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Single-molecule magnets (SMMs) have been shown to possess bewildering phenomena leading to their proposal in several futuristic applications ranging from data storage devices to the basic unit of quantum computers. The main characteristic for the proposal of SMMs in such schemes is their inherent and intriguing quantum mechanical properties, which in turn, could be exploited in novel devices with larger capacities, such as for data storage or enhanced properties, such as quantum computers. In the quest of SMMs displaying such intriguing quantum effects, herein, we explore the synthesis, structural, and magnetic characterization of a dimeric dysprosium-based SMM composed of a tetradentate Schiff-base ligand with formula [Dy2(HL)2(benz)2(NO3)2]. Magnetic studies show that the complex is an SMM, while sub-Kelvin μ-SQUID studies revealed the exchange-bias characteristics of the system attributed to the presence of exchange interaction between the Dy3+ pair.

In this article, we have designed and synthesized a new, convenient and efficient phenanthroquinone-pyridoxal based fluorogenic probe PQPY, highly suitable for the selective and sensitive detection of nitric oxide in an aerated aqueous (7 : 3/H2O : MeCN) medium at pH 7.0 (10 mM HEPES buffer). Upon addition of nitric oxide, this probe exhibits emission in the green region (λem = 505 nm) which is ascribed to ICT (intramolecular charge transfer) from the phenanthroquinone moiety to the imidazole -N-N[double bond, length as m-dash]O fragment. The apparent formation constant, Kf, of the NO product of the ligand is (1.00 ± 0.2) × 105 M-1 and the LOD is 78 nM. The substantial enhancement of the life-time of the ligand (τ0 = 2.68 ns) occurs due to binding with nitric oxide (τ0 = 3.96 ns). This probe is low cytotoxicity, cell permeable and suitable for living cell imaging application.

A novel highly sensitive and selective fluorescent chemosensor L has been synthesized and characterized by various physicochemical techniques. In 3 : 7 water : MeCN (v/v) at pH 7.2 (10 mM HEPES buffer, μ = 0.05 M LiCl), it selectively recognizes Fe3+ through 1 : 1 complexation resulting in a 106-fold fluorescence enhancement and a binding constant of 8.10 × 104 M−1. The otherwise non-fluorescent spirolactam form of the probe results a dual-channel (absorbance and fluorescence) recognition of Fe3+via CHEF (chelation enhanced fluorescence) through the opening of the spirolactam ring. We have also carried out fluorescence titration and anisotropy (r) studies in pure water in the presence of SDS (sodium dodecyl sulphate). Based on the dependence of FI (fluorescence intensity) and r on [SDS] it was proposed that the probe is trapped between two SDS monolayers which again interact among themselves by π⋯π stacking. As a result, there is an increase in FI up to [SDS] ∼ 7 mM – a phenomenon reminiscent of aggregation-induced enhancement of emission (AIEE). Beyond this concentration of SDS (7 mM), micelle formation takes place and the π⋯π stacked polymer now becomes a monomer and is trapped inside the micellar cavity. As a result, there is a decrease in FI at [SDS] > 7 mM. But for anisotropy, it increases with [SDS] beyond 7 mM. Ligand, metal, and SDS interactions are well established through different optical and morphological studies. [L–Fe(NO3)]2+ thin films on FTO (Fluorine-doped Tin Oxide) glass substrates have been designed with the help of the spin-coating deposition technique. The deposited film of thickness 1.6 × 10−5 cm is well characterized by optical band gap calculation with a direct band gap, eg ∼ 1.6 eV. FESEM was also performed for the [L–Fe(NO3)]2+/FTO film. The current–voltage characteristics were measured by the two-probe technique. Light-dependent exciton generation was carried out by taking the top and bottom contacts with graphite paste on FTO and on the [L–Fe(NO3)]2+ films for the measurement of switching behavior. The response ratio curve for the light-induced frequency-switching phenomena has been obtained. The frequency taped here is the oscillation frequency of the photo-generated electron and the hole in an exiton. Thus, the light-induced frequency-switching behavior and Schottky barrier diode characteristics of the material were established.

A hydrazone-based conjugate Nap-hyz-pyz (H3L3) with potential N2O2 donor atoms was found to act as a dual channel (colori- and fluori-metric) sensor towards Al3+ and PPi in H2O-MeOH (6 : 4, v/v) at pH 7.2 (40 mM HEPES buffer) at 25 °C. The formation constants, Kf = (3.49 ± 1.77) × 104 and (3.78 ± 0.1) × 104 M-1, of the sensor towards Al3+ were determined by absorption and fluorescence titrations, respectively. The 1 : 1 stoichiometry of the reaction was determined by Job's method and confirmed by ESI-MS+ (m/z) studies. The LOD for Al3+, as determined by the 3σ method, was found to be 114.54 nM. Most strikingly, the addition of ∼115 μM PPi to the Nap-hyz-pyz-Al3+ ensemble (20 μM ligand and 74 μM Al3+) leads to complete quenching of fluorescence. The fluorescence response of Nap-hyz-pyz towards Al3+ was not perturbed by the presence of 5 equivalents or more of other ions and inorganic anions. The structure of the [Al(L3)(H2O)] complex was delineated by DFT calculations. TD-DFT studies were performed to investigate various spectral transitions. Based on changes in the fluorescence intensities of Nap-hyz-pyz in the presence of Al3+ and PPi at 487 nm, INHIBIT and molecular logic gates were constructed and interpreted. The probe was found to be bio-compatible and cell permeable with no or negligible cytotoxicity; thus, it provides a good opportunity for in vitro cell imaging studies of these ions. The presence of ATP or Pi did not interfere with the fluorescent detection of PPi. Thus, these evident and excellent sensing capabilities of Nap-hyz-pyz towards Al3+ and PPi were further scrutinized in HepG2 cell lines.

A new oxime–imine functionalized highly ordered mesoporous SBA-15 ( SBA-15-NH 2 -DAMO ) has been synthesized via post-synthesis functionalization of SBA-15 with 3-aminopropyl-triethoxysilane followed by the Schiff base condensation with diacetylmonooxime, which was further reacted with Ni(ClO 4 ) 2 to yield the functionalized nickel catalyst SBA-15-NH 2 -DAMO-Ni. All the synthesized materials were thoroughly characterized using different characterization techniques. It was found that SBA-15-NH 2 -DAMO-Ni catalyzes the one-pot oxidation of olefins like styrene, cyclohexene, cyclooctene, 1-hexene and 1-octene to the corresponding benzaldehyde, cyclohexene-1-ol and cyclooctene-oxide, respectively under solvent-free conditions by using tert- butylhydroperoxide as oxidant.

A new rhodamine 6G-benzylamine-based sensor (L1), having only hydrocarbon skeletons in the extended part, was synthesized and characterized by single-crystal X-ray crystallographic study. It exhibited excellent selective and sensitive recognition of trivalent metal ions M3+ (M = Fe, Al and Cr) over mono- and di-valent and other trivalent metal ions. A large enhancement of the fluorescence intensity for Fe3+ (41-fold), Al3+ (31-fold) and Cr3+ (26-fold) was observed upon the addition of 3.0 equivalent of these metal ions into the probe in H2O/CH3CN (4 : 1, v/v, pH 7.2) with naked eye detection. The corresponding Kf values were evaluated to be 9.4 × 103 M−1 (Fe3+), 1.34 × 104 M−1 (Al3+) and 8.7 × 103 M−1 (Cr3+). Quantum yields of the L1, [L1–Fe3+], [L1–Al3+] and [L1–Cr3+] complexes in H2O/CH3CN (4 : 1, v/v, pH 7.2) were found to be 0.012, 0.489, 0.376 and 0.310, respectively, using rhodamine-6G as standard. LODs for Fe3+, Al3+ and Cr3+ were determined by 3σ methods and found to be 1.28, 1.34 and 2.28 μM, respectively. Cyanide ion scavenged Fe3+ from the [Fe3+–L1] complex and quenched its fluorescence via its ring-closed spirolactam form. Advanced level molecular logic devices using different inputs (2 and 4 inputs) as advanced level logic gates and memory devices were constructed. The large enhancement in fluorescence emission of L1 upon complexation with M3+ metal ions makes the probe suitable for the bio-imaging of M3+ (M = Fe, Al and Cr) in living cells.

A simple molecular probe displays highly selective turn-on response toward NO by the unprecedented NO-induced formation of a 1,2,3,4-oxatriazole ring exhibiting no interference from various endogenous biomolecules including DHA, AA, etc. Kinetics of the reactions between NO and the probe provide a mechanistic insight into the formation of 1,2,3,4-oxatriazole which showed that, though initially 1,2,3,4-oxatriazole is formed and extractable in solid form, it exists in equilibrium with the ring opened azide form which ultimately hydrolyzed and converted to carboxylic acid and nitrate. The reaction displays second-order dependence on [NO] and first-order on [Probe]. The probe is water-soluble, cell permeable, and noncytotoxic and appropriates for live cell imaging. This constitutes the first report where there is a direct evidence of NO-induced ring closing reaction of an acyl hydrazide moiety leading to the formation of 1,2,3,4-oxatriazole.

We report herein the development of a novel, diformyl-p-cresol (DFC)–thiosemicarbazide (TS) based sensor (DFC–TS) that selectively and sensitively recognizes Zn2+ by both UV-Vis and fluorescence methods. The gradual addition of Zn2+ to a solution of the ligand developed a new absorption band at 430 nm, while the bands at 370 and 316 nm gradually decrease generating one well defined isosbestic point at 390 nm exhibiting ∼17 fold turn-on fluorescent enhancement (FE). When we plot absorbance (at 430 nm) vs. [Zn2+] there is a gradual increase in absorption with [Zn2+], becoming saturated at ∼1 equivalent of Zn2+ and then again it increases with the increase in [Zn2+] and ultimately becomes saturated at ∼2 equivalents of added Zn2+. This clearly demonstrates that the Zn2+ binding event to the ligand occurs in two steps, one at a time. Non-linear least-squares computer-fitting of these data gives the parameters: K′f1 = (9.70 ± 5.51) × 105 M−1, n = (1.28 ± 0.05) for the first step and K′f2 = (1.11 ± 0.65) × 105 M−1 and n = (1.01 ± 0.06) for the second step. So far, this study provides the opportunity where we have successfully, for the first time, determined the stepwise formation constants; though they have values of the same order of magnitude. The ground state geometries of DFC–TS, both enol and keto forms and [Zn(DFC–TS)(OAc)], [Zn(DFC–TS)(OAc)]−, and [Zn2(DFC–TS)(OAc)2] were optimized using the Gaussian-03 suit program and bond distances of all species are in reasonable agreement with the reported values.

A novel 3-hydroxymethyl-5-methylsalicylaldehydenaphthyl-hydrazone (H3SAL-NH) exhibits ESIPT behaviour due to proton transfer from the phenolic OH group to the azomethine N atom in the excited state. Through this ESIPT behaviour together with cis–trans isomerization of the azomethine group, the free ligand becomes very weakly fluorescent. However, in the presence of Zn2+ and Al3+ the ESIPT and isomerization are blocked due to coordination to the metal ions thereby causing turn on fluorescence for Al3+ and Zn2+. Moreover, Zn2+ can easily be displaced from the [H2SAL-NH–Zn2+] complex by Al3+ thereby enhancing the differential selectivity for Al3+ over Zn2+. This probe was found to be selective for Al3+ over Zn2+ in the presence of Na2H2EDTA, under both intra- and extracellular conditions. The LODs for Zn2+ and Al3+ were determined by 3σ methods and were found to be 3.1 nM and 0.92 nM, respectively. Thus, the differentially selective turn-on fluorescence behaviour of H3SAL-NH for Zn2+ and Al3+ is based on the combined blocking of ESIPT and CN isomerization, and a chelation-enhanced fluorescence (CHEF) effect. The coordination modes of the complexes were investigated through spectroscopic and computational studies. H3SAL-NH also exhibits good photostability and very low cytotoxicity and is useful for fluorescence imaging of Zn2+ and Al3+ ions in live HepG2 cells.

In this report, the interaction between a phenanthrene–pyrene-based fluorescent probe (PPI) and bovine serum albumin (BSA), a transport protein, has been explored by steady-state emission spectroscopy, fluorescence anisotropy, far-ultraviolet circular dichroism (CD), time-resolved spectral measurements, and molecular docking simulation study. The blue shift along with emission enhancement indicates the interaction between PPI and BSA. The binding of the probe causes quenching of BSA fluorescence through both static and dynamic quenching mechanisms, revealing a 1:1 interaction, as delineated from Benesi–Hildebrand plot, with a binding constant of ∼105 M–1, which is in excellent agreement with the binding constant extracted from fluorescence anisotropy measurements. The thermodynamic parameters, ΔH°, ΔS°, and ΔG°, as determined from van’t Hoff relationship indicate the predominance of van der Waals/extensive hydrogen-bonding interactions for the binding phenomenon. The molecular docking and site-selective binding studies reveal the predominant binding of PPI in subdomain IIA of BSA. From the fluorescence resonance energy transfer study, the average distance between tryptophan 213 of the BSA donor and the PPI acceptor is found to be 3.04 nm. CD study demonstrates the reduction of α-helical content of BSA protein on binding with PPI, clearly indicating the change of conformation of BSA.

A new, highly sensitive probe L2 for the selective detection of Hg2+ in organo-aqueous (H2O:CH3CN, 1:1, v/v, HEPES buffer, pH 7.2) medium has been synthesized from rhodamine 6G-hydrazide and 4-nitroindole-3-carboxaldehyde. It was thoroughly characterized by physicochemical techniques including single crystal X-ray diffraction studies. The reaction of L2 with Hg2+ gives a 1:1 stoichiometry resulting in a 146 fold fluorescence enhancement and a binding constant (Kf) of 3 × 104 M−1. The spirolactam form of the probe is non-fluorescent; however, it shows dual channel (absorbance and fluorescence) recognition of Hg2+ via CHEF effect through the opening of the spirolactam ring. The quantum yields of L2 (0.00045) and L2-Hg2+ (0.29) show the higher stability of complex in the excited state over the free ligand. The 44.5 nM LOD value demonstrates the detection of Hg2+ at a very low concentration range. Cell imaging studies show the cytoplasmic recognition of Hg2+ by L2. Experimental results are comparable with theoretical values obtained by DFT studies. The fluorescence emission of the complex was completely quenched by I- and from the reversibility studies an advance level INHIBIT logic gate and memory device can be framed.

In the present work, two compartmental ligands H2L1 and H2L2 were in situ generated during the syntheses of new trinuclear complexes, [Cu2Ni(L1)(2,2′-bpy)2(NO3)2][ClO4]2 (5), [Cu3(L2)(NO3)2][ClO4]2 (6), and [Cu3(L2)(NCS)2(NO3)]+ that co-crystallize in 7 with a [Cu6(L2)2Na2(NO3)6(NCS)4] unit to give the final molecular formula [Cu6(L2)2Na2(NO3)6(NCS)4][Cu3(L2)(NCS)2(NO3)]2(NO3)2·5H2O (7). The magnetic property studies of 5–7 revealed weak CuII–CuII ferromagnetic interactions in compound 6 (JCu–Cu/kB = +1.4(1) K) and 7 (JCu–Cu/kB = +1.6) while in intranuclear CuII–NiII–CuII compound 5, the magnetic coupling between two CuII ions is switched off by the diamagnetic square planar NiII bridge. The catalytic epoxidation of two olefins, namely styrene and cyclooctene, by tert-BuOOH (TBHP) was also explored in the presence of a catalytic amount of 5, 6 or 7 in MeCN. For styrene oxidation, 5 exhibited ∼57% styrene epoxide selectively (conversion ∼37%) with a TON of about 925 along with benzaldehyde (∼43%), whereas 6 exhibited conversion up to ∼63% (TON ∼ 1575) with a good selectivity towards epoxide (∼71%). For compound 7, this conversion is more important (TON ∼ 8108) probably due to the presence of more active sites involved in the epoxidation. The concerted path was found to be operative for styrene oxidation while a radical path was suggested for the oxidation of cyclooctene.

A new, easily synthesizable chemosensor, DFC-EN-p-Ph-NO2, derived by the Schiff base condensation between 2,6-diformyl-p-cresol and N-(4-nitrophenyl)ethylenediamine, with potential N4O donor atoms was found to act as a dual channel (colori- and fluorimetric) sensor towards Al3+ and PPi emitting at 486 nm (blue region) and 534 nm (green region), respectively in MeOH–H2O (8 : 2, v/v) at pH 7.2 (10 mM HEPES buffer), μ = 0.05 M (LiCl), temperature 25 °C. The binding stoichiometries and formation constants of the sensor towards both Al3+ and PPi were determined by the combined UV-Vis and fluorescence titrations and Job's method, and confirmed by MS (m/z) studies. The corresponding detection limits as calculated by the 3σ method are: 7.55 μM and 3.34 μM. The most interesting part of this study is that on addition of 230 μM PPi to an ensemble of DFC-EN-p-Ph-NO2−Al3+ (20 μM Ligand and 380 μM Al3+) the fluorescence is totally quenched but on further addition of PPi a new emission peak appears at 534 nm. All biologically relevant metal ions and toxic heavy metals did not interfere with the detection of Al3+ ion. Its bio-compatibility with respect to its good solubility in mixed organo-aqueous media (MeOH–H2O) and cell permeability with no or negligible cytotoxicity provide good opportunities towards in vitro cell imaging studies of these ions. In particular, the fluorescent detection of PPi was not interfered by the presence of 400 μM of ATP or Pi although most reported PPi sensors that work in aqueous solution displayed cross-sensitivities toward ATP or Pi. The obvious excellent sensing capability of DFC-EN-p-Ph-NO2 towards PPi and Al3+ was further scrutinized in HCT116 cell lines without much cytotoxicity. The modes of 1 : 1 binding of DFC-EN-p-Ph-NO2 towards Al3+ and PPi were delineated by DFT calculations.

We have synthesized four mononuclear manganese(III) complexes (1–4) of four closely related bidentate NO donor Schiff-base ligands, out of which three (2–4) were structurally characterized. Crystal structure determination reveals that all these complexes are in octahedral geometries. Magnetic studies have been carried out on complexes 2, 3 and 4 in the temperature range 2–300 K under a magnetic field of 0.1 T which yielded negative ZFS parameters of −2.96, –3.51 and −3.72 cm−1 respectively. The catecholase activities of complexes 1–4 have been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in DCM at 25 °C, which were found to follow the Michalis–Menton type relation giving the highest TON (Kcat) for the so far reported Mn(III) complexes.

Department of Chemistry, Jadavpur University, Jadavpur, Kolkata-700 032, India E-mail : m_ali2062@yahoo.com Fax : 91-33-24146223 Department of Molecular & Human Genetics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mallick Road, Kolkata-700 032, India Manuscript received 20 June 2017, accepted 25 June 2017 An easily synthesizable rhodamine-based chemosensor, L2 , selectively recognizes Hg2+ and Al3+ ions in the presence of all biologically relevant and toxic heavy metal ions. Very low detection limit (47 nM for Hg2+) along with cell permeability and negligible cytotoxicity provides a good opportunity towards cell imaging of Hg2+. SEM studies reveal rod-like microstructure for L2 in water, which changes to a porous microstructure in the presence of Hg2+. It was interesting to note that the presence of SDS solubilized the otherwise insoluble probe in pure aqueous medium. In case of Al3+ it was astonishingly observed a fluorescence quenching on increasing the SDS concentration, while a ~33-fold enhancement of FI of [L2 -Hg2+] complex was observed compared to that in the absence of SDS, making the prove selective towards Hg2+ over Al3+ in the aqueous SDS medium. In SDS/water system, there is a steep rise in FI, reaches a maximum at ~7 mM of SDS and then fluorescence intensity decreases gradually with the increase in [SDS] up to 28 mM. These observations clearly signify the SDS-assisted formation of polymer aggregates of the complex on the surface of monolayer of SDS formed in pre-micellar concentrations with higher FI, which is converted to the monomer being trapped inside the micellar cavity beyond the critical micellar concentration (cmc) with comparatively lower FI, indicating an interesting AIEE phenomenon. This proposition is further supported by the dependence of fluorescence anisotropy (r) on [SDS].

Two mononuclear complexes namely [NiII(L)] (1) and [CoIII(L)](NO3) (2) of a hexacoordinating N4O2 donor Schiff base ligand were synthesized and characterized by single crystal X-ray studies. In compound 2 the central cobalt is in + 3 oxidation state while ‘in’ compound 2, the nickel ion is in + 2 oxidation state. The two complexes are isostructural with octahedral coordination environment exhibiting helical twist topology. They also display strong H-bonding as well as CH-π interactions to generate 1D chain.

Vanadium exchanged zeolite Y has been synthesized by simple ion-exchange on NaY and resulting V–Y material has been employed as a heterogeneous catalyst for highly selective and direct one-pot liquid phase oxidation of cyclohexane to cyclohexanone under solvent-free conditions at room temperature. The catalyst (V–Y) has been thoroughly characterized by powder X-ray diffraction (PXRD), N 2 sorption, transmission electron microscopic (TEM), Fourier transform infrared (FT IR), UV–visible, X-ray photoelectron spectroscopic (XPS) and atomic absorption spectroscopic (AAS) analyses. The selective oxidation reaction proceeds smoothly over this V-containing heterogeneous catalyst in the presence of tert -butylhydroperoxide (TBHP) as oxidant and the progress of the reaction has been monitored thoroughly by gas chromatographic (GC) and gas chromatography coupled with mass spectrometric (GC–MS) analyses. The recycling efficiency of the V–Y catalyst has been tested by conducting the catalytic reaction repeatedly with the recovered catalyst, where almost retention of the original catalytic activity and selectivity after five reaction cycles has been observed. The effect of oxidant amounts on the catalytic reaction has been studied. Mechanistic pathway for the catalytic reaction over this inexpensive, non-air sensitive, eco-friendly and reusable vanadium exchanged zeolite has been proposed, suggesting future potential of V–Y in solvent-free liquid phase selective oxidation reactions under very mild conditions.

A new pyrene based highly sensitive and selective Al3+ sensor, pyrene-2-(pyridin-2-ylmethylsulfanyl)-ethylamine (PP), was found to exhibit a turn-on fluorescence enhancement (FE) as high as 7.4 fold with Kd (2.55 ± 0.10) × 10−4 M and n = 1. This probe binds reversibly with Al3+ in the presence of H2EDTA2−, both under intra- and exctracellular conditions. LOD determined by 3σ methods was found to be 15 nM while LOQ = 52.8 nM. The tentative coordination environment in the Al3+–PP complex was delineated by DFT calculations both on the free ligand and complex. The TDDFT calculations reveal spectral features comparable to the experimental ones.

A newly designed oxime based probe, 2,4-dihydroxyacetophenone-oxime (DHAO), was found to recognize H2AsO4- selectively with ∼3 fold "turn-on" fluorescence enhancement and LOD of 29 μM, K = (2.10 ± 0.54) × 104 M-1 in purely aqueous medium. The structures of the DHAO and its adduct with H2AsO4- were optimized by DFT calculations. Intracellular imaging of As(V) in HepG2 cells demonstrate the possibilities of in vitro/in vivo applications for selective monitoring of such species.

Public policies are problem oriented and solve a public problem. Making decision and policies does not solve problems by itself but they must be executed effectively. As executing policies is a main step of policy making, formulating indicators for implementing policy is necessary. In this article we conducted a content analysis of elites’ opinions to improve implementation of public policies. Therefore, three major factors have been introduced including policy making, environmental policy implementation and organizational structure factors. Sample data were taken from agricultural organizations of Tehran and Qom. For data gathering library research, interview and questionnaire were used. To analyze the data, k-s, Pearson’s correlation coefficient, confirmatory factors analysis and means comparisons were applied using SPSS and LISREL. Results show all of proposed indicators and measures are valid for implementation of public policies and about important of indicators between two participant groups, indicators in Tehran groups is more important.

A simple salicylaldimine-based receptor equipped with rhodamine moiety (L3) has been designed and synthesized for detection of Al3+ ions, which exhibits high sensitivity over other metal ions in aqueous buffer-methanol solution at physiological pH. It displays quick responses through visible colorimetric as well as fluorogenic changes on 1:1 binding to Al3+, as delineated by absorption and fluorescence titrations and also by Job’s method and ESI-MS+ studies. However, it exhibits calorimetric but not fluorometric responses towards Cu2+ and hence limits its colorimetric application towards the detection of Al3+ in the presence of Cu2+ ions. The properties of the probe like (i) solubility in aqueous buffer-methanol, (ii) cell-permeability and (iii) non-toxic nature towards cell may provide an opportunity for the in vitro/ in vivo bio study. The detection limit of Al3+ calculated by the 3σ method was found to be 24.8 pM. It is also found to be useful in the construction of logic gates; namely ‘OR’ gate (from absorption) and molecular ‘keypad lock’ (from emission) by the two chemical inputs (Al3+ and Cu2+) in the proper sequence of addition. The keypad lock operation is particularly important, as the output of the system depends not only on the proper combination but also on the order of input signals, creating the correct password that can be used to ‘‘open’’ this molecular keypad lock through strong fluorescence emission at 552 nm. Besides, “OFF–ON–OFF” fluorescence behavior observed in the presence of Al3+ and EDTA strengthens the potential applications of the L3–Al3+ system as a device with ‘INHIBIT’ logic gate functions. As a whole, its various logic gate properties may improve its impact for the development of new-generation ‘intelligence’ digital devices. To the best of our knowledge, this is the first report on the fluorescence emission of a rhodamine derivative induced by Al3+ binding with such multiple logic gate operations accompanied by its application to cell-biology.

A new mesoporous silicotitaniumphosphate material has been synthesized by using a non-conventional phosphorous source trimethyl phosphite with the aid of Pluronic F127 as structure directing agent (SDA). The mesopores are generated due to the slow hydrolysis of the reactant materials in the presence of supramolecular-assembly of non-ionic surfactant under the evaporation induced self-assembly (EISA) process. The material has been characterized by powder XRD, N2 sorption, TEM, SEM–EDS, TG–DTA, FT-IR, XPS, 29Si, 31P MAS NMR and UV–vis spectroscopic techniques. This new mesoporous material has considerably high BET surface area (379 m 2 g −1 ) and narrow pore size distribution with a peak pore width of 5.4 nm. The material showed good catalytic activity in the liquid phase Friedel–Crafts benzylation reaction suggesting strong acidity on its surface. It can also be used as good adsorbent for the removal of toxic metal ions As(III/V), Cd(II) and Hg(II) from the contaminated water. © 2010 Elsevier B.V. All rights reserved.

The molecular structure of the title salt, C(11)H(17)N(4)(+).H(2)PO(4)(-), has been determined from single-crystal X-ray analysis and compared with the structure calculated by density functional theory (DFT) at the BLYP level. The crystal packing in the title compound is stabilized primarily by intermolecular N-H...O, O-H...N and O-H...O hydrogen bonds and pi-pi stacking interactions, and thus a three-dimensional supramolecular honeycomb network consisting of R(4)(2)(10), R(4)(4)(14) and R(4)(4)(24) ring motifs is established. The HOMO-LUMO energy gap (1.338 eV; HOMO is the highest occupied molecular orbital and LUMO is the lowest unoccupied molecular orbital) indicates a high chemical reactivity for the title compound.

Rate constants for the nucleophilic substitution reactions of imidazolide (IZ − ) and benzimidazolide (BIZ − ) ions with 4 - Cr - Z and 5 in MeOH at 25 °C are reported and Hammett ρ values are evaluated to be 1.50 ± 0.10 and 1.51 ± 0.08 for 4 - Cr - Z -IZ − and 4 - Cr - Z -BIZ − reactions, respectively. The comparable reactivity and also almost identical ρ values for these reactions indicate that there is no difference in sensitivity towards electronic effects due to slightly bigger size of BIZ − over IZ − and bond formation at the transition states are equally progressed. The higher ρ values for these reactions compared to those with a wide range of nucleophiles may arise mainly due to lower polarity of the solvent MeOH which enhances the requirement for stabilization of the negative charge in the transition state by the Z-substituents.

The coordination chemistry of two aminebis(phenolate) ligands (H2L1 and H2L2) around vanadium(V) is described. Vanadium(V) oxo complexes (1, 2 and 3) of all the ligands were obtained readily by the reaction between the ligand precursors and [VO(acac)2]. Single crystal X-ray structure analysis showed that all of the complexes are penta-coordinated with trigonal bipyramidal geometry in NO4 coordination environment. The tripodal nitrogen atom of the respective ligands and monodentate alkoxo group occupy apical positions. These complexes structurally resemble very closely to the active sites of vanadium haloperoxidases (VHPO) and were found to catalyze the oxidation of toluene to benzoic acid and isomers of xylene to the corresponding hydroxy acids with turn over numbers ranging between 134 and 188. Based on mass spectra the mechanism of the catalytic process was proposed to proceed through the formation of hydroxo–hydroperoxo intermediate, which is different from halo peroxidase reactions.

The aminolysis of α-isobutyl-α-(methylthio)methylene Meldrum's acid 7 with primary amines, namely, n-butylamine, glycinamide, and methoxyethylamine in DMSO–H2O (50:50, v/v) at 20 °C is overall second-order but first-order in both 7 and amines. The reaction with aminoacetonitrile (AA) is overall third-order, first-order in substrate, and second-order in amine at low amine concentration, while at high amine concentration and high pH the dependence on amine is first-order. A general three-step mechanism has been proposed for all these reactions. For the former group of amines, the first step is a rate-limiting attack of the amine to form the tetrahedral intermediate (TA±), followed by a fast acid–base equilibrium and a fast RNH3+- or H2O-assisted leaving group expulsion. For AA, general base catalysis was confirmed from the dependence of kA on [AA]f and on [OH–]. For all four amines, a good Brønsted plot of log k1 vs. pKaAH in DMSO–H2O (50:50, v/v) with βnuc = 0.34 ± 0.02 was observed. These observations are consistent with the suggested mechanism.Key words: nucleophilic vinylic substitution reactions, primary amines, α-isobutyl-α-(methylthio)methylene Meldrum's acid, three-step mechanism.

A kinetic study of the reaction of hydroxide ion with (CO) 5 Mo C(XCH 2 CH 2 OH)(C 6 H 5 ) (X = O for Mo–OR , and X = S for Mo–SR ), and (CO) 5 W C(OCH 2 CH 2 OH)(C 6 H 4 –Z) ( W–OR(Z) ) is reported. The results are consistent with a pathway in basic solution that involves rapid deprotonation of the OH group followed by rate-limiting cyclization. The parameter k 1 K OH for the reaction of W–OR(Z) was determined as a function of the phenyl substituents. They were found to correlate well with the Hammett equation. The dependence of the reactivity on the metal atoms in the complexes M–OR (M = Cr, Mo and W) shows that the reactivity decreases slightly down the group of the Periodic Table, while for M–SR the reactivity increases slightly down the group. A plausible explanation of these results is offered based on electronegativity values of the metal atoms. The much higher ρ ( k 1 K OH ) value for W–OR(Z) over W–SR(Z) arises mainly due to the stabilization of the reactant carbene complex by the stronger π-donor effect of oxygen over sulfur.

A new transition-metal-free, sodium metaperiodate (NaIO4)-mediated direct oxidation of methylarenes and benzylic bromides to the corresponding aromatic carboxylic acids is described. Under the same reaction conditions, benzylic alcohols are selectively oxidized to afford the corresponding aldehydes in good yields without undergoing overoxidation. Unprecedentedly, oxidation of benzyl bromide, toluene, or benzyl alcohol with NaIO4 underwent nuclear bromination followed by oxidation to give 4-bromobenzoic acid in 60−79% yields.

Kinetic studies of the aminolysis of [methyl(thiomethyl)carbene]pentacarbonyl chromium(0),(CO)5Cr C(CH3)(SCH3) (1-Cr(S)) and [methyl(thiomethyl)carbene]pentacarbonyltungsten(0), (CO)5W C(CH3)(SCH3) (1-W(S)), with morpholine, a secondary amine, in 50% acetonitrile–50% H2O (v/v at 25 °C) is reported. The second-order rate constant (kA in m−1 s−1) increases with amine concentration, giving a linear dependence with an intercept on the rate axis and a tendency towards leveling off at higher amine concentration. The reaction was found to undergo general base catalysis. The mechanism proposed is very similar to those for ester reactions, involving a nucleophilic addition of amine to the substrate to yield a zwitterionic tetrahedral intermediate ( T A ± ) in the first step, followed by deprotonation to form T A - in the second step, which, in the third step, converted to product by H2O and/or conjugate acid of the base (BH+), assisted MeS− expulsion. The reactivity (k1) of 1-W(S) was found to be higher than that of 1-Cr(S), whereas, comparable ( k 3 H 2 O K a ± / k - 1 K w ) , water catalyzed and ( k 3 BH K a ± / k - 1 K a BH ) , BH+ catalyzed, leaving group departure were found for both the carbenes complexes. All these observations have been explained successfully.