The order–disorder phase transition associated with the uprise of reorientational motion in (DABCOH2)2+, in the supramolecular salts of general formula [1⋅(DABCOH2)]X2 (where 1=12‐crown‐4, DABCO=1,4‐diazabicyclo[2.2.2]octane, and X=Cl− or Br−), has been investigated by variable temperature X‐ray diffraction on single crystals and powder samples, as well as by DSC and solid‐state NMR spectroscopy (SSNMR). The two compounds undergo a reversible phase change at 292 and 290 K, respectively. The two crystalline materials form solid solutions [1⋅(DABCOH2)]Cl2xBr2(1−x) in the whole composition range (0 < x<1), with a decrease in the temperature of transition to a minimum of ca 280 K, corresponding to x=0.5. Activation energy values for the dynamic processes, evaluated by variable‐temperature 13C magic‐angle spinning (MAS) SSNMR and line‐shape analysis are ca. 50 kJ mol−1 in all cases. Combined diffraction and spectroscopic evidence has allowed the detection of a novel dynamic process for the (DABCOH2)2+ dications, based on a room temperature precessional motion that is frozen out below the disorder–order transition; to the best of the authors’ knowledge this phenomenon has never been observed before.

Precessional Motion in Crystalline Solid Solutions of Ionic Rotors

ROSSI, FEDERICA;Chierotti, Michele R;Gobetto, Roberto
2018-01-01

Abstract

The order–disorder phase transition associated with the uprise of reorientational motion in (DABCOH2)2+, in the supramolecular salts of general formula [1⋅(DABCOH2)]X2 (where 1=12‐crown‐4, DABCO=1,4‐diazabicyclo[2.2.2]octane, and X=Cl− or Br−), has been investigated by variable temperature X‐ray diffraction on single crystals and powder samples, as well as by DSC and solid‐state NMR spectroscopy (SSNMR). The two compounds undergo a reversible phase change at 292 and 290 K, respectively. The two crystalline materials form solid solutions [1⋅(DABCOH2)]Cl2xBr2(1−x) in the whole composition range (0 < x<1), with a decrease in the temperature of transition to a minimum of ca 280 K, corresponding to x=0.5. Activation energy values for the dynamic processes, evaluated by variable‐temperature 13C magic‐angle spinning (MAS) SSNMR and line‐shape analysis are ca. 50 kJ mol−1 in all cases. Combined diffraction and spectroscopic evidence has allowed the detection of a novel dynamic process for the (DABCOH2)2+ dications, based on a room temperature precessional motion that is frozen out below the disorder–order transition; to the best of the authors’ knowledge this phenomenon has never been observed before.
24
56
15059
15066
https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201803071
crystal engineering; crystalline solid solutions; mechanochemistry; molecular motion in crystals
d'Agostino, Simone; Fornasari, Luca; Grepioni, Fabrizia; Braga, Dario; Rossi, Federica; Chierotti, Michele R; Gobetto, Roberto
File in questo prodotto:
File Dimensione Formato  
Precessional Motion in Crystalline Solid Solutions of Ionic Rotors.docx

Open Access dal 20/01/2020

Descrizione: articolo completo
Tipo di file: POSTPRINT (VERSIONE FINALE DELL’AUTORE)
Dimensione 1.67 MB
Formato Microsoft Word XML
1.67 MB Microsoft Word XML Visualizza/Apri
chem eur j2018,24,15059_completo.pdf

Accesso riservato

Descrizione: articolo completo
Tipo di file: PDF EDITORIALE
Dimensione 3.2 MB
Formato Adobe PDF
3.2 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1687273
Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus 11
  • ???jsp.display-item.citation.isi??? 11
social impact