ORGANIC-INORGANIC MOLECULAR AGGREGATES AND THEIR ASSOCIATION WITHIN LONG-RANGE ORDERED CRYSTALLINE ASSEMBLIES - RELEVANCE TO THE TEMPLATE EFFECT IN SOLID-STATE CHEMISTRY

A series of conducting radical cation salts of 1,2-bis(4,5-dimethyltet rathiafulvalen-4'- [bis(DMTTF)ethane], a bifunctional donor with two q uasi-degenerate redox functionalities, has been prepared by electrocry stallization; two kinds of binary radical cation salts, [bis(DMTTF)eth ane](3)[Re(6)Q(6)Cl(8)], Q = Se, 1; S, 2 and [bis(DMTTF)ethane](2)[Re( 6)Q(5)Cl(9)], Q = Se, 3; S, 4 and a ternary phase [bis(DMTTF)ethane](5 )[Re6Se6Cl8][Re6Se5Cl9], 5, have been obtained. All five compounds pre sent the same one-dimensional (1D) structural organization in which a stack of donor molecules is surrounded by cluster anions. The degree o f oligomerization of the radical cation moieties within the stack is s hown to be controlled solely by the cluster anion charge. Thus, the lo ng-range ordered merging of 1 and 3 has led to the formation of the mo lecular alloy 5. The electronic properties of 1-5 deduced from the ban d structure calculations and the magnetic properties observed by singl e-crystal EPR are analysed in relation with the structural changes and the spin distribution on the TTF moieties. The role of the organic ch alcogen-inorganic chalcogen interactions is also discussed. In particu lar, the spin-Peierls transition observed in 1 and absent in 2 is show n to be associated with significant donor-anion interactions only pres ent in 1. Finally, the relation between the degree of purity of 1 and the absence of a pseudo-gap in the spin-Peierls transition is demonstr ated.