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Stacking of planar organic radicals: strong non-covalent or weak covalent interactions?. Krešimir Molčanov , 1 Valentina Milašinović, 1 Nikita Bogdanov, 2 Elena V. Boldyreva 2,3 1 Ruđer Bošković Institute, Bijenička 54, 1 0000 Zagreb, Croatia
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Stacking of planar organic radicals: strong non-covalent or weak covalent interactions? Krešimir Molčanov,1 Valentina Milašinović,1 Nikita Bogdanov,2 Elena V. Boldyreva2,3 1Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia 2Novosibirsk State University, 630090 Novosibirsk, Russia 3Boreskov Institute of Catalysis, 5 Ac. Lavrentieva avenue, 630090 Novosibirsk, Russia
IUCrJ, 2019, 6, 156-166. Angew. Chem., Int. Ed., DOI: 10.1002/anie.201908875 Cryst. Growth Des., DOI: 10.1021/acs.cgd.9b00540
Multicentric two-electron bonding: tetracyanoethylene, the prototype Miller & Novoa, Acc. Chem. Res., 2007, 40, 189-196. Cui, Lischka, Mueller, Plasser, Kertesz, ChemPhysChem, 2014,15, 165-176. IUCrJ, 2019, 6, 156-166.
Pancake bonding: multicentric two-electron bonding between planar radicals R. S. Mulliken, 1960s pancake bonds σ-bonds IUCrJ, 2019, 6, 156-166. Cryst. Growth Des., DOI: 10.1021/acs.cgd.9b00540
In-depth study of pancake bonding • X-ray charge density/quantum crystallography • Variable-temperature crystallography (80 – 400 K) • High-pressure crystallography
Pancake bonding: three types of stacks equidistant radicals trimers dimers 2.84 Å 2.86 Å 2.84 Å 3.17 Å 3.60 Å 3.59 Å B A IUCrJ, 2019, 6, 156-166. Cryst. Growth Des., 2016, 16, 4777-4782. Chem. Eur. J., 2018, 24, 8292-8297.
Pancake bonded dimers: Anything that can go wrong will go wrong, and at the worst possible time. Edward A. Murphy
Pancake bonded dimers: N-MePy·Cl4Q N-Me-4-CNPy·DDQ (triclinic) CrystEngComm, 2018, 20, 1862-1873. Cryst. Growth Des., 2016, 16, 4777-4782.
Pancake bonded dimers: N-MePy·Cl4Q N-Me-4-CNPy·DDQ 2.92 Å 2.86 Å 3.49 Å 3.60 Å 2.92 Å 2.86 Å CrystEngComm, 2018, 20, 1862-1873. Cryst. Growth Des., 2016, 16, 4777-4782.
Pancake bonded dimers (N-MePy·Cl4Q): critical points ρmax > 0.095 e Å-3 2.86 Å ρmax < 0.040 e Å-3 3.60 Å (3, -1) bond (3, +1) ring cenroid Cryst. Growth Des., 2019, 19, 391-402. (3, +3) cage centroid
Pancake bonded dimers(N-MePy·Cl4Q): HOMO orbitals Covalent contribution: –9.4 kcal mol-1 Cryst. Growth Des., 2019, 19, 391-402.
Pancake bonded dimers (N-Me-4-CNPy·DDQ): variable temperature Linear expansion coefficient: ≈ 10-4 Å K-1 Interplanar distance / Å T / K
Pancake bonded dimers (N-Me-4-CNPy·DDQ): high pressure 3.49 Å Interplanar distance / Å 3.00 Å 2.93 Å 2.96 Å 2.92 Å 2.75 Å p / GPa
Pancake bonded dimers (N-Me-4-CNPy·DDQ):phase transition? 6 GPa 0 GPa 0 0 b b 2.93 Å 2.92 Å c c 2.75 Å 3.49 Å a a 2.93 Å 2.92 Å
Pancake bonded trimers: [N-Me-4-(Me)2NPy]2(Cl4Q)3 –0,58 Charges from Pval: +0.96 –0,76 –1.92 –0,58 +0.96 2– 1+ 1+ Chem. Eur. J., 2018, 24, 8292-8297.
Pancake bonded trimers: critical points ρmax > 0.077 e Å-3 2.84 Å 3.59 Å ρmax < 0.045 e Å-3 (3, -1) bond (3, +1) ring cenroid (3, +3) cage centroid Chem. Eur. J., 2018, 24, 8292-8297.
Pancake bonded trimers: HOMO orbitals Covalent contribution: –4.11 kcal mol-1 Chem. Eur. J., 2018, 24, 8292-8297.
Pancake bonded trimers: variable temperature Linear expansion coefficients: ≈ 2.4 10-4 Å K-1 Interplanar distance / Å ≈ 7.7 10-5 Å K-1 T / K
Pancake bonded trimers: high pressure 3.59 Å Interplanar distance / Å 3.09 Å 2.84 Å 2.84 Å 2.70 Å p / GPa
Pancake bonded trimers: pressure-induced phase transition? 5.19 GPa 0 GPa
Pancake bonded trimers: pressure-induced phase transition? 5.19 GPa 0 GPa 2.84 Å 2.70 Å 2.84 Å 2.84 Å B 3.59 Å 3.09 Å A 2.70 Å 2.84 Å
Pancake bonding in stacks of equidistant radicals N-MePy·Cl4Q N-MePy·Br4Q (orthorhombic) Cryst. Growth Des., 2016, 16, 4777-4782.
Pancake bonding in stacks of equidistant radicals N-MePy·Cl4Q N-MePy·Br4Q (orthorhombic) 3.28 Å 3.17 Å 3.28 Å 3.17 Å 3.28 Å 3.17 Å Cryst. Growth Des., 2016, 16, 4777-4782.
Pancake bonding in stacks of equidistant radicals (N-MePy·Cl4Q): critical points ρmax < 0.050 e Å-3 3.17 Å (3, -1) bond (3, +1) ring cenroid Cryst. Growth Des., 2019, 19, 391-402. (3, +3) cage centroid
Pancake bonding in stacks of equidistant radicals (N-MePy·Cl4Q): HOMO orbitals Covalent contribution: –2.9 kcal mol-1 Cryst. Growth Des., 2019, 19, 391-402.
Pancake bonding in stacks of equidistant radicals (N-MePy·Br4Q): variable temperature Interplanar distance / Å Linear expansion coefficient: ≈ 1.9·10-4 Å K-1 T / K
Conclusions • Linear expansion coefficients for pancake bonds and weak stacking contacts are ca. 10-5– 10-4 Å K-1 • Phase transitions at high pressure • The shortest pancake bonds at high pressure: 2.07 Å (trimers) and 2.75 Å (dimers) • The „long” contact between dimers: 2.93 Å • At high pressure: pancake-bonded polymers • Possible long-range ordering and conductivity • In progress: high-pressure conductivity and magnetism
CAD4 The 80’s never ended.
Acknowledgements University of Zagreb Vladimir Stilinović Damir Pajić Nikolina Novosel Krešo Zadro RBI, Zagreb Marijana Jurić Lidija Androš Dubraja Nadica Maltar-Strmečki Ana Šantić Dijana Žilić Darko Babić Valentina Milašinović Universität Göttingen Dietmar Stalke Serhiy Demeshko Université de Lorraine Christian Jelsch Claude Lecomte Emmanuel Wenger KI, Ljubljana Jernej Stare Gregor Mali UNAM, Mexico City Bruno Landeros Jesús Hernández-Trujillo University of Ljubljana Anton Meden Georgetown Univ., USA Miklosz Kertesz Zhongyu Mou Rigaku Oxford Diffraction Ltd. Marcus Winter Dyanne Cruikshank Croatian Science Foundation, grant no. IP-2014-09-4079 Croatian Academy of Sciences and Arts French-Croatian bilateral, Slovenian-Croatian bilateral, German-Croatian bilateral