Search results for " io"
showing 10 items of 2766 documents
Regioselective Bromination and Functionalization of Dibenzo[hi,st]ovalene as Highly Luminescent Nanographene with Zigzag Edges.
2019
Dibenzo[hi,st]ovalene (DBOV) is a nanographene with a combination of zigzag and armchair edges, consisting of 38 sp2 carbons. Excellent optical properties with strong red emission have been demonstrated. Here we report the regioselective bromination of DBOV bearing two mesityl groups (DBOV-Mes) by treatment with N-bromosuccinimide (NBS) under mild conditions. The dibrominated DBOV was further subjected to transition-metal-catalyzed cross-coupling reactions, that is, Suzuki and Sonogashira coupling, demonstrating the edge-decoration of DBOV with different functional groups. Notably, DBOVs arylated at the bay regions showed intense red emission and enhanced fluorescence quantum yields of up t…
Radical cation and dication of a 4H-dithieno[2,3-b:3′,2′-e][1,4]-thiazine
2017
A p-tert-butylphenyl substituted 4H-dithieno[2,3-b:3′,2′-e][1,4]thiazine was synthesized by twofold Buchwald–Hartwig coupling. The electronic properties (UV/Vis, cyclic voltammetry and spectroelectrochemistry) and the DFT- and TD DFT-calculated electronic structure reveal that the parent system and the radical cation and dication oxidation products are highly polarizable π-systems with strong charge transfer contributions. The radical cation and the dication were prepared by oxidation with antimony(V) pentachloride, giving stable deeply colored salts. EPR spectroscopy of the radical cation furnishes hyperfine coupling constants with the nitrogen nucleus and the α-thienyl protons. The dicati…
Stepwise Construction of Heterobimetallic Cages by an Extended Molecular Library Approach.
2017
Two novel heterobimetallic complexes, a trigonal-bipyramidal and a cubic one, have been synthesized and characterized using the same C3-symmetric metalloligand, prepared by a simple subcomponent self-assembly strategy. Adopting the molecular library approach, we chose a mononuclear, preorganized iron(II) complex as the metalloligand capable of self-assembly into a trigonal-bipyramidal or a cubic aggregate upon coordination to cis-protected C2-symmetric palladium(II) or unprotected tetravalent palladium(II) ions, respectively. The trigonal-bipyramidal complex was characterized by NMR and UV–vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffrac…
Studies on the Reduction of [(C 5 Me 5 ) 2 Mo 2 O 5 ] in Methanol/Water/Acetate Solutions by On‐Line Electrochemical Flowcell and Electrospray Mass S…
2003
The complex [Cp*2Mo2O5] (Cp* = η5-C5Me5) and its electrochemical reduction products in acetic acid/acetate-buffered (pH = 4.0) water/methanol solutions were investigated by combined electrochemical (EC) flowcell and on-line electrospray ionization mass spectrometry (ESI-MS). Mono-, di-, tri-, and tetranuclear organometallic molybdenum oxides were identified in the starting solution. The effect of the relevant ESI-MS parameters (ionic mode, heated capillary voltage, and heated capillary temperature) and of the concentration on the observed distribution of ions in the mass spectrometer was studied in order to minimize side reactions in the ESI chamber. It was verified that reduction in the ES…
Photolysis of Tertiary Amines in the Presence of CO2: The Paths to Formic Acid, α-Amino Acids, and 1,2-Diamines
2017
The photolysis of triethylamine (1a) in the presence of carbon dioxide leads to the hydrogenation of CO2, the α-C-C coupling of triethylamine (1a), and the CO2-insertion into the α-C-H σ-bond of amine 1a. This reaction is proposed to proceed through the radical ion pair [R3N·+·CO2·-] generated by the photoionization of amine 1a and the electron capture by CO2. The presence of lithium tetrafluoroborate in the reaction medium promotes the efficient and stereoselective α-C-C coupling of 1a by enhancing the production of α-dialkylamino radicals and the isomerization of N,N,N',N'-tetraethylbutane-2,3-diamine (4a).
Equipping metallo-supramolecular macrocycles with functional groups: Assemblies of pyridine-substituted urea ligands
2012
A series of di-(m-pyridyl)-urea ligands were prepared and characterized with respect to their conformations by NOESY experiments and crystallography. Methyl substitution in different positions of the pyridine rings provides control over the position of the pyridine N atoms relative to the urea carbonyl group. The ligands were used to self-assemble metallo-supramolecular M(2)L(2) and M(3)L(3) macrocycles which are generated in a finely balanced equilibrium in DMSO and DMF according to DOSY NMR experiments and ESI FTICR mass spectrometry. Again, crystallography was used to characterize the assemblies. Methyl substitution in positions next to the pyridine nitrogen prevents coordination, while …
Hexanuclear manganese(III) single-molecule magnets based on oxime and azole-type ligands
2019
Abstract Two novel hexanuclear manganese(III) complexes belonging to the Mn6 family of single-molecule magnets (SMMs), of formulae [Mn6(μ3-O)2(H2N-sao)6(bta)2(EtOH)6]·2EtOH·4H2O (1) and [Mn6(μ3-O)2(H2N-sao)6(pta)2(EtOH)6]·4EtOH (2) [H2N-saoH2 = salicylamidoxime, bta = 1,2,3-benzotriazolate anion, pta = 5-phenyl-tetrazolate anion], have been synthesized and characterized structurally and magnetically. Both compounds crystallize in the triclinic system with space group P 1 ¯ (1 and 2). In their crystal packing, adjacent Mn6 complexes are connected through non-coordinating solvent molecules, which are H-bonded to N atoms of azole rings and –NH2 groups of salicylamidoxime ligand. The study of t…
Functionalized phosphonates as building units for multi-dimensional homo- and heterometallic 3d-4f inorganic-organic hybrid-materials.
2016
Using the multifunctional ligand H4L (2,2'-bipyridinyl-5,5'-diphosphonic acid), a new family of inorganic-organic hybrid-materials was prepared. The ligand shows a very high flexibility regarding the coordination mode, leading to a large structural diversity. The compounds 1a, 1b ([M(H2L)(H2O)4]·2.5H2O; M = Co(2+) (a), Ni(2+) (b)), 2 ([Gd2(H2H'L)2(H2H'2L)(H2O)6]Cl4·14H2O), 3a, 3b, 3c ([MCo(iii)(H2L)3(H2O)2]·6.5H2O; M = Gd(3+) (a), Dy(3+) (b) and Tb(3+) (c)), and 4 ([GdNi(ii)(H2L)3(H2O)3]NaCl·6H2O) were isolated and characterized with single crystal X-ray diffraction. Depending on the used metal ions and on the stoichiometry, either discrete entities (0D), extended 2D layers or 3D frameworks…
A carboxylate-bridged NiII8 cluster with a distorted cubane topology: structure, magnetism and density functional studies
2016
Using a dicarboxylate ligand appended with (2-pyridyl)ethylamine unit, a new cluster [NiII8(L4)6(DMF)2(CH3OH)2(H2O)6][ClO4]4·2CH3OH·2CH3CO2C2H5 (1) [L4(2−): 3-[N-{2-(pyridin-2-yl)ethyl}amino]-bis(propionate)] has been synthesized, through ‘coordination-driven self-assembly’. The crystal structure of 1 reveals a centrosymmetric octanuclear carboxylate-bridged nickel(II) tetracation, with a distorted cubane topology. The four crystallographically independent nickel(II) centres differ markedly in their coordination environment. Magnetic studies (2–300 K) reveal that in 1 the net magnetic-exchange is antiferromagnetic. Based on geometric parameters associated with two interacting nickel(II) cen…
6-Polyamino-substituted quinolines: synthesis and multiple metal (CuII, HgIIand ZnII) monitoring in aqueous media
2019
Chemoselective palladium-catalyzed arylation of polyamines with 6-bromoquinoline has been explored to prepare chelators for the detection of metal cations in aqueous media. The introduction of a single aromatic moiety into non-protected polyamine molecules was achieved using the commercially available Pd(dba)2/BINAP precatalyst to afford nitrogen chelators, in which the aromatic signalling unit is directly attached to the polyamine residue. Water-soluble receptors were then synthesized using N-alkylation of these polyamines by hydrophilic coordinating residues. By combining rich photophysical properties of the 6-aminoquinoline unit with a high coordination affinity of chelating polyamines a…