Rubrene (5,6,11,12-tetraphenyltetracene) is a red colored

polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...

. Rubrene is used as a sensitiser in

chemoluminescence Chemiluminescence (also chemoluminescence) is the emission of light (luminescence) as the result of a chemical reaction. There may also be limited emission of heat. Given reactants A and B, with an excited intermediate ◊, : + -> lozenge - ...

and as a yellow light source in

lightstick A glow stick, also known as a light stick, chem light, light wand, light rod, and rave light, is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light ...

Electronic properties

As an

organic semiconductor Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in the form of molecular crystals or ...

, the major application of rubrene is in

organic light-emitting diode An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light i ...

s (OLEDs) and

organic field-effect transistor An organic field-effect transistor (OFET) is a field-effect transistor using an organic semiconductor in its channel. OFETs can be prepared either by vacuum evaporation of small molecules, by solution-casting of polymers or small molecules, or ...

s, which are the core elements of flexible displays. Single-crystal

transistors upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

can be prepared using crystalline rubrene, which is grown in a modified zone furnace on a temperature gradient. This technique, known as physical vapor transport, was introduced in 1998. Rubrene holds the distinction of being the organic semiconductor with the highest carrier mobility, reaching 40 cm²/(V·s) for

holes A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of en ...

. This value was measured in OFETs prepared by peeling a thin layer of single-crystalline rubrene and transferring to a Si/SiO₂ substrate.

Crystal structure

Several polymorphs of rubrene are known. Crystals grown from vapor in vacuum can be

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

triclinic 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is ...

, and

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

motifs. Orthorhombic crystals (

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...

B_bam) are obtained in a closed system in a two-zone furnace at ambient pressure.

Synthesis

Rubrene is prepared by treating 1,1,3-Triphenyl-2-propyn-1-ol with

thionyl chloride Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately per year bein ...

. :

The resulting chloro

allene In organic chemistry, allenes are organic compounds in which one carbon atom has double bonds with each of its two adjacent carbon centres (). Allenes are classified as diene#Classes, cumulated dienes. The parent compound of this class is propa ...

undergoes

dimerization A dimer () (''wikt:di-, di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, Covalent bond, covalent or Intermolecular force, intermolecular. Dimers also have significant im ...

and

dehydrochlorination In chemistry, dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate. The reaction is usually associated with the synthesis of alkenes, but it has wider applications. Dehydrohalogenation from alkyl hali ...

to give rubrene. : Rubrene synthesis

Redox properties

Rubrene, like other polycyclic aromatic molecules, undergoes redox reactions in solution. It oxidizes and reduces reversibly at 0.95 V and −1.37 V, respectively vs

SCE SCE is an abbreviation with multiple meanings: Science * Short-channel effect, a secondary effect describing the reduction in threshold voltage Vth in MOSFETs with non-uniformly doped channel regions as the gate length increases * Saturated calomel ...

. When the cation and anion are co-generated in an electrochemical cell, they can combine with annihilation of their charges, but producing an excited rubrene molecule that emits at 540 nm. This phenomenon is called

electrochemiluminescence Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrogenerated chemiluminescence, electrochemically generated intermediates undergo a highl ...

References

{{reflist Polycyclic aromatic hydrocarbons Organic semiconductors Fluorescent dyes