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

Abstract

1,3,5-Tris(1-naphthyl)benzene (1), 1,3-bis(1-naphthyl)-5-(2-naphthyl)benzene (2), and 1-(1-naphthyl)-3,5bis(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 13 C 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. Variabletemperature 13 C NMR studies of 2 establish barriers of ca. 12 kcal/mol for rotation about the 1-naphthylaryl bond and <9 kcal/mol for rotation about the 2-naphthyl-aryl bond. Again, these values display good agreement with the barriers of 14 and 2 kcal/mol computed using molecular mechanics calculations (MM2). Earlier syntheses of 1,3,5-tris(1-naphthyl)benzene (1) provided materials that were poorly characterized by modern standards. 1 H and 13 C NMR spectra of one such material, a sample widely used in studies of glasses and supercooled liquids, establish the structure of the material as 2, not 1. This revised structural assignment necessitates a re-evaluation of the earlier literature. Differential scanning calorimetry (DSC) establishes that tris(naphthyl)benzenes 1, 2, and 3 melt (T m ) 182, 194, and 147 °C, respectively) and form glasses upon cooling (T g ) 81, 77, and 67 °C, respectively). Given its low melting point and glass transition temperature, 1-(1-naphthyl)-3,5-bis(2-naphthyl)benzene ( 3) is an attractive candidate for future studies of molecular dynamics of glassy materials.o-Terphenyl and 1,3,5-tris(1-naphthyl)benzene (1, TRNB) are rare examples of low-molecular weight, nonpolar compounds that spontaneously form stable supercooled liquids. The liquid, supercooled liquid, glassy, and crystalline states of o-terphenyl and 1,3,5-tris(1-naphthyl)benzene (1) are all experimentally

Nonlinear Kinetic and Thermodynamic Properties of Monomeric Organic Glasses

“…50 The best-fit enthalpy value of ∆µ is 1189 kJ mol -1 ) 400 kJ (mol rotatable bonds) -1 , a factor of 1.6 smaller than the value for viscosity (1.87 × 10 3 kJ mol -1 ). 47 The value of ∆µ per bond is a factor of 7 larger than the NMR derived rotational energy barriers.…”

An Ionic Molecular Glass as Electron Injection Layer for Efficient Polymer Light‐Emitting Diode

“…A mixture of 1 (0.7 g, 2.09 mmol), 4,4,5,5-tetramethyl-2-(3,5-di (1-naphthyl)phenyl-1,3,2-dioxaborolane (2 g, 4.39 mmol), [22] Pd(PPh 3 ) 4 (0.10 g, 0.09 mmol), aqueous sodium carbonate (2 M, 8 mL), ethanol (10 mL), and toluene (25 mL) was deoxygenated and then heated at reflux under nitrogen for 20 h. The reaction mixture was allowed to cool to room temperature and water was added. After separation, the aqueous layer was extracted with dichloromethane.…”

Memory effect in enthalpy relaxation of two metal–alloy glasses

“…To overcome this difficulty, Hofer et al [48] have used the anneal-and-scan procedure in DSC to study the memory effect in 0.4 Na 2 O, 0.1 CaO, 0.05 Al 2 O 3 , 0.5 SiO 2 , 0.4 P 2 O 5 network structure glass, poly(methyl methacrylate) and in 1,3,5-tri-a-naphthylbenzene rigid molecular glass, now recognized as 1,3-bis (1-naphthyl)-5-(2-naphthyl) benzene [69]. Here, we use their technique [48].…”