Fréchet-type dendrons bearing azobenzene units and flexible oligo(ethylene glycol) spacers: synthesis, characterization, thermal and optical properties

Figures & data

Scheme 1 Assignments for compounds (a) 6 and (b) 7.

Scheme 2 Assignments for compound 12.

Scheme 3 Assignments for compounds (a) 13G1OH, (b) 14G1OH and (c) 15G1OH.

Scheme 4 Assignments for compounds (a) 19G2OH, (b) 20G2OH and (c) 21G2OH.

Figure 1 Synthesis of the precursor dyes and the first-generation dendrons.

Figure 2 Synthesis of the second-generation dendrons.

Figure 3 ¹H NMR spectra of: (a) First-generation dendron 14G₁OH and (b) Second-generation dendron 20G₂OH.

Figure 4 ¹³C NMR spectra of: (a) First-generation dendron 14G₁OH and (b) Second-generation dendron 20G₂OH.

Table 1. Thermal and optical properties of the dendrons.

Dendrons	T 10 (°C)	T g (°C)	T m (°C)	λ max (nm)	Cut off (nm)	Dipole moment μ (D) ^∗
13G1OH	302	–	40	480	628	8.06
14G1OH	324	−26.2	–	409	527	1.39
15G1OH	219	−33.3	–	409	531	1.11
19G2OH	295	–	28	478	615	8.49
20G2OH	305	−14.6	–	409	529	2.78
21G2OH	192	−31.1	–	409	531	1.55
^∗Calculated by the semi-empirical method PM3.

Figure 5 TGA curves of the obtained dendrons.

Figure 6 Absorption spectra of the dendrons in CHCl₃ solution.

Figure 7 Texture observed upon heating (a) at 27, (b) at 33 and (c) 35 °C, respectively (magnification ×100).