Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin

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Armand Budzianowski and Andrzej Katrusiak

Acta Crystallographica Section B
Structural Science
Volume 58, Part 1 (February 2002)
Acta Cryst. (2002). B58, 125-133 [doi:10.1107/S0108768101017955]

Abstract

Conformational disorder and inversions of the lactone ring induce structural transformations in the crystals of 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin, C14H18O3. The onset of ordering of the lactone ring at 300K proceeds continuously, changes the space group from P21/m to P21/c and doubles the unit cell; the abrupt inversion of the lactone rings at 225K changes the crystal translational symmetry in the (010) plane. The mechanism combining the molecular conformation and dynamics with the crystal structure, its symmetry, and phase transitions is presented.

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Competing hydrogen-bonding patterns and phase transitions of 1,2-diaminoethane at varied temperature and pressure

 Armand Budzianowski Anna Olejniczak and Andrzej Katrusiak

Acta Crystallographica Section B
Structural Science
Volume 62, Part 6 (December 2006)
Acta Cryst. (2006). B62, 1078-1089 [doi:10.1107/S010876810602982X]

Abstract

1,2-Diaminoethane has been in-situ pressure- and temperature-frozen; apart from two known low-temperature phases, I[alpha] and II, three new phases, I[beta], I[gamma] and III, have been observed and their structures determined by X-ray diffraction. The measurements at 0.1MPa were carried out at 274, 243 and 224K, and 296K measurements were made at 0.15GPa (phase I[alpha]), at 0.3 and 1.1GPa (phase I[beta]), at 1.5GPa (phase I[gamma]), and at 0.2, 0.3 and 0.5 GPa (phase III). All these phases are monoclinic, space group P21/c, but the unit-cell dimension of phases I[alpha] and III are very different at 296 K: aI[alpha]=5.078(5), bI[alpha]=7.204(8), cI[alpha]=5.528(20)Å, [beta]I[alpha]=115.2(2)° at 0.15GPa, and aIII=5.10(3), bIII=5.212 (2), cIII=7.262 (12)Å, [beta]III = 111.6(4)° at 0.2GPa, respectively; in both phases Z=2. An ambient-pressure low-temperature phase II has been observed below 189K. Discontinuities in the unit-cell dimensions and in the N...N distance mark the isostructural transition between phases I[alpha] and I[beta] at 0.2GPa, which can be attributed to a damping process of the NH2 group rotations. In phase I[gamma] the unit-cell parameter a doubles and Z increases to 4. The molecule has inversion symmetry in all the structures determined. 1,2-Diaminoethane can be considered as a simple structural ice analogue, but with NH...N hydrogen bonds and with the H-atom donors (four in one molecule) in excess over H-atom acceptors (two per molecule). Thus, the transformations of 1,2-diaminoethane phases involving the conformational dynamics affect the hydrogen-bonding geometry and molecular association in the crystal. The 1,2-diaminoethane:1,2-dihydroxyethane mixture has been separated by pressure-freezing, and a solid 1,2-diaminoethane crystal in liquid 1,2-dihyroxyethane has been obtained.

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Anomalous Protonic-Glass Evolution from Ordered Phase in NH···N Hydrogen-Bonded DabcoHBF4 Ferroelectric

Armand Budzianowski and Andrzej Katrusiak, Marek Szafrański

J. Phys. Chem. B, 2008, 112 (51), pp 16619–16625 DOI: 10.1021/jp801316a

REPRINTED WITH PERMISSION FROM J. Phys. Chem. B, 2008, 112 (51), pp 16619–16625 DOI: 10.1021/jp801316a. COPYRIGHT (2008) AMERICAN CHEMICAL SOCIETY.

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Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4- dihydrocoumarin

Armand Budzianowski and Andrzej Katrusiak


Acta Crystallographica Section B
Structural Science
Volume 58, Part 1 (February 2002)
Acta Cryst. (2002). B58, 125-133 [ doi:10.1107/S0108768101017955 ]
Authorised by IUCr electronic reprint of the article
Revised pages 131 and 132
[doi:10.1107/S0108768102003518/bm9046sup1.pdf]

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