Intermolecular Bonding Interactions Within Acenaphthene Peri-Diselenide Radical Cations: Combining Chalcogen Bonding and Pancake Bonding
Abstract
Cyclic 1,2-diselenides are known to exhibit three σ-holes around the Se atoms—two in the prolongation of the Se–Se bond and one merging the two electron-depleted areas in the prolongation of the C–Se bonds. Among them, naphthalene peri-diselenides were recently isolated in their radical cation form with halometallates, affording 1:1 salts, where charge activation upon oxidation leads to strong Se•••Cl/Br chalcogen bond (ChB) interactions. Acenaphthene peri-diselenide (1) is shown here to be readily oxidized to its cation radical, showing various association modes of the 1+• species in the solid state. When engaged in electrocrystallization experiments with (Bu4N)(FeCl4), acenaphthene peri-diselenide (1) afforded two salts of the radical cation, formulated as (1)2(Fe2Cl6O) and (1)(FeCl4), depending on the electrocrystallization conditions. In both salts, short and highly directional Se•••Cl chalcogen bond (ChB) interactions take place, simultaneously involving all three σ-holes surrounding the diselenide bridge, with the reduction ratio (relative to the van der Waals Se•••Cl contact distance of 1.90 + 1.75 = 3.65 Å) reduced to 0.89. In addition, while cation radicals in (1)2(Fe2Cl6O) adopt head-to-tail alternated stacks without any intermolecular Se•••Se contacts, they organize in (1)FeCl4 into twisted-cofacial dimers, with an intra-dimer Se•••Se contact as short as 3.197(2) Å, i.e., a reduction ratio of 0.84. Such structural organization is reminiscent of those observed in dithiadiazolyl/diselenadiazolyl radicals, which associate into dimers, most often in a cis-cofacial geometry. Here, the 1+• radicals adopt either a head-to-tail (trans-cofacial) geometry (in the Fe2Cl6O2− salt) or a distorted twisted-cofacial geometry (in the FeCl4− salt), further stabilized by the chelating FeCl4−.
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BibTeX
@article{padikkal2026intermolecular,
title = {{Intermolecular Bonding Interactions Within Acenaphthene Peri-Diselenide Radical Cations: Combining Chalcogen Bonding and Pancake Bonding}},
author = {Hrudya Pariyacheri Padikkal and Olivier Jeannin and nicolas quemere and Ie-Rang Jeon and Marc Fourmigué},
journal = {Crystals},
year = {2026},
month = aug,
doi = {10.3390/cryst16090555},
url = {https://hal.science/hal-05741454v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Intermolecular Bonding Interactions Within Acenaphthene Peri-Diselenide Radical Cations: Combining Chalcogen Bonding and Pancake Bonding
AU - Hrudya Pariyacheri Padikkal
AU - Olivier Jeannin
AU - nicolas quemere
AU - Ie-Rang Jeon
AU - Marc Fourmigué
PY - 2026
DA - 2026/08/26
JO - Crystals
DO - 10.3390/cryst16090555
UR - https://hal.science/hal-05741454v1
AB - Cyclic 1,2-diselenides are known to exhibit three σ-holes around the Se atoms—two in the prolongation of the Se–Se bond and one merging the two electron-depleted areas in the prolongation of the C–Se bonds. Among them, naphthalene peri-diselenides were recently isolated in their radical cation form with halometallates, affording 1:1 salts, where charge activation upon oxidation leads to strong Se•••Cl/Br chalcogen bond (ChB) interactions. Acenaphthene peri-diselenide (1) is shown here to be readily oxidized to its cation radical, showing various association modes of the 1+• species in the solid state. When engaged in electrocrystallization experiments with (Bu4N)(FeCl4), acenaphthene peri-diselenide (1) afforded two salts of the radical cation, formulated as (1)2(Fe2Cl6O) and (1)(FeCl4), depending on the electrocrystallization conditions. In both salts, short and highly directional Se•••Cl chalcogen bond (ChB) interactions take place, simultaneously involving all three σ-holes surrounding the diselenide bridge, with the reduction ratio (relative to the van der Waals Se•••Cl contact distance of 1.90 + 1.75 = 3.65 Å) reduced to 0.89. In addition, while cation radicals in (1)2(Fe2Cl6O) adopt head-to-tail alternated stacks without any intermolecular Se•••Se contacts, they organize in (1)FeCl4 into twisted-cofacial dimers, with an intra-dimer Se•••Se contact as short as 3.197(2) Å, i.e., a reduction ratio of 0.84. Such structural organization is reminiscent of those observed in dithiadiazolyl/diselenadiazolyl radicals, which associate into dimers, most often in a cis-cofacial geometry. Here, the 1+• radicals adopt either a head-to-tail (trans-cofacial) geometry (in the Fe2Cl6O2− salt) or a distorted twisted-cofacial geometry (in the FeCl4− salt), further stabilized by the chelating FeCl4−.
SN - 2073-4352
ER -