English

• 0.   Introduction

  Polyoxometalates with oxygen/fluorine donor groups show an impressive structural and electronic diversity in the past few years^[1-7], and extensive syn-thetic research has been carried out in this field^[8-11]. As a result, a large number of novel compounds with cluster-like anionic structures have been reported previously. These novel anionic polyoxometalate structures may be spherical, basket-shaped, half-spherical, bowl-shaped and so on, which show application potentials in catalytic, magnetic, optical, electroconductive, and molecular adsorption materials, as well as their interesting structural features^[12-17].

  However, the tunable synthesis and relative design for these structures are still a challenge for inorganic chemists. The synthetic routines for these compounds are quite diversiform. For example, some spherical polyoxometates have been obtained by capping guest molecule and assembling into the half-spherical or bowl-type molecule, etc, and gradually completing the sphere; some obtained by using cations as structure directing agents, in order to develop novel structural building units, and direct towards the rational synthesis of novel polyoxometalate.

  We and other groups have made a series of compounds featuring different polyoxofluorovanadate anionic clusters of zero-dimensional (0D), one-dimen-sional (1D) and two-dimensional (2D) structures^{[1, 18-20]}, with different metal counter ions, e.g. K(Ⅰ) Ca(Ⅱ) and Sr(Ⅱ), an indicative that the counter cations may effectively tune the formation of polyoxofluorovanadate anionic clusters. Similar observations have been also available in other anionic metal clusters with oxygen/sulphur donor groups when organic cations being counter ions in the past. Herein we report a rare structure of V₁₄-based polyoxofluorovanadate anionic cluster, containing both coordinative methylimidazole and protonated methylimidazole cations, i.e. (HL)₆[V₁₄O₃₆F₂L₂]·4H₂O (1, L=1-methylimidazole), together with a theoretical investigation of electronic structure, possible information mechanism, and structure-property relationship analysis.

  1.   Experimental

  1.1   Synthesis

  Compound 1 was obtained by a reaction of V₂O₅ (0.091 g, 0.5 mmol), L (0.494 g, 6 mmol), and HF (ca. 30%, w/w) in an aqueous solution of 1.25 mL. The mixture was heated in Teflon-lined steel autoclaves with an inner volume of 23 mL for one day at 155 ℃ and then cooled to room temperature at a speed of 5 ℃·h^-1. After washing with water and acetone, dried at room temperature, black green crystals were obtained. The compound is stable on air and in water. Yield: ca. 40%. Anal. Calcd. for C₃₂H₆₂F₂N₁₆O₄₀V₁₄(%): C 18.64, H 3.03, N 10.87; Found(%): C 18.78, H 3.11, N 10.80. FTIR (KBr, cm^-1): 3 750 (m), 2 998 (m), 2 558 (m), 2 337 (s), 2 204 (m), 2 070 (w), 1 890 (s), 1 772 (s), 1 583 (m), 1 348 (w), 1 276 (w), 1 233 (w), 924 (m), 839 (s), 687 (w), 485 (w).

  1.2   X-ray analysis

  A crystal of 1 with dimension of 0.48 mm×0.29 mm×0.20 mm was mounted on glass rod for determin-ing crystal structure. X-ray diffraction measurement was performed on a Bruker SMART-CCD diffractometer with graphite-monochromated Mo Kα(λ=0.071 073 nm) radiation in the ω scanning mode at 20 ℃. The SADABS program was used for the absorption correction^[21], and the direct method was adopted to solve and refine the structure based on F² by full-matrix least-squares techniques using the SHELXTL 97 program package^[22]. All of the non-hydrogen atoms were refined anisotropically, and the hydrogen atoms of the organic ligands were geometrically placed and refined using a riding model. The hydrogen atoms attached to lattice water were located from the different Fourier maps. The final refinement leads to a satisfactory result of R₁ 0.045 8, wR₂ 0.132 4, and the goodness-of-fit 1.027. Experimental details of the X-ray determination and major geometrical parameters of 1 are presented in Table 1 and 2, respectively.

  Table 1

  

  Table 1.  Crystal data and structure refinement for 1

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  Empirical formula	C32H62F2N16O40V14
  Formula weight	2 062.14
  Crystal system	Monoclinic
  Space group	P21/c
  a / nm	1.389 73(12)
  b / nm	1.281 36(11)
  c / nm	1.998 84(18)
  β / (°)	107.141(1)
  V / nm3	3.401 3(5)
  Z	2
  μ / mm-1	1.936
  θ range for data collection / (°)	2.25~27.50
  Index ranges	-18 ≤ h ≤ 17; -16 ≤ k ≤ 16; -24 ≤ l ≤ 25
  Total reflection	23 797
  Unique reflections (Rint)	7 564 (0.040 6)
  Completeness to θmax	96.8
  Observed data, restraint, parameter	7 564, 6, 485
  S on F2	1.027
  R1a [I>2σ(I)]	0.045 8
  wR2b (all data)	0.132 4
  Largest difference peak and hole / (e·nm-3)	786 and -626
  a R1=∑||Fo|-|Fc||/∑|Fo|; b wR2=[∑w(Fo2-Fc2)2/∑w(Fo2)2]1/2.

  Table 2

  

  Table 2.  Selected bond lengths (nm) and bond angles (°) for 1

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  V(1)-O(8)	0.160 5(3)	V(3)-O(7)#1	0.193 8(2)	V(6)-O(14)	0.172 2(3)
  V(1)-O(9)	0.174 2(3)	V(3)-O(4)	0.199 7(2)	V(6)-O(7)	0.180 3(2)
  V(1)-O(3)	0.194 2(3)	V(3)-V(4)	0.305 2(1)	V(6)-O(2)	0.180 5(2)
  V(1)-O(5)	0.194 8(2)	V(4)-O(12)	0.161 0(2)	V(6)-O(5)	0.243 3(3)
  V(1)-O(2)	0.207 5(2)	V(4)-O(6)	0.171 1(2)	V(7)-O(18)	0.162 3(3)
  V(1)-F(1)	0.219 3(2)	V(4)-O(4)	0.191 5(2)	V(7)-O(19)	0.162 9(3)
  V(2)-O(17)	0.159 5(3)	V(4)-O(2)	0.193 5(2)	V(7)-O(14)	0.199 1(3)
  V(2)-O(16)	0.172 6(3)	V(4)-O(3)	0.200 8(2)	V(7)-O(5)	0.200 8(2)
  V(2)-O(4)	0.193 4(2)	V(5)-O(15)	0.161 0(3)	V(7)-N(1)	0.212 4(4)
  V(2)-O(5)#1	0.197 7(2)	V(5)-O(6)#1	0.193 3(3)	F(1)-V(2)#1	0.222 8(2)
  V(2)-O(7)#1	0.209 4(2)	V(5)-O(13)	0.194 4(3)	O(5)-V(2)#1	0.197 7(2)
  V(2)-F(1)#1	0.222 8(2)	V(5)-O(16)#1	0.196 5(3)	O(6)-V(5)#1	0.193 3(3)
  V(3)-O(11)	0.161 2(2)	V(5)-O(9)	0.197 7(3)	O(7)-V(3)#1	0.193 8(2)
  V(3)-O(13)	0.171 5(3)	V(5)-F(1)	0.221 5(2)	O(7)-V(2)#1	0.209 4(2)
  V(3)-O(3)	0.191 8(2)	V(6)-O(10)	0.160 7(3)	O(16)-V(5)#1	0.196 5(3)
  O(8)-V(1)-O(9)	102.79(13)	O(11)-V(3)-O(3)	105.17(12)	O(13)-V(5)-O(16)#1	156.21(11)
  O(8)-V(1)-O(3)	101.76(13)	O(13)-V(3)-O(3)	96.08(11)	O(15)-V(5)-O(9)	101.80(13)
  O(9)-V(1)-O(3)	97.24(11)	O(11)-V(3)-O(7)#1	104.93(12)	O(6)#1-V(5)-O(9)	155.94(11)
  O(8)-V(1)-O(5)	102.43(12)	O(13)-V(3)-O(7)#1	94.21(11)	O(13)-V(5)-O(9)	84.25(11)
  O(9)-V(1)-O(5)	97.51(12)	O(3)-V(3)-O(7)#1	143.99(11)	O(16)#1-V(5)-O(9)	85.30(11)
  O(3)-V(1)-O(5)	147.99(11)	O(11)-V(3)-O(4)	103.59(12)	O(15)-V(5)-F(1)	176.07(13)
  O(8)-V(1)-O(2)	96.78(12)	O(13)-V(3)-O(4)	150.41(11)	O(6)#1-V(5)-F(1)	81.35(9)
  O(9)-V(1)-O(2)	160.21(11)	O(3)-V(3)-O(4)	76.37(10)	O(13)-V(5)-F(1)	81.48(9)
  O(3)-V(1)-O(2)	75.65(10)	O(7)#1-V(3)-O(4)	77.73(10)	O(16)#1-V(5)-F(1)	75.19(9)
  O(5)-V(1)-O(2)	80.95(10)	O(11)-V(3)-V(4)	116.44(10)	O(9)-V(5)-F(1)	75.01(9)
  O(8)-V(1)-F(1)	176.73(11)	O(13)-V(3)-V(4)	123.99(8)	O(10)-V(6)-O(14)	104.51(14)
  O(9)-V(1)-F(1)	80.23(10)	O(7)#1-V(3)-V(4)	107.48(7)	O(10)-V(6)-O(7)	106.10(13)
  O(3)-V(1)-F(1)	78.98(9)	O(12)-V(4)-O(6)	105.49(13)	O(14)-V(6)-O(7)	114.45(13)
  O(5)-V(1)-F(1)	75.76(9)	O(12)-V(4)-O(4)	106.96(12)	O(10)-V(6)-O(2)	105.87(13)
  O(2)-V(1)-F(1)	80.29(8)	O(6)-V(4)-O(4)	95.64(11)	O(14)-V(6)-O(2)	111.28(12)
  O(17)-V(2)-O(16)	103.34(14)	O(12)-V(4)-O(2)	104.13(12)	O(7)-V(6)-O(2)	113.66(11)
  O(17)-V(2)-O(4)	102.74(13)	O(6)-V(4)-O(2)	94.34(11)	O(10)-V(6)-O(5)	178.50(12)
  O(16)-V(2)-O(4)	97.92(11)	O(4)-V(4)-O(2)	143.33(11)	O(14)-V(6)-O(5)	74.03(11)
  O(17)-V(2)-O(5)#1	102.50(13)	O(12)-V(4)-O(3)	105.04(12)	O(7)-V(6)-O(5)	74.96(10)
  O(16)-V(2)-O(5)#1	96.75(11)	O(6)-V(4)-O(3)	149.46(11)	O(2)-V(6)-O(5)	74.49(10)
  O(4)-V(2)-O(5)#1	146.88(11)	O(4)-V(4)-O(3)	76.18(10)	O(18)-V(7)-O(19)	109.36(17)
  O(17)-V(2)-O(7)#1	97.49(13)	O(2)-V(4)-O(3)	77.40(10)	O(18)-V(7)-O(14)	100.18(15)
  O(16)-V(2)-O(7)#1	159.09(11)	O(12)-V(4)-V(3)	118.50(10)	O(19)-V(7)-O(14)	95.21(15)
  O(4)-V(2)-O(7)#1	75.49(10)	O(6)-V(4)-V(3)	122.94(8)	O(18)-V(7)-O(5)	118.14(14)
  O(5)#1-V(2)-O(7)#1	80.27(10)	O(2)-V(4)-V(3)	107.18(7)	O(19)-V(7)-O(5)	132.41(14)
  O(17)-V(2)-F(1)#1	176.12(12)	O(15)-V(5)-O(6)#1	101.63(13)	O(14)-V(7)-O(5)	79.80(11)
  O(16)-V(2)-F(1)#1	79.52(10)	O(15)-V(5)-O(13)	100.59(14)	O(18)-V(7)-N(1)	96.89(17)
  O(4)-V(2)-F(1)#1	79.30(9)	O(6)#1-V(5)-O(13)	96.74(11)	O(19)-V(7)-N(1)	91.09(17)
  O(5)#1-V(2)-F(1)#1	74.42(9)	O(15)-V(5)-O(16)#1	102.44(14)	O(14)-V(7)-N(1)	158.67(13)
  O(7)#1-V(2)-F(1)#1	79.75(8)	O(6)#1-V(5)-O(16)#1	84.41(11)	O(5)-V(7)-N(1)	80.91(13)
  O(11)-V(3)-O(13)	106.0(1)
  Symmetry codes:#1:-x,-y,-z.

  CCDC: 761054.

  1.3   Calculation details

  The DFT theory level of DMol3 code^[23-26] was employed to calculate the geometry, electronic density, frontier orbital, and charge population of the [V₁₄O₃₆F₂L₂]^6- anion and relative 2e oxidation species, [V₁₄O₃₆F₂L₂]^4-, using the X-ray geometric data, and spin unrestricted/restricted open/close-shell system as input data. Other options for the optimization were as follows: functional DFT exchange-correlation potential functional, i.e. the PWC local potential (LDA); basis DND; pseudopotential ECP; integration grid medium; charge -6/-4; multiplicity auto; quality medium. The counter ion, HL⁺ cation, and lattice water are neglected. All calculations were performed on a commercial Dell precision computer.

  2.   Results and discussion

  The monoclinic solid of 1 contains [V₁₄O₃₆F₂L₂]^6- anion, HL⁺ cation^[27-28] and lattice waters (Fig. 1), which are linked each other by way of complicated inter-molecular hydrogen bondings: N6…O12#1 (Symmetry codes: #1: -x, -y+1, -z+1; 0.290 6 nm), N6…O11#2 (Symmetry codes: #2: x, -y+1/2, z+1/2; 0.298 6 nm), N4…O9#3 (Symmetry codes: #3: -x+1, y+1/2, -z+1/2; 0.264 1 nm), N8…O10#4 (Symmetry codes: #4: x+1, -y+3/2, z+1/2; 0.287 3 nm), N8…O13#5 (Symmetry codes: #5: -x+1, y+3/2, -z+1/2; 0.308 2 nm), O1W…O19 (0.339 3 nm), O1W…O15#6 (Symmetry codes: #6: x, y+1, z; 0.287 8 nm), O2W…O18#7 (Symmetry codes: #7: x, y, z+1; 0.274 6 nm), O2W…O2W#8 (Symmetry codes: #8: -x+1, -y+1, -z+2; 0.274 3 nm). The offset and head-to-end π-π stacking interaction with an inter-plane distance of ca. 0.345 nm between adjacent imidazole rings of protonated HL⁺ cations can also be observed. Both the former and latter contribute the stability of the crystalline solid.

  Figure 1

  

  Figure 1.  Perspective view of the unsymmetrical unit of crystalline 1 with 50% probability thermal ellipsoids

  V: green, O: red, N: blue, F: light blue, C: gray

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  The [V₁₄O₃₆F₂L₂]^6- anion is centrosymmetrical, and contains four types of vanadium polyhedra. Two trimers of edge-sharing VO₅F octahedra form the heart of the polyanion. In each trimer, the vertex shared by the three octahedra is fluorine, which is characterized by bond valence analysis (0.72, close to theoretical value 1 of F atom). Four VO₅ square pyramids bridge the two trimers via vertex-sharing μ₂-O and edge-sharing μ₃-O atoms. On the external side of each trimer, one VO₅ and one VO₄N trigonal bipyramids are grafted by way of μ₃-O and μ₄-O atoms, while in the axial direction of VO₄N trigonal bipyramid the V-N bonding interactions locate between V center and organic L ligand.

  The connection between the six VO₅F octahedrons, four VO₅ square pyramids and four VO₅/VO₄N trigonal bipyramids of [V₁₄O₃₆F₂L₂]^6- anion is very complicated, as the bridging O atoms are very diversities (containing μ₂-O, μ₃-O and μ₄-O atoms). Moreover there are terminal μ₁-O atoms per V centers, and organic ligands (L) scattering on the face of the shell-shaped cluster anion.

  For the [V₁₄O₃₆F₂L₂]^6- anion, a 0D ring-like ladder-chains cluster skeleton frame geometry, i.e. the [V₁₀O₂₀] ladder (Fig. 2), can be easily found, together with two VO₅F fragments of octahedral grafted above and below the [V₁₀O₂₀] ladder, and two VO₃L fragments of trigonal bipyramidal located on the two sides of the [V₁₀O₂₀] ladder. These core ring-like [V₁₀O₂₀] ladder and grafted VO₅F and VO₃L fragments around the ladder are arranged in a centrosymmetric style. A possible self-assembling process of [V₁₄O₃₆F₂L₂]^6- anion from core [V₁₀O₂₀] ladder, grafted VO₅F and VO₃L fragments is roughly depicted in Fig. 2. It is noted that the decomposition into core [V₁₀O₂₀] ladder, and grafted VO₅F and VO₃L fragments may be arbitrary and not secret, but the theoretical importance and effect of electronic structure of these fragment compositions will be clearly shown in later discussion.

  Figure 2

  

  Figure 2.  Self-assembling process of [V₁₄O₃₆F₂L₂]^6- anion from a ring-like [V₁₀O₂₀] ladder, two grafted [VO₅F] and [VO₃L] fragments

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  Bond valence sum calculations indicate very interesting situation for the [V₁₄O₃₆F₂L₂]^6- anion, as the valence state of all ten V centers of the [V₁₀O₂₀] ladder to be +5, while those of the four V centers grafted to the ladder to be +4.4~4.6, which is in agreement with the charge balance, and the previous observation of the ladder-like chains structures of vanadium oxide cluster compounds being +5 valence state. However the valence state of ca. +4.5 for V centers is vague and unacceptable. The reasonable value of V centers is +4 or +5, an indicative that the four grafted V centers are probably mixed-valence.

  The presence of fluorine in a vanadium oxide polyanionic compounds is often observed, generally as encapsulating inside the polyanion. The fluorine atoms should play the role of template for the self-assembling process of final cluster-like polyoxofluoro-vanadate compounds. However, the coordination of two organic L ligands into the surface of the vanadium oxide polyanionic cluster are rarely observation. The introduction of organic ligands will obviously change the electronic structure, and therefore tune the physical and chemical properties. The [V₁₄O₃₆F₂L₂]^6- anion may be, as it were, a potentially important polyoxofluorovanadate functional material.

  DFT-based theoretical calculations of Dmol3 module for [V₁₄O₃₆F₂L₂]^6- anion shows interesting result. For comparison its 2e oxidation species [V₁₄O₃₆F₂L₂]^4- anion was also calculated. These results of electron population analysis clearly show that two d¹ electrons of V (+4) centers of [V₁₄O₃₆F₂L₂]^6- anion populate on the grafted VO₅F fragments, while the grafted VO₃L fragments are away from those d electrons (Fig. 3), an indicative that the former is +4 oxidation state and the latter +5 oxidation state for vanadium centers. The d electrons are moderately delocated over four μ₂-oxo-linking V centers of the [V₁₀O₂₀] ladder, which may interpret the observation fact of the two grafted VO₅F fragments being ca. +4.5 in bond valence sum calculation. While the abnormity of observed bond valence sum of V centers (+5 oxidation state) of the grafted VO₃L fragments may be ascribed to the large steric effect from adjacent big [V₁₀O₂₀] ladder and L ligand, which decrease the bond valence value of V centers.

  Figure 3

  

  Figure 3.  Calculated frontier orbital energy levels and diagrams of [V₁₄O₃₆F₂L₂]^6- and relative [V₁₄O₃₆F₂L₂]^4- anion

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  A comparison of frontier orbitals of [V₁₄O₃₆F₂L₂]^6- and relative 2e oxidizing anion, [V₁₄O₃₆F₂L₂]^4- (Fig. 3), indicates very interesting phenomenon. For the latter the HOMO is d-p π orbital between V centers and terminal O atoms of grafted VO₃L fragments, while the LUMO and LUMO+1 d orbitals of V centers of grafted VO₅F fragments with moderate charge delocalization over four V atoms of the [V₁₀O₂₀] ladder. The chemical property of [V₁₄O₃₆F₂L₂]^4- anion should be associated with the terminal V=O (d-p) π orbital of grafted VO₃L fragments. The energy gap of LUMO-HOMO is ca. 1.59 eV. However it greatly decreases to ca. 0.53 eV after a 2e reduction to [V₁₄O₃₆F₂L₂]^6- anion, indicating that the [V₁₄O₃₆F₂L₂]^6- anion is more excellent semicon-ductor in conductivity. After the 2e reduction the HOMO, LUMO and LUMO+1 in [V₁₄O₃₆F₂L₂]^4- become HOMO-1, HOMO and LUMO of [V₁₄O₃₆F₂L₂]^6-, respe-ctively (Fig. 3). Now please note that the frontier HOMO, namely d orbital of grafted VO₅F fragments, being moderate delocalization over other V centers of the [V₁₀O₂₀] ladder contributes greatly to the small energy gap, and therefore, more excellent conductivity of [V₁₄O₃₆F₂L₂]^6- anionic semiconducting material than [V₁₄O₃₆F₂L₂]^4- anionic semiconducting material can be expected. Owing to HOMO being of d orbital of grafted VO₅F fragments the solid material of [V₁₄O₃₆F₂L₂]^6- anion should be chemically active for d electron of V centers, which is wholly different from the case of [V₁₄O₃₆F₂L₂]^4- anionic material.

  Let us look into in detail the diagrams of frontier orbital, the additional two electrons will occupy the LUMO or LUMO+1 orbital of [V₁₄O₃₆F₂L₂]^4- anion and become the HOMO of [V₁₄O₃₆F₂L₂]^6- anion. Though the 2e reduction process is not preferred in energy as the electrons will populate onto the anti-bonding LUMO or LUMO+1 orbital of [V₁₄O₃₆F₂L₂]^4- anion, this process will lead obviously the increasing structural stability of the skeleton frame of core [V₁₀O₂₀] ladder and simultaneously activate the grafted VO₅F and VO₃L fragments (this can be easily seen from the frontier orbital). In other words, the special geometry (including core [V₁₀O₂₀] ladder, and grafted VO₅F and VO₃L fragments) and interesting electronic figuration of [V₁₄O₃₆F₂L₂]^6- anion ensure that this anionic material has a stronger core [V₁₀O₂₀] ladder skeleton frame, and more active grafted VO₅F and VO₃L fragments, which will dominate the chemical and physical properties and improve the behavior as inorganic functional solid. It is concluded that [V₁₄O₃₆F₂L₂]^6- anionic material, to some extent should be very special in including semiconducting property, catalytic property and chemical reactivity. Therefore it is valuable to further investigate it theoretically and experimentally, and we′ll pay much attention to it in our laboratory in the future.

  3.   Conclusions

  In summary, a rare tetradecanuclear polyoxo-fluorovanadate cluster with 1-methylimidazole (L), containing [V₁₄O₃₆F₂L₂]^6- anion, was synthesized and characterized by X-ray diffraction method. The anion is decomposed into a special core of 0D ring-shaped cluster-like skeleton frame, i.e. the [V₁₀O₂₀] ladder, and two grafted VO₅F and VO₃L fragments are around the ladder core. DFT theoretical and bond valence sum calculations of [V₁₄O₃₆F₂L₂]^6-, indicated that the grafted VO₅F fragments are V(+4) oxidation state, while other V centers are V(+5) oxidation state. The frontier orbital analyses showed that [V₁₄O₃₆F₂L₂]^6- anion, should be chemically active in d orbital of grafted VO₅F fragments, while its 2e oxidation species, the [V₁₄O₃₆F₂L₂]^4- anion should be chemically active in the terminal V=O (d-p) π orbital of grafted VO₃L fragments. The 2e reduction from [V₁₄O₃₆F₂L₂]^4- to [V₁₄O₃₆F₂L₂]^6- anion, being unfavorable in energy, but leads to the increasing structural stability of the core [V₁₀O₂₀] ladder, and at the same time the increasing activity of the grafted VO₅F and VO₃L fragments, together with a great decrease of energy gap (from 1.59 to 0.53 eV). Based on the special electron structure, the [V₁₄O₃₆F₂L₂]^6- anionic materials may be quite important candidates of potential appli-cations in semiconducting industry catalytic materials and chemical reactivity. It is valuable to further investigate it theoretically and experimentally in the future.

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• 

  Figure 1  Perspective view of the unsymmetrical unit of crystalline 1 with 50% probability thermal ellipsoids

  V: green, O: red, N: blue, F: light blue, C: gray

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  Figure 2  Self-assembling process of [V₁₄O₃₆F₂L₂]^6- anion from a ring-like [V₁₀O₂₀] ladder, two grafted [VO₅F] and [VO₃L] fragments

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  Figure 3  Calculated frontier orbital energy levels and diagrams of [V₁₄O₃₆F₂L₂]^6- and relative [V₁₄O₃₆F₂L₂]^4- anion

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  Table 1.  Crystal data and structure refinement for 1

  Empirical formula	C32H62F2N16O40V14
  Formula weight	2 062.14
  Crystal system	Monoclinic
  Space group	P21/c
  a / nm	1.389 73(12)
  b / nm	1.281 36(11)
  c / nm	1.998 84(18)
  β / (°)	107.141(1)
  V / nm3	3.401 3(5)
  Z	2
  μ / mm-1	1.936
  θ range for data collection / (°)	2.25~27.50
  Index ranges	-18 ≤ h ≤ 17; -16 ≤ k ≤ 16; -24 ≤ l ≤ 25
  Total reflection	23 797
  Unique reflections (Rint)	7 564 (0.040 6)
  Completeness to θmax	96.8
  Observed data, restraint, parameter	7 564, 6, 485
  S on F2	1.027
  R1a [I>2σ(I)]	0.045 8
  wR2b (all data)	0.132 4
  Largest difference peak and hole / (e·nm-3)	786 and -626
  a R1=∑||Fo|-|Fc||/∑|Fo|; b wR2=[∑w(Fo2-Fc2)2/∑w(Fo2)2]1/2.

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  Table 2.  Selected bond lengths (nm) and bond angles (°) for 1

  V(1)-O(8)	0.160 5(3)	V(3)-O(7)#1	0.193 8(2)	V(6)-O(14)	0.172 2(3)
  V(1)-O(9)	0.174 2(3)	V(3)-O(4)	0.199 7(2)	V(6)-O(7)	0.180 3(2)
  V(1)-O(3)	0.194 2(3)	V(3)-V(4)	0.305 2(1)	V(6)-O(2)	0.180 5(2)
  V(1)-O(5)	0.194 8(2)	V(4)-O(12)	0.161 0(2)	V(6)-O(5)	0.243 3(3)
  V(1)-O(2)	0.207 5(2)	V(4)-O(6)	0.171 1(2)	V(7)-O(18)	0.162 3(3)
  V(1)-F(1)	0.219 3(2)	V(4)-O(4)	0.191 5(2)	V(7)-O(19)	0.162 9(3)
  V(2)-O(17)	0.159 5(3)	V(4)-O(2)	0.193 5(2)	V(7)-O(14)	0.199 1(3)
  V(2)-O(16)	0.172 6(3)	V(4)-O(3)	0.200 8(2)	V(7)-O(5)	0.200 8(2)
  V(2)-O(4)	0.193 4(2)	V(5)-O(15)	0.161 0(3)	V(7)-N(1)	0.212 4(4)
  V(2)-O(5)#1	0.197 7(2)	V(5)-O(6)#1	0.193 3(3)	F(1)-V(2)#1	0.222 8(2)
  V(2)-O(7)#1	0.209 4(2)	V(5)-O(13)	0.194 4(3)	O(5)-V(2)#1	0.197 7(2)
  V(2)-F(1)#1	0.222 8(2)	V(5)-O(16)#1	0.196 5(3)	O(6)-V(5)#1	0.193 3(3)
  V(3)-O(11)	0.161 2(2)	V(5)-O(9)	0.197 7(3)	O(7)-V(3)#1	0.193 8(2)
  V(3)-O(13)	0.171 5(3)	V(5)-F(1)	0.221 5(2)	O(7)-V(2)#1	0.209 4(2)
  V(3)-O(3)	0.191 8(2)	V(6)-O(10)	0.160 7(3)	O(16)-V(5)#1	0.196 5(3)
  O(8)-V(1)-O(9)	102.79(13)	O(11)-V(3)-O(3)	105.17(12)	O(13)-V(5)-O(16)#1	156.21(11)
  O(8)-V(1)-O(3)	101.76(13)	O(13)-V(3)-O(3)	96.08(11)	O(15)-V(5)-O(9)	101.80(13)
  O(9)-V(1)-O(3)	97.24(11)	O(11)-V(3)-O(7)#1	104.93(12)	O(6)#1-V(5)-O(9)	155.94(11)
  O(8)-V(1)-O(5)	102.43(12)	O(13)-V(3)-O(7)#1	94.21(11)	O(13)-V(5)-O(9)	84.25(11)
  O(9)-V(1)-O(5)	97.51(12)	O(3)-V(3)-O(7)#1	143.99(11)	O(16)#1-V(5)-O(9)	85.30(11)
  O(3)-V(1)-O(5)	147.99(11)	O(11)-V(3)-O(4)	103.59(12)	O(15)-V(5)-F(1)	176.07(13)
  O(8)-V(1)-O(2)	96.78(12)	O(13)-V(3)-O(4)	150.41(11)	O(6)#1-V(5)-F(1)	81.35(9)
  O(9)-V(1)-O(2)	160.21(11)	O(3)-V(3)-O(4)	76.37(10)	O(13)-V(5)-F(1)	81.48(9)
  O(3)-V(1)-O(2)	75.65(10)	O(7)#1-V(3)-O(4)	77.73(10)	O(16)#1-V(5)-F(1)	75.19(9)
  O(5)-V(1)-O(2)	80.95(10)	O(11)-V(3)-V(4)	116.44(10)	O(9)-V(5)-F(1)	75.01(9)
  O(8)-V(1)-F(1)	176.73(11)	O(13)-V(3)-V(4)	123.99(8)	O(10)-V(6)-O(14)	104.51(14)
  O(9)-V(1)-F(1)	80.23(10)	O(7)#1-V(3)-V(4)	107.48(7)	O(10)-V(6)-O(7)	106.10(13)
  O(3)-V(1)-F(1)	78.98(9)	O(12)-V(4)-O(6)	105.49(13)	O(14)-V(6)-O(7)	114.45(13)
  O(5)-V(1)-F(1)	75.76(9)	O(12)-V(4)-O(4)	106.96(12)	O(10)-V(6)-O(2)	105.87(13)
  O(2)-V(1)-F(1)	80.29(8)	O(6)-V(4)-O(4)	95.64(11)	O(14)-V(6)-O(2)	111.28(12)
  O(17)-V(2)-O(16)	103.34(14)	O(12)-V(4)-O(2)	104.13(12)	O(7)-V(6)-O(2)	113.66(11)
  O(17)-V(2)-O(4)	102.74(13)	O(6)-V(4)-O(2)	94.34(11)	O(10)-V(6)-O(5)	178.50(12)
  O(16)-V(2)-O(4)	97.92(11)	O(4)-V(4)-O(2)	143.33(11)	O(14)-V(6)-O(5)	74.03(11)
  O(17)-V(2)-O(5)#1	102.50(13)	O(12)-V(4)-O(3)	105.04(12)	O(7)-V(6)-O(5)	74.96(10)
  O(16)-V(2)-O(5)#1	96.75(11)	O(6)-V(4)-O(3)	149.46(11)	O(2)-V(6)-O(5)	74.49(10)
  O(4)-V(2)-O(5)#1	146.88(11)	O(4)-V(4)-O(3)	76.18(10)	O(18)-V(7)-O(19)	109.36(17)
  O(17)-V(2)-O(7)#1	97.49(13)	O(2)-V(4)-O(3)	77.40(10)	O(18)-V(7)-O(14)	100.18(15)
  O(16)-V(2)-O(7)#1	159.09(11)	O(12)-V(4)-V(3)	118.50(10)	O(19)-V(7)-O(14)	95.21(15)
  O(4)-V(2)-O(7)#1	75.49(10)	O(6)-V(4)-V(3)	122.94(8)	O(18)-V(7)-O(5)	118.14(14)
  O(5)#1-V(2)-O(7)#1	80.27(10)	O(2)-V(4)-V(3)	107.18(7)	O(19)-V(7)-O(5)	132.41(14)
  O(17)-V(2)-F(1)#1	176.12(12)	O(15)-V(5)-O(6)#1	101.63(13)	O(14)-V(7)-O(5)	79.80(11)
  O(16)-V(2)-F(1)#1	79.52(10)	O(15)-V(5)-O(13)	100.59(14)	O(18)-V(7)-N(1)	96.89(17)
  O(4)-V(2)-F(1)#1	79.30(9)	O(6)#1-V(5)-O(13)	96.74(11)	O(19)-V(7)-N(1)	91.09(17)
  O(5)#1-V(2)-F(1)#1	74.42(9)	O(15)-V(5)-O(16)#1	102.44(14)	O(14)-V(7)-N(1)	158.67(13)
  O(7)#1-V(2)-F(1)#1	79.75(8)	O(6)#1-V(5)-O(16)#1	84.41(11)	O(5)-V(7)-N(1)	80.91(13)
  O(11)-V(3)-O(13)	106.0(1)
  Symmetry codes:#1:-x,-y,-z.

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