Fine Structures of 8‐G‐1‐(<i>p</i>‐YC₆H₄C ≡ CSe)C₁₀H₆ (G = H, Cl, and Br) in Crystals and Solutions: Ethynyl Influence and Y‐ and G‐Dependences

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