Literature DB >> 25161498

Crystal structure of poly[[(acetato-κO){μ3-N-[(pyridin-4-yl)meth-yl]pyrazine-2-carboxamidato-κ(4) N:N (1),N (2):N (4)]copper(II)] dihydrate]: a metal-organic framework (MOF).

Dilovan S Cati1, Helen Stoeckli-Evans2.   

Abstract

The title compound, [Cu(C11H9N4O)(CH3CO2)]·2H2O (CuL), is a hydrated copper acetate complex of the ligand N-[(pyridin-4-yl)meth-yl]pyrazine-2-carboxamide (HL). Complex CuL has a metal-organic framework (MOF) structure with a 10 (3) network topology. The ligand coordinates in a bidentate and a bis-monodentate manner, bridging three equivalent Cu(II) atoms via the pyridine N atom and the second pyrazine N atom. The Cu(II) atom has a fivefold coordination sphere, CuN4O, being coordinated to three N atoms of the ligand and the acetate O atom in the equatorial plane and to the second pyrazine atom in the apical position. This gives rise to a fairly regular square-pyramidal geometry. In the crystal, the water mol-ecules are linked to each other and to the three-dimensional framework via O-H⋯O hydrogen bonds. There are also a number of C-H⋯O hydrogen bonds present within the framework.

Entities:  

Keywords:  10 (3) network topology; copper(II); crystal structure; metal-organic framework; pyrazine-2-carboxamide

Year:  2014        PMID: 25161498      PMCID: PMC4120597          DOI: 10.1107/S1600536814011520

Source DB:  PubMed          Journal:  Acta Crystallogr Sect E Struct Rep Online        ISSN: 1600-5368


Chemical context

The ligand N-[(pyridin-4-yl)meth­yl]pyrazine-2-carboxamide (HL) is one of a series of ligands which were synthesized in order to study their coordination behaviour towards first-row transition metals (Cati, 2002 ▶; Cati et al., 2004 ▶; Cati & Stoeckli-Evans, 2014 ▶). HL is expected to coordinate in a bidentate and possibly a monodentate manner, with eventual bridging of metal atoms to construct two- or three-dimensional networks. A excellent review on the subject of coordination polymers and network structures has been published by Batten et al. (2009 ▶).

Structural commentary

The title compound, CuL, is a copper acetate complex of the ligand N-[(pyridin-4-yl)meth­yl]pyrazine-2-carboxamide (HL) [Cati & Stoeckli-Evans, 2014 ▶]. In complex CuL the ligand coordinates in a bidentate and a bis-monodentate manner, so bridging three equivalent copper atoms (Fig. 1 ▶). This gives rise to the formation of a three-dimensional coordination polymer, or MOF (metal–organic framework) structure, as shown in Fig. 2 ▶. The coppercopper distances are 7.156 (2) Å via the bridging pyrazine ring (Cu1Cu1iii) and 7.420 (2) Å via the pyridine N atom Cu1Cu1iv; see Fig. 1 ▶). Atom Cu1 has a fivefold coordination sphere, CuN4O, with three N atoms (N1, N3 and N4i) and the acetate O atom, O2, in the equatorial plane and the second pyrazine N atom, N2ii, in the apical position [Fig. 2 ▶; symmetry codes: (i) x, −y, z − ; (ii) x − , −y + , z − ]. The apical Cu1—N2 bond distance of 2.393 (3) Å is considerably longer that the Cu1–N1, Cu1—N3 and Cu1—N4 bond lengths [2.003 (8), 1.964 (9) and 1.993 (7) Å, respectively], and the Cu1O2 bond length [1.947 (7) Å] in the equatorial plane. Bond angles O2Cu1—N3 and N4—Cu1—N1 are 172.2 (3) and 170.6 (3)°, respectively, and this leads to a perfect square-pyramidal geometry with τ = 0.03 (τ = 0 square-pyramidal; τ = 1 trigonal-bipyramidal; Addison et al., 1984 ▶). The pyridine ring is inclined to the pyrazine ring by 79.6 (5)° compared to 84.33 (12)° in the free ligand (Cati & Stoeckli-Evans, 2014 ▶). The bond distances and angles are normal when compared with geometrical parameters of related copper(II) complexes in the Cambridge Structural Database (Version 5.35, last update November 2013; Allen, 2002 ▶), and are similar to those observed in the mononuclear copper(II) acetate complex of the analogous ligand N-[(pyridin-2-yl)methyl]pyrazine-2-carboxamide (Moh­a­­madou et al., 2012 ▶). The title compound crystallizes with two solvent water mol­ecules per asymmetric unit.
Figure 1

A view of the asymmetric unit of complex CuL, with atom labelling [symmetry codes: (i) x, −y, z − ; (ii) x − , −y + , z − ; (iii) x + , −y + , z + ; (iv) x, −y, z + ]. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2

A view along the a axis of the metal–organic framework (MOF) structure of complex CuL. Solvent water mol­ecules and H atoms have been omitted for clarity.

Supra­molecular features

The three-dimensional network of the title MOF structure has a 10 (3) network topology (Fig. 3 ▶). It is one of the most commonly encountered 3-connected three-dimensional nets with ten-membered rings (Wells, 1984 ▶). It is a cubic (10,3)-a net, also known as the srs (SrSi2) net, which is chiral [note that the Flack x parameter = −0.01 (3)]. Such structures contain fourfold helices along the three axes all of the same hand (Batten et al., 2009 ▶).
Figure 3

A view of the 10 (3) network topology of the title metal–organic framework (MOF) structure, illustrating the 3-connected three-dimensional nets with ten-membered rings.

In the crystal of CuL, the water mol­ecules are located in the cavities of the MOF structure. They are hydrogen bonded to one another and to the ligand and acetate carbonyl O atoms (Table 1 ▶ and Fig. 4 ▶). There are also a number of C—H⋯O hydrogen bonds present within the framework (Table 1 ▶).
Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A D—HH⋯A DA D—H⋯A
O1W—H1WA⋯O3i 0.84 (3)2.13 (5)2.908 (9)154 (9)
O1W—H1WB⋯O3iii 0.84 (3)2.23 (5)2.964 (10)146 (8)
O2W—H2WA⋯O1W 0.86 (3)2.11 (4)2.951 (10)165 (10)
O2W—H2WB⋯O1iv 0.85 (3)2.20 (3)3.033 (8)169 (10)
C2—H2⋯O2v 0.952.372.987 (13)123
C8—H8⋯O3vi 0.952.573.364 (11)141
C9—H9⋯O2W vii 0.952.503.358 (12)151

Symmetry codes: (i) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

Figure 4

A view along the c axis of the crystal packing of complex CuL, with the hydrogen bonds involving the water mol­ecules shown as dashed lines (see Table 1 ▶ for details; H atoms not involved in these hydrogen bonding have been omitted for clarity).

Database survey

A search of the Cambridge Structural Database (Version 5.35, last update November 2013; Allen, 2002 ▶) indicated that no complexes of the ligand HL have been described previously. The analogous ligand N-[(pyridin-2-yl)methyl]pyrazine-2-carboxamide has been described as well as a number of metal complexes. These include the mononuclear copper acetate complex (Mohamadou et al., 2012 ▶). Here this ligand coordin­ates in a tridentate manner but in a number of other complexes it coordinates in a bis-monodentate manner via the pyridine N atom and a pyrazine N atom; for example, in two polymeric mercury chloride complexes (Khavasi et al., 2010 ▶), and a polymeric silver tetra­fluoro­borate complex (Hellyer et al., 2009 ▶).

Synthesis and crystallization

The synthesis of the ligand N-[(pyridin-4-yl)meth­yl]pyrazine-2-carboxamide (HL) has been described elsewhere (Cati, 2002 ▶; Cati & Stoeckli-Evans, 2014 ▶). Complex CuL was prepared by adding Cu(acetate)H2O (64 mg, 0.318 mmol) to a hot solution (323 K) of HL (68 mg, 0.318 mmol) in dry methanol (25 ml). In 2 min a precipitate appeared and heating was stopped and the mixture stirred as the temperature decreased to room temperature. After 30 min the precipitate was filtered off and washed with dry methanol. It was then dissolved in a mixture of water (12 ml) and methanol (15 ml) and stirred with warming to between 313 to 323 K for 15 min. The resulting blue solution was allowed to stand at room temperature and yielded blue crystals in a few days [yield 72 mg, 61%]. Analysis for C13H12CuN4O3·2(H2O) (M = 371.84). Calculated (%): C 41.99, H 4.34, N 15.07. Found: C 42.17, H 4.33, N 14.75.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▶. The water H atoms were located in difference Fourier maps were refined with distance restraints: O—H = 0.84 (2) and H⋯H = 1.35 (2) Å with U iso(H) = 1.5Ueq(O). The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.95 Å with U iso(H) = 1.2U eq(C).
Table 2

Experimental details

Crystal data
Chemical formula[Cu(C11H9N4O)(C2H3O2)]·2H2O
M r 371.84
Crystal system, space groupMonoclinic, C c
Temperature (K)153
a, b, c (Å)7.8256 (12), 22.331 (2), 8.9976 (13)
β (°)110.040 (16)
V3)1477.2 (4)
Z 4
Radiation typeMo Kα
μ (mm−1)1.51
Crystal size (mm)0.40 × 0.30 × 0.30
 
Data collection
DiffractometerStoe IPDS I
Absorption correctionMulti-scan (MULscanABS in PLATON; Spek, 2009)
T min, T max 0.979, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections5730, 2705, 1778
R int 0.070
(sin θ/λ)max−1)0.615
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.040, 0.072, 0.78
No. of reflections2705
No. of parameters203
No. of restraints8
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.40, −0.59
Absolute structureFlack x determined using 665 quotients [(I +)−(I )]/[(I +)+(I )] (Parsons & Flack, 2004)
Absolute structure parameter−0.01 (3)

Computer programs: EXPOSE in IPDSI, CELL and INTEGRATE in IPDSI (Stoe & Cie, 2004 ▶), SHELXS97 and SHELXL2013 (Sheldrick, 2008 ▶), Mercury (Macrae et al., 2008 ▶), PLATON (Spek, 2009 ▶) and publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) CuL. DOI: 10.1107/S1600536814011520/hb0008sup1.cif Structure factors: contains datablock(s) CuL2. DOI: 10.1107/S1600536814011520/hb0008CuL2sup2.hkl CCDC reference: 1004264 Additional supporting information: crystallographic information; 3D view; checkCIF report
[Cu(C11H9N4O)(C2H3O2)]·2H2OF(000) = 764
Mr = 371.84Dx = 1.672 Mg m3
Monoclinic, CcMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 2705 reflections
a = 7.8256 (12) Åθ = 2.1–26.1°
b = 22.331 (2) ŵ = 1.51 mm1
c = 8.9976 (13) ÅT = 153 K
β = 110.040 (16)°Block, turquoise blue
V = 1477.2 (4) Å30.40 × 0.30 × 0.30 mm
Z = 4
Stoe IPDS I diffractometer2705 independent reflections
Radiation source: fine-focus sealed tube1778 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.070
φ rotation scansθmax = 25.9°, θmin = 2.9°
Absorption correction: multi-scan (MULscanABS in PLATON; Spek, 2009)h = −9→9
Tmin = 0.979, Tmax = 1.000k = −27→26
5730 measured reflectionsl = −11→10
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.040H-atom parameters constrained
wR(F2) = 0.072w = 1/[σ2(Fo2) + (0.007P)2] where P = (Fo2 + 2Fc2)/3
S = 0.78(Δ/σ)max < 0.001
2705 reflectionsΔρmax = 0.40 e Å3
203 parametersΔρmin = −0.59 e Å3
8 restraintsAbsolute structure: Flack x determined using 665 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: −0.01 (3)
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
xyzUiso*/Ueq
Cu10.44720 (19)0.13211 (4)0.83884 (18)0.0155 (2)
O10.3072 (8)0.1995 (2)1.2004 (7)0.0248 (16)
O20.5973 (10)0.1326 (3)0.7054 (9)0.0169 (15)
O30.7386 (8)0.0439 (3)0.7464 (8)0.0266 (15)
N10.5958 (11)0.1988 (3)0.9695 (9)0.0155 (9)
N20.7658 (12)0.2933 (3)1.1646 (9)0.0155 (9)
N30.3109 (12)0.1421 (4)0.9844 (11)0.0155 (9)
N40.3255 (10)−0.0570 (3)1.2361 (9)0.0155 (9)
C10.7378 (15)0.2255 (5)0.9510 (12)0.018 (3)
H10.78390.21200.87200.022*
C20.8206 (16)0.2742 (5)1.0483 (12)0.018 (3)
H20.91910.29401.03040.021*
C30.6208 (15)0.2647 (4)1.1831 (13)0.015 (2)
H30.57710.27741.26440.018*
C40.5351 (15)0.2174 (5)1.0852 (11)0.014 (2)
C50.3707 (11)0.1848 (3)1.0932 (10)0.0146 (19)
C60.1512 (13)0.1078 (4)0.9801 (12)0.015 (2)
H6A0.07740.09870.86890.018*
H6B0.07570.13201.02620.018*
C70.2058 (11)0.0497 (3)1.0721 (11)0.0124 (17)
C80.1360 (11)−0.0045 (4)1.0059 (11)0.020 (2)
H80.0425−0.00610.90530.024*
C90.2044 (13)−0.0571 (4)1.0884 (13)0.020 (2)
H90.1638−0.09441.03810.024*
C100.3872 (11)−0.0036 (3)1.3001 (11)0.019 (2)
H100.4747−0.00281.40390.023*
C110.3310 (12)0.0503 (4)1.2239 (10)0.016 (2)
H110.37750.08711.27480.019*
C120.6927 (13)0.0907 (5)0.6705 (13)0.016 (2)
C130.7531 (12)0.1058 (4)0.5323 (10)0.024 (2)
H13A0.77240.06870.48200.035*
H13B0.86690.12850.57010.035*
H13C0.65910.12980.45520.035*
O1W0.7662 (12)0.0650 (3)0.0791 (10)0.0313 (19)
H1WA0.764 (17)0.042 (4)0.151 (8)0.047*
H1WB0.752 (15)0.044 (4)−0.002 (7)0.047*
O2W0.9960 (9)0.1546 (3)0.2989 (8)0.0358 (18)
H2WA0.925 (10)0.134 (4)0.222 (8)0.054*
H2WB1.072 (10)0.169 (4)0.261 (10)0.054*
U11U22U33U12U13U23
Cu10.0184 (5)0.0119 (4)0.0183 (5)−0.0019 (8)0.0092 (4)−0.0025 (8)
O10.032 (4)0.021 (3)0.032 (4)−0.011 (3)0.025 (4)−0.013 (3)
O20.023 (4)0.008 (3)0.023 (4)0.000 (3)0.012 (3)−0.004 (3)
O30.025 (4)0.019 (3)0.037 (5)0.009 (3)0.013 (3)0.005 (3)
N10.018 (2)0.0133 (18)0.018 (2)−0.0018 (16)0.009 (2)0.0013 (17)
N20.018 (2)0.0133 (18)0.018 (2)−0.0018 (16)0.009 (2)0.0013 (17)
N30.018 (2)0.0133 (18)0.018 (2)−0.0018 (16)0.009 (2)0.0013 (17)
N40.018 (2)0.0133 (18)0.018 (2)−0.0018 (16)0.009 (2)0.0013 (17)
C10.017 (6)0.017 (5)0.020 (6)−0.004 (4)0.007 (5)−0.002 (5)
C20.019 (6)0.022 (6)0.016 (6)−0.003 (5)0.011 (5)−0.001 (5)
C30.018 (6)0.014 (5)0.016 (6)−0.005 (4)0.012 (5)−0.001 (4)
C40.023 (6)0.010 (5)0.012 (5)−0.005 (4)0.010 (5)0.001 (4)
C50.015 (5)0.016 (4)0.014 (5)−0.002 (3)0.006 (4)0.001 (4)
C60.013 (6)0.010 (5)0.021 (6)−0.002 (4)0.004 (5)0.003 (4)
C70.011 (4)0.009 (4)0.018 (5)0.002 (3)0.006 (4)0.006 (4)
C80.012 (5)0.020 (4)0.027 (6)0.001 (4)0.005 (4)0.000 (4)
C90.020 (5)0.012 (5)0.028 (7)−0.004 (4)0.009 (5)0.002 (4)
C100.024 (6)0.017 (4)0.017 (6)0.000 (3)0.009 (5)0.002 (4)
C110.023 (5)0.007 (4)0.018 (5)−0.003 (4)0.008 (5)−0.004 (4)
C120.007 (5)0.022 (6)0.019 (6)0.001 (4)0.004 (5)0.001 (5)
C130.019 (5)0.035 (5)0.022 (6)0.004 (4)0.014 (5)−0.003 (4)
O1W0.047 (5)0.019 (4)0.033 (5)−0.002 (4)0.019 (5)0.001 (3)
O2W0.042 (5)0.038 (4)0.034 (5)−0.007 (3)0.022 (4)−0.006 (3)
Cu1—O21.947 (7)C3—H30.9500
Cu1—N31.964 (9)C4—C51.500 (13)
Cu1—N4i1.993 (7)C6—C71.520 (11)
Cu1—N12.003 (8)C6—H6A0.9900
Cu1—N2ii2.393 (8)C6—H6B0.9900
O1—C51.270 (9)C7—C81.376 (11)
O2—C121.300 (12)C7—C111.382 (12)
O3—C121.232 (11)C8—C91.395 (13)
N1—C11.323 (13)C8—H80.9500
N1—C41.349 (12)C9—H90.9500
N2—C21.330 (13)C10—C111.381 (11)
N2—C31.360 (13)C10—H100.9500
N2—Cu1iii2.393 (8)C11—H110.9500
N3—C51.332 (11)C12—C131.512 (12)
N3—C61.455 (13)C13—H13A0.9800
N4—C101.341 (10)C13—H13B0.9800
N4—C91.342 (13)C13—H13C0.9800
N4—Cu1iv1.992 (7)O1W—H1WA0.84 (3)
C1—C21.405 (14)O1W—H1WB0.84 (3)
C1—H10.9500O2W—H2WA0.86 (3)
C2—H20.9500O2W—H2WB0.85 (3)
C3—C41.393 (13)
O2—Cu1—N3172.2 (3)O1—C5—N3127.8 (8)
O2—Cu1—N4i90.7 (3)O1—C5—C4118.5 (8)
N3—Cu1—N4i97.0 (3)N3—C5—C4113.7 (8)
O2—Cu1—N190.4 (3)N3—C6—C7110.9 (8)
N3—Cu1—N182.1 (4)N3—C6—H6A109.5
N4i—Cu1—N1170.6 (3)C7—C6—H6A109.5
O2—Cu1—N2ii86.5 (3)N3—C6—H6B109.5
N3—Cu1—N2ii91.3 (3)C7—C6—H6B109.5
N4i—Cu1—N2ii101.5 (3)H6A—C6—H6B108.0
N1—Cu1—N2ii87.8 (2)C8—C7—C11118.6 (8)
C12—O2—Cu1131.5 (6)C8—C7—C6121.3 (8)
C1—N1—C4119.4 (8)C11—C7—C6120.1 (8)
C1—N1—Cu1127.3 (7)C7—C8—C9119.2 (9)
C4—N1—Cu1113.3 (7)C7—C8—H8120.4
C2—N2—C3116.9 (9)C9—C8—H8120.4
C2—N2—Cu1iii117.4 (7)N4—C9—C8122.6 (9)
C3—N2—Cu1iii125.3 (7)N4—C9—H9118.7
C5—N3—C6118.6 (9)C8—C9—H9118.7
C5—N3—Cu1115.9 (6)N4—C10—C11123.8 (8)
C6—N3—Cu1125.5 (7)N4—C10—H10118.1
C10—N4—C9117.0 (7)C11—C10—H10118.1
C10—N4—Cu1iv120.3 (6)C10—C11—C7118.6 (8)
C9—N4—Cu1iv121.4 (6)C10—C11—H11120.7
N1—C1—C2119.9 (10)C7—C11—H11120.7
N1—C1—H1120.0O3—C12—O2124.0 (9)
C2—C1—H1120.0O3—C12—C13122.0 (9)
N2—C2—C1122.3 (10)O2—C12—C13113.9 (8)
N2—C2—H2118.9C12—C13—H13A109.5
C1—C2—H2118.9C12—C13—H13B109.5
N2—C3—C4121.3 (10)H13A—C13—H13B109.5
N2—C3—H3119.3C12—C13—H13C109.5
C4—C3—H3119.3H13A—C13—H13C109.5
N1—C4—C3120.1 (10)H13B—C13—H13C109.5
N1—C4—C5115.0 (8)H1WA—O1W—H1WB107 (4)
C3—C4—C5124.9 (9)H2WA—O2W—H2WB104 (4)
C4—N1—C1—C2−2.0 (14)N1—C4—C5—N30.4 (12)
Cu1—N1—C1—C2176.4 (8)C3—C4—C5—N3178.4 (10)
C3—N2—C2—C1−1.9 (15)C5—N3—C6—C7−95.5 (10)
Cu1iii—N2—C2—C1172.1 (9)Cu1—N3—C6—C785.8 (10)
N1—C1—C2—N22.8 (17)N3—C6—C7—C8−128.6 (9)
C2—N2—C3—C40.5 (14)N3—C6—C7—C1149.7 (12)
Cu1iii—N2—C3—C4−173.0 (8)C11—C7—C8—C9−5.2 (12)
C1—N1—C4—C30.5 (14)C6—C7—C8—C9173.2 (8)
Cu1—N1—C4—C3−178.0 (8)C10—N4—C9—C8−3.5 (12)
C1—N1—C4—C5178.7 (9)Cu1iv—N4—C9—C8−171.0 (7)
Cu1—N1—C4—C50.1 (11)C7—C8—C9—N45.7 (13)
N2—C3—C4—N10.2 (16)C9—N4—C10—C111.1 (11)
N2—C3—C4—C5−177.7 (9)Cu1iv—N4—C10—C11168.8 (6)
C6—N3—C5—O11.8 (14)N4—C10—C11—C7−0.9 (12)
Cu1—N3—C5—O1−179.4 (7)C8—C7—C11—C102.9 (12)
C6—N3—C5—C4−179.5 (9)C6—C7—C11—C10−175.5 (8)
Cu1—N3—C5—C4−0.7 (10)Cu1—O2—C12—O3−17.2 (15)
N1—C4—C5—O1179.2 (8)Cu1—O2—C12—C13166.2 (7)
C3—C4—C5—O1−2.8 (15)
D—H···AD—HH···AD···AD—H···A
O1W—H1WA···O3i0.84 (3)2.13 (5)2.908 (9)154 (9)
O1W—H1WB···O3v0.84 (3)2.23 (5)2.964 (10)146 (8)
O2W—H2WA···O1W0.86 (3)2.11 (4)2.951 (10)165 (10)
O2W—H2WB···O1vi0.85 (3)2.20 (3)3.033 (8)169 (10)
C2—H2···O2iii0.952.372.987 (13)123
C8—H8···O3vii0.952.573.364 (11)141
C9—H9···O2Wviii0.952.503.358 (12)151
  6 in total

1.  The Cambridge Structural Database: a quarter of a million crystal structures and rising.

Authors:  Frank H Allen
Journal:  Acta Crystallogr B       Date:  2002-05-29

2.  Temperature-dependent supramolecular motif in coordination compounds.

Authors:  Hamid Reza Khavasi; Bahareh Mir Mohammad Sadegh
Journal:  Inorg Chem       Date:  2010-06-21       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.  Self-assembly of cuII and niII [2 x 2] grid complexes and a binuclear CuII complex with a new semiflexible substituted pyrazine ligand: multiple anion encapsulation and magnetic properties.

Authors:  Dilovan S Cati; Joan Ribas; Jordi Ribas-Ariño; Helen Stoeckli-Evans
Journal:  Inorg Chem       Date:  2004-02-09       Impact factor: 5.165

5.  Structure validation in chemical crystallography.

Authors:  Anthony L Spek
Journal:  Acta Crystallogr D Biol Crystallogr       Date:  2009-01-20

6.  Crystal structures of N-(pyridin-2-ylmeth-yl)pyrazine-2-carboxamide (monoclinic polymorph) and N-(pyridin-4-ylmeth-yl)pyrazine-2-carboxamide.

Authors:  Dilovan S Cati; Helen Stoeckli-Evans
Journal:  Acta Crystallogr Sect E Struct Rep Online       Date:  2014-06-23
  6 in total

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