First-principles study on the electronic structures and contact properties of graphene/XC (X = P, As, Sb, and Bi) van der Waals heterostructures.

The electrical contacts at the van der Waals (vdW) interface between two-dimensional (2D) semiconductors and metal electrodes could dramatically affect the device performance. Herein, we construct a series of graphene (Gr)/XC (X = P, As, Sb, and Bi) vdW heterostructures, in which XC monolayers have aroused considerable attention recently as an emerging class of 2D semiconductors. The electronic structures and contact properties of Gr/XC vdW heterostructures are investigated systematically using first-principles calculations. The band structures indicate that both Gr/PC and Gr/AsC heterostructures form n-type Schottky contacts with Schottky barrier heights (SBHs) of 0.01 eV and 0.43 eV, respectively, while both Gr/SbC and Gr/BiC heterostructures preferably form Ohmic contacts. The different X atoms result in different work functions, electron flows, charge distributions and orientations of the dipole moment in Gr/XC heterostructures. Moreover, the tunneling probabilities increase with the increasing atom radius of X from P to Bi, indicating the most improved current and smaller contact resistance at the interfaces of Gr/BiC compared to Gr/PC, Gr/AsC and Gr/SbC heterostructures. Our work could provide meaningful information for designing high-performance nanoelectronic devices based on Gr/XC heterostructures.

Pd(II) and Zn(II) based complexes with Schiff base ligands: synthesis, characterization, luminescence, and antibacterial and catalytic activities.

Two new metal complexes involving Schiff base ligands, namely, [Pd(L1)2] (1) and [Zn(L2)2] (2), [HL1: 2,4-dibromo-6-((E)-(mesitylimino)methyl)phenol and HL2: 2-((E)-(2,6-diisopropylphenylimino)methyl)-4,6-dibromophenol], have been solvothermally synthesized and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Both 1 and 2 are mononuclear cyclometalated complexes with square planar and tetrahedral coordination geometry, respectively. 1 and 2 display photoluminescence in the solid state at 298 K (fluorescence lifetimes τ = 5.521 µs at 508 nm for 1; τ = 3.697 µs at 506 nm for 2). These Schiff base ligands and their metal complexes have been screened for antibacterial activity against several bacteria strains, and the results are compared with the activity of penicillin. Moreover, the Suzuki reaction of 4-bromoanisole with phenylboronic acid by 1 has also been studied.

Atomistic picture of isothermal volume relaxation behavior of atactic polystyrene glass provided by a molecular dynamics simulation.

Using an atomistic molecular dynamics (MD) simulation, we study the volume relaxation behavior of atactic polystyrene and attempt to correlate this macroscopic behavior with certain microscopic aspects. To this end, the gyration radius, the dimensionless relative shape anisotropy, the mean-squared displacement, and the non-Gaussian parameter are examined simultaneously. Our result shows that the structures characterized at different length scales change in a self-similar way and these changes are intimately correlated to the translational mobility of atoms. The initial incubation of structural changes at the different scales originates from the restriction of mobility due to the cage effect. The applicability of the MD simulation to the investigation of the bulk properties is discussed.

2,6-Dichloro-N-(4-methyl-phen-yl)benzamide.

In the title compound, C(14)H(11)Cl(2)NO, the two benzene rings are non-coplanar [dihedral angle = 60.9 (3)°]. In the crystal, an amide N-H⋯O hydrogen bond links the mol-ecules into chains which extend along (001).

Methyl 2-{[2,8-bis-(trifluoro-meth-yl)quinolin-4-yl]-oxy}acetate.

In the crystal structure of the title compound, C(14)H(9)F(6)NO(3), mol-ecules are connected by inter-molecular C-H⋯O hydrogen bonds. The best planes through the benzene and pyridyl rings make a dihedral angle of 1.59 (12)°.

2-Chloro-5-(chloro-meth-yl)pyridine.

The title compound, C(6)H(5)Cl(2)N, is almost planar, with an r.m.s. deviation of 0.0146 Šfor all atoms except for the 5-choloromethyl Cl atom. The offset Cl atom lies above this plane with a Cl-C-C angle of 111.11 (17)°. In the crystal, mol-ecules are connected via inter-molecular C-H⋯N hydrogen bonds, forming dimers.

2-Amino-4-(2,4-dichloro-phen-yl)-6-(naphthalen-1-yl)nicotinonitrile.

In the crystal structure of the title compound, C(22)H(13)Cl(2)N(3), the mol-ecules are connected via inter-molecular C-H⋯N and N-H⋯N hydrogen bonds, forming a three-dimensional network. The dihedral angles between naphthyl ring system and the pyridyl and benzene rings are 55.04 (7) and 75.87 (7)°, respectively, whereas the pyridyl and benzene rings are oriented at a dihedral angle of 59.56 (8)°.

2-Benzyl-sulfanyl-3-(2,2,2-trifluoro-ethoxy)pyridine.

The title compound, C(14)H(12)F(3)NOS, was synthesized by the reaction of 2-chloro-3-(2,2,2-trifluoro-eth-oxy)pyridine and phenyl-methane-thiol. The dihedral angle between the aromatic rings is 76.7 (2)°. In the crystal structure, weak aromatic π-π stacking between inversion-related pairs of pyridine rings [centroid-to-centroid separation = 3.776 (2) Å] may help to establish the packing.

Diethyl 2-[(4-bromo-anilino)methyl-idene]malonate.

In the title compound, C(14)H(16)BrNO(4), inter-molecular C-H⋯O hydrogen bonds link the mol-ecules, forming a stable structure. An intra-molecular N-H⋯O hydrogen bond results in the formation of a six-membered ring and helps to establish the mol-ecular conformation which is almost planar, with an r.m.s deviation of 0.0842 Å.

meso-Dimethyl 2,5-dibromo-hexa-ne-dioate.

The title compound, C(8)H(12)Br(2)O(4), lies about a crystallographic center of inversion at the midpoint of the central C-C bond. The latter is also repsonsible for the observation of the meso form. There are no intra-molecular hydrogen bonds, but mol-ecules are connected by inter-molecular C-H⋯O inter-actions, forming a three-dimensional network.