The invention generally concerns bifuran imide and methods of using same in the construction of furan-based polymers for organic electronics.
The field of organic electronics depends on the discovery of new materials which π-conjugated backbones endow them with desired properties. Good candidate materials are those that demonstrate small gaps between their highest occupied and lowest unoccupied molecular orbitals (small HOMO-LUMO gaps), strong fluorescence and good solid-state packing. A planar backbone results in good charge delocalization and mobility. These criteria are currently met by only a limited number of materials, with oligo- and polythiophenes and their derivatives currently dominating the field (nT, see
In a previous report, a new family of organic electronic materials have been disclosed, being the oxygen-containing analogues of oligothiophenes, namely, oligofurans (nF, n=3-9,
Bithiophene-imide (BTI,
Herein, the inventors of the technology disclose the development of bifuran-imide units as building units for the construction of stable furan linear or cyclic oligomers and polymers (nBFI) bearing a variety of functional groups, e.g., alkyl substituents such as hexyl (nBFI-H) or 2-ocyldodecyl (nBFI-OD) substituents.
The technology disclosed herein demonstrates the significantly better stability of bifuran-imide as compared with α-oligofurans and their potential uses.
The stable furan linear or cyclic oligomers and polymers (nBFI) of the invention have been prepared from novel building blocks that may be used in the construction of even higher or larger structural homologues of the compounds disclosed and exemplified herein. Thus, the invention further provides a synthetic toolbox comprising a variety of starting materials and intermediates that may be highly useful in the synthesis of not only furan-based materials but also in a variety of other related materials.
The innovative synthetic toolbox comprises a plurality of furan derivatives that may be substituted to afford further structural modifications, thereby granting the synthetic chemist with the ability to tailor different or improved electronic, optic or physical characteristic to the final compound.
In a first aspect, there is provided a compound of the general Formula (I):
wherein
each of R1 and R2, independently of the other, may be selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S;
each of R3, R4, R5 and R6, independently of the other, may be selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN, —CO2H, —OH, —SH, —NR′R″R″′, —NO2, (C1-C30alkyl)3Si— (C1-C30alkyl)3Sn—, trifluoromethanesulfonate (triflate) and halogen, wherein each of R′, R″ and R″′ may be the same or different and may be selected from hydrogen, C1-C10alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl; wherein in case of charged amine groups, the group is associated with at least one counter-ion.
In some embodiments, at least one of R1 and R2 is H. In some embodiments, both of R1 and R2 are H.
In some embodiments, at least or both of R1 and R2 is an alkyl or aryl, thereby forming an ester. The alkyl or aryl may be selected from C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S.
In some embodiments, at least one of R3, R4, R5 and R6 is H. In some embodiments, at least two of R3, R4, R5 and R6 are H. In some embodiments, each of R3, R4, R5 and R6 is H.
In some embodiments, at least one of R3, R4, R5 and R6 is C1-C30alkyl. In some embodiments, at least two of R3, R4, R5 and R6 are C1-C30alkyl. In some embodiments, each of R3. R4, R and R6 is C1-C30alkyl.
The invention further provides 2,2-bifuran-3,3′-dicarboxylic acid (herein compound 2), being a compound of Formula (I), having the structure:
or a derivative thereof.
The invention further provides use of compound 2 in the construction of furan based materials.
Further provided is a compound of Formula (II):
wherein
each of R1, R2, R3 and R4, independently of the other, may be selected from hydrogen, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN, —CO2H, —OH, —SH, —NR′R″R″′, —NO2, (C1-C30alkyl)3Si—, (C1-C30alkyl)3Sn—, trifluoromethanesulfonate (triflate) and halogen, wherein each of R′, R″ and R″′ may be the same or different and may be selected from hydrogen, C1-C10alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl; wherein in case of charged amine groups, the group is associated with at least one counter-ion.
In some embodiments, at least one of R1 and R2 is H. In some embodiments, both of R1 and R2 are H.
In some embodiments, at least one of R3 and R4 is H. In some embodiments, both of R3 and R4 are H.
In some embodiments, at least one of R1, R2, R3 and R4 is H. In some embodiments, at least two of R1, R2, R3 and R4 are H. In some embodiments, each of R1, R2, R3 and R4 is H.
The invention further provides 2,2′-bifuran-3,3′dicarboxylic anhydride (herein compound 3), a compound of Formula (II), having the structure
or a derivative thereof.
The invention further provides a compound of the general Formula (III):
wherein
R is selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN and —CO2H;
each of R1, R2, R3 and R4, independently of the other, may be selected from hydrogen, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN, —CO2H, —OH, —SH, —NR′R″R″′, —NO2, (C1-C30alkyl)3Si—, (C1-C30alkyl)3Sn—, trifluoromethanesulfonate (triflate), halogen and RA (further defined hereinbelow), wherein each of R′, R″ and R″′ may be the same or different and may be selected from hydrogen, C1-C10alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl; wherein in case of charged amine groups, the group is associated with at least one counter-ion.
In some embodiments, at least one of R1 and R2 is H. In some embodiments, both of R1 and R2 are H.
In some embodiments, at least one of R3 and R4 is H. In some embodiments, both of R3 and R4 are H.
In some embodiments, at least one of R1 and R2 is a halide selected from Br, I, Cl, and F. In some embodiments, both of R1 and R2 are halides, as selected. In some embodiments, the halide is Br.
In some embodiments, at least one of R1 and R2 is (C1-C30alkyl)3Sn—. In some embodiments, both of R1 and R2 are (C1-C30alkyl)3Sn—.
In some embodiments, at least one of R1, R2, R3 and R4 is H. In some embodiments, at least two of R1, R2, R3 and R4 are H. In some embodiments, each of R1, R2, R3 and R4 is H.
In some embodiments, at least one of R1 and R2 is C1-C30alkyl. In some embodiments, both of R1 and R2 are C1-C30alkyl.
In some embodiments, at least one of R1, R2, R3 and R4 is C1-C30alkyl. In some embodiments, at least two of R1, R2, R3 and R4 are C1-C30alkyl.
As used herein, the group RA is a group selected from:
wherein
the wavy line designates a bond formed between RA1 and position R1, R2, R3 or R4 on a compound of Formula (III);
each of R5, R6, R7 and R8, independently of the other, may be selected from hydrogen, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN, —CO2H, —OH, —SH, —NR′R″R″′, —NO2, (C1-C30alkyl)3Si—, (C1-C30alkyl)3Sn—, trifluoromethanesulfonate (triflate) and halogen, wherein each of R′, R″ and R″′ may be the same or different and may be selected from hydrogen, C1-C10alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl; wherein in case of charged amine groups, the group is associated with at least one counter-ion; or a covalent bond;
n is an integer indicating the number of repeating monomers, being between 1 and 100;
such that when RA is RA2, in a repeating end of a chain monomer, R6 may be H or C1-C30alkyl; and in a repeating mid-chain monomer, R6 is a bond connecting two monomers.
In some embodiments, R8 is selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN and —CO2H In some embodiments, at least one of R5, R6, R7 and R8 is H. In some embodiments, both of R6 and R8 are H.
In some embodiments, at least two of R5, R6, R7 and R8 are H. In some embodiments, each of R5, R6, R7 and R8 is H.
In some embodiments, at least one of R6 and R8 is C1-C30alkyl. In some embodiments, both of R6 and R8 are C1-C30alkyl.
In some embodiments, at least one of R5, R6, R7 and R8 is C1-C30alkyl. In some embodiments, at least two of R5, R6, R7 and R8 are C1-C30alkyl.
In some embodiments, R6 is Sn(C1-C30alkyl)3 or a halide selected from Br, I, Cl and F. In some embodiments, R6 is Br or Sn(C1-C30alkyl)3.
In some embodiments, R6 is Sn(C1-C30alkyl)3 and each of R5, R7 and R8 is C1-C30alkyl or H. In some embodiments, R6 is Sn(C1-C30alkyl)3 and each of R5, R7 and R8 is H.
The invention further provides 2,2′-bifuran-3,3′-dicarboximide, a compound of Formula (III), having the structure general structure
wherein R is selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN and —CO2H.
In a compound of Formula (III), the presence of a group RA allows for the construction of oligomers or polymers, linear or cyclic of bifuran compounds of the invention. Thus, the invention further provides dimers, trimers, tetramers, pentamers, hexamers, heptamers, octamers, nonamers, decamers and higher homologues of a compound of Formula (III), wherein one or both of R1 and R2 is RA2. In some embodiments, the number of furan rings in higher homologues, e.g., oligomers or polymers, is at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200, or between 10 and 20, between 20 and 30, between 30 and 40, between 40 and 50, between 50 and 60, between 60 and 70, between 70 and 80, between 80 and 90, between 90 and 100, between 100 and 110, between 110 and 120, between 120 and 130, between 130 and 140, between 140 and 150, between 150 and 160, between 160 and 170, between 170 and 180, between 180 and 190, between 190 and 200.
In some embodiments, the number of furan rings in oligomers or polymers of the invention is between 3 and 50, between 3 and 45, between 3 and 40, between 3 and 35, between 3 and 30, between 3 and 25, between 3 and 20, between 3 and 15, between 3 and 10, between 3 and 9, between 3 and 8, between 3 and 7, between 3 and 6, between 3 and 5, between 5 and 45, between 5 and 40, between 5 and 35, between 5 and 30, between 5 and 25, between 5 and 20, between 5 and 15, between 5 and 10, between 10 and 45, between 10 and 40, between 10 and 35, between 10 and 30, between 10 and 25, or between 10 and 15.
In some embodiments, the number of furan rings in compounds of the invention is between 3 and 16, between 3 and 15, between 3 and 14, between 3 and 13, between 3 and 12, between 3 and 11, between 3 and 10, between 3 and 9, between 3 and 8, between 3 and 7 or between 3 and 6.
The invention further provides a compound of the general Formulae (IV) or (V) or (VI):
wherein
in each of compounds of Formulae (IV), (V) and (VI): each R, R1, R2, R3 and R4 may be the same or different and may be selected as indicated herein above, e.g., with reference to Formula (III). In a compound of Formula (V), the wavy line designates a point or a bond of connectivity to yield higher homologues of the indicated dimer. The integer n designates the number of monomer units, and may be selected between 1 and 30.
Also provided is the macrocycle having the oligofuran backbone, the bifuranimide α,α′-tetramer C-4BFI, shown below, wherein each R may be the same or different and may be as selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN and —CO2H.
In some embodiments, compounds of the general Formula (V) or (VI) may be linear or cyclic. Where the compound is cyclic, for example, the wavy line designates bond of connectivity to the carbon atom substituted with variant R2.
In dimers, trimers, tetramers, . . . etc, oligomers or polymers of Formula (V) or (VI), each of the variant groups (designated R, R1, R2 . . . etc) may be the same or different. Each variant may be different. The integer n designates the number of monomer units, and may be selected between 1 and 30.
In some embodiments, in a compound of Formula (VI), R1 and R2 may be H or as selected above. In some embodiments, in a compound of Formula (VI), R1 and R2 may be a halide selected from Br, I, Cl and F or Sn(C1-C30alkyl)3.
As used herein with reference to any of the aforementioned specific or general Formulae structures, the variant “C1-C30alkyl” is an alkyl having between 1 and 30 carbon atoms, or between 5 and 30, 10 and 30, 15 and 30, 20 and 30, 25 and 30, 1 and 25, 1 and 20, 1 and 15, 1 and 10, 1 and 5, 2 and 30, 3 and 29, 4 and 28, 5 and 27, 6 and 26, 7 and 25, 8 and 24, 9 and 23, 10 and 22, 11 and 21, 12 and 20, 13 and 19, 14 and 18, 15 and 17, 1 and 5, 5 and 10, 10 and 15, 15 and 20 or between 20 and 30 carbon atoms. The C1-C30alkyl may be a linear alkyl or a branched alkyl group. The C1-C30alkyl may be substituted or unsubstituted.
In some embodiments, in all cases where C1-C30alkyl (e.g., as an alkyl variant or in the group Sn(C1-C30alkyl)3, or in any other variant group) is selected, it may be selected as above, or from alkyls having between 1 and 29, 1 and 28, 1 and 27, 1 and 26, 1 and 25, 1 and 24, 1 and 23, 1 and 22, 1 and 21, 1 and 20, 1 and 19, 1 and 18, 1 and 17, 1 and 16, 1 and 15, 1 and 14, 1 and 13, 1 and 12, 1 and 11, 1 and 10, 1 and 9, 1 and 8, 1 and 7, 1 and 6, 1 and 5, 1 and 4 or between 1 and 3 carbon atoms.
In some embodiments, the C1-C30alkyl group is selected from alkyl groups having between 1 and 5, or 1 and 10, or 1 and 15, or between 1 and 20 carbon atoms.
In some embodiments, the C1-C30alkyl group is selected from alkyl groups having between 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 carbon atoms.
As used herein with reference to any of the aforementioned specific or general Formulae structures, variant R (in the endocyclic group N—R) is selected as above or from alkyls having between 1 and 29, 1 and 28, 1 and 27, 1 and 26, 1 and 25, 1 and 24, 1 and 23, 1 and 22, 1 and 21, 1 and 20, 1 and 19, 1 and 18, 1 and 17, 1 and 16, 1 and 15, 1 and 14, 1 and 13, 1 and 12, 1 and 11, 1 and 10, 1 and 9, 1 and 8, 1 and 7, 1 and 6, 1 and 5, 1 and 4 or 1 and 3. In some embodiments, R is an alkyl group selected from alkyls having between 1 and 5, or 1 and 10, or 1 and 15, or between 1 and 20 carbon atoms.
Any of the alkyl variants recited herein may be substituted or unsubstituted. In cases where the alkyl is substituted, any one or more hydrogen atom may be replaced by one or more atoms or groups of atoms. For example, an alkyl being designated as C1-C5alkyl comprises between 1 and 5 carbon atoms and a number of additional atoms. In cases where the alkyl is not substituted, a C1-C5alkyl comprises between 3 and 11 hydrogen atoms. Each of these hydrogen atoms may be relaced by a different atom or a group of atoms. Substitutions may be selected from halides such as I, Br, Cl and F, —CF3, —OH, —NO2, amines, —COOH or esters thereof, aryl groups and others.
In some embodiments, the alkyl is a fluorinated, e.g., perfluorinated, alkyl.
It should be noted that where the alkyl is substituted by two non-hydrogen atoms, it may be regarded an alkylene.
The invention further provides a compound selected from:
and substituted derivatives thereof.
The invention further provides a method of synthesis of a compound of the general Formula (I), the method comprising reacting a dihalobifuran under lithiation conditions in the presence of carbon dioxide to afford the diacidbifuran compound. The dihalo precursor may be selected from any dihalobifuran, e.g., dibromobifuran. The reaction may be carried out in the presence of a lithiation agent such as butyllithium, and subsequently quenched with carbon dioxide.
The invention further provides a method of synthesis of a compound of the general Formula (II), the method comprising reacting a bifuran-dicarboxylic acid under condensation/cyclization conditions in the presence of acetic anhydride.
The invention further provides a method of synthesis of a dimer, trimer, a tetramer, a higher homologue, an oligomer or a polymer of a compound of general Formula (III), (IV), (V) or (VI), the method comprising reacting a functionally substituted bifuran-imide (optionally obtained from bifuran dicarboxylic anhydride by reaction with an alkyl amine such as hexylamine or 2-octyldodecylamine, followed by in situ treatment with SOCl2) under conditions, such as the Stille coupling conditions, to afford a dimer of the bifuran imide. The dimer may be further substituted to afford the trimer and higher homologues.
In some embodiments, functionalized bifuran imide, such a mono- or dibromobifuran imide, was reacted under lithiation conditions in the presence of a trialkyl tin halide to afford the trialkylstannyl derivative. The stannyl derivative may for example be formed by reacting the bifuran imide with a lithiation agent such as lithium diisopropylamide (LDA) followed by treatment with tributyltin chloride.
The method thus afford a bifuranimide mono or disubstituted with a trialkylstannyl group(s), e.g., tributylstannyl group(s).
The stannyl substituted bifuran imide may thereafter be reacted under the Pd-catalyzed Stille coupling reaction, attaching e.g., a monobromobifuran-imide or a dibromobifuran-imide to a stannyl derivative, to provide a dimer, a trimer or higher homologs.
In some embodiments, the bifuran imide is brominated or otherwise substituted to afford a functionalizes bifuran imide derivative that can be chain elongated or further treated to dimerize, trimerize or provide higher homologs such as oligomers and polymers. For example, bromination of bifuran imide may be achieved with molecular bromine to give monobromobifuran-imide and dibromobifuran-imide, depending on the amount of the bromine used.
Compounds of the invention thus may be used in methods of synthesis of oligomers or polymers comprising bifuranimide units. In some embodiments, compounds so obtained may comprise one or more bifuran imide units. The length of the oligomer or polymer that is based on the bifuran imide unit may be determined based on the number of furan rings (wherein each bifuran imide unit comprises two furan rings) or on the number of bifuran imide units. Notwithstanding the length of the oligomer or polymer, each bifuran imide unit in an oligomer or polymer of the invention may be the same or different. The differences in the bifuran units may be, for example, in the N-substitution, in the substitution of one furan ring as compared to the other within the same bifuran imide unit, in the substitution of one bifuran imide unit in comparison to another unit, in the positions of substitution, in the presence of one or more linker or midchain groups that are not bifuran imide units, and others.
Each oligomer or polymer of the invention may be used for a different application or for the construction of a different device. As further detailed below, compounds of the invention may be used for the construction of high molecular weight polymers, which unlike their thiophene analogues, are better candidates as p-type semiconductors. Compounds of the invention show considerable photostability, with little bleaching even after prolonged ambient light exposure, and thus are suitable building unit for organic electronics. In fact, these building units exhibit blue emission in an almost-perfect match with the European Broadcasting Union (EBU) blue standard. Combined with a good fluorescence efficiency, they can be applied in light emitting devices as blue emitters.
Thus, the invention further provides a device constructed of or comprising a blue emitter in the form of a compound according to the present invention. The device may be a blue light emitting device of any type known in the art, such as OLED and OLET.
In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
Reagents and chemicals used here are commercially available and were used without further purification unless otherwise stated. Flash chromatography (FC) was performed using CombiFlash SiO2 columns. The compounds 3,3′-dibromo-2,2′-bifuran, 2-octyldodecylamine, and N-(2-octyldodecyl)-2,2′-bithiophene-3,3′dicarboximide were synthesized according to the procedures detailed in the literature.
1H and 13C NMR spectra were recorded in solution on a Brücker-AVIII 400 MI-z and 500 MHz spectrometer using tetranethylsilane (TMS) as the external standard. The spectra were recorded using chloroform-d, methanol-d4 as solvents. Chemical shifts are expressed in δ units. High resolution mass spectra were measured on a HR Q-TOF LCMS and Waters Micromass GCT_Preniier Mass Spectrometer using ESI and field desorption (FD) ionization. Molecular weights and size distribution were determined by gel permeation chromatography (GPC) in chloroform (with 0.025% toluene as internal standard) against PS standards with a flow rate of 1 ml/min. GPC was performed on a Polymer Standards Service (PSS) system consisting of a PSS SDV linear M column, refractive index and UV detectors (Thermo). Data analysis and standard calibration (with PS standards) were performed using PSS WinGPC UniChrom software V8.20. Build 5350. UV-vis absorption and fluorescence spectra of synthesized compounds were recorded on an Agilent Technologies Cary series UV-Vis-NIR spectrophotometer. Fluorescence measurements were carried out with a Horiba Scientific Fluoromax-4 spectrofluorometer.
A solution of lithium diisopropylamide (LDA) (37.4 mL, 2.0 M in hexane) was added dropwise to a solution of 3-bromo-furan (10 g, 68.04 mmol) in dry THF (60 mL) at −78° C. under N2. The reaction mixture was then stirred under the same conditions. After 1.5 h, CuCl2 (10 g, 74.8 mmol) was added in one portion and the resulting solution was allowed to reach room temperature slowly and was stirred overnight. The reaction mixture was then added into 100 ml water with 5 g glycine at 0° C., filtered, filtrate extracted with diethyl ether (3×80 mL), dried (Na2SO4) and concentrated. The residue obtained was purified by flash column chromatography on silica gel with hexane as eluent to give 1 as a white solid (6.7 g, 69%). 1H NMR (400 MHz, Chloroform-d): δ 7.47 (d, J=1.9 Hz, 2H), 6.55 (d, J=1.9 Hz, 2H).
To a solution of n-BuLi (31.2 mL, 50.0 mmol, 1.6 M in hexane) in dry THF (50 mL), 3,3′-dibromobifuran (1) (5.84 g, 20.0 mmol) in dry THF (40 mL) was added dropwise over the period of 30 minutes at −70° C. The resulting solution was stirred at −70° C. until it becomes white slurry (about 2 hours). To the slurry was added dry ice (7.0 g, 160.0 mmol) at −70° C. Then, the mixture was gradually warmed to room temperature. After stirring for 5 hours at room temperature, the reaction mixture was quenched with methanol (5 mL), and the solvent was removed under a reduce pressure. The crude product was purified by flash column chromatography on silica gel using AcOH/CH2Cl2/methanol (1:4:95) as eluent to give 2 light yellow solid (3.38 g, 76%). 1H NMR (400 MHz, Methanol-d): δ 7.68 (d, J=2.0 Hz, 2H; H—C (5)), 6.87 (d, J=1.9 Hz, 2H, H—C (4)); 13C NMR (101 MHz, Methanol-d): δ 165.75 (2C (6)), 147.34 (2C (2)), 145.11 (2C (5)), 121.08 (2C (3)), 112.99 (2C (4)); HRMS (ESI): calcd for C10H6O6 (M+H)+: 223.0243, found: 223.0237.
A solution of (2,2-bifuran)-3,3′dicarboxylic acid (2) (3.3 g, 14.9 mmol) in acetic anhydride (100 mL) was stirred under refluxed condition for 12 h. Acetic anhydride was removed by distillation under reduced pressure. The residue thus obtained was purified by flash column chromatography on silica gel using hexane/ethyl acetate (4:1) as eluent to give anhydride 3 as a light yellow solid (2.46 g, 81%). 1H NMR (400 MHz, Chloroform-d): δ 7.61 (d, J=1.6 Hz, 2H; H—C (5)), 7.11 (d, J=1.6 Hz, 2H; H—C (4)); 13C NMR (101 MHz, Chloroform-d): δ 154.35 (2C (6)), 145.35 (2C (2)), 144.74 (2C (5)), 116.27 (2C (3)), 113.93 (2C (4)); HRMS (ESI): calcd for C10H6O6 (M+H)+: 205.0137, found: 205.0130.
To a solution of anhydride 3 (2.04 g, 10.0 mmol) in dry CH2Cl2 (100 mL) was added a solution of 1-hexylamine (1.6 mL, 12.0 mmol) in CH2Cl2(20 mL) dropwise under N2. After addition, the reaction mixture was stirred under reflux 12 h. The reaction mixture was cooled to room temperature and then SOCl2 (1.1 mL, 15.0 mmol) was added dropwise. The reaction mixture was again refluxed for 15 h. The reaction was quenched sat. aq. solution of NaHCO3 (50 mL). The separated aqueous layer extracted with CH2Cl2 (2×50 mL), dried (Na2SO4), filtered, and concentrated. The residues obtained was purified by flash column chromatography on silica gel using hexane and ethyl acetate (4:1) as eluent to give BFI-H as a white solid (2.53 g, 88%). 1H NMR (500 MHz, Chloroform-d): δ 7.54 (d, J=1.9 Hz, 2H; H—C (5)), 7.15 (d, J=1.9 Hz, 2H; H—C (4)), 4.21 (t, J=7.8, 2H; —CH2(7)), 1.69-1.63 (m, 2H; —CH2(8)), 1.42-1.30 (m, 6H; —CH2(9-11), 0.88 (t, J=7.1 Hz, 3H; —CH3(12)); 13C NMR (101 MHz, Chloroform-d): δ 160.42 (2C (6)), 143.64 (2C (5)), 143.49 (2C (2)), 120.40 (2C (3)), 114.17 (2C (4)), 45.29 (C (7)), 31.65 (C (10)), 27.61 (C (8)), 26.98 (C (9)), 22.71 (C (11)), 14.17 (C (12)); HRMS (ESI): calcd for C16H18NO4 (M+H)+: 288.1230, found: 288.1254.
Bromine (0.18 mL, 3.6 mmol) and catalytic amount of FeCl3 (10 mg, 2 mol %) were added to the solution of imide BFI-H (0.862 g, 3.0 mmol) in CH2Cl2 (40 mL) and the reaction mixture was stirred in dark for 4 h. After completion of reaction it was quenched by sat. aq. solution of Na2SO3 and stirred for further 30 min. The reaction mixture poured into CH2Cl2 (150 mL) and washed with water (2×100 mL), brine, dried (Na2SO4), filtered, and concentrated. The residue obtained was purified by flash column chromatography on silica gel using hexane and CH2Cl2 (1:1) as eluent to give 4a as a white solid (0.62 g, 56%). 1H NMR (500 MHz, Chloroform-d): δ 7.55 (d, J=1.9 Hz, 1H; H—C (5′)), 7.15 (d, J=1.9 Hz, 1H; H—C (4′)), 7.07 (s, 1H; H—C (4)), 4.18 (t, J=7.8, 2H; —CH2(7)), 1.67-1.61 (m, 2H; —CH2(8)), 1.40-1.30 (m, 6H; —CH2(9-11)), 0.88 (t, J=7.1 Hz, 3H; —CH3(12)); 13C NMR (125 MHz, Chloroform-d): δ 160.1 (C (6)), 159.4 (C (6′)), 144.6 (C (2′)), 144.0 (C (5′)), 142.5 (C (2)), 125.7 (C (3)), 121.9 (C (5)), 120.5 (C (3′)), 115.6 (C (4)), 114.3 (C (4′)), 45.4 (C (7)), 31.7 (C (10)), 27.6 (C (8)), 27.0 (C (9)), 22.7 (C (11)), 14.2 (C (12)); HRMS (ESI): calcd for C16H16Br2NO4 (M+H)+: 366.0341, found: 366.0357.
Bromine (0.62 mL, 12.0 mmol) and catalytic amount of FeCl3 (10 mg, 2 mol %) were added to the solution of imide BFI-H (0.862 g, 3.0 mmol) in CH2Cl2 (40 mL) and the reaction mixture was stirred in dark for 4 h. After completion of reaction it was quenched by sat. aq. solution of Na2SO3 and stirred for further 30 min. The reaction mixture poured into CH2Cl2 (150 mL) and washed with water (2×100 mL), brine, dried (Na2SO4), filtered, and concentrated. The residues obtained was purified by flash column chromatography on silica gel using hexane and ethyl acetate (9:1) as eluent to give 4b as a white solid (1.29 g, 97%). 1H NMR (500 MHz, Chloroform-d): δ 7.06 (s, 2H; H—C (4), 4.16 (t, J=7.8, 2H; —CH2(7)), 1.65-1.59 (m 2H; —CH2(8)), 1.38-1.29 (m 6H; —CH2(9-11)), 0.88 (t, J=7.1 Hz, 3H; —CH3(12)); 13C NMR (125 MHz, Chloroform-d): δ 159.1 (2C (6)), 143.5 (2C (2)), 126.1 (2C (3)), 121.9 (2C (5)), 115.7 (2C (4)), 45.5 (C (7)), 31.6 (C (10)), 27.5 (C (8)), 26.9 (C (9)), 22.7 (C (11)), 14.2 (C (12)); HRMS (ESI): calcd for C16H16Br2NO4 (M+H)+: 445.9421, found: 445.9435.
A solution of LDA (0.55 mL, 2.0 M in hexane, 1.1 mmol) was added dropwise to a solution of N-hexyl-2,2′-bifuran-3,3′-dicarboximide (BFI-H) (287 mg, 1.0 mmol) in dry THF (15 mL) at −85° C. under N2 and stirred for 1 h. Bu3SnCl (0.33 mL, 1.2 mmol) was added dropwise, and the reaction mixture was allowed to reach room temperature and stirred for 2 h. The mixture was quenched with water, extracted with CH2Cl2 (2×40 mL), dried (Na2SO4), filtered, and evaporated. The residue obtained was purified by flash column chromatography on silica gel basified with trimethylamine using hexane as eluent to give 5 as a colorless oil (300 mg. 52%). 1H NMR (400 MHz, Chloroform-d): δ 7.53 (d, J=1.9 Hz, 1H), 7.25 (s, 1H), 7.15 (d, J=1.9 Hz, 1H), 4.22 (t, J=7.7, 2H), 1.68-1.55 (m, 8H), 1.39-1.30 (m, 12H), 1.20-1.15 (m, 6H), 0.90 (t, J=7.2 Hz, 12H); 13C NMR (101 MHz, Chloroform-d): δ 165.72, 160.90, 160.65, 147.59, 144.09, 143.22, 125.17, 120.64, 119.33, 114.05, 45.19, 31.67, 28.97 (3C), 27.67, 27.25 (3C), 27.01 22.72, 14.18, 13.74 (3C), 10.59 (3C); HRMS (ESI) calcd for C28H44NO4Sn (M+H)+: 578.2292, found: 578.2290.
Pd(PPh3)4 (18 mg, 0.016 mmol) was added to a solution of N-Hexyl-5-bromo-2,2′-bifuran-3,3′-dicarboximide (4a) (146 mg, 0.40 mmol) and N-Hexyl-5-(tributylstannyl)-2,2′-bifuran-3,3′-dicarboximide (5) (300 mg, 0.52 mmol) in dry and degassed toluene (10 mL), and the reaction mixture was stirred at 90° C. for 24 h under nitrogen. Then reaction mixture was cooled to room temperature and solvent was evaporated under reduced pressure. The residue obtained was purified by flash column chromatography on silica gel using hexane and dichloromethane (1:8) as eluent to give 2BFI-H as a yellow solid (140 mg, 61%). 1H NMR (500 MHz, Chloroform-d): δ 7.60 (d, J=1.9 Hz, 2H; H—C (5)), 7.47 (s, 2H; H—C (4′)), 7.18 (d, J=1.9 Hz; H—C (4)), 4.21 (t, J=7.8, 4H; —CH2(7)), 1.71-1.63 (m, 4H; —CH2(8)), 1.42-1.30 (m, 12H; —CH2(9-11)), 0.89 (t, J=7.1 Hz, 6H; —CH3(12)); 13C NMR (125 MHz, Chloroform-d): δ 160.06 (2C (6)), 159.80 (2C (6′)), 144.78 (2C (5′)), 144.26 (2C (5)), 143.30 (2C (2′)), 142.62 (2C (2)), 121.78 (2C (3)), 121.40 (2C (3′)), 114.54 (2C (4)), 111.44 (2C (4′)), 45.42 (2C (7)), 31.66 (2C (10)), 27.60 (2C (8)), 26.98 (2C (9)), 22.73 (2C (11)), 14.19 (2C (12)); HRMS (ESI): calcd for C32H33N2O8 (M+H)+: 573.2237, found: 573.2229.
Pd(PPh3)4 (18 mg, 0.016 mmol) was added to a solution of N-Hexyl-5,5′-dibromo-2,2′-bifuran-3,3′-dicarboximide (4b) (111 mg, 0.25 mmol) and N-Hexyl-5-(tributylstannyl)-2,2′-bifuran-3,3′-dicarboximide (5) (432 mg, 0.75 mmol) in dry and degassed toluene (10 mL), and the reaction mixture was stirred at 90° C. for 24 h under nitrogen. Then reaction mixture was cooled to room temperature and solvent was evaporated under reduced pressure. The residue obtained was purified by flash column chromatography on silica gel using dichloromethane and ethyl acetate (95:5) as eluent to give 3BFI-H as a yellow solid (96 mg, 45%). 1H NMR (500 MHz, Chloroform-d): δ 7.63 (d, J=1.9 Hz, 2H; H—C (5)), 7.52 (s, 2H; H—C (3″)), 7.45 (s, 2H; H—C (4′)), 7.18 (d, J=1.8 Hz, 2H; H—C (4)), 4.20 (t, J=7.6, 6H; —CH2(7)), 1.67 (quint, J=7.6 Hz, 6H; —CH2(8)), 1.43-1.33 (m, 18H; —CH2(9-11)), 0.90 (t, J=7.1 Hz, 3H; —CH3(12)); 13C NMR (125 MHz, Chloroform-d): δ 160.01 (2C (6)), 159.68 (2C (6′)), 159.41 (2C (6″)), 145.28 (2 C (2′)), 144.49 (2C (2″)), 144.39 (2C (5)), 143.41 (2C (5″)), 142.52 (2C (2)), 142.28 (2 C (5′)), 122.72 (2C (4″)), 121.81 (2C (3)), 121.56 (2C (3′)), 114.59 (2C (4)), 112.00 (2 C (3″)), 111.66 (2C (4′)), 45.56 (1C (7′)), 45.43 (2C (7)), 31.66 (3C (10)), 27.61 (2C (8)), 27.59 (1C (8′)), 26.99 (3C (9)), 22.75 (3C (11)), 14.21 (3C (12)); HRMS (ESI): calcd for C16H16Br2NO4 (M+H)+: 366.03410, found: 366.03574.
To a solution of anhydride 3 (1.5 g, 7.34 mmol) in dry CH2Cl2 (80 mL) was added a solution of 2-octyldodecylamine (2.4 g, 8.07 mmol) in CH2Cl2(20 mL) dropwise under N2. After addition, the reaction mixture was stirred under reflux 12 hr. The reaction mixture was cooled to room temperature and then SOCl2 (0.87 mL, 12.0 mmol) was added dropwise. The reaction mixture was again refluxed for 15 hr. The reaction was quenched sat. aq. solution of NaHCO3 (20 mL). The aqueous layer extracted with CH2Cl2 (2×80 mL), dried (Na2SO4) and concentrated. The residues obtained was purified by flash column chromatography on silica gel using hexane and ethyl acetate (9:1) as eluent to give BFI-OD as a colorless oil (2.81 g, 79%). 1H NMR (500 MHz, Chloroform-d): δ 7.54 (d, J=1.9, 2H; H—C (5)), 7.16 (d, J=1.9, 2H; H—C (4)), 4.24 (d, J=7.2, 2H; —CH2—CH3), 1.84 (m, 1H; —CH2—CH3), 1.38-1.18 (m, 32H; 16(CH2)), 0.87 (t, J=7.1 Hz, 3H; (CH3)), 0.86 (t, J=6.8 Hz, 3H; (CH3)); 13C NMR (125 MHz, Chloroform-d): δ 160.84 (2C (6)), 143.60 (2C (5)), 143.41 (2C (2)), 120.41 (2C (3)), 114.35 (2C (4)), 48.56, 36.45, 32.07, 32.03, 31.85 (2C), 30.21 (2C), 29.79, 29.77, 29.74, 29.69, 29.48, 29.44, 26.65 (2C), 22.82, 22.80, 14.25 (2C); HRMS (ESI): calcd for C16H16Br2NO4 (M+H)+: 445.94211, found: 445.94357.
Bromine (0.32 mL, 6.0 mmol) and catalytic amount of FeCl3 (5 mg, 2 mol %) were added to the solution of N-(2-octyldodecyl)-2,2′-bifuran-3,3′-dicarboximide (BFI-OD) (0.73 g, 3.0 mmol) in CH2Cl2 (40 mL) and the reaction mixture was stirred in dark for 4 hr. After completion of reaction it was quenched by sat. aq. solution of Na2SO3 and stirred for further 30 min. The reaction mixture poured into CH2Cl2 (100 mL) and washed with water (2×60 mL), brine, dried (Na2SO4), filtered and concentrated. The residues obtained was purified by flash column chromatography on silica gel using hexane and ethyl acetate (9:1) as eluent to give 4c as a colorless oil (0.93 g, 96%). 1H NMR (500 MHz, Chloroform-d): δ 7.07 (s, 2H; H—C (4)), 4.19 (d, J=7.3, 2H; —CH2—CH3), 1.84 (m, 1H; —CH2—CH), 1.34-1.18 (m, 32H; 16(CH2)), 0.87 (t, J=7.0 Hz, 3H; (CH3)), 0.86 (t, J=7.0 Hz, 3H; (CH3)); 13C NMR (125 MHz, Chloroform-d) δ 159.46 (2C (6)), 143.45 (2C (2)), 126.08 (2C (3)), 121.92 (2C (5)), 115.86 (2C (4)), 48.76, 36.37, 32.08, 32.06, 31.80 (2C), 30.18 (2C), 29.80 (2C), 29.74, 29.70, 29.50, 29.46, 26.60 (2C), 22.84, 22.83, 14.27 (2C); HRMS (ESI): calcd for C16H16Br2NO4 (M+H)+: 445.94211, found: 445.94357.
A solution of LDA (0.42 mL, 2.0 M in hexane, 0.84 mmol) was added dropwise to a solution of N-(2-octyldodecyl)-2,2′-bifuran-3,3′-dicarboximide (BFI-OD) (185 mg, 0.38 mmol) in dry THF (15 mL) at −85° C. under N2 and stirred for 1 h. Bu3SnCl (0.23 mL, 0.84 mmol) was added dropwise, and the reaction mixture was allowed to reach room temperature and stirred for 2 h. The mixture was quenched with water, extracted with CH2Cl2 (2×40 mL), dried (Na2SO4), filtered, and evaporated. The residue obtained was purified by flash column chromatography on silica gel basified with trimethylamine using hexane as eluent to give 6 as colorless oil (331 mg, 81%). 1H NMR (400 MHz, Chloroform-d): δ 7.25 (s, 2H; H—C (4)), 4.25 (d, J=7.1, 2H; —CH2—CH), 1.93-1.86 (m, 1H; —CH2—CH), 1.64-1.56 (m, 12H; 6(CH2) 1.42-1.13 (m, 56H; 28(CH2)), 0.91 (t, J=7.0 Hz, 18H; (CH3)), 0.87 (t, J=7.0 Hz, 3H; (CH3)), 0.86 (t, J=7.0 Hz, 3H; (CH3)); 13C NMR (125 MHz, Chloroform-d) δ 164.87 (2C), 161.55 (2C), 148.06 (2C), 125.30 (2C), 119.45 (2C), 48.45, 36.62, 32.08, 32.06, 31.93 (2C), 30.26 (2C), 29.81, 29.80 (2C), 29.73, 29.50, 29.46, 29.01 (6C), 27. 30 (6C), 26.77 (2C), 22.84, 22.82, 14.27 (2C), 13.79 (6C), 10.62 (6C); ); HRMS (ESI) calcd for C54H97NO4Sn2 (M)+: 1062.5534, found: 1062.5573.
Pd(PPh3)4 (29 mg, 5 mol %) was added to a solution of N-(2-octyldodecyl)-5,5′-dibromo-2,2′-bifuran-3,3′-dicarboximide (4c) (321 mg, 0.50 mmol) and N-(2-octyldodecyl)-5,5′-bis(tributylstannyl)-2,2′-bifuran-3,3′-dicarboximide (6)(531 mg, 0.50 mmol) in dry and degassed DMF (10 mL), and the reaction mixture was stirred at 90° C. for 24 h under nitrogen. The reaction mixture was then allowed to cool to room temperature and poured into 200 mL of methanol, and the precipitate was collected by filtration to give 530 mg of orange solid. The crude material was transferred to a Soxhlet extractor and extracted for 48 h with methanol and a further 24 h with acetone, and then recovered by extraction with hexane. The hexane solution was concentrated, and the polymer precipitated with 150 mL of methanol, filtered, and dried to give poly(BFI-OD) as an orange solid (350 mg 36%). 1H NMR (500 MHz, Chloroform-d): δ 7.5 (bs, 2H), 4.20 (bs, 2H), 1.80 (bs, 1H), 1.64-1.00 (m, 32H), 0.75 (bs, 6H); 13C NMR (125 MHz, Chloroform-d) δ 159.19, 144.98, 141.82, 122.94, 112.04, 48.82, 36.52, 32.10, 30.31, 30.16, 29.94, 29.86, 29.82, 29.76, 29.58, 29.55, 26.77, 22.87, 14.29, 14.26; GPC (30° C.) Molecular weight: Mn=12.4 kDa, Mw=33.7 kDa, PDI=2.71.
Bromine (0.21 mL, 4.13 mmol) and a catalytic amount of FeCl3 (13 mg, 2 mol %) were added to a solution of imide L-1BFI (2.0 g, 4.13 mmol) in CH2Cl2 (50 mL) and the reaction mixture was stirred in the dark for 4 h. After completion of the reaction, it was quenched using a sat. aq. solution of Na2S2O3 and stirred for a further 30 min. The reaction mixture was poured into CH2Cl2 (150 mL) and washed with water (2×100 mL), brine, dried (Na2SO4), filtered, and concentrated. The residue obtained was purified by flash column chromatography on silica gel using hexane and CH2Cl2 (1:1) as eluent to give 4a (
A solution of lithium diisopropylamide (LDA; 2.3 mL, 2.0 M in hexane, 4.54 mmol) was added dropwise to a solution of N-(2-octyldodecyl)-2,2′-bifuran-3,3′-dicarboximide (L-1BFI) (2.0 g, 4.13 mmol) in dry THF (80 mL) at −90° C. under N2 and stirred for 1 hr. Bu3SnCl (1.68 mL, 6.19 mmol) was added dropwise, and the reaction mixture was allowed to reach at 0° C. and stirred for 2 hr. The mixture was quenched with water, extracted with CH2Cl2 (2×80 mL), dried (Na2SO4), filtered, and evaporated. The residue obtained was purified by flash column chromatography on silica gel basified with trimethylamine using hexane as eluent to give 2 (
To a two-neck flask equipped with a condenser was added 4 (1.88 g, 3.34 mmol), hexabutyldistannane (969 mg, 1.67 mmol), tetrakis(triphenylphosphine)palladium(0) [Pd(PPh3)4] (192 mg, 0.167 mmol), and 70 mL dry toluene. The reaction mixture was refluxed under argon for 48 h. After cooling to room temperature, the solvent was evaporated under reduced pressure and the residue obtained was purified by flash column chromatography on silica gel using hexane and CH2Cl2 (1:3) as the eluent to give L-2BFI (
Bromine (0.11 mL, 1.98 mmol) and a catalytic amount of FeCl3 (2 mg, 2 mol %) were added to a solution of imide L-2BFI (
Tetrakis(triphenylphosphine)palladium(0) [(Pd(PPh3)4] 25 mg, 0.021 mmol) was added to a solution of 2 (
Bromine (0.041 mL, 0.794 mmol) and a catalytic amount of FeCl3 (0.86 mg, 2 mol %) were added to a solution of imide L-4BFI (
A solution of Bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2] (37 mg, 0.13 mmol) and 2,2′-dipyridyl (21 mg, 0.13 mmol) in dry THF (15 mL) was stirred for 15 min at 50° C. under argon atmosphere. After cooling to room temperature, the violet solution was transferred to a solution of compound 3 (
Herein the synthesis of a BFI unit, and its corresponding oligomers and polymers (nBFI) bearing hexyl (nBFI-H) or 2-ocyldodecyl (nBFI-OD) substituents, as new building units (
The synthesis of BFI monomer, dimer, trimer, and polymer is depicted in
Attempts to synthesize the homopolymer of BFI-H by Stille polymerization of 4b resulted in an insoluble polymer. The distannylated product of BFI-OD, namely 6, was therefore coupled with 4c to produce poly(BFI-OD), which is considerably more soluble than the hexyl analogue. This was first evident from the NMR spectrum of poly(BFI-OD), which could be recorded in CDCl3 with no heating, whereas the NMR spectrum of the corresponding thiophene-based homopolymer, poly(BTI-OD) was recorded at 120° C. in 1,2-tetrachloroethane. Gel permeation chromatography (GPC) was used to determine polymer molecular weight versus polystyrene. Poly(BFI-OD) was found to have a molecular weight (Mw) of 27000 D and a polydispersity index (PDI) of 2.1, corresponding to a mean chain length of ˜60 monomer units (˜120 furan rings). This is significantly longer than for the thiophene analogue, which consists of only ˜15 monomer units. This difference in mean chain length reflects the better solubility of poly(BFI-OD), as greater solubility permits the formation of longer polymer chains.
The single X-ray crystal structures of 3, BFI-H, and 2BFI-H were obtained by slow diffusion of hexane into dichloromethane at room temperature. The anhydride 3 and BFI-H (
One of the most pronounced differences between furan and thiophene is the exo ring angle, with a value of 129° for 2,5-dimethylthiophene and 134° for 2,5-dimethylfuran. Consequently, bifurans fused to a 5 membered ring are expected to be highly strained, whereas fusion to a 7 membered ring should produce significantly less strain.
UV-vis absorption and emission spectra of BFI-H, 2BFI-H, 3BFI-H, BFI-OD, and poly(BTI-OD) in chloroform are displayed in
For 2BFI-H and 3BFI-H, the emission spectra (
To attain a better understanding of the strong fluorescence properties of BFI-containing materials, their fluorescence lifetime (Kf) was measured. The KNR values (Table 1) for the monomers are very small, in the range of 0.05-0.06 ns−1, indicating a rigid backbone, and increase for the dimer and trimer. However, the polymer has a similarly low value as the trimer, of 0.18 ns−1.
As oligofurans are prone to photooxidation, the photostability of the BFI series was studied by exposing them to identical ambient light conditions, together with 4F for comparison. As expected, 4F underwent rapid photooxidation, with less than 50% of the initial absorption remaining after 2 h (
In order to obtain a better assessment of the energy levels of BFI-containing materials, their properties were studied using DFT calculations at the B3LYP/6-31G(d) level of theory.
aMeasured in the CHCl3;
bmeasured as thin film;
cCalculated according to the equation kF = Φf /τF;
dCalculated according to the equation Φf = kF/(kF + kNR);
eEgap =1242/λonset; EHOMO = −(4.8 −EFc/Fc+1/2 + Eonsetoxi1); ELUMO = EHOMO + Egap.
The synthesis, structure, and properties of the first macrocycle having an oligofuran backbone, the bifuranimide α,α′-tetramer C-4BFI, shown below, has also been achieved (each R may be the same or different and may be as selected from H, C1-C30alkyl, C2-C10alkenyl, C2-C10alkynyl, C6-C10aryl, C5-C10heteroaryl comprising between 1 and 5 heteroatoms selected from N, O, S; —CN and —C2H).
In accordance with the inventors' calculations, and in contrast with macrocyclic oligothiophenes of the same size, C-4BFI is planar, as verified by crystallographic analysis, and exhibits remarkably strong intermolecular interactions. In solution and as a solid, C-4BFI self-assembles via π-stacking. Scanning tunneling microscopy (STM) imaging reveals the formation of ordered multilayers at the solid-liquid interface.
To find the ideal candidate for macrocyclization, the inventors calculated the electronic structures (at the DFT/B3LYP/6-311G(d) level) of C-nBFI molecules of various sizes (
The synthesis started with preparation of the linear tetramer L-4BFI by Stille coupling of stannane 1 with the dibrominated product of L-2BFI (2) (
Single crystals of C-4BFI were grown by slow diffusion of acetone into dichloromethane solution, yielding red needles. The single crystal X-ray analysis shows that the macrocycle is planar (
This contrasts sharply with both calculated and experimental data for oligocyclicthiphenes. Calculations show that cyclic octathiophene adopts a non-planar cone conformation. Likewise, in the smallest structure available for macrocyclic thiophenes, the thiophene rings twist with dihedral angles of 26-34°. The bond distance between the adjacent BFI units is 1.43 Å, which is an indication of strong conjugation and quinoid character. The inner diameter of C-4BFI macrocycles is 7.33 Å, corresponding to a van der Waals cavity of 4.3 Å. This is similar to the predicted inner cavity for 24-crown-8 ether (4-4.5 Å),38 yet achieved in a highly rigid π-conjugated structure that is interesting as a host for supramolecular engineering of optoelectronic materials.
The macrocycles pack in a slip-stacked motif (
The UV-Vis absorption spectrum of the linear tetramer, L-4BFI, displays the expected π-π* transition, with two vibronic peaks at 457 nm and 489 nm corresponding to a C═C backbone stretch of 0.17 eV (˜1400 cm−1;
The absorption spectrum of C-4BFI in hexane at high dilution is similar to that observed in dichloromethane, with a strong S0→S2 transition and a weak S0→S1 tail. Increasing the concentration leads to the emergence of new transitions at 535 nm and 489 nm, until a solid film is formed in which only these new transitions can be observed (
The self-assembly of C-4BFI at the solid-liquid interface was imaged using STM. The macrocycles adopt a lamellar arrangement with an oblique unit cell (a=1.7±0.1 nm, b=2.4±0.1 nm, γ=84±1°,
In summary, a new building unit, bifuran-imide, was introduced and used to synthesize oligomers and the homopolymer. Unlike the corresponding thiophene analogue, the polymer was highly soluble, allowing us to obtain a polymer with high molecular weight. Notwithstanding their solubility, these materials have a strong quinoid character, as evident from the short interring bond in the X-ray structure, and the vibronic features in their absorption spectra. The obtained oligomers and polymers exhibit strong fluorescence with quantum yields reaching up to 81% in solution. The monomer, BFI-H, also demonstrated strong blue emission in the solid state. Compared with their parent oligofurans, bifuran-imides are significantly more stable under ambient conditions. It is therefore suggested that this new unit can replace furan in organic electronic materials.
Filing Document | Filing Date | Country | Kind |
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PCT/IL2019/050511 | 5/6/2019 | WO | 00 |
Number | Date | Country | |
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62667645 | May 2018 | US |