*2.3. (TMTSF)*4*(I*3*)*4·*THF*

The crystal structure of the 4:4 salt is shown in Figure 8; and its crystallographic and refinement data are summarized in Table 1. The crystal system is orthorhombic with the space group *Pnma*. The major building blocks of the crystal are the tetramers of TMTSF molecules and I− <sup>3</sup> anions in addition to the THF molecules coming from the crystal growth solvent. Since the composition of TMTSF : I− <sup>3</sup> is 1:1, the average valence of TMTSF should be 1+.

The TMTSF molecules in a tetramer are labeled K, L, M, and N as in Figure 8. They are not crystallographically identical to one another, while every molecule is on a mirror plane parallel to the *ac*-plane. Thus, it is natural to consider that the valence of these TMTSF molecules is not the same within the tetramer. This is discussed in Section 3.

The arrangement of the TMTSF molecules in the tetramer is shown in Figure 9. There are no short Se··· Se contacts between the nearest tetramers. The normal to the molecular plane defined with the four Se atoms is almost parallel to the stacking direction (*c*-axis) but slightly tilted. The angle between the normal to each molecular plane and the *c*-axis is 2.11◦, 1.85◦, 1.34◦, and 2.04◦ for K, L, M, and N, respectively.

**Figure 8.** The crystal structure of (TMTSF)4(I3)4·THF at room temperature viewed along (**a**) the *b*-axis and (**b**) *a*-axis, respectively. The crystallographically independent TMTSF molecules are labeled K, L, M, and N. The molecules in a half unit cell is shown in each of (**a**,**b**).

**Figure 9.** Donor arrangement in a tetramer of (TMTSF)4(I3)4·THF. Hydrogen atoms are not shown for clarity. The crystallographically independent TMTSF molecules are labeled K, L, M and N, respectively. The broken lines show the Se··· Se contacts shorter than 4.0 Å. The interplanar distances are *d*<sup>1</sup> = 3.599(5) Å (K–L), *d*<sup>2</sup> = 3.92(7) Å (L–M), and *d*<sup>3</sup> = 3.53(2) Å (M–N), respectively.

The tetramer is regarded as made of two non-equivalent dimers K–L and M–N as is obvious in Figure 9. The intradimer distance *d*<sup>1</sup> = 3.60 Å (K–L) and *d*<sup>3</sup> = 3.63 Å (M–N) is much shorter than the interdimer distance *d*<sup>2</sup> = 3.92 Å (L–M). There are four short Se··· Se contacts within each of the dimers (K–L and M–N), while there are only two contacts between the dimers (L–M) and it is rather long (3.98 Å).

Each TMTSF tetramer is surrounded by six I− <sup>3</sup> tetramers and vice varsa. In this sense, the 4:4 salt is similar to the rock salt NaCl. In addition, there is no strong interaction between the nearest TMTSF tetramers. Thus, the system is probably insulating, though the electrical conductivity is not known due to the rarity of its single crystals.

Among the exotic TMTSF salts, (TMTSF)4(TMTSF)[Nb6Cl18]·(CH2Cl2)0.5 also has a TMTSF tetramer as a building unit [62,63]. In this case, however, a one-dimensional TMTSF stacks are formed by the repetition of tetramers resulting in its moderate electrical conductivity (0.5 S·cm−1) at room temperature. The orthorhombic rock-salt-like structure with the TMTSF and I− <sup>3</sup> tetramers of the 4:4 salt is unique even in the exotic TMTSF salts.

#### **3. Discussion**

#### *3.1. Valence and Bond Lengths of TMTSF Molecules*

The knowledge of the valence of donors in conducting salts is essential to understand their electronic states because it determines the band filling and, therefore, Fermi energy. Once the band structure is available, one can predict whether the system has a Fermi surface or not. In Bechgaard salts, where the ratio of the TMTSF molecule to the monovalent anion is 2:1, the valence of the TMTSF molecule is (1/2)+. In the exotic TMTSF salts, however, the evaluation is sometimes not so simple due to the existence of non-equivalent TMTSF molecules.

Some authors reported the attempts to estimate the valence of TMTSF molecules partially oxidized in salts on the basis of the intramolecular bond lengths [46,60,63,71]. Indeed, there seems to be a kind of correlation between the valence and the bond lengths of TMTSF molecules in the neutral crystal (TMTSF0) [76]; the 2:1 radical salts (TMTSF0.5<sup>+</sup>) [5,52,77–80]; and (TMTSF)NO3 [69], (TMTSF)[Cr(Br4SQ)2(Br4Cat) (SQ = semiquinonate, Cat = catecholate) [70], and (TMTSF)3PW12O40 [68] (TMTSF1<sup>+</sup>) as tabulated in Table 2.

Here we label the bond lengths *e*, *fi*, *gi*, and *hi* as in the inset of Table 2, where the subscript *i* distinguishes the chemically equivalent bonds from one another. For example, the length of the central and outer C=C bonds (*e*, *h*1, and *h*2) have rough tendency to increase when the molecular valence changes from 0 to 1+, while the C−Se single bonds (*fi* and *gi*) tend to become shorter.

Please note that we chose the BF4, PF6, and NbF6 Bechgaard salts because they are representatives of the 2:1 radical salts with small (radius *r* = 2.72 Å), middle (*r* = 2.95 Å) [81] and large (*r* = 3.20 Å) [5] counter anions, respectively. (TMTSF)2NO3 is the last Bechgaard salt that we could find the atomic coordinate of hydrogen atoms for the quantum mechanical energy calculations. (TMTSF)2Ni(tds)2 (tds = [bis(trifluoromethyl)ethylene]diselenolato) [52] also has the 2:1 composition, but it is one of the exotic TMTSF salts with two crystallographically independent TMTSF molecules A and A' at room temperature.

On the other hand, (TMTSF)NO3, (TMTSF)[Cr(Br4SQ)2(Br4Cat), and (TMTSF)3PW12O40 are examples of TMTSF1<sup>+</sup> simply from their chemical compositions.

We also carried out quantum mechanical calculations [82] on the basis of the density functional theory (DFT, B3LYP/6-31G(d,p)) as well as Hartee–Fock (HF) calculations followed by Møller–Plesset correlation energy calculations truncated at the second order (MP2, 6-31G(d,p)) for TMTSF0, TMTSF1<sup>+</sup>, and TMTSF2<sup>+</sup> to obtain each optimized structure for comparison. The calculated bond lengths as well as those of the TMTSF molecules in the I3 salts are also summarized in Table 2.

The rough correlation noted above is shown by plotting the *e*; and the averages of *fi*, *gi*, and *hi* (*f* , *g*, and *h*) against the donor valence in Figure 10. The bond lengths observed in the I3 salts are indicated by the arrows at the right-side vertical axis in each plot.

In case of the central C=C bond *e* (Figure 10a), the DFT and MP2 results coincide to each other showing the almost linear valence dependence. On the other hand, the DFT and MP2 calculations give 1–2% difference in the other bond lengths from each other, though they are still close. The experimental bond lengths are mostly around the lines connecting the calculated points, but we see exceptionally scattered points at the valence = 0.5 and 1.

**Table 2.** Comparison of bond lengths in TMTSF molecules in the crystals of neutral TMTSF and some salts. Each of *f* , *g*, and *h* is the average such as *f* = (*f*<sup>1</sup> + *f*<sup>2</sup> + *f*<sup>3</sup> + *f*4)/4.

*<sup>e</sup> <sup>f</sup>*<sup>1</sup>

*g*1

*f*3

*g*3


<sup>1</sup> Neutral crystal [76]. <sup>2</sup> (TMTSF)2BF4 at the anion ordered state at 20 K with two crystallographically independent TMTSF molecules (A and B) [77]. <sup>3</sup> (TMTSF)2PF6 at 20 K with the neutron diffraction structural analysis [78]. <sup>4</sup> (TMTSF)2PF6 [79]. <sup>5</sup> (TMTSF)2NO3 at 125 K [80]. <sup>6</sup> (TMTSF)2NbF6 [5]. <sup>7</sup> (TMTSF)2Ni(tds)2 (tds = [bis(trifluoromethyl)ethylene]diselenolato) [52]. <sup>8</sup> (TMTSF)NO3 [69]. <sup>9</sup> (TMTSF)[Cr(Br4SQ)2(Br4Cat)] ·(CH2Cl2)2 (SQ = semiquinonate, Cat = catecholate) [71]. <sup>10</sup> (TMTSF)3PW12O40 [68]. <sup>11</sup> Optimized structures calculated by the density-functional theory method (B3LYP/6-31G(d,p)) [82]. <sup>12</sup> Optimized structures obtained by Hartree–Fock calculations (6-31G(d,p)) followed by Møller–Plesset correlation energy calculations truncated at second order [82] .

The optimized structures are of the isolated molecules in vacuum and highly symmetric. On the other hand, the TMTSF molecules in the crystals are affected by their surroundings as well as by the formation of their own energy bands. Therefore, they are rather unsymmetric, even if the chemical structure of TMTSF is symmetric. This is the reason we compared the "average" bond lengths such as *f* . In addition, the energy of TMTSF molecule also depends on bond angles, which are not considered here. Therefore, the scattering of the experimental data in Figure 10 is very natural.

Furthermore, the bond lengths observed for the crystallographically independent TMTSF molecules (PWO A and B) in (TMTSF)3PW12O40 are anomalously far from the others at the valence = 1. The deviation is qualitatively understood assuming that A is close to neutral and B is more oxidized

than 1+. This is consistent with the results of the quantum mechanical energy calculations discussed in Section 3.

**Figure 10.** Dependence of the bond lengths (**a**) *e*, (**b**) *f* , (**c**) *g*, and (**d**) *h* of the TMTSF molecules in the crystals on the valence expected from their chemical compositions. The open and closed circles show the corresponding bond lengths in the optimized structures by the quantum mechanical calculations (see text and the caption in Table 2). The solid lines are guides to the eye.

A more important result we see here is, however, the unsystematic scattering of the arrows from A to Q at the right-side vertical axes. We can expect, for example, the monomers R and C in the 8:5 and 5:2 salts are probably less oxidized. Indeed, the C and R are far from the others in Figure 10a,b, but that is not the case in Figure 10c,d. Another difficulty is about K, L, M, and N in the 4:4 salt, where their average valence is most likely 1+ and higher than the others in the 8:5 and 5:2 salts. They are, however, inside the distribution.

It should be noted that Rosoka et al. [60] proposed an equation to estimate the effective valence by combining the bond lengths of the target molecule with those in the crystals of the neutral and cation radical salts. Although they succeeded in evaluating the TMTSF valence close to (2/3)+ in (TMTSF)3(TFPB)2 by the equation, we do not adopt their method in this study due to the low correlation in Figure 10. Instead, we carried out the quantum mechanical energy calculations, which consider all the information of each molecule not only the bond lengths but also bond angles, and even electron correlations.

#### *3.2. Valence of TMTSF Molecule Estimated from Total Energy*

#### 3.2.1. Principles

The method we propose here to estimate the valence of TMTSF molecules in the crystals is as follows. This is base on the quantum mechanical calculations with the DFT or MP2 method used in the previous subsection.


The Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> are the energy increase of the TMTSF molecule from those at its neutral and cationic states with their optimized conformations, respectively. Therefore, the Δ*E*<sup>0</sup> will be smaller than the Δ*E*1<sup>+</sup> when a TMTSF molecule in a crystal has a conformation which is more stable at a less oxidized state than at a more oxidized one. On the other hand, the Δ*E*1<sup>+</sup> will become smaller than the Δ*E*<sup>0</sup> when a conformation approaches to what is stable at a valence close to 1+. In addition, if the effective valence of a molecule is (1/2)+ with a conformation in a crystal, the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> will be comparable to each other. These are schematically shown in Figure 11a.

**Figure 11.** (**a**) Schematic image of Δ*E*<sup>0</sup> (red), Δ*E*1<sup>+</sup> (blue), and Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> (green) as functions of the nuclear coordinates of a TMTSF molecule in a crystal. (**b**) Simplified images of Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> as multidimensional paraboloids, which are the functions of bond lengths and bond angles of a TMTSF molecule in a crystal. The thin green line C0 represents the path when the conformation changes continuously keeping the optimum one at each effective valence. In reality, the molecular conformations are not optimum in crystals, thus the molecules will be somewhere on the thick pink curve C1 (see text).

These relations are simply expressed by the Δ*E*<sup>0</sup> − Δ*E*1+. The energy increase Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> as functions of the nuclear coordinates/conformation are approximated by parabolas in the vicinity of their minima. Although the curvatures of the parabolas would be different from each other in general, the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> changes monotonically as shown by the green curve in Figure 11a as long as the difference between the curvatures is not so large.

The green curve (Δ*E*<sup>0</sup> − Δ*E*1+) becomes negatively and positively large at the bottom of the blue (Δ*E*0) and red (Δ*E*1+) curves, respectively. In addition, the green curve becomes almost zero when the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> are comparable to each other, where one can probably expect that the effective molecular valence is also in the middle between 0 and 1+. When the effective molecular valence changes continuously from 0 to 1+, the optimum conformation smoothly changes from that of TMTSF<sup>0</sup> to that of TMTSF1<sup>+</sup> on the horizontal axis. Then the <sup>Δ</sup>*E*<sup>0</sup> <sup>−</sup> <sup>Δ</sup>*E*<sup>1</sup> will scale the molecular valence.

Actually the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> are multivariable functions of the nuclear coordinates. Thus, each of the red and blue curves in Figure 11a is just one aspect of the multidimensional paraboloid, which is schematically shown in the two-dimensional space in Figure 11b, where the atomic coordinates in Figure 11a are separated into the bond lengths and bond angles. Each of the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> is zero at a point in the multidimensional parametric space, where the molecule has the optimized conformation for each valence.

Using the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> as a gauge of the valence corresponds to use the green line C0 in Figure 11b connecting the points of Δ*E*<sup>0</sup> = 0 and Δ*E*1<sup>+</sup> = 0. It corresponds to the green curve Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> in Figure 11a, when one adds the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> as the third axis in Figure 11b.

In reality, the "paraboloids" would have rather complicated contours in the multidimensional space; and the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> is not a curve but a multidimensional plane. In addition, even if the valence of a TMTSF molecule in a crystal is exactly 0 or 1+, its conformation is not the optimum one. Therefore each TMTSF molecule in different crystals or even at different temperatures is somewhere on a thick path connecting the points of Δ*E*<sup>0</sup> = 0 and Δ*E*1<sup>+</sup> = 0 such as the pink curve C1 in Figure 11b. The estimate of the effective molecular valence shown below will hold as long as the pink curve is not so thick and not far from the green line in the multidimensional space.

#### 3.2.2. Energy Calculations

The results by the DFT and MP2 calculations are summarized in Tables 3 and 4, respectively. The *E*<sup>0</sup> and *E*1<sup>+</sup> of the crystals are calculated by using the experimentally determined atomic coordinates whose significant figures are typically three or four. The change in the atomic positions from material to material results in the difference among the last four digits of the *E*<sup>0</sup> and *E*1+ in the tables. Therefore we estimated that the resulting Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> would have three significant figures at most.

The energy differences Δ*E*0, Δ*E*1+, and Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> are shown as histograms in Figure 12. The results by the DFT calculations (Figure 12a,b) are similar to those by the MP2 (Figure 12c,d), but the latter is considered to be more plausible in the absolute values as described below.

At first glance, both the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> are almost the same for each TMTSF molecule in the crystals, thus one might feel that it does not tell anything. The large values (5–6 eV) in Figure 12a,c, just show the conformations of the TMTSF molecules are far from the optimized ones for the neutral and monocationic states.

It is, however, interesting that the results for the BF4, PF6, and NO3 salts are very close to zero. This is probably because the crystal structures determined at low temperatures were used only for these salts, while the others are those at room temperature. It is reasonable because the optimized conformations by the calculations correspond to those at 0 K and no thermal oscillations are considered.

The relatively small size of the BF− <sup>4</sup> , PF<sup>−</sup> <sup>6</sup> , and NO<sup>−</sup> <sup>3</sup> anions may contribute to suppress the Δ*E*<sup>0</sup> and Δ*E*1+. However, this is inconsistent with that the neutral crystal gives the large values. To find the conclusive results, we need the crystal structures of an identical material both at low and high temperatures, but the present authors could not find such reports. The atomic coordinate of hydrogen atoms is needed for this purpose, but it is often unavailable in early works.

Even though the thermal oscillations might affect the Δ*E*<sup>0</sup> and Δ*E*1+, their effect seems to be canceled to an extent after calculating the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> as in Figure 12b,d. One can see a rough tendency that the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> increases from negative to positive values as the effective valence changes from 0 to 1+ for the materials reported previously. This suggests that the effects making the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> large are regarded as systematic errors depending on materials. For example, the anharmonicity of the molecular vibrations always increase the bond lengths. This will increase both the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> in a similar manner.

**Figure 12.** Visualization of (**a**) Δ*E*<sup>0</sup> and Δ*E*1+; and (**b**) Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> obtained by the DFT calculations in Table 3. (**c**,**d**) The correspondents by the HF energy calculations and its correlation-energy correction by the MP2 calculations in Table 4.

One significant exception in the tendency is the smaller value for TMTSF1<sup>+</sup> in (TMTSF)NO3 than those for TMTSF(1/2)+ of (TMTSF)2NO3, (TMTSF)2NbF6, and (TMTSF)2Ni(tds)2. The reason is unclear, but it would be the representative showing the limitation of the present method to determine the absolute values of the effective valence as discussed in the previous subsection.

On the other hand, the negative and large positive values of the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> for (TMTSF)3PW12O40 (PWO A and B) are well understood as follows. The material has a "criss–cross" stacking of the monomer A and the dimer B–B along the *a*-axis [68]. As is shown in Figure 10, the bond lengths observed in the material are anomalous as TMTSF1+; and suggest that A is close to neutral and B is more oxidized than 1+. In Figure 12b,d, now we see that A and B show large negative and positive values of the Δ*E*<sup>0</sup> − Δ*E*1+, respectively. If A is exactly neutral, the valence of B is (3/2)+ due to PW12O40<sup>3</sup>−. This is consistent with the positively large <sup>Δ</sup>*E*<sup>0</sup> − <sup>Δ</sup>*E*1<sup>+</sup> assuming also that we can extrapolate the relation between the effective valence and Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> to above 1+.

By considering the variation in the materials as well as in the methods to determine their crystal structures, the correlation between the effective valence of the TMTSF molecules and the value Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> seems reasonably high. Despite the difficulty in determining the absolute value of the effective valence, it is probably possible to compare the degree of oxidation of the non-equivalent TMTSF molecules in the identical material as in (TMTSF)3PW12O40.

### 3.2.3. (TMTSF)5(I3)2

It should be noted that the crystal structure of (TMTSF)2PF6 used for the DFT and MP2 calculations was obtained by the neutron diffraction. It means that the C−H bond lengths are less precise and shorter in the materials other than (TMTSF)2PF6 (20 K) since neutrons are scattered by protons directly. It might change the Δ*E*<sup>0</sup> and Δ*E*1<sup>+</sup> of the others slightly from the actual values, but the change will probably cancel out each other in Δ*E*<sup>0</sup> − Δ*E*1+.

Finally, we can estimate the valence of TMTSF molecules in the present I3 salts.

At a glance, the large negative value of the monomer C is noticeable. This is the strong evidence that the monomer C in the 5:2 salt is close to neutral. Assuming it is exactly neutral, the valence of the donors in the stacks is estimated as (2/3)+ on average because the 5:2 salt is regarded as a 3:2 salt by omitting C. We believe that each of A and B has almost the same valence (2/3)+ as the Δ*E*<sup>0</sup> − Δ*E*1<sup>+</sup> is almost the same.

Within the band picture, all of these seem consistent with the semiconducting behavior of the *ρ*. The one-dimensional stack made of the trimers will result in three separated energy bands. Then the lower two are filled, while the highest one remains empty at 0 K.

Another interesting possibility comes up when the upper two bands merge leaving the lowest third band apart. Then the upper band will be half-filled with highly one-dimensional nature. In such electronic systems, the Mott insulating state could be realized when the bandwidth is relatively small as compared with the on-site Coulomb energy [83]. The origin of the semiconducting state should be elucidated in a future work.

**Table 3.** The total energies of TMTSF molecules at neutral and cationic states (*E*<sup>0</sup> and *E*1+); their relative values with respect to those calculated for the optimized structures (Δ*E*<sup>0</sup> = *E*<sup>0</sup> − *E*0(optimized for 0) and Δ*E*1<sup>+</sup> = *E*1<sup>+</sup> − *E*1+(optimized for 1+)); and their difference (Δ*E*<sup>0</sup> − Δ*E*1+) as a measure of the valence of each conformation of TMTSF molecule. The calculations of *E*<sup>0</sup> and *E*1+ were carried out on the basis of the density-functional theory (B3LYP, 6-31G(d,p)) [82].


<sup>1</sup> 1 hartree = 27.211386245988(53) eV. <sup>2</sup> Neutral crystal [76]. <sup>3</sup> (TMTSF)2BF4 at the anion ordered state at 20 K with two crystallographically independent TMTSF molecules (A and B) [77]. <sup>4</sup> (TMTSF)2PF6 at 20 K by the neutron diffraction structural analysis [78]. <sup>5</sup> (TMTSF)2NO3 at 125 K [80]. <sup>6</sup> (TMTSF)2NbF6 [5]. <sup>7</sup> (TMTSF)2Ni(tds)2 (tds = [bis(trifluoromethyl)ethylene]diselenolato) [52]. <sup>8</sup> (TMTSF)NO3 [69]. <sup>9</sup> (TMTSF)[Cr(Br4SQ)2(Br4Cat)] · (CH2Cl2)2 (SQ = semiquinonate, Cat = catecholate) [71]. <sup>10</sup> (TMTSF)3PW12O40 [68].

**Table 4.** The total energies of TMTSF molecules at neutral and cationic states (*E*<sup>0</sup> and *E*1+); their relative values with respect to those calculated for the optimized structures (Δ*E*<sup>0</sup> = *E*<sup>0</sup> − *E*0(optimized for 0) and Δ*E*1<sup>+</sup> = *E*1<sup>+</sup> − *E*1+(optimized for 1+)); and their difference (Δ*E*<sup>0</sup> − Δ*E*1+) as a measure of the valence of each conformation of TMTSF molecule. The *E*<sup>0</sup> and *E*1+ were obtained by Hartree–Fock (HF) calculations (6-31G(d,p)) followed by Møller–Plesset correlation energy calculations truncated at second order (MP2) [82].


<sup>1</sup> 1 hartree = 27.211386245988(53) eV. <sup>2</sup> Neutral crystal [76]. <sup>3</sup> (TMTSF)2BF4 at the anion ordered state at 20 K with two crystallographically independent TMTSF molecules (A and B) at 20 K [77]. <sup>4</sup> (TMTSF)2PF6 at 20 K by the neutron diffraction structural analysis [78]. <sup>5</sup> (TMTSF)2NO3 at 125 K [80]. <sup>6</sup> (TMTSF)2NbF6 [5]. <sup>7</sup> (TMTSF)2Ni(tds)2 (tds = [bis(trifluoromethyl)ethylene]diselenolato) [52]. <sup>8</sup> (TMTSF)NO3 [69]. <sup>9</sup> (TMTSF)[Cr(Br4SQ)2(Br4Cat)] · (CH2Cl2)2 (SQ = semiquinonate, Cat = catecholate) [71]. <sup>10</sup> (TMTSF)3PW12O40 [68].
