Donor Building Blocks Research Articles

A Novel Building Block for Donor–Acceptor Conjugated Polymers Containing Perylene, Poly(p-phenylenevinylene), and Fullerene

A series of new polymers containing perylene, poly(p-phenylenevinylene) (PPV) and/or pendant fullerene units have been synthesized by Wittig condensation. All of the polymers were characterized by 1HNMR, FT-IR, and GPC. The optical properties of the polymers were studied by UV-vis and FL spectra. The cyclic voltammetry showed us a good candidate for a photoinduced electron-transfer system. And the photocurrent measurement revealed an interesting phenomenon that the photocurrent increased with the contents of the fullerene in the polymers increased.

A series of Ni(II) pyridyloximato (pao −) compounds [Ni(pao) 2(L) 2] (L = unidentate ligand): as a coordination donor building block in the assembly with Mn(III) salen analogues

A series of mononuclear Ni(II) compounds [Ni(pao) 2 (L) 2 ] (pao - = 2-pyridyloximate, L = pyridine (1), 4-picoline (2), 4-ethylpyridine (3), 4-tert-butylpyridine (4), and N-methylimidazole (5)) were synthesized and characterized. The structures of 1 - 3 were determined by X-ray crystallography and revealed that all compounds have the same structural motif with trans coordination fashion for the identical ligands. For magnetic data, the best-fitting to an S = 1 ground state with the zero-field splitting effect found to have the zero-field splitting parameter |D| of 3 ∼ 4 K in this series. These compounds are good coordination donor building blocks for assembly with Mn(III) salen analogues as coordination acceptor building blocks to form 1-D magnetic chains.

Evidence for single-chain magnet behavior in a Mn(III)-Ni(II) chain designed with high spin magnetic units: a route to high temperature metastable magnets.

We herein present the synthesis, crystal structure, and magnetic properties of a new heterometallic chain of MnIII and NiII ions, [Mn2(saltmen)2Ni(pao)2(py)2](ClO4)2 (1) (saltmen2- = N,N'-(1,1,2,2-tetramethylethylene) bis(salicylideneiminate) and pao- = pyridine-2-aldoximate). The crystal structure of 1 was investigated by X-ray crystallographic analysis: compound 1 crystallized in monoclinic, space group C2/c (No. 15) with a = 21.140(3) A, b = 15.975(1) A, c = 18.6212(4) A, beta = 98.0586(4) degrees , V = 6226.5(7) A3, and Z = 4. This compound consists of two fragments, the out-of-plane dimer [Mn2(saltmen)2]2+ as a coordination acceptor building block and the neutral mononuclear unit [Ni(pao)2(py)2] as a coordination donor building block, forming an alternating chain having the repeating unit [-Mn-(O)2-Mn-ON-Ni-NO-]n. In the crystal structure, each chain is well separated with a minimum intermetallic distance between Mn and Ni ions of 10.39 A and with the absence of interchain pi overlaps between organic ligands. These features ensure a good magnetic isolation of the chains. The dc and ac magnetic measurements were performed on both the polycrystalline sample and the aligned single crystals of 1. Above 30 K, the magnetic susceptibility of this one-dimensional compound was successfully described in a mean field approximation as an assembly of trimers (Mn...Ni...Mn) with a NiII...MnIII antiferromagnetic interaction (J = -21 K) connected through a ferromagnetic MnIII...MnIII interaction (J'). However, the mean field theory fails to describe the magnetic behavior below 30 K emphasizing the one-dimensional magnetic character of the title compound. Between 5 and 15 K, the susceptibility in the chain direction was fitted to a one-dimensional Ising model leading to the same value of J'. Hysteresis loops are observed below 3.5 K, indicating a magnet-type behavior. In the same range of temperature, combined ac and dc measurements show a slow relaxation of the magnetization. This result indicates the presence of a metastable state without magnetic long-range order. This material is the first experimental design of a heterometallic chain with ST = 3 magnetic units showing a "single-chain magnet" behavior predicted in 1963 by R. J. Glauber for an Ising one-dimensional system. This work opens new perspectives for one-dimensional systems to obtain high temperature metastable magnets by combining high spin magnetic units, strong interunit interactions, and uniaxial anisotropy.

Total synthesis of sialylated and sulfated oligosaccharide chains from respiratory mucins.

The total syntheses of several complex oligosaccharide moieties that occur in the core structure of sulfated mucins are reported. A trisaccharide acceptor was obtained through regio- and stereoselective sialylation of methyl (6-O-pivaloyl-beta-D-galactopyanosyl)(1-->3)-4,6-O-benzylidene-2-a cetamido-2-deoxy-alpha-D-galactopyranoside with a novel sialyl donor. A tetrasaccharide, pentasaccharide, and hexasaccharide were constructed in predictable and controlled manner with high regio- and stereoselectivity after the successful preparation and employment of a disaccharide donor, trisaccharide donor, disaccharide acceptor, and trisaccharide acceptor building blocks. Finally, a mild oxidative cleaving method was adopted for the selective removal of 2-naphthylmethyl (NAP) in the presence of benzyl groups.

Pyrazinedioxide–Tetracyanoethylene Arrays in the Solid State—New Donor–Acceptor Interaction for Crystal Engineering

Ladder and web polymorphic forms of cocrystals of tetramethylpyrazinedioxide (TMPDO) and tetracyanoethylene (TCNE) are obtained by rapid or slow crystallization, respectively. In the thermodynamically less stable, purple (TMPDO)2− TCNE crystals the donor and acceptor building blocks are linked through N+O−°C(alkene) interactions to form one-dimensional ladders (see picture below).