This article was downloaded by: [Said Salem]On: 06 June 2013, At: 03:13Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Phase Transitions: A MultinationalJournalPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/gpht20

The structural transformationof monoclinic [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O intoorthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermalbehaviorSalem Saïd a , Noureddine Mhadhbi a , Fadhel Hajlaoui a , SamiaYahyaoui a , Alexander J. Norquist b , Tahar Mhiri a , ThierryBataille c & Houcine Naïli aa Laboratoire Physico-Chimie de l’Etat Solide, Département deChimie , Université de Sfax, BP 1171 , Sfax , 3000 , Tunisieb Department of Chemistry, Haverford College , Haverford , PA ,19041 , USAc Institut des Sciences Chimiques de Rennes UMR CNRS 6226 ,Université de Rennes 1 UEB, Avenue du Général Leclerc , RennesCedex , F-35042 , FrancePublished online: 23 May 2013.

To cite this article: Salem Saïd , Noureddine Mhadhbi , Fadhel Hajlaoui , Samia Yahyaoui ,Alexander J. Norquist , Tahar Mhiri , Thierry Bataille & Houcine Naïli (2013): The structuraltransformation of monoclinic [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O into orthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermal behavior, Phase Transitions: AMultinational Journal, DOI:10.1080/01411594.2013.787617

To link to this article: http://dx.doi.org/10.1080/01411594.2013.787617

PLEASE SCROLL DOWN FOR ARTICLE

Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representationthat the contents will be complete or accurate or up to date. The accuracy of anyinstructions, formulae, and drug doses should be independently verified with primarysources. The publisher shall not be liable for any loss, actions, claims, proceedings,demand, or costs or damages whatsoever or howsoever caused arising directly orindirectly in connection with or arising out of the use of this material.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

The structural transformation of monoclinic [(R)-C5H14N2]

[Cu(SO4)2(H2O)4]�2H2O into orthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermal behavior

Salem Sa€ıda, Noureddine Mhadhbia, Fadhel Hajlaouia, Samia Yahyaouia,

Alexander J. Norquistb, Tahar Mhiria, Thierry Bataillec and Houcine Na€ılia*

aLaboratoire Physico-Chimie de l’Etat Solide, D�epartement de Chimie, Universit�e de Sfax, BP1171, 3000 Sfax, Tunisie; bDepartment of Chemistry, Haverford College, Haverford, PA 19041,USA; cInstitut des Sciences Chimiques de Rennes UMR CNRS 6226, Universit�e de Rennes 1 UEB,

Avenue du G�en�eral Leclerc, F-35042 Rennes Cedex, France

(Received 13 December 2012; final version received 17 March 2013)

Single crystals of [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) were grown through theslow evaporation of a solution containing H2SO4, (R)-C5H12N2 and CuSO4�5H2O.These crystals spontaneously transform to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) overthe course of four days at room temperature. The same single crystal on the samemounting was used for the determination of the structure of (1) and the unit cell deter-mination of (2). A second single crystal of the transformed batch has served for thestructural determination of (2). Compound 1 crystallizes in the noncentrosymmetricspace group P21 (No. 4) and consists of trimeric [Cu(SO4)2(H2O)4]

2� anions, [(R)-C5H14N2]

2þ cations and occluded water molecules. Compound 2 crystallizes inP21212 (No. 18) and contains [Cu(H2O)6]

2þ cations, [SO4]2� anions and occluded

water molecules. The thermal decompositions of compounds 1 and 2 were studied bythermogravimetric analyses and temperature-dependent X-ray diffraction.

Keywords: noncentrosymmetric; spontaneous transformations; intermediate hydrates;anhydrous compounds

1. Introduction

Open-framework organically templated metal sulfates have been the subject of intense

research owing to their interesting structural chemistry and potential in applications such

as ferroelectricity, catalysts and optical activity.[1–8] The range of metals incorporated

includes lanthanides, actinides and transition metals.[9–12] The dimensionalities of the

metal sulfates in these compounds range from 0D molecular anions and hexaaqua com-

plexes to 3D framework materials.[13–17]

During the last decades specific interest has been directed toward the syntheses of

noncentrosymmetric sulfates materials in the presence of organic molecules, [5,6,16,18–

20] owing to possible synergies between the inorganic and organic components.[21] Our

interests are directed toward the creation of new noncentrosymmetric materials that

exhibit nonlinear optical (NLO) activities.[22] As crystallographic noncentrosymmetry is

a base requirement for NLO properties, it is essential to understand the forces that govern

the formation of new noncentrosymmetric materials. Several strategies [23,24] are

*Corresponding author. Email: houcine_naili@yahoo.com

� 2013 Taylor & Francis

Phase Transitions, 2013

http://dx.doi.org/10.1080/01411594.2013.787617

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

currently employed to direct noncentrosymmetry in new compounds, including the use of

chiral organic amines.[5,6,25,26]

In an attempt to synthesize noncentrosymmetric open-framework sulfates materials,

we have prepared two copper sulfates templated by (R)-2-methylpiperazine, [(R)-

C5H14N2][Cu(SO4)2 (H2O)4]�2H2O (1) and [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2), which

possess supramolecular architectures.[(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) sponta-

neously transforms to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) over the course of four days.

The structures of both compounds were determined using single crystal X-ray diffraction

and their respective thermal stabilities were probed using thermogravimetric analyses and

temperature-dependent X-ray diffraction.

2. Experimental section

2.1. Materials

CuSO4�5H2O (99%, Merck), (R)-(–)-2-methylpiperazine (99%, Aldrich) and H2SO4

(96%, Carlo Erba) were used as received. Deionized water was used in these syntheses.

2.2. Synthesis

Single crystals of the compound [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) were grown

from an aqueous solution of H2SO4, [(R)-C5H12N2] and CuSO4�5H2O in a 1/3/1 molar

ratio. After a few days, transparent blue crystals were isolated from the solution. The

experimental powder X-ray diffraction pattern for the compound matches a simulated

from single crystal structure data, indicating that the compound 1 was isolated as single

phase. Reaction yields ranged between 70 and 85%, based upon copper.

[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) was formed spontaneously from a sample of

[(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) in air. Removal of single crystals of [(R)-

C5H14N2][Cu(SO4)2(H2O)4]�2H2O from the aqueous solution in which they were grown

results in a direct transformation to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) over the course

of four days.

2.3. Single-crystal X-ray diffraction

The same single crystal on the same mounting was used for the determination of the struc-

ture of [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) and the unit cell determination of [(R)-

C5H14N2]2[Cu(H2O)6](SO4)3 (2). Initial data were collected shortly after removing the

crystal from its supernatant liquid, resulting in the structure of 1. This crystal was then

allowed to transform to 2 over the course of four days, to perform indexing and space

group determination. As the crystal deteriorates during the transformation, a second sin-

gle crystal was selected from the transformed batch, after removing the pale blue powder

formed at the surface of the crystal. X-ray diffraction data set was then collected, which

resulted in the structural determination of 2.

Suitable single crystals were carefully selected under a polarizing microscope and

glued to a glass fiber mounted on a four-circle Nonius Kappa CCD area-detector diffrac-

tometer. Intensity data sets were collected using MoKa radiation through the program

COLLECT.[27,41] Corrections for Lorentz-polarization effect, peak integration and

background determination were carried out with the program DENZO.[28,42] Frame

scaling and unit cell parameters refinement were performed with the program

2 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

SCALEPACK.[27] Analytical absorption corrections were performed by modeling the

crystals faces.[29]

The structure analyses of 1 and 2 were carried out with the monoclinic and ortho-

rhombic symmetry, space group P21 (No. 4) and P21212 (No. 18) respectively, according

to the automated search for space group available in WinGX.[30] Copper and sulfur sites

were located using the direct methods with program SHELXS-97 [31] and SIR92.[32]

The oxygen atoms and the organic moieties were found from successive Fourier calcula-

tions using SHELXL-97.[31] The aqua H atoms were located in a difference map and

refined with O–H distance restraints of 0.85(1) A�and H–H restraints of 1.39(1) A

�so that

the H–O–H angle fitted to the ideal value of a tetrahedra angle. H atoms bonded to C and

N atoms were positioned geometrically and allowed to ride on their parent atoms, with

C–H and N–H bonds were fixed at 0.97 and 0.89 A�, respectively. Crystallographic data

and structural refinements are provided in Table 1. Selected bond distances and angles, as

well as probable hydrogen bonds are given in Tables 2, 3 and 4, respectively.

2.4. Infrared spectroscopy

Infrared measurements were obtained using a Perkin-Elmer FTIR Spectrometer as KBr

pellets in the range 4000–400 cm�1.

2.5. Thermogravimetric analysis

Thermogravimetric (TG) measurements were performed with a Rigaku Thermoflex

instrument under flowing air for [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) and

Table 1. Crystal data and structure refinement for [(R)-C5H14N2][Cu(H2O)4](SO4)2�2H2O (1) and[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2).

Compound[(R)-C5H14N2][Cu(H2O)4]

(SO4)2�2H2O[(R)-C5H14N2]2

[Cu(H2O)6](SO4)3

Empirical formula C5H26CuN2O14S2 C10H40CuN4O18S3Formula weight 465.94 664.22Temperature (K) 293(2) 298(2)Crystal system Monoclinic OrthorhombicSpace group P21 (No. 4) P21212 (No. 18)a (A

�) 7.5676(2) 9.6250(10)

b (A�) 10.1942(3) 20.5640(10)

c (A�) 10.8184(3) 6.8860(10)

b (deg) 94.417(2) 90V (A

� 3) 832.11(4) 1362.94(3)Z 2 2rcalc, (g cm

�3) 1.860 1.618l (A

�) 0.71073 0.71073

m (mm�1) 1.637 1.112Flack parameter �0.03(2) 0.09(2)R1

a 0.0320 0.0380WR2

b 0.0816 0.0939Residual electron densities (eA

� �3) 0.60 and �0.62 �0.53 and 0.42

aR1 ¼S║Foj � Fc║ /SjFoj; bwR2 ¼ [Sw(Fo2 – Fc

2)2 / [Sw(Fo2)2]1/2.

Phase Transitions 3

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

Table 2. Selected bond distances (A�) and angles (�) for [(R)-C5H14N2][Cu(H2O)4](SO4)2�2H2O

(1).

Octahedron around Cu Tetrahedron around S1

Cu–O1 2.387(3) S1–O1 1.480(3)Cu–O5 2.357(3) S1–O2 1.461(3)Cu–Ow1 1.973(3) S1–O3 1.485(3)Cu–Ow2 1.995(3) S1–O4 1.493(3)Cu–Ow3 1.962(3) O2–S1–O1 110.4(2)Cu–Ow4 2.002(3) O3–S1–O2 110.55(19)Ow3–Cu–Ow1 179.49(17) O1–S1–O3 109.62(17)Ow3–Cu–Ow2 89.55(12) O4–S1–O2 109.9(2)Ow1–Cu–Ow2 90.79(16) O1–S1–O4 108.33(17)Ow3–Cu–Ow4 90.28(15) O4–S1–O3 108.0(2)Ow1–Cu–Ow4 89.38(12) Tetrahedron around S2Ow2–Cu–Ow4 179.7(2) S2–O5 1.483(3)Ow3–Cu–O5 90.81(12) S2–O6 1.476(3)Ow1–Cu–O5 89.57(12) S2–O7 1.461(3)Ow2–Cu–O5 89.38(13) S2–O8 1.466(3)Ow4–Cu–O5 90.89(13) O7–S2–O8 110.7(2)Ow3–Cu–O1 90.01(12) O7–S2–O6 108.7(2)Ow1–Cu–O1 89.61(12) O8–S2–O6 109.81(19)Ow2–Cu–O1 90.36(13) O7–S2–O5 107.84(17)Ow4–Cu–O1 89.38(12) O8–S2–O5 110.1(2)O1–Cu–O5 179.14(14) O6–S2–O5 109.59(18)

Table 3. Selected bond distances (A�) and angles (�) for [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2).

Octahedron around Cu

Cu–Ow1 2.108(3) O8–S2–O6(ii) 119.4(7)Cu–Ow2 2.089(3) O5–S2–O8(ii) 99.7(4)Cu–Ow3 2.023(3) O5–S2–O7(ii) 113.6(5)Ow1–Cu–Ow2 94.73(15) O5–S2–O6(ii) 107.1(4)Ow1–Cu–Ow2(i) 85.61(14) O6–S2–O7(ii) 113.8(6)Ow1–Cu–Ow3 92.21(11) O5–S2–O6 107.1(4)Ow1–Cu–Ow3(i) 176.48(15) O7–S2–O8(ii) 102.6(4)Ow2–Cu–Ow3 87.39(14) O7–S2–O6(ii) 113.8(6)Ow2–Cu–Ow3(i) 92.29(14) O5–S2–O7 113.6(5)Tetrahedron around S1 O8-S2-O7(ii) 102.6(4)S1–O1 1.486(3) O5–S2–O8 99.7(4)S1–O2 1.458(3) O6–S2–O8 119.4(7)S1–O3 1.477(3)S1–O4 1.472(3)O3–S1–O1 109.53(18)O3–S1–O4 109.47(19)O1–S1–O4 107.16(17)O3–S1–O2 108.82(15)O1–S1–O2 110.81(17)O4–S1–O2 111.01(17)Tetrahedron around S2S2–O5 1.468(5)S2–O6 1.379(7)S2–O7 1.483(7)S2–O8 1.498(8)

Symmetry codes: (i) –x–1, –y–1, z; (ii) –x–2, –y–1, z.

4 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2), in the temperature range 20–900�C, with a heating

rate of 15�C h–1 in platinum crucibles.

2.6. Powder X-ray diffraction

Temperature-dependent powder X-ray diffraction (TDXD) was performed with a powder

diffractometer, with CuKa1 radiation [λ(Ka1) ¼ 1.5406 A�] selected with a incident-beam

quartz monochromator combining the curved-position-sensitive detector from INEL

(CPS 120) and a high-temperature attachment from Rigaku. These data were collected in

air, with a heating rate of 7�C h�1 from ambient to about 600�C. Temperature calibration

was carried out with standard materials in the involved temperature range.

Table 4. Hydrogen-bonding geometry (A�).

[(R)-C5H14N2][Cu(H2O)4](SO4)2�2H2O (1)

D–H� � �A d(D–H) (A�) d(H� � �A) (A� ) d(D� � �A) (A� ) ff D–H� � �A (�)

N1–H1A� � �O1 0.90 1.97 2.859(4) 170.2N1–H1B� � �O3I 0.90 1.93 2.801(6) 163.1N2–H2A� � �O6II 0.90 1.87 2.761(6) 168.0N2–H2B� � �O5III 0.90 1.96 2.842(4) 168.0Ow3–Hw6� � �O6 0.91 1.80 2.697(5) 168.4Ow3–Hw5� � �O4I 0.95 1.74 2.644(5) 157.8Ow2–Hw4� � �O2IV 0.95 1.81 2.756(5) 172.8Ow2–Hw3� � �Ow6 0.95 1.80 2.706(5) 157.6Ow1–Hw2� � �O7VII 0.89 1.79 2.670(5) 170.4Ow1–Hw1� � �O3 0.95 1.79 2.642(4) 147.8Ow4–Hw8� � �Ow5 0.93 1.85 2.769(5) 168.0Ow4–Hw7� � �O8VIII 0.91 1.83 2.736(4) 170.5Ow5–Hw9� � �O7 0.94 2.57 2.835(5) 96.4Ow5–Hw10� � �O8V 0.97 2.15 2.882(5) 131.6Ow6–Hw11� � �O2VI 0.92 1.97 2.868(5) 164.1Ow6–Hw12� � �O4 0.95 1.90 2.815(5) 162.2

Symmetry codes: I–xþ2, y–1/2, –zþ1; II –xþ1, yþ1/2, –zþ1; III x, y, zþ1; IV x–1, y, zþ1; V–xþ1,y–1/2, –z; VI �xþ2, y þ 1/2, –zþ1; VII –xþ1, yþ1/2, –z; VIII xþ1, y, z.

[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2)

N1–H7� � �O2 0.88 2.59 3.212(6) 129N1–H7� � �O3 0.88 1.89 2.759(6) 169N1–H8� � �O4V 0.89 1.84 2.730(6) 173N2–H12� � �O1VI 0.88 2.12 2.940(6) 153N2–H12� � �O4VI 0.88 2.26 2.995(6) 141N2–H13� � �O5 0.88 1.94 2.809(6) 169N2–H13� � �O6II 0.88 2.58 3.194(6) 128Ow1–Hw1� � �O1I 0.95 1.87 2.745(6) 153Ow1–Hw2� � �O7II 0.95 2.13 2.917(6) 139Ow1–Hw2� � �O8II 0.95 1.96 2.868(6) 159Ow2–Hw3� � �O3 0.95 1.80 2.726(6) 164Ow2–Hw4� � �O2III 0.95 1.76 2.705(6) 174Ow3–Hw6� � �O7IV 0.95 1.70 2.603(6) 157Ow3–Hw6� � �O8IV 0.95 2.11 2.876(6) 137

Symmetry codes: I –x–1, –y–1, z; II –x–2, –y–1, z; III –x, –y, z; IV x, y, zþ1; V xþ1/2, –y–1/2, –z;VI xþ1, y, z.

Phase Transitions 5

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

3. Results

3.1. Structure descriptions

The structure of [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) consists of [Cu

(SO4)2(H2O)4]2– molecular anions, [(R)-C5H14N2]

2þ cations and occluded water mole-

cules. The four bound water molecules occupy the equatorial coordination sites of the

Cu2þ center, with distances ranging between 1.958(3) and 2.002(3) A�. The two bound

[SO4]2– anions reside in the axial positions, with Cu–O distances of 2.357(3) and 2.387

(3) A�, indicating the presence of a Jahn–Teller distortion on the Cu2þ. S–O bonds range

between 1.461(3) and 1.493(3) A�. The S1–O1–Cu1 and S2–O5–Cu1 angles are 130.71

(16) and 131.28(16) �, respectively. The cis–O–Cu–O angles range between 89.38(12)

and 90.89(13) �, while the trans–O–Cu–O angles deviate from the ideal value by approxi-

mately 1�. Selected Cu–O bond lengths and the O–Cu–O are listed in Table 2. Similar

[MII(SO4)2(H2O)4]2� anions have been reported previously.[5,31]

The [(R)-C5H14N2]2þ cations and occluded water molecules in 1 reside between [Cu

(SO4)2(H2O)4]2� anions, forming an extensive three-dimensional hydrogen-bonding net-

work (see Figure 1). Compound 1 is part of an enantiomeric pair with [(S)-C5H14N2][Cu

(SO4)2(H2O)4]�2H2O.[6] The N–H���O cation–anion hydrogen-bonding distances range

between 2.761(6) and 2.859(4) A�. The presence of the [(R)-C5H14N2]

2þ cations was con-

firmed using infrared spectroscopy. C–H bands were observed at 1409 and 2963 cm�1,

while N–H bands were present at 1618 and 3107 cm�1. The S–O band was centered at

1113 cm�1 for compound 1.

Figure 1. Three-dimensional packing in [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1). Selectedhydrogen-bonding interactions are shown as dashed lines.

6 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) contains discreet [Cu(H2O)6]2þ, [(R)-

C5H14N2]2þ and [SO4]

2� ions. Two Cu–O distances of 2.023(3) A�, two others of 2.089

(3) A�and two remaining Cu–O bonds of 2.108(3) A

�are observed. Two distinct [SO4]

groups are present in 2.[S(1)O4] is ordered, while [S(2)O4] is disorder over a two-fold

axis of rotation (see Figure 2). S–O bond distances range between 1.379(7) and 1.498(8)

A�. Hydrogen bonds are present between the [Cu(H2O)6]

2þ, [(R)-C5H14N2]2þ and [SO4]

2�

ions (see Figure 3). The hexaaquacopper ions in this compound display the so-called [2 þ2 þ 2] [32,33] type of coordination that has often been observed, which is not consistent

with Jahn–Teller distortion.

As in compound 1, an extensive hydrogen-bonding network is present in 2. Each [Cu

(H2O)6]2þ is surrounded by six [SO4]

2�, as shown in Figure 4. In addition, the [(R)-

C5H14N2]2þ cations donate hydrogen bonds to neighboring [SO4]

2� anions. The N–H���Odistances range between 2.730(6) and 3.212(6) A

�, while the Ow–H���O distances range

between 2.603(6) and 2.917(6) A�. These values agree with those currently observed in

copper sulfates containing the organic groups.[34,35]

Compounds 1 and 2 were investigated using bond valence sums.[36] The calculated

SSi values for each cation correspond to their assigned oxidation states, with Cu2þ and

S6þ sums ranging between 2.07 and 2.08 and between 5.91 and 6.33, respectively. Full

tables of bond valence sums are provided as supplemental material with the online ver-

sion of the article.

Both compounds 1 and 2 crystallize in noncentrosymmetric groups, owing the pres-

ence of a single enantiomer of [2-methylpiperazineH2]2þ. The Flack parameters for the

Figure 2. Thermal ellipsoid plot of [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2). Displacement ellipsoidsare drawn at the 50% probability level. Hydrogen bonds are represented by dashed lines.

Phase Transitions 7

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

Figure 3. Three-dimensional packing of [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2).

compounds 1 and 2 are –0.03(2) and 0.09(2), respectively. As noted above, the use of chi-

ral organic amines to favor the formation of new non-centrosymmetric materials is well

known.[6,25,34,37,38] The possibility of pseudosymmetry in 1 and 2 was investigated.

PLATON [39] was used to probe for missing symmetry in both compounds. In the case

of 1, the possibility of a missed inversion center at (0.248, 0.396, 0.25) was examined.

This position is at the center of the [(R)-C5H14N2]2þ ring. However, the presence of a sin-

gle methyl group on each cation destroys this inversion center, and only pseudosymmetry

is observed among the [Cu(SO4)2(H2O)4]2� anions and occluded water molecules. The

contribution of this single methyl group is sufficient to force noncentrosymmetry and

crystallization in P21 (No. 4). This assignment is supported by the lack of a systematic

absence among the h0l reflections. No pseudosymmetry was detected in 2.

3.2. Structural transformation

The transformation of compound 1 into compound 2 requires both structural and compo-

sitional changes. Specifically, the compositional changes required for this transformation

are shown in Scheme 1.

2½ðRÞ-C5H14N2�½CuðSO4Þ2ðH2OÞ4��2H2O ð1Þ! ½ðRÞ-C5H14N2�2½CuðH2OÞ6�ðSO4Þ3 ð2Þ þ ½CuðH2OÞ6�½SO4�

ðScheme1Þ:

8 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

Figure 4. Local bonding environment: (a) of the [Cu(SO4)2(H2O)4]2� anions in (1) and (b) of the

[Cu(H2O)6]2þ cations in (2).

Phase Transitions 9

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

The amine:Cu:SO4 ratio is 1:1:2 in 1 and 2:1:3 in 2, which requires the loss of both Cu

and SO4 groups during the observed transformation. In addition, the [Cu(SO4)2(H2O)4]2�

molecular anions present in compound 1 are not observed in compound 2. Instead, all

Cu–Osulfate bonds have been replaced with Cu–Ow bonds. While the chemical transforma-

tion of 1 into 2 drastically modifies its chemical formula, it is worthy to note that there are

implicit symmetry relationships between the two structures. Indeed, examining the atomic

positions of Cu, S1 and S2 in the structure of 1, it is apparent that S1 is related to S2, and

Cu is related to itself, by the symmetry operation 1/2 þ x, 1/2 � y, 1/2 þ z. This operator

cannot be applied to the amine group, as the latter is an enantiomeric form of 2-

methylpiperazine, while a racemic mixture of both eniantomers or a positional disorder

would be suitable for this symmetry. In the present case, the heavy atoms are symmetry

related by operators located at x ¼ 1=4 and z ¼ 1=4 (resp.3/4). In addition, compound 1 crys-

tallizes in space group P21 which is the maximal non-isomorphic subgroup of space group

P21212 adopted by compound 2. Then it is obvious that the additional symmetry operators

available for heavy atoms in compound 1 (S.G. P21) correspond to the two transformation

matrices necessary for the cosets decomposition of space group P21212 into isomorphic

supergroup P21.

3.3. Thermal stabilities

[(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) is not stable at room temperature. After

approximately four days, [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1) transforms into

[(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2). All samples of 2 were prepared through this trans-

formation process. This includes the single crystal of 2, on which single crystal X-ray dif-

fraction experiments were performed.

In order to probe the thermal stabilities of these two compounds, both temperature-

dependent X-ray diffraction (TDXD) studies and thermogravimetric analyses (TGA)

were performed. The TGA traces and TDXD plots for compounds 1 and 2 are shown in

Figures 5 and 6, respectively. The thermal decomposition of 1 occurs via several dis-

tinct steps. First, five water molecules are lost between 55 and 100�C, with an observed

weight loss of 19.75 % (19.33% calculated). The resulting intermediate phase was iden-

tified from on the TDXD plot as [(R)-C5H14N2]Cu(SO4)2�H2O, based upon the TGA

studies. This phase is stable between 110 and 180�C, after which the last water mole-

cule releases. It is accompanied with structure changes, as shown by the modifications

of the powder patterns in the TDXD plot, until the crystalline anhydrous phase is

observed from 190 to 250�C. At this temperature, a new crystallized phase appears on

the TDXD plot, which is in agreement with the inflexion observed on the TG curve at

�250�C. The weight loss is associated with the decomposition of the [(R)-C5H14N2]2þ

cations into ammonium groups, and the departure of 1/2 sulfate. While not structurally

identified, such a compound is expected to have the global formula

CuSO4�1/2(NH4)2SO4. This phase is not stable and totally decomposes at 350�C into

CuSO4 (observed weight loss of 66.33%, calculated 65.74%), with behavior similar to

potassium yttrium squarate [40] and other templated copper sulfates.[5,13] Cu2OSO4

appears as a secondary phase between 550 and 600�C, with observed and calculated

weight losses of 72.32 and 73.29%, respectively.[43] CuO is observed by 650�C. Noconversion from 1 to 2 was observed in the TGA or TDXD experiments because this

process is too slow to be observed using these techniques.

10 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

The thermal decomposition of 2 differs only from 1 in the first stages corresponding to

the dehydration. Indeed, contrary to 1, compound 2 remains stable until �90�C, at whichpoint it loses six water molecules per formula unit. It is worth noting that the release of

the residual water is slow (120–190�C) and corresponds to an amorphous state, as shown

on the TDXD plot (Figure 6). Reaching the anhydrous phase [(R)-C5H14N2]2Cu(SO4)3 at

�190�C leads to its crystallization. Above, this temperature, the decomposition of the

amine groups and the departure of the sulfate anions go through the same process as

described for phase 1.

Figure 5. TGA curves for the decomposition: (a) of [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1)and (b) of [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2).

Phase Transitions 11

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

4. Conclusion

Two new organically templated copper sulfates, [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O

(1) and [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2), are reported. While crystals of compound

1 were formed slowly from an aqueous solution, the formation of 2 was accessible only

through a slow transformation of one. The results appear to resolve long-standing confu-

sion about the origins of this transformation and its impact on the crystalline architecture.

In fact, these compounds crystallize in noncentrosymmetric space groups, P21 and

P21212, respectively, owing to the presence of [(R)-C5H14N2]2þ. Thermal analysis stud-

ies, using TGA and TDXD, demonstrate similar decomposition routes for the two

compounds.

Figure 6. TDXD plots for the decomposition: (a) of [(R)-C5H14N2][Cu(SO4)2(H2O)4]�2H2O (1)and (b) of [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2).

12 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

Acknowledgments

Grateful thanks are expressed to Dr T. Roisnel (Centre de Diffractom�etrie X, Universit�e de RennesI) for assistance in single-crystal X-ray diffraction data collection.

Note on supplementary material

Crystallographic data (excluding structure factors) for the structures reported in this paper have alsobeen deposited with the Cambridge Crystallographic Data Center as supplementary publication no.CCDC 859886 and 859887.

References

[1] Kirpichnikova LF, Shuvalov LA, Ivanov NR, Prasolov BN, Andreyev EF. Ferroelectricity inthe dimethylaminaluminiumsulphate crystal. Ferroelectrics. 1989;96:313–317.

[2] Behera JN, Gopalkrishnan KV, Rao CNR. Synthesis, structure, and magnetic properties ofamine-templated open-framework nickel(II) sulfates. Inorg Chem. 2004;43:2636–2642.

[3] Yuan Y-P, Wang R-Y, Kong D-Y, Mao J-G, Clearfield A. [H2en]2{La2M(SO4)6(H2O)2} (M1=4 Co, Ni): First organically templated 3d–4f mixed metal sulfates. J Solid State Chem.2005;178:2030–2035.

[4] Rao CNR, Behera JN, Dan M. Organically-templated metal sulfates, selenites and selenates.Chem Soc Rev. 2006;35:375–387.

[5] Hajlaoui F, Yahyaoui S, Na€ıli H, Mhiri T, Bataille T. Synthesis, structural characterisation andthermal decomposition of a new organic–inorganic hybrid material (C5H14N2)[Cu(SO4)2(H2O)4]�H2O. Polyhedron. 2009;28:2113–2118.

[6] Hajlaoui F, Yahyaoui S, Na€ıli H, Mhiri T, Bataille T. Crystal structure, phase transition andthermal decomposition of a copper (II) sulfate dihydrate containing a chiral organic ammo-nium cation. Inorg Chim Acta. 2010;363:691–695.

[7] Yahyaoui S, Rekik W, Na€ıli H, Mhiri T, Bataille T. Synthesis, crystal structures, phase transi-tion characterization and thermal decomposition of a new dabcodiium hexaaquairon(II) bis(sulfate): C6H14N2)[Fe(H2O)6](SO4)2. J Solid State Chem. 2007;180:3560–3570.

[8] Sivashankar V, Siddheswaran R, Bharthasarathi T, Murugakoothan P. Growth and characteri-zation of new semiorganic nonlinear optical zinc guanidinium sulfate single crystal. J CrystGrowth. 2009;311:2709–2713.

[9] Bataille T, Louer DJ. New linear and layered amine-templated lanthanum sulfates. Solid StateChem. 2004;177:1235–1243.

[10] Zhao X, Chen Z, Zhao B, Shi W, Cheng P. Crystal structures and luminescent properties oftwo novel coordination polymers containing Ln3þ and SO4

2-. Inorg Chem Commun.2007;10:1433–1436.

[11] Behera JN, Rao CNR. Organically-templated zinc and thorium sulfates with chain and layeredstructures. Anorg Allg Chem. 2005;631:3030–3036.

[12] Doran MB, Norquist AJ, O’Hare D. Exploration of composition space in templated uraniumsulfates. Inorg Chem. 2003;42:6989–6995.

[13] Na€ıli H, Rekik W, Bataille T, Mhiri T. Crystal structure, phase transition and thermal behav-iour of dabcodiium hexaaquacopper(II) bis(sulfate), (C6H14N2)[Cu(H2O)6](SO4)2. Polyhe-dron. 2006;25:3543–3554.

[14] Rekik W, Na€ıli H, Bataille T, Mhiri T. Synthesis, crystal structure, phase transition and ther-mal behaviour of a new dabcodiium hexaaquanickel(II) bis(sulphate), (C6H14N2)[Ni(H2O)6](SO4)2. J Organomet Chem. 2006;691:4725–4732.

[15] Rekik W, Na€ıli H, Mhiri T, Bataille T. A new dabco templated metal sulfate, (C6H14N2)[Mn(H2O)6](SO4)2. Chemical preparation, hydrogen-bonded structure and thermal decomposition.J Chem Crystallogr. 2007;37:147–155.

[16] Fleck M, Bohaty L, Tillmanns E. Structural characterisation of MII guanidinium sulphatehydrates (MII ¼Mn, Fe, Co, Ni, Cd, VO). Solid State Sci. 2004;6:469–477.

[17] Wilson RE, Skanthakumar S, Knope KE, Cahill CL, Soderholm L. An open-framework tho-rium sulfate hydrate with 11.5 A

�voids. Inorg Chem. 2008;47:9321–9326.

[18] Cheetham AK, Ferey G, Loiseau T. Open-framework inorganic materials. Angew Chem IntEd Engl. 1999;38:3268–3292.

[19] Haushalter RC, Mundi LA. Reduced molybdenum phosphates: octahedral-tetrahedral frame-work solids with tunnels, cages, and micropores. Chem Mater. 1992;4:31–48.

Phase Transitions 13

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3

[20] Muller EA, Cannon RJ, Sarjeant AN, Ok KM, Halasyamani PS, Norquist AJ. Directed synthe-sis of noncentrosymmetric molybdates. Cryst Growth Des. 2005;5:1913–1917.

[21] Hagrman D, Hammond RP, Haushalter R, Zubieta J. Organic/inorganic composite materials:hydrothermal syntheses and structures of the one-, two-, and three-dimensional copper(II)sulfate�organodiamine phases [Cu(H2O)3(4,4’-bipyridine)(SO4)]�2H2O, [Cu(bpe)2][Cu(bpe)(H2O)2(SO4)2]�2H2O, and [Cu(bpe)(H2O)(SO4)] (bpe =trans-1,2-Bis(4-pyridyl)ethylene).Chem Mater. 1998;10:2091–2100.

[22] Chen C, Liu G. Recent advances in nonlinear optical and electro-optical materials. Annu RevMater Sci. 1986;16:203–243.

[23] Evans OR, Lin W. Crystal engineering of NLO materials based on metal�organic coordina-tion networks. Acc Chem Res. 2002;35:511–522.

[24] Halasyamani PS. Asymmetric cation coordination in oxide materials: influence of lone-pair cati-ons on the intra-octahedral distortion in d0 transition metals. Chem Mater. 2004;16:3586–3592.

[25] Veltman TR, Stover AK, Sarjeant AN, Ok KM, Halasyamani PS, Norquist AJ. Directed syn-thesis of noncentrosymmetric molybdates using composition space analysis. Inorg Chem.2006;45:5529–5537.

[26] Lii K, Chen, C-Y. Synthesis and characterization of (R-C5H14N2)2[Ga4(C2O4)(H2PO4)2(PO4)4]�2H2O, a layered gallium phosphatooxalate containing a chiral amine. InorgChem. 2000;39:3374–3378.

[27] De Meulenaer J, Tompa H. The absorption correction in crystal structure analysis. Acta Crys-tallogr. 1965;19:1014–1018.

[28] Farrugia LJ. WinGX suite for small-molecule single-crystal crystallography. J Appl Crystal-logr. 1999;32:837–838.

[29] Sheldrick GM. SHELX-97, Programs for crystal structure solution. G€ottingen: University ofG€ottingen; 1997.

[30] Altomare A, Cascarano G, Giacovazzo C, Guagliardi A. Completion and refinement of crystalstructures with SIR92. J Appl Crystallogr. 1993;26:343–350.

[31] Rekik W, Naili H, Mhiri T, Bataille T. [NH3(CH2)2NH3][Co(SO4)2(H2O)4]: chemical prepara-tion, crystal structure, thermal decomposition and magnetic properties. Mat Res Bul.2008;43:2709–2718.

[32] Glowiak T, Podgorska I. X-ray, spectroscopic and magnetic studies of hexaaquacopper(II) di(diphenylphosphate) diglycine. Inorg Chim Acta. 1986;125:83–88.

[33] Blackburn AC, Gallucci JC, Gerkin RE. Structure of hexaaquacopper(II) bromate. Acta Cryst.1991;C47:2019–2023.

[34] Hajlaoui F, Yahyaoui S, Na€ıli H, Mhiri T, Bataille T. Synthesis and crystal structures of a newnon-centrosymmetric hybrid materials intercalating a chiral organic group. J Struc Chem.2012;53:359–365.

[35] Hajlaoui F, Na€ıli H, Yahyaoui S, Turnbull Mark M, Mhiri T, Bataille T. Synthesis, characteri-zation and magnetic properties of four new organically templated metal sulfates [C5H14N2][MII(H2O)6](SO4)2, (M

II = Mn, Fe, Co, Ni). J Dalton Trans. 2011;40:11613–11620.[36] Brown ID. VALENCE: a program for calculating bond valences. J Appl Crystallogr.

1996;29:479–480.[37] Choyke SJ, Blau SM, Larner AA, Narducci SA, Yeon J, Halasyamani PS, Norquist AJ. Noncen-

trosymmetry in new templated gallium fluorophosphates. Inorg Chem. 2009;48:11277–11282.[38] Hajlaoui F, Na€ıli H, Yahyaoui S, Norquist AJ, Mhiri T, Bataille T. Synthesis, crystal structures

and thermal behaviour of organic–inorganic hybrids incorporating a chiral diamine. J Organo-met Chem. 2012;700:110–116.

[39] Spek AL. Single-crystal structure validation with the program PLATON. J Appl Crystallogr.2003;36:7–13.

[40] Mahe N, Bataille T. Synthesis, crystal structure from single-crystal and powder X-ray diffrac-tion data, and thermal behavior of mixed potassium lanthanide squarates: thermal transforma-tions of layered [Ln(H2O)6]K(H2C4O4)(C4O4)2 into pillared LnK(C4O4)2 (Ln ¼ Y, La, Gd,Er). Inorg Chem. 2004;43:8379–8386.

[41] Nonius. Kappa CCD program software. Delft: Nonius BV; 1998.[42] Otwinowski Z, Minor W, Carter CW, Sweet RM. Methods in enzymology, 276. New York:

Academic Press; 1997, p. 307.[43] Faber J, Fawcett T. The Powder Diffraction File: present and future. Acta Cryst. 2002;

B58:325–332.

14 S. Sa€ıd et al.

Dow

nloa

ded

by [

Said

Sal

em]

at 0

3:13

06

June

201

3