Chemiluminescence from reactions with bis-cyclometalated iridium complexes in acidic aqueous solution.

Chemical reactions between certain bis-cyclometalated iridium complexes, cerium(IV) and organic reducing agents in aqueous solution produce an emission of light which in some cases is more intense than that from analogous reactions with conventional ruthenium-based reagents, thus providing a new avenue for chemically-initiated luminescence detection.

Computer molecular models of low-rank coal and char containing inorganic complexes.

Molecular models of low-rank coal containing water, aqua-ionic species, and transition metal aqua-complexes, were optimised using semi-empirical (SE) quantum mechanics; the model was constructed with properties similar to brown coal; 10-20 wt% water was hydrogen bonded to coal oxygen groups, and the remainder was bulk water. Single point self-consistent field (1scf) computations of coal models provided octahedral mono-, and di-nuclear complexes of Cr, Fe, Co, and Ni, but SE computations often provided distorted structures. Models of char were developed by transforming the coal model containing multi-nuclear metal species into char according to pyrolysis chemistry; the composition of char models containing iron oxides was similar to char samples obtained over 250-800 degrees C.

4-(piperidin-1-yl)pyridinium hexafluorophosphate at 150 K.

Structural characterization of the title compound, C(10)H(15)N(2)(+).PF(6)(-), shows it to be ionic, with the pyridine rather than the piperidine N atom being protonated and forming hydrogen bonds to the counter-ions, resulting in two independent ion pairs. A number of unusual features are noted, in particular the remarkably close inter-ring hydrogen contacts [1.

Tetraphenylarsonium tetraiodothallate(III).

The As and Tl atoms in title compound, (C(24)H(20)As)[TlI(4)], sit on fourfold inversion centres, resulting in a [TlI(4)](-) anion with D(2d) symmetry and a Tl-I bond length of 2.7691 (3) A. The tetrahedral anion is tetragonally distorted, being flattened in the direction of the c axis of the tetragonal unit cell, so that the two unique I-Tl-I angles differ by about 9 degrees.

A second polymorph of 1,1,4,4-tetramethylpiperazinium pentabromothallate(III).

A new polymorph of the title compound, (C8H20N2)[TlBr5], contains cations located about crystallographic centres of inversion and trigonal-bipyramidal anions which have a C2 axis passing through the equatorial plane of the anion. The anion has the least distorted geometry seen so far in any structure possessing this anion and the axial Tl-Br bonds are about 0.13 A longer than the equatorial Tl-Br bonds, consistent with related structures.