Ruthenium complexes of easily accessible tridentate ligands based on the 2-aryl-4,6-bis(2-pyridyl)-s-triazine motif: absorption spectra, luminescence properties, and redox behavior

A family of tridendate ligands 1 a-e, based on the 2-aryl-4,6-di(2-pyridyl)-s-triazine motif, was prepared along with their hetero- and homoleptic Ru(II) complexes 2 a-e ([Ru(tpy)(1 a-e)](2+); tpy=2,2':6',2"-terpyridine) and 3 a-e ([(Ru(1 a-e)(2)](2+)), respectively. The ligands and their complexes were characterized by (1)H NMR spectroscopy, ES-MS, and elemental analysis. Single-crystal X-ray analysis of 2 a and 2 e demonstrated that the triazine core is nearly coplanar with the non-coordinating ring, with dihedral angles of 1.2 and 18.6 degrees, respectively. The redox behavior and electronic absorption and luminescence properties (both at room temperature in liquid acetonitrile and at 77 K in butyronitrile rigid matrix) were investigated. Each species undergoes one oxidation process centered on the metal ion, and several (three for 2 a-e and four for 3 a-e) reduction processes centered on the ligand orbitals. All compounds exhibit intense absorption bands in the UV region, assigned to spin-allowed ligand-centered (LC) transitions, and moderately intense spin-allowed metal-to-ligand charge-transfer (MLCT) absorption bands in the visible region. The compounds exhibit relatively intense emissions, originating from triplet MLCT levels, both at 77 K and at room temperature. The incorporation of triazine rings and the near planarity of the noncoordinating ring increase the luminescence lifetimes of the complexes by lowering the energy of the (3)MLCT state and creating a large energy gap to the dd state.     

A Review of HER4 (ErbB4) Kinase,Its Impact on Cancer,and Its Inhibitors

HER4 is a receptor tyrosine kinase that is required for the evolution of normal body systems such as cardiovascular, nervous, and endocrine systems, especially the mammary glands. It is activated through ligand binding and activates MAPKs and PI3K/AKT pathways. HER4 is commonly expressed in many human tissues, both adult and fetal. It is important to understand the role of HER4 in the treatment of many disorders. Many studies were also conducted on the role of HER4 in tumors and its tumor suppressor function. Mostly, overexpression of HER4 kinase results in cancer development. In the present article, we reviewed the structure, location, ligands, physiological functions of HER4, and its relationship to different cancer types. HER4 inhibitors reported mainly from 2016 to the present were reviewed as well.     

Tetranuclear Gold(I) Clusters with Nitrogen Donor Ligands: Luminescence and X-Ray Structure of Gold(I) Naphthyl Amidinate Complex

The syntheses and characterization of gold(I) naphthyl, pentafluorophenyl, and trifluoromethylphenyl amidinate complexes are reported. The tetranuclear clusters are obtained from the reaction of Au(tetrahydrothiophene)Cl with the potassium salt of the corresponding amidinate in a THF solvent. The crystal structures of the gold(I) naphthyl, 2, and pentafluorophenyl, 3, amidinates show a short Au···Au distance of ~3. 0 Å typical of compounds having an aurophilic interaction. The gold atoms are arranged in a square (Au···Au···Au = 87°–92°) in the pentafluorophenyl derivative and in a parallelogram (Au···Au···Au = 68°–110°) in the naphthyl amidinate complexes. The naphthyl and trifluoromethylphenyl complexes are visibly luminescent in the solid state at liquid nitrogen temperature displaying asymmetric emission bands at 538 and 473 nm, respectively. The luminescent lifetimes of these species are in the millisecond range indicating phosphorescent processes.     

Hot zones evolution and dynamics in heterogeneous catalytic systems

Stationary and complex moving hot regions formed for temperatures close to the extinction temperature of uniformly ignited states of several catalytic systems, such as thin rings and hollow cylinders, a thin radial flow reactor (RFR) and a shallow packed bed. IR imaging revealed that the hot and cold regions (temperature difference of the order of 100 degrees C) were separated by a sharp (about 3 mm wide) temperature front. The transition from the branch of uniformly ignited to the states with a hot region was usually supercritical. In some experiments a disjoint branch of states with hot regions existed and two qualitatively different states with hot zones existed under the same operating conditions. A very intricate periodic motion of a hot zone was observed in a shallow packed bed reactor. For example, Fig. 16 shows a hot zone which splits and later coalesces several times during the long (14 h) period. Hot pulse motions were observed on a single catalytic pellet. These were caused by global coupling between the surface reaction rate and the ambient reactant concentration and the inherent nonuniformity of the catalytic activity. It is not yet clear what rate processes generate the transversal hot zones in uniform packed bed reactors. (c) 2002 American Institute of Physics.     

Relaxation times and line widths of isotopically-substituted nitroxides in aqueous solution at X-band

Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties. Spin lattice relaxation times, spin packet line widths, nuclear hyperfine splitting, and overall lineshapes were characterized for six low molecular weight nitroxides in dilute deoxygenated aqueous solution at X-band. The nitroxides included 6-member, unsaturated 5-member, or saturated 5-member rings, most of which were isotopically labeled. The spectra are near the fast tumbling limit with T₁∼T₂ in the range of 0.50–1.1 μs at ambient temperature. Both spin–lattice relaxation T₁ and spin–spin relaxation T₂ are longer for ¹⁵N- than for ¹⁴N-nitroxides. The dominant contributions to T₁ are modulation of nitrogen hyperfine anisotropy and spin rotation. Dependence of T₁ on nitrogen nuclear spin state m_I was observed for both ¹⁴N and ¹⁵N. Unresolved hydrogen/deuterium hyperfine couplings dominate overall line widths. Lineshapes were simulated by including all nuclear hyperfine couplings and spin packet line widths that agreed with values obtained by electron spin echo. Line widths and relaxation times are predicted to be about the same at 250 MHz as at X-band.     

Proximity effects of a symmetry-breaking interface on spins of photoexcited electrons

We study reflection of optically spin-oriented hot electrons as a means to probe the semiconductor crystal symmetry and its intimate relation with the spin-orbit coupling. The symmetry breaking by reflection manifests itself by tipping the net-spin vector of the photoexcited electrons out of the light propagation direction. The tipping angle and the pointing direction of the net-spin vector are set by the crystal-induced spin precession, momentum alignment, and spin-momentum correlation of the initial photoexcited electron population. We examine nonmagnetic semiconductor heterostructures and semiconductor-ferromagnet systems and show the unique signatures of these effects.     

Stoichiometrically Controlled Revocable Self‐Assembled “Spiro” versus Quadruple‐Stranded “Double‐Decker” Type Coordination Cages

The simple combination of Pd^II with the tris‐monodentate ligand bis(pyridin‐3‐ylmethyl) pyridine‐3,5‐dicarboxylate, L , at ratios of 1:2 and 3:4 demonstrated the stoichiometrically controlled exclusive formation of the “spiro‐type” Pd₁L₂ macrocycle, 1 , and the quadruple‐stranded Pd₃L₄ cage, 2 , respectively. The architecture of 2 is elaborated with two compartments that can accommodate two units of fluoride, chloride, or bromide ions, one in each of the enclosures. However, the entry of iodide is altogether restricted. Complexes 1 and 2 are interconvertible under suitable conditions.     

X-ray Structures and Computational Studies of Two Bioactive 2-(Adamantane-1-carbonyl)-N-substituted Hydrazine-1-carbothioamides

Two biologically active adamantane-linked hydrazine-1-carbothioamide derivatives, namely 2-(adamantane-1-carbonyl)-N-(tert-butyl)hydrazine-1-carbothioamide) 1 and 2-(adamantane-1-carbonyl)-N-cyclohexylhydrazine-1-carbothioamide 2, have been synthesized. X-ray analysis was conducted to study the effect of the t-butyl and cyclohexyl moieties on the intermolecular interactions and conformation of the molecules in the solid state. X-ray analysis reveals that compound 1 exhibits folded conformation, whereas compound 2 adopts extended conformation. The Hirshfeld surface analysis indicates that the contributions of the major intercontacts involved in the stabilization of the crystal structures do not change much as a result of the t-butyl and cyclohexyl moieties. However, the presence and absence of these contacts is revealed by the 2D-fingerprint plots. The CLP–Pixel method was used to identify the energetically significant molecular dimers. These dimers are stabilized by different types of intermolecular interactions such as N–H···S, N–H···O, C–H···S, C–H···O, H–H bonding and C–H···π interactions. The strength of these interactions was quantified by using the QTAIM approach. The results suggest that N–H···O interaction is found to be stronger among other interactions. The in vitro assay suggests that both compounds 1 and 2 exhibit urease inhibition potential, and these compounds also display moderate antiproliferative activities. Molecular docking analysis shows the key interaction between urease enzyme and title compounds.     

Content Analysis of Gender‐related Differential Item Functioning TIMSS Items in Mathematics in Jordan

The purpose of this study is to analyze items that exhibit gender‐related Differential Item Functioning (DIF) in Mathematics in Jordan. Data was taken from the TIMSS 1999 of Jordan, which includes responses of 5,299 eighth grade students. Mantel‐Haenszel (MH) DIF procedure was applied to 124 multiple‐choice items. The results showed that 37 items exhibited gender‐related DIF. The analysis of the content of these items reflected some patterns that need further investigation. All the DIF items in measurement content favored male students while most of the DIF items in algebraic and data analysis contents favored female students. Most of the DIF items that negatively impacted on females were unfamiliar items that required some risk taking such as estimation, expectation, or approximation. On the other hand, most of the DIF items that favored females were familiar items which have one specific correct answer. Some implications for both research and teaching practice are provided.