A stable Mn(II) coordination polymer demonstrating proton conductivity and quantitative sensing of oxytetracycline in aquaculture.

The construction and investigation of dual-functional coordination polymers (CPs) with proton conduction and luminescence sensing is of great significance in clean energy and agricultural monitoring fields. In this work, an Mn-based coordination polymer (Mn-CP), namely, [Mn0.5(HL)] (H2L = HOOCC6H4C6H4CH2PO(OH)OCH3), was hydrothermally synthesized. Mn-CP has a one-dimensional (1D) chain structure, in which uncoordinated -COOH groups can serve as potential sites for fluorescence sensing. Moreover, Mn-CP shows good water and pH stabilities, offering the feasibility for proton conduction and sensing applications. Mn-CP displays comparatively high proton conductivity of 1.07 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), which is promising for proton conduction materials. Moreover, it can serve as a repeatable, highly selective, and visualized fluorescence sensor for detecting oxytetracycline (OTC). More importantly, Mn-CP reveals an amazing quantitative sensing of OTC in actual samples such as seawater, aquaculture freshwater, soil infiltration solutions, and tap water. This work proves the excellent application potential of dual-functional CPs in the field of clean energy and environmental protection, especially for the fluorescence detection of antibiotics in aquaculture systems.

Construction and Application of Fluorescent Probes with Imine Protective Groups for Hypochlorite Detection.

Several fluorescent probes have been designed to detect ClO- in biological systems based on the isomerization mechanism of C = N bonds. Particularly, fluorescein has emerged as an important fluorophore for detecting ClO- because of its unique properties. Previously, we introduced the fluorescein analog F-1 with an active aldehyde group. In this study, two ClO- fluorescent sensors (F-2 and F-3) with imine groups were designed and synthesized using diaminomaleonitrile and 2-hydrazylbenzothiazole as amines. The electron cloud distribution of F-2 and F-3 in ground and excited states was explored via Gaussian calculations, reasonably explaining their photophysical properties. The fluorescence detection of ClO- in solution using the two probes (F-2 and F-3) was realized based on the mechanism of imine deprotection with ClO-. NaClO concentration titration demonstrated that the colorimetric detection of ClO- with the naked eye could be achieved using both F-2 and F-3. However, after adding ClO-, the fluorescence intensity of probe F-2 increased, whereas that of probe F-3 first decreased and then increased. Probes F-2 and F-3 exhibited good selectivity, anti-interference capability, and sensitivity, with the detection limits of 169.95 and 37.30 µM, respectively. Owing to their low cell toxicity, probes F-2 and F-3 can be applied to detect ClO- in vivo. The design approach adopted in this study will further advance the future development of ClO- chemical probes through the removal of C = N bond isomerization.

Dual-Functional Eu-Metal-Organic Framework with Ratiometric Fluorescent Broad-Spectrum Sensing of Benzophenone-like Ultraviolet Filters and High Proton Conduction.

The construction of attractive dual-functional lanthanide-based metal-organic frameworks (Ln-MOFs) with ratiometric fluorescent detection and proton conductivity is significant and challenging. Herein, a three-dimensional (3D) Eu-MOF, namely, [Eu4(HL)2(SBA)4(H2O)6]·9H2O, has been hydrothermally synthesized with a dual-ligand strategy, using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L = H2O3PCH2-NC5H9-COOH) and 4-sulfobenzoic acid monopotassium salt (KHSBA = KO3SC6H4COOH) as organic linkers. Eu-MOF showed ratiometric fluorescent broad-spectrum sensing of benzophenone-like ultraviolet filters (BP-like UVFs) with satisfactory sensitivity, selectivity, and low limits of detection in water/ethanol (1:1, v/v) solutions and real urine systems. A portable test paper was prepared for the convenience of actual detection. The potential sensing mechanisms were thoroughly analyzed by diversified experiments. The synergistic effect of the forbidden energy transfer from the ligand to Eu3+, the internal filtration effect (IFE), the formation of a complex, and weak interactions between the KHSBA ligand and BP-like UVFs is responsible for the ratiometric sensing effect. Meanwhile, Eu-MOF displayed relatively high proton conductivity of 2.60 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), making it a potential material for proton conduction. This work provides valuable guidance for the facile and effective design and construction of multifunctional Ln-MOFs with promising performance.

Highly pH-stable lanthanide MOFs: a tunable luminescence and ratiometric luminescent probe for sulfamethazine.

By selecting a bisphosphonic ligand H4L (H4L = 4-F-C6H4CH2N(CH2PO3H2)2) and a coligand oxalate (H2C2O4), three isostructural lanthanide metal-organic frameworks (Ln-MOFs) with a 2D layer structure, [Ln(H3L)(C2O4)]·2H2O (Ln = Eu (1), Gd (2), or Tb (3)), were hydrothermally prepared. By tuning the molar ratio of Eu3+, Gd3+, and Tb3+ in the above reactions, six bimetallic or trimetallic doped Ln-MOFs (EuxTb1-x (x = 0.02 (4), 0.04 (5), and 0.06 (6)), Gd0.94Eu0.06 (7), Gd0.96Tb0.04 (8) and Gd0.95Tb0.03Eu0.02 (9)) were obtained. The powder X-ray diffraction (PXRD) patterns of doped Ln-MOFs 4-9 show that they are isomorphous with 1-3. The bimetallic doped Ln-MOFs show a gradual variation of luminous colors between yellow-green, yellow, orange, pink, and light blue. Meanwhile, the trimetallic doped Gd0.95Tb0.03Eu0.02 Ln-MOF (9) displays near white-light emission with a quantum yield of 11.39%. Interestingly, the luminous inks of 1-9 are invisible and color tunable, which makes it possible to promote their anti-counterfeiting applications. Additionally, 3 displays good thermal, water, and pH stabilities, which provides the feasibility for its sensing application. The luminescence sensing experiments show that 3 can serve as a highly selective, reusable, and ratiometric luminescent sensor of sulfamethazine (SMZ). Moreover, 3 shows an excellent SMZ detection performance in real samples, such as mariculture water and real urine. Owing to the visible variation of the response signal under a UV lamp, portable SMZ test paper was prepared.

Post-synthetic functionalization of Zn-CP by Tb3+ ions: a ratiometric luminescent sensor for the ultraviolet filter benzophenone.

Developing high-accuracy luminescent sensors for detecting emerging environmental pollutants is of great importance and is still a challenge. Utilizing a 4-carboxyphenylphosphonic acid (H3pbc) ligand, a novel one-dimensional (1D) Zn-based coordination polymer with the formula [Zn2(Hpbc)2(2,2'-bipy)(H2O)]·H2O (Zn-CP, H3pbc = 4-HOOCC6H4PO3H2, 2,2'-bipy = 2,2'-bipyridine) has been hydrothermally synthesized. Each of the 1D chains was linked via π-π stacking interactions and formed a supramolecular framework. Furthermore, due to the existence of uncoordinated -COOH groups, the terbium-functionalized hybrid (Tb3+@Zn-CP) was prepared by introducing Tb3+ ions into the structure through coordinated postsynthetic modification (PSM). Tb3+@Zn-CP shows the characteristic emission of Tb3+ ions due to the "antenna effect" of the H3pbc ligand. Based on the excellent luminescence properties and structural stabilities of Zn-CP and Tb3+@Zn-CP, they can be used as highly sensitive and selective luminescent probes of the UV filter BP (benzophenone) depending on multiquenching effects. In addition, their obvious color change can be easily distinguished by the naked eye under ultraviolet light, which was successfully used in the preparation of portable BP test paper. More importantly, Tb3+@Zn-CP is the first example of CPs as a ratiometric luminescent sensor for BP. This work provides a novel strategy for the construction of ratiometric luminescent probes of BP-type UVFs through coordinated postsynthetic modification.

Two Stable Cd-MOFs as Dual-Functional Materials with Luminescent Sensing of Antibiotics and Proton Conduction.

Construction and investigation of dual-functional metal-organic frameworks (MOFs) with luminescent sensing and proton conduction provide widespread applications in clean energy and environmental monitoring fields. By selecting a phosphonic acid ligand 4-pyridyl-CH2N(CH2PO3H2)2 (H4L) and coligand 2,2'-biimidazole (H2biim), two cadmium-based MOFs [Cd1.5(HL)(H2biim)0.5] (1) and (H4biim)0.5·[Cd2(L)(H2biim)Cl] (2) with different structures and properties have been hydrothermally synthesized by controlling reaction temperature. Based on the excellent thermal and chemical stabilities, and good luminescent stabilities in water solution, 1 and 2 can serve as luminescent sensors of chloramphenicol (CAP) with different quenching constant (KSV) values and detection limits (LODs) in water, simulated environmental system, and real fish water system. Meanwhile, different sensing effects and possible sensing mechanisms are analyzed in detail. Moreover, 1 and 2 can also serve as good proton-conducting materials. The proton conductivities can reach up to 1.41 × 10-4 S cm-1 for 1 and 1.02 × 10-3 S cm-1 for 2 at 368 K and 95% relative humidity (RH). Among them, 2 shows better luminescent sensing and proton conduction performance than 1, which indicates that different crystal structures have a great impact on the properties of MOFs. Through the discussion of the relationship between structures and properties in detail, the possible reasons for the differences in properties are obtained, which can provide theoretical guidance for the rational design of this kind of dual-functional MOFs in the future.

Investigation on fluorescein derivatives with thermally activated delayed fluorescence and their applications in imaging.

Fluorescein derivatives with thermally activated delayed fluorescence (TADF) show much stronger competition ability and vaster prospects than traditional fluorescein dyes due to their prominent long lifetime. It will be of great significance to synthesize more fluorescein derivatives with TADF. In this work, compounds DCF-MPYA and FL with TADF properties were obtained by fine tuning the substituents' structure on the basis of fluorescein derivative DCF-MPYM. Their long-lived triplet excited states (21.78 µs, 32.0 µs) were proved by nanosecond time-resolved transient difference absorption spectra. The steady-state and time-resolved fluorescence spectra showed that DCF-MPYA and FL exhibited red fluorescence around 645 nm and 651 nm, respectively. The results of sensitivity to oxygen and heavy atoms further demonstrated that the time-resolved fluorescence spectra originate from the delayed fluorescence. The time correlated single-photon counting (TCSPC) data indicated that DCF-MPYA and FL showed long-lived lifetimes of 13.16 µs and 23.72 µs, respectively. The energy gap (ΔE ST) between the singlet (S1) and triplet (T1) states of DCF-MPYA and FL was calculated to be 3.32 meV and 9.98 meV from the decay rate of DF as a function of temperature. The small energy gap is conducive to the occurrence of efficient TADF at room temperature. Meanwhile, Gaussian calculation was employed to observe the electron density of DCF-MPYA and FL in the ground and excited states. The calculation results indicate that the shapes and energy levels of the highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs), and LUMOs+1 for the monoanion and dianion forms are similar and thus DCF-MPYA and FL exhibit almost the same luminescence properties. Finally, DCF-MPYA and FL with low toxicity were used in confocal and time-resolved fluorescence imaging. Our construction strategy will be beneficial for developing more fluorescein derivatives with TADF in the future.

Dual-Functional Metal-Organic Framework for Luminescent Detection of Carcinoid Biomarkers and High Proton Conduction.

It remains a challenge to exploit dual-functional metal-organic frameworks (MOFs) for applications, including luminescence detection and proton conduction. With the deliberate selection of the bifunctional organic ligand 5-sulfoisophthalic acid monosodium salt (NaH2bts), and the phosphonic acid ligand N,N'-piperazine (bismethylenephosphonic acid; H4L), a robust three-dimensional (3D) noninterpenetrating dual-functional MOF, [Tb(H2L)(H2bts)(H2O)]·H2O (1), has been synthesized hydrothermally. On the basis of the excellent thermal and chemical as well as superior luminescence stabilities in water and solutions with different pHs, 1 can serve as the simple, rapid, and highly selective and sensitive luminescence detection of the carcinoid biomarkers 5-hydroxytryptamine (HT) and its metabolite 5-hydroxyindole-3-acetic acid (HIAA) with detection limits of nanomolar magnitude in water and in simulated blood plasma and urine systems. Due to the change in the signals that could be readily differentiated by the naked eye under a UV lamp, a portable test paper has been developed. The probable quenching mechanisms are discussed in detail. In addition, a great number of hydrogen-bonding networks are formed among the uncoordinated carboxylic oxygen atoms, sulfonate oxygen atoms, protonated nitrogen atoms, and water molecules, which provide potential proton-hopping sites for proton conduction, leading to a maximum proton conductivity of 2.3 × 10-4 S cm-1 at 368 K and 95% relative humidity. The above results suggest that rationally designed dual-functional MOFs can open an avenue for the development of occupational diagnostic tools and alternative energy technology.

Assembly of tetra-nuclear YbIII-containing selenotungstate clusters: synthesis, structures, and magnetic properties.

Two tetra-nuclear YbIII-incorporated selenotungstate clusters, Keggin (C2H8N)6Na14[Yb4Se6W44O160(H2O)12]·40H2O (1) and Wells-Dawson (C2H8N)4Na14[Yb4Se6W45O159(OH)6(H2O)11]·38H2O (2), have been isolated through a pH-controlled assembly, which exhibit the first YbIII-containing polyoxotungstates with selenium heteroatoms. Their assemblies rely on the structure-directing effects of SeO32- anion templates to give rise to available Se-containing Keggin-/Wells-Dawson-type motifs. Both compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, power X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as electrospray ionization mass spectrometry (ESI-MS). Furthermore, systematic magnetic studies revealed that 1 exhibits field-induced single-molecule magnetic behavior with a pre-exponential factor of τ0 = 6.60(7) × 10-8 s and a relaxation energy barrier of ΔE/kB = 39.44(2) K, while 2 only displays antiferromagnetic interactions between the ytterbium centers.

A Mixed-Valence {Fe13 } Cluster Exhibiting Metal-to-Metal Charge-Transfer-Switched Spin Crossover.

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal-to-metal charge transfer (MMCT) and spin-crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a FeII -triazole moiety and generates a mixed-valence complex {[(Tp4-Me )FeIII (CN)3 ]9 [FeII 4 (trz-ph)6 ]}⋅[Ph3 PMe]2 ⋅[(Tp4-Me )FeIII (CN)3 ] (1; trz-ph=4-phenyl-4H-1,2,4-triazole). Moreover, MMCT occurs between FeIII and one of the FeII sites after heat treatment, resulting in the generation of a new phase, {[(Tp4-Me )FeII (CN)3 ][(Tp4-Me )FeIII (CN)3 ]8 [FeIII FeII 3 (trz-ph)6 ]}⋅ [Ph3 PMe]2 ⋅[(Tp4-Me )FeIII (CN)3 ] (1 a). Structural and magnetic studies reveal that MMCT can tune the two-step SCO behavior of 1 into one-step SCO behavior of 1 a. Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin-transition materials with accessible multi-electronic states.

Self-Assembly of Nanoscale Lanthanoid-Containing Selenotungstates: Synthesis, Structures, and Magnetic Studies.

The reaction of mid-lanthanide (Ln) ions with the preformed {Se6W39} precursor under reasonably acidic aqueous conditions in the presence of organic amine cations results in an unprecedented nanoscale lanthanide-functionalized polyoxotungstate family, which are rare examples of mid-lanthanide-containing selenotungstates. (C4H10NO)9Na3[Dy3Se3.5W30O107.5(H2O)10]·22H2O (1) and (NH4)3(C2H8N)Na2[Dy4Se6W38O132(H2O)26(OH)6]·18H2O (2) reveal a trimeric Keggin assembly and a cyclic {Se6W38}-based chain, respectively, whereas (NH4)4Na8[Gd4Se6W48O166(H2O)20(OH)4]·21H2O (3) and (NH4)9(C2H8N)4Na5[Ln6Se6W58O202(H2O)20(OH)4]·58H2O (4; Ln = Gd, Tb, or Dy) are a few examples of polyoxometalates consisting of both classical Keggin and Wells-Dawson building blocks, and (NH4)4(C2H8N)5Na13[Ln4Se8W56O196(H2O)x(OH)10]·40H2O (5; Ln = Gd, Tb, or Dy; x = 12 for Gd and Tb and 10 for Dy) features the largest "pure" Wells-Dawson selenotungstate {Se8W56} bearing a length of 3.73 nm. A library of Se-templated species involving the first reported Keggin {α-SeW8} and Wells-Dawson {α-Se2W16} building blocks as well as some decisive assembly factors during the synthesis is responsible for these architectures. All of the compounds were structurally characterized in the solid and solution by single-crystal X-ray diffraction, IR, thermogravimetric-differential thermal analysis, and electrospray ionization mass spectrometry. Magnetic properties indicate that 1 and 4-Dy show probable single-molecule-magnet behavior with obvious frequency dependence, whereas 3 and 4-Gd present the antiferromagnetic interactions between the GdIII centers.

Effect of Intermolecular Interactions on Metal-to-Metal Charge Transfer: A Combined Experimental and Theoretical Investigation.

Understanding the effects of intermolecular interactions on metal-to-metal charge transfer (MMCT) is crucial to develop molecular devices by grafting MMCT-based molecular arrays. Herein, we report a series of solvent-free {Fe2 Co2 } compounds sharing the same cationic tetranuclear {[Fe(PzTp)(CN)3 ]2 [Co(dpq)2 ]2 }2+ (PzTp- =tetrakis(pyrazolyl)borate, dpq=dipyrido[3,2-d:2',3'-f]quinoxaline) square units but having anions with different size, including BF4 - , PF6 - , OTf- , and [Fe(PzTp)(CN)3 ]- . Intermolecular π⋅⋅⋅π interactions between dpq ligands, which coordinate to cobalt ions in the {[Fe(PzTp)(CN)3 ]2 [Co(dpq)2 ]2 }2+ units, can be modulated by introducing different counterions, regulating the distortion of the CoN6 octahedron and ligand field around the cobalt ions. This change results in different MMCT behavior. Computational analyzes reveal the substantial role of the intermolecular interactions tuned by the presence of different counteranions on the MMCT behavior.

Switching single chain magnet behavior via photoinduced bidirectional metal-to-metal charge transfer.

The preparation of single-chain magnets (SCMs) with photo-switchable bistable states is essential for the development of high-density photo-recording devices. However, the reversible switching of the SCM behavior upon light irradiation is a formidable challenge. Here we report a well-isolated double zigzag chain {[Fe(bpy)(CN)4]2[Co(phpy)2]}·2H2O (bpy = 2,2'-bipyridine, phpy = 4-phenylpyridine), which exhibits reversible redox reactions with interconversion between FeIIILS(µ-CN)CoIIHS(µ-NC)FeIIILS (LS = low-spin, HS = high-spin) and FeIIILS(µ-CN)CoIIILS(µ-NC)FeIILS linkages under alternating irradiation with 808 and 532 nm lasers. The bidirectional photo-induced metal-to-metal charge transfer results in significant changes of anisotropy and intrachain magnetic interactions, reversibly switching the SCM behavior. The on-switching SCM behavior driven by light irradiation at 808 nm could be reversibly switched off by irradiation at 532 nm. The results provide an additional and independent way to control the bistable states of SCMs by switching in the 0 → 1 → 0 sequence, with potential applications in high density storage and molecular switches.

Terbium Oxalatophosphonate as Efficient Multiresponsive Luminescent Sensors for Chromate Anions and Tryptophan Molecules.

A stable 2D terbium oxalatophosphonate with green luminescence, namely, [Tb2(H3L)(C2O4)3(H2O)4]·2H2O (1), has been hydrothermally obtained by using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L) and oxalate ligand. The luminescent investigation indicates that the emission behavior of compound 1 shows high water and pH stabilities. It can be applied as a multiresponsive luminescent probe with high selectivity, high sensitivity, recycling capability, and fast sensing of CrO4 2-, Cr2O7 2- anions and tryptophan (Trp) molecules in aqueous solution through the luminescence quenching effect. Moreover, the sensing results can be distinguished by the naked eye under the irradiation of UV light of 254 nm. In addition, the probable mechanisms for the quenching behavior are also discussed, which can be mainly attributed to the competitive absorption of excitation energy between compound 1 and the analytes.

A Series of Linear {FeIII2 FeII } Complexes with Paramagnetic Building-Block-Modified Spin Crossover Behaviors.

Tuning of the spin crossover (SCO) behavior through paramagnetic building blocks with different steric hindrance effects is of great interest in terms of the synergy between SCO and magnetic interactions. Herein, the steric effect of specified FeIII building blocks is modified, from the large Tp* (hydridotris(3,5-dimethylpyrazol-1-yl)borate) analogue to a small Tp (hydrotris(pyrazolyl)borate) derivative; the FeII SCO unit and FeIII paramagnetic ions are incorporated into three well isolated trinuclear complexes featuring thermally induced and light-induced SCO properties. Reanalysis of the structures reveals that π-π stacking interactions play a key role in the thermal hysteresis and anomalous octahedral distortion parameter Σ around the FeII ion. The Tp* ligand showing the largest steric hindrance induces elongated FeII -N bond lengths and bending of the C≡N-FeII angle in 1, as well as having a relatively large electron donor effect, which leads to the lowest thermal transition temperature among the three compounds.

Photo- and Electronically Switchable Spin-Crossover Iron(II) Metal-Organic Frameworks Based on a Tetrathiafulvalene Ligand.

A major challenge is the development of multifunctional metal-organic frameworks (MOFs), wherein magnetic and electronic functionality can be controlled simultaneously. Herein, we rationally construct two 3D MOFs by introducing the redox active ligand tetra(4-pyridyl)tetrathiafulvalene (TTF(py)4 ) and spin-crossover FeII centers. The materials exhibit redox activity, in addition to thermally and photo-induced spin crossover (SCO). A crystal-to-crystal transformation induced by I2 doping has also been observed and the resulting intercalated structure determined. The conductivity could be significantly enhanced (up to 3 orders of magnitude) by modulating the electronic state of the framework via oxidative doping; SCO behavior was also modified and the photo-magnetic behavior was switched off. This work provides a new strategy to tune the spin state and conductivity of framework materials through guest-induced redox-state switching.

12-Metal 36-membered ring based W(V)-Co(II) layers showing spin-glass behavior.

The present study describes the designed synthesis, X-ray structures, and magnetic properties of two 2D cyano bridged heterobimetallic W(V)-Co(II) networks, {[W(CN)8]2[Co(phpy)4]3}·2CH3OH·2H2O (1) and {[W(CN)8]2[Co(4-spy)4]3}·6H2O (2) (phpy = 4-phenylpyridine, 4-spy = 4-styrylpyridine). Both compounds consist of cyano-bridged 12-metal 36-membered ring units, Co6W6(CN)12, joined by organic linkers into a 2D plane. The layer presents a corrugated configuration in compound 1 and a plane configuration in compound 2 due to different π-π stacking interactions. Magnetic measurements reveal that both 1 and 2 have a transition to the spin glass-like phase due to competitive magnetic interactions.

Single-molecule magnet behavior in three cyano-bridged heterometallic Fe(III)-Ni(II) clusters.

One trinuclear and two tetranuclear cyanide-bridged Fe(III)-Ni(II) complexes were synthesized via treatment of a tricyanometallate with divalent Ni salts in the presence of 1-butylimidazole, 2,2-bipyrimidyl and 1,10-phenanthroline, respectively. Magnetic property studies demonstrated that the three complexes exhibit single-molecule magnet behavior as a result of strong intracluster ferromagnetic coupling and weak intercluster magnetic interactions.

Lanthanide(III) oxalatophosphonates: syntheses, crystal structures and luminescence properties.

By the introduction of oxalate as the second ligand, five new lanthanide oxalatophosphonate hybrids with a 2D layered structure, namely, [Ln(H2L)(C2O4)(H2O)]·2H2O [Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5), H3L = H2O3PCH2NCH2(CH2CH2OPO2H)], have been hydrothermally synthesized and structurally characterized by X-ray single-crystal diffraction, X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Compounds 1-5 are isostructural and exhibit a 2D layer formed by the interconnection of a 1D zigzag chain of {Ln(C2O4)}(+) with the phosphonate ligands. The effect of lanthanide contraction induces the decrease of the lattice parameters and crystal size from Nd to Dy. The luminescence properties of compounds 2-5 have been studied.

Two novel lead(II) carboxyphosphonates with a layered and a 3D framework structure: syntheses, crystal structures, reversible dehydration/hydration, and luminescence properties.

Two novel lead(II) carboxyphosphonates with a layered and a 3D framework structure, namely, [Pb2Cl3(H2L)]·H2O (1) and [Pb2(HL)(HBTC)] (2) (H3L = H2O3PCH2-NC5H9-COOH, H3BTC = 1,3,5-benzenetricarboxylic acid), have been synthesized under hydrothermal conditions and structurally characterized. For compound 1, the interconnection of Pb(1)O2Cl3, Pb(2)O2Cl3, and CPO3 polyhedra via corner- and edge-sharing forms a 1D chain. The adjacent chains connect with each other by sharing the chloride anion, thereby generating a 2D layered structure in the ab-plane. The lattice water molecules are located between adjacent layers. Compound 2 exhibits a 3D pillared-layered structure. The Pb(1)O5, Pb(2)O5, and CPO3 polyhedra are interconnected into a 1D double chain via corner- and edge-sharing, which is further linked to adjacent chains through carboxyphosphonate ligands to form a 2D double layer structure. Neighboring double layers are bridged through the second linkers HBTC(2-), leading to a 3D pillared-layered structure with a 1D channel system along the a-axis. An interesting feature of compound 1 is the presence of the dehydration/hydration properties. It is worth noting that compound 2 can be stable up to a high temperature. The luminescent properties of compounds 1 and 2 have also been studied.