Iodoplumbate mit vier‐ und fünffach koordinierten Pb2+‐Ionen

Iodoplumbates with Tetra‐ and Penta‐coordinated Pb²⁺ Ions In contrast to all known iodoplumbates with octahedrally coordinated Pb²⁺ ions, square pyramidal geometry is observed in the iodoplumbate chains of (Pr₄N)[PbI₃] ( 1 ) and [Mg(dmf)₆][PbI₃]₂ ( 2 ), whereas the isolated anions in (Ph₄P)₂[Pb₂I₆] ( 3 ) and [Bu₃N–(CH₂)₃–NBu₃][PbI₄] ( 4 ) contain tetra‐coordinated lead atoms. (Pr₄N)[PbI₃] ( 1 ): a = 910.86(6), b = 1221.46(7), c = 1907.7(1) pm, V = 2122.5(2) · 10⁶ pm³, space group P2₁2₁2₁; [Mg(dmf)₆][PbI₃]₂ ( 2 ): a = 891.24(9), b = 1025.34(7), c = 1234.82(9) pm, α = 92.938(8), β = 106.457(8), γ = 98.100(7)°, V = 1066.4(2) · 10⁶ pm³, space group P1; (Ph₄P)₂[Pb₂I₆] ( 3 ): a = 1174.5(1), b = 722.29(7), c = 3104.8(4) pm, β = 100.50(1)°, V = 2589.8(5) · 10⁶ pm³, space group P2₁/n; [Bu₃N–(CH₂)₃–NBu₃][PbI₄] ( 4 ): a = 2178.3(1), b = 1008.63(5), c = 1888.3(1) pm, β = 110.003(5)°, V = 3898.6(4) · 10⁶ pm³, space group P2/c.     

A Rational Approach to Tetra-Functional Photo-Switches

α,ω-Bis(1,8-dichloroanthracen-10-yl)alkanes with (CH₂)_n-linker units (n=1–4) were synthesized starting from 1,8-dichloroanthracen-10(9H)-one. This was transformed into anthracenes with allyl, bromomethyl and propargyl substituents in position 10; these were converted in various C−C-bond formation reactions (plus hydrogenation), leading to two anthracene units flexibly linked by α,ω-alkandiyl groups. 1,2-Ethandiyl- and 1,3-propandiyl-linked derivatives were functionalized with ethynyl groups in positions 1, 8, 1’ and 8’, and these terminally functionalized by Me₃Sn groups using Me₂NSnMe₃. All linked bisanthracenes were subjected to UV light induced cyclomerization and a series of 9,10 : 9’,10’-photo-cyclomers were obtained. Their thermal cycloreversion and (repeated) switchability was demonstrated. 1,3-Bis{1,8-bis[(trimethylstannyl)ethynyl]anthracen-10-yl}propane served as model compound for photo-switchable acceptor molecules and its open and closed forms were characterized by NMR and DOSY experiments.     

Sorption and separation of CO2 via nanoscale AlO(OH) hollow spheres

The CO(2) uptake on nanoscale AlO(OH) hollow spheres (260 mg g(-1)) as a new material is comparable to that on many metal-organic frameworks although their specific surface area is much lower (530 m(2) g(?1)versus 1500-6000 m(2) g(?1)). Suited temperature-pressure cycles allow for reversible storage and separation of CO(2) while the CO(2) uptake is 4.3-times higher as compared to N(2).     

Carbon dioxide reduction by an Al–O–P frustrated Lewis pair

The reaction of tBu₂P(O)H with Bis₂AlH (Bis = CH(SiMe₃)₂) afforded the adduct tBu₂P(H)–O–Al(H)Bis₂ (3). It slowly releases H₂ to form the first oxygen-bridged geminal Al/P frustrated Lewis pair tBu₂P–O–AlBis₂. It is capable of reversibly binding molecular hydrogen to afford 3, shown by NMR and H/D scrambling experiments, and forms a 1,2-adduct with CO₂. Importantly, the H₂ adduct 3 reduces CO₂ in a stoichiometric reaction leading to the formic acid adduct tBu₂P(H)–O–Al(CO₂H)Bis₂. The formation of the different species was explored by density functional theory calculations which provide support for the experimental results. All products were characterized by NMR spectroscopy as well as X-ray diffraction experiments and elemental analyses.

Addition vs. reduction: the geminal FLP Bis₂Al–O–PtBu₂ can reversibly bind molecular hydrogen, it reacts with CO₂ to give an adduct, and its hydrogen adduct reduces CO₂ to an adduct of formic acid.     

High sensitive competitive immunodetection of 2,4-dichlorophenoxyacetic acid using enzymatic amplification with electrochemical detection

The amplification cycle consisting of NADH independent oligosaccharide dehydrogenase (ODH) and laccase has been recently reported to be highly sensitive to several catecholamines and p-aminophenol. A competitive immunoassay for 2,4-dichlorophenoxyacetic acid has been developed by combining this amplification cycle with β-galactosidase as enzyme label resulting in p-aminophenol as product. The combination of enzymatic amplification cycles with a competitive immunoassay yields a highly sensitive measurement of 2,4-dichlorophenoxyacetic acid. Using a monoclonal antibody the linear range of the assay was between 0.02 and 100 ng/l and the c₅₀ was found at 0.2 ng/l; the detection limit was at 5 pg/l (25 fmol/l) corresponding to 5 amol.     

Dichlorosilane-dimethyl ether aggregation: a new motif in halosilane adduct formation

The crystal structures of (H(3)C)(2)O, H(2)SiCl(2) and an adduct of these were determined by low-temperature X-ray crystallography on crystals grown in situ at low temperatures on a diffractometer. The adduct of (H(3)C)(2)O and H(2)SiCl(2) has the composition [(H(3)C)(2)O.H(2)SiCl(2)](2) and contains a four-membered Si(2)O(2) ring, with the Cl atoms pointing to the outside and the Si-H functions pointing to the inner side of the ring. The Si(2)O(2) ring has two longer and two shorter SiO bonds and thus deviates from a square. Quantum chemical calculations give a geometry for [(H(3)C)(2)O.H(2)SiCl(2)](2) which has D(2h) symmetry and allow to obtain an estimate for the adduct formation energies, which are -13.4 kJ mol(-1) for the formation of the mono adduct [(H(3)C)(2)O + H(2)SiCl(2)-->(H(3)C)(2)O.H(2)SiCl(2)], -14.4 kJ mol(-1) for the dimerization of two mono adducts [(H(3)C)(2)O.H(2)SiCl(2)-->[(H(3)C)(2)O.H(2)SiCl(2)](2)] and -41.2 kJ mol(-1) for the reaction 2 (H(3)C)(2)O + 2 H(2)SiCl(2)-->[(H(3)C)(2)O.H(2)SiCl(2)](2). The results are used to rationalize the strongly reduced reactivity of H(2)SiCl(2) towards nucleophilic substitution reactions in (H(3)C)(2)O at low temperatures.