Wydział Chemii

Magdalena Węcławik

Anna Gągor

Anna Piecha

Ryszard Jakubas

Wojciech Medycki

2013

CrystEngComm

15

5633-5640

10.1039/c3ce40559a

Naukowa

Angielski

Artykuł

The reaction of imidazole with hydroiodic acid leads to three products crystallizing as ionic salts; [C3N2H5 + ][I2], [C3N2H5 + ]2[I4 22] and [C3N2H3I2 + ][I2]. All the analogs were characterized by single-crystal X-ray diffraction, while the first two were additionally studied by calorimetric, dilatometric, dielectric and proton magnetic resonance methods. At room temperature (RT), [C3N2H5 + ][I2] adopts the centrosymmetric, trigonal space group (R3¯). The crystal structure consists of disordered imidazolium cations and discrete I2 ions. [C3N2H5 + ][I2] undergoes two discontinuous phase transitions (PTs) at 180/185 K and 113/ 123 K (cooling–heating), both of them governed by the imidazolium cation dynamics. [C3N2H5 + ]2[I4 22] consists of disordered imidazolium cations and quite rare and exotic [I4] 22 tetraiodide counterion. It undergoes continuous PT at 204 K of the ferroelastic type with a symmetry change from orthorhombic Fddd to monoclinic C2/c. The mechanism of PT is complex and consists of ‘order–disorder’ and ‘displacive’ contributions that are assigned to the dynamics of cations and to the distortion of the [I4 22] rods, respectively. [C3N2H3I2 + ][I2] is built up of discrete 4,5-diiodoimidazolium cations and isolated I2 ions. A characteristic feature of this compound is the presence of a layered structure in which moieties are held together by strong I…I halogen interactions and N–H…I hydrogen bonds.

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http://dx.doi.org/10.1039/c3ce40559a

https://www.rsc.org/