Reversible phase transition of 2-carboxypyridinium perchlorate–pyridinium-2-carboxylate (1/1)

2015 ◽  
Vol 71 (4) ◽  
pp. 247-251 ◽  
Author(s):  
Bi-Qin Wang ◽  
Hai-Biao Yan ◽  
Zheng-Qing Huang ◽  
Yun-Hua Zhang ◽  
Jing Sun
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Rotation Axis ◽  
Acid Group ◽  
Carboxylic Acid Group ◽  
Tetrahedral Geometry ◽  
Space Group ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
Hydrogen Bonded

The title salt, C6H6NO2+·ClO4−·C6H5NO2, was crystallized from an aqueous solution of equimolar quantities of perchloric acid and pyridine-2-carboxylic acid. Differential scanning calorimetry (DSC) measurements show that the compound undergoes a reversible phase transition at about 261.7 K, with a wide heat hysteresis of 21.9 K. The lower-temperature polymorph (denoted LT;T= 223 K) crystallizes in the space groupC2/c, while the higher-temperature polymorph (denoted RT;T= 296 K) crystallizes in the space groupP2/c. The relationship between these two phases can be described as: 2aRT=aLT; 2bRT=bLT;cRT=cLT. The crystal structure contains an infinite zigzag hydrogen-bonded chain network of 2-carboxypyridinium cations. The most distinct difference between the higher (RT) and lower (LT) temperature phases is the change in dihedral angle between the planes of the carboxylic acid group and the pyridinium ring, which leads to the formation of different ten-membered hydrogen-bonded rings. In the RT phase, both the perchlorate anions and the hydrogen-bonded H atom within the carboxylic acid group are disordered. The disordered H atom is located on a twofold rotation axis. In the LT phase, the asymmetric unit is composed of two 2-carboxypyridinium cations, half an ordered perchlorate anion with ideal tetrahedral geometry and a disordered perchlorate anion. The phase transition is attributable to the order–disorder transition of half of the perchlorate anions.

Reversible phase transition of pyridinium-3-carboxylic acid perchlorate

2010 ◽  
Vol 66 (3) ◽  
pp. 387-395 ◽  
Author(s):  
Heng-Yun Ye ◽  
Li-Zhuang Chen ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Relative Displacement ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Dsc Measurements ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
Hydrogen Bonded

Pyridinium-3-carboxylic acid perchlorate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show that this compound undergoes a reversible phase transition at ∼ 135 K with a wide hysteresis of 15 K. Dielectric measurements confirm the transition at ∼ 127 K. Measurement of the unit-cell parameters versus temperature shows that the values of the c axis and β angle change abruptly and remarkably at 129 (2) K, indicating that the system undergoes a first-order transition at T c = 129 K. The crystal structures determined at 103 and 298 K are all monoclinic in P21/c, showing that the phase transition is isosymmetric. The crystal contains one-dimensional hydrogen-bonded chains of the pyridinium-3-carboxylic acid cations, which are further linked to perchlorate anions by hydrogen bonds to form well separated infinite planar layers. The most distinct differences between the structures of the higher-temperature phase and the lower-temperature phase are the change of the distance between the adjacent pyridinium ring planes within the hydrogen-bonded chains and the relative displacement between the hydrogen-bonded layers. Structural analysis shows that the driving force of the transition is the reorientation of the pyridinium-3-carboxylic acid cations. The degree of order of the perchlorate anions may be a secondary order parameter.

Crystal Data for Two Molybdates MIV (MoO4)2 With MIV = Zr, Hf

1987 ◽  
Vol 2 (1) ◽  
pp. 36-38 ◽  
Author(s):  
M. Auray ◽  
M. Quarton ◽  
P. Tarte
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Automatic Indexing ◽  
Space Group ◽  
Reversible Phase Transition ◽  
Cell Dimensions ◽  
Zirconium Molybdate ◽  
Reversible Phase

AbstractTwo molybdates MIV (MoO4)2 (with MIV = Hf or Zr) were synthesized by solid state reaction between MIVO2 and MoO3. Zirconium molybdate undergoes a reversible phase transition at 952 K.Hf(MoO4)2 and H.T. Zr(MoQ4)2, obtained as single crystals, are trigonal, space group with Z = 6; the cell dimensions are respectively a = 10.1005(3), c = 11.7230(5)Å; V = 1035.76(11)Å3; Dm(298 K) = 4.78(4), Dx = 4.792 Mg m−3 and a = 10.1409(3), c = 11.7097(5)Å; V = 1042.88(11)Å3; Dm (298 K) = 3.91(4), Dx = 3.926 Mg m−3.L.T. Zr(MoO4)2, indexed by the Visser automatic indexing program (1969) was found to be monoclinic, possible space group P2, P21 or Pm with Z = 4; the cell dimensions are a = 9.7557(5), b = 7.9373(5), c = 7.4631(4)Å, β = 97.959°(5); V = 572.3(5)Å Dm(298 K) = 4.74(5), Dx = 4.770 Mg m−3. Powder diffraction data were obtained at 293 K on a counter diffractometer with Ni-filtered copper radiation ( = 1.5418 Å).

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI2(dmf)2

1998 ◽  
Vol 54 (5) ◽  
pp. 663-670 ◽  
Author(s):  
R. A. Edwards ◽  
A. J. Easteal ◽  
O. P. Gladkikh ◽  
W. T. Robinson ◽  
M. M. Turnbull ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Intermolecular Forces ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Cell Parameters ◽  
Reversible Phase Transition ◽  
Higher Temperature ◽  
High Temperature Form ◽  
Reversible Phase

At 228 K crystals of ZnI2(dmf)2 show a reversible phase transition which does not disrupt the lattice. Above the transition temperature the space group is C2/c and the cell contains eight symmetrically equivalent molecules. Cooling to below the transition temperature has little effect on the cell parameters or on the Zn- and I-atom positions, but the space group is now P21/n and the asymmetric unit comprises two conformationally different molecules. These arise from cooperative rotations of either ca +25 or −43° about the Zn—O bond of one of the dmf ligands in the high-temperature form. This displacive transition involves large movements of some atoms. The corresponding chloride and bromide are isomorphous with the higher temperature C2/c form, but it is only with the iodide that the weaker intermolecular forces permit the unusual phase change. The transition has been followed by differential scanning calorimetry, which gives an enthalpy change of 1.44 (5) kJ mol−1.

scholarly journals 2,8-Dimethyltricyclo[5.3.1.13,9]dodecane-syn-2,syn-8-diol–propanoic acid (1/1)

2009 ◽  
Vol 65 (6) ◽  
pp. o1241-o1241 ◽  
Author(s):  
Yuji Mizobe ◽  
Roger Bishop ◽  
Donald C. Craig ◽  
Marcia L. Scudder
Keyword(s):  
Carboxylic Acid ◽  
Layer Structure ◽  
Acid Group ◽  
Propanoic Acid ◽  
Monoclinic Space Group ◽  
Carboxylic Acid Group ◽  
Screw Axis ◽  
Supramolecular Synthon ◽  
Compound C ◽  
Hydrogen Bonded

The racemic title compound, C14H24O2·C3H6O2, crystallizes in the monoclinic space groupP21/cas a 1:1 diol/carboxylic acid cocrystal,A–B. The lattice incorporates infinite chains of the alcohol–carboxylic acid–alcohol supramolecular synthon, (...O—H...O=C(R)—O—H...O—H...), in which the hydrogen-bonded molecules (A—B—A)nsurround a pseudo-threefold screw axis. The carboxylic acid group functions like an extended alcohol hydroxy group. Each diol,A, takes part in two such threefold screw arrangements, leading to a hydrogen-bonded layer structure, with adjacent layers containing diol molecules of opposite handedness. The central C atom of the propano bridge is disordered over two sites of occupancies 0.75 (1) and 0.25 (1). The methyl group of the propanoic acid molecule is disordered over two sites of occupancies 0.68 (1) and 0.32 (1).

Reversible structural phase transition of pyridinium-4-carboxylic acid perchlorate

2010 ◽  
Vol 43 (5) ◽  
pp. 1031-1035 ◽  
Author(s):  
Heng-Yun Ye ◽  
Hong-Ling Cai ◽  
Jia-Zeng Ge ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Structural Phase ◽  
Differential Scanning Calorimetry Measurement ◽  
Scanning Calorimetry ◽  
Reflection Index ◽  
Space Group ◽  
Cell Parameters ◽  
Bonding Effect ◽  
Reversible Phase Transition

Pyridinium-4-carboxylic acid perchlorate (C6H6NO2·ClO4) was synthesized and separated as crystals. Differential scanning calorimetry measurement shows that this compound undergoes a reversible phase transition at about 122 K with a heat hysteresis of 1.8 K. A dielectric anomaly observed at 127 K further confirms the phase transition. The low-temperature (LT;T= 103 K) structure has space groupP21/cand cell parametersa= 17.356 (6),b= 13.241 (3),c= 16.161 (7) Å, β = 138.055 (17)°. The high-temperature (HT;T= 298 K) structure has space groupP21/cand cell parametersa= 5.5046 (11),b= 13.574 (3),c= 11.834 (2) Å, β = 99.35 (3)°, but can be re-described using new axesa′ =a,b′ =b,c′ = −2a+c,V′ =Vto give the cella′ = 5.5046 (11),b′ = 13.574 (3),c′ = 17.424 (3) Å, β′ = 137.92 (3)° and space groupP21/c. The associated coordinate transformation isx′ =x+ 2z,y′ =y,z′ =zand the associated reflection index transformation ish′ =h,k′ =k,l′ =l− 2h. The relationship between the two cells is 3a,b,c(HT) approximatesa,b,c(LT). The crystal comprises one-dimensional hydrogen-bonded chains of the pyridinium-4-carboxylic acid cations and perchlorate anions. A precise analysis of the main packing and structural differences as well as the changes in the intermolecular interactions between the HT phase and the LT phase reveals that the disorder–order transition of the perchlorate anions may be the driving force of the transition, and the hydrogen-bonding effect may contribute to the transition as a secondary parameter.

A low temperature reversible phase transition for 1,1'-bis-(ferrocenyldimethylsilyl)ferrocenylene, (η5-FcSiMe2C5H4)2Fe, an oligomeric model for silyleneferrocenylene polymers

2000 ◽  
Vol 78 (11) ◽  
pp. 1511-1518 ◽  
Author(s):  
Mikhail Yu Antipin ◽  
Ivan I Vorontsov ◽  
Irene I Dubovik ◽  
Vladimir Papkov ◽  
Francisco Cervantes-Lee ◽  
...  
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Phase Space ◽  
Low Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Space Group ◽  
Reversible Phase Transition ◽  
Reversible Phase

We have reinvestigated the solid state structure of 1,1'-bis-(ferrocenyldimethylsilyl)ferrocenylene, (η5-FcSiMe2C5H4)2Fe, Fc = (η5-C5H5)Fe(η5-C5H4). Using a DSC technique we observed a reversible phase transition for this compound at 169(3)K with ΔH = 1.1 kJ/mol, and ΔS = 6.54 J/mol K. A single crystal X-ray diffraction study has demonstrated that this phase change involves a transformation from a high temperature phase, space group P21/c, Z = 2, to a triclinic low temperature phase, space group P[Formula: see text], Z = 4. The phase transition involves the loss of the molecular crystallographic center of symmetry and rotations about the terminal and central cyclopentadienyl ring pairs. The results are compared to those reported for ferrocene.Key words: solid state, phase transition, silyleneferrocenylene.

scholarly journals Crystal structure and Hirshfeld surface analysis of 1-carboxy-2-(3,4-dihydroxyphenyl)ethan-1-aminium chloride 2-ammonio-3-(3,4-dihydroxyphenyl)propanoate: a new polymorph ofL-dopa HCl and isotypic with its bromide counterpart

2016 ◽  
Vol 72 (11) ◽  
pp. 1628-1632
Author(s):  
Perumal Kathiravan ◽  
Thangavelu Balakrishnan ◽  
Perumal Venkatesan ◽  
Kandasamy Ramamurthi ◽  
María Judith Percino ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Positive Charge ◽  
Acid Group ◽  
Hirshfeld Surface ◽  
Monoclinic Space Group ◽  
Amino Group ◽  
Carboxylic Acid Group ◽  
Acta Cryst ◽  
Space Group ◽  
Molecular Salt

The title molecular salt, C9H12NO4+·Cl−·C9H11NO4, is isotypic with that of the bromide counterpart [Kathiravanet al.(2016).Acta Cryst.E72, 1544–1548]. The title salt is a second monoclinic polymorph of the L-dopa HCl structure reported earlier in the monoclinic space groupP21[Jandacek & Earle (1971).Acta Cryst.B27, 841–845; Mostad & Rømming (1974).Acta Chemica Scand.B28, 1161–1168]. In the title compound, monoclinic space groupI2, one of the dopa molecules has a positive charge with a protonated α-amino group and the α-carboxylic acid group uncharged, while the second dopa molecule has a neutral charge, the α-amino group is protonated and the α-carboxylic acid is deprotonated. In the previously reported form, a single dopa molecule is observed in which the α-amino group is protonated and the α-carboxylic acid group is uncharged. The invariant and variations of various types of intermolecular interactions present in these two forms of dopa HCl structures are discussed with the aid of two-dimensional fingerprint plots.

scholarly journals Dimethylammonium 2-amino-5-nitroterephthalate hemihydrate

IUCrData ◽  
2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Martin Krueger ◽  
Martin Albat ◽  
Florian Pieper ◽  
Norbert Stock
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Water Molecule ◽  
Rotation Axis ◽  
Acid Group ◽  
Amino Group ◽  
Carboxylate Group ◽  
Asymmetric Unit ◽  
Carboxylic Acid Group ◽  
Compound C

The asymmetric unit of the title compound, C2H8N+·C8H5N2O6−·0.5H2O, comprises a monodeprotonated 2-amino-5-nitroterephthalate anion and a dimethylammonium counter-ion on general positions and a water molecule that lies on a twofold rotation axis. Extensive hydrogen bonding is observed between the carboxylate group and the dimethylammonium ion, the water molecule and the carboxylic acid group, as well as between the amino group, the water molecule and the carboxylic acid group (N—H...O and O—H...O hydrogen bonds are involved).

scholarly journals A monoclinic polymorph of 2-(4-nitrophenyl)acetic acid

IUCrData ◽  
2016 ◽  
Vol 1 (12) ◽  
Author(s):  
Alan R. Kennedy ◽  
Lygia Silva de Moraes
Keyword(s):  
Acetic Acid ◽  
Carboxylic Acid ◽  
Aromatic Ring ◽  
Dihedral Angle ◽  
Molecular Conformation ◽  
Acid Group ◽  
Carboxylic Acid Group ◽  
Monoclinic Form ◽  
Intermolecular Contacts ◽  
Hydrogen Bonded

A new monoclinic form of 4-nitrophenylacetic acid, C8H7NO4, (I), differs from the known orthorhombic form both in its molecular conformation and in its intermolecular contacts. The conformation is different as the plane of the carboxylic acid group in (I) is more nearly perpendicular to the plane of the aromatic ring [dihedral angle = 86.9 (3)°] than in the previous form (74.5°). Both polymorphs display hydrogen-bondedR22(8) carboxylic acid dimeric pairs, but in (I), neighbouring dimers interact through nitro–nitro N...O dipole–dipole contacts rather than the nitro–carbonyl contacts found in the orthorhombic form.

Sign in / Sign up

Export Citation Format

Share Document