Erhard T. K. Haupt

Structural characterisation of humic acid-bound PAH residues in soil by 13C-CPMAS-NMR-spectroscopy: evidence of covalent bonds

The fate of 13C-labelled phenanthrene and fluoranthene in different soil systems during biodegradation was studied. The soil humic acid fraction was isolated followed by structural characterisation using 13C-cross polarisation magic angle spinning nuclear magnetic resonance spectroscopy (13C-CPMAS-NMR). It could be demonstrated that especially the ratio between the concentrations of polycyclic aromatic hydrocarbons (PAHs) and soil humus matrix limits the usefulness of this analytical tool. Based on these results a ratio of 13C-activity(PAH)/13C-activity(soil) approximately 1.5/1.0 in the test material was suggested. The chemical transformation of a PAH and its bound residue formation in a soil system detected by changes of chemical shifts in the 13C-NMR spectrum was proven for the first time. Structural information obtained by NMR spectra were verified by alkaline hydrolysis of PAH/humus-associations and following identification of cleavage products. Ester-bound phenanthrene metabolites such as 1-hydroxy-2-naphthoic acid, ortho-phthalic acid and 3,4-dihydroxybenzoic acid were detected. Additional structural assignments indicated the presence of ether-bound phenanthrene derivatives as well. Using isotopic labelling techniques a quantitative evaluation of bound residue distribution was undertaken. Fifty to seventy percent of phenanthrene metabolites which could be related to the added 13C(1)-phenanthrene were ester bound via their carboxyl groups.

A spherical 24 butyrate aggregate with a hydrophobic cavity in a capsule with flexible pores: confinement effects and uptake-release equilibria at elevated temperatures.

Compounds like zeolites exhibiting nanoscale holes and channels can serve as filters and traps or hosts for molecular guests. They play an important role in many areas of chemistry and materials science as they can be used for different tasks, for example, for separation and storage purposes. 2] Our related interest concerns molecular (i.e., discrete) porous metal oxide based capsule analogues, which specifically allow encapsulation of a large number of different guests; for general remarks regarding inorganic host–guest chemistry, see Ref. [3]. It was our aim to integrate within a capsule s cavity an unprecedented structurally well-defined, mostly hydrophobic aggregate. This goal was achieved with a robust, spherical, porous capsule of the type [{pentagon}12{linker}30] [{(Mo)Mo5O21(H2O)6}12{Mo2O4(ligand)}30] [4–7] allowing, generally speaking, a wide range of applications. 8] The capsules interiors can be modified by introducing a variety of species coordinating weakly to the 30 dinuclear {Mo2} linkers. This approach has now allowed, as intended, the encapsulation of the quasi-spherical, partly compact 24butyrate aggregate, whose constituents show under the confined conditions interesting interactions (an attractive, up-to-date research field) detectable by ROESY NMR spectroscopy in agreement with the related distances. Remarkably, the present scenario automatically generates an unprecedented hydrophobic cavity and shell at the center of the capsule that is spanned by 72 H atoms originating from 24 butyrate CH3 groups. Furthermore, the resulting capsule skeleton is stable even at rather high temperatures, which allows the observation of a strong uptake–release exchange of the butyrates with the future option to introduce into the capsule system different species that can react with one another under confined conditions. The pictorial title “flexible” refers to one of the important properties of the capsules, that is, the option of reversible pore widening, which will be discussed in comparison with formally related scenarios of spherical viruses. Compound 1 containing the capsule 1 a loaded with the 24butyrate aggregate (Figure 1) is obtained by the reaction of an aqueous solution of heptamolybdate with hydrazinium sulfate (as reducing agent) and butyric acid and a subsequent recrystallization process. (The product s recrystallization was primarily performed to obtain higher-quality crystals.) This synthetic procedure is similar to that which led to the first published related capsule-type compound with 30 acetate ligands obtained in a facile high-yield synthesis, while the

Hydrophobic interactions and clustering in a porous capsule: option to remove hydrophobic materials from water.

The investigation of hydrophobic interactions under confined conditions is of tremendous interdisciplinary interest. It is shown that based on porous capsules of the type {(pentagon)}(12){(linker)}(30) ≡ {(Mo)Mo(5)(12){Mo(2)(ligand)}(30), which exhibit different hydrophobic interiors-achieved by coordinating related ligands to the internal sites of the 30 {Mo(2)} type linkers-there is the option to study systematically interactions with different uptaken/encapsulated hydrophobic molecules like long-chain alcohols as well as to prove the important correlation between the sizes of the related hydrophobic cavities and the option of water encapsulations. The measurements of 1D- and 2D-NMR spectra (e.g. ROESY, NOESY and HSQC) allowed the study of the interactions especially between encapsulated n-hexanol molecules and the hydrophobic interior formed by propionate ligands present in a new synthesized capsule. Future detailed studies will focus on interactions of a variety of hydrophobic species with different deliberately constructed hydrophobic capsule interiors.

Reactions inside a porous nanocapsule/artificial cell: encapsulates' structuring directed by internal surface deprotonations

In the cavities of unprecedentedly functionalised, spherical, porous capsules of the type {Pentagon}12{Linker}30 identical with [{(Mo)Mo5O21(H2O)6}12{Mo2O4(ligand)}30]n- reactions with the ligands -i.e. at the internal shell surfaces - can be performed, in the present case deliberate aquation/hydration and deprotonation reactions at the linker fragments {(Mo2O4)C2O4H}+ similar to that reported in the literature for [(NH3)5CoC2O4H]2+ in solution.

Confinement and step-wise reopening of channels in an artificial cell/inorganic capsule: a 7Li NMR study.

In previous contributions we have demonstrated that the anionic porous molybdenum oxide based capsule(s) [Lin {(Mo)Mo5O21 ACHTUNGTRENNUNG(H2O)6}12ACHTUNGTRENNUNG{Mo V 2O4ACHTUNGTRENNUNG(SO4)}30] 72 n (1a ; n 5) of the compound [(CH3)2NH2]44Li28 n·1a· 250H2O (1; Figure 1) can be considered as models for cellular cation transport, in particular with respect to the exchange of lithium ions between the interior of the capsules and the surrounding solution. Additionally, we could show that appropriate cationic organic species, such as formamidinium cations (FA·H), can act as “corks”/guests; that is, they are able to close, in a supramolecular fashion, the pores exhibiting crown-ether function, and separate the interior from the exterior. From Li NMR spectra it has been deduced that separate signals can be observed for the various lithium species present. However, the characteristics of the internal lithium cations (Li confined in the cavity of the capsule) were only deduced indirectly, because Li ions are involved in exchange processes (Figure 1, bottom). Here, we present an NMR study that allows for a precise interpretation of the processes associated with the exchange and confinement of capsule associated lithium cations. In particular we show that stepwise re-opening of the pores (partial release of the formamidinium plugs) is possible by addition of defined amounts of water, an incident which models ligand-gated ion channels. A first indication of the differentiation between external and internal lithium cations arises from the study of the diffusion behaviour of the system as depicted by the Li NMR signals. If a solution of 1 (preparation according to reference [1]) in dimethyl sulfoxide (DMSO) and treated with FA·HCl is investigated in a Li DOSY experiment, a substantial difference in the diffusion coefficients of encapsulated lithium cations moving with the capsule (Li 1a) as compared to solvated Li ([LiACHTUNGTRENNUNG(dmso)nACHTUNGTRENNUNG(H2O)4 n] ) is to be expected. This is in fact observed (Figure 2). The Stokes (”hydrodynamic”) radius obtained for 1a from the diffusion coefficient (9.3?10 11 ms ) is 1.2 nm. Keeping in mind the ambiguities with the calibration of the diffusion experiments, the determined value is in reasonable agreement to r=1.5 nm obtained from the single-crystal X-ray structure analysis of 1. [a] Dr. E. T. K. Haupt, C. Wontorra, Prof. Dr. D. Rehder Department Chemie, UniversitFt Hamburg 20146 Hamburg (Germany) Fax: (+49)40428382893 E-mail : erhard.haupt@chemie.uni-hamburg.de rehder@chemie.uni-hamburg.de [b] Dr. A. Merca, Prof. Dr. A. MJller FakultFt fJr Chemie der UniversitFt Postfach 100131, 33501 Bielefeld (Germany) Figure 1. Top: Schematic space-filling representation of the uptake and release of cations (counterion transport) through the pores of the highly charged anionic capsule 1a (Mo blue, O red). Bottom: View of two of the 20 pores of 1a (MoO6 octahedra of the pentagonal units blue and of the {Mo2} type linker groups red; for details see reference [1]). The disorder of the sulfates observed by X-ray crystallography (S yellow, O red) comes about by the (not directly observable) Li ions.

Picking up 30 CO2 Molecules by a Porous Metal Oxide Capsule Based on the Same Number of Receptors

30 receptors in waiting position: In the porous (pentagon)(12)(linker)(30)-type molybdenum oxide capsule (see picture), the 30 positively charged linkers (five unsaturated shown for illustration in green, the others contain CO(3)(2-) ligands) can act as receptors for neutral and negatively charged ligands. Bubbling CO(2) into the solution containing the acetate-type capsules leads to the upload of CO(2) based on 30 coordinated CO(3)(2-) ligands.

An Unstable Paramagnetic Isopolyoxomolybdate Intermediate Non‐Homogeneously Reduced at Different Sites and Trapped in a Host Based on Chemical Adaptability

Under special conditions, solutions of polyoxometalates can “behave” as unique constitutional dynamic libraries (CDLs) containing building blocks that may reversibly associate, thereby allowing a continuous change in constitution through reorganization, while external stimulants can influence the scenario. This is especially valid in case of polyoxomolybdate chemistry; for related basic aspects of CDLs see Refs. [2, 3]. In this context, a variety of nanosized clusters with fascinating structures and properties could be even deliberately obtained. The mentioned solution properties can be related to the chemical adaptability of related clusters based on the flexibility of their building blocks, for example, in case of the giant molecular wheels of the type {Mo154} and {Mo176} [1b] with the formulas [{Mo1}{Mo2}{Mo8}]n m (n = 14, 16; m = 28, 32). Here we report on a reduction pathway of an aqueous solution of the diamagnetic [Mo36O112(H2O)16] 8 [7a,b] (structure in Figure S1, Supporting Information), which leads to an unprecedentedly reduced polyoxomolybdate, that is, a paramagnetic unstable derivative of the {Mo36}-type cluster trapped in an appropriately enlarged {Mo154}-type wheel/host formed on the release of special building blocks. Results from X-ray crystallography, EPR spectra, and DFT calculations prove that the paramagnetic {Mo36} cluster shows an unprecedented type of electronic and magnetic structure with different uncoupled Mo centers—an interesting result, as all known reduced polyoxomolybdates with an even number of 4d electrons are according to a literature search diamagnetic. This offers the option to study not only new types of exchange interactions, but also interesting reactivities of the Mo centers. The whole system and especially the trapped cores are stabilized by an unprecedented dense hydrogen-bonding system in between the two mentioned highly reduced components. Altogether we can refer here to an extremely complex system in which several parts are intrinsically related, that is, structurally, electronically, and magnetically. Wheel-shaped {Mo154}and {Mo176}-type clusters and their derivatives are usually obtained without encapsulated guests upon reduction of acidic aqueous solutions of molybdates. However, based on an appropriate (deficit) amount of reducing agent, it was now possible to obtain compound 1, in which the paramagnetic eight-electron reduced {Mo36} clusters/intermediates are trapped in defective/enlarged {Mo154}-type wheel segments (Figure 1), which are linked to chains (Figure S2, Supporting Information).

Cellular cation transport studied by 6, 7Li and 23Na NMR in a porous Mo132 Keplerate type nano‐capsule as model system

Li+ ions can interplay with other cations intrinsically present in the intra‐ and extra‐cellular space (i.e. Na+, K+, Mg2+ and Ca2+) and have therapeutic effects (e.g. in the treatment of bipolar disorder) or toxic effects (at higher doses), likely because Li+ interferes with the intra‐/extra‐cellular concentration gradients of the mentioned physiologically relevant cations. The cellular transmembrane transport can be modelled by molybdenum‐oxide‐based Keplerates, i.e. nano‐sized porous capsules containing 132 Mo centres, monitored through 6/7Li as well as 23Na NMR spectroscopy. The effects on the transport of Li+ cations through the ‘ion channels’ of these model cells, caused by variations in water amount, temperature, and by the addition of organic cationic ‘plugs’ and the shift reagent [Dy(PPP)2]7− are reported. In the investigated solvent systems, water acts as a transport mediator for Li+. Likewise, the counter‐transport (Li+/Na+, Li+/K+, Li+/Cs+ and Li+/Ca2+) has been investigated by 7Li NMR and, in the case of Li+/Na+ exchange, by 23Na NMR, and it has been shown that most (in the case of Na+ and K+), all (Ca2+) or almost none (Cs+) of the Li cations is extruded from the internal sites of the artificial cell to the extra‐cellular medium, while Na+, K+ and Ca2+ are partially incorporated. Copyright

CHELATISIERTE ENOLATE VON α-PHOSPHONYLIERTEM ACETALDEHYD

Abstract Es wird gezeigt, daβ mit Lithiumbutyl bei tiefen Temperaturen das Lithiumenolat 6 aus 2 zuganglich ist, wahrend bei Normaltemperatur 2 mit LiBu oder Zinkacetat bevorzugt unter Aldolkondensation zu den Metall-Komplexen des doppelt phosphonylierten Butadienolats oder dem freien E-Enol 8 reagieren. Die Verbindungen werden NMR-spektroskopisch charakterisiert. Einmal gebildetes Li-Enolat 6 ist stabil und zeigt einen selektiven HID-Austausch. It is demonstrated that the lithium enolate 6 is available from 2 with lithiumbutyl at reduced temperature, while the reaction of 2 with Li-butyl or zinc acetate at normal temperature preferably yields the metal-complexes of the doubly phosphonylated butadienolate or the free E-enol 8 via aldolkondensation. The compounds are characterized by nmr-spectroscopy. Once formed Li-enolate 6 is stable and shows a selective H/D-exchange.

Synthesis and Structure of Complexes of the Diethyl Ester of 2-Dimethylamino-2-oxoethylphosphonic Acid with Lanthanide Nitrates

The lanthanide complexes LnL 2 (NO 3 ) 3 ( 3a-g ) are obtained where Ln is La, Sm, Yb, Er, Ce, Eu, Gd, and L is the diethyl ester of 2-dimethylamino-2-oxoethylphosphonic acid [(C 2 H 5 O) 2 P(O)CH 2 CON(CH 3 ) 2 ] 1 . They are characterized by elemental analysis, i.r. and NMR spectroscopy. The crystal structure of 3a is determined by single crystal X-ray diffraction. The complex is found to crystallize in the triclinic space group P 1 with a = 8.4220(17) Å, b = 11.123(2) Å, c = 17.560(4) Å, f = 87.20(3);, g = 82.27(3);, n = 76.89(3);, V = 1587.3(5) Å 3 , Z = 2, calcd = 1.614 mg/m 3 , R = 0.047, R w = 0.107, S = 1.034 for 5762 reflections with I > 2 (I). The structure contains monomeric units of the complex with the lanthanum atom coordinated by 10 oxygen atoms, six of them from the three bidentate nitrate ions and four from the two phosphonate ligands. The coordination is realized by both phosphoryl and amide-carbonyl oxygen atoms. The stereochemistry of the starting ligand 1 is investigated by NMR spectroscopy.