4,4-Bis(1H-pyrrol-2-yl)pentanol

The title achiral compound, C13H18N2O, crystallized in the chiral monoclinic space group P21. The pyrrole rings are inclined to one another by 62.30 (11)°, and the propanol chain is in an extended conformation. In the crystal, the two pyrrole NH groups are involved in intermolecular N—H⋯O hydrogen bonds, leading to the formation of a helical arrangement propagating along the b axis. An interesting feature of the crystal structure is the absence of any conventional hydrogen bonds involving the hydroxy H atom. There is, however, a weak intermolecular O—H⋯π interaction involving one of the pyrrole rings.

The title achiral compound, C 13 H 18 N 2 O, crystallized in the chiral monoclinic space group P2 1 . The pyrrole rings are inclined to one another by 62.30 (11) , and the propanol chain is in an extended conformation. In the crystal, the two pyrrole NH groups are involved in intermolecular N-HÁ Á ÁO hydrogen bonds, leading to the formation of a helical arrangement propagating along the b axis. An interesting feature of the crystal structure is the absence of any conventional hydrogen bonds involving the hydroxy H atom. There is, however, a weak intermolecular O-HÁ Á Á interaction involving one of the pyrrole rings.
In the title compound the pyrrole ring mean-planes are inclined to one another by 62.30 (11)°, and the propanol chain is in the extended conformation. In the 5 compounds located in the CSD this angle varies between 68.5 to 89.6 °.
In the crystal the molecules are linked by conventional N-H···N intermolecular hydrogen bonds leading to the formation of helical chains propagating along the b axis ( Fig. 2 and Table 1). The basic unitary hydrogen bonding graph set can be described by an R 2 3 (16) ring, while the basic binary graph set is a C(8) chain. This gives an extended notation of (Bernstein et al., 1995). A fuller hydrogen bonding graph set analysis can be obtained using the program Mercury (Macrea et al., 2006).

Refinement
In the final cycles of refinement, in the absence of significant anomalous scattering effects, 1239 Friedel pairs were merged and Δf " set to zero. The OH and NH H-atoms, located in a difference electron-density map, were freely refined: O-H = 0.83 (3) Å; N-H = 0.88 (2) -0.90 (2) Å. The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.95, 0.99 and 0.98 Å for CH, CH 2 and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.2 for CH and CH 2 H-atoms, and 1.5 for CH 3 H-atoms. Fig. 1. A view of the molecular structure of the title compound, with the displacement ellipsoids drawn at the 50% probability level.  Table 1

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. In the final cycles of refinement, in the absence of significant anomalous scattering effects, 1239 Friedel pairs were merged and Δf " set to zero. The OH and NH hydrogen atoms were located in difference electron-density maps and were freely refined. The C-bound H-atoms were included in calculated positions and treated as riding.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.41371 (