1.4- Diynes special

A subsidiary approach involves nuclear modification of the arylsilanes so obtained. The requisite organometallics can be prepared from aryl halides, or by deprotonation of a suitably activated (c.g. methoxy-substituted) arene. A more specialized route involves cycloaddition between alkynylsilanes and diynes. 

Special cases are 39 and 41 in which two diyne moieties are separated by a bicyclic framework. In both compounds the sharp and easily recognizable PE bands of the triple bonds can be used to investigate long-range interactions. In 39 the interaction between both acetylenic moieties was found to be small i. In 41, however, a splitting of 0.5 eV has been detected (see Figure 10). It has been traced back to a strong interaction between the valence orbitals of the bicyclo[l. 1. Ijpentane moiety and the tt-MOs of the triple bonds . ... 

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