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1.
Org Lett ; 21(14): 5708-5712, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31283244

RESUMO

The absolute configurations of the two enantiomers of a topologically chiral [2]catenane were determined unambiguously based on HPLC resolution and X-ray crystal analysis. Although structurally dissimilar to simple amino acids, the optical rotations of these separated [2]catenanes share the Clough-Lutz-Jirgensons behavior of amino acids: the optical rotation flips direction in the presence of acid and base, the first example of such behavior for a mechanically interlocked topologically chiral catenane.

2.
Dalton Trans ; 48(31): 11732-11742, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31298242

RESUMO

Treatment of [Ru]-C[triple bond, length as m-dash]CPh (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with trimethylsilyl azide afforded the cationic nitrile complex {[Ru]NCCH2Ph}[N3] (2) and the further cycloaddition of 2 with trimethylsilyl azide at 60 °C afforded the N(2)-bound tetrazolato complex [Ru]N4CCH2Ph (3). The regiospecific alkylation of 3 gave a series of cationic N(2)-bound N(4)-alkylated-5-benzyl tetrazolato complexes {[Ru]N4(CH2R)CCH2Ph}[Br] (4a, R = C6F5; 4b, R = Ph; 4c, R = 4-CN-C6H4; 4d, R = 2,6-F2-C6H3; 4e, R = 6-CH2Br-C5NH3) and the subsequent cleavage of the Ru-N bond of 4a-4e gave N(1)-alkylated-5-benzyl tetrazoles N4(CH2R)CCH2Ph (5a-5e) in good to excellent yields and [Ru]-Br, which, on reacting with phenylacetylene, resulted in the formation of 1 thus forming a reaction cycle. The structures of 2, 3, 4a, 4c and 5a were confirmed by single-crystal X-ray diffraction analysis.

3.
Dalton Trans ; 48(27): 9912-9915, 2019 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-31233062

RESUMO

A novel trinuclear complex [Ni3(µ3-dbay)4Cl2]I3 (1) with a mixed-valence state was prepared by reacting the tridentate ligand 1,13,14-triaza-dibenz[a,j]anthracene (dibenzanthyridine = dbay) with anhydrous NiCl2 and sodium tetraphenylborate. The title compound provides the first example of a trinuclear nickel-anthyridine-based string complex in which the metal framework of complex 1 consists of NiII-NiI-NiII. X-ray crystallography, magnetic susceptibility and detailed EPR measurements were performed to characterize the structure and magnetic properties of this unique complex.

4.
Dalton Trans ; 48(23): 8464-8477, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31116203

RESUMO

We report the syntheses, characterization, electronic structures and magnetic properties of four redox pairs of novel nickel-extended metal-atom chain (EMAC) complexes containing pyridine-, naphthyridine- and sulfonyl-containing ligands (H2Tspnda and H2Mspnda) (1-2 and 5-6). We further study the corresponding phenyl-substituted ligands (H2Tsphpnda and H2Msphpnda) (3-4 and 7-8) to examine the details of ligand effects. The X-ray structure of one-electron-reduced [Ni5]9+ complexes shows shorter Ni-Ni bond distances (2.2646(6) for 1, 2.2943(7) for 3, 2.2436(11) for 5 and 2.2322(8) Å for 7) in comparison with an average Ni-Ni distance of 2.3187(8) Å for these complexes, indicative of a partial metal-metal bond interaction in the mixed-valence [Ni2]3+ (S = 3/2) unit. The most striking result is that the [Ni2]3+ site migrates from Ni(1)-Ni(2) to Ni(2)-Ni(3) when we replace the p-tolyl-sulfonyl group with methyl-sulfonyl group. These complexes present a rare example of the effect of crystal packing on the symmetric molecular structure yielding unsymmetric electronic distribution. Cyclic voltammetry measurements show four reversible redox waves and display the lower potentials of the [Ni5]9+ complexes. These unusual lower potentials facilitate one-electron oxidation of these four complexes to [Ni5]10+-core forms. We applied the magnetic susceptibility and EPR measurements to examine the magnetic properties of these four [Ni5]9+-core pentanickel complexes and study the bonding nature of these mixed-valence [Ni2]3+ units. Indeed, the results of EPR measurements reflect the migration of the mixed-valence site and the change of symmetry. Surprisingly, the oxidized [Ni5]10+ counterparts behave differently: complex 2 exhibits an antiferromagnetic interaction with J = -13.59 cm-1 between the two terminal Ni ions, while the others (4, 6 and 8) display diamagnetic properties as all of the Ni2+ ions are in low-spin (S = 0) states. These three complexes, to the best of our knowledge, are the first examples of all Ni2+ ions in a null spin configuration for pentanickel chains. Even though the structures of these complexes are similar to each other, their corresponding electronic structure and oxidized products show drastic changes in their magnetic properties and bonding nature. These differences of the properties and bonding nature of these pentanickel complexes are attributed to the ligand effects.

5.
ACS Appl Mater Interfaces ; 11(4): 4084-4092, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30604616

RESUMO

During the last two decades, spectacular development of light-emitting diodes (LEDs) has been achieved owing to their widespread application possibilities. However, traditional LEDs suffer from unavoidable energy loss because of the down conversion of photons, toxicity due to the involvement of rare-earth materials in their production, higher manufacturing cost, and reduced thermal stability that prevent them from all-inclusive applications. To address the existing challenges associated with current commercially available white LEDs, herein, we report a broad-band emission originating from an intrinsic lanthanide-free single-molecule-based LED. Self-assembly of a butterfly-shaped strontium-based compound {[Sr(H2btc)2(MeOH)(H2O)2]·2H2O} (1) was achieved through the reaction of Sr(NO3)2 with 1,2,3-benzenetricarboxylic acid hydrate (1,2,3-H3btc) under hydrothermal conditions. A white LED based on this single molecule exhibited a remarkable broad-band luminescence spectrum with Commission Internationale de l'Eclairage (CIE) coordinates at (0.33, 0.32) under 30 mA current injection. Such a broad luminescence spectrum can be attributed to the simultaneous existence of several emission lines originating from the intramolecular interactions within the structure. To further examine the nature of the observed transitions, density functional theory (DFT) calculations were carried out to explore the geometric and electronic properties of the complex. Our study thus paves the way toward a key step for developing a basic understanding and the development of high performance broad-band light-emitting devices with environment-friendly characteristics based on organic-inorganic supramolecular materials.

6.
Dalton Trans ; 48(6): 1950-1954, 2019 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-30644928

RESUMO

An SHG-active noncentrosymmetric (3,4)-connected Zn(ii)-organic framework, {[Zn2(4-abpt)(3,4-pydc)2]·2DMAc·3MeOH·H2O}n (1-Zn), was synthesized using a mixed-ligand system. The 1-Zn framework undergoes metal metathesis, with the complete exchange of the tetrahedrally coordinated ZnII ions with CuII ions while retaining the integrity of the network.

7.
Inorg Chem ; 57(18): 11732-11737, 2018 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-30179003

RESUMO

Although boron-containing radicals are promising materials for molecular electronic devices, the electronic effect of the σ-donating yet π-accepting boron center on the stability of open-shell species has been less discussed. In this work, the role of a tricoordinate boron center in π-conjugated radicals was explored through electron paramagnetic resonance measurement of several boron-linked bisphenol radicals and diradicals. Replacing the bridging methine fragment of a neutral Galvinoxyl radical with an arylboryl group led to the corresponding boron-linked radical anion that requires excessive steric protection at the boron center to be persistent in solution. Experimental and theoretical investigations revealed that the introduction of boron would diminish the quinoidal character of the phenoxyl radical and increase both the electrophilicity and nucleophilicity of the open-shell species. Therefore, it is important to consider the steric protection of the boron center in boron-containing π-conjugated organic radicals.

8.
Dalton Trans ; 47(28): 9341-9346, 2018 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-29951660

RESUMO

A new 3D coordination polymer {[Co2(µ-OH2)(TTPA)(DTDN)2·DMF]·H2O}n (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, DTDN = 6,6'-dithiodinicotinate) was synthesised and characterised. The redox properties of this framework were elucidated by solid state electrochemical and spectroelectrochemical data. This is the first investigation of the redox behaviour of TTPA in coordination polymers. Furthermore, the incorporation of a paramagnetic Co(ii) metal ion into the framework caused 1 to show spin-flop behaviour as the result of a field-induced magnetic transition. The incorporation of two flexible ligands and Co(ii) metal ions represents a feasible approach for the advancement of multifunctional materials.

9.
Chemistry ; 24(45): 11649-11666, 2018 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-29889320

RESUMO

The heterotrimetallic complexes [FeMFe(dpa)4 Cl2 ] (M=Ni (1), Pd (2), and Pt (3); dpa- =dipyridylamido) featuring two high-spin iron centers linked by Group 10 metals were synthesized and their physical properties were investigated. Oxidation of 1-3 with suitable oxidants in CH2 Cl2 solution yielded the mixed-valent species [1]+/2+ -[3]+/2+ . The solution properties of [1]0/+/2+ -[3]0/+/2+ were characterized by 1 H NMR and UV/Vis/NIR spectroscopy as well as spectroelectrochemisty. The mixed-valent states of [1]+ -[3]+ obtained by electrochemical or chemical oxidation are classified as class II valence delocalization. The solid-state structures of 1-3, [1]+ , [3]+ , and [1]2+ were determined by single-crystal X-ray diffraction analysis, exhibiting a linear metal framework with an approximate D4 symmetry. The spin states and magnetic properties were studied by using SQUID magnetometry, EPR and Mössbauer spectroscopy, and DFT calculations. Antiferromagnetic interactions between terminal high-spin iron centers are present within [1]0/+/2+ -[3]0/+/2+ and the |J| values increase with the central metal ion changing from Ni to Pt. The DFT calculations reproduce the antiferromagnetic coupling and ascribe it to a σ-type exchange pathway. The substitution of the central metal not only influences the spin-spin interactions but also the degree of electronic delocalization between the terminal iron sites along the Fe-M-Fe chains.

10.
J Org Chem ; 83(11): 6133-6141, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29732894

RESUMO

A transition-metal-free approach for the preparation of N-arylketimines has been developed from the direct reaction of aryldiazonium salts, arenes, and nitriles in a one-pot fashion with the consecutive formation of N-C and C-C bonds. This approach proceeds via an in situ generation of N-arylnitrilium intermediate, which then undergoes intermolecular arylation. This three-component strategy offers a step- and atom-efficient way to N-arylketimines from easily accessible reagents under mild reaction conditions. The characterization of stereochemistry of ketimine was achieved by X-ray crystallographic structure and theoretical calculation. Operational simplicity, shorter reaction time, excellent functional group compatibility, and scalability are the key features of this report.

11.
Chemistry ; 24(37): 9274-9284, 2018 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-29714039

RESUMO

Spontaneous formation of the heteroleptic cadmium(II) bis(terpyridine) complex under ambient conditions can be achieved by a combination of 6,6''-di(2,6-dimethoxylphenyl)-substituted and unsubstituted terpyridine-based ligands. Building on this dynamic heteroleptic complexation, diverse metallo-supramolecular macrocycles and cages were readily assembled in quantitative yields from the predesigned multicomponent systems. The complementary ligation reinforced self-recognition to facilitate the shape-dependent self-sorting of a four-component dynamic library into two well-defined parallelograms. In addition, the subtle lability difference between homoleptic and heteroleptic complexes led to the site-selective CdII -ZnII transmetalation in the Sierpinski triangle. Facile construction of a dodecanuclear tetrahedral metallocage was also realized by using two self-recognizable tritopic building blocks. The photophysical study of the metallo-supramolecules assembled from the d10 metal ions revealed intense ligand-based photoluminescence in solution. The self-assembly strategy described here provides an efficient methodology for building pre-programmable, sophisticated supramolecular architectures furnished with photoactivity.

12.
Org Lett ; 20(8): 2416-2419, 2018 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-29611414

RESUMO

Simple cyclophanes containing four distant amino N atoms or ether O atoms behave as hosts for the threading of guest diarylguanidinium ions. The recognition system exhibits high synthetic flexibility, allowing unique O-free [2]rotaxanes to be synthesized efficiently (yields of up to 80%) through both "threading-followed-by-stoppering" and "clipping" approaches.

13.
J Org Chem ; 83(10): 5619-5628, 2018 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-29701970

RESUMO

Sodium ion-controlled switching from "folded" to "linear" states results in significant changes in the molecular shape of a [2]catenane, such that it mimics the operation of a gin trap, with a fluorescent alarm signal appearing when pyrene side arms were present on its two macrocyclic components.

14.
Dalton Trans ; 47(5): 1422-1434, 2018 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-29292429

RESUMO

The CoRu2(dpa)4Cl2 (1) (dpa: 2,2'-dipyridylamide) is synthesized by the reaction of Ru2(OAc)4Cl and Co3(dpa)4Cl2. By mixing 1 with NH3, Co2+ can be removed and result in the formation of unique binuclear complex 4,0-Ru2(dpa)4Cl (2) featuring one coordination pocket supported by free pyridine groups. Hence, this complex can act as an outstanding precursor for the formation of heterotrimetallic chains with MRu2 cores. A series of M-Ru25+ complexes (M = Co2+ (3), Ag+ (4), Mn2+ (5), Fe2+ (6), Zn2+ (7), Cd2+ (8), Pd2+ (9), Rh2+ (10), and Ir2+ (11)) were prepared and isolated, representing the most complete series of heterotrimetallic chains to date. All these metal string complexes are in a linear trimetallic framework helically wrapped by four dpa- ligands, characterized by X-ray diffraction measurements. The bending of the trinuclear metal cores in RhRu2 (10) and IrRu2 (11) (∠Ru-Ru-Rh: 167.58° and ∠Ru-Ru-Ir: 167.61°) indicates that a heterometallic metal-metal bonds (Ru-Rh; Ru-Ir) are generated. The studies from DFT calculation of 10 and 11 coincide with the experimental results. Furthermore, the MRu25+ distances are regulated by the factors including the bonding force of M-pyridyl and the static repulsion between M and Ru25+ unit. Interestingly, the trend for these distances is in line with that observed in trans-M(py)4Cl2 complexes.

15.
Org Lett ; 19(21): 5840-5843, 2017 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-29028343

RESUMO

A transition metal-free synthesis of multisubstituted quinazolin-4(3H)-imines has been realized by the direct reaction of aryldiazonium salts, nitriles, and 2-cyanoanilines in a one-pot fashion. This strategy utilizes the in situ formation of reactive N-arylnitrilium intermediate, which undergoes further tandem cyclization with consecutive formation of N-C bonds. Broad functional group compatibility, mild conditions, shorter time, and operational simplicity are the notable features of this report.

16.
Phys Chem Chem Phys ; 19(37): 25471-25477, 2017 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-28900646

RESUMO

Herein, the excited-state dynamics of an extended metal atom chain complex, Cr3(dpa)4Cl2 (dpa = dipyridylamide), in tetrahydrofuran solution were investigated using femtosecond transient absorption spectroscopy. Upon excitation at a wavelength of 330 nm, two distinct excited-state absorption species with varied dynamics were identified and assigned to the symmetric (s-) and unsymmetric (u-) Cr3(dpa)4Cl2. The major species is s-Cr3(dpa)4Cl2 that undergoes rapid conversion at less than 100 fs from the ligand-centred π-π* state, which is the initially accessed state, to the metal-centred d-d state and then vibrational cooling accompanying the structural relaxation at a time constant ∼2.2 ps. Most of the s-form is recovered to the ground state at ∼200 ps. For u-Cr3(dpa)4Cl2, a similar rapid conversion to d-d states is observed, and the geometric/vibrational relaxation is ∼0.8 ps. The second recovery of the ground state with approximately equal amplitude is observed at a time constant of ∼5 ns. This might be because many d-d states exist and about half of them inefficiently couple with the ground state surface.

17.
Inorg Chem ; 56(17): 10543-10548, 2017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28820245

RESUMO

1,2-Boryl migration of N-boryl N-heterocyclic carbene to 2-boryl imidazole is proposed to proceed through generation and recombination of two radical intermediates, namely, a neutral diarylboron radical and a N-heterocyclic carbene radical. Crossover experiments suggest that these two radical species are stable enough to escape solvent cages and recombine intermolecularly. The presence of radical intermediates is further supported by spin trapping experiments. Besides, the coordination of Li+ cation is found to be critical for the stability of the NHC radical.

18.
Chem Commun (Camb) ; 53(63): 8886-8889, 2017 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-28737805

RESUMO

Using the planar 1,8-naphthyridin-2(1H)-one (Hnpo) ligand, novel nonhelical HMSCs [Mo2M(npo)4(NCS)2] (M = Fe, Co, Ni) were synthesised and they exhibited high single-molecule conductance.

19.
Chemistry ; 23(41): 9756-9760, 2017 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-28577323

RESUMO

We have prepared [2]rotaxanes, the behavior of which as switchable catalysts depends on their pirouetting motion, which can be controlled through the addition and removal of Na+ ions. At least three sequential on/off cycles of a Michael reaction can be performed in situ when using the NaTFPB/[2.2.2]cryptand reagent pair to switch "on" and "off" the catalytic ability of the [2]rotaxanes.

20.
Chem Commun (Camb) ; 53(34): 4673-4676, 2017 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-28405649

RESUMO

Striding to extend the length of metal-atom strings, oligo-α-pyridylamino ligands are modulated with naphthyridyl moieties leading to the undeca-nickel mixed-valence complexes [Ni11(bnatpya)4Cl2]4+ (1) and [Ni11(bnatpya)4Cl2]2+ (2). The first single-molecule conductance measurements of a linear undeca-nickel chain were performed.

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