Sequential Assembly and Stabilization of Cu6S6 Octahedral Clusters in NaCl-, NiAs-, and CdI2-Related Structures and Their Utility toward Thermochromism and Multicomponent Hantzsch Reaction.

Seven new inorganic-organic coordination polymer compounds have been synthesized and their structures are determined by single-crystal structure determination. The compounds were prepared by the sequential assembly of a [Cu6(mna)6]6- moiety in the presence of a Mn salt and a secondary amine ligand. Of the seven compounds, [{Cu6(mna)6}Mn3(H2O)(H2O)1.5]·5.5H2O (I), [{Cu6(mna)6}Mn3(H2O)(Im)1.5]·3.5H2O (Ia), [{Cu6(mna)6}{Mn(BPY)(H2O)}2{Mn(H2O)4}]·2H2O (III), and [{Cu6(mna)6}{Mn(BPE)0.5(H2O)2}2{Mn(BPE)(H2O)2}] (IV) have a three-dimensional structure, whereas [{Cu6(mna)4.5(Hmna)1.5}{Mn(BPA)(H2O)2}{Mn(H2O)}]{Mn0.25(H2O)3}·7H2O (II), [{Cu6(mna)6}{Mn(4-BPDB)0.5H2O}{Mn(H2O)2}].{Mn(H2O)6}·6H2O (V), and [{Cu6(mna)4(Hmna)2}·{Mn(H2O)3}2]·(4-APY)2·6H2O (VI) have a two-dimensional structure. Some of the prepared compounds exhibit structures that closely resemble the classical inorganic structures, such as NaCl (Ia, III), NiAs (I), and CdI2 (IV and VI). The stabilization of such simple structures from the assembly of octahedral Cu6S6 clusters and different Mn species and aromatic nitrogen-containing ligands suggests the subtle interplay between the constituent reactants. The compounds were examined for the multicomponent Hantzsch reaction, which gave the product in good yields. The compounds, II and VI, on heating to 70 °C change color reversibly from pale yellow to deep red, which suggests the possible use of these compounds as thermochromic materials. The present study suggests that the Cu6S6 octahedral clusters can be assembled into structures that resemble classical inorganic structures.

Multistep Cascade Catalytic Reactions Employing Bifunctional Framework Compounds.

Multistep cascade reactions are important to achieve atom as well as step economy over conventional synthesis. This approach, however, is limited due to the incompatibility of the available reactive centers in a catalyst. In the present study, new MOF compounds, [Zn2(SDBA)(3-ATZ)2]·solvent, I and II, with tetrahedral Zn centers as good Lewis acidic sites and the free amino group of the 3-amino triazole ligand as a strong Lewis base center were shown to perform 4-step cascade/tandem reaction in a facile manner. Effective conversion of benzaldehyde dimethyl acetal in the presence of excess nitromethane at 100 °C in water to 1-(1,3-dinitropropan-2-yl) benzene was achieved in 10 h with yields of ∼95% (I) and ∼94% (II). This 4-step cascade reaction proceeds via deacetalization (Lewis acid), Henry (Lewis base), and Michael (Lewis base) reactions. The present work highlights the importance of spatially separated functional groups in multistep tandem catalysis─the examples of which are not common.

Fixing CO2 under Atmospheric Conditions and Dual Functional Heterogeneous Catalysis Employing Cu MOFs: Polymorphism, Single-Crystal-to-Single-Crystal (SCSC) Transformation and Magnetic Studies.

New copper compounds, [Cu(C14H8O6)(C10H8N2)(H2O)] (1), [Cu(C14H8O6)(C10H8N2)(H2O)]·(C3H7ON)2 (2), [Cu(C14H8O6)(C10H8N2)(H2O)2]·(C3H7ON) (3), [Cu(C14H8O6)(C10H8N4)] (4), and [Cu(C14H8O6)(C10H8N4)]·(H2O) (5), were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as the primary ligand and 4,4'-bipyridine (1-3) and 4,4'-azopyridine (4-5) as the secondary ligands. Single-crystal studies indicated that compounds 1-4 have two-dimensional layer structures and compound 5 has a three-dimensional structure. Compounds 1-3 were isolated from the same reaction mixture but by varying the time of reaction. The framework structures of compounds 1-3 are similar and may be considered as polymorphic structures. Compounds 4 and 5 can also be considered polymorphic with a change in dimensionality of the structure. Compounds 1-3 can be formed through a single-crystal-to-single-crystal transformation under a suitable solvent mixture. The Cu center was explored for the Lewis acid-catalyzed cycloaddition reaction of epoxide and CO2 under ambient conditions in a solventless condition and also for the synthesis of propargylamine derivatives by three-component coupling reactions (A3 coupling) in a DCM medium. The Lewis basic functionality of the MOF (-N═N- group) has been explored for the Henry reaction (aldol condensation) in a solventless condition. In all of the catalytic reactions, good yields and recyclability were observed. The magnetic studies indicated that compounds 1 and 4 have antiferromagnetic interactions and compound 5 has ferromagnetic interactions. The present studies illustrated the rich diversity that the copper-containing compounds exhibit in extended framework structures.

Influence of indoor volatile organic compounds and its relative respiratory effects among children living in rural biomass cooking households of Tamil Nadu and Andhra Pradesh.

PURPOSE: Exposures to volatile organic compounds (VOCs) cause respiratory symptoms among children, a known vulnerable group. Reports on exposures to VOCs and respiratory symptoms among South Indian children living in biomass-using households are not available thus far. METHODS: A cross-sectional study was conducted among 313 rural children to assess the influence of emitted VOCs on their respiratory health. Standard analytical procedures for VOCs and Pulmonary Function Test (PFT), allied questionnaires, and all ethical considerations were fulfilled in the study. RESULTS: The increase in VOC concentrations was observed proportional to the amount of burnt biomass fuel in two selected sites in Tamil Nadu (TN) and Andhra Pradesh (AP). Houses cooked for more than 60 min showed a remarkable increase in VOC concentrations and was observed as statistically significant (p < 0.01) in AP households. Among the younger children, the peak expiratory flow rate (PEFR) values were found significantly higher than comparatively older children in both the sites, TN and AP. However, the trend with respect to FEV1 is statistically significant (p < 0.01) among AP children. CONCLUSIONS: This study reports reduced lung function for a considerable proportion of the VOC-exposed selected children. Based on PFT, the children who were interpreted to be normal were found to be exposed to lesser indoor TVOC concentrations in comparison with the children of the households having restrictive or obstructive impairments. Diagnostic ratios with Benzene/Toluene (B/T) and Xylene/Ethyl benzene (X/E) confirmed the presence of VOCs-emissions from adjacent cooking fuels only. The observed results of this study recommends cleaner cooking fuel-use for better respiratory health among the citizens across the country, which in turn, in line with the Pradhan Mantri Ujjwala Yojana (PMUY), Government of India.

Monitoring of polycyclic aromatic hydrocarbons emitted from kerosene fuel burning and assessment of health risks among women in selected rural and urban households of South India.

Polycyclic aromatic hydrocarbons (PAHs) are well-known hazardous substances; nevertheless, research on their exposure and health concerns associated with kerosene fuel emissions is limited. In this study, PAH (combined gaseous and particle phase) monitoring was carried out in the kitchen and living room in selected households. Personal exposure and cooking time monitoring were also carried out, simultaneously. The study's findings revealed that BaP, BA, BbF, and Nap were the most prevalent PAHs in both the summer and winter seasons, regardless of urban or rural households. The estimated values of average incremental lifetime cancer risks were found to be greater than the USEPA level, i.e., 1 × 10-6, in both urban and rural households, regardless of seasonal fluctuation. In both seasons, the non-carcinogenic risk for developmental and reproductive effects was higher in rural women than in urban women, and in case of developmental risk it showed greater than unity (rural: 1.11 and urban 1.03) in the winter season. On the other hand, Monte Carlo simulation model revealed that concentrations of PAHs (97.1% and 97.5%) and exposure duration (51.7% and 56.7%) were the most sensitive factors contributed for health risk estimations for urban and rural area in both seasons, respectively. Furthermore, the results clearly showed that women who were using kerosene for cooking were at a greater risk of acquiring both carcinogenic and non-carcinogenic health consequences from PAH exposure from kerosene cookstoves. It was recommended that they should utilize clean fuel, either by using LPG under the PMUY scheme or by using electricity/solar power to reduce health risks for better health.

Blue-Emitting Ligand-Mediated Assembly of Rare-Earth MOFs toward White-Light Emission, Sensing, Magnetic, and Catalytic Studies.

New lanthanide carboxylate compounds with two- (2D) and three-dimensional (3D) structures have been prepared by employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as an organic linker. The compounds, [Ln(C14H8O6)(C7O3H4)·2H2O]·4(H2O), Ln = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy and [Ln(C7O3H4)3·(C3H7ON)·(H2O)]·2(H2O)(C3H7NO), Ln = La, Ce, Pr, have two- and three-dimensional structures, respectively. In all compounds, lanthanide ions are connected together, forming a dimer, which is connected by the 2,5-BPTA ligand. In the two-dimensional structure, there are two 2,5-BPTA moieties present, and in the three-dimensional structure, there are three 2,5-BPTA moieties present. The lanthanide centers are nine-coordinated, the 2D structure has a tricapped trigonal prismatic arrangement, and the 3D structure has a monocapped distorted square antiprismatic arrangement. The Pr compound forms in both 2D and 3D structures, whose formation depends on the time of the reaction (2 days─2D and 5-6 days─3D). The ligand emits in the blue region, and using the characteristic emission of Eu3+ (red) and Tb3+ (green) ions, we achieve white light emission in the (Y0.96Tb0.02Eu0.02) compound. The overall quantum yield for the white light emission is 28%. The strong green luminescence of the Tb3+-containing compound was employed to selectively sense the Cr3+ and Fe3+ ions in aqueous solution with limits of detection (LODs) at 0.41 and 8.6 ppm, respectively. The Tb compound was found to be a good heterogeneous catalyst for the Ullman-type O-arylation reaction between phenol and bromoarene with yields of 95%. Magnetic studies on the Gd-, Tb-, and Dy-containing compounds showed weak exchange interactions within the dimeric Ln2 units. The present work demonstrates the many utilities of the rare-earth-containing MOFs, especially toward white-light emission, metal-ion sensing, and heterogeneous catalysis.

Stuffed Tridymite Structures: Synthesis, Structure, Second Harmonic Generation, Optical, and Multiferroic Properties.

The stuffed tridymite structure Ba(Zn/Co)1-x Si1-x M2x O4 (M=Al3+ and Fe3+ ) is explored for the possible multiferroic behavior and to develop new inorganic colored materials. The compounds were synthesized by employing conventional solid-state chemistry methods in the temperature range 1100-1175 °C for 24 h. The powder X-ray diffraction (PXRD) and Rietveld refinement studies indicate that the compounds stabilize in the P63 space group (no. 173). The refinement results were also rationalized by employing Raman spectroscopic studies. The compounds were found to be second harmonic generation (SHG) active and show weak ferroelectric behavior. The co-substitution of Co2+ and Fe3+ in the structure gives rise to a weak ferromagnetic behavior to the compound, BaCo0.75 Si0.75 Fe0.5 O4 , making it a multiferroic material. The optical studies on the prepared compounds exhibited blue color (Co2+ in Td geometry), purple color (Ni2+ in Td geometry), and simultaneous substitution of Co2+ and Fe3+ gives rise to blue-green color owing to metal-to-metal charge transfer (MMCT) effect.

New Members of SHG Active Dugganite Family, A3BC3D2O14 (A = Ba, Pb; B = Te, Sb; C = Al, Ga, Fe, Zn; D = Si, Ge, P, V): Synthesis, Structure, and Materials Properties.

A family of compounds, A3BC3D2O14 (A = Ba, Pb; B = Te, Sb; C = Al, Ga, Fe, Zn; D = Si, Ge, P, V), with the Dugganite structure was prepared employing traditional solid-state chemistry methods. PXRD and Rietveld refinement studies indicate that the compounds are stabilized in P321 space group (no. 150). The compounds are found to be SHG active with values ranging from 1.9 to 15.0 × KDP. The compounds exhibit high dielectric constants and low loss in our studies. The noncentrosymmetry related properties of the new Dugganites were understood by band structure calculations. We also explored the present Dugganite-structured oxides for the development of new inorganic colored materials by substituting Co2+, Ni2+, Cu2+, and Fe3+ in place of Zn2+. Thus, substitution of Co2+ and Fe3+ together tunes the blue color of the cobalt compound to blue-green color arising from metal-to-metal charge transfer (MMCT) of Fe3+ and Co2+ ions. The tetrahedrally coordinated Ni2+ in the Dugganite imparts a magenta color.

Exposures to fine particulate matter (PM2.5) and birthweight in a rural-urban, mother-child cohort in Tamil Nadu, India.

BACKGROUND: Exposure to PM2.5 (fine particulate matter

Assembling Porphyrins into Extended Network Structures by Employing Aromatic Dicarboxylates: Synthesis, Metal Exchange, and Heterogeneous Catalytic Studies.

Three new metal-organic porphyrinic framework compounds of zinc and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) have been synthesized under solvothermal conditions. The compounds [Zn5 (C40 H24 N8 )(C8 H4 O4 )2 (NO3 )6 (DMA)2 ] (DMA)3 (H2 O)8 (1; DMA=dimethylacetamide), [Zn3 (C40 H24 N8 )(C8 H4 O4 )2 (DMF)](DMF)5 (H2 O)12 (2), and [Zn3 (C40 H24 N8 )(C12 H6 O4 )2 (DMA)2 ](H2 O)7 (3) have two (1) and three dimensionally (2 and 3) extended structures. All the three structures contain porphyrinic units connected through the carboxylate linkers. The nitrates bind the metal centers and are not hydrogen bonded. The different binding modes of nitrate in the structure of 1 are observed for the first time in a porphyrin-based MOF. The openness of the structure allowed us to explore metal exchange through a room-temperature metathetic route. Compound 2 undergoes 100 % exchange with copper, whereas compound 3 exchanges 70 % with copper. The copper-exchanged compounds Cu∈2 and Cu∈3 were observed to be good heterogeneous catalysts for many important organic reactions. The chemo and regioselective enamination of ß-ketoesters, preparation of propargylamine derivatives as well as regioselective cycloadditions of alkyne and azide (click reactions) have been carried out with good yields and selectivity. All the compounds have been characterized by PXRD, IR, UV/Vis, atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (for Cu exchange).

Stabilization of a Tetrahedral (Mn(5+)O4) Chromophore in Ternary Barium Oxides as a Strategy toward Development of New Turquoise/Green-Colored Pigments.

An experimental investigation of the stabilization of the turquoise-colored chromophore Mn(5+)O4 in various oxide hosts, viz., A3(VO4)2 (A = Ba, Sr, Ca), YVO4, and Ba2MO4 (M = Ti, Si), has been carried out. The results reveal that substitution of Mn(5+)O4 occurs in Ba3(VO4)2 forming the entire solid solution series Ba3(V1-xMnxO4)2 (0 < x ≤ 1.0), while with the corresponding strontium derivative, only up to about 10% of Mn(5+)O4 substitution is possible. Ca3(VO4)2 and YVO4 do not stabilize Mn(5+)O4 at all. With Ba2MO4 (M = Ti, Si), we could prepare only partially substituted materials, Ba2M1-xMn(5+)xO4+x/2 for x up to 0.15, that are turquoise-colored. We rationalize the results that a large stabilization of the O 2p-valence band states occurs in the presence of the electropositive barium that renders the Mn(5+) oxidation state accessible in oxoanion compounds containing PO4(3-), VO4(3-), etc. By way of proof-of-concept, we synthesized new turquoise-colored Mn(5+)O4 materials, Ba5(BO3)(MnO4)2Cl and Ba5(BO3)(PO4)(MnO4)Cl, based on the apatite-Ba5(PO4)3Cl-structure.

Van der Waals force: a dominant factor for reactivity of graphene.

Reactivity control of graphene is an important issue because chemical functionalization can modulate graphene's unique mechanical, optical, and electronic properties. Using systematic optical studies, we demonstrate that van der Waals interaction is the dominant factor for the chemical reactivity of graphene on two-dimensional (2D) heterostructures. A significant enhancement in the chemical stability of graphene is achieved by replacing the common SiO2 substrate with 2D crystals such as an additional graphene layer, WS2, MoS2, or h-BN. Our theoretical and experimental results show that its origin is a strong van der Waals interaction between the graphene layer and the 2D substrate. This results in a high resistive force on graphene toward geometric lattice deformation. We also demonstrate that the chemical reactivity of graphene can be controlled by the relative lattice orientation with respect to the substrates and thus can be used for a wide range of applications including hydrogen storage.

High proton mobility, solvent induced single crystal to single crystal structural transformation, and related studies on a family of compounds formed from Mn3 oxo-clusters.

The reaction between 4,4'-sulfonyldibenzoic acid (H2SDBA) and manganese under mild conditions resulted in the isolation of two new three-dimensional compounds, [Mn4(C14H8O6S)4(DMA)2]·3DMA, I, and [Mn3(C14H8O6S)3(DMA)2(MeOH)]·DMA, IIa. Both structures have Mn3 trimer oxo cluster units. While the Mn3 oxoclusters are connected through octahedral manganese forming one-dimensional Mn-O-Mn chains in I, the Mn3 units are isolated in IIa. The SDBA units connect the Mn-O-Mn chains and the Mn3 clusters giving rise to the three-dimensional structure. Both compounds have coordinated and free solvent molecules. In IIa, two different solvent molecules are coordinated, of which one solvent can be reversibly exchanged by a variety of other similar solvents via a solvent-mediated single crystal to single crystal (SCSC) transformation. The free lattice DMA solvent molecules in I can be exchanged by water molecules resulting in hydrophilic channels. Proton conductivity studies on I reveals a high proton mobility with conductivity values of ∼0.87 × 10(-3) Ω(-1) cm(-1) at 34 °C and 98% RH, which is comparable to some of the good proton conductivity values observed in inorganic coordination polymers. We have also shown structural transformation of I to IIa through a possible dissolution and recrystallization pathway. In addition, both I and IIa appear to transform to two other manganese compounds [H3O][Mn3(µ3-OH)(C14H8O6S)3(H2O)](DMF)5 and [H3O]2[Mn7(µ3-OH)4(C14H8O6S)6(H2O)4](H2O)2(DMF)8 under suitable reaction conditions. We have partially substituted Co in place of Mn in the Mn3 trimer clusters forming [CoMn2(C14H8O6S)3(DMA)2(EtOH)]·DMA, III, a structure that is closely related to IIa. All the compounds reveal antiferromagnetic behavior. On heating, the cobalt substituted phase (compound III) forms a CoMn2O4 spinel phase with particle sizes in the nanometer range.

Bifunctional MOFs in Heterogeneous Catalysis.

The ever-increasing landscape of heterogeneous catalysis, pure and applied, utilizes many different catalysts. Academic insights along with many industrial adaptations paved the way for the growth. In designing a catalyst, it is desirable to have a priori knowledge of what structure needs to be targeted to help in achieving the goal. When focusing on catalysis, one needs to cope with a vast corpus of knowledge and information. The overwhelming desire to exploit catalysis toward commercial ends is irresistible. In today's world, one of the requirements of developing a new catalyst is to address the environmental concerns. The well-established heterogeneous catalysts have microporous structures (<25 Å), which find use in many industrial processes. The metal-organic framework (MOF) compounds, being pursued vigorously during the last two decades, have similar microporosity with well-defined pores and channels. The MOFs possess large surface area and assemble to delicate structural and compositional variations either during the preparation or through postsynthetic modifications (PSMs). The MOFs, in fact, offer excellent scope as simple Lewis acidic, Brönsted acidic, Lewis basic, and more importantly bifunctional (acidic as well as basic) agents for carrying out catalysis. The many advances that happened over the years in biology helped in the design of many good biocatalysts. The tools and techniques (advanced preparative approaches coupled with computational insights), on the other hand, have helped in generating interesting and good inorganic catalysts. In this review, the recent advances in bifunctional catalysis employing MOFs are presented. In doing so, we have concentrated on the developments that happened during the past decade or so.

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn(bpe)1/2(BPTA)H2O]·H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA)(bpmh)]·2H2O (4); and Cu(BPTA)(bpmh)1.5(H2O)]·H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole both in aqueouos solution as well as simple paper strips. The Cu compound 5 loses the coordinated water molecule at 100 °C without any structural change, which was examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the MOF was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

Synthesis, Optical, Dielectric, SHG, Magnetic and Visible Light Driven Catalytic Studies on Compounds Belonging to the Swedenborgite Structure.

A new compound, InBaZn3GaO7, with swedenborgite structure along with transition metal (TM) substituted variants have also been prepared. The structure contains layers of tetrahedral ions (Zn2+/Ga3+) connected by octahedrally coordinated In3+ ion forming the three-dimensional structure with voids where the Ba2+ ions occupy. The TM substituted compounds form with new colors. The origin of the color was understood based on the ligand-field transitions. The near IR reflectivity studies indicate that the Ni - substituted compounds exhibit good near - IR reflectivity behavior, making them possible candidates for 'cool pigments'. The temperature dependent dielectric studies indicate that the InBaZn3GaO7 compound undergoes a phase transition at ~360 °C. The compounds are active towards second harmonic generation (SHG). Magnetic studies show the compounds, InBaZn2CoFeO7 and InBaZn2CuFeO7 to be anti-ferromagnetic in nature. The copper containing compounds were found to be good catalysts, under visible light, for the oxidation of aromatic alkenes. The many properties observed in the swedenborgite structure-based compounds suggests that the mineral structure offers a fertile ground to investigate newer compounds and properties.

Proton conduction in metal-organic frameworks and related modularly built porous solids.

Proton-conducting materials are an important component of fuel cells. Development of new types of proton-conducting materials is one of the most important issues in fuel-cell technology. Herein, we present newly developed proton-conducting materials, modularly built porous solids, including coordination polymers (CPs) or metal-organic frameworks (MOFs). The designable and tunable nature of the porous materials allows for fast development in this research field. Design and synthesis of the new types of proton-conducting materials and their unique proton-conduction properties are discussed.

Turn-off luminescence sensing, white light emission and magnetic studies of two-dimensional lanthanide MOFs.

The lanthanide metal organic framework compounds [Ln(BPTA)1.5(Bpy)]·0.5DMF (Ln = Y, Eu, Gd, Tb, Dy; 1a-5a) and [Ln(BPTA)1.5(Phen)]·0.5DMF (Ln = Y, Eu, Gd, Tb, Dy; 1b-5b) were prepared by employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as the primary ligand and 2,2'-bipyridine (1a-5a) and 1,10-phenanthroline (1b-5b) as the secondary ligands. Single-crystal structural studies on [Gd(BPTA)1.5(Bpy)]·0.5DMF (3a) and [Dy(BPTA)1.5(Phen)]·0.5DMF (5b) indicated that the compounds have a two-dimensional structure. The Y compound exhibits blue emission, and the other compounds exhibit emission in the expected regions (λex = 350 nm). White light emission was achieved by careful mixing of the red (Eu3+) and green (Tb3+) components in the blue emitting Y compound. Thus, Y0.96Tb0.02Eu0.02 (bpy) and Y0.939Tb0.06Eu0.001 (phen) were found to show white emission when excited using a wavelength of 350 nm. The introduction of N-N-containing ancillary ligands (i.e., bpy and phen) increased the overall quantum yield (QY) of white light emission to 31% and 43%, respectively. The high QY observed for the Tb and Eu compounds was found to be sensitive and selective for the fluorometric detection of azinphos-methyl pesticide and trinitrophenol (TNP) in an aqueous medium at the ppb level. The same behaviour was observed when utilising the compounds as onsite paper strip sensors. Their magnetic properties were also studied, revealing for the Tb and Dy derivatives slow relaxation of the magnetisation at low temperature. The present study highlights the usefulness of rigid π-conjugated molecules such as 2,2'-bipyridine and 1,10-phenanthroline in enhancing the many utilities of rare-earth-containing MOFs towards white light emission, the sensing of harmful and dangerous substances and magnetic properties.

Metal-ion metathesis in metal-organic frameworks: a synthetic route to new metal-organic frameworks.

A porous metal-organic framework, Mn(H(3)O)[(Mn(4)Cl)(3)(hmtt)(8)] (POST-65), was prepared by the reaction of 5,5',10,10',15,15'-hexamethyltruxene-2,7,12-tricarboxylic acid (H(3)hmtt) with MnCl(2) under solvothermal conditions. POST-65(Mn) was subjected to post-synthetic modification with Fe, Co, Ni, and Cu according to an ion-exchange method that resulted in the formation of three isomorphous frameworks, POST-65(Co/Ni/Cu), as well as a new framework, POST-65(Fe). The ion-exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasma-atomic emission spectrometry (ICP-AES), powder X-ray diffraction (PXRD), and Brunauer-Emmett-Teller (BET) surface-area analysis. Single-crystal X-ray diffractions studies revealed a single-crystal-to-single-crystal (SCSC)-transformation nature of the ion-exchange process. Hydrogen-sorption and magnetization measurements showed metal-specific properties of POST-65.

Highly luminescent and thermally stable lanthanide coordination polymers designed from 4-(dipyridin-2-yl)aminobenzoate: efficient energy transfer from Tb3+ to Eu3+ in a mixed lanthanide coordination compound.

Herein, a new aromatic carboxylate ligand, namely, 4-(dipyridin-2-yl)aminobenzoic acid (HL), has been designed and employed for the construction of a series of lanthanide complexes (Eu(3+) = 1, Tb(3+) = 2, and Gd(3+) = 3). Complexes of 1 and 2 were structurally authenticated by single-crystal X-ray diffraction and were found to exist as infinite 1D coordination polymers with the general formulas {[Eu(L)(3)(H(2)O)(2)]}(n) (1) and {[Tb(L)(3)(H(2)O)].(H(2)O)}(n) (2). Both compounds crystallize in monoclinic space group C2/c. The photophysical properties demonstrated that the developed 4-(dipyridin-2-yl)aminobenzoate ligand is well suited for the sensitization of Tb(3+) emission (Φ(overall) = 64%) thanks to the favorable position of the triplet state ((3)ππ*) of the ligand [the energy difference between the triplet state of the ligand and the excited state of Tb(3+) (ΔE) = (3)ππ* - (5)D(4) = 3197 cm(-1)], as investigated in the Gd(3+) complex. On the other hand, the corresponding Eu(3+) complex shows weak luminescence efficiency (Φ(overall) = 7%) due to poor matching of the triplet state of the ligand with that of the emissive excited states of the metal ion (ΔE = (3)ππ* - (5)D(0) = 6447 cm(-1)). Furthermore, in the present work, a mixed lanthanide system featuring Eu(3+) and Tb(3+) ions with the general formula {[Eu(0.5)Tb(0.5)(L)(3)(H(2)O)(2)]}(n) (4) was also synthesized, and the luminescent properties were evaluated and compared with those of the analogous single-lanthanide-ion systems (1 and 2). The lifetime measurements for 4 strongly support the premise that efficient energy transfer occurs between Tb(3+) and Eu(3+) in a mixed lanthanide system (η = 86%).