| 1. |
- Arkhypchuk, Anna I., et al.
(författare)
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Oxaphospholes and Bisphospholes from Phosphinophosphonates and alpha,beta-Unsaturated Ketones
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:41, s. 13692-13704
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of a {W(CO)(5)}-stabilized phosphinophosphonate 1, (CO)(5)WPH(Ph)P(O)(OEt)(2), with ethynyl- (2a-f) and diethynylketones (7-11, 18, and 19) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)(3)Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5-dihydro-1,2-oxaphospholes 3 and 4. When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)(3)Si or (Et)(3)Si acetylene terminus is present, as in 7, 8, and 19, an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene-decorated oxaphospholes 14, 15, 24, and 25. Diacetylenic ketones 10 and 11, with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl-bridged bisphospholes 16 and 17. Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene-decorated oxaphospholes is more exothermic for the trimethylsilyl-containing substrates. The pathway to the latter compounds contains a 1,3-shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3-shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high-lying transition state TS(E-F)(R=Ph) of 37kcalmol(-1) is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl-terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17.
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| 2. |
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| 3. |
- Jafri, Syed Hassan Mujtaba, 1979-, et al.
(författare)
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Nanomolecular electronic devices based on AuNP molecule nanoelectrodes using molecular place-exchange process
- 2020
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Ingår i: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 31:22
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of electronics applications based on molecular electronics devices is hampered by the difficulty of placing a single or a few molecules with application-specific electronic properties in between metallic nanocontacts. Here, we present a novel method to fabricate 20 nm sized nanomolecular electronic devices (nanoMoED) using a molecular place-exchange process of nonconductive short alkyl thiolates with various short chain conductive oligomers. After the successful place-exchange with short-chain conjugated oligomers in the nanoMoED devices, a change in device resistance of up to four orders of magnitude for 4,4 '-biphenyldithiol (BPDT), and up to three orders of magnitude for oligo phenylene-ethynylene (OPE), were observed. The place-exchange process in nanoMoEDs are verified by measuring changes in device resistance during repetitive place-exchange processes between conductive and nonconductive molecules and surface-enhanced Raman spectroscopy. This opens vast possibilities for the fabrication and application of nanoMoED devices with a large variety of molecules.
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| 4. |
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| 5. |
- Akkarasamiyo, Sunisa, et al.
(författare)
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Tsuji-Trost Reaction of Non-Derivatized Allylic Alcohols
- 2018
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 24:14, s. 3488-3498
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Tidskriftsartikel (refereegranskat)abstract
- Palladium-catalyzed allylic substitution of non-derivatized enantioenriched allylic alcohols with a variety of uncharged N-, S-, C- and O-centered nucleophiles using a bidentate BiPhePhos ligand is described. A remarkable effect of the counter ion (X) of the XPd[kappa(2)-BiPhePhos][kappa(3)-C3H5] was observed. When ClPd[kappa(2)-BiPhePhos][eta(3)-C3H5] (complexI) was used as catalyst, non-reproducible results were obtained. Study of the complex by X-ray crystallography, (PNMR)-P-31 spectroscopy, and ESI-MS showed that a decomposition occurred where one of the phosphite ligands was oxidized to the corresponding phosphate, generating ClPd[kappa(1)-BiPhePhosphite-phosphate][eta(3)-C3H5] species (complexII). When the chloride was exchanged to the weaker coordinating OTf- counter ion the more stable Pd[kappa(2)-BiPhePhos][eta(3)-C3H5](+)+[OTf] (-) (complexIII) was formed. ComplexIII performed better and gave higher enantiospecificities in the substitution reactions. ComplexIII was evaluated in Tsuji-Trost reactions of stereogenic non-derivatized allylic alcohols. The desired products were obtained in good to excellent yields (71-98%) and enantiospecificities (73-99%) for both inter- and intramolecular substitution reactions with only water generated as a by-product. The methodology was applied to key steps in total synthesis of (S)-cuspareine and (+)-lentiginosine. A reaction mechanism involving a palladium hydride as a key intermediate in the activation of the hydroxyl group is proposed in the overall transformation.
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| 6. |
- Arkhypchuk, Anna I., et al.
(författare)
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Isolation and Characterization of a Monoprotonated Hydroporphyrin
- 2018
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :48, s. 7051-7056
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Tidskriftsartikel (refereegranskat)abstract
- A simple protocol for the controlled preparation of mono- and diprotonated hydroporphyrins (chlorins) is presented. The chlorins carried 10-aryl groups with electron-neutral (phenyl), electron-donating (p-OMe-C6H4) or electron-withdrawing (pentafluorophenyl) substituents. The protonation reactions were readily followed by UV/Vis absorption spectroscopy, enabling the determination of the first (4.8-5.3) and second pK(a)'s (1.7-0.5). Both mono- and diprotonated species were fully characterized by H-1 NMR spectroscopy, which, in combination with theoretical studies, showed that these macrocycles were significantly distorted in solution. A 10-phenyl-substituted monoprotonated chlorin was characterized by X-ray crystallography. This is the first structurally characterized hydroporphyrin monocation, and the first crystal structure of a sterically unencumbered singly protonated tetrapyrrole. The photostabilities of the mono- and diprotonated 10-phenylchlorins were measured upon irradiation into their Soret bands; protonation yielded increased photostabilities.
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| 7. |
- Arkhypchuk, Anna I., et al.
(författare)
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Synthesis and Characterization of Ferrocenyl Chlorins, 1,1'-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues
- 2017
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:5, s. 3044-3054
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterization of meso-ferrocenyl-substituted hydroporphyrins (chlorins) and 1,1' -linked chlorin dimers. The dipyrromethane chlorin precursors were also transformed into Fc-substituted BODIPYs and 1,1'-ferrocenyl-linked BODIPY dimers. The chlorin dimers were studied by 1D and 2D NMR experiments and DFT calculations, which showed that their solution structures were dependent on the central metal. Monomeric and dimeric Ni(II) chlorins had similar H-1 NMR spectra. Monomeric and dimeric free base, Zn(II), and Pd(II) chlorins, on the other hand, showed significantly more different spectra. The eclipsed conformer of the free base chlorin dimer was calculated to be energetically more favored than the open form. The chlorin and BODIPY fluorescence emissions were quenched in the Fcsubstituted compounds; these could be recovered by oxidation of the Fe(II) center. Cyclic voltammetry showed up to five oxidation waves for the free base chlorin dimer, which suggests that the macrocycles were not behaving independently of each other.
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| 8. |
- Arkhypchuk, Anna I., et al.
(författare)
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Tuning the Optical Properties of 1,1'-Biphospholes by Chemical Alterations of the P-P Bridge
- 2014
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2014:10, s. 1760-1766
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Tidskriftsartikel (refereegranskat)abstract
- 2,5-Di(1-naphthyl)-1-phenylphosphole (2) was prepared from phenylphosphine and dinaphthylbutadiyne in 70% yield, and oxidized to its oxide 3. Treatment of 2 with a solution of potassium naphthalide results in selective formation of phospholide anion 4, which can be oxidized with iodine to afford biphosphole 5. The crystal structure of 5 exhibits an unusual s-trans conformation across the P-P bridge that is most stabilized by - stacking of the naphthyl substituents. Biphosphole 5 can be oxidized to its mono-oxidized 6 and dioxide 7. Generally, all phosphole oxidations lead to decreased pyramidalization of the P centres and, consequently, to significantly redshifted lowest-energy absorption maxima. Mono-oxidized biphosphole 6, which consists of an ordinary phosphole and an electron-deficient oxidized phosphole, features a unique low-energy optical transition (shoulder at 430 nm), which is tentatively assigned to a charge-transfer transition. The UV/Vis spectrum of dioxide 7 lacks this transition. At the same time, the emission maximum of 7 is bathochromically shifted by 80 nm relative to that of 5.
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| 9. |
- Arkhypchuk, Anna, et al.
(författare)
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Mechanism of the Phospha-Wittig-Horner Reaction
- 2013
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 52:25, s. 6484-6487
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Barnå, Fredrik, et al.
(författare)
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Synthesis and crystal structures of boryl ortho-silylaryl trifluoromethanesulfonates
- 2024
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Ingår i: Acta Crystallographica Section E: Crystallographic Communications. - : International Union Of Crystallography. - 2056-9890. ; 80:2, s. 143-147
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and structural characterization of three crystalline borylated ortho-silylaryl trifluoromethanesulfonates: 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(trimethylsilyl)phenyl trifluoromethanesulfonate, C16H24BF3O5SSi (1a), 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(trimethylsilyl)phenyl trifluoromethanesulfonate, C16H24BF3O5SSi (1b), and 2-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-6-(trimethylsilyl)phenyl trifluoromethanesulfonate, C17H26BF3O5SSi (2), which are versatile aryne precursors. For all three compounds, the heteroatom substituents are almost coplanar with the central aromatic moiety. C—heteroatom bonding metrics are unexceptional and fall withing the typical range of C—B, C—Si, and C—O single bonds. Despite numerous electronegative sites, only weak intermolecular interactions are observed in the solid state.
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