Molecular complexes of diethyl N, N ′-1,3-phenyldioxalamate and resorcinols: Conformational switching through intramolecular three-centered hydrogen-bonding

The mechanochemically induced complexation between diethyl N,N′-1,3-phenyldioxalamate tweezers and resorcinol, orcinol, 4,6-di-tert-butyl-1,3-benzenediol, and 4-hexyl-1,3-benzenediol is described. IR-spectroscopy, X-ray powder diffraction, ¹³C CPMAS, and single X-ray diffraction allowed establishing the structures of the complexes as hydrogen-bonded heterodimers and heterotetramers. Complexation occurs through O-H···O=C hydrogen-bonding interactions with the participation of phenolic OH and amide carbonyl groups. The initial conformation and steric factors coming from the 1,3-benzenediols exert a strong influence on the final structure of the complex formed. Complexation twists both oxalyl arms by 180°, strengthens the intramolecular (amide) CO···H(Csp²)···OC(amide) three-centered hydrogen bond, and moves apart the oxalyl arms to allow the accommodation of the 1,3-benzenediol inside the cavity. The supramolecular architectures of the complexes in 1-D are directed by R¹ ₂(6), R²₂(10), and R¹₂(6) adjacent hydrogen-bonding ring motifs; meanwhile, the 2-D and 3-D arrays are driven by multipolar interactions. Theoretical DFT calculations at the B3LYP/6-31G(d,p) level of theory were performed to support the experimental findings. The complexes herein reported constitute the first examples of molecular complexes with phenyldioxalamate.