Self-assembly of the hexabromorhenate(IV) anion with protonated benzotriazoles: X-ray structure and magnetic propertiesJosé Martínez-Lillo,*a John Kong,a Miguel Julveb and Euan K. Brechin*a

aEaStCHEM School of Chemistry, The University of Edinburgh, West Mains Road, EH9 3JJ Edinburgh, Scotland, UK. bInstituto de Ciencia Molecular (ICMol), Universitat de València, C/ Catedrático José Beltrán 2, 46980, Paterna, Valencia, Spain. ABSTRACT: Two novel ReIV compounds of formulae [HBTA]2[ReIVBr6] (1) and [HMEBTA]2[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotriazole] have been synthesised and mag-neto-structurally characterised. 1 and 2 crystallize in the triclinic system with space group Pī. In both compounds, the rhenium ion is six-coordinate, bonded to six bromo ions in a regular octahedral geo-metry. Short ReIV−Br···Br−ReIV contacts, - stacking and H-bonding interactions occur in the crystal lat-tice of both 1 and 2, generating novel supramolecular structures based on Re IV ion. The different disposi-tions of the cations and the intermolecular Br···Br contacts in 1 and 2 play an important structure-prop-erty role, with the magnetic properties of 1 and 2 revealing a significant antiferromagnetic coupling between ReIV ions through intermolecular Br···Br interactions. In 1, these interactions account for a max-imum in the magnetic susceptibility at ca. 10 K.

Benzotriazole and its derivatives constitute a family of versatile heterocyclic compounds with properties which make them very useful in a wide variety of different research fields.1-3 For example, they are very effective corrosion inhibitors for copper and its alloys,1,2 are used in antifreezing agents in heating and cooling systems, hydraulic fluids and also exhibit important applications in the pharmaceutical industry.2,3

Benzotriazole can behave either as an weak acid or a Brønsted base (Chart 1). When it acts as a cation, it can afford aesthetically pleasing, structurally interesting networks which are gener-ally stabilized by means of hydrogen bonds and type interactions.4

The hexahalo anions of ReIV (a 5d3 ion) have been investigated for decades, mainly due to their fascinating magnetic properties.5 Significant antiferromagnetic interactions between the para-magnetic and highly anisotropic ReIV metal ions occur in hexahalorhenate(IV) salts of univalent cations, [ReIVX6]2− (X = Cl, Br and I).5-7 It is well-known that such magnetic interactions are trans-mitted by means of weak Re–X···X–Re intermolec-ular contacts in the crystal lattice.7,8 Given that the intermolecular halogen···halogen distance de-pends on the countercation size, bulky cations such as tetraphenylarsonium (AsPh4)+ and tetra-n-butylammonium (NBu4)+ can preclude magnetic coupling between adjacent paramagnetic anions of ReIV due to large X···X separation.8

The use of more suitable cations can provide new insights into the properties of this type of materi-als.9-13

Chart 1. The molecular structures of: (A) 1H-benzotriazole (BTA) and (B) 1-(methoxymethyl)-1H-benzotriazole (MEBTA).

The most studied [ReIVX6]2− salts to date have been those obtained with the hexachlororhenate(IV) salts, some of which ex-hibit spin canting and ferromagnetic behaviour.12

A search of the literature and Cambridge Struc-tural Database (CSD) reveals that the magnetic properties of 32% of the 65 compounds based on hexahalo anions of ReIV published to date have been investigated. From them, only three re-ported works deal with magneto-structural stud-ies on the [ReIVBr6]2- anion.13

Herein we report the synthesis and magneto-structural characterisation of two novel Re(IV) compounds of formulae [HBTA]2[ReIVBr6] (1) and

[HMEBTA]2[ReIVBr6] (2) {BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotria-zole} which represent the first magneto-struc-tural study based on protonated benzotriazoles.

Results and Discussion

Synthesis. Compounds 1 and 2 were synthe-sised from potassium hexabromorhenate(IV) in a 0.5 M HBr solution, in the presence of protonated 1H-benzotriazole (BTA) and 1-(methoxymethyl)-1H-benzotriazole (MEBTA), respectively. While crystals of 1 are obtained in two weeks after slow evaporation at room temperature, those of 2 grow in a few hours by standing in the fridge (at 3 °C). It is worth noting that 1 can also be prepared starting from 1-(hydroxymethyl)-1H-benzotria-zole, given that in these reaction conditions it un-dergoes dissociation of the -CH2OH group. This fact has been previously observed and reported under basic reaction conditions.14

Structure Description of 1 and 2. Both 1 and 2 crystallise in the triclinic crystal system with space group Pī (Table 1). Their structures are made up of the hexabromorhenate(IV) anion (1 and 2) [ReBr6]2-, and [HBTA]+ (1) and [HMEBTA]+

(2) cations which are self-assembled through an extended network of hydrogen bonds, Br···Br and ···Br type intermolecular interactions. Three bromo ions are present in the asymmetric unit of 1 and 2, together with a rhenium ion located on an inversion centre and a protonated organic cation (Figs. 1 and 2).

Figure 1. ORTEP drawing of the molecular structure of the [HBTA]+ cations and the [ReBr6]2- anion of 1.

Thermal ellipsoids are depicted at the 50 % probabil-ity level [Symmetry code: (a) = 1-x,-y,-z].

Each Re(IV) ion in 1 and 2 is six-coordinate and bonded to six bromo ions in a regular octahedral geometry. The values of two Re–Br bond lengths [Re–Br(2) and Re–Br(2a), 2.536(1) in 1 and 2.515(1) Å in 2] are somewhat longer than those of the other four [average value of 2.505(1) in 1 and 2.506(1) Å in 2], in agreement with those of all previously reported compounds based on the anionic [ReBr6]2- unit.

Figure 2. ORTEP drawing of the molecular structure of the [HMEBTA]+ cations and the [ReBr6]2- anion of 2. Thermal ellipsoids are depicted at the 50 % prob-ability level [Symmetry code: (a) = 1-x,1-y,1-z].

Table 1. Summary of the Crystal Data for Compounds 1 and 2

Compound 1 2Formula C12H12N6Br6Re C16H20N6O2Br6ReMr 905.94 994.04Crystal system triclinic triclinicSpace group Pī Pīa/Å 7.355(1) 8.191(1)

b/Å 8.085(1) 8.845(1)

c/Å 8.635(1) 9.757(1)

/° 86.99(1) 69.85(1)/° 77.63(1) 71.27(1)/° 84.01(1) 82.04(1)V / Å3 498.6(1) 628.1(1)Z 1 1Dc/g cm-3 3.017 2.628(Mo-K)/mm-1 18.124 14.404

2

F(000) 411 459Goodness-of-fit on F2

1.027 1.064

R1 [I > 2(I)] 0.0217 0.0229

wR1 [I > 2(I)] 0.0455 0.0500

max, min/e.Å-3 1.106 and -0.996 1.012 and -1.601

Figure 3. View of the one-dimensional arrangement of [HBTA]+ cations and [ReBr6]2- anions in the crystal of 1 mediated through Br···Br contacts (dashed red lines). Color code: pink, Re; olive green, Br; blue, N; grey, C; black, H.

The benzotriazoles cations exhibit protonation on the N(3) atom and are planar with average C–C, N–N and C–N bond length values in agreement with those found in the salt [HBTA][HSO4].4e 2 is the first reported example of a complex contain-ing the protonated 1-(methoxymethyl)-1H-benzo-triazole cation, precluding any further structural comparisons.

Figure 4. Perspective view of the two-dimensional arrangement of [ReBr6]2- anions and organic cations of 1 through N-H···Br intermolecular interactions (dashed lines). Color code: pink, Re; olive green, Br; blue, N; grey, C; black, H.

In the crystal of 1, the shortest Br···Br contact of 3.665(1) Å [Br(1)···Br(1a), (a) = 1-x, -y, -1-z] di-rects chains of [ReBr6]2- anions which grow along the crystallographic c axis (Figure 3). Adjacent an-ionic chains are interlinked through hydrogen bonds involving bromo ions and the –NH groups of neighbouring [HBTA]+ cations (Table 2), to-gether with additional Br···Br contacts of 4.032(1) Å [Br(2)···Br(2b), (b) = 2-x, -y, -z], resulting in a corrugated layered structure which grows in the ac plane (Fig. 4). ···Br and ··· type interactions [···Br distances of approximately 3.46 Å, with the shortest intercentroids distance being ca. 3.63 Å] contribute to stabilizing the crystal structure in 1 (Fig. S1). A three-dimensional supramolecular framework can be described by taking into ac-count interlayer Br···Br contacts of 3.822(1) Å [Br(3)···Br(3c), (c) = 1-x, 1-y, -z] (Figure 5).Table 2. Hydrogen-bonding Interactions in 1a

D-H···A D-H/Å H···A/Å D···A/Å (DHA)/°3

N(1)-H(1)···N(2a) 0.860 2.52(1) 2.955(1) 112.3(1)

N(1)-H(1)···Br(2b) 0.860 2.60(1) 3.418(1) 158.5(1)

N(3)-H(3)···Br(2) 0.860 2.80(1) 3.418(1) 130.3(1)

N(3)-H(3)···Br(3c) 0.860 2.81(1) 3.379(1) 124.9(1)

N(3)-H(3)···Br(2c) 0.860 3.06(1) 3.568(1) 119.6(1)

aSymmetry codes: (a) = -x+2, -y, -z+1; (b) = x, y, z+1; (c) = -x+2, -y, -z.

Figure 5. View of a fragment of the 3D crystal pack-ing of 1 showing two adjacent layers connected by Br···Br contacts (dashed red lines). Color code: pink, Re; olive green, Br; blue, N; grey, C; black, H.

4

Figure 6. View of the one-dimensional arrangement of [HMEBTA]+ cations and [ReBr6]2- anions in the crystal of 2 mediated through Br···Br contacts [Br(1)···Br(1a), (a) = -x, 1-y, -1-z] (dashed red lines) and N-H···Br interac-tions [N(3)-H(3)···Br(1b), (b) = 1-x, 1-y, 1-z] (dashed green lines). Color code: pink, Re; olive green, Br; blue, N; grey, C; black, H.

In the crystal of 2, the nearest Br···Br contact of 3.345(1) Å [Br(1)···Br(1a), (a) = -x, 1-y, -1-z] gen-erates chains of [ReBr6]2- anions which grow along the crystallographic a axis (Figure 6). These chains are reasonably well-separated from each other by the intercalated [HMEBTA]+ cations.

Figure 7. Perspective view of the two-dimensional arrangement of [ReBr6]2- anions and organic cations of 2 through short Br···Br intermolecular interactions (dashed red lines). Color code: pink, Re; olive green, Br; blue, N; grey, C; black, H.

The additional Br···Br contacts of 4.421(1) Å [Br(2)···Br(2b), (b) = 1-x, 2-y, 1-z] in 2 results in a layered structure that can be observed in the ab plane (Fig. 7). N-H···Br H-bonds (the N···Br distance being ca. 3.26 Å) (Fig. 6) and ··· parallel-dis-placed stacking interactions between neighbour-

ing [HMEBTA]+ molecules (intercentroid distances of ca. 3.91 Å) also contribute to stabilizing the crystal structure in 2 (Fig. S1).

Magnetic properties of 1 and 2

Dc magnetic susceptibility measurements were carried out on microcrystalline samples of 1 and 2 in the 300–4 K temperature range, under an ex-ternal magnetic field of 0.1 T. The MT vs. T plots of 1 and 2 are given in Figs. 8 and 9, respectively. At room temperature the MT values are 1.57 (1) and 1.56 cm3 mol-1 K (2), which are as expected for a magnetically isolated ReIV (SRe = 3/2) mononuclear complex with g = 1.8–1.9.6-9 Upon cooling, the values of MT decrease, at first slowly, and then more abruptly with decreasing the tem-perature, reaching final values of 0.12 (1) and 0.63 (2) cm3 mol-1 K at 4.0 K (Figs. 8 and 9). The decrease of the MT values observed for 1 and 2 are likely due to the presence of intermolecular interactions and zero-field splitting (zfs) effects.6-9

A maximum of the magnetic susceptibility occurs at ca. 10 K in the M vs. T plot for 1 (inset Fig. 8), characteristic of an antiferromagnetically coupled system. No maximum of the susceptibility is ob-served in 2 (inset Fig. 9).

H= D [ ( SZ )2− S ( S+1) /3 ] + g // βHZ SZ +g¿ β (HX S X+HY SY ) (1 )

5

χM=χ //+2 χ ¿

3(2)

where

χ //=Nβ2g//

2

4k (T−θ )1+9 exp (−2D /kT )1+exp (−2D /kT )

χ¿=Nβ2 g¿

2

k (T−θ )1+(3kT /4D ) [1−exp(−2D /kT )]1+exp (−2D /kT )

A detailed inspection of the crystal packing of both compounds reveals that short Br···Br con-tacts between the paramagnetic [ReBr6]2- anions generate chains that further develop into sheets. Taking these facts into consideration, we have used the Hamiltonian of eq(1) and its derived the-oretical expression for the magnetic susceptibility (eq. 2),15 including a θ term to account for the in-termolecular interactions, in order to analyse the magnetic behaviour of 1 and 2.

Figure 8. Plot of the MT product vs. T for 1. The solid red line represents the best-fit of the experi-mental data (see text). The inset shows the temper-ature dependence of the magnetic susceptibility (M vs. T).

Best least-squares fits of the experimental data in the 4-300 K temperature range afforded the pa-rameters: |D| = 6.4 cm-1, g = 1.87 and θ = 4.8 K with R = 4.1 x 10-5 for 1, and |D| = 5.9 cm-1, g = 1.80 and θ = 1.4 K with R = 1.9 x 10-5 for 2 {R being the agreement factor defined as i[(MT)iobs (MT)icalc]2 / [(MT)iobs]2}.

Figure 9. Plot of the MT product vs. T for 2. The solid red line represents the best-fit of the experi-mental data (see text). The inset shows the temper-ature dependence of the magnetic susceptibility (M vs. T).

The theoretical curves (red solid lines in Figs. 8 and 9) match the experimental data well in the whole temperature range, the g and D values cal-culated for 1 and 2 are in agreement with those previously reported for compounds based on the [ReBr6]2- anion.13 The negative θ values obtained from the fit imply the occurrence of significant an-tiferromagnetic exchange through Re-Br···Br-Re in-termolecular interactions, θ being larger in com-pound 1 due to the different spatial arrangement of the organic cations in the crystal; in both com-pounds a 1D motif is observed, but these chains are more separated in 2.The additional Br···Br interaction which propa-gates the layered structure is shorter in 1 [ca. 4.03 Å (1) versus ca. 4.42 (2)], and there is a third Br···Br contact (ca. 3.82 Å) leading to a three-dimensional framework in 1, but not in 2. These results suggest that it is not simply the shortest intermolecular contacts that are impor-tant in determing the magnetic behaviour of these materials (the shortest Br···Br separation (ca. 3.35 Å) occurs in 2), but that the number of halogen interactions is also relevant. Here the lat-ter appears to dominate, resulting in a larger θ value and the observation of a maximum in the magnetic susceptibility.

Conclusions

In summary, the crystal structures and magnetic properties of two novel ReIV compounds of formu-lae [HBTA]2[ReIVBr6] (1) and [HMEBTA]2[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotriazole] have been studied. Weak intermolecular interactions such as

6

Re−Br···Br−Re contacts, - stacking and H-bond-ing interactions occur in the crystal lattice of both 1 and 2, which self-assemble novel supramolecu-lar structures based on [ReBr6]2- anions and proto-nated benzotriazoles. Both the different disposi-tions of the organic cations and the total number of intermolecular Br···Br contacts in 1 and 2 play a crucial role in determining the structure-property relationship.

Experimental Section

Materials and Physical Measurements

All manipulations were performed under aerobic conditions, using materials as received (reagent grade). Potassium hexabromorhenate(IV), K2ReBr6, was prepared following the synthetic method described in the literature.16

Elemental analyses (C, H, N) were performed by MEDAC Ltd. Infrared spectra of 1 and 2 were recorded with a PerkinElmer Spectrum 65 FT-IR (ATR device) spectrometer in the 4000-500 cm-1

region. Variable-temperature, solid-state direct current (dc) magnetic susceptibility data down to 4.0 K were collected on a Quantum Design MPMS-XL SQUID magnetometer equipped with a 7 T dc magnet. Diamagnetic corrections were applied to the observed paramagnetic susceptibilities using Pascal’s constants.17,18

Preparation of the Compounds 1 and 21. K2ReBr6 (0.10 mmol, 74.0 mg) and 1H-benzotri-azole (0.15 mmol, 18.0 mg) were dissolved in HBr (0.5 M, 15.0 mL). The solution was heated at 90 °C by stirring for 20 minutes. The resulting yellow solution was filtered while hot and left to evapo-rate at room temperature. Red-orangish crystals of 1 were grown in 2 weeks, which were suitable for X-ray diffraction studies. Yield: 31 %. We ob-served that 1 is also obtained when we used 1H-benzotriazole-1-methanol instead of 1H-benzotri-azole. Anal. Cald. (found) for C12H12N6Br6Re (1): C, 15.9 (16.1); H, 1.3 (1.4); N, 9.3 (9.3) %. IR peaks (ATR/cm-1): 3175(w), 2981(s), 2972(s), 2922(s), 2886(m), 2844(m), 1612(w), 1470(w), 1454(w), 1370(m), 1258(w), 1248(w), 1159(m), 1054(vs), 1033(vs), 1003(s), 981(m), 897(w), 760(m), 661(m), 637(w).2. K2ReBr6 (0.10 mmol, 74.0 mg) and 1-(methoxymethyl)-1H-benzotriazole (0.15 mmol, 24.5 mg) were dissolved in HBr (0.5 M, 5.0 mL). The obtained yellow solution was stirred for 20 minutes and a yellow precipitate of 2 was formed. The precipitate was filtered and the yellow filtrate left standing in the fridge (at 3 °C). In a few hours X-ray quality crystals of 2 were formed. Yield: 60 %. Anal. Cald. (found) for C16H20O2N6Br6Re (2): C, 19.3 (19.5); H, 2.0 (1.9); N, 8.5 (8.3) %. IR peaks

(ATR/cm-1): 3132(w), 3075(m), 3057(m), 3023(m), 3000(m), 2932(m), 2844(m), 1605(m), 1457(s), 1363(m), 1323(s), 1255(m), 1219(m), 1193(s), 1156(s), 1109(vs), 1095(vs), 1039(s), 911(s), 780(s), 752(vs), 730(vs), 657(m), 612(s).

X-ray data collection and structure refine-ment

X-ray diffraction data on single crystals of dimen-sions 0.34 x 0.20 x 0.12 (1) and 0.25 x 0.18 x 0.14 mm3 (2) were collected on a Bruker-Nonius X8APEXII CCD area detector diffractometer with graphite-monochromated Mo-K radiation (λ = 0.71073 Å). Crystal parameters and refinement results for 1 and 2 are summarized in Table 1. The structures of 1 and 2 were solved by direct methods and subsequently completed by Fourier recycling using SHELXTL.19,20 The final full-matrix least-squares refinements on F2, minimising the function w(Fo-Fc)2, reached convergence with the values of the discrepancy indices given in Ta-ble 1. The graphical manipulations were per-formed with the DIAMOND21 program. CCDC 1011545 (1) and 1011546 (2). See http://www.rsc.org/suppdataxxx for crystallographic data in CIF or other electronic format.

ASSOCIATED CONTENT Supporting Information. X-ray crystallographic data in CIF format for compounds 1 and 2. Figure S1. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATIONCorresponding Author*(E.K.B.) E-mail: ebrechin@staffmail.ed.ac.uk. Tel: +44 (0)131 650 7545.*(J.M.-L.) E-mail: lillo@uv.es.

NotesThe authors declare no competing financial interest.

ACKNOWLEDGMENT Financial support from the European Union (Marie Curie Project No. 272659) is gratefully acknowl-edged. JML is indebted to the European Union for a postdoctoral Marie Curie Intra-European Fellowship. EKB thanks the EPSRC. The authors thank Dr. Gary Nichol for single-crystal X-ray diffraction measure-ments.

REFERENCES1 (a) Dugdale, I.; Cotton, J. B. Corros. Sci., 1963,

3, 69. (b) Finšgar, M.; Milošev, I. Corros. Sci., 2010, 52, 2737.

2 Sease, C. Stud. Conserv., 1978, 23, 76.3 Kale, R. R.; Prasad, V.; Mohapatra, P. P.; Tiwari,

V. K. Monatsh. Chem. 2010, 141, 1159.

7

4 (a) Giordano, F. Acta Cryst. 1980, B36, 2458. (b) Sotofte, I.; Nielsen, K. Acta Chem. Scand. A 1981, 35, 739. (c) Emsley, J.; Reza, N. M.; Dawes, H. M.; Hurst-house, M. B. Chem. Commun., 1985, 1458. (d) Meng, X.-G.; Qian, J.-L. Acta Cryst. 2006, E62, o4178. (e) Ramos-Organillo, A.; Contreras, R. Acta Cryst. 2006, C63, o501. (f) Sieron, L. Acta Cryst. 2007, E63, o2089. (g) Sieron, L. Acta Cryst. 2008, E64, m58. (h) Dobrzy-cki, L.; Wozniak, K. CrystEngComm, 2008, 10, 577. (i) Zeng, B.; Li, J.; Wang, G.-D. Acta Cryst. 2011, E67, o1464. (j) Chen, S.-P.; Hu, L.; Zhang, Y.-Q.; Deng, P.; Li, C.; Chen, X.; Yuan, L.-J.; Chem. Commun., 2012, 48, 552. (k) Belter, R. K.; Fronczek, F. R.; Acta Cryst. 2013, E69, o606.

5 (a) Nelson, C. M.; Boyd, G. E.; Smith, W. T. J. J. Am. Chem. Soc., 1954, 76, 348. (b) Figgis, B. N.; Lewis, J.; Mabbs, F. E. J. Chem. Soc., 1961, 3138. (b) Busey, R. H.; Sonder, E. J. Chem. Phys., 1962, 36, 93. (c) Busey, R. H.; Dearman, H. H.; Bevan, R. B. Jr. J. Phys. Chem., 1962, 66, 82. (d) Busey, R. H.; Bevan, R. B.; Gilbert, R. A. J. Phys. Chem. 1965, 69, 3471. (e) Minkiewicz, V.; Shirane, G.; Frazer, B.; Wheeler, R.; Dorain, P. J. Phys. Chem. Solids, 1968, 29, 881.

6 (a) Tomkiewicz, A.; Korybut-Daszkiewcz, B.; Zygmunt, A.; Mroziński, J. J. Mol. Struc., 2002, 613, 115. (b) Tomkiewicz, A.; Zygmunt, A.; Mroziński, J. J. Mol. Struc., 2003, 644, 97. (c) Tomkiewicz, A.; Boča, R.; Na-horska, M.; Mroziński, J. J. Mol. Struc., 2005, 734, 143.

7 (a) Martínez-Lillo, J.; Armentano, D.; De Munno, G.; Lloret, F.; Julve, M.; Faus, J. Cryst. Growth Des., 2006, 6, 2204. (b) Martínez-Lillo, J.; Kong, J.; Barros, W. P.; Faus, J.; Julve, M.; Brechin, E. K. Chem. Commun., 2014, 50, 5840.

8 Chiozzone, R.; González, R.; Kremer, C.; De Munno, G.; Cano, J.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chem. 1999, 38, 4745.

9 (a) Martínez-Lillo, J.; Armentano, D.; De Munno, G.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chim. Acta, 2006, 359, 3291. (b) Martínez-Lillo, J.; Armentano, D.; De Munno, G.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chim. Acta, 2006, 359, 4343. (c) Martínez-Lillo, J.; Armentano, D.; Marino, N.; Arizaga, L.; Chiozzone, R.; González, R.; Kremer, C.; Cano, J.; Faus, J. Dalton Trans. 2008, 4585. (d) Martínez-Lillo, J.; Armentano, D.; Mastropietro, T. F.; Julve, M.; Faus, J.; De Munno, G. Cryst. Growth Des., 2011, 11, 1733.

10 (a) González, R.; Romero, F.; Luneau, D.; Ar-mentano, D.; De Munno, G.; Kremer, C.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chim. Acta, 2005, 358, 3995. (b) González, R.; Chiozzone, R.; Kremer, C.; Guerra, F.; De Munno, G.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chem. 2004, 43, 3013. (c) Armentano, D.; Martínez-Lillo, J. In-org. Chim. Acta, 2012, 380, 118.

11 Pop, F.; Allain, M.; Auban-Senzier, P.; Martínez-Lillo, J.; Lloret, F.; Julve, M.; Canadell, E.; Avarvari, N. Eur. J. Inorg. Chem. 2014, DOI:10.1002/ejic.201400125.

12 Martínez-Lillo, J.; Armentano, D.; De Munno, G.; Marino, N.; Lloret, F.; Julve, M.; Faus, J. CrystEngComm, 2008, 10, 1284.

13 (a) González, R.; Chiozzone, R.; Kremer, C.; Guerra, F.; De Munno, G.; Lloret, F.; Julve, M.; Faus, J. In-org. Chem. 2004, 43, 3013. (b) Suzuki, K. I.; Kodama, T.; Kikuchi, K.; Fujita, W. Chem. Lett., 2010, 39, 1096. (c) Martínez-Lillo, J. Polyhedron, 2014, 67, 213.

14 Tabernor, J.; Jones, L. F.; Heath, S. L.; Muryn, C.; Aromí, G.; Ribas, J.; Brechin, E. K.; Collison, D. Dalton Trans., 2004, 975.

15 Kahn, O. Molecular Magnetism; VCH: New York, 1993.

16 Kleinberg, J. (Ed.), Inorganic Synthesis, Vol. VII, McGraw-Hill, New York, 1963, 189.

17 Earnshaw, A. Introduction to Magnetochem-istry, Academic Press, London, Kahn, 1968.

18 Bain, G. A.; Berry, J. F. J. Chem. Educ., 2008, 85, 532.

19 Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.

20 SHELXTL; Bruker Analytical X-ray Instruments: Madison, WI, 1998.

21 DIAMOND 3.2d, Crystal Impact GbR, CRYSTAL IMPACT; K. Brandeburg & H. Putz GBR, Bonn, 5 Ger-many, 2000.

8

For Table of Contents Use Only

Two novel Re(IV) compounds of formulae [HBTA]2[ReIVBr6] (1) and [HMEBTA]2[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotriazole] have been synthesized and mag-neto-structurally characterized. Short ReIV−Br···Br−ReIV contacts, - stacking and H-bonding inter-actions occur in their crystal lattice, generating novel supramolecular structures based on Re(IV). The different dispositions of the cations and the intermolecular Br···Br contacts in 1 and 2 play an important structure-property role, with the magnetic properties of 1 and 2 revealing a significant antiferromagnetic coupling between Re(IV) ions through intermolecular Br···Br interactions.

9