Literature DB >> 29850042

A new cadmium coordination polymer based on 4-amino-4H-1,2,4-triazole.

Maha Said1, Habib Boughzala1.   

Abstract

A new cadmium coordination polymer, poly[bis-(4-amino-4H-1,2,4-triazolium) [bis-(μ2-4-amino-4H-1,2,4-triazole-κ2N1:N2)tetra-μ2-chlorido-tetra-chlorido-tri-cad-mium(II)] dihydrate], {(C2H5N4)2[Cd3Cl8(C2H4N4)2]·2H2O} n , was synthesized by the reaction of 4-amino-4H-1,2,4 triazole with cadmium(II) chloride in aqueous solution. With an unusual architecture, the crystal structure exhibits two distorted octa-hedral coordinations of CdII joined by edge sharing. The first is composed by four chlorine and two N atoms from the triazole ligands. The second is formed by five Cl atoms and by one N atom from the triazole ligand. The charge of the resulting two-dimensional anionic framework is balanced by the organic triazole cations. The lattice water mol-ecules form a network of hydrogen bonding. N-H⋯Cl and π-π stacking inter-actions are also involved in the supra-molecular network stability.

Entities:  

Keywords:  cadmium(II); crystal structure; hybrid coordination polymer; triazole

Year:  2018        PMID: 29850042      PMCID: PMC5956325          DOI: 10.1107/S2056989018000464

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

The last decade has seen a large number of investigations of CdII hybrid coordination polymers (HCPs). Indeed, these materials exhibit a wide variety of polymeric frameworks with attractive properties. The coordination sphere of CdII is variable, with coordination numbers ranging from four to eight, corresponding to different geometries (tetra­hedral, square planar, square pyramidal, trigonal bipyramidal, octa­hedral, penta­gonal bipyramidal, bicapped triangular prismatic and dodeca­hedral; Li & Du, 2011 ▸). Many factors should be considered in the self-assembly processes of HCPs, such as the nature of the organic ligands, temperature, pH values, solvents, and so on (Guo et al., 2013 ▸). The choice of the organic ligands is an important factor that greatly influences the structure and stabilization of the coordination architecture formed (Tao et al., 2000 ▸; Choi & Jeon, 2003 ▸). In this regard, organic building units that are based on five-membered N-heterocycles such as 1,2,4 triazole exhibit a strong and typical property of acting as bridging ligands between two metal centres. These bridges can adopt various different geometries, depending on the donor atoms of the ligand and the properties of the metal (Haasnoot et al., 2000 ▸). The reaction of 4-amino-4H-1,2,4 triazole (NH2trz) with cadmium dichloride leads to the formation of the title two-dimensional coordination polymer.

Structural commentary

The asymmetric unit of the studied compound, completed by the atoms necessary to achieve the coordination around the Cd ions, is represented in Fig. 1 ▸. It comprises one and a half CdII cations [with Cd2 occupying the special position (, , )], one triazole mol­ecule (NH2trz), one triazolium cation (NH2trzH)+, four chloride anions and one lattice water mol­ecule. Cd1 and Cd2 are bridged by the coordinated triazole mol­ecule (NH2trz) through atoms N1 and N2, and by the two chlorine atoms Cl1 and Cl3.
Figure 1

ORTEP of the asymmetric unit of the studied compound plus the atoms necessary to complete the coordination around the Cd ions. Cd2 is on the special position (, , ). Displacement ellipsoids are drawn at the at the 50% probability level. [Symmetry codes: (i) x,  − y, − + z; (ii) 1 − x, 1 − y, 1 − z.]

Both metals show an octa­hedral coordination geometry. Cd1 is surrounded by the five chloride anions Cl1, Cl2, Cl3, Cl4, Cl2i [symmetry code: (i) x,  − y, z − ] and the nitro­gen N1 of the coordinated triazole ring (NH2trz). On the other hand, Cd2 is bonded to four equatorial chloride anions (Cl1, Cl3, Cl1ii and Cl3ii) and two axial nitro­gen atoms, N2 and N2ii, belonging to the coordinated triazole (NH2trz) and to its symmetry-related analogue, respectively [symmetry code: (ii) 1 − x, 1 − y, 1 − z). As a result of the bridge formed by atoms N1 and N2 of the triazole ligand, the Cd1⋯Cd2 distance is 3.6145 (7) Å. Selected geometrical parameters are summarized in Table 1 ▸, showing that the octa­hedron around Cd1 is more distorted than the one around Cd2.
Table 1

Selected geometric parameters (Å, °)

Cd1—N12.365 (4)Cd1—Cl12.6769 (14)
Cd1—Cl42.5120 (14)Cd2—N22.393 (5)
Cd1—Cl22.6148 (13)Cd2—Cl32.5874 (16)
Cd1—Cl32.6418 (14)Cd2—Cl12.6332 (14)
Cd1—Cl2i 2.6754 (13)  
    
N1—Cd1—Cl4174.37 (11)Cl3—Cd1—Cl184.86 (4)
Cl2—Cd1—Cl1174.60 (4)Cl3—Cd2—Cl186.85 (5)

Symmetry code: (i) .

When symmetry is applied, a Cd3Cl8(NH2trz)2 building block is formed. These trinuclear units are connected via the chloride ions Cl2 to build up infinite inorganic corrugated sheets in the bc plane, stacked along the a-axis direction (Fig. 2 ▸). The triazolium cations (NH2trzH)+ and the water mol­ecules are located in the inter­layer space (Fig. 3 ▸), inter­acting with the anionic framework by hydrogen bonds. Thus, the overall three-dimensional network consists of alternate organic–inorganic hybrid layers, responsible for the inter­esting behaviour of this class of materials.
Figure 2

Crystal packing showing the two-dimensional anionic framework of the title compound.

Figure 3

Corrugated anionic sheets with the non-coordinating triazolium cations and water mol­ecules located in the inter­layer space. Displacement ellipsoids are drawn at the 50% probability level.

Supra­molecular features

The crystal structure of the title compound is mainly stabilized by hydrogen-bonding and π–π stacking inter­actions. In particular, a number of O—H⋯Cl, O—H⋯N, N—H⋯O and N —H⋯Cl hydrogen bonds is present (Table 2 ▸), involving the lattice water mol­ecules, the triazolium cations, the organic ligands and the chlorine anions. These hydrogen bonds connect the organic and inorganic moieties, leading to a self-organized, hydrated hybrid structure.
Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A D—HH⋯A DA D—H⋯A
O1W ii—HW2ii⋯Cl10.86 (6)2.68 (7)3.239 (6)124 (6)
N4iii—H4B iii⋯Cl31.00 (8)2.60 (7)3.399 (5)136 (5)
N8iv—H8A iv⋯Cl20.852.643.370 (5)144
O1W ii—HW1ii⋯Cl40.86 (7)2.67 (8)3.319 (6)134 (8)
N8—H8B⋯Cl40.902.533.423 (5)172
N5v—H5v⋯O1W 0.75 (8)1.97 (8)2.649 (8)151 (8)
O1W—HW2⋯N4vi 0.86 (6)2.44 (6)3.247 (9)157 (6)

Symmetry codes: (ii) ; (iii) ; (iv) ; (v) ; (vi) .

The chloride anions around Cd1 and Cd2 form hydrogen bonds both with the amine H atoms of the (NH2trz) ligands and with the H atoms of the water mol­ecules (Figs. 4 ▸ and 5 ▸; Table 2 ▸): Cl1⋯HW2ii—O1W ii, Cl3⋯H4B iii—N4iii, Cl4⋯HW1ii—O1W ii, Cl4⋯H8B-N8, and Cl2⋯H8A iv—N8iv [symmetry codes: (iii) 1 − x,  + y,  − z; (iv) x, y, 1 + z].
Figure 4

Hydrogen bonds (red dashed lines) involving the chloride anions around Cd1. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry codes: (i) x,  − y, − + z; (ii) 1 − x, 1 − y, 1 − z; (iii) 1 − x,  + y,  − z; (iv) x, y, 1 + z; (vi) x,  − y,  + z.]

Figure 5

Hydrogen bonds (red dashed lines) involving the chloride anions around Cd2. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry codes: (i) x,  − y, − + z; (ii) 1 − x, 1 − y, 1 − z; (iii) 1 − x,  + y,  − z.]

Besides forming hydrogen bonds with the chloride anions Cl1 and Cl4, the water mol­ecules also inter­act with the triazole ligands and with the lattice triazolium cations, acting as acceptor and donor, respectively (Fig. 6 ▸ and Table 2 ▸): O1W⋯H5v–N5v and N4vi⋯HW2—O1W [symmetry codes: (v) x − 1,  − y,  + z; (vi) x,  − y, z + ].
Figure 6

The hydrogen-bonding inter­actions around a single water mol­ecule involving the chlorine atoms, the (NH2trz) ligand and the (NH2trzH)+ cation. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry codes: (ii) 1 − x, 1 − y, 1 − z; (v) −1 + x,  − y,  + z; (vi) x,  − y,  + z.]

Finally, the coordinated triazole rings (NH2trz) are connected along the c-axis direction through π–π stacking inter­actions, with a centroid–centroid distance of 3.761 (7) Å.

Database survey

Recently, a great deal of attention has been paid to the rational design and synthesis of new hybrid coordination polymers (HCPs) composed of metal ions and bridging ligands due to their fascinating structural diversity and their potential application as functional materials (Xiong et al., 2001 ▸; Liao et al., 2004 ▸; Gao et al., 2008 ▸). These coordination polymers exhibit a wide range of infinite zero- to three-dimensional frameworks with inter­esting structural features, which result from coordination bonding, hydrogen-bonding and aromatic π–π stacking inter­actions as well as van der Waals forces (Su et al., 2003 ▸). A search of the latest version of the Cambridge Structural Database (Version 5.38; Groom et al., 2016 ▸) based on the organic fragment ‘4-amino-4H-1,2,4-triazole’ of the studied compound yielded 70 hits. The structure of the chloro-cadmate PEPWIR (Zhai et al., 2006 ▸) is probably the nearest to that of the title compound, even if it lacks the water mol­ecules of crystallization and the protonated triazole cations. This is probably due to the difference in the stoichiometry of the initial reagents and to the solvent used in the chemical synthesis. Two other related compounds comprising 4-amino-4H-1,2,4-triazole in combination with chloride ligands are the coordination polymer ROFJED (Wang et al., 2014 ▸) and the discrete complex GAVFEP (Xuan-Wen, 2005 ▸).

Synthesis and crystallization

The compound was prepared by the reaction of 4-amino-4H-1,2,4 triazole and CdCl2·H2O (molar ratio 1:1) in an equal volume of water and ethanol (10 ml) mixed with 2 ml of hydro­chloric acid (37%). The solution was stirred for 1 h. Colourless crystals suitable for X-ray diffraction were grown in two weeks by slow evaporation at room temperature.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. Atoms H1, H2 and H3 were placed in calculated positions and refined using a riding model: C—H = 0.93 Å with U iso(H) = 1.2U eq(C). The other hydrogen atoms were found in the difference-Fourier map. The coordinates of H8A, H8B and H4A of the amine terminal groups were kept fixed, with U so(H)= 0.05.
Table 3

Experimental details

Crystal data
Chemical formula(C2H5N4)2[Cd3Cl8(C2H4N4)2]·2H2O
M r 995.21
Crystal system, space groupMonoclinic, P21/c
Temperature (K)298
a, b, c (Å)12.685 (3), 15.498 (3), 7.375 (2)
β (°)97.12 (3)
V3)1438.6 (6)
Z 2
Radiation typeMo Kα
μ (mm−1)2.98
Crystal size (mm)0.71 × 0.21 × 0.21
 
Data collection
DiffractometerEnraf–Nonius CAD-4
Absorption correctionψ scan (North et al., 1968)
T min, T max 0.799, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections3670, 3136, 2654
R int 0.032
(sin θ/λ)max−1)0.638
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.040, 0.123, 1.06
No. of reflections3136
No. of parameters190
No. of restraints5
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)1.58, −1.99

Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994 ▸), XCAD4 (Harms & Wocadlo, 1995 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸), DIAMOND (Brandenburg, 2006 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989018000464/xi2006sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989018000464/xi2006Isup2.hkl CCDC reference: 1810807 Additional supporting information: crystallographic information; 3D view; checkCIF report
(C2H5N4)2[Cd3Cl8(C2H4N4)2]·2H2OF(000) = 956
Mr = 995.21Dx = 2.298 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 12.685 (3) ÅCell parameters from 25 reflections
b = 15.498 (3) Åθ = 10–15°
c = 7.375 (2) ŵ = 2.98 mm1
β = 97.12 (3)°T = 298 K
V = 1438.6 (6) Å3Prism, colourless
Z = 20.71 × 0.21 × 0.21 mm
Enraf–Nonius CAD-4 diffractometerRint = 0.032
Radiation source: Enraf Nonius FR590θmax = 27.0°, θmin = 2.1°
non–profiled ω/2τ scansh = −16→16
Absorption correction: ψ scan (North et al., 1968)k = −19→1
Tmin = 0.799, Tmax = 1.000l = −9→1
3670 measured reflections2 standard reflections every 120 min
3136 independent reflections intensity decay: 8%
2654 reflections with I > 2σ(I)
Refinement on F2Hydrogen site location: mixed
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.040w = 1/[σ2(Fo2) + (0.0848P)2 + 1.0345P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.123(Δ/σ)max = 0.001
S = 1.06Δρmax = 1.58 e Å3
3136 reflectionsΔρmin = −1.99 e Å3
190 parametersExtinction correction: SHELXL2014 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
5 restraintsExtinction coefficient: 0.0041 (7)
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.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.
xyzUiso*/Ueq
Cd10.72922 (3)0.36225 (2)0.60671 (4)0.02384 (16)
Cd20.50000.50000.50000.02726 (18)
Cl10.65520 (10)0.45547 (8)0.31268 (16)0.0291 (3)
Cl20.78296 (10)0.26723 (9)0.89644 (16)0.0307 (3)
Cl30.63396 (12)0.47886 (9)0.79095 (17)0.0379 (3)
Cl40.91217 (11)0.42626 (9)0.6250 (2)0.0369 (3)
N10.5591 (3)0.2978 (3)0.5599 (6)0.0271 (9)
N20.4709 (4)0.3474 (3)0.5015 (6)0.0300 (9)
N30.4303 (4)0.2130 (3)0.4573 (6)0.0284 (9)
N40.3704 (5)0.1390 (3)0.3952 (8)0.0427 (12)
N51.0964 (5)0.2603 (4)0.1439 (8)0.0406 (11)
N61.1503 (5)0.3284 (4)0.0808 (9)0.0552 (15)
N70.9940 (4)0.3688 (3)0.1463 (6)0.0341 (10)
N80.9074 (4)0.4233 (3)0.1599 (6)0.0388 (11)
C10.5314 (4)0.2172 (3)0.5326 (7)0.0301 (10)
H10.57550.16990.56130.036*
C20.3953 (4)0.2949 (4)0.4392 (8)0.0326 (11)
H20.32730.31140.38950.039*
C31.0035 (5)0.2844 (4)0.1816 (8)0.0371 (12)
H30.95280.24930.22530.044*
C41.0865 (6)0.3931 (4)0.0848 (11)0.0481 (16)
O1W0.1792 (5)0.3900 (4)0.5653 (10)0.0663 (15)
H41.103 (5)0.450 (4)0.066 (9)0.038 (17)*
H51.127 (6)0.219 (5)0.158 (11)0.05 (2)*
H8A0.85240.40020.10150.050*
H8B0.91530.42710.28270.050*
H4A0.42980.09770.36120.050*
H4B0.350 (6)0.120 (4)0.516 (11)0.045 (19)*
HW20.237 (4)0.396 (5)0.638 (9)0.07 (3)*
HW10.142 (6)0.435 (4)0.580 (14)0.11 (4)*
U11U22U33U12U13U23
Cd10.0255 (2)0.0249 (2)0.0204 (2)0.00043 (12)0.00023 (14)0.00166 (12)
Cd20.0335 (3)0.0216 (3)0.0261 (3)0.00527 (19)0.0016 (2)0.00027 (18)
Cl10.0363 (6)0.0285 (6)0.0229 (5)0.0036 (5)0.0046 (5)0.0044 (4)
Cl20.0347 (6)0.0341 (7)0.0227 (6)−0.0022 (5)0.0013 (5)0.0100 (5)
Cl30.0507 (8)0.0372 (7)0.0235 (6)0.0143 (6)−0.0041 (5)−0.0085 (5)
Cl40.0327 (7)0.0366 (7)0.0410 (7)−0.0101 (5)0.0027 (5)−0.0007 (6)
N10.026 (2)0.026 (2)0.029 (2)0.0019 (16)0.0020 (16)0.0019 (16)
N20.032 (2)0.029 (2)0.028 (2)0.0029 (18)0.0022 (17)−0.0003 (17)
N30.040 (2)0.025 (2)0.022 (2)−0.0059 (18)0.0095 (17)−0.0032 (15)
N40.054 (3)0.034 (3)0.042 (3)−0.020 (2)0.011 (2)−0.009 (2)
N50.046 (3)0.034 (3)0.041 (3)−0.001 (2)0.003 (2)0.000 (2)
N60.054 (3)0.047 (3)0.071 (4)0.002 (3)0.031 (3)0.005 (3)
N70.035 (2)0.043 (3)0.025 (2)−0.0025 (19)0.0072 (18)−0.0042 (18)
N80.044 (3)0.034 (2)0.040 (3)−0.002 (2)0.009 (2)−0.006 (2)
C10.034 (3)0.025 (2)0.031 (3)0.003 (2)0.002 (2)0.002 (2)
C20.030 (3)0.034 (3)0.034 (3)−0.001 (2)0.003 (2)−0.001 (2)
C30.042 (3)0.037 (3)0.031 (3)−0.007 (2)0.001 (2)0.007 (2)
C40.051 (4)0.037 (3)0.061 (4)−0.007 (3)0.023 (3)0.000 (3)
O1W0.057 (3)0.043 (3)0.095 (5)−0.011 (3)−0.002 (3)−0.002 (3)
Cd1—N12.365 (4)N4—H4A1.0400
Cd1—Cl42.5120 (14)N4—H4B1.01 (8)
Cd1—Cl22.6148 (13)N5—C31.299 (9)
Cd1—Cl32.6418 (14)N5—N61.369 (8)
Cd1—Cl2i2.6754 (13)N5—H50.75 (8)
Cd1—Cl12.6769 (14)N6—C41.292 (9)
Cd2—N2ii2.393 (5)N7—C31.336 (7)
Cd2—N22.393 (5)N7—C41.362 (8)
Cd2—Cl32.5874 (16)N7—N81.399 (7)
Cd2—Cl3ii2.5875 (16)N8—H8A0.850
Cd2—Cl12.6332 (14)N8—H8B0.900
Cd2—Cl1ii2.6333 (14)C1—H10.9300
N1—C11.306 (7)C2—H20.9300
N1—N21.382 (6)C3—H30.9300
N2—C21.297 (7)C4—H40.92 (6)
N3—C11.335 (7)O1W—HW20.862 (10)
N3—C21.346 (7)O1W—HW10.857 (10)
N3—N41.419 (6)
N1—Cd1—Cl4174.37 (11)N1—N2—Cd2115.6 (3)
Cl4—Cd1—Cl3100.40 (5)C1—N3—C2106.4 (4)
Cl2—Cd1—Cl393.13 (5)C1—N3—N4128.4 (5)
N1—Cd1—Cl2i83.80 (11)C2—N3—N4125.0 (5)
Cl4—Cd1—Cl2i91.57 (5)N3—N4—H4A102.00
Cl2—Cd1—Cl2i89.53 (3)N3—N4—H4B98 (4)
N1—Cd1—Cl183.54 (11)H4A—N4—H4B108.00
Cl4—Cd1—Cl193.40 (5)C3—N5—N6110.8 (5)
Cl2—Cd1—Cl1174.60 (4)C3—N5—H5133 (6)
Cl3—Cd1—Cl184.86 (4)N6—N5—H5116 (6)
Cl2i—Cd1—Cl191.39 (4)C4—N6—N5104.5 (6)
N2ii—Cd2—Cl392.46 (11)C3—N7—C4106.0 (5)
N2—Cd2—Cl387.54 (12)C3—N7—N8129.0 (5)
N2ii—Cd2—Cl3ii87.54 (11)C4—N7—N8125.0 (5)
N2—Cd2—Cl3ii92.46 (12)N7—N8—H8A108.00
N2ii—Cd2—Cl197.50 (11)N7—N8—H8B97.00
N2—Cd2—Cl182.50 (11)H8A—N8—H8B121.00
Cl3—Cd2—Cl186.85 (5)N1—C1—N3109.7 (5)
Cl3ii—Cd2—Cl193.15 (5)N1—C1—H1125.2
N2ii—Cd2—Cl1ii82.50 (11)N3—C1—H1125.2
N2—Cd2—Cl1ii97.50 (11)N2—C2—N3109.7 (5)
Cl3—Cd2—Cl1ii93.15 (5)N2—C2—H2125.1
Cl3ii—Cd2—Cl1ii86.85 (5)N3—C2—H2125.1
Cd2—Cl1—Cd185.79 (4)N5—C3—N7107.6 (5)
Cd1—Cl2—Cd1iii146.79 (5)N5—C3—H3126.2
Cd2—Cl3—Cd187.44 (4)N7—C3—H3126.2
C1—N1—N2107.0 (4)N6—C4—N7111.1 (6)
C1—N1—Cd1130.5 (3)N6—C4—H4126 (4)
N2—N1—Cd1120.0 (3)N7—C4—H4122 (4)
C2—N2—N1107.2 (4)HW2—O1W—HW1106 (3)
C2—N2—Cd2136.6 (4)
D—H···AD—HH···AD···AD—H···A
O1Wii—HW2ii···Cl10.86 (6)2.68 (7)3.239 (6)124 (6)
N4iv—H4Biv···Cl31.00 (8)2.60 (7)3.399 (5)136 (5)
N8v—H8Av···Cl20.852.643.370 (5)144
O1Wii—HW1ii···Cl40.86 (7)2.67 (8)3.319 (6)134 (8)
N8—H8B···Cl40.902.533.423 (5)172
N5vi—H5vi···O1W0.75 (8)1.97 (8)2.649 (8)151 (8)
O1W—HW2···N4iii0.86 (6)2.44 (6)3.247 (9)157 (6)
  5 in total

1.  Enantioseparation of Racemic Organic Molecules by a Zeolite Analogue This work was supported by The Major State Basic Research Development Program (Grant No. G2000077500), the National Natural Science Foundation of China, the Camille Dreyfus Teacher-Scholar Program, the National Science Foundation of the USA (CHE-9904338), and the University of Tennessee SARIF EPPE Fund.

Authors:  Ren-Gen Xiong; Xiao-Zeng You; Brendan F. Abrahams; Ziling Xue; Chi-Ming Che
Journal:  Angew Chem Int Ed Engl       Date:  2001-12-03       Impact factor: 15.336

2.  Formation of dinuclear, macrocyclic, and chain structures from HgI(2) and a semirigid benzimidazole-based bridging ligand: an example of ring-opening supramolecular isomerism.

Authors:  Cheng-Yong Su; Andrea M Goforth; Mark D Smith; Hans-Conrad zur Loye
Journal:  Inorg Chem       Date:  2003-09-08       Impact factor: 5.165

3.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

4.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

5.  The Cambridge Structural Database.

Authors:  Colin R Groom; Ian J Bruno; Matthew P Lightfoot; Suzanna C Ward
Journal:  Acta Crystallogr B Struct Sci Cryst Eng Mater       Date:  2016-04-01
  5 in total

北京卡尤迪生物科技股份有限公司 © 2022-2023.