Tianlu Sheng

Redox‐Responsive Photochromism and Fluorescence Modulation of Two 3D Metal–Organic Hybrids Derived from a Triamine‐Based Polycarboxylate Ligand

Photochromism is defined as the reversible transformation of a chemical species, induced by the absorption of electromagnetic radiation, to a form with a different vibronic absorption spectra. Photochromic materials have attracted considerable interest owing to prospective real or potential applications in many fields, including protection (in spectacles, photobarriers, anti-fake, and camouflage), decoration, information storage, displays, optical switches, photomechanics, and so forth. Although numerous photochromic families have been reported to date, those based on an electron-transfer (redox) chemical process, especially for metal–organic complexes (MOCs), are rare. One of the biggest challenges in photochromic MOCs without photochromic organic ligands is to design photoinduced bistable systems based on different electron-transfer mechanisms, such as metal-centered electron transition (MC), ligand-tometal charge transfer (LMCT), metal-to-metal charge transfer (MMCT), intra ACHTUNGTRENNUNGli ACHTUNGTRENNUNGgand charge transfer (ILCT), and ligand-to-ligand charge transfer (LLCT). Structurally well-defined hybrids will give us better insight into the structure–photochromism relationships; nevertheless, few hybrids based on transition metals have been explored with simultaneous characterization of their structure and photochromism. Chopoorian and Loeffler have discovered the electron-attractive ability of a porous glass matrix indicated by the blue radical-ion species after the irradiation with UV light, in which an aqueous solution of p-phenylenediaminetetraacetic acid (p-PTDA) is absorbed. Thus, in the presence of electron-accepting components, organic ligands containing N ACHTUNGTRENNUNG(CH2CO2H)2 groups in MOCs may undergo a similar electron-transfer process. However, no coordination polymer constructed from ligands containing N ACHTUNGTRENNUNG(CH2CO2H)2 groups shows photochromism so far. Guo and coworkers have reported the only metal-assisted LLCT photochromic MOC, [Cd2(ic)(mc)(4,4’-bipy)3]·4H2O (ic = itaconate, mc=mesaconate, bipy= bipyridine), which undergoes an interesting photochromic transformation from yellow to blue upon UV irradiation. Herein, we report two photochromic MOCs with adjustable fluorescent intensities, [Zn3ACHTUNGTRENNUNG(TTHA)(4,4’bipy)1.5 ACHTUNGTRENNUNG(H2O)2]·6H2O (1 a) and [Zn3ACHTUNGTRENNUNG(TTHA)(4,4’-bipy)1.5ACHTUNGTRENNUNG(H2O)2]·3H2O (2 a), derived from a novel triamine-based polycarboxylate ligand containing the N ACHTUNGTRENNUNG(CH2CO2H)2 group, 1,3,5-triazine-2,4,6-triamine hexaacetic acid (H6TTHA), as electron donor, although the ligand H6TTHA itself does not exhibit photochromism, and 4,4’-bipy as electron capturer. The photochromic mechanisms based on electron-transfer chemical processes have been verified with direct and powerful ESR and X-ray photoelectron spectroscopy (XPS) measurements. Yellow needlelike crystals of 1 a and prismatic crystals of 2 a were obtained by the hydrothermal reactions of ZnACHTUNGTRENNUNG(NO3)2, H6TTHA, and 4,4’-bipy in a molar ratio of 3:1:2 at 140 8C and 120 8C for 72 h, respectively. The single-crystal X-ray diffraction data reveal that complexes 1 a and 2 a are 3D networks. As shown in Figure 1 and S3 in the Supporting Information, the 3D frameworks can be described as 2D layers constructed of Zn ions and TTHA pillared by the coordinated 4,4’-bipy groups. The biggest difference between the structures of complexes 1 a and 2 a is the coordination modes of the ligands (Scheme 1). Due to the flexibility, six of the arms show sig[a] Q.-L. Zhu, Prof. T.-L. Sheng, Dr. R.-B. Fu, S.-M. Hu, Prof. L. Chen, C.-J. Shen, X. Ma, Prof. X.-T. Wu State Key Lab of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Science, Fuzhou Fujian 350002 (P.R. China) Fax: (+86) 591-8371-9238 E-mail : wxt@fjirsm.ac.cn [b] Q.-L. Zhu, C.-J. Shen, X. Ma Graduate School of the Chinese Academy of Sciences Beijing, 100049 (P.R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003274. Figure 1. 2D layer (left) and 3D framework along the c axis (right) in complex 1 a.

A novel 2D net-like supramolecular polymer constructed from Ln6Cu24 node and trans-Cu(Gly)2 bridge

A 2D net-like lanthanide-copper heterometallic supramolecular network {Ln6Cu27} 1 was synthesized with Ln6Cu24 octahedral cluster as the node and trans-Cu(glycinato)2 group as the linker. The compound represents the first example of 2D polymer with high-nuclear 3d–4f heterometallic cluster as the node.

Structural Diversity of Infinite 3d―4f Heterometallic Cluster Compounds Driven by Various Lanthanide Radii

The syntheses, structures, and characterization of six Ln(3+)-Cu(2+)-glycine (Hgly) coordination polymers are described in this paper. They represent three types of structures. Type I (Ln=La (1), Pr (2), and Sm (3)) is a 1D catenarian polymer comprising [Ln(2)] nodes bridged by four cis-Cu(gly)(2) linkers. Type II (Ln=Eu (4) and Dy (5)) is a 2D open framework with a 4(4)-net, composed of novel [Ln(6)Cu(22)] cluster nodes linked by trans-Cu(gly)(2) linkers. Furthermore, the inner structures of the [Ln(6)Cu(22)] nodes, and the connection mode between the nodes and linkers are slightly different for 4 and 5. Type III (Ln=Er (6)) is a 3D open framework with a novel 3(6)4(18)5(3)6 topology, made up of [Er(6)Cu(24)] cluster nodes and trans-Cu(gly)(2) linkers. The rich variety of the resulting structures owes itself mainly to the interselection between the dynamic control of metalloligands and cationic components. A transition from frequency dependence to frequency independence is observed in the field-induced magnetization lag for 1-3. The frequency dependence at low temperatures may come from the antiferromagnetic Cu--Cu interaction through the [Ln(2)] nodes, whereas the frequency independence may be due to the disappearance of the antiferromagnetic Cu--Cu interaction at high temperatures.

Two luminescent enantiomorphic 3D metal–organic frameworks with 3D homochiral double helices

Two enantiomorphic Cd(II) coordination polymers with three-dimensional homochiral double helices have been assembled respectively from two tripodal enantiopure amino acid derivatives, which exhibit (3,4)-connected (6(3))(6(3).10(3)) topology and strong purple fluorescence.

Effect of Functionalized Groups on Gas‐Adsorption Properties: Syntheses of Functionalized Microporous Metal–Organic Frameworks and Their High Gas‐Storage Capacity

The microporous metal-organic framework (MMOF) Zn4O(L1)2⋅9 DMF⋅9 H2O (1-H) and its functionalized derivatives Zn4O(L1-CH3)2⋅9 DMF⋅9 H2O (2-CH3) and Zn4O(L1-Cl)2⋅9 DMF⋅9 H2O (3-Cl) have been synthesized and characterized (H3L1=4-[N,N-bis(4-methylbenzoic acid)amino]benzoic acid, H3L1-CH3=4-[N,N-bis(4-methylbenzoic acid)amino]-2-methylbenzoic acid, H3L1-Cl=4-[N,N-bis(4-methylbenzoic acid)amino]-2-chlorobenzoic acid). Single-crystal X-ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three-dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm(2) g(-1). Their pore volumes and surface areas decrease in the order 1-H>2-CH3 >3-Cl. Gas-adsorption studies show that the H2 uptakes of these samples are among the highest of the MMOFs (2.37 wt% for 3-Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate-adsorbent interaction plays a more important role in the gas-adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas-adsorption properties at high pressure.

Three New Structural Types of Mo/Ag/S Polymeric Complexes

Wavelike, zigzag, and helical polymers are formed by the reaction of [MoS4 ]2- , Ag2 S, and a complementary cation. The framework of the polymeric anions depends on the valence state of the latter. For example, the butterfly-type anionic chain shown in the picture is formed upon use of a divalent cation. There is a general tendency that a higher valence state of the cation will induce a more compact chain structure.

Syntheses, structural aspects, luminescence and magnetism of four coordination polymers based on a new flexible polycarboxylate

Four novel coordination polymers, {Na2[Co3(H2TTHA)2(H2O)12](H2O)2}·4(H2O) (1), {Na[Cu4(H2TTHA)(HTTHA)(H2O)8](H2O)3}·5(H2O) (2), [Cd3(TTHA)(H2O)4] (3) and [Ca5(HTTHA)2(H2O)8] (4), (H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) have been synthesized by self-assembly of the flexible hexapodal acid H6TTHA and corresponding metal salts. The four complexes exhibit novel frameworks with different topologies due to diverse coordination modes and different conformations of the flexible H6TTHA. Complex 1 shows a 3D network with (4,4,6)-connected topology constructed from parallel one-dimensional hybrid ribbons with nearly planar 24-membered rings, in which all Co(II) atoms are located in one plane. Complex 2 features a 3D (3,4,4,4,7)-connected network bridged by sodium ions from 2D layer structures which are formed through the interconnection of the tetranucleate units and the flexible ligands. Complex 3 possesses hybrid layers constructed from zigzag Cd–O chains. These layers are further linked by the TTHA6− ligands with two configurations, leading to another 3D (3,3,8)-connected framework. The metal ions in complex 4 are connected into wall-like infinite metal chains which are bridged by the carboxylate groups of ligands into a 3D (3,3)-connected hybrid framework. The framework is further furnished with the ligands forming hydrophobic channels with approximate sizes 3.5 A × 9 A based on the distances of the opposite atoms. The enantiometric pairs of ligands are formed in spite of no asymmetric carbon atom in complexes 1–3. Variable temperature magnetic studies down to 2 K reveal antiferromagnetic interactions in complexes 1 and 2. Complexes 3 and 4 are both highly emissive at room temperature. And the luminescent intensities are largely enhanced once they are frozen to 10 K.

A Luminescent Metal–Organic Framework Thermometer with Intrinsic Dual Emission from Organic Lumophores

A new mixed-ligand metal-organic framework (MOF), ZnATZ-BTB, has been constructed as a luminescent ratiometric thermometer by making use of the intrinsic dual emission at cryogenic temperatures. Its twofold interpenetrated network promotes the Dexter energy transfer (DET) between the mixed organic lumophores. The temperature-dependent luminescent behavior arises from the thermal equilibrium between two separated excited states coupled by DET, which is confirmed by Boltzmann distribution fitting. The small excited-state energy gap allows ZnATZ-BTB to measure and visualize cryogenic temperatures (30-130 K) with significantly high relative sensitivity (up to 5.29% K(-1) at 30 K). Moreover, it is the first example of a ratiometric MOF thermometer the dual emitting sources of which are widely applicable mixed organic ligands, opening up new opportunities for designing such devices.

A series of d10 coordination polymers constructed with a rigid tripodal imidazole ligand and varied polycarboxylates: syntheses, structures and luminescence properties

Five novel Zn(II)/Cd(II) coordination polymers, [Zn2(tib)(L1)(μ2-OH)(HCOO)·2H2O]n (1), [Cd2(tib)2(L1)(NO3)2·2H2O·4DMF]n (2), [Cd2(tib)2(L2)(NO3)2·2H2O·4DMF]n (3), [Cd(tib)(L3)·H2O·2DMF]n (4) and [Cd3(tib)4(L4)·5/2NO3·1/2OH·3DMF]n (5) (tib = 1,3,5-tris(1-imidazolyl)benzene, H2L1 = terephthalic acid, H2L2 = isophthalic acid, H2L3 = 1,4-naphthalenedicarboxylic acid, H3L4 = (1α,3α,5α)-1,3,5-cyclohexanetricarboxylic acid, DMF = N,N-dimethylformamide), have been synthesized under solvothermal conditions. In compound 1, two-dimensional (2D) Zn-tib layers are pillared by L1 to afford a (3,5)-connected three-dimensional (3D) framework with topology (63)(69·8). Compound 2 displays a 2D + 2D → 2D interpenetrated bi-layer array based on a 2D (3,4) network. Compound 3 is characterized as an infinite one-dimensional (1D) chain structure, which is further extended into a 3D supramolecular architecture via weak π⋯π stacking interactions. Compound 4 possesses a 3D 2-fold interpenetrated architecture with the Schlafli symbol (42·65·83)(42·6). Compound 5 features a fascinating petal shaped (3,5)-connected network with a (42·6·84·103)3(42·6)3(83)2 topology which until now has never been documented. In this series of compounds, the diversity of the structures is tuned by the coordination geometries of the metal ions and the nature of the varied co-ligands. Furthermore, the luminescence properties of compounds 1–5 at room temperature have also been studied in detail.

Effect of anions on the self-assembly of two Cd–organic frameworks: syntheses, structural diversity and photoluminescence properties

By employing a rigid tripodal ligand 1,3,5-tris(1-imidazolyl)benzene (tib) to assemble with two different Cd(II) salts, we have obtained two distinct cationic metal–organic frameworks, [Cd(tib)2·2NO3·4DMF]n (1) and [Cd(tib)2·2ClO4·4DMF]n (2) (DMF = N,N-dimethylformamide). The compounds were structurally characterized by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Both compounds 1 and 2 are constructed based on 2D square lattice (sql) nets, through ligand-to-axial (L–A), pillared by triangular tib ligands, resulting in two diverse 3D pillar-layered architectures. Compound 1 features a cationic framework with a (3,6)-connected rtl topology and has rhomboid channels; while for 2, the 2D layers repeat in an ⋯ABAB⋯ staggered stacking mode pillared by tib ligands, resulting in a different cationic framework from 1 with a pyr net. The results demonstrate that counterions NO3− and ClO4− play an important role in the fabrication of structures of 1 and 2. Furthermore, the photoluminescence of compounds 1 and 2 have been investigated in the solid state at ambient temperature.