Synthesis, characterization, and reactions of 6,13-disubstituted 2,3,9,10-tetrakis(trimethylsilyl)pentacene derivatives

Pentacene has been actively studied as relevant materials in organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). However, the low solubility and low stability of pentacene in common organic solvents have hindered its applications. When exposed to light or at high concentration, pentacene is found to dimerize easily. Many research groups are currently working on the design and synthesis of novel substituted pentacenes, but few of them systematically reported physical properties such as molecular spectroscopy and electronic properties, which might elucidate the influence of substituents on HOMO-LUMO gaps. Furthermore, the reactive nature of the central ring in pentacenes makes pentacenes good dienes for Diels-Alder reactions. In this paper, a series of soluble 6,13-disubstituted 2,3,9,10-tetrakis(trimethylsilyl)pentacenes were synthesized and characterized. Their reactions, structures, and physical properties were also studied. In addition, bulky o-carboranyl substituted pentacene derivative 15 and 6-chloro-2,3,9,10-tetrakis(trimethylsilyl)pentacene (16) were synthesized for the first time. Compound 16 possesses the largest dihedral angle (7.7° with two adjacent benzene rings) and shows a wave structure. Diels-Alder reactions with acceptable efficiency were carried out between 16 and various dienophiles.