Jinling Miao

Structure and Photoluminescence Tuning Features of Mn2+- and Ln3+-Activated Zn-Based Heterometal–Organic Frameworks (MOFs) with a Single 5-Methylisophthalic Acid Ligand

In attempts to investigate whether the photoluminescence properties of the Zn-based heterometal-organic frameworks (MOFs) could be tuned by doping different Ln(3+) (Ln = Sm, Eu, Tb) and Mn(2+) ions, seven novel 3D homo- and hetero-MOFs with a rich variety of network topologies, namely, [Zn(mip)](n) (Zn-Zn), [Zn(2)Mn(OH)(2)(mip)(2)](n) (Zn-Mn), [Mn(2)Mn(OH)(2)(mip)(2)](n) (Mn-Mn), [ZnSm(OH)(mip)(2)](n) (Zn-Sm), [ZnEu(OH)(mip)(2)](n) (Zn-Eu1), [Zn(5)Eu(OH)(H(2)O)(3)(mip)(6)·(H(2)O)](n) (Zn-Eu2), and [Zn(5)Tb(OH)(H(2)O)(3)(mip)(6)](n) (Zn-Tb), (mip = 5-methylisophthalate dianion), have been synthesized hydrothermally based on a single 5-methylisophthalic acid ligand. All compounds are fully structurally characterized by elemental analysis, FT-IR spectroscopy, TG-DTA analysis, single-crystal X-ray diffraction, and X-ray powder diffraction (XRPD) techniques. The various connectivity modes of the mip linkers generate four types of different structures. Type I (Zn-Zn) is a 3D homo-MOF with helical channels composed of Zn(2)(COO)(4) SBUs (second building units). Type II (Zn-Mn and Mn-Mn) displays a nest-like 3D homo- or hetero-MOF featuring window-shaped helical channels composed of Zn(4)Mn(2)(OH)(4)(COO)(8) or Mn(4)Mn(2)(OH)(4)(COO)(8) SBUs. Type III (Zn-Sm and Zn-Eu1) presents a complicated corbeil-like 3D hetero-MOF with irregular helical channels composed of (SmZnO)(2)(COO)(8) or (EuZnO)(2)(COO)(8) heterometallic SBUs. Type IV (Zn-Eu2 and Zn-Tb) contains a heterometallic SBU Zn(5)Eu(OH)(COO)(12) or Zn(5)Tb(OH)(COO)(12), which results in a 3D hetero-MOF featuring irregular channels impregnated by parts of the free and coordinated water molecules. Photoluminescence properties indicate that all of the compounds exhibit photoluminescence in the solid state at room temperature. Compared with a broad emission band at ca. 475 nm (λ(ex) = 380 nm) for Zn-Zn, compound Zn-Mn exhibits a remarkably intense emission band centered at 737 nm (λ(ex) = 320 nm) due to the characteristic emission of Mn(2+). In addition, the fluorescence intensity of compound Zn-Mn is stronger than that of Mn-Mn as a result of Zn(2+) behaving as an activator for the Mn(2+) emission. Compound Zn-Sm displays a typical Sm(3+) emission spectrum, and the peak at 596 nm is the strongest one (λ(ex) = 310 nm). Both Zn-Eu1 and Zn-Eu2 give the characteristic emission transitions of the Eu(3+) ions (λ(ex) = 310 nm). Thanks to the ambient different crystal-field strengths, crystal field symmetries, and coordinated bonds of the Eu(3+) ions in compounds Zn-Eu1 and Zn-Eu2, the spectrum of the former compound is dominated by the (5)D(0) → (7)F(2) transition (612 nm), while the emission of the (5)D(0) → (7)F(4) transition (699 nm) for the latter one is the most intense. Compound Zn-Tb emits the characteristic Tb(3+) ion spectrum dominated by the (5)D(4) → (7)F(5) (544 nm) transition. Upon addition of the different activated ions, the luminescence lifetimes of the compounds are also changed from the nanosecond (Zn-Zn) to the microsecond (Zn-Mn, Mn-Mn, and Zn-Sm) and millisecond (Zn-Eu1, Zn-Eu2, and Zn-Tb) magnitude orders. The structure and photoluminescent property correlations suggest that the presence of Mn(2+) and Ln(3+) ions can activate the Zn-based hetero-MOFs to emit the tunable photoluminescence.

Fluorescent Zn-based hetero-MOFs design via single metal site substitution

Two pairs of novel Zn-based MOFs with the same structures are synthesized. The exchange mechanism between the primary MOFs and the substituted MOFs is discussed. The utilization of the single metal site substitution in pre-formed Zn-based MOFs appears suited to the design of isostructural Zn-based hetero-MOFs with different photoluminescence properties.

Effects of substitution position on crystal packing, polymorphism and crystallization-induced emission of (9-anthryl)vinylstyrylbenzene isomers

Three (9-anthryl)vinylstyrylbenzene (ASB) position isomers were synthesized and compared. Substitution position affects temperature-induced polymorphism, crystal packing and crystallization-induced emission (CIE) properties. Different from 1,2-ASB and 1,4-ASB, 1,3-ASB undergoes a crystal-to-crystal phase transition upon heating. The crystal structure of a new phase (1,3-ASB-β) was successfully solved. Thus, the solid emission of 1,3-ASB could be tuned by polymorphism. In contrast, the solid emission of 1,4-ASB is controlled by its crystallinity. In the crystal structures of 1,2-ASB and 1,3-ASB-β, the adjacent interacting anthryls are inclined to adopt an edge-to-face configuration with C–H⋯π interactions. In contrast, the adjacent anthracene rings in the 1,4-ASB crystals are parallel to each other with π⋯π interactions. Furthermore, multiple intermolecular interaction modes such as C–H⋯π and H⋯H interactions coexist in the crystal structure of 1,4-ASB, which collectively results in a closer packing. Interestingly, 1,4-ASB displays CIE behaviour. In contrast, the emission of the other two isomers is quenched in the solid state. The effect of substitution position on the photophysical properties is systematically studied.

Conformation twisting induced orientational disorder, polymorphism and solid-state emission properties of 1-(9-anthryl)-2-(1-naphthyl)ethylene

Polymorphism is important to study the structure–property relationship with a minimum number of variables. Compound 1-(9-anthryl)-2-(1-naphthyl)ethylene (ANE) can form three polymorphs by controlling the crystallization conditions, which belong to the P212121 space group for ANE-a, P21/c space group for ANE-b and P space group for ANE-c, respectively. Orientational disorder was found in ANE-b and ANE-c polymorphs. The emission maximum of the three polymorphs are 496, 470 and 490 nm, respectively. Each is blue-shifted from that of a concentrated solution. The formation of orientational disorder and the blue-shift behavior in emission are closely related to the degree of conformational twisting. A large dihedral angle between the anthracene and naphthalene rings is helpful to induce orientational disorder and blue-shift in the solid emission maximum. The emission efficiency of ANE solution and polymorphs is 42% (CH2Cl2 solution), 28% (ANE-a), 22% (ANE-b) and 47% (ANE-c), respectively. The ANE-c polymorph emits even more efficiently than the solution. This is attributed to the different packing environments, which produce distinct PL decay dynamics. For the three polymorphs, the decay behaviors are all double-exponential and the fluorescence efficiency is enhanced as the proportion of the short-lived component increases. This study shows that compound ANE is a kind of tunable solid-state fluorescent material and the molecular conformation plays an important role in the orientational disorder, aggregate packing and solid-state emission.

Novel metal–organic frameworks (MOFs) based on heterometallic nodes and 5-methylisophthalate linkers

Based on 5-methylisophthalate organic linkers, two novel metal–organic frameworks (MOFs) have been assembled from Zn2Na(COO)6 and Zn5K(COO)12 secondary building units (SBUs), which contain 3D anionic frameworks with 1D nanotubular helical channels replete with hydrated alkali metal cation clusters.

cis-Dichloridobis(triphenyl­phosphine-κP)platinum(II) chloro­form solvate

In the title compound, [PtCl2(C18H15P)2]·CHCl3, each PtII centre adopts a nearly square-planar coordination geometry formed by two P atoms [Pt—P = 2.2481 (17) and 2.2658 (19) Å] and two Cl anions [Pt—Cl = 2.3244 (19) and 2.3548 (17) Å]. The Cl atoms of the chloroform solvent molecule are disordered over two orientations in a 0.778 (11):0.222 (11) ratio. The crystal packing is stabilized by weak intermolecular C—H⋯Cl hydrogen bonds, exhibiting voids with a volume of 215 Å3.

3-Carboxy­methyl-1,3-benzimidazolium-1-acetate monohydrate

The title compound, C11H10N2O4·H2O, has a zwitterionic structure, in which the benzimidazole ring system is planar, with a maximum deviation of 0.007 (3) Å. The carboxyl/carboxylate groups adopt a trans configuration. In the crystal structure, intermolecular O—H⋯O hydrogen bonds involving the hydroxy/oxide O atoms link the molecules into a one-dimensional chain. These chains are further linked by O—H⋯O hydrogen bonds involving the water molecules into a two-dimensional network. π–π contacts between the benzimidazole rings [centroid–centroid distance = 3.5716 (4) Å] lead to the formation of a three-dimensional supramolecular structure.

1,3-Bis(carboxy-meth-yl)imidazolium triiodide 1-carboxyl-atomethyl-3-carboxy-methyl-imidazolium.

In the title compound, C7H9N2O4 +·I3 −·C7H8N2O4, the two imidazolium units are hydrogen bonded through the carboxyl groups. The units are further linked via intermolecular O—H⋯O hydrogen bonding, resulting in a one-dimensional ladder-type structure. As a result, the two carboxy groups of each imidazolium unit adopt a cis configuration with respect to the imidazolium ring.

An ortho­rhom­bic polymorph of 1-[(ferrocen­yl)(hydr­oxy)meth­yl]-1,2-dicarba-closo-dodecaborane

An orthorhombic polymorph of the title compound, [Fe(C5H5)(C8H17B10O)] or C13H22B10FeO, is described here in addition to the known monoclinic polymorph [Crundwell et al. (1999 ▶). Acta Cryst. C55, IUC9900087]. The asymmetric unit contains four independent molecules with Ccage–Ccage distances of 1.636 (16)–1.700 (16) Å, and with the methylhydroxy groups disordered over two positions in each molecule [occupancy ratios 0.80 (2):0.20 (2), 0.59 (3):0.41 (3), 0.60 (2):0.40 (2) and 0.793 (17):0.207 (17)].

Bis{2-[(2-pyrid­yl)imino­meth­yl]phenolato}copper(II)

In the title compound, [Cu(C12H9N2O)2], the CuII atom lies on a crystallographic inversion center and has a nearly square-planar geometry. The CuII center coordinates to the phenolic O and azomethine N atoms of the two symmetry-related 2-[(2-pyridyl)iminomethyl]phenolate ligands. The pyridyl N atoms do not coordinate to the CuII atom but participate in intramolecular C—H⋯N hydrogen bonding. π–π stacking between the benzene rings and between the pyridyl rings [centroid–centroid distances 3.8142 (5) and 3.8142 (5) Å, respectively] links the molecules into a chain propagating parallel to [100].