| 1. |
- Bredyuk, O.A., et al.
(författare)
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Three-Dimensional Polymeric Thallium(I) Morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n and Its Capability of Binding Gold(III) from Solutions : Chemisorption Synthesis of a Heteronuclear Gold(III)–Thallium(III) Complex of the Ionic Type, ([Au{S2CN(CH2)4O}2][TlCl4])n, the Role of Secondary Interactions Tl…O, Tl…S, and Au…S in the Supramolecular Self-Organization, 13C MAS NMR, and Thermal Behavior
- 2017
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Ingår i: Russian journal of coordination chemistry. - : Maik Nauka Publishing. - 1070-3284 .- 1608-3318. ; 43:10, s. 638-651
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline polymeric thallium(I) morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n (I) and the heteronuclear ion–polymeric gold(III)–thalium(III) complex ([Au{S2CN(CH2)4O}2][TlCl4])n (II) are preparatively isolated and characterized by X-ray diffraction analysis and 13C MAS NMR spectroscopy. According to the X-ray diffraction data, the main structural units of compounds I and II (CIF files CCDC 1548079 and 1548080) are presented by the binuclear centrosymmetric molecule [Tl2{S2CN(CH2)4O}2], noncentrosymmetric complex cation [Au{S2CN(CH2)4O{2]+, and isomeric complex anions [TlCl4]–. The formation of the three-dimensional polymeric structure (coordination number of Tl is 7), which is not characteristic of thallium(I) dithiocarbamates, is a consequence of the participation of the secondary Tl…O and Tl…S bonds of two types in the supramolecular self-organization of compound I. Nonequivalent secondary interactions of the first type join the binuclear molecules [Tl2{S2CN(CH2)4O}2] into polymer layers, which, in turn, form the three-dimensional polymeric framework due to the secondary bonds Tl…S. The revealed ability of freshly precipitated compound I to the chemisorption of gold(III) from solutions (2 M HCl) makes it possible to obtain heteronuclear supramolecular complex II as an individual form of binding. In the structure of the latter, the pairs of stronger secondary Au…S bonds join the gold(III) cations into dimers [Au2{S2CN(CH2)4O}4]2+ of the angular structure, the structural ordering of which is achieved in the cationcationic polymeric chain ([Au2{S2CN(CH2)4O}4]2+)n of the helical type involving the pairs of less strong Au…S bonds between the adjacent binuclear units. The distorted tetrahedral anions [TlCl4]– are localized between the polymeric chains. The study of the thermal behavior of compounds I and II by simultaneous thermal analysis makes it possible to establish the character of thermal transformations of the substances and to identify Tl2S (I), TlCl, and elemental gold (II) as thermolysis products
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| 2. |
- Chaudhary, Himanshu, et al.
(författare)
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Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability
- 2019
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Ingår i: Journal of Colloid and Interface Science. - : Academic Press. - 0021-9797 .- 1095-7103. ; 556, s. 172-179
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Tidskriftsartikel (refereegranskat)abstract
- The rich pool of protein conformations combined with the dimensions and properties of carbon nanotubes create new possibilities in functional materials and nanomedicine. Here, the intrinsically disordered protein α-synuclein is explored as a dispersant of single-walled carbon nanotubes (SWNTs) in water. We use a range of spectroscopic methods to quantify the amount of dispersed SWNT and to elucidate the binding mode of α-synuclein to SWNT. The dispersion ability of α-synuclein is good even with mild sonication and the obtained dispersion is very stable over time. The whole polypeptide chain is involved in the interaction accompanied by a fraction of the chain changing into a helical structure upon binding. Similar to other dispersants, we observe that only a small fraction (15–20%) of α-synuclein is adsorbed on the SWNT surface with an average residence time below 10 ms
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| 3. |
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| 4. |
- De Oliveira, Danilo Hirabae, et al.
(författare)
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Structural conversion of the spidroin C-terminal domain during assembly of spider silk fibers
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- The major ampullate Spidroin 1 (MaSp1) is the main protein of the dragline spider silk. The C-terminal (CT) domain of MaSp1 is crucial for the self-assembly into fibers but the details of how it contributes to the fiber formation remain unsolved. Here we exploit the fact that the CT domain can form silk-like fibers by itself to gain knowledge about this transition. Structural investigations of fibers from recombinantly produced CT domain from E. australis MaSp1 reveal an α-helix to β-sheet transition upon fiber formation and highlight the helix No4 segment as most likely to initiate the structural conversion. This prediction is corroborated by the finding that a peptide corresponding to helix No4 has the ability of pH-induced conversion into β-sheets and self-assembly into nanofibrils. Our results provide structural information about the CT domain in fiber form and clues about its role in triggering the structural conversion of spidroins during fiber assembly.
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| 5. |
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| 6. |
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| 7. |
- Gowda, Vasantha, 1986-, et al.
(författare)
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Bi(III) Complexes Containing Dithiocarbamate Ligands: Synthesis, Structure Elucidation by X‐ray Diffraction, Solid‐State 13C/15N NMR, and DFT Calculations
- 2020
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Ingår i: ChemistrySelect. - : John Wiley & Sons. - 2365-6549. ; 5:29, s. 8882-8891
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Tidskriftsartikel (refereegranskat)abstract
- We report on syntheses, characterisation by nuclear magnetic resonance (NMR) spectroscopy, X‐ray diffraction (XRD) measurements, and density functional theory (DFT) calculations of electronic/molecular structure and NMR chemical shifts of complexes of Bi(III), having the molecular formulae: [Bi{S2CN(C2H5)2)}3] (1), [Bi{S2CN(C2H5)2)}2(C12H8N2)NO3)] (2), and [Bi2{S2CN(CH2)5}6 H2O] (3). The powder XRD patterns of complexes (1) and (2) resembled the corresponding calculated powder XRD patterns for previously reported single crystal structures. Single crystal XRD structure of complex (3), reported in this work, adopted an orthorhombic system with a space group Pbca with a=10.9956(3) Å, b=27.7733(8) Å, c=35.1229(10) Å and α=β=γ=90°. The experimental solid‐state 13C/15N NMR data of the complexes (1)‐(3) were in accord with their X‐ray single crystal structures. The unit cell of the complex (3) shows a weak supramolecular Bi S interaction leading to the formation of a non‐centrosymmetric binuclear molecule [Bi2{S2CN(CH2)5}6 H2O], which displays structural inequivalence in both 13C/15N NMR, and XRD data. Assignments of resonance lines in solid‐state 13C/15N NMR spectra of complexes (1)‐(3) were assisted by chemical shift calculations using periodic DFT methods. The findings of the present multidisciplinary approach will contribute in designing molecular models and further understanding of the structures and properties of (diamagnetic) metal complexes, including heavy metal ones.
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| 8. |
- Gowda, Vasantha
(författare)
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Combined experimental and theoretical studies of dithiocarbamate complexes of yttrium, lanthanum and bismuth
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal-dithiocarbamate complexes find wide-ranging applications in nanomaterial and metalseparation science, and have potential use as chemotherapeutic, pesticides, and as additives tolubricants. A highly versatile dialkyldithiocarbamate (R2NCS2–) ligand can form stablecomplexes with all the transition elements and also the majority of main group, lanthanide andactinide elements. Here we present structural investigations of the molecular and electronicstructures of dialkyldithiocarbamate complexes with yttrium(III), lanthanum(III), andbismuth(III) of molecular formula [Y{S2CN(C2H5)2}3PHEN], [La{S2CN(C2H5)2}3PHEN], and[Bi2{S2CN-n(C4H9)2}6] (where PHEN=1,10-Phenanthroline) . The experimental solid-state 13Cand 15N cross polarization magic-angle-spinning (CP-MAS) NMR results are reported for allthese three complexes. We also report new single-crystal X-ray structures of heterolepticyttrium, lanthanum, and homoleptic bismuth dialkyldithiocarbamate complexes. Thecomparative analysis of powder XRD patterns and solid-state 13C and 15N CP-MAS spectra ofpolycrystalline yttrium(III) and lanthanum(III) diethyldithiocarbamato-phenanthrolinecomplexes shows the presence of significant structural differences. The diethyldithiocarbamatophenanthrolinecomplex of yttrium has a very similar structural type to a previously reported Xraydiffraction structure for [Nd{S2CN(C2H5)2}3PHEN] whereas, the crystal structure of[La{S2CN(C2H5)2}3PHEN] is considerably more complex. Our NMR and single-crystal X-raydiffraction results suggested polymorphism for bismuth di-n-butyldithiocarbamate complex.Finally, the experimental NMR results are complemented by chemical shifts obtained usingquantum chemical methods and verified the spectral assignments. Overall, our workdemonstrates how different experimental and theoretical methods can be combined that canafford insights into the solid-state structure and bonding environments of metal complexes.
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| 9. |
- Gowda, Vasantha, et al.
(författare)
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DFT calculations in the assignment of solid-state NMR and crystal structure elucidation of a lanthanum(iii) complex with dithiocarbamate and phenanthroline
- 2016
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 45:48, s. 19473-19484
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Tidskriftsartikel (refereegranskat)abstract
- The molecular, crystal, and electronic structures as well as spectroscopic properties of a mononuclear heteroleptic lanthanum(iii) complex with diethyldithiocarbamate and 1,10-phenanthroline ligands (3 : 1) were studied by solid-state 13C and 15N cross-polarisation (CP) magic-angle-spinning (MAS) NMR, X-ray diffraction (XRD), and first principles density functional theory (DFT) calculations. A substantially different powder XRD pattern and 13C and 15N CP-MAS NMR spectra indicated that the title compound is not isostructural to the previously reported analogous rare earth complexes with the space group P21/n. Both 13C and 15N CP-MAS NMR revealed the presence of six structurally different dithiocarbamate groups in the asymmetric unit cell, implying a non-centrosymmetric packing arrangement of molecules. This was supported by single-crystal X-ray crystallography showing that the title compound crystallised in the triclinic space group P1[combining macron]. In addition, the crystal structure also revealed that one of the dithiocarbamate ligands has a conformational disorder. NMR chemical shift calculations employing the periodic gauge including projector augmented wave (GIPAW) approach supported the assignment of the experimental 13C and 15N NMR spectra. However, the best correspondences were obtained with the structure where the atomic positions in the X-ray unit cell were optimised at the DFT level. The roles of the scalar and spin-orbit relativistic effects on NMR shielding were investigated using the zeroth-order regular approximation (ZORA) method with the outcome that already the scalar relativistic level qualitatively reproduces the experimental chemical shifts. The electronic properties of the complex were evaluated based on the results of the natural bond orbital (NBO) and topology of the electron density analyses. Overall, we apply a multidisciplinary approach acquiring comprehensive information about the solid-state structure and the metal-ligand bonding of the heteroleptic lanthanum complex.
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| 10. |
- Gowda, Vasantha, 1986-
(författare)
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Experimental and Computational Magnetic Resonance Studies of Selected Rare Earth and Bismuth Complexes
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors.This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initioquantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions.The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided aunique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state 13C and 15NNMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated 1H/13C/15N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their 1H and 13C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the 1H and 13C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements.The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.
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