**3. Synthesis and properties of trityloxy group containing glassy derivatives of pyranylidene and isophorene**

Our key for obtaining glass forming materials is the synthesis of such electron donor substituent containing aldehyde which would ensure the formation of an amorphous structure of our newly synthesized derivatives of pyranylidene and isophorene. We have synthesized such a compound - 4-(bis(2-(trityloxy)ethyl)amino) benzaldehyde [31-32] **75**, in Fig.16.

#### **3.1. Preparation of molecular glasses**

208 Organic Light Emitting Devices

**25a-33a H3C O**

**D =**

significance is the same as for previous figures.

**25a H3C O CH3**

**H**

**H O**

> **O H**

previous figures.

**CH3**

**H3C**

**Piperidine CH3CN H D O**

**<sup>N</sup> <sup>N</sup> <sup>N</sup> <sup>N</sup>**

**62 63 64 65**

**N N N N**

**Figure 14.** Synthesis of fully functional di-styryl substituted derivatives of pyranylidene. Color

**H O**

**H O**

**CH3**

**<sup>N</sup> H3C CH3**

**H3C CH3**

**Piperidine**

**67-69**

**n-propylalcohol**

**N**

**N Et**

**N**

**S**

**68**

**69**

**H O**

**Figure 15.** Synthesis of polymeric derivatives of pyranylidene. Color significance is the same as for

**O 67**

**58-66 O**

**58 59 60**

**N Et N**

**O**

**70**

**71**

**72**

**N**

**n**

**n**

**n**

**N S**

> **N Et**

**O**

**O**

**O**

**N N**

**N N**

**H3C**

**66**

**N**

**<sup>N</sup> Et Et**

**61**

**<sup>O</sup> CH3**

**D D**

**A**

**A**

For obtaining a red luminescent glass forming derivative of isophorene, we start with (3,5,5 trimethylcyclohex-2-enone) (compound **29** in Fig.16) as already described in Fig.9. It is subjected to the *Knoevenagel* condensation reaction with malononitrile (**28**). However, 2-(3,5,5 trimethylcyclohex-2-enylidene)malononitrile (**61**) which is formed during the reaction is not isolated because 4-(bis(2-(trityloxy)ethyl)amino) benzaldehyde (**75**) is added to the reaction mixture after 2 hours [31, 37] for further reaction. 2-(3-(4-(Bis(2-(trityloxy)ethyl)amino)styryl)- 5,5-dimethylcyclohex-2-enylidene)malononitrile (**IWK)** was obtained in good yield after its separation and purification by liyquid column chromatography as described in [31].

**Figure 16.** "One pot" synthesis of **IWK.** (See previous figures for explanation of color significance).

For obtaining red luminescent glass forming derivatives of pyranylidene, we use three different electron acceptor fragment containing derivatives of pyranylidene (compounds **25a** in Fig.17). Malononitrile (in compounds **74a and 75a**), indene-1,3-dione (in compounds **74b and 75b**) and barbituric acid (in compounds **74c and 75c**) are used as electron acceptor fragment carrying compounds [32].

In the *Knoevenagel* condensation reaction with compound **25a** and 4-(bis(2- (trityloxy)ethyl)amino) benzaldehyde (**73**) a mixture of mono- (**ZWK-1**, **DWK-1**, **JWK-1**) and bis- (**ZWK-2**, **DWK-2**, **JWK-2**) condensation products is obtained. Their separation is

complicated but nevertheless a large part of each product was separated by liquid column chromatography (silicagel and dichloromethane for **ZWK-1** and **ZWK-2**, dichloromethane: hexane = 4:1 for **DWK-1** and **DWK-2**, dichloromethane: ethyl acetate = 4:1 for **JWK-1** and **JWK-2**). The physical properties of compounds **WK-1**, **WK-2** and **IWK** are described in detail further in this chapter.

Synthesis and Physical Properties of Red Luminescent

Glass Forming Pyranylidene and Isophorene Fragment Containing Derivatives 211

**Figure 18.** Thermogravimetric analysis of compounds **WK-1** and **WK-2.** A sample of each compound is constantly weighed during heating. At some temperature (Td) the mass of the sample starts to decrease rapidly - this indicates when the respective compound starts to decompose and is no longer thermally

from +25°C to +250°C at a heating rate of 10°C/min [32]. After the first heating scan samples of the compounds were cooled to 25°C at a rate of 50°C/min and heated for a second time from +25°C to +250°C at a rate of 10°C/min. The Tg value is obtained from the second heating scan (see Fig.19) and for almost all compounds is higher than 100°C. We could not obtain usable DSC curves for **DWK-1**. The compounds with two N,N-ditrityloxyethylamino electron donor fragments have higher Tg compared to those with only one electron donor fragment, which may be attributed to the different numbers of bulky trityloxyethyl groups attached to the two electron donor fragment. In a larger number of bulky groups Tg increases by 8°C from **ZWK-1** to **ZWK-2** and 7°C from **JWK-1** to **JWK-2**. Pyranylidene type compounds with barbituric acid as electron acceptor, e.g. **JWK-1** and **JWK-2** have the highest Tg values compared to **ZWK-1**, **ZWK-2** and **DWK-2**, which may be due to the

stable.

**Figure 17.** Synthesis of glass forming derivatives of pyranylidene. Py - pyridine. (See previous figures for explanation of color significance). Since compounds **74a-c** and **75a-c** are our obtained red lightemitting materials, we have assigned specific names for each (**ZWK-1**, **ZWK-2**, **DWK-1**, **DWK-2**, **JWK-1** and **JWK-2**) [28-30, 32, 46].
