Swivel cruciform

In the synthesis of the swivel-cruciform binaphthyl-based oligomers 27 and 28, bromination of commercially available l,l -binaphthol followed by a Williamson reaction gives binaphthyl ethers with various alkoxy groups [43], The dibromi-... 

Scheme 3.11 Structure of swivel-cruciform core fragments...

Other swivel-cruciforms based on a 1,1 -binaphthyl core were prepared by Rajca et al. according to the procedure in Scheme 3.14 [44]. It is noteworthy that the solubility of the resulting materials in chloroform follows the order (S)-31 (2 X 10-1 mol L-1) > rac-31 (8 X 10-4 mol L-1) > 32 (2 X 10-5 mol L-1). Although the energies of the jt-jt transition for 31 and 32 were essentially identical, the extinction coefficient of 31 was approximately double that of the linear model compound 32. Both findings demonstrate the well-documented function of the binaphthyl unit to act as a conjugation barrier with little electronic communication between naphthalene units. 

Bazan and coworkers also prepared anthracene-substituted swivel cruciforms 33 with binaphthyl cores [44, 45]. They attached the anthracene units to the binaphthyl in the 6,6 -positions by a Suzuki-type cross-coupling reaction (Scheme 3.15). Based on the aforementioned findings that the alkoxy chain length influences the solid-state properties of these types of materials, they produced two de-... 

Scheme 3.12 Synthesis of swivel-cruciform binaphthyl-based oligomers 27 and 28, according to Bazan and coworkers [43].

Scheme 3.14 Synthesis of binaphthyl-based swivel-cruciforms 31, after Rajca et al. [44]. For comparison, the structure of a model compound 32 is also shown.

Scheme 3.15 Synthesis of anthracene-substituted swivel-cruciforms 33 with a binaphthyl core, according to Bazan and coworkers [45],...

Based on the perception that interchain interactions should be suppressed by introducing nonplanar units into the PFO chains, we decided to prepare random copolymers incorporating swivel-cruciform binaphthyl moieties into the polymer backbone [46], Furthermore, as shown in the previous examples on low molecular weight chromophores by Bazan and coworkers, the distorted nature of the binaphthyl unit should simultaneously facilitate the formation of a glassy, amorphous state. PFO and random copolymers 34, incorporating binaphthyl units,... 

Scheme 3.17 Synthesis of the binaphthyl-based swivel-cruciform 35 [50].

However, as mentioned previously, the yield in the preparation of 35 was particularly poor and so an alternative path towards a swivel-cruciform arrangement was developed wherein the core of the cruciform was a tetrasubstituted biphenyl unit. For proof of concept, we synthesized the terphenyl dimer 2,5,2, 5 -tetra(4-tert-butylphenyl)-l,T-biphenyl (36) via the strategy depicted in Scheme 3.18 [50]. Compound 36 was obtained in a nickel[0]-mediated (microwave-assisted) Yamamoto-type coupling of the chloroterphenyl derivative 37 in reasonable yields using THF as the solvent at temperatures of about 130 °C [57, 58],... 

Scheme 3.18 Synthetic approach towards the swivel-cruciform terphenyl dimer 36 [50].

Scheme 3.21 Structures of the other extended swivel cruciforms 42-47.

The thermal properties of the swivel cruciforms 40-47 were analyzed by DSC. Remarkably, the cruciforms 45, 43, 44 (R = tat-butyl), 46 and 42 show distinctly increased Tg values of 95, 130, 140, 130 and 225 °C, respectively. Only the fluori-nated derivatives 45 and 46 display clear melting transitions in DSC with Tm = 228 and 257 °C, respectively. 

Scheme 3.23 Synthesis of the swivel-cruciform dimer 49 with dithienyl—phenylene—dithienyl arms.

Hence we synthesized a related swivel-cruciform dimer 49 with dithienyl-phe-nylene-dithienyl arms by a synthetic strategy similar to the already described oh-... 

The absorption and emission spectra of 50a, 54 and the linear distyrylbenzene model compound 55 in dilute solution were rather similar. However, the solid-state emission maxima lmax>em °f the swivel-cruciforms were red-shifted by 25 (50a) and 13 nm (54) relative to the model compound 55. This may be a consequence of some electronic interaction between the arms within the partially pla-... 

Scheme 3.24 Synthesis of swivel-cruciform oligophenylenevi-nylene dimers 50a-d, according to Ma and coworkers [74, 75].

Scheme 3.25 Synthesis of a swivel-cruciform oligophenylenevi-nylene trimer 54 by Ma and coworkers [76], For comparison, the structure of distyrylbenzene (55) is also given...

DBST (p,p -dibutylsexithiophene) 77, 80 ff DCNDBQT (a,cD-dicyano-p,p -dibutyl-quaterthiophene) 76 ff deep level transient spectroscopy (DLTS) 428, 437, 438 deep trap 437, 433, 441 deformation pattern 264, 276 degradation 373 ff., 393 ff, 553 demodulated reader signal 9 density functional theory (DFT) 264, 539 density of states (DOS) 428, 437 depth profile 404 ff., 436, 544 de-trapping 428, 437 ff, 441 device simulation 433, 435 dewetting, post-deposition 220 ff. DHBTP-SC ((dihexylbithiophene)2-phe-nyl swivel cruciform) 96 ff. 

DHPT-SC (u,a -dihexylpentathiophene based swivel cruciform) 96 ff dielectric interface 516 dielectrics 27... 

Organic Transistors Utilising Highly Soluble Swivel-Cruciform Oligothiophenes... 

Here, we summarise results obtained on soluble swivel-cruciform oligothiophenes. The term swivel-cruciform reflects the fact that the single bond connection of the two non-substituted oligothiophenes at the central thienylene moieties permits, in contrast to the corresponding spiro-type dimers [21], a certain degree of rotation of the arms. This leads to a good solubility even without the attachment of solubilising alkyl chains. Initially, a series of swivel-cruci-... 

Figure 6.1 Molecular structure of the conjugated organic materials used in this work his(terthiophene) (BT3), bis(pentathiophene) (BT5), his(heptathiophene) (BT7), a,a -dihexylpentathiophene based swivel cruciform (DHPT-SC) and (dihexylbithiophene)2-phenyl swivel cruciform (DHBTP-SC).

Table 6.1 Root-mean-square roughness (Rrms) the mean roughness (RJ for both swivel cruciforms calculated using Veeco software and using AFM images shown in Figures 6.6a-d and 6.7a-d.

As shown in Figure 6.13 there are significant differences in the temperature dependent mobilities obtained for the swivel-cruciforms. Firstly, the tempera-... 

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