WO2015097078A2

WO2015097078A2 - Small molecule heteroacenes as semiconductors

Info

Publication number: WO2015097078A2
Application number: PCT/EP2014/078659
Authority: WO
Inventors: Miquel PLANELLS; Iain Mcculloch; Jenny Elizabeth DONAGHEY; Roland Martin
Original assignee: Solvay Sa; Imperial Innovations Ltd
Priority date: 2013-12-24
Filing date: 2014-12-19
Publication date: 2015-07-02
Also published as: WO2015097078A3

Abstract

Heteroacene compounds having a structure represented by the following formula I and their use in organic electronic devices.

Description

Small molecule heteroacenes as semiconductors

Technical field

[0001] The present invention relates to heteroacenes and to their use in organic electronic devices as senniconductors.

Background art

[0002] Senniconductors are used in electronic components such as transistors, diodes and integrated circuits. While organic senniconductors may replace in certain cases inorganic senniconductors, their specific properties are predicted to enable many new applications if problems regarding stability and production efficiency are overcome. Examples are applications such as solar cells, displays, sensors, RFID tags and smart-ID tags.

[0003] Organic semiconductors have several advantages compared to

conventional inorganic semiconductors. They enable flexible devices and have a low weight. Ideally organic thin film transistors (OTFTs), organic photovoltaic cells (OPV) and photodetectors, organic light emitting diodes (OLEDs), memory arrays and sensors, and even whole circuits can be printed at high speed over large areas, thus lowering the cost and increasing the efficiency of production. Especially radio-frequency identification (RFID) tags and smart labels have to be thin and flexible. Displays based on organic semiconductors which are not planar but bent have been developed.

[0004] Organic TFTs are essentially built like inorganic TFTs. They comprise a gate electrode, a gate insulator, a source electrode, a drain electrode and a semiconductor layer. The latter is an organic semiconductor in case of OTFTs. The gate electrode controls the conductivity of the semiconductor layer, and it thereby controls the strength of the current between source electrode and drain electrode.

[0005] Polythiophenes are well-known organic semiconductors and have been intensively researched. They have an extended conjugated ττ-system from which an electron can be easily removed. The speed with which the hole can move depends on the applied electric field and is measured as hole mobility (unit cm²V-¹S^"1). Instead of removing an electron it is possible to add an electron and subsequently to measure the electron mobility. The term carrier mobility relates to both electron and hole mobility. It should be noted that the carrier mobility is usually measured within a transistor setup and can thus vary depending on the specific setup. Nevertheless values measured with different transistors can convey a general order of magnitude of the achieved carrier mobility for a given semiconductor. The carrier mobility of the organic semiconductor layer is, among other factors, affected by the size of the π-system, substituents, the efficiency of n- stacking and the degree of order in the layer which depends further on the processing conditions.

[0006] Compounds for organic semiconductors which are to be used as electronic components in any of these applications should have a high carrier mobility. Additionally, a high stability towards air, humidity and light is desirable. If the printing of said devices is intended, the organic

semiconductors have to be dissolvable in suitable organic solvents.

[0007] A large planar heteroacene system with six fused rings has been used as a copolymer by L. Biniek et al. with thiophene as a second monomeric species (Biniek et al., Macromolecules, 2013, 46, 727-735). A hole mobility of 0.1 cm²V-¹S^"1 has been measured for the resulting polymer. A similar system has been disclosed by R. Rieger et al. with a carrier mobility of 0.001 cm²V- s-¹ (Rieger et al., Macromolecules, 2010, 43, 6264-6267).

[0008] WO 201 1/067192 discloses a range of polymers based on the same core aromatic system as disclosed in the references mentioned above for use as semiconductors. The general formula of these polymers is given below, wherein pi is a monocyclic or polycyclic moiety.

[0009] A single working example is provided in said patent application and the respective product has a carrier mobility of 0.001 cm²V-¹S^"1

[0010] A problem of said polymers is their low solubility in organic solvents which is disadvantageous if printing of integrated or logic circuits is intended. If these polymers can be dissolved at all environmentally problematic chlorinated solvents are usually necessary.

[001 1] All of the above mentioned polymers are based on the same core system and usually have a low solubility in organic solvents (cf. Rieger et al.).

[0012] One way to solve this problem of low solubility is to use a non-polymeric conjugated π-system. Such a planar aromatic structure with six fused rings has been disclosed in US 7,816,673. One of the structures disclosed in this reference is shown below. However, carrier mobility is not very high at 0.08 cm²V- s-¹.

Problems to be solved

[0013] There is a need for compounds which are useful as organic

semiconductors in organic electronic devices and which can be dissolved in environmentally acceptable solvents. As mentioned above, known polymeric heteroacenes usually show a low solubility in most solvents. A significantly higher solubility in non toxic solvents would improve the fabrication of organic thin films and corresponding electronic devices.

[0014] Furthermore, charge mobility and stability versus light, humidity and air often are very low. Non-polymeric π-systems as shown above, have not exhibited significantly improved properties compared to conventional polymeric compounds in this respect. In order to improve the lifetime and efficiency of organic electronic devices these properties have to be improved as well.

Object of the present invention [0015] It was thus an object of the present invention to provide a use of small molecules as organic semiconductors in at least one layer of organic electronic devices, wherein these molecules have improved properties regarding carrier mobility, stability and additionally have a higher solubility in suitable solvents than polymeric derivatives of the prior art as disclosed above.

[0016] This object is achieved by the use of compounds as disclosed in claim 1.

[0017] A further object of the invention is to provide certain new compounds

according to claim 3 which are suitable for the use in accordance with the present invention.

[0018] Especially preferred embodiments of the present invention are described in the dependent claims and the detailed description hereinafter.

Detailed description of the invention

[0019] The present invention relates to heteroacenes and to their use as

semiconductors in organic electronic devices. Small molecules according to the invention show a satisfactory solubility in suitable solvents. They can be substituted with different groups to tune the desired properties of high charge carrier mobility, improved solubility and stability.

[0020] Hereinafter, a class of heteroacenes and their use as semiconductors in organic electronic devices is disclosed. Functional groups which tune desired properties are identified.

[0021] The present invention relates to the use of heteroacene compounds

having a structure represented by the following formula I

wherein

- Y and Y' are independently selected from a group consisting of a nitrogen atom and a CR-group, - Χι , Χι', X2 and X2' are independently selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom and a NR'-group,

- R' is a Ci-Cio group independently selected from hydrogen, alkyl,

heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and preferably is R' an unsubstituted alkyl or alkenyl group or a hydrogen atom,

- R, Ri , Ri', R2, R2', R3 and R3' are independently selected from the group consisting of

o a hydrogen atom,

o a halogen atom,

o cyano group,

o a nitro group,

o a Ci-C3o group, preferably a Ci-Cio group, which is selected from alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and,

o a combination of up to three Ci-Cio groups, preferably up to two Ci- C10 groups, the same or different within each combination, which are selected from alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be substituted or unsubstituted,

as organic semiconductors in at least one layer of organic electronic devices.

] The term "a combination of is used within the set of claims and refers to a connection of at least two distinct Ci-Cio groups by the formation of at least one covalent bond or by sharing a common bond. A combination of a cycloalkyl and a second cycloalkyl or an aryl to obtain a bicyclic ring system with two fused rings is thus possible as well. "Formation" and "combination" do not refer to a specific synthetic route, but indicate how a person skilled in the art would combine these groups in order to obtain a complete structure. Preferably one or two bonds are formed and

particularly preferably one bond is formed. Especially preferred are heteroacenes which comprise no such combinations of groups.

[0023] The molecules of the present invention show preferably a 2-fold rotational symmetry to improve synthetic accessibility and to favour order in the solid state. They comprise preferably at least one electron withdrawing group R, Ri ,

R2, R2', R3 or R3' to improve stability. Compounds according to claim 3 and claims dependent thereon represent preferred compounds for use in accordance with claim 1.

[0024] Groups which are alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl,

heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl and which may be substituted or unsubstituted will be described in detail hereafter. Descriptions and preferences stated subsequently apply to the

compounds of claim 3 as well.

[0025] An alkyl group may be linear or branched. Some embodiments of

heteroacenes according to the invention comprise at least one alkyl group selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso- butyl, tert-butyl, n-pentyl, sec-pentyl, 3-pentyl, 2-methylbutyl, 3- methylbutyl, 3-methylbut-2-yl, 2-methylbut-2-yl, neo-pentyl, n-hexyl, 2- hexyl; 3-hexyl, 2-methylpentyl, 3-methylpentyl, iso-hexyl, 1 ,1 - dimethylbutyl, 1 ,2-dimethylbutyl, 1 ,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3- dimethylbutyl, 2-ethylbutyl, neo-hexyl, 1 ,1 ,2-trimethylpropyl, 1 ,2,2- trimethylpropyl, 1-ethyl-1 -methylpropyl, 1 -ethyl-2-methylpropyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl.

[0026] An alkenyl group contains at least one internal or terminal double bond in an alkyl group. An alkynyl group contains at least one internal or terminal triple bond in an alkyl group.

[0027] An aromatic group refers to an aromatic ring or a combination of aromatic rings. It is not necessary for every ring within the aromatic system to be aromatic in order for the entire group to be an aromatic group as a whole. A heteroacene according to the invention can thus include naphthyl, anthracenyl and/or benzyl groups, to name only a few examples. [0028] A cycloalkyi group refers to a non-aromatic ring or a combination of non- aromatic rings. Conjugated bonds are possible. A heteroacene according to the invention can thus include e.g. cyclohexyl groups and/or cyclopentyl groups.

[0029] A heteroalkyi group is an alkyl group in which at least one Ch -group, CH- group or carbon atom has been replaced by at least one heteroatom or by a group in such a way that a heteroatom replaces the removed carbon. If all carbon atoms are replaced the resulting group is not considered a heteroalkyi group. A heteroacene according to the invention can thus include alkoxy groups, (alkyl)sSn-groups or (alkyl)sSi-groups. Preferred heteroalkyi groups comprise silicon, nitrogen, oxygen or sulphur as a heteroatom. Particularly preferred are ethers and thioethers.

[0030] A heteroalkenyl group is an alkenyl group in which at least one Chb-group, CH-group or carbon atom has been replaced by at least one heteroatom or by a group in such a way that a heteroatom replaces the removed carbon. If all carbon atoms are replaced the resulting group is not considered a heteroalkenyl group. A heteroacene according to the invention can thus be a (alkyl)sSi-alkenyl group.

[0031] A heterocycloalkyl group is a cycloalkyi group in which at least one Chb- group, CH-group or carbon atom has been replaced by at least one heteroatom or by a group in such a way that a heteroatom replaces the removed carbon. If all carbon atoms are replaced the resulting group is not considered a heterocycloalkyl group. Preferred heterocycloalkyl groups are shown below.

X = 0, S, Se, NH, PH, SiH ₂

The position of chemical bond(s) of these moieties to any other parts of the molecule is (are) not indicated; such chemical bonds can replace any hydrogen within the heterocycloalkyl structures shown above.

[0032] A heteroalkynyl group is an alkynyl group in which at least one Chb-group, CH-group or carbon atom has been replaced by at least one heteroatom or by a group in such a way that a heteroatom replaces the removed carbon. If all carbon atoms are replaced the resulting group is not considered a heteroalkynyl group. A preferred heteroalkynyl group is a (R")3Si-alkynyl group as shown below, wherein R" is an alkyl or an alkenyl group. Especially preferred is a (R")3Si-alkynyl group, wherein R" at each occurrence independently is selected from a C1-C6 alkyl or a C2-C8 alkenyl group.

[0033] A heteroaryl group is an aryl group in which at least one Chb-group, CH- group or carbon atom has been replaced by at least one heteroatom or by a group in such a way that a heteroatom replaces the removed carbon. If all carbon atoms are replaced the resulting group is not considered a heteroaryl group. Preferred heteroaryl groups are shown below. Fused bicyclic systems of one of the groups as shown below and pyridine or benzene are preferred heteroaryl groups, too.

The position of chemical bond(s) of these moieties to any other molecules is (are) not indicated; such chemical bonds can replace any hydrogen within the heteroaryl structures shown.

[0034] The term "substituted" indicates that the corresponding substituted group has a substituent which is covalently bound. A substituted group is any group such as alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl,

heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl in which at least one hydrogen atom is substituted by at least one functional group. Possible functional groups may be, but are not limited to, hydroxyl groups, carbonyl groups, ester groups, halogen atoms, cyano groups, amino groups, nitro groups and thiol groups. Preferred examples of substituted heteroalkyl groups include amides and esters. Preferred examples of substituted alkyl groups include CF3-groups and ketones.

[0035] The present invention relates to the use of heteroacene compounds in organic electronic devices. These organic electronic devices are preferably organic thin-film transistors and organic-light-emitting-diodes, organic solar cells, sensors, RFID tags, smart labels, memory elements and integrated or logic circuits.

[0036] Heteroacenes according to the invention are preferably suitable for

printing of organic thin film transistors (OTFTs) and/or semiconductor layers and especially preferable using an ink-jet printing method. In such applications they are preferably used as component of an ink composition.

[0037] Preferred heteroacenes according to the invention are stable in ambient air for a at least one hour, preferably for at least one week and most preferably for at least one month. Stable under certain conditions and in a fixed timeframe indicates that a material comprising heteroacenes according to the invention does not significantly change its electronic properties due to exposure to air, humidity and/or light. A change of electronic properties due to an excitation of a photochemical transition state of a molecule without a corresponding irreversible breaking or formation of a chemical bond is not considered an indicator of instability. Preferred heteroacene compounds in accordance with the present invention are represented by one of formulas II to IV

IV

wherein

- R, R2, R2', R3, R3', R5, R5', R6 and Re' are independently selected from the group consisting of

o a hydrogen atom,

o a halogen atom,

o cyano group,

o a nitro group,

- at least one of R₄ and R₄' is selected from the group consisting of o a chlorine atom,

o a fluorine atom,

o a cyano group, o a nitro group,

o a Ci-C3o group, preferably a C1-C10 group, which is selected from

alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and,

o a combination of up to three Ci-Cio groups, preferably up to two Ci- C10 groups, the same or different within each combination, which are selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be substituted or unsubstituted,

- Y and Y' are independently selected from a group consisting of a

nitrogen atom and a CR-group and

- Xi , Xi', X2, X2', X3, X3', X4 and X₄' are independently selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom and a NR'-group and wherein X3 and/or X₄ is different from S, preferably X3 or X₄, and wherein R' is a Ci-Cio group independently selected from hydrogen, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and preferably is R' an unsubstituted alkyl or alkenyl group.

[0039] Heteroacene compounds represented by formula II are particularly

preferred. Additionally, heteroacene compounds represented by formula III are preferred as well. Without being bound to any theory, it is believed that the electron withdrawing character of the nitrogen atoms in the compounds of formula III is beneficial for the use in accordance with the present invention.

[0040] Another preferred heteroacene compound is according to any of the above formulas I to IV, wherein at least one of R2, R2', R3, R3', R4, R4', R5, R5', R6 and Re' is a Ci-C3o alkyl group, a (R")3Si-alkynyl group or a fluorine atom.

[0041] Alkyl groups are preferred as they usually increase the solubility of the heteroacene compounds in organic solvents. Preferred embodiments according to the invention are shown below, n, n' and n" are integers from 1 to 12 and preferably are n > 5, n' < 6 and n" < 6.

X = 0, S, Se, NH

[0042] Preferred are also compounds which comprise electron withdrawing

groups attached to the fused rings of the heteroacene. Such electron withdrawing groups or atoms usually increase the stability of the

compound.

[0043] A preferred electron withdrawing group is a fluorine atom, a chlorine atom, a cyano group, a (R")3Si-alkynyl group, an electron withdrawing

heteroalkyl group or an electron withdrawing heteroaryl group, wherein R" is a Ci-Cio group selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted. Especially preferred for R" are unsubstituted alkenyl groups or unsubstituted alkyl groups.

[0044] In a particularly preferred embodiment a heteroacene compound

according to the invention electron withdrawing groups comprise only fluorine atoms, chlorine atoms, cyano groups and (R")3Si-alkynyl groups.

[0045] Especially preferred are also heteroacene compounds in accordance with one of the structures ll-IV wherein at least one of R2, R2', R3 and R3' is an electron withdrawing group. Preferred embodiments with two electron withdrawing groups are shown below. X is selected from O, S, Se and NH.

Preferred are also compounds which comprise more than two electron withdrawing groups attached to the fused rings of the heteroacene compound. Especially preferred embodiments are shown below, n, n' and n" are integers from 1 to 12 and preferably are n > 5, n' < 6 and n" < 6.

X = O, S, Se, NH

Preferred are also compounds which comprise electron withdrawing group as well as alkyl groups attached to the fused rings of the heteroacene. These compounds show a combination of increased solubility and stability. Especially preferred embodiments are shown below, n, n' and n" are integers from 1 to 12 and preferably are n > 5, n' < 6 and n" < 6.

X = 0, S, Se, NH

[0049] Particularly preferred are also such heteroacene compounds in

accordance with any of the above structures wherein X is a sulphur atom.

[0050] Particularly preferred are also such heteroacene compounds in

accordance with any of the above examples comprising fluorine atoms or (R")3Si-alkynyl groups in which said groups or atoms are replaced by nitrile groups.

[0051] Heteroacene compounds, wherein Ri is the same as Ri' or R₄ is the same as R₄' are preferred. Especially preferred are heteroacene compounds wherein (if present) also R2 is the same as R2', R3 is the same as R3', R4 is the same as R₄', R5 is the same as R5', R6 is the same as R6', Xi is the same as Χι', X2 is the same as X2', X3 is the same as X3', X4 is the same as X₄' and Y is the same as Y'. These compounds show a higher synthetic accessibility and thus production of semiconducting materials with defined characteristics is facilitated. Particularly preferred are compounds which show a 2-fold rotational symmetry.

[0052] Heteroacene compounds having a molecular weight in the range of from

284-3000 g/mol, particularly 284-1000 g/mol, are preferred and considered as small molecules. [0053] Polymers or oligomers comprising repeating units obtained by replacing R5, R5', R6 and R6' in formulas III or IV by chemical bonds have also proved to be suitable for use in accordance with the present invention. Such polymers or oligomers are also novel and constitute another embodiment of the present invention. They can be obtained in accordance with synthetic methods known to the skilled person so that no further details need to be given here.

[0054] Compositions comprising at least one of the heteroacene compounds are preferably used as organic semiconductors and especially compositions comprising additionally at least one amorphous molecular or polymer binder which is electrically insulating or semiconducting in addition to the heteroacene compounds are preferred.

[0055] Organic electronic devices comprising at least one layer comprising at least one heteroacene compound represented by formulas I to IV are preferred. Especially preferred are organic electronic devices selected from organic thin-film transistors, an organic-light-emitting-diodes, organic solar cells, sensors, RFID tags, smart labels, memory elements and integrated or logic circuits.

[0056] The heteroacene compounds according to the present invention can be synthesized using a reaction pathway with a Stille coupling or a Suzuki and a Negishi coupling. A reaction pathway with a Stille coupling is shown below and a reaction pathway with a Suzuki and a Negishi coupling is shown within the examples.

2. CISnMe₃

Materials and methods used within the examples are described, insofar as a person skilled in the art would require such information. All starting materials were reagent grade and purchased from commercial suppliers unless otherwise specified. Anhydrous solvents were bought from Acros Organics under molecular sieve (less than 0.01 % H2O). Characterization: 1H and ¹³C NMR spectra were recorded on Bruker Advance 400 spectrometer (400 MHz for ¹H and 100 MHz for ¹³C) at 298 K. The deuterated solvents are indicated; chemical shifts, δ, are given in ppm, referenced to the solvent residual signal (¹H, ¹³C). Purification by silica plug indicates a similar procedure to column chromatography on silica gel, wherein only a short column is used and only impurities which do not run well on the column are separated. Such a procedure can be useful, as less solvent, silica gel and time are needed. Especially useful is such a procedure for compounds which are not indefinitely stable under conditions of column chromatography. If compounds are sufficiently stable a column chromatography can often be used instead, but might be less time efficient.

[0058] (Example 1 : 3,6-dibromothieno[3,2-b]thiophene

2,5-dibromothieno[3,2-b]thiophene (12.0 g, 40 mmol) was added in a oven-dried round flask with 600 ml_ of dry Et.20. The mixture was cooled down to -78 °C and 50 ml_ of LDA 2M in THF was added dropwise at -78 °C under Argon atmosphere. The mixture was allowed to warm up at room temperature, and stirred overnight in the dark. Afterwards, the crude product was quenched with chilled water, extracted with Et^O and washed with brine. The organic layer was dried over MgSO₄ and filtered off. The crude product was purified by column chromatography (S1O2, toluene) to afford the product as pale white solid (1 1.8 g, 96% yield).

1H NMR (400 MHz, CDCI3) δ_Η: 7.34 (s, 2H). ¹³C NMR (100 MHz, CDCI3) 5c: 139.4; 125.3; 103.2.

[0059] (Example 2: 3,6-dibromo-2,5-diiodothieno[3,2-b]thiophene

3,6-dibromothieno[3,2-b]thiophene (12.0 g, 40 mmol) was added in a round bottom flask with 600 ml_ of CHC and 300 ml_ of AcOH. N- iodosuccinimide (40.5 g, 180 mmol) was added portion wise over 30 minutes and the mixture was at r.t. under Argon for 4 days. Afterwards, 650 ml_ of distilled water was poured and the mixture stirred for 1 hour. The formed precipitate was filtered off, washed with 300 ml_ of water and 30 ml_ of MeOH, dried under air to afford the product as pale white solid (18.6 g, 84% yield).

¹³C NMR (100 MHz, DMSO-de) 5_C: 141.6; 1 1.6; 87.7.

[0060] Example 3: 3,6-dibromo-2,5-bis(3-bromothiophen-2-yl)thieno[3,2- b]thiophene

3,6-dibromo-2,5-diiodothienot[3,2-b]thiophene (1.87 g, 3.4 mmol) and

Pd(PPh3)4 (196 mg, 0.17 mmol) were added in an oven-dried microwave vial. A 0.5 M solution of (3-bromothiophen-2-yl)zinc(ll) bromide in THF

(18 ml_, 9 mmol) was added and the solution degassed for 30 minutes.

The mixture was heated for 1 minute at 80 °C and 9 minutes at 100 °C in a microwave reactor. The crude solution was cooled down and quenched with water. The formed precipitate was filtered off, washed with MeOH, acetonitrile and dried under air to afford the product as yellow solid

(1.85 g, 88% yield).

¹H NMR (400 MHz, CDCIs) δ_Η: 7.48 (d, J = 5.4 Hz, 2H); 7.13 (d, J = 5.4 Hz, 2H).¹³C NMR (100 MHz, CDCIs) 5_C: not soluble enough.

[0061] Example 4: 1 ,1 '-(5,5'-(3,6-dibromothieno[3,2-b]thiophene-2,5-diyl)bis(4- bromothiophene-5,2-diyl))bis(decan-1-one)

The compound of Example 3 (1.86 g, 3 mmol) was added in a round bottom flask with 120 ml_ of CH2CI2. The mixture was cooled down to 0 °C and AICI3 (1.2 g, 9 mmol) was added portion wise followed by the injection of decanoyl chloride (18.6 ml_, 90 mmol). The mixture was allowed to warm to room temperature and stirred under Argon atmosphere for 72 h. Afterwards, the mixture was quenched by the addition of MeOH at 0 °C and then stirred for an extra 16 h. at room temperature The crude product was purified by silica plug (CH2CI2) followed by recrystallization in hexane to afford the product as yellow solid (977 mg, 35% yield).

1H NMR (400 MHz, CDCI3) δ_Η: 7.68 (s, 2H); 2.89 (t, J = 7.4 Hz, 4H); 1.76 (m, 4H); 1.27 (m, 24H); 0.88 (t, J = 7.0 Hz, 6H).

¹³C NMR (100 MHz, CDC ) 5_C: 192.4; 144.8; 140.4; 136.0; 134.5; 130.9; 1 13.1 ; 105.5; 39.1 ; 31.9; 29.5; 29.4; 29.3 (x2); 24.5; 22.7; 14.1.

[0062] Example 5: (Z)-2,2'-(tetradec-7-ene-7,8-diyl)bis(4,4,5,5-tetramethyl-1 ,3,2- dioxaborolane)

Bis(pinacolato)diboron (5.6 g, 22 mmol) and Pt(PPh₃)4 (995 mg, 0.8 mmol) were placed in an oven-dried flask under argon with 30 ml_ of anhydrous and degassed DMF. Tetradec-7-yne (5 ml_, 20 mmol) was added via syringe and the mixture stirred at 80 °C overnight. After cooling to room temperature, the reaction mixture was quenched with distilled water (100 ml_) and extracted with hexane (100 ml_). The organic phase was washed with water again, dried over MgSO₄ and filtered off. The crude product was purified by column chromatography (S1O2, Hexanes / 5% EtOAc) to afford the product as colourless oil (7.8 g, 86% yield).

¹H NMR (400 MHz, CDCb) δ_Η: 2.16 (t, J = 6.9 Hz, 4H); 1.26 (m, 40H), 0.86 (t, J = 6.9 Hz, 6H).¹³C NMR (100 MHz, CDCb) 5_C: 144.2; 83.3; 31.9; 31.0; 29.9 (x2); 25.0; 22.7; 14.7.

[0063] Example 6: (Z)-2,2'-(but-2-ene-2,3-diyl)bis(4,4,5,5-tetramethyl-1 ,3,2- dioxaborolane)

Bis(pinacolato)diboron (8.4 g, 33 mmol) and Pt(PPh₃)4 (1 g, 0.75 mmol) were placed in an oven-dried flask under argon with 60 ml_ of anhydrous and degassed DMF. 2-Butyne (2.6 ml_, 30 mmol) was added via syringe and the mixture stirred at 80 °C overnight. After cooling to room

temperature, the reaction mixture was quenched with distilled water (300 ml_) and extracted with Et2O (300 ml_). The organic phase was washed with water again, dried over MgSO₄ and filtered off. The crude product was purified by column chromatography (S1O2, CHC ) to afford the product as white solid (9.12 g, 98% yield).

¹H NMR (400 MHz, CDC ) δ_Η: 1.69 (s, 6H); 1.24 (m, 24H). ¹³C NMR (100 MHz, CDCb) 5c: 140.1 ; 83.3; 24.9; 16.4.

Example 7: (Z)-2,2'-(hex-3-ene-3,4-diyl)bis(4,4,5,5-tetramethyl-1 ,3,2- dioxaborolane)

Bis(pinacolato)diboron (8.4 g, 33 mmol) and Pt(PPh3)4 (1 g, 0.75 mmol) were placed in an oven-dried flask under argon with 60 ml_ of anhydrous and degassed DMF. 3-Hexyne (3.4 ml_, 30 mmol) was added via syringe and the mixture stirred at 80 °C overnight. After cooling to room

temperature, the reaction mixture was quenched with distilled water (300 ml_) and extracted with Et2O (300 ml_). The organic phase was washed with water again, dried over MgSO₄ and filtered off. The crude product was purified by column chromatography (S1O2, CHCb) to afford the product as white solid (9.7 g, 96% yield).

¹H NMR (400 MHz, CDC ) δ_Η: 2.17 (q, J = 7.3 Hz, 4H); 1.24 (m, 24H); 0.92 (t, J = 7.3 Hz, 6H).¹³C NMR (100 MHz, CDCb) 5_C: 145.3; 83.3; 24.9; 23.6; 14.3. [0065] Example 8: (Z)-1 ,2-bis(4,4,5,5-tetramethyl-1 ,3,2-dioxaborolan-2-yl)-1 ,2- bis(trimethylsilyl)ethene

Bis(pinacolato)diboron (16.4 g, 64 mmol) and Pt(PP i3)4 (1 g, 0.75 mmol) were placed in an oven-dried flask under argon with 1 15 mL of anhydrous and degassed DMF. Bis(trimethylsilyl)acetylene

(10 g, 58 mmol) was added via syringe and the mixture stirred at 90 °C for 48 h. After cooling to room temperature, the reaction mixture was quenched with distilled water (300 mL) and extracted with Et2O (300 mL). The organic phase was washed with water again, dried over MgSO₄ and filtered off. The crude product was purified by silica plug in CH2CI2 followed by column chromatography (S1O2, Hexanes/CHC 1 : 1 ). Pure product was obtained by recrystallization in MeOH as white solid (3.4 g, 14% yield).

¹H NMR (400 MHz, CDCI3) δ_Η: 2.17 (q, J = 7.3 Hz, 4H); 1.24 (m, 24H); 0.92 (t, J = 7.3 Hz, 6H). ¹³C NMR (100 MHz, CDC ) 5_C: 83.6; 26.4; 1.12.

[0066] Example 9:

4,5,10,1 1 -Tetrahexylthieno[3',2':6,7][1]benzothieno[3,2-b]-thieno[3,2- g][1]benzothiophene

The tetrabrominated compound of example 3 (310 mg, 0.5 mmol),

Pd(OAc)2 (5.6 mg, 0.025 mmol) and SPhos (2-Dicyclohexylphosphino- 2',6'-dimethoxybiphenyl, 20 mg, 0.05 mmol) were added in an oven-dried microwave vial and dried over high vacuum for 30 minutes. Diboronic ester (493 mg, 1.1 mmol) was added to a round bottom flask with 10 mL of THF and the mixture was degassed by bubbling argon for 1 hour. Afterwards, the mixture was transferred via cannula to the microwave vial and stirred under argon. Then, 3 ml_ of a previously degassed 2M NaOH aqueous solution was added via syringe and the mixture was stirred at 80 °C overnight. The mixture was quenched by adding NH₄CI aqueous solution and extracted with Et2O. The organic phase was dried over MgSO₄ and filtered off. The crude product was purified by column chromatography (S1O2, Hexanes) to afford the product as yellow solid (75 mg, 22% yield). 1H NMR (400 MHz, CDCI3) δ_Η: 7.50 (d, J = 5.4 Hz, 2H); 7.43 (d, J = 5.4 Hz, 2H); 3.25 (t, J = 8.1 Hz, 4H); 3.08 (t, J = 8.1 Hz, 4H); 1.72 (m, 16H); 1.39 (m, 16H); 0.96 (t, J = 6.9 Hz, 6H); 0.93 (t, J = 6.9 Hz, 6H).

1³C NMR (100 MHz, CDC ) 5_C: 138.0; 133.9; 132.9; 132.0; 131.5; 131.1 ; 130.5; 124.2; 123.8; 31.9 (x2); 31.8 (x2); 31.2; 30.6; 30.1 ; 30.0; 22.9; 22.8; 14.3 (x2).

[0067] A very large range of heteroacenes is accessible by the synthetic methods in the examples using Stille, Negishi and/or Suzuki couplings.

[0068] The heteroacene compounds used in accordance with the present

invention preferably have electron or hole mobilities of at least 1 cm²Vs^"1 measured using a field-effect transistor in the saturation mode.

[0069] Accordingly, the heteroacene compounds in accordance with the present invention when used in at least one layer of organic electronic devices yield such devices with improved properties compared to the devices of the prior art.

[0070] High carrier mobility makes these compounds interesting new materials in semiconducting applications. Heteroacene compounds according to the invention have a well defined structure and molecular weight as opposed to previously disclosed polymers, as well as a higher solubility in

environmentally acceptable solvents. Solubility can be further increased by the use of hydrophobic substituents and results in improved processability. Additionally, stability is increased if electron withdrawing substituents are used

Claims

1. Use of heteroacene compounds having a structure represented by the

following formula I

wherein

Y and Y' are independently selected from a group consisting of a nitrogen atom and a CR-group,

Xi , Xi',X2 and X2' are independently selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom and a NR'-group,

R' is a Ci-io group independently selected from hydrogen, alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted,

R, Ri , Ri', R2, R2', R3 and R3' are independently selected from the group consisting of

o a hydrogen atom,

o a halogen atom,

o cyano group,

o a nitro group,

o a Ci-C3o group which is selected from alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and,

o a combination of up to three Ci-io groups, the same or different within each combination, which are selected from alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be substituted or unsubstituted,

as organic semiconductors in at least one layer of organic electronic devices.

2. Use in accordance with claim 1 wherein the organic electronic device is

selected from organic thin-film transistors, organic-light-emitting-diodes, organic solar cells, sensors, RFID tags, smart labels, memory elements and integrated or logic circuits.

3. Heteroacene compounds in accordance with any of formulas II to IV

IV

wherein

o a hydrogen atom,

o a halogen atom,

o cyano group,

o a nitro group,

o a Ci-C3o group which is selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted, and,

o a combination of up to three Ci-do groups, the same or different within each combination, which are selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be substituted or unsubstituted

- at least one of R₄ and R₄' is selected from the group consisting of

o a chlorine atom,

o a fluorine atom,

o a cyano group,

o a nitro group,

o a combination of up to three Ci-io groups, the same or different within each combination, which are selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be substituted or unsubstituted,

- Y and Y' are independently selected from a group consisting of a nitrogen atom and a CR-group and

- Xi , Xi', X2, X2', X3, X3', X4 and X₄' are independently selected from the group consisting of an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom and a NR'-group and wherein X3 and/or X₄ is different from S and wherein R' is a Ci-do group independently selected from hydrogen, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted.

4. Heteroacene compounds in accordance with claim 3 represented by formula II.

5. Heteroacene compounds in accordance with claim 3 represented by formula III.

6. Heteroacene compounds in accordance with claim 3, 4 and 5, wherein at least one of R2, R2', R3 and R3' is an electron withdrawing group.

7. Heteroacene compounds in accordance with claim 6, wherein the electron withdrawing group is a fluorine atom, a chlorine atom, a cyano group, a (R")3Si-alkynyl group, an electron withdrawing heteroalkyi group or an electron withdrawing heteroaryl group, wherein R" is a Ci-do group independently selected from alkyl, heteroalkyi, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl, each of which may be a substituted or unsubstituted.

8. Heteroacene compounds according to any claims 3 to 5, wherein at least one of R₂, R2', Rs, Rs', R4, R4', Rs, Rs', Re and R₆' is a Ci-C₃o alkyl group, a (R")₃Si- alkynyl group or a fluorine atom.

9. Heteroacene compounds according to any of claims 3 to 8, wherein R₄ is the same as R₄'.

10. Heteroacene compounds according to any of claims 3 to 9, wherein

o R2 is the same as R2',

o R₄ is the same as R₄'

o Xi is the same as Xi',

o X2 is the same as X2',

o X₄ is the same as X₄' and

o Y is the same as Y'.

1 1. Heteroacene compounds according to any of claims 3 to 10, having a

molecular weight in the range of from 284-3000 g/mol.

12. Compositions comprising at least one of the heteroacene compounds

according to any of claims 3 to 1 1.

13. Compositions according to claim 12, comprising at least one amorphous

molecular or polymer binder which is electrically insulating or semiconducting.

14. Organic electronic device comprising at least one layer comprising at least one heteroacene compound represented by formulas I to IV.

15. Organic electronic device in accordance with claim 14 selected from organic thin-film transistors, an organic-light-emitting-diodes, organic solar cells, sensors, RFID tags, smart labels, memory elements and integrated or logic circuits.