Cyclic phosphazene compounds and use thereof in organic light emitting diodes

1. An organic light-emitting diode, comprising at least one cyclic phosphazene compound of formula (I)

wherein:

n is from 3 to 8;

R 1 and R 2 are each the same or different, and each independently a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryloxy, a substituted or unsubstituted alkyloxy, an unsubstituted or substituted cycloalkyl, an unsubstituted or substituted heterocycloalkyl, an unsubstituted or substituted alkenyl, an unsubstituted or substituted alkynyl, an unsubstituted or substituted aralkyl, or F;

or

R 1 and R 2 are each independently, in the n groups of formula (I), joined to one another via a bond, a C 1 -C 6 -alkylene bridge, an arylene bridge, or a C 2 -C 6 -alkenylene bridge, such that R 1 and R 2 together with the phosphorus atom to which they are joined form a cycle;

wherein at least one of R 1 and R 2 is joined to at least one of the phosphorus atoms of the at least one cyclic phosphazene compound of formula (I) not via an oxygen atom, and

wherein the at least one cyclic phosphazene compound is a matrix material in a light-emitting layer, a hole/exciton blocker material, an electron conductor, an electron injection material, an electron/exciton blocker material, a hole injection material and/or a hole conductor.

2. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound, the at least one R 1 or R 2 joined to the at least one of the phosphorus atoms of the at least one cyclic phosphazene compound of the formula (I), is joined via a carbon atom.

3. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound, n is 3.

4. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound, the at least one R 1 or R 2 joined to the at least one of the phosphorus atoms of the at least one cyclic phosphazene compound of formula (I) not via an oxygen atom, is an unsubstituted or substituted aryl radical or an unsubstituted or substituted heteroaryl radical.

5. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound,

R 1 and R 2 are each the same or different, and are each independently substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl.

6. The organic light-emitting diode according to claim 2 , wherein the at least one cyclic phosphazene compound has formula (Ia)

wherein:

(het)aryl is an unsubstituted or substituted C 6-14 -aryl, or an unsubstituted or substituted heteroaryl which has from 5 to 14 ring atoms and is joined to the P of the phosphazene ring via a carbon atom;

R 1 and R 2 are each the same or different, and are each independently a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryloxy, or a substituted or unsubstituted alkyloxy;

Or

R 1 and R 2 are each independently joined to one another via a bond, a C 1 -C 6 -alkylene bridge, an arylene bridge, or a C 2 -C 6 -alkenylene bridge, such that R 1 and R 2 together with the phosphorus atom to which they are joined form a cycle.

7. The organic light-emitting diode according to claim 6 , wherein all R 1 , R 2 , and (het)aryl radicals in the at least one cyclic phosphazene compound of formula (Ia) are identical.

8. The organic light-emitting diode according to claim 1 , wherein the at least one cyclic phosphazene compound is a matrix material in the light-emitting layer and/or a hole/exciton blocker material and/or an electron conductor.

9. The organic light-emitting diode according to claim 1 , having an emission maximum between 400 and 500 nm.

10. The organic light-emitting diode according to claim 1 , comprising a light-emitting layer comprising at least one matrix material and at least one emitter material, wherein the at least one matrix material comprises the at least one cyclic phosphazene compound according to claim 1 .

11. A device selected from the group consisting of a stationary visual display unit, an illumination, and a mobile visual display unit, comprising at least one organic light-emitting diode according to claim 1 .

12. The organic light emitting diode according to claim 6 , wherein in wherein the at least one cyclic phosphazene compound of formula (Ia),

R 1 and R 2 , in the case where they are joined to one another, together independently, in the n groups of formula (I), form one of:

wherein:

R 3 is, in each case, independently a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryloxy, a substituted or unsubstituted alkyloxy, an unsubstituted or substituted cycloalkyl, an unsubstituted or substituted heterocycloalkyl, an unsubstituted or substituted alkenyl, an unsubstituted or substituted alkynyl, am unsubstituted or substituted aralkyl or halogen, or pseudohalogen;

X is a heteroatom;

x is, in each case, independently 0, 1, 2, 3, or 4; and

y is, in each case, each independently 0, 1, or 2.

13. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound, R 1 or R 2 are the same or different, and are each independently a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, a substituted or unsubstituted aryloxy, or a substituted or unsubstituted alkyloxy.

14. The organic light-emitting diode according to claim 1 , wherein, in the at least one cyclic phosphazene compound, n is 3 or 4.

15. The organic light-emitting diode according to claim 6 , wherein, in the at least one cyclic phosphazene compound of formula (Ia),

(het)aryl is phenyl, a C 1 -C 6 -alkylphenyl, a C 1 -C 6 -dialkylphenyl, a C 1 -C 6 -alkoxyphenyl or a C 1 -C 6 -dialkoxyphenyl.

16. The organic light-emitting diode according to claim 6 , wherein, in the at least one cyclic phosphazene compound of formula (Ia),

(het)aryl is an unsubstituted or substituted carbazolyl, an unsubstituted or substituted azacarbazolyl, or an unsubstituted or substituted pyridyl.