Crystal structures of four chiral imine-substituted thio­phene derivatives

A series of thio­phenes substituted in positions 2 and 5 by imine groups have been synthesized using a solvent-free approach, and their crystal structures determined. The substituents are chiral groups, and the expected absolute configuration for each mol­ecule was confirmed by refinement of the Flack parameter. The compounds are 2,5-bis­[(S)-(+)-(1,2,3,4-tetra­hydro­naphthalen-1-yl)imino]­thio­phene, C(26)H(26)N(2)S, (I), 2,5-bis­{[(R)-(−)-1-(4-meth­oxy­phen­yl)eth­yl]imino­meth­yl}thio­phene, C(24)H(26)N(2)O(2)S, (II), 2,5-bis­{[(R)-(−)-1-(4-fluoro­phen­yl)eth­yl]imino­meth­yl}thio­phene, C(22)H(20)F(2)N(2)S, (III), and 2,5-bis­{[(S)-(+)-1-(4-chloro­phen­yl)eth­yl]imino­meth­yl}thio­phene, C(22)H(20)Cl(2)N(2)S, (IV). A common feature of all four mol­ecules is the presence of twofold symmetry. For (I), which crystallizes in the triclinic space group P1, this symmetry is non-crystallographic, but for (II) in C2 and the isomorphous structures (III) and (IV) that crystallize in P2(1)2(1)2, the twofold symmetry is crystallographically imposed with one half of each mol­ecule in the asymmetric unit. The comparable mol­ecular symmetry in the four structures is also reflected in similar packing, with mol­ecules aggregated to form chains through weak C—H⋯S inter­actions.