Reactivity of phosphonodithioato-dppt Ni(II) mixed ligand complexes with halogens: first example of a metal-coordinating tribromide anion.

The first example of a metal complex containing a tribromide anion is presented and characterised by X-ray diffraction. Hybrid DFT calculations were used to investigate the nature of the bond in coordinating trihalides and the differences with the corresponding mono-halide complexes.

A unique case of oxidative addition of interhalogens IX (X=Cl, Br) to organodiselone ligands: nature of the chemical bonding in asymmetric I-Se-X polarised hypervalent systems.

The reactivity of the imidazoline-2-selone derivatives 1,1'-methylenebis(3-methyl-4-imidazoline-2-selone) (D1) and 1,2-ethylenebis(3-methyl-4-imidazoline-2-selone) (D2) towards the interhalogens IBr and ICl has been investigated in the solid state with the aim of synthesising "T-shaped" hypervalent chalcogen compounds featuring the extremely rare linear asymmetric I-E-X moieties (E=S, Se; X=Br, Cl). X-ray diffraction analysis and FT-Raman measurements provided a clear indication of the presence in the compounds obtained of discrete molecular adducts containing I-Se-Br and I-Se-Cl hypervalent moieties following a unique oxidative addition of interhalogens IX (X=Cl, Br) to the organoselone ligands. In all asymmetric hypervalent systems isolated, a strong polarisation was observed, with longer bond lengths at the selenium atom involving the most electronegative halogen.

Gold(III) complexes of asymmetrically aryl-substituted 1,2-dithiolene ligands featuring potential-controlled spectroscopic properties: an insight into the electronic properties of bis(pyren-1-yl-ethylene-1,2-dithiolato)gold(III).

The electrochemical, UV/Vis-NIR absorption, and emission-spectroscopic features of (TBA(+))(1(-)) and the corresponding neutral complex 1 were investigated (TBA(+)=tetrabutylammonium; 1(-)=[Au(III)(Pyr,H-edt)(2)](-); Pyr,H-edt(2-)=pyren-1-yl-ethylene-1,2-dithiolato). The intense electrochromic NIR absorption (λ(max)=1432 nm; ε=13000 M(-1) cm(-1) in CH(2)Cl(2)) and the potential-controlled visible emission in the range 400-500 nm, the energy of which depends on the charge of the complex, were interpreted on the grounds of time-dependent DFT calculations carried out on the cis and trans isomers of 1, 1(-), and 1(2-). In addition, to evaluate the nonlinear optical properties of 1(x-) (x=0, 1), first static hyperpolarizability values β(tot) were calculated (β(tot)=78×10(-30) and 212×10(-30) esu for the cis isomer of 1(-) and 1, respectively) and compared to those of differently substituted [Au(Ar,H-edt)(2)](x-) gold dithiolenes [Ar=naphth-2-yl (2), phenyl (3); x=0, 1].

Synthesis and characterization of novel gold(III) complexes of asymmetrically aryl-substituted 1,2-dithiolene ligands featuring potential-controlled spectroscopic properties.

The tetrabutylammonium (TBA(+)) salts of square-planar monoanionic gold complexes of the unsymmetrically substituted Ar,H-edt(2-) 1,2-dithiolene ligands (Ar,H-edt(2-)=arylethylene-1,2-dithiolato; Ar=phenyl (1(-)), 2-naphthyl (2(-)), and 1-pyrenyl (3(-))) were synthesized and characterized by spectroscopic and electrochemical methods and the corresponding neutral species (1, 2, and 3, respectively) were obtained in CH(2)Cl(2) solution at room temperature by diiodine oxidation. The single-crystal X-ray diffraction structural data collected for (TBA(+))(2(-)), supported by DFT theoretical calculations, are consistent with the ene-1,2-dithiolate form of the ligand and the Au(III) oxidation state. All complexes feature intense near-IR absorptions (at about 1.

A selective, nontoxic, OFF-ON fluorescent molecular sensor based on 8-hydroxyquinoline for probing Cd(2+) in living cells.

In spite of the fact that cadmium(II) has been recognized as a highly toxic element and that excessive exposure to this metal ion has been reported to have many adverse effects on human health, very few selective and specific fluorescent probes are available for imaging Cd(2+) in living cells. Herein, we report the spectroscopic and photochemical characterization of 5-(5-chloro-8-hydroxyquinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a fluorescent sensor for the selective imaging of Cd(2+) in living cells. In particular, the response of L to Cd(2+) was first assessed in aqueous solutions, sodium dodecyl sulfate micelles, and liposomes, and subsequently in living cells by fluorescence microscopy techniques.

Synthesis and coordination properties of quinoline pendant arm derivatives of [9]aneN(3) and [9]aneN(2)S as fluorescent zinc sensors.

The coordination chemistry of three new quinoline pendant arm derivatives of [9]aneN(3) (L(1), L(2)) and [9]aneN(2)S (L(3)) toward Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been investigated both in solution and in the solid state. The protonation constants for L(1)-L(3) and stability constants with the aforementioned metal ions have been determined potentiometrically in 0.10 M NMe(4)Cl MeCN/H(2)O (1:1 v/v) solution at 298.

Investigation on the reactivity of dithiophosphonato/dithiophosphato Ni(II) complexes towards 2,4,6-tris-2-pyridyl-1,3,5-triazine: developments and new perspectives.

The reactions between tptz and differently substituted dithiophosphonato [Ni(ROpdt)2] [ROpdt = (RO)(4-MeOC6H4)PS2-; R = Et (2); Pr (3); i-Pr (4); Bu (5)] and dithiophosphato [Ni((EtO)2PS2)2] (6) Ni(II) complexes have been investigated, and the characterisation of the resulting neutral mixed complexes (2.tptz)-(6.tptz) is reported.

Interaction of mixed-donor macrocycles containing the 1,10-phenanthroline subunit with selected transition and post-transition metal ions: metal ion recognition in competitive liquid-liquid solvent extraction of Cu(II), Zn(II), Pb(II), Cd(II), Ag(I), and Hg(II).

Two new mixed aza-thia crowns 5-aza-2,8-dithia[9]-(2,9)-1,10-phenanthrolinophane (L(4)) and 2,8-diaza-5-thia[9]-(2,9)-1,10-phenanthrolinophane (L(7)) have been synthesized and characterized. The coordination behavior of L(4) and L(7) toward the metal ions Cu(II), Zn(II), Pb(II), Cd(II), Hg(II), and Ag(I) was studied in aqueous solution by potentiometric methods, in CD3CN/D2O 4:1 (v/v) by (1)H NMR titrations and in the solid state. The data obtained were compared with those available for the coordination behavior toward the same metal ions of structurally analogous mixed donor macrocyclic ligands L(1)-L(3), L(5), L(6): all these contain a phenanthroline subunit but have only S/O/N(aromatic) donor groups in the remaining portion of the ring and are, therefore, less water-soluble than L(4) and L(7).

Interaction of methimazole with I2: X-ray crystal structure of the charge transfer complex methimazole-I2. implications for the mechanism of action of methimazole-based antithyroid drugs.

The antithyroid drug methimazole (MMI) reacts with molecular iodine to form, in a multistep process, 1-methylimidazole as final product. In this process, the charge transfer complex MMI-I 2 and the ionic disulfide [(C 4H 6N 2S-) 2] (2+) ( 1, dication MMI disulfide) have been isolated and their X-ray crystal structures solved. Dication MMI disulfide perchlorate acts effectively both in reducing I 2 to I (-) ions and in showing antioxidant properties in inactivating the enzyme lactoperoxidase compound I.

The nature of the chemical bond in linear three-body systems: from i3- to mixed chalcogen/halogen and trichalcogen moieties.

The 3 centre-4 electrons (3c-4e) and the donor/acceptor or charge-transfer models for the description of the chemical bond in linear three-body systems, such as I(3) (-) and related electron-rich (22 shell electrons) systems, are comparatively discussed on the grounds of structural data from a search of the Cambridge Structural Database (CSD). Both models account for a total bond order of 1 in these systems, and while the former fits better symmetric systems, the latter describes better strongly asymmetric situations. The 3c-4e MO scheme shows that any linear system formed by three aligned closed-shell species (24 shell electrons overall) has reason to exist provided that two electrons are removed from it to afford a 22 shell electrons three-body system: all combinations of three closed-shell halides and/or chalcogenides are considered here.

New fluorescent chemosensors for heavy metal ions based on functionalized pendant arm derivatives of 7-anthracenylmethyl-1,4,10-trioxa-7,13-diazacyclopentadecane.

Two new ligands 7-anthracenylmethyl-13-methylpyridyl-1,4,10-trioxa-7,13-diazacyclopentadecane (L4) and 7-anthracenylmethyl-13-(2,2-dimethyl-2-hydroxyethyl)-1,4,10-trioxa-7,13-diazacyclopentadecane (L(5)) have been synthesized and characterized. Both derive from 7-anthracenylmethyl-1,4,10-trioxa-7,13-diazacyclopentadecane (L(3)) and differ for having a differently functionalized pendant arm covalently attached to the remaining secondary nitrogen donor of the macrocyclic framework. The protonation and coordination behavior of L(4), L(5), and the unbranched L(3) with metal ions have been studied in MeCN/H2O (1:1 v/v, 298.

Investigation into the reactivity of the coordinatively unsaturated phosphonodithioato [Ni(MeOpdt)2] towards 2,4,6-tris(2-pyridyl)-1,3,5-triazine: goals and achievements.

The reaction between the coordinatively unsaturated phosphonodithioato complex [Ni(MeOpdt)2] (1) [MeOpdt = (MeO)(4-MeOC(6)H(4))PS2-] and tptz [2,4,6-tris(2-pyridyl)-1,3,5-triazine] has been investigated. Spectrophotometric and conductometric titrations showed the formation of a neutral and an ionic species, i.e.

Reactions Between Chalcogen Donors and Dihalogens/Interalogens: Typology of Products and Their Characterization by FT-Raman Spectroscopy.

The chemical bond and structural features for the most important classes of solid products obtained by reacting chalcogen donors with dihalogens and interhalogens are reviewed. Particular attention is paid to the information the FT-Raman spectroscopy can confidently give about each structural motif considered in the absence of X-ray structural analyses.

Tuning the selectivity/specificity of fluorescent metal ion sensors based on N2S2 pyridine-containing macrocyclic ligands by changing the fluorogenic subunit: spectrofluorimetric and metal ion binding studies.

Two new fluorescent chemosensors for metal ions have been synthesized and characterized, and their photophysical properties have been explored; they are the macrocycles 5-(2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L5) and 5-(5-chloro-8-hydroxyquinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L6). Both systems have a pyridyl-thioether-containing 12-membered macrocycle as a binding site. The coordination properties of these two ligands toward CuII, ZnII, CdII, HgII, and PbII have been studied in MeCN/H2O (1:1 v/v) and MeCN solutions and in the solid state.

[M(R-dmet)2] bis(1,2-dithiolenes): a promising new class intermediate between [M(dmit)2] and [M(R,R'-timdt)2] (M = Ni, Pd, Pt).

We report the first examples of metal dithiolenes belonging to the class [M(R-dmet)(2)] [R-dmet = formally monoreduced N-substituted thiazolidine-2,4,5-trithione; R = Et, M = Ni (1), Pd (2), Pt (3)]. A comparative spectroscopic, electrochemical, and density functional theory theoretical investigation indicates that [M(R-dmet)(2)] complexes show features intermediate between those of the dithiolenes belonging to the previously reported classes [M(R,R'-timdt)(2)] and [M(dmit)(2)] (R,R'-timdt = formally monoreduced N,N'-disubstituted imidazolidine-2,4,5-trithione; dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato). UV-vis-near-IR spectroscopy and cyclic voltammetry/differential pulsed voltammetry measurements performed on 1 and 3 proved that the new dithiolenes are stable as neutral, monoanionic, and bianionic species and feature a near-IR electrochromic absorption falling at about 1000 and 1250 nm for neutral and monoanionic species, respectively.

Coordination chemistry of N-aminopropyl pendant arm derivatives of mixed N/S-, and N/S/O-donor macrocycles, and construction of selective fluorimetric chemosensors for heavy metal ions.

The coordination chemistry of the N-aminopropyl pendant arm derivatives (L1c-4c) of the mixed donor macrocyclic ligands [12]aneNS2O, [12]aneNS3, [12]aneN2SO, and [15]aneNS2O2(L1a-4a) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in aqueous solution has been investigated. The protonation and stability constants with the aforementioned metal ions were determined potentiometrically and compared, where possible, with those of the unfunctionalised macrocycles. The measured values show that Hg(II) and Cu(II) in water have the highest affinity for all ligands considered, with the N-aminopropyl pendant arm weakly coordinating the metal centres.

DFT calculations, structural and spectroscopic studies on the products formed between IBr and N,N'-dimethylbenzoimidazole-2(3H)-thione and -2(3H)-selone.

The NBO charge distribution calculated at DFT level on the [LEX](+) species [LE=N,N'-dimethylbenzoimidazole-2(3H)-thione (3) and -2(3H)-selone (4)(Scheme 1); X=I, Br] suggests that the most likely products from the reaction 3 of 4 and with IBr are the 10-X-2 charge-transfer (CT) adduct and the 10-Se-3 "T-shaped" hypervalent adduct featuring a linear Br--Se--I system, respectively. This prediction is confirmed by the synthesis, and X-ray diffraction analysis of 3.IBr (I) and 4.

Monoreduced [M(R,R'timdt)2]- dithiolenes (M = Ni, Pd, Pt; R,R'timdt = disubstituted imidazolidine-2,4,5-trithione): solid state photoconducting properties in the third optical fiber window.

Electrochemically monoreduced [M(R,R'timdt)(2)](-) dithiolenes, showing unprecedented wavelength selective photoconducting properties in the third optical fiber window (1500-1800 nm), fine-tunable through modifications in the chemical structure, allowed for the fabrication of a test photodetector with a bit rate of about 85 kbit s(-1).

Coordination chemistry of a new cofacial binucleating macropolycycle derived from 1,4,7-triazacyclononane.

We have prepared and characterized a new phenol-based compartmental ligand (H(2)L) incorporating 1,4,7-triazacyclononane ([9]aneN(3)), and we have investigated its coordination behavior with Cu(II), Zn(II), Cd(II), and Pb(II). The protonation constants of the ligand and the thermodynamic stabilities of the 1:1 and 2:1 (metal/ligand) complexes with these metal ions have been investigated by means of potentiometric measurements in aqueous solutions. The mononuclear [M(L)] complexes show remarkably high stability suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions are also involved in binding the metal ion.

Coordination properties of new bis(1,4,7-triazacyclononane) ligands: a highly active dizinc complex in phosphate diester hydrolysis.

The synthesis and characterization of three new bis([9]aneN(3)) ligands, containing respectively 2,2'-bipyridine (L(1)), 1,10-phenanthroline (L(2)), and quinoxaline (L(3)) moieties linking the two macrocyclic units, are reported. Proton binding and Cu(II), Zn(II), Cd(II), and Pb(II) coordination with L(1)-L(3) have been studied by potentiometric titrations and, for L(1) and L(2), by spectrophotometric UV-vis measurements in aqueous solutions. All ligands can give stable mono- and dinuclear complexes.

First example of an infinite polybromide 2D-network.

The reaction of the neutral dithiolene [Pd(Et2timdt)2] (Et2timdt = formally monoreduced diethylimidazolidine-2,4,5-trithione) with an excess of Br2 yielded few crystals of [1(Et) x 2Br](2+)(Br-)2(Br2)3 as a by-product (1(Et) = 4,5,9,10-tetrathiocino-[1,2-b:5,6-b']-1,3,6,8-tetraethyl-diimidazolyl-2,7-dithione); X-ray diffraction analysis showed that this compound represents the first example of a polybromide 2D-network templated by [1(Et) x 2Br](+2) dications, and featuring all the Br-Br distances shorter than those found in solid state bromine.

Fluorometric chemosensors. Interaction of toxic heavy metal ions Pb(II), Cd(II), and Hg(II) with novel mixed-donor phenanthroline-containing macrocycles: spectrofluorometric, conductometric, and crystallographic studies.

The macrocycles L(1)-L(3) incorporating N(2)S(3)-, N(2)S(2)O-, and N(2)S(2)-donor sets, respectively, and containing the 1,10-phenanthroline unit interact in acetonitrile solution with heavy metal ions such as Pb(II), Cd(II), and Hg(II) to give 1:1 ML, 1:2 ML(2), and 2:1 M(2)L complex species, which specifically modulate the photochemical properties of the ligands. The stoichiometry of the complex species formed during spectrofluorometric titrations and their formation constants in MeCN at 25 degrees C were determined from fluorescence vs M(II)/L molar ratio data. The complexes [Pb(L(1))][ClO(4)](2).

An unprecedented example of a cis-phosphonodithioato nickel(II) complex built by an extensive hydrogen bonding supramolecular network.

The P-N bond hydrolysis of the 4-methoxyphenyl-ammonium ethylamido-phosphonodithioato ligand during its complexation to NiII leads to the first example of phosphonodithioato nickel(II) complex having a cis configuration; this complex is stabilised in the solid state by an extensive and intricate network of hydrogen bondings involving the released ethylenediamine and a water molecule.

Anti-thyroid drug methimazole: X-ray characterization of two novel ionic disulfides obtained from its chemical oxidation by I(2).

Interaction of methimazole (MMI, 1-methyl-imidazole-2-thione) with I2 in solvents having different polarity gives two new stable compounds containing a dication disulfide and a monocation disulfide arranged in dimers, respectively. These two species could represent effective intermediates in the reaction of MMI with an active iodine species in the thyroid gland and therefore shed more light on the mechanism of action of MMI as an antithyroid drug.

1,2-Bis(3-methyl-imidazolin-2-ylium iodobromoselenanide)ethane: Oxidative Addition of IBr at the Se Atom of a >C=Se Group.

Almost linear I-Se-Br groups with d(Se-Br)>d(Se-I) occur in 1⋅2 IBr, the first "T-shaped" Se adduct with IBr, which was synthesized by the oxidative addition of IBr to 1,2-bis(3-methylimidazoline-2-selonyl)ethane (1) in MeCN. Density functional theory calculations indicate the intramolecular Br⋅⋅⋅H interactions as being responsible for the peculiar structural features of the I-Se-Br groups.