14990-02-4Relevant articles and documents
Control of relative direction and amplitude in extension/contraction motions of molecular strands induced by ion binding
Stadler, Adrian-Mihail,Ramirez, Juan,Lehn, Jean-Marie
, p. 5369 - 5378 (2010)
The shape of ligand strands composed of six-membered aza-heterocycles (het) connected at the a and α' positions by hydrazone (hyz) units is determined in a predictable fashion by the nature of the heterocyclic groups (pyridine, pyrimidine, pyrazine etc.), and covers the range from extended linear to compact helical structures. The binding of metal ions to the coordination subunits, defined by the hethyz sequences, leads to marked shape changes by inter-converting bent and linear conformations of the subunits, thus inducing relative motions of strand domains either in the same (con-sense, "twirling") or in opposite (dis-sense, "flapping") directions. The amplitude of the motion induced by metal-ion binding and release and the relative directions of the formal motions can be controlled by the nature of the heterocyclic units. Thus, motions around a central 4,6-disubstituted pyrimidine are dis-sense motions, whereas there are con-sense motions around a central 2,5-disubstituted pyrazine unit, as illustrated by model ligands 1 and 2, respectively. The more extended helical 3 and undulating (zigzag shape) 4 ligands undergo larger-amplitude motions combining the relative displacements displayed by 1 and 2. Ligands 3 and 4 form linear tetranuclear PbII and Zn" complexes, thus producing an extension motion. The same holds for [Ru(4)(terpy)4](PF6)8 (terpy = terpyridine). Reversible acid-base-triggered molecular motions have been generated with [Zn4;)(OTf)8] (TfOH = triflic acid
Synthesis and characterization of Co(II) and Mn(II) [M3L3] triangles
Dais, Tyson N.,Brown, Michael J.,Coles, Martyn P.,Laur, Fran?ois,Price, Jason R.,Rowlands, Gareth J.,Plieger, Paul G.
, p. 175 - 182 (2019)
Abstract: We report an improved method to make the ligand N,N′-(pyrazine-2,5-diylbis(methanylylidene))bis(2-(pyridin-2-yl)ethanamine) (L) and the subsequent complexation of this ligand to make the triangular metallo-macrocycles [Co3L3/sub
RuII multinuclear metallosupramolecular rack-type architectures of polytopic hydrazone-based ligands: Synthesis, structural features, absorption spectra, redox behavior, and near-infrared luminescence
Stadler, Adrian-Mihail,Puntoriero, Fausto,Nastasi, Francesco,Campagna, Sebastiano,Lehn, Jean-Marie
, p. 5645 - 5660 (2010)
A novel class of polytopic hydrazone-based ligands was synthesized. They gave heteroleptic RuII polynuclear rack-like complexes of formula [Runterpyn molecular strand)]2n+ (terpy = 2,2′:6′,2″-terpyridine). The new rack-like systems can be viewed as being made of two identical or roughly identical peripheral subunits separated by several similar metal-containing spacer subunits. The presence of pyrazine or pyrimidine units within the molecular multitopic strands introduces additional chemical diversity; whereas a pyrimidine unit leads to appended orthogonal subunits that are on the same side with regard to the main molecular strand, a pyrazine unit leads to orthogonal subunits that lie on different sides. Mixing pyrazine and pyrimidine units within the same (bridging) molecular strand also allows peculiar and topographically controlled geometries to be obtained. Redox studies provided evidence that each species undergoes reversible redox processes at mild potentials, which can be assigned to specific subunits of the multicomponent arrays. Non-negligible electronic coupling takes place among the various subunits, and some electron derealization ex-tending over the overall bridging molecular strand takes place. In particular, oxidation data suggest that the systems can behave as p-type "molecular wires" and reduction data indicate that n-type electron conduction can occur within the multimetallic framework. All the multinuclear racks exhibit 3MLCT emission, both at 77 K in rigid matrix and at 298 K in fluid solution, which takes place in the near-infrared region (emission maxima in the 1000-1100 nm region), and is quite structured. Rigidity of the molecular structures and derealization within the large bridging ligands are proposed to contribute to the occurrence of the rather uncommon MLCT infrared emission, which is potentially interesting for optical communication devices.
Synthesis, structural features, absorption spectra, redox behaviour and luminescence Properties of ruthenium(II) rack-type dinuclear complexes with ditopic, hydrazone-based ligands
Stadler, Adrian-Mihail,Puntoriero, Fausto,Campagna, Sebastiano,Kyritsakas, Nathalie,Welter, Richard,Lehn, Jean-Marie
, p. 3997 - 4009 (2005)
The isomeric bis(tridentate) hydrazone ligand strands 1a-c react with [Ru(terpy)Cl3] (terpy = 2,2':6'.2"-terpyridine) to give dinuclear rack-type compounds 2a-c, which were characterised by several techniques, including X-ray crystallography and NMR methods. The absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in rigid matrix at 77 K) of the ligand strands 1a-c and of the metal complexes 2a-c have been studied. Compounds 1a-c exhibit absorption spectra dominated by intense π-π* bands, which, in the case of 1b and 1c, extend within the visible region, while the absorption spectra of the rack-type complexes 2a-c show intense bands both the in the UV region, due to spin-allowed ligand-centred (LC) transitions, and in the visible, due to spin-allowed metal-to-ligand charge-transfer (MLCT) transitions. The energy position of these bands strongly depends on the ligand strand: in the case of 2a. the lowest energy MLCT band is around 470 nm, while in 2b and 2c, it lies beyond 600 nm. Ligands 1a-c undergo oxidation processes that involve orbitals based mainly on the CH3-N-N= fragments. The complexes 2a-c undergo reversible metal-centred oxidalion, while reductions involve the hydrazone-based ligands: in 2b and 2c, the bridging ligand is reduced twice and in 2a once before reduction of the peripheral terpy ligands takes place. Ligands 1a-c exhibit luminescence from the lowest-lying 1π-π* level. Only for complex 2a does emission occur; this may be attributed to a 3MLCT state involving the bridging ligand. Taken together, the results clearly indicate that the structural variations introduced translate into interesting differences in the spectroscopic, luminescence and redox properties of the ligand strands as well as of the rack-type metal complexes.
MnO2 mediated sequential oxidation/olefination of alkyl-substituted heteroarenes with alcohols
Zhang, Chunyan,Li, Zehua,Fang, Yanchen,Jiang, Shaohua,Wang, Maorong,Zhang, Guoying
supporting information, (2020/02/15)
A practical and efficient ligand-free MnO2 mediated sequential oxidation and olefination has been developed for the facile synthesis of a broad range of unsaturated N-heteroazaarenes from simple alkyl-substituted heteroarenes and alcohols. The procedure tolerates a series of functional groups, such as methoxyl, chloro, bromo, iodo, vinyl, phenolic and hetero groups, providing the olefination products in moderate to good yields.The protocol could be conducted at mild conditions and used environmentally friendly air as the clear oxidant.
Iron-Catalyzed Coupling of Methyl N-Heteroarenes with Primary Alcohols: Direct Access to E-Selective Olefins
Das, Jagadish,Vellakkaran, Mari,Sk, Motahar,Banerjee, Debasis
supporting information, p. 7514 - 7518 (2019/10/02)
An efficient Fe-catalyzed system is reported for direct α-olefination of methyl-substituted N-heteroarenes with primary alcohols. The catalytic dehydrogenative coupling enables a series of functionalized E-olefinated N-heteroaromatics with excellent selectivity (>99%). Initial mechanistic studies including deuterium-labeling experiments provide evidence for the participation of the benzylic C-H/D bond of alcohols.
Nickel-catalysed direct α-olefination of alkyl substituted N-heteroarenes with alcohols
Das, Jagadish,Vellakkaran, Mari,Banerjee, Debasis
supporting information, p. 7530 - 7533 (2019/07/04)
Catalytic α-olefination of alkylheteroarenes with primary alcohols via dehydrogenative coupling is presented. A simple nickel catalyst system stabilised by readily available nitrogen ligands enables a series of interesting E-configured vinylarenes (confirmed by X-ray crystal-structure analysis) to be synthesised in good to excellent yields with olefin/alkane selectivity of >20:1. Hydrogen and water are generated as byproducts and quantitative determination of H2 was performed.
Self-Assembly of Cyclohelicate [M3L3] Triangles Over [M4L4] Squares, Despite Near-Linear Bis-terdentate L and Octahedral M
Hogue, Ross W.,Dhers, Sébastien,Hellyer, Ryan M.,Luo, Jingwei,Hanan, Garry S.,Larsen, David S.,Garden, Anna L.,Brooker, Sally
supporting information, p. 14193 - 14199 (2017/10/07)
Self-assembly of 1:1:2 MII(BF4)2 (M=Zn or Fe), pyrazine-2,5-dicarbaldehyde (1) and 2-(2-aminoethyl)pyridine gave trimetallic triangle architectures rather than the anticipated tetrametallic [2×2] squares. Options for the n
Fabrication of nanocrystals from diolefin derivatives and their solid-state photoreaction behavior
Miura, Hirohiko,Takahashi, Shu,Kasai, Hitoshi,Okada, Shuji,Yase, Kiyoshi,Oikawa, Hidetoshi,Nakanishi, Hachiro
experimental part, p. 510 - 517 (2011/10/09)
Nanocrystals of seven p-phenylenediacrylates, i.e., dimethyl (la), didecyl (lb), diundecyl (1c), ditetradecyl (1d), dipentadecyl (1e), dioctadecyl (1f), and dicholesteroyl (1g) derivatives, and 2,5-distyrylpyrazine (2) were fabricated by the reprecipitation method and their photochemical reaction behaviors were investigated in comparison to those of bulk crystals. The bulk crystals of 1a- 1c and 2 were found to be photoreactive, whereas those of 1d-1g were less photoreactive. In contrast, all of the nanocrystals of 1a-1g and 2 showed high photoreactivity. Nanocrystals of la and 2 were demonstrated to have the same packing as the corresponding polymerizable bulk crystals, and they gave the corresponding polymers by photoirradiation. The polymer crystal structures in their nanocrystals were confirmed to be the same as those in bulk crystals by X-ray and electron diffraction analyses. Their single-crystal-to-single-crystal transformation was established by their nanocrystallization. On the other hand, other nanocrystals (1b-1g) were found to have different packings compared with the corresponding bulk crystals. After photoirradiation, their crystallinity was degraded to form amorphous products.
A New Series of Electroluminescent Organic Compounds
Nohara, Masao,Hasegawa, Masaki,Hosokawa, Chishio,Tokailin, Hiroshi,Kusumoto, Tadashi
, p. 189 - 190 (2007/10/02)
A new series of electroluminescent organic compounds, 2,5-distyrylpyrazine derivatives, were prepared and investigated on EL properties.The high brightness was achieved in some of these compounds at a low dc voltage of about 10 V.
