2O (1) and [Fe(bpp)2][N(CN)2]2·H2O (2) (bpp = 2,6-bis(pyrazol-3-yl)pyridine) exhibiting hydrogen-bonded networks of low-spin [Fe(bpp)2]2+ complexes and [Cr(CN)6]3− or [N(CN)2]− anions, with solvent molecules located in the voids. Desolvation of 1 is accompanied by a complete low-spin (LS) to a high-spin (HS) transformation that becomes reversible after rehydration by exposing the sample to the humidity of air. The influence of the lattice water on the magnetic properties of spin-crossover [Fe(bpp)2]X2 complex salts has been documented. In most cases, it stabilises the LS state over the HS one. In other cases, it is rather the contrary. The second part of this paper is devoted to unravelling the reasons why the lattice solvent stabilises one form over the other through magneto-structural correlations of [Fe(bpp)2]2+ salts bearing anions with different charge/size ratios (Xn−). The [Fe(bpp)2]2+ stacking explaining these two different behaviours is correlated here with the composition of the second coordination sphere of the Fe centers and the ability of these anions to form hydrogen bonds and/or π–π stacking interactions between them or the bpp ligand. [ABSTRACT FROM AUTHOR]

In this work, we present a facile preparation of a paper-based glucose assay for rapid, sensitive, and quantitative measurement of glucose in blood plasma and urine. Two copper phosphorescent complexes [Cu(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu1) and [Cu(2,9-dimethyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu2) and a new silver congener [Ag(P3)CNAg(P3)][B(C6H3(CF3)2)4] (Ag3) (P3 = PPh2C6H4-PPh-C6H4PPh2 [bis(o-diphenylphosphinophenyl)phenylphosphine]) have been synthesized and their oxygen sensing abilities were investigated. The dimetallic phosphine-based Ag3 complex, having a high oxygen sensing ability, was employed as an efficient signal transducer in enzymatic reactions to recognize blood plasma glucose and urine glucose, which provided a wide linear response for a concentration range between 1.0 and 35 mM and a rapid response, with a limit of detection (LOD) of 0.09 mM for glucose. In practical application, this Ag3 paper-based device offers great analytical reliability and accuracy upon monitoring glucose concentrations in blood plasma. [ABSTRACT FROM AUTHOR]

A zinc tetrasulfanido complex supported by a bis(carboxamide)pyridine ligand framework has been synthesized by the insertion of elemental sulfur into the zinc–S(thiolate) bond of a zinc dithiolate complex ([LZn]2−). This paper reports on sulfur transfer reactions of this polysulfanido complex ([1]2−) and compares this behavior to known reactions of metal polysulfido complexes. Complex [1]2− was demonstrated to be in exchange with [LZn]2− and free elemental sulfur in solution. Although triphenylphosphine abstracts sulfur from [1]2− to form [LZn]2−, complex [LZn]2− can abstract sulfur from the zinc polysulfido complex (TMEDA)ZnS6 (TMEDA = N,N,N′,N′-tetramethylethylenediamine). The tetrasulfanido complex [1]2− can also transfer sulfur to dimethyl acetylenedicarboxylate to form a zinc dithiolene complex. These studies demonstrate that the zinc complex with a tetrasulfanido moiety can undergo similar reactions as metal complexes with purely inorganic polysulfido groups, although the final metal-containing products are different. [ABSTRACT FROM AUTHOR]

In this paper, we focused on the analysis of the effects mediated by different cyclic dithiocarbamic ligands (DTC) on three classes of antiproliferative coordination compounds, namely, Ru(iii) complexes with the general formulae [Ru(DTC)3] and [Ru2(DTC)5]Cl, and the neutral Cu(ii) derivatives of the type [Cu(DTC)2]. In particular, we present the synthesis and characterization of a library of total 23 coordination compounds containing Ru(iii) or Cu(ii) as the biologically-active metal center and two or more dithiocarbamato (DTC) ligands derived from cyclic amines (aliphatic or aromatic). Several techniques including elemental analysis, X-ray crystallography, ESI-MS, 1H-NMR spectroscopy, FT-IR and UV-Vis spectrophotometry were used to characterize the compounds, which highlighted the different electronic behaviors generated by the substituents within the DTC moiety. Moreover, the synthesized compounds were tested for their stability in order to investigate their antiproliferative activity against 3 human cancer cell lines, namely, HeLa, HepG2 and HepG2/SB3. In particular, HepG2/SB3 was chosen for its aggressiveness due to upregulation of the anti-apoptotic protein SerpinB3. Finally, the most promising compounds are studied in terms of log P. Overall, the results reveal the drug-likeness of some of the derivatives of copper(ii) and ruthenium(iii). [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and structural characterisation of a series of cyclooctatetraenyl (C8H8) complexes of calcium and strontium, most of them containing the bis(trimethylsilyl)amido ligand. Mixing MI2 (M = Ca, Sr), KN(SiMe3)2 and K2(C8H8) in thf in a 2 : 2 : 1 ratio gave the inverse sandwich amido complexes [[{(Me3Si)2N}M(thf)x]2(μ-C8H8)] (M = Ca, x = 1; M = Sr, x = 2) (1-Ca, 1-Sr) in fair to good yields. From a 1 : 1 : 1 ratio, the mixed potassium calcium complex [[{(Me3Si)2N}Ca(thf)](μ-C8H8)K] (2) was obtained in good yield. The reaction of 2 with a 1 : 1 mixture of CaI2 and KN(SiMe3)2 yielded 1-Ca confirming that the reaction could be carried out stepwise. Attempts at making heterobimetallic calcium strontium amido complexes from the reaction of 2 with Sr{N(SiMe3)2}2 led to redistribution reactions which afforded the potassium strontium complex [[K{(Me3Si)2N}2Sr]2(μ-C8H8)] (3) among other species. Complex 3 was more conveniently synthesised in fair yield starting from a 2 : 4 : 1 molar mixture of SrI2, KN(SiMe3)2 and K2(C8H8), respectively. Treatment of 2 with PhC≡CH in benzene yielded an insoluble complex tentatively formulated as the polymeric complex [CaK(CCPh)(C8H8)(thf)x]n (4). Upon dissolution in thf, 4 underwent a redistribution reaction yielding the X-ray characterised [{Ca(μ-C8H8)2}K2(thf)2] (5) and a homoleptic calcium alkynyl complex [Ca(CCPh)2(thf)x]. Several compounds were characterised by X-ray diffraction as discrete or polymeric structures where Ca…Cπ interactions were identified in some cases. Despite identified drawbacks, such as the lability of the coordinated thf ligands and facile redistribution reactions, this study represents the first synthetic approach to cyclooctatetraenyl heavy alkaline-earth metal amido complexes. [ABSTRACT FROM AUTHOR]

Efficient synthesis and structure elucidation of carbon–calcium σ-bonded compounds are of remarkable interest and importance in organometallic chemistry of the heavier s-block metals. In this paper, we report that styryl and biphenyl calcium complexes with well-defined structures can be facilely obtained via metathesis reaction between their corresponding dilithio compound and calcium iodide. Single-crystal X-ray structural analysis of these calcium complexes revealed their unique iodide-bridged or dicalcium-bridged structures. Their reactivity toward nitrous oxide was disclosed. [ABSTRACT FROM AUTHOR]

Non-metallic η²-H2 complexes are extremely rare; moreover in the case of boranes (with the exception of the BH5 molecule) the existence of such structures was only indicated by computational studies. In a recent paper we have demonstrated that external electron donor groups can stabilize the η²-H2 complexes, similar to the backdonation in the case of transition metals. In this paper we present evidence of a new stabilizing effect: electron donation from the B-R bonds to the H2 σ* orbital. The stability and electronic structure of several mono-, di-, and trisubstituted borane-H2 complexes were investigated by ab initio calculations. SiR3 groups were found to facilitate the σ(B-R)σ*(H-H) interaction, increasing the stability of the η² complexes. Furthermore in the case of tris(trimethyl)silylborane, the exceptional stability of a novel neutral pentavalent borane structure is shown. [ABSTRACT FROM AUTHOR]

The synthetic methodologies, physico-chemical peculiarities, properties, and structure of metal chelate dendrimers and star and hyperbranched polymers are considered. These compounds are subdivided into molecular, intracomplex, and macrocyclic types which in turn are classified depending on the nature of the donor atoms (N,N-, N,O-, N,S-, O,O-, O,S-, S,S-, P,P-chelates, etc.). Special attention is paid to the features of the preparation of metal chelate star polymers by “arm-first”, “core-first” and click-to-chelate approaches. The main data on the synthesis, spatial structure and properties of the metal chelate hyperbranched polymers are summarized. The basic concepts and synthetic strategies leading to the different types of supramolecular metal chelate dendrimers are analyzed. The problems and future prospects of metal chelate dendrimers and star and hyperbranched polymers are outlined. The bibliography includes papers published after 2010. [ABSTRACT FROM AUTHOR]

Heterogeneous metal complex catalysts for the water oxidation reaction have ever been desired for the development of devices simulating photosynthesis. This paper describes the design of highly active and robust heterogeneous iridium complex catalysts for chemical water oxidation. The heterogeneous catalyst (Ir-BPy-NT) was prepared by the post-synthetic metalation of bipyridine-containing mesoporous organosilica nanotubes (BPy-NT) with an [IrCp*Cl(μ-Cl)]2 (Cp* = η5-pentamethylcyclopentadienyl) complex. The as-prepared Ir-BPy-NT catalyst showed enhanced durability with high reaction activity compared to the analogous homogeneous and the conventional heterogeneous ones, due to the stable nanotube structures as well as the isolated active sites. The unique one-dimensional nanotubes with large pore diameters can also reduce the diffusion limitation and facilitate the transport of reactants and products during reactions. [ABSTRACT FROM AUTHOR]

The paper describes three methods for the preparation of methoxysiloxide complexes, a rare class of complexes of relevance to room temperature vulcanization (RTV) of polysiloxanes. The salt metathesis reaction involves the use of the recently described reagent NaOSi(OMe)2Me with various metal chlorides to give Cp*2Ti[OSi(OMe)2Me](OMe), (Me,MeN2N)NiOSi(OMe)2Me, (IPr)CuOSi(OMe)2Me, and (triphos)CoOSi(OMe)2Me (Cp* = C5Me5, triphos = Me(CH2PPh2)3). Several attempted reactions gave methoxide complexes instead, a pathway that is attributed to the intermediacy of κ2-OSi(OMe)2Me species. The diol Cp*2Zr(OH)2 reacts with excess (MeO)3SiMe to give Cp*2Zr[OSi(OMe)2Me]2. In contrast the less nucleophilic Cp*2Ti(OH)2 was unreactive. The third route to methoxysiloxide complexes involves the reaction of Cp*2M(O)(py) with (MeO)3SiMe to give Cp*2M[OSi(OMe)2Me](OMe) in nearly quantitative yield (M = Ti, Zr). The structures of Cp*2Ti[OSi(OMe)2Me](OMe), Cp*2Zr[OSi(OMe)2Me](OMe), (IPr)CuOSi(OMe)2Me, and (triphos)CoOSi(OMe)2Me were confirmed by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Based on ligands dfppyH and pidpyH, cyclometalated Ir(iii) complexes [Ir(dfppy)2(pidpyH)](PF6) (1·PF6) and [Ir(dfppy)2(pidpy)] (2) have been synthesized. The crystal structures indicate that each {Ir(dfppy)2}+ unit is coordinated by a neutral ligand pidpyH in 1·PF6, while by a pidpy− anion in 2. The packing structure of 1·PF6 only exhibits electrostatic interactions and van der Waals interactions among [Ir(dfppy)2(pidpyH)]+ cations and PF6− ions. In contrast, the neighboring molecules in 2 are linked into a supramolecular chain structure through aromatic stacking interactions between two dfppy− ligands. In solution, 1·PF6 and 2 show acid/base-induced structural transformation due to the protonation/deprotonation of their pyridyl groups and/or imidazole units, which can be confirmed by their 1H NMR spectra. At room temperature, compounds 1·PF6, 2 and pidpyH in CH2Cl2 reveal TFA-induced luminescence switching behaviors, from a non-luminescence state to a luminescence state with an emission at 582 nm for both 1·PF6 and 2, and emission switching from 392 nm to 502 nm for pidpyH. These switching behaviors are associated with the protonation of pyridyl groups and/or imidazole units in 1·PF6, 2 and pidpyH. Moreover, compounds 1·PF6 and 2 were used as photosensitizers (PS) for reduction of water to hydrogen under the same experimental conditions. It was found that the amount of evolved hydrogen and the PS turnover number are 512 μmol and 102 for 1·PF6, and 131 μmol and 26 for 2, respectively. Thus, compound 1·PF6 has better photocatalytic activity than 2. In this paper, we discuss the modulation of luminescence and photocatalytic activities of 1·PF6 and 2 by varying the coordination mode and/or protonation extent of pidpyH/pidpy− ligands. [ABSTRACT FROM AUTHOR]

Hydrogen production from water splitting is nowadays recognized as a target, fundamental reaction for the production of clean fuels. Indeed, tremendous efforts have been devoted towards the research of suitable catalysts capable of performing this reaction. With respect to heterogeneous systems, molecular catalysts such as metal complexes are amenable to chemical functionalization in order to fine tune the catalytic properties. In this paper a new class of tris(2-pyridylmethyl)-amine (TPMA) cobalt(ii) complexes (CoL0–4) has been synthesized and employed as hydrogen evolving catalysts under photochemical conditions taking advantage of Ru(bpy)32+ (where bpy is 2,2′-bipyridine) as a light-harvesting sensitizer and ascorbic acid as a sacrificial electron donor. Tuning of the photocatalytic activity has been attempted through the introduction of different substituents at the catalyst periphery rather than through a direct chemical modification of the chelating TPMA ligand. The results show that CoL0–4 behave as competent hydrogen evolving catalysts (HECs), although the effects played by the different substituents on the catalysis are relatively modest. Possible reasons supporting the observed behavior as well as possible improvements of the aforementioned tuning approach are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a gadolinium(iii) complex that shows blue phosphorescence in the crystalline state at room temperature under air atmosphere; color of the crystals can be changed to pale-green from blue by doping of 1-naphthol. [ABSTRACT FROM AUTHOR]

This paper presents the first dysprosium(iii) complex, [{(MeMeArO)3tacn}DyIII(THF)] (1Dy), that shows oxygen-sensitive luminescence. The synthesis, structure and oxygen-sensitive luminescence properties of 1Dy are reported (Φ = 0.050 and τ = 17.7 μs under N2, Φ = 0.011 and τ = 4.1 μs under O2 and KSV = 305 M−1 in THF; KSV = 0.0077%−1 in polystyrene film). The oxygen sensitive mechanism of 1Dy is discussed based on the photophysical properties of the corresponding gadolinium(iii) complex, [{(MeMeArO)3tacn}GdIII(THF)]. [ABSTRACT FROM AUTHOR]

In this paper we present a first insight into the cytotoxic action mode of copper(i) iodide or copper(i) thiocyanate complexes with a phosphine derivative of sparfloxacin (a 3rd generation fluoroquinolone antibiotic agent) and 2,9-dimethyl-1,10-phenanthroline or 2,2′-biquinoline as auxiliary ligands. The in vitro cytotoxic activity of the new complexes was tested against two cancer cell lines (CT26 – mouse colon carcinoma and A549 – human lung adenocarcinoma). An ICP-MS study revealed a marked time-dependent intracellular copper accumulation of the tested compounds. In addition, confocal microscopy imaging showed accumulation of the complexes inside whole cells and their emission of blue light. The complexes generate reactive oxygen species in the cancer cells, which was examined by using two different fluorescent probes. Moreover, (i) DNA intercalation studied by luminescence spectroscopy, circular dichroism and molecular docking, and (ii) plasmid DNA damage also demonstrate their significant cytotoxicity. All these observed biological effects contribute to the induction of apoptosis, observed at a great predominance. [ABSTRACT FROM AUTHOR]

This paper presents a 1,4,7,10-teraazacyclododecane-based tetrakis-phenol as a protonated ligand precursor and its oxygen-sensitive luminescent terbium(iii) complex with an extendable phenol pendant arm (Φ = 0.91 under N2, Φ = 0.031 under air), in which the potentially N4O4-octadentate ligand unprecedentedly coordinates to the Tb3+ ion in a N4O3-heptadentate fashion. [ABSTRACT FROM AUTHOR]

The platinum(ii) half-lantern dinuclear complexes [{Pt(bzq)(μ-C7H4NS2-κN,S)}2] (A) and [{Pt(bzq)(μ-C7H4NOS-κN,S)}2] (B) [bzq = benzo[h]quinolinate, C7H4NS2 = 2-mercaptobenzothiazolate, C7H4NOS = 2-mercaptobenzoxazolate] in solution of DMSO–H2O undergo a dramatic color change from yellowish-orange to purple and turn-off phosphorescence in the presence of a small amount of Hg2+, being discernible by the naked-eye and by spectroscopic methods. Other metal ions as Ag+, Li+, Na+, K+, Ca2+, Mg2+, Ba2+, Pb2+, Cd2+, Zn2+ and Tl+ were tested and, even in a big excess, showed no interference in the selective detection of Hg2+ in water. Job's plot analysis indicated a 1 : 1 stoichiometry in the complexation mode of Hg2+ by A/B. The phosphorescence quenching attributed to the formation of [A/B : Hg2+] complexes showed binding constants of K = 1.13 × 105 M−1 (A) and K = 1.99 × 104 M−1 (B). The limit of detection has been also evaluated. In addition, dried paper test strips impregnated in DMSO solutions of A and B can detect concentration of Hg2+ in water as low as 1 × 10−5 M for B and 5 × 10−5 M for A, making these complexes good candidates to be used as real-time Hg2+ detectors. The nature of the interaction of the Pt2 half-lantern complex A with the Hg2+ cation, has been investigated by theoretical calculations. [ABSTRACT FROM AUTHOR]

A theoretical investigation into eighteen recently synthesized Pt(II) complexes [(R1n-CNC-R2n)Pt(L)] with doubly deprotonated cyclometalated R1n-CNC-R2n ligands (n = 1-9, R1n-CNC-R2n = 2,6- diphenylpyridine derivatives) and L ligands (L = DMSO, 1-9; L = -CuN≡Ar, 1a-9a), which are used as emitters in orange-red emitting diodes, is reported in this paper. Geometric and electronic structures, absorption and emission spectra, phosphorescence quantum yields, and electroluminescence (EL) efficiency were investigated by DFT and TDDFT methods. We focused on the influence of the primary ligand (R1n-CNC-R2n) and auxiliary ligand (L) on the optical and electronic properties of Pt(II) complexes by introducing carbazole, fluorene, and thiophene group in the primary ligand and/or the replacement of DMSO by -CuN-Ar as an ancillary ligand. The incorporation of carbazole, fluorene, and thiophene into the primary ligand caused the red-shift of absorption and emission spectra. The metal-ligand bond length is contracted where -CuN-Ar was employed as the secondary ligand, which facilitate the metal to ligand charge transfer (MLCT). The larger involvement of MLCT character in emission process is beneficial for improving the quantum yields of 2a-9a. For EL efficiency, all the complexes have a good balance of reorganization energy as potential systems for fabricating effective OLEDs devices except for 1 and 1a. In addition, two new molecules were designed with comparable or better EL efficiency. [ABSTRACT FROM AUTHOR]

Recently, a new {RuNO}6 complex, [Ru(L)(PPh3)(NO)(Cl)]2+ (where L = 1-phenyl-1-(pyridin-2-yl)-2-(pyridin-2-ylmethylene)hydrazine), was reported which exhibits a one-electron quasireversible oxidation. The oxidized product, [Ru(L)(PPh3)(NO)(Cl)]3+, was isolated and proposed to be a highly unusual {RuNO}5 complex. In this paper, we investigate the electronic structure of both of these ruthenium complexes by DFT calculations and find that the oxidized species is best described as a {RuNO}6 complex with a co-ligand radical. [Ru(L)(PPh3)(NO)(Cl)]2+ is therefore oxidized to [Ru(L+·)(PPh3)(NO)(Cl)]3+, i.e. this is an interesting example of a complex with two non-innocent ligands simultaneously bound to a ruthenium center. [ABSTRACT FROM AUTHOR]

A new mononuclear ruthenium(II) complex, trans-[Ru(dmb)2(Cl)(EtOH)](PF6) (dmb = 4,4′-dimethyl-2,2′- bipyridine), has been prepared and characterized by elemental analysis, spectroscopic techniques and single crystal X-ray structure determination. The complex was studied as a precatalyst for the electrocatalytic reduction of CO2 to CO in an acetonitrile solution by cyclic voltammetry (CV). The catalytic mechanism was investigated by means of quantum chemical calculations to gain deeper insight into the process of CO2 reduction. The results suggest that the reaction proceeds in six steps initiating by the two sequential 1ē reductions at the dmb ligands followed by CO2 addition to give a metallocarboxylate intermediate. This intermediate undergoes further reduction and loses a CO molecule. The results reported in this paper are of great significance in providing theoretical insight into a class of electrocatalysts for reduction of CO2 to CO. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and a detailed investigation in solution, through 1H NMR, optical absorption, fluorescence spectroscopy and second-order nonlinear optical studies, on the structure and photophysical properties of a series of unsymmetrical alkoxy-derivatized Schiff-base ZnII species bearing on one side an alkyl ammonium bromide as a Lewis base. Overall results suggest that these complexes are present in solution of dichloromethane as dimeric aggregates in which each molecular unit mutually interacts with another unit through intermolecular Zn...Br- interactions. This represents an alternative approach to control the supramolecular architecture of Lewis acidic, Schiff-base ZnII complexes. [ABSTRACT FROM AUTHOR]

The synthesis of ligands 1-L–6-L that feature the 6-[9,9-di(2-ethylhexyl)-7-R-9H-fluoren-2-yl]-2,2′-bipyridine (C^N^N) core (R = 4-R′-phenylethynyl with R′ = NO2, benzothiazol-2-yl (BTZ), H and OCH3 or R = 4′-BTZ-phenyl or BTZ) and their platinum complexes 1–6 were reported in this paper. The photophysical properties of these ligands and the Pt(ii) complexes, including the UV-vis absorption spectra, emission characteristics at room temperature and at 77 K, and the triplet transient difference absorption spectra, were systematically investigated in order to understand the effects of the substituent at the 4-position of the 1-ethynylphenyl component and the extension of π-conjugation between the C^N^N core and the BTZ substituent. Reverse saturable absorption (RSA) of complexes 1–6 was demonstrated at 532 nm using 4.1 ns laser pulses. The UV-vis absorption spectra of 1-L–6-L are featured by strong 1π,π* transitions in the blue spectral region, and the absorption bands are effectively red-shifted by substitution at the 4-position of the ethynylphenyl motif and by the extended π-conjugation of the linkage. A similar effect was observed for the fluorescence spectra of these ligands in CH2Cl2 at room temperature, but the nature of the fluorescence varies from 1π,π* fluorescence in 3-L and 6-L, to intraligand charge transfer (1ILCT) fluorescence in 1-L, 2-L and 5-L; while 4-L possesses mixed 1π,π*/1ILCT characters. All ligands exhibit moderate triplet transient absorption (TA) in the visible spectral region, with substitution at the 4-position of the ethynylphenyl component broadening of the TA bands, while extended π-conjugation of the linkage inducing red-shifts of the TA bands. For Pt(ii) complexes 1–6, their UV-vis absorption spectra constitute red-shifted 1π,π* transitions and low-energy metal-to-ligand charge transfer (1MLCT/1ILCT) tails. The emission of these complexes at room temperature in CH2Cl2 predominantly originates from the C^N^N core localized 3π,π* state, probably mixed with minor 3MLCT character. 4-Position substitution and extended π-conjugation on the ligands exert a negligible effect on the shape and energy of the emission spectra. Similar to their respective ligands, 1–6 all exhibit broader and red-shifted TA spectra with respect to their ligands and both the 4-position substitution and extended π-conjugation bathochromically shift the TA band maxima. The nonlinear transmission experiments carried out for 1–6 at 532 nm reveal that all complexes exhibit strong reverse saturable absorption (RSA), and the degree of RSA follows this trend: 6 ＜4 ＜5 ＜2≤3 ＜1. The RSA performance is efficiently improved by electron-withdrawing substituents (NO2 and BTZ) and by extending the π-conjugation; while electron-donating substituent (OCH3 in 4) decreases the RSA at 532 nm. [ABSTRACT FROM AUTHOR]

During the last decade, our research group has prepared a number of metal dithiocarbamato derivatives of Pt, Pd and Au that were expected to resemble the main features of cisplatin together with higher activity, improved selectivity and bioavailability, and lower side-effects. Furthermore, we have already published the synthesis, characterization and in vitrocytotoxicity studies of novel ruthenium(iii) dithiocarbamato complexes such as [RuL3] monomers (11) and α-[Ru2L5]Cl dimers (12) with five different dithiocarbamate ligands. As both the monomer and the dinuclear complexes have shown significant antitumor activity in different human tumor cell lines, we decided to widen the characterization studies and to analyse thoroughly their behavior in physiological-like medium by UV-visible and CD spectroscopy. In the present paper we report on the crystal structure of [Ru(DMDT)3], [Ru(PDT)3] and [Ru(ESDT)3] complexes and we determine the spin state of the paramagnetic Ru(iii) by means of Evans' method. Then, we discuss in detail the UV-visible spectral data of the complexes in different medium. All the studied complexes are stable in dimethyl sulfoxide, and show low solubility in phosphate buffered saline solution, particularly the monomer species, even at low concentration, while increased solubility for both types of complexes have been found in the presence of bovine serum albumin (BSA). Moreover, no changes on the coordination sphere of the metal, as well as no direct interaction between the BSA protein and the complex have been identified by UV-visible spectroscopy. However, some conformational changes on the BSA structure, induced by the ruthenium(iii) complexes have been confirmed by CD spectroscopy, indicating a probable secondary electrostatic interaction between the metal complex and the peptide. In addition, no significant interaction has been demonstrated with the components of Dulbecco's Modified Eagle's Medium, used for the in vitroassays. [ABSTRACT FROM AUTHOR]

Metallo-organic compounds are interesting to study for their antitumor activity and related applications. This paper deals with the syntheses, characterization, structure determination of a copper complex of anthracenyl terpyridine (1) and its plasmid cleavage and cytotoxicity towards different cancer cell lines. The complex binds CT-DNA through partial intercalation mode. The plasmid cleavage studies carried out using pBR322 and pUC18 resulted in the formation of all the three forms of the plasmid DNA. Plasmid cleavage studies carried out with a non-redoxable Zn2+complex (2) supported the role of the redox activity of copper in 1. The complex 1showed remarkable antiproliferative activity against cancer cell lines, viz., cervical (HeLa, SiHa, CaSki), breast (MCF-7), liver (HepG2) and lung (H1299). A considerable lowering was observed in the IC50values of HPV-infected (viz., HeLa, SiHa, CaSki) vs.non-HPV-infected cell lines (MCF-7, HepG2, H1299). Antiproliferative activity of 1was found to be much higher than the carboplatin when treated with the same cell lines. Incubation of the cells with 1results in granular structures only with the HPV-infected cells and not with others as studied by phase contrast and fluorescence microscopy. The lower IC50value observed in case of 1with HPV-infected cell lines may be correlated with the involvement of HPV oncoprotein. The role of HPV has been further augmented by transfecting the MCF-7 cells (originally not possessing HPV copy) with e6 oncoprotein cDNA. To our knowledge this is the first copper complex that causes cell death by interacting with HPV oncoprotein followed by exhibition of remarkable antiproliferative activity. [ABSTRACT FROM AUTHOR]

The deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (Mb-CO) UV-vis assay is the principal method used for quantifying the rates of CO release from CO-releasing molecules (CO-RMs) that might possess therapeutic benefits. Some issues emerge when the Mb-CO assay is utilized for testing CO-RMs with novel structures, which are comprehensively discussed here for the first time. Two methods for processing raw UV-vis spectroscopic data generated from the assay are presented in this paper. [ABSTRACT FROM AUTHOR]

High-valent transition-metal-substituted Keggin-type polyoxometalates (POMs) are active and robust oxidation catalyst. The important oxidized intermediates of these POM complexes are very difficult to be characterized by using the experimental method, and thus no detail information is available on such species. In the present paper, density functional theory (DFT) calculations have been carried out to characterize the electronic structures of a series of mono-ruthenium-substituted Keggin-type POMs. We find that the aquaruthenium(ii/iii/iv) species possess dxy2dxz2dyz2, dxy2dxz2dyz1, and dxy2dxz1dyz1electronic configuration, respectively, and hydroxyl/oxoruthenium(iv/v/vi) species possess dxy2dxz1π*yz1, dxy2π*xz1π*yz1, dxy1π*xz1π*yz1, and dxy1π*xz1π*yz0electronic configuration, respectively. Mulliken spin population shows that spin density is localized on the ruthenium center in aquaruthenium(ii/iii/iv) POM complexes, and the RuOaunit in hydroxyl/oxoruthenium(iv/v/vi) POM complexes. The Oaatom has substantial radical character in oxoruthenium(iv/v) species, and the radical character of the Oaatom are significantly weakened in the oxoruthenium(vi) species. The relevant energy of the important Ru–Oaπ*-antibonding unoccupied orbitals with high RuOacompositions of oxoruthenium(iv/v/vi) POM complexes decrease in the order: oxoruthenium(iv) > oxoruthenium(v) > oxoruthenium(vi). The pH-independent multiple reduction energies for Ru(iii/ii), Ru(v/iv), and Ru(vi/v) couples are calculated, which is in agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper a series of eight Ti(iv) piperazine based complexes have been prepared and fully characterised in the solid-state by X-ray crystallography and in solution viaNMR spectroscopy. In the solid-state either Ti2(L)(OiPr)6or Ti2(L)2(OiPr)4were observed depending upon the nature of the starting ligand. For complexes with less sterically demanding ligands (1H2and 2H2) an equilibrium was observed: 2 Ti2(L)(OiPr)6⇔ Ti2(L)2(OiPr)4+ 2 Ti(OiPr)4. The thermodynamic properties (ΔG, ΔHand ΔS) have been investigated viavariable temperature NMR spectroscopy. With more sterically demanding ligands (3–8H2) the Ti2(L)(OiPr)6form was the most prevalent in the solid-state and in solution. These complexes have been tested for the production of polylactide under melt and solution conditions with high conversions being obtained. [ABSTRACT FROM AUTHOR]

Research progress in the organometallic dithiolene complexes such as [Cp(or Cp*)M(dithiolene)] (M = Co, Rh, Ir, Ni), [(C6R6)Ru(dithiolene)] and [(C4R4)Pt(dithiolene)] complexes during the past decade is described and the reactivities, structures and electrochemical behavior are summarized in this paper. The five-membered metalladithiolene ring (MS2C2) undergoes addition reactions to the MS bond to form 18-electron adducts by an imido, alkylidene, alkene or norbornene group and also undergoes dimerizations on the basis of the unsaturation in the ring. The aromaticity of the ring causes substitution reactions on the dithiolene carbon by a C-centered radical, S-centered radical or succinimide group when the ring has a C–H bond. Furthermore a dithiolene–dithiolene homo-coupling reaction by an acid or dithiolene–aryl cross-coupling occurs based on the aromaticity in the ring. Dissociations of the 18-electron adducts are observed by those thermolyses, photolyses, electrochemical redox reactions and other chemical reactions with tertiary phosphorus compounds. One representative example of them is the imido adduct dissociation with PR3under heating toward the intramolecular imido migration to a Cp ligand. Since all products are rearomatized by those adduct dissociations, it is concluded that the ‘coexistence of aromaticity and unsaturation’ in the metallacycle mediates the diverse chemical reactions. [ABSTRACT FROM AUTHOR]

For over 30 years cisplatin has been one of the most active antitumour agents in clinical use, nevertheless research for overcoming cisplatin toxicity and resistance or for improving its efficacy has never ceased. In this context we have recently proposed dinuclear Pt complexes with bridging geminal bisphosphonates as novel Pt-prodrugs with potential activity at the bone surface after embedment in inorganic matrices and implantation at the tumour site. In the present paper we report the synthesis and full characterization of four new platinum complexes having a dinuclear structure with a bisphosphonate (2-ammonium-1-hydroxyethane-1,1-diyl-bisphosphonate or 3-ammonium-1-hydroxypropane-1,1-diyl-bisphosphonate, AHBP-H and PAM-H, respectively) acting as a bridging ligand between two platinum moieties (cis-[Pt(NH3)2]2+, directly related to cisplatin, and [Pt(cis-1,4-DACH)]2+, known to be able to overcome the cisplatin resistance). Moreover, as a preliminary investigation, the in vitrocytotoxicity of the new complexes has been evaluated on a panel of 13 human tumour cell lines including cisplatin- and multidrug-resistant sublines. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis, crystal structures, and magnetic properties of a series of mixed-valence polynuclear manganese complexes bridged by a dianionic 1,2,4-triazole-based ligand L2−(H2L = 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole). Complexes 1to 3show a similar binuclear structure, with the central core of [MnIIMnIII(L)2] and some other small molecules also coordinated to the two Mn centers. The two [MnIIMnIII(L)2] subunits can be further connected by different dicarboxylic acids to construct non-charged tetranuclear complexes 4to 7. In these complexes, each deprotonated dianionic ligand L2−acts as a μ2-bridged ligand to coordinate two Mn centers viathe 1,2,4-triazole ring. Bond valence sum (BVS) calculations and Mn surrounding bond lengths indicate that the Mn center coordinated to the pyridine N atoms in the +2 oxidation state, while another Mn center coordinated to the phenolic O atoms is in the +3 oxidation state. The MnIIIcentre shows Jahn–Teller elongation along one of the axes. Magnetic studies show the presence of ferromagnetic MnIII–MnIIcoupling in the binuclear (1–3) and tetranuclear (4–7) complexes with the magnetic coupling constant (J) ranging from 0.58 to 1.17 cm−1, based on the Hamiltonian H= −2JS1·S2(S1= 5/2 and S2= 2). In all cases both z′J′ (intermolecular interactions) and Dparameter (Zero Field Splitting of the Mn (III) ion) has been introduced to improve the corresponding fit. The relationship of the coupling interaction between the MnII/MnIIIand their electronic structures is discussed. [ABSTRACT FROM AUTHOR]

The substitution reactions between asymmetric bis-chelate ligands and alkenyl chloro derivatives of palladium(ii) of the type [Pd(L–L′)(Rx)Cl] (L–L′ = 2-phenylsulfanylmethyl-pyridine (HN–SPh), 2-methyl-6-phenylsulfanylmethyl-pyridine (MeN–SPh), 2,2′-bipyridinyl (BiPy), Rx = –CCOOMeCMeCOOMe (Ra), –CCOOEtCMeCOOEt (Rb), –CCOOt-BuCMeCOOt-Bu (Rc), –(CCOOMeCCOOMe)2Me (Rd)) with phosphoquinoline moieties (8-diphenylphosphanyl-quinoline (DPPQ), 8-diphenylphosphanyl-2-methyl-quinoline (DPPQ-Me)) usually leads to the formation of the stable geometrical isomer bearing these groups in the cisposition thanks to the mutual transinfluence of the alkenyl and phosphine groups. However, when the leaving group MeN–SPh and the entering ligand DPPQ are involved, the fast and quantitative substitution reaction leads to the formation of a couple of geometrical isomers [Pd(DPPQ)(Rx)Cl]-transP and [Pd(DPPQ)(Rx)Cl]-cisP (Rx = Ra, Rb, Rc, Rd) in which the alkenyl and the phosphine groups are in mutual transor cisposition. The substrate [Pd(DPPQ)(Rx)Cl]-transP (Rx = Ra, Rb, Rc) slowly interconverts into its thermodynamically stable -cisP counterpart while the bulky [Pd(DPPQ)(Rd)Cl]-transP displays no tendency to isomerize, thereby allowing separation of the two geometrical forms. Also, the ligand DPPQ-Me induces the formation of the -transP geometrical isomer which is only detectable at low temperature since it rapidly interconverts into the -cisP derivative at RT. The kinetics of the interconversion process, a reasonable explanation of the observed phenomenon based on theoretical calculations, and eventually an unequivocal structure determination of the stable [Pd(DPPQ)(Rx)Cl]-cisP substrate are reported in the present paper. [ABSTRACT FROM AUTHOR]

The Laplaza/Cummins L3Mo (L = N(R)Ar) system is a very important complex for activating small molecules such as N2. Previous experimental work has shown that CS2binds to the L3Mo system and forms an Mo–CS–Mo intermediate, while the environmentally important CO2molecule is unreactive. The aim of this paper is to explain why there is this contrast in reactivity. We have used density functional methods to show that at first glance the reaction of 3L3Mo + CO2should proceed smoothly to give L3Mo–O + L3Mo–CO–MoL3. However initial coordination of the CO2molecule to L3Mo does not take place because of the bending of CO2, the energy required to cross from the doublet to the quartet state, and the lower metal–CO2binding energy compared to metal–CS2. The subsequent formation of the L3Mo–CO–MoL3intermediate is similarly unfeasible due to steric and entropic effects. We have provided a molecular orbital rationalization for these effects and have also shown that it is important to take account of steric factors in order to get an accurate understanding of the energetic picture. [ABSTRACT FROM AUTHOR]