Molecular and crystal structure of crown ethers containing biphenyl fragment

The results of the experimental (IR, UV and 1H NMR spectroscopy, mass-spectrometry and X-ray crystallography) and theoretical (ab initio quantum-chemical method using the B3LYP functional and cc-pVDZ basis set) study of the molecular and crystalline structure of 2,2′-biphenylen-14-crown-4 (1), -17-crown-5 (2), -20-crown-6 (3) and bis-(2,2′-biphenylen)-28-crown-8 (4) are discussed. The increase in the macrocycle results in the transfer from its crown-like conformation into the boat and following chair-like conformation. The conformation of the cyclic polyethers’ 1–4 aliphatic part is additionally stabilized by the intramolecular CH ⋯ O hydrogen bonds, and the conformation of the biphenyl fragment in all compounds 1–4 stays practically the same and is stipulated mainly by the repulsion between the ortho,ortho′-oxygen atoms as well as steric interaction of the CH fragment of the aromatic ring and the closest to it methylene groups. The crown ethers’ 1–4 molecular packing in the crystals is defined by the tendency to parallel orientation of the biphenyl benzene rings and macroheterocycles.