Evaluation of the Solid State Dipole Moment and Pyroelectric Coefficient of Phosphangulene by Multipolar Modeling of X-ray Structure Factors

Abstract

The electron density distribution of the molecular pyroelectric material phosphangulene has been studied by multipolar modeling of X-ray diffraction data. The "in-crystal" molecular dipole moment has been evaluated to 4.7 D corresponding to a 42% dipole moment enhancement compared with the dipole moment measured in a chloroform solution. It is substantiated that the estimated standard deviation of the dipole moment is about 0.8 D. The standard uncertainty (s.u.) of the derived dipole moment has been derived by splitting the dataset into three independent data-sets. A novel method for obtaining pyroelectric coefficients has been introduced by combining the derived dipole moment with temperature-dependent measurements of the unit cell volume. The derived pyroelectric coefficient of 3.8(7) x 10-6 Cm 2K-1 is in very good agreement with the measured pyroelectric coefficient of p = 3 +/- 1 x 10-6 Cm-2 K-1. This method for obtaining the pyroelectric coefficient uses information from the X-ray diffraction experiment alone and can be applied to much smaller crystals than traditional methods.

Building Large Structures with Curved Aromatic Surfaces by Complexing Metals with Phosphangulene

“…Molecules of the compound have a well-defined conical shape and an electron-rich aromatic surface (Figure ). Studies of phosphangulene and its derivatives during the last 20 years have reflected a preoccupation with the effects of their distinctive nonplanar topology. − For example, the shape helps induce molecules of phosphangulene to crystallize as parallel π-stacks . In addition, the concave electron-rich aromatic surface of phosphangulene is geometrically and electronically complementary to the convex electron-poor surfaces of fullerenes such as C 60 and C 70 .…”

Synthesis, Structure, and Properties of Azatriangulenium Salts

“…In recent years, the triangulene skeleton has been used in the construction of macrocyclophanes23–25 and in stable triplet π biradicals 26, 27. The TOTA + cation intercalates into double and triple helical DNA, where it acts as a photonuclease,28 while the pyroelectric phosphangulene29, 30 and other triangulene derivatives have been extensively studied in the solid state 31, 32…”

The supramolecular assemblies based on heteroatom-containing triangulenes

“…42% when going from the solubilized to the crystalline state (m = 4.7 D). 83 The S-containing derivatives 30b-d were reported by Yamamura et al 22 With increasing number of S-bridges, the cone angles increased and, consequently, the bowl depths decreased (30a: d = 2.43 Å; 30d: 2.03 Å). Not only the molecular parameters, but also the packing behavior was affected by the nature of the bridges.…”