The title compound, C25H24N3O3P, was obtained by catalytic phospho-nation of 4'-(4-bromphen-yl)-2,2':6',2''-terpyridine. The terpyridine moiety is nearly planar, the dihedral angles between the central and the outer rings being 4.06 (9) and 5.39 (9)°. The N atoms in the two pyridine rings are oriented nearly anti-periplanar to that of the central ring. The benzene ring is rotated out of the pla...

Given a finite metacyclic group G, a central extension F having the projective lifting property over all fields is constructed. This extension and its group rings are used to investigate the faithful irreducible projective representations of G and the fields over which they can be realized. A full description of the finite metacyclic groups having central simple twisted group rings over fields ...

this paper is an attempt to generalize, simultaneously, the ring of real-valued continuous functions and the ring of real-valued measurable functions.

We report here the electrochemistry, luminescence, and electrogenerated chemiluminescence (ECL) of 3,6-dispirobifluorene-N-phenylcarbazole (DSBFNPC). DSBFNPC contains two spirobifluorene groups covalently attached to the N-phenylcarbazole core. The optimized geometry as determined from semiempirical MNDO calculations shows that the phenyl group is twisted 89 degrees from the plane of central ca...

The mol-ecular structure of the title compound, C(17)H(20)N(4)O(5), contains a central fused-ring system, comprised of six- and five-membered rings. This unit is linked by C(2) chains to two 2-oxo-1,3-oxazolidine five-membered rings. The central fused-ring system is essentially planar, with a maximum deviation of 0.008 (1) Å from the mean plane. Both oxazolidine five-membered rings are also nea...

In the title compound, C(31)H(25)ClO(3), the central ring of the xanthene core shows a shallow boat conformation, while the outer six-membered rings display envelope conformations. The dihedral angle between the outer aromatic rings is 88.1 (3)° and the dihedral angles between the chloro-benzene ring and the two phenyl rings are 69.5 (2) and 69.6 (2)°.

In the mol-ecule of the title compound, C(28)H(22)S(2), the two thio-phene rings are twisted with respect to the central benzene ring, making dihedral angles of 71.59 (12) and 50.71 (12)°. The two terminal benzene rings are oriented at dihedral angles of 37.59 (11) and 20.12 (11)° to their bonded thio-phene rings.

We consider rings equipped with a closure operation defined in terms of a collection of commuting idempotents, generalising the idea of a topological closure operation defined on a ring of sets. We establish the basic properties of such rings, consider examples and construction methods, and then concentrate on rings which have a closure operation defined in terms of their lattice of central ide...

The title mol-ecule, C(18)H(12)N(4)S(3), consists of three essentially planar fragments, viz. two methyl-substituted benzonitrile rings and a substituted thia-diazole ring. The dihedral angles between the substituted benzonitrile rings and the central thia-diazole ring are 28.29 (10) and 78.83 (6)°, and the dihedral angle between the two benzonitrile rings is 72.89 (7)°.

Many nearby stars are surrounded by a bright ring or disk of cold dust. Our calculations show that these disks and rings of dust are signposts of recent planet formation. Bright rings appear because dust associated with the formation of a planet absorbs and scatters light from the central star. The calculations explain the rings observed so far and predict that all nascent solar systems have du...