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1.
ACS Omega ; 4(7): 12012-12017, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31460313

RESUMO

Three-dimensional selective laser sintering printing was utilized to produce porous, solid objects, in which the catalytically active component, Pd/SiO2, is attached to an easily printable supporting polypropylene framework. Physical properties of the printed objects, such as porosity, were controlled by varying the printing parameters. Structural characterization of the objects was performed by helium ion microscopy, scanning electron microscopy, and X-ray tomography, and the catalytic performance of the objects was tested in the hydrogenation of styrene, cyclohexene, and phenylacetylene. The results show that the selective laser sintering process provides an alternative and effective way to produce highly active and easily reusable heterogeneous catalysts without significantly reducing the catalytic efficiency of the active Pd/SiO2 component. The ability to control the size, porosity, mechanical properties, flow properties, physical properties, and chemical properties of the catalyst objects opens up possibilities to optimize devices for different reaction environments including batch reactions and continuous flow systems.

2.
Chem Commun (Camb) ; 55(74): 11095-11098, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31460525

RESUMO

The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron-nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized using standard Schlenk techniques and worked up and handled readily under atmospheric conditions. Through transmetallation via diarylzinc reagents a series of derivatives were synthesized which show broad visible to near-IR light absorption profiles that highlight the versatility of this BN substituted core for use in optoelectronic devices. The synthesis is efficient, scalable and allows for tuning through changes in substituents on the planar heterocyclic core and at boron. Exploratory evaluation in organic solar cell devices as non-fullerene acceptors gave power conversion efficiencies of 2%.

3.
Chem Asian J ; 14(5): 647-654, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30644629

RESUMO

The anion-binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1 H NMR spectra of the foldamers in [D6 ]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the release of ordered solvent molecules solvating the free foldamer and the anion to the bulk solution upon complex formation. The introduction of electron-withdrawing substituents in foldamers 2 and 3 had only a slight effect on the thermodynamic constants for chloride binding compared to the parent receptor. Remarkably, the binding of chloride to foldamer 3 not only produced the expected 1:1 complex but also open aggregates with 1:2 (host:anion) stoichiometry.

4.
Angew Chem Int Ed Engl ; 58(1): 154-158, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30408328

RESUMO

Flexible, chelating bis(NHC) ligand 2, able to accommodate both cis- and trans-coordination modes, was used to synthesize (2)Ni(η2 -cod), 3. In reaction with GeCl2 , it produced (2)NiGeCl2 , 4, featuring a T-shaped Ni0 and a pyramidal Ge center. Complex 4 could also be prepared from [(2)GeCl]Cl, 5, and Ni(cod)2 , in a reaction that formally involved Ni-Ge transmetalation, followed by coordination of the extruded GeCl2 moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ-donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)2 Ni(cod) complexes 9 and 10, as well as (NHC)2 GeCl2 derivative 11, incorporating ligands that cannot accommodate a wide bite angle, failed to produce isolable Ni-Ge complexes. The isolation of (2)Ni(η2 -Py), 12, provides further evidence for the reluctance of the (2)Ni0 fragment to act as a σ-Lewis acid.

5.
J Comput Chem ; 40(3): 572-580, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30575086

RESUMO

Composite quantum chemical methods W1X-1 and CBS-QB3 are used to calculate the gas phase standard enthalpy of formation, entropy, and heat capacity of 38 phosphines and phosphine oxides for which reliable experimental thermochemical information is limited or simply nonexistent. For alkyl phosphines and phosphine oxides, the W1X-1, and CBS-QB3 results are mutually consistent and in excellent agreement with available G3X values and empirical data. In the case of aryl-substituted species, different computational methods show more variation, with G3X enthalpies being furthest from experimental values. The calculated thermochemical data are subsequently used to determine Benson group additivity contributions for 24 Benson groups and group pairs involving phosphorus, thereby allowing fast and accurate estimations of thermochemical data of many organophosphorus compounds of any complexity. Such data are indispensable, for example, in chemical process design or estimating potential hazards of new chemical compounds. © 2018 Wiley Periodicals, Inc.

6.
Inorg Chem ; 57(21): 13901-13911, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30351085

RESUMO

Condensation of persilylated nicotinimideamide and isonicotinimideamide with sulfur monochloride affords double salts of the 3-, 4-pyridyl-substituted 1,2,3,5-dithiadiazolylium DTDA cations of the general formula [3-, 4-pyDTDA][Cl][HCl] in which the pyridyl nitrogen serves as a noninnocent base. Reduction of these salts with triphenylantimony followed by deprotonation of the intermediate-protonated radical affords the free base radicals [3-, 4-pyDTDA], the crystal structures of which, along with those of their diselenadiazolyl analogues [3-, 4-pyDSDA], have been characterized by powder or single-crystal X-ray diffraction. The crystal structures consist of "pancake" π-dimers linked head-to-tail into ribbonlike arrays by η2-S2---N(py) intermolecular secondary bonding interactions. Methylation of the persilylated (iso)nicotinimide-amides prior to condensation with sulfur monochloride leads to N-methylated double chloride salts Me[3-, 4-pyDTDA][Cl]2, which can be converted by metathesis into the corresponding triflates Me[3-, 4-pyDTDA][OTf]2 and then reduced to the N-methylated radical triflates Me[3-, 4-pyDTDA][OTf]. The crystal structures of both the N-methylated double triflate and radical triflate salts have been determined by single-crystal X-ray diffraction. The latter consist of trans-cofacial π-dimers strongly ion-paired with triflate anions. Variable temperature magnetic susceptibility measurements on both the neutral and radical ion dimers indicate that they are diamagnetic over the temperature range 2-300 K.

7.
J Phys Chem Lett ; 9(13): 3624-3630, 2018 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-29897759

RESUMO

One of the first steps in designing ferromagnetic (FM) molecular materials of p-block radicals is the suppression of covalent radical-radical interactions that stabilize a diamagnetic ground state. In this contribution, we demonstrate that FM coupling between p-block radicals can be achieved by constructing mixed dimers from different radicals with differing symmetries of their singly occupied molecular orbitals. The applicability of this approach is demonstrated by studying magnetic interactions in organic radical dimers built from different derivatives of the well-known phenalenyl radical. The calculated enthalpies of dimerization for different homo- and heterodimers show that the formation of a mixed dimer with FM coupling is favored compared to the formation of homodimers with antiferromagenetic (AFM) coupling. We argue that cocrystallization of radicals with specifically tuned morphologies of their singly occupied molecular orbitals is a feasible and promising approach in designing new organic magnetic materials.

8.
Inorg Chem ; 57(11): 6491-6502, 2018 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-29745653

RESUMO

The first-row transition-metal(II) dithiolates M(SAriPr4)2 [AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2; M = Cr (1), Mn (3), Fe (4), Co (5), Ni (6), and Zn (7)] and Cr(SArMe6)2 [2; ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2] and the ligand-transfer reagent (NaSAriPr4)2 (8) are described. In contrast to their M(SAriPr6)2 (M = Cr, Mn, Fe, Co, Ni, and Zn; AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) congeners, which differ from 1 and 3-6 in having p-isopropyl groups on the flanking aryl rings of the terphenyl substituents, compounds 1 and 4-6 display highly bent coordination geometries with S-M-S angles of 109.802(2)° (1), 120.2828(3)° (4), 91.730(3)° (5), and 92.68(2)° (6) as well as relatively close metal-flanking aryl ring η6 interactions with metal-centroid distances of 2.11477(6) Å (1), 1.97188(3) Å (2), 2.15269(6) Å (4), 1.62058(9) Å (5), and 1.724(8) Å (6). However, the d5 (Mn) and d10 (Zn) complexes 3 and 7 display linear or near-linear coordination with no close metal-ligand distances. The nonlinear geometries of 1 and 4-6 also contrast with those of their AriPr4-substituted alkoxo and amido congeners, which have strictly linear coordination. Complexes 1-7 were synthesized by the reaction of the lithium or sodium thiolate salt with the metal dihalide or, in the case of 3, by the reaction of the thiol with the amido complex Mn[N(SiMe3)2]2. All compounds were characterized by electronic spectroscopy, X-ray crystallography, and magnetic measurements using Evans' method and SQUID magnetometry. It was concluded that, despite the large bulk of the AriPr4 substituents, the absence of p-isopropyl groups on the flanking rings of the ligand permits close secondary metal-flanking ring distances. The compounds are characterized by more intense colors and display magnetic moments that are generally lower than the spin-only values, in agreement with the covalent character of the close metal-flanking ring η6 interactions.

9.
Angew Chem Int Ed Engl ; 57(3): 749-754, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-29152832

RESUMO

An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs.

10.
Dalton Trans ; 47(3): 734-741, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29239418

RESUMO

The reactions of 1-bora-7a-azaindenide anions, prepared in moderate to excellent yields by reduction of the appropriate 1-bora-7a-azaindenyl chlorides with KC8 in THF, with alkyl halides and carbon dioxide were studied. With alkyl halides (CH2Cl2, CH3I and BrCH(D)CH(D)tBu), the anions behave as boron anions, alkylating the boron centre via a classic SN2 mechanism. This was established with DFT methods and via experiments utilizing the neo-hexyl stereoprobe BrCH(D)CH(D)tBu. These reactions were in part driven by a re-aromatization of the six membered pyridyl ring upon formation of the product. Conversely, in the reaction of the 1-bora-7a-azaindenide anions with CO2, a novel carboxylation of the C-2 carbon alpha to boron was observed. Computations indicated that while carboxylation of the boron centre was kinetically feasible, the products of B-carboxylation were not thermodynamically favored relative to the observed C-2 carboxylated species, which were formed preferably due to the generation of both C-C and B-O bonds. In these products, the pyridyl ring remains non-aromatic, in part accounting for the observed reversibility of carboxylation.

11.
Chemistry ; 24(3): 672-680, 2018 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-29119625

RESUMO

Four-membered rings with a P2 BCh core (Ch=S, Se) have been synthesized by the reaction of phosphinidene chalcogenide (Ar*P=Ch) and phosphaborene (Mes*P=BNR2 ). The mechanistic pathways towards these rings are explained by detailed computational work that confirmed the preference for the formation of P-P, not P-B, bonded systems, which seems counterintuitive given that both phosphorus atoms contain bulky ligands. The reactivity of the newly synthesized heterocycles, as well as that of the known (RPCh)n rings (n=2, 3), was probed by the addition of N-heterocyclic carbenes, which revealed that all investigated compounds can act as sources of low-coordinate phosphorus species.

12.
Dalton Trans ; 46(46): 16004-16008, 2017 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-29116268

RESUMO

The condensation reaction of 2-aminobenzenethiols and 3-aminopyrazinethiols with 2-amino-6-fluoro-N-methylpyridinium triflate afforded thioether derivatives that were found to undergo Smiles rearrangement and cyclocondensation with sulphur monochloride to yield new hybrid 1,4-thiazine-1,2,3-dithiazolylium cations. The synthesized cations were readily reduced to the corresponding stable neutral radicals with spin densities delocalized over both 1,4-thiazinyl and 1,2,3-dithiazolyl moieties.

13.
Inorg Chem ; 56(21): 13500-13509, 2017 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-29027797

RESUMO

The reactivity of 4-membered (RPCh)2 rings (Ch = S, Se) that contain phosphorus in the +3 oxidation state is reported. These compounds undergo ring expansion to (RPCh)3 with the addition of a Lewis base. The 6-membered rings were found to be more stable than the 4-membered precursors, and the mechanism of their formation was investigated experimentally and by density functional theory calculations. The computational work identified two plausible mechanisms involving a phosphinidene chalcogenide intermediate, either as a free species or stabilized by a suitable base. Both the 4- and 6-membered rings were found to react with coinage metals, giving the same products: (RPCh)3 rings bound to the metal center from the phosphorus atom in tripodal fashion.

14.
Dalton Trans ; 46(38): 12790-12793, 2017 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-28932832

RESUMO

The first lanthanide complex of a 1,2,4-benzotriazinyl radical (1), Dy(1)(tbacac)3 (2, tbacac = 2,2,6,6-tetramethyl-3,5-heptane-dionato), was synthesised and found to have an antiferromagnetically ordered ground state with a metamagnetic phase diagram and a critical field of 0.91 T at 1.85 K. The application of a small dc field revealed the single-molecule magnet behaviour of 2, illustrating the coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization.

15.
Dalton Trans ; 46(5): 1377-1381, 2017 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-28091656

RESUMO

The first examples of p-block coordination complexes of biquinoline, namely [(biq)BCl2]Cl and [(biq)BCl2]˙, were synthesized and structurally characterized. The acquired data allowed the estimation of the ligand charge state based on its metrical parameters. The subsequent use of this protocol, augmented with theoretical calculations, revealed ambiguities in the published data for transition metal complexes of biquinoline.

16.
Angew Chem Int Ed Engl ; 56(22): 6236-6240, 2017 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-28071846

RESUMO

Four-membered rings with a P2 Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N-heterocyclic carbene, resulting in a base-stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3-dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2 Ch2 rings can liberate phosphinidene chalcogenides.

17.
Dalton Trans ; 45(32): 12691-701, 2016 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-27453403

RESUMO

A high-yield synthesis of [Li{S(H)C(PPh2S)2}]2 [Li2·(3)2] was developed and this reagent was used in metathesis with ZnCl2 and NiCl2 to produce homoleptic complexes 4 and 5b in 85 and 93% yields, respectively. The solid-state structure of the octahedral complex [Zn{S(H)C(PPh2S)2}2] (4) reveals notable inequivalence between the Zn-S(C) and Zn-S(P) contacts (2.274(1) Å vs. 2.842(1) and 2.884(1) Å, respectively). Two structural isomers of the homoleptic complex [Ni{S(H)C(PPh2S)2}2] were isolated after prolonged crystallization processes. The octahedral green Ni(ii) isomer 5a exhibits the two monoprotonated ligands bonded in a tridentate (S,S',S'') mode to the Ni(ii) centre with three distinctly different Ni-S bond lengths (2.3487(8), 2.4500(9) and 2.5953(10) Å). By contrast, in the red-brown square-planar complex 5b the two ligands are S,S'-chelated to Ni(ii) (d(Ni-S) = 2.165(2) and 2.195(2) Å) with one pendant PPh2S group. DFT calculations revealed that the energetic difference between singlet and triplet state octahedral and square-planar isomers of the Ni(ii) complex is essentially indistinguishable. Consistently, VT and (31)P CP/MAS NMR spectroscopic investigations indicated that a mixture of isomers exists in solution at room temperature, while the singlet state square-planar isomer 5b becomes favoured at -40 °C.

18.
Chemistry ; 21(44): 15843-53, 2015 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-26493885

RESUMO

A series of d-block metal complexes of the recently reported coordinating neutral radical ligand 1-phenyl-3-(pyrid-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (1) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, Mn(II) , Fe(II) , Co(II) , or Ni(II) , with 1,1,1,5,5,5-hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single-crystal X-ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn(1)(hfac)2 ] and [Fe(1)(hfac)2 ] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the metal cation, whereas the interaction was found to be ferromagnetic in the analogous Ni(II) complex [Ni(1)(hfac)2 ]. The magnetic properties of the complex [Co(1)(hfac)2 ] were difficult to interpret owing to significant spin-orbit coupling inherent to octahedral high-spin Co(II) metal ion. As a whole, the reported data clearly demonstrated the favorable coordinating properties of the radical 1, which, together with its stability and structural tunability, make it an excellent new building block for establishing more complex metal-radical architectures with interesting magnetic properties.

19.
Dalton Trans ; 44(41): 18247-59, 2015 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-26426745

RESUMO

The reactions of dipyridylmethane (dpma) with group 13 trichlorides were investigated in 1 : 1 and 1 : 2 molar ratios using NMR spectroscopy and X-ray crystallography. With 1 : 1 stoichiometry and Et2O as solvent, reactions employing AlCl3 or GaCl3 gave mixtures of products with the salt [(dpma)2MCl2](+)[MCl4](-) (M = Al, Ga) as the main species. The corresponding reactions in 1 : 2 molar ratio gave similar mixtures but with [(dpma)MCl2](+)[MCl4](-) as the primary product. Pure salts [(dpma)AlCl2](+)[Cl](-) and [(dpma)AlCl2](+)[AlCl4](-) could be obtained by performing the reactions in CH3CN. In the case of InCl3, a neutral monoadduct (dpma)InCl3 formed regardless of the stoichiometry employed. A neutral adduct (dpma)(BCl3)2 was obtained from the reaction between dpma and BCl3 in Et2O using 1 : 2 stoichiometry. With 1 : 1 molar ratio of reagents, a mixture of products and deprotonation of the methylene bridge in [(dpma)BCl2](+) was observed. The experimental data showed that the structural flexibility of the dpma ligand results in more diverse coordination chemistry with group 13 elements than that observed for bipyridine (bpy), while computational investigations indicated that the investigated metal-ligand interactions are, to a first approximation, independent of the ligand type. Electrochemical and chemical attempts to reduce the cations [(dpma)MCl2](+) showed that, in stark contrast to the chemistry of the related [(bpy)BCl2](+) cation, the neutral radicals [(dpma)MCl2]˙ are extremely unstable. Differences in the redox behaviour of dpma and bpy could be rationalized with the electronic structure of the ligand and that of the methylene bridge in particular. As a whole, the facile reactivity of the methylene bridge in the dpma ligand renders it amenable to further reactivity and functionalization that is not possible in the case of bpy.

20.
Angew Chem Int Ed Engl ; 54(44): 12914-7, 2015 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-26332337

RESUMO

The characterization of the unstable Ni(II) bis(silylamide) Ni{N(SiMe3 )2 }2 (1), its THF complex Ni{N(SiMe3 )2 }2 (THF) (2), and the stable bis(pyridine) derivative trans-Ni{N(SiMe3 )2 }2 (py)2 (3), is described. Both 1 and 2 decompose at ca. 25 °C to a tetrameric Ni(I) species, [Ni{N(SiMe3 )2 }]4 (4), also obtainable from LiN(SiMe3 )2 and NiCl2 (DME). Experimental and computational data indicate that the instability of 1 is likely due to ease of reduction of Ni(II) to Ni(I) and the stabilization of 4 through dispersion forces.

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