AUTHOR=Jia Yuanyin , Dong Ming , Wang Bin , Li Chunju 

TITLE=Synthesis and Host–Guest Properties of Acyclic Pillar[n]naphthalenes

JOURNAL=Frontiers in Chemistry

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00828

DOI=10.3389/fchem.2019.00828

ISSN=2296-2646

ABSTRACT=<p>Here we report a new class of synthetic receptors, acyclic pillar[<italic>n</italic>]naphthalene (<italic>n</italic> = 2–4, <bold>Dimer</bold>, <bold>Trimer</bold>, and <bold>Tetramer</bold>) oligomers, which are made up of 2,3-diethoxynaphthalene units linked by methylene bridges at the 1- and 4-positions. They can be synthesized through a one-step condensation of 2,3-diethoxynaphthalene monomer and paraformaldehyde in the presence of BF<sub>3</sub>•(Et)<sub>2</sub>O catalyst. The crystal structure of <bold>Tetramer</bold> has an interesting pseudo-cycle shaped structure in the solid state. Their complexation behaviors toward several organic ammonium cations (<bold>1</bold><sup>+</sup>-<bold>15</bold><sup>+</sup>) and electron–deficient neutral guests (<bold>16</bold>–<bold>17</bold>), were examined by means of <sup>1</sup>H NMR spectroscopy. <bold>Tetramer</bold> shows good host-guest properties toward the ammonium guests, giving association constants (<italic>K</italic><sub>a</sub>) in the magnitude of 10<sup>2</sup>-10<sup>4</sup> M<sup>−1</sup>, which are comparable with those for some macrocyclic hosts.</p>