Structures and photoluminescence of coordination polymers assembled from bifunctional ligand containing both tetrazole and imidazole groups

Three new coordination polymers, namely, {[Cu₂(IPT)(SO₄)(OH)(H₂O)]·H₂O}_n (HIPT = 5-(4-(1H-imidazol-1-yl)phenyl)- 1H-tetrazolate, 1), {[Cd₂(IPT)(NPA)(OH)]·H₂O}_n (H₂NPA = 5-nitroisophthalic acid, 2), and {[Zn₂(IPT)(IDC)(H₂O)]·3H₂O}_n (H₃IDC = 1H-imidazole-4,5-dicarboxylic acid, 3), were assembled from a bifunctional organic ligand containing both tetrazole and imidazole groups with/without the aid of carboxylate coligands. Compound 1 possesses 2D structure built by 1D [Cu₂(IPT)(SO₄)(OH)]_n secondary building blocks and IPT⁻ linkers. The 2D networks are linked into 3D supramolecular framework via water chains in helical conformation. Compound 2 displays 3D pillar-layer framework with 2D layers based on tetranuclear Cd(II) SBUs and NPA^2 − pillars. Compound 3 exhibits a 3D framework constructed from the interconnection of 1D [Zn-IDC]_n chains and binuclear Zn₂(IPT)₂ rings. The thermal stabilities of porous compound 3 and luminescent properties of compounds 2 and 3 have also been studied in detail. They exhibit intense solid-state fluorescent emissions at room temperature.     

Pillar-layered Zn–triazolate–carboxylate frameworks tuned by the bend angles of ditopic ligands

In the utilization of three ditopic ligands with different bend angles as pillars, we reported herein three pillar-layered Zn–triazolate–carboxylate frameworks, namely, [Zn₂(ATRZ)₂(BDC)]_n (1), [Zn₂(ATRZ)₂(TPDC)]_n·2nDMF (2) and [Zn₂(ATRZ)₂(ADDC)]_n (3) (ATRZ = 3-amino-1,2,4-triazole, H₂BDC = 1,4-benzenedicarboxylic acid, H₂TPDC = 2,5-thiophenedicarboxylic acid, and H₂ADDC = 1,3-adamantanedicarboxylic acid). Single crystal structural analyses demonstrate that different geometries of ditopic carboxylate pillars not only result in Zn–ATRZ layers adopting various corrugated configurations, but also give rise to 3,4-connected self-interpenetrated net of 1 and non-interpenetrated nets of 2 and 3. All these compounds exhibit high thermal stability and blue photoluminescence.     

Two different Zn(II) interpenetrating networks derived from different dicarboxylate ligands mixed with a flexible imidazole-based ligand

Two interpenetrating networks based on 1,4-bis(2-methylimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (bmimx), namely, {[Zn₂(bmimx)₂(cba)₂]·2.5H₂O}_n (1) and {[Zn(bmimx)(suc)]·2H₂O}_n (2) (H₂cba = 4,4′-carbonyldibenzoic acid, H₂suc = succinic acid) have been prepared at hydrothermal condition by varying the dicarboxylate ligands. Single-crystal X-ray diffraction indicates that complex 1 shows a 4-connected dmp net with 3-fold interpenetration which contains 1D (Zn − cba)_n right- and left-handed helical chains; complex 2 shows a dia topology with 4-fold interpenetration. The results indicate that the spacers of dicarboxylate coligands have an important effect on the interpenetrating characters and ultimate frameworks. Moreover, the photoluminescence properties of the two complexes were studied in the solid state at room temperature.     

Synthesis and characterization of an unprecedented 3D lanthanide coordination polymer assembled by cubane-like clusters and a flexible V-shaped dicarboxylate ligand

A lanthanide coordination polymer based on H₂sfdb ligand, namely [Tb₄(sdbc)₄(phen)₂(μ₃-OH)₄]_n ∙ 1.5nH₂O (1) (H₂sfdb = 4,4′-sulfonyldibenzoic acid, phen = 1,10-phenanthroline) has been hydrothermal synthesized and characterized. Compound 1 exhibits an unprecedented three-dimensional framework that comprised new cubane-like hydroxo clusters [Tb₄(μ₃-OH)₄]^8 + as the nodes and flexible (sfdb)^2 − ligands as the linkers. In 1, (sfdb)^2 − ligands display completely different four kinds of coordination modes. Interestingly, not only the carboxylate groups but also one oxygen atom of sulfonyl group of (sfdb)^2 − ligand are coordinated with Tb^III ions in 1, which is first found in the compounds based on H₂sfdb ligand. The luminescence experiments show that Tb^III compound exhibits the typical Tb^III-centered luminescence.     

Tunable photoluminescence of a dual-emissive zinc(II) coordination polymer with an in-situ generated tetrazole derivative and benzenetetracarboxyli

Hydrothermal reaction of the cyano-substituted derivative, NaN₃, ZnCl₂ and H₄PMA (H₄PMA = 1,2,4,5-benzenetetracarboxylic acid) yielded a dual-emissive coordination polymer: {[Zn₂(PMA)(tzmb)₂]∙6H₂O}_n (1) (tzmb = N-(tetrazolmethyl)-4,4′-bipyridinium). In 1, the μ₂-κN2,κN6 tzmb and μ₄-bridging PMA^4 − connect four-coordinated Zn(II) atoms to form a 2D (4,4)-connected topologic structure. The solid-state sample of 1 exhibits tunable blue-to-white-to-yellow photoluminescence (PL) upon variation of excitation wavelengths, and the PL appearance has been studied by the theoretical calculation.     

Three new d10 coordination polymers based on 2-(2-pyridyl)benzimidazole ligand: Synthesis,structures and properties

Three coordination polymers containing 2-(2-pyridyl)benzimidazole (PyHBIm) ligand, namely {[Zn₃(PyBIm)₃(PyHBIm)₂(tma)(H₂O)]?H₂O}_n (1), [Zn(PyHBIm)(oba)]_n (2), [Cd(PyHBIm)(oba)]_n (3), (tma = trimesate, oba = 4,4′-oxybis-(benzoate)), have been prepared through hydrothermal reaction. Compound 1 exhibits one-dimensional (1D) helical structure. However, compounds 2 and 3 display 1D meso-helical structure. These 1D structures are further assembled into three-dimensional (3D) networks through aromatic π–π stacking interactions and hydrogen bonding interactions. Moreover they all exhibit strong photoluminescence at room temperature and may be good candidates for potential luminescence materials.     

Co-existence of heterometallic Zn2Er and ZnEr arrayed chromophores for the sensitization of near-infrared (NIR) luminescence

With the Zn-Schiff-base [ZnL(Py)] from the simple Salen-type Schiff-base ligand H₂L (H₂L = N,N′-bis(salicylidene)ethylene-1,2-diamine) as the precursor, two co-crystallized heterometallic (Zn₂Ln and ZnLn array) complexes [Zn₂Ln(L)₂(Py)₂(NO₃)₂]·[ZnLn(L)(Py)(NO₃)₃(H₂O)]·NO₃·mMeOH·nS (Ln = Er(1), S = CH₃CN, m = 2, n = 1 or Gd(2), S = H₂O, m = 1, n = 3) were obtained by the further reaction with Ln(NO₃)₃·6H₂O, respectively. The result of their photophysical properties shows the intramolecular effective energy transfer has been demonstrated in the Zn₂Er and ZnEr arrayed complex 1, and the co-existence of different chromophores should be a potentially new way to the fine-tuning properties of NIR luminescence from Er³⁺ ions.     

A pair of novel helical Zn(II) enantiomers constructed from l- and d-threonine Schiff bases: Synthesis,crystal structures and properties

Two novel homochiral helical Zn(II) coordination polymers, {[Zn₂(nap-l-thr)₂(H₂O)₂]·H₂O}_n (1) and {[Zn₂(nap-d-thr)₂(H₂O)₂]·H₂O}_n (2) (H₂nap-l-thr = N-(2-hydroxy-1-naphthylmethylidene)-l-threonine, H₂nap-d-thr = N-(2-hydroxy-1-naphthylmethylidene)-d-threonine) have been successfully synthesized and characterized by elemental analysis, IR, UV–visible and single-crystal X-ray diffraction. It is interesting to note that both complexes are a pair of enantiomers: 1 exhibits 1D right-handed helical chain of [Zn-COO⁻]_∞ and 2 is 1D left-handed helical chain of [Zn-COO⁻]_∞. There are various hydrogen bonds between the adjacent helical chains which result in a 2D homochiral supramolecular layer structure. Notably, under similar synthetic procedure by using the NO₃⁻, CH₃COO⁻, Cl⁻ salts of Zn^2 + ion as a starting reagent, and identical compounds were obtained. In addition, the chiral nature of complexes 1 and 2 are confirmed by the results of circular dichroism (CD) spectra measurements. Thermal stability and luminescence properties were also investigated.     

Synthesis,structure and luminescent property of a new Zn(II) coordination polymer with isolated tetrahedral {Zn4O} clusters as building subunits

A new luminescent Zn(II) coordination polymer, namely [Zn₄(L)₂(μ₄-O)(H₂O)₂(DMF)]_n (1 H₃L = biphenyl-3,4,5-tricarboxylic acid, DMF = N,N′-dimethyl formamide) has been synthesized by combining the H₃L ligand with Zn(II) salts under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features μ₄-oxygen-bridged tetrahedral {Zn₄O} clusters as building subunits, which are further bridged by L^3 − ligands into a complicated three-dimensional (3D) architecture. Topological analysis reveals that it can be reduced into a (3, 6)-connected topological network with the schläfli symbol of {4 · 6²}₂{4² · 6⁹ · 8⁴}. In addition, the luminescent property of 1 was also investigated in the solid state at room temperature.     

Diverse architectures of hybrid materials induced by different mixed-ligands and applications in luminescence

For investigating the effects of different azacyclo-assisting ligands and O-donor bridging ligands on the structural construction, three different structural complexes, namely, {Zn(DBTA)(phen)(H₂O)}_n (1) (DBTA = 2, 5-Dibromo-terephthalic acid, phen = 1,10-Phenanthroline), [Zn(DBTA)(bimb)]_n (2) (bimb (1,4-bis(imidazole-1-ylmethyl)benzene) and {[Zn₂(bmimb)(PO₄)₂]·(H₂O)₂}_n (3) (bmimb = 1,2-bis(methylimidazole-1-ylmethyl) benzene) have been constructed by different mixed-ligands and Zn atoms. Their structures have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, and Infrared spectroscopy. Complex 1 exhibits a common 2D layer with 4,4-connected topology. Complex 2 features an interesting 2-fold interpenetrating net with the aid of long-chain flexible azacyclo-assisting ligands. Complex 3 shows 3D supramolecular architecture with tetranuclear water cluster filling in the pores. Their fluorescence properties were also measured.     

Influence of hydrothermal synthesis temperature on the structures of two 3D coordination polymers

Two 3D coordination polymers [Zn(μ₄-dmbdc)]_n, 1 and [Zn₅(μ₃-OH)₄(μ₅-dmbdc)₂(μ₄-dmbdc)]_n, 2 (H₂dmbdc = 2,5-dimethylbenzenedicarboxylic acid) have been prepared by hydrothermal syntheses with temperature as the only variable. The structure feature is the presence of monoatomic coordination bridges, i.e. μ₃-OH and μ₂-O (from μ₃-COO⁻ of μ₅-dmbdc) in 2 synthesized at higher temperature. The coordination number of zinc ion and the bridging number of the carboxyl group increase with the increasing synthesis temperature, resulting in the formation of the more stable and condensed phase.     

Three unique MOFs constructed by 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and dicarboxylates: From rhombic tetrameric zinc(II) 2D layer to 2D + 2D → 3D polycatenated frameworks

Three metal–organic networks, namely, [Zn₂(Hnip)(4-bpdb)(nip)₂(μ₃-OH)] (1), {[Zn(tbip)(4-bpdb)_1.5]·CH₃OH}_n (2), and {[Ni(1,3-bdc)(4-bpdb)]·2H₂O}_n (3) (4-bpdb = 1.4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, H₂nip = 5-nitroisophthalic acid, H₂tbip = 5-tert-butylisophthalic acid, and 1,3-H₂bdc = 1,3-benzenedicarboxylic acid) are synthesized under hydrothermal conditions. The structure of 1 is built around uncommon rhombic {Zn₄} clusters with double T_d and double O_h Zn(II) geometries, which extend into a 2D network by the rigid deprotonated H₂nip and 4-bpdb bridges. Meanwhile, 2 presents a novel 2D → 3D parallel polycatenated framework assembled from 2D bilayers with cuboids as the fundamental building units. Compound 3 features an interesting 2D → 3D inclined polycatenated network based on 4⁴-sql subunits. Moreover, the thermal stabilities, photoluminescence, and magnetic properties of the compounds are also discussed.     

Synthesis,structure, photoluminescence and theoretical calculation on a novel Zn(II) coordination polymer with (4,8)-connected topology

A new compound, namely [Zn₂(pbdc)_1.5(TAZ)]_n 2nH₂O (1 H₂pbdc = terephthalic acid, HTAZ = 1H-1,2,4-triazole), has been hydrothermally synthesized from H₂pbdc, HTAZ and Cd(II) salts. Single crystal X-ray diffraction analysis reveals that compound 1 represents an unprecedented (4,8)-connected 3D topological network. Notably, two TAZ ligands in uniform μ₃-1,2,4 bridging mode connect four Zn(II) ions together, giving rise to a [Zn₄(TAZ)₂] metallo-ligand subunit, which are further bridged via pbdc ligands in two kinds of coordination modes, resulting in the final 3D complicated framework. The relevant density of states (DOS) calculation result showed that the luminescence of 1 mainly originates from HTAZ intraligand charge transition.     

Two 2D metal–organic frameworks based on 2,2′-bibenzimidazole ligand with (6,3) net topology

Two 2D metal–organic frameworks (MOFs), {[Zn₄(Hbbim)₄(bbim)₂] 2H₂O}_n (1) and [Cd₂(Hbbim)₂(bbim)]_n (2) (H₂bbim = 2,2′-bibenzimidazole) were obtained by solvothermal reaction and characterized by single crystal X-ray diffraction analysis. Different metal ions, Cd(II)/Zn(II), adopt very different coordination geometries though two title compounds both have a 2D honeycomb network with (6,3) topology. The frameworks of compounds 1 and 2 are stable below 360 °C and 475 °C, respectively. Solid-state luminescent spectroscopy of compound 2 exhibits an emission peak at 407 nm.     

Hydrothermal syntheses and characterization of a series of mixed-ligand luminescent CdII frameworks with novel 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate ligand and benzenedicarboxylate isomers

Under similar hydrothermal synthetic conditions using a novel flexible ligand 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetonitrile (PPAN), benzenedicarboxylate isomers (H₂pa = phthalate, H₂ip = isophthalate, and H₂tp = terephthalate) and Cadmium(II) acetate, three novel mixed-ligand Cd(II) coordination polymers {[Cd₂(PPAA)₂(μ-pa)(H₂O)]·2H₂O}_n (1), {[Cd₄(PPAA)₄ (μ₄-ip)₂]·2H₂O}_n (2) and {[Cd₂(PPAA)₂(μ-tp)]·2H₂O}_n (3) (PPAA⁻ = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate) have been isolated, in 1–3 PPAN, and are also hydrolyzed into a novel PPAA⁻ ligand. Complex 1 is a 1D coordination polymer in which the tetra-nuclear [Cd₄(PPAA)₄]^4 + structural units are extended by tri-dentate μ-pa^2 − ligands. Complex 2 contains binuclear [Cd₂(PPAA)₂]^4 + structural units, which are extended by four tetra-dentate μ₄-ip^2 − ligands to link eight neighboring binuclear [Cd₂(PPAA)₂]^4 + units ultimately forming a 2D layered framework, while complex 3 contains 1D double chain containing [Cd(PPAA)]_n cation structural units, which are further extended by tetradentate μ-tp^2 − ligands to form a new 2D layered framework. All the complexes have been investigated by elemental analysis, FT-IR, thermal analysis and fluorescence characterization. The flexible coordination modes of PPAA⁻ are also briefly analyzed. The flexible coordination modes of PPAA⁻ and benzenedicarboxylate isomers also reveal great potential in the construction of these novel mixed-ligand luminescent frameworks with diverse structural motifs and unique functional properties.     

Fluorescent selectivity for small molecules of two coordination polymers based on a tetracarboxylate ligand

Two coordination polymers [Cd(tptc)_0.5(4,4′–bibp)]_n (1) and {[Zn₃(Htptc)₂(phen)₂]·1.5H₂O}_n (2) (H₄tptc = terphenyl-3,3″,5,5″-tetracarboxylic acid, 4,4′-bibp = 4,4′-bis(imidazolyl)biphenyl, and phen = 1,10-phenanthroline) were synthesized under solvothermal conditions. Complex 1 displays a 3D structure with a Schläfli symbol of {4⁴.6²}{4⁸.6²⁰}. Complex 2 possesses a 2D layer network, incorporating [Zn₃(COO)₆] second building units (SBUs), which is packed into a 3D supramolecular architecture by π ⋯ π interactions. Both of them exhibit strong luminescence characteristics. It is worth to note that complexes 1 and 2 show potential application to detect small organic molecules.     

Three d10 coordination polymers based on rigid ligands with flexible functional groups: Syntheses,structures and luminescence

Three coordination polymers, namely, {[Zn(L)(BPY)]·DMF·H₂O}_n (1), {[Zn(L)(TPY)]·0.5H₂BDC·H₂O}_n (2), {[Cd(L)(H₂O)₂]·DMF}_n (3), have been synthesized based on a rigid linear carboxylate ligand (H₂L = 2′,5′-dimethoxy-[1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic acid) and different lengths of pyridine ligands (TPY = 4,3′:5′,4″-terpyridine; BPY = 4,4′-bipyridine). These complexes have been characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. Complex 1 is a 6-connected 3-fold interpenetrating pcu net with point symbol {4¹² ∙ 6³}, 2 and 3 can be simplified as 4-connected sql nets with point symbol {4⁴ ∙ 6²}. In addition, their photoluminescent properties are also investigated in detail.     

Synthesis,structure and proton conductivity of a metal–organic framework with rich hydrogen-bonds between the layers

A two-dimensional structure Zn₄(5-mtz)₄(l-mal)₂(H₂O)₂ (1, 5-mtz = 5-methyltetrazole, l-mal = l-malic acid) has been hydrothermally prepared and characterized by powder and single crystal X-ray diffraction, thermogravimetric (TG) analyses and IR spectroscopy. The 5-mtz and l-malic acid ligands connect the Zinc atoms to form two kinds of 1D chains, [Zn-5-mtz]_n chain and [Zn-l-mal]_n chain. These chains crosslink each other by sharing the Zn atoms to form the layer structure. Rich H-bond network is formed by H-bond interaction between coordinated water and uncoordinated N atoms of 5-mtz in adjacent layers. The proton conductivity of 1 was 1.33 × 10^− 5 S cm^− 1 at 60 °C under 95% RH. This indicates that 1 is a potential candidate material for proton conductivity.     

Diversity of carboxylate coordination in two novel zinc(II) cinnamate complexes

Two novel mixed-ligand zinc(II) complex compounds [Zn(cinn)₂(mpcm)]_n (1) and [Zn(p-HO-cinn)₂(nia)(H₂O)₂] · H₂O (2) (cinn = cinnamato, mpcm = methyl-3-pyridylcarbamate, nia = nicotinamide) were prepared and characterized by elemental analysis, infrared spectroscopy, single crystal X-ray diffraction and thermal analysis. Diverse modes of carboxylate coordination were found in the complexes. In 1 the cinnamate ligands coordinate as monodentate and bridging (syn–anti), respectively. The syn–anti carboxylate bridges connect the molecules of 1 to infinite polymeric helical chains. The structure of 2 is monomeric. One of the carboxylate oxygens of p-hydroxycinnamate is semi-coordinated (Zn–O = 2.549(2) Å).     

A chiral 3D polymer with right- and left-helices based on 2,2′-biimidazole: Synthesis,crystal structure and fluorescent property

A novel three-dimensional (3D) polymer [Cd₂(Hbiim)₄]_n (H₂biim = 2,2′-biimidazole) 1 was obtained through hydrothermal reaction and characterized by single crystal X-ray diffraction, and the fluorescent property was also determined. Compound 1 crystallizes in a monoclinic chiral space group P2₁ and contains two types of helical chains. Hbiim⁻ partially deprotonated of H₂biim exhibits two different coordination modes, which contributes greatly to the formation of the 3D chiral framework. Compound 1 exhibits blue fluorescence at 488 nm in the solid-state upon excitation at 430 nm.