Mancheol Suh

Self-assembly of one-dimensional coordination polymer from nickel(II) macrocyclic complex and 2,6-pyridinedicarboxylate ligand

Abstract The reaction of [Ni(L)(H2O)2]Cl2 (L=2,5,9,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane) with 2,6-pyridinedicarboxylate (pdc) generates one-dimensional coordination polymer [Ni(L)(pdc)]·H2O (1). In the polymeric framework, the nickel(II) ion has an octahedral geometry and is bridged by two pdc ligands. The magnetic susceptibility measurement for 1 exhibits a weak antiferromagnetic interaction ( J=−1.04(3) cm −1 ; H=−JΣSi·Si+1) between the S=1 nickel(II) paramagnetic centers.

Synthesis and properties of nickel(II) and copper(II) complexes of a di-N-acetamide tetraaza macrocycle

Abstract The syntheses of the hexadentate ligand 2,13-bis(acetamido)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane (L2) and its complexes with Ni(II) and Cu(II) are described. Crystal structures of H2L2·2HClO4 (1), [Ni(L2)](ClO4)2 (2) and [Cu(L2)](ClO4)2 (3) are reported. The two pendant acetamide groups of the macrocyclic ligand 1 are trans to each other and the absolute configuration is a trans-IV in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant acetamide groups at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.

Synthesis, properties, and X-ray structure of [Cu(dpa)Cl2] (dpa = di-(2-picolyl)amine)

The mono(dpa)copper(II) complex [Cu(dpa)Cl2] (1) (dpa = di-(2-picolyl)amine) has been synthesized and structurally characterized. It crystallizes in the monoclinic system P21/n with a = 8.155(1), b = 12.560(1), c = 12.817(2) Å, β = 91.64(2)°, V = 1312.3(2) Å3, Z = 4. The copper atom is coordinated by three nitrogen atoms from the dpa ligand and two chlorides in a distorted square-pyramidal environment. Cyclic voltammetric data show that 1 undergoes the reversible one-electron oxidation to the Cu(III) and the reversible one-electron reduction to the Cu(I) state.

A laboratory study of hydraulic fracturing breakdown pressure in tablerock sandstone

We carried out hydraulic fracturing tests in hollow cylinders of Tablerock sandstone subjected to vertical (σν), confining (σh) and pore (Po) pressures. Borehole fluid was injected at a constant flow rate until a peak pressure was reached, and vertical fracture was observed. Based on the analysis of pressure-time records, we submit that breakdown occurs before peak pressurePp in the first cycle. In a series of tests in which σh, σν, andP0 were kept constant throughout, breakdown pressurePc increased significantly with wellbore pressurization rate, and appeared to asymptotically approach to an upper and lower bound corresponding to fast and slow rates, respectively as expected by Detournay and Cheng (1992). Another series of tests conducted at a preset pressurization rate in unjacketed specimens (σh=Po) revealed that (Pc-Po) increased with confining/pore pressure, contrary to the constant (Pc-Po) based on the Terzaghi’s effective stress law. We modified the Detournay-Cheng criterion by replacing the Terzaghi’s effective stress with a general effective stress. More series of hydraulic fracturing tests in jacketed specimens reinforced the applicability of the modified Detournay-Cheng criterion to Tablerock sandstone in terms of correctly estimating the relationship between the unknown far-field stress and the typically known test parameters: breakdown pressure, initial pore pressure and pressurization rate.

Impact of magnetic survey design on the imaging of small archeological objects Practicability in gradiometer surveying

There are various strategies for magnetic surveying. Most are designed to capture a wide range of sources from near surface to deep subsurface structure. Magnetics, particularly magnetic gradiometry, is often used for discovering small objects at very shallow depths that have environmental or archaeological importance.

Structural framework and its formation of the Kalpin thrust belt, Tarim Basin, north-west China, from Landsat TM data

The geological feature of the Kalpin thrust belt, Tarim Basin, China, has been a controversial issue, because of remoteness and lack of information. In this paper, Landsat Thematic Mapper (TM) data are used to discuss the structural framework of the area and its forming mechanism; the results were confirmed in the field. The PCI EASI/PACE 6.2 PC version was chosen to process the image data. The false colour composite images elaborately chosen could discriminate clearly strata of different ages and geological structures in the area. From detailed imagery interpretation, it is found that the thrust belt could be divided clearly into three parts with different deformation features from the west to the east. The west part is characterized by thrusts and folds of various sizes. The middle part consists of imbricate thrusts, transverse tear faults and some fault-related folds. The east part is expressed by the pile-up of strata sheets separated by complex thrusts and tear faults. During the Late Tertiary, the strong compression from the Tian Shan Mountains made the Kalpin Uplift thrust southward over three different structural units, thus producing entirely different structural styles within the thrust belt.

X-ray crystal structure of a macrocyclic tetraamine nitrito nickel(II) complex

The compound [Ni(L)(η2-NO2)]ClO4 (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized and structurally characterized. It crystallizes in the monoclinic system, space group P21/c with a = 26.899(5), b = 8.476(2), c = 23.633(5) Å, β = 115.12(13)°, V = 4878.6(17) Å3, and Z = 4. Each nickel(II) ion has a six-coordinated bicapped square-pyramidal geometry with four secondary amines of the macrocycle and two oxygen atoms of the bidentate nitrito group. Electronic spectra and effective magnetic moment of the complex also exhibit a high-spin six-coordinated geometry.

Delineation of Egyptian mud bricks using magnetic gradiometer techniques

A near-surface magnetic gradiometer survey of a site at Hawara, Fayoum city is used to delineate archaeological features made by mud bricks at shallow depths in the northeast of the pyramid of Amenemhat III. Magnetic survey data were processed to a precise forward processing sequence, including clipping, de-sloping, removing stripes and edge discontinuities, de-spiking, filtering, interpolating, and finally detecting statistically significant results. The processed magnetic data indicate high amplitude anomalies in the northeastern part of the pyramid Amenemhat III, suggesting the presence of shallow cemeteries of mud brick walls. Low pass filtering of the vertical gradient data helped reveal the relatively deep mud brick features in the generally shallow section. These features were isolated using a statistical detection technique, and verified by the correlation with the surrounding mud brick discoveries. This required the analysis of the magnetic behavior of exposed mud bricks and man-made objects for comparison with the magnetic signature of buried material. These were then matched with the vertical magnetic gradients of the exposed mud brick features from here and three other Egyptian localities. They are mostly the extension of the 12th Dynasty cemeteries, which exist in the western and southwestern parts of the study area.