Synthesis, Structure, White-Light Emission, and Temperature

Jan 4, 2016 - Two series of EuIII/TbIII coordination polymers based on (2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline and glutaric acid have be...
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Synthesis, Structure, White-Light Emission, and Temperature Recognition Properties of Eu/Tb Mixed Coordination Polymers Ran An, Hui Zhao, Huai-Ming Hu,* Xiaofang Wang, Meng-Lin Yang, and Ganglin Xue Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710127, China S Supporting Information *

ABSTRACT: Two series of EuIII/TbIII coordination polymers, [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb (2)) and [LnL(glu)(H2O)]n (Ln = Eu (3), Tb (4)) [HL = (2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline, H2glu = glutaric acid] have been hydrothermally synthesized by controlling the pH values and characterized by elemental analysis, infrared spectra, and singlecrystal X-ray diffraction. Isomorphic compounds 1 and 2 exhibit 6connected 3D network with the pcu topological net, containing left- and right-handed helical chains. Isomorphic compounds 3 and 4 show 3,4-connected 2D new topology with the point symbol of (42·63·8)(42·6). Multicolor luminescence can be tailored from red to green regions by singly varying the mixing molar ratio of EuIII/TbIII cations. The mixing component of 1Eu/2Tb = 4:6 not only achieves white-light emission with the CIE coordinate of (0.323, 0.339) upon excitation at 405 nm but also presents a temperature recognition property with the significantly high sensitivity of 0.68% per K in the 50−225 K temperature range upon excitation at 370 nm.

1. INTRODUCTION Recently, studies of white-light-emitting materials are on the rise because they have potential applications in the field of lighting and are environmentally friendly.1 Specifically, lanthanide−organic frameworks (LOFs) emitting three primary colors are the ideal candidates to design white-light-emitting materials due to their high photoluminescence (PL) efficiency, long-lived luminescence, and various emission spectra.2 Beyond that, compared with transition metal ions, lanthanide ions have more characteristic spectral bands which have lower susceptibility to crystal field and exchange perturbations because of the shielding effect of 5s2 and 5p6 shells to the environment.2c,3 Effective sensitization of the lanthanide metal ions depends on the sizable energy gap of the metal ion between the lowest-lying emissive state and the highest sublevel of its ground multiplet.4 The energy gaps of EuIII and TbIII [ΔE = 12 300 (5D0 → 7F6) and 14 800 (5D4 → 7F0) cm−1, respectively] are relatively sizable, and the energy transfer can be more effective than that of GdIII [ΔE = 32 200 (6P7/2 → 8S7/2) cm−1],4a,5 which makes single-component,6 isostructural EuIII (red-emissive) and TbIII (green-emissive)-doped materials attract more attention in the design of white-light-emitting materials.7 In addition, the Eu/ Tb-codoped lanthanide metal−organic framework has been utilized to develop luminescent thermometers because they are noninvasive and accurate compared with conventional temperature sensors.8 Many lanthanide compounds with novel structures and special luminescence were successfully synthesized by a hydrothermal method.9 Because LnIII cations have various coordination numbers, the reasonable choices of organic © XXXX American Chemical Society

ligands and pH values are particularly important to obtain the expected lanthanide compounds by the hydrothermal method.4b Both lattice and coordinated water molecules may lead to a quenching of the LnIII luminescence via O−H vibrations.10 Therefore, it is favorable to choose polydentate ligands and a suitable pH value to minimize vibration-induced deactivation processes. 1,10-Phenanthroline can design a rigid metal-ion environment for better protection against water interaction.11 Recently, many 1,10-phenanthroline derivatives have been used to construct lanthanide coordination polymers as a rational choice for white-light-emitting materials introducing single dopant and codopants.1b,12 Our group has recently reported compounds of PbII and LnIII cations based on 2-(2,4disulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline.13 Then, on this basis, we synthesized the 2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline ligand (HL, Scheme 1). The Scheme 1. Schematic Drawing of the HL Ligand

Received: October 15, 2015

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DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX

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Anal. Calcd (%) for C24H19EuN4O8S (675.46): C, 42.67, H, 2.84, N, 8.29%. Found: C, 43.01, H, 2.90, N, 8.02%. IR (KBr, cm−1): 3387(w), 3269(vw), 3071(w), 2976(w), 2190(vw), 1668(w), 1585(vs), 1543(w), 1456(w), 1421(s), 1243(s), 1172(vs), 1133(m), 1084(s), 1058(m), 1024(s), 945(m), 812(s), 738(s), 704(m), 659(m), 557(m), 488(m). Synthesis of [TbL(glu)(H2O)]n (4). The synthesis process of compound 4 was similar to that for compound 3, but with the substitution of Eu(NO3)3·6H2O to Tb(NO3)3·6H2O. Yield: 43.3 mg (63.5%) based on HL. Anal. Calcd (%) for C24H19TbN4O8S (682.42): C, 42.24, H, 2.81, N, 8.21%. Found: C, 42.34, H, 2.73, N, 8.14%. IR (KBr, cm−1): 3384(w), 3265(vw), 3069(w), 2972(w), 2187(vw), 1670(w), 1583(vs), 1540(w), 1457(w), 1419(s), 1240(s), 1169(vs), 1132(m), 1084(s), 1055(m), 1021(s), 948(m), 813(s), 735(s), 702(m), 661(m), 560(m), 485(m).

multidentate HL ligand is an excellent chromophore and also can improve the rigidity of compounds.14 Besides, the terminal sulfonic group has various coordination modes.15 Therefore, the HL ligand should be a practicable ligand which can transfer energy to the lanthanide centers efficiently, leading to high luminescence and achieving white-light emissions further. In this paper, we first reported four lanthanide compounds based on the HL ligand and glutaric acid (H2glu) by carefully changing the pH values under hydrothermal conditions, namely, [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb (2)), [LnL(glu)(H2O)]n (Ln = Eu (3), Tb (4)). For two series of compounds, multicolor luminescence can be tailored from red to green regions by singly varying the mixing molar ratios of EuIII and TbIII compounds. White-light emission with the CIE coordinates of (0.323, 0.339) is achieved upon excitation at 405 nm when the mixing ratio of 1Eu and 2Tb is 4:6, and the absolute quantum yield is 6.03%, which is modest compared to that of traditional phosphors.16 The temperature-dependent PL spectra for the mixing components of 1Eu/2Tb = 4:6 indicate a temperature recognition property in the range of 50−225 K upon excitation at 370 nm.

Scheme 2. Reaction Routes of Compounds 1−4

2. EXPERIMENTAL APPROACH

2.3. Single-Crystal Structure Determination. Single-crystal diffraction data of compounds 1−4 were collected using a Bruker Smart APEX II CCD diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at room temperature. Empirical absorption corrections were applied based on the SADABS program. The structures were solved by direct methods and refined by the fullmatrix least-squares based on F2 using SHELXTL-97. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms of organic ligands were generated geometrically. Crystal data and structural refinement parameters for 1−4 are summarized in Table S1 in the Supporting Information. Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 1410511−1410514 for 1−4. These data can be obtained free of charge via www.ccdc.can.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax, (+44) 1223−336033; or e-mail, [email protected]. uk).

2.1. Materials and Characterizations. The HL ligand was prepared from 1,10-phenanthroline according to literature methods.13 Hydrated Eu(NO3)3 and Tb(NO3)3 were synthesized by dissolving Eu2O3 (99.99%) and Tb4O7 (99.99%) in concentrated nitric acid, respectively. All other chemicals were reagent grade and used as received without further purification. The IR spectra were recorded on a Bruker EQUINOX-55 Fourier transform infrared spectrometer (frequency range from 4000 to 400 cm−1) using KBr pellets. Elemental analyses (C, H, N) were performed using a Vario EL elemental analyzer. Thermogravimetric analyses (TGA) were conducted on a Universal V2.6 DTA system by heating from 30 to 900 °C at 10 °C/ min. Powder X-ray diffraction (PXRD) measurements were performed on a Bruker D8 ADVANCE X-ray powder diffractometer with Cu Kα (1.5418 Å). Fluorescence spectra for the solid samples were recorded at room temperature on a Hitachi F-4500 spectrophotometer. Quantum efficiency was measured using the integrating sphere on a FluoroMax-4 spectrophotometer. The temperature-dependent luminescence spectra were recorded on an Edinburgh Instrument FLSP920 spectrometer. 2.2. Synthesis of Compounds. Synthesis of [EuL(glu)]n·2nH2O (1). Eu(NO3)3·6H2O (73.21 mg, 0.2 mmol), HL (37.64 mg, 0.1 mmol), H2glu (13.21 mg, 0.1 mmol), and H2O (10 mL) were mixed and stirred for 30 min at room temperature. Then, the mixture was adjusted to pH 4.0 with 0.5 mol L−1 NaOH solution, sealed in a 25 mL Teflon-lined stainless steel autoclave, and maintained at 180 °C for 3 days. When cooled to room temperature, pale yellow block crystals were obtained. Yield: 37.5 mg (54.2%) based on HL. Anal. Calcd (%) for C24H21EuN4O9S (693.47): C, 41.57, H, 3.13, N, 8.08%. Found: C, 41.21, H, 2.83, N, 8.22%. IR (KBr, cm−1): 3432(w), 3218(vw), 3086(vw), 1588(vs), 1548(vw), 1424(s), 1350(vw), 1275(vw), 1222(w), 1180(m), 1134(w), 1084(m), 1015(m), 883(vw), 816(m), 790(w), 740(s), 701(m), 618(s), 560(m). Synthesis of [TbL(glu)]n·2nH2O (2). The synthesis process of compound 2 was similar to that for compound 1, but with the substitution of Eu(NO3)3·6H2O to Tb(NO3)3·6H2O (74.61 mg, 0.2 mmol). Yield: 40.2 mg (57.4%) based on HL. Anal. Calcd (%) for C24H21TbN4O9S (700.43): C, 41.15, H, 3.02, N, 8.00%. Found: C, 43.05, H, 3.21, N, 7.82%. IR (KBr, cm−1): 3429(w), 3216(vw), 3080(vw), 1590(vs), 1545(vw), 1420(s), 1347(vw), 1270(vw), 1225(w), 1184(m), 1130(w), 1082(m), 1014(m), 882(vw), 813(m), 786(w), 742(s), 698(m), 615(s), 556(m). Synthesis of [EuL(glu)(H2O)]n (3). The synthesis process of compound 3 was similar to that for compound 1, but with the pH of the mixture changed to 6.0. Yield: 40.2 mg (59.5%) based on HL.

3. RESULTS AND DISCUSSION 3.1. Crystal Structure of [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb(2)). X-ray crystallography reveals that compounds 1 and 2 are isostructural. Herein, compound 1 is taken as an example to depict the structure in detail. Compound 1 crystallizes in the monoclinic system with the P21/n space group and exhibits a 3D framework structure. The asymmetric unit contains one independent EuIII cation, one L− and one glu2− anion, and two lattice water molecules (Figure 1a). The nine-coordinated Eu1 is completed by two nitrogen atoms (N1, N2) and two oxygen atoms (O1D, O2D) from the L− ligand and five oxygen atoms (O4, O5A, O6C, O7B, O7C) from glu2− anions. The Eu−N and Eu−O bond lengths are in the range of 2.550(3)−2.630(3) and 2.297(3)−2.745(3)Å, respectively, and O−Eu−O bond angles vary from 73.96(10) to 139.11(10)°. The average distances of the Ln−O, Ln−N, and Ln···Ln of compound 1 are longer than that of compound 2, corresponding to the lanthanide contraction effect (Table S2 in the Supporting Information). The L− ligands exhibit the μ2-η2:η2 coordination mode and bridge the EuIII cations to form 1D left- and righthanded helical chains of [EuL−]∞ running along the crystallographic 21 axis with a pitch of 14.906 Å. The adjoining left- and right-handed helical chains are bridged by oxygen atoms from glu2− anions, giving rise to an achiral 2D layer in the bc plane B

DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX

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Different from compound 1, the L− ligands exhibit the μ2-η1:η2 coordination mode and bridge the TbIII cations to form the 1D loop chain (Figure 2b), in which the [Tb(CO2)]2 subunits are joined by two oxygen atoms from glu2− anions. The adjacent chains are bridged by glu2− anions, giving rise to a 2D doublelayer structure (Figure 2c). If we define the glu2− anion as a 3connected node and the TbIII cation as a 4-connected node, then the simplified structure is a 3,4-connected 2D new topology with the point symbol of (42·63·8)(42·6) (Figure 2d). 3.3. Photoluminescence Properties. The PL spectra of the free HL ligand and compounds 1−4 have been investigated at room temperature. As shown in Figure 3, the free HL ligand displays a broad emission band at 515 nm upon excitation at 370 nm. Compounds 1 and 3 display the characteristic red emissions of the EuIII cation from 5D0 to 7FJ (J = 0 → 4) at 580, 593, 618, 652, and 696 nm with CIE coordinates of (0.612, 0.346) for 1 and (0.601, 0.344) for 3, respectively, when excited at 370 nm.9c,17 Due to the ligand-centered emission which is completely quenched in 1 and 3, the EuIII cations are sensitized effectively by HL ligands via the antenna effect. The electric dipole transitions 5D0 → 7F2 (618 nm) are much higher than the magnetic dipole transitions 5D0 → 7F1 (593 nm) and show strong fluorescence presenting red color.18 Compounds 2 and 4 excited at 370 nm display green luminescence in the narrow emission bands at 493, 546, 590, 617, and 698 nm with CIE coordinates of (0.223, 0.388) for 2 and (0.223, 0.374) for 4, which can be assigned to 5D4 → 7FJ (J = 6 → 0).19 It can be seen from Figure 3c, that the ligand-centered emission also appears at 523 nm, with a red shift of 8 nm compared with the free HL ligand, which indicates that the energy of the ligand may transfer partly. In order to gain insights into the energy levels of the HL ligand in theory, we performed theoretical calculations for the HOMO and LUMO energy levels, which, respectively, are −0.211 and −0.072 eV by the Gaussian 09 program (Figure S1 in the Supporting Information). The energy level of the T1 excited state is 3.391 eV (2.73 × 104 cm−1) using (TD)-DFT at the B3LYP/6-31G(d) level.20 Figure S2 in the Supporting Information shows the solid-state ultraviolet spectrum of HL, which indicates that the energy level of HL is 2.07 × 104 cm−1. In theory, the 5D0 level of EuIII and the 5D4 level of TbIII are 17 277 and 20 500 cm−1, respectively, which can occur at the energy transfer from T1 to EuIII or TbIII cations, followed by generating f−f transitions of EuIII or TbIII cations (Figure S3 in the Supporting Information). In the past few years, mixed ligand coordinates have drawn much attention because of their polydentate, easy to synthesize and noticeable synergy effects on fluorescence properties compared with single carboxylate-coordinated EuIII/TbIII complexes. Li et al. reported that EuIII/TbIII frameworks display highly efficient red/green emissions based on the mixed ligand.1c,12a In our paper, the HL ligand is an excellent chromophore with an extended π-conjugated system to sensitize EuIII/TbIII ions effectively. As a versatile bridge ligand, H2glu contributes significantly to prevent water molecules from binding to the EuIII/TbIII ions, further improving the luminescence efficiency. In our case, different combinations of the isostructural EuIII/ TbIII compounds have been obtained that correspond to the mixing molar ratios of EuIII/TbIII that change from 1:9 to 9:1, and tunable color can be generated from green to orange-pink, and red, and the designed white light. As we can see clearly from Figure 4 and Table S3 in the Supporting Information, two groups of characteristic emissions and corresponding CIE

Figure 1. (a) Coordination environment of EuIII cation in 1. The hydrogen atoms are omitted for clarity. (b) Achiral 2D layer containing the adjoining left- and right-handed helical chains. (c) 3D framework along the b-axis. (d) The pcu topology with the point symbol of (412·63). Symmetry codes: A = (−x + 1, −y, −z), B = (−x, −y, −z), C = (x + 1, y, z), D = (−x + 1.5, y − 0.5, −z + 0.5).

(Figure 1b). Finally, each binuclear [Eu2O2(CO2)2] subunit of the 2D layer is connected by two glu2− ligands to produce a 3D framework along the b-axis (Figure 1c). If we define the [Eu2O2(CO2)2] subunit as a 6-connected node, the simplified structure is a 6-connected pcu topology with the point symbol of (412·63) (Figure 1d). 3.2. Crystal Structure of [LnL(glu)(H2O)]n (Ln = Eu (3), Tb(4)). The X-ray diffraction analysis shows that compounds 3 and 4 have an isostructural 2D layer structure with the triclinic P1̅ space group. With compound 4 as an example, the asymmetric unit consists of one independent TbIII cation, one L− and one glu2− anion, and one coordinated water molecule. As shown in Figure 2a, Tb1 is eight-coordinated by two

Figure 2. (a) Coordination environment of TbIII cation in 4. The hydrogen atoms are omitted for clarity. (b) 1D loop chain connected by the L− ligand. (c) 2D double-layer structure. (d) New topology with the point symbol of (42·63·8)(42·6). Symmetry codes: A = (−x + 1, −y, −z + 1), B = (x, y − 1, z), C = (−x + 1, −y + 1, −z).

nitrogen atoms (N1, N2) and one oxygen atom (O1A) from the L− anion, four oxygen atoms (O4, O5, O6C, O7B) from glu2− anions, and one coordinated water (O8) molecule. The Tb−N and Tb−O bond lengths are in the range of 2.550(4)− 2.562(4) and 2.250(3)−2.460(4) Å, respectively, and the O− Tb−O bond angles vary from 86.01(13) to 148.54(12)°. The lanthanide contraction effect has also been reflected in the average distances of the Ln−O, Ln−N, and Ln···Ln in compounds 3 and 4 (Table S2 in the Supporting Information). C

DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 3. (a) Excitation and emission spectra of the HL ligand. (b) Emission spectra of compounds 1 and 3 (λex = 370 nm). (c) Emission spectra of compounds 2 and 4 (λex = 370 nm).

coordinates (1Eu-mixed 2Tb and 3Eu-mixed 4Tb, respectively) change according to the mole ratio of EuIII/TbIII cations varying from 1:9 to 9:1, in turn, when excited at 370 nm. With the increase of mole ratio of the EuIII cation, the intensities of TbIII/5D4 → 7F5 (546 nm) decrease gradually, corresponding to the increase of EuIII/5D0 → 7F2 (618 nm). The variation trends of the CIE coordinates are similar for two groups of mixing components. As shown in Figure 4b, points a and k represent CIE coordinates of compounds 1 and 2, respectively, points b− j represent CIE coordinates for 1Eu-mixed 2Tb, which change from (0.558, 0.347) to (0.300, 0.413). In Figure 4d, points A and K represent CIE coordinates of compounds 3 and 4, respectively, points B−J represent that the CIE coordinates for 3Eu-mixed 4Tb change from (0.564, 0.342) to (0.301, 0.406). What is more noteworthy is that the CIE coordinate (0.323, 0.339) (the point l in Figure 4b) excited at 405 nm is very close to the ideal coordinate for pure white light (0.333, 0.333) according to the 1931 CIE coordinate diagram when the mixing molar ratio of 1Eu/2Tb is 4:6 (the quantum yield is 6.03%). Selected mixing molar ratios and corresponding CIE coordinates for two groups of mixing components are shown in Table S4 in the Supporting Information upon excitation at 405 nm. Regrettably, we failed to get the white light by changing the excitation wavelength for different mole ratios of 3Eu-mixed 4Tb compounds.

In order to investigate the potential as luminescent thermometers, the temperature-dependent PL spectra for the mixing components of 1Eu/2Tb = 4:6 have been studied in the 25−300 K temperature range upon excitation at 370 nm. As expected, the emission spectra simultaneously display both 5D0 → 7F0−4 (EuIII) and 5D4 → 7F6−2 (TbIII), as shown in Figure 5a. The EuIII and TbIII cations display similar temperaturedependent luminescence behaviors. The curves of the intensity for EuIII/5D0 → 7F2 (618 nm) and TbIII/5D4 → 7F5 (546 nm) decrease with the increasing temperature (Figure 5b) due to the thermal activation of the nonradiative energy transfer processes. The emission intensity of TbIII cations decreases by 93%, and it is faster than that of EuIII cations, which decrease by 34% in the range of 50−225 K. The temperature can be readily correlated to the emission intensity ratio of the 5D4 → 7F5 (TbIII, 546 nm) to 5D0 → 7F2 (EuIII, 618 nm) transition (ITb/ IEu), which does not require any additional calibration of luminescence intensity. The temperature can be linearly related to ITb/IEu by the equation from 50 to 225 K. T = 233.255 − 146.247 ITb/IEu

The temperature sensitivity of 1Eu/2Tb = 4:6 is 0.68% per K. This reveals that 1Eu/2Tb = 4:6 is a potentially useful luminescent thermometer.8 3.4. PXRD and Thermogravimetric Analysis. PXRD was carried out to check the phase purity of compounds 1−4. The D

DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 4. (a) Emission spectra of 1Eu-mixed 2Tb components in different mole ratios (λex = 370 nm). (b) CIE x−y chromaticity diagram of 1Eumixed 2Tb components in different mole ratios (λex = 370 nm) [the CIE coordinates of (0.323, 0.339) are called point l (1Eu/2Tb = 4:6, λex = 405 nm)]. (c) Emission spectra of 3Eu-mixed 4Tb components in different mole ratios (λex = 370 nm). (d) CIE x−y chromaticity diagram of 3Eu-mixed 4Tb components in different mole ratios (λex = 370 nm).

Figure 5. (a) Temperature-dependent PL spectra for the mixing components of 1Eu/2Tb = 4:6 in the temperature range of 25−300 K upon excitation at 370 nm. (b) Curves of the intensity for EuIII/5D0 → 7F2 (618 nm) and TbIII/5D4 → 7F5 (546 nm) with increasing temperature. (Inset) Fitted curves of the integrated intensity ratio for 1Eu/2Tb = 4:6 from 50 to 225 K.

isomorphous structures, thermal behaviors are similar for compounds 1, 2 and 3, 4, respectively. Thus, we take compounds 1 and 3 for examples to analyze in detail. Compound 1 starts to lose two lattice water molecules at about 150 °C, with a weight loss of 5.4% (calcd 5.2%). The second weight loss of 26.8% from 380 to 610 °C can be also attributed to the complete decomposition of organic ligands

measured patterns are in good agreement with simulated patterns based on the single-crystal X-ray diffraction (Figure S4 in the Supporting Information). The TGA results show that these four compounds have good thermal stability (Figure S5 in the Supporting Information). TGA was performed by heating from 30 to 900 °C at a speed of 10 °C/min under a nitrogen atmosphere. Because of E

DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

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(calcd 27.3%). Then, the skeleton begins to collapse after 680 °C. For 3, the initial weight loss of 3.1% is consistent with that of the calculated value (2.7%), corresponding to the loss of one coordinated water molecule at 200 °C. After the stationary phase in the temperature range of 230−450 °C, a two-step weight loss of 26.3% can be attributed to the complete decomposition of organic ligands at 450 °C (calcd 25.8%); the next is the decomposition of the framework at about 700 °C. The TGA results show that the two series of compounds have good thermal stability.

4. CONCLUSIONS In summary, we successfully synthesized two series of isomorphic europium and terbium compounds by carefully controlling the pH values under hydrothermal conditions. All compounds show characteristic emissions accordingly. Two groups of various colors can be tailored from red to green by singly varying the mixing molar ratio of EuIII and TbIII compounds. White-light emission with the quantum yield of 6.03% is achieved in a suitable molar ratio of the multicomponents. The mixing components of 1Eu/2Tb = 4:6 present a temperature recognition property at 50−225 K.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b02375. UV−vis data, molecular orbital diagrams, CIE coordinates, and PXRD and TGA diagrams (PDF) X-ray data for compound 1 (CIF) X-ray data for compound 2 (CIF) X-ray data for compound 3 (CIF) X-ray data for compound 4 (CIF)

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AUTHOR INFORMATION

Corresponding Author

*Tel/Fax: 0086-29-81535026. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant Nos. 21173164 and 21473133).

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REFERENCES

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DOI: 10.1021/acs.inorgchem.5b02375 Inorg. Chem. XXXX, XXX, XXX−XXX