Two new mononuclear cationic complexes in which the TbIII ion is bis-chelated by the tripodal alcohol 1,1,1-tris-(hy-droxy-meth-yl)propane (H3LEt, C6H14O3) were prepared from Tb(NO3)3·5H2O and had their crystal and mol-ecular structures solved by single-crystal X-ray diffraction analysis after data collection at 100 K. Both products were isolated in reasonable yields from the same reaction mixture by using different crystallization conditions. The higher-symmetry complex dinitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) nitrate di-meth-oxy-ethane hemisolvate, [Tb(NO3)2(H3LEt)2]NO3·0.5C4H10O2, 1, in which the lanthanide ion is 10-coordinate and adopts an s-bicapped square-anti-prismatic coordination geometry, contains two bidentate nitrate ions bound to the metal atom; another nitrate ion functions as a counter-ion and a half-mol-ecule of di-meth-oxy-ethane (completed by a crystallographic twofold rotation axis) is also present. In product aqua-nitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) dinitrate, [Tb(NO3)(H3LEt)2(H2O)](NO3)2, 2, one bidentate nitrate ion and one water mol-ecule are bound to the nine-coordinate terbium(III) centre, while two free nitrate ions contribute to charge balance outside the tricapped trigonal-prismatic coordination polyhedron. No free water mol-ecule was found in either of the crystal structures and, only in the case of 1, di-meth-oxy-ethane acts as a crystallizing solvent. In both mol-ecular structures, the two tripodal ligands are bent to one side of the coordination sphere, leaving room for the anionic and water ligands. In complex 2, the methyl group of one of the H3LEt ligands is disordered over two alternative orientations. Strong hydrogen bonds, both intra- and inter-molecular, are found in the crystal structures due to the number of different donor and acceptor groups present.
Two new mononuclear cationic complexes in which the TbIII ion is bis-chelated by the tripodal alcohol 1,1,1-tris-(hy-droxy-meth-yl)propane (H3LEt, C6H14O3) were prepared from Tb(NO3)3·5H2O and had their crystal and mol-ecular structures solved by single-crystal X-ray diffraction analysis after data collection at 100 K. Both products were isolated in reasonable yields from the same reaction mixture by using different crystallization conditions. The higher-symmetry complex dinitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) nitrate di-meth-oxy-ethane hemisolvate, [Tb(NO3)2(H3LEt)2]NO3·0.5C4H10O2, 1, in which the lanthanide ion is 10-coordinate and adopts an s-bicapped square-anti-prismatic coordination geometry, contains two bidentate nitrate ions bound to the metal atom; another nitrate ion functions as a counter-ion and a half-mol-ecule of di-meth-oxy-ethane (completed by a crystallographic twofold rotation axis) is also present. In product aqua-nitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) dinitrate, [Tb(NO3)(H3LEt)2(H2O)](NO3)2, 2, one bidentate nitrate ion and one water mol-ecule are bound to the nine-coordinate terbium(III) centre, while two free nitrate ions contribute to charge balance outside the tricapped trigonal-prismatic coordination polyhedron. No free water mol-ecule was found in either of the crystal structures and, only in the case of 1, di-meth-oxy-ethane acts as a crystallizing solvent. In both mol-ecular structures, the two tripodal ligands are bent to one side of the coordination sphere, leaving room for the anionic and water ligands. In complex 2, the methyl group of one of the H3LEt ligands is disordered over two alternative orientations. Strong hydrogen bonds, both intra- and inter-molecular, are found in the crystal structures due to the number of different donor and acceptor groups present.
Our interest in developing synthetic routes for the synthesis of mono- or polynuclear complexes containing lanthanide(III) ions is based on the possibility that these compounds behave as single-ion (SIM) or single-molecule (SMM) magnets (Benelli & Gatteschi, 2015 ▸; Gatteschi et al., 2006 ▸; Frost et al., 2016 ▸; Meng et al., 2016 ▸). In such chemical species, it is usually possible to exploit the strong spin-orbit coupling, the relatively high-spin angular momentum and the large magnetic anisotropy presented by lanthanides to maximize the energy barrier for the reversal of the magnetization (Luzon & Sessoli, 2012 ▸; Vieru et al., 2016 ▸; Sessoli & Powell, 2009 ▸) and therefore increase the technological applicability of these materials.With this objective in mind, our first steps were the synthesis and characterization of complexes containing Ln
III ions that could be used as building blocks for polynuclear 3d–4f block metal aggregates. The first report of a heterometallic complex of this type that showed SMM behaviour described the tetranuclear molecule [{CuII
LTbIII(Hfac)2}2] [H3
L = 1-(2-hydroxybenzamido)-2-(2-hydroxy-3-methoxy-benzylideneamino)ethane and Hfac = hexafluoroacetylacetone], obtained by self-assembly (Osa et al., 2004 ▸). Magnetic studies of the product revealed ferromagnetic exchange and slow relaxation of the magnetization at low temperatures, with a potential energy barrier Δ/kB of 21 K (14.7 cm−1).After this report, many other heterometallic complexes containing 3d and 4f ions with different structures and nuclearities were characterized as single-molecule magnets (Liu et al., 2015 ▸). In 2014, a trinuclear complex of dysprosium(III) and iron(II) presented the largest potential energy barrier reported to date for this type of system. The molecule, formulated as [FeII
2DyIII
L
2(H2O)]ClO4·2H2O, L = 2,2′,2′′-{[nitrilotris(ethane-2,1-diyl)]tris(azanediyl)methylene}tris(4-chlorophenol), and also synthesized in a self-assembly reaction, presents two iron(II) ions in different coordination environments (octahedral and distorted trigonal prismatic) bound to a dysprosium(III) ion in quasi-D
5 symmetry, which is pointed out by the authors as fundamental for the observed SMM behaviour and for the impressive potential energy barrier of 459 K (319 cm−1) (Liu et al., 2014 ▸). This value, although lower than the record figures reported for lanthanide-containing SIM compounds (Liu et al., 2016 ▸), still reveals the potential of mixed 3d–4f metal complexes to behave as quantum magnets.Despite these good results, most of the experimental procedures employed for the preparation of these polynuclear compounds involve self-assembly reactions, which often compete with the rational design of the desired molecules. Many efforts have been directed recently to the development of synthetic routes that allow for greater predictability of the formed products, both structural and with respect to their magnetic properties, employing simple and elegant experimental procedures that include modular synthesis approaches (Kahn, 1997 ▸; Stumpf et al., 1993 ▸).In this context, the present work involved reactions between the tripodal alcohol H3
L
Et [1,1,1-tris(hydroxymethyl)propane] and Tb(NO3)3·5H2O that generated the new, cationic complexes [Tb(H3
L
Et)2(NO3)2](NO3)·0.5glyme (product 1) and [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2 (product 2). In both cases, the coordination environment of the lanthanide ion is similar to that observed in the central unit (core) of star-shaped heterometallic SMMs of general formula [M
3
M′(L
Et)2(dpm)3] (M and M′ = transition metal(III) ions; L
Et = EtC(CH2O)3
3− tripodal alkoxide and Hdpm = dipivaloylmethane) (Accorsi et al., 2006 ▸; Totaro et al., 2013 ▸; Westrup et al., 2014 ▸; Gregoli et al., 2009 ▸). Complexes 1 and 2 were characterized by elemental and X-ray diffraction analysis, together with vibrational (infrared) spectroscopy. These products are potential building blocks to be subsequently combined, in stoichiometric proportions, with other 3d and 4f starting materials to give heterometallic products with potentially interesting magnetic properties.
Structural commentary
The crystals of product 1 contain the mononuclear complex [Tb(H3
L
Et)2(NO3)2](NO3)·0.5glyme (Fig. 1 ▸), in which the terbium(III) ion is 10-coordinate, being connected to six hydroxyl groups of the tripodal alcohol molecules and to two bidentate nitrate ions. There is also one nitrate ion (acting as a counter-ion); a solvating dimethoxyethane (glyme) molecule is shared between two units of the cationic complex. The complete gylme molecule is completed by a crystallographic twofold rotation axis.
Figure 1
ORTEP representation of product 1, [Tb(H3
L
Et)2(NO3)2](NO3)·0.5C4H10O2 (H3
L
Et = 1,1,1-tris(hydroxymethyl) propane and C4H10O2 = dimethoxyethane), with the atom-numbering scheme. There is disorder in the tripodal ligand of C21, with the minor component shown with striped bonds. Hydrogen atoms were omitted for clarity, and displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) −x + , y, 1 − z.]
The geometric arrangement of the oxygendonor atoms about the metal atom in 1 is closer to a distorted s-bicapped square antiprism, Fig. 2 ▸, than to an s-bicapped dodecahedron (Rohrbaugh & Jacobson, 1974 ▸). The choice of the bicapped square-antiprismatic coordination sphere is mainly based on the angles between the coordinating oxygen atoms presented in Table 1 ▸, which are closer to the expected 90° values of the square planes in the former (Fig. 2 ▸) than to the alternating ca 77 and 100° angles in the latter (Rohrbaugh & Jacobson, 1974 ▸).
Figure 2
Plot of the coordination sphere (left) and schematic representation of the coordination environment about the terbium(III) atom in product 1. The two mutually rotated square faces O2–O12–O14–O23 and O13—O22—O24—O4 are capped by atoms O1 and O5, respectively.
Table 1
Selected non-bonding angles (°) in the molecular structure of product 1
O24⋯O22⋯O13
101.47
O2⋯O23⋯O14
86.82
O22⋯O13⋯O4
83.25
O23⋯O14⋯O12
100.40
O13⋯O4⋯O24
81.56
O14⋯O12⋯O2
86.34
O4⋯O24⋯O22
93.06
O12⋯O2⋯O23
84.98
The mean square planes represented in Fig. 2 ▸ form a dihedral angle of 5.58° in the complex cation of 1. The capping atoms, O1 and O5, both belong to the bidentate NO3
− ligands and form the two longest Tb—O bonds in the structure of 1, 2.5697 (13) and 2.5874 (14) Å, respectively. Because of the typically small bite angles of the chelating nitrate ions, 49.50 (4)° for O2—Tb1—O1 and 50.12 (4)° for O4—Tb1—O5, the Tb—O1 and Tb—O5 bonds are significantly bent towards O2 and O4, respectively, creating additional structural distortion.The average Tb—O bond involving the bidentate nitrate ligands in 1 [2.549 Å, and Table 2 ▸] is shorter than that described by Delangle and co-workers for the lanthanum(III) cation [La(H3
L
1)2(NO3)2]+, H3
L
1 = cis,cis-1,3,5-trihydroxycyclohexane; average = 2.681 Å; Delangle et al., 2001 ▸]. This agrees with the smaller effective ionic radius of the TbIII ion as compared to that of LaIII (for example 1.095 versus 1.216 Å for nine-coordination respectively; Shannon, 1976 ▸). The effective ionic radius for 10-coordinate terbium(III) is not available in the literature. The mean Tb—O bond to the tripodal H3
L
Et ligands is 2.404 Å, again significantly shorter than in the lanthanum(III)–cyclic triol analogue mentioned above (average = 2.542 Å). The lack of other reported lanthanide complexes with a bis(tripodal alcohol)-bis(bidentate nitrate) coordination environment similar to that found in 1 restricts further comparisons.
Table 2
Metal–oxygen distances (Å) in the two complexes, 1 and 2
Complex 1
Complex 2
Tb1—O1
2.5697 (13)
Tb1—O1
2.4706 (10)
Tb1—O2
2.5418 (13)
Tb1—O2
2.4762 (9)
Tb1—O4
2.4953 (13)
Tb1—O10
2.3786 (9)
Tb1—O5
2.5874 (14)
Tb1—O12
2.4078 (13)
Tb1—O12
2.3597 (9)
Tb1—O13
2.4245 (14)
Tb1—O13
2.4119 (9)
Tb1—O14
2.3810 (14)
Tb1—O14
2.3545 (9)
Tb1—O22
2.3583 (13)
Tb1—O22
2.3734 (9)
Tb1—O23
2.4749 (14)
Tb1—O23
2.4344 (9)
Tb1—O24
2.3790 (13)
Tb1—O24
2.4112 (9)
O12—Tb1—O13
66.85 (5)
O12—Tb1—O13
68.99 (3)
O14—Tb1—O12
76.53 (5)
O14—Tb1—O12
72.38 (3)
O22—Tb1—O12
136.11 (5)
O12—Tb1—O22
140.67 (3)
O12—Tb1—O23
130.08 (5)
O12—Tb1—O23
131.17 (3)
O24—Tb1—O12
147.08 (5)
O12—Tb1—O24
141.14 (3)
O14—Tb1—O13
70.11 (5)
O14—Tb1—O13
70.72 (3)
O22—Tb1—O13
71.20 (5)
O22—Tb1—O13
71.69 (3)
O13—Tb1—O23
129.41 (5)
O13—Tb1—O23
123.37 (3)
O24—Tb1—O13
128.37 (5)
O24—Tb1—O13
134.33 (3)
O22—Tb1—O14
77.75 (5)
O14—Tb1—O22
93.64 (3)
O14—Tb1—O23
70.24 (5)
O14—Tb1—O23
69.97 (3)
O24—Tb1—O14
133.94 (5)
O14—Tb1—O24
138.28 (3)
O22—Tb1—O23
70.76 (5)
O22—Tb1—O23
71.90 (3)
O22—Tb1—O24
72.47 (5)
O22—Tb1—O24
72.06 (3)
O24—Tb1—O23
67.19 (5)
O24—Tb1—O23
68.34 (3)
O2—Tb1—O1
49.50 (4)
O1—Tb1—O2
51.89 (3)
O4—Tb1—O1
104.45 (4)
O10—Tb1—O1
124.95 (3)
O1—Tb1—O5
154.57 (4)
O10—Tb1—O2
73.09 (3)
O4—Tb1—O2
62.06 (4)
O2—Tb1—O5
107.78 (4)
O4—Tb1—O5
50.12 (4)
O12—Tb1—O1
69.27 (5)
O12—Tb1—O1
88.98 (3)
O13—Tb1—O1
125.17 (4)
O13—Tb1—O1
71.02 (3)
O14—Tb1—O1
69.06 (4)
O14—Tb1—O1
141.34 (3)
O22—Tb1—O1
130.92 (4)
O22—Tb1—O1
79.51 (3)
O23—Tb1—O1
64.60 (4)
O23—Tb1—O1
139.42 (3)
O24—Tb1—O1
106.31 (4)
O24—Tb1—O1
75.88 (3)
O12—Tb1—O2
80.97 (5)
O12—Tb1—O2
73.16 (3)
O13—Tb1—O2
144.10 (5)
O13—Tb1—O2
110.27 (3)
O14—Tb1—O2
118.55 (4)
O14—Tb1—O2
142.17 (3)
O22—Tb1—O2
142.88 (5)
O22—Tb1—O2
123.21 (3)
O23—Tb1—O2
83.39 (4)
O23—Tb1—O2
125.81 (3)
O24—Tb1—O2
73.14 (4)
O24—Tb1—O2
69.33 (3)
O12—Tb1—O4
72.71 (5)
O12—Tb1—O10
75.77 (3)
O13—Tb1—O4
92.32 (5)
O10—Tb1—O13
141.19 (3)
O14—Tb1—O4
148.71 (4)
O14—Tb1—O10
83.74 (3)
O22—Tb1—O4
122.01 (4)
O22—Tb1—O10
140.58 (3)
O23—Tb1—O4
136.38 (5)
O10—Tb1—O23
70.30 (3)
O24—Tb1—O4
77.30 (5)
O10—Tb1—O24
83.96 (3)
O12—Tb1—O5
98.74 (5)
O13—Tb1—O5
64.19 (5)
O14—Tb1—O5
131.61 (5)
O22—Tb1—O5
73.45 (4)
O23—Tb1—O5
131.18 (4)
O24—Tb1—O5
71.11 (5)
The slow mixing of a hexane layer into the same reaction mixture that gave product 1 afforded another set of colourless crystals, product 2, in high yield (see Synthesis and crystallization). As for 1, crystals of 2 were practically insoluble at room temperature in hexane, toluene, thf, glyme and acetonitrile, but soluble in the last three solvents after heating at ca 323 K.Single-crystal X-ray diffraction analysis of 2 revealed again a mononuclear complex, this time of formula [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2 (Fig. 3 ▸), in which the coordination number of the metal atom is nine. In this case, the terbium(III) atom is coordinated by six hydroxyl groups of the tripodal alcohols, a bidentate nitrate ion and one water molecule probably coming from the Tb(NO3)3·5H2O starting material. Two distinct non-coordinating nitrate anions complete the charge balance in the product.
Figure 3
ORTEP representation of product 2, [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2, with the atom-numbering scheme. The terminal methyl group on C15 is disordered; the bonding of the minor component is shown with a striped bond. Displacement ellipsoids correspond to the 50% probability level. Hydrogen bonds are indicated by double-dashed lines.
The geometry adopted by the metal atom in 2 is close to a tri-capped trigonal prism, as reported for complexes [Ln(H3
L
1)2(NO3)(H2O)](NO3)2 (Ln = HoIII, EuIII and YbIII; H3
L
1 = cis,cis-1,3,5-trihydroxycyclohexane; Husson et al., 1999 ▸; Delangle et al., 2001 ▸). The two triangular faces, defined by O10–O12–O14 and O1–O22–O24, are nearly parallel, with a dihedral angle of 5.14° between the normals to the mean planes. The three rectangular faces, in turn, formed by O1–O12–O14–O22, O1–O10–O12–O24 and O10–O14–O22–O24, are capped by O13, O2 and O23, respectively. In these rectangular faces, the longer O⋯O distance is on average 3.345 Å, while the shorter is 2.961 Å (mean value). The alternative geometry of a monocapped square antiprism, as described for [Y(H3
L
Me)2(NO3)(H2O)](NO3)2 (Chen et al., 1997 ▸), appears less suitable to characterize 2 because of a much less regular placement of the coordinating oxygen atoms in the two square planes, O10–O12–O13–O23 and O1–O2–O22–O24, that are typical of this polyhedral arrangement.The coordination of the TbIII atom by the two tripodal ligands in both 1 and 2 is very similar. In the [M
3
M′(L
Et)2(dpm)3] complexes (M and M′ = d-block metals), as above (Accorsi et al., 2006 ▸; Totaro et al., 2013 ▸; Westrup et al., 2014 ▸; Gregoli et al., 2009 ▸), the central metal is six-coordinate and the two tripodal ligands are inverted about that atom in an approximately octahedral arrangement; here, the CB⋯M ⋯CB′ angle is close to 180° (where CB and CB′ are the bridgehead carbon atoms in the tripodal ligand). In our complexes 1 and 2, with 10- and 9-coordinate atoms, the tripodal ligands are tilted apart, with C11—Tb1—C21 angles of 129.7 and 135.5°, respectively; this arrangement allows more space for the extra ligands in the coordination sphere. In both 1 and 2, all the extra ligands, nitrate ions and water molecules, lie on the plane that bisects the tripodal ligands; the number of extra coordinating atoms determines the distribution in the bisecting plane and overall geometrical patterns, as described above.According to Table 2 ▸, the metal–oxygen distances involving the H3
L
Et ligands in 1 and 2 vary from 2.3583 (13) to 2.4749 (14) (complex 1) and from 2.3545 (9) to 2.4344 (9) Å (complex 2), these ranges being slightly larger than those reported for the Ln
3+ complexes of the trihydroxycyclohexane ligands (Delangle et al., 2001 ▸). This probably arises from the different flexibilities of H3
L
Et and the cyclic alcohols used in the syntheses, which allow for distortions of the lanthanide coordination environments. Also, the more crowded environment of the 10-coordinated metal ion in 1 as compared to 2 probably causes the larger observed variation.The Tb—O bond lengths involving the nitrate ions in 2 are intermediate when compared to the analogous complexes of EuIII, HoIII and YbIII (Delangle et al., 2001 ▸; Husson et al., 1999 ▸) (Table 3 ▸). This is in agreement with the gradual decrease of the effective ionic radii of these ions (1.120, 1.095, 1.072 and 1.042 Å for EuIII, TbIII, HoIII and YbIII, respectively, in 9-coordinate environments; Shannon, 1976 ▸). The same pattern is observed for the average metal–oxygen bond of the water molecule (Table 3 ▸).
Table 3
Bond lengths (Å) involving the metal cations and the nitrate/water ligands in the lanthanide complexes [Tb(H3
LEt)2(NO3)(H2O)](NO3)2
and [Ln(H3
L
1)(NO3)(H2O)](NO3)2 (Ln = EuIII, HoIII and YbIII; H3
L
1 = cis,cis-1,3,5-trihydroxycyclohexane)
Eu—O(NO3)
2.4869 (12)
Eu—O(NO3)
2.517 (2)
Eu—O(H2O)
2.4279 (14)
Tb—O(NO3)
2.4706 (10)
Tb—O(NO3)
2.4762 (9)
Tb—O(H2O)
2.3786 (9)
Ho—O(NO3)
2.450 (9)
Ho—O(NO3)
2.454 (8)
Ho—O(H2O)
2.377 (8)
Yb—O(NO3)
2.448 (6)
Yb—O(NO3)
2.439 (7)
Yb—O(H2O)
2.331 (7)
Notes: (a) this work, product 2; (b) Delangle et al. (2001); Husson et al. (1999).
It has been demonstrated (Delangle et al., 2001 ▸) that the formation of Ln(H3
L)2 complexes (Ln = LaIII, PrIII, NdIII, EuIII and YbIII; L = cis,cis-1,3,5- or cis,cis-1,2,3-trihydroxycyclohexane) in solution is strongly dependent on the metal:ligand ratio and on the chemical nature of the metal ion, its ionic radius, the polarity of the solvent and the nature of the counter-ion, either nitrate or triflate.In the present work, the reaction between hydrated terbium(III) nitrate and H3
L
Et led to the isolation of two distinct products, 1 and 2, from the same reaction mixture, with modification only of the crystallization conditions. Product 2, [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2, was obtained in higher yield and after a shorter time interval (24 h) than the more symmetrical 1, [Tb(H3
L
Et)2(NO3)2](NO3)·0.5glyme. The preparation of 2 is also easier to reproduce than that of 1; the former appears to be favoured by addition of a less polar solvent (hexane) to the reaction mixture. The isolation of 1, on the other hand, seems to be subjected to a very subtle control of the crystallization conditions, and this is probably the reason why there are fewer reports of similar, anhydrous Ln(H3
L)2 products in the literature. The presence of solvating glyme in the crystals of 1 suggests that the use of other solvents with different stereo requirements could be a strategy to help the crystallization of this water-free complex.
Supramolecular features
The three hydroxyl groups in both complexes are all donor groups to hydrogen bonds. The acceptor atoms are oxygen atoms of nitrate ions and, in complex 1, an oxygen atom of the glyme molecule (Fig. 4 ▸). In complex 2, the water ligand forms two hydrogen bonds to two non-coordinating nitrate ions (Fig. 5 ▸). Thus, in both compounds, all the ions and the glyme molecule are linked in an extensive three-dimensional hydrogen-bonded network.
Figure 4
ORTEP representation of hydrogen bonding interactions about the ions and glyme molecule of product 1, Tb(H3
L
Et)2(NO3)2](NO3)·0.5C4H10O2, with hydrogen bonds indicated by double-dashed lines. Hydrogen atoms on carbon atoms have been omitted for clarity.
Figure 5
ORTEP representation of hydrogen bonding interactions about the ions of product 2, [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2, with hydrogen bonds indicated by double-dashed lines.
In both complexes, there are also some intermolecular C—H⋯O interactions, which may be described as ‘weak hydrogen bonds’. These are included in Tables 4 ▸ and 5 ▸ with the stronger O—H⋯O bonds.
Table 4
Hydrogen-bond geometry (Å, °) for 1
D—H⋯A
D—H
H⋯A
D⋯A
D—H⋯A
O12—H12O⋯O9i
0.72 (2)
1.98 (2)
2.683 (2)
167 (3)
O13—H13O⋯O32
0.74 (2)
2.04 (2)
2.774 (2)
170 (3)
O14—H14O⋯O2ii
0.74 (2)
2.07 (3)
2.7935 (19)
165 (3)
O22—H22O⋯O8
0.73 (2)
2.01 (3)
2.735 (2)
172 (3)
O23—H23O⋯O4ii
0.69 (2)
2.16 (2)
2.8550 (19)
175 (2)
O24—H24O⋯O1iii
0.74 (3)
1.93 (3)
2.6624 (19)
171 (3)
C22—H22B⋯O3iv
0.99
2.44
3.358 (3)
153
C24—H24B⋯O7v
0.99
2.49
3.220 (3)
130
C29—H29A⋯O7v
0.99
2.41
3.27 (3)
146
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .
Table 5
Hydrogen-bond geometry (Å, °) for 2
D—H⋯A
D—H
H⋯A
D⋯A
D—H⋯A
O10—H1OA⋯O7i
0.75 (2)
2.03 (2)
2.7420 (14)
159 (2)
O10—H1OB⋯O5ii
0.79 (2)
2.00 (2)
2.7703 (14)
167 (2)
O13—H13O⋯O8
0.77 (2)
1.91 (2)
2.6695 (14)
169 (2)
O12—H12O⋯O5iii
0.74 (2)
1.93 (2)
2.6713 (13)
174 (2)
O14—H14O⋯O6
0.73 (2)
1.97 (2)
2.6992 (14)
174 (2)
O23—H23O⋯O6ii
0.71 (2)
2.09 (2)
2.7669 (14)
161 (2)
O22—H22O⋯O9
0.76 (2)
1.94 (2)
2.6609 (14)
157 (2)
O24—H24O⋯O8iv
0.73 (2)
1.97 (2)
2.6650 (14)
158 (2)
C14—H14A⋯O7i
0.99
2.58
3.3462 (17)
135
C23—H23A⋯O3v
0.99
2.51
3.4003 (16)
149
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .
Database survey
Delangle and co-workers (Delangle et al., 2001 ▸; Husson et al., 1999 ▸) reported the preparation of a variety of mononuclear complexes of various lanthanide(III) ions, specifically LaIII, PrIII, NdIII, HoIII, EuIII and YbIII, with the trialcohols cis,cis-1,3,5-trihydroxycyclohexane (H3
L
1) and cis,cis-1,2,3-trihydroxycyclohexane(H3
L
2) as models for the coordination of monosaccharides. In those compounds, as in 1 and 2, the metal atoms are coordinated to two trialcohol molecules and bidentate/monodentate O-donor anions (nitrate or triflate), or to these anions and water molecules.Monosaccharide-derived polyols have also been used as chelating ligands for lanthanide(III) ions. LnCl3 and Ln(NO3)3 (Ln = LaIII, TbIII and SmIII) were shown to form chain-like complexes with d-galactitol in which the alditol provides three hydroxyl groups to coordinate one metal ion and three other hydroxyl groups to coordinate another; in all cases, there are two alditol molecules bound to each lanthanide (Su et al., 2002 ▸; Yu et al., 2011 ▸). Other authors have employed erythritol, whose molecule functions as two bidentate ligands or as a three-hydroxyldonor to a variety of lanthanide(III) chlorides (Ce, Pr, Nd, Eu, Gd and Tb; Yang et al., 2012 ▸; Yang, Xie et al., 2005 ▸; Yang, Xu et al., 2005 ▸). These studies describe several possible binding modes of these polyols to lanthanide ions.As far as tripodal alcohol ligands are concerned, mononuclear yttrium(III) complexes of 1,1,1-tris(hydroxymethyl)propane (H3
L
Et) and 1,1,1-tris(hydroxymethyl)ethane (H3
L
Me), as well as of the aminopolyalcohol (HOCH2)3CN(CH2CH2OH)2, H5
L
N(EtOH)2, were described by Chen and co-workers while investigating chelate complexes for radiotherapeutic applications (Chen et al., 1997 ▸). In two of the reported products, those prepared from H3
L
Me and H5
L
N(EtOH)2, the coordination sphere of the eight-coordinate yttrium atom contains chloride instead of nitrate ligands. A more recent study (Xu et al., 2015 ▸), in its turn, describes a dysprosium(III) complex with H3
L
Et that is isostructural to product 2 (present work) and has been employed to investigate possible biomedical applications of the binding of rare earth metal ions to the apoferritin protein.
Synthesis and crystallization
All experimental operations were performed under N2(g) (99.999%, Praxair) or under vacuum of 10−3 Torr, using Schlenk and glove-box techniques. Solvents (dimethoxyethane and hexane) were purified according to procedures described in the literature (Perrin & Armarego, 1997 ▸). Terbium(III) nitrate pentahydrate and 1,1,1-tris(hydroxymethyl)propane (H3
L
Et) were purchased from Aldrich; the latter was dissolved in thf/toluene (1:1), crystallized at 153 K, isolated by filtration and stored under N2 at room temperature prior to use. Elemental analysis (C, H and N) were performed under argon by MEDAC Laboratories Ltd. (Chobham, Surrey, UK), using a Thermal Scientific Flash EA 1112 Series Elemental Analyzer. Infrared spectra (FTIR, Nujol mulls) were obtained on a BIORAD FTS 3500GX instrument in the range of 400-4000 cm−1.
Synthesis of [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2·0.5glyme (product 1)
A solution containing 1.91 g (4.39 mmol) of Tb(NO3)3·5H2O in 50 ml of dimethoxyethane (glyme) received the addition of 1.11 g (8.27 mmol) of solid 1,1,1-tris(hydroxymethyl)propane to form a colourless solution that was refluxed for 15 min. After this period of time, the heating was turned off and a 32 ml aliquot of the reaction mixture was withdrawn for the isolation of product 2 (described below). The remaining 18 ml were cooled down to 153 K for four days, without forming any solid. The solution was then dried under vacuum and the resulting solid was almost completely redissolved in 7.5 ml of glyme. A fine suspension was obtained which, after seven days at 153 K, gave colourless crystals that were isolated and dried under vacuum (complex 1). Yield: 360 mg, 0.547 mmol (12.5% based on the total amount of terbium employed in the reaction). If the yield was extrapolated to the total volume of the reaction mixture (50 ml) instead of the 18 ml effectively employed for crystallization, it could reach 34.7%. Elemental analysis: calculated for [Tb(H3
L
Et)2(NO3)2](NO3)·0.5glyme (C14H33N3O16Tb) C 25.54, H 5.05, N 6.38%. Found C 25.34, H 5.08, N 6.60%. FTIR (Nujol mull, cm−1, s = strong, m = medium, w = weak, sh = shoulder): 3359m, 3220m ν(O—H); 1050sh, 1020s, 942s, mainly ν(C—O); 1271s νa(NO2), 1041s νs(NO2).
Isolation of [Tb(H3
L
Et)2(NO3)(H2O)](NO3)2 (product 2)
The 32 ml aliquot of the reaction mixture described in the synthesis of 1 above received the careful addition of a hexane layer (20 ml) at room temperature, and was allowed to stand for 24 h. During this period it was possible to observe the formation of a large number of colourless crystals, which were isolated by filtration and dried under vacuum (complex 2). Yield: 1.36 g, 2.15 mmol (49.1% based on the total amount of terbium employed in the reaction). If the yield was extrapolated to the total volume of the reaction mixture (50 ml) instead of 32 ml actually employed for crystallization of 2, this yield could reach 76.7%). Elemental analysis: calculated for C12H30N3O16Tb C 22.83, H 4.79, N 6.66%. Found C 22.69, H 4.84, N 6.78. FTIR (Nujol mull, cm−1): 3475m, 3350s, 3184s ν(O—H); 1620w δ(O—H), 1050s, 1035s, 949s, mainly ν(C—O); 1278s νa(NO2), 1037s νs(NO2).
Refinement
Crystal data, data collection and structure refinement details for both complexes 1 and 2 are summarized in Table 6 ▸.
Table 6
Experimental details
1
2
Crystal data
Chemical formula
[Tb(NO3)2(C6H14O3)2]NO3·0.5C4H10O2
[Tb(NO3)(C6H14O3)2(H2O)](NO3)2
Mr
658.35
631.31
Crystal system, space group
Monoclinic, I2/a
Monoclinic, P21/c
Temperature (K)
100
100
a, b, c (Å)
20.1864 (13), 10.2997 (6), 23.832 (2)
9.1440 (6), 12.7870 (7), 19.7151 (12)
β (°)
108.004 (3)
101.796 (2)
V (Å3)
4712.4 (6)
2256.5 (2)
Z
8
4
Radiation type
Mo Kα
Mo Kα
μ (mm−1)
3.08
3.22
Crystal size (mm)
0.14 × 0.11 × 0.09
0.36 × 0.19 × 0.18
Data collection
Diffractometer
Bruker D8 VENTURE/PHOTON100 CMOS
Bruker D8 VENTURE/PHOTON100 CMOS
Absorption correction
Multi-scan (SADABS; Bruker, 2014 ▸)
Multi-scan (SADABS; Bruker, 2014 ▸)
Tmin, Tmax
0.694, 0.746
0.636, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections
172878, 5889, 5031
244328, 5629, 5542
Rint
0.071
0.023
(sin θ/λ)max (Å−1)
0.670
0.670
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.018, 0.036, 1.07
0.012, 0.029, 1.13
No. of reflections
5889
5629
No. of parameters
344
326
H-atom treatment
H atoms treated by a mixture of independent and constrained refinement
H atoms treated by a mixture of independent and constrained refinement
Disorder was noted in both structures: in compound 1, the methylene groups in the three CH2OH groups in one tripodal ligand were each found to be disordered over two sets of sites, with an occupancy ratio of 0.911 (7) : 0.089 (7), whereas in 2, the disorder is in a terminal methyl group, which is disordered over two orientations, with an occupancy ratio of 0.827 (4) : 0.173 (4).All the hydroxyl and waterhydrogen atoms were located clearly in difference maps and were refined freely and satisfactorily. All the remaining hydrogen atoms were set in idealized positions and refined as riding on the parent carbon atoms.Crystal structure: contains datablock(s) Compound-1, Compound-2, global. DOI: 10.1107/S2056989017001116/hb7653sup1.cifStructure factors: contains datablock(s) Compound-1. DOI: 10.1107/S2056989017001116/hb7653Compound-1sup2.hklClick here for additional data file.Supporting information file. DOI: 10.1107/S2056989017001116/hb7653Compound-1sup4.cdxStructure factors: contains datablock(s) Compound-2. DOI: 10.1107/S2056989017001116/hb7653Compound-2sup3.hklClick here for additional data file.Supporting information file. DOI: 10.1107/S2056989017001116/hb7653Compound-2sup5.cdxCCDC references: 1529079, 1529078Additional supporting information: crystallographic information; 3D view; checkCIF report
Primary atom site location: structure-invariant direct methods
Least-squares matrix: full
Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.018
Hydrogen site location: mixed
wR(F2) = 0.036
H atoms treated by a mixture of independent and constrained refinement
S = 1.07
w = 1/[σ2(Fo2) + (0.015P)2 + 5.6056P] where P = (Fo2 + 2Fc2)/3
5889 reflections
(Δ/σ)max = 0.001
344 parameters
Δρmax = 0.77 e Å−3
0 restraints
Δρmin = −0.54 e Å−3
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Primary atom site location: structure-invariant direct methods
Least-squares matrix: full
Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.012
H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.029
w = 1/[σ2(Fo2) + (0.0128P)2 + 1.457P] where P = (Fo2 + 2Fc2)/3
S = 1.13
(Δ/σ)max = 0.001
5629 reflections
Δρmax = 0.74 e Å−3
326 parameters
Δρmin = −0.26 e Å−3
0 restraints
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Authors: Stefania Accorsi; Anne-Laure Barra; Andrea Caneschi; Guillaume Chastanet; Andrea Cornia; Antonio C Fabretti; Dante Gatteschi; Cecilia Mortalo; Emiliano Olivieri; Francesca Parenti; Patrick Rosa; Roberta Sessoli; Lorenzo Sorace; Wolfgang Wernsdorfer; Laura Zobbi Journal: J Am Chem Soc Date: 2006-04-12 Impact factor: 15.419
Authors: Pasquale Totaro; Kátia Cristina M Westrup; Marie-Emmanuelle Boulon; Giovana G Nunes; Davi F Back; Andersson Barison; Samuele Ciattini; Matteo Mannini; Lorenzo Sorace; Jaísa F Soares; Andrea Cornia; Roberta Sessoli Journal: Dalton Trans Date: 2013-04-07 Impact factor: 4.390