Acceptor-donor stacks

Figure 2 Relationship of (a) TCNQ in acceptor stack, (b) TTF in donor stack and (c) stacking arrangement of TCNQ anions in (TTF)(TCNQ) showing plane of symmetry uniting molecules in a stack...

In this expression, the subscripts and superscripts A and D refer to the acceptor and donor stacks, respectively. 

Two chain compounds, such as TTF-TCNQ and its derivatives, where both donor (TTF) stacks and acceptor (TCNQ) stacks give comparable contributions to the electrical conductivity. Although these compounds... 

Electron donor-acceptor (EDA) stacks have been accessed by Percec et al. [90] using partially fluorinated dendrons (Fig. 14) to form LC columnar phases. The self-assembly of the dendrons is primarily driven by phase segregation of the fluorinated chains and the aromatic units. Functionalization of the dendrons at their apex with either an aromatic electroactive donor (29a) or an acceptor (29b) group yields LC columnar structures, further aided by the additional interaction between the aromatic units, which have optoelec-... 

Our understanding of the difference between TTF-TCNQ and TSeF-TCNQ will enable us to explain the effects of donor stack doping in these two compounds. Donor stack doping by TTF in TSeF-TCNQ interferes with the hybridization between the donor and acceptor stacks. Therefore the 3 dimensional ordering temperature of the undoped acceptor stack should increase as the hybridization is diminished. The donor stack ordering temperature would be determined on the other hand by competition between the doping effect which will tend to lower it and the diminished hybridization which will tend to increase it. 

Well-known donor and acceptor molecules are tetrathi-afulvalene (TTF) and tetracyanoquinodimethane (TCNQ), respectively. A 1 1 TCNQ TTF salt exhibits a high room-temperature conductivity (5 x lO S m ) and metallic behavior is observed as the temperature is reduced to 54 K (i.e., the conductivity increases with decreasing temperature). The molecules in such compounds are arranged in segregated stacks, in which donors and acceptors form separate donor stacks (DDDDDD...) and acceptor stacks... 

---