TY - JOUR

T1 - The Halogen Bond in Weakly Bonded Complexes and the Consequences for Aromaticity and Spin-Orbit Coupling

AU - Cunha, Ana V.

AU - Havenith, Remco W. A.

AU - van Gog, Jari

AU - De Vleeschouwer, Freija

AU - De Proft, Frank

AU - Herrebout, Wouter

N1 - Funding Information:
The work of R.W.A.H. was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities (contract no. 17197 7095) and R.W.A.H. and A.V.C. thank S. Dolas (SURF, NL) for allowing us to perform calculations on the experimental AMD platform kleurplaat maintained and operated by SURF Open Innovation Lab. F.D.V. acknowledges the VUB for the Strategic Research Program awarded to the ALGC research group. F.D.V. and F.D.P. wish to acknowledge the Vrije Universiteit Brussel for the support through a Strategic Research Program (SRP).
Publisher Copyright:
© 2023 by the authors.

PY - 2023/1/12

Y1 - 2023/1/12

N2 - The halogen bond complexes CF (Formula presented.) X⋯Y and C (Formula presented.) F (Formula presented.) X⋯Y, with Y = furan, thiophene, selenophene and X = Cl, Br, I, have been studied by using DFT and CCSD(T) in order to understand which factors govern the interaction between the halogen atom X and the aromatic ring. We found that PBE0-dDsC/QZ4P gives an adequate description of the interaction energies in these complexes, compared to CCSD(T) and experimental results. The interaction between the halogen atom X and the (Formula presented.) -bonds in perpendicular orientation is stronger than the interaction with the in-plane lone pairs of the heteroatom of the aromatic cycle. The strength of the interaction follows the trend Cl < Br < I; the chalcogenide in the aromatic ring nor the hybridization of the C–X bond play a decisive role. The energy decomposition analysis shows that the interaction energy is dominated by all three contributions, viz., the electrostatic, orbital, and dispersion interactions: not one factor dominates the interaction energy. The aromaticity of the ring is undisturbed upon halogen bond formation: the (Formula presented.) -ring current remains equally strong and diatropic in the complex as it is for the free aromatic ring. However, the spin-orbit coupling between the singlet and triplet (Formula presented.) states is increased upon halogen bond formation and a faster intersystem crossing between these states is therefore expected.

AB - The halogen bond complexes CF (Formula presented.) X⋯Y and C (Formula presented.) F (Formula presented.) X⋯Y, with Y = furan, thiophene, selenophene and X = Cl, Br, I, have been studied by using DFT and CCSD(T) in order to understand which factors govern the interaction between the halogen atom X and the aromatic ring. We found that PBE0-dDsC/QZ4P gives an adequate description of the interaction energies in these complexes, compared to CCSD(T) and experimental results. The interaction between the halogen atom X and the (Formula presented.) -bonds in perpendicular orientation is stronger than the interaction with the in-plane lone pairs of the heteroatom of the aromatic cycle. The strength of the interaction follows the trend Cl < Br < I; the chalcogenide in the aromatic ring nor the hybridization of the C–X bond play a decisive role. The energy decomposition analysis shows that the interaction energy is dominated by all three contributions, viz., the electrostatic, orbital, and dispersion interactions: not one factor dominates the interaction energy. The aromaticity of the ring is undisturbed upon halogen bond formation: the (Formula presented.) -ring current remains equally strong and diatropic in the complex as it is for the free aromatic ring. However, the spin-orbit coupling between the singlet and triplet (Formula presented.) states is increased upon halogen bond formation and a faster intersystem crossing between these states is therefore expected.

KW - density functional theory

KW - energy decomposition analysis

KW - halogen bonds

KW - ring current analysis

KW - spin-orbit coupling

UR - http://www.scopus.com/inward/record.url?scp=85146755875&partnerID=8YFLogxK

U2 - 10.3390/molecules28020772

DO - 10.3390/molecules28020772

M3 - Article

C2 - 36677828

AN - SCOPUS:85146755875

SN - 1431-5157

VL - 28

JO - Molecules

JF - Molecules

IS - 2

M1 - 772

ER -