Putting Fullerenes in Their Place: Cocrystallizing C₆₀ and C₇₀ with Phosphangulene Chalcogenides

Abstract

The distinctive conical shape and electron-rich aromatic surface of phosphangulene (1) and its derivatives offer a geometric and electronic complement to the convex electron-poor surface of fullerenes such as C60 and C70. In crystals of phosphangulene itself, molecules form π-stacks that are efficiently packed. In contrast, the corresponding oxide (2a), sulfide (2b), and selenide (2c) have an awkward shape that prevents effective stacking and forces crystallization to produce structures with abnormally large intermolecular separations. As a result, chalcogenides 2a–c are strongly disposed to form cocrystals with C60 and C70. Structural studies of a series of cocrystals show that compounds 2a–c disrupt the normal organization of fullerenes and reposition them in diverse new ways that introduce a degree of separation but do not eliminate fullerene–fullerene contacts needed to ensure direct electronic communication.

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

“…One possible way to manipulate organization is by using shape-complementary additives, such as derivatives of phosphangulene. 10,16 By focusing on the conical shape of phosphangulene, previous work has not fully exploited other useful properties of the compound. In particular, researchers have largely overlooked its ability to form complexes with transition metals, which offers a simple way to create complex molecular structures with curved aromatic surfaces for binding fullerenes.…”

“…Each bound phosphangulene can surround only about one-fourth of the total surface of C 60 , as shown by the structures of cocrystals of phosphangulene chalcogenides with fullerenes. 10 As a result, complexes of phosphangulene are well designed to interact with neighboring fullerenes without completely enveloping them. In contrast, many previous efforts to devise suitable partners for binding fullerenes have targeted ways to surround them.…”

“…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 .…”

“…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 . As a result, various derivatives of phosphangulene have been used to bind fullerenes in solution and to produce cocrystals that control how fullerenes are positioned in the solid state. − For such reasons, phosphangulene and related compounds have drawn the attention of chemists, and the seminal early work of Krebs and co-workers has led to a surge of creative new studies in recent years, particularly by the group of Nabeshima. − …”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…Wuest et al reported X-ray crystal structures of various polymorphs of phosphangulene chalcogenides 116.2a – c 235 and those of the various solvates originating from the cocrystallization of 116.2a – c with C 60 or C 70 . 236 Furthermore, they characterized the crystal structures of the bis(phosphangulene)iminium salts (including [ 116.9 ][Br]) 237 and the silver(I) ( 116.10 + ) and copper(I) ( 116.11 + ) complexes featuring a metal center that is tetracoordinated by phosphangulene ( Scheme 116 ). 238 …”