Organic Small Molecules for Photonics and Electronics from the [2.2]Paracyclophane Scaffold

Abstract

In the search for molecules for organic photonics and electronics, several strategies have been used to modulate physical and chemical properties of [2.2]paracyclophane derivatives by sequential functionalization of their three‐dimensional cores. This review summarizes the major design and synthetic strategies for tuning paracyclophane‐containing small molecules by introducing various moieties featuring (hetero)aromatic rings directly connected to each other, as well as alternating (hetero)aryl and ethylene or ethynylene units. Several examples are presented that elucidate the structural, optical, and electronic consequences of incorporating these fragments in the aromatic decks, particularly relating to applications in organic optoelectronics.

Chiral Isothiourea-Catalyzed Kinetic Resolution of 4-Hydroxy[2.2]paracyclophane

“…Substituted [2.2]paracyclophanes are fascinating planar chiral molecules [1][2][3][4][5][6][7][8][9][10][11][12] which have been systematically investigated since Brown and Farthing discovered the formation of the unsubstituted parent [2.2]paracyclophane 1 via gas phase pyrolysis of para-xylene in 1949 already [5]. Over the years, these compounds established themselves as a unique class of "bent and battered" [6] strained molecules with remarkable chemical and physical properties [1][2][3][4][7][8][9]. Besides their potential applications in material and polymer chemistry [1,2,[7][8][9], these planar chiral molecules have been very successfully used in asymmetric catalysis [3,4,[10][11][12].…”

“…Over the years, these compounds established themselves as a unique class of "bent and battered" [6] strained molecules with remarkable chemical and physical properties [1][2][3][4][7][8][9]. Besides their potential applications in material and polymer chemistry [1,2,[7][8][9], these planar chiral molecules have been very successfully used in asymmetric catalysis [3,4,[10][11][12]. Accordingly, the development of methods for the asymmetric synthesis of enantiomerically pure, or at least enantiomerically enriched, derivatives that can be utilized as building blocks for more demanding ligands and catalysts became a task of high importance.…”

Beyond Simple Substitution Patterns – Symmetrically Tetrasubstituted [2.2]Paracyclophanes as 3D Functional Materials

“…The extraordinary configuration of the molecule displays a face‐to‐face arrangement of a two slightly‐bent aromatic rings, with short inter‐ring distances between 2.83 and 3.09 Å. It allows an effective transannular charge transfer between the benzene rings, leading to unique applications of PC derivatives in optoelectronics, non‐linear optics, chemical vapor deposition or photoluminescent conjugated polymers , , . Until recently, most of these materials were based on mono‐ or disubstituted PCs due to their well‐known chemistry .…”

“…It allows an effective transannular charge transfer between the benzene rings, leading to unique applications of PC derivatives in optoelectronics, non-linear optics, chemical vapor deposition or photoluminescent conjugated polymers. [2,7,9] Until recently, most of these materials were based on mono-or disubstituted PCs due to their well-known chemistry. [10] Higher substituted PCs were barely isolated, [11,12] although the formation of symmetrical tetrasubstituted PCs was reported by the elimination of sulfur for appropriately substituted 2,11-dithia [3.3]paracyclophanes in low yields.…”

Substituent effect on inter-ring interaction in paracyclophanes

“…Due to their electronic properties and rigid structure, [2.2]paracyclophanes have found an application in manifold branches of chemistry and technology. As an example, let us mention the designing of optoelectronic materials [1,2], materials for photonics and electronics [3], catalysts in polymer synthesis [4], synthesis of chiro-optically active compounds [5,6], as well as in biology and medicine [7] or supramolecular chemistry [8]. One of the important challenges is the synthesis of new functionalized [2.2]paracylophanes and the investigation of the substituents' influence on their chemical, electronic, and structural properties [3].…”