Linkage Isomers of Triangular Pd Metallacycles and Catalysis in Aqueous Suzuki Coupling Reaction.

The water-soluble trinuclear Pd metallacycles [Pd(tmeda)(4-Spy)]3(X)3 (tmeda = tetramethylethylenediamine, X = OTf, 2; NO3, 3) were synthesized from the ambidentate ligand 4-pyridylthiolate (Spy-) and [Pd(tmeda)X2] in 80 and 70% yield, respectively. Two possible linkage isomers are found in solution (slow interconversion found in the NMR) and in the solid state. Density functional calculations showed that the energy of the isomer with a D3-symmetric arrangement of the SPy ligand and all Pd atoms having N∧NPdSN coordination is only 7 kcal/mol lower. When reacting [Pd(tmeda)(NO3)2] with 4,4'-biphenyldithiolate (S2bph2-), the tetranuclear [{Pd(tmeda)}4(µ-S2bph)2](NO3)4 (1) was formed. A new type of undecanuclear Pd cluster was separated as a minor product from an acetone solution of 2 in air. The new complexes represent the first examples of water-soluble Pd metallacycles constructed from a pyridine-thiolate ligand. They show catalytic activity with turnover numbers ranging from 9 to 420 in aqueous Suzuki cross-coupling reactions using phenyl boronic acid and a number of aryl halides. An optimized system gave a TON of 6,900,000 and a TOF of 492,857 h-1. The catalyst could be reused eight times, and the activity has been attributed to the formation of PdNPs.

Modulation of ΔEST and room temperature phosphorescence in carbazole derivatives.

A simple strategy to modulate the singlet-triplet energy gap in 3,6-diaryl-N-acetophenylcarbazole derivatives is developed. Different substituents significantly influenced ΔEST, which is correlated for the first time with the singlet-triplet state dipole moments. Phosphorescence at ambient conditions in powder form (τ is up to 248 µs) and ultra long lifetime (up to 2.2 s) at 77 K is observed.

One-pot synthesis of unsubstituted and methyl substituted-pyrazinyl diselenides and monoselenides: structural, optical property characterization and DFT calculations.

Organoselenium compounds have long been fascinated researchers owing to their wide range of applications, such as in anticancer, in catalysis, and as molecular precursors for metal selenides. In this view, herein, the one-pot synthesis of dimethyl substituted and unsubstituted dipyrazinyl monoselenides, [(2-pyz)2Se] and [(2,5-Me2-3-pyz)2Se], and the corresponding dipyrazinyl disenides, [(2-pyzSe)2] and [(2,5-Me2-3-pyzSe)2], is demonstrated by the reduction of selenium metal using sodium borohydride at room temperature and a subsequent alkylation using the corresponding pyrazinyl halide in ethanol. All the diselenides and monoselenides were characterized using IR, UV-vis, photoluminescence, and NMR (1H, 13C{1H}, and 77Se{1H}) spectroscopy. The molecular structures of the diselenides and monoselenides were unambiguously determined by single-crystal X-ray diffraction (SC-XRD). The optical properties, including absorption, excitation, emission, and quantum yield, of these organoselenium compounds were examined. Additionally, DFT calculations were performed to determine the HOMO and LUMO orbitals, band gap, and oscillator strength of these ligands.

Hydrogen-bonded linear chain assemblies of palladium(II)-selenoether complexes: solid state aggregates as templates for nano-structural Pd17Se15 leading to efficient electrocatalytic activity.

A analogous series of 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted selenoether complexes of palladium [PdCl2(RSeC6H4dmpz)]; (R = CH2COOH (1), CH2CH2COOH (2), and CH2CH2OH (3); dmpz = dimethylpyrazole) were ably synthesized in a facile manner and exhaustively characterized. Insight into molecular structures of these complexes was keenly probed through single crystal X-ray diffraction (XRD) analysis, unfolding the structural scaffolds and laying into molecular aggregation, availed through hydrogen bonding interactions borne out of tethered protic groups. The complexes were converted to capping free palladium selenide (Pd17Se15) nanoparticles through pyrolysis and evaluated for their electrocatalytic efficacy towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. In an alkaline medium, PSNP1 (Pd17Se15) obtained from the hydrogen bonded aggregate of complex PdCl2L1 (1) produced good HER activity. PSNP1 had a little decrease in current density after 300 continuous cycles, which proves that the catalyst presents high stability in the recycling process. For the electrocatalytic oxidation of CH3OH, the electrocatalytic rate constant (k) obtained was 0.3 × 103 cm3 mol-1 s-1.

Molecular Precursor-Driven Synthesis of Copper Telluride Nanostructures for LIB Anode Application.

Copper tellurides have garnered substantial interest for their applicability as an electrocatalyst for water splitting, battery anodes and photodetectors, etc. Moreover, synthesis of phase pure metal tellurides using the multi-source precursor method is challenging. Therefore, a facile synthesis protocol for copper tellurides is anticipated. The current study involves a simplistic single source molecular precursor pathway for the synthesis of orthorhombic-Cu2.86Te2 nano blocks and -Cu31Te24 faceted nanocrystals employing the [Cu{TeC5H3(Me-5)N}]4 cluster in thermolysis and pyrolysis, respectively. The pristine nanostructures were carefully characterized by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopic techniques (scanning electron microscopy and transmission electron microscopy), and diffuse reflectance spectroscopy to know the crystal structure, phase purity, elemental composition, distribution of elements, morphology, and optical band gap. These measurements suggests that the reaction conditions fetch nanostructures of different sizes, crystal structures, morphologies, and band gaps. As prepared nanostructures were evaluated for lithium-ion batteries (LIBs) anode material. The cells fabricated with orthorhombic Cu2.86Te2 and orthorhombic Cu31Te24 nanostructures deliver capacities of 68 and 118 mA h/g after 100 cycles. The LIB anode made up of Cu31Te24 faceted nanocrystals exhibited good cyclability and mechanical stability.

Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation.

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

Di-tert-butyltin(IV) 2-pyridyl and 4,6-dimethyl-2-pyrimidyl thiolates: versatile single source precursors for the preparation of SnS nanoplatelets as anode material for lithium ion batteries.

New air and moisture stable di-tert-butyltin complexes derived from 2-mercaptopyridine (HSpy), [tBu2Sn(Spy)2], [tBu2Sn(Cl)(Spy)] and 4,6-dimethyl-2-mercaptopyrimidine (HSpymMe2) [tBu2Sn(Cl)(SpymMe2)], have been prepared and utilized as single-source molecular precursors for the preparation of orthorhombic SnS nanoplatelets by a hot injection method and thin films by aerosol assisted chemical vapour deposition (AACVD). The complexes were characterized by NMR (1H, 13C, 119Sn) and elemental analysis and their structures were unambiguously established by the single crystal X-ray diffraction technique. Thermolysis of these complexes in oleylamine (OAm) produced SnS nanoplatelets. The morphologies, elemental compositions, phase purity and crystal structures of the resulting Oam-capped nanoplatelets were determined by electron microscopy (SEM, TEM), energy dispersive X-ray spectroscopy (EDS) and pXRD, while the band gaps of the nanoplatelets were evaluated by diffuse reflectance spectroscopy (DRS) and were blue shifted relative to the bulk material. The morphology and preferential growth of the nanoplatelets were found to be significantly altered by the nature of the molecular precursor employed. The synthesized SnS nanoplatelets were evaluated for their performance as anode material for lithium ion batteries (LIBs). A cell comprised of an SnS electrode could be cycled for 50 cycles. The rate capability of SnS was investigated at different current densities in the range 0.1 to 0.7 A g-1 which revealed that the initial capacity could be regained.

Coordination Polymers of Palladium Bridged by Carboxylate and Dimethylaminoalkylselenolate Ligands.

Coordination polymers of palladium stabilized by dimethylaminoalkylselenolate and carboxylate ligands are reported. The reaction of [PdCl(SeCH2 CH2 NMe2 )]3 with AgOTf followed by treatment with sodium acetate afforded [Pd(0) Pd(II) 4 (SeCH2 CH2 NMe2 )3 (OAc)3 ](OTf)2 (1) in which one of the Pd atoms is in the zero oxidation state. In the absence of NaOAc, a tetranuclear complex, [Pd(II) 4 (SeCH2 CH2 NMe2 )4 (OTf)](OTf)3 (2), is isolated from the same reaction. Subsequent treatment with NaO2 CR afforded [Pd4 (SeCH2 CH2 NMe2 )4 (O2 CR)4 ] (R=tBu (3) and Ph (4)). The reaction of [PdCl(SeCH2 CH2 CH2 NMe2 )]2 with AgOTf and NaOAc yielded an ionic binuclear complex, [Pd(II) 2 (SeCH2 CH2 CH2 NMe2 )2 (OAc)](OTf) (5). These complexes have been characterized by NMR spectroscopy, crystal structures, and in some cases by X-ray photoelectron spectroscopy, cyclic voltammetry and mass spectrometry. Complexes 1 and 5 are associated through secondary interactions and coordinate bonds, respectively, to generate polymeric structures in the solid state.

Platinum-Mediated Activation of Coordinated Organonitriles by Telluroethers in Tetrahydrofuran: Isolation, Structural Characterization, and Density Functional Theory Analysis of Intermediate Complexes.

The reactions of [PtCl2(NCR)2] with telluroethers (ArAr'Te) in organic solvents have been investigated. The reactions in dichloromethane yield [PtCl2(TeArAr')2], while those in tetrahydrofuran (THF) give different products depending on the steric demands of the aryl groups on tellurium, the molarity of the reactants, and the reaction conditions. The reactions between [PtCl2(PhCN)2] and TeArAr' in 1:1 molar ratio at room temperature in THF yield several products, like [PtCl2(TeArAr')2] (Ar/Ar' = Ph/Ph, o-tol/Mes, Mes/Mes), [PtCl2(PhCN){NC(O)Ph[TeMes(o-tol)]}], and [PtCl2{NC(O)Ph(TeMes2)}2]. The reaction with TeMes2 in refluxing THF gave [PtCl2{NC(Ph)C4H7O}{NC(O)Ph(TeMes2)}] and [PtCl(TeMes2){Te(Mes)CH2C6H2Me2}], depending on the duration of heating. Reaction of [PtCl2(PhCN)2] with TeArMes afforded [PtCl2(TeArMes)2] (Ar = Ph, o-tol, and Mes), the formation of which decreased with increasing steric demand of the Ar group, together with [PtCl2{NC(O)Ph(TeArMes)}2]. The telluroether in the latter binds to nitrogen, and tellurium exists in the formal oxidation state of +4 (from XPS). The tellurium in these complexes exhibits secondary interactions with platinum (J((195)Pt-(125)Te) = 309-347 Hz) and with the carbonyl oxygen. These complexes slowly dissociate in solution to give [PtCl2(TeMesAr){NC(O)Ph(TeMesAr)}], finally leading to the formation of [PtCl2(TeMesAr)2]. Molecular structures of trans-[PtCl2(PhCN){NC(O)Ph[TeMes(o-tol)]}], trans-[PtCl2{NC(O)Ph(TeMes2)}2], trans-[PtCl2{NC(Ph)C4H7O}{NC(O)Ph(TeMes2)}], trans-[PtCl2{NC(O)Ph[TeMes(o-tol)]}2], trans-[PtCl2(TeMes2){NC(O)Ph(TeMes2)}], trans-[PtCl2{NC(O)Me(TeMes2)}2], and [PtCl(Te-o-tol){NC(O)Ph}2] have been unambiguously established by single-crystal X-ray diffraction analyses. Density functional theory calculations for some of the complexes were performed, and geometrical parameters are in good agreement with the values obtained from X-ray analyses.

Cyclopalladation of telluro ether ligands: synthesis, reactivity and structural characterization.

Treatment of [PdCl2(PhCN)2] with diaryl telluride in 1 : 2 molar ratio gave mononuclear palladium complexes, trans-[PdCl2(TeR2)2] () (R = Mes () (Mes = 2,4,6-trimethylphenyl), Ph (), o-tol () (o-tol = ortho-tolyl)). Reaction of [PdCl2(TeMes2)2] with one equivalent of [PdCl2(PhCN)2] or Na2PdCl4 with TeRR' afforded chloro-bridged binuclear complexes, [Pd2(µ-Cl)2Cl2(TeRR')2] () (R/R' = Mes/Mes (); Mes/Ph (); Ph/Ph ()). A toluene-methanol solution of trans-[PdCl2(TeMes2)2] on refluxing for 30 minutes yielded a binuclear cyclopalladated complex, [Pd2(µ-Cl)2{CH2C6H2(4,6-Me2)TeMes)}2] (). When the refluxing was prolonged, a mononuclear complex cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] () was isolated. Treatment of palladium acetate with TeMes2 afforded an acetato-bridged analogue of , [Pd2(µ-OAc)2{CH2C6H2(4,6-Me2)TeMes}2] () together with a very minor component, a tetranuclear complex, [Pd(µ-OAc)(µ-TeMes)]4 (). This reaction with unsymmetrical tellurides, MesTeR, also gave cyclopalladated complexes [Pd2(µ-OAc)2{CH2C6H2(4,6-Me2)TeR}2] (R = o-tol () and Ph ()) in which 2-methyl of the mesityl group of the telluride was exclusively metallated. The complex trans-[PdCl2(TeMes2)2] on refluxing in xylene gave palladium telluride, Pd7Te3. These complexes were characterized by elemental analyses, IR and NMR ((1)H, (13)C and (125)Te) spectroscopy. The molecular structures of trans-[PdCl2(TeMes2)2] (), [Pd2(µ-Cl)2Cl2(TeMes2)2]·2acetone (·2acetone), cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] (), [Pd2(µ-OAc)2{CH2C6H2(4,6-Me2)TeMes)}2]·toluene (·toluene), [Pd2(µ-OAc)2{CH2C6H2(4,6-Me2)Tetol-o}2] () and [Pd(µ-OAc)(µ-TeMes)]4 () were established by single crystal X-ray diffraction analyses. The mononuclear complex was isolated in two polymorphic forms each with the trans configuration.

Synthesis, structures and DFT calculations of 2-(4,6-dimethyl pyrimidyl)selenolate complexes of Cu(I), Ag(I) and Au(I) and their conversion into metal selenide nanocrystals.

The complexes [M{SeC4H(Me-4,6)2N2}]6 (M = Cu (1), Ag (2)) and [Au{SeC4H(Me-4,6)2N2}(PEt3)] (3) have been prepared and characterized by elemental analyses, UV-vis, NMR ((1)H, (13)C, (77)Se) spectroscopy and single crystal X-ray diffraction. The crystal structures of [Cu{SeC4H(Me-4,6)2N2}]6·H2O (1·H2O), [Ag{SeC4H(Me-4,6)2N2}]6·6MeOH·H2O (2·6MeOH·H2O) and [Au{SeC4H(Me-4,6)2N2}(PEt3)] (3) revealed that their metal centers acquire distorted square-pyramidal, trigonal and linear geometries, respectively. DFT calculations have been carried out to rationalize nuclearity in copper(i) chalcogenolate complexes. The calculations suggest that there is hardly any energy difference between the tetrameric and hexameric forms. Thermal behavior of [Cu{SeC4H(Me-4,6)2N2}]6 was studied by thermogravimetric analysis. Thermolysis of [M{SeC4H(Me-4,6)2N2}]6 (M = Cu, Ag) in 1-dodecanethiol (DDT) at 150 °C gave a cubic phase of Cu7Se4 and an orthorhombic phase of Ag2Se, respectively. Copper selenide (Cu7Se4) thin films were deposited on glass and silicon substrates by using [Cu{SeC4H(Me-4,6)2N2}]6 at 400 °C by AACVD.

Cyclopalladation of dimesityl selenide: synthesis, reactivity, structural characterization, isolation of an intermediate complex with C-H···Pd intra-molecular interaction and computational studies.

The reaction of dimesityl selenide (Mes2Se) with either PdCl2(PhCN)2 in toluene or PdCl2 in toluene-acetonitrile yields a chloro-bridged binuclear palladium complex, [Pd2Cl2(µ-Cl)2(Mes2Se)2] (1), whereas with Na2PdCl4 in refluxing ethanol, a cyclometallated palladium complex, [Pd2(µ-Cl)2{MesSeC6H2(Me2)CH2}2] (2) is afforded. 2 can also be obtained when 1 is refluxed in ethanol. On treatment with Pb(Epy)2 in dichloromethane, 2 afforded the Epy-bridged binuclear complexes, [Pd2(µ-Epy)2{MesSeC6H2(Me2)CH2}2] (3; E = S (3a) or Se (3b)). Treatment of 2 with PPh3 yields a bridge-cleaved monomeric complex, [PdCl{MesSeC6H2(Me2)CH2}(PPh3)]. The molecular structures of 1-3 were established by X-ray diffraction analyses. All the complexes are dimeric, with the palladium atoms acquiring a distorted square planar configuration. There are intra-molecular C-H···Pd interactions (d(M-H): 2.75 Å and

Reactivity of 2-chalcogenopyridines with palladium-phosphine complexes: isolation of different complexes depending on the nature of chalcogen atom and phosphine ligand.

Reactions of either Pd(0) phosphine complexes with dipyridyldichalcogenides or [PdCl2(P∩P)] (P∩P = dppe, dppp) with pyridylchalcogenolate ions have been examined and a variety of Pd(II) complexes have been isolated and characterized. Oxidative addition of {SeC5H3(3-R)N}2 (R = H or Me) to [Pd(P∩P)2] (P∩P = dppe, dppp) gave either a mononuclear complex, [Pd{2-Se-C5H3(3-R)N}2(P∩P)] (for P∩P/R: dppe/H or Me; dppp/H) or a cationic binuclear complex, [Pd2{µ-SeC5H3(3-Me)N}2(dppp)2]2+ (4b) (R = Me) whereas reactions involving the tellurium analogue exclusively afforded trinuclear complexes, [Pd3(µ-Te)2(P∩P)3]Cl2 (P∩P = dppe (2) or dppp (6)). The latter was also obtained in the substitution reaction between [PdCl2(P∩P)] and NaTeC5H3(3-R)N. The substitution reactions between [PdCl2(dppe)] and Pb{EC5H3(3-R)N}2 yielded mononuclear complexes, [Pd{2-E-C5H3(3-R)N}2(dppe)] (1a­1e) (E = S, Se or Te) while in the case of [PdCl2(dppp)], the reactions resulted in the formation of mono-, bi- and tri- nuclear complexes depending on the nature of the chalcogen atom (E = S, Se or Te) and the substituent on the pyridyl ring (R = H or Me). Treatment of dipyridyl ditellurides, {TeC5H3(3-R)N}2 (R = H or Me), with [Pd(PPh3)4] gave expected tellurolate complexes, [Pd{2-TeC5H3(3-R)N}2(PPh3)2] (7a, 7b) which on prolonged standing in CDCl3 solution gave green crystals of [PdCl{2-Te(Cl)2C5H3(3-Me)N}(PPh3)] (9). The molecular structures of {TeC5H3(3-Me)N}2, [Pd2{µ-TeC5H3(3-Me)N}2(dppp)2]Cl2·3H2O (5·3H2O), [Pd3(µ-Te)2(dppp)3]Cl2·3CHCl3 (6·3CHCl3) and [PdCl{2-Te(Cl)2C5H3(3-Me)N}(PPh3)] (9) were established by single crystal X-ray diffraction analyses.

Diorganotin(IV) 2-pyridyl selenolates: synthesis, structures and their utility as molecular precursors for the preparation of tin selenide nanocrystals and thin films.

Reactions of R(2)SnCl(2) (R = Me, Et, (t)Bu) with NaSeC(5)H(3)(R'-3)N (R' = H or Me) gave complexes of the composition [R(2)Sn{2-SeC(5)H(3)(R'-3)N)}(2)], which on treatment with R(2)SnCl(2) afforded chloro complexes, [R(2)Sn{2-SeC(5)H(3)(R'-3)N}Cl]. These complexes were characterized by elemental analyses and UV-vis and NMR ((1)H, (13)C, (77)Se and (119)Sn) spectroscopy. The crystal structures of [R(2)Sn(SeC(5)H(4)N)(2)] (R = Me or (t)Bu) and [Me(2)Sn{2-SeC(5)H(3)(Me-3)N}Cl] were determined by single crystal X-ray diffraction. The tin atom in the former two structures acquires a skew trapezoidal configuration, whereas in the latter it adopts a distorted trigonal bipyramidal geometry. Thermolysis of [R(2)Sn(2-SeC(5)H(4)N)(2)] (R = Me, Et or (t)Bu) and [Et(2)Sn{2-SeC(5)H(3)(Me-3)N}(2)] in oleylamine (OA) afforded tin selenide nanostructures. Thin films of SnSe were deposited on glass and silicon substrates by the AACVD of [(t)Bu(2)Sn(2-SeC(5)H(4)N)(2)]. The nanostructures and thin films were characterized by XRD, EDX, AFM, SEM, TEM and SAED techniques. The photovoltaic properties of the thin films have been evaluated.

Copper(I) 2-pyridyl selenolates and tellurolates: synthesis, structures and their utility as molecular precursors for the preparation of copper chalcogenide nanocrystals and thin films.

The complexes, [Cu{EC(5)H(3)(R-3)N}](4) (E/R = Se/Me or Te/R; R = H or Me) were isolated by the reaction between CuCl and NaEC(5)H(3)(R-3)N and were characterized by elemental analyses, uv-vis and NMR ((1)H, (13)C) spectroscopy. The crystal structures of [Cu{SeC(5)H(3)(Me-3)N}](4) and [Cu(TeC(5)H(4)N)](4) revealed that the molecules are tetrameric in which each copper atom lies at the vertex of the tetrahedron and each face of the tetrahedron is capped by the bridging pyridylchalcogenolate ligand. Thermal behavior of these complexes was studied by thermogravimetric analysis. Depending on reaction conditions, thermolysis gave both stoichiometric and non-stoichiometric copper chalcogenides, which were characterized by XRD, EDX, SEM, TEM and SAED techniques. These precursors were used for the preparation of nanocrystals and for deposition of thin films of copper chalcogenides by AACVD (Aerosol Assisted Chemical Vapor Deposition).

Oligomeric allyl-palladium(II) complexes of ß-substituted ethylselenolates: syntheses, structures and thermal decomposition.

Tri-nuclear allyl-palladium complexes, [Pd(µ-SeCH(2)CH(2)COOR)(η(3)-C(3)H(4)R')](3) (R = H, Me, Et and R' = H, Me), have been synthesized by the reaction of [Pd(2)(µ-Cl)(2)(η(3)-C(3)H(4)R')(2)] with NaSeCH(2)CH(2)COOR. These complexes exist in a dynamic equilibrium with a dimeric form in solution and are fluxional at room temperature as shown by variable temperature (1)H NMR spectroscopy. The DFT calculations indicate that there is a negligible energy difference between the dimer and the trimer, and suggest that the delicate balance between the steric factors and angular strain decides the reaction products. These complexes (with R' = H) on treatment with [Pd(2)(µ-Cl)(2)(η(3)-C(3)H(5))(2)] afforded hetero-bridged complexes [Pd(2)(µ-Cl)(µ-SeCH(2)CH(2)COOR)(η(3)-C(3)H(5))(2)] (R = Me, Et). All the complexes have been characterized by NMR ((1)H, (13)C, (77)Se) spectroscopy. The molecular structure of [Pd(µ-SeCH(2)CH(2)COOEt)(η(3)-C(3)H(5))](3) revealed a chair conformation of the six-membered Pd(3)Se(3) ring, in which all the allyl groups lie at one side of the ring (similar to three axial 1,3,5-hydrogens of cyclohexane). Thermolysis of [Pd(µ-SeCH(2)CH(2)COOEt)(η(3)-C(3)H(5))](n) in diphenyl ether or hexadecylamine (HDA) yielded Pd(7)Se(4) as characterized by powder XRD.

Synthesis, characterization and structures of 2-(3,5-dimethylpyrazol-1-yl)ethylseleno derivatives and their probable glutathione peroxidase (GPx) like activity.

A series of 2-(3,5-dimethylpyrazol-1-yl)ethylseleno derivatives has been synthesized. The glutathione peroxidase like catalytic activity of these compounds has been studied in a model system, in which reduction of hydrogen peroxide with dithiothreitol (DTT(red)), in the presence of an organoselenium compound was investigated by (1)H NMR spectroscopy. All these compounds exhibit GPx like catalytic activities and the catalytic reaction proceeds through a selenoxide intermediate, identified by (77)Se{(1)H} NMR spectroscopy.

2-Pyridyl selenolates of antimony and bismuth: Synthesis, characterization, structures and their use as single source molecular precursor for the preparation of metal selenide nanostructures and thin films.

Reactions of SbCl(3) and BiCl(3) with M'Se-C(5)H(3)(R-3)N (M' = Li or Na; R = H or Me) gave homoleptic selenolate complexes of the general formula [M{Se-C(5)H(3)(R-3)N}(3)] (M = Sb or Bi). The complexes were characterized by elemental analysis, UV-vis and NMR ((1)H, (13)C and (77)Se) spectroscopy. The single crystal X-ray analysis of [M{Se-C(5)H(3)(Me-3)N}(3)].nH(2)O (M/n = Sb/1.5 and Bi/0.5) revealed that the antimony complex adopts a trigonal pyramidal configuration with monodentate selenolate ligands while the bismuth analogue acquires a distorted square pyramidal configuration defined by two chelating and one monodentate selenolate groups. Pyrolysis of [M{Se-C(5)H(3)(Me-3)N}(3)] either in a furnace or in hexadecylamine (HDA) at different temperatures gave a variety of M(2)Se(3) nanostructures. Thin films of metal selenides have also been deposited on glass substrate by aerosol-assisted chemical vapor deposition (AACVD). Both nanostructures and thin films of metal selenides were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM).

Tellurium(0) as a ligand: synthesis and characterization of 2-pyridyltellurolates of platinum(II) and structures of [Pt{2-Te-3-(R)C5H3N}2Te(PR'3)] (R = H or Me).

Treatment of toluene solutions of the ditellurides [Te(2){C(5)H(3)N(R)-3}(2)] (R = H or Me) with [Pt(PPh(3))(4)] yielded two types of complexes, [Pt{2-Te-3-(R)C(5)H(3)N}(2)(PPh(3))(2)] (1a-d) as the major products and [Pt{2-Te-3-(R)C(5)H(3)N}(2)Te(PPh(3))] (2a-d) as minor products. The above complexes can also be obtained by the reaction of [PtCl(2)(PR'(3))(2)] (PR'(3) = PPh(3) or PPh(2)(2-C(5)H(4)N)) with 2 equiv of Na(2-Te-C(5)H(3)R). The complexes were characterized by elemental analyses and UV-vis, NMR ((1)H and (31)P), and (in part) XPS spectroscopy. The molecular structures of [Pt(2-Te-C(5)H(4)N)(2)Te(PPh(3))] (2a) and [Pt{2-Te-C(5)H(3)(Me)N}(2)Te(PPh(3))] (2b) were established by single crystal X-ray diffraction. Both complexes exhibit a distorted square-planar configuration at the platinum(II) centers. The two mutually trans positioned 2-pyridinetellurolate ligands [2-Te-C(5)H(3)(R)N] coordinate to the central platinum atom in a monodentate fashion through the tellurium atoms. The tellurium(0) atom adopts a "bent T" configuration as it is bridging the 2-Te- C(5)H(3)(R)N molecules via N-Te-N bonds (166 degrees angle) and coordinates to Pt(II) in the trans position to PPh(3). The novel bis(pyridine)tellurium(0) arrangement resembles the bis(pyridine)iodonium structure. The calculated NICS indices and ELF functions clearly show that the compounds 2a and 2b are aromatic in the region defined by the Te-C-N-Te-Pt five-membered rings.

Bis(3-methyl-2-pyridyl)ditelluride and pyridyl tellurolate complexes of zinc, cadmium, mercury: Synthesis, characterization and their conversion to metal telluride nanoparticles.

Treatment of an acetonitrile solution of metal chloride with bis(3-methyl-2-pyridyl)ditelluride, [Te(2)(pyMe)(2)], in the same solvent yielded complexes of composition [MCl(2){Te(2)(pyMe)(2)}] (M = Zn or Cd) whereas reactions of [MCl(2)(tmeda)] with NaTepyR (R = H or Me) gave tellurolate complexes of the general formula [M(TepyR)(2)] (M = Cd or Hg). When the cadmium complex [Cd(Tepy)(2)] was crystallized in the presence of excess tmeda, [Cd(Tepy)(2)(tmeda)] was formed exclusively. These complexes were characterized by elemental analyses, uv-vis, (1)H NMR data. The crystal structures of [ZnCl(2){Te(2)(pyMe)(2)}] and [Cd(Tepy)(2)(tmeda)] were established by single crystal X-ray diffraction. In the former zinc is coordinated to nitrogen atoms of the pyridyl group, while in the latter the coordination environment around tetrahedral cadmium is defined by the two neutral nitrogen atoms of tmeda, and two pyridyl tellurolate ligands. Thermal behavior of some of these complexes was studied by thermogravimetric analysis. Pyrolysis of [M(Tepy)(2)] in a furnace or in coordinating solvents such as hexadecylamine/tri-n-octylphosphine oxide (HDA/TOPO) at 350 and 160 degrees C, respectively gave MTe nanoparticles, which were characterized by uv-vis, photoluminiscence, XRD, EDAX and TEM.