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 near-infrared (NIR) luminescence of three solvent-induced pseudo-polymorphic complexes from a bimetallic Zn–Nd Schiff-base molecular unit

Three solvent-induced pseudo-polymorphic bimetallic Zn–Nd complexes [ZnNdL(OAc)(NO₃)₂(DMF)] · solvate (solvate: MeCN (1), THF (2), EtOH (3); H₂L = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine) were obtained, and their solid NIR luminescence related to the packing structure from the intermolecular π–π interactions was discussed.     

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.     

Coupling of cyclohexene oxide (CHO) and carbon disulfide (CS2) catalyzed by the asymmetric bis-Schiff-base Zn(II) complex

Based on the self-assembly of the asymmetric bis-Schiff-base ligand H₂L (H₂L = 4-((E)-(2-((E)-3,5-dibromo-2-hydroxybenzylideneamino)phenylimino)(phenyl)methyl-1-(4-chlorophenyl)-3-methyl-1H-pyrazol-5-ol) and Zn(OAc)₂·2H₂O, a new [Zn(L)] (1) was obtained and shown to efficiently catalyze the coupling of CHO (cyclohexene oxide) and CS₂ (carbon disulfide) in activation with [PPN]Cl (PPN⁺ = bis(triphenylphosphoranyidene)-ammonium), n-Bu₄NBr or n-Bu₄NI, where both poly[thio]carbonates and cyclic [thio]carbonates were produced, and the strong O/S exchange afforded the limited formation of trithiocarbonate in the cyclic [thio]carbonate byproducts.     

First example of PMMA-supported and highly luminous color-purity red-light metallopolymer based on a tris-β-diketonate Zn2 +-Eu3 +-complex

Through the copolymerization of a complex monomer [Zn(L)(4-vinyl-Py)Eu(TTA)₃] (2; H₂L = N,N′-bis(salicylidene)cyclohexane-1.2-diamine; 4-vinyl-Py = 4-vinyl-pyridine and HTTA = 2-thenoyltrifluoroacetonate) with MMA (methyl methacrylate), the first example of PMMA-supported and highly luminous (Ф_Eu^L = 63.1%) color-purity red-light metallopolymer poly(MMA-co-2) based on a tris-β-diketonate Zn^2 +-Eu^3 +-complex is obtained.     

Syntheses,structures, and magnetic properties of ethoxy-bridged dinuclear iron(III) complexes containing tetradentate ligands

Dinuclear iron(III) complexes, [(phenO)Fe(SO₄)]₂·2CH₃OH (1) and [(bpmapO)Fe(NO₃)]₂(NO₃)₂·3CH₃OH (2) have been prepared by the reaction of phenOH/bpmapOH and FeSO₄·7H₂O/Fe(NO₃)₃·9H₂O in methanol, respectively (phenOH = N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine, bpmapOH = N-(bis(2-pyridylmethyl)amino)-2-methylpropan-2-ol). Both complexes are ethoxy-bridged dinuclear species and the iron(III) ions in 1 and 2 have distorted octahedral geometries. Both complexes show strong antiferromagnetic interactions through the bridged ethoxy groups within the dimeric units.     

Pure white-light and color-tuning of PMMA-supported hybrid materials doped with (TTA)3-Zn2 +-Eu3 + and (BA)3-Zn2 +-Tb3 + complexes

Based on the doping of red-light-emitting 2 ([Zn(L)(4-vinyl-Py)Eu(TTA)₃]; H₂L = N,N′-bis(salicylidene)cyclohexane-1,2-diamine, 4-vinyl-Py = 4-vinyl-pyridine, HTTA = 2-thenoyltrifluoroacetonate) and cyan-light-emitting 4 ([Zn(L)(4-vinyl-Py)Tb(BA)₃]; HBA = 1-phenyl-1,3-butanedione) in PMMA, hybrid materials of 2@4@PMMA with improved physical properties including color-tunable for white-light (CIE coordinate 0.373, 0.319) were obtained.     

Synthesis,characterisation and cryomagnetic studies of a novel homonuclear Nd(III) Schiff base dimer

A novel homodinuclear complex [Nd^III(L)(NO₃)]₂ (1) has been synthesised [H₂L = N¹,N³- bis(salicylideneimino)diethylenetriamine, a pentadentate Schiff base with N₃O₂ donor set] and characterised with spectroscopic and micro-analytical techniques. Single crystal X-ray diffraction study reveals a centrosymmetric binuclear neutral entity [space group, P2₁/n; a = 12.911(5); b = 11.938(5); c = 13.960(5) Å; Z = 4] where Nd(III) metal centers are bridged together by two phenoxo oxygen atoms each coming from the two ligands. The most interesting fact is that two similar “salen” moieties of each ligand are behaving completely different in their coordination. In the doubly deprotonated ligand (L²⁻), one phenoxo oxygen is mono coordinated to the metal, whereas its immediate neighbour on the other end bridges the two Nd(III) centers. The distance between the Nd(III) centers is found to be 3.884(3) Å. Temperature dependence (2–300 K) magnetic susceptibility study suggests the presence of an antiferromagnetic interaction operating via two phenoxo bridges.     

Unsymmetrical exo-dentate IN− ligand for further self-assembly with the Zn–Nd Salen-type Schiff-base ligands

With the hetero-binuclear Zn–Nd complex from the ethylene- or phenylene-linkered Salen-type Schiff-base ligand as the building block, further self-assembly of the unsymmetrical exo-dentate IN^? (IN^? = isonicotinic) anion gave a 2D layer polymeric [ZnL¹Nd(IN)(NO₃)₂]_n (1) (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine) or a discrete binuclear [ZnL²Nd(IN)(NO₃)₂(DMF] (2) (H₂L² = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine) complex, respectively. The change of linker flexibility of two Salen-type Schiff-base ligands (H₂L¹ and H₂L²) resulted in the difference of structures and NIR luminescent properties of their mixed-ligands complexes.     

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.     

Crystal structure and magnetic dynamics of a novel salen type and β-diketonate Dy2 complex

A novel salen type dinuclear dysprosium complex e.g., [Dy₂(H₂L)(acac)₆]·4CH₃OH (1) [H₂L = N,N′-(1.3-propylene)bis(3-methoxysalicylideneimine) has been isolated by reactions of Dy(acac)₃·H₂O (acac = acetylacetonate) with salen type (H₂L), respectively. X-ray crystallographic analyses reveal that asymmetric Dy(III) ions for 1 was bridged by one ligand displaying bicapped trigonal prism coordination geometry. Magnetic measurement shows that complex 1 exhibit slow relaxations under zero dc field. The presence of two magnetic relaxations in complex 1 is associated with the presence of minute differences in bond lengths around Dy(III) center.     

NIR luminescence comparison of Zn-Nd Schiff-base complex doped or single-nodal grafted into PMMA

Through doping or grafting of a new ZnNd Schiff-base complex monomer [Zn(L)(4-vinyl-Py)Nd(NO₃)₃] (2; H₂L = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine; 4-vinyl-Py = 4-vinyl-pyridine) into PMMA (poly(methyl methacrylate)), two kinds of hybrid materials 2@PMMA and Poly(2-co-MMA) with significantly improved physical properties including good Nd^3 +-centered near-infrared (NIR) luminescence were obtained. Especially the single-nodal ZnNd-grafted Poly(2-co-MMA) soluble in organic solvents exhibits the high sensitization efficiency (η_sens = Φ_Nd^L/Φ_Nd^Nd = 81%) even at a high feed molar ratio up to 1:50.     

Two highly connected frameworks and one polythreading architecture based on multidentate N-donor ligands: Syntheses,structures, characterizations and photoluminescent properties

Three coordination polymers based on multidentate N-donor ligands and polycarboxylate anions, namely, [Co₃(4,4′-tmbpt)₄(btc)₂]·9.5H₂O (1), [Ag₄(4,4′-tmbpt)(btec)(H₂O)₂]·H₂O (2) and [Zn(4,4′-tmbpt)(btec)_0.5(H₂O)]·0.5H₂O (3) (4,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole, H₃btc = 1,3,5-benzenetricarboxylic acid, and H₄btec = 1,2,4,5-benzenetetracarboxylic acid) have been prepared under hydrothermal condition. Compound 1 displays a 3D (3,6,8)-connected framework with (4·6²)(4⁴·6¹⁰·8)(4¹⁴·6¹²·8²) topology. Compound 2 is a 3D (4,5,8)-connected framework with (4³·6²·8)(4³·6⁵·8²)(4⁸·6²)(4¹⁰·6¹⁰·8⁸) topology. Compound 3 exhibits a 2D → 3D polythreading architecture. The photoluminescent spectra indicate that at room temperature, compounds 2 and 3 emit green and blue luminescence, respectively.     

Single-nodal linking for Zn2 +-Nd3 +-containing metallopolymer with efficient near-infrared (NIR) luminescence

Through the single-nodal copolymerization of MMA (methyl methacrylate) and a vinyl-containing complex monomer [Zn(L)(4-vinyl-Py)Nd(NO₃)₃] (2; H₂L = N,N′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine; 4-vinyl-Py = 4-vinyl-pyridine) with the both ¹π-π* and ³π-π* sensitizing approach to Nd^3 + ion, the Zn^2 +-Nd^3 +-containing metallopolymer Poly(MMA-co-2) exhibits good physical properties including an attractive Nd^3 +-centered NIR sensitization efficiency (Φ^L_Nd = 1.22% and η = Φ^L_Nd/Φ^Nd_Nd = 82%).     

Conformational isomerism of a flexible fluorinated bis-pyridinecarboxamide ligand in the structural direction of two distinct layered CuII coordination polymers

Reaction of a flexible pyridinecarboxamide ligand N,N′-[(2,3,5,6-tetrafluoro-1,4-phenylene) bis(methylene)]bis(pyridine-4-carboxamide) (H₂tfpbbp) with Cu^II chloride or perchlorate affords two coordination polymers {[Cu(H₂tfpbbp)(tfpbbp)(H₂O)] · 2DMF · 4H₂O}_n (1) and {[Cu(H₂tfpbbp)₂(ClO₄)₂] · 3H₂O}_n (2). Both complexes have 2-D (4,4) layered networks extended by the exo-bidentate bridging ligands, which however consist of distinct [Cu–ligand]₄ meshes owing to the conformational difference of ligands. Their spectroscopic, thermal, and fluorescence properties have also been investigated.     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.     

Two helical one-dimensional copper(II) coordination polymers based on N-(2-hydroxylbenzyl)glycine and N-(2-hydroxylbenzyl)-l-alanine: Syntheses,crystal structures and magnetic studies

Two new helical Cu(II) coordination polymers, [Cu(2,2′-bpy)(Hsgly)]Cl · 2H₂O(H₂sgly = N-(2-hydroxylbenzyl)glycine) (1) and [Cu(2,2′-bpy)(Hsala)](NO₃) · 2H₂O(H₂sala = N-(2-hydroxylbenzyl)-l-alanine) (2) were synthesized. Single crystal X-ray diffraction analysis indicated that both complexes showed helical chains arrangement of Cu(II) centers bridged by carboxyl groups. The magnetic measurements showed complex 1 exhibited ferromagnetic interaction while there was no interaction between the Cu(II) centers in complex 2.     

A self-assembled porous Zn(II) metal–organic framework based on fluorinated bis-pyridinecarboxamide derivative ligand: Synthesis,structure and properties

A zinc metal–organic framework [Zn(tfpbbp)(Ac)₂]_n (1) has been prepared by reacting N, N′-[(2,3,5,6-tetrafluoro-1,4-phenylene)bis(methylene)]bis(pyridine-4-carboxamide) (tfpbbp) with Zn(Ac)₂ · 2H₂O and characterized by single crystal X-ray diffraction and TGA analysis. Single crystal X-ray diffraction analysis indicates that in solid-state (1) is a 1-D zigzag chain, which further self-assembles into a 3-D supramolecular porous structure through hydrogen bonding interactions. The polymer (1) exhibits photoluminescent property at room temperature.     

Syntheses and structures of cadmium(II) and cobalt(II) coordination polymers based on 1,1′-(2,2′-oxybis(ethane-2,1-diyl))bis(1H-imidazole) and carboxylate ligands

Two novel coordination polymers containing Cd(II) and Co(II) metals, connected via 1,1′-(2,2′-oxybis(ethane-2,1-diyl))bis(1H-imidazole) (L) ligand, have been synthesized. Compound [Cd(L)₂(p-BDC)] · 2H₂O (1) (p-BDC = 1,4-benzenedicarboxylate anion) is a three-dimensional interdigitated supramolecular architecture. Compound [Co(L)(BTCA)_0.5] (2) (BTCA = 1,2,3,4-butanetetracarboxylate anion) possesses a unique (3,4)-connected 3D framework with (8³)₂(8⁵ · 10) topology.     

Synthesis and characterization of nickel phosphonopropionate hybrid materials

Hydrothermal reaction of nickel acetate with 3-phosphonopropionic acid and 4,4′-bipyridine resulted in two novel phosphonate compounds Ni(HO₃PC₂H₄COO)(4,4′-bpy)(H₂O) · 0.5(4,4′-bpy) (bpy = bipyridine) (I) and Ni(O₃PC₂H₄COOH)(4,4′-bpy)(H₂O)₃ · H₂O (II). Single-crystal X-ray studies reveal that self-assemblies between the ligands and metal ion result in layer (I) and chain (II) structures. Magnetic measurement of I indicate there are ferromagnetic couplings between adjacent Ni²⁺ ions (C = 1.29 cm³ mol⁻¹ K and θ = 2.25 K).