Persistent Room‐Temperature Radicals from Anionic Naphthalimides: Spin Pairing and Supramolecular Chemistry

2019 ◽  
Vol 25 (54) ◽  
pp. 12497-12501 ◽  
Author(s):  
Wenhuan Huang ◽  
Biao Chen ◽  
Guoqing Zhang
Keyword(s):  
Supramolecular Chemistry ◽  
Room Temperature ◽  
Spin Pairing

Synthesis of dipyrrin-containing architectures

2005 ◽  
Vol 09 (11) ◽  
pp. 745-759 ◽  
Author(s):  
Kannan Muthukumaran ◽  
Syeda Huma H. Zaidi ◽  
Lianhe Yu ◽  
Patchanita Thamyongkit ◽  
Matthew E. Calder ◽  
...  
Keyword(s):  
Supramolecular Chemistry ◽  
Phosphonic Acid ◽  
Building Block ◽  
Room Temperature ◽  
Light Harvesting ◽  
Zinc Complexes ◽  
Trans Configuration ◽  
Zinc Porphyrins ◽  
Self Assembled ◽  
Acid Unit

Dipyrrins are valuable precursors to dyes [dipyrrinatoboron difluoride, bis(dipyrrinato)-zinc(II) complexes] and serve as ligands in a variety of self-assembled materials. Six new dipyrrin-containing architectures have been synthesized. The architectures include bis(dipyrrinato) complexes containing copper(II) or palladium(II), a dipyrrin bearing a protected phosphonic acid unit, a porphyrin bearing two dipyrrins in a trans configuration, a linear diphenylethyne-linked dipyrromethane-dipyrrin building block, and a triad composed of two zinc porphyrins joined via an intervening bis(dipyrrinato)copper(II) complex. Two porphodimethenatozinc complexes were prepared and found to have Φ f ≤ 0.002 (in toluene at room temperature), which is substantially less than the analogous bis(dipyrrinato)zinc complexes. Taken together, the syntheses described herein should broaden access to dipyrrins for use as complexation motifs in supramolecular chemistry and as pigments in light-harvesting applications.

scholarly journals Hydrogen-bonded host–guest systems are stable in ionic liquids

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Teresa Naranjo ◽  
Rubén Álvarez-Asencio ◽  
Patricia Pedraz ◽  
Belén Nieto-Ortega ◽  
Sara Moreno-Da Silva ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Melting Point ◽  
Supramolecular Chemistry ◽  
Organic Solvents ◽  
Electrostatic Interactions ◽  
Room Temperature ◽  
Binding Constants ◽  
Force Spectroscopy ◽  
Solvation Processes ◽  
Hydrogen Bonded

Abstract We show that H-bonded host–guest systems associate in ionic liquids (ILs), pure salts with melting point below room temperature, in which dipole–dipole electrostatic interactions should be negligible in comparison with dipole-charge interactions. Binding constants (Ka) obtained from titrations of four H-bonded host–guest systems in two organic solvents and two ionic liquids yield smaller yet comparable Ka values in ionic liquids than in organic solvents. We also detect the association event using force spectroscopy, which confirms that the binding is not solely due to (de)solvation processes. Our results indicate that classic H-bonded host–guest supramolecular chemistry takes place in ILs. This implies that strong H-bonds are only moderately affected by surroundings composed entirely of charges, which can be interpreted as an indication that the balance of Coulombic to covalent forces in strong H-bonds is not tipped towards the former.

Metal complexes of 1,10-Phenanthroline derivatives. VIII. Complexs of 1,10-Phenanthroline-2-carbaldehyde imines

1974 ◽  
Vol 27 (10) ◽  
pp. 2121 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather
Keyword(s):  
High Spin ◽  
Room Temperature ◽  
Spin Transition ◽  
Significant Rise ◽  
High Field Strength ◽  
Aryl Group ◽  
Metal Atoms ◽  
Spin Pairing ◽  
Aryl Amines ◽  
Derivatives Of

Iron(11), cobalt(11) and nickel(11) complexes [ML2] [BF4]2 of a series of related tridentate imine derivatives of 1,l0-phenanthroline-2-carbaldehyde [N-(l,l0-phenanthrolin-2-ylmethylene)alkyl-(or aryl)amines in which the alkyl or aryl group is methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, phenyl or benzyl] are described. From the electronic spectra of the nickel complexes an order of field strengths is established which correlates reasonably well with the bulkiness of the imine moiety. All the ligands except that where R = But effect spin-pairing in iron(11) at room temperature. When R = But the iron(11) complex is essentially high-spin at room temperature but is predominantly low-spin at 83 K. The magnetism of this substance is typical for that of iron(11) systems in which a gradual spin transition, 5T2 ←→ lAl occurs. In the complexes where R = Bu Bu8, Ph, a significant rise in the magnetic moment above room temperature is observed, indicating the presence of some metal atoms in the 5T2 state. Certain of the ligands of high field strength (R = Me, Et, Pr, Pr1) yield cobalt(11) complexes whose magnetism is indicative of a gradual quartet-doublet transition. The remaining cobalt(11) complexes are high spin.

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Hepatocyte Alterations in Guinea Pigs FED Polychlorinated Biphenyls (PCBs), Dibenzodioxins (PCDD), AND DIBENZOFURANS (PCDF)

1982 ◽  
Vol 40 ◽  
pp. 56-57
Author(s):  
J. N. Turner ◽  
D. N. Collins
Keyword(s):  
Guinea Pigs ◽  
Room Temperature ◽  
Dose Group ◽  
Methyl Cellulose ◽  
Uranyl Acetate ◽  
Target Organ ◽  
Office Building ◽  
Lead Citrate ◽  
Control Groups ◽  
Cooling Fluid

A fire involving an electric service transformer and its cooling fluid, a mixture of PCBs and chlorinated benzenes, contaminated an office building with a fine soot. Chemical analysis showed PCDDs and PCDFs including the highly toxic tetra isomers. Guinea pigs were chosen as an experimental animal to test the soot's toxicity because of their sensitivity to these compounds, and the liver was examined because it is a target organ. The soot was suspended in 0.75% methyl cellulose and administered in a single dose by gavage at levels of 1,10,100, and 500mgm soot/kgm body weight. Each dose group was composed of 6 males and 6 females. Control groups included 12 (6 male, 6 female) animals fed activated carbon in methyl cellulose, 6 males fed methyl cellulose, and 16 males and 10 females untreated. The guinea pigs were sacrificed at 42 days by suffocation in CO2. Liver samples were immediately immersed and minced in 2% gluteraldehyde in cacadylate buffer at pH 7.4 and 4°C. After overnight fixation, samples were postfixed in 1% OsO4 in cacodylate for 1 hr at room temperature, embedded in epon, sectioned and stained with uranyl acetate and lead citrate.

Domain Formation in Synthetic Quartz

1971 ◽  
Vol 29 ◽  
pp. 156-157
Author(s):  
Joseph J. Comer
Keyword(s):  
Electron Beam ◽  
Room Temperature ◽  
Domain Formation ◽  
Synthetic Quartz ◽  
Transmission Electron ◽  
Black Spots ◽  
Diffraction Mode ◽  
Domain Boundaries ◽  
Kikuchi Lines ◽  
Straight Lines

Domains visible by transmission electron microscopy, believed to be Dauphiné inversion twins, were found in some specimens of synthetic quartz heated to 680°C and cooled to room temperature. With the electron beam close to parallel to the [0001] direction the domain boundaries appeared as straight lines normal to <100> and <410> or <510> directions. In the selected area diffraction mode, a shift of the Kikuchi lines was observed when the electron beam was made to traverse the specimen across a boundary. This shift indicates a change in orientation which accounts for the visibility of the domain by diffraction contrast when the specimen is tilted. Upon exposure to a 100 KV electron beam with a flux of 5x 1018 electrons/cm2sec the boundaries are rapidly decorated by radiation damage centers appearing as black spots. Similar crystallographio boundaries were sometimes found in unannealed (0001) quartz damaged by electrons.

A Liquid Nitrogen Cooled Stage for STEM

1974 ◽  
Vol 32 ◽  
pp. 444-445
Author(s):  
Louis T. Germinario
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Liquid Nitrogen ◽  
Room Temperature ◽  
Objective Lens ◽  
Thermal Drift ◽  
Specimen Holder ◽  
Resolution Capability ◽  
Focal Position

A liquid nitrogen stage has been developed for the JEOL JEM-100B electron microscope equipped with a scanning attachment. The design is a modification of the standard JEM-100B SEM specimen holder with specimen cooling to any temperatures In the range ~ 55°K to room temperature. Since the specimen plane is maintained at the ‘high resolution’ focal position of the objective lens and ‘bumping’ and thermal drift la minimized by supercooling the liquid nitrogen, the high resolution capability of the microscope is maintained (Fig.4).

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

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