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Article

Multidimensional Transition Metal Complexes Based on 3-Amino-1H-1,2,4-triazole-5-carboxylic Acid: From Discrete Mononuclear Complexes to Layered Materials

by
Bing Liu
1,2,†,
José A. Fernandes
1,†,
João P. C. Tomé
3,4,
Filipe A. Almeida Paz
1,* and
Luís Cunha-Silva
2,*
1
Department of Chemistry, CICECO–Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
2
REQUIMTE/LAQV & Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
3
Department of Chemistry, University of Aveiro, QOPNA, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
4
Department of Organic and Macromolecular Chemistry, Ghent University, B-9000 Ghent, Belgium
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Molecules 2015, 20(7), 12341-12363; https://doi.org/10.3390/molecules200712341
Submission received: 1 June 2015 / Revised: 22 June 2015 / Accepted: 25 June 2015 / Published: 7 July 2015
(This article belongs to the Special Issue Metal-Organic Frameworks: Chemistry and Applications)
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Versions Notes

Abstract

:
The synthesis and structural characterization of five transition metal complexes with different dimensionality and incorporating residues of 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H2atrc) is reported: [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2), [Fe2(Hatrc)4(OH)2]·6H2O (3), [Cd(Hatrc)2(H2O)]n (4), and [Mn(atrc)(H2O)]n·nH2O (5). These materials could be prepared from solution (1–3), diffusion (4), or hydrothermal reactions (5) with various anions and L:M ratios. Structural details were revealed by single crystal X-ray diffraction. The discrete units composing compounds 1–3, the polymeric 1D chain of 4 and the 2D layer of 5 are further extended into 3D supramolecular architectures through the formation of hydrogen bonds.

1. Introduction

The rational strategy to design new coordination complexes, especially Metal-Organic Frameworks (MOFs) or coordination networks, by self-assembly has received remarkable interest due to their fascinating structural features and potential to be applied as novel functional materials [1,2,3,4,5,6,7]. The final assembly can be influenced by numerous factors, such as geometric requirements of metal centers, shape and nature of the ligands, reaction routes, solvents, templates, pH of the reactive medium and counterions [8,9,10,11,12]. At the moment, immense research activity is focused on integrating the advantages of metal centers and organic spacers in a complementary way. The inorganic component imparts magnetism, mechanical strength and thermal stability, while the organic part offers a way to improved luminescence, structural diversifications, and processability [13,14,15,16]. The effort exerted in this field promotes the understanding of the structure-property relationship, being attributed to the purposeful design and controlled synthesis of the aimed complexes [17,18,19,20,21].
One fruitful selection of the organic building units relies on five-membered N-heterocycles, such as pyrazole, imidazole, triazole, tetrazole, which are good representatives for small and simple organic bridging ligands. 1,2,4-Triazole residues, presenting a hybrid of pyrazole and imidazole, represent a class of ligands that can combine different substituent groups, thus constituting a good building block for the preparation of metal complexes and materials with structural, optical and magnetic properties [22,23,24,25,26,27,28,29,30,31]. Herein, 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H2atrc) [32], comprising a triazole ring with three N-donors and a carboxylic acid group, was chosen as the organic building unit, being expected to lead to the formation of polynuclear compounds and multidimensional frameworks. A meticulous survey in the literature and in Cambridge Structural Database (CSD, Version 5.36 updated November 2014) [33] revealed the existence of only five structures with residues of H2atrc (this molecule being the sole organic ligand). Two of these known compounds comprise discrete complexes ([Cd(Hatrc)2(H2O)2] [34] and (NH4)2[Cd(Hatrc)4] [35]), whereas the other two are isotypical 3D MOFs ([M(Hatrc)2(H2O)]n; M2+ = Sr2+ or Ba2+) [36]. The remaining compound is an interesting tubular structure formed by the crystal packing of [Cu(atrc)(H2O)] complex units, whose channels have an internal diameter of ca. 8.5 Å. Clusters of 12 molecules of water of crystallization are included in the channels [37].
The rarity of (H)atrc-M systems is most likely caused by the fact that H2atrc produces highly insoluble precipitates, even when using mild synthetic conditions. As part of our ongoing research work dealing with the preparation of functional coordination complexes [38,39,40,41] and new MOFs [42,43,44,45,46,47], we have isolated a series of transition metal (TM) complexes with H2atrc anionic residues. These materials show distinct dimensionalities and were prepared by several methods: [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2) (mononuclear complexes), [Fe2(Hatrc)4(OH)2]·6H2O (3; dinuclear complex) were isolated by slow evaporation; [Cd(Hatrc)2(H2O)]n (4; 1D MOF) was prepared by diffusion method; [Mn(atrc)(H2O)]n·nH2O (5; 2D MOF) was synthesized using a typical hydrothermal approach.

2. Results and Discussion

2.1. Synthesis

All compounds were directly isolated from the solutions or contents of autoclaves mostly as good quality single crystals. The influence of several parameters, such as the type of metal centers, anions, inorganic/organic bases, ligand:metal ratio, volume of water, temperature and stirring in the formation and crystallization of the compounds was investigated. A number of drawbacks in the crystallization process were found:
(i)
the use NaOH or triethylamine (Et3N) to deprotonate H2atrc in reactions with transition metal salts (such as Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+) led to poor crystalline powders;
(ii)
the use of temperatures above 60 °C in the reactions with the aforementioned metals also led to the formation of microcrystalline powders;
(iii)
with the use of less than ca. 6 mL of water in the systems mixed crystals of the new materials and the parent H2atrc ligand were easily produced;
(iv)
with 30 min of stirring, the clear mixed solutions become cloudy and no pure single crystals were produced.
As a result of this study and optimization, the most adequate reaction conditions for each compound were ultimately optimized for a mixture of an aqueous solution of H2atrc and the metal, without stirring and standing at ambient temperature. The optimized conditions (see Experimental Section for details) were used in the reactions of H2atrc with several metal salts. The use of distinct Zn2+ salts [ZnCl2, Zn(NO3)2·6H2O, ZnSO4·7H2O and Zn(ClO4)·6H2O] with H2atrc at a ratio of 0.1:0.1–0.6 mmol (with a step of 0.1 mmol) resulted always in the isolation of the same complex 1, indicating that this is a governing product under the fixed conditions. A similar phenomena was observed for the Mn2+ complexes, but the optimized reaction conditions are not suitable for the Cu2+, Ni2+ and Co2+, whose products appeared as powders [Cu2+ and Ni2+ series] or solutions [Co2+ series; slow evaporation of the solution did not result in suitable crystals], ultimately indicating that the metal centers play a decisive role in the formation of the final compounds.
While the slow evaporation process allowed the preparation of mononuclear ([Zn(Hatrc)2(H2O)] (1) and [Mn(Hatrc)2(H2O)2]·2H2O (2)) and dinuclear ([Fe2(Hatrc)4(OH)2]·6H2O (3)) complexes, the diffusion process and hydrothermal reaction conducted to the formation of 1D ([Cd(Hatrc)2(H2O)]n (4)) and 2D ([Mn(atrc)(H2O)]n·nH2O (5)) coordination networks.

2.2. Mononuclear Complexes

Complex 1, [Zn(Hatrc)2(H2O)], crystallizes in the orthorhombic space group Pbcn with a crystallographic C2 rotation axis located along the Zn1–O1W bond. The metal center coordinates to one water molecule to two symmetry related Hatrc− moieties, having a distorted trigonal bipyramidal coordination geometry whose triangular equatorial plane is formed by O1W, N14 and N14a (symmetry operation: a = 1−x, y, 1.5−z), while the axial positions are occupied by O12 and O12a atoms (Figure 1). The metal center is ideally located in the triangular plane with no deviation from the best least-squares plane fitted by the three coordinated atoms. The {ZnN2O3} trigonal bipyramid displays τ = (β − α)/60 = 0.6255, where α and β are the two largest angles found in the metal coordination center (Please note: τ = 0 for an ideal square pyramid, and τ = 1 for an ideal trigonal bipyramid) [48]. The Hatrc− residue adopts a typical N,O-bidentate chelating mode (Scheme 1, type I) with the Zn–O and Zn–N found within the expected ranges (Table 1). Considering compounds 1, 2 and the isotypical [Cd(Hatrc)2(H2O)2]·2H2O [34], the distances between the metal centers and the atoms in the first coordination sphere follow the tendency of the ionic radius Zn2+ < Mn2+ < Cd2+. Conversely, the O–M–N bite angles subtended by the Hatrc− residue follow, as expected, the opposite tendency (Table 1).
Molecules 20 12341 g011 550
Scheme 1. Coordination modes of Hatrc− (type I and II) and atrc2− (type III) anionic residues found in compounds 1–5.
Scheme 1. Coordination modes of Hatrc− (type I and II) and atrc2− (type III) anionic residues found in compounds 1–5.
Molecules 20 12341 g011
Molecules 20 12341 g001 550
Figure 1. Schematic representation of the mononuclear complex [Zn(Hatrc)2(H2O)] present in compound 1, showing the labelling scheme for all non-H atoms composing the asu and those forming the metal coordination sphere. Non-H atoms of the asu are drawn as thermal ellipsoids at the 30% probability level and the remaining atoms as spheres with arbitrary radius. For selected bond lengths and angles see Table 1. Symmetry transformation: a = 1−x, y, 1.5−z.
Figure 1. Schematic representation of the mononuclear complex [Zn(Hatrc)2(H2O)] present in compound 1, showing the labelling scheme for all non-H atoms composing the asu and those forming the metal coordination sphere. Non-H atoms of the asu are drawn as thermal ellipsoids at the 30% probability level and the remaining atoms as spheres with arbitrary radius. For selected bond lengths and angles see Table 1. Symmetry transformation: a = 1−x, y, 1.5−z.
Molecules 20 12341 g001
Adjacent [Zn(Hatrc)2(H2O)] complexes interact via strong hydrogen bonds leading to the formation of a 2D supramolecular structure (layers) extended in the ab plane of the unit cell (Figure 2a). The intermolecular hydrogen bonds involved in the formation of these layers are of the type O1W–H1WA···O11 and O1W–H1WA···O12 (yellow dashed lines in Figure 2a; Table 2). Neighboring layers pack close along the [001] direction and are interconnected into a 3D supramolecular architecture network via the N11–H11A···O11 interaction (orange dashed lines in Figure 2b; Table 2). Furthermore, the distance between the centroid of triazole ring and N11 is 3.510(3) Ǻ, pointing to the existence of a weak N11–H11A···π stacking interaction in the crystal structure (not shown), which also contributes for the stabilization of the 3D supramolecular architecture.
Table
Table 1. Selected bond lengths (Å) and angles (°) for the metal coordination centers of mononuclear complexes [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2) and, for comparison, [Cd(Hatrc)2(H2O)2]·2H2O [34].
Table 1. Selected bond lengths (Å) and angles (°) for the metal coordination centers of mononuclear complexes [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2) and, for comparison, [Cd(Hatrc)2(H2O)2]·2H2O [34].
1 2Ref [34]
Zn1–O1W1.975(5)Mn1–O1W2.206(2)Cd1–O32.384(2)
Zn1–N141.981(3)Mn1–N142.239(3)Cd1–N12.255(3)
Zn1–O122.171(3)Mn1–O12.186(2)Cd1–O12.345(2)
N14–Zn1–O1279.57(12)O1–Mn1–N1476.23(8)O1–Cd1–N173.14(5)
O12–Zn1–O12 a168.94(17)O1–Mn1–O1 b180.0
O1W–Zn1–O1295.53(9)O1–Mn1–O1W87.38(8)
N14–Zn1–N14 a131.5(2)N14–Mn1–N14 b180.0
O1W–Zn1–N14114.25(11)O1W–Mn1–N1490.44(8)
O1–Mn1–N14 b103.77(8)
O1–Mn1–O1W b92.62(8)
O1W–Mn1–N14 b89.56(9)
O1W–Mn1–O1W b180.0
Symmetry transformations used to generate equivalent atoms: (a) 1−x, y, 1.5−z; (b) 1−x, 1−y, 1−z.
Table
Table 2. Hydrogen-bonding geometrical details for the interactions present in the crystal structures of [Zn(Hatrc)2(H2O)] (1) and [Mn(Hatrc)2(H2O)2]·2H2O (2).
Table 2. Hydrogen-bonding geometrical details for the interactions present in the crystal structures of [Zn(Hatrc)2(H2O)] (1) and [Mn(Hatrc)2(H2O)2]·2H2O (2).
D–H···AD···A/Å<DHA/°
1N11–H11A···O11 c2.749(4)171
N1–H1A···O12 a3.191(5)141
N1–H1A···O1W d3.322(4)144
N1–H1A···N12 c2.964(5)167
O1W–H1WA···O11 e2.781(3)158
O1W–H1WA···O12 e3.031(3)131
2N11–H11A···O2W f2.820(3)142
N12–H12A···O2W g2.957(5)116
N1–H1A···O1W h2.957(4)173
N1–H1B···O2W f3.115(4)142
N1–H1B···O2W h3.141(4)128
O1W–H1WA···O1 i2.689(3)160
O1W–H1WB···O2 j2.639(3)162
O2W–H2WB···O2 j2.757(3)175
O2W–H2WA···N12 k2.959(3)152
Symmetry transformations: (a) 1−x, y, 1.5−z; (c) −0.5+x, 0.5−y, 2−z; (d) −0.5+x, −0.5+y, 1.5−z; (e) −0.5+x, 0.5+y, 1.5−z; (f) −x, 1−y, −z; (g) x, −1+y, z; (h) −1+x, y, z; (i) 2−x, 1−y, 1−z; (j) x, 1+y, z; (k) 1−x, 1−y, −z.
Molecules 20 12341 g002 550
Figure 2. Ball-and-stick representation of (a) the 2D hydrogen-bonded network and (b) 3D hydrogen-bonded supramolecular network (layers with alternating colors) in the crystal structure of compound 1. Hydrogen bonds are represented as yellow (those forming the 2D network) and orange (inter-layer connections) dashed lines. Geometric details on the represented interactions are listed in Table 2.
Figure 2. Ball-and-stick representation of (a) the 2D hydrogen-bonded network and (b) 3D hydrogen-bonded supramolecular network (layers with alternating colors) in the crystal structure of compound 1. Hydrogen bonds are represented as yellow (those forming the 2D network) and orange (inter-layer connections) dashed lines. Geometric details on the represented interactions are listed in Table 2.
Molecules 20 12341 g002
Compound 2, [Mn(Hatrc)2(H2O)2]·2H2O features a mononuclear complex (Figure 3) with the asu being composed of one metal center (Mn1), one Hatrc− anionic ligand and one coordinated water molecule. An additional uncoordinated water molecule of crystallization is, however, present. The metal center has a distorted octahedron geometry, with the equatorial plane formed by O1, N14 and their symmetrical counterparts (O1b and N14b, symmetry transformation: b: 1−x, 1−y, 1−z); O1W and O1Wb occupy the axial positions (Figure 3 and Table 1). The coordination fashion of the ligand is of type I, as that observed in compound 1. Bond-valence-sum (BVS) calculations gives a value of 2.02 for Mn1, indicating that Mn1 has the +2 oxidation state (command Calc Coord in PLATON [49]). This compound is isotypical to the already described compound [Cd(Hatrc)2(H2O)2]·2H2O [34].
Molecules 20 12341 g003 550
Figure 3. Mononuclear anionic complex [Mn(Hatrc)2(H2O)2] found in 2 showing the labelling scheme for all non-H atoms composing the asu and the metallic coordination environment. Crystallographically independent non-H atoms are represented as thermal ellipsoids drawn at the 50% probability level. Symmetry-related atoms are represented as spheres with arbitrary radius. For selected bond lengths and angles see Table 1. Symmetry operation: b = 1−x, 1−y, 1−z.
Figure 3. Mononuclear anionic complex [Mn(Hatrc)2(H2O)2] found in 2 showing the labelling scheme for all non-H atoms composing the asu and the metallic coordination environment. Crystallographically independent non-H atoms are represented as thermal ellipsoids drawn at the 50% probability level. Symmetry-related atoms are represented as spheres with arbitrary radius. For selected bond lengths and angles see Table 1. Symmetry operation: b = 1−x, 1−y, 1−z.
Molecules 20 12341 g003
Individual [Mn(Hatrc)2(H2O)2] complexes present in compound 2 are interconnected through strong hydrogen bonds of type N–H···O1W involving the coordinated water molecules and adjacent Hatrc− residues into 1D chains running parallel to the a-direction of the unit cell (Figure 4a), forming a graph set motif of the type R22(12) [50]. Chains further grow into supramolecular layers by way of the lattice water molecules O2W, which act as bridges between adjacent chains: O2W–H2WB···O2, O2W–H2WA···N12 and N11–H11A···O2W (Figure 4b and Table 3). Layers pack along the b-axis of the unit cell mediated by hydrogen bonds, ultimately originating the extended 3D supramolecular structure in 2 (Figure 4c).
Molecules 20 12341 g004 550
Figure 4. Ball-and-stick representation of (a) the 1D hydrogen-bonded chain; (b) the 2D layer and (c) the 3D supramolecular network (layers alternating between original and green color) present in compound 2. Hydrogen bonds are represented by dashed light-green lines. For details on the represented interactions see Table 2.
Figure 4. Ball-and-stick representation of (a) the 1D hydrogen-bonded chain; (b) the 2D layer and (c) the 3D supramolecular network (layers alternating between original and green color) present in compound 2. Hydrogen bonds are represented by dashed light-green lines. For details on the represented interactions see Table 2.
Molecules 20 12341 g004
Table
Table 3. Selected bond lengths (Å) and angles (°) of the binuclear complex [Fe2(Hatrc)4(OH)2] present in compound 3, and of the coordination networks [Cd(Hatrc)2(H2O)]n (4) and [Mn(atrc)(H2O)]n·nH2O (5).
Table 3. Selected bond lengths (Å) and angles (°) of the binuclear complex [Fe2(Hatrc)4(OH)2] present in compound 3, and of the coordination networks [Cd(Hatrc)2(H2O)]n (4) and [Mn(atrc)(H2O)]n·nH2O (5).
3 4 5
Fe1–O51.949(2)Cd1–N242.239(5)Mn1–N12 n2.192(2)
Fe1–O5 l1.979(2)Cd1–N142.299(5)Mn1–O1W2.194(2)
Fe1–O42.030(2)Cd1–O32.344(5)Mn1–O12.2179(19)
Fe1–O12.041(3)Cd1–O4 m2.397(4)Mn1–O2 o2.2531(19)
Fe1–N142.096(3)Cd1–O1W2.407(5)Mn1–N11 o2.255(2)
Fe1–N242.113(3)Cd1–O22.434(4)Mn1–N142.299(2)
Cd1–O3 m2.593(4)
O5–Fe1–O5 l76.37(10)N24–Cd1–N14125.39(19)N12 n–Mn1–O1W88.23(8)
O5–Fe1–O4165.65(10)N24–Cd1–O373.44(17)N12 n–Mn1–O1100.41(8)
O5–Fe1–O192.88(10)N24–Cd1–O4 m140.30(17)N12 n–Mn1–O2 o168.57(8)
O5–Fe1–N1497.93(10)N24–Cd1–O1W88.15(19)N12 n–Mn1–N11 o97.87(8)
O5–Fe1–N2497.79(10)N24–Cd1–O287.70(17)N12 n–Mn1–N1494.18(8)
O5 l–Fe1–O490.56(10)N24–Cd1–O3 m87.73(17)O1W–Mn1–O194.82(7)
O5 l–Fe1–O1164.41(10)N14–Cd1–O388.21(18)O1W–Mn1–O2 o83.68(7)
O5 l–Fe1–N1492.25(11)N14–Cd1–O4 m85.21(17)O1W–Mn1–N11 o98.93(8)
O5 l–Fe1–N2495.89(11)N14–Cd1–O1W137.85(19)O1W–Mn1–N14170.92(9)
O4–Fe1–O1101.08(10)N14–Cd1–O270.68(17)O1–Mn1–O2 o88.34(7)
O4–Fe1–N1488.36(10)N14–Cd1–O3 m127.60(17)O1–Mn1–N11 o157.40(8)
O4–Fe1–N2477.40(10)O3–Cd1–O4 m138.78(15)O1–Mn1–N1476.15(8)
O1–Fe1–N1477.89(11)O3–Cd1–O1W77.05(17)O2 o–Mn1–N11 o75.53(8)
O1–Fe1–N2496.75(11)O3–Cd1–O2135.96(16)O2 o–Mn1–N1495.06(8)
N14–Fe1–N24163.63(11)O3–Cd1–O3 m143.57(3)N11 o–Mn1–N1489.42(8)
O4 m–Cd1–O1W80.97(16)
O4 m–Cd1–O279.08(15)
O4 m–Cd1–O3 m52.60(14)
O1W–Cd1–O2143.05(16)
O1W–Cd1–O3 m71.32(16)
O2–Cd1–O3 m71.83(15)
Symmetry transformations used to generate equivalent atoms: (l) x, 0.5−y, 0.5−z; (m) 1.5−x, 0.5+y, 0.5−z; (n) −x, 0.5+y, 0.5−z; (o) x, 0.5−y, z−0.5.

2.3. Binuclear Complex

Compound 3, [Fe2(Hatrc)4(OH)2]·6H2O, is composed by a discrete neutral binuclear unit (Figure 5). The asu is composed of one independent Fe3+ center, two anionic Hatrc− ligands, one μ2-bridging OH− anion and three lattice water molecules. Besides the presence of the aforementioned anions, the charge of the metallic center is supported by Bond Valence Sum (BVS) calculations, which produces a value for the ferric atom of ca. 3.01, thereby indicating that iron center is indeed in the +3 oxidation state [49]. The six-coordinated Fe1 center displays a distorted octahedral coordination geometry with the apical positions being occupied by N14 and N24 from two coordinated triazole moieties. The carboxylic oxygen atoms O2 and O4 from two distinct carboxylate groups plus O5 and O5l from two crystallographic equivalent hydroxyl moieties shape the equatorial plane of the octahedron (symmetry transformation to generate equivalent atoms: l = x, 0.5−y, 0.5−z). The resulting binuclear [Fe2(Hatrc)4(OH)2] complex is thus formed due two μ2-OH− bridging anions, with the Fe1–O5 distances being 1.954(2) and 1.985(3) Ǻ, well within the expected values for Fe–O distances in the Fe–OH–Fe moiety [1.936–2.085 Å, CSD version 5.36, updated in November 2014, 17 observations], and imposing an internuclear Fe1···Fe1l separation of 3.087(1) Ǻ (Figure 5 and Table 3 for geometric details on selected bond lengths and angles). It is noteworthy that the coordination mode of Hatrc− found in 3 is identical to that described for compounds 1 and 2.
Molecules 20 12341 g005 550
Figure 5. Representation of the binuclear complex [Fe2(Hatrc)4(OH)2] present in compound 3, showing the labelling scheme for all non-H atoms composing the asu and the Fe1 coordination environment. Non-H atoms of the asu are represented as thermal ellipsoids (70% probability level) and the remaining atoms as spheres with arbitrary radii. For selected bond lengths and angles see Table 3. Symmetry operation: l = x, 0.5−y, 0.5−z.
Figure 5. Representation of the binuclear complex [Fe2(Hatrc)4(OH)2] present in compound 3, showing the labelling scheme for all non-H atoms composing the asu and the Fe1 coordination environment. Non-H atoms of the asu are represented as thermal ellipsoids (70% probability level) and the remaining atoms as spheres with arbitrary radii. For selected bond lengths and angles see Table 3. Symmetry operation: l = x, 0.5−y, 0.5−z.
Molecules 20 12341 g005
Supramolecular interactions are of two main types: those involving solely individual Fe3+ complexes and those that interconnect complexes with lattice water molecules. Neighboring [Fe2(Hatrc)4(OH)2] complexes are interconnected through strong hydrogen bonds of the type N–H···O into 1D supramolecular chains that run parallel to the c-direction of the unit cell. 2D supramolecular layers placed in the bc plane of the unit cell are formed by hydrogen bonds of type N1–H1B···O2 (Figure 6a,b; Table 4 for geometrical details on the hydrogen bonds). Adjacent layers are fused into a 3D supramolecular architecture by ways of several strong N–H···O, O–H···N and O–H···O interactions (Figure 6c and Table 4).
Table
Table 4. Geometrical details on the hydrogen bonds present in compound [Fe2(Hatrc)4(OH)2]·6H2O (3).
Table 4. Geometrical details on the hydrogen bonds present in compound [Fe2(Hatrc)4(OH)2]·6H2O (3).
D–H···AD···A/Å<DHA/°D–H···AD···A/Å<DHA/°
N11–H11A···O2W2.746(4)171O1W–H1WA···O3Wu2.847(4)174
N1–H1A···O3W p2.905(4)151O1W–H1WB···N22t2.914(4)179
N1–H1B···O2 q3.023(4)173O2W–H2WA···O1Wv2.678(4)154
N21–H21A···O2W r2.903(4)135O2W–H2WB···O2 q2.842(4)145
N21–H21A···O1 s2.866(4)128O3W–H3WA···O42.719(3)166
N2–H2A···O3 t2.914(4)163O3W–3WB···N12 k2.830(4)175
N2–H2B···O1W2.872(4)154O5–H5A···O3 t2.829(3)159
Symmetry transformations used to generate equivalent atoms: (k) 1−x, 1−y, −z; (p) x, 0.5−y, −0.5−z; (q) 1−x, y−0.5, z−0.5; (r) 0.5+x y, −z; (s) 1.5−x, 1−y, z; (t) x, y, 1+z; (u) 1.5−x, 1−y, 1+z; (v) 0.5−x, 0.5−y, 0.5−z.
Molecules 20 12341 g006 550
Figure 6. Ball-and-stick representation of the 2D hydrogen-bonded layer present in compound 3 viewed along the (a) [001] and (b) [100] directions of the unit cell (1D supramolecular chains represented in alternate colors); (c) Perspective view of the 3D supramolecular framework (layers alternate between colors) present in the crystal structure of 3. Dashed yellow lines represent the hydrogen bonds. Geometric details on these supramolecular interactions are summarized in Table 4.
Figure 6. Ball-and-stick representation of the 2D hydrogen-bonded layer present in compound 3 viewed along the (a) [001] and (b) [100] directions of the unit cell (1D supramolecular chains represented in alternate colors); (c) Perspective view of the 3D supramolecular framework (layers alternate between colors) present in the crystal structure of 3. Dashed yellow lines represent the hydrogen bonds. Geometric details on these supramolecular interactions are summarized in Table 4.
Molecules 20 12341 g006

2.4. One-Dimensional Chain (1D)

Compound 4, [Cd(Hatrc)2(H2O)]n, crystallizes in monoclinic space group P21/n with one Cd2+ cation, two Hatrc− ligands and one coordinated water composing the asu, which features the building unit of a 1D coordination chain (Figure 7). The Cd1 center coordinates to three Hatrc− anionic ligands and one water molecule (Figure 7a), displaying a coordination geometry which resembles a relatively rare seven-coordinated capped trigonal prism: the atom groups N14, O2, O4 and N24, O3 and O1W build the two opposite triangular facets, and another symmetrical O3 is the capping atom located at the rectangular facet fitted by O2, O4, N24 and O1W (selected bond distances and angles are in given in Table 3). Although seven-coordinated Cd2+ centers are not so numerous as those of four or six-coordinated, a search in the CCDC [33] gives up to 700 related hits. Limiting the search to 1,2,4-triazole residues only, 33 examples of seven-coordinated cadmium(II) are known: three of them are single-capped octahedra [48,51,52,53] while the remaining ones are pentagonal bipyramids. The two crystallographically distinct Hatrc− ligands in compound 4 adopt two different coordination fashions: one is a η2-type (type I in Scheme 1) and the other is η4-type (type II in Scheme 1). The first coordination mode is the same as those observed in compounds 1–3, chelating to the metal center by one carboxylate O-atom and the 4-positioned N-atom of the triazole ring to form a five-membered ring. The η4-type Hatrc− ligand adopts both the N,O-bidente chelating mode described previously, and O,O-bidente-chelating mode to bind two adjacent Cd2+ centers: two O-atoms of the carboxylate group chelate to one metal center to form a four-membered ring. As a consequence of the aforementioned linkages of the η4-Hatrc− ligand, the neighboring Cd1 centers are interconnected into wave-like 1D [Cd(Hatrc)]n chains running parallel to the b-direction of the unit cell and comprising two kinds of five and four-membered rings. The η2-Hatrc− ligands connect Cd1 centers on both sides of the chain. This, alongside with the coordinated water molecules, ultimately form the 1D coordination polymer (chain) [Cd(Hatrc)2(H2O)]n (Figure 7b).
Molecules 20 12341 g007a 550Molecules 20 12341 g007b 550
Figure 7. Schematic representation of the (a) Cd2+ coordination environment present in compound [Cd(Hatrc)2(H2O)]n (4) showing the labeling scheme for all non-hydrogen atoms composing the asu and the Cd1 coordination environment. Non-H atoms of the asu are represented as thermal ellipsoids drawn at the 70% probability level and the remaining atoms as spheres with arbitrary radii; (b) 1D coordination chain present in compound 4. For selected bond lengths (in Å) and angles (in degrees) see Table 3. Symmetry operation: m = 1.5−x, y+0.5, 0.5−z.
Figure 7. Schematic representation of the (a) Cd2+ coordination environment present in compound [Cd(Hatrc)2(H2O)]n (4) showing the labeling scheme for all non-hydrogen atoms composing the asu and the Cd1 coordination environment. Non-H atoms of the asu are represented as thermal ellipsoids drawn at the 70% probability level and the remaining atoms as spheres with arbitrary radii; (b) 1D coordination chain present in compound 4. For selected bond lengths (in Å) and angles (in degrees) see Table 3. Symmetry operation: m = 1.5−x, y+0.5, 0.5−z.
Molecules 20 12341 g007aMolecules 20 12341 g007b
Neighboring chains interact trough cooperative N–H···O hydrogen bonds, in particular interactions of the type N11–H11A···O4, N2–H2A···O1W and N21–H21A···O1, leading to the formation of 2D supramolecular layers as depicted in Figure 8a (see Table 5 for geometrical details on the existent hydrogen bonds). Additionally, these supramolecular layers are interconnected to other adjacent ones via strong N–H···O and O–H···O interactions forming a 3D supramolecular architecture (Figure 8b and Table 5).
Table
Table 5. Geometrical details on the hydrogen bonds present in the supramolecular networks [Cd(Hatrc)2(H2O)]n (4) and [Mn(atrc)(H2O)]n·nH2O (5).
Table 5. Geometrical details on the hydrogen bonds present in the supramolecular networks [Cd(Hatrc)2(H2O)]n (4) and [Mn(atrc)(H2O)]n·nH2O (5).
D–H···AD···A/Å<DHA/° D–H···AD···A/Å<DHA/°
4N11–H11A···O4 w2.769(7)1695N1–H1A···O A2.966(3)156
N1–H1A···O1W x3.200(8)162N1–H1B···O1W f3.224(3)151
N1–H1B···N22 w3.211(8)153O1W–H1WA···O2 b2.748(3)161
N21–H21A···O1 y2.684(6)164O1W–H1WB···O2W B2.714(3)152
N2–H2A···O1W m3.064(8)155O2W–H2WB···N12.872(3)160
N2–H2B···N12 y3.037(8)158O2W–H2WA···N14 C3.186(3)138
O1W–H1WB···O1 z2.747(7)165O2W–H2WA···N12 D3.183(3)129
O1W–H1WA···O2 x2.698(7)158O2W–H2WA···N11 D3.159 (3)121
Symmetry transformations used to generate equivalent atoms: (b) 1−x, 1−y, 1−z; (f) −x, 1−y, −z; (m) 1.5−x, 0.5+y, 0.5−z; (w) 0.5+x, −0.5−y, z−0.5; (x) 1.5−x, −0.5+y, 0.5−z; (y) 0.5+x, 0.5−y, 0.5+z; (z) 0.5+x, 0.5−y, 0.5+z; (A) −1+x, 0.5−y, −0.5+z; (B) 1+x, 0.5−y, 0.5−z; (C) x, 0.5−y, z−0.5; (D) −x, −y, −z.
Molecules 20 12341 g008 550
Figure 8. Ball-and-stick representation of the (a) 2D hydrogen-bonded network formed between adjacent 1D coordination chains (represented with alternating colors) and the (b) 3D hydrogen-bonded supramolecular network viewed in perspective along the [010] direction of the unit cell (layers represented with alternating colors) present in compound 4. Hydrogen bonds are represented as dashed yellow lines. Geometric details on these interactions are summarized in Table 5.
Figure 8. Ball-and-stick representation of the (a) 2D hydrogen-bonded network formed between adjacent 1D coordination chains (represented with alternating colors) and the (b) 3D hydrogen-bonded supramolecular network viewed in perspective along the [010] direction of the unit cell (layers represented with alternating colors) present in compound 4. Hydrogen bonds are represented as dashed yellow lines. Geometric details on these interactions are summarized in Table 5.
Molecules 20 12341 g008

2.5. Coordination Layer (2D)

The structure of compound 5, as unveiled from single-crystal XRD analysis, was formulated as [Mn(atrc)(H2O)]·H2O, featuring a 2D coordination layered structure. The asu comprises one Mn2+ center, one fully deprotonated atrc2− anionic ligand, one coordinated and one lattice water molecule. The Mn1 metal center is coordinated by three crystallographic equivalent atrc2− and one water molecule, leading to a six-coordinated coordination environment with a geometry that resembles a distorted octahedron: N14, N12n, O2o and O1W atoms form the equatorial plane, and O1 and N11o occupy the two axial positions (Figure 9; for details concerning bond lengths and angles see Table 3; symmetry operations: n = −x, 0.5+y, 0.5−z and o = x, 0.5−y, −0.5+z). BVS calculations gave a charge of +2.02 for Mn center suggesting that the oxidation state of Mn1 should be +2, in good agreement with the charge assignment from the crystal structure determination.
Molecules 20 12341 g009 550
Figure 9. Mixed ellipsoid and ball-and-stick representation of the Mn2+ coordination environment present in compound [Mn(atrc)(H2O)]·H2O (5), showing the labeling scheme for all non-H atoms composing the asu and the first metal coordination sphere. Non-H atoms of the asu are represented as thermal ellipsoids drawn at the 90% probability level and the remaining atoms as spheres with arbitrary radius. For selected bond lengths and angles see Table 3. Symmetry operations: n = −x, 0.5+y, 0.5−z; o = x, 0.5−y, −0.5+z.
Figure 9. Mixed ellipsoid and ball-and-stick representation of the Mn2+ coordination environment present in compound [Mn(atrc)(H2O)]·H2O (5), showing the labeling scheme for all non-H atoms composing the asu and the first metal coordination sphere. Non-H atoms of the asu are represented as thermal ellipsoids drawn at the 90% probability level and the remaining atoms as spheres with arbitrary radius. For selected bond lengths and angles see Table 3. Symmetry operations: n = −x, 0.5+y, 0.5−z; o = x, 0.5−y, −0.5+z.
Molecules 20 12341 g009
Each atrc2− residue in 5 connects to three Mn2+ metal centers through two N,O-bidentate interactions (chelating two metal cations through N11/O2 and N14/O1) and one monodentate-N mode to bind the fourth Mn2+ by N12 (Scheme 1, type III). As a consequence of these coordination modes, a 2D coordination framework (layer) based on the interconnection of [Mn8(atrc)8] macro rings is ultimately (Figure 10a). The 2D layers pack along the [100] direction of the unit cell being mediated by numerous strong O–H···O, O–H···N and N–H···O hydrogen-bonding interaction leading to the formation of a 3D supramolecular architecture (Figure 10b).
The coordination fashions of the organic ligand (Scheme 1) can be related with the structural features and dimensionality of the reported complexes. In mild conditions, H2atrc tends to firstly deprotonate the hydrogen atom of the carboxylic acid group. The resulting anionic Hatrc− ligand chelates one metal center using the 4-positioned N-atom and one O-atom of the carboxylate group to form a rather stable five-membered chelate ring (type I in Scheme 1), as observed in compounds 1–3. The coordination fashion of Hatrc− in compound 4 (type II in Scheme 1) has one more chelating carboxylate group than type I. Usually, a more complex coordination fashion tends to promote more complicated structures. With the use of a higher synthetic temperature and the presence of a strong base (NaN3 or NaOH), the hydrogen atom on the 1-positioned N is liberated, thereby giving rise to a bidentate-chelating-N,O and one monodentate-N coordination donor (type III) contributing to the construction of a higher dimensional network.
Molecules 20 12341 g010 550
Figure 10. Ball-and-stick representation of (a) the 2D coordination layer and (b) 3D hydrogen-bonded network viewed along the [001] direction of the unit cell of compound 5 (layers represented with alternating colors). Hydrogen bonds are represented as dashed light-green lines. Geometric details on the represented supramolecular interactions are listed in Table 5.
Figure 10. Ball-and-stick representation of (a) the 2D coordination layer and (b) 3D hydrogen-bonded network viewed along the [001] direction of the unit cell of compound 5 (layers represented with alternating colors). Hydrogen bonds are represented as dashed light-green lines. Geometric details on the represented supramolecular interactions are listed in Table 5.
Molecules 20 12341 g010

3. Experimental Section

3.1. Materials and Methods

Most of the reagents and solvents were used directly as supplied commercially without further purification: 3-amino-1H-1,2,4-triazole-5-carboxylic acid (98%, Sigma-Aldrich, St-Louis, MO, USA, 4,4′-bipyridine hydrate (Sigma-Aldrich, , 98%), ZnSO4·6H2O (99.5%+, Merck, Kenilworth, NJ, USA), MnCl2·4H2O (Sigma-Aldrich, 99.0%+), Mn(OAc)2·4H2O (Sigma-Aldrich, 99.0%+), CdBr2·4H2O (98.0%, Sigma-Aldrich), Fe(NO3)3·9H2O (99.0%+, Merck), NaN3 (99.0%+, Sigma-Aldrich). Microcrystalline materials of Mn(ClO4)2·6H2O and Cd(ClO4)2·6H2O were isolated by freezing a reaction solution of HClO4 with excess of MnCO3 or CdCO3, respectively. (Caution: handling of perchlorate in solution or in the dry state should be performed in very small amounts and very carefully because these complexes are explosive in contact with organic or other readily oxidizable substances).

3.2. Synthesis

[Zn(Hatrc)2(H2O)] (1). H2atrc (4.992 mmol, 0.6394 g) was dissolved in 500 mL of hot water, cooled to ambient temperature and then mixed with a 5 mL ZnSO4·7H2O (5.019 mmol, 1.4404 g) aqueous solution without stirring. Single crystals suitable for X-ray diffraction were obtained from the standing solution over a period of two weeks. FT-IR (KBr): 3435 (νOH), 3327 (νN–H(···O)), 3220 (νN–H(···O), νNH2), 3121 (νNH2), 2940 (νNH, νCH), 2792 1656 (νO–H(···N)), 1599 (νC=O), 1535 (νC=N), 1477 1306 (νC–O), 1120 (δCH, νrg), 1063 820 (γO–H(···N)), 763 727 (γO–H, ρCH), 642 (γrg, νCN), 491 (ωNH2), 399 (δC–O) cm−1. FT-Raman: 3435 (νN–H(···O)), 3285 (νN–H(···O), νNH2), 3220 (νNH2), 3142, 1656 (νC=O), 1535, 1499, 1456, 1434 (δNH, νrg), 1378 (νC–O), 1299 (δCH, νrg), 1106 (γCNH, γrg, νCN (ring)), 1070 (νC–O, νC–C), 1042 (γO–H(···N)), 813 (γO–H(···N), γCNH, γNH2, ϕrg, ωCN), 756 (γO–H, ρCH), 491 (δC–O), 392 (τNH2), 199 (νM–N, ϕ(out of plane)NH2, γNCN), 149, 120 cm−1.
[Mn(Hatrc)2(H2O)2]·2H2O (2). A similar procedure to that previously described for 1 was employed: 5 mL of a MnCl2·4H2O (5.005 mmol, 0.9904 g) aqueous solution and 500 mL of a H2atrc (5.003 mmol, 0.6408 g) aqueous solution promoted the formation of colorless block single crystals. FT-IR (KBr): 3306 (νN–H(···O)), 3170 (νNH2), 3020 (νNH, νCH), 2784 1685 (νO–H(···N)), 1628 (νC=O), 1556 (νC=N), 1499 1363 (δNH, νrg), 1249 (νC–O), 1113 (δCH, νrg), 1049 (νC–O, νC–C), 820 (γO–H(···N)), 777 699 (γrg, νCN), 627 (ρCOO), 463 (ωNH2), 399 (δC–O) cm−1. FT-Raman: 3177, 3020 (νNH, νCH), 1685 (νC=O), 1553, 1506 (νrg, δCH, δNH), 1420, 1363 (νC–O), 1242 (δCH, νrg), 1113 (γCNH, γrg, νCN (ring)), 1049 (γO–H(···N)), 799 (γO–H(···N), γCNH, γNH2, ϕrg, ωCN), 727 (γrg, νCN), 570 (ωNH2), 463 (δC–O), 399 (τNH2), 227 (νM–N), 192 (νM–N, ϕ(out of plane)NH2, γNCN), 127, 99 cm−1.
[Fe(Hatrc)2(OH)]2·6H2O (3). An identical experimental procedure as that described for 1 was employed: 4.9985 mmol, (2.0194) g of Fe(NO3)3·9H2O (5 mL) with 5.004 mmol, 0.6410 g of H2atrc (500 mL) produced orange block single crystals. FT-IR (KBr): 3392 (νN–H(···O)), 3258 (νN–H(···O), νNH2), 3195 (νNH2), 2941 (νNH, νCH), 2772 1650 (νO–H(···N)), 1551 (νC=N), 1459 1354 (δNH, νrg), 1269 (νC–O), 1013 (δCH, νrg), 909 (νC–O, νC–C), 839 (γO–H(···N)), 754 726 (γO–H, ρCH), 655 (γrg, νCN), 592 (ρCOO), 458 (ωNH2), 402 (δC–O) cm−1. FT-Raman: 3392 (νN–H(···O), νNH2), 3329 (νNH2), 3181, 1643 (νC=O), 1544, 1466, 1410 (δNH, νrg), 1376 (νC–O), 1114 (γCNH, γrg, νCN (ring)), 754 (γO–H, ρCH), 564 (ωNH2), 500 (δC–O), 402 (τNH2), 303 (νM–N), 162, 112 cm−1.
[Cd(Hatrc)2(H2O)]n (4). 5 mL of a mixture of MeOH and H2O (v:v = 1:1) was gently added dropwise onto 9 mL of an aqueous solution containing H2atrc (0.100 mmol, 0.0128 g) and CdBr2·4H2O (0.0999 mmol, 0.0344 g). 8 mL of a MeOH solution of 4,4′-bipyridine (0.0948 mmol, 0.0148 g) was added carefully as a third layer. Colorless block single crystals were obtained on the inner wall of the glass tube after a one week diffusion process. FT-IR (KBr): 3363 (νN–H(···O)), 3235 (νN–H(···O), νNH2), 3142 (νNH2), 2970 (νNH, νCH), 2799 1670 (νO–H(···N)), 1620 (νC=O), 1528 (νC=N), 1477 1370 (δNH, νrg), 1292 (νC–O), 1128 (δCH, νrg), 1070 806 (γO–H(···N)), 756 713 (γO–H, ρCH), 663 (γrg, νCN), 620 (ρCOO), 477 (ωNH2), 413 (δC–O) cm−1. FT-Raman: 3370 (νN–H(···O), νNH2), 3135, 3070 (νNH, νCH), 1606 (νC=N), 1528, 1485, 1434 (δNH, νrg), 1385 (νC–O), 1292 (δCH, νrg), 1235, 1106 (γCNH, γrg, νCN (ring)), 1070 (νC–O, νC–C), 1013 (γO–H(···N)), 856 (γO–H(···N), γCNH, γNH2, ϕrg, ωCN), 763 (γO–H, ρCH), 656 (ρCOO, ), 563 (ωNH2), 484 (δC–O), 406 (τNH2), 270, 220 (νM–N), 199 (νM–N, ϕ(out of plane)NH2, γNCN), 127 cm−1.
[Mn(atrc)(H2O)]n·nH2O (5). Method 1: H2atrc (0.602 mmol, 0.0771 g) was treated with NaOH (0.6 mmol, 0.0240 g) in 15 mL of water with stirring at ambient temperature for 30 min to get a clear colorless solution. This solution was mixed with Mn(ClO4)2·6H2O (0.199 mmol, 0.0722 g) in a 25 mL Teflon-lined stainless-steel reaction vessel. The mixture was heated at 100 °C for 5 days in a furnace and then cooled to obtain colorless crystals of 5. The same product can be obtained from the similar procedure using MnCl2·4H2O or Mn(OAc)2·4H2O instead of Mn(ClO4)·6H2O.
Method 2: H2atrc (0.400 mmol, 0.0512 g) mixed with NaN3 (0.400 mmol, 0.0260 g) in 18 mL of water was stirred at ambient temperature for 30 min to get a clear colorless solution, which was mixed with MnCl2·4H2O (0.205 mmol, 0.0406 g) in a 25 mL Teflon-lined stainless steel reaction vessel. The mixture was heated at 100 °C for 5 days in a furnace and then cooled slowly to ambient temperature to isolate a colorless crystalline material of compound 5. FT-IR (KBr): 3375 (νN–H(···O)), 3240 (νN–H(···O), νNH2), 1620 (νC=O), 1505 (νC=N), 1318 (νC–O), 1106 (δCH, νrg), 849 (γO–H(···N)), 746 656 (γrg, νCN), 489 (ωNH2), 425 (δC–O) cm−1.

3.3. Single Crystal X-ray Diffraction

Single crystals of compounds 1–5 were manually harvested from the crystallization vials and mounted on Hampton Research CryoLoops using FOMBLIN Y perfluoropolyether vacuum oil (LVAC 25/6, purchased from Aldrich) [54] with the help of a Stemi 2000 stereomicroscope equipped with Carl Zeiss lenses. Data were collected with a Bruker X8 Kappa APEX II charge-coupled device (CCD) area-detector diffractometer (Mo-Kα graphite-monochromated radiation, λ = 0.71073 Å) controlled by the APEX2 software package [55], and equipped with an Oxford Cryosystems Series 700 cryostream monitored remotely using Cryopad [56]. Images were processed using SAINT+ [57], and data were corrected for absorption by the multi-scan semi-empirical method implemented in SADABS [58]. The structures of compounds 1–5 were solved by direct methods using SHELXS [59] and refined using SHELXL [60] by full-matrix least-squares technique on F2. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms attached to C atoms were placed at geometrically calculated positions to their carrier atoms and refined with isotropic thermal parameters included in the final stage of the refinement, with Uiso = 1.2 × Ueq of the atoms which they are attached. Hydrogen atoms associated with the water molecules and nitrogen atoms were located in difference Fourier maps. The N–H, O–H and H···H distances were fixed using with Uiso = 1.5 × Ueq of the atoms to which they are attached, plus appropriated DFIX distances (N–H 0.88 Å, O–H 0.95 Å and H···H 1.54 Å). A summary of the structural determination and refinement details for compounds 1–5 is listed in Table 6. The highest peaks and deepest holes found in the structures refinement is listed in Table 7. CCDC 1403898-1403902 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Table
Table 6. Crystal and structure refinement data for compounds 1–5.
Table 6. Crystal and structure refinement data for compounds 1–5.
12345
Empirical formulaC6H8N8O5ZnC6H14MnN8O8C12H26Fe2N16O16C6H8CdN8O5C3H6MnN4O4
Color and HabitColorless PlateColorless blockOrange blockColorless blockColorless block
Crystal Size (mm3)0.42 × 0.21 × 0.070.08 × 0.04 × 0.030.07 × 0.02 × 0.020.07 × 0.03 × 0.040.12 × 0.11 × 0.05
Crystal systemOrthorhombicTriclinicOrthorhombicMonoclinicMonoclinic
Space groupPbcnPīPnnaP21/nP21/c
a (Ǻ)9.537(3)5.2482(9)27.111(6)8.9893(13)8.1472(6)
b Ǻ6.865(2)6.5330(11)12.697(3)8.9785(13)9.9846(7)
c (Ǻ)17.120(5)10.6128(18)7.7352(17)13.9642(16)9.3679(6)
α (°)9090.532(10)909090
β (°)90102.774(11)90108.117(5)113.994(4)
γ (°)90109.139(10)909090
V (Ǻ3)1120.8(6)333.93(10)2662.6(11)1071.2(3)696.20(8)
Z42444
Dc (Mg m−3)2.0001.8961.9012.3852.071
μ (mm−1)2.2321.0521.1972.0811.877
F (000)6801951560752436
θ (°)3.66 to 26.374.01 to 29.463.41 to 25.353.07 to 25.022.74 to 26.37
Data completeness
Reflections measured8019507412255137937382
Independent reflections1146 (Rint = 0.0331)1055 (Rint = 0.0411)2418 (Rint = 0.0652)1878 (Rint = 0.0512)1418(Rint = 0.1497)
Final R1, wR2 [I > 2σ(I)]0.0393, 0.08670.0514, 0.08280.0436, 0.08070.0432, 0.11280.0388, 0.0896
R1, wR2 (all data)0.0568, 0.09440.0603, 0.08570.087, 0.09250.0481, 0.11500.0474, 0.0935
Δρmax/min (eǺ−3)0.389, −0.5550.384, −0.4870.364, −0.4330.729, −0.9740.555, −0.569
R1 = (Σ||Fo| − |Fc || /Σ |Fo|). wR2 = [Σ (w(Fo2 − Fc2)2)/Σ (w |Fo2|2)]1/2.
Table
Table 7. Highest peaks and deepest holes for structure refinement data for compounds 1–5.
Table 7. Highest peaks and deepest holes for structure refinement data for compounds 1–5.
Δρmax/(eǺ−3)Distance/ǺfromΔρmin/(eǺ−3)Distance/Ǻfrom
10.3890.85O1W−0.5550.70Zn1
20.3841.17Mn1−0.4870.61Mn1
30.3640.52N24−0.4330.64Fe1
40.7290.63O3−0.9741.29H1A
50.5550.90Mn1−0.5690.96Mn1

4. Conclusions

Employing 3-amino-1H-1,2,4-triazole-5-carboxylic acid as the organic ligand yielded the first series of five compounds, namely mononuclear [Zn(Hatrc)2(H2O)] (1), [Mn(Hatrc)2(H2O)2]·2H2O (2)], binuclear [Fe2(Hatrc)4(OH)2]·6H2O (3), 1D zigzag chain [Cd(Hatrc)2(H2O)]n (4), and 2D layer [Mn(atrc)(H2O)]n·nH2O (5). All compounds were isolated as single crystals.
In this series, (H)atrc ligands adopt three types of connection fashions: in 1–3, they chelate preferentially with the metal centers via the carboxylic O atom and the 4-position N atom to form a five-membered ring; in 4, with one more metal center chelated by two carboxylic O atoms, the discrete units can shape a polymeric 1D chain; in 5, based on the fashion in 4, two more metal centers are bound through, on the one hand, a similar five-membered ring being formed by the 2-positioned N atom and the second carboxylic O atom and, on the other, the fourth metal being connected to the 1-positioned N atom. The various coordination fashions play, in this respect, a significant role in the structural fabrication of the various compounds. The residual uncoordinated donor sites in the anionic ligands in compounds 1–4 open the possibility to use compounds 1–4 as precursors of building blocks to further isolate multidimensional frameworks. With the rich existence of donors and acceptors in the present structures, the hydrogen-bonding interactions with the various water molecules incorporated into the materials play key roles in the supramolecular organization leading to the formation of 3D supramolecular architectures.

Supplementary Materials

Supplementary materials can be accessed at: https://www.mdpi.com/1420-3049/20/07/12341/s1.

Acknowledgments

Fundação para a Ciência e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER through Programa Operacional Factores de Competitividade (COMPETE), CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013) and REQUIMTE/LAQV (Ref. FCT UID/QUI/50006/2013) financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement.
We wish to thank FCT for funding the R & D projects FCOMP-01-0124-FEDER-041282 (Ref. FCT EXPL/CTM-NAN/0013/2013) and FCOMP-01–0124-FEDER-041445 (Ref. FCT EXPL/QEQ-QUI/0199/2013) and CICECO for specific funding towards the purchase of the single-crystal diffractometer. FCT is also gratefully acknowledged for the Post-Doctoral research grants Nos. SFRH/BPD/63736/2009 and SFRH/BPD/47566/2008 (to J.A.F. and B.L., respectively).

Author Contributions

B.L. and L.C.-S. designed and carried out the synthesis and preliminary characterization of the compounds. J.A.F. and F.A.A.P. carried out the crystallographic studies. J.P.C.T. was responsible for the analysis and discussion of the characterization of the organic linker supervising B.L in this task. All authors actively contributed to the writing up of the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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  • Sample Availability: Samples of the compounds are not available from the authors.

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MDPI and ACS Style

Liu, B.; Fernandes, J.A.; Tomé, J.P.C.; Paz, F.A.A.; Cunha-Silva, L. Multidimensional Transition Metal Complexes Based on 3-Amino-1H-1,2,4-triazole-5-carboxylic Acid: From Discrete Mononuclear Complexes to Layered Materials. Molecules 2015, 20, 12341-12363. https://doi.org/10.3390/molecules200712341

AMA Style

Liu B, Fernandes JA, Tomé JPC, Paz FAA, Cunha-Silva L. Multidimensional Transition Metal Complexes Based on 3-Amino-1H-1,2,4-triazole-5-carboxylic Acid: From Discrete Mononuclear Complexes to Layered Materials. Molecules. 2015; 20(7):12341-12363. https://doi.org/10.3390/molecules200712341

Chicago/Turabian Style

Liu, Bing, José A. Fernandes, João P. C. Tomé, Filipe A. Almeida Paz, and Luís Cunha-Silva. 2015. "Multidimensional Transition Metal Complexes Based on 3-Amino-1H-1,2,4-triazole-5-carboxylic Acid: From Discrete Mononuclear Complexes to Layered Materials" Molecules 20, no. 7: 12341-12363. https://doi.org/10.3390/molecules200712341

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