Doping dimethylphenazine (M2P)-TCNQ and diethylphenazine (E2P)-TCNQ with phenazine gave rise to new conducting compounds with segregated stacks : (M2P)0.5 (P)0,5 TCNQ and (E2P)0,55 (P)0,45 TCNQ. The room temperature electrical conductivities are in the range 10-100 &#937;-1 cm-1 for (1) and 1-10 &#937;-1cm-1 for (2). The paramagnetism of both compounds could be separated into contributions from TCNQ and Phenazine stacks. The structural electrical and magnetic similarities of (1) with the well-known N-methylphenazinium (NMP)-TCNQ led to a reexamination of its magnetic properties. It was shown that an estimate of the charge transfer can be obtained from the temperature dependence of the magnetic susceptibility

Dietz, Klaus

Flandrois, Serge

Keller, Heimo J.

Koch, P.

Queckbörner, Jobst G.

Schweitzer, Dieter

Dietz, K.

Flandrois, S.

Keller, H.

Queckbörner, J.

Schweitzer, D.

MPG.PuRe

Doped dialkylated phenazines: A novel series of highly conducting organic solids

Online Publikationen der Universität Stuttgart

OtemicaScripla. 1981. 17, 93-94. 
'3 
Doped Dialkylated Phenazines: A Novel Series of Highly 
Conducting Organic Solids 
K. Dietz. S. F1androis· H. 1. Keller. P. Koch, 1. QueckbOmer · and D. Schweitler 
AnorpDisch.Che.miJc~es Ins~t~t. cler Universitit., He~dclber, Foderal Republic of Germany. Cenln: de Recherche Paul Pascal, Talencc, France and 
Mu-Plancl:-JnslitUt ru r Me(hZlD1SChe Forschung, HeIdelberg, Federal Republic of Gennany 
Proceedings from the "International Conference on Low Dimensional 
Synthetic Metals". 
Hel5ingor. Denmark, August 10- 15, 1980 
• Conference participant 
Abstract 
Doptd dilJlkylared phena:ines; a nord serin of highly rol!ducting OI'ganic 
solids. Dietz, K.:I Flandrois, S.; ' Keller, H. 1.;1 Koch, P.;' QueckbOmer. 
1.;1 Schweitzer. D.l (Anorganisch-Chemisches Institut., Univel$itilt Heidel-
berg.' 1m Neuenheimer FcJd 210, 6900 Heidelberg, Gcnnany: Centre de 
Recherche Paul Pascal, J Domaine Univcl$itaire, 33405 Talenoe. France and 
Max-Planck-Institut rur Medirinisdte Forscllung,l Abtcilung nir Mole-
kularc PhySik, 0 -6900 Heidelberg. Fedcral Rcpublic of Germany. 
Doping dimethylphcnazine (M,Pl - TCNQ and dicthylphenazine (E,PI -
TCNQ wilh phenazine ga~'e rise to new conduC1ing compounds with segre-
pted stacks : (M , P)G.5 (P)(1,5 TCNQ (/) and (El P)o." (P)o . ., TCNQ (2). 
The room tcmperature clectrical conductivities an: in the range 10- too 
n - Iem - I fot (/) and 1-10 n - Iem - I for (2). The paramagnetism of both 
compounds could be s-eparated into contributions from TCNQ and 
Phenatine stacks. The structural. electrical and magnetic similarities ofll) 
with the well·known N-mcthylphenazinium (NMP)- TCNQ led to a reexa· 
mination of its magnetic properUes.. II was shown that an estimate of the 
charge transfer can be obtained from the temperatu re dependcnce of the 
magnctic susocptibility. 
lotroduction 
Pheoazine derivatives are able to form many charge trander com-
plexeswith TCNQ [I]. One of them. NMP - TCNQ. wasforadecade 
the best organic conductor and has received considerable a ttcntion. 
However some questions still remain concerning for example the 
dcgree of charge transfer from NMP to TCNQ, the nature of its 
conductivity or the interpretation of its magnetic properties. Recent 
progress in the unders tanding of this system was obtaincd by doping 
NM P - TCNQ with neutral phenazine [2). NM P molecules can 
easily be substituted by phenazine molecules, to givc compounds of 
formula (NMP),(P)I _ . TCNQ with 0.5 <x < I. As it is reasonable 
to assume 00 charge transfer from phenazine to TCNQ. the effect 
of doping is a reduction of the charge transfer and hence a reduction 
of the band filling. 
Our purpose was to replace NM P by othcr phenazine dcrivatives. 
Oirnethylphenazine (M lP) and Oicthylphcnazine (ElP) were chosen. 
They are known to form with TCNQ mixed Slack complcxes of 
-ADAO- type. However by doping with Phenazine, segregated 
Slack complexes a re obtained. Morcover, whereas NMP" is dia-
magnetic, M zP." and EzP: are cation-radicals, so that the amount 
of charge transfer can be obtained directly from magnetic measure-
ments, if we are able to distinguish the respective contributions 10 ~P 
of TCNQ and MzP: or EIP:. In this paper we show that thiS 
separation is possible and can be extended to NM P - TCNQ. 
Sample preparation .nd characterization 
By cooling down to room temperature hot acetonitrile solulions of 
MzP(or ElP), Phenazineand TCNQ, crystals of(MlP)'{Ph _. TCNQ 
or (E1P),(P)I . ' TCNQ precipitated. We tried to vary x by changing 
the ratio [M1P]![P] or [E1P]![P] in the solution. However our 
analyses by UV spectroscopy and high pressure liquid chromato-
graphy showed us that only one phase could be obtained: (M1P)o.s 
(Plo.s TCNQ for M1P or (E:P)o.H (P)O.4S TCNQ for ElP compound 
The crystal structure of(M1P)o.s (Plo , TCNQ was recently deter-
mined [3]. Regular segrcgated stacks ofphenazine species and TCNQ 
molecules are present in the crystal. The interplanar distance is 3.44 
A in the phenazine stack, where the distribution of M1P and P is 
random, and 3.26 A in the TCNQ stack. compared to 3.36 and 3.26 
A respectively for NMP- TCNQ [4]. The crystal structure: deter-
mination of ElP compound is in progress. Preliminary results show 
that segregated stacks are also present. but probably not regular [5]. 
Results .nd Discussion 
1) Conductivity 
The d. c. clectrical conductivities of single crystals were measured by 
a standard four-probe method. The room temperature values arc: 
50-100 O - Icm-l for (M1P)o" (P)o., TCNQ and 1-10 n - Icm - I 
for (EzP)o.H(PIo .• , TCNQ. The temperature dependences given in 
figure J show that EzP compound has a semi-conducting behavior. 
whereas M1P compound behaves metal-like at high temperature. The 
maximum ratio uluu.-I.I has the value generally found in con· 
ducting TCNQ ion-radical salts. At low temperature the compound 
becomes insulating. 
o. . • • 
. 
• 
. 
• 
• 
• 
• .
........ -.. .... . ........ .. . .. .' . 
• • 
• 
• 
o~ ____ ~ __ ~·~~ ____ ~ 
o 100 200 T IKJ 300 
Fig. I . Single crystal electncal conductIvIties of(MIP)G., (P)o.! TCNQ (dots) 
and (EJPIo" (P)MI TCNQ (crosses). 
Chemica Scripta 17 
94 K. Diel: er at 
x,·! { ..... CGS nIe-1 ).1 
• 
• 
• • 
• • • 
r 
• 
• 
100 200 T (K) 300 
Fig. 2. Paramagnetic susotptibililY or (MlP)o., (P)o., TCNQ (dots) and 
(E,plo." (Plo .• , TCNQ (crosscs). 
2) MtlBnetism 
The magnetic susceptibility investigations were carried out by 
using the Faraday method. The paramagnetism was obtained by 
substracting from the measured values the core diamagnetism cal· 
culated from Pascal constants or measured on separate constituents. 
The temperature dependenocs of the molar paramagnetic suscepti· 
bility x, are shown in figure 2, where Ilx, is plotted venus lemperature. 
For both compounds a Curie-Weiss law is obeyed from about 100 K 
down to 10 K. Moreover the Curie constants. determined from the 
slopes of the siraight lines below 100 K, correspond within the 
accuracy toO.50and 0.55 mole o[spins respectively for M1P and E1P 
compound., i.e. to the stoichiomelriccoefTicient ofM 2P and E1P. This 
result means that below 100 K the paramagnetic behavior is domi-
nated by phenazine stacks and that the charge transfer is total from 
M1Por ElP to TCNQ. A weak antiferromagnetic interaction between 
the spins of phenazine stacks exists, as shown by the small negative 
Curie-Weiss temperature : 0- - to K. 
For T> 100 K the paramagnetism deviates from Curie-Weiss 
behavior. This is due to the contribution of TCNQ stacks. By su~ 
stracting from the lotal susceptibility the Curie-Weiss susceptibility 
due 10 phenazine stacks it is possible to obtain the TCNQ contribu-
tion to ilp- The results are shown in figure 3. Although the accuracy is 
probably nOI very good in panicular at low temperature, the room 
x,.xt (till" CCS "",~_11 
5 • • 
• 
• 
• 
3 
2 • 
°O~------~~~------'ao~------v/300 
T (KI 
Fig. J. Paramagnetic 5u.sccplibilily of TCNQ stacks in (MlPIo.J {Plo.J 
TCNQ (dolS) and (ElPIo.H (Plo u TCNQ (crosscs). 
Chemica Scripta 17 
temperature values have the expected order of magnitude, compared 
with other TCNQ ion-radical salts. 
Finally these results allow us to reinterpret the magnetic behavior 
of NMP- TCNQ. whose crystal Siructure is very similar to that of 
(M1Plo.)(P)o.s TCNQ. The magneticsusceptibilityofNMP - TCNQ 
has been measured by many authon including ourselves. Severe 
discrepancies exisl from one author 10 anolher, particularly at low 
temperatu~ which have been explained by the presence in the NMP 
stacks of neutral phenazine mole<:ules or NM PH: ion·radicals . 
Neverlheless the examination of published (and non·published) 
data leads to the conclusion thai in the range to-tOO K a Curie-
Weiss law is obeyed like in our M1P compound. This Curie-Weiss 
law was already pointed out by earlier worken [6]. For all the data 
the Curie-Weiss constants are in the range corresponding to 0.2 - 0.4 
mole o[spins. i.e. to a back charge transfcr 0£0.2100.4 electrons from 
TCNQ to NMP. so that the ionicity of TCNQ in NMP - TCNQ 
deduced from Xp would be 0.6-0.8. This result is in good agreement 
with recent C. T. determination by Xray scanering experiments [7] 
wt-lich gave a value of 0.66 electron per TCNQ. 
Rdert0ee5 
I. Soos, Z G~ Keller, H. J .. Moroni. W. and NOlhe, D., Ann. N. Y. Acad. 
Sci. 1978, 313, 442. 
2. Epstein. A. J. and Miller. J. S~ The Physics and Chemislry of low-
Dimensional Solids (Ed. L. Alcacer). p. 339, Reidel, Dorchechl. 1980. 
3. Endres. H .. Keller, H. J .. Moroni, W. and N61he, D., to be published. 
4. Frilchic, C. J., ACla Crysl. 1966. 18, 892. 
5. Endres. H~ private communication. 
6. Epstein, A. J .. Elemad, S~ Garito, A. F. and tlccger. A. J., Phys. Rev. 
S 1971, 5, 952. 
7. Pouge!, J. P., Chemica Scripta 1981 , 17. 85. 
Anorflllllud,·Chemisenes lrufilNt 
Ullh'ersilat lIeideJiHrg 
1m Ntwnheimer Ftld 270 
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Ctl1tre dl!" Rtchtreht P(lul Pau:(l/ 
Dowwil1t UIIIL"'ftrJilaiu 
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Abl~illlllgfur Molt kulllre Ph,·sik 
D-6900 HeldtliHrg, Fedtra/ Republic 0/ Gtrman,. 


Doped dialkylated phenazines : a novel series of highly conducting organic solids

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Doped dialkylated phenazines : a novel series of highly conducting organic solids

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