DBTTF-TCNQ: A fractionally-charged organic salt with a mixed-stack crystalline motif

Polymorphism in the 1:1 Charge‐Transfer Complex DBTTF–TCNQ and Its Effects on Optical and Electronic Properties

“…The α-polymorph exhibited a shift to 1426 cm −1 in our measurements, corresponding to a degree of charge transfer of 0.5 e . This value is in agreement with the value reported in the literature based on IR spectroscopy [25] . The weakly intense peak present at 1450 cm −1 was predicted to correspond with the C=C stretching on the donor moiety, and was thus not used for the calculation of the degree of charge-transfer.…”

“…Techniques to quantify the degree of charge transfer exploit the change in the bond lengths and vibration frequencies of the acceptor/donor as a result of the partial addition/loss of charge. These include Raman and IR spectroscopies, X‐ray and neutron scattering . In this study we determined the degree of charge‐transfer via Raman spectroscopy by evaluating the dependence of the TCNQ ν 4 (exocyclic CC stretching) vibration frequency on the surrounding charge .…”

“…These form an excellent system for the study of the effect of D/A interactions on the optical properties and charge transport in CT complexes because the constituent molecules are exactly the same, but variations in their molecular packing result in different functionality. We will refer to the known, triclinic polymorph as the α‐polymorph . Crystals of this structure adopt a rectangular shape (Figure c), whereas the crystals of the new, previously‐unreported polymorph (which we will call the β‐polymorph), are elliptical in shape (Figure d).…”

The 1:1 charge-transfer complex dibenzotetrathiafulvalene–pyromellitic dianhydride (DBTTF–PMDA)

“…CT complexes of the acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) have been widely explored. Examples include the organic metal with donor tetrathiafulvalene (TTF) (Ferraris et al, 1973) or the ambipolar semiconductor with dibenzotetrathiafulvalene (DBTTF) (Kistenmacher et al, 1981;Takahashi et al, 2006;Wu et al, 2013). With the exception of a few reports, CT complexes containing pyromellitic dianhydride (PMDA) as an acceptor have received little attention.…”

“…General properties and potential applications of chargetransfer complexes in electronic devices are outlined by Goetz et al (2014); Horiuchi et al (2006); Tsutsumi et al (2012); Kobayashi et al (2012); Kagawa et al (2010); Herbstein (2005); Ferraris et al (1973); Kistenmacher et al (1981); Takahashi et al (2006); Wu et al (2013). Related CT structures, containing the acceptor pyromellitic dianhydride (PMDA) include anthracene-PMDA (Robertson & Stezowski, 1978), phenanthrene-PMDA (Evans & Robinson, 1977), pyrene-PMDA (Herbstein & Snyman, 1969) and two polymorphs of biphenylene-PMDA (Stezowski et al, 1986).…”