Isomeric and Isostructural Oligothienylsilanes–Structurally
Similar, Physicochemically Different: The Effect of Interplay between
C–H···C(π), S···C(π),
and Chalcogen S···S Interactions
Krzysztof Durka
Krzysztof Gontarczyk
Sergiusz Luliński
Janusz Serwatowski
Krzysztof Woźniak
10.1021/acs.cgd.6b00358.s001
https://acs.figshare.com/articles/journal_contribution/Isomeric_and_Isostructural_Oligothienylsilanes_Structurally_Similar_Physicochemically_Different_The_Effect_of_Interplay_between_C_H_C_S_C_and_Chalcogen_S_S_Interactions/3487682
The
solid state and solution properties of tris(2-thienyl)methylsilane, <b>I</b>, tetrakis(2-thienyl)silane, <b>III</b>, and their
positional isomers bearing 3-thienyl groups (<b>II</b> and <b>IV</b>) were investigated and compared. The tris(thienyl)silanes
(<b>I</b>, <b>II</b>) crystallize in different space groups,
but their respective structural motifs are very comparable. In turn,
the tetrathienyl isomers are isostructural. Furthermore, in all studied
systems the same set of C–H···C(π), S···C(π),
S···S, C–H···S interactions are
engaged in supramolecular structure formation. These interactions
are interchangeable as thienyl rings (excluding structure <b>II</b>) are affected by 2-fold positional disorder. Despite the high level
of structural similarity, the studied thienylsilanes show very different
physicochemical behavior: (1) much higher melting points and larger
enthalpies of fusion for <b>II</b> (mp = 71.3 °C, Δ<i>H</i> = 20.9 kJ mol<sup>–1</sup>) and <b>IV</b> (mp = 221.2 °C, Δ<i>H</i> = 29.1 kJ mol<sup>–1</sup>) with respect to their isomeric counterparts <b>I</b> (mp = 28.6 °C, Δ<i>H</i> = 16.0 kJ
mol<sup>–1</sup>) and <b>III</b> (mp = 131.5 °C,
Δ<i>H</i> = 27.0 kJ mol<sup>–1</sup>), (2)
different temperature-dependence unit-cell evolution, and (3) much
lower solubility of <b>IV</b> compared to <b>III</b>.
The computations show that the strength of interactions decreases
in the series C(α)–H···C(π) >
C(β)–H···C(π)
> S···C(π) ≫ S···S.
In
a combination with crystal symmetry, this leads to a different distribution
of energy within the corresponding crystal structures, and as a consequence,
results in their different macroscopic behaviors. In addition, the
solid–liquid equilibrium studies suggest that the specific
S···S chalcogen bonding between molecules of <b>IV</b> is responsible for decreased solubilities of this compound.
To characterize the specific interactions involving sulfur atoms (S···S
and S···C(π)), the quantum theory of atoms in
molecules has been successfully applied.
2016-07-05 00:00:00
thienyl
supramolecular structure formation
interaction
crystal
mp
tris
Δ H
isomers
III
kJ
molecule
IV
II