Pengfei Yan

Heilongjiang University, Charbin, Heilongjiang Sheng, China

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Publications (90)360.59 Total impact

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    ABSTRACT: A dinuclear dysprosium(III) complex, namely [Dy2(L)2(NO3)2(MeOH)4] (1) has been synthesized by Schiff base ligand salicylidene-o-aminophenol (H2L) with Dy(NO3)3·6H2O. Single crystal X-ray diffraction reveals that the dysprosium (III) centre in the dinuclear unit is 8-coordinated bridged by the phenoxo group of two Schiff base ligands, giving a dodecahedron geometry. Magnetic susceptibility studies reveal that complex 1 shows single molecule magnetic behavior with an energy barrier of 75.9 K.
    No preview · Article · Jan 2016 · Synthetic Metals
  • Hongfeng Li · Peng Chen · Wenbin Sun · Lei Zhang · Pengfei Yan
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    ABSTRACT: Multiple-stranded helicates are of interest in respect of their simplicity in geometry and significance in biology and materials. Bis-β-diketones have shown their advantage in terms of structure and geometry in the construction of multiple-stranded helicates, but further studies on their properties are limited due to their poor crystallization. In this study, solvents are found to play a decisive role in the crystallization of triple-stranded helicates. [Dy2(BTB)3(H2O)4] is used as a precursor to solvent-dependently crystallize three complexes [Dy2(BTB)3(CH3OH)4]·3CH3OH (), [Dy2(BTB)3(DME)2] () and [Dy2(BTB)3(DOA)(H2O)2]·4.5DOA () (BTB = 3,3'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl), where the key structural motif of the triple-stranded helicate, [Dy2(BTB)3], is retained. Four methanol molecules are found to ligate to Dy(3+) ions in , while each Dy(3+) ion is chelated by one DME molecule in . Interestingly, it is observed that 1,4-dioxane as a bridge ligates to two adjacent Dy(3+) ions, giving rise to the formation of a 1D chain structure. Magnetic measurement shows that and display slow magnetic relaxation under zero dc field, while single molecular magnet behavior is obtained for under an applied dc field of 2000 Oe.
    No preview · Article · Jan 2016 · Dalton Transactions
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    ABSTRACT: A series of HMq-bridged dinuclear dysprosium complexes, namely, [Dy(acac)2(CH3OH)]2(μ-HMq)2 (1), [Dy(DBM)2]2(μ-HMq)2(n-C6H14) (2), [Dy(hmac)2]2(μ-HMq)2 (3) and [Dy(hfac)3]2(μ-HMq)2 (4) (HMq = 2-methyl-8-hydroxyquinoline, acac = acetylacetone, DBM = dibenzoylmethane, hmac = hexamethylacetylacetonate and hfac = hexafluoroacetylacetonate), were structurally and magnetically characterized. X-ray crystallographic analysises of the structures reveal that HMq serves as the effective bridge to link two Dy(III) centers by means of the phenoxyl oxygen and nitrogen atoms and the periphery β-diketonate ligands complete the coordination sphere by bidentated oxygen atoms. The different substituents on the β-diketonate terminal lead to different coordination models mostly due to the steric hindrance of these substituents, and the electron-withdrawing or donating effects on which likely influenced the strength of ligand fields and the Dy(III) ion anisotropy. Measurements of alternating-current (ac) susceptibility on complexes 1-4 reveal that complexes 3 and 4 display significant zero-field single-molecule magnetic (SMM) behavior with barrier energy Ueff/kB = 14.8 K, τ0 = 1.8×10-5 s and Ueff/kB = 9.2 K, τ0 = 1.7×10-5 s, respectively, whereas 1 and 2 exhibit field-induced SMM behavior, and these differences are attributed to the alteration on the periphery β-diketonate ligands. Their distinct slow magnetic relaxation behaviors were related to their different individual Dy(III) ions magnetic anisotropy and intramolecular coupling, which were confirmed by ab initio calculation.
    No preview · Article · Jan 2016 · Dalton Transactions
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    ABSTRACT: Three complexes with formula {Dy(q)2(L)}2(μ3-OH)2{Dy(q)(L)}2(solvents) (where q = 8-quinolinolate; L = acetylacetone (acac) with (CH2Cl2)2 = solvent (), 1,3-diphenyl-1,3-propanedione (DBM) and (CH2Cl2)2 = solvent (), and hexafluoroacetylacetone (hfac) and CHCl3 = solvent ()) were structurally and magnetically characterized. They have similar Dy4 structural cores bridged by N and O atoms from 8-quinolinolate, and only differ in the peripheral β-diketonate ligands. The variable-frequency and temperature alternating-current (ac) magnetic susceptibility measurements reveal that complexes and display significant zero-field single-molecule-magnet (SMM) behavior, while complex exhibits the field-induced SMM behavior, albeit they possess the nearly same primary coordination sphere. The ac susceptibility measurement on the diluted samples verified that their relaxation was of purely molecular origin, and their distinct slow magnetic behaviors were related to the replacement of the peripheral β-diketonate ligand, which is responsible for their different individual Dy(iii) ions' magnetic anisotropy and intramolecular coupling, as confirmed by ab initio calculation.
    Full-text · Article · Jan 2016 · Dalton Transactions
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    ABSTRACT: New heteronuclear Zn2Ln2 clusters [Zn2L2Ln2(hfac)6)] (Ln = Eu (1), Tb (2) and Dy (3)) have been synthesized based on a flexible Schiff base (H2L = N,N'-bis(salicylidene)-3,6-dioxa-1,8-diaminooctane) and β-diketonate ligand (hfac = hexafluoroacetylacetonate). The structures of the isomorphous complexes 1–3 were determined by single-crystal X-ray crystallography. Photophysical studies indicate that the short intramolecular distance of Zn•••Ln allows energy transfer from Zn2Ln2-based sensitizers to the Eu(III) and Tb(III) centres, the lanthanide luminescence is indeed “lighted up” by excitation of the zinc complex. More interestingly, white-light emission was realized by codoping Eu(III) ion into the Dy(III) complex for the first time.
    No preview · Article · Dec 2015 · CrystEngComm
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    ABSTRACT: To investigate the influence of POM species, temperature and counterions on the structures of POM-MOFs containing Cu-tda second building units (SBUs), six new complexes with various dimensionalities, e.g. three dimensional (3D) [Cu(H2tda)(H2O)2]4[SiW12O40]·12H2O (), two dimensional (2D) [Cu2(H2tda)2(H2O)3]·[Cu(H2tda)(H2O)2]·[PMo12O40]·5H2O (), H-bond 2D [Cu(H2tda)(H2O)2]3·[PMo12O40]·[Cu(Htda)(H2O)3]·8H2O (), one dimensional (1D) [Cu2(H2tda)2(H2O)4]2·[Cu2(tda)2(H2O)4]·[HPW12O40]·5H2O (), 1D [Cu2(H2tda)2(H2O)4][SiW12O40]·(TMA)2·3H2O (), and zero dimensional (0D) [Cu(H2tda)(H2O)3][SiW12O40]·(TMA)3·H2O (), were isolated depending on the reaction conditions. It is observed that the POM species, temperature and counterions exhibit an essential effect on the structures, which results in the formation of various dimensional POM-MOF complexes . In addition, photocatalytic degradation of RhB by complexes , and under UV irradiation was also investigated.
    No preview · Article · Dec 2015 · Dalton Transactions
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    ABSTRACT: A series of mononuclear lanthanide Zn–Dy–Zn type single-molecule magnets (SMMs) were synthesized and magnetically characterized. The four molecules ([Zn2(L1)2DyCl3]·2H2O (1), [Zn2(L1)2Dy(MeOH)Br3]·3H2O (2), [Zn2(L1)2Dy(H2O)Br2]·[ZnBr4]0.5 (3) and [Zn2(L2)2DyCl3]·2H2O (4)) all display remarkable magnetic relaxation behavior with a relatively high energy barrier and hysteresis temperature, despite possessing a low local geometry symmetry of the center Dy(III) ions. Ab initio studies revealed that the symmetry of the charge distribution around the Dy(III) ion is the key factor to determine the relaxation of the SMMs. The four complexes orient their magnetic easy axes along the negative charge-dense direction of the first coordination sphere. The entire molecular magnetic anisotropy was therefore controlled by a single substituent atom in the hard plane which consists of five coordination atoms (perpendicular to the easy axis), and the lower charge distribution on this hard plane in combination with the nearly coplanarity of the five coordination atoms ultimately lead to the prominent magnetic slow relaxation. This offers an efficient and rational method to improve the dynamic magnetic relaxation of the mononuclear lanthanide SMMs that usually possess a low local geometry symmetry around the lanthanide(III) center.
    Full-text · Article · Dec 2015 · Chemical Science
  • wenyi chu · Qingyan Sun · Xu Yao · Pengfei Yan · Guanghui An · Guangming Li
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    ABSTRACT: A series of three luminescent single molecule magnets of β-diketone mononuclear dysprosium complexes, namely, Dy(tfa)3(H2O)2·Me2CO (1), Dy(tfa)3(bpy) (2) and Dy(tfa)3(phen) (3) (tfa = trifluoroacetylacetonate, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, C3H6O = Me2CO) have been isolated. Single-crystal X-ray analysis shows all the central Dy(iii) ions are eight-coordinated adopting the coordination geometries of the distorted dodecahedron, bicapped trigonal prism and square antiprism for complexes 1-3, respectively. Magnetic analyses exhibit slow magnetic relaxation with the barrier heights (Ueff/kB) of 41 K, 33 K and 55 K for complexes 1-3, respectively. Photo-luminescent analysis reveal that complexes 1-3 exhibit the typical yellow luminescence of Dy(iii) ions. The correlation between the structure and physical properties has been investigated.
    No preview · Article · Nov 2015 · RSC Advances
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    ABSTRACT: Two salen type dinuclear dysprosium complexes, namely [Dy(H2L) (NO3)3]2·CH2Cl2·CH3OH·H2O (1) and [Dy(H2L1)2(NO3)3]2·2CH2Cl2·2CH3OH (2) [H2L = N,N′-(1,3-propylene)bis(3-methoxysalicylideneimine) and H2L1 = N,N′-(1,3-propylene)bis(salicylideneimine)], were isolated from the reactions of Dy(NO3)3·6H2O with two different but similar salen type ligands (H2L and H2L1), respectively. X-ray crystallographic analyses revealed that two crystallographically equivalent Dy(iii) ions for 1 and two crystallographically non-equivalent Dy(iii) ions for 2 were both bridged by two ligands displaying broken hula hoop-like and hula hoop-like coordination geometries for complexes 1 and 2, respectively, which resulted in the distinct magnetic properties that complex 2 exhibited with relatively higher energy barriers under a 2 kOe dc field.
    No preview · Article · Nov 2015 · RSC Advances
  • Bing Li · Hongfeng Li · Peng Chen · Wenbin Sun · Cheng Wang · Ting Gao · Pengfei Yan
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    ABSTRACT: A bis-β-diketone, bis(4,4,4-trifluoro-1,3-dioxobutyl)(2,2'-bithienyl) (BTT), which can be looked upon as coupling of two mono-β-diketones (2-thenoyltrifluoroacetone, TTA) at the 5,5'-position of thiophene ring, has been designed for exploring the advantages of binuclear helical structure in sensitizing the lanthanide NIR luminescence. The Yb(iii) ion was selected as the luminescent center, and its corresponding mono-β-diketone complex Yb(TTA)3(DMSO) () and bis-β-diketone complex Yb2(BTT)3(DMSO)4 () were synthesized and isolated. X-ray crystallographical analysis reveals that the bis-β-diketone complex Yb2(BTT)3(DMSO)4 adopts a triple-stranded dinuclear structure, in which the two Yb(iii) ions are helically wrapped by three ligands, and each Yb(iii) ion is eight-coordinated by six oxygen atoms from three ligands and two oxygen atoms from the coordinated DMSO molecules. Whereas, the mono-β-diketone complex Yb(TTA)3(DMSO) is a mononuclear structure, the central Yb(iii) ion is coordinated by seven oxygen atoms from three ligands and a DMSO molecule. The photophysical properties related to the electronic transition are characterized by the absorbance spectra, the emission spectra, the emission quantum yields, the emission lifetimes, and the radiative (kr) and nonradiative rate constants (knr). The luminescence quantum yield experiment reveals that the dinuclear complex has about 10 times luminescence enhancement compared with the mononuclear complex. This enhancement mainly benefits from its helical structure, which effectively depresses the nonradiative transition caused by high-energy oscillators in ligands, and the part-encapsulated structure decreases the probability of solvents entering the metal centers.
    No preview · Article · Oct 2015 · Physical Chemistry Chemical Physics
  • Hui XU · Dongxue Ding · Zhen Zhang · Ying Wei · Pengfei Yan
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    ABSTRACT: Two quaternary ambipolar phosphine oxide host materials, 9-(4-(9-(4′-(2-(diphenylphosphoryl)phenoxy)biphenyl-4-yl)-9H-fluoren-9-yl)phenyl)-9H-carbazole (9CzFDPESPO) and 9-(4-(9-(3′-(diphenylphosphoryl)-4′-(2-(diphenylphosphoryl)phenoxy)biphenyl-4-yl)-9H-fluoren-9-yl)phenyl)-9H-carbazole (9CzFDPEPO), were designed and prepared with mixed indirect and multi-insulating linkages to investigate the spatial effect on the electroluminescence performance of high-energy-gap hosts in blue phosphorescence and thermally activated delayed fluorescence light-emitting diodes (PHOLEDs and TADF OLEDs), in comparison to a ternary analogue 9-(4-(9-(4-(diphenylphosphoryl)phenyl)-9H-fluoren-9-yl)phenyl)-9H-carbazole (9CzFSPO). The donor-acceptor (D-A) distance in 9CzFDPESPO is elongated through the involvement of diphenylene as a π-extender, while the second phosphine oxide acceptor on diphenylene of 9CzFDPEPO is utilized to make its D-A distance comparable to that of 9CzFSPO. The single-molecular optoelectronic properties of these three hosts were uniform, owing to the effectively suppressed intramolecular electronic coupling by indirect and multi-insulating linkages. Their similar high triplet energy of 3.0 eV and the suitable energy levels of the highest occupied and the lowest unoccupied molecular orbitals around -6.1 and -2.5 eV, respectively, provide effective energy transfer and carrier injection. In contrast, 9CzFDPESPO shows the highest hole mobility owing to its longest D-A distance, directly indicating the spatial effect. As expected, with the most effectively suppressed spatial effect, 9CzFDPESPO endowed its blue phosphorescence and TADF devices with a state-of-the-art performance, e.g. external quantum efficiencies of 22.5% and 16.7%, respectively, which were the best results for quaternary host materials reported so far. This journal is
    No preview · Article · Oct 2015 · Journal of Materials Chemistry C
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    ABSTRACT: Helical structures are vital in chemistry and biochemistry and their importance has been reconsidered since the structure of DNA was revealed. Over the past decades, the advantages of the helical structures of bis-β-diketonate-based multiple-stranded Ln3+ complexes have been speculated with respect to their unique structures. Based on our previous study, we have designed a V-shaped bis-β-diketone ligand, H2MBDA, which has been utilized to crystallographically synthesize triple-stranded and quadruple-stranded dinuclear Dy3+ complexes. In contrast to the absence of crystallographical results in previous studies, the successful crystallization in this study has contributed to the functionalization of the -CF3 groups into the ligand as the termini, which have played a key role in the crystallization through intermolecular weak interactions. Both complexes display slow magnetic relaxation. The auxiliary ligand, phenanthroline, contributes to both tuning the structure and strengthening the anisotropy barrier.
    No preview · Article · Aug 2015 · CrystEngComm
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    ABSTRACT: A series of five β-diketone erbium complexes with various azacyclo-auxiliary ligands, namely, Er(Hbta)3(H2O)2 (1), Er(Hbta)3(bpy) (2), Er(Hbta)3(phen) (3), Er(Hbta)3(dpq) (4) and Er(Hbta)3(dppz) (5) (Hbta = benzoyltrifluoroacetone, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, dpq = pyrazino[2,3-f][1,10]phenanthroline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine) have been isolated and characterized by X-ray crystallographic analysis. Near-infrared luminescence analysis reveals that all complexes 1-5 exhibit strong NIR luminescence of Er(iii) ions around 1535 nm with the highest lifetime of 4.532 μs, quantum yield of 3.24 × 10-4 and broadband emission around 1.5 μm for complex 5, in which the azacyclo-auxiliary ligand absorbs and transfers the energy leading to complete quenching of the ligand-associated visible emission. The energy transfer processes among benzoyltrifluoroacetone, the Er(iii) ion and the auxiliary ligands in complexes 1-5 have been investigated. This journal is
    No preview · Article · Jul 2015 · RSC Advances
  • Rui Jia · Ting Gao · Yu Yang · Wenbin Sun · Ruoxi Chen · Pengfei Yan · Guangfeng Hou
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    ABSTRACT: The luminescence properties of the tetranuclear bimetallic lanthanide complexes Sm2Eu2 (1) and Eu2Tb2 (2), were compared with those of the analogous homometallic complexes [Sm4(μ3-OH)2(salen)2(acac)6(CH3OH)2]·CH3OH (3) and [Eu4(μ3-OH)2(salen)2(acac)6(CH3OH)2] (4) [H2salen = N, N′-ethylenebis(salicylideneimine), Hacac = acetylacetonate]. X-ray crystallographic analysis reveals that complexes 3 and 4 have planar tetranuclear structures. For the Eu2Tb2 configurational isomer, the TbIII ion in complex 2 mainly serves as a sensitizer. The quantum yields and lifetime measurements for 2 support the premise that Ln/Ln energy transfer occurs in such lanthanide bimetallic complexes, along with the usual ligand-to-metal triplet energy pathways. Complexes 3 and 4 exhibit the characteristic metal-centered emission.
    No preview · Article · Jul 2015 · Zeitschrift für anorganische Chemie
  • Yanping Dong · Pengfei Yan · Xiaoyan Zou · Guangming Li
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    ABSTRACT: A series of four β-diketone mononuclear dysprosium complexes, namely, Dy(DBM)3(bpy) (1), Dy(DBM)3(phen)·Tol (2), Dy(DBM)3(dpq)·Tol (3), and Dy(DBM)3(dppz) (4) (bpy = 2, 2'-bipyridine, phen = 1, 10-phenanthroline, dpq = dipyrazine [2, 3-f: 2´, 3´-h] quinoxaline, dppz = dipyrido [3, 2-a:2´, 3´-c] phenazine, Tol = toluene) have been isolated by the reactions of Dibenzoylmethane (DBM), azacyclo-auxiliary ligands and DyCl3·6H2O. X-ray crystallographic analysis reveals that complexes 1−4 are all eight-coordinated mononuclear structures. The azacyclo-auxiliary ligands have a dramatic effect on the structure and magnetic characteristics of complexes 1−4, originated from different degrees deviation from ideal coordination symmetry. Complexes 1 and 2 display a single relaxation mode under 0 Oe and complexes 3 and 4 display two single relaxation modes under 2000 Oe.
    No preview · Article · Jun 2015
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    ABSTRACT: Self-assembly of 2-aldehyde-8-hydroxyquinoline, histamine dichloride and LnX3•6H2O (X− = OAc−, NO3− and ClO4−) affords a series of lanthanide complexes Nd3(nma)2(OAc)7∙3CH3OH∙0.5H2O (1a), Ln3(nma)2(OAc)7∙2CH3OH [Ln = Tb (1b) and Dy (1c)], [Ln(nma)(NO3)2(DMSO)]∙CH3OH [Ln = Nd (2a), Tb (2b), Dy (2c) and Er (2d)] and [Dy(nma)2]∙ClO4∙0.5CH3OH (3) (Hnma = N-(2-(8-hydroxylquinolinyl)methane(2-(4-imidazolyl)ethanamine)). It is noted that the formation and structures of 1–3 are anion-dependent, where diverse coordination modes are detected for acetates in trinuclear 1 as compared to single coordination mode for nitrates in mononuclear 2. In the case of 3, the Dy3+ ion is completely encapsulated by two ligands with uncoordinated perchlorate anion balancing the charge. Magnetic measurement shows that the Dy complexes of 1c, 2c and 3 exhibit slow relaxations under zero dc field. It is noted that single molecular magnet behavior is obtained for 2c and 3 under an applied dc field of 2000 Oe.
    No preview · Article · Jun 2015 · CrystEngComm
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    Hongfeng Li · Tianyu Zhu · Peng Chen · Wenbin Sun · Ting Gao · Pengfei Yan
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    ABSTRACT: Two chemical structure similar ligands, mono-β-diketone (p-methoxylbenzoyl)trifluoroacetone (MBTF) and bis-β-diketone 1,2-bis(4,4'-bis(4,4,4-trifluoro-1,3-dioxobutyl))phenoxyl ethane (BTPE) have been designed and prepared for the purpose of building the relationships between the structures and luminescence properties of Eu(III) complexes. Structures of their Eu(III) complexes [Eu(MBTF)3(DMSO)(H2O)] and [Eu2(BTPE)3(DMSO)4] have been defined by single crystal X-ray crystallography. The mono-β-diketone complex [Eu(MBTF)3(DMSO)(H2O)] is a mononuclear structure, the central Eu(III) ion is coordinated by eight oxygen atoms from three ligands and two solvents, in an distorted trigonal-dodecahedral (8-TDH) geometry. Whereas, the bis-β-diketone complex [Eu2(BTPE)3(DMSO)4] adopts triple-stranded dinuclear structure in which the two Eu(III) are helically wrapped by three bis-bidentate ligands, and each Eu(III) ion is eight-coordinated by six oxygen atoms from the ligands and two oxygen atoms from the coordinated DMSO molecules, in a distorted square-antiprismatic (8-SAP) geometry. The photophysical properties related to the electronic transition are characterized by the absorbance spectra, the emission spectra, the emission quantum yields, the emission lifetimes, and the radiative (kr) and nonradiative rate constants (knr). The mono-β-diketone complex [Eu(MBTF)3(DMSO)(H2O)] offers a relatively high emission quantum yield (38%, in solid) compared to that observed in the bis-β-diketone complex [Eu2(BTPE)3(DMSO)4] (25%, in solid). This enhancement of emission quantum yield in mono-β-diketone complex can be attributed to its lower site symmetry around the Eu(III) ion, lower non-radiative rate constant and higher energy transfer efficiency from ligand to metal ion.
    Full-text · Article · May 2015 · Physical Chemistry Chemical Physics
  • Guanghui An · Pengfei Yan · Jingwen Sun · Yuxin Li · Xu Yao · Guangming Li
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    ABSTRACT: The racemate-to-homochiral approach is a method to transform or separate a racemic mixture into homochiral compounds. This protocol, if without an external chiral source, is categorized into chiral symmetry breaking. The resolution processes without chiral induction are highly important for the investigation of the origin of homochirality in life, pharmaceutical synthesis, the chemical industry and materials science. Besides the studies on the models and mechanisms used to explain the racemate-to-homochiral approach which may give the probable origin of homochirality in life, recent developments in this field have been plotted towards the separation of enantiomers for the synthesis of pharmaceuticals and chiral chemicals. Direct synthesis of chiral metal–organic framework (MOF) coordination polymers has been achieved as well. In this highlight, we will disclose the comparison of spontaneous resolution and chiral symmetry breaking resolution, and describe the evolution of models and mechanisms for chiral symmetry breaking resolution and its applications in enantiomer resolution and materials science.
    No preview · Article · Apr 2015 · CrystEngComm
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    ABSTRACT: Three new Salen-type lanthanide coordination polymers, [Ln2(H2L)2(NO3)4(CH3O)2]n (Ln = Sm (1), Eu (2) and Lu (3); H2L = N,N’-bis(salicylidene)- 1,4-butanediamine), have been synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra and thermogravimetric analysis. Single-crystal X-ray diffraction studies reveal that complexes 1-3 are isostructural 2D coordination polymers based on dinuclear units, where the μ2-(methoxy-O)2-bridged Ln2O2 cores are linked by four Salen-type ligands in a bidentate mode. Each lanthanide ion is eight-coordinated by eight oxygen atoms, forming a distorted dodecahedral geometry. Luminescence analysis in the solid state at room temperature indicates that complex 1 exhibits the co-luminescence of the ligand and SmIII ions and complex 2 shows the characteristic red luminescence of EuIII ions. Furthermore, the energy transfer mechanisms are described and discussed.
    No preview · Article · Apr 2015 · Polyhedron
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    ABSTRACT: A series of three salen-type lanthanide complexes, e.g., [Dy4(L)2(HL)2Cl2(μ3-OH)2]2Cl2(OH)2·3CH3CH2OH·H2O (1) and [Ln4(L)2(HL)2Cl2(μ3-OH)2]Cl2·5CH3OH·4CH2Cl2 (Ln = Tb(III), 2; Ho(III), 3) have been isolated by the reactions of H2L (H2L = N,N'-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine) with LnCl3·6H2O. X-ray crystallographic analysis reveals that all complexes 1-3 are isostructural, in which four Ln ions and eight O atoms form the distorted defective dicubane {Dy4O8} cores. Magnetic studies indicate that complex 1 exhibits two slow magnetic relaxation processes with effective energy barrier Ueff = 55.71 K under a zero direct-current field, which is attributed to the two coordination geometries of the Dy(III) ions with a salen-type ligand and coordination of a chloride counterion. It represents the highest energy barrier among the salen-type tetranuclear lanthanide single-molecule magnets.
    No preview · Article · Mar 2015 · Inorganic Chemistry