Crystal Engineering of Schiff Base Zn(II) and Cd(II) Homo- and Zn(II)M(II) (M = Mn or Cd) Heterometallic Coordination Polymers and Their Ability to Accommodate Solvent Guest Molecules

Based on solvothermal synthesis, self-assembly of the heptadentate 2,6-diacetylpyridine bis(nicotinoylhydrazone) Schiff base ligand (H₂L) and Zn(II) and/or Cd(II) salts has led to the formation of three homometallic [CdL]_n (1), {[CdL]∙0.5dmf∙H₂O}_n (2) and {[ZnL]∙0.5dmf∙1.5H₂O}_n (3), as well as two heterometallic {[Zn_0.75Cd_1.25L₂]∙dmf∙0.5H₂O}_n (4) and {[MnZnL₂]∙dmf∙3H₂O}_n coordination polymers. Compound 1 represents a 1D chain, whereas 2–5 are isostructural and isomorphous two-dimensional structures. The entire series was characterized by IR spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction and emission measurements. 2D coordination polymers accommodate water and dmf molecules in their cage-shaped interlayer spaces, which are released when the samples are heated. Thus, three solvated crystals were degassed at two temperatures and their photoluminescent and adsorption–desorption properties were recorded in order to validate this assumption. Solvent-free samples reveal an increase in volume pore, adsorption specific surface area and photoluminescence with regard to synthesized crystals.     

Synthesis,crystal structure,spectroscopic and thermal investigations of neodymium(III) biphenyl-4,4′-dicarboxylate framework

The three-dimensional complex {[Nd(bpdc)_1.5(DMF)]·1.4DMF}_n (DMF=N,N′-dimethylformamide, bpdc=biphenyl-4,4′-dicarboxylate) was synthesized using the solvothermal method. The crystal structure of the neodymium(III) complex has been determined by single-crystal X-ray diffraction method at 100(2) K. The polymeric structure consists of neodymium polyhedra bridged by bpdc ligands. Eight-coordinated Nd(III) atoms are surrounded by seven oxygen atoms from six bpdc moieties and one oxygen atom from the DMF molecule. The 3D structure of the complex contains two types of channels occupied by DMF molecules. Thermal analysis revealed that DMF molecules are lost in a stepwise manner. The infrared spectrum confirmed full deprotonation of acid and presence of DMF molecules in the structure.      

Zinc coordination polymers with rigid dicarboxylates and semirigid 3,5-bis(imidazole-1-yl) pyridine: syntheses,structural topologies,and luminescent properties

Two metal coordination polymers, {[Zn(bpdc)(bip)]·2H₂O}_n (1) and [Zn(tdc)(bip)] (2) [H₂bpdc?=?biphenyl-4,4’-dicarboxylate, H₂tdc?=?thiophene-2,5-dicarboxylate, bip?=?3,5-bis(imidazole-1-yl)pyridine], have been synthesized and characterized by IR, elemental analysis, XRD, and X-ray single-crystal diffraction. In 1, bpdc and bip link Zn(II) ions into a corrugated 2D layer. The corrugated 2D layers polycatenate each other, yielding a 2D→3D polycatenation net. In 2, dinuclear Zn(II) units are formed by bip and further connected by tdc to construct a 2D 3-connected framework. The luminescent properties of 1 and 2 are investigated in the solid state at room temperature.     

Solution equilibria of zinc(II) and cadmium(II) complexes with 2,2′-bipyridine in N,N-dimethylacetamide at 25°C

Complexation of zinc(II) and cadmium(II) ions with 2,2-bipyridine (bpy) are studied in N,N-dimethylacetamide (DMA) by calorimetry. Formation constants, enthalpies, and entropies of five mononuclear complexes, [Zn(bpy)_n]²⁺ (n=1–3) and [Cd(bpy)_n]²⁺ (n=1,2), are determined, and compared with the corresponding values in an analogous but less bulky solvent, N,N-dimethylformamide (DMF). The zinc complexes are more stable and the formation is more exothermic in DMA than in DMF, whereas the solvent effect on the cadmium complexes are rather small. A largely positive value of the enthalpy of transfer of Zn²⁺ from DMF to DMA shows that the greater stability of the zinc complexes in DMA is due to the weaker solvation of the metal ion, which is caused by the steric hindrance of DMA molecules. The transfer enthalpies become smaller in the order Zn²⁺>[Zn(bpy)]²⁺>[Zn(bpy)₂]²⁺>[Zn(bpy)₃]²⁺ and dictate gradual relaxation of the steric effect in the complexes. On the other hand, the transfer enthalpies of Cd²⁺ and its complexes are all small, indicating that the hindrance is insignificant in the vicinity of this larger cation.     

Construction Of Two New 6‐connected Manganese(II) Metal Organic Frameworks via Isomeric Biphenyldicarboxylates Based on the Dinuclear Secondary Building Unit

Two coordination polymers, namely {[Mn(2,4′‐bpdc)(bimb)(H₂O)_0.5] · 0.5H₂O}_n ( 1 ) and [Mn(4,4′‐bpdc)(bimb)]_n · 2.5H₂O ( 2 ) [2,4′‐bpdc = biphenyl‐2,4′‐dicarboxylate, 4,4′‐bpdc = biphenyl‐4,4′‐dicarboxylate, and bimb = 1,4‐bis(1‐imidazol‐yl)‐2,5‐dimethyl benzene], were hydrothermally synthesized by reactions of manganese(II) salt with the rigid ligand 1,4‐bis(1‐imidazol‐yl)‐2,5‐dimethyl benzene and isomeric biphenyl dicarboxylate ligands. Complex 1 has an unusual 6‐connected three‐dimensional (3D) architecture with point symbol (4⁴.6¹¹). Complex 2 has also a 3D structure with two‐interpenetrated pcu topology with point symbol (4¹².6³). Structural comparisons show that the positions of the carboxylate groups in the ligand backbone play an important role in governing the structural topologies of these complexes.     

Syntheses and Crystal Structures of a Series of Coordination Polymers Constructed From C2‐Symmetric Ligand 1,3‐Adamantanedicarboxylic Acid

This article systematically investigates the influence of the properties of inhomogeneous N‐auxiliary ligands and pH value on the helical structures of complexes based on C₂‐symmetric ligand 1,3‐adamantanedicarboxylic acid (H₂ADC). Five kinds of neutral ligands (phen=1,10‐phenanthroline, bipy=4,4′‐bipyridine, bpa=1,2‐bis(4‐pyridyl)ethane, bpe=1,2‐bis(4‐pyridyl)ethane, and bpp=1,3‐bis(4‐pyridyl)propane) were selected, and a series of new Zn^II/Co^II dicarboxylates have been synthesized by slow diffusion, namely, [Zn(phen)(ADC)(H₂O)]₂ ? CH₃OH ( 1 ), {[Zn(ADC)(bpe)] ? H₂O}_n ( 2 ), {[Zn(ADC)(bipy)] ? 2 H₂O}_n ( 3 ), {[Zn(ADC)(bpa)]₂ ? 5 H₂O}_n ( 4 ), {[Zn(ADC)(bpp)]₂ ? CH₃OH}_n ( 5 ), {[Zn(ADC)(bpp)]}_n ( 6 ), {[Co(ADC)(bpp)(CH₃OH)(H₂O)] ? CH₃OH ? 2 H₂O}_n ( 7 ), and {[Co(ADC)(bpp)]}_n ( 8 ). Single‐crystal X‐ray structural analysis shows that complex 1 forms a 0D dinuclear with closed‐loop unit. The complex 2 is a 2D layer framework. Compounds 3 and 4 are isomorphous with a small discrepancy and present one‐dimensional chainlike structures. It is interesting that the 2D organic–inorganic hybrid frameworks containing meso‐helical chains have been observed. Compound 5 is a 2D interpenetrated network with (4,4) topology, in which homochiral left‐handed helical chains are arranged in an ABAB sequence parallel to the plane defined by (a,c), and right‐handed helical chains running along the a axis are also observed in the solid state, resulting in a meso‐helical structure. Compounds 6 , 7 , and 8 crystallize in a chiral space group P212121. Highly dimensional 6 and 8 are essentially isostructural and present a threefold interpenetrated 3D diamondoid network containing three helical chains, whereas 7 exhibits a 2D grid layer with a left‐handed helical chain. Furthermore, thermal stability, X‐ray powder diffraction, and the luminescent properties of 1 , 2 , 3 , 4 , 5 , 6 are also discussed.     

Syntheses,Structures and Characterization of Four Metal‐Organic Frameworks constructed by 2,2′,6,6′‐Tetramethoxy‐4,4′‐biphenyldicarboxylic Acid

Four metal‐organic frameworks (MOFs), {[Mn_3.5L(OH)(HCOO)₄(DMF)] · H₂O} ( 1 ), {[In_2.5L₂O(OH)_1.5(H₂O)₂] · DMF · CH₃CN · 2H₂O} ( 2 ), {[Pb₄L₃O(DMA)] · CH₃CN} ( 3 ), and {[LaL(NO₃)(DMF)₂] · 2H₂O} ( 4 ) were synthesized by utilizing the ligand 2,2′,6,6′‐tetramethoxy‐4,4′‐biphenyldicarboxylic acid (H₂L) via solvothermal methods. All MOFs were characterized by single‐crystal X‐ray diffraction, powder X‐ray diffraction, thermogravimetric analysis, and infrared spectroscopy. In 1 , the Mn²⁺ ions are interconnected by formic groups in situ produced via DMF decomposition to form a rare 2D macrocyclic plane, which is further linked by L^2– to construct the final 3D network. In 2 , 1D zip‐like infinite chain is formed and then interconnected to build the 3D framework. In 3 , a [Pb₆(μ₄‐O)₂(O₂C)₁₀(DMA)₂] cluster with a centrosymmetric [Pb₆(μ₄‐O)₂]⁸⁺ octahedral core is formed in the 3D structure. In 4 , the La³⁺ ions are connected with each other through carboxylate groups of L^2– to generate 1D zigzag chain, which is further linked by L^2– to construct a 3D network with sra topology. Solid photoluminescence properties of 3 and 4 were also investigated.     

A Cd(II) Luminescent Coordination Grid as a Multiresponsive Fluorescence Sensor for Cr(VI) Oxyanions and Cr(III), Fe(III), and Al(III) in Aqueous Medium

Hydro(solvo)thermal reactions of Cd(NO₃)₂, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H₂bdc) afforded a luminescent coordination polymer, {[Cd(Br-1,3-bdc)(NI-mbpy-34)(H₂O)]∙2H₂O}_n (1). Single-crystal X-ray diffraction analysis showed that 1 features a two-dimensional (2-D) gridlike sql layer with the point symbol of (4⁴·6²), where the Cd(II) center adopts a {CdO₅N₂} pentagonal bipyramidal geometry. Thermogravimetric (TG) analysis confirmed the thermal stability of 1 up to about 340 °C, whereas XRPD patterns proved the maintenance of crystallinity and framework integrity of 1 in CH₂Cl₂, H₂O, CH₃OH, and toluene. Photoluminescence studies indicated that 1 displayed intense blue fluorescence emissions in both solid-state and H₂O suspension-phase. Owing to the good fluorescent properties, 1 could serve as an excellent turn-off fluorescence sensor for selective and sensitive Cr(VI) detection in water, with LOD = 15.15 μM for CrO₄²⁻ and 14.91 μM for Cr₂O₇²⁻, through energy competition absorption mechanism. In addition, 1 could also sensitively detect Cr³⁺, Fe³⁺, and Al³⁺ ions in aqueous medium via fluorescence-enhancement responses, with LOD = 2.81 μM for Cr³⁺, 3.82 μM for Fe³⁺, and 3.37 μM for Al³⁺, mainly through an absorbance-caused enhancement (ACE) mechanism.     

Supramolecular Architectures with Open Frameworks Constructed by Transitional Metal Ions,Linear Dicarboxylic Acid,and 2,2′‐Bipyridine

Four new transitional metal supramolecular architectures, [Zn(cca)(2,2′‐bpy)]_n · n(2,2′‐bpy) ( 1 ), [Cu(cca)(2,2′‐bpy)]_n ( 2 ), [Zn(bpdc)(2,2′‐bpy)(H₂O)]_n · 0.5nDMF · 1.5nH₂O ( 3 ), and [Co(bpdc)(2,2′‐bpy)(H₂O)]_n · nH₂O ( 4 ) (H₂cca = p‐carboxycinnamic acid; H₂bpdc = 4,4′‐biphenyldicarboxylic acid; 2,2′‐bpy = 2,2′‐bipyridine) were synthesized by hydrothermal reactions and characterized by single crystal X‐ray diffraction, elemental analyses, and IR spectroscopy. Although the metal ions in these four compounds are bridged by linear dicarboxylic acid into 1D infinite chains, there are different π–π stacking interactions between the chains, which results in the formation of different 3D supramolecular networks. Compound 1 is of a 3D open‐framework with free 2,2′‐bpy molecules in the channels, whereas compound 2 is of a complicated 3D supramolecular network. Compounds 3 and 4 are isostructural. Both compounds have open‐frameworks.     

杂金属杯[4]配位聚合物的合成与表征

合成了4个杂金属杯[4]配位聚合物{[Cd（L）（tpa）]·3H₂O}_n（1）,{[Zn2（L）₂（tpa）₂]·3H₂O}_n（2）,{[Co（L）（oba）]·2DMA·0.5H₂O}_n（3）和{[Zn（L）（oba）]·DMA}_n（4）（L=2-（1H-咪唑基-甲基）-6-（3-（1H-咪唑基-甲基）-5-叔丁基-2-羟基）苄基-4-叔丁基苯酚,H₂tpa=对苯二甲酸,H₂oba=4,4''-二苯醚二甲酸）,并通过元素分析、热重、红外光谱、固态紫外、单晶X射线衍射和粉末X射线衍射对其进行了表征。单晶结构分析表明晶体1是单斜晶系,P2₁/n空间群,而晶体2,3和4均为三斜晶系,P1空间群。化合物1,2,3和4是由0维[M（N₄O₂C₂₉H₃₆）]（M=Zn,Co,Cd）的杂金属杯[4]与配体对苯二甲酸和4,4''-二苯醚二甲酸形成的一维配位聚合物。     

Self-Assembly of ZnII/CdII/PbII Coordination Polymers with a Tripodal Ligand Derived from Aromatase Inhibitor Letrozole Derivative

Reactions of the aromatase inhibitor letrozole derivative 4,4'-(1H-1,2,4-triazol-1-yl)methylene-bis(benzonic acid) (H₂tzmb) with Zn^II, Cd^II, or Pb^II salts under similar conditions resulted in the generation of three coordination polymers, namely, {[Zn(tzmb)(H₂tzmb)] · H₂O}_n ( 1 ), [Cd(tzmb)(H₂O)₂]_n ( 2 ), and {[Pb(tzmb)(H₂O)] · DMF}_n ( 3 ), respectively. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, and thermogravimetric analyses. Complex 1 features a twofold 2D → 2D interpenetrated network based on corrugated 6³- hcb layers, and complex 2 exhibits a flat 2D 4.8²- fes network, whereas complex 3 presents a 3D hex net based on infinite rod-shaped secondary building units. The remarkable structural diversity may illustrate the powerful effect of metal ions on coordination assemblies. The spectroscopic, thermal, and photoluminescent properties of complexes 1 – 3 were investigated. In addition, the catalytic activity of 1 in the solvent-free ring-opening polymerization of ε-caprolactone was also discussed.     

A zinc(II)-based two-dimensional MOF for sensitive and selective sensing of HIV-1 ds-DNA sequences

Coordination reaction of a known three-dimensional (3D) polymer precursor {Na₃[Na₉(Cbdcp)₆(H₂O)₁₈]}_n (A, Cbdcp = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium) with Zn(NO₃)₂·6H₂O in H₂O or H₂O/DMF at 100 °C and in the presence of aspirin, 5-fluorouracil (5-FU) as modulators, trans-1,2-bis(4-pyridyl)ethylene (bpe) or 1,2-bis(4-pyridyl)ethane (bpea) as ancillary ligands afforded six novel Zn(II)-based metal-organic frameworks (MOFs), that is, {[Zn(Cbdcp)(H₂O)₃]·H₂O}_n (1, 1D zigzag chain), {[Zn(HCbdcp)₂]·H₂O}_n (2, 2D sheet), {[Zn(Cbdcp)(bpe)_1/2]·2H₂O}_n (3, 3D polymer), {[Zn(Cbdcp)(bpe)_1/2]·2H₂O}_n (4, 2D network), {[Zn(Cbdcp)(bpea)_1/2]·2H₂O}_n (5, 3D polymer) and {[Zn(Cbdcp)(bpea)_1/2]·2H₂O}_n (6, 2D network). Among them, compound 2 contains aromatic rings, positively charged pyridinium, Zn²⁺ cation centers and carboxylic acid groups lined up on the 2D sheet structure with a certain extended surface exposure. The unique structure of 2 facilitates effective association with carboxyfluorescein (FAM) labeled probe single stranded DNA (probe ss-DNA, delineates as P-DNA) to yield a P-DNA@2 system, and leads to fluorescence quenching of FAM via a photoinduced electron transfer process. The P-DNA@2 system is effective and reliable for the detection of human immunodeficiency virus 1 ds-DNA (HIV ds-DNA) sequences and capable of distinguishing complementary HIV ds-DNA from mismatched target sequences with the detection limit as low as 10 pM (S/N = 3).     

杂金属杯[4]配位聚合物的合成与表征

合成了4个杂金属杯[4]配位聚合物{[Cd（L）（tpa）]·3H₂O}_n（1）,{[Zn₂（L）₂（tpa）₂]·3H₂O}_n（2）,{[Co（L）（oba）]·2DMA·0.5H₂O}_n（3）和{[Zn（L）（oba）]·DMA}_n（4）（L=2-（1H-咪唑基-甲基）-6-（3-（1H-咪唑基-甲基）-5-叔丁基-2-羟基）苄基-4-叔丁基苯酚,H₂tpa=对苯二甲酸,H₂oba=4,4''-二苯醚二甲酸）,并通过元素分析、热重、红外光谱、固态紫外、单晶X射线衍射和粉末X射线衍射对其进行了表征。单晶结构分析表明晶体1是单斜晶系,P2₁/n空间群,而晶体2,3和4均为三斜晶系,P1空间群。化合物1,2,3和4是由0维[M（N₄O₂C₂₉H₃₆）]（M=Zn,Co,Cd）的杂金属杯[4]与配体对苯二甲酸和4,4''-二苯醚二甲酸形成的一维配位聚合物。     

含磷钼酸及2,2’-联吡啶-3,3’-二羧酸配体的铜配位聚合物的合成、晶体结构与电化学性质

在水热条件下合成了一个新的化合物{[Cu₄(PMo₁₂O₄₀)(H₂O)₅(H₂bpdc)(Hbpdc)(bpdc)₂]·6H₂O}_n(H₂bpdc=2, 2’-联吡啶-3, 3’-二羧酸), 并用元素分析、IR、TG和X-射线衍射等手段进行了表征。结果表明本化合物的晶体结构中, 最小不对称单元包含1个 [Cu₄(H₂O)₅(H₂bpdc)(Hbpdc)(bpdc)₂]³⁺阳离子, 1个[PMo₁₂O₄₀]^3-阴离子和6个结晶水分子。Cu(Ⅱ)与相邻[PMo₁₂O₄₀]^3-的桥氧原子配位, 形成一维链状结构。电化学研究表明, 化合物存在三步氧化还原过程。     

两个基于Cd(Ⅱ)金属有机骨架化合物在金属离子和有机分子发光传感中的应用

合成了2个镉（Ⅱ）金属有机骨架化合物{[Cd（L）（fma）]·0.5H₂O}_n（1）和{[Cd（L）_0.5（sdb）]·DMF}_n（2）（L=E,E-2,5-二己氧基-1,4-双（2-乙烯-吡啶基）苯,H₂fma=延胡酸,H₂sdb=4,4''-磺酰基二苯甲酸）,研究了它们在金属离子和有机分子的发光传感中的应用。结果表明,Fe³⁺对配位聚合物1和2的发光强度有明显的猝灭作用。此外,聚合物1和2还对水杨醛具有明显的猝灭能力。     

Four Co(II)/Zn(II) coordination polymers with a multidentate ligand: syntheses,structures, thermal,and photoluminescent properties

Two pairs of isostructural transition metal coordination polymers, {[Co(L)(H₂O)]_n} (1) and {[Zn(L)(H₂O)]_n} (3), {[Co(L)(4,4′-bipy)(H₂O)]·H₂O}_n (2) and {[Zn(L)(4,4′-bipy)(H₂O)]·H₂O}_n (4) (H₂L = N-pyrazinesulfonyl-glycine acid and 4,4′-bipy = 4,4′-bipyridine), have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental and thermogravimetric analyses. The structures show that 1 and 3 display 2-D polymeric grid frameworks with a 3-connected (4, 8²) topology. 2 and 4 also exhibit a 2-D polymeric grid structure, but are constructed by a 4-connected (4, 4) topology. The adjacent 2-D polymeric grid frameworks for 1–4 are further linked by hydrogen bonding O–H?O interactions to form 3-D supramolecular interweaved orderly networks. The fluorescent properties of 3 and 4 were investigated in the solid state.     

1-D wave-like chain,twofold 2-D layer,and chiral 3-D open framework based on multidentate ligand: structural diversities,thermal properties,and photoluminescence

From 1-D to 3-D zinc coordination polymers based on multifunctional flexible 4-(1,2,4-triazole-methylene)-benzonitrile (tzbt), {[Zn(tzbt)₂(bdc)]·2H₂O}_n (1), [Zn(tzbc)₂]_n (2), and [Zn(bpdc)(H₂O)]_n (3) (bdc = 1,4-benzenedicarboxylic acid, tzbc = 4-(1,2,4-triazole-methylene)-benzoic acid, bpdc = 4,4′-biphenyldicarboxylic acid), were synthesized under hydrothermal conditions. The tzbt was synthesized by N-alkylation and hydrolyzed in situ to produce tzbc (in 2). Single-crystal X-ray diffraction analysis reveals that 1 displays 1-D wave-like chains based on [Zn(bdc)]_n. 2 is a chiral twofold interpenetrating 2-D architecture constructed with “V”-shaped tzbc. 3 is a 3-D chiral compound constructed from achiral H₂bpdc with right-handed helical chains. 1–3 display stable blue-emitting luminescence with emission maxima ranging from 383 to 410 nm, depending on ligand-centered π*→π transitions. The effects of different polarity solvents and temperature on luminescence are discussed. TGA and VT-XPRD reveal that 2 has thermal stability to 360 °C.     

肉桂酸及其衍生物的Eu(Ⅲ)配合物的合成、结构及荧光性质研究

以肉桂酸C9H8O2(HL)及其衍生物对位取代肉桂酸R-L(R=CH3,Cl,NO2,OCH3,OH)为配体,分别与Eu3+配位,得到系列Eu3+配合物。X-射线单晶解析结果表明:对甲基肉桂酸铕(1)和对氯肉桂酸铕(2)为一维高分子链,对硝基肉桂酸铕(3)为双核结构。通过FT-IR和UV-Vis光谱分析了配体在配位前后的变化。记录和解析了各配合物的荧光光谱,研究了对位取代基吸电子性和配位小分子对配合物发光性能的影响。     

Solvothermal Syntheses,Crystal Structures,and Luminescent Properties of Two Coordination Polymers with Different Interpenetrated Diamond Topology

Two coordination polymers, namely, {[Zn(bpea) (bmp)] · H₂O}_n ( 1 ) and {[Ni(bpea)(bimb)] · DMF}_n ( 2 ) [H₂bpea = biphenylethene‐4,4′‐dicarboxylate, bmp = 1,4‐bis(2‐methylimidazol‐3‐ium‐1‐yl)biphenyl and bimb = 1,4‐bis(1‐imidazol‐yl)‐2,5‐dimethyl benzene], were synthesized under solvothermal conditions with mixed organic ligands. Single crystal X‐ray diffraction reveals that complex 1 features a three‐dimensional (3D) structure with a sixfold interpenetrating dia net. Complex 2 shows a 3D fivefold interpenetrating dia topology. Furthermore, the solid state luminescent properties of complexes 1 and 2 were investigated at room temperature.     

A Systematic Study of Fluorescence‐Based Detection of Nitroexplosives and Other Aromatics in the Vapor Phase by Microporous Metal–Organic Frameworks

A systematic study is conducted on four microporous metal–organic framework compounds built on similar ligands but different structures, namely [Zn₃(bpdc)₃(bpy)] ? 4 DMF ? H₂O ( 1 ), [Zn₃(bpdc)₃(2,2′dmbpy)] ? 4 DMF ? H₂O ( 2 ), [Zn₂(bpdc)₂(bpe)] ? 2 DMF ( 3 ), and [Zn(bpdc)(bpe)] ? DMF ( 4 ) (bpdc=4,4′‐biphenyldicarboxylate; bpy=4,4′‐bipyridine; 2,2′dmbpy=2,2′‐dimethyl‐4,4′bipyridine; bpe=1,2‐bis(4‐pyridyl)ethane; DMF=N,N′‐dimethylformamide) to investigate their photoluminescence properties and sensing/detection behavior upon exposure to vapors of various aromatic molecules (analytes) including nitroaromatic explosives. The results show that all four compounds are capable of detecting these molecules in the vapor phase through fluorescence quenching or enhancement. Both electrochemical measurements and theoretical calculations are performed to analyze the analyte–MOF interactions, to explain the difference in signal response by different analytes, and to understand the mechanism of fluorescence quenching or enhancement observed in these systems. Interestingly, compound 3 also shows an emission frequency shift when exposed to benzene (BZ), chlorobenzene (ClBZ), and toluene (TO), which provides an additional variable for the identification of different analytes in the same category.