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During an attempt to grow crystals of the nonlinear optical material Cd
3Zn
3B
4O
12 using a KBF
4 flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn
2KB
2O
6F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner-sharing ZnO
3F tetrahedra and BO
3 triangles. Both Zn and B reside on threefold rotation axes, while the F
- anion is located at a site of 3.2 symmetry. The Cd
II (site symmetry
) and K
+ (site symmetry 3.2) ions occupy six- and nine-coordinate interlayer sites, respectively. The BO
3 triangles and ZnO
3 pyramids from the ZnO
3F tetrahedra share bridging O atoms with each other to form an extended [ZnBO
3] layer parallel to (001). Although these layers are similar to the [
MBO
3] layers seen in other compounds, they are uniquely bridged here by the Cd centres and F
- anions to form a three-dimensional framework. In so doing, a series of channels is formed along the [010] direction and the K
+ cations are found in these channels.
Supporting information
The precursor Cd3Zn3B4O12 was synthesized from CdO (99.8%), ZnO
(99.95%) and H3BO3 (99.99%) according to the published procedure (Zhang
et al., 2008). A mixture of appropriate quantities [Please
give mole
ratio or exact quantities] of Cd3Zn3B4O12 and KBF4 (99.0%) was
ground to fine powder in a mortar and compressed into a Pt crucible. The
sample was gradually heated to 1073 K and kept at this temperature for 1 d for
complete melting. It was then cooled to 973 K at a rate of 1 K h-1, followed
by cooling to room temperature at 20 K h-1. Colourless crystals of the title
compound of millimetre dimensions could be isolated mechanically from the
solidified melt for further study.
Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS (Bruker, 1997); data reduction: XSCANS (Bruker, 1997); 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).
cadmium dizinc potassium borate fluoride
top
Crystal data top
CdZn2KB2O6F | Dx = 4.176 Mg m−3 |
Mr = 418.86 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, P31c | Cell parameters from 32 reflections |
Hall symbol: -P 3 2c | θ = 4.9–23.0° |
a = 5.0381 (6) Å | µ = 10.93 mm−1 |
c = 15.1550 (19) Å | T = 295 K |
V = 333.13 (7) Å3 | Block, colourless |
Z = 2 | 0.14 × 0.1 × 0.1 mm |
F(000) = 388 | |
Data collection top
Bruker P4 diffractometer | 547 reflections with I > 2σ(I) |
Radiation source: sealed tube | Rint = 0.053 |
Graphite monochromator | θmax = 37.5°, θmin = 2.7° |
ω scans | h = −8→8 |
Absorption correction: empirical (using intensity measurements) (North et al., 1968) | k = −8→8 |
Tmin = 0.243, Tmax = 0.335 | l = −25→25 |
2534 measured reflections | 3 standard reflections every 97 reflections |
599 independent reflections | intensity decay: none |
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)] = 0.037 | w = 1/[σ2(Fo2) + (0.0015P)2 + 4.4689P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.083 | (Δ/σ)max < 0.001 |
S = 1.03 | Δρmax = 1.55 e Å−3 |
599 reflections | Δρmin = −2.29 e Å−3 |
23 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0201 (17) |
Crystal data top
CdZn2KB2O6F | Z = 2 |
Mr = 418.86 | Mo Kα radiation |
Trigonal, P31c | µ = 10.93 mm−1 |
a = 5.0381 (6) Å | T = 295 K |
c = 15.1550 (19) Å | 0.14 × 0.1 × 0.1 mm |
V = 333.13 (7) Å3 | |
Data collection top
Bruker P4 diffractometer | 547 reflections with I > 2σ(I) |
Absorption correction: empirical (using intensity measurements) (North et al., 1968) | Rint = 0.053 |
Tmin = 0.243, Tmax = 0.335 | 3 standard reflections every 97 reflections |
2534 measured reflections | intensity decay: none |
599 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.037 | 23 parameters |
wR(F2) = 0.083 | 0 restraints |
S = 1.03 | Δρmax = 1.55 e Å−3 |
599 reflections | Δρmin = −2.29 e Å−3 |
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 | Uiso*/Ueq | |
Cd1 | 0.0000 | 0.0000 | 0.5000 | 0.01415 (15) | |
Zn1 | 0.3333 | 0.6667 | 0.38347 (5) | 0.01304 (16) | |
K1 | 0.0000 | 1.0000 | 0.2500 | 0.0247 (4) | |
F1 | 0.3333 | 0.6667 | 0.2500 | 0.0320 (15) | |
B1 | 0.6667 | 0.3333 | 0.4055 (4) | 0.0145 (10) | |
O1 | 0.3844 (6) | 0.3166 (6) | 0.40507 (17) | 0.0181 (5) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.01407 (18) | 0.01407 (18) | 0.0143 (2) | 0.00704 (9) | 0.000 | 0.000 |
Zn1 | 0.0119 (2) | 0.0119 (2) | 0.0153 (3) | 0.00596 (10) | 0.000 | 0.000 |
K1 | 0.0266 (6) | 0.0266 (6) | 0.0209 (8) | 0.0133 (3) | 0.000 | 0.000 |
F1 | 0.041 (2) | 0.041 (2) | 0.014 (2) | 0.0204 (12) | 0.000 | 0.000 |
B1 | 0.0153 (15) | 0.0153 (15) | 0.013 (2) | 0.0077 (7) | 0.000 | 0.000 |
O1 | 0.0146 (10) | 0.0176 (10) | 0.0234 (11) | 0.0090 (9) | 0.0023 (8) | 0.0037 (9) |
Geometric parameters (Å, º) top
Cd1—O1i | 2.297 (3) | K1—F1 | 2.9087 (3) |
Cd1—O1ii | 2.297 (3) | K1—O1xiii | 2.954 (3) |
Cd1—O1iii | 2.297 (3) | K1—O1xiv | 2.954 (3) |
Cd1—O1iv | 2.297 (3) | K1—O1xv | 2.955 (3) |
Cd1—O1v | 2.297 (3) | K1—O1xi | 2.955 (3) |
Cd1—O1 | 2.297 (3) | K1—O1xvi | 2.955 (3) |
Cd1—K1vi | 3.7888 (5) | K1—O1viii | 2.955 (3) |
Cd1—K1vii | 3.7888 (5) | K1—Zn1xi | 3.5430 (5) |
Zn1—O1viii | 1.933 (3) | K1—Zn1xv | 3.5430 (5) |
Zn1—O1ix | 1.933 (3) | F1—Zn1xvii | 2.0228 (7) |
Zn1—O1 | 1.933 (3) | F1—K1x | 2.9087 (3) |
Zn1—F1 | 2.0228 (7) | F1—K1vii | 2.9087 (3) |
Zn1—K1vii | 3.5430 (5) | B1—O1xviii | 1.382 (3) |
Zn1—K1 | 3.5430 (5) | B1—O1 | 1.382 (3) |
Zn1—K1x | 3.5430 (5) | B1—O1xix | 1.382 (3) |
K1—F1xi | 2.9087 (3) | O1—K1vii | 2.954 (3) |
K1—F1xii | 2.9087 (3) | | |
| | | |
O1i—Cd1—O1ii | 180.000 (1) | O1xiii—K1—O1xi | 124.25 (11) |
O1i—Cd1—O1iii | 84.93 (10) | O1xiv—K1—O1xi | 63.31 (8) |
O1ii—Cd1—O1iii | 95.07 (10) | O1xv—K1—O1xi | 168.50 (11) |
O1i—Cd1—O1iv | 84.93 (10) | F1xi—K1—O1xvi | 84.25 (5) |
O1ii—Cd1—O1iv | 95.07 (10) | F1xii—K1—O1xvi | 124.59 (5) |
O1iii—Cd1—O1iv | 84.93 (10) | F1—K1—O1xvi | 62.12 (5) |
O1i—Cd1—O1v | 95.07 (10) | O1xiii—K1—O1xvi | 63.31 (8) |
O1ii—Cd1—O1v | 84.93 (10) | O1xiv—K1—O1xvi | 168.51 (11) |
O1iii—Cd1—O1v | 95.07 (10) | O1xv—K1—O1xvi | 63.31 (8) |
O1iv—Cd1—O1v | 180.0 | O1xi—K1—O1xvi | 110.82 (10) |
O1i—Cd1—O1 | 95.08 (10) | F1xi—K1—O1viii | 124.59 (5) |
O1ii—Cd1—O1 | 84.92 (10) | F1xii—K1—O1viii | 84.25 (5) |
O1iii—Cd1—O1 | 180.0 | F1—K1—O1viii | 62.12 (5) |
O1iv—Cd1—O1 | 95.08 (10) | O1xiii—K1—O1viii | 168.51 (11) |
O1v—Cd1—O1 | 84.92 (10) | O1xiv—K1—O1viii | 63.31 (8) |
O1i—Cd1—K1vi | 51.22 (7) | O1xv—K1—O1viii | 110.82 (10) |
O1ii—Cd1—K1vi | 128.78 (7) | O1xi—K1—O1viii | 63.31 (8) |
O1iii—Cd1—K1vi | 51.22 (7) | O1xvi—K1—O1viii | 124.25 (11) |
O1iv—Cd1—K1vi | 51.22 (7) | F1xi—K1—Zn1 | 114.236 (3) |
O1v—Cd1—K1vi | 128.78 (7) | F1xii—K1—Zn1 | 114.236 (4) |
O1—Cd1—K1vi | 128.78 (7) | F1—K1—Zn1 | 34.816 (10) |
O1i—Cd1—K1vii | 128.78 (7) | O1xiii—K1—Zn1 | 156.96 (5) |
O1ii—Cd1—K1vii | 51.22 (7) | O1xiv—K1—Zn1 | 90.68 (5) |
O1iii—Cd1—K1vii | 128.78 (7) | O1xv—K1—Zn1 | 111.83 (5) |
O1iv—Cd1—K1vii | 128.78 (7) | O1xi—K1—Zn1 | 57.56 (5) |
O1v—Cd1—K1vii | 51.22 (7) | O1xvi—K1—Zn1 | 94.03 (5) |
O1—Cd1—K1vii | 51.22 (7) | O1viii—K1—Zn1 | 33.07 (5) |
K1vi—Cd1—K1vii | 180.0 | F1xi—K1—Zn1xi | 34.816 (10) |
O1viii—Zn1—O1ix | 117.19 (5) | F1xii—K1—Zn1xi | 114.237 (3) |
O1viii—Zn1—O1 | 117.19 (5) | F1—K1—Zn1xi | 114.236 (3) |
O1ix—Zn1—O1 | 117.19 (5) | O1xiii—K1—Zn1xi | 94.03 (5) |
O1viii—Zn1—F1 | 99.75 (8) | O1xiv—K1—Zn1xi | 57.56 (5) |
O1ix—Zn1—F1 | 99.75 (8) | O1xv—K1—Zn1xi | 156.96 (5) |
O1—Zn1—F1 | 99.75 (8) | O1xi—K1—Zn1xi | 33.07 (5) |
O1viii—Zn1—K1vii | 90.12 (8) | O1xvi—K1—Zn1xi | 111.84 (5) |
O1ix—Zn1—K1vii | 147.13 (8) | O1viii—K1—Zn1xi | 90.68 (5) |
O1—Zn1—K1vii | 56.50 (8) | Zn1—K1—Zn1xi | 90.632 (14) |
F1—Zn1—K1vii | 55.184 (10) | F1xi—K1—Zn1xv | 114.237 (3) |
O1viii—Zn1—K1 | 56.50 (8) | F1xii—K1—Zn1xv | 34.816 (10) |
O1ix—Zn1—K1 | 90.12 (8) | F1—K1—Zn1xv | 114.236 (3) |
O1—Zn1—K1 | 147.13 (9) | O1xiii—K1—Zn1xv | 57.56 (5) |
F1—Zn1—K1 | 55.184 (10) | O1xiv—K1—Zn1xv | 94.03 (5) |
K1vii—Zn1—K1 | 90.633 (14) | O1xv—K1—Zn1xv | 33.07 (5) |
O1viii—Zn1—K1x | 147.13 (8) | O1xi—K1—Zn1xv | 156.96 (5) |
O1ix—Zn1—K1x | 56.50 (8) | O1xvi—K1—Zn1xv | 90.68 (5) |
O1—Zn1—K1x | 90.12 (8) | O1viii—K1—Zn1xv | 111.84 (5) |
F1—Zn1—K1x | 55.184 (10) | Zn1—K1—Zn1xv | 131.528 (6) |
K1vii—Zn1—K1x | 90.633 (15) | Zn1xi—K1—Zn1xv | 131.529 (6) |
K1—Zn1—K1x | 90.633 (15) | Zn1—F1—Zn1xvii | 180.0 |
F1xi—K1—F1xii | 120.0 | Zn1—F1—K1 | 90.0 |
F1xi—K1—F1 | 120.0 | Zn1xvii—F1—K1 | 90.0 |
F1xii—K1—F1 | 120.0 | Zn1—F1—K1x | 90.0 |
F1xi—K1—O1xiii | 62.13 (5) | Zn1xvii—F1—K1x | 90.0 |
F1xii—K1—O1xiii | 84.25 (5) | K1—F1—K1x | 120.0 |
F1—K1—O1xiii | 124.59 (5) | Zn1—F1—K1vii | 90.0 |
F1xi—K1—O1xiv | 84.25 (5) | Zn1xvii—F1—K1vii | 90.0 |
F1xii—K1—O1xiv | 62.13 (5) | K1—F1—K1vii | 120.0 |
F1—K1—O1xiv | 124.59 (5) | K1x—F1—K1vii | 120.0 |
O1xiii—K1—O1xiv | 110.82 (10) | O1xviii—B1—O1 | 119.999 (6) |
F1xi—K1—O1xv | 124.59 (5) | O1xviii—B1—O1xix | 119.997 (6) |
F1xii—K1—O1xv | 62.13 (5) | O1—B1—O1xix | 119.998 (6) |
F1—K1—O1xv | 84.25 (5) | B1—O1—Zn1 | 123.19 (18) |
O1xiii—K1—O1xv | 63.31 (8) | B1—O1—Cd1 | 121.6 (2) |
O1xiv—K1—O1xv | 124.25 (11) | Zn1—O1—Cd1 | 106.79 (12) |
F1xi—K1—O1xi | 62.13 (5) | B1—O1—K1vii | 114.4 (3) |
F1xii—K1—O1xi | 124.59 (5) | Zn1—O1—K1vii | 90.43 (9) |
F1—K1—O1xi | 84.25 (5) | Cd1—O1—K1vii | 91.48 (9) |
Symmetry codes: (i) y, −x+y, −z+1; (ii) −y, x−y, z; (iii) −x, −y, −z+1; (iv) x−y, x, −z+1; (v) −x+y, −x, z; (vi) −x, −y+1, −z+1; (vii) x, y−1, z; (viii) −x+y, −x+1, z; (ix) −y+1, x−y+1, z; (x) x+1, y, z; (xi) x, y+1, z; (xii) x−1, y, z; (xiii) −x+y, y+1, −z+1/2; (xiv) −y, x−y+1, z; (xv) −y, −x+1, −z+1/2; (xvi) x, x−y+1, −z+1/2; (xvii) −y+1, −x+1, −z+1/2; (xviii) −x+y+1, −x+1, z; (xix) −y+1, x−y, z. |
Experimental details
Crystal data |
Chemical formula | CdZn2KB2O6F |
Mr | 418.86 |
Crystal system, space group | Trigonal, P31c |
Temperature (K) | 295 |
a, c (Å) | 5.0381 (6), 15.1550 (19) |
V (Å3) | 333.13 (7) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 10.93 |
Crystal size (mm) | 0.14 × 0.1 × 0.1 |
|
Data collection |
Diffractometer | Bruker P4 diffractometer |
Absorption correction | Empirical (using intensity measurements) (North et al., 1968) |
Tmin, Tmax | 0.243, 0.335 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2534, 599, 547 |
Rint | 0.053 |
(sin θ/λ)max (Å−1) | 0.856 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.083, 1.03 |
No. of reflections | 599 |
No. of parameters | 23 |
Δρmax, Δρmin (e Å−3) | 1.55, −2.29 |
Selected bond lengths (Å) topCd1—O1 | 2.297 (3) | K1—F1 | 2.9087 (3) |
Zn1—O1 | 1.933 (3) | K1—O1i | 2.954 (3) |
Zn1—F1 | 2.0228 (7) | B1—O1 | 1.382 (3) |
Symmetry code: (i) −x+y, y+1, −z+1/2. |
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Recently, numerous studies have been carried out on inorganic nonlinear optical (NLO) borate crystals, which are widely used in optical communication, laser medicine and signal processing (Becker, 1998). Some fluoride borates display good NLO properties, including KBe2BO3F2 (Wu et al., 1996), Ln3(BO3)2F3 (Ln = Sm, Eu and Gd) (Corbel et al., 1998), BaMBO3F2 (M = Ga and Al) (Park & Barbier, 2000) and ABe2BO3F2 (McMillen & Kolis, 2008). In the present work, KBF4 was added as a flux in the ternary CdO–ZnO–B2O3 system in an attempt to grow the NLO crystal Cd3Zn3B4O12 (Zhang, 2008), of interest in part due to its reported fluorescence behaviour (Harrison & Hummel, 1959). The title new fluoride borate crystal, CdZn2KB2O6F, was unexpectedly obtained and has been structurally characterized.
CdZn2KB2O6F belongs to the trigonal P31c space group and the structure consists of (001) layers formed by corner-sharing ZnO3F tetrahedra and BO3 triangles, linked by Cd atoms occupying six-coordinate interlayer sites with K atoms in interlayer channels (Fig. 1). The Zn atom is coordinated by three O atoms and an F atom to form a slightly flattened ZnO3F tetrahedron (O—Zn—O angles ~117° and O—Zn—F angles \sim 100°). The BO3 triangles are planar with ideal angles, as required by the threefold symmetry, and with B—O bonds comparable with those in other borates (Sun et al., 2003; Haberer & Huppertz, 2009).
The [BO3] triangles and [ZnO3] pyramids from the [ZnO3F] tetrahedra share bridging O atoms with each other to form an infinite [ZnBO3] layer (Fig. 2), which is related to the layers observed in crystals of Sr2Be2B2O7 (SBBO), KBe2BO3F2 (KBBF) and BaAlBO3F2 (BABF) (Becker, 1998). In the title crystal structure, the [ZnBO3] layers are distributed one upon another along the (001) direction, connected by Cd and F atoms. In SBBO, the [BO3] groups are linked through [BeO4] tetrahedra to form [Be2B2O7] layers, which are stacked in a coplanar orientation along (001) (Chen et al., 1995). In KBBF and BABF, [BO3] and [BeO3F]/[AlO3F2] sheets are very similarly stacked along (001). The layers in these crystals are essentially the same as those in CdZn2KB2O6F, with the Zn sites occupied by Be/Al atoms instead. Unlike the crystals of SBBO, KBBF and BABF, a series of CdO6 octahedra and bridging F atoms link adjacent ZnBO3 layers alternately to form a unique three-dimensional framework (Fig. 3).
Six O atoms from adjacent layers coordinate the Cd atoms to form a slightly distorted CdO6 octahedron. The F atoms are two-coordinate and bond two Zn atoms from different layers. The Zn—F bonds here make the Zn atoms deviate slightly from the BO3 layers by ~0.33 Å. The bridging Cd and F atoms together connect the [ZnBO3] layers to form a three-dimensional open framework. In this way, channels are formed along the (010) direction and the K+ cations occupy these channels. Each K+ ion is surrounded by six O atoms and three F atoms (Table 1).
The crystalline powder of CdZn2KB2O6F exhibited distinct blue photoluminescence, with emission peaks at 471 and 483 nm by excitation at 389 and 400 nm, respectively. The luminescence may be caused by the planar sandwich layers coordinated to the Cd2+ ions, which affect the charge transfer between the Cd2+ ions and the layers in a process similar to ligand-to-metal charge transfer (LMCT).