Poly[bis­(tri­methyl­ammonium) [hexa-μ-cyanido-cadmium(II)dicopper(I)]]

Nishikiori, S.; Yoshida, J.; Yuge, H.

doi:10.1107/S2414314617017710

metal-organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 2| Part 12| December 2017| x171771

https://doi.org/10.1107/S2414314617017710

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Poly[bis(trimethylammonium) [hexa-μ-cyanido-cadmium(II)dicopper(I)]]

Shin-ichi Nishikiori,^a ^* Jun Yoshida ^b and Hidetaka Yuge ^b

^aDepartment of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan, and ^bDepartment of Chemistry, School of Science, Kitasato University, Kitasato 1-15-1, Sagamihara, Kanagawa 252-0373, Japan
^*Correspondence e-mail: cnskor@mail.ecc.u-tokyo.ac.jp

Edited by H. Ishida, Okayama University, Japan (Received 1 December 2017; accepted 12 December 2017; online 15 December 2017)

The title compound, {(C₃H₁₀N)₂[CdCu₂(CN)₆]}_n, has been synthesized as an alternative to the high-emitting complexes containing more expensive metals. The CN⁻ ligands make linkages between the Cu^I and Cd^II ions to form the coordination polymer, [CdCu₂(CN)₆]_n²⁻, which is a three-dimensional framework classified as pyrite net (pyr). The net has a void space for accommodating a trimethylammonium ion located on a threefold rotation axis. The Cd^II ion lies on a special position with site symmetry -3 and is octahedrally coordinated by six N atoms. The Cu^I ion is located on a threefold rotation axis and has a trigonal-planar coordination geometry formed by three C atoms. In the three-dimensional net, two Cu^I ions are arranged closely [Cu⋯Cu = 3.9095 (5) Å], but the distance is not short enough to suggest a Cu^I–Cu^I interaction. The crystal studied was a merohedral twin (twin operation 2_[101]), the refined component ratio being 0.9202 (7):0.0798 (7). A powder of the title compound shows strong luminescence with an emission maximum at 509 nm and a quantum yield of 98% at room temperature.

Keywords: crystal structure; coordination polymer; pyrite net; Cu^I; Cd^II; cyanido complex; luminescence.

CCDC reference: 1810643

Structure description

The title compound, a coordination polymer formed by Cu^I and Cd^II ions and bridging CN⁻ ligands, has been synthesized as an alternative to the high-emitting complexes containing more expensive metals. Combinations of Cu^I, CN⁻ and other building ligands have previously been used for such purposes (Lim et al., 2008 ; Dembo et al., 2010 ). The objective of the present work was to build a more robust and lower energy loss coordination polymer by adding Cd^II ions. These ions are well known as excellent building blocks for three-dimensional net structures (Iwamoto, 1996 ), and exhibit no emissive d–d metal-centred levels (Barbieri et al., 2008 ). A powder of the title compound showed luminescence with an emission maximum at 509 nm and a quantum yield of 98% at room temperature.

The Cu^I ion resides on a threefold rotation axis and has a trigonal-planar coordination geometry by the C atoms of three CN⁻ ligands. The N-terminals of the CN⁻ ligands are linked to the Cd^II ions, which are located on special positions with $[\overline{3}]$ site symmetry (Fig. 1). The orientation of the bridging CN⁻ ions was confirmed by ¹¹³Cd CP/MAS NMR spectra, which showed a single peak at a chemical shift of 191 p.p.m. [referenced to an external Cd(NO₃)₂·4H₂O standard]. This chemical shift indicates that each Cd^II ion is octahedrally coordinated by six N atoms (Nishikiori et al., 1990 ). The Cu^I—CN—Cd^II linkages form an infinite [CdCu₂(CN)₆]_n²⁻ three-dimensional net. The topology of this net is characterized as pyr (pyrite net; Fig. 2), the same as that of MOF-150 (Chae et al., 2003 ). The two closest Cu(CN)₃ units, which reside on the same threefold rotation axis, are stacked in a staggered conformation with an inversion centre at their mid point (Fig. 3). The distance between the two Cu^I ions [3.9095 (5) Å] precludes a Cu^I–Cu^I interaction, the contribution of which to luminescence behaviour has previously been discussed (Nishikawa et al., 2016 ). The (CH₃)₃NH⁺ ions that balance the negative charges of the three-dimensional polymer are trapped in the voids of the pyrite net. The principal axis of the (CH₃)₃NH⁺ ion coincides with the threefold rotation axis on which the Cu^I and Cd^II ions reside. The lone H atom of the (CH₃)₃NH⁺ ion is oriented towards the Cd^II ion (Fig. 3).

Figure 1
The coordination forms of the Cd^II and Cu^I ions and the structure of the trimethylammonium ion in the title compound. All displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted for clarity. [Symmetry codes: (i) –z + $[{1\over 2}]$ , –x + 1, y − $[{1\over 2}]$ ; (ii) −y + 1, z + $[{1\over 2}]$ , −x + $[{1\over 2}]$ ; (iii) −x + 1, −y + 1, −z; (iv) z + $[{1\over 2}]$ , x, −y + $[{1\over 2}]$ ; (v) y, −z + $[{1\over 2}]$ , x − $[{1\over 2}]$ ; (vi) z, x, y; (vii) y, z, x.]

Figure 2
Pyrite net (pyr) of the coordination polymer [CdCu₂(CN)₆]_n²⁻. The CN⁻ ligands linking the Cd^II (octahedral coordination sphere) and the Cu^I (trigonal-planar coordination sphere) ions are represented as solid lines.

Figure 3
An arrangement of the Cd^II (octahedral coordination sphere), Cu^I (trigonal-planar coordination sphere) and (CH₃)₃NH⁺ ions on the threefold rotation axis running along the diagonal line of the unit cell. The distance between Cu1 and Cu1^ix is 3.9095 (5) Å. [Symmetry codes: (viii) x + $[{1\over 2}]$ , −y + $[{3\over 2}]$ , 1 − z; (ix) 1 − x, 1 − y, 1 − z; (x) x − $[{1\over 2}]$ , −y + $[{1\over 2}]$ , −z; (xi) x − $[{1\over 2}]$ , −y + $[{1\over 2}]$ , −z.]

Synthesis and crystallization

The title compound was prepared from an aqueous solution containing Cd(CN)₂, CuCN, NaCN and (CH₃)₃NHCl. Into 20 ml of water Cd(CN)₂ (0.33 g, 2 mmol), CuCN (0.18 g, 2 mmol) and NaCN (0.40 g, 8.2 mmol) were added. The mixture was warmed with stirring until it turned to a clear solution. Then, (CH₃)₃NHCl (0.19 g, 2 mmol) was dissolved into the solution. After keeping the solution at 278 K for a week, colourless crystals of the title compound were obtained. Analysis calculated for C₁₂H₂₀CdCu₂N₈: C 27.94, H 3.91, N 21.72%; found: C 27.85, H 3.98, N 21.87%.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. In the final stage, the refinement was carried out assuming merohedral twinning, as suggested by the PLATON program (Spek, 2015 ), with the twin operation 2_[101], and the final BASF parameter was 0.0798 (7).

Table 1
Experimental details

Crystal data
Chemical formula	(C₃H₁₀N)₂[CdCu₂(CN)₆]
M_r	515.87
Crystal system, space group	Cubic, Pa $[\overline{3}]$
Temperature (K)	296
a (Å)	12.3775 (9)
V (Å³)	1896.3 (4)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	3.34
Crystal size (mm)	0.32 × 0.29 × 0.22

Data collection
Diffractometer	Bruker APEXII
Absorption correction	Multi-scan (SADABS; Bruker, 2012 )
T_min, T_max	0.627, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	11150, 861, 772
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.677

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.017, 0.044, 1.11
No. of reflections	861
No. of parameters	38
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.28
Computer programs: APEX2 and SAINT (Bruker, 2012), SHELXS97 (Sheldrick 2008 ), SHELXL2017 (Sheldrick, 2015 ), VESTA 3 (Momma & Izumi, 2011 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1810643

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314617017710/is4021sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617017710/is4021Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick 2008); program(s) used to refine structure: SHELXL2017 (Sheldrick, 2015); molecular graphics: VESTA 3 (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

Poly[bis[(trimethylammonium) [hexa-µ-cyanido-cadmium(II)dicopper(I)] top

Crystal data top

(C₃H₁₀N)₂[CdCu₂(CN)₆]	Mo Kα radiation, λ = 0.71073 Å
M_r = 515.87	Cell parameters from 5459 reflections
Cubic, Pa3	θ = 2.9–28.5°
a = 12.3775 (9) Å	µ = 3.34 mm⁻¹
V = 1896.3 (4) Å³	T = 296 K
Z = 4	Block, colourless
F(000) = 1016	0.32 × 0.29 × 0.22 mm
D_x = 1.807 Mg m⁻³

Data collection top

Bruker APEXII diffractometer	861 independent reflections
Radiation source: fine-focus sealed tube	772 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
Detector resolution: 8.3333 pixels mm^-1	θ_max = 28.8°, θ_min = 1.7°
phi and ω scans	h = −16→11
Absorption correction: multi-scan (SADABS; Bruker, 2012)	k = −14→16
T_min = 0.627, T_max = 0.746	l = −15→16
11150 measured reflections

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) = 0.044	H-atom parameters constrained
S = 1.11	w = 1/[σ²(F_o²) + (0.0208P)² + 0.6318P] where P = (F_o² + 2F_c²)/3
861 reflections	(Δ/σ)_max < 0.001
38 parameters	Δρ_max = 0.28 e Å⁻³
0 restraints	Δρ_min = −0.28 e Å⁻³

Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refined as a 2-component twin.

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

	x	y	z	U_iso*/U_eq
Cd1	0.500000	0.500000	0.000000	0.02365 (9)
Cu1	0.40882 (2)	0.40882 (2)	0.40882 (2)	0.03148 (11)
N1	0.48328 (15)	0.49244 (15)	0.18799 (14)	0.0413 (4)
C1	0.46209 (16)	0.46692 (16)	0.27362 (15)	0.0335 (4)
N2	0.29859 (12)	0.70141 (12)	0.20141 (12)	0.0338 (6)
H2	0.344303	0.655696	0.155697	0.041*
C2	0.20128 (19)	0.6377 (2)	0.23072 (19)	0.0521 (6)
H2A	0.222902	0.572912	0.267472	0.078*
H2B	0.162203	0.619101	0.166360	0.078*
H2C	0.155818	0.679893	0.277288	0.078*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cd1	0.02365 (9)	0.02365 (9)	0.02365 (9)	0.00096 (6)	0.00096 (6)	−0.00096 (6)
Cu1	0.03148 (11)	0.03148 (11)	0.03148 (11)	0.00670 (10)	0.00670 (10)	0.00670 (10)
N1	0.0470 (10)	0.0483 (11)	0.0286 (8)	−0.0062 (8)	0.0020 (7)	0.0031 (7)
C1	0.0340 (9)	0.0340 (9)	0.0324 (9)	0.0042 (8)	0.0033 (8)	0.0028 (7)
N2	0.0338 (6)	0.0338 (6)	0.0338 (6)	0.0038 (6)	0.0038 (6)	−0.0038 (6)
C2	0.0514 (13)	0.0599 (14)	0.0450 (12)	−0.0161 (11)	0.0071 (10)	−0.0003 (11)

Geometric parameters (Å, º) top

Cd1—N1	2.3379 (17)	N1—C1	1.137 (3)
Cd1—N1ⁱ	2.3379 (17)	N2—C2	1.485 (3)
Cd1—N1ⁱⁱ	2.3379 (17)	N2—C2ⁱ	1.485 (3)
Cd1—N1ⁱⁱⁱ	2.3379 (17)	N2—C2ⁱⁱ	1.485 (3)
Cd1—N1^iv	2.3379 (17)	N2—H2	0.9800
Cd1—N1^v	2.3379 (17)	C2—H2A	0.9600
Cu1—C1	1.9371 (19)	C2—H2B	0.9600
Cu1—C1^vi	1.9371 (19)	C2—H2C	0.9600
Cu1—C1^vii	1.9371 (19)

N1—Cd1—N1ⁱ	87.44 (6)	C1—Cu1—C1^vii	119.24 (8)
N1—Cd1—N1ⁱⁱ	87.44 (6)	C1^vi—Cu1—C1^vii	119.24 (8)
N1—Cd1—N1ⁱⁱⁱ	180.00	Cd1—N1—C1	163.66 (17)
N1—Cd1—N1^iv	92.56 (6)	Cu1—C1—N1	170.85 (18)
N1—Cd1—N1^v	92.56 (6)	C2—N2—C2ⁱ	111.25 (16)
N1ⁱ—Cd1—N1ⁱⁱ	87.44 (6)	C2—N2—C2ⁱⁱ	111.25 (16)
N1ⁱ—Cd1—N1ⁱⁱⁱ	92.56 (6)	C2ⁱ—N2—C2ⁱⁱ	111.25 (16)
N1ⁱ—Cd1—N1^iv	180.00	C2—N2—H2	108.00
N1ⁱ—Cd1—N1^v	92.56 (6)	C2ⁱ—N2—H2	108.00
N1ⁱⁱ—Cd1—N1ⁱⁱⁱ	92.56 (6)	C2ⁱⁱ—N2—H2	108.00
N1ⁱⁱ—Cd1—N1^iv	92.56 (6)	N2—C2—H2A	109.00
N1ⁱⁱ—Cd1—N1^v	180.00	N2—C2—H2B	109.00
N1ⁱⁱⁱ—Cd1—N1^iv	87.44 (6)	N2—C2—H2C	109.00
N1ⁱⁱⁱ—Cd1—N1^v	87.44 (6)	H2A—C2—H2B	109.00
N1^iv—Cd1—N1^v	87.44 (6)	H2A—C2—H2C	109.00
C1—Cu1—C1^vi	119.24 (8)	H2B—C2—H2C	109.00

Symmetry codes: (i) −z+1/2, −x+1, y−1/2; (ii) −y+1, z+1/2, −x+1/2; (iii) −x+1, −y+1, −z; (iv) z+1/2, x, −y+1/2; (v) y, −z+1/2, x−1/2; (vi) z, x, y; (vii) y, z, x.

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