Naslov
Reversible Spin-Peierls Transition in 2,3-dichloro- 5,6-dicyano-p-benzoquinone salt with 2-amino-5- methyl-N-methylpyridinium

Autori
Stanić, Petra ; Molčanov, Krešimir

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
17th European Powder Diffraction Conference: Book of Abstracts / Popović, Jasminka ; Štefanić, Zoran - Zagreb : Hrvatska udruga kristalografa, 2022, 132-132

Skup
17th European Powder Diffraction Conference (EPDIC17)

Mjesto i datum
Šibenik, Hrvatska, 31.05.2022. - 03.06.2022

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
π-stacking ; DDQ ; radical anions ; polymorphic transition

Sažetak
Crystals of planar organic radicals are interesting because of pronounced π-stacking interactions. π- stacking usually occurs between aromatic rings and it is considered mostly as weak interaction. However, it can also occur between planar radicals. [1] Recent studies in crystal engineering show that the close contact of two planar radicals usually involves spin coupling and that the energy of such contacts may be as high as the energy of strong intermolecular interactions (−20 kcal mol-1). [2] Interest in stacking of organic radicals and charge transfer compounds in crystals can be attributed to their interesting magnetic and conductive properties. Therefore, these types of compounds have an important role in crystal engineering of functional materials such as optoelectronics, magnetic, and conductive molecular materials. [1, 3] Here we present an interesting novel material, 2, 3- dichloro-5, 6-dicyano-p-benzoquinone salt with 2- amino-5-methyl-N-methylpyridinium, (DDQ) (2a5mNpy), with a reversible temperature polymorphic phase transition leading to a change in magnetic and conductive properties. The salt was characterized by SCXRD, and later studied by means of SCXRD, PXRD, DSC and SQUID magnetometry in a temperature range from 100 to 400 K. We also measured conductive properties of (DDQ)(2a5mNpy) by impedance spectroscopy (293 - 373 K) on a single crystal and a pressed pellet. The polymorph transition in (DDQ)(2a5mNpy) occurs around 270K. The high-temperature phase (ht) remains stable up to 400K. In it DDQ radical anions are parallel and stack in columns with equidistant interplanar separations (ca 3.25 Å). Because of the short distance between rings, this type of radical anion stack shows semiconductive properties and long- range magnetic ordering. In low-temperature phase (lt) DDQ moieties form Peierls-distorted stacks, stacks of dimers, with alternating shorter (ca 2.9 Å) and longer separation (ca 3.3 Å) between DDQ rings. In lt phase, radical dimers have coupled spins so it is diamagnetic and insulator.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA