Synthesis and Characterization of Organic Materials with Conveniently Accessible Supercooled Liquid and Glassy Phases:  Isomeric 1,3,5-Tris(naphthyl)benzenes

• Published in: Journal of physical chemistry (1952) 1996-01, Vol.100 (3), p.1081-1090
• Main Authors: Whitaker, Craig M, McMahon, Robert J
• Format: Article
• Language: English
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/jp9529329

1,3,5-Tris(1-naphthyl)benzene (1), 1,3-bis(1-naphthyl)-5-(2-naphthyl)benzene (2), and 1-(1-naphthyl)-3,5-bis(2-naphthyl)benzene (3) easily supercool and form glasses on cooling from the melt. We synthesized 1, 2, and 3 using Suzuki's conditions to effect the cross-coupling reactions of 1,3,5-tribromobenzene with 1-naphthylboronic acid and/or 2-naphthylboronic acid. Variable-temperature 13C NMR studies of 1 establish a barrier of ca. 12 kcal/mol for rotation about the aryl−aryl bond; this value displays good agreement with the barrier of 13 kcal/mol computed using molecular mechanics calculations (MM2). This relatively low rotational barrier is inconsistent with the previously held notion that 1,3,5-tris(1-naphthyl)benzene (1) exists as a mixture of noninterconverting rotational isomers (atropisomers) in solution at room temperature. Variable-temperature 13C NMR studies of 2 establish barriers of ca. 12 kcal/mol for rotation about the 1-naphthyl−aryl bond and