A family of organic chromophores that, like pyrene, forms emissive excimers is reported. Their chemical and photophysical properties are superior to pyrene for the design of chemo- and biosensors. Unlike hydrophobic pyrene, which requires excitation by cell-damaging UV irradiation, these polar dyes absorb strongly in the visible range, and their excimers emit brightly in the red to far-red region of the electromagnetic spectrum. The intensity of the emission signal is greatly increased upon formation of a preassociated dimer that is triggered upon aggregation or crystallization. In demonstration of the potential of this new family of excimer-forming dyes, a probe that is capable of detecting label-free DNA in water down to 10 pM and also doubles as a visualization agent for DNA in gel electrophoresis is reported.

The synthesis of the one-dimensional K2Hg3Q4 (Q = S, Se) and Cs2Hg3Se4 and the three-dimensional A2Hg6S7 (A = K, Rb, Cs), and A2Hg6Se7 (A = Rb, Cs) in reactive A2Q x fluxes is reported. Pale yellow, hexagonal plates of K2Hg3S4 crystallize in space group Pbcn, with a = 10.561(5) Å, b = 6.534(3) Å, and c = 13.706(2) Å, V = 945.8(7) Å, d calc = 5.68 g/cm3, and final R = 5.7%, R w = 6.3%. Red, hexagonal plates of K2Hg3Se4 crystallize in space group Pbcn, with a = 10.820(2) Å, b = 6.783(1) Å, and c = 14.042(2) Å, V = 1030.6(5) Å, d calc = 6.42 g/cm3, and final R = 7.7%, R w = 8.4%. Orange yellow, hexagonal plates of Cs2Hg3Se4 crystallize in space group Pbcn, with a = 12.047(4) Å, b = 6.465(2) Å, and c = 14.771(6) Å, V = 1150.4(7) Å, d calc = 6.83 g/cm3, and final R = 5.5%, R w = 6.2%. Black needles of K2Hg6S7 crystallize in space group P4̄21 m, with a = 13.805(8) Å and c = 4.080(3) Å, V = 778(1) Å, d calc = 6.43 g/cm3, and final R = 3.1%, R w = 3.6%. Black needles of Rb2Hg6S7 crystallize in space group P42 nm, with a = 13.9221(8) Å and c = 4.1204(2) Å, V = 798.6(1) Å, d calc = 6.65 g/cm3, and final R = 4.3%, R w = 5.0%. Black needles of Cs2Hg6S7 crystallize in space group P42 nm, with a = 13.958(4) Å and c = 4.159(2) Å, V = 810.2(8) Å, d calc = 6.94 g/cm3, and final R = 4.3%, R w = 4.4%. Black needles of Cs2Hg6Se7 crystallize in space group P42 nm, with a = 14.505(7) Å and c = 4.308(2) Å, V = 906(1) Å, d calc = 7.41 g/cm3, and final R = 3.6%, R w = 4.0%. The A2Hg3Q4 compounds contain linear chains. The A2Hg6Q7 compounds display noncentrosymmetric frameworks with A+ cations residing in tunnels formed by both tetrahedral and linear Hg atoms. K2Hg6S7, Rb2Hg6S7, Cs2Hg6S7, Rb2Hg6Se7, and Cs2Hg6Se7 display room-temperature bandgaps of 1.51, 1.55, 1.61, 1.13, and 1.17 eV, respectively. Bandgap engineering through S/Se solid solutions of the type Rb2Hg6Se7 - x S x and Cs2Hg6Se7 - x S x is possible in these materials. All A2Hg6Q7 melt congruently, with melting points of 556 ± 10 °C, except for Rb2Hg6Se7 which degrades. Rb2Hg6S7 can undergo ion exchange reactions with LiI to give Li1.8Rb0.2Hg6S7.

No abstract

This work presents the synthesis, structure determination and magnetic properties of a new complex, phenethylammonium tetrachloromanganate(II), (C(6)H(5)CH(2)CH(2)NH(3))(2)MnCl(4) (Mn-PEA). Single crystals of Mn-PEA were obtained from methanol solution using the solvent-evaporation method at room temperature. The crystal structure of Mn-PEA was determined by single-crystal X-ray diffraction (orthorhombic, space group Pbca, a = 7.2075(9), b = 7.3012(14), c = 39.413(6) Å and Z = 4). The structure consisted of an extended [MnCl(4)](2-) network and two phenethylammonium cations to form a two-dimensional halide perovskite structure. Temperature-dependent magnetization measurements indicated that Mn-PEA acted as a weak ferromagnet below T(C) = 44.3 K due to spin canting. Below T(C), the magnetic behavior differed significantly from the behavior commonly observed among weak ferromagnets. The susceptibility depended strongly on the crystal orientation, the external magnetic field strength, and the magnetic history. The isothermal magnetization for two orientations revealed a ferromagnetic moment with a spin-canting angle of 0.04° and a spin-flop transitions with H(sf) = 3.5 T. The weak ferromagnetism, which manifested as spontaneous magnetization and magnetic hysteresis near a field strength of zero, was driven by interplay between the easy axis and the antisymmetric Dzyaloshinsky-Moriya (DM) interaction, leading to directional dependent magnetic behavior.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.