Fused TCNQ acceptors

Another interesting type of heterocyclic-fused TCNQ acceptors were the thiadiazole-fused TCNQ derivatives 49 and 50 reported by Yamashita and co-workers who described TCNQ acceptors bearing two thiadiazole units fused to the central TCNQ ring (49) [119] or only one (50) [120]. 

These results can be generalized in the sense that they allow a correlation of the acceptor ability of fused TCNQ derivatives with Ti-deficient or Ti-excessive character of the heterocyclic rings. Thus, the reduction potentials for a number of heterocyclic fused TCNQ derivatives [128] reveals a pattern in which the higher reduction potentials belong to systems with Ti-deficient heterocycles (see Table 1.9). 

Complexes, charge-transfer of fused 1,2-dichalcogenoles, 58, 73 of phenoxachalcogenins with acceptors formation, 58, 101 thermodynamic parameters, 58, 102 of tetratellurafulvalenes, 58, 81 Complexes, charge transfer, azonia-aromatics with TCNQ, 55, 352 Complexes, see also Ligands, coordinated, and the various metals Condensation reactions, forming vinylene betaines, 60, 216... 

The other approach used to form more planar n-extended acceptor molecules involves the use of heterocyclic systems. Despite the steric crowding introduced by ring fusion, it has been shown experimentally that planar molecules are formed when pentagonal heterocyclic systems bearing no peri hydrogen atoms are fused to the TCNQ ring. 

Now the TCNQ ring is simultaneously fused to bodi benzene and thiophene rings as a hybrid acceptor between the TCAQ molecule and the dithiophene-fused... 

In agreement with previous studies [107,108], recently the use of ab initio molecular orbital (mo) calculations have been used to account for the distortion from planarity of some derivatives of TCNQ and, particularly, those containing heterocycles fused to the TCNQ ring. Additionally, MO methods have also been used to predict the reduction potential of novel TCNQ derivatives and the results suggest that it is possible to extend the 7r-system of TCNQ without weakening the electron acceptor ability [129]. 

P3MBET) [137] in composite films with a series of TCNQ derivatives containing fused aromatic rings as acceptors. The results were compared with the photophysical studies carried out previously with these polymers and Ceo as acceptor [138]. 

The LUMOs of 92 (-5.31 eV) and 94 (-5.36 eV) are calculated to be destabilized by ca. 1 eV with respect to the LUMOs of TCNQ (—6.23 eV) and DCNQI (—6.67 eV). This destabilization justifies the lower reduction potentials measured for 92 and 94 (see Table 1.20) and should be ascribed to two main factors (a) the extension of the acceptor moiety by the fusing of one benzene ring, which introduces new antibonding interactions with the TCNQ or DCNQI ring and (b) the loss of planarity of the acceptor moiety. The former explains the shift to more negative values obtained for... 

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