Xianying Duan

Four 2D metal–organic networks incorporating Cd-cluster SUBs: hydrothermal synthesis, structures and photoluminescent properties

Hydro(solvo)thermal reactions between 1,1′-biphenyl-2,2′,3,3′-tetracarboxyl acid (H4bptc) and Cd(NO3)2·4H2O at the presence of the ‘second’ ligands of bpydo, bpe, bpp and bix (bpydo = 4,4′-bipyridine-N,N′-dioxide; bpe = 1,2-bis-(4-pyridyl)ethane; bpp = 1,3-Bis-(4-pyridyl)propane; bix = 1,4-bis(imidazol-1-yl-methyl)benzene) yield four new 2D metal–organic coordination polymers [Cd9(bptc)4(μ3-OH)2(H2O)14]·(bpydo)·2H2O (2), [Cd2(bptc)(bpe)(H2O)2]·H2O (3), [Cd4(bptc)(Hbptc)(bpp)(μ3-OH)(H2O)4] (4), [Cd2(bptc)(bix)(H2O)] (5). Compound 2 presents a 2D grid structure with heptanuclear cadmium cluster and two kinds of discrete Cd atoms secondary building units (SUBs), 3 has a 2D structure with the novel Schlafli symbol of (4.62)(43.63)(44.610.8), 4 gives a 2D grid structure with a pentanuclear cadmium cluster, binuclear cadmium cluster and discrete Cd atom SUBs, and 5 has a 2D distorted CdI2-type topology structure with the Schlafli symbol of (43)2(46.66.83). The novel achiral crown-ether-like cycles in 2, 4 and 5 are found and occupied by the single Cd atom or binuclear cadmium cluster. All compounds give strong luminescent emission and have potential application as optical materials.

Three coordination polymers with helical chains based on methylenediisophthalic acid (H4MDIP)

Based on methylenediisophthalic acid (H4MDIP), three novel coordination polymers {[Mn2(MDIP)(bime)(H2O)2]2·2H2O}n (1) [bime = 1,2-ethanediylbis(imidazole)], {[Mn3(HMDIP)2(H2O)4]·4,4′-bipy·3H2O}n (2) [4,4′-bipy = 4,4′-bipyridine], and {[Co5(MDIP)2(H2O)6(μ-OH)2]·7H2O}n (3) have been synthesized and characterized by IR spectra, single-crystal X-ray diffraction analyses and thermal stability studies. The introduction of the bime and 4,4′-bipy ligands into Mn(CH3COO)2·4H2O and H4MDIP system leads to the formation of complexes 1 and 2, and the absence of the second ligand in the Co(NO3)2·6H2O and H4MDIP system leads to shape complex 3. Complex 1 is a 3D architecture with [Mn(–OCO–)]∞ helical chain. Coordination polymer2 is a 2D sheet structure with trinuclear unit, in which two kinds of 21 helical chains ([Mn(IP)]∞ (IP = isophthalic acid) and [Mn(MDIP)]∞) are included. Complex 3 exhibits the 3D porous structure with a pentanuclear cobalt unit in which a 1D shallow helical chain of hydrogen-bonded water molecules is shaped. From the topology point of view, complex 1 exhibits a (4,6)-connected network with the Schlafli symbol (42.63.8)2(44.62.74.84.9), complex 2 displays a (3,6)-connected network with CdI2 topology, and complex 3 displays a (4, 8)-connected network with Schlafli symbol (44.62)2(416.612) which is a decorated scu net.

Syntheses, structures and properties of a series of organic–inorganic complexes based on methylenediisophthalic acid (H4MDIP)

Six new inorganic–organic polymers {Mg(H2MDIP)(H2O)4]·3H2O}n (1), {Ca2(MDIP)(H2O)4]·CH3OH·4H2O}n (2), {[Sr2(MDIP)(H2O)7]·2H2O}n (3), {[Ba(MDIP)0.5(H2O)4]·H2O}n (4), {[Mn(H2MDIP)(H2O)]2·H2O}n (5) and {[Co(H2MDIP)(H2O)]2·H2O}n (6) were obtained by self-assembly of the corresponding metal salts with methylenediisophthalic acid (H4MDIP), and their structures were determined by single-crystal X-ray diffraction studies. Monodentate coordination mode of H2MDIP2− in 1 results in a 1D chiral chain (right-handness) with a monoclear magnesium center. Complexes 2–4 have 2D layer networks, and each MDIP4− ligand coordinates to Ca(II), Sr(II) or Ba(II) atoms using four carboxylate groups: the chelating-mono coordination mode in 2 leads to a 1D helical chain, yet the chelating-mono and chelating coordination modes lead to binuclear [Sr–O–Sr] and [Ba–O–Ba] units in 3–4. Both 5 and 6 have 2D grid structures with a binuclear [M–O–C–O–M] unit (M = Mn2+, Co2+). The luminescence properties of 1–4 have been investigated in the solid state at ambient temperature and it was found that the strong emissions vary from blue to yellow–green fluorescence depending on the metal ions. Compound 1 exhibits good second-harmonic generation activity, approximately 1.1 times that of urea.

Three-dimensional metal–organic frameworks constructed from bix and 1,2,4-benzenetricarboxylate

Two new metal–organic complexes [Cd1.5(btrc)(bix)]n (1) and [Zn2(btrc)(Hbtrc)0.5(bix)2]n(2) (H3btrc = 1,2,4-benzenetricarboxylate; bix = 1,4-bis(imidazol-1-ylmethyl)-benzene) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Complex 1 represents a three-dimensional (3D) structure based on the 2D sheets and bix pillars. Complex 2 exhibits unique architecture. The two complexes exhibit strong fluorescent emissions in their solid states at room temperature.

Syntheses and solid state structures of hybrid d10 metal–organic frameworks based on methylenediisophthalic acid (H4MDIP)

Four novel hybrid d10 metal complexes [Zn(H2MDIP)(4,4′-bpy)0.5]n1 (4,4′-bpy = 4,4′-bipyridine, H4MDIP = methylenediisophthalic acid), [Zn2(MDIP)(bix)·H2O]n2 [bix = 1,4-bis(imidazol-1-ylmethyl)-benzene], {[Cd(H2MDIP)(H2O)]2·H2O}n3, {[Cd2(MDIP)(H2O)2(en)2]·2H2O}n4 (en = ethylenediamine) based on tetracarboxylate acid were synthesized and their structures were determined by X-ray single-crystal diffraction. Complexes 1–2 are 2D grid and undulated structures with four-coordinated Zn2+ ions, respectively; 3–4 are 2D grid and double-sheet structures with six-coordinated Cd2+ ions, respectively. MDIP in complexes 1 and 3 act as V-shaped and Y-shaped ligands, respectively, yet in 2 and 4 MDIP act as similar X-shaped ligands. Diverse topologies, thermal and luminescent properties of complexes 1–4 have also been investigated.

A novel 2D coordination polymer with unprecedented [Ag]7 chains and two 3D silver–organic frameworks constructed by methylenediisophthalic acid (H4MDIP) with strong Ag–Ag interactions

Using a hydrothermal synthesis method, three novel silver complexes {Ag2(H2MDIP)(o-bix)2·H2O}n(1) (H4MDIP = methylenediisophthalic acid, o-bix = 1,2-bis (imidazol-1-ylmethyl)- benzene, {Ag8(MDIP)2(m-bix)}n(2) (m-bix = 1,3-bis(imidazol-1-ylmethyl)-benzene), {Ag4(MDIP)(p-bix)3·H2O}n(3) (p-bix = 1,4-bis(imidazol-1-ylmethyl)-benzene) were synthesized based on tetracarboxylic acid and auxiliary ligands containing N donors. Their structures have been characterized by X-ray crystallography. Complexes 1 and 3 have special 3D supramolecular networks constructed by hydrogen bonding, π–π stacking and electronic interactions to link the metal cations, anions and water molecules together. Complex 2 exhibits a unique 2D architecture with unprecedented [Ag]7 chains connected by strong Ag–Ag interactions. Thermal stabilities and luminescent properties of complexes 1–3 were investigated.

Design and constructions of three novel metal–organic frameworks based on pillared-layer motifs

Three novel 3D metal–organic frameworks, [Co2(butca)(o-bix)2·8H2O]n (1), [Co2(butca)(m-bix)2·2H2O]n (2) and [Co2(butca)(p-bix)2·3H2O]n (3) (butca = 1,2,3,4-butane-tetracarboxylic acid; o-bix = 1,2-bis(imidazol-1-ylmethyl)-benzene; m-bix = 1,3-bis(imidazol-1-ylmethyl)-benzene; and p-bix = 1,4-bis(imidazol-1-ylmethyl)-benzene), have been successfully synthesized from a 2D layer compound [Co2(butca)(H2O)5·2H2O]n (0) employing a three isomer pillars insertion reaction, and their structures were determined by single-crystal X-ray diffraction studies. Complexes 1 and 2 are isostructural. Interestingly, there exist metal-bix double-helical chains in these two 3D frameworks, which are arranged left- and right-handed alternately. Different from 1 and 2 which have only one coordination model, Co atoms in 3 have two types of different coordination enviroments. The Co1 ions are exclusively bridged by cis-bix ligands to give one 26-number ring through spontaneous resolution. At the same time, the Co2 ions are wholely connected with tran-bix ligands to form a 1-D zigzag chain. Moreover, the relationship between a 2D layer structure and 3D metal–organic frameworks based on the pillared-layer motifs is discussed. This work has significant potential for the study of crystal engineering of transition metal coordination networks.

Prolonging luminescent lifetimes by introducing bis(maleonitriledithiolato)metalate anions with a fluorescent organic cation

A new organic fluorescent ionic compound [MOBIP]I (1) (MOBIP+ = 1-methyl-2-oxo-3 -(1H-benzimidazol-2(3H)-ylidene)-2,3-dihydropyridinium) was synthesized and used to prepare seven maleonitriledithiolate metal complexes [MOBIP] n [M(mnt)2] by substitution of the iodide ion with [M(mnt)2] n − (M = Cu2+ (2), Ni2+ (3a), Ni3+ (3b), Zn2+ (4), Cd2+ (5), Pd2+ (6), and Pt2+ (7)). An investigation of fluorescence properties shows that these complexes are a new series of solution luminescent complexes of maleonitriledithiolate derivatives with strong blue light fluorescence in daylight by irradiation with UV light with high quantum yields. They display similar symmetric emissions with λem at the deep blue region of ∼426 nm upon excitation at ∼364 nm in DMF, caused by L–L transition of MOBIP+. Existence of [M(mnt)2] n − anions in the solution prolongs the fluorescent lifetimes. For all these compounds in the solid state, the fluorescent emission is blue-shifted and more narrow than that in solution. Based on their crystal structure analysis, the weak stacking interactions in compounds cause the difference of their fluorescence spectrum. Investigations of variable-temperature magnetic susceptibility indicate that 2 has weak antiferromagnetic coupling, while 3b exhibits stronger antiferromagnetic coupling.