Cover Picture

The cover picture shows a section of the electron charge density of the first metal carbide endohedral metallofullerene (Sc(2)C(2))@C(84) obtained from a synchrotron X-ray powder diffraction study by the maximum entropy method (MEM). The several density maxima, which correspond to scandium and carbon atoms, are clearly seen inside the C(84) carbon cage. The MEM charge density distribution also reveals that the C(84) cage has D(2d) symmetry (no. 23) and that the C(2) axis is parallel to the <100> face-centered cubic (fcc) direction of the unit cell. As a consequence of the site symmetry being 4mm, the C(2) axis of (Sc(2)C(2))@C(84) is oriented to six equivalent <100> directions and shows a merohedral disorder. The resultant Sc small middle dot small middle dot small middle dotSc distances and C-C bond lengths of the Sc(2)C(2) cluster are 0.429(2) and 0.142(6) nm, respectively. The observed C-C bond length is between that of a typical single and a double bond, and is very close to that of the C-C bond (0.143 nm) combining two pentagons in a C(60) molecule. More about this fascinating structure can be found in the contribution by Shinohara and co-workers on p. 397 ff.     

Long-range magnetic ordering of quasi-one-dimensional S=1/2 Heisenberg antiferromagnet Sr2Cu(PO4)2

Magnetic properties of quasi-one-dimensional S=1/2 Heisenberg antiferromagnet Sr₂Cu(PO₄)₂ were investigated by temperature and field dependence of AC susceptibility down to 0.03 K. A sharp peak was observed at on the temperature dependence of AC susceptibility indicating long-range magnetic ordering. Taking into account the exchange constant, (Hamiltonian =J∑S_iS_i+1), the ratio k_BT_N/J is 0.06%. Sr₂Cu(PO₄)₂ is, therefore, one of the best one-dimensional Heisenberg antiferromagnet known so far.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

Metal-induced supramolecualr chirality in an optically active polythiophene aggregate

Chiral polythiophenes (PTs), in sharp contrast to other optically active polymers, exhibit optical activity in the pi-pi* transition region which is derived from the chirality of the main chain when they self-assemble to form a supramolecular pi-stacked aggregate with intermolecular interactions in a poor solvent or in a film. We now report that the regioregular, optically active PT poly[(R)-3-[4-(4-ethyl-2-oxazolin-2-yl)phenyl]thiophene] (poly-1) exhibits unique split-type induced circular dichroism (ICD) in the pi-pi* transition region of the main chain upon complexation with various metal salts such as trifluoromethanesulfonates of copper(I), copper(II), silver(I), and zinc(II), and iron(II) perchlorate in chloroform, which is a good solvent for poly-1. The appearance of ICD and slight changes in the UV/Vis spectra (no color change), except for the zinc salts, indicated that the chirality may not be induced by chiral pi-stacked aggregates of poly-1, but by the chirality of the main chain, for example, a predominantly one-handed helical structure induced by intermolecular coordination of the oxazoline groups to metal ions. The sign of the Cotton effect depends on the metal salt; most metal salts induced ICDs with similar Cotton-effect patterns, while zinc salts caused an inversion of the signs of the Cotton effect of poly-1 accompanied by a gradual red shift in the absorption of up to 125 nm. The changes in the conformation and the size of the poly-1 aggregates induced by different metal salts were also investigated by (1)H NMR titrations, static light scattering (SLS), atomic force microscopy (AFM), and membrane filtration. On the basis of these results, we propose a possible model for the chiral supramolecular aggregates of poly-1 with metal salts.     

Computation of Rotation Matrices Making Lined‐Up to the Local Cartesian Coordinates

Rotation matrices were expressed in terms of Gaunt coefficients and complex spherical harmonics. The rotation matrices were calculated using two different ways. In the first, Gaunt coefficients and normalized complex spherical harmonics were directly calculated using binomial coefficients; in the second, Gaunt coefficients and complex spherical harmonics were recursively calculated. The methods were compared with respect to accuracy and computation time (CPU) for low and very high quantum numbers.     

Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties

Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF₆. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002     

IMMUNOLOGICALLY ACTIVE LESIONS INDUCED ON DOUBLE-STRANDED DNA WITH ULTRAVIOLET

Abstract— Some immunochemical properties of double-stranded DNA irradiated with UV were studied, using a radioimmunoassay with irradiated [³H]-DNA and experimentally produced antibodies to DNA. Reactivity of antibodies revealed that irradiated DNA contained an immunologically active structure other than the irradiated DNA specific structure, resembling that of thermally denatured DNA. inhibition assay demonstrated that while DNA-antibody binding was effectively inhibited by mixed purine and pyrimidine oligonucleotides, thymine dimer containing pyrimidine oligonucleotides derived from the irradiated DNA showed no appreciable inhibition. The antigenic structure specific for irradiated DNA was found to be thermally labile in low salt medium. Cupric and ferrous ions and cysteine added to the DNA solution inhibited antigenicity formation during irradiation, but these substances exhibited no effect on dimer formation in irradiated frozen thymine solution. Calcium ions and histidine were inert for the former reaction but inhibited the latter effectively. This suggests that different mechanisms are involved in the 2 processes. The immunologically active UV-induced lesions appeared to depend mainly on a conformational structure change of the DNA strands rather than on a single modified base moiety.     

Thermal decompositions of some divalent transition metal complexes of triethanolamine

The thermal behaviours of the Ti(II), Mn(II), Fe(II), Ni(II), Cu(II) and Zn(II) complexes of triethanolamine were studied by means of thermogravimetry, differential thermogravimetry, differential thermal analysis infrared spectrophotometry and elemental analysis. The sequence of thermal stability of the metal complexes, determined by using the initial decomposition temperature, was found to be Ti(II)?Mn(II)>Fe(II)>Ni(II)>Zn(II)>Cu(II). Some of the kinetic parameters, such as the activation energy and order of reaction for the initial decomposition reaction, were calculated and the relationship between the thermal stability and the chemical structure of the complexes is discussed.     

Preliminary Analyses of Radionuclides in Afşin-Elbistan Lignite Samples

This preliminary study describes the concentration of radionuclides ²³⁸U, ²³²Th, ⁴⁰K, and ²²⁶Ra in Afin-Elbistan lignite samples which are primarily used for power generation in the Afin-Elbistan Coal-Fired Power Plant. The results show that the concentration of ²³⁸U is higher in the Afin-Elbistan lignite compared to various world coals whereas the opposite is observed with ²³²Th and ⁴⁰K.