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, C-13 CPMAS,. and single X-ray diffraction allowed establishing the structures of the complexes as hydrogen-bonded heterodimers and heterotetramers. Complexation occurs through O-H center dot center dot center dot 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 degrees, strengthens the intramolecular (amide)CO center dot center dot center dot H(Csp(2))center dot center dot center dot 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 R-2(1)(6), R-2(2)(10), and R-2(1)(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.