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OAc--Dependent Self-Assembly of Luminescent Homoleptic [Ln9(OH-Salen)5(OH)4(OAc)10] and {[Ln6(OHMeO-Salen)5(OH)(OAc)2(H2O)2]#(OAc)} Complexes Guorui Fu, Li BAONING, Jiahao Guo, Lin Liu, Kaimeng Zhang, feng weixu, and Xingqiang Lü Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b01490 • Publication Date (Web): 28 Dec 2017 Downloaded from http://pubs.acs.org on December 31, 2017

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Crystal Growth & Design

OAc--Dependent Self-Assembly of Luminescent Homoleptic [Ln9(OH-Salen)5(OH)4(OAc)10]

and

{[Ln6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]⋅⋅(OAc)} Complexes

Guorui Fu,†,# Baoning Li,†,# Jiahao Guo,† Lin Liu,† Kaimeng Zhang,† Weixu Feng,*‡ and Xingqiang Lü,* †,§

†

School of Chemical Engineering, Shaanxi Key Laboratory of Degradable Medical Material,

Northwest University, Xi'an 710069, Shaanxi, China ‡

Department of Applied Chemistry, School of Science, Northwestern Polytechnical University,

Xi'an 710029, Shaanxi, China §

MOE Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen

University, Guangzhou 510275, Guangdong, China

1

ACS Paragon Plus Environment

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ABSTRACT Two series of OAc--dependent unique homoleptic nonanuclear [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (1-7) and hexanuclear {[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (8-14) are obtained from the self-assembly

of

the

partially

deprotonated

(N,N'-bis(salicylidene)(propylene-2-ol)-1,3-diamine)

or

OH-H2Salen OH-MeO-H2Salen

ligand ligand

H3L1 H3L2

(N,N'-bis(3-methoxysalicylidene)(propylene-2-ol)-1,3-diamine) with Ln(OAc)3 (Ln = La, Eu, Tb, Gd, Nd, Yb or Er), respectively. The result of their photophysical properties shows that the sensitization for single-component near-white-light of complex 2, efficient Eu3+-centered red-light (ΦLEu = 13.4%) of complex 9 or or Tb3+-centered yellowish-green-light (ΦLTb = 8.1% and 21.3%) of complexes 3 and 10, and Nd3+- or Yb3+-centered NIR luminescence (η =

ΦLLn/ΦLnLn = 67-75% and 76-85%) for complexes 5-6 and 12-13, is arisen from the ligands' 3

π-π* excited state, due to effective intramolecular energy transfer and multiple Ln3+-to-Ln3+

electron-communications.

Keywords: Nonanuclear and Hexanuclear Framework; (HLn)2--co-(Ln)3-; Multiple Bonding Modes of OAc- Anion; Ln3+-Centered Visible and NIR Luminescence; Energy Transfer

2


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INTRODUCTION In contrast to structural certainty of 3d-1-6 or 3d-4f-Salen complex7-10 with one cis-N2O2 core preferentially affine to the medium Lewis-acidic 3d metal ion, self-assembly of the 4f systems is more complicated due to H2Salen's multiple bonding modes arisen from high and variable coordination numbers, and flexible coordination geometries of 4f Ln3+ ion within.11-12 On one hand, the neutral H2Salen ligand can directly coordinate to Ln3+ ion by its one or two µ-O-phenoxide atoms, affording to discrete or polymeric complexes. On the other hand, besides the influential factors of counter-anion and reaction condition, the H2Salen, (Salen)2and/or the (HSalen)- coordination modes of the Salen-type ligands with rigid or flexible linkers also make their Ln3+-directed self-assembly of a predetermined structure rather challenging.

Moreover, Ln3+-incorporated interesting properties including Ln3+-centered

unique visible-to-near-infrared (NIR) photo-luminescence with potential applications in materials,13-16 catalysis17-18 and bio-science19-20 further contribute significantly to the increasing popularity of this field. As a matter of fact, for the typical compartmental Salen-type Schiff-base ligands, NO3- or Cl--dependent mononuclear ([Ln(H2Salen)(NO3)3]21), dinuclear ([Ln(H2Salen)2(NO3)3]222 or {[Ln(H2Salen)2Cl2]2⋅2Cl}23) to 1D ({Ln(H2Salen)2(NO3)3}n24), 2D ([Ln(H2Salen)1.5(NO3)3]n25) or 3D ([Ln(H2Salen)(NO3)2Cl]n26)

polymeric

complexes

are

obtained,

in

which

the

discrete-to-polymeric structures are mainly based on the flexible H2Salen ligand with two µ-O-phenoxide atoms chelated to the same or the different Ln3+ ions, respectively. In avoidance of the interference of counter-anion, homoleptic dinuclear ([Ln2(Salen)3]27-28) or tetranuclear ([Ln4(Salen)6]29-30) framework is founded from the primitive structure unit of 3



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[Ln2(Salen)3]n (n = 1-2). Moreover, under a weak alkaline condition, the partial H2Salen ligands are deprotonated, from which, the H2Salen-co-(HSalen)- or H2Salen-co-(Salen)2bonding modes are inclined to construct homoleptic µ3-OH--cooperated trinuclear ([Ln3(Salen)3(HSalen)(OH)2]31) or anion-independent hexanuclear ([Ln6(Salen)9(H2Salen)2]31) Ln3+-complexes, respectively. As to MeO-H2Salen ligands with both the inner cis-N2O2 core and the outer O2O2 portion, similar anion-related mononuclear ({[Ln(MeO-H2Salen)2]X3};32 X= PF6- or NO3-), to binuclear ([{Ln2(MeO-H2Salen)2](X)6}21,33) (X- = PF6-, NO3- or OAc-) and to polymeric ({[Ln(MeO-H2Salen)2(X)3}n32) (X- = PF6- and NO3-) structural manner is regulated. Upon the further deprotonation, higher-clusters' homoleptic anion-dependent trinuclear ([Ln3(MeO-Salen)3Cl(OAc)2]34 and [Ln3(MeO-Salen)4Cl]35), µ3-OH--cooperated tetranuclear ({[Ln4(MeO-Salen)2(MeO-HSalen)2](OH)2X4}36-38 {[Ln4(MeO-Salen)2](OH)2(OAc)6)}39)

or

(X-

pentanuclear

=

NO3-

or

Cl-)

and

({[Ln5(MeO-Salen)4](OH)2(NO3)5}40)

complexes are obtained with a special charge balance from the contributions of anion, µ3-OH- and/or the partial protonation of imino N atoms of the MeO-Salen ligands. From the viewpoint of desirable photophysical property for Ln3+-templated Salen or MeO-Salen systems, elaborations of electronic communication41-42 between multiple Ln3+-species, compatible energy difference43-44 of the ligand's 3π-π* level matching with the Ln3+-emitting one, and effective suppression of oscillator-vibrated luminescence quenching45 are so enslaved to good sensitization efficiency. Worthy of notice, through another approach to simple OH-modification, the propylene-2-ol-linked flexible H2Salen or MeO-H2Salen ligand (H3L1 of OH-H2Salen or H3L2 of OH-MeO-H2Salen as shown in Scheme 1 or 2) affords similar while homoleptic hexanuclear 4


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[Ln6(Ln)4(OH)4X2]46-47 (n = 1, X- = NO3- or Cl-; n = 2, X- = Cl-) complexes, which motivates us the further concerning of their higher-nuclearity frameworks. Toward this end, the realization of their partial deprotonations should also be expectable, where besides an additional coordinating O atom from the -OH group, multiple possible bonding modes ((Ln)3- and (HLn)2-; also shown in Schemes 1-2) of the two flexible H3Ln (n = 1-2) ligands, together with the retrofiting charge balance must be beneficial to the formation of new Ln3+-clusters. Moreover, by the usage of OAc- instead of NO3- or Cl- anion, its promising advantages of more versatile coordination modes (free µ0-OAc--mode to Ln3+-, (Ln3+)2- or (Ln3+)3-bridged µ1-µ6-OAc--modes; Scheme 3) and stronger Ln3+-affinity should further take effect. Herein, we describe two series of homoleptic [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (Ln = La, Eu, Ln, Tb, Gd, Nd, Yb, or Er, 1-7) or {[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (Ln = La, Eu, Ln, Tb, Gd, Nd, Yb, or Er, 8-14) formed from the reaction of the H3Ln (n = 1-2) ligand and Ln(OAc)3, respectively. To the best of our knowledge, the H3L1-induced nonanuclear framework of complexes 1-7 as the highest-nuclearity one within homoleptic Ln3+-Salen-clusters to date, and the H3L2-induced interesting hexanuclear framework of complexes 8-14 are the first examples of (Ln)3--co-(HLn)2--

and

OAc--co-OH--cooperated

Ln3+-clusters

with

OH-H2Salen

or

OH-MeO-H2Salen ligands. Meanwhile, the sensitization for their Ln3+-centered visible or NIR emissions is also discussed.

5



Scheme 1. Molecular Structure and Bonding Modes of the OH-H2Salen Ligand H3L1 for Nonanuclear Ln3+-Complexes 1-7

Scheme 2. Molecular Structure and Bonding Modes of the OH-MeO-H2Salen Ligand H3L2 for Hexanuclear Ln3+-Complexes 8-14

Scheme 3. Versatile Bonding Modes of the OAc- Anion in Complexes 1-14

6


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EXPERIMENTAL SECTION Synthesis of [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; Ln = Gd, 4; Ln = Nd, 5; Ln = Yb, 6 or Ln = Er, 7). To a stirred solution of the OH-H2Salen ligand H3L1 (0.149 g, 0.5 mmol) in absolute MeCN (6 mL), Et3N (210 μL) was added, and the resultant mixture was continuously stirred at RT for 3 h. Then another solution of Ln(OAc)3·6H2O (0.5 mmol; Ln = La, 0.212 g; Ln = Eu, 0.219 g; Ln = Tb, 0.222 g; Ln = Gd, 0.221 g; Ln = Nd, 0.215 g; Ln = Yb, 0.229 g or Ln = Er, 0.226 g) in absolute MeOH (6 mL) was added, and the resulting mixture was refluxed for another 3 h. After cooling to RT, each of the clear pale yellow solution was filtered. Diethyl ether was allowed to diffuse slowly into the respective filtrate at RT, and pale yellow microcrystal products of 1-7 were obtained in a few weeks, respectively. For [La9(L1)3(HL1)2(μ3-OH)4(OAc)10] (1): Yield: 0.728 g, 43%. Anal. Found: C, 37.35; H, 3.25; N, 4.26. Calcd for C105H111N10O39La9: C, 37.23; H, 3.30; N, 4.14. FT-IR (KBr, cm−1): 3307 (b), 3042 (w), 3025 (w), 2986 (w), 2938 (w), 2470 (w), 2451 (w), 2397 (w), 2349 (w), 2325 (w), 2231 (w), 2245 (w), 1686 (m), 1605 (s), 1541 (vs), 1448 (s), 1415 (s), 1352 (m), 1053 (w), 1028 (w), 1011 (w), 959 (w), 945 (w), 762 (w), 679 (m), 646 (m), 613 (w), 570 (w), 511 (w), 489 (w), 471 (w). 1H NMR (400 MHz, DMSO-d6): δ (ppm) 8.32 (s, 10H, -C=N), 8.06 (s, 6H, -Ph), 7.95 (s, 4H, -Ph), 7.09 (m, 16H, -Ph), 6.37 (m, 14H, -Ph), 3.17 (s, 2H, -OH), 2.89 (s, 20H, -CH2), 2.33 (m, 5H, -CH), 2.09 (s, 30H, -OAc), 1.23 (s, 4H, -OH-). ESI-MS (in MeCN) m/z: 3388.21 (100%), [M-H]+. The characterization of other complexes 2-7 was shown in Supporting information.

Synthesis of {[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (Ln = La, 8; Ln = Eu, 9; Ln = Tb, 10; Ln = Gd, 11; Ln = Nd, 12; Ln = Yb, 13 or Ln = Er, 14). To a stirred solution of the 7



OH-MeO-H2Salen ligand H3L2 (0.179 g, 0.5 mmol) in absolute MeCN (6 mL), Et3N (210 μL) was added, and the resultant mixture was continuously stirred at RT for 3 h. Then another solution of Ln(OAc)3·6H2O (0.5 mmol; Ln = La, 0.212 g; Ln = Eu, 0.219 g; Ln = Tb, 0.222 g; Ln = Gd, 0.221 g; Ln = Nd, 0.215 g; Ln = Yb, 0.229 g or Ln = Er, 0.226 g) in absolute EtOH (6 mL) was added, and the resulting mixture was refluxed for another 3 h. After cooling to RT, each of the clear pale yellow solution was filtered. Diethyl ether was allowed to diffuse slowly into the respective filtrate at RT, and pale yellow microcrystal products of 8-14 were obtained in a few weeks, respectively. For {[La6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (8): Yield: 0.696 g, 49%. Anal. Found: C, 42.75; H, 4.02; N, 4.86. Calcd for C101H110N10O34 La6: C, 42.69; H, 3.90; N, 4.93. FT-IR (KBr, cm−1): 3412 (b), 3064 (w), 2939 (w), 2843 (w), 1639 (s), 1551 (vs), 1454 (s), 1415 (s), 1342 (w), 1292 (w), 1217 (m), 1170 (w), 1078 (w), 1049 (w), 1020 (w), 964 (w), 943 (w), 852 (w), 785 (w), 741 (m), 667 (m), 644 (w), 615 (w), 545 (w), 471 (w). 1H NMR (400 MHz, DMSO-d6): δ(ppm) 8.04 (m, 10H, -C=N), 7.03 (d, 6H, -Ph), 6.90 (q, 6H, -Ph), 6.76 (d, 6H, -Ph), 6.41 (m, 6H, -Ph), 6.27 (m, 6H, -Ph), 4.37 (s, 1H, -OH), 3.91 (s, 5H, -CH), 3.78 (m, 30H, -OMe), 2.89 (s, 3H, -OAc), 2.67 (s, 3H, -OAc), 2.33 (s, 3H, -OAc), 1.76 (m, 20H, -CH2), 1.23 (s, 1H, -OH-). ESI-MS (in MeCN) m/z: 2782.39 (100%), [M-(OAc)]+. The characterization of other complexes 9-14 was shown in Supporting information.

RESULTS AND DISCUSSION Synthesis and Characterization of Complexes 1-7 from OH-H2Salen Ligand H3L1 and Complexes 8-14 from OH-MeO-H2Salen Ligand H3L2. From reaction of equimolar amounts of Ln(OAc)3⋅6H2O (Ln = La, Eu, Tb, Nd, Yb, Er or Gd) and the OH-H2Salen Schiff-base ligand H3L1 8


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with an inner cis-N2O2 core in the presence of access Et3N, a series of homoleptic [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] complexes 1-7 are obtained, respectively. However, the use of the OH-MeO-H2Salen Schiff-base ligand H3L2 with both the inner cis-N2O2 core and the outer O2O2

moiety

in

replacement,

gives

another

series

of

homoleptic

{[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} complexes 8-14. In contrast to the good solubility of complexes 1-7 based on the OH-H2Salen Schiff-base ligand H3L1 with a flexible OH-propylene linkage in common solvents except H2O, complexes 8-14 are more soluble in absolute MeCN, which should further be attributed to the charge of the two components ([Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]+ and OAc-) in each of the seven complexes. The two series of complexes 1-7 and 8-14 were well-characterized by EA, FT-IR (Figure S1), 1H NMR (Figure S2) and ESI-MS (Figure S3). In the FT-IR spectra (Figure S1), besides the broad band absorptions at 3707-3812 cm-1 for complexes 1-7 or 3712-3819 cm-1 for complexes 8-14 assigned to the OH-vibration of the partial deprotonated ligand ((HL1)2- or (HL2)2-), the coordinated µ3-OH- anion and/or the coordinated H2O, respectively, their characteristic strong absorptions of the ν(C=N) vibration at 1632-1638 cm-1 for complexes 1-7 or 1631-1638 cm-1 for complexes 8-14 are also observed. Meanwhile, for the two series of complexes, two additional strong absorptions at 1600-1611 and 1412-1422 cm-1 for complexes 1-7 or 1600-1611 and 1412-1422 cm-1 for complexes 8-14, should be tentatively attributed to the respective νas vibration and νs vibration of OAc- anions with different linking modes (also shown in Scheme 3). As to the 1H NMR spectra (Figure S2) for both the anti-ferromagnetic La9-arrayed complex 1 and La6-arrayed complex 8, a similar slightly-spread shift (δ from 8.32 to 1.23 ppm for complex 1 and δ from 8.04 to 1.23 ppm for 9



Page 10 of 34

complex 8) of the proton resonances of the ligands relative to that the free ligand H3L1 or H3L2 was exhibited due to the coordination of La3+ ions. Moreover, the proton resonances of the -OH group (δ = 3.17 ppm) from the (HL1)- ligands, the coordinated OAc- anions (δ = 2.09 ppm) and the coordinated µ3-OH- anions (δ = 1.23 ppm) appear for complex 1, while the proton resonances of the -OH group (δ = 4.37 ppm) from the (HL1)- ligands, the free (δ = 2.89 ppm) and the coordinated OAc- anions (δ = 2.67 and 2.33 ppm) and the coordinated µ3-OHanions (δ = 1.23 ppm) for complex 8 are observed, respectively. Furthermore, ESI-MS spectra (Figure S3) of the two series of complexes display the respective similar patterns, where the strong mass peak at m/z 3388.21 (1), 3505.73 (2), 3568.38 (3), 3553.31 (4), 3436.22 (5), 3695.42 (6) or 3643.39 (7) assigned to the major species {[Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10]-H}+ of complexes 1-7, while 2782.39 (8), 2860.74 (9), 2902.51 (10), 2892.46 (11), 2814.40 (12), 2797.20

(13)

or

2952.51

(14)

attributed

to

the

major

species

[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]+ of complexes 8-14 was shown, respectively. These observations indicate that the respective discrete homoleptic [Ln9(OH-Salen)5(OH)4(OAc)10] or [Ln6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]+ unit can be retained in the corresponding dilute solution.

X-ray Single-Crystal Structural Analysis and Self-Assembly. The molecular structure of complex 3 as the representative of complexes 1-7 or complex 14⋅H2O as the representative of complexes 8-14 was determined by X-ray single-crystal diffraction analysis. Crystallographic data for the two complexes are presented in Table 1, and selected bond parameters are given in Tables S1-2. Complex 3 crystallizes in the monoclinic space group of P21/c, and the 10


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asymmetrical unit is composed of nine Tb3+ ions, two (HL1)2-- ((HLA1)2- and (HLB1)2-) and three (L1)3--mode ((LC1)2- and (LD1)2- with Mode-II while (LE1)2- with Mode I) (also in Scheme 1) ligands, four µ3-OH- and ten OAc- anions. As shown in Figure 1a, each of the terminal two eight-coordinate Tb3+ ions (Tb6 and Tb8) located into the corresponding cis-N2O2 core of one (HL1)2--mode ligand ((HLA1)2- for Tb6 or (HLB1)2- for Tb8), is bridged through two µ-O-phenoxide atoms (O11 or O30 from one (HL1)2--mode ligand ((HLA1)2- or (HLB1)2-) and O7 or O26 from the other (L1)2--mode ligand ((LC1)2- or (LD1)2-), one O atom (O9 or O36) from one µ3-OAc- anion and one O atom (O8 or O27) from one µ3-OH- anion, to the central other seven Tb3+ ions surrounded by three (L1)3--mode ligands ((LC1)2-, (LD1)2- and (LE1)2-), resulting in the formation of a homoleptic nonanuclear [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] host structure shown in Figure 1b. According to the coordination differences of the central seven Tb3+ ions, they can be divided into four types: Tb1 or Tb3 ion has the similar nine-coordinate coordination environment, which is composed of one imine-N atom (N5 or N6), one OH-O atom (O19) and one µ-phenoxide-O atom (O20 or O21) from the same (L1)2--mode ligand ((LE1)2-), one µ3-OH--O atom (O24 or O3), and five O atoms (O1, O2, O23, O38 and O39 for Tb1; O1, O2, O4, O5 and O22 for Tb3) from three OAc- anions. For Tb4 and Tb7 ions, their similar nine-coordinate environments consist of one imine-N atom (N1 or N7), one OH-O atom (O7 or O26) and one µ-phenoxide-O atom (O6 or O25) from the corresponding (L1)2--mode ligand ((LC1)2- or (LD1)2-), two µ3-OH--O atoms (O3 and O8 or O24 and O27) from two µ3-OH- anions, and four OAc--O atoms (O4, O9, O10 and O14 or O28, O36, O37 and O38) from three OAcanions, respectively. Tb5 or Tb9 is eight-coordinate, and their similar coordination sphere is saturated by one imine-N atom (N4 or N10), one OH-O atom (O7 or O26) and two 11



Page 12 of 34

µ-phenoxide-O atom (O11 and O18 or O26 and O30) from two different (HL1)2- and (L1)2--mode ligands ((HLA1)2- and (LC1)2- for Tb5; (HLB1)2- and (LD1)2- for Tb9), one µ3-OH--O atom (O8 or O27), and three O atoms (O14, O16 and O17 for Tb5; O28, O33 and O34 for Tb9) from three OAc- anions. The central Tb2 is unique, and its eight-coordinate sphere is saturated by two µ-phenoxide-O atoms (O6 and O25) from two different (L1)2--mode ligands ((LC1)2- and (LD1)2-), two O atoms (O3 and O24) from two µ3-OH- anions, and four O atoms (O1, O2, O15 and O29) from four OAc- anions. Interestingly enough, the ten coordinated OAc- anions bridged to nine Tb3+ ions also have multiple bonding modes (also in Scheme 3): two with the µ2-OAc--mode bridging to one Tb3+ ion (Tb5 or Tb9), four with the µ3-OAc--mode bridging to two Tb3+ ions (Tb1 and Tb7; Tb3 and Tb4, Tb4 and Tb6 or Tb7 and Tb8); two with the µ4-OAc--mode bridging to three Tb3+ ions (Tb2, Tb4 and Tb5 or Tb2, Tb7 or Tb9) and two with the µ5-OAc--mode bridging to three Tb3+ ions (Tb1, Tb2 and Tb3). It is worth noting that within the Ln9(OH-Salen)5 cluster of complex 3, the nine Tb3+ ions are linked in a macro-cyclic arrangement,

where

the

terminal

Tb⋅⋅⋅Tb

separations

(3.5483(5)-3.6225(5)

or

3.5421(5)-3.6180(5) Å) among Tb4-Tb5-Tb6 or Tb7-Tb8-Tb9 ions are slightly shorter than those (3.7892(5)-3.8458(4) Å) between the central three Tb3+ ions (Tb1-Tb2-Tb3).

12


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Figure 1. Perspective drawing of complex 3. (a) View of the [Tb9(L1)3(HL1)2(μ3-OH)4(OAc)10]; H atoms are omitted for clarity. (b) View of the central Tb9-core with protons of two -OH groups from two (HL1)2- ligands and four μ3-OH- anions.

13



Page 14 of 34

Complex 14⋅H2O crystallizes in the triclinic space group P-1, while its asymmetrical unit is composed of one cation [Er6(L2)4(HL2)(µ3-OH)(µ-OAc)2(H2O)2], one free OAc- anion and one solvate H2O. As shown in Figure 2a, four (L2)3--mode ((LA2)3- and (LE2)3- with Mode-I; (LB2)3with Mode-II while (LC2)3- with Mode-III; also in Scheme 2) ligands and one (HL2)2--mode ((HLD2)2- also in Scheme 2) ligand at the apical position link with six Er3+ ions in an angular arrangement,

affording

to

the

formation

of

a

homoleptic

hexanuclear

[Er6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]+ cationic host. Base on the coordination environment specificity of the six Er3+ ions within, five types of unique Er3+ ions are observed and shown in Figure 2b. Each of the two terminal Er3+ ions (Er1 and Er6) occupies at the cis-N2O2 core of the respective (L2)3--mode ligand (LA2)3- or (LE2)3-), and its eight-coordinate sphere is similarly saturated by one µ-phenoxide-O atom (O7 for Er1 or O13 for Er6) and one MeO-O atom (O6 for Er1 or O14 for Er6) from one (L2)3--mode ligand ((LB2)3- or (LC2)3-), one N2O3 portion (two imine-N atoms (N1 and N2 for Er1 or N9 and N10 for Er6), one OH-O atom (O5 for Er1 or O25 for Er6) and two µ-phenoxide-O atom (O2 and O3 for Er1 or O22 and O23 for Er6) from another (L2)3--mode ligand ((LA2)3- or (LE2)3-), and one O atom (O26 for Er1 or O32 for Er6) from the coordinated H2O. As to eight-coordinate Er2 or Er5 ion, in addition to the similar coordination of one OH-O atom (O5 for Er2 or O25 for Er5) from one (L2)3--mode ligand ((LA2)3- or (LE2)3-), one µ-phenoxide-O atom (O12 for Er2 or O17 for Er5) and one MeO-O atom (O11 for Er2 or O16 for Er5) from the second (L2)3-- ((LC2)3-) or (HL2)2--mode ((HLD2)2-) ligand, one imine-N (N3 for Er2 or N6 for Er5), one OH-O (O10 for Er2 or O31 for Er5) and one µ-phenoxide-O atom (O7 for Er2 or O13 for Er5) from the third (L2)3--mode ligand ((LB2)3- or (LC2)3-), and one OAc--O atom (O29 for Er2 or O30 for Er5; µ6-OAc--mode also shown in 14


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Scheme 3), their difference lies in the remainder of the OAc--O atom (O27; µ1-OAc--mode also shown in Scheme 3) for Er2 while the µ3-OH--O atom (O15) for Er5 ion, respectively. The uniqueness of Er3 ion is arisen from its nine-coordinate, and the coordination environment is composed of two sets of NO2 portions (one imine-N atom (N4 or N5), one µ-phenoxide-O atom (O8 or O15) and one OH-O atom (O10 or O31) from two (L2)3--mode ligands (,(LB2)3- and (LC2)3-), one µ3-OH--O atom (O15) and two OAc--O atoms (O29 and O30; µ6-OAc--mode also shown in Scheme 3) from the same OAc- anion. As to eight-coordinate Er4 ion, its special occupation into the cis-N2O2 core of the (HL2)2--mode ligand ((HLD2)3-), one µ-phenoxide-O atom (O8) and one OH-O atom (31) from two different (L2)3--mode ligands ((LB2)3- and (LC2)3-), together with one µ3-OH--O atom (O15) are exhibited. Noticeably, the two terminal Er1⋅⋅⋅Er2 and Er5⋅⋅⋅Er6 separations (3.7545(10) and 3.7705(10) Å) are slightly larger than those (3.4771(10)-3.6703(9) Å) between the central four Er3+ ions (Er2-Er3-Er4-Er5), which should attribute to the angular while not cyclic array of the six Er3+ ions in complex 14⋅H2O. Moreover, the charge of the cationic [Er6(L2)4(HL2)(µ3-OH)(µ-OAc)2(H2O)2] host is balanced by one free OAc- anion (µ0-OAc--mode also shown in Scheme 3). As to the bulk phase purity of complexes 1-7 or complexes 8-14, it was convincingly established by X-ray powder diffraction (PXRD) measurements. The PXRD results (Figure S4) show that despite the slightly different intensities probably due to preferred orientation, the peak positions of the measured patterns for samples 1-7 or samples 8-14 closely match those of the simulated one of complex 3 or complex 14⋅H2O, respectively, demonstrating that a single phase is correspondingly formed for each sample of complexes 1-7 or complexes 8-14.

15



Figure 2. Perspective drawing of the cationic host of complex 14⋅H2O. (a) View of the [Er6(L2)4(HL2)(µ3-OH)(OAc)2(H2O)2]; H atoms are omitted for clarity. (b) View of the central Er6-core with protons of one -OH group from one (HL2)2- ligand, one μ3-OH- anion and two coordinated H2O molecules.

In a comparison of complex 3 with complex 14⋅H2O, the formation of their nonanuclear 16


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or hexanuclear host should be strictly arisen from the usage of ligand OH-H2Salen (H3L1) with one inner cis-N2O2 core or OH-MeO-H2Salen (H3L2) with both one inner cis-N2O2 core and one outer O2O2 moiety with Ln(OAc)3, respectively. On one hand, the introduction of the outer O2O2 moiety renders the OH-MeO-H2Salen (H3L2) ligand up to hepta-dentate bonding for its hexanuclear while not nonanuclear Ln3+-cluster. Moreover, through the partial deprotonation of the ligands, although both of complexes 3 and 14⋅H2O are five-ligands-adoptive, more negative charge of the four-fifths deprotonated, also contributes to the formation of lower hexanuclear complex 14⋅H2O relative to nonanuclear complex 3 with the three in five ligands. Furthermore, the structural difference of the two complexes is embodied from more OH--co-OAc- portions, especially with µ2-5-OAc--modes (also in Scheme 3) of the ten OAcanions in complex 3 than those with µ0-, µ1- and µ6-OAc--modes (also in Scheme 3) of the three OAc- anions in complex 14⋅H2O for their stability. Evidently, the two complexes with (Ln)3--co-(HLn)2--mode ligands appear to be OAc--dependent, while are incomparable to NO3-or Cl--dependent hexanuclear [Ln6(Ln)4(OH)4X2]46-47 (H3L1 and X- = NO3- or Cl-; H3L2 and X- = Cl-) complexes with the only (Ln)3--mode ligands. It is of special interest to compare the self-assembly of the two OAc--induced complexes with that of OAc--independent dinuclear ([Ln2(Salen)3]27-28) or tetranuclear ([Ln4(Salen)6]29-30) complex from the typical H2Salen ligand or that of OAc--dependent tetranuclear ({[Ln4(MeO-Salen)2](OH)2(OAc)6}39) complexes from the MeO-H2Salen ligand. The higher-nuclearity formation of nonanuclear complex 3 or hexanuclear complex 14⋅H2O should be undoubtedly assigned to the introduction of a backbone OH-goup of the H3Ln ligand, endowing the multidentate ability and the multiple-charging effect for more Ln3+-species. Thermogravimetric (TG) analyses (Figure S5) 17



of the two representative complexes 3 and 14⋅H2O show that their structure decomposition temperatures (416 °C for complex 3 and 473 °C for complex 14⋅H2O) can be up to 400 °C, despite a slight weight loss (< 1%) indicative of the loss of solvated H2O in the 25-120 °C range for complex 14⋅H2O.

Photophysical Properties and Energy Transfer of Two Series of Complexes 2-7 and 9-14. The photophysical properties of the two series of complexes 2-7 and 9-14 have been examined in dilute MeCN solution at RT or 77 K, and summarized in Table 2 and Figures 3-4 and S6-11. As shown in Figures S6-7, similar respective ligand-centered solution absorption spectra (225-227, 257-260 and 331-334 nm for complexes 2-7 or 228-230, 267-270 and 343-346 nm for complexes 9-14) for the two series of complexes in the UV-visible region are observed, in which all including the intra-ligand π-π*-transitted lowest energy absorptions are red-shifted upon coordination of Ln3+ ions as compared to that (216, 256 and 314 nm for H3L1 or 222, 262 and 328 nm for H3L2) of the free ligand H3L1 or H3L2, respectively. For complex 2, it is typical of dual-emitting, as shown in Figure 3a, where the combination of the dominated ligand-based emission (λem = 470 nm and τ = 3.6 ns) with the weak Eu3+-centered (5D0 → 7FJ, J = 1, 2, 3 and 4) characteristic emission endows an almost white-light (Figure 3b;

Φem = 7.2%) with a CIE (Common International de I'Eclairage) chromatic coordinate of x = 0.274 and y = 0.345. As to complex 3, only Tb3+-centered (5D4 → 7FJ, J = 6, 5, 4 and 3) yellowish-green-light (CIE chromatic coordinate of x = 0.288 and y = 0.511; τobs = 108.21 µs at 546 nm of 5D4 → 7F5 transition and ΦTbL = 21.3%) is exhibited. By contrast, the [Gd9(OH-Salen)5(OH)4(OAc)10]-based complex 4 displays the ligands-based band-like 18


Page 18 of 34

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fluorescent emission (λem = 470 nm, τ = 3.4 ns and Φem = 0.07% in Figure S8) at RT and the broader band with a maximum at 496 nm (0-phonon component at 443 nm with τobs = 1.62 µs) under 77 K, respectively. However, for the two complexes 5-6, besides the similar weak ligands-based visible emission (λem = 470 nm and τ < 1 ns also in Figure S8) with a low quantum yield (Φem < 10-5), as shown in Figure 4, photo-excitation (λex = 360 nm) renders the ligand-field splitting characteristic emissions of Nd3+ ion (896, 1064 and 1338 nm; 4F3/2 → 4IJ/2, J = 9, 11 and 13; τobs = 1.14 µs, ΦNdNd = τobs/τ0 = 0.46% based on τ0 = 0.25 ms48 and ΦLNd = 0.31%) for complex 5 or Yb3+ ion (978 nm; 2F5/2 → 2F7/2; τobs = 11.34 µs, ΦYbYb = τobs/τ0 = 0.57% based on τ0 = 2.0 ms48 and ΦLYb = 0.43%) for complex 6, respectively. Moreover, unlike that for complex 5 or 6, the Er3+-centered NIR emission of complex 7 is too weak to be detected despite a similar weak ligand-centered residual visible emission (470 nm, τ < 1 ns and Φem < 10-5 also in Figure S8). These observations suggest that efficient ligand-to-metal energy transfer (LMET)43-44 occurs in both complexes 2-3 in the visible region and complexes 5-6 in the NIR one.

19



Figure 3. Photophysical property of complexes 2-3 and 9-10 in dilute MeCN solution (5×10-6 M) at RT. (a) Visible emission and excitation spectra. (b) CIE chromatic coordinates.

20


Page 20 of 34

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Figure 4. NIR emission and excitation spectra of complexes 5-6 and 12-13 in dilute MeCN solution (5×10-6 M) at RT.

The change of use of the OH-MeO-H2Salen ligand H3L2 instead of the OH-H2Salen ligand H3L1

results

in

structural

changes

from

[Ln9(OH-Salen)5(OH)4(OAc)10]

to

{[Ln6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]⋅(OAc)}, and the different photophysical properties of complexes 9-14 also shown in Table 2 and Figures 3-4, S9-11. As shown in Figure 3, although the similar dual-emitting character of complex 9 to that of complex 2, the Eu3+-centered (5D0 → 7FJ, J = 1, 2, 3 and 4; τ = 35.76 µs) characteristic emissions dominate in complex 9, affording an almost red-light (CIE chromatic coordinate of x = 0.543 and y = 0.337 shown in Figure 3b; ΦLEu = 13.4%). Meanwhile, despite the only Tb3+-centered (τ = 18.63 µs) characteristic luminescence comparable to that of complex 3, the relatively weaker yellowish-green-light (CIE chromatic coordinate of x = 0.349 and y = 0.548 shown in Figure 3b;

ΦLTb = 8.1%) for complex 10 is exhibited even in a naked-eye sight. Interesting enough, upon photo-excitation (λex = 345 nm) of the H3L2-induced chromophores, the H3L2-based residual 21



visible emission (Figure S9) for each of complexes 12-14 is almost quenched, while the stronger Nd3+- or Yb3+-centered characteristic NIR luminescence (Figure 4) of complex 12 or 13 with the longer lifetime (τobs = 1.32 µs for complex 12; τobs = 13.28 µs for complex 13) and the larger quantum yield (ΦNdNd = 0.53% and ΦLNd = 0.40% for complex 12; ΦYbYb = 0.68% and

ΦLYb = 0.58%) than that of the respective complex 5 or 6 is exhibited, despite also no Er3+-centered characteristic NIR emission detected for complex 14 similar to that of complex 7. It is of a particular interest to explore the possible energy transfer mechanism for the sensitization of Eu3+- or Tb3+ ion in complexes 2-3 and 9-10 or Nd3+- or Yb3+ ion in complexes 5-6 and 12-13. Based on the 0-phonon phosphorescence (443 nm and τ = 1.62 µs; Figure S8) of the [Gd9(OH-Salen)5(OH)4(OAc)10] complex 4 at 77 K, the triplet (3π-π*) energy level at 22573 cm-1 is obtained. With regard to the singlet (1π-π*; 27624 cm-1) energy level reasonably estimated by the lower wavelength of its UV-visible absorbance edge, the slightly larger energy gap ∆E1 (1π-π*-3π-π*, 5051 cm-1) than 5000 cm-1, as shown in Figure 5, endows an effective intersystem crossing process according to the Reinhoudt's empirical rule.49 Nonetheless, for complex 2, the energy gap ∆E2 (3π-π*-5D0, 5287 cm-1) between the ligands' triplet (3π-π*) energy level and the first excited state level (17286 cm-1) of 5D0 for Eu3+ ion is large enough to operate heavy non-radiative deactivation,43-44 from which, ineffective ligand-to-metal energy transfer43-44 should result in its dual-emitting (Figure 3a) with ligand-based emission dominated. Noticeably, the integration (Figure 3b) from the dual-emitting emissions renders complex 2 a rare single-component near-white-light example50-51 as far as we know. As to the Tb3+-centered yellowish-green-light of complex 3 22


Page 22 of 34

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with an attractive quantum yield of 21.3%, it should be arisen from the suitable energy gap

∆E2 (3π-π*-5D4, 2028 cm-1) well within the ideal 2000-4500 cm-1 range according to the Latva's empirical rule.52 On the same principle, regulated by the appropriate energy gap (∆E2' = 3

π-π*-5D0, 4406 cm-1) between the ligand H3L2's lower triplet (3π-π*; 21692 cm-1) energy level

and the first excited state level of 5D0 for Eu3+ ion and effective intersystem crossing process (∆E1' = 1π-π*-3π-π*, 5190 cm-1), efficient red-light (ΦLEu = 13.4%) of complex 9 incomparable to near-white-light of complex 2 is observed. Moreover, as for complex 10 in comparison to complex 3 with the similar Tb3+-centered yellowish-green-light, heavy back energy transfer23 from its too smaller energy gap (∆E2' = 3π-π*-5D4, 1147 cm-1) than 1500 cm-1 should be reason to the lower efficiency (ΦLTb = 8.1%) than that (ΦLTb = 21.3%) of complex 3. In consideration of similar six OH-oscillators (four µ3-OH- anions and two OH-groups from two (HL1)2--mode ligands) around nine Ln3+ ions for complexes 2 and 3 to those (one µ3-OH- anion, one OH-group from one (HL2)2--mode ligand and four OH-groups from two coordinated H2O molecules) around six Ln3+ ions for complexes 9-10, their direct oscillators-vibrated quenching effects45 are presumed to be equivalent, in a certain sense. Therefore, the relatively lower efficiency sensitization (ΦLEu = 13.4% for complex 9; ΦLTb = 8.1% for complex 10) from the same chromophores to both red-light complex 9 and yellowish-green-light complex

10,

should

be

further

resulted

from

the

fewer

hexanuclearity

of

{[Ln6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]⋅(OAc)}-complexes 9-10 relative to that (ΦLTb = 21.3%) of [Ln9(OH-Salen)5(OH)4(OAc)10]-complex 3 with the stronger Ln3+-to-Ln3+ electronic communication.41-42 In contrast, for the sensitization of Nd3+- or Yb3+ ion in complexes 5-6 and 12-13, the excitation spectra of the NIR-emitting complexes H3L1-based 5-6 or 23



Page 24 of 34

H3L2-based 12-13, monitored at the respective NIR hypersensitive-emission peak (1064 nm of Nd3+ ion for complex 5 or 12; 978 nm of Yb3+ ion for complex 6 or 13), are similar to those monitored at their respective weak residual ligands-based visible emission peak (Figure S9), respectively. This result clearly demonstrates that the NIR emission of complexes 5-6 or complexes 12-13 originates from their respective ligands' π-π* transitions, and energy transfer43-44 takes place also through the 1π-π*-to-3π-π* and subsequent 3π-π*-to-Ln3+*-to-Ln3+ processes. As the reason to relatively lower NIR sensitization efficiencies (η = ΦLNd/ΦNdNd = 67% for

complex

5;

η

=

ΦLYb/ΦYbYb

=

75%

for

complex

6)

of

the

[Ln9(OH-Salen)5(OH)4(OAc)10]-complexes 5-6 than those (η = 76% for complex 12; 85% for complex 13) of the corresponding {[Ln6(OH-MeO-Salen)5(OH)(OAc)2(H2O)2]⋅(OAc)}-complexes 12-13, it should also be due to the relatively larger energy gap (3π-π*-4F3/2 of 11316 cm-1 for complex 5 versus 10435 cm-1 for complex 12; 3π-π*-2F5/2 of 12358 cm-1 for complex 6 versus 11467 cm-1 for complex 13) between the energy-donating 3π-π* level and the emitting level (4F3/2 or 2F5/2) of Nd3+ or Yb3+ ion in complex 5 or 6 especially in that compromise quenching effect. Attributed the energy gap (3π-π*-4I13/2 of 15963 cm-1 for complex 7 versus 15082 cm-1 for complex 14) outreached, no Er3+-centered characteristic NIR emission for complex 7 or 14 is observed. In comparison, due to the oscillators-vibrated quenching effect, the NIR quantum yields of complexes 5-6 and 12-13 are intermediate to those of reported Nd- or Yb-Salen complexes,53 their higher nuclearity of hexanuclear Eu3+-complex 9 or nonanuclear Tb3+-complex 3 renders the red-light (ΦLEu = 13.4%) or yellowish-green-light (ΦLTb = 21.3%) highly efficient among all reported Eu- or Tb-Salen complexes,53 respectively.

24


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Figure 5. Schematic energy level diagram and possible energy transfer process for the sensitization of Eu3+ or Tb3+ ion in complexes 2-3 and 9-10 or Nd3+ or Yb3+ ion in complexes 5-6 and 12-13.

CONCLUSIONS Through the reaction of the partially deprotonated OH-H2Salen ligand H3L1 or the OH-MeO-H2Salen ligand H3L2 with Ln(OAc)3 (Ln = La, Eu, Tb, Gd, Nd, Yb or Er), the combination of (HLn)2--co-(HLn)3- and OH--co-OAc- induces the obtainment of two series of unique homoleptic nonanuclear complexes [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (1-7) and hexanuclear complexes {[Er6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (8-14), respectively. The OAc--dependent self-assembly through the partial deprotonation of the OH-modified ligands provides an opportunity to the formation of higher nuclearity Ln3+-complexes. Moreover, their photophysical properties show that more OH-Salen or OH-MeO-Salen ligands may work as the chromophores to sensitize single-component near-white-light of complex 2, efficient Eu3+- or Tb3+-centered red-light (ΦLEu = 13.4%) of complex 9 or yellowish-green-light (ΦLTb = 25



8.1% and 21.3%) of complexes 3 and 10, and Nd3+- or Yb3+-centered NIR luminescence (η =

ΦLLn/ΦLnLn = 67-75% and 76-85%) of complexes 5-6 and 12-13, respectively. The specific design of polynuclear Ln3+-complexes from the OH-H2Salen ligands in facilitating the Ln3+-centered luminescence through further suppression of oscillators-vibrated quenching is now under way.

ASSOCIATED CONTENT Supporting information The general information on the starting materials and the methods; the synthesis and characterization of the ligands H3L1 and H3L2, complexes 2-7 and 9-14; X-ray crystallography and crystallographic files of complexes 3 and 14⋅H2O in CIF format; selected bond lengths and angles for complexes 3 and 14⋅H2O in Tables S1-2; the FT-IR, 1H NMR, ESI-MS, PXRD and TG curves in Figures S1-5; UV-visible absorption spectra of the ligands H3L1 and H3L1 and their complexes 2-7 and 9-14 in Figures S6-7; the visible emission and excitation spectra of complexes 4-7 and 11-14 at RT or 77 K in Figures S8-9; the luminescent decay curves in Figures S10-11. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHER INFORMATION Corresponding Author *

E-mail: [email protected]; [email protected]. Phone: 86-29-88302312 (o).

ORCID 26


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Xingqiang Lü: 0000-0001-9704-1690 Author Contributions #

Guorui Fu and Baoning Li contributed equally to the study.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work is funded by the National Natural Science Foundation (21373160, 91222201, 21173165), the Program for New Century Excellent Talents in University from the Ministry of Education of China (NCET-10-0936), the Doctoral Program (20116101110003) of Higher Education, the Science, Technology and Innovation Project (2012KTCQ01-37) of Shaanxi Province in P. R. of China.

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Page 32 of 34

Table 1. Crystal Data and Refinement for Complexes 3 and 14·H2O Compound

3

14·H2O

Empirical formula

C105H111N10O39Tb9

C101H112N10O35Er6

Formula weight

3567.40

3029.56

Crystal system

Monoclinic

Triclinic

Space group

P21/c

P-1

a/Å

23.3144(7)

14.8532(18)

b/Å

21.0865(6)

15.0770(18)

c/Å

34.6005(11)

27.842(3)

α (°)

90

77.372(2)

β (°)

90.719(2)

75.703(2)

γ (°)

90

77.507(2)

17008.9(9)

5808.2(12)

4

2

ρ/g cm

1.393

1.732

Crystal size/mm

0.30 × 0.25 × 0.22

0.27 × 0.24 × 0.20

Temperature/K

100 K

296.15 K

6831

2952

3.747

4.365

θ range, deg

1.131-27.561

1.868-25.558

reflns measd

38783

21352

reflns used

198

2057

params

1540

1384

R (I > 2σ(I))

R1 = 0.0440

R1 = 0.0678

wR2 = 0.0963

wR2 = 0.1690

R1 = 0.0825

R1 = 0.1321

wR2 = 0.1160

wR2 = 0.2052

1.018

0.957

V/Å

3

Z -3

F(000) µ(Mo-Kα)/ mm

R (all data) S

-1

32


Page 33 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. Photophysical Properties of Complexes 2-7 and 9-14 in Dilute MeCN Solution (5× ×10-6 M) at RT or 77 K compd

excitation

emission

[log(ε/dm mol cm )]

λex/nm

λem/nm (τ, Φ )

2

227(1.20), 260(0.45), 332(0.23)

363

470(3.6 ns), 590, 616(5.6 µs), 652, 695

3

227(1.18), 260(0.44), 331(0.22)

364

490, 546(108.21 µs), 584, 622

4

226(1.23), 258(0.46), 334(0.26)

361

470(3.4 ns, 0.07%)

441

496 (443 nm of 0-phonon, 1.62 µs; 77 K)

absorption λab/nm 3

-1

-1

5

225(1.21), 257(0.43), 333(0.24)

364

470(w), 896, 1064(1.14 µs), 1338

6

225(1.23), 258(0.45), 334(0.26)

360

470(w), 978(11.34 µs)

7

226(1.22), 260(0.44), 334(0.25)

362

470(w)

9

228(0.75), 268(0.32), 344(0.11)

274, 341

492(w), 590, 616(35.76 µs), 652, 695

10

228(0.78), 270(0.33), 346(0.12)

272, 343

490, 546(18.63 µs), 584, 623

11

228(0.76), 268(0.33), 344(0.12)

272, 344

489(1.6 ns, 0.04%)

365

518 (461 nm of 0-phonon, 2.74 µs; 77 K)

12

230(0.79), 267(0.33), 343(0.13)

273, 346

492(w), 896, 1064(1.32 µs) , 1334

13

228(0.78), 270(0.34), 346(0.12)

271, 345

492(w), 978(13.28 µs)

14

228(0.79), 268(0.34), 346(0.12)

272, 344

492(w)

33



Page 34 of 34

Table of Content

Within the unique nonanuclear [Ln9(L1)3(HL1)2(μ3-OH)4(OAc)10] (Eu, 2; Tb; 3; Nd, 5 or Yb, 6) and hexanuclear {[Ln6(L2)4(HL2)(μ3-OH)(OAc)2(H2O)2]·(OAc)} (Eu, 9; Tb; 10; Nd, 12 or Yb, 13) complexes,

single-component

near-white-light

for

complex

2,

efficient

yellowish-green-light for complex 3 and red-light for complex 9, and Nd3+- or Yb3+-centered NIR luminescence for complexes 5-6 and 12-13 are exhibited, respectively.

34


Dependent Self-Assembly of Luminescent ... - ACS Publications

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