Strongly coupled zinc phthalocyanine-tin porphyrin dyad performing ultra-fast single step charge separation over a 34 A distance

A zinc(II) phthalocyanine-tin(IV) porphyrin dyad with a strong electronic coupling was synthesized and upon light excitation shown to exhibit ultra-fast, long-range electron transfer in a single step.     

Nodal operator splitting adaptive finite element algorithms for the Navier–Stokes equations

Solution algorithms for solving the Navier–Stokes equations without storing equation matrices are developed. The algorithms operate on a nodal basis, where the finite element information is stored as the co-ordinates of the nodes and the nodes in each element. Temporary storage is needed, such as the search vectors, correction vectors and right hand side vectors in the conjugate gradient algorithms which are limited to one-dimensional vectors. The nodal solution algorithms consist of splitting the Navier–Stokes equations into equation systems which are solved sequencially. In the pressure split algorithm, the velocities are found from the diffusion–convection equation and the pressure is computed from these velocities. The computed velocities are then corrected with the pressure gradient. In the velocity–pressure split algorithm, a velocity approximation is first found from the diffusion equation. This velocity is corrected by solving the convection equation. The pressure is then found from these velocities. Finally, the velocities are corrected by the pressure gradient. The nodal algorithms are compared by solving the original Navier–Stokes equations. The pressure split and velocity–pressure split equation systems are solved using ILU preconditioned conjugate gradient methods where the equation matrices are stored, and by using diagonal preconditioned conjugate gradient methods without storing the equation matrices. © 1998 John Wiley & Sons, Ltd.     

Unexpected dual orbital effects in radical addition reactions involving acyl, silyl and related radicals

Molecular orbital calculations reveal that acyl and silyl radicals add to numerous types of pi-systems through simultaneous SOMO-LUMO and LUMO-HOMO interactions of the radical with the radicalophile respectively.     

Accumulative charge separation inspired by photosynthesis

Molecular systems that follow the functional principles of photosynthesis have attracted increasing attention as a method for the direct production of solar fuels. This could give a major carbon-neutral energy contribution to our future society. An outstanding challenge in this research is to couple the light-induced charge separation (which generates a single electron-hole pair) to the multielectron processes of water oxidation and fuel generation. New design considerations are needed to allow for several cycles of photon absorption and charge separation of a single artificial photosystem. Here we demonstrate a molecular system with a regenerative photosensitizer that shows two successive events of light-induced charge separation, leading to high-yield accumulation of redox equivalents on single components without sacrificial agents.     

Site-selective detection of vibrational modes of an iron atom in a trinuclear complex

Nuclear inelastic scattering (NIS) experiments on the trinuclear complex [⁵⁷Fe{L-N₄(CH₂Fc)₂} (CH₃CN)₂](ClO₄)₂ have been performed. The octahedral iron ion in the complex was labelled with ⁵⁷Fe and thereby exclusively the vibrational modes of this iron ion have been detected with NIS. The analysis of nuclear forward scattering (NFS) data yields a ferrous low-spin state for the ⁵⁷Fe labelled iron ion. The simulation of the partial density of states (pDOS) for the octahedral low-spin iron(II) ion of the complex by density functional theory (DFT) calculations is in excellent agreement with the experimental pDOS of the complex determined from the NIS data obtained at 80 K. Thereby it was possible to assign almost each of the experimentally observed NIS bands to the corresponding molecular vibrational modes.     

Six-membered ring chelate complexes of Ru(II): structural and photophysical effects

The structural and photophysical properties of Ru(II)-polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.     

Characterization of ordered bilinear contexts

Measurement situations arise in all kinds of empirical sciences if quantitative models of observed phenomena are supposed to be formulated. According to representational measurement theory, measurement should be based on geometric coordinatization theorems. Such theorems detemine the conditions under which there exist representations of data by specific numerical structures. This paper is concerned with bilinear measurement models. In this case, a data table containing ordered attribute values for certain objects is represented by embedding simultaneously the objects into an ordered vector spaceV, the attributes into its dual spaceV ^*, and the attribute values into the underlying ordered field (K,) connected as follows: an objectg has the valuew of the attribute _m (x _g ) =r _w for the corresponding vectorx _g , the linear form _m , and the scalarr _w (relational notation: (x _g , _m ,r _w E). The image structure (V, V ^*, (K, ),E) of such an embedding is called an ordered bilinear context. The structure of ordered bilinear contexts is analysed and a representation theorem is proved characterizing ordered bilinear contexts synthetically.The author has been supported by the Studienstiftung des Deutschen Volkes and the DFG-Forschungs-stipendium Wi 1495/1-1. This paper reports on parts of the author's dissertation [22].     

Development of a solid phase extraction for 13 'new' generation antidepressants and their active metabolites for gas chromatographic-mass spectrometric analysis

A solid phase extraction procedure (SPE) for 13 'new' antidepressants (venlafaxine, fluoxetine, viloxazine, fluvoxamine, mianserin, mirtazapine, melitracen, reboxetine, citalopram, maprotiline, sertraline, paroxetine and trazodone) together with eight of their metabolites (O-desmethylvenlafaxine, norfluoxetine, desmethylmianserine, desmethylmirtazapine, desmethylcitalopram, didesmethylcitalopram, desmethylsertraline and m-chlorophenylpiperazine) from plasma is optimized using HPLC-DAD as monitoring system. Special attention has been paid to the choice of washing and eluting solvent, resulting in a highly concentrated, clean and moisture free extract, also suitable for GC-MS. A total number of 10 sorbents (apolar, polymeric, ion-exchange and mixed mode) was evaluated. Based on recovery, reproducibility and absence of interfering substances the strong cation exchanger gave the best results. Recoveries were determined at low and high therapeutic and toxic levels and ranged between 70 and 109% for all compounds, except for trazodone (39%).