ABSTRACT
Despite the recent surge of interest in two-dimensional (2D) inorganic nanosheets derived from photoactive coordination polymers of lanthanide ions having interesting optical properties, research in this area is still in its infancy. Luminescent lanthanide ions, Eu(iii) or/and Tb(iii), as well as a bis-terpyridine ligand (L), were used in this study as the building blocks for the synthesis of the archetypical layered structure of coordination polymers (CPs) (L·Eu/L·Tb). 2D-nanosheets were obtained through exfoliation of the layered precursor of CPs in a suitable solvent system following a sonication-assisted strategy. These nanosheets exhibit lateral sizes on the micrometer scale (0.3-1 µm) and an ultrathin thickness of 2-6.5 nm. 1,1-Diamino-2,2-dinitroethene or FOX-7 is an insensitive high explosive; in a binder mixture, it exhibits a slightly superior detonation velocity of 8870 m s-1 in comparison to RDX. The insensitive nature of FOX-7 makes it a key component for the development of low vulnerable high explosive compositions for further application in weaponry. The growing demand for FOX-7, for use as a suitable replacement of conventional explosives, is of serious concern to human security. Achieving rapid and efficient detection of this unexplored explosive is a challenging task. In the present study, the developed luminescent nanosheets were used for the first time for micromolar level detection of FOX-7 both in solution and in the solid state. A visually distinct color change of the nanosheets from red (L·Eu) and green (L·Tb) to colorless was witnessed upon UV light irradiation during the detection process. Notably, the solid-state detection technique could be exploited for developing a commercial spray kit for quick onsite screening of this important explosive.
ABSTRACT
Unique dependence on the nature of metal salt and reaction conditions for coordination assembly reactions of varying architecture and nuclearity have been identified in V-shaped [Co3L4] and planar disc-like [Co7L6] compounds: [CoL2(µ-L)2(µ-OH2)2(CF3CO2)2] (1) and [Co(µ-L)6(µ-OMe)6]Cl2 (2) (HL = 2-{(3-ethoxypropylimino)methyl}-6-methoxyphenol). At room temperature varying reaction conditions, cobalt-ligand ratios and use of different bases allowed unique types of coordination self-assembly. The synthetic marvel lies in the nature of aggregation with respect to the two unrelated cores in 1 and 2. Complex 1 assumes a V-shaped arrangement bound to L(-), water and a trifluoroacetate anion, while 2 grows around a central Co(II) ion surrounded by a {Co} hexagon bound to methoxide and L(-). Magnetic measurements revealed that the intermetallic interactions are antiferromagnetic in nature in the case of complex 1 and ferromagnetic in the case of 2 involving high spin cobalt(ii) ions with stabilization of the high-spin ground state in the latter case. In MeCN solutions complexes 1 and 2 showed catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBCH2) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in air. The kinetic study in MeCN revealed that with respect to the catalytic turnover number (kcat) 2 is more effective than 1 for oxidation of 3,5-DTBCH2.
Subject(s)
Biomimetic Materials/chemical synthesis , Catechol Oxidase/chemistry , Cobalt/chemistry , Coordination Complexes/chemical synthesis , Magnetics , Benzoquinones/chemistry , Biomimetic Materials/chemistry , Catalysis , Catechols/chemistry , Coordination Complexes/chemistry , Models, Molecular , Oxidation-ReductionABSTRACT
A [Ni(II)4] staircase complex was serendipitously prepared from the reaction of the binucleating Schiff base proligand 2,6-bis[[(3-hydroxypropyl)imino]methyl]-4-methylphenol (H3L2) and 3,5-dimethylpyrazole (Me2pzH) with nickel(II) nitrate in a reaction at room temperature, initially aimed to yield a dinuclear complex. From a room temperature metal ion/ligand reaction, the proligand H3L2 in situ transformed to modified forms HL3(2-) and HL4(2-), allowing the [Ni4] formation. Variable-temperature magnetic behavior of a [Ni4] complex reveals antiferromagnetic interactions with stabilization of a diamagnetic ground state (ST = 0).