Synthetic organic spin chemistry for structurally well-defined open-shell graphene fragments

Abstract

Graphene, a two-dimensional layer of sp(2)-hybridized carbon atoms, can be viewed as a sheet of benzene rings fused together. Three benzene rings can be combined in three different ways, to yield linear anthracene and angular phenanthrene, where the rings share two C-C bonds, and the phenalenyl structure where three C-C bonds are shared between the rings. This third structure contains an uneven number of carbon atoms and, hence, in its neutral state, an uneven number of electrons--that is, it is a radical. All three structures may be viewed as being sections of graphene. Extension of this concept leads to an entire family of phenalenyl derivatives--'open-shell graphene fragments'--that are of substantial interest from the standpoint of fundamental science as well as in view of their potential applications in materials chemistry, in particular quantum electronic devices. Here we discuss current trends and challenges in this field.

Zero-energy states of graphene triangular quantum dots in a magnetic field

“…[11][12][13] Considerable experimental effort has been made aiming at producing graphene nanostructures with desired shape and edges. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Among graphene nanostructures, nanoribbons and quantum dots are of particular interest. In graphene quantum dots, a size-dependent energy gap opens, [33][34][35] and its magnitude is determined by shape and edge termination.…”

Effects of long-range disorder and electronic interactions on the optical properties of graphene quantum dots

“…Moreover, the electronic and optical properties of graphene can be manipulated at the nanoscale in a desired way by controlling lateral size, shape, type of edge, doping level and the number of layers in graphene nanostructures [11][12][13][14][15][16]. Among those various nanostructures of graphene, graphene quantum dots (GQDs) [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] offer a possibility to simultaneously control the electronic, magnetic and optical functionalities in a single material.…”

Near-infrared absorption of π-stacking columns composed of trioxotriangulene neutral radicals

“…One-dimensional (1D) columns of ion-radical species of tetracyanoquinodimethane and tetrathiafulvalene derivatives exhibit NIR absorption bands at 1000-2000 nm. [7][8][9][10] 1D π-stacked arrays of neutral π-radicals, which we term 'π-stacked radical polymers', 11 are constructed without formation of the σ-bonds, and absorb long-wavelength light. Phenalenyl (PNL) is a carbon-centered neutral π-radical with a delocalized spin structure.…”