A mononuclear platinum(II) complex with mixed bpy and H4tg(-) ligands, [Pt(H4tg-S)2(bpy)]·2H2O (1a; bpy = 2,2'-bipyridine and H5tg = 1-thio-β-D-glucose), is photoluminescent in the solid state and undergoes facile and reversible removal of solvated water molecules accompanied by changes in its absorption and emission wavelengths. The analogous dmbpy complex, [Pt(H4tg-S)2(dmbpy)]·H2O (2a; dmbpy = 4,4'-dimethyl-2,2'-bipyridine), is also emissive in the solid state, but its absorption and emission spectra remain unchanged after dehydration. X-ray crystallographic analyses revealed that the difference in the chromism of 1a and 2a is due to the difference in their hydrogen-bonding networks, which involve solvated water molecules.

In the title complex, cis-[PtCl2(C11H9N)2], the PtII ion is situated in a slightly distorted square-planar environment coordinated by two N atoms from two 2-phenyl­pyridine ligands and two Cl atoms. The two pyridyl planes are inclined with dihedral angles of 59.1 (2) and 61.84 (19)° with respect to the PtCl2N2 plane. In the crystal, the complex mol­ecules display inter- and intra­molecular π–π stacking inter­actions, with centroid-centroid distances of 3.806 (5)–3.845 (5) Å, which form a one-dimensional column structure along the a axis.

Mechanical grinding of the ClO4(-) salt of [Pt(H4tg-S)(terpy)](+) (H5tg = 1-thio-β-D-glucose, terpy = 2,2':6',2''-terpyridine), newly prepared from [PtCl(terpy)](+) and H4tg(-), caused its emission band at 630 nm to shift to 667 nm, while such mechanochromism was not observed for the PF6(-) salt that shows an emission band at 670 nm.

The effect of electrode potential and film thickness on the kinetic parameters of the oxidation process of polythiophene (PT) was investigated by an a.c. impedance method and conductivity measurements. The conductivity of a PT film increased with its oxidation and reached a limiting value at higher potentials than 0.8 V despite a rise in oxidation state of PT. The oxidation of the PT film lowered the activation energy of electric conduction, which suggested the broadening of a polaron band. An increase in the oxidized form of thiophene unit brings about the decrease in charge transfer resistance at the polymer electrode in the lower potential range than the half-wave potential of PT. Both the redox capacitance of the polymer and d.c. resistance associated with the diffusion of a charge carrier indicated the dependence on the potential and film thickness which was expected from a finite diffusion model. A large capacitance of the order of 1—30 mF cm−2 in the oxidized state is explained in terms of the charge saturation effect due to the finite thickness and porous nature of the polymer film.

In the crystal structure of the non-solvate form of the title compound, [Au2Cl2(C30H24P2)], two almost linear P—AuI—Cl units [175.87 (3) and 171.48 (3)°] are in a skewed arrangement with a Cl—Au⋯Au—Cl torsion angle of −65.29 (3)° so as to form an intra­molecular Au⋯Au inter­action [3.0563 (2) Å]. The complex mol­ecules are connected each other through inter­molecular C—H⋯π inter­actions, giving a sheet structure parallel to the bc plane.