Fine Structures of 8‐G‐1‐( p ‐YC 6 H 4 C ≡ CSe)C 10 H 6 (G = H, Cl, and Br) in Crystals and Solutions: Ethynyl Influence and Y‐ and G‐Dependences

Fine structures of 8‐G‐1‐( p ‐YC 6 H 4 C ≡ CSe)C 10 H 6 [ 1 (G = H) and 2 (G = Cl): Y = H ( a ), OMe ( b ), Me ( c ), F ( d ), Cl ( e ), CN ( f ), and NO 2 ( g )] are determined by the X‐ray analysis. Structures of 1 , 2 , and 3 (G = Br) are called A if each Se–C sp bond is perpendicular to the naphthyl plane, whereas they are B when the bond is placed on the plane. Structures are observed as A for 1a – c bearing Y of nonacceptors, whereas they are B for 1e – g with Y of strong acceptors. The change in the structures of 1e – g versus those of 1a – c is called Y‐dependence in 1 . The Y‐dependence is very specific in 1 relative to 1‐( p ‐YC 6 H 4 Se)C 10 H 7 ( 4 ) due to the ethynyl group: the Y‐dependence in 1 is almost inverse to the case of 4 due to the ethynyl group. We call the specific effect “ Ethynyl Influence. ” Structures of 2 are observed as B : the A ‐type structure of 1b changes dramatically to B of 2b by G = Cl at the 8‐position, which is called G‐dependence. The structures of 2 and 3 are examined in solutions based on the NMR parameters.