Commensurate super-structure of the {Cu(NO3)(H2O)}(HTae)(Bpy) coordination

polymer. An example of 2D hydrogen bonding networks as magnetic exchange

pathway.

Inorganic Chemistry

Roberto Fernández de Luis,*,a Edurne S. Larrea

b Joseba Orive,

d Luis Lezama,

a,c María

I. Arriortua.*,a,b

aBCMaterials (Basque Center for Materials, Applications &

Nanostructures),Technological Park of Zamudio, Camino de Ibaizabal, Bndg. 500-1st,

48160, Derio, Spain.

bDepartamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología,

c

Departamento de Química Inorgánica, Universidad del País Vasco, UPV/EHU. 48940,

Leioa, Spain.

dDepartamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y

Matemáticas (FCFM), Universidad de Chile. Av. Beauchef 851, Santiago 8370448,

Chile.

roberto.fernandez@bcmaterials.net, edurne.serrano@ehu.eus, joseba.orive@ing.uchile.cl, luis.lezama@ehu.eus, maribel.arriortua@ehu.eus

Crystal structure refinement:

An initial analysis of the reciprocal space revealed the average orthorhombic unit cell with lattice parameters a=23.2967(6) Å, b=13.0779(3) Å and c= 6.92670(10) Å. However a careful study of the less intense reflections showed the existence of a commensurate five fold structure along the c* reciprocal axis, giving rise to the orthorhombic super-cell a= 23.282(1) Å, b= 13.0700(7) Å and c= 34.631(2) Å. Data reductions were carried out both with the average cell (avoiding the information of the commensurate satellite reflections) and super-cell. The average crystal structure was solved in the Pnna (52) orthorhombic space group. One copper atom, and the oxygen, nitrogen and carbon atoms belonging to the Bpy and HTae organic ligands were located. A nitrate group, disordered in two different positions was located in successive refining cycles. Taking into account the charge neutrality principle, the sum of the occupation factors of the two disordered nitrate molecules was restricted to 0.25. Both were refined with isotropic thermal displacements and the N-O and O-O bond distances were restricted to 1.25(1) Å and 2.15(1) Å in order to maintain the geometry of the nitrate groups. As will be described in more detail in the Result and Discussion section, the copper cations are equatorially coordinated by two oxygen and two nitrogen atoms belonging to one HTae and two Bpy molecules, respectively. The disordered nitrate groups, and concretely the O1A and O1B oxygen atoms are located in the apical positions of an elongated copper octahedral coordination environment, in good agreement with the Jahn Teller effect observed for Cu(II) cations. Afterwards, the analysis of the thermal displacements of the oxygen atoms within the nitrate groups revealed that the thermal displacement for the O1A and O1B atoms is considerably lower than the values found for the O2A/O2B and O3A/O3B atoms. In a first approach, this difference was explained because of the O1A/O1B oxygen atoms are bonded to the copper cations. However, after the study of the super-structure, it was found that there is a site occupancy disorder of nitrate groups and coordinated water molecules in the apical position of the copper octahedra. In fact, the oxygen atoms of the coordinated water molecules lie approximately on the same position that the O1A and O1B atoms belonging to the nitrate groups. Finally, the occupation factors of the O1A and O1B atoms were fixed to 0.5, 0.25 associated to the nitrate groups, and the other 0.25 to the oxygen atoms of the coordinated water molecules. The H1A proton located at 4d special position, and belonging to the HTae ligand, was found in the difference Fourier Map and refined isotropically. The nitrogen and oxygen atoms of the disordered nitrate groups (O1A/O1B, O2A/O2B, O3A/O3B, N1A/N1B) were refined with common isotropic thermal parameters. The hydrogen atoms of the coordinated water molecules were not located in the Fourier density map. In a second stage and after the study of the reciprocal space (see Results and Discussion section for more detailed information), the crystallographic cell for the super-structure was indexed. There is a five fold commensurate modulation of the “c” parameter. Space groups compatible with the super-cell were checked using the Subgroups tool of the Bilbao Crystallographic Server [1] (Scheme S1). Among the suggested space groups, eight of them fulfill the observed commensurate modulation, Pnna, Pnn2, P21/c, P2/c, P21, P2, P-1 and P1. The crystal structures solved in the orthorhombic Pnna and Pnn2 space groups give rise to symmetry-imposed disorders of the nitrate and water coordination molecules, [2] in addition to non-positive definite anisotropic thermal displacements observed even for the copper cations. For the P21/c space group, the real coordination environment of five

crystallographically independent copper cations was clearly observed after solving and refining the crystal structure. The symmetry imposed disorders are overcome and the real long range order of the framework was revealed. Finally, the P21/c structure was transformed to the non-standard P21/n space group in order to have a direct relationship between the “c” parameter of the average crystal structure and the five fold “c” parameter of the super-structure. Due to the strong pseudo-symmetry of the super-structure with the orthorhombic Pnna space group, and the weak data of the reflections related with the super-structure, there are several problems with the anisotropic thermal displacements of carbon, oxygen and nitrogen atoms. [3] In fact, equal anisotropic thermal displacement parameters have been used for each of the crystallographically independent moieties being Bpy, HTae, nitrate and coordination water molecules. Both for the average and super-structure the protons belonging to the HTae ligand were found in the difference Fourier Map and refined with common isotropic thermal parameters (UIso(H)= 0.03 Å2). [4] Anisotropic thermal parameters were used for all atoms, except for the hydrogen ones belonging to the organic molecule, which were fixed geometrically, allowing them to ride on their parent carbon atoms (C-H 0.93 Å; UIso(H)= 1.2Ueq(C) Å2) for the hydrogen atoms belonging to the pyridyl groups of the Bpy and (C-H 0.96 Å; UIso(H)= 1.2Ueq(C) Å2) for the methyl groups of the HTae ligand. The hydrogen atoms for the coordinated water molecules were not located in the Fourier density map. The simplifications of the crystal structures, hydrogen bonding analyses and topological studies were carried out with TOPOS Pro [5] and PLATON [6] software.

Scheme S1 (a).- Graph of subgroups (a single representative of the conjugacy class) connecting the space group Pnna (#52) and space groups with point group 2 with wave

vector(s): (0,0,2/5). (b).- Transformation matrixes of the group-subgroup transformations between the average space group (Pnna (#52)) and the possible super-space groups. The plausible group-subgroup paths with a superstructure containing a

five fold c parameter have been highlighted.

(a)

(b)

Table S1.- Hydrogen bond distances (Å) and angles (º) for the average structure. Average structure

Donor-H Acceptor D-H (Å) H···A (Å) D···A (Å) D-H···A (º) O2 - H1A O2ii 1.228(8) 1.228(8) 2.449(5) 172(6) C1 - H1 O1Aiii 0.93 2.44 3.310(8) 157 C1 - H1 O1Biii 0.93 2.45 3.224(8) 141 C5 - H5 O1Bii 0.93 2.23 2.806(8) 120 C8 - H8C O1i 0.96 2.57 3.477(6) 157

Symmetry codes: (i)= ½-x, -y, z; (ii)= x, ½-y, ½-z; (iii)= x, ½-y, -½-z.

Table S2.- Hydrogen bond distances (Å) and angles (º) for the super-structure. Super-Structure

Donor-H Acceptor D-H (Å) H···A (Å) D···A (Å) D-H···A(º) O3- H1A O4 1.23(5) 1.23(5) 2.451(8) 176(9) O7 - H2A O8 1.09(7) 1.38(7) 2.457(8) 168(8) O11 – H3A O12 1.22(5) 1.22(5) 2.441(8) 173(7) O15 – H4A O16 1.31(7) 1.20(7) 2.489(8) 165(5) O19 – H5A O20 1.38(7) 1.11(8) 2.461(8) 161(8) C1 – H1 O1Ai 0.93 2.40 3.188(12) 142 C6 – H6 O9Aii 0.93 2.48 3.238(14) 138 C100 – H10A O14A 0.96 2.54 3.363(12) 144 C11 – H11 Ow2i 0.93 2.50 3.384(9) 160 C15 – H15 O6A 0.93 2.50 2.992(10) 120 C16 – H16 Ow4ii 0.93 2.49 3.374(9) 159 C20 – H20 O1A 0.93 2.42 2.968(10) 118 C21 – H21 Ow1v 0.93 2.48 3.333(9) 151 C26 – H26 O9A 0.93 2.35 3.041(12) 130 C30 - H30 O12Aii 0.93 2.39 3.211(10) 147 C31 – H31 O6Av 0.93 2.44 3.206(9) 140 C36 – H36 O13Aviii 0.93 2.47 3.229(10) 138 C41 – H41 Ow3v 0.93 2.45 3.345(9) 160 C45 – H45 O13A 0.93 2.44 3.027(11) 122 C46 – H46 O12A 0.93 2.44 2.972(12) 117 C50 – H50 Ow5viii 0.93 2.52 3.376(9) 154 C55- H55B O17iii 0.96 2.51 3.297(12) 148 C55- H55C O8Aii 0.96 2.54 3.363(9) 135 C66 – H66A O5A 0.96 2.49 3.290(10) 141 C70 – H70A O2A 0.96 2.47 3.274(10) 141 C71 – H71B O10iv 0.96 2.51 3.440(9) 161 C75 – H75C O11Aii 0.96 2.57 3.325(12) 135 C76 – H76A O8A 0.96 2.54 3.362(12) 145 C81- H81C O6vii 0.96 2.60 3.417(9) 143 C85 – H85C O5vi 0.96 2.56 3.390(9) 146 C95 – H95B O1ix 0.96 2.56 3.511(9) 169 C96 – H96A O11A 0.96 2.50 3.312(12) 144 Symmetry codes:

(i)= -x, -1-y, -z,

(ii)=x, -1+y, z,

(iii)=1/2+-x, -3/2+y, 1/2-z,

(iv)= 1/2-x, -1/2+y, 1/2-z,

(v)= x, 1+y, z,

(vi)= -1/2-x, 3/2+y, 1/2-z,

(vii)= -1/2-x, 1/2+y, 1/2-z,

(viii)= -x, 2-y, 1-z,

(ix)= 1/2-x, 5/2+y, 1/2-z.

Powder X-ray diffraction

Two Rietveld refinements of the powder patterns were carried out; the first one with the average orthorhombic structural model, and the second one with the super-structural monoclinic model. Due to the large volumes of the unit cells, and to the high number of crystallographic independent atoms in the asymmetric units, the structural variables were not refined.

The final full 2θ(º) and a detailed 2θ(º) range of the fits for both Rietveld refinements are shown in Fig. S1. Although the agreement factors for both refinements are very similar, there are several weak satellite reflections (asterisks in Fig. S1)) that are not modeled if the average structural model is used.

The Rietveld refinement with the super-structural model not only takes into account the satellite reflections, but also models better the intensities of some average reflections. Despite the fact that the super-structural model has been obtained by single-crystal X-ray diffraction at 100K, and the powder pattern has been recorded at room temperature, the fit is good enough to assure that there are not impurities in the sample.

Fig. S1. Final 2θ full range fit and detail of 5º-25º 2θ range after the Rietveld refinement with the average structural model ((a.1) and (a.2)) and super-structural model ((b.1) and

(b.2)).

Figure S2.- (a) Shape map for geometrical distortions of the octahedron and the

trigonal prism. (b) Enlargement of the data region for the copper coordination spheres of the super-structure, located within the red square.

Continuous shape measures of the metal coordination environments were carried out with Shape v2.1 program. [7] The values obtained for the copper(II) environments in the super-structure are, as expected, very near to the ideal octahedral geometry, with values for S(Oh) and S(D3h) near 16 and 2, respectively. (Fig. S2 (a)). The distortion of the five crystallographic independent copper cations follows approximately a linear tendency depending on their coordination species, from the Cu(1) and Cu(4) atoms with two water molecules completing their coordination environment, the Cu(3) with a mixed coordination sphere including one nitrate group and one water molecule to the Cu(2) and Cu(5) cations, which are axially bonded to two nitrate groups (Fig. S2 (b)). [8]

Figure S3.- Thermogravimetry and DSC curves.

Figure S4.- Thermodiffractometry.

Figure S5.- Simplification of the Cu-Bpy metal organic chains, and the effect of their thermal elongation in the cell parameters.

Figure S6.- Thermal evolution of the cell parameters (a-c) and cell volume (d) including the low temperature (-173ºC) single crystal X-ray diffraction data.

(a) (b)

(c) (d)

Figure S7.- IR spectra for CuHTaeBpy_RT (blue line) and CuHTaeBpy_HT (red line).

Figure S8.- UV-Vis spectra for CuHTaeBpy_RT (blue line) and CuHTaeBpy_HT (red line).

Figure S9.- EPR X-band spectra for CuHTaeBpy_RT (red line) and CuHTaeBpy_HT (blue line).

Figure S10.- The best χmT product fit assuming an Ising Chain S=1/2 model for

(a.1) CuHTeBpy_RT and (b.1) CuHTeBpy_HT and 2D Heisenberg AF model for (a.1) CuHTeBpy_RT and (a.2) CuHTeBpy_HT (b.2).

Ising Chain S=½ model:

kTJekT

SSNg

/2

22

33

)1(

−+

+µ

AF Heisenberg 2D model:

6)/(003797.0

5)/(4833.0

4)/(250.0

3)/(333.1

2)/(2/21

2093844.0

TJkTJkTJkTJkTJkTJk

g

++++++

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