Tris(1 H-benzimidazol-2-ylmeth-yl)amine methanol tris-olvate

Abstract

The structure of the tertiary amine tris-(1H-benzimidazol-2-ylmeth-yl)amine (C₂₄H₂₁N₇, abbreviated ntb) has been previously reported twice as solvates, namely the monohydrate and the aceto-nitrile-methanol-water (1/0.5/1.5) solvate, both with the tripodal conformation formed via multiple hydrogen bonds. Now, we report the tri-methanol adduct, ntb·3CH₃OH, where the amine has the stair conformation featuring one benzimidazole group oriented in the opposite direction from the other two. The asymmetric unit contains one-half amine, completed through the mirror plane m in space group Pmn2₁ to form the ntb mol-ecule, with the H atom for each imidazole moiety equally disordered between both N sites available in the imidazole ring. The asymmetric unit also contains one and a half methanol mol-ecules, one being placed in general position with the hy-droxy H atom disordered over two sites with occupancy ratio 1:1, while the other lies on the m mirror plane, and has thus its hy-droxy H atom disordered by symmetry. As in the previously reported solvates, all imine and amine groups of the ntb mol-ecules and the methanol mol-ecules are involved in N-H⋯O and O-H⋯N hydrogen bonds. In the title compound, however, the involved H atom is systematically a disordered H atom provided by an imidazole group or a methanol mol-ecule.

Keywords: crystal structure; hydrogen bonds; methanol solvate; mol­ecular conformation; tripodal N-donor ligand.

Figure 1

Mol­ecular structure of the title compound, with displacement ellipsoids for non-H atoms at the 50% probability level. For all disordered H atoms, a single site was retained, in order to emphasize the O—H⋯N and N—H⋯O hydrogen bonds (dotted lines). Non-labelled atoms are generated by the symmetry operation 1 − x, y, z.

Figure 2

View of the title compound rotated by ca 90° in comparison with Fig. 1 ▸, showing the stair-like conformation for ntb. All H atoms bonded to heteroatoms are shown. Green H atoms are disordered by symmetry, while purple H atoms are positionally disordered, all having the same half occupancy. The orange line is the trace of the m mirror normal to the a axis.