Synthesis, crystal and molecular structures of three triphenylsilanol amine adducts

Three 1: 1 adducts of triphenylsilanol with aromatic amines, Ph₃SiOH:L where L = 4-phenylpyridine, 4,4′-bipyridine and acridine, compounds 1, 2 and 3, respectively, have been prepared and their crystal structures analysed. In compounds 1, 2 and 3 the O-H⋯N hydrogen-bonding is only within the 1:1 adducts. The O-H⋯N hydrogen bonds are moderately strong for all three adducts, with O⋯N distances of 2.768(3), 2.789(4) and 2.7631(14) Å, and O-H⋯N angles of 163.1, 164.2 and 176(2)° for 1, 2 and 3, respectively. The adducts of 4-phenylpyridine, 1, and 4,4′-bipyridine, 2, are essentially isomorphous. They adopt structures in which phenyl groups on the silanols interact via C-H⋯π interactions to form double layers with the hydroxy groups directed away from the hydrophobic core. The amines interact via π-π interactions to form layers which are hydrogen-bonded to the silanol layers via the hydroxy groups. There is π-π stacking present in all three structures, with the strongest exhibited in 3. There are also numerous C-H⋯π interactions in all three structures, for example in 3 seven C-H⋯π interactions can be identified.