Terpyridine–Lanthanide Complexes Respond to Fluorophosphate Containing Nerve Gas G-Agent Surrogates

Terpyridine-Functionalized Calixarenes: Synthesis, Characterization and Anion Sensing Applications

Lanthanide complexes have been developed and are reported herein. These complexes were derived from a terpyridine-functionalized calix[4]arene ligand, chelated with Tb3+ and Eu3+. Synthesis of these complexes was achieved in two steps from a calix[4]arene derivative: (1) amide coupling of a calix[4]arene bearing carboxylic acid functionalities and (2) metallation with a lanthanide triflate salt. The ligand and its complexes were characterized by NMR (1H and 13C), fluorescence and UV-vis spectroscopy as well as MS. The photophysical properties of these complexes were studied; high molar absorptivity values, modest quantum yields and luminescence lifetimes on the ms timescale were obtained. Anion binding results in a change in the photophysical properties of the complexes. The anion sensing ability of the Tb(III) complex was evaluated via visual detection, UV-vis and fluorescence studies. The sensor was found to be responsive towards a variety of anions, and large binding constants were obtained for the coordination of anions to the sensor.

Emergence of a New [NNN] Pincer Ligand via Si-H Bond Activation and β-Hydride Abstraction at Tetravalent Cerium

The cerium(IV) pyrazolate complexes [Ce(Me2 pz)4 ]2 and [Ce(Me2 pz)4 (thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me2 pz)3 (bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me2 pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si-H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2 pz)4 ]2 is treated with [Li{N(SiMe3 )2 }], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2 (Me2 pz)9 ] and the stable mixed-ligand ceric species [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] were obtained.

Luminescent Europium(III) "Turn-On" Sensor for G-Series Chemical Warfare Simulants: A Mechanistic Investigation

A thermodynamically stable terpyridine-dicarboxylate based emissive Eu(III) probe, [Eu(OH-TPDC)] (1), was designed as a time-resolved "turn-on" luminescent probe for the selective sensing of diethyl chlorophosphate (DCP), a G-series nerve agent simulant through modulation of sensitization of ⁵D₀ → ⁷F_J transitions from Eu(III) via quenching of nonradiative vibrational energy transfer.

Adaptable Eu-containing polymeric films with dynamic control of mechanical properties in response to moisture

Self-healing polymers often have a trade-off between healing efficiency and mechanical stiffness. Stiff polymers that sacrifice their chain mobility are slow to repair upon mechanical failure. We herein report adaptable polymer films with dynamically moisture-controlled mechanical and optical properties, therefore having tunable self-healing efficiency. The design of the polymer film is based on the coordination of europium (Eu) with dipicolylamine (DPA)-containing random copolymers of poly(n-butyl acrylate-co-2-hydroxy-3-dipicolylamino methacrylate) (P(nBA-co-GMADPA)). The Eu-DPA complexation results in the formation of mechanically robust polymer films. The coordination of Eu-DPA has proven to be moisture-switchable given the preferential coordination of lanthanide metals to O over N, using nuclear magnetic resonance and fluorescence spectroscopy. Water competing with DPA to bind Eu3+ ions can weaken the cross-linking networks formed by Eu-DPA coordination, leading to the increase of chain mobility. The in situ dynamic mechanical analysis and ex situ rheological studies confirm that the viscofluid and the elastic solid states of Eu-polymers are switchable by moisture. Water speeds up the self-healing of the polymer film by roughly 100 times; while it can be removed after healing to recover the original mechanical stiffness of polymers.

Luminescent europium(iii) and terbium(iii) complexes of β-diketonate and substituted terpyridine ligands: synthesis, crystal structures and elucidation of energy transfer pathways

A series of coordinatively saturated Ln^III complexes: [Ln(R-TPY)(TTA)₃] (1–6) were designed and structurally characterized and plausible energy transfer (ET) pathways determined using a theoretical method.

Qualitative colorimetric analysis of a Ir(iii)/Eu(iii) dyad in the presence of chemical warfare agents and simulants on a paper matrix

The addition of G- and V-series organophosphorus chemical warfare agents and simulants to a paper-based assay of a dual-luminescent Ir(iii)/Eu(iii) dyad generated different emissive responses between the classes and compound types. The emission responses are complex and based not only on altering the balance between red Eu(iii)-based and blue Ir(iii)-based luminescent components, but also incorporate other factors such as analyte volatility, concentration and UV absorption. The extent of this emission colour change was analysed colorimetrically and related to the change in RGB output over time.

A dual emissive Ir(iii)/Eu(iii) dyad in a paper-based luminescence assay for liquid chemical warfare agents demonstrated clear visual responses.

Solid-state sensors based on Eu3+-containing supramolecular polymers with luminescence colour switching capability

Polymers that exhibit changes of their luminescence colour in response to external stimuli are attractive candidates for sensing systems. We herein report the preparation of europium-based metallosupramolecular polymers, which can be processed into films and coatings that display readily detectable luminescence colour changes in response to various types of analytes.

Visual detection of a nerve agent simulant using chemically modified paper strips and dye-assembled inorganic nanocomposite

Chromogenic probe with oxidized bis-indolyl scaffold has been synthesized for the detection of a nerve gas mimicking agent, DCNP (diethyl cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the release of cyanide ion through the indole group mediating the hydrolysis of phosphorous-hetero atom bond and, thereafter, the Michael addition of the liberated CN^- ion to the electron deficient C[double bond, length as m-dash]C bond of the bis-indolyl moiety. The reaction featured a remarkable change in color from red to colorless at ambient condition. Then, low-cost and portable paper strips were designed for a rapid and on-site vapor phase detection of DCNP without involving any sophisticated instrument or skilled personnel. Finally, a dye assembled inorganic nanocomposite material was devised to achieve a more sensitive 'turn-on' detection of DCNP in water.

Discrimination of tabun mimic diethyl cyanophosphonate from sarin mimic diethyl chlorophosphate via Zn(ii)-triggered photoinduced electron transfer-decoupled excited state intramolecular proton transfer processes

PET-coupled ESIPT platform and its Zn²⁺ complex are used for the discrimination of the nerve agent mimics DCNP and DCP.

Rapid ‘naked eye’ response of DCP, a nerve agent simulant: from molecules to low-cost devices for both liquid and vapour phase detection

A rhodamine-based new chemosensor, RHM, has been designed and synthesized. It reacts selectively with the organophosphate compound, DCP, a well-known nerve gas simulant (both in the liquid and vapour phase).

Polynorbornene derived 8-hydroxyquinoline paper strips for ultrasensitive chemical nerve agent surrogate sensing

The detection of nerve agent simulants is achieved by the photoinduced electron transfer (PET) mechanism.

Interactions of the G-series organophosphorus chemical warfare agent sarin and various simulants with luminescent lanthanide complexes

G-series organophosphorus chemical warfare agent sarin, and various simulants, interact with simple lanthanide complexes producing fluorescence quenching via a dynamic mechanism.

Nitroxide-Mediated Controlled Free Radical Polymerization of the Chelate Monomer 4-Styryl-tris(2-pyridyl)borate (StTpyb) and Supramolecular Assembly via Metal Complexation

The reaction of 4-(dibromoboryl)styrene with 2-pyridylmagnesium chloride resulted in the formation of 4-styryl-tris(2-pyridyl)borate free acid (StTypb), a new polymerizable nonpyrazolyl "scorpionate" ligand. StTypb did not undergo self-initiated polymerization under ambient conditions and proved to slowly polymerize through standard radical polymerization at 90 °C. Nitroxide-mediated polymerization (NMP) of StTypb at 135 °C proceeded with good control, resulting in a polymer of M_n = 27400 and PDI = 1.21. The TEMPO-terminated homopolymer successfully initiated the polymerization of styrene, generating an amphiphilic block copolymer with DP_n of 1200 and 78 for the PS and the StTypb block, respectively. A similar block copolymer with DP_n of 29 and 20 for the PS and the StTypb block respectively was obtained in a reverse polymerization procedure from a PS macroinitiator. The self-assembly of these block copolymers was examined in selective solvents and preliminary metal complexation studies were performed.

Unusual red shift of the sensor while detecting the presence of Cd2+ in aqueous environment

A norbornene derived 8-hydroxyquinoline (N8HQ) is designed and synthesized. A "turn-on" ratiometric fluorescent response is observed for Cd(2+) in aqueous solution upon binding with N8HQ with a characteristic huge red shift of 164 nm. A lowest detection limit of 1.6 nM of Cd(2+) is achieved in the presence of other heavy metals.

Unusual emission from norbornene derived phosphonate molecule--a sensor for Fe(III) in aqueous environment

This communication describes the synthesis and characterization of norbornene derived phosphonates (NDP1 to NDP3). The unusual fluorescence of NDP1 is attributed to the difference between the positions of HOMO and LUMO wave functions that lead to the prevention of non-radiative relaxation pathways. Due to the significant non-radiative relaxation pathway, the control molecule NDP2 shows weak fluorescence whereas NDP3 shows no fluorescence at all. Similar experiments are carried out on NDPH1, the homopolymer of NDP1. Our hypothesis is further strengthened as there is no emission from NDPH1. The unusual fluorescence is utilized as a new fluorometric sensor that selectively detects Fe(III) ions.

A rhodamine-deoxylactam based sensor for chromo-fluorogenic detection of nerve agent simulant

N-(rhodamine B)-deoxylactam-5-amino-1-pentanol (dRB-APOH) was designed and prepared as the chromo-fluorogenic sensor for detection of a nerve agent simulant via analyte triggered tandem phosphorylation and opening of the intramolecular deoxylactam. The successful detection of diethyl chlorophosphate suggests the utility of rhodamine-deoxylactams as the chromo-fluorogenic signal reporting platform for design of sensors targeting reactive chemical species via various chemistries.

Self-assembling zeolite crystals into uniformly oriented layers

We report important progress made in the synthesis of oriented functional layers of nanochannel materials by using coordination chemistry as a tool. Zeolite L (ZL) crystals have been arranged into oriented layers through the coordinative interactions between a functional organic linker (L) and metal cations used for connecting the different parts. As organic linker we used a terpyridyl ligand bearing a urea group and a reactive siloxane part. Two strategies that lead to monolayers with different properties are described. The first consists of reacting the siloxane group of ligand L with OH groups of the substrate (S), and selectively reacting the siloxane group of L with OH groups located at the base of the ZL crystals. Next, metal cations M(n+), for example, Zn(2+) or Cu(2+), are coordinated to the terpy group on the modified substrate. To this the modified ZL is added and coordinatively bound by the terpy(Mn(n+))terpy interaction, leading to oriented ZL layers. The second method consists of reacting substrate S and ligand L in the presence of a metal cation. A layer with reactive siloxane groups is formed on S to which the ZL crystals are bound by the reaction of the hydroxyl groups of their base. Zn(2+), Cu(2+), and lanthanide ions Eu(3+) and Tb(3+)have been tested successfully, all of them leading to high-quality ZL monolayers with open channels, accessible for accepting guests, oriented perpendicularly with respect to the surface of S.