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Molecular Complexes of Diethyl N,N′‑1,3-Phenyldioxalamate and Resorcinols: Conformational Switching through Intramolecular Three-Centered Hydrogen-Bonding

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posted on 05.02.2014, 00:00 by Juan Saulo González-González, Francisco J. Martínez-Martínez, Efrén V. García-Báez, Alejandro Cruz, Luis M. Morín-Sánchez, Susana Rojas-Lima, Itzia I. Padilla-Martínez
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 R12(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.