Lin-Jiang Shen

A low-dimensional molecular spin system with two steps of magnetic transitions and liquid crystal property.

A low-dimensional compound [C(6)-Apy][Ni(mnt)(2)] (1, where mnt(2-) = maleonitriledithiolate, C(6)-Apy(+) = 4-amino-1-hexylpyridinium) has been designed and synthesized, which has layer arrangement of anions and cations and shows two steps of magnetic transitions. The low temperature magnetic transition has an uncommon hysteresis loop, while the crystal structure investigations disclosed no structural transition with the magnetic transition. The high temperature magnetic transition exhibits two remarkable features: (1) it synchronously occurs with a crystalline-to-mesophase transition in the first heating process and (2) the structural changes that accompany the solid-mesophase transition are irreversible. A diamagnetic and isostructural compound, [C(6)-Apy][Cu(mnt)(2)], is further characterized by structure, DSC and POM techniques, which revealed also the existence of an irreversible crystalline-to-mesophase transition in the same temperature interval of [C(6)-Apy][Ni(mnt)(2)]. Therefore, the high-temperature magnetic transition in 1 is driven by release of the structural strains, but not magnetoelastic interactions. The mesophase exhibits the characteristic of smectic A phase, and the alkyl chain melting in the cation layers probably lead to the formation of mesophase. It is noticeable that the finding of a mesophase occurring in a hexyl hydrocarbon chain molecular system is in contrast to a suggested rule that at least a dodecyl chain is required. Our results will shed a light on the design and preparation of a new low-dimensional molecular system combining magnetic transition and liquid crystal properties.

Ion-pair complexes with strong near infrared absorbance: Syntheses, crystal structures and spectroscopic properties

Three ion-pair complexes, [4-NH(2)-Py](2)[M(mnt)(2)] (4-NH(2)-Py(1+)=4-amino-pyridinium; mnt(2-)=maleonitriledithiolate; M=Pt (1), Pd (2) or Ni (3)), have been synthesized and characterized. In the crystal of 1, the strong H-bonding interaction was found from the protonated N-atom of pyridinium to the CN group of [Pt(mnt)(2)](2-) together with a weak Pt...H interaction between the anion and the cation. The crystals of 2 and 3 are isostructural with very similar lattice parameters and packing structures, which are distinct from the crystal of 1. Two kinds of strong H-bonding interactions are observed in the crystals of 2 and 3 between the CN groups of [M(mnt)(2)](2-) anion and the protonated N-atom of 4-NH(2)-Py(1+) cation as well as the CN groups of [M(mnt)(2)](2-) anion and the amino group of 4-NH(2)-Py(1+) cation. Complex 1 shows an intense near-IR absorbance in acetonitrile and solid state, such an absorption band is probably assigned to IPCT transition as well as a trace amount of [Pt(mnt)(2)](1-) species; complex 3 possesses a weak near-IR absorption band which can be attributed to the mixture of d-d transition in [Ni(mnt)(2)](2-) and IPCT transition as well as a trace amount of [Ni(mnt)(2)](1-) species.

Chemical In Situ Polymerization of Polypyrrole Nanoparticles on the Hydrophilic/Hydrophobic Surface of SiO2 Substrates

Polypyrrole (PPy) nanoparticles formed by chemical in situ polymerization were deposited on the hydrophilic/hydrophobic surface of SiO2 substrates to give the diversely morphology, respectively. The morphologies of PPy nanoparticles deposit were investigated using optical microscope, scanning electron microscope (SEM), and atomic force microscope (AFM) imaging techniques. The morphology of Y- and T-shape wrinkles was observed on the hydrophilic surface of SiO2 substrate, while the morphology of polygon-shape wrinkles on the hydrophobic surface of SiO2 substrate, and this distinction is due to the difference of the surface energy between the hydrophilic and hydrophobic surface of SiO2 substrate and so-called “memory effect.”

Two spin systems based on [Ni(dmit)2]− building blocks exhibiting 1-D chain and 2-D sheet structures: crystal structures and magnetic properties

The crystal structures and magnetic properties for two ion-pair complexes, [MG][Ni(dmit)2] (1) and [RhB][Ni(dmit)2] (2) (MG+ = N-(4-((4-(dimethylamino)phenyl)(phenyl)methylene)cyclohexa-2,5-dienylidene)-N-methylmethanaminium, RhB+ = 9-(2-carboxyphenyl)-3,6-bis(diethylamino)xanthylium; dmit2− = 1,3-dithiole-2-thione-4,5-dithiolate), have been investigated. Complex 1 crystallizes in the monoclinic space group P21/c, the stacking interactions between the GM+ and [Ni(dmit)2]− lead to the anion exhibiting a banana-shaped molecular geometry; the neighboring anions form a 1-D alternating chain along the crystallographic [1 1 0] direction via intermolecular lateral-to-lateral and head-to-head S ··· S contacts. The temperature dependence of magnetic susceptibility from 2–350 K does not display the magnetic character of a 1-D chain; the magnetic susceptibility data were fit to the Curie–Weiss equation to give C = 0.351(15) emu K mol−1, θ = −3.51(28) K, and χ 0 = 8.00(3) × 10−5 emu mol−1. Complex 2 belongs to the triclinic space group P-1 with two crystallographic inequivalent [Ni(dmit)2]− anions, which exhibit perfect planar geometry. Two ethyl groups of RhB+ are disordered over two positions at 296 K, and one becomes ordered at 150 K. The [Ni(dmit)2]− anions form a 2-D molecular layer via intermolecular lateral-to-lateral and head-to-lateral S ··· S interactions with the anionic layer parallel to the crystallographic (0 1 −1) plane. The temperature variation of magnetic susceptibility from 2 to 350 K shows that antiferromagnetic coupling dominates in the anionic layer, and the disorder–order changes of cationic structure are not coupled to magnetic property.

Preparation, Characterization, and Conductivity of Polyaniline Doped with 12-Tungstoboric Acid

The Keggin type 12-tungstoboric acid (H5BW12O40) was prepared. Aniline was oxidized in an aqueous solution of H5BW12O40 to synthesize a series of polyanilines doped with the 12-tungstoboric acid (PANI-[H5BW12O40]), using ammonium persulfate as an oxidant. The effects of the initial weight ratio x (x) of H5BW12O40 to aniline on the properties of PANI-[H5BW12O40] were investigated by FTIR, UV-vis, XRD, and conductivity measurement. The results showed that PANI in PANI-[H5BW12O40] was in the emeraldine salt state, and the 12-tungstoboric anions were incorporated into the chains of PANI more and more with increasing values of x. The oxidation degree of PANI in PANI-[H5BW12O40] was strongly dependent on x. As the weight ratio x reached 0.040, the oxidation degree of PANI in PANI-[H5BW12O40] increased obviously. The reason that electrical conductivity of PANI-[H5BW12O40] decreased sharply at x was attributed to the increase of the oxidation degree resulted by the excess of H5BW12O40 used in the preparation.

Syntheses, Crystal Structures, and Spectroscopic Properties of Two Ion-Pair Charge Transfer Compounds Containing Bis(maleonitriledithiolato) Platinum/Palladium(II) Anion and Substituted Benzylpyridinium

Two ion-pair charge-transfer compounds, [CNBzNH2Py]2[ M(mnt)2]·MeCN (CNBzNH2Py+ = 1-(4’-cyanobenzyl)-4-aminopyridinium; mnt2− = maleonitriledithiolate; M=Pt (1), Pd (2)), have been synthesized and characterized. The x-ray single-crystal studies revealed that both of the crystals crystallize in the monoclinic space group P21/c with an asymmetric unit containing one [CNBzNH2Py]+ cation and a half of the [M(mnt)2]2− anion together with one MeCN molecular; there is no evident change of the crystal system, and the dihedral angles between the phenyl and pyridine rings and the N3/C10/C11 reference plane of the cation, as well as the stacking modes of the anions and the cations, when the metal ion is changed from Pt(II) to Pd(II). There exist π…π interactions between the neighboring benzene ring and CN group of the cations, as well as H-bonding interactions between the CN group of the MeCN molecular and the NH2 group of the cation in both of the compounds. Ultraviolet/visible (UV-vis) spectrum studies disclosed that these show different absorption bands in the UV-vis regions.

Synthesis of Novel 2-amino-6-oxo-3-(piperidinyla- midino)-4-aryl-6,7-dihydro-pyrano(2,3-d)-5,7-thiazol Derivatives by Domino Reaction under Microwave Irradiation

Seven novel 2-amino-6-oxo-3-(piperidinylamidino)-4-aryl-6,7-dihydro-pyrano[2,3-d]-5,7-thiazol derivatives, which are different with the products of 2-amino-3-cyano-6-oxo-4-aryl-6,7-dihydropyrano[2,3-d]-5,7-thiazol derivatives in the conventional heating conditions, were synthesized by using arylidenemalononitrile, 2,4-thiazolidinedione and piperidine in one-pot via microwave irradiation techniques. The reaction condition is mild and we get these new compounds highefficiently in a very short reaction times, which provides an elegant methodology for the synthesis of highly functionalized pyrano[3,2-d]-5,7-thiazole derivatives. At the end, the reaction mechanism was

Improvement of Electron Transport Properties of Polypyrrole Nano-films by In-situ Polymerization under High Pressure

The conducting polypyrrole (PPy) nanofilms have been in-situ polymerized on quartz substrates under various high reaction pressures (0.1–600 MPa). The effects of the applied pressure on films have been carefully investigated through UV-Vis, FT-IR, SEM, AFM and conductivity measurement. The effect of the applied pressure on the thickness and the electrical conductivity of the PPy films have been discussed. A three-dimensional relationship between film thickness, reaction pressure, and the conductivity of the films has also been described in text. Our results may provide a guide for studying in-situ polymerization of pyrrole and its derivatives under high reaction pressure.