Polymorphism in R-tamsulosin (an alpha blocker): The unexpected manifestation of a sulfonamide⋯o-diethoxybenzene heterosynthon

Three polymorphs and a hydrochloride salt of R-tamsulosin drug are sustained by an unanticipated sulfonamide⋯o-diethoxybenzene heterosynthon which resembles the molecular recognition of sulfonamide crown ether complexes. The multi-point binding favors this heterosynthon over the robust sulfonamide dimer or catemer homosynthons.