Bis(μ-biphenyl-2,2′-dicarboxyl­ato)bis­[(2,2′-bipyridine)cobalt(II)]

An, Z.; Niu, X.-C.

doi:10.1107/S1600536808037288

metal-organic compounds

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ISSN: 2056-9890

Volume 64| Part 12| December 2008| Page m1556

doi:10.1107/S1600536808037288

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Bis(μ-biphenyl-2,2′-dicarboxylato)bis[(2,2′-bipyridine)cobalt(II)]

Zhe An ^a ^* and Xian-Chun Niu ^b

^aSchool of Chemistry and Life Science, Maoming University, Maoming 525000, People's Republic of China, and ^bSchool of Chemical and Environmental Engineering, Maoming University, Maoming 525000, People's Republic of China
^*Correspondence e-mail: anz_md@163.com

(Received 28 October 2008; accepted 11 November 2008; online 20 November 2008)

In the title compound, [Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂], the Co^II atom is coordinated by two N atoms from one 2,2′-bipyridine ligand and two O atoms from two biphenyl-2,2′-dicarboxylate (2,2′-dpa) ligands in a distorted planar geometry. Longer Co—O contacts [2.437 (3) and 2.552 (3) Å] are formed to the second O atom of each coordinated carboxylate group so that these groups approximate a bidentate coordination mode and the coordination geometry around Co^II approaches distorted octahedral. The 2,2′-dpa ligands bridge two Co^II atoms, forming a cyclic dinuclear complex around a centre of inversion.

Related literature

For metal-organic frameworks containing 2,2′-dpa, see: Rueff et al. (2003 ); Wang et al. (2006 ); Xu et al. (2006 ).

Experimental

Crystal data

[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂]
M_r = 910.64
Monoclinic, P 2₁ /n
a = 11.236 (2) Å
b = 13.198 (2) Å
c = 13.393 (2) Å
β = 102.90 (2)°
V = 1936.1 (5) Å³
Z = 2
Mo Kα radiation
μ = 0.92 mm⁻¹
T = 296 (2) K
0.39 × 0.27 × 0.21 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2001 ) T_min = 0.715, T_max = 0.830
10081 measured reflections
3408 independent reflections
2591 reflections with I > 2σ(I)
R_int = 0.040

Refinement

R[F² > 2σ(F²)] = 0.035
wR(F²) = 0.093
S = 1.00
3408 reflections
280 parameters
H-atom parameters not refined
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.28 e Å⁻³

Data collection: APEX2 (Bruker, 2004 ); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808037288/bi2316sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808037288/bi2316Isup2.hkl

checkCIF report

Comment top

biphenyl-2,2'-dicarboxylic acid (H₂dpa) has been demonstrated to be a useful ligand for constructing metal-organic frameworks (Rueff et al., 2003; Wang et al., 2006; Xu et al., 2006). The title compound is a cyclic dinuclear Co^II compound in which biphenyl-2,2'-dicarboxylate (2,2'-dpa) acts as a bridging ligand.

As shown in Figure 1, each Co^II atom is coordinated by two N atoms from one 2,2'-bipyridine ligand and two O atoms from two biphenyl-2,2'-dicarboxylate ligands, forming a distorted planar geometry. The Co—O and Co—N bond lengths are in the range 1.948 (2)–1.964 (2) and 1.968 (3)–1.989 (3) Å, respectively. Longer Co—O contacts (2.437 (3) and 2.552 (3) Å) are formed to the second O atom of each coordinated carboxylate group, so that these groups approximate a bidentate coordination mode and the coordination geometry around Co^II approaches distorted octahedral. The biphenyl-2,2'-dicarboxylate ligand acts as a bridge between Co^II atoms to form a cyclic dinuclear complex around a centre of inversion.

Related literature top

For metal-organic frameworks containing 2,2'-dpa, see: Rueff et al. (2003); Wang et al. (2006); Xu et al. (2006).

Experimental top

A mixture of cobalt(II) chloride hexahydrate (0.1 mmol), 2,2'-bipyridine (0.1 mmol), biphenyl-2,2'-dicarboxylic acid (0.2 mmol) and H₂O (16 ml) in a 25 ml Teflon-lined stainless steel autoclave was kept at 463 K for five days. Red crystals were obtained after cooling to room temperature with a yield of 12%. Elemental analysis calculated: C 63.25, H 3.51, N 6.15%; found: C 63.21, H 3.39, N 6.09%.

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. Molecular unit in the title compound showing displacement ellipsoids at 30% probability for non-H atoms. Non-labelled atoms are related to labelled atoms by the symmetry code: 1-x, 1-y, 1-z.

Bis(µ-biphenyl-2,2'-dicarboxylato)bis[(2,2'-bipyridine)cobalt(II)] top

Crystal data top

[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂]	F(000) = 932
M_r = 910.64	D_x = 1.562 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3408 reflections
a = 11.236 (2) Å	θ = 2.1–25.0°
b = 13.198 (2) Å	µ = 0.92 mm⁻¹
c = 13.393 (2) Å	T = 296 K
β = 102.90 (2)°	Block, red
V = 1936.1 (5) Å³	0.39 × 0.27 × 0.21 mm
Z = 2

Data collection top

Bruker APEXII CCD diffractometer	3408 independent reflections
Radiation source: fine-focus sealed tube	2591 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.040
ϕ and ω scans	θ_max = 25.0°, θ_min = 2.1°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −13→13
T_min = 0.715, T_max = 0.830	k = −15→15
10081 measured reflections	l = −15→7

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.093	H-atom parameters not refined
S = 1.00	w = 1/[σ²(F_o²) + (0.049P)² + 0.1211P] where P = (F_o² + 2F_c²)/3
3408 reflections	(Δ/σ)_max = 0.005
280 parameters	Δρ_max = 0.23 e Å⁻³
0 restraints	Δρ_min = −0.28 e Å⁻³

Crystal data top

[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂]	V = 1936.1 (5) Å³
M_r = 910.64	Z = 2
Monoclinic, P2₁/n	Mo Kα radiation
a = 11.236 (2) Å	µ = 0.92 mm⁻¹
b = 13.198 (2) Å	T = 296 K
c = 13.393 (2) Å	0.39 × 0.27 × 0.21 mm
β = 102.90 (2)°

Data collection top

Bruker APEXII CCD diffractometer	3408 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2001)	2591 reflections with I > 2σ(I)
T_min = 0.715, T_max = 0.830	R_int = 0.040
10081 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.035	0 restraints
wR(F²) = 0.093	H-atom parameters not refined
S = 1.00	Δρ_max = 0.23 e Å⁻³
3408 reflections	Δρ_min = −0.28 e Å⁻³
280 parameters

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Co1	0.69884 (3)	0.33942 (2)	0.55976 (3)	0.0362 (8)
C1	0.4768 (3)	0.3112 (2)	0.5772 (2)	0.0376 (7)
C2	0.3402 (2)	0.30053 (19)	0.5493 (2)	0.0340 (6)
C3	0.2858 (3)	0.2453 (2)	0.4630 (2)	0.0432 (7)
H3	0.3352	0.2114	0.4268	0.052*
C4	0.1603 (3)	0.2389 (2)	0.4292 (2)	0.0479 (8)
H4	0.1263	0.2007	0.3715	0.057*
C5	0.0866 (3)	0.2894 (2)	0.4814 (2)	0.0466 (8)
H5	0.0021	0.2864	0.4591	0.056*
C6	0.1389 (3)	0.3447 (2)	0.5672 (2)	0.0420 (7)
H6	0.0882	0.3789	0.6021	0.050*
C7	0.2648 (2)	0.35125 (19)	0.6036 (2)	0.0341 (6)
C8	0.7126 (2)	0.4230 (2)	0.3940 (2)	0.0368 (7)
C9	0.6933 (2)	0.4851 (2)	0.2986 (2)	0.0344 (6)
C10	0.6914 (2)	0.5897 (2)	0.2997 (2)	0.0331 (6)
C11	0.6643 (3)	0.6406 (2)	0.2068 (2)	0.0427 (7)
H11	0.6649	0.7111	0.2066	0.051*
C12	0.6363 (3)	0.5892 (2)	0.1142 (2)	0.0483 (8)
H12	0.6156	0.6251	0.0530	0.058*
C13	0.6393 (3)	0.4859 (2)	0.1133 (2)	0.0477 (8)
H13	0.6215	0.4506	0.0516	0.057*
C14	0.6691 (3)	0.4344 (2)	0.2050 (2)	0.0417 (7)
H14	0.6732	0.3641	0.2044	0.050*
C15	0.8778 (3)	0.4946 (2)	0.6591 (2)	0.0466 (8)
H15	0.8341	0.5399	0.6116	0.056*
C16	0.9763 (3)	0.5291 (3)	0.7318 (3)	0.0563 (9)
H16	0.9998	0.5967	0.7320	0.068*
C17	1.0395 (3)	0.4634 (3)	0.8038 (3)	0.0573 (9)
H17	1.1048	0.4862	0.8543	0.069*
C18	1.0053 (3)	0.3639 (3)	0.8004 (2)	0.0515 (8)
H18	1.0474	0.3180	0.8481	0.062*
C19	0.9069 (2)	0.3323 (2)	0.7249 (2)	0.0395 (7)
C20	0.8635 (2)	0.2279 (2)	0.7100 (2)	0.0384 (7)
C21	0.9169 (3)	0.1475 (3)	0.7677 (3)	0.0558 (9)
H21	0.9813	0.1576	0.8238	0.067*
C22	0.8741 (3)	0.0524 (3)	0.7416 (3)	0.0638 (10)
H22	0.9100	−0.0032	0.7792	0.077*
C23	0.7776 (3)	0.0393 (2)	0.6593 (3)	0.0611 (10)
H23	0.7492	−0.0255	0.6396	0.073*
C24	0.7238 (3)	0.1219 (2)	0.6068 (3)	0.0512 (8)
H24	0.6560	0.1132	0.5531	0.061*
N1	0.8438 (2)	0.39788 (17)	0.65536 (17)	0.0389 (6)
N2	0.7664 (2)	0.21450 (17)	0.63096 (18)	0.0400 (6)
O1	0.53335 (17)	0.28601 (15)	0.50773 (15)	0.0449 (5)
O2	0.53139 (18)	0.34378 (16)	0.66074 (17)	0.0561 (6)
O3	0.7602 (2)	0.33887 (15)	0.39642 (18)	0.0615 (7)
O4	0.67220 (18)	0.45631 (14)	0.46882 (15)	0.0419 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Co1	0.0383 (19)	0.0317 (18)	0.0364 (19)	0.0024 (15)	0.0038 (15)	−0.0010 (15)
C1	0.0442 (17)	0.0298 (15)	0.0383 (17)	−0.0005 (13)	0.0083 (15)	−0.0045 (13)
C2	0.0371 (15)	0.0266 (14)	0.0379 (17)	−0.0029 (12)	0.0076 (13)	−0.0027 (12)
C3	0.0447 (18)	0.0380 (17)	0.0477 (19)	−0.0056 (13)	0.0124 (15)	−0.0125 (14)
C4	0.0467 (18)	0.0432 (17)	0.050 (2)	−0.0131 (15)	0.0029 (16)	−0.0116 (15)
C5	0.0365 (16)	0.0453 (18)	0.054 (2)	−0.0079 (14)	0.0016 (16)	−0.0012 (16)
C6	0.0369 (16)	0.0431 (17)	0.0467 (19)	−0.0014 (14)	0.0106 (14)	−0.0031 (15)
C7	0.0364 (15)	0.0271 (14)	0.0370 (16)	−0.0039 (12)	0.0045 (13)	0.0022 (12)
C8	0.0388 (16)	0.0325 (16)	0.0370 (17)	0.0033 (13)	0.0040 (14)	−0.0015 (13)
C9	0.0343 (15)	0.0353 (15)	0.0324 (16)	0.0019 (12)	0.0050 (13)	0.0012 (13)
C10	0.0306 (14)	0.0333 (15)	0.0347 (16)	0.0017 (12)	0.0060 (13)	−0.0009 (13)
C11	0.0490 (18)	0.0375 (16)	0.0417 (18)	0.0070 (13)	0.0103 (15)	0.0072 (14)
C12	0.0558 (19)	0.055 (2)	0.0330 (17)	0.0089 (16)	0.0067 (15)	0.0071 (15)
C13	0.0503 (18)	0.058 (2)	0.0329 (17)	0.0039 (16)	0.0044 (15)	−0.0060 (15)
C14	0.0448 (17)	0.0371 (16)	0.0405 (18)	0.0011 (13)	0.0041 (15)	−0.0048 (14)
C15	0.0478 (18)	0.0430 (18)	0.0472 (19)	−0.0048 (15)	0.0067 (16)	0.0030 (15)
C16	0.054 (2)	0.056 (2)	0.058 (2)	−0.0192 (17)	0.0091 (18)	−0.0071 (18)
C17	0.0416 (18)	0.078 (3)	0.048 (2)	−0.0164 (18)	0.0013 (16)	−0.0016 (19)
C18	0.0378 (17)	0.070 (2)	0.0420 (19)	−0.0044 (16)	−0.0002 (15)	0.0102 (16)
C19	0.0322 (15)	0.0532 (18)	0.0326 (16)	0.0027 (14)	0.0059 (13)	0.0054 (14)
C20	0.0358 (15)	0.0466 (17)	0.0337 (16)	0.0079 (13)	0.0099 (14)	0.0081 (14)
C21	0.0496 (19)	0.059 (2)	0.057 (2)	0.0149 (17)	0.0072 (17)	0.0198 (17)
C22	0.061 (2)	0.051 (2)	0.082 (3)	0.0163 (18)	0.023 (2)	0.028 (2)
C23	0.068 (2)	0.0381 (19)	0.079 (3)	0.0010 (17)	0.021 (2)	0.0111 (18)
C24	0.057 (2)	0.0408 (18)	0.056 (2)	−0.0040 (16)	0.0150 (17)	0.0012 (16)
N1	0.0384 (13)	0.0417 (15)	0.0352 (14)	0.0009 (11)	0.0056 (11)	0.0031 (11)
N2	0.0421 (14)	0.0380 (14)	0.0397 (15)	0.0009 (11)	0.0087 (12)	0.0045 (11)
O1	0.0396 (11)	0.0581 (14)	0.0366 (12)	0.0006 (10)	0.0072 (10)	−0.0038 (10)
O2	0.0415 (12)	0.0719 (15)	0.0515 (14)	−0.0037 (11)	0.0030 (11)	−0.0269 (12)
O3	0.0940 (18)	0.0411 (13)	0.0539 (14)	0.0263 (12)	0.0263 (14)	0.0070 (11)
O4	0.0513 (12)	0.0396 (11)	0.0350 (11)	0.0073 (9)	0.0101 (10)	0.0016 (9)

Geometric parameters (Å, º) top

Co1—O4	1.9469 (18)	C11—H11	0.930
Co1—O1	1.9651 (19)	C12—C13	1.365 (4)
Co1—N2	1.970 (2)	C12—H12	0.930
Co1—N1	1.989 (2)	C13—C14	1.377 (4)
Co1—C8	2.514 (3)	C13—H13	0.930
C1—O2	1.228 (3)	C14—H14	0.930
C1—O1	1.281 (3)	C15—N1	1.330 (4)
C1—C2	1.503 (4)	C15—C16	1.378 (4)
C2—C3	1.388 (4)	C15—H15	0.930
C2—C7	1.404 (4)	C16—C17	1.372 (4)
C3—C4	1.384 (4)	C16—H16	0.930
C3—H3	0.930	C17—C18	1.366 (4)
C4—C5	1.370 (4)	C17—H17	0.930
C4—H4	0.930	C18—C19	1.385 (4)
C5—C6	1.378 (4)	C18—H18	0.930
C5—H5	0.930	C19—N1	1.351 (3)
C6—C7	1.392 (4)	C19—C20	1.461 (4)
C6—H6	0.930	C20—N2	1.351 (3)
C7—C10ⁱ	1.497 (4)	C20—C21	1.370 (4)
C8—O3	1.230 (3)	C21—C22	1.360 (5)
C8—O4	1.267 (3)	C21—H21	0.930
C8—C9	1.493 (4)	C22—C23	1.373 (5)
C9—C10	1.380 (4)	C22—H22	0.930
C9—C14	1.393 (4)	C23—C24	1.364 (4)
C10—C11	1.387 (4)	C23—H23	0.930
C10—C7ⁱ	1.497 (4)	C24—N2	1.326 (4)
C11—C12	1.386 (4)	C24—H24	0.930

O4—Co1—O1	93.51 (8)	C13—C12—H12	120.1
O4—Co1—N2	162.73 (9)	C11—C12—H12	120.1
O1—Co1—N2	95.93 (9)	C12—C13—C14	119.1 (3)
O4—Co1—N1	94.86 (9)	C12—C13—H13	120.5
O1—Co1—N1	160.30 (9)	C14—C13—H13	120.5
N2—Co1—N1	80.88 (9)	C13—C14—C9	121.7 (3)
O4—Co1—C8	29.68 (8)	C13—C14—H14	119.2
O1—Co1—C8	94.82 (9)	C9—C14—H14	119.2
N2—Co1—C8	134.56 (9)	N1—C15—C16	121.5 (3)
N1—Co1—C8	101.27 (9)	N1—C15—H15	119.2
O2—C1—O1	121.7 (3)	C16—C15—H15	119.2
O2—C1—C2	122.2 (3)	C17—C16—C15	119.7 (3)
O1—C1—C2	116.1 (2)	C17—C16—H16	120.1
C3—C2—C7	118.5 (2)	C15—C16—H16	120.1
C3—C2—C1	119.5 (3)	C18—C17—C16	119.1 (3)
C7—C2—C1	121.9 (2)	C18—C17—H17	120.5
C4—C3—C2	122.2 (3)	C16—C17—H17	120.5
C4—C3—H3	118.9	C17—C18—C19	119.1 (3)
C2—C3—H3	118.9	C17—C18—H18	120.4
C5—C4—C3	119.4 (3)	C19—C18—H18	120.4
C5—C4—H4	120.3	N1—C19—C18	121.4 (3)
C3—C4—H4	120.3	N1—C19—C20	113.7 (2)
C4—C5—C6	119.3 (3)	C18—C19—C20	124.8 (3)
C4—C5—H5	120.3	N2—C20—C21	121.1 (3)
C6—C5—H5	120.3	N2—C20—C19	114.6 (2)
C5—C6—C7	122.4 (3)	C21—C20—C19	124.3 (3)
C5—C6—H6	118.8	C22—C21—C20	119.0 (3)
C7—C6—H6	118.8	C22—C21—H21	120.5
C6—C7—C2	118.2 (3)	C20—C21—H21	120.5
C6—C7—C10ⁱ	116.6 (3)	C21—C22—C23	119.5 (3)
C2—C7—C10ⁱ	125.2 (2)	C21—C22—H22	120.2
O3—C8—O4	121.5 (3)	C23—C22—H22	120.2
O3—C8—C9	119.8 (3)	C24—C23—C22	119.5 (3)
O4—C8—C9	118.5 (2)	C24—C23—H23	120.2
O3—C8—Co1	72.13 (17)	C22—C23—H23	120.2
O4—C8—Co1	49.52 (13)	N2—C24—C23	121.1 (3)
C9—C8—Co1	166.2 (2)	N2—C24—H24	119.5
C10—C9—C14	119.3 (3)	C23—C24—H24	119.5
C10—C9—C8	122.7 (3)	C15—N1—C19	119.1 (3)
C14—C9—C8	117.9 (2)	C15—N1—Co1	125.7 (2)
C9—C10—C11	118.4 (3)	C19—N1—Co1	115.06 (19)
C9—C10—C7ⁱ	121.8 (2)	C24—N2—C20	119.7 (3)
C11—C10—C7ⁱ	119.2 (2)	C24—N2—Co1	125.0 (2)
C12—C11—C10	121.7 (3)	C20—N2—Co1	115.23 (18)
C12—C11—H11	119.1	C1—O1—Co1	103.46 (17)
C10—C11—H11	119.1	C8—O4—Co1	100.80 (16)
C13—C12—C11	119.7 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula	[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂]
M_r	910.64
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	296
a, b, c (Å)	11.236 (2), 13.198 (2), 13.393 (2)
β (°)	102.90 (2)
V (Å³)	1936.1 (5)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.92
Crystal size (mm)	0.39 × 0.27 × 0.21

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2001)
T_min, T_max	0.715, 0.830
No. of measured, independent and observed [I > 2σ(I)] reflections	10081, 3408, 2591
R_int	0.040
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.093, 1.00
No. of reflections	3408
No. of parameters	280
H-atom treatment	H-atom parameters not refined
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.28

Computer programs: APEX2 (Bruker, 2004), SAINT-Plus (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Acknowledgements

The authors acknowledge financial support from Maoming University.

References

Bruker (2001). SADABS and SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2004). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
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