Organic molecules, in particular for use in optoelectronic devices

10919880 ยท 2021-02-16

Assignee

Inventors

Cpc classification

International classification

Abstract

Organic molecules are provided that exhibit emission maxima in the blue, sky-blue or green spectral range. The organic molecules exhibit emission maxima between 420 nm and 520 nm, preferably between 440 nm and 495 nm, more preferably between 450 nm and 470 nm. The photoluminescence quantum yields of the organic molecules are 20% or more. The molecules exhibit thermally activated delayed fluorescence (TADF). The molecules can be used in an optoelectronic device, for example an organic light-emitting diode (OLED), leading to higher efficiencies of the device. Corresponding OLEDs have a higher stability than OLEDs with known emitter materials and comparable color.

Claims

1. An organic molecule, comprising a structure of Formula I, ##STR00232## wherein T=is selected from the group consisting of R.sup.A and R.sup.1; V=is selected from the group consisting of R.sup.A and R.sup.1; W=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is selected from the group consisting of R.sup.A and R.sup.2; X=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.2; Y=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.2; R.sup.T=is selected from the group consisting of CN and R.sup.I; R.sup.V=is selected from the group consisting of CN and R.sup.I; R.sup.W=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is selected from the group consisting of CN and R.sup.I; R.sup.X=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.I; R.sup.Y=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.I; and two second chemical moieties, each independently of one another comprising a structure of Formula II, ##STR00233## wherein the first chemical moiety is linked to each of the two second chemical moieties via a single bond; #=represents the binding site of a single bond linking the second chemical moieties to the first chemical moiety; Z=is at each occurrence independently from another selected from the group consisting of a direct bond, CR.sup.3R.sup.4, CCR.sup.3R.sup.4, CO, CNR.sup.3, NR.sup.3, O, SiR.sup.3R.sup.4, S, S(O) and S(O).sub.2; wherein R.sup.A is selected from the group consisting of a structure of Formula A1 and a structure of Formula A2, ##STR00234## wherein $ represents the binding site of the single bond connecting R.sup.A and the first chemical moiety; R.sup.1, identically or differently at each occurrence, is selected from the group consisting of: hydrogen, deuterium, C.sub.1-C.sub.5-alkyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkenyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkynyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; and C.sub.6-C.sub.18-aryl, which is optionally substituted with one or more substituents R.sup.6; R.sup.2, identically or differently at each occurrence, is selected from the group consisting of: hydrogen, deuterium, C.sub.1-C.sub.5-alkyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkenyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkynyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; and C.sub.6-C.sub.18-aryl, which is optionally substituted with one or more substituents R.sup.6; R.sup.I, identically or differently at each occurrence, is selected from the group consisting of: hydrogen, deuterium, C.sub.1-C.sub.5-alkyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkenyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; C.sub.2-C.sub.8-alkynyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; and C.sub.6-C.sub.18-aryl, which is optionally substituted with one or more substituents R.sup.6; R.sup.Tz, identically or differently at each occurrence, is selected from the group consisting of hydrogen, deuterium, C.sub.1-C.sub.5-alkyl, wherein one or more hydrogen atoms are optionally substituted by deuterium; and C.sub.6-C.sub.18-aryl, which is optionally substituted with one or more substituents R.sup.6; R.sup.a, R.sup.3 and R.sup.4, identically or differently at each occurrence, are selected from the group consisting of: hydrogen, deuterium, N(R.sup.5).sub.2, OR.sup.5, Si(R.sup.5).sub.3, B(OR.sup.5).sub.2, OSO.sub.2R.sup.5, CF.sub.3, CN, F, Br, I, C.sub.1-C.sub.40-alkyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-alkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-thioalkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkenyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkynyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.6-C.sub.60O-aryl, which is optionally substituted with one or more substituents R.sup.5; and C.sub.3-C.sub.57-heteroaryl, which is optionally substituted with one or more substituents R.sup.5; R.sup.5, identically or differently at each occurrence, is selected from the group consisting of hydrogen, deuterium, N(R.sup.6).sub.2, OR.sup.6, Si(R.sup.6).sub.3, B(OR.sup.6).sub.2, OSO.sub.2R.sup.6, CF.sub.3, CN, F, Br, I, C.sub.1-C.sub.40-alkyl, which is optionally substituted with one or more substituents R.sup.6 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, P(O)(R.sup.6), SO, SO.sub.2, NR.sup.6, O, S or CONR.sup.6; C.sub.1-C.sub.40-alkoxy, which is optionally substituted with one or more substituents R.sup.6 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, P(O)(R.sup.6), SO, SO.sub.2, NR.sup.6, O, S or CONR.sup.6; C.sub.1-C.sub.40-thioalkoxy, which is optionally substituted with one or more substituents R.sup.6 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, P(O)(R.sup.6), SO, SO.sub.2, NR.sup.6, O, S or CONR.sup.6; C.sub.2-C.sub.40-alkenyl, which is optionally substituted with one or more substituents R.sup.6 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, P(O)(R.sup.6), SO, SO.sub.2, NR.sup.6, O, S or CONR.sup.6; C.sub.2-C.sub.40-alkynyl, which is optionally substituted with one or more substituents R.sup.6 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, P(O)(R.sup.6), SO, SO.sub.2, NR.sup.6, O, S or CONR.sup.6; C.sub.6-C.sub.60-aryl, which is optionally substituted with one or more substituents R.sup.6; and C.sub.3-C.sub.57-heteroaryl, which is optionally substituted with one or more substituents R.sup.6; R.sup.6, identically or differently at each occurrence, is selected from the group consisting of: hydrogen, deuterium, OPh, CF.sub.3, CN, F, C.sub.1-C.sub.5-alkyl, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF.sub.3, or F; C.sub.1-C.sub.5-alkoxy, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF.sub.3, or F; C.sub.1-C.sub.5-thioalkoxy, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF.sub.3, or F; C.sub.2-C.sub.5-alkenyl, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF.sub.3, or F; C.sub.2-C.sub.5-alkynyl, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF.sub.3, or F; C.sub.6-C.sub.18-aryl, which is optionally substituted with one or more C.sub.1-C.sub.5-alkyl substituents; C.sub.3-C.sub.17-heteroaryl, which is optionally substituted with one or more C.sub.1-C.sub.5-alkyl substituents; N(C.sub.6-C.sub.18-aryl).sub.2, N(C.sub.3-C.sub.17-heteroaryl).sub.2, and N(C.sub.3-C.sub.17-heteroaryl)(C.sub.6-C.sub.18-aryl); wherein the substituents R.sup.a, R.sup.3, R.sup.4 or R.sup.5 optionally form, independently from each other, a mono- or polycyclic, aliphatic, aromatic and/or benzo-fused ring system with one or more substituents R.sup.a, R.sup.3, R.sup.4 or R.sup.5; wherein exactly one substituent selected from the group consisting of T, V and W is R.sup.A, exactly one substituent selected from the group consisting of R.sup.T, R.sup.V and R.sup.W is CN, exactly one substituent selected from the group consisting of W, Y and X represents the binding site of a single bond linking the first chemical moiety and one of the two second chemical moieties and exactly one substituent selected from the group consisting of R.sup.W, R.sup.Y and R.sup.X represents the binding site of a single bond linking the first chemical moiety and one of the two second chemical moieties.

2. The organic molecule according to claim 1, wherein the first chemical moiety comprises a structure of Formula Ia-1: ##STR00235## wherein Y.sup.D=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties; R.sup.D=is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties; R.sup.Z=is selected from the group consisting of R.sup.I and CN; and wherein exactly one substituent selected from the group consisting of R.sup.V, R.sup.T and R.sup.Z is CN; and wherein apart from that the definitions in claim 1 apply.

3. The organic molecule according to claim 1, wherein R.sup.1, R.sup.2 and R.sup.I, identically or differently at each occurrence, are selected from the group consisting of H, methyl, mesityl, tolyl and phenyl.

4. The organic molecule according to claim 1, wherein R.sup.Tz is independently from each other selected from the group of H, methyl and phenyl.

5. The organic molecule according to claim 1, wherein the two second chemical moieties, identically or differently at each occurrence, comprise a structure of Formula IIa: ##STR00236## wherein # and R.sup.a are defined as in claim 1.

6. The organic molecule according to claim 1, wherein the two second chemical moieties, identically or differently at each occurrence, comprise a structure of Formula IIb: ##STR00237## wherein R.sup.b=identically or differently at each occurrence, is selected from the group consisting of: deuterium, N(R.sup.5).sub.2, OR.sup.5, Si(R.sup.5).sub.3, B(OR.sup.5).sub.2, OSO.sub.2R.sup.5, CF.sub.3, CN, F, Br, I, C.sub.1-C.sub.40-alkyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-alkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-thioalkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkenyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkynyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.6-C.sub.60-aryl, which is optionally substituted with one or more substituents R.sup.5; and C.sub.3-C.sub.57-heteroaryl, which is optionally substituted with one or more substituents R.sup.5; and wherein apart from that the definitions in claim 1 apply.

7. The organic molecule according to claim 1, wherein the two second chemical moieties, identically or differently at each occurrence, comprise a structure of Formula IIc: ##STR00238## wherein R.sup.b, identically or differently at each occurrence, is selected from the group consisting of deuterium, N(R.sup.5).sub.2, OR.sup.5, Si(R.sup.5).sub.3, B(OR.sup.5).sub.2, OSO.sub.2R.sup.5, CF.sub.3, CN, F, Br, I, C.sub.1-C.sub.40-alkyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-alkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.1-C.sub.40-thioalkoxy, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkenyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.2-C.sub.40-alkynyl, which is optionally substituted with one or more substituents R.sup.5 and wherein one or more non-adjacent CH.sub.2-groups are optionally substituted by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, P(O)(R.sup.5), SO, SO.sub.2, NR.sup.5, O, S or CONR.sup.5; C.sub.6-C.sub.6O-aryl, which is optionally substituted with one or more substituents R.sup.5; and C.sub.3-C.sub.57-heteroaryl, which is optionally substituted with one or more substituents R.sup.5; and wherein apart from that the definitions in claim 1 apply.

8. The organic molecule according to claim 6, wherein Rb, identically or differently at each occurrence, is selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3, Ph, which is optionally substituted with one or more substituents independently from each other selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3 and Ph; pyridinyl, which is optionally substituted with one or more substituents independently from each other selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3 and Ph; pyrimidinyl, which is optionally substituted with one or more substituents independently from each other selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3 and Ph; carbazolyl, which is optionally substituted with one or more substituents independently from each other selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3 and Ph; triazinyl, which is optionally substituted with one or more substituents independently from each other selected from the group consisting of Me, .sup.iPr, .sup.tBu, CN, CF.sub.3, and Ph; and N(Ph).sub.2.

9. A method for preparing an organic molecule according to claim 1, comprising providing a bromo-fluorobenzonitrile, substituted with either one R.sup.1 and two R.sup.2 or two R.sup.1 and one R.sup.2, as a reactant.

10. A composition, comprising: (a) at least one organic molecule according to claim 1 in the form of an emitter and/or a host, and (b) one or more emitter and/or host materials, which differ from the organic molecule of claim 1 and (c) optionally, one or more dyes and/or one or more solvents.

11. An optoelectronic device, comprising one organic molecule according to claim 1 in form of a device selected from the group consisting of organic light-emitting diode (OLED), light-emitting electrochemical cell, OLED-sensor, organic diode, organic solar cell, organic transistor, organic field-effect transistor, organic laser and down-conversion element.

12. The optoelectronic device according to claim 11, comprising: a substrate, an anode, and a cathode, wherein the anode or the cathode are disposed on the substrate, and at least one light-emitting layer, which is arranged between anode and cathode and which comprises the organic molecule.

13. The optoelectronic device according to claim 11 comprising the organic molecule, in form of a device selected from the group consisting of organic light-emitting diode, (OLED), light-emitting electrochemical cell, OLED-sensor, organic diode, organic solar cell, organic transistor, organic field-effect transistor, organic laser and down-conversion element.

14. The optoelectronic device according to claim 11 comprising a substrate, an anode, and a cathode, wherein the anode or the cathode are disposed on the substrate, and at least one light-emitting layer, which is arranged between anode and cathode and which comprises the organic molecule.

15. A method for producing an optoelectronic device, wherein the organic molecule according to claim 1 is used, comprising the processing of the organic compound by vacuum evaporation method or from a solution.

16. The method for producing an optoelectronic device comprising the step of: processing by vacuum evaporation method or from a solution the at least one organic molecule according to claim 1 wherein the organic molecule is used in the form of an emitter and/or a host, in a composition with one or more emitter and/or host materials, which differ from the organic molecule of claim 1 and optionally, one or more dyes and/or one or more solvents.

Description

FIGURE LEGENDS

(1) FIG. 1 Emission spectrum of example 1 (10% by weight) in PMMA.

(2) FIG. 2 Emission spectrum of example 2 (10% by weight) in PMMA.

(3) FIG. 3 Emission spectrum of example 3 (10% by weight) in PMMA.

(4) FIG. 4 Emission spectrum of example 4 (10% by weight) in PMMA.

(5) FIG. 5 Emission spectrum of example 5 (10% by weight) in PMMA.

(6) FIG. 6 Emission spectrum of example 6 (10% by weight) in PMMA.

(7) FIG. 7 Emission spectrum of example 7 (10% by weight) in PMMA.

SUMMARY

(8) The invention relates to an organic compound, in particular for the application in organic optoelectronic devices. According to the invention, the organic compound has a first chemical moiety with a structure of formula I,

(9) ##STR00230##

(10) and two second chemical moieties, each at each occurrence independently from another with a structure of formula II,

(11) ##STR00231##

(12) wherein the first chemical moiety is linked to each of the two second chemical moieties via a single bond;

(13) wherein

(14) T, V is selected from the group consisting of R.sup.A and R.sup.1;

(15) W is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is selected from the group consisting of R.sup.A and R.sup.2;

(16) X is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.2;

(17) Y is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.sup.2;

(18) R.sup.T, R.sup.V is selected from the group consisting of CN and R.sup.1;

(19) R.sup.W is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is selected from the group consisting of CN and R.sup.1; R.sup.x, R.sup.Y is the binding site of a single bond linking the first chemical moiety to one of the two second chemical moieties or is R.