Water Stability and Luminescence of Lanthanide Complexes of Tripodal Ligands Derived from 1,4,7‐Triazacyclononane: Pyridinecarboxamide versus Pyridinecarboxylate Donors

A series of europium(III) and terbium(III) complexes of three 1,4,7‐triazacyclononane‐based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6′,6″‐[1,4,7‐triazacyclononane‐1,4,7‐triyltris(methylene)]tris[pyridine‐2‐carboxylic acid] (H₃tpatcn), ‐tris[pyridine‐2‐carboxamide] (tpatcnam), and ‐tris[pyridine‐2‐carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50‐fold decrease for the carboxamide derivative in comparison to the picolinic acid (=pyridine‐2‐carboxylic acid) based ligand. Detailed analysis of the radiative rate constants and the energy of the triplet states for the three ligand systems revealed a less efficient energy transfer for the carboxamide‐based systems. The stability of the three ligand systems in H₂O was investigated. Although hydrolysis of the ethyl ester occurred in H₂O for the [Ln(tpatcnes)](OTf)₃ complexes, the tripositive [Ln(tpatcnam)](OTf)₃ complexes and the neutral [Ln(tpatcn)] complexes showed high stability in H₂O which makes them suitable for application in biological media. The [Tb(tpatcn)] complex formed easily in H₂O and was thermodynamically stable at physiological pH (pTb 14.9), whereas the [Ln(tpatcnam)](OTf)₃ complexes showed a very high kinetic stability in H₂O, and once prepared in organic solvents, remained undissociated in H₂O.     

Three 2D Ln‐Sulfoterephthalate Complexes with 4,4′‐Bisbiphenyl‐imidazole Featuring Helical Chains

A series of Ln‐sulfoterephthalate coordiantion polymers, namely, [Ln(2‐stp)(4,4′‐bbpi) (H₂O)₂] · H₂O [Ln = Eu ( 1 ), Tb ( 2 ), Dy ( 3 )] (2‐H₃stp = 2‐sulfoterephthalate; 4,4′‐bbpi = 4,4′‐bisbiphenyl‐imidazole), were prepared by hydrothermal method and characterizatied by EA, IR, TGA, and PXRD technologies. Single crystal X‐ray diffraction analyses show that the three complexes are isostructral two‐dimensional network featuring helical chain structures. The fluorescence studies show that the emissions of the coordination polymers exhibit the characteristic peaks of lanthanide ions, which means they could be potential fluorescence materials.     

N,N′‐Bis(Salicylidene)‐1,2‐Cyclohexanediamine Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Luminescence Properties

The salen‐type ligand H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine] was utilized for the synthesis of two lanthanide(III) coordination polymers [LnH₂L(NO₃)₃MeOH]_n [Ln = Eu ( 1 ) and Ln = Lu ( 2 )]. The single‐crystal X‐ray diffraction analyses of 1 and 2 revealed that they are isomorphous and exhibit one‐dimension neutral structure, in which H₂L effectively functions as a bridging ligand and give rise to a chain‐like polymer. The luminescent properties of polymers in solid state and in solution were investigated and 1 exhibits typical red luminescence of Eu^III ions in solid state and dichloromethane solution and 2 emits the ligand‐centered blue luminescence. The energy transfer mechanisms in these luminescent lanthanide polymers were described through calculation of the lowest triplet level of ligand H₂L.     

Synthesis of Lanthanide Coordination Polymers with Benzophenone-4,4′-dicarboxylate： Effect of Lanthanide Contraction on Structures

Four lanthanide coordination polymers with benzophenone‐4,4′‐dicarboxylic acid (H₂bpndc) and 1,10‐phenanthroline (phen), [Ln₂(bpndc)₃(phen)] (Ln=La (1), Pr (2) and Tb (3)), [Yb(bpndc)₁₅(phen)].05H₂O (4) were obtained through solvothermal synthesis. The crystallographic data show that 1, 2, and 3 are isostructural, the Ln(III) ions in 1, 2 and 3 are all eight‐ and ten‐coordinated, respectively, and thus the Ln(III) ions are connected by bpndc ligands, resulting in an interpenetrating 3D structure. While in 4, the Yb(III) ions are eight‐coordinated and connected by bpndc ligands into a 3D structure with 1D rhombic channels, which result from the effect of lanthanide contraction from La(III) to Yb(III) ions, and the bpndc ligands in 1, 2, 3, and 4 display three types of coordination modes.     

Hydrothermal Syntheses and Structural Studies of Lanthanide Coordination Polymers Involving In‐Situ Decarboxylation and their Luminescence Properties

Lanthanide coordination polymers with the formula [Ln(pydc)₂]·H₂O (Ln = La, 1 ; Nd, 2 ; pydc = 3,4‐pyridinedicarboxylate) and [Ln(pydc)(ina)(H₂O)₂] (Ln = Sm, 3 ; Eu, 4 ; Tb, 5 ; Dy, 6 ; pydc = 3,4‐pyridinedicarboxylate, ina = isonicotinate) were synthesized by treating Ln^III nitrates with 3,4‐pyridinedicarboxylic acid under hydrothermal conditions. Single‐crystal and powder X‐ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. The lighter lanthanide compounds 1 and 2 consist of extended two‐dimensional layer structures with the thickness of ca. 1.7 nm. While the heavier lanthanide compounds 3 ‐ 6 have pydc‐bridged double chain structures with one chelating carboxylate group of ina ligand and two water molecules on each metal center. Interestingly, decarboxylation occurred and pydc was partially transformed into ina in the hydrothermal reactions of 3 ‐ 6 . The fluorescence activities of compounds 4 and 5 are reported.     

Nanometrization of Lanthanide‐Based Coordination Polymers

Heteronuclear lanthanide‐based coordination polymers are microcrystalline powders, the luminescence properties of which can be precisely tuned by judicious choice of the rare‐earth ions. In this study, we demonstrate that such materials can also be obtained as stable solutions of nanoparticles in non‐toxic polyols. Bulk powders of the formula [Ln_2?2xLn′_2x(bdc)₃ ? 4 H₂O]_∞ (where H₂bdc denotes 1,4‐benzene‐dicarboxylic acid, 0≤x≤1, and Ln and Ln′ denote lanthanide ions of the series La to Tm plus Y) afford nanoparticles that have been characterized by dynamic light‐scattering (DLS) and transmission electron microscopy (TEM) measurements. Their luminescence properties are similar to those of the bulk materials. Stabilities versus time and versus dilution with another solvent have been studied. This study has revealed that it is possible to tune the size of the nanoparticles. This process offers a reliable means of synthesizing suspensions of nanoparticles with tunable luminescence properties and tunable size distributions in a green solvent (glycerol). The process is also extendable to other coordination polymers and other solvents (ethylene glycol, for example). It constitutes a new route for the facile solubilization of lanthanide‐based coordination polymers.     

Three Transition Metal(II) Coordination Polymers Constructed by a Semi‐rigid Bis‐pyridyl‐bis‐amide and Dicarboxylates Mixed Ligands: Assembly,Structures and Properties

Three coordination polymers, namely [Co(BDC)( L )] · H₂O ( 1 ), [Co(NPH)( L )] · H₂O ( 2 ), and [Ni(NPH)( L )(H₂O)₃] · H₂O ( 3 ) [H₂BDC = 1, 3‐benzenedicarboxylic acid, H₂NPH = 3‐nitrophthalic acid, L = N,N′‐bis(3‐pyridyl)‐terephthalamide] were hydrothermally synthesized by self‐assembly of cobalt/nickel chloride with a semi‐rigid bis‐pyridyl‐bis‐amide ligand and two aromatic dicarboxylic acids. Single crystal X‐ray diffraction analyses revealed that complexes 1 and 2 are two‐dimensional (2D) coordination polymers containing a one‐dimensional (1D) ribbon‐like Co‐dicarboxylate chain and a 1D zigzag Co‐ L chain. Although the coordination numbers of Co^II ions and the coordination modes of two dicarboxylates are different in complexes 1 and 2 , they have a similar 3, 5‐connected {4².6⁷.8}{4².6} topology. In complex 3 , the adjacent Ni^II ions are linked by L ligands to form a 1D polymeric chain, whereas the 1D chains does not extend into a higher‐dimensional structure due to the ligand NPH with monodentate coordination mode. The adjacent layers of complexes 1 and 2 and the adjacent chains of 3 are further linked by hydrogen bonding interactions to form 3D supramolecular networks. Moreover, the thermal stabilities, fluorescent properties, and photocatalytic activities of complexes 1 – 3 were studied.     

One‐dimensional Salen‐type Chain‐like Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Fluorescence Properties

Four salen‐type lanthanide(III) coordination polymers [LnH₂L(NO₃)₃(MeOH)_x]_n [Ln = La ( 1 ), Ce ( 2 ), Sm ( 3 ), Gd ( 4 )] were prepared by reaction of Ln(NO₃)₃ · 6H₂O with H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine]. Single‐crystal X‐ray diffraction analysis revealed that H₂L effectively functions as a bridging ligand forming a series of 1D chain‐like polymers. The solid‐state fluorescence spectra of polymers 1 and 2 emit single ligand‐centered green fluorescence, whereas 3 exhibits typical red fluorescence of Sm^III ions. The lowest triplet level of ligand H₂L was calculated on the basis of the phosphorescence spectrum of Gd^III complex 4 . The energy transfer mechanisms in the lanthanide polymers were described and discussed.     

Anionically Substituted 1,1′,1″‐Methylidynetris[1H‐pyrazole] Ligands for the Formation of Neutral Lanthanide Complexes in Water: Synthesis,Characterization, and Photophysical Properties

The six‐step synthesis of the new podand‐type ligand 6,6′,6″‐[methylidenetri(1H‐pyrazole‐1,3‐diyl)]tris[pyridine‐2‐carboxylic acid] (LH₃) is described. Reaction of LH₃ with LnCl₃ ?6 H₂O (Ln=Eu, Gd, Tb) in MeOH resulted in the isolation of [LnL]?HCl complexes characterized by elemental analysis, mass and IR spectroscopy. Photophysical studies of the Eu and Tb complexes in aqueous solutions revealed the characteristic luminescence features of the metal atoms, indicative of an efficient ligand‐to‐metal energy‐transfer process. Determination of the luminescence quantum yields in H₂O showed the Tb complex to be highly luminescent (?=15%), while, for the Eu complex, the quantum efficiency was only 2%. Excited‐state‐lifetime measurements in H₂O and D₂O evidenced the presence of ca. three H₂O molecules in the first coordination sphere of the complexes. Investigation of the Gd complex allowed the determination of the ligand‐centered triplet state and showed the ligand to be well suited for energy transfer to the metal. The luminescence properties of the complexes are described, and the properties of the ligand as a suitable complexation pocket is questioned.     

Syntheses,Structures, Electrochemistry,and Electrocatalysis of Three Copper(II) Coordination Polymers constructed from 5‐[4‐(1H‐Imidazol‐1‐yl)phenyl]‐1H‐tetrazole

Three coordination polymers (CPs) based on the 5‐[4‐(1H‐imidazol‐1‐yl)phenyl]‐1H‐tetrazole ( HL ) ligand, namely, [Cu(μ₂‐ L )(μ₄‐pbda)(H₂O)] ( 1 ), [Cu₂(μ‐Hbtc)(H₂btc)(μ₃‐OH)(μ₄‐ HL )] ( 2 ) and [Cu₅(μ₃‐ L )(μ₄‐ L )(μ₃‐ip)(μ₃‐OH)(H₂O)₂] · 2H₂O ( 3 ) (H₂pbda = 1,4‐benzenedicarboxylic acid, H₃btc = 1,3,5‐benzenetricarboxylic acid, H₂ip = isophthalic acid) were hydrothermally synthesized and structurally characterized. Complex 1 represents “weave”‐type 2D layers consisting of wave‐like 1D chains and 1D straight chains, which are further connected by hydrogen bonds to form a 3D supramolecular structure. Complex 2 exhibits a uninodal (4)‐connected 2D layer with a point symbol of {4⁴ · 6²}, in which the L ligand can be described as μ₅‐bridging and the H₂btc^– ions display multiple kinds of coordination modes to connect Cu^II ions into 1D “H”‐type Cu‐H₂btc chains. In complex 3 , 2D Cu‐ L layers with two kinds of grids and 1D “stair”‐type Cu‐ip chains link each other to construct a 3D {4¹² · 6³} framework, which contains the pentanuclear subunits. Deprotonated degree and coordination modes of carboxylate ligands may consequentially influence the coordination patterns of main ligands and the final structures of complexes 1 – 3 . Furthermore, electrochemical behaviors and electrocatalytic activities of the title complexes were analyzed at room temperature, suggesting practical applications in areas of electrocatalytic reduction toward nitrite and hydrogen dioxide in aqueous solutions, respectively.     

Two new CdII and ZnII coordination polymers incorporating 1‐aminobenzene‐3,4,5‐tricarboxylic acid: synthesis,crystal structure and characterization

Aminobenzoic acid derivatives are widely used in the preparation of new coordination polymers since they contain O‐atom donors, as well as N‐atom donors, and have a rich variety of coordination modes which can lead to polymers with intriguing structures and interesting properties. Two new coordination polymers incorporating 1‐aminobenzene‐3,4,5‐tricarboxylic acid (H₃abtc), namely, poly[(μ₃‐1‐amino‐5‐carboxybenzene‐3,4‐dicarboxylato)diaquacadmium(II)], [Cd(C₉H₅NO₆)(H₂O)₂]_n, (I), and poly[[bis(μ₅‐1‐aminobenzene‐3,4,5‐tricarboxylato)triaquatrizinc(II)] dihydrate], {[Zn₃(C₉H₄NO₆)₂(H₂O)₃]·2H₂O}_n, (II), have been prepared and structurally characterized by single‐crystal X‐ray diffraction. In polymer (I), each tridentate 1‐amino‐5‐carboxybenzene‐3,4‐dicarboxylate (Habtc^2?) ligand coordinates to three Cd^II ions to form a two‐dimensional network structure, in which all of the Cd^II ions and Habtc^2? ligands are equivalent, respectively. Polymer (II) also exhibits a two‐dimensional network structure, in which three crystallographically independent Zn^II ions are bridged by two crystallographically independent pentadentate 1‐aminobenzene‐3,4,5‐tricarboxylate (abtc^3?) ligands. This indicates that changing the metal ion can influence the coordination mode of the H₃abtc‐derived ligand and further influence the detailed architecture of the polymer. Moreover, the IR spectra, thermogravimetric analyses and fluorescence properties were investigated.     

Hydrothermal Syntheses and Crystal Structures of Two Layered Nickel(II) Coordination Polymers Based on 1,2,3‐Benzenetricarboxylic Acid

The hydrothermal reactions of Ni(II), 1,2,3‐benzenetricarboxylic acid (1,2,3‐H₃btc) and 4,4′‐bipyridine (4,4′‐bpy)/1,2‐bis(4‐pyridyl)ethane (bpa) yield two layered nickel(II) coordination polymers, [Ni₂(1,2,3‐btc)(OAc)‐(4,4′‐bpy)₂(H₂O)]·2H₂O ( 1 ) and [Ni(ip)(bpa)] ( 2 ) (ip=isophthalate), respectively. Both complexes are 2‐D coordination network based on 1‐D Ni‐carboxylate chains. The 1,2,3‐btc ligand adopts 3‐bridging mode in complex 1 , but transformed to isophthalate (ip) ligand through decarboxylation in 2 . The formation of the two complexes indicates that hydrothermal conditions andin‐situ ligand reaction have significant effect on constructing coordination polymers.     

Photochromism and decolorization controlled by auxiliary ligands of complexes derived from 1‐methyl‐4,4′‐bipyridinium cation

Three 1‐methyl‐4,4′‐bipyridinium (MQ⁺)‐based complexes, {[Cd(MQ)(p‐BDC)Br]?H₂O}_n ( 1 ), {[Cd(MQ)(m‐BDC)(H₂O)Br]?3H₂O}_n ( 2 ) and Cu(MQ)Br₂ ( 3 ) (p‐H₂BDC = 1,4‐benzenedicarboxylic acid, m‐H₂BDC = 1,3‐benzenedicarboxylic acid), have been synthesized and structurally characterized. Compounds 1 and 2 are one‐dimensional coordination polymers constituted of one coordinated MQ⁺ cation, one coordinated Br^? ion and chains of Cd²⁺ ions connected by deprotonated BDC^2? units, which both have photochromism but different decolorization behaviors. The structures and photoresponsive behaviors controlled by auxiliary ligands have been explored. Compound 3 is constituted of one Cu⁺ center, one MQ⁺ ligand and two coordinated Br^? ions in a ‘V’ configuration, exhibiting no photochromism.     

Construction of Four Coordination Polymers based on 2‐[4‐(Pyridine‐4‐yl)phenyl]‐1H‐imidazole‐4,5‐dicarboxylic Acid

The imidazole‐based dicarboxylate ligand 2‐(4‐(pyridin‐4‐yl)phenyl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PyPhIDC), was synthesized and its coordination chemistry was studied. Solvothermal reactions of Ca^II, Mn^II, Co^II, and Ni^II ions with H₃PyPhIDC produced four coordination polymers, [Ca(μ₃‐HPyPhIDC)(H₂O)₂]_n ( 1 ), {[M₃(μ₂‐H₂PyPhIDC)₂(μ₃‐HPyPhIDC)₂₆(H₂O)₂] · 6H₂O}_n [M = Mn ( 2 ), Co ( 3 )], and {[Ni(μ₃‐HPyPhIDC)(H₂O)] · H₂O}_n ( 4 ). Compounds 1 – 4 were analyzed by IR spectroscopy, elemental analyses, and single‐crystal and powder X‐ray diffraction. Compound 1 displays a one‐dimensional (1D) infinite chain. Compounds 2 and 3 are of similar structure, showing 2D network structures with a (4,4) topology based on trinuclear clusters. Compound 4 has another type of 2D network structure with a 3‐connected (4.8²) topology. The results revealed that the structural diversity is attributed to the coordination numbers and geometries of metal ions as well as the coordination modes and conformations of H₃PyPhIDC. Moreover, the thermogravimetric analyses of all the compounds as well as luminescence properties of the H₃PyPhIDC ligand and compound 1 were also studied.     

Construction of three types of lanthanide complexes based on 3,4‐dimethylbenzoic acid and 5,5′‐dimethyl‐2,2′‐bipyridine: Syntheses,Structures, Thermodynamic properties,Luminescence, and Bacteriostatic activities

Three novel lanthanide complexes [Er (3,4‐DMBA)₃(5,5′‐DM‐2,2′‐bipy)(H₂O)] ( 1 ); [Tb₂ (3,4‐DMBA)₆(5,5′‐DM‐2,2′‐bipy)₂(H₂O)] ( 2 ); [Eu (3,4‐DMBA)₃(3,4‐DMHBA)(5,5′‐DM‐2,2′‐bipy)]₂ ( 3 ) (3,4‐DMHBA = 3,4‐dimethylbenzoic acid, 5,5′‐DM‐2,2′‐bipy =5,5′‐dimethyl‐2,2′‐bipyridine) were successfully synthesized via conventional solution method at room temperature and structurally characterized by single crystal diffraction. The structures of the complexes 1 – 3 were confirmed on the basis of elemental analysis, coordination titration analysis, IR and XRD. The molecular structures of complexes 2 and 3 are very particular: complex 2 has two same central metal ions but each metal ion has different coordination environment; in structure of the complex 3 , there are eight carboxylic acid ligands coordinated to the central metal ions, which have rarely been reported previously. The thermal decomposition mechanism of complexes 1 – 3 were investigated by the technology of simultaneous TG/DSC‐FTIR. The heat capacities of the complexes were recorded by means of DSC over the range of from 253.15 K to 345.15 K. The thermodynamic parameters, the smoothed values of heat capacities, enthalpy (H_T‐H_298.15K) and entropy (S_T‐S_298.15K) were also calculated. The bacteriostatic activities of the complexes were evaluated against Staphylococcus aureus, Escherichia coli and Candida albicans. What's more, the luminescence properties of complexes 2 and 3 were discussed, and their fluorescence lifetimes as well as the quantum yield of the Eu (III) were measured. To elucidate the energy transfer process of complexes 2 and 3, the energy levels of the relevant electronic states have been estimated.     

Triazine‐Cored Lanthanide‐Based Metal–Organic Frameworks Featuring Unique Water Chains and Strong Characteristic Emissions

A new triazine‐cored tricarboxylic acid, N,N′,N“‐1,3,5‐triazine‐2,4,6‐triyltris(cis‐4‐aminocyclohexane‐carboxylic acid) (H₃L), has been prepared by replacing the chlorine atoms of cyanuric chloride with cis‐4‐aminocyclohexane‐carboxylic acid, which has been used for the construction of a series of triazine‐cored lanthanide‐based metal–organic frameworks (MOFs). All these MOFs were structurally authenticated, revealing that they are isostructural and exist as two‐dimensional (2D) coordination networks with the general formula [Ln(L)(H₂O)₂]?5.5 H₂O (Ln= 1?Gd , 2?Tb , 3?Eu ). A unique one‐dimensional water chain, composed of primary tetrameric cyclic rings and dodecameric cyclic rings, has been found entrapped in the lattice. Moreover, all these compounds display bright characteristic photoluminescence. Particularly, for 1 , apart from the strong blue emission peak (Φ_f=20.6 %) corresponding to the intraligand transition under near‐UV excitation, the characteristic emissions of Gd³⁺ cation (Φ_f=5.0 %) were unexpectedly observed upon excitation at 273 nm.     

Two Coordination Polymers Constructed from Pillared M–O (M = Na+ or Ba2+) Subunits with 3‐Formyl‐4‐hydroxybenzenesulfonic Acid as Ligand

Two new coordination polymers, [Na(H₂L)(H₂O)₂]_n ( 1 ) and [Ba(H₂L)₂(H₂O)]_n ( 2 ) (H₃L = 3‐formyl‐4‐hydroxybenzenesulfonic acid) were synthesized and structurally characterized. The H₂L^– ligand shows three different bridging modes, μ₃ in 1 , μ₃ and μ₄ in 2 . Compound 1 presents a 2D pillared structure, whereas 2 forms a 3D framework. Both 1 and 2 show blue luminescence at 380 nm in aqueous solution, however, their solid state emissions are at 406 and 446 nm, respectively.     

A new two‐dimensional managnese(II) coordination polymer constructed by 2,2′‐(1,2‐phenylene)bis(1H‐imidazole‐4,5‐dicarboxylate)

In recent years, N‐heterocyclic carboxylate ligands have attracted much interest in the preparation of new coordination polymers since they contain N‐atom donors, as well as O‐atom donors, and have a rich variety of coordination modes which can lead to polymers with intriguing structures and interesting properties. A new two‐dimensional coordination polymer, namely poly[[μ₃‐2,2′‐(1,2‐phenylene)bis(4‐carboxy‐1H‐imidazole‐5‐carboxylato)‐κ⁶O⁴,N³,N^3′,O^4′:O⁵:O^5′]manganese(II)], [Mn(C₁₆H₈N₄O₈)]_n or [Mn(H₄Phbidc)]_n, has been synthesized by the reaction of Mn(OAc)₂·4H₂O (OAc is acetate) with 2,2′‐(1,2‐phenylene)bis(1H‐imidazole‐4,5‐dicarboxylic acid) (H₆Phbidc) under solvothermal conditions. In the polymer, each Mn^II ion is six‐coordinated by two N atoms from one H₄Phbidc²⁻ ligand and by four O atoms from three H₄Phbidc²⁻ ligands, forming a significantly distorted octahedral MnN₂O₄ coordination geometry. The Mn^II ions are linked by hexadentate H₄Phbidc²⁻ ligands, leading to a two‐dimensional structure parallel to the ac plane. In the crystal, adjacent layers are further connected by N—H…O hydrogen bonds, forming a three‐dimensional structure in the solid state.     

Synthesis,Crystal Structures,and Properties of Copper(II), Zinc(II), and Cadmium(II) Coordination Polymers Based on 5‐Nitro‐isophthalate and 1,2‐(2‐Pyridyl)‐1,2,4‐triazole

Three coordination polymers, namely {[Cu(5‐nipa)(L²²)](H₂O)₂}_n ( 1 ), [Zn(5‐nipa)(L²²)(H₂O)]_n ( 2 ), and {[Cd₂(5‐nipa)₂(L²²)(H₂O)₃](H₂O)_3.6}_n ( 3 ), were prepared under similar synthetic method based on 1,2‐(2‐pyridyl)‐1,2,4‐triazole (L²²) and ancillary ligand 5‐nitro‐isophthalic acid (5‐H₂nipa) with Cu^II, Zn^II, and Cd^II perchlorate, respectively. All the complexes were characterized by IR spectroscopy, elemental analysis, and powder X‐ray diffraction (PXRD) patterns. Single‐crystal X‐ray diffraction indicates that complexes 1 and 2 show similar 1D chain structures, whereas complex 3 exhibits the 2D coordination network with hcb topology. The central metal atoms show distinct coordination arrangements ranging from distorted square‐pyramid for Cu^II in 1 , octahedron for Zn^II in 2 , to pentagonal‐bipyramid for Cd^II in 3 . The L²² ligand adopts the same (η³,μ₂) coordination fashion in complexes 1 – 3 , while the carboxyl groups of co‐ligand 5‐nipa^2– adopt monodentate fashion in 1 and 2 and bidentate chelating mode in 3 . These results indicate that the choice of metal ions exerts a significant influence on governing the target complexes. Furthermore, thermal stabilities of complexes 1 – 3 and photoluminescent properties of 2 and 3 were also studied in the solid state.     

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln₄K⁴ L₆(H₂O)_x]?yH₂O}_n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H₂L (H₂L= L ‐DTTA) with LnCl₃?6 H₂O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln³⁺ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.