Crystal structures of two therapeutically active 2-imidazolines: naphazoline nitrate and tymazoline hydrochloride monohydrate

Abstract

Naphazoline·HNO₃ (1): C₁₄H₁₅N₃O₃,M _r =273.3, crystallizes in the orthorhombic space group Pbca(Z=8) witha=12.028(1),b=14.408(2) andc=15.894(2) Å,V=2754.4 ų,D _x =1.318 g cm⁻³,μ=0.70 mm⁻¹,λ (CuKα)=1.54178 Å,F(000)=1152. FinalR=0.092 andwR=0.088 for 1348 observed reflections collected on a diffractometer. The structure was solved with direct methods, it shows two distinct positions of the naphthyl group with populations about 0.5, which differ by a 180β rotation. As in other arylmethyl-2-imidazolines, the imidazoline ring is approximately perpendicular to the aromatic ring. The molecules are linked by two hydrogen bonds N(3)-H⋯O (nitrate anion)⋯H-N(1) into infinite chains running along the 2₁ axis in the [100] direction. Tymazoline·HC1·H₂O (2): C₁₄H₂₃ClN₂O₂,M _r =286.8, crystallizes in the monoclinic space groupP2₁/n (Z=4) witha=8.136(1),b=10.015(1),c=18.601(1) Å and,β=97.20(1)°,V=1503.7 ų D _x =1.266 g cm⁻³,μ=2.27 mm⁻¹, λ(CuKα)=1.54178 Å,F(000)=636. FinalR=0.115 andwR=0.119 for 3073 observed reflections collected on a diffractometer. The structure was solved with direct methods. Unlike other aryloxymethyl-2-imidazolines, the molecule is almost planar with an angle of 12.8(2)° between the two rings. Hydrogen bonding networks consist of N(1)-H⋯O (water)⋯Cl⁻⋯H-N(3) chains joined by an additional link O(water)-H⋯Cl⁻ between chains running in opposite directions.