Hydrogen bonding and dimeric self-association of 2-pyrrolidinone: An ab initio study

Ab initio calculations on the different associated structures of 2-pyrrolidinone with water and with itself were carried out using 3-21G and 6-31G^* basis sets at the Hartree–Fock level, including electron correlation using second-order Møller–Plesset perturbation theory. The calculated free energy changes for the intermolecular hydrogen bonded dimer and hydrated species indicated that the molecular systems with cyclic dimerization and association with two water molecules are dominant. The results are compared to the available experimental data in the literature.     

Thermal degradation of amphetamine sulphate

The pyrolysis of amphetamine sulphate was studied in a laboratory flow reactor in the range 350–1000°C. The identifications and quantitative determinations of most gaseous and condensed products by means of gas chromatography and mass spectrometry made possible the suggestion of a thermal degradation scheme. The presence of sulphate in the initial molecule led to oxidation reactions in addition to the usual thermal reactions that occur during the pyrolysis of organic materials.     

Langmuir–Blodgett Films of Single-Molecule Nanomagnets

Magnetic Langmuir–Blodgett films containing well-organized monolayers of single-molecule magnets are reported. The single-molecule magnets in question are high-spin molecular clusters of the type [Mn₁₂O₁₂(carboxylate)₁₆]. The structure of such multilayered inorganic–organic composites is depicted schematically in the figure.     

Two-dimensional supramolecular networks generated from weak AgCpy interactions: Synthesis, structural, thermal and fluorescence studies of silver(I) complexes of 5,5-diethylbarbiturato with pyridine-2-ylmethanol and 2,6-dimethoxypyridine

Two new silver(I) complexes [Ag(barb)(pym)]·H₂O (1) and [Ag(barb)(dmpy)]·1.5H₂O (2) (barb = 5,5-diethylbarbiturate, pym = pyridine-2-ylmethanol and dmpy = 2,6-dimethoxypyridine) have been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. In both complexes, the silver(I) ions are linearly coordinated by the N atoms of a barb anion and a pym or a dmpy ligand, forming mononuclear species. The molecules of 1 and 2 are doubly bridged by N–HO hydrogen bonds involving the barb moieties and these hydrogen-bonded dimers are assembled into two-dimensional layered networks through weak AgC_py (η¹) interactions of ca. 3.3 Å. Additionally, the thermal and fluorescent properties of these complexes are also investigated.     

Indium phosphide nanofibers prepared by electrospinning method: Synthesis and characterization

Nine sets of (3 × 3) InP nanofiber samples have been successfully prepared at three different voltages (20, 25, 30 kV) and at three separate heights (5, 7, 10 cm) by electrospinning with a constant precursor flow rate of 0.3 mLh⁻¹. The crystalline structure, thermal, morphologies and nanostructure, electrical, and optical properties of the samples are characterized by X‐ray powder diffractometer (XRD) and thermal gravity‐differential scanning calorimeter (TG‐DSC), scanning electron microscopy (SEM), by Four‐Point Probe Technique (FPPT,) and ultraviolet/visible spectrometry (UV/VIS), respectively. From these measurements, we have found the formation of stoichiometric nanostructured InP with zinc‐blende structure and having lattice parameter of a = 5.874 Å, weight loss of 64.59% and crystallization temperature of 500°C, average fiber diameter of 65.82 nm, the activation energies, E_a, of the samples, and band gap energy, E_g, of the nanofibers developed at constant applied voltage 30 kV. The band gap energies determined at different distances 5, 7, and 10 cm are found to be as 1.29, 1.37, and 1.30 eV, respectively.     

Suppression of parasitic lasing in high energy, high repetition rate Ti:sapphire laser amplifiers

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.     

Pressure‐Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic Fe^III₂Co^II₂ square complex into a molecular switch exhibiting a full dia‐ to paramagnetic transition: Fe^IICo^III ? Fe^IIICo^II. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure‐enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising‐like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors.     

Analysis of an M/G/∞ queue with batch arrivals and batch-dedicated servers

We analyze an M/G/∞ queue with batch arrivals, where jobs belonging to a batch have to be processed by the same server. The number of jobs in the system is characterized as a compound Poisson random variable through a scaling of the original arrival and batch size processes.     

Transition metal complexes with thiosemicarbazide-based ligands,Part IX. Cobalt(II) and nickel(II) complexes with 2-furaldehydeS-methylisothiosemicarbazone; crystal and molecular structure of aqua-bis(2-furaldehydeS-methylisothiosemicarbazone)cobalt(II)-diperchlorate

Summary The reaction of a warm ethanolic solution of Co^II perchlorate or rodanide and Ni^II acetate with 2-furaldehydeS-methylisothiosemicarbazone (HL), yielded the complexes [Co(HL)₂(H₂O)](ClO₄)₂ (1), [Co(HL)₃] [Co(NCS)₄] (2) and NiL₂, respectively. Both Co^II complexes are high-spin, whereas the Ni^II complex is in lowspin state (diamagnetic). An x-ray analysis of (1) showed it to have atrans-trigonal bipyramidal configuration in which one coordination site in the equatorial plane is occupied by one H₂O molecule. HL, a bidentate ligand, is coordinatedvia N(1) and N(4). The tris(ligand) cation in complex (2) has an octahedral configuration. Complex NiL₂ has a square-planar configuration.The deep purple plate-like crystals of (1) are monoclinic with space group C2/c, having cell parameters:a=11.369(3),b=13.029(4),c=17.438(5) Å; =103.39(2)^o. The structure was solved by the heavy-atom method and refined by least-squares method to an R value of 0.060 for 1761 observed reflections.