TY - JOUR
T1 - Five more phases of the structural family [M(H2O) 2(15-crown-5)](NO3)2
AU - Siegler, Maxime A.
AU - Hao, Xiang
AU - Parkin, Sean
AU - Brock, Carolyn Pratt
PY - 2008
Y1 - 2008
N2 - The structures of five more phases of the structural family of compounds [M(H2O)2(15-crown-5)](NO3)2 have been determined. All of these phases are stable at room temperature or above, but transform to other phases if cooled slowly. All five phase transitions take place without significant damage to the single crystal. The M = Co phase, which has a three-dimensional hydrogen-bonding pattern, is a disordered version of the structure known at room temperature; Z' changes from 2 to 1/2. The other four structures have a two-dimensional hydrogen-bonding pattern, are all modulated variants of the same basic cell (or subcell) and are at least mostly ordered. For M = Mg and Zn the structure found somewhat above room temperature is the Z' = 8 variant found previously for M = Fe. For M = Cu and Ni the Z' = 2 phase found is the same as seen previously for one of the room-temperature polymorphs with M = Mn. There are now two phases and one transition known for each M studied that has a two-dimensional hydrogen-bonding pattern. The changes in the modulation patterns during these transitions are Z' 3 ↔ 8 (Mg, Fe, Zn), Z' 3 ↔ 2 (Mn, Ni) and Z' 5 ↔ 2 (Cu). In all two-dimensional hydrogen-bonded crystals the alternation pattern of conformational enantiomers along the modulation direction becomes more perfect above the phase transition. All stable [M(H2O)2(15-crown-5)](NO3) 2 phases whose existence at accessible temperatures is indicated by differential scanning calorimetry (DSC) have now been characterized.
AB - The structures of five more phases of the structural family of compounds [M(H2O)2(15-crown-5)](NO3)2 have been determined. All of these phases are stable at room temperature or above, but transform to other phases if cooled slowly. All five phase transitions take place without significant damage to the single crystal. The M = Co phase, which has a three-dimensional hydrogen-bonding pattern, is a disordered version of the structure known at room temperature; Z' changes from 2 to 1/2. The other four structures have a two-dimensional hydrogen-bonding pattern, are all modulated variants of the same basic cell (or subcell) and are at least mostly ordered. For M = Mg and Zn the structure found somewhat above room temperature is the Z' = 8 variant found previously for M = Fe. For M = Cu and Ni the Z' = 2 phase found is the same as seen previously for one of the room-temperature polymorphs with M = Mn. There are now two phases and one transition known for each M studied that has a two-dimensional hydrogen-bonding pattern. The changes in the modulation patterns during these transitions are Z' 3 ↔ 8 (Mg, Fe, Zn), Z' 3 ↔ 2 (Mn, Ni) and Z' 5 ↔ 2 (Cu). In all two-dimensional hydrogen-bonded crystals the alternation pattern of conformational enantiomers along the modulation direction becomes more perfect above the phase transition. All stable [M(H2O)2(15-crown-5)](NO3) 2 phases whose existence at accessible temperatures is indicated by differential scanning calorimetry (DSC) have now been characterized.
KW - Hydrogen bonding
KW - Phase transitions
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U2 - 10.1107/S0108768108034046
DO - 10.1107/S0108768108034046
M3 - Article
C2 - 19029703
AN - SCOPUS:56849088341
SN - 0108-7681
VL - 64
SP - 738
EP - 749
JO - Acta Crystallographica Section B: Structural Science
JF - Acta Crystallographica Section B: Structural Science
IS - 6
ER -