Abstract
We report two hitherto unknown polymorphs of the charge transfer (CT) cocrystal perylene:tetracyanoquinodimethane (TCNQ) grown by physical vapor transport (PVT) in argon atmosphere. One of the polymorphs, named β, has stoichiometry 1:1 and adds to the three known structures with stoichiometry 1:1 (α), 2:1, and 3:1. Interestingly, below (280 ± 10) K the β structure undergoes a phase transition to what we refer to as the γ polymorph, with halving of the unit cell and reduction of symmetry from monoclinic to triclinic. Both new crystal structures present two alternating stacks with different intermolecular and intramolecular geometries. In stack S-I the perylene molecules show substantial deviations from planarity, with the angle between the naphthalene intramolecular moieties of 6.69°, and with the perylene and TCNQ molecular centroids shifted by 1.95 Å. In the second stack, S-II, the perylene is planar, and the centroids almost coincident. Structural investigations on bond length complemented by vibrational IR spectroscopy indicate that in the new polymorphs the degree of charge transfer, ρ, can be 0 or 0.12. The higher value of ionicity to be due to donor-acceptor pairs in the S-II, while molecules in S-I are closer to neutrality. Thus, the ionicity of the donor-acceptor pair depends on the stack and is comparable to that of the α polymorph which we redetermined as ρ = 0.15 ± 0.05.
| Original language | English |
|---|---|
| Pages (from-to) | 2003-2009 |
| Number of pages | 7 |
| Journal | Crystal Growth and Design |
| Volume | 18 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 4 Apr 2018 |
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ASJC Scopus subject areas
- Chemistry(all)
- Materials Science(all)
- Condensed Matter Physics
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New Polymorphs of Perylene-Tetracyanoquinodimethane Charge Transfer Cocrystals. / Henderson, J.; Masino, M.; Hatcher, L. E.; Kociok-Köhn, G.; Salzillo, T.; Brillante, A.; Raithby, P. R.; Girlando, A.; Da Como, E.
In: Crystal Growth and Design, Vol. 18, No. 4, 04.04.2018, p. 2003-2009.Research output: Contribution to journal › Article
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TY - JOUR
T1 - New Polymorphs of Perylene-Tetracyanoquinodimethane Charge Transfer Cocrystals
AU - Henderson, J.
AU - Masino, M.
AU - Hatcher, L. E.
AU - Kociok-Köhn, G.
AU - Salzillo, T.
AU - Brillante, A.
AU - Raithby, P. R.
AU - Girlando, A.
AU - Da Como, E.
PY - 2018/4/4
Y1 - 2018/4/4
N2 - We report two hitherto unknown polymorphs of the charge transfer (CT) cocrystal perylene:tetracyanoquinodimethane (TCNQ) grown by physical vapor transport (PVT) in argon atmosphere. One of the polymorphs, named β, has stoichiometry 1:1 and adds to the three known structures with stoichiometry 1:1 (α), 2:1, and 3:1. Interestingly, below (280 ± 10) K the β structure undergoes a phase transition to what we refer to as the γ polymorph, with halving of the unit cell and reduction of symmetry from monoclinic to triclinic. Both new crystal structures present two alternating stacks with different intermolecular and intramolecular geometries. In stack S-I the perylene molecules show substantial deviations from planarity, with the angle between the naphthalene intramolecular moieties of 6.69°, and with the perylene and TCNQ molecular centroids shifted by 1.95 Å. In the second stack, S-II, the perylene is planar, and the centroids almost coincident. Structural investigations on bond length complemented by vibrational IR spectroscopy indicate that in the new polymorphs the degree of charge transfer, ρ, can be 0 or 0.12. The higher value of ionicity to be due to donor-acceptor pairs in the S-II, while molecules in S-I are closer to neutrality. Thus, the ionicity of the donor-acceptor pair depends on the stack and is comparable to that of the α polymorph which we redetermined as ρ = 0.15 ± 0.05.
AB - We report two hitherto unknown polymorphs of the charge transfer (CT) cocrystal perylene:tetracyanoquinodimethane (TCNQ) grown by physical vapor transport (PVT) in argon atmosphere. One of the polymorphs, named β, has stoichiometry 1:1 and adds to the three known structures with stoichiometry 1:1 (α), 2:1, and 3:1. Interestingly, below (280 ± 10) K the β structure undergoes a phase transition to what we refer to as the γ polymorph, with halving of the unit cell and reduction of symmetry from monoclinic to triclinic. Both new crystal structures present two alternating stacks with different intermolecular and intramolecular geometries. In stack S-I the perylene molecules show substantial deviations from planarity, with the angle between the naphthalene intramolecular moieties of 6.69°, and with the perylene and TCNQ molecular centroids shifted by 1.95 Å. In the second stack, S-II, the perylene is planar, and the centroids almost coincident. Structural investigations on bond length complemented by vibrational IR spectroscopy indicate that in the new polymorphs the degree of charge transfer, ρ, can be 0 or 0.12. The higher value of ionicity to be due to donor-acceptor pairs in the S-II, while molecules in S-I are closer to neutrality. Thus, the ionicity of the donor-acceptor pair depends on the stack and is comparable to that of the α polymorph which we redetermined as ρ = 0.15 ± 0.05.
UR - http://www.scopus.com/inward/record.url?scp=85044965196&partnerID=8YFLogxK
U2 - 10.1021/acs.cgd.7b01391
DO - 10.1021/acs.cgd.7b01391
M3 - Article
AN - SCOPUS:85044965196
VL - 18
SP - 2003
EP - 2009
JO - Crystal Growth and Design
JF - Crystal Growth and Design
SN - 1528-7483
IS - 4
ER -