Search

Neodymium nickelate, NdNiO3, attracts attention due to the simultaneous occurrence of several phase transitions around the same temperature. The electronic properties of NdNiO3 are extremely complex as structural distortion, electron correlation, charge ordering, and orbital overlapping play significant roles in the transitions. We report the effects of electron and hole injection via doping a single 3d metal, V, in the NdNiO3 nanostructure to understand the variations in the electronic properties without any structural distortion. A reversible resistivity modulation of more than five orders of magnitude via hole doping and complete suppression of the metal to insulator transition via electron doping is observed along with the switching of major charge carriers. The modulation of electronic properties without any structural distortion and external strain opens up new directions to consider the NdNi1−xVxO3 nanostructures applicable as emerging electronic devices. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) containing multiple carboxylate and sulfonate linkers together with positively charged rare earth metals can offer new opportunities in heterogeneous catalysis. The high efficiency of the CO2 fixation reaction at low temperature and pressure over MOF-based catalysts is very challenging as it involves the renewable feedstock CO2 as a C1 source for the synthesis of value-added fine chemicals. Here we develop a new microporous La(III) based MOF through the solvothermal reaction using 5-sulfoisophthalic acid as the ligand, and the resulting La-5-SIP-MOF showed a high catalytic activity for the synthesis of cyclic carbonates from epoxides through the CO2 fixation reaction at room temperature and moderate (3–5 MPa) pressure. The optimum product yield was obtained in only 1 h reaction with the desired yield up to 98%. The La-5-SIP-MOF was characterized by using different analytical techniques such as single crystal X-ray diffraction, FTIR, PXRD, N2 adsorption/desorption study, UHR-TEM, solid UV-vis spectroscopy and TGA. The recycling efficiency and the structural stability of this MOF catalyst is also very high, suggesting a sustainable future of this La-MOF in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) bearing multicarboxylate linkers are in great demand for designing robust heterogeneous catalysts. A new microporous Ce(iii)-based metal organic framework (Ce2NDC3) has been synthesized under solvothermal conditions, which showed strong paramagnetism and a CO2 uptake capacity of 1.64 mmol g−1 (7.23 weight%) at 273 K. The Ce2NDC3 showed high catalytic activity in CO2 fixation for the synthesis of cyclic carbonates with a maximum yield of 92% at ambient temperature and pressure. This rare earth metal-based MOF has been well characterized by single crystal X-ray diffraction, PXRD, N2 adsorption/desorption, UHR-TEM, FESEM, FTIR, 13C MAS NMR and TGA. Here, we have carried out magnetic analysis, which revealed that the Ce(iii) in this MOF exhibited 2F5/2 magnetism in the ground state. The Ce2NDC3 catalyst showed high recycling efficiency in CO2 fixation reactions, together with retention of the MOF structure after several rounds of reuse. Presumably, the presence of acidic Ce(iii) metal ions and microporosity in the coordinated polymer network is responsible for the high catalytic activity. [ABSTRACT FROM AUTHOR]

We demonstrate a novel method of simultaneous photoassisted hetero-phase synthesis, doping, and micro-scale patterning of conductive materials. The patterning is performed by controlled self-assembly mediated by a micro-bubble induced in an optical tweezers configuration. The high temperature generated due to the light field of the tweezers also drives diverse chemical reactions that lead to the in situ formation of conducting metal-oxides and polymers due to a charge transfer mechanism with soft oxometalates (SOMs). We synthesize two conducting polymers – polypyrrole and polyaniline – doped by the metal oxides Mo–O2 and Mo–O3, from dispersions of the respective organic compounds with the SOMs, and form permanent patterns out of them by continuous self-assembly arising from manipulation of the micro-bubble using Marangoni flows generated by the tweezers. The electrically conducting patterns of width varying between around 4–50 μm, are written in the form of simple Hall-bar geometries, and a four-probe measurement technique yields conductivities on the order of ∼450–600 Siemens cm−1– which is much higher than that reported for both polypyrrole and polyaniline in earlier work. This technique can easily be used in patterning complicated electrical circuits in mesoscopic length scales, and can also be extended to solution processed electronic device development by green chemical routes. [ABSTRACT FROM AUTHOR]

Starting from the proligand 2-[(6-methylpyridin-2-yl)]imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate(1·PF6), three new complexes, viz. [Au(1)2] [PF6] (2), [1/2AuCl2, 1/2AuCl4]− [(1H)]+ (3), and [Au(1)Cl3] (4), have been synthesized and characterized employing different spectroscopic methods. [Au(1)Cl3] (4) has been synthesized by the disproportionation process. During the transformation of 2 to 4, the annelated proligand stabilizes both Au(i) and Au(iii), and the isolation of the intermediate (3) confirms the conversion of Au(i) → Au(iii) through the disproportionation pathway. The solid state structures of 2, 3 and 4 have been determined. Linear geometry was observed in 2, whereas complex 4 adopted square-planar geometry. Gold complexes 2 and 4 have been subjected to growth inhibitory studies. Complex 2 induced apoptosis in HepG2 cells along with increased expression of proteins involved in the mitochondrial death pathway, suggesting that apoptosis may occur via the mitochondrial death pathway. [ABSTRACT FROM AUTHOR]

A series of CO2-promoted Cu(II) coordination polymers in different coordination environments has been synthesized. The molecular description and properties of the four complexes have been investigated by CHN, MS, UV-VIS, IR, PXRD, TEM, SQUID, SC-XRD, NLDFT, and electrical property characterizations. Single crystal X-ray structure determination of [Cu(bpy)(C2O4)]n (1) and [Cu(2-AMP)2(C2O4)]n (2) depicts their polynuclearity [bpy = 2,2'-bipyridine, 2-AMP = 2-aminopyridine; 2-AMP is a cleaved ligand of starting ligand L¹ = N-(phenyl(pyridin-2-ylamino)methyl)pyridin-2-amine]. Both complexes have distorted octahedral geometry. Starting from another tripodal ligand L² [L² = 2-((((2-(pyridin-2-yl)ethyl)(pyridin-2-yl)-methyl)amino)methyl)phenol, L2' (cleaved L² ligand) = 2-(pyridin-2-yl)-N-((pyridin-2-yl)methyl)ethanamine], a mononuclear complex [Cu(L²)(Cl)] (3) has been obtained with a distorted square pyramidal geometry. Polynuclear complexes 1, 2, and 4 are CO2-mediated functional materials that have been produced in benzonitrile solvent medium. Interestingly, complex 4 of cleaved L² ligand is a wonderful copper-based functional material with appreciable surface area. Powder XRD and TEM analysis of complex 4 supports its mesoporosity. Moreover, all four complexes can function as semiconductors over a wide temperature range. [ABSTRACT FROM AUTHOR]

Radiolabeled complexes of monoamino polycarboxylic, polyamino monocarboxylic and thiol containing amino acid ligands were prepared from a fac-[99mTc(CO)3(H2O)3]+ precursor.The overall radiochemical yield was 94–98%. The complexes exhibited substantial in vitro and in vivo stability. The corresponding Re(i) complexes of the ligands DAPA, Asp and CysH were prepared and characterized by means of IR, NMR, and MS spectroscopic studies, as well as X-ray crystallography (for those containing d,l-DAPA and d,l-Asp ). The rhenium complexes have been structurally correlated with the technetium complexes by means of HPLC studies. The reaction of Re(CO)5Cl with d,l-Asp in presence of triethylamine led to the formation of a new class of cyclic dimeric complexes formed by the OON donor atom set of the tridentate ligands. The amino carboxylate ligand system formed well defined complexes with a fac-[M(CO)3(H2O)3]+ core and shows good promise in 99mTc(CO)3 tracer development. [ABSTRACT FROM AUTHOR]

Novel Au(i)-N-heterocyclic carbene complexes, 1-methyl-3-(2-pyridylmethyl)-benzimidazolylidenegold(i)-chloride, 1; 1-benzyl-3-(2-pyridylmethyl)-benzimidazolylidenegold(i)chloride, 2; and Pt(ii)-N-heterocyclic carbene complexes 1-methyl-3-(2-pyridylmethyl) benzimidazolylidene platinum(ii)chloride, 3; and 1-benzyl-3-(2-pyridylmethyl) benzimidazolylidene platinum-(ii)chloride, 4, have been synthesized, based on CN-donor proligands 1-alkyl-3-(2-pyridylmeth-yl)-benzimidazoliumchloride L1 and L2 [alkyl, R = –CH3 = L1; R = –CH2Ph = L2]. All the compounds have been synthesized and characterized by different spectroscopic methods. The Au(i) complexes 1 and 2 have been synthesized by a silver carbene transfer method. The solid-state structures of 1 and 3 have been determined by single crystal X-ray diffraction studies. The square planar Pt(ii) complexes 3 and 4 show a reversible Pt(ii)/Pt(iv) couple at 0.69 eV and 0.67 eV respectively. Among the complexes 1–4, complexes 1 and 3 have been used for cytotoxicity studies on the cell lines B16F10 (mouse melanoma), HepG2 (human hepatocarcinoma) and HeLa (human cervical carcinoma). IC50 values are compared with cisplatin, among 1 and 3, the Au(i) complex 1 is more effective than Pt(ii) complex 3. [ABSTRACT FROM AUTHOR]

One Co(ii) SCO coordination polymer [Co(enbzpy)(μ1,5-dca)]n(PF6)n (1·PF6) has been isolated and characterised structurally and magnetostructurally. The properties of 1·PF6 are compared with the reported perchlorate analogue [Co(enbzpy)(μ1,5-dca)]n(ClO4)n (1·ClO4). The gradual spin transition in 1·PF6 in contrast to an abrupt spin transition with a hysteresis loop in 1·ClO4 has been analysed in terms of structural factors. [ABSTRACT FROM AUTHOR]

Neodymium nickelate, NdNiO 3 , attracts attention due to the simultaneous occurrence of several phase transitions around the same temperature. The electronic properties of NdNiO 3 are extremely complex as structural distortion, electron correlation, charge ordering, and orbital overlapping play significant roles in the transitions. We report the effects of electron and hole injection via doping a single 3d metal, V, in the NdNiO 3 nanostructure to understand the variations in the electronic properties without any structural distortion. A reversible resistivity modulation of more than five orders of magnitude via hole doping and complete suppression of the metal to insulator transition via electron doping is observed along with the switching of major charge carriers. The modulation of electronic properties without any structural distortion and external strain opens up new directions to consider the NdNi 1- x V x O 3 nanostructures applicable as emerging electronic devices.

Metal organic frameworks (MOFs) bearing multicarboxylate linkers are in great demand for designing robust heterogeneous catalysts. A new microporous Ce(iii)-based metal organic framework (Ce 2 NDC 3 ) has been synthesized under solvothermal conditions, which showed strong paramagnetism and a CO 2 uptake capacity of 1.64 mmol g -1 (7.23 weight%) at 273 K. The Ce 2 NDC 3 showed high catalytic activity in CO 2 fixation for the synthesis of cyclic carbonates with a maximum yield of 92% at ambient temperature and pressure. This rare earth metal-based MOF has been well characterized by single crystal X-ray diffraction, PXRD, N 2 adsorption/desorption, UHR-TEM, FESEM, FTIR, 13 C MAS NMR and TGA. Here, we have carried out magnetic analysis, which revealed that the Ce(iii) in this MOF exhibited 2 F 5/2 magnetism in the ground state. The Ce 2 NDC 3 catalyst showed high recycling efficiency in CO 2 fixation reactions, together with retention of the MOF structure after several rounds of reuse. Presumably, the presence of acidic Ce(iii) metal ions and microporosity in the coordinated polymer network is responsible for the high catalytic activity.

One Co(ii) SCO coordination polymer [Co(enbzpy)(μ1,5-dca)]n(PF6)n (·PF6) has been isolated and characterised structurally and magnetostructurally. The properties of ·PF6 are compared with the reported perchlorate analogue [Co(enbzpy)(μ1,5-dca)]n(ClO4)n (·ClO4). The gradual spin transition in ·PF6 in contrast to an abrupt spin transition with a hysteresis loop in ·ClO4 has been analysed in terms of structural factors.

A series of CO2-promoted Cu(II) coordination polymers in different coordination environments has been synthesized. The molecular description and properties of the four complexes have been investigated by CHN, MS, UV-VIS, IR, PXRD, TEM, SQUID, SC-XRD, NLDFT, and electrical property characterizations. Single crystal X-ray structure determination of [Cu(bpy)(C2O4)]n (1) and [Cu(2-AMP)2(C2O4)]n (2) depicts their polynuclearity [bpy = 2,2'-bipyridine, 2-AMP = 2-aminopyridine; 2-AMP is a cleaved ligand of starting ligand L1= N-(phenyl(pyridin-2-ylamino)methyl)pyridin-2-amine]. Both complexes have distorted octahedral geometry. Starting from another tripodal ligand L2 [ L2 = 2-((((2-(pyridin-2-yl)ethyl)(pyridin-2-yl)methyl)amino)methyl)phenol, L2' (cleaved L(2) ligand) = 2-(pyridin-2-yl)-N-((pyridin-2-yl)methyl)ethanamine], a mononuclear complex [Cu(L(2))(Cl)] (3) has been obtained with a distorted square pyramidal geometry. Polynuclear complexes 1, 2, and 4 are CO2-mediated functional materials that have been produced in benzonitrile solvent medium. Interestingly, complex 4 of cleaved ligand L2 is a wonderful copper-based functional material with appreciable surface area. Powder XRD and TEM analysis of complex 4 supports its mesoporosity. Moreover, all four complexes can function as semiconductors over a wide temperature range.

Radiolabeled complexes of monoamino polycarboxylic, polyamino monocarboxylic and thiol containing amino acid ligands were prepared from a fac-[(99m)Tc(CO)3(H2O)3](+) precursor.The overall radiochemical yield was 94-98%. The complexes exhibited substantial in vitro and in vivo stability. The corresponding Re(I) complexes of the ligands DAPA, Asp and CysH were prepared and characterized by means of IR, NMR, and MS spectroscopic studies, as well as X-ray crystallography (for those containing D,L-DAPA and D,L-Asp). The rhenium complexes have been structurally correlated with the technetium complexes by means of HPLC studies. The reaction of Re(CO)5Cl with D,L-Asp in presence of triethylamine led to the formation of a new class of cyclic dimeric complexes formed by the OON donor atom set of the tridentate ligands. The amino carboxylate ligand system formed well defined complexes with a fac-[M(CO)3(H2O)3](+) core and shows good promise in (99m)Tc(CO)3 tracer development.

Three types of atropisomeric unsymmetrical diimine complexes, tetrahedral (L(R)(Φ))MX(2) (M = Zn, Cd; X = Cl, Br; R = Me, CMe(3), OH, OMe, Cl; 1a-k, type-I), tetrahedral (L(Me2)(Φ))ZnBr(2) (2, type-II) and square planar (L(OH)(ϕ))PdCl(2) (3, type-III) with different photoluminescence properties, have been reported (L(R)(Φ) = (E)-4-R-N-(pyridine-2-ylmethylene)aniline; Φ = dihedral angle between the diimine unit including the pyridine ring and the phenyl ring planes). In crystals, Φ = 0° for type-I, 90° for type-II and 63° for type-III atropisomers have been confirmed by single crystal X-ray structure determinations of 1c, 1e, 2 and 3·H(2)O isomers. Optimizations of geometries in methanol have established Φ = 28-32° for type-I, 90.83° for type-II and 43.44° for type-III isomers. In solids, type-I atropisomers with Φ = 0, behave as conjugated 14πe systems facilitating π-π stacking and are brightly luminescent at room temperature while type-II and type-III isomers in solid and type-I isomers in solutions are more like non-conjugated 8πe + 6πe systems and non-emissive. Frozen glasses of acetonitrile, methanol and dichloromethane-toluene mixture at 77 K of type-I isomers are emissive and display structured excitation and emission spectra for R = Me, CMe(3), OMe species. Excitation and emission maxima of frozen glasses (λ(ex) = 320-380 nm; λ(em) = 440-485 nm) are red shifted in the solid (λ(ex) = 390-455 nm; λ(em) = 470-550 nm). TD-DFT calculations on 1b, 1d, 1f and stacked (1b)(2) isomers and luminescence lifetime measurements have elucidated that an excited (1)ILCT state has been the origin of emission of the type-I isomers and delocalizations of the photoactive π(diimine) and π(diimine)(*) orbitals of the L(R)(Φ) over the stacked layers shift the λ(ext) and λ(em) of solids to lower energies than those in frozen glasses. The trends of diimine ligand based electron transfer events of the complexes in DMF have been investigated by cyclic voltammetry at 298 K., (This journal is © The Royal Society of Chemistry 2011)