3‐Nitrophenol–4,4′‐bipyridyl N,N′‐dioxide (2/1): a DFT study and CSD analysis of DPNO molecular complexes

The title 2:1 complex of 3‐nitrophenol (MNP) and 4,4′‐bipyridyl N,N′‐dioxide (DPNO), 2C₆H₅NO₃·C₁₀H₈N₂O₂ or 2MNP·DPNO, crystallizes as a centrosymmetric three‐component adduct with a dihedral angle of 59.40 (8)° between the planes of the benzene rings of MNP and DPNO (the DPNO moiety lies across a crystallographic inversion centre located at the mid‐point of the C—C bond linking its aromatic rings). The complex owes its formation to O—H...O hydrogen bonds [O...O = 2.605 (3) Å]. Molecules are linked by intermolecular C—H...O and C—H...N interactions forming R₂¹(6) and R₂²(10) rings, and R₆⁶(34) and R₄⁴(26) macro‐rings, all of which are aligned along the [01] direction, and R₂²(10) and R₂¹(7) rings aligned along the [010] direction. The combination of chains of rings along the [01] and [010] directions generates the three‐dimensional structure. A total of 27 systems containing the DNPO molecule and forming molecular complexes of an organic nature were analysed and compared with the structural characteristics of the dioxide reported here. The N—O distance [1.325 (2) Å] depends not only on the interactions involving the O atom at the N—O group, but also on the structural ordering and additional three‐dimensional interactions in the crystal structure. A density functional theory (DFT) optimized structure at the B3LYP/6‐311G(d,p) level is compared with the molecular structure in the solid state.