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The title compound represents a new structure type, in which distorted VO6 octa­hedra are bridged by iodate groups to form infinite two-dimensional [VO2(IO3)2]- layers that are separated by octa­hedrally coordinated Li+ cations.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106027193/em3001sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106027193/em3001Isup2.hkl
Contains datablock I

Comment top

Two types of nonlinear optical (NLO) materials are well known. The first kind, such as LiNbO3, BaTiO3 etc., contain high-valent d0 transition metals that are readily susceptible to second-order Jahn–Teller (SOJT) distortions, giving rise to distorted MO6n- octahedra. The second kind, e.g. α-LiIO3 and KIO3, contain pyramidal IO3- ligands with stereochemically active nonbonding electron pairs (Halasyamani & Poeppelmeier, 1998). If an SOJT-distorted transition metal and anions containing nonbonding electron pairs were combined in the same crystal, and furthermore, they were arranged in a manner favourable for producing a large NLO effect, a new class of NLO materials would be expected. Based on this idea, several vanadyl iodates, A[VO2(IO3)2] (A = K or Rb) (References?) and A[(VO)2(IO3)3O2] (A = NH4, Rb or Cs), have recently been synthesized, among which the last three compounds show large second-harmonic generation (SHG) responses of about 500 times that of α-SiO2 (Sykora, Ok, Halasyamani, Wells & Albrecht-Schmitt, 2002). However, the Li-containing vanadyl iodates have not been reported to date. The current interest in these materials has enabled us to discover Li[VO2(IO3)2], which does not exhibit SHG effects but which crystallizes in a unique structural type different from those of the K and Rb analogues. We report its crystal structure here.

Li[VO2(IO3)2] represents a new structure type (Pearson symbol mP48; Villars & Calvert, 1991) and is characterized by VO6 octahedra that are bridged by iodate groups to form an infinite two-dimensional [VO2(IO3)2]1- layer parallel to the [102] plane, as shown in Fig. 1. The anionic layers are stacked approximately along the [102] direction, with the interlayer void spaces filled by Li+ cations to balance charge. Each Li+ ion is coordinated by six O atoms in a slightly distorted octahedral geometry, with Li—O distances in the range 2.021 (9)–2.228 (9) Å. The average Li—O bond distance of 2.099 Å is close to Shannon's crystal radii sum of 2.11 Å (Shannon, 1976) and is also comparable with those found in LiIO3 (2.111 Å; Svensson et al., 1983) and LiH4IO6·H2O (2.135 Å; Kraft & Jansen, 1994), all featuring octahedrally coordinated Li+.

There is one crystallographically unique V atom, which occupies a distorted octahedron, with two short vanadyl VO bonds to O7 and O8, and four V—O—I links via atoms O2, O3, O5 and O6 (Fig. 2). The cis O—V—O octahedral angles vary from 77.19 (15) to 100.4 (2)°, and the trans angles are in the range 158.36 (17)–169.25 (19)°, deviating significantly from the expected values of 90 and 180°, respectively. The V atoms are susceptible to SOJT distortion and are displaced out of the centre of an idealized VO6 octahedron along a C2 axis of the octahedron by about 0.406 Å, thus resulting in the formation of two short [V—O7 = 1.632 (4) and V—O8 = 1.649 (4) Å], two intermediate [V—O6 = 1.992 (4) and V—O3 = 1.998 (4) Å] and two long [V—O2 = 2.196 (4) and V—O5 = 2.239 (4) Å] bonds (Table 1). This is very similar to the situation for octahedral MoVI atoms observed in AMoO3(IO3) (A = K, Rb or Cs; Sykora, Ok, Halasyamani & Albrecht-Schmitt, 2002), but slightly different from the situation for VV atoms in the previously reported vanadyl iodates A[(VO)2(IO3)3O2] (A = NH4, Rb or Cs), where the distortion of the VO6 group toward one O atom leads to a `one short + two intermediate + three long' V—O bonding scheme (Sykora, Ok, Halasyamani, Wells & Albrecht-Schmitt, 2002). The V—O bond distances observed in Li[VO2(IO3)2] compare well with those found in A[(VO)2(IO3)3O2] (A = NH4, Rb or Cs) [1.620 (9)–2.227 (8) Å] and (NH4)(VO2)3(SeO3)2 [1.637 (10)–2.198 (11) Å; Vaughey et al., 1994].

The I atoms occupy two different crystallographic sites. They are both coordinated by three O atoms, forming trigonal–pyramidal geometries. Each IO3- group acts as a bidentate ligand bonded to two V5+ centres via two µ2-O atoms, with the third O atom terminal. The I—O bond lengths for the O atoms bound to the V5+ centres [1.810 (4)–1.855 (4) Å] are slightly longer than those for the terminal O atoms [1.793 (4) and 1.798 (4) Å], as expected, and both are in good agreement with the values observed in A[VO2(IO3)2] (A = K or Rb). The O—I—O bond angles are normal, lying in the range 96.8 (2)–101.27 (19)°. The refined structural model was further supported by bond-valence sum (BVS) calculations (Brown & Altermatt, 1985), which gave reasonable values of 1.10, 4.95 and 4.92–4.95 for Li, V and I atoms, respectively.

In the family of compounds A[VO2(IO3)2] (A = Li, Na, K, Rb or Cs), only the K and Rb phases have been structurally characterized to date. Their crystal structures contain five-coordinate VV atoms that are bound by two terminal O atoms, one of which is monodentate, and two bridging iodate anions, to create a fundamental [VO2(IO3)3]2- building unit. Adjacent [VO2(IO3)3]2- units are linked together through bridging iodate anions to generate a one-dimensional [VO2(IO3)2]- chain. These chains are further separated by nine-coordinate K+ and 11-coordinated Rb+ cations, giving rise to different space-group symmetries (P21/n for the K phase and P1 for the Rb phase) (Sykora, Ok, Halasyamani, Wells & Albrecht-Schmitt, 2002). The structural differences between A[VO2(IO3)2] (A = Li, K or Rb) are related not only to the variation in the coordination environments around the V atoms, but also to the cation size effect: six-coordinate octahedral geometry is preferred by the smaller Li+ ions, a nine-coordinate environment is observed for the K+ ions, and a higher coordination number of 11 is required for the larger Rb+ cations.

Experimental top

Li2CO3 (0.487 mmol), V2O5 (0.489 mmol), I2O5 (0.983 mmol) and H2O (2 ml) were weighed and sealed in a 15 ml Teflon-lined stainless steel vessel. This was heated in an oven at 443 K for one week under autogenous pressure and then cooled slowly to room temperature. The product consisted of yellow block-like crystals of Li[VO2(IO3)2], the largest having dimensions of 0.6 × 0.6 × 0.4 mm, in a pale-yellow mother liquor. The crystals, in about 50% yield (based on V), were isolated by washing the reaction product with deionized water and anhydrous ethanol, followed by drying with anhydrous acetone. The powder X-ray diffraction pattern of the ground crystals is in good agreement with that calculated from the single-crystal data. The IR spectrum of Li[VO2(IO3)2] exhibits three sets of bands characteristic of VO6 and IO3- groups. They are the VO6 stretching vibrations occurring at 920.0 and 872.5 cm-1, the IO3- symmetric (ν1) and antisymmetric (ν3) stretching modes in the range 712.0–819.2 cm-1, and the IO3- bending modes between 418.4 and 481.7 cm-1.

Refinement top

All atoms were refined anisotropically, except Li, which was refined isotropically.

Computing details top

Data collection: Rigaku/AFC Diffractometer Control Software (Rigaku Corporation, 1994); cell refinement: Rigaku/AFC Diffractometer Control Software; data reduction: Rigaku/AFC Diffractometer Control Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The crystal structure of Li[VO2(IO3)2], projected along the [010] direction. Black circles denote Li atoms, cross-hatched circles V atoms, shaded circles I atoms and open circles O atoms.
[Figure 2] Fig. 2. The local coordination geometries of V and I in Li[VO2(IO3)2], with displacement ellipsoids drawn at the 50% probability level and the Li+ ion omitted. [Symmetry codes: (i) -x, 1 - y, 1 - z; (ii) 1 - x, 1/2 + y, 3/2 - z.]
Lithium bis[iodato(V)]dioxovanadate top
Crystal data top
Li[VO2(IO3)2]F(000) = 784
Mr = 439.68Dx = 4.623 Mg m3
MonoclinicP21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 25 reflections
a = 9.994 (2) Åθ = 20.2–22.4°
b = 5.202 (1) ŵ = 11.35 mm1
c = 13.798 (3) ÅT = 290 K
β = 118.28 (3)°Block, yellow
V = 631.7 (3) Å30.2 × 0.2 × 0.1 mm
Z = 4
Data collection top
Rigaku AFC-7R
diffractometer
2681 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.008
Graphite monochromatorθmax = 35.0°, θmin = 2.3°
ω/2θ scansh = 1614
Absorption correction: ψ scan
(Kopfmann & Huber, 1968)
k = 08
Tmin = 0.125, Tmax = 0.313l = 022
3029 measured reflections3 standard reflections every 150 reflections
2777 independent reflections intensity decay: 1.8%
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.036Secondary atom site location: difference Fourier map
wR(F2) = 0.102 w = 1/[σ2(Fo2) + (0.0331P)2 + 13.2592P]
where P = (Fo2 + 2Fc2)/3
S = 1.25(Δ/σ)max = 0.001
2777 reflectionsΔρmax = 2.58 e Å3
104 parametersΔρmin = 2.60 e Å3
Crystal data top
Li[VO2(IO3)2]V = 631.7 (3) Å3
Mr = 439.68Z = 4
MonoclinicP21/cMo Kα radiation
a = 9.994 (2) ŵ = 11.35 mm1
b = 5.202 (1) ÅT = 290 K
c = 13.798 (3) Å0.2 × 0.2 × 0.1 mm
β = 118.28 (3)°
Data collection top
Rigaku AFC-7R
diffractometer
2681 reflections with I > 2σ(I)
Absorption correction: ψ scan
(Kopfmann & Huber, 1968)
Rint = 0.008
Tmin = 0.125, Tmax = 0.3133 standard reflections every 150 reflections
3029 measured reflections intensity decay: 1.8%
2777 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0360 restraints
wR(F2) = 0.102 w = 1/[σ2(Fo2) + (0.0331P)2 + 13.2592P]
where P = (Fo2 + 2Fc2)/3
S = 1.25Δρmax = 2.58 e Å3
2777 reflectionsΔρmin = 2.60 e Å3
104 parameters
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
xyzUiso*/Ueq
I10.57929 (3)0.30811 (6)0.67238 (2)0.00600 (8)
I20.07444 (3)0.32376 (6)0.66973 (2)0.00558 (8)
V10.26661 (10)0.77925 (16)0.55011 (7)0.00729 (14)
O10.6885 (5)0.5834 (9)0.6730 (4)0.0137 (7)
O20.3883 (4)0.4125 (7)0.5782 (3)0.0103 (6)
O30.5714 (4)0.3814 (8)0.8005 (3)0.0089 (6)
O40.0777 (5)0.4328 (8)0.7941 (3)0.0112 (6)
O50.1877 (5)0.5828 (9)0.6584 (3)0.0140 (7)
O60.1151 (4)0.4451 (7)0.5678 (3)0.0100 (6)
O70.1511 (5)1.0191 (8)0.5299 (3)0.0128 (7)
O80.3593 (5)0.8869 (9)0.4864 (3)0.0140 (7)
Li10.2400 (9)0.2272 (16)0.4400 (7)0.0023 (12)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.00596 (13)0.00648 (13)0.00548 (12)0.00022 (8)0.00264 (9)0.00006 (8)
I20.00557 (12)0.00554 (12)0.00575 (12)0.00056 (8)0.00276 (9)0.00036 (8)
V10.0082 (3)0.0062 (3)0.0067 (3)0.0006 (2)0.0028 (3)0.0002 (2)
O10.0121 (16)0.0151 (18)0.0156 (17)0.0053 (14)0.0079 (14)0.0023 (14)
O20.0094 (14)0.0070 (14)0.0098 (14)0.0005 (12)0.0007 (12)0.0017 (12)
O30.0108 (14)0.0114 (15)0.0058 (13)0.0022 (12)0.0050 (12)0.0010 (12)
O40.0157 (16)0.0110 (16)0.0083 (14)0.0036 (13)0.0068 (13)0.0023 (12)
O50.0119 (16)0.0171 (18)0.0132 (16)0.0073 (14)0.0060 (14)0.0007 (14)
O60.0080 (14)0.0070 (14)0.0101 (14)0.0000 (12)0.0003 (12)0.0009 (12)
O70.0108 (15)0.0118 (16)0.0143 (16)0.0029 (13)0.0047 (13)0.0018 (13)
O80.0168 (17)0.0139 (17)0.0141 (16)0.0016 (14)0.0096 (14)0.0011 (14)
Geometric parameters (Å, º) top
I1—O11.798 (4)V1—O3ii1.998 (4)
I1—O21.810 (4)V1—O22.196 (4)
I1—O31.846 (4)V1—O52.239 (4)
I2—O41.793 (4)Li1—O22.021 (9)
I2—O51.814 (4)Li1—O8iii2.060 (9)
I2—O61.855 (4)Li1—O4iv2.069 (9)
V1—O71.632 (4)Li1—O6i2.085 (9)
V1—O81.649 (4)Li1—O7iii2.132 (9)
V1—O6i1.992 (4)Li1—O1v2.228 (9)
O1—I1—O2101.27 (19)Li1—O2—V198.7 (3)
O1—I1—O397.61 (19)I1—O3—V1vi123.5 (2)
O2—I1—O396.70 (18)I2—O4—Li1vii117.0 (3)
O4—I2—O596.8 (2)I2—O5—V1145.9 (2)
O4—I2—O699.60 (18)I2—O6—V1i121.9 (2)
O5—I2—O697.86 (19)I2—O6—Li1i133.5 (3)
O7—V1—O8100.4 (2)V1i—O6—Li1i103.4 (3)
O7—V1—O6i96.09 (19)V1—O7—Li1viii91.8 (3)
O8—V1—O6i99.5 (2)V1—O8—Li1viii93.9 (3)
O7—V1—O3ii97.76 (19)O2—Li1—O8iii93.4 (4)
O8—V1—O3ii94.27 (19)O2—Li1—O4iv175.0 (5)
O6i—V1—O3ii158.36 (17)O8iii—Li1—O4iv91.6 (4)
O7—V1—O2169.25 (19)O2—Li1—O6i79.2 (3)
O8—V1—O289.12 (19)O8iii—Li1—O6i164.3 (5)
O6i—V1—O277.19 (15)O4iv—Li1—O6i96.0 (4)
O3ii—V1—O286.48 (16)O2—Li1—O7iii90.8 (4)
O7—V1—O591.1 (2)O8iii—Li1—O7iii73.9 (3)
O8—V1—O5167.3 (2)O4iv—Li1—O7iii90.6 (3)
O6i—V1—O584.60 (16)O6i—Li1—O7iii92.3 (3)
O3ii—V1—O578.61 (15)O2—Li1—O1v96.5 (4)
O2—V1—O580.01 (17)O8iii—Li1—O1v105.5 (4)
I1—O1—Li1v138.1 (3)O4iv—Li1—O1v82.0 (3)
I1—O2—Li1125.9 (3)O6i—Li1—O1v89.1 (3)
I1—O2—V1134.0 (2)O7iii—Li1—O1v172.6 (5)
Symmetry codes: (i) x, y+1, z+1; (ii) x+1, y+1/2, z+3/2; (iii) x, y1, z; (iv) x, y+1/2, z1/2; (v) x+1, y+1, z+1; (vi) x+1, y1/2, z+3/2; (vii) x, y+1/2, z+1/2; (viii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaLi[VO2(IO3)2]
Mr439.68
Crystal system, space groupMonoclinicP21/c
Temperature (K)290
a, b, c (Å)9.994 (2), 5.202 (1), 13.798 (3)
β (°) 118.28 (3)
V3)631.7 (3)
Z4
Radiation typeMo Kα
µ (mm1)11.35
Crystal size (mm)0.2 × 0.2 × 0.1
Data collection
DiffractometerRigaku AFC-7R
diffractometer
Absorption correctionψ scan
(Kopfmann & Huber, 1968)
Tmin, Tmax0.125, 0.313
No. of measured, independent and
observed [I > 2σ(I)] reflections
3029, 2777, 2681
Rint0.008
(sin θ/λ)max1)0.806
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.102, 1.25
No. of reflections2777
No. of parameters104
w = 1/[σ2(Fo2) + (0.0331P)2 + 13.2592P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)2.58, 2.60

Computer programs: Rigaku/AFC Diffractometer Control Software (Rigaku Corporation, 1994), Rigaku/AFC Diffractometer Control Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 1999), SHELXL97.

Selected bond lengths (Å) top
I1—O11.798 (4)I2—O41.793 (4)
I1—O21.810 (4)I2—O51.814 (4)
I1—O31.846 (4)I2—O61.855 (4)
 

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