English

• 1. INTRODUCTION

  In the last two decades, great attention has been paid to metal iodates not only due to their versatile structural chemistry but also to their promising nonlinear optical (NLO) properties, ferroelectric, piezoelectric and pyroelectric performances^[1-3]. In metal iodates, the IO₃ trigonal pyramid bearing the lone electron pair on iodine can not only be beneficial for the generation of acentric structures, but also contribute to large SHG response, high optical-damage thresholds, and high thermal stabilities^[4]. So far, metal iodates including alkali metal, transition metal, lanthanide, and actinide iodates have been documented^[5-7], among which rare earth metal iodates are special because of their unique f electron configurations^[8-10]. These rare earth iodates can exhibit one-dimensional chains (Ln = Yb, Lu), two-dimensional layers (Ln = Y, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er. Yb and Lu) and three-dimensional networks (Ln = La, Y, Dy, Pr, Nd, Sm, Gd, Tb, Ho, Tm, Yb, and Lu) built from LnO_x polyhedra (Ln = rare earth elements, x = 7 or 8) and IO_x (x = 3, 4) trigonal pyramids or tetrahedra^[10-13]. However, due to their variable coordination numbers, flexible coordination geometry of rare earth ions, and uncontrollability in the self-assembly process of IO₃ trigonal pyramids with LnO_x polyhedrons, there is still a great space for the discovery of new structural topologies. More importantly, compared with the extensive attention on the second-order nonlinear optical properties of rate earth iodates, much less attention has been paid to their third-order nonlinear optical performance^[14]. It's known to all that rare earth ions possess unique luminescent characteristics with high color purity and high emission efficiency^{[15, 16]}. Herein, a new layer-like yttrium iodate [Y(IO₃)₃(H₂O)₂]_n (1) has been prepared, which is constructed from unique circle-shaped I₄O₁₆ polyiodate anion. Interestingly, the third-order nonlinear optical property can be observed, and theoretical calculation was conducted to reveal its electronic structure.

  2. EXPERIMENTAL

  2.1 Materials and method

  All the reactants including Y(NO₃)₃·2(H₂O) and I₂O₅ were of reagent grade and used as purchased. FTIR spectrum was recorded as KBr discs on a Shimadzu IR-408 infrared spectrophotometer in the 400~4000 cm^-1 region. X-ray powder diffraction (PXRD) was performed on a Philips X'Pert-MPD diffractometer with CuKα radiation (λ = 1.54056 Å). UV-Vis spectrum was taken on a Shimadzu UV-2101 PC UV-Vis scanning spectrophotomete equipped with an integrating sphere at ambient temperature. During the third-order nonlinear optical measurement, incident and transmitted pulsed energies are measured simultaneously by two energy detectors (RJP-765 energy probes, laser precision, Laserprobe Corp), which are linked to a computer through an RS232 interface.

  2.2 Synthesis

  1 was prepared by typical hydrothermal method. Y(NO₃)₃·(H₂O)₂ (0.1545 g, 0.5 mmol) and I₂O₅ (0.3300 g, 1.0 mmol) were dissolved in 10 mL deionized water to generate a suspension. The mixture was stirred constantly for 1 h and then transferred into a 25 mL Teflon-lined autoclave. The autoclave was heated to 170 ℃, and held at this temperature for 4 d. Finally, the reaction system was cooled to room temperature in two days. Yellow block crystals can be obtained with yield of 29.3% (0.095 g, based on Y). The product was washed with acetone and distilled water, and dried in air. IR (cm^-1): 3414(s), 3199(s), 1671(w), 1604(w), 1097(m), 741(s), 670(s), 406(m).

  2.3 The third-order nonlinear measurements

  5 mg as-synthesized sample was powdered well and dispersed in ethanol using ultrasonic processing. The resultant mixture was spin-coated (1500 rpm, 30 s) onto pre-cleaned quartz glass substrates and dried in vacuum for 24 h. The nonlinear optical refraction and absorption were obtained with a linearly polarized laser light (7 ns, 10 Hz, 532 nm) generated from a mode-locked Q-switched Nd: YAG laser.

  2.4 Computational details

  The calculated model was constructed from its cif file by using the material studio 7.0 software^[17], which is a user-friendly module for material design. During the band structure and density of states (DOS) calculations, no structure optimization was conducted. A 3×2×2 Monkhorst-Pack grid with a total number of 6 k points in the irreducible Brillouin zone and 45 empty bands were adopted. The number of plane waves included in the basis was determined by a cutoff energy E_c of 435.4 eV. The calculation was based on density function theory (DFT)^[18], in which wave functions were explained in a plane wave basis set and the spin polarized version of the PW91 GGA was employed for the exchange-correlation functional in the CASTEP code^[19].

  2.5 X-ray crystallography

  A yellow single crystal with dimensions of 0.30 mm × 0.28 mm× 0.20 mm was placed on a Bruker APEX II CCD area detector equipped with a graphite-monochromatic MoKα radiation (λ = 0.71073 Å) at 296(2) K. A total of 3759 reflections were collected by a ϕ-ω scan mode at room temperature in the range of 2.20≤θ≤27.49º with index ranges of –9≤h≤9, –19≤k≤9 and –9≤l≤12 including 2209 independent ones (R_int = 0.0399), of which 2164 were observed with I > 2σ(I). Data collection and reduction were performed using the APEX II software^[20]. All absorption corrections were performed using the multi-scan program. The structure was solved by direct methods using SHELXS-97 program^[21] and refined with SHELXL-97^[22] by full-matrix least-squares techniques on F². All non-hydrogen atoms were refined anisotropically, while the hydrogen atoms were located geometrically and refined isotropically. The final R = 0.0366 and wR = 0.1032 (w = 1/[σ²(F_o²) + (0.1048P)² + 2.9345P], where P = (F_o² + 2F_c²)/3), S = 0.846, (Δ/σ)_max = 0.000, (Δρ)_max = 1.778 and (Δρ)_min = –3.552 e/ų. Selected bond lengths and bond angles are given in Table 1.

  Table 1

  

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (º)

  DownLoad: CSV

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Y(1)–O(1)	2.471(5)		Y(1)–O(2)d	2.416(5)		Y(1)–O(3)c	2.378(5)
  Y(1)–O(6)a	2.381(5)		Y(1)–O(7)a	2.308(6)		Y(1)–O(9)b	2.322(5)
  Y(1)–O(10)	2.377(6)		Y(1)–O(11)	2.305(5)		I(1)–O(1)	1.813(5)
  I(1)–O(2)	1.805(5)		I(1)–O(3)	1.828(5)		I(2)–O(4)	1.804(5)
  I(2)–O(5)	1.805(5)		I(2)–O(6)	1.840(5)		I(3)–O(7)	1.815(5)
  I(3)–O(8)	1.786(5)		I(3)–O(9)	1.828(5)
  Angle	(º)		Angle	(º)		Angle	(º)
  O(2)–I(1)–O(1)	100.0(2)		O(2)–I(1)–O(3)	98.2(2)		O(1)–I(1)–O(3)	95.8(3)
  O(5)–I(2)–O(4)	102.8(2)		O(5)–I(2)–O(6)	98.4(2)		O(4)–I(2)–O(6)	99.4(2)
  O(8)–I(3)–O(7)	97.3(3)		O(8)–I(3)–O(9)	97.4(2)		O(7)–I(3)–O(9)	93.6(3)

  Symmetry codes: a: x, y+1, z; b: –x+1, –y, –z+1; c: –x+1, –y+1, –z+1; d: x+1, y, z

  3. RESULTS AND DISCUSSION

  3.1 Description of the structure

  The asymmetric unit of [Y(IO₃)₃(H₂O)₂]_n (1) contains one Y atom and fifteen independent non-hydrogen atoms including three I and eleven O atoms. Two polymorphs of 1 have been previously reported^{[23, 24]}, whose real structures were different from that of 1 greatly. In detail, both polymorphs with formula of Y(IO₃)₃·(H₂O)₂ are 3-D networks, but the title compound is a 2-D layer. The Y center is coordinated to six O donors from six IO₃ polyhedra and two oxygen atoms of two water molecules, generating a monocapped trigonal prism geometry (Fig. 1a). This kind of coordinated environment is generally observed in rare earth iodate complex^[3]. The Y–O bond distances are in the range of 2.322(5)~2.471(5) Å, and the O–Y–O angles are between 71.02(18) and 147.5(2)º, which are in good consistency with the other rare earth iodates^[10]. Capping atom O(1) corresponds to the longest Y–O bond length. In the iodate groups, due to the lone pair electrons on iodine atoms, three strong I–O bonds (1.786(5)~1.840(5) Å) and one weak I···O bond (2.845(30) Å for I(1), 2.587(33) Å for I(2), 2.562(38) Å for I(3)) can be observed, corresponding to an AX₃E configuration (Fig. 1b, imaginary line means the I···O weak bonds). The O–I···O angles (155.53(20)º for I(1), 171.01(19)º for I(2), and 172.76(20)º for I(3)) deviate from 180º to some extent. When I···O weak bonds are considered, all iodine atoms are in trigonal pyramidal geometry, and a unique circle-shaped I₄O₁₂ polyiodate based on vertex-sharing of I(2)O₄ and I(3)O₄ trigonal pyramid is generated (Fig. 1c). To the best of our knowledge, this circle-shaped I₄O₁₂ polyiodate is unique and has never been documented, in which elongated O–I–O lengths are observed. If these weak I···O weak bonds are not taken into account, three kinds of coordination schemes towards yttrium atom of iodate groups can be found: a. I(1)O₃ coordinates to three Y ions to give a trimonodentate way, b. I(3)O₃ binds with two Y ions to present monodentate (via O(7)) and bismondentate (via O(9)), c. I(2)O₃ links with one Y ion in a to monodentate (via O(6)) fashion (Fig. 1d~f). In a direction, based on the μ₃ linkage model of I(3)O₃, adjacent YO₈ monocapped trigonal prisms are connected into a 1-D ladder-like double chain (Fig. 2a). Finally, neighboring 1-D ladder-like double chains are linked into a 2-D wave-like layer via circle-shaped I₄O₁₂ polyiodate (Fig. 2b). Adjacent 2-D layers are stacked into a quasi-3-D network via possible hydrogen bonds between coordinated waters and iodate groups (O···O distances at neighboring layers of 2.763(10) Å, (Fig. 2c)). But in one Y(IO₃)₃·(H₂O)₂ polymorph, the 1-D ladder-like double chain is the same with the title compound, but its 1-D chains are linked by I₂O₈ dimers to generate a 3-D network^[24].

  Figure 1

  

  Figure 1.  Coordinated environment of Y (a) and I (b); (c) structure of circle-shaped I₄O₁₂ polyiodate; coordinated models of I(1)O₃ (d), I(3)O₃ (e) and I(2)O₃ (f)

  DownLoad: Full-Size Img PowerPoint

  Figure 2

  

  Figure 2.  (a) 1-D ladder-like double chain structure based on μ₃ linkage model of I(3)O₃; (b) 2-D layer based on circle-shaped I₄O₁₂ polyiodate; (c) quasi-3-D network based on hydrogen bonds

  DownLoad: Full-Size Img PowerPoint

  3.2 PXRD, IR and UV-Vis absorption spectra

  The purity of as-synthesized sample was verified by Powder X-ray diffraction (PXRD) (Fig. 3a). As expected, the experimental curve is in good agreement with the simulated one, suggesting its good purity. As illustrated by the IR spectrum in Fig. 3b, the bands at 3414 and 1671, 1604 cm^-1 can be assigned to the stretching and bending modes of O–H groups, and the bands at 741, 670 cm^-1 are the asymmetric and symmetric stretching modes of I–O in iodates^[25]. Besides, the band at 406 cm^-1 could be attributed to the Y–O vibration^[9]. The UV-Vis diffuse reflectance spectra of 1 are presented in Fig. 3c, which was further converted to optical gap by the Kubelka-Munk transformation^[26]. As shown in Fig. 3b, a strong absorption range (200~365 nm) with peaks at 294 nm can be found, which might be led by the ligand-to-metal charge transfers (CT) from the O-2p orbitals of iodate to the 4d orbitals of Y³⁺ ion^[27]. The large optical gap of 3.49 eV calculated from Kubelka-Munk transformation is accordance to its absorption cutoff edge of 400 nm, which is consistent with other metal iodates^[28].

  Figure 3

  

  Figure 3.  (a) PXRD pattern, (b) IR spectrum and (c) absorbance spectra of 1 (Inset: Tauc plot showing the optical gap)

  DownLoad: Full-Size Img PowerPoint

  3.3 Three-order nonlinear optical property

  The open aperture transmission was carried out to reveal its nonlinear absorption coefficient (Fig. 4). Interestingly, film of 1 exhibits the third-order nonlinear optical property judged from its open-aperture Z-scan trace in Fig. 4. The Z-scan trace illustrates a model of a peak in pre-focus and a valley in post-focus, and this peak-valley fashion hints a negative nonlinear refractive index and a characteristic self-defocusing behavior^{[14, 29]}. The third-order NLO absorption coefficient β can be estimated to be –0.66 × 10^-5 mW^-1. Deduced from the absorbed spectrum, the absorption peak of 1 is far away from 532 nm, so the NLO performance of 1 could be attributed to third-order nonlinear reverse saturation absorption.

  Figure 4

  

  Figure 4.  Z-scan data for 1 film obtained under an open aperture configuration

  DownLoad: Full-Size Img PowerPoint

  3.4 Theoretical calculation

  The structure/property relationship was built by electronic structure calculation. Previous work suggests that the third-order nonlinear optical properties are also related to their frontier orbital including top of the valence band (VB) and the bottom of the conduction band (CB)^[30]. The charge densities in the frontier molecular orbitals, band structure and density of states of 1 based on DFT calculation are shown in Fig. 5. It exhibits a direct band gap of 3.32 eV, which is consistent with its experimental data of 3.49 eV. PDOS hints that the top of VB is mainly composed by O-2p orbital of iodates, while the nonbonding states of I-5p mixed with Y-5p account for the in-plane dispersion of the conduction-band minimum. These components were further verified by their charge densities in the frontier molecular orbitals (left of Fig. 5). This result indicates that the third order nonlinearity of 1 stems mainly from the electron transition within iodates.

  Figure 5

  

  Figure 5.  Charge densities in the frontier molecular orbitals (left), band structure (middle) and projected density of states (PDOS, right) for 1

  DownLoad: Full-Size Img PowerPoint

  4. CONCLUSION

  A new wave-like layer yttrium iodate has been prepared, which was further characterized by FTIR, PXRD and UV-Vis spectra. 1 was further characterized by IR and powder X-ray diffraction (PXRD). The wave-like layer of 1 is constructed from unique circle-shaped I₄O₁₆ polyiodate anion, which is further linked into a quasi-3-D supramolecular network by hydrogen bonds. Interestingly, 1 exhibits a reverse saturation absorption and a self-defocusing effect with the nonlinear absorption coefficient β being –0.66 × 10^-5 mW^-1, which stems mainly from the electron transition from O-2p to I-5p orbitals within iodates upon theoretical calculation.

  
  
• 1. [1]

     Dunn, M. H.; Ebrahimzadeh, M. Parametric generation of tunable light from continuous-wave to femtosecond pulses. Science 1999, 286, 1513–1517. doi: 10.1126/science.286.5444.1513

  2. [2]

     Wickleder, M. S. Inorganic lanthanide compounds with complex anions. Chem. Rev. 2002, 102, 2011–2087. doi: 10.1021/cr010308o

  3. [3]

     Hu, C. L.; Mao, J. G. Recent advances on second-order NLO materials based on metal iodates. Coord. Chem. Rev. 2015, 288, 1–17. doi: 10.1016/j.ccr.2015.01.005

  4. [4]

     Pan, C. Y.; Mai, H. D.; Chen, W. Z.; Zhao, F. H.; Yang, H. M. The synthesis, structure, and tunable emission spectra of a new phosphor Sm(IO₃)₃·2H₂O. Z. Anorg. Allg. Chem. 2014, 640, 429–433. doi: 10.1002/zaac.201300432

  5. [5]

     Shehee, T. C.; Sykora, R. E.; Ok, K. M.; Halasyamani, P. S.; Albrecht-Schmitt, T. E. Hydrothermal preparation, structures, and NLO properties of the rare earth molybdenyl iodates, RE(MoO₂)(IO₃)₄(OH) (RE = Nd, Sm, Eu). Inorg. Chem. 2003, 42, 457–462. doi: 10.1021/ic025992j

  6. [6]

     Sykora, R. E.; McDaniel, S. M.; Wells, D. M.; Albrecht-Schmitt, T. E. Mixed-metal uranium(Ⅵ) iodates: hydrothermal syntheses, structures, and reactivity of Rb[UO₂(CrO₄)(IO₃)(H₂O)], A₂[UO₂(CrO₄)(IO₃)₂] (A = K, Rb, Cs), and K₂[UO₂(MoO₄)(IO₃)₂]. Inorg. Chem. 2002, 41, 5126–5132. doi: 10.1021/ic025773y

  7. [7]

     Sykora, R. E.; Ok, K. M.; Halasyamani, P. S.; Wells, D. M.; Albrecht-Schmitt, T. E. New one-dimensional vanadyl iodates: hydrothermal preparation, structures, and NLO properties of A[VO₂(IO₃)₂] (A = K, Rb) and A[(VO)₂(IO₃)₃O₂] (A = NH₄, Rb, Cs). Chem. Mater. 2002, 14, 2741–2749. doi: 10.1021/cm020021n

  8. [8]

     Chen, J.; Hu, C. L.; Mao, F. F.; Yang, B. P.; Zhang, X. H.; Mao, J. G. REI₅O₁₄ (RE = Y and Gd): promising SHG materials featuring the semicircle-shaped I₅O₁₄^3- polyiodate anion. Angew. Chem. Int. Ed. 2019, 58, 11666–11669. doi: 10.1002/anie.201904383

  9. [9]

     Xiao, L.; Cao, Z.; Yao, J.; Lin, Z.; Hu, Z. A new cerium iodate infrared nonlinear optical material with a large second-harmonic generation response. J. Mater. Chem. C 2017, 5, 2130–2134. doi: 10.1039/C6TC05269J

  10. [10]

      Phanon, D.; Mosset, A.; Gautier-Luneau, I. New iodate materials as potential laser matrices. Preparation and characterization of α-M(IO₃)₃ (M = Y, Dy) and β-M(IO₃)₃ (M = Y, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er). Structural evolution as a function of the Ln³⁺ cationic radius. Solid State Sci. 2007, 9, 496–505. doi: 10.1016/j.solidstatesciences.2007.04.004

  11. [11]

      Assefa, Z.; Ling, J.; Haire, R. G.; Albrecht-Schmittc, T. E.; Sykora, R. E. Syntheses, structures, and vibrational spectroscopy of the two-dimensional iodates Ln(IO₃)₃ and Ln(IO₃)₃(H₂O) (Ln: Yb, Lu). J. Solid State Chem. 2006, 179, 3653–3663. doi: 10.1016/j.jssc.2006.07.042

  12. [12]

      Pan, C. Y.; Mai, H. D.; Chen, W. Z.; Zhao, F. H.; Yang, H. M. Synthesis, structure, and properties of a new Er^Ⅲ iodate. Aust. J. Chem. 2014, 67, 763–767. doi: 10.1071/CH13570

  13. [13]

      Sykora, R. E.; Assefa, Z.; Haire, R. G. Synthesis, structure, and spectroscopic properties of Am(IO₃)₃ and the photoluminescence behavior of Cm(IO₃)₃. Inorg. Chem. 2005, 44, 5667–5676. doi: 10.1021/ic050386k

  14. [14]

      Lian, Z.; Zhao, N.; Liu, P.; An, C.; Wang, A.; Yang, F. Crystal structures and investigation of the third-order nonlinear optical properties of four coordination polymers by using the Z-scan technique. CrystEngComm. 2018, 20, 5833–5843. doi: 10.1039/C8CE01283K

  15. [15]

      Eliseeva, S. V.; Bünzli, J. C. G. Lanthanide luminescence for functional materials and bio-sciences. Chem. Soc. Rev. 2010, 39, 189–227. doi: 10.1039/B905604C

  16. [16]

      Binnemans, K. Lanthanide-based luminescent hybrid materials. Chem. Rev. 2009, 109, 4283–4374. doi: 10.1021/cr8003983

  17. [17]

      Materials studio user's manual, version 7.0, Accelrys Inc., San Diego, CA 2016.

  18. [18]

      Perew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phy. Rev. Lett. 1996, 77, 3865–3868. doi: 10.1103/PhysRevLett.77.3865

  19. [19]

      Segall, M.; Probert, M.; Pickard, C.; Hasnip, P.; Clark, S.; Refson, K.; Payne, M. First principles methods using CASTEP. Z. Krystallogr. 2005, 220, 567–570.

  20. [20]

      Bruker. APEXII software, Version 6.3.1, Bruker AXS Inc, Madison, Wisconsin, USA 2004.

  21. [21]

      Sheldrick, G. M. SHELXS-97: Program for the Solution of Crystal Structures. University of Gottingen, Germany 1997.

  22. [22]

      Sheldrick, G. M. SHELXL-97: Program for the Refinement of Crystal Structures. University of Gottingen, Germany 1997.

  23. [23]

      Hector, A. L.; Henderson, S. J.; Levason, W.; Webster, M. Hydrothermal synthesis of rare earth iodates from the corresponding periodates: structures of Sc(IO₃)₃, Y(IO₃)₃·2H₂O, La(IO₃)₃·1/2H₂O and Lu(IO₃)₃·2H₂O. Z. Anorg. Allg. Chem. 2002, 628, 198–202. doi: 10.1002/1521-3749(200201)628:1<198::AID-ZAAC198>3.0.CO;2-L

  24. [24]

      Hector, A. L.; Henderson, S. J.; Levason, W.; Webster, M. Synthesis and properties of scandium, yttrium and lanthanum periodates. Crystal structures of Y(H₂O)₃{IO₄(OH)₂} and Y(H₂O)₂(IO₃)₃. Inorg. Chim. Acta 2000, 298, 43–49. doi: 10.1016/S0020-1693(99)00409-0

  25. [25]

      Ok, K. M.; Halasyamani, P. S. New metal iodates: syntheses, structures, and characterizations of noncentrosymmetric La(IO₃)₃ and NaYI₄O₁₂ and centrosymmetric β-Cs₂I₄O₁₁ and Rb₂I₆O₁₅(OH)₂·H₂O. Inorg. Chem. 2005, 44, 9353–9359. doi: 10.1021/ic051340u

  26. [26]

      Kubelka, P.; Munk, F. Z. An article on optics of paint layers. Z. Technol. Phys. 1931, 12, 593−601.

  27. [27]

      Lin, J.; Liu, Q.; Yue, Z.; Diefenbach, K.; Cheng, L.; Lin, Y.; Wang, J. Q. Expansion of the structural diversity of f-element bearing molybdate iodates: synthesis, structures, and optical properties. Dalton Trans. 2019, 48, 4823–4829. doi: 10.1039/C8DT05120H

  28. [28]

      Sykora, R. E.; Deakin, L.; Mar, A.; Skanthakumar, S.; Soderholm, L.; Albrecht-Schmitt, T. E. Isolation of intermediate-valent Ce(Ⅲ)/Ce(Ⅳ) hydrolysis products in the preparation of cerium iodates: electronic and structural aspects of Ce₂(IO₃)₆(OH_x) (x ≈ 0 and 0.44). Chem. Mater. 2004, 16, 1343–1349. doi: 10.1021/cm035147e

  29. [29]

      Liu, R. Q.; Zhao, N.; Yang, F. X.; Wang, A. R.; Liu, P.; An, C. X.; Lian, Z. X. Enhanced third-order nonlinear optical properties of three 2D coordination polymers based on bis(imidazole) ligands and dicarboxylic ligands. Polyhedron 2016, 111, 16–25. doi: 10.1016/j.poly.2016.03.015

  30. [30]

      Hou, H. W.; Wei, Y. L.; Song, Y. L.; Mi, L. W.; Tang, M. S.; Li, L. K.; Fan, Y. T. Metal ions play different roles in the third-order nonlinear optical properties of d¹⁰ metal-organic clusters. Angew. Chem. 2005, 117, 6221–6228. doi: 10.1002/ange.200463004

• 

  Figure 1  Coordinated environment of Y (a) and I (b); (c) structure of circle-shaped I₄O₁₂ polyiodate; coordinated models of I(1)O₃ (d), I(3)O₃ (e) and I(2)O₃ (f)

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) 1-D ladder-like double chain structure based on μ₃ linkage model of I(3)O₃; (b) 2-D layer based on circle-shaped I₄O₁₂ polyiodate; (c) quasi-3-D network based on hydrogen bonds

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) PXRD pattern, (b) IR spectrum and (c) absorbance spectra of 1 (Inset: Tauc plot showing the optical gap)

  下载: 全尺寸图片 幻灯片
  

  Figure 4  Z-scan data for 1 film obtained under an open aperture configuration

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Charge densities in the frontier molecular orbitals (left), band structure (middle) and projected density of states (PDOS, right) for 1

  下载: 全尺寸图片 幻灯片

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (º)

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Y(1)–O(1)	2.471(5)		Y(1)–O(2)d	2.416(5)		Y(1)–O(3)c	2.378(5)
  Y(1)–O(6)a	2.381(5)		Y(1)–O(7)a	2.308(6)		Y(1)–O(9)b	2.322(5)
  Y(1)–O(10)	2.377(6)		Y(1)–O(11)	2.305(5)		I(1)–O(1)	1.813(5)
  I(1)–O(2)	1.805(5)		I(1)–O(3)	1.828(5)		I(2)–O(4)	1.804(5)
  I(2)–O(5)	1.805(5)		I(2)–O(6)	1.840(5)		I(3)–O(7)	1.815(5)
  I(3)–O(8)	1.786(5)		I(3)–O(9)	1.828(5)
  Angle	(º)		Angle	(º)		Angle	(º)
  O(2)–I(1)–O(1)	100.0(2)		O(2)–I(1)–O(3)	98.2(2)		O(1)–I(1)–O(3)	95.8(3)
  O(5)–I(2)–O(4)	102.8(2)		O(5)–I(2)–O(6)	98.4(2)		O(4)–I(2)–O(6)	99.4(2)
  O(8)–I(3)–O(7)	97.3(3)		O(8)–I(3)–O(9)	97.4(2)		O(7)–I(3)–O(9)	93.6(3)

  下载: 导出CSV
•