Chalcogen-bonded donor-acceptor complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4-]pyrazine with halide ions

New complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4- b ]pyrazine 1 with halide anions X − (X = Cl, Br, I) are prepared. With XRD, DFT, QTAIM and NBO, it is found that the complexes are formed via Se-X − chalcogen bonding. Diffuse reflectance spectroscopy of polycrystalline samples and UV/Vis spectr...

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Published in:New journal of chemistry 2022-08, Vol.46 (3), p.1449-1451
Main Authors: Radiush, Ekaterina A, Pritchina, Elena A, Chulanova, Elena A, Dmitriev, Alexey A, Bagryanskaya, Irina Yu, Slawin, Alexandra M. Z, Woollins, J. Derek, Gritsan, Nina P, Zibarev, Andrey V, Semenov, Nikolay A
Format: Article
Language:English
Subjects:
Bonding strength
Chalcogen bonds
Charge transfer
Chemical equilibrium
Complex formation
Complexation
Diffuse reflectance spectroscopy
Dispersion
Electron density
Molecular orbitals
Perturbation theory
Spectrophotometry
Spectrum analysis
Titration
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Summary:New complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4- b ]pyrazine 1 with halide anions X − (X = Cl, Br, I) are prepared. With XRD, DFT, QTAIM and NBO, it is found that the complexes are formed via Se-X − chalcogen bonding. Diffuse reflectance spectroscopy of polycrystalline samples and UV/Vis spectroscopy of solutions of [ 1 -X] − reveal significant spectral changes upon complexation. According to time-dependent DFT, these changes are caused by the appearance of charge transfer bands (p-AO(X) → LUMO( 1 )) in the visible region. The equilibrium constants for complex formation were measured with UV/Vis spectrophotometric titration and found to be significantly lower than those reported for structurally similar complexes of 3,4-dicyano-1,2,5-selena(tellura)diazoles, which indicates relatively weak chalcogen bonding in [ 1 -X] − . Dispersion-corrected DFT reproduces well the Gibbs free energies of complexation. The QTAIM descriptors and NBO analyses using second-order perturbation theory suggest that the Se-X − chalcogen bonding in the studied complexes is predominantly electrostatic and dispersive in nature with a small but significant contribution from donor-acceptor (or orbital) interactions. The strongest contribution to the latter comes from negative hyperconjugation, i.e. donation of the electron density of the lone-pair of X − onto the σ *-MO of the Se-N bond of 1 . With halides X − (X = Cl, Br, I) 5,6-dicyano-[1,2,5]selenadiazolo[3,4- b ]pyrazine 1 forms chalcogen-bonded complexes [ 1 -X] − structurally defined by XRD. UV/Vis spectra of [ 1 -X] − feature red-shifted charge-transfer bands in the Vis part.
ISSN:1144-0546
1369-9261
DOI:10.1039/d2nj02345h