Crystal structure of [2,6-di­fluoro-3-(pyridin-2-yl-κN)pyridin-4-yl-κC4](pentane-2,4-dionato-κ2O,O′)platinum(II)

Park, K.-M.; Lee, J.; Kang, Y.

doi:10.1107/S2056989015004375

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 71| Part 4| April 2015| Pages 354-356

doi:10.1107/S2056989015004375

Open

access

Crystal structure of [2,6-difluoro-3-(pyridin-2-yl-κN)pyridin-4-yl-κC⁴](pentane-2,4-dionato-κ²O,O′)platinum(II)

Ki-Min Park,^a Jieun Lee ^b and Youngjin Kang ^b ^*

^aResearch Institute of Natural Science, Gyeongsang National University, Jinju 660-701, Republic of Korea, and ^bDivision of Science Education, Kangwon National University, Chuncheon 220-701, Republic of Korea
^*Correspondence e-mail: kangy@kangwon.ac.kr

Edited by M. Weil, Vienna University of Technology, Austria (Received 12 February 2015; accepted 3 March 2015; online 11 March 2015)

The asymmetric unit of the title compound, [Pt(C₁₀H₅F₂N₂)(C₅H₇O₂)], comprises one Pt^II atom, one 2,6-difluoro-2,3-bipyridine ligand and one acetylacetonate anion. The Pt^II atom adopts a distorted square-planar coordination geometry, being C,N-chelated by the 2,6-difluoro-3-(pyridin-2-yl)pyridin-4-yl ligand and O,O′-chelated by the pentane-2,4-dionate ligand. The two pyridine rings of the bipyridine ligand are approximately coplanar, making a dihedral angle of 1.2 (2)°. A variety of intra- and intermolecular C—H⋯O and C—H⋯F hydrogen bonds, as well as π–π interactions [centroid–centroid distances = 4.337 (3) and 3.774 (3) Å] contribute to the stabilization of the molecular and crystal structures, and result in the formation of a three-dimensional supramolecular framework.

Keywords: crystal structure; platinum(II); CNO₂ coordination set; hydrogen bonding; π–π interactions.

CCDC reference: 1051825

1. Chemical context

Cyclometalated platinum(II) compounds with C,N-chelating ligands have been considered as an attractive research area due to their wide applications, such as biological imaging, non-linear optics, oxygen sensing and organic light-emitting diodes (OLEDs) (Hudson et al., 2012 ). In particular, phenylpyridine (ppy) based platinum(II) β-diketonate compounds have been widely studied because of their excellent stability and high quantum efficiency in OLEDs (Rao et al., 2012 ). However, examples of platinum(II) compounds with C,N-chelating bipyridine ligands are scarce. Herein, we report the result of our investigation on the crystal structure of a novel platinum(II) compound with fluorinated bipyridine and acetylacetonate (acac, O,O) ligands.

2. Structural commentary

The molecular structure of the title compound is shown in Fig. 1. The asymmetric unit consists of one Pt^II atom, one 2,6-difluoro-2,3-bipyridine ligand and one acetylacetonate anion. The Pt^II atom is four-coordinated by the C,N-chelating 2′,6′-difluoro-2,3′-bipyridinato ligand and by the O,O′-chelating pentane-2,4-dionato ligand, forming a distorted square-planar coordination sphere due to narrow ligand bite angles, which range from 81.28 (17) to 93.25 (13)°. The Pt—C bond length of 1.951 (4) Å is shorter than the Pt—N bond length of 1.995 (4) Å due to the more electronegative fluorine substituent on the C-bound pyridine ring. The Pt—C, Pt—N and Pt—O bond lengths (Table 1) are in normal ranges as reported for similar Pt^II compounds, e.g. [Pt(Bppy)(acac)] (Bppy is a boron-functionalized phenylpyridine; Rao et al., 2012). Within the C,N-bidentate ligand of the title compound, the two pyridine rings are approximately co-planar, making a dihedral angle of 1.2 (2)°, indicating that an effective π conjugation of the two pyridine rings occurs in the title compound. The molecular structure is stabilized by weak intramolecular C—H⋯O and C—H⋯F hydrogen bonds (Table 2).

Table 1
Selected bond lengths (Å)

Pt1—C1	1.951 (4)	Pt1—O1	2.074 (3)
Pt1—N2	1.995 (4)	Pt1—O2	2.001 (3)

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯O2	0.95	2.57	3.040 (5)	111
C7—H7⋯F2	0.95	2.31	2.917 (6)	121
C10—H10⋯F1ⁱ	0.95	2.32	3.180 (5)	150
C10—H10⋯O1	0.95	2.41	3.006 (5)	120
C12—H12⋯F2ⁱⁱ	0.95	2.44	3.361 (5)	163
C15—H15A⋯F1ⁱ	0.98	2.54	3.481 (6)	161
Symmetry codes: (i) x, y, z+1; (ii) x-1, y-1, z.

Figure 1
View of the molecular structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level; dashed lines represent intramolecular C—H⋯O and C—H⋯F hydrogen bonds.

3. Supramolecular features

Intermolecular C—H⋯F hydrogen bonds between neighboring molecules lead to the formation of a two-dimensional supramolecular network extending parallel to the ( $[\overline{1}]$ 10) plane (Fig. 2, Table 2). These networks are interlinked by π–π interactions [Cg1—Cg2ⁱ = 4.337 (3) Å and Cg1—Cg2ⁱⁱ = 3.774 (3) Å, where Cg1 and Cg2 are the centroids of the N1, C1–C5 and the N2, C6–C10 rings, respectively; symmetry codes: (i) −x + 1, −y + 2, −z + 2; (ii) −x + 2, −y + 2, −z + 2], resulting in the formation of an overall three-dimensional supramolecular framework (Fig. 3).

Figure 2
The two-dimensional supramolecular network formed through C—H⋯F interactions (yellow dashed lines). H atoms not involved in intermolecular interactions have been omitted for clarity.

Figure 3
The three-dimensional supramolecular network formed through π–π stacking interactions (black dashed lines). Yellow dashed lines indicate the C—H⋯F interactions. H atoms not involved in intermolecular interactions have been omitted for clarity.

4. Synthesis and crystallization

The title compound was synthesized according to a previous report (Rao et al., 2012). Slow evaporation from a dichloromethane/hexane solution afforded yellow crystals suitable for X-ray crystallography analysis.

5. Refinement

Crystal data, data collection and crystal structure refinement details are summarized in Table 3. All H atoms were positioned geometrically and refined using a riding model, with d(C—H) = 0.95 Å, U_iso(H) = 1.2U_eq(C) for Csp²-H, and 0.98 Å, U_iso(H) = 1.5U_eq(C) for methyl protons.

Table 3
Experimental details

Crystal data
Chemical formula	[Pt(C₁₀H₅F₂N₂)(C₅H₇O₂)]
M_r	485.36
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	180
a, b, c (Å)	8.0442 (6), 9.8711 (7), 10.1458 (7)
α, β, γ (°)	97.683 (1), 112.320 (1), 99.410 (1)
V (Å³)	718.12 (9)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	9.80
Crystal size (mm)	0.27 × 0.24 × 0.12

Data collection
Diffractometer	Bruker APEXII CCD area detector
Absorption correction	Multi-scan (SADABS; Bruker, 2006 )
T_min, T_max	0.177, 0.386
No. of measured, independent and observed [I > 2σ(I)] reflections	7062, 2810, 2773
R_int	0.023
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.017, 0.053, 1.07
No. of reflections	2810
No. of parameters	199
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.51, −1.27
Computer programs: APEX2 and SAINT (Bruker, 2006), SHELXS97, SHELXL97 and SHELXTL (Sheldrick, 2008 ) and DIAMOND (Brandenburg, 2005 ).

Supporting information

CCDC reference: 1051825

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S2056989015004375/wm5128sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015004375/wm5128Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

[2,6-Difluoro-3-(pyridin-2-yl-κN)pyridin-4-yl-κC⁴](pentane-2,4-dionato-κ²O,O')platinum(II) top

Crystal data top

[Pt(C₁₀H₅F₂N₂)(C₅H₇O₂)]	Z = 2
M_r = 485.36	F(000) = 456
Triclinic, P1	D_x = 2.245 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.0442 (6) Å	Cell parameters from 2773 reflections
b = 9.8711 (7) Å	θ = 2.1–26.0°
c = 10.1458 (7) Å	µ = 9.80 mm⁻¹
α = 97.683 (1)°	T = 180 K
β = 112.320 (1)°	Block, yellow
γ = 99.410 (1)°	0.27 × 0.24 × 0.12 mm
V = 718.12 (9) Å³

Data collection top

Bruker APEXII CCD area-detector diffractometer	2810 independent reflections
Radiation source: fine-focus sealed tube	2773 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.023
φ and ω scans	θ_max = 26.0°, θ_min = 2.1°
Absorption correction: multi-scan (SADABS; Bruker, 2006)	h = −9→9
T_min = 0.177, T_max = 0.386	k = −12→12
7062 measured reflections	l = −12→12

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)] = 0.017	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.053	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.0295P)² + 1.5655P] where P = (F_o² + 2F_c²)/3
2810 reflections	(Δ/σ)_max = 0.002
199 parameters	Δρ_max = 0.51 e Å⁻³
0 restraints	Δρ_min = −1.27 e Å⁻³

Special details top

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.

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 > σ(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
Pt1	0.541428 (18)	0.778516 (13)	0.974446 (14)	0.01645 (7)
F1	0.6043 (5)	0.8519 (4)	0.4799 (3)	0.0462 (8)
F2	0.9252 (4)	1.1982 (3)	0.8748 (3)	0.0362 (6)
O1	0.4622 (4)	0.7037 (3)	1.1284 (3)	0.0240 (6)
O2	0.3730 (4)	0.6133 (3)	0.8158 (3)	0.0231 (6)
N1	0.7621 (5)	1.0252 (4)	0.6783 (4)	0.0294 (8)
N2	0.7143 (5)	0.9517 (4)	1.1169 (4)	0.0197 (7)
C1	0.6273 (6)	0.8664 (4)	0.8434 (5)	0.0209 (8)
C2	0.5731 (6)	0.8150 (5)	0.6931 (5)	0.0251 (8)
H2	0.4892	0.7267	0.6431	0.030*
C3	0.6477 (6)	0.8990 (5)	0.6230 (5)	0.0290 (9)
C4	0.8076 (6)	1.0704 (4)	0.8184 (5)	0.0245 (8)
C5	0.7490 (5)	0.9996 (4)	0.9079 (4)	0.0205 (8)
C6	0.7995 (6)	1.0466 (4)	1.0634 (5)	0.0210 (8)
C7	0.9196 (6)	1.1711 (4)	1.1559 (5)	0.0263 (9)
H7	0.9801	1.2372	1.1190	0.032*
C8	0.9507 (6)	1.1986 (5)	1.3023 (5)	0.0295 (9)
H8	1.0316	1.2836	1.3659	0.035*
C9	0.8626 (6)	1.1006 (5)	1.3545 (5)	0.0279 (9)
H9	0.8829	1.1168	1.4544	0.034*
C10	0.7447 (6)	0.9790 (5)	1.2585 (5)	0.0249 (8)
H10	0.6829	0.9121	1.2937	0.030*
C11	0.3374 (6)	0.5912 (4)	1.0981 (5)	0.0219 (8)
C12	0.2383 (6)	0.5027 (4)	0.9600 (5)	0.0247 (9)
H12	0.1450	0.4256	0.9525	0.030*
C13	0.2611 (6)	0.5149 (4)	0.8326 (5)	0.0230 (8)
C14	0.1488 (7)	0.4045 (5)	0.6953 (5)	0.0328 (10)
H14A	0.1816	0.4288	0.6163	0.049*
H14B	0.0170	0.3996	0.6684	0.049*
H14C	0.1746	0.3131	0.7117	0.049*
C15	0.3027 (7)	0.5529 (5)	1.2257 (5)	0.0305 (10)
H15A	0.3822	0.6245	1.3142	0.046*
H15B	0.3306	0.4613	1.2389	0.046*
H15C	0.1728	0.5479	1.2072	0.046*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Pt1	0.01828 (10)	0.01327 (9)	0.01850 (9)	0.00005 (6)	0.00925 (7)	0.00501 (6)
F1	0.062 (2)	0.0564 (19)	0.0253 (14)	0.0043 (16)	0.0257 (14)	0.0124 (13)
F2	0.0389 (15)	0.0238 (13)	0.0495 (17)	−0.0032 (11)	0.0244 (13)	0.0138 (12)
O1	0.0251 (15)	0.0198 (14)	0.0209 (14)	−0.0073 (12)	0.0087 (12)	0.0017 (11)
O2	0.0242 (14)	0.0179 (14)	0.0241 (14)	−0.0014 (11)	0.0095 (12)	0.0034 (11)
N1	0.031 (2)	0.033 (2)	0.034 (2)	0.0088 (16)	0.0200 (17)	0.0187 (17)
N2	0.0176 (16)	0.0169 (16)	0.0235 (17)	0.0015 (13)	0.0083 (14)	0.0045 (13)
C1	0.029 (2)	0.0176 (19)	0.025 (2)	0.0086 (16)	0.0169 (18)	0.0103 (16)
C2	0.027 (2)	0.025 (2)	0.022 (2)	0.0021 (17)	0.0101 (17)	0.0073 (16)
C3	0.032 (2)	0.037 (2)	0.021 (2)	0.0097 (19)	0.0124 (18)	0.0108 (18)
C4	0.023 (2)	0.021 (2)	0.035 (2)	0.0044 (16)	0.0161 (18)	0.0130 (17)
C5	0.0191 (18)	0.0190 (19)	0.025 (2)	0.0043 (15)	0.0102 (16)	0.0065 (16)
C6	0.0198 (18)	0.0182 (19)	0.028 (2)	0.0041 (15)	0.0119 (17)	0.0077 (16)
C7	0.023 (2)	0.0170 (19)	0.037 (2)	0.0004 (16)	0.0115 (18)	0.0070 (17)
C8	0.025 (2)	0.021 (2)	0.031 (2)	−0.0002 (17)	0.0042 (18)	−0.0021 (17)
C9	0.029 (2)	0.027 (2)	0.022 (2)	0.0038 (18)	0.0074 (17)	−0.0002 (17)
C10	0.028 (2)	0.024 (2)	0.023 (2)	0.0032 (17)	0.0120 (17)	0.0037 (16)
C11	0.023 (2)	0.020 (2)	0.028 (2)	0.0037 (16)	0.0136 (17)	0.0129 (16)
C12	0.021 (2)	0.0175 (19)	0.034 (2)	−0.0024 (16)	0.0119 (18)	0.0086 (17)
C13	0.0207 (19)	0.0160 (19)	0.027 (2)	−0.0004 (15)	0.0065 (17)	0.0040 (16)
C14	0.031 (2)	0.025 (2)	0.029 (2)	−0.0074 (18)	0.0057 (19)	−0.0023 (18)
C15	0.030 (2)	0.032 (2)	0.032 (2)	0.0008 (19)	0.016 (2)	0.0124 (19)

Geometric parameters (Å, º) top

Pt1—C1	1.951 (4)	C7—C8	1.389 (7)
Pt1—N2	1.995 (4)	C7—H7	0.9500
Pt1—O1	2.074 (3)	C8—C9	1.384 (7)
Pt1—O2	2.001 (3)	C8—H8	0.9500
F1—C3	1.352 (5)	C9—C10	1.379 (6)
F2—C4	1.349 (5)	C9—H9	0.9500
O1—C11	1.282 (5)	C10—H10	0.9500
O2—C13	1.288 (5)	C11—C12	1.399 (6)
N1—C4	1.316 (6)	C11—C15	1.506 (6)
N1—C3	1.327 (6)	C12—C13	1.391 (6)
N2—C10	1.343 (5)	C12—H12	0.9500
N2—C6	1.361 (5)	C13—C14	1.504 (6)
C1—C5	1.406 (6)	C14—H14A	0.9800
C1—C2	1.410 (6)	C14—H14B	0.9800
C2—C3	1.368 (6)	C14—H14C	0.9800
C2—H2	0.9500	C15—H15A	0.9800
C4—C5	1.387 (6)	C15—H15B	0.9800
C5—C6	1.457 (6)	C15—H15C	0.9800
C6—C7	1.393 (6)

C1—Pt1—N2	81.28 (17)	C6—C7—H7	120.0
C1—Pt1—O2	92.90 (16)	C9—C8—C7	119.3 (4)
N2—Pt1—O2	174.15 (12)	C9—C8—H8	120.4
C1—Pt1—O1	174.40 (14)	C7—C8—H8	120.4
N2—Pt1—O1	93.25 (13)	C10—C9—C8	118.6 (4)
O2—Pt1—O1	92.55 (12)	C10—C9—H9	120.7
C11—O1—Pt1	123.4 (3)	C8—C9—H9	120.7
C13—O2—Pt1	123.9 (3)	N2—C10—C9	122.4 (4)
C4—N1—C3	113.8 (4)	N2—C10—H10	118.8
C10—N2—C6	119.9 (4)	C9—C10—H10	118.8
C10—N2—Pt1	123.4 (3)	O1—C11—C12	125.5 (4)
C6—N2—Pt1	116.7 (3)	O1—C11—C15	115.4 (4)
C5—C1—C2	117.9 (4)	C12—C11—C15	119.1 (4)
C5—C1—Pt1	114.5 (3)	C13—C12—C11	127.3 (4)
C2—C1—Pt1	127.4 (3)	C13—C12—H12	116.4
C3—C2—C1	116.6 (4)	C11—C12—H12	116.4
C3—C2—H2	121.7	O2—C13—C12	127.1 (4)
C1—C2—H2	121.7	O2—C13—C14	113.0 (4)
N1—C3—F1	113.5 (4)	C12—C13—C14	119.9 (4)
N1—C3—C2	127.9 (4)	C13—C14—H14A	109.5
F1—C3—C2	118.6 (4)	C13—C14—H14B	109.5
N1—C4—F2	113.7 (4)	H14A—C14—H14B	109.5
N1—C4—C5	126.6 (4)	C13—C14—H14C	109.5
F2—C4—C5	119.7 (4)	H14A—C14—H14C	109.5
C4—C5—C1	117.2 (4)	H14B—C14—H14C	109.5
C4—C5—C6	127.6 (4)	C11—C15—H15A	109.5
C1—C5—C6	115.3 (4)	C11—C15—H15B	109.5
N2—C6—C7	119.9 (4)	H15A—C15—H15B	109.5
N2—C6—C5	112.2 (4)	C11—C15—H15C	109.5
C7—C6—C5	128.0 (4)	H15A—C15—H15C	109.5
C8—C7—C6	119.9 (4)	H15B—C15—H15C	109.5
C8—C7—H7	120.0

N2—Pt1—O1—C11	176.1 (3)	C2—C1—C5—C6	180.0 (4)
O2—Pt1—O1—C11	−3.1 (3)	Pt1—C1—C5—C6	3.4 (5)
C1—Pt1—O2—C13	−175.2 (3)	C10—N2—C6—C7	0.7 (6)
O1—Pt1—O2—C13	3.5 (3)	Pt1—N2—C6—C7	178.9 (3)
C1—Pt1—N2—C10	−179.3 (4)	C10—N2—C6—C5	−179.6 (4)
O1—Pt1—N2—C10	1.9 (3)	Pt1—N2—C6—C5	−1.4 (4)
C1—Pt1—N2—C6	2.6 (3)	C4—C5—C6—N2	179.1 (4)
O1—Pt1—N2—C6	−176.2 (3)	C1—C5—C6—N2	−1.3 (5)
N2—Pt1—C1—C5	−3.2 (3)	C4—C5—C6—C7	−1.2 (7)
O2—Pt1—C1—C5	176.2 (3)	C1—C5—C6—C7	178.4 (4)
N2—Pt1—C1—C2	−179.4 (4)	N2—C6—C7—C8	−0.6 (6)
O2—Pt1—C1—C2	0.0 (4)	C5—C6—C7—C8	179.8 (4)
C5—C1—C2—C3	1.4 (6)	C6—C7—C8—C9	0.5 (6)
Pt1—C1—C2—C3	177.4 (3)	C7—C8—C9—C10	−0.6 (7)
C4—N1—C3—F1	−178.8 (4)	C6—N2—C10—C9	−0.8 (6)
C4—N1—C3—C2	0.9 (7)	Pt1—N2—C10—C9	−178.9 (3)
C1—C2—C3—N1	−1.8 (7)	C8—C9—C10—N2	0.8 (7)
C1—C2—C3—F1	177.9 (4)	Pt1—O1—C11—C12	0.5 (6)
C3—N1—C4—F2	179.4 (4)	Pt1—O1—C11—C15	178.7 (3)
C3—N1—C4—C5	0.3 (6)	O1—C11—C12—C13	3.4 (7)
N1—C4—C5—C1	−0.6 (6)	C15—C11—C12—C13	−174.8 (4)
F2—C4—C5—C1	−179.6 (4)	Pt1—O2—C13—C12	−1.3 (6)
N1—C4—C5—C6	179.1 (4)	Pt1—O2—C13—C14	179.2 (3)
F2—C4—C5—C6	0.0 (6)	C11—C12—C13—O2	−3.0 (7)
C2—C1—C5—C4	−0.3 (6)	C11—C12—C13—C14	176.4 (4)
Pt1—C1—C5—C4	−176.9 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···O2	0.95	2.57	3.040 (5)	111
C7—H7···F2	0.95	2.31	2.917 (6)	121
C10—H10···F1ⁱ	0.95	2.32	3.180 (5)	150
C10—H10···O1	0.95	2.41	3.006 (5)	120
C12—H12···F2ⁱⁱ	0.95	2.44	3.361 (5)	163
C15—H15A···F1ⁱ	0.98	2.54	3.481 (6)	161

Symmetry codes: (i) x, y, z+1; (ii) x−1, y−1, z.

Acknowledgements

This work was supported by the Industrial Strategic Technology Development Program (10039141) funded by the MOTIE (Ministry of Trade, Industry & Energy, Korea), KEIT (Korea Evaluation Institute of Industrial Technology) and the 2014 Research Grant from Kangwon National University (C1010838-01-01).

References

Brandenburg, K. (2005). DIAMOND. Crystal Impact GbR, Germany. Google Scholar
Bruker (2006). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Hudson, Z. M., Blight, B. A. & Wang, S. (2012). Org. Lett. 14, 1700–1703. Web of Science CrossRef CAS PubMed Google Scholar
Rao, Y., Schoenmakers, D., Chang, Y.-L., Lu, J., Lu, Z.-H., Kang, Y. & Wang, S. (2012). Chem. Eur. J. 18, 11306–11316. Web of Science CSD CrossRef CAS PubMed Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.