Supplementary Materials: a Cadmium Anionic 1-d Coordination Polymer {[cd(h2o)6][cd2(atr)2(µ2-btc)2(h2o)4] 2h2o}n within a 3-d Supramolecular Charge-assisted Hydrogen-bonded and Π -stacking Network

Figure S1. Colorless crystals of 1-D {[Cd(H2O)6][Cd2(atr)2(µ2-btc)2(H2O)4] 2H2O}n 1. Figure S2. IR spectra (ATR) for comparison between the compound 1 and mixed ligands of atr and H3btc.

Crystals 2016, 6,23 which was not hydrothermally stable under the synthesis conditions of 125 °C in water, so that the hydrolysis product 4-amino-1,2,4-triazole (atr) was incorporated instead (Scheme 1).Scheme 1. Triazole ligands relevant in this work and indication of the hydrolysis of btr to atr.
Comparison between the FT-IR spectra (attenuated total reflection, ATR) of the crystalline product and the mixture of atr and H3btc ligands (Figure S2, Supplementary Information) shows significant differences in the fingerprint region which suggests that the ligands became coordinated to the metal ion.Multiple weak broad peaks between 3300 and 3100 cm -1 can be assigned to the O-H/N-H stretching vibrations of aqua ligands and the amino group of the atr ligand [26].The absence of a peak at ca 1715 cm −1 indicates the full deprotonation of the H3btc ligand.Additionally, the asymmetric and symmetric stretching vibrations of the carboxylate group [27,28] are observed at 1607 cm −1 , 1204 cm −1 , and 1527 cm −1 , 1110 cm −1 , which reveal different binding modes of the carboxylate group.Bands at 752 cm −1 and 731 cm −1 in the fingerprint region are due to 1,3,5-trisubstituted benzene [27].Furthermore, a band at 612 cm −1 can be assigned to the vibrational mode of the triazole ring of the atr ligand [29].
The sample was dissolved in DMSO-d6 via heating in an ultrasonic bath at 50 °C.For the NMR analysis of the crystalline product an excess NaCN was added to the sample in order to bind the Cd 2+ ions as stable cyanido complexes and to free the ligands so that a ligand ratio can be determined.After centrifugation, the pipette-separated supernatant was measured.The 1 H NMR spectrum (Figure S3, Supplementary Information) then shows both atr and btc ligand signals.The signal of the two protons of the triazole ring in the atr ligand appears at 9.17 ppm and the signal for the (protonated) amino group is observed at 6.30 ppm.The signal at 8.36 is assigned to the three protons of the btc benzene ring.Signals for residual Et3N appeared at ~0.89-0.92 and ~2.37-2.42ppm.The integration ratio between atr: btc and NH3 + is 1.0:1.7:1.7 which agrees with two H-atoms for the triazole ring, three H-atoms of btc (1:1.5) and three H-atoms for the protonated amino group (1:1.5).
The title compound crystallizes in the monoclinic crystal system with the P21/c space group.The crystallographic asymmetric unit (Figure 1a) consists of a Cd(II) ion with benzene-tricarboxylate (btc 3-), 4-amino-1,2,4-triazole (atr), and two aqua ligands, plus a half-occupied cationic hexaaquacadmium(II) complex and a lattice water molecule.The original precursor compound 4,4'-bis(1,2,4-triazol-4-yl) (btr) is not incorporated as a ligand into the structure due to the in situ hydrolysis into 4-amino-1,2,4-triazole (atr), which was then found instead.Yet, the slow delivery of atr in the course of the reaction is apparently crucial for the product formation.When the reaction was carried out with atr directly instead of btr no crystals or precipitate formed.The charge-neutral product formula is 1-D {[Cd(H2O)6][Cd2(atr)2(µ2-btc)2(H2O)4] 2H2O}n, 1, named Scheme 1. Triazole ligands relevant in this work and indication of the hydrolysis of btr to atr.
Comparison between the FT-IR spectra (attenuated total reflection, ATR) of the crystalline product and the mixture of atr and H 3 btc ligands (Figure S2, Supplementary Information) shows significant differences in the fingerprint region which suggests that the ligands became coordinated to the metal ion.Multiple weak broad peaks between 3300 and 3100 cm ´1 can be assigned to the O-H/N-H stretching vibrations of aqua ligands and the amino group of the atr ligand [26].The absence of a peak at ca 1715 cm ´1 indicates the full deprotonation of the H 3 btc ligand.Additionally, the asymmetric and symmetric stretching vibrations of the carboxylate group [27,28] are observed at 1607 cm ´1, 1204 cm ´1, and 1527 cm ´1, 1110 cm ´1, which reveal different binding modes of the carboxylate group.Bands at 752 cm ´1 and 731 cm ´1 in the fingerprint region are due to 1,3,5-trisubstituted benzene [27].Furthermore, a band at 612 cm ´1 can be assigned to the vibrational mode of the triazole ring of the atr ligand [29].
The sample was dissolved in DMSO-d 6 via heating in an ultrasonic bath at 50 ˝C.For the NMR analysis of the crystalline product an excess NaCN was added to the sample in order to bind the Cd 2+ ions as stable cyanido complexes and to free the ligands so that a ligand ratio can be determined.After centrifugation, the pipette-separated supernatant was measured.The 1 H NMR spectrum (Figure S3, Supplementary Information) then shows both atr and btc ligand signals.The signal of the two protons of the triazole ring in the atr ligand appears at 9.17 ppm and the signal for the (protonated) amino group is observed at 6.30 ppm.The signal at 8.36 is assigned to the three protons of the btc benzene ring.Signals for residual Et 3 N appeared at ~0.89-0.92 and ~2.37-2.42ppm.The integration ratio between atr: btc and NH 3 + is 1.0:1.7:1.7 which agrees with two H-atoms for the triazole ring, three H-atoms of btc (1:1.5) and three H-atoms for the protonated amino group (1:1.5).
The title compound crystallizes in the monoclinic crystal system with the P2 1 /c space group.The crystallographic asymmetric unit (Figure 1a) consists of a Cd(II) ion with benzene-tricarboxylate (btc 3´) , 4-amino-1,2,4-triazole (atr), and two aqua ligands, plus a half-occupied cationic hexaaquacadmium(II) complex and a lattice water molecule.The original precursor compound 4,4 1 -bis(1,2,4-triazol-4-yl) (btr) is not incorporated as a ligand into the structure due to the in situ hydrolysis into 4-amino-1,2,4-triazole (atr), which was then found instead.Yet, the slow delivery of atr in the course of the reaction is apparently crucial for the product formation.When the reaction was carried out with atr directly instead of btr no crystals or precipitate formed.The Cd1 ion forms a coordination polymeric chain with benzene-tricarboxylate (btc 3-), 4-amino-1,2,4-triazole (atr), and two aqua ligands.The Cd1 atom is seven-fold coordinated in a distorted pentagonal-bipyramidal fashion by a triazole nitrogen atom of atr and six oxygen atoms; two of them belong to axial aqua ligands.The other four O-atoms come from the carboxylate groups of two fully deprotonated btc 3-ligands, which coordinate in a bidentate chelating mode.The O-atoms of btc 3-and the N-atom of atr form the equatorial plane of the pentagonal bipyramid.One of these chelated Cd-O bonds is slightly longer (Cd1-O6 = 2.766(5) Å) than the range of the other Cd-O bonds (Cd1-O =   The Cd1 ion forms a coordination polymeric chain with benzene-tricarboxylate (btc 3´) , 4-amino-1,2,4-triazole (atr), and two aqua ligands.The Cd1 atom is seven-fold coordinated in a distorted pentagonal-bipyramidal fashion by a triazole nitrogen atom of atr and six oxygen atoms; two of them belong to axial aqua ligands.The other four O-atoms come from the carboxylate groups of two fully deprotonated btc 3´l igands, which coordinate in a bidentate chelating mode.The O-atoms of btc 3´a nd the N-atom of atr form the equatorial plane of the pentagonal bipyramid.One of these chelated Cd-O bonds is slightly longer (Cd1-O6 = 2.766(5) Å) than the range of the other Cd-O bonds (Cd1-O = 2.258(5)-2.412(5)Å).The atr ligand coordinates to Cd1 through the imine N1-atom of the triazole ring as a terminal ligand; the other imine N atom (N2) and the amino group remain without Cd coordination but engage in hydrogen bonding (see below).The tri-anionic btc 3´l igands coordinate as bridges between two Cd1 atoms to form the one-dimensional mixed-ligand chain (Figure 1b); the third carboxylate group remains uncoordinated but is part of the hydrogen-bonding network.This chain is a polyanion and has the formula of [ ] 2+ sits on an inversion center as a special position (Figure 1a).Hexa-coordinated cadmium can have a coordination environment in-between octahedral and trigonal prismatic [30,31].
The infinite anionic chains are stacked parallel to each other along the c direction (Figure 1b) through significant π-π interactions [36] between the adjacent benzene rings of the btc 3´l igands and the adjacent triazole rings of the atr ligands, respectively (Figure 2a).Strong π-stacking interactions have rather short centroid-centroid contacts (<3.8 Å) and near parallel ring planes which translate into a sizable overlap of the aryl-plane areas.The centroid-centroid distance of adjacent btc-benzene rings is 3.726(4) Å and for neighboring triazole rings it is 3.598(4) and 3.997(4) Å (Figure 2a).The interplanar angle of the benzene rings is 4 ˝; the triazole rings are exactly parallel by symmetry; (see Supplementary Information for further details, Scheme S1 and Table S1).In addition to π-stacking the inter-chain packing is controlled by charge-assisted amino-N-H¨¨¨p ´qO 2 C-hydrogen bonds (N4-H¨¨¨O1 and O3, Figure 2b and Table 2).The carboxylate groups of btc 3´a s hydrogen bond acceptors carry negative ionic charges.Such charge-assisted H-bonds are usually stronger and shorter than neutral H-bonds [37][38][39][40][41][42].
Together, the π-π interactions between adjacent anionic chains and the hydrogen bonds between cationic complexes and anionic chains and lattice water molecules build a 3-D supramolecular network (Figure 1c).

Materials and Methods
Reagents and solvents were obtained from commercial sources and used without any further purification.The bis(1,2,4-triazol-4-yl) ligand (btr) was synthesized under inert conditions according to previous work [43] from hydrazine monohydrate, N 2 H 4 ¨H2 O, N,N 1 -dimethylformamide azine [44], and p-toluenesulfonic acid monohydrate in dry toluene.A programmable oven type (UFP 400) from Memmert GmbH (Schwabach, Germany) was used for the hydrothermal synthesis.The reactions were carried out in DURAN ® (DURAN Group GmbH, Wertheim, Germany) culture glass tubes with PTFE-faced sealing wad, diameter 12 mm, height 100 mm, and DIN thread 14 GL, closed with a red screw cap (Figure S4, Supplementary Information), suitable for hydro-/solvothermal synthesis for coordination polymer synthesis up to 150 ˝C instead of an autoclave.The contents only come into contact with the glass and polytetrafluoroethylene (PTFE) seal.Elemental analyses were performed on a Vario MicroCube from Elementar GmbH.The light microscopy images were observed with a Leica MS5 binocular eyepiece with transmitted light and polarization filter.The images of isolated crystals were taken with a Nikon COOLPIX 4500 (Tokyo, Japan) digital camera through a special ocular connection.Infrared spectra were recorded with a Bruker Optik TENSOR 37 spectrophotometer (Bruker Optik GmbH, Ettlingen, Germany) using a Diamond ATR (Attenuated Total Reflection) unit from 4000 to 500 cm ´1.The following abbreviations were used to classify spectral bands: br (broad), sh (shoulder), very weak (vw), w (weak), m (medium), s (strong), and vs (very strong).The 1 H-NMR spectra were recorded on a Bruker Advance DRX 500 MHz NMR spectrometer with calibration against the residual protonated solvent signal DMSO-d 6 (2.50   1 -bis(1,2,4-triazol-4-yl) (btr) (16.3 mg, 0.12 mmol) was combined in 1 mL of water in a DURAN glass tube and shaken for about 3 min.Then a solution of benzene-1,3,5-tricarboxylic acid (H 3 btc) (8.4 mg, 0.04 mmol) and Et 3 N/H 2 O (0.75 mL of 0.16 mol/L, 3eq. to H 3 btc) in 2.5 mL of water prepared in an ultrasonic bath at 45-50 ˝C was added to the previous mixture.The sealed glass tube was shaken for about 5 min and then placed in a programmable furnace, heated to 125 ˝C for 3 h and held at that temperature for 48 h, then cooled at a rate of 5 ˝C/h to ambient temperature.The resulting colorless crystals were separated from powdery precipitate and washed with the mother liquor.Yield: (14 mg, 30% based on metal salt).FT-IR (ATR, cm

Single Crystal X-Ray Structure
A suitable single crystal (Figure S1, Supplementary Information) was carefully selected under a polarizing microscope and mounted in oil in a glass loop.Data collection: Bruker AXS APEX II CCD area-detector diffractometer with multilayer mirror monochromator, Mo-Kα radiation (λ = 0.71073 Å) from microsource, double-pass method with ϕand ω-scans; data collection with APEX2, cell refinement and data reduction with SAINT [45], experimental absorption correction with SADABS [46].Structure analysis and refinement: All structures were solved by direct methods using SHELXL2014; refinement was done by full-matrix least squares on F 2 using the SHELX-97 program suite [47].Non-hydrogen atoms were refined with anisotropic displacement parameters.All non-hydrogen positions were found and refined with anisotropic temperature factors.Hydrogen atoms for aromatic CH were positioned geometrically (CH = 0.95 Å) and refined using a riding model (AFIX 43) with U iso (H) = 1.2U eq (C).Hydrogen atoms on aqua ligands and on the amino, NH 2 group were treated in a mixed refinement.On O7 and O8 the H atoms were positioned geometrically (O-H = 0.95 Å, N-H = 0.88 Å) and refined using a riding model (AFIX 93) with U iso (H) = 1.5U eq (O,N).On O9, O10, O11, O12 and N4 the H atoms could be found and refined with U iso (H) = 1.5U eq (O,N) and DFIX constraints (0.95, 0.05) for H9B, O10B, H11B, N4B, and O12A.H12B was found but had to be kept fixed upon further refinement (AFIX 1).The two highest peaks in the electron density map are within 1.52 Å of the Cd1 atom, the next two highest peaks are within 1.5 Å of Cd2.Details of the X-ray crystal data structure determination and refinement are provided in Table 3. Graphics were drawn with DIAMOND (Version 3.2) [48] Analyses on the supramolecular π-π -stacking interactions were done with PLATON for Windows [49].CCDC No. 1451376 contains the supplementary crystallographic data for this paper.These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html.

Figure 1 .
Figure 1.(a) Extended asymmetric unit of 1 (70% thermal ellipsoids, hydrogen atoms with arbitrary radii), showing also part of the hydrogen bonds (orange dashed lines).Symmetry transformations i = x + 1, y, z; ii = -x + 1, −y + 1, −z + 1; iii = x − 1, y, z.Section of the packing diagram of (b) the anionic chains and (c) the full structure with the [Cd(H2O)6] 2+ cations and the crystal water molecules highlighted in space-filling mode.Selected distances and angles are given inTable 1 and details of H-bonds in Table 2.

Figure 1 .
Figure 1.(a) Extended asymmetric unit of 1 (70% thermal ellipsoids, hydrogen atoms with arbitrary radii), showing also part of the hydrogen bonds (orange dashed lines).Symmetry transformations i = x + 1, y, z; ii = -x + 1, ´y + 1, ´z + 1; iii = x ´1, y, z.Section of the packing diagram of (b) the anionic chains and (c) the full structure with the [Cd(H 2 O) 6 ] 2+ cations and the crystal water molecules highlighted in space-filling mode.Selected distances and angles are given inTable 1 and details of H-bonds in Table 2.

Table 1
and details of H-bonds in Table2.

Table 1
and details of H-bonds in Table2.

Table 2 .
Details of the hydrogen bonding interactions in 1 a .

Table 2 .
Details of the hydrogen bonding interactions in 1 a .
Supplementary Materials: