The energy gap law established for aromatic hydrocarbons and rare earth ions relates the nonradiative decay rate to the energy gap of a transition through a multiphonon emission process. We show that this energy gap law can be applied to the phosphoresce of a series of conjugated polymers and monomers for which the radiative decay rate has been enhanced through incorporation of a heavy metal. We find that the nonradiative decay rate from the triplet state T(1) increases exponentially with decreasing T(1)-S(0) gap for the polymers and monomers at 300 and 20 K. Comparison of the nonradiative decay of polymers with that of their corresponding monomers highlights the role of electron-lattice coupling.

A variety of straight-chain alkynes with extended n-conjugation through benzene, anthracene and thiophene linker units in the backbone, H-C=C-R'-C=C-R-C=C-R'-C=C-H (R=p-C6H4, 9,10-C,4H8, 2,5-C4H,S; R'=p-CsH4, p-C6H4-C6H4-~) has been synthesized. The alkynyl chromophores with an anthracene spacer unit are highly emissive in solution with luminescence quantum yields of up to 0.5. The platinum o-acetylide polymeric complexes of the above ligands show strong absorptions associated with metal-to-alkynyl ligand charge transfer (MLCT) transitions. It is clear that the n-conjugation is maintained through the metal centres and the optical gap for the polymer,

Mal N, mal O: Raman‐spektroskopische und photokristallographische Studien an Einkristallen identifizierten den Komplex [Ni(dppe)(η1‐NO2)Cl] als das erste System, das im Festkörper eine reversible und vollständige Umwandlung in ein metastabiles Isomer, in diesem Fall [Ni(dppe)(η1‐ONO)Cl], eingeht.

RU&(CO)~q(~3-q2 : q2 : l12-c6H6)(t16-c6H6)] and [OS3(CO)9(p3-q2 : q2 : q2-C6H6)l A new co-ordination mode for benzene ligands in cluster complexes, in which the ring is symmetrically placed above a metal triangle has been crystallographically established in the carbonyl complexes [RU&(CO)11 (p3-q2 : q2 q2-c6Hs)(q6-c6H6)] and [OS3(CO)9(p3-72 7' : q2-C&j)].

The structures of six new tetrazines have been determined and their molecular packing has been compared to the supermolecular architecture observed in related carboxylic acid dimers. In the tetrazines, covalent NN bonds are considered to replace the intermolecular OH⋅⋅⋅O hydrogen bonds of the carboxylic acids. In the systems investigated, it is apparent that, in the majority of cases, the covalent six‐membered ring of the tetrazine is an appropriate replacement for the carboxylic acid synthon. This apparent interplay between molecular and supramolecular units may have applications in the crystal engineering of new materials.