Stabilization of Supramolecular Networks of Polyiodides with Protonated Small Tetra-azacyclophanes

Abstract

Polyiodide chemistry is among the first historically reported examples of supramolecular forces at work. To date, owing to the increasingly recognized role of halogen bonding and the incorporation of iodine-based components in several devices, it remains an active field of theoretical and applied research. Herein we re-examine azacyclophanes as a class of ligands for the stabilization of iodine-dense three-dimensional networks, showing how we devised novel possible strategies starting from literature material. The new set of azacyclophane ligands affords novel crystal structures possessing intriguing properties, which develop on a double layer. At a macroscopic level, the obtained networks possess a very high iodine packing density (less than 2 times more diluted than crystalline I2): a simple parameter, IN, is also introduced to quickly measure and compare iodine packing density in different crystals. On the microscopic level, the present study provides evidence about the ability of one of the ligands to act as a three-dimensional supramolecular mold for the template synthesis of the rarely observed heptaiodide (I7−) anion. Therefore, we believe our approach and strategy might be relevant for crystal engineering purposes.

Noncovalent Bonds, Spectral and Thermal Properties of Substituted Thiazolo[2,3-b][1,3]thiazinium Triiodides

“…The chemistry of polyhalides has attracted particular attention due to the vast diversity of applicable properties related to the ability of halogens to form different types of contacts [10][11][12][13][14][15]. Polyiodides represent an absolute majority among polyhalide structures [16][17][18][19][20][21]. The interest in polyiodide derivatives is based on their enormous structural diversity of packing motives resulting in the formation of anionic ribbons, layers, channels and sheets [22][23][24].…”

Crystal structure of bis(1,3-phenylenedimethanaminium) bis(triiodide) tetraiodide – water (1/2) , C8H16I5N2O

“…Bond lengths and angles in the cation are in the range of expectation [28][29][30]. Even though nitrogen-based cations containing an aryl and an alky moiety are well known to stabilize polyiodes [31], it was surprising that not even the crystal structure of the 1,3-phenylenedimethanaminium hydroiodide is reported. The 1,3-phenylenedimethanaminium has a conformational flexibility by a rotation about the C1-C2 and C6-C8 single bonds, respectively (left part of the figure).…”

Synthesis and structures of polyiodide radical cation salts of donors combining tetrathiafulvalene with multiple thiophene or oligo-thiophene substituents

“…The six S⋯S contacts between the tetrathio-TTF moieties of the radical cation pair lie in range 3.3727(15)-3.5531(16) Å ( Table 3). The overlapping thiophene groups are tightly packed together, each linker sulfur atom makes a short contact to a thiophene ring of the other donor (S⋯S(thiophene): 3.439(4), S⋯C(thiophene): 3.472(7) and 3.48(6) Å) and there are further contacts between overlapping thiophene rings: S⋯C: 3.36(7)-3.521 (16) and C⋯C: 3.47(8)-3.585(18) Å ( Table 3). There is rotational disorder about the S-C(thiophene) bond for the two thiophene groups which are projected out to the side of the TTF, in ratios 3 : 2 and 2 : 1 for the two rings.…”

“…Indeed, the structure of the pentaiodide ion can be considered as an iodine molecule forming a halogen bond to a triiodide ion (Table 4). 16 For these two salts this halogen bond would be 3.2565(6) Å long, with an I-I-Î⋯I-I angle of 95.6°, in 15A, and 3.1808(6) Å long, with an angle of 97.3°, in 15B. Some comparisons of contacts in 15A.I 5 and 15B.I 5 are shown in Table 4.…”

“…A wide range of polyiodide networks have been reported, in particular, though not exclusively, with nitrogen containing cations. 16,17 Shao has reported a very similar polyiodide complex 22.I 5 where the thiophenes in 15A and 15B are replaced by 4-fluorophenyl groups (Scheme 3) (vide infra) and the radical cation pair adopts a similar structure. 18 The tetraphenyl analogue 21 also forms a pentaiodide salt, containing the same structural motif for the radical cation pair but the pentaiodide anions are organised "end-to-end" to form a chain.…”