Three closely related 4,5,6,7-tetra­hydro-1H-pyrazolo­[4,3-c]pyridines: synthesis, mol­ecular conformations and hydrogen bonding in zero, one and two dimensions

In each of 1-(4-fluoro­phen­yl)-5-methyl­sulfonyl-3-[4-(tri­fluoro­meth­yl)phen­yl]-4,5,6,7-tetra­hydro-1H-pyrazolo­[4,3-c]pyridine, C21H19F4N3O2S, (I), 1-(4-chloro­phen­yl)-5-methyl­sulfonyl-3-[4-(tri­fluoro­meth­yl)phen­yl]-4,5,6,7-tetra­hydro-1H-pyrazolo­[4,3-c]pyridine, C21H19ClF3N3O2S, (II), and 1-(3-methyl­phen­yl)-5-methyl­sulfonyl-3-[4-(tri­fluoro­meth­yl)phen­yl]-4,5,6,7-tetra­hydro-1H-pyrazolo[4,3-c]pyridine, C22H22F3N3O2S, (III), the reduced pyridine ring adopts a half-chair conformation with the methyl­sulfonyl substituent occupying an equatorial site. Although compounds (I) and (II) are not isostructural, having the space groups Pbca and P212121, respectively, their mol­ecular conformations are very similar, but the conformation of compound (III) differs from those of (I) and (II) in the relative orientation of the N-benzyl and methyl­sulfonyl substituents. In compounds (II) and (III), but not in (I), the tri­fluoro­methyl groups are disordered over two sets of atomic sites. Mol­ecules of (I) are linked into centrosymmetric dimers by C—H⋯π(arene) hydrogen bonds, molecules of (II) are linked by two C—H⋯O hydrogen bonds to form ribbons of R33(18) rings, which are themselves further linked by a C—Cl⋯π(arene) inter­action, and a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules of (III) into sheets. Comparisons are made with the structures of some related compounds