A Dicyanomethylene‐Substituted Triangulene: Effects of Molecular‐Symmetry Reduction and Electron‐Accepting Substituents on a Fused Polycyclic Neutral π‐Radical System

A triangulene‐based C₂‐symmetric 33 π‐conjugated stable neutral π‐radical, 2^. , which possesses two dicyanomethylene groups and one oxo group, has been designed, synthesized, and isolated as an analogue of tris(dicyanomethylene) derivative 1^. and trioxo derivative TOT^. with C₃ symmetry. Effects of molecular‐symmetry reduction and electron‐accepting substituents on this fused polycyclic neutral π‐radical system were studied in terms of their molecular structure, electronic‐spin structure, and electrochemical and optical properties with the help of theoretical calculations. Interestingly, this system ( 2^. ) has a four‐stage redox ability, like TOT^. , as well as low frontier energy levels and a small SOMO–LUMO gap, similar to 1^. , in spite of the loss of the degenerate LUMOs in symmetry‐lowered 2^. , which is associated with the attachment of the weaker electron‐accepting oxo group instead of the dicyanomethylene group in 1^. . These prominent results are attributable to the structural and electronic properties in the triangulene‐based highly delocalized fused polycyclic neutral π‐radical system.     

Structural Identification of DNA Adducts Derived from 3‐Nitrobenzanthrone,a Potent Carcinogen Present in the Atmosphere

3‐Nitrobenzanthrone is a powerful bacterial mutagen and carcinogen to mammals. To obtain precise information on DNA‐adduct formation by 3‐nitrobenzanthrone, a number of DNA adducts, including N‐(2′‐deoxyguanosin‐8‐yl)‐3‐aminobenzanthrone ( 13 a ), 2‐(2′‐deoxyguanosin‐N²‐yl)‐3‐aminobenzanthrone ( 14 a ), N‐(2′‐deoxyadenosin‐8‐yl)‐3‐aminobenzanthrone ( 15 a ), 2‐(2′‐deoxyadenosin‐N⁶‐yl)‐3‐aminobenzanthrone ( 16 a ), and their N‐acetylated counterparts 13 b , 14 b , 15 b , and 16 b were synthesized by palladium‐catalyzed aryl amination of the corresponding nucleoside and bromobenzanthrone derivatives. Among these DNA adducts, DNA adducts 13 a , 13 b , 14 a , 14 b , and 16 a were identified in the reaction mixture of nucleosides (2′‐deoxyguanosine, 2′‐deoxyadenosine, or DNA) with N‐acetoxy‐3‐aminobenzanthrone or N‐acetyl‐N‐acetoxy‐3‐aminobenzanthrone, both of which are recognized as activated metabolites of 3‐nitrobenzanthrone. The formation of these multiple DNA adducts may help explain the potent mutacarcinogenicity of 3‐nitrobenzanthrone.     

Preparation, structure, and magnetic interaction of a Mn(hfac)2-bridged [2-(3-pyridyl)(nitronyl nitroxide)-Mn(hfac)2]2 chain complex

A new one-dimensional chain complex, Mn(hfac)(2)-bridged [2-(3-pyridyl)(nitronyl nitroxide)Mn(hfac)(2)](2), was prepared and its structure and magnetic properties were elucidated; the complex exhibited a large antiferromagnetic interaction of J(1)=-185 K between the three Mn(ii) atoms and the two nitronyl nitroxides to give S=13/2 spin units and a small ferromagnetic interaction of J(3)'=+0.02 K between these spin units at low temperatures (50-1.9 K), compatible with the theoretical analysis for model compounds.     

THz imaging of cyclotron emission in quantum Hall conductors

Recent studies of cyclotron emission microscopy on quantum Hall related states are reported. The topics include non-equilibrium between edge and bulk states, current-induced breakdown of the quantum Hall effect, and the emission threshold at hot spots. Experimental method of scanning-type terahertz microscopes developed towards photon-counting level sensitivity is also described.     

Light scattering from crystalline superstructure in tubular-extruded polybutene-1 films

Light scattering from polybutene-1 films prepared by tubular extrusion was studied in order to investigate its crystalline superstructure and the deformation mechanism. Analysis of the light-scattering patterns together with electron micrographs, indicate the existence of sheaflike crystalline superstructures. The sheaves are aligned nearly side by side with their axes preferentially oriented perpendicular to the machine direction. The H_v scattering patterns exhibit a “butterfly” appearance. Analysis of the patterns in terms of scattering and azimuthal angles at which the scattering intensity is a maximum yields information on the size and shape of the sheaflike texture. The information should be of importance in studies of anisotropic crystal growth caused by molecular orientation in the melt and of the deformation mechanism of the texture. The deformation behavior should be representative of that of different parts of spherulites, at least qualitatively; the deformation of the texture along the machine and transverse directions corresponds to deformation of equatorial and meridional regions of a spherulite, respectively.     

Investigation of radiopharmaceuticals for pancreatic imaging: accumulation of amines in the pancreas.

To develop radiopharmaceuticals for pancreatic imaging, radioiodinated ethyl benzene derivatives containing various functional groups (amino, carboxyl, and methyl groups) were synthesized and the effects of these functional groups were compared in vitro and in vivo. At 2 min after intravenous injection, the amino derivative, 2-(4-iodophenyl)-N,N-dimethyl ethylamine, displayed about twice the pancreatic uptake and a more than 8-fold higher pancreas/liver ratio than the carboxyl and methyl derivatives. This high and selective in vivo accumulation on the amino derivative in the pancreas was well supported by in vitro studies on the uptake by pancreatic tissue slices. The mechanism promoting pancreatic accumulation of radiopharmaceuticals with an amino group is also discussed.