1. X-ray charge density reveals fine details in π-stacks of semiquinone radicals which determine conductivity
Krešimir Molčanov, Christian Jelsch, Ana Šantić, Vladimir Stilinović, Emmanuel Wenger, Biserka Kojić-Prodić

2. 25th Slo-Cro Crystallographic
Meeting, Ljubljana, june 2017.
photo by N. Bedeković

3. Semiquinone radicals .. X = Cl : Cl4Q X = Br : Br4Q X = Cl, CN : DDQ
X = F :
F4Q

4. Two polymorphs of N-MePy∙Cl4Q
triclinic
orthorhombic a b c b a c
Molčanov, Stilinović, Šantić, Maltar-Strmečki, Pajić, Kojić-Prodić, Cryst. Growth Des., 2016, 16,

5. N-MePy·Cl4Q, triclinic 2.903(1) Å 3.663(1) Å Peierls-type deformation
Dimers with coupled spins
Diamagnetic
2.903(1) Å
Cryst. Growth Des., 2016, 16,

6. Interactions between the rings (diamagnet, dimer)
2.90 Å
Offset: 2.07 Å
0.5 e Å-3

7. Interactions between the rings (diamagnet, between dimers)
3.66 Å
Offset: 2.8 Å
0.5 e Å-3

8. Critical points (diamagnet)
ρmax > e Å-3
2.90 Å
ρmax < e Å-3
3.66 Å
(3, -1) bond
(3, +1) ring cenroid
(3, +3) cage centroid

9. N-MePy·Cl4Q, orthorhombic
3.283(1) Å
1D antiferromagnetic coupling in a stack
Semiconductor:
σ ≈ 10-6 ( cm)-1
EDC ≈ 0.34 eV
3.283(1) Å
3.283(1) Å
Cryst. Growth Des., 2016, 16,

10. Interactions between the rings (antiferromagnet)
3.28 Å
Offset: 2.06 Å
0.5 e Å-3

11. Critical points (antiferromagnet)
ρmax < e Å-3
3.28 Å
(3, -1) bond
(3, +1) ring cenroid
(3, +3) cage centroid

12. Stacking geometry: dimer vs. equdistant stack
equidistant
2.90 Å
3.28 Å
Offset: 2.07 Å
Offset: 2.06 Å

13. Conductivity? e- e- e- e- e- Semiconductor Isolator huge ΔE 2.90 Å
3.28 Å e-
huge ΔE
3.66 Å
3.28 Å e- e-
2.90 Å
3.28 Å
ΔE = 0.34 eV

14. Electric conductivity
vs. interplanar distance (100 K)
Cl4Q∙N-MePy
Br4Q∙N-MePy
DDQ∙N-Me2Pic
3.2855(16) Å
3.1587(13) Å
3.122(3) Å

15. Inductive effect of the substituents
Br4Q
Cl4Q
DDQ
LUMO
LUMO
LUMO ΔE ΔE ΔE
HOMO
HOMO
HOMO

16. [N-Me-4-(Me)2NPy]2(Cl4Q)3
A charge-transfer complex
2.84 Å
2.84 Å
1.32 Å
3.59 Å
≈1.76 Å

17. [N-Me-4-(Me)2NPy]2(Cl4Q)3
A charge-transfer complex
–0,58
Charges derived from Pval:
+0.96
–0,76
–1.92
–0,58
+0.96 2– 1+ 1+

18. Interactions between the rings
ρmax < e Å-3
3.59 Å
2.84 Å
ρmax > e Å-3

19. Conclusions energy of interaction exceeds 15 kcal mol-1
dominant interaction is spin coupling (interplanar distance)
secondary: electrostatic (offset)
possible electron transfer between the rings: semiconductivity
magnetic properties can be tuned by tuning geometry of stacking

20. Thank you for your attention!
Acknowlegdements
Thank you for your attention!
RBI, Zagreb
Marijana Jurić
Lidija Androš Dubraja
Nadica Maltar-Strmečki
Dijana Žilić
Valentina Milašinović
Lidija Kanižaj
University of Zagreb
Damir Pajić
Nikolina Novosel
Krešo Zadro
KI, Ljubljana
Jernej Stare
Gregor Mali
Jože Grdadolnik
Rigaku Oxford Diffraction Ltd.
Marcus Winter
Dyanne Cruikshank
Université de Lorraine
Claude Lecomte
Croatian Science Foundation, grant no. IP
Croatian Academy of Sciences and Arts
French-Croatian bilateral, Slovenian-Croatian bilateral