《过程材料6-外文文献》由会员分享，可在线阅读，更多相关《过程材料6-外文文献（17页珍藏版）》请在金锄头文库上搜索。
1、Activation of Hydrogen- and Halogen-Bonding Interactions in Tetrathiafulvalene-Based Crystalline Molecular Conductors4.3. Radical Cation Salts of Halogenated Tetrathiafulvalenes4.3.1. C-Hal.Halanion Interactions 4.3.2. C-Hal.O,Sanion Interactions 4.3.3. C-Hal.N Interactions 4.3.4. Evolution of Halog
2、en Bonding in TTF Salts4.4. Halogen Bonding Interactions in the Anionic Network5. Concluding Remarks 6. Acknowledgments 4.3. Radical Cation Salts of Halogenated TetrathiafulvalenesA distinction will be made among the various salts of halogenated tetrathiafulvalenes between (i) those incorporating ha
3、logenated anions (Br-, IBr2-, I3-),where Hal.Halanion interactions were expected, and (ii) those incorporating other heteroatoms as Lewis bases for Hal.B interactions, essentially organic and inorganic nitriles where Hal.NC interactions were anticipated.4.3.1. C-Hal.Halanion InteractionsCrystals of
4、neutral, chlorinated tetrathiafulvalenes exhibit at best close-packed Cl.Cl interactions.Because of the strong electronegative character of the chlorine atom, Cl-substituted TTFs oxidize at higher potentials than the bromo or iodo derivatives151 and their radical cation salts have not been investiga
5、ted to any extent. A 2:1 salt of EDT-TTFCl2 has been obtained by chemical oxidation with the strong TCNQF4 oxidant,152 while electrocrystallization experimentsafforded a 1:1 salt with ClO4-, (EDT-TTFCl2)-(ClO4), and with EDO-TTFCl2 and (n-Bu4NPF6), a 2:1salt formulated as (EDO-TTFCl2)2(PF6) was obta
6、ined.153 Short type I Cl.Cl contacts were onlyobserved in (EDT-TTFCl2)2(TCNQF4) with Cl.Cl =3.42 and 1= 2 =126. Note also that a shorter type I contact (3.38 , 1= 2 = 146) was observed in neutral EDO-TTFCl2.145On the other hand, several salts of o-dibromotetrathiafulvalene derivatives have been synt
7、hesized, essentially with inorganic polyhalides such as I3- or IBr2- with the objective to promote cation.anion, Br.Br, or Br.I interactions. And indeed,such interactions have been clearly observed while they were essentially absent in the neutral donor molecules. For example, in the 1:1 o-TTF(SMe)2
8、Br2-I3 salt shown in 4.3,140,148 the shortest BrI (3.63 , 1= 72, 2 = 164) contact involves the terminal iodine atom of I3- (d1 in 4.3). The I3- anion thus bridges two adjacent cations through I3Br and I3S (d2) contacts while a I3Br (3.85 , 1=72, 2 =164) contact (d3) with a neighboring donor molecule
9、along c results in the formation of an extended two-dimensional network.Table 15. Structurally Characterized Radical Cation Salts of Halogenated TTFs with HalHal InteractionsIn the 2:1 I3- and IBr2- salts of EDT-TTFBr2,154 organic slabs adopt the so-called structure of BEDT-TTF salts. Two short HalH
10、al contacts shown in 4.4 are identified, one between donor molecules (BrBr ) 3.46 , 1= 97, 2 = 152 in the IBr2- salt, BrBr ) 3.51 , 1= 98, 2 = 150 in the I3- salt) and one between EDT-TTFBr2 and the terminal atom of either (Br-I-Br)- (BrBranion ) 3.42 , 1=109, 2 = 165) or I3- (BrIanion ) 3.51 , 1=11
11、0, 2 = 165) anion, with both having the characteristics of a strong, type II halogen bond. Moreover,it was shown that the presence of HalHal interactions between the partially oxidized molecules contributes not only to the structural stabilization but also to the electronic delocalization. Indeed, t
12、he presence of nonzero atomic coefficients on the halogen atoms in the HOMO of EDT-TTFBr2 or EDT-TTFI2,together with the short HalHal contacts, leads to a sizable increase of the band dispersion and stabilizes a rare structure through the side-by-side arrangement of the inversion-centered dyads conn
13、ected by HalHal interactions. Both salts are semiconductors with room-temperature conductivities around 1 S cm-1, a large value when compared with other structures such as -(BEDT-TTF)2(ICl2) (see Table 15).(EDT-TTF-I)2Br, reported in 1995 by Imakubo and Kato, is the first, seminal, and elegant examp
14、le of halogen bonding in tetrathiafulvalene salts.139 As exemplified in 4.5, two partially oxidized EDT-TTF-I molecules are linked to the bromide anion via a perfectly linear and very short (3.21 , Danis ) 3.60 ) IBr contact. Note also the stabilizing contribution of two C-HBr- hydrogen bonds from t
15、wo neighboring donor molecules, whose structural characteristics (HBr = 2.61 , C-HBr =177) are well in the range described in section 3 for such interactions. As a consequence of both halogen and hydrogen bonding, all four molecules and bromide anion are fully coplanar. The salt is a semiconductor w
16、ith RT =1 S cm-1 and an activation energy of 51 meV.Other examples of strong II interactions are found in the 1:1 salt155 (EDO-TTFI2)2(I)2.(I2), where two donor molecules are linked to two I- anions through the short and linear contacts (3.40 , 2 = 163, 173) shown in 4.6. Further interaction of Iwith a diiodine molecule (II =3.40 ) actually generates I4 2- species and a
