The synthesis and crystal structures of a series of six crystalline potassium salts of hypodiphosphoric acid, H(4)P(2)O(6), are reported, namely potassium hydrogen phosphonophosphonate, K(+)·H(3)P(2)O(6)(-), (I), dipotassium dihydrogen hypodiphosphate monohydrate, 2K(+)·H(2)P(2)O(6)(2-)·H(2)O, (II), dipotassium dihydrogen hypodiphosphate dihydrate, 2K(+)·H(2)P(2)O(6)(2-)·2H(2)O, (III), pentapotassium hydrogen hypodiphosphate dihydrogen hypodiphosphate dihydrate, 5K(+)·HP(2)O(6)(3-)·H(2)P(2)O(6)(2-)·2H(2)O, (IV), tripotassium hydrogen hypodiphosphate tetrahydrate, 3K(+)·HP(2)O(6)(3-)·4H(2)O, (V), and tetrapotassium hypodiphosphate tetrahydrate, 4K(+)·P(2)O(6)(4-)·4H(2)O, (VI). All the hypodiphosphate anions, viz. H(3)P(2)O(6)(-), H(2)P(2)O(6)(2-), HP(2)O(6)(3-) and P(2)O(6)(4-), adopt a staggered conformation. The P-P bond lengths [2.1722 (7)-2.1892 (10) Å] do not depend on the basicity of the anion. The compounds are organized into different types of one-, two- or three-dimensional polymeric hydrogen-bonded networks, or simply exist in the form of isolated or dimeric units. The coordination numbers of the K(+) cations range from 6 to 9, and the cationic sublattices are polymeric one-, two- or three-dimensional networks, or isolated [KO(6)] or dimeric [K(2)O(12)] polyhedra.
The rise of OLED technology for display applications over the past decade was impressive. Today, OLED displays can be found everywhere, for example, in smartphones, TVs, smartwatches, monitors, cars, or digital cameras. However, as technology advances, the need for better OLED materials which help to improve energy efficiency and resolution of OLED displays is growing. While for the red and green pixels, phosphorescent materials have allowed for a boost in performance, the use of fluorescent materials for the blue pixel still limits the efficiency of OLED displays. Academic research has demonstrated many improvements regarding the efficiency of blue OLEDs using phosphorescent or TADF materials. However, studies on the limitations of device lifetime are rare. In the present chapter, the development of blue OLEDs based on TADF emitters is discussed from an industrial point of view. First, the material design principles for TADF molecules as well as the requirements for efficient blue TADF emitters are discussed. Moreover, a short literature overview on the latest improvements in blue TADF materials in academia and industry is presented. Finally, an outlook on this technology, its industrial possibilities, and alternatives is given.
Given the hexadenticity of the monoanionic ligand in the procatalyst [Mn(tpena)(H2O)](ClO4) {tpena– = N,N,N′‐tris(2‐pyridylmethyl)ethylenediamine‐N′‐acetate}, it is perhaps surprising that this complex can catalyze the epoxidation of alkenes. When peracetic acid is used as terminal oxidant, the selectivity and rates of reactions are comparable with those reported for the manganese complexes of the commonly employed neutral tetradentate N4 ligands under analogous conditions. Cyclooctene conversion rates are similar when tert‐butyl hydroperoxide (TBHP) is used; however, the selectivity is greatly diminished. In the absence of organic substrates, [MnII(tpena)]+ catalyzes water oxidation by TBHP (initial rate ca. 23 mmol/h when [Mn] = 0.1 mM, at room temp.). To explain the variations in the selectivity of catalytic epoxidations and the observation of competing water oxidation, we propose that several metal‐based oxidants (the “cooks”) can be generated from [MnII(tpena)]+. These embody different potencies. The most powerful, and hence least selective, is proposed to be the isobaric isomer of [MnIV2(O)2(tpena)2]2+, namely an oxylic radical complex, [(tpena)MnIII(μ2‐O)MnIV(O·)(tpena)]2+. The formation of this species depends on the catalyst concentration, and it is favoured when TBHP is used as the terminal oxidant. The generation of the less potent [MnIV(O)(tpena)]+, which we propose as the direct oxidant in epoxidation reactions, is favoured in non‐aqueous solutions when peracetic acid is used as the terminal oxidant.
5-Cyanotetrazole readily forms from (CN) 2 and HN 3 . The coordination abilities of the 5-cyanotetrazolate anion N 4 CCN -(ctz) towards Cu II ions were examined and a series of complexes and coordination polymers were synthesized and characterized by single-crystal structure analyses: PPh 4 [Cu (ctz) 3 ] (1), [Cu(ctz) 2 (bipy)] (2, bipy = 2,2Ј-bipyridine), [CuCl(py) 4 ](ctz)·2py (3, py = pyridine), [Cu 2 (ctz) 6 Cu(CH 3 CN) 2 -(H 2 O) 2 ]·2CH 3 CN (4a), [Cu 2 (ctz) 6 Cu(H 2 O) 3 {(CH 3 ) 2 CO}]· 3(CH 3 ) 2 CO (4b), [Cu(ctz) 2 (py) 4 ] (5), [Cu 2 (ctz) 4 (bipy) 2 ] (6) and [Cu 2 (ctz) 2 (tpm) 2 (NO 3 )]NO 3 [7, tpm = tris(pyrazol-1-yl)methane]. As ctz is a multidentate linker, additional neutral coligands such as monodentate py, bidentate bipy and tridentate tpm ligands were used to avoid the formation of noncrystalline polymers. The structures of 1-7 reflect the versatile [a]
The mononuclear iron(II) complex [Fe(tpm)2]2+(tcp–)2 (1) containing the neutral tripodal N3‐donor ligand tris(pyrazol‐1‐yl)methane (tpm) and the mononegative tetracyanopyrrolide (tcp) as counter‐anion was characterized by X‐ray diffraction on twinned crystals and investigated in the solid state by magnetic susceptibility measurements and differential scanning calorimetry. Structural investigations at 123 K reveal Fe–N distances typical for low‐spin d6 iron(II). Compound 1 undergoes a gradual, incomplete spin crossover in the examined temperature range 1.9–400 K. Comparisons are made with known analogous [Fe(tpm)2]2+(X–)2 compounds bearing different anions X, which display similar crossover behavior.
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