Ordnung muss sein: heteroelement order and disorder in polyoxovanadates.

The first mixed antimonato-germanato polyoxovanadates were synthesized using two different strategies, highlighting the critical role of the precursors. Following the traditional route using multiple single sources as precursors the polyanions [V15Sb2Ge4O42(OH)4(H2O)]6- (1) and [V15Sb3Ge3O42(OH)3(H2O)]6- (2) are obtained, which display disorder of their Sb/Ge positions, indicating that clusters of different compositions are in equilibrium in solution. In contrast, if the water-soluble single-source precursor {Ni(en)3}3[V15Sb6O42(H2O)]·ca. 15H2O is reacted with GeO2, {Ni(en)3}3[V15Sb3Ge3O42(OH)3(H2O)]·≈9H2O (3) forms, in which Sb and Ge occupy distinct positions that might have been formed via partial substitution reactions in the {V15Sb6} precursor.

From ligand exchange to reaction intermediates: what does really happen during the synthesis of emissive complexes?

In situ monitoring of the formation of emissive complexes is essential to enable the development of rational synthesis protocols, to provide accurate control over the generation of structure-related properties (such as luminescence) and to facilitate the development of new compounds. In situ luminescence analysis of coordination sensors (ILACS) utilizes the sensitivity of the spectroscopic properties of lanthanide ions to their coordination environment to detect structural changes during crystallization processes. Here, ILACS was utilized to monitor the formation of [Eu(bipy)2(NO3)3] (bipy = 2,2'-bipyridine) during co-precipitation synthesis. Validity of the ILACS results was ensured by concomitant utilization of in situ monitoring of other reaction parameters, including in situ measurements of pH value, ionic conductivity, and infrared spectra, as well as ex situ and synchrotron-based in situ X-ray diffraction analyses. Gradual desolvation of the Eu3+ ions and attachment of ligands were detected by an exponential increase of the intensity of the 5D0 → 7FJ (J = 0-4) transitions in the emission spectrum. Additionally, the in situ emission spectra show a decrease in the crystallization rate and an increase in the induction time in response to a reduction in the concentration of the starting solutions from 12 mM until crystallization ceased at starting reactant concentrations <6 mM. An increase to a three-fold higher concentration leads to the formation of a reaction intermediate, and its stability was determined to be highly concentration-dependent. The in situ luminescence measurements also demonstrated the existence of a ligand exchange process within the [Eu(bipy)2(NO3)3] complex upon addition of a phen (phen = 1,10'-phenanthroline) solution and the generation of a new phen-containing emissive complex. In attempting to solve the structure of this new phen-containing complex, a different, but nevertheless previously unsynthesized complex, [Eu(phen)2(NO3)3]bipy, was obtained, which shows characteristic Eu3+ luminescence in the red spectral range.

In situ ligand exchange-mediated 0D/1D transformation of a polyoxovanadate.

The antimonato-polyoxovanadate {NiII(en)3}3[VSbO42(H2O)]·ca.15H2O was utilized as a synthon for the solvothermal in situ generation of the new compound {NiII(phen)3}2[{NiII(en)2}VSbO42(H2O)]·19H2O, a rearrangement induced by ligand metathesis. While in the precursor structure cations and anions are isolated, the solid-state structure of the product is characterized by 1D chains consisting of alternating [V15Sb6O42(H2O)]6- cluster shells and [Ni(en)2]2+ units covalently linked to neighboring clusters via terminal oxygen atoms. Water clusters composed of sixteen hydrogen-bonded H2O molecules are located in void spaces of the structure. The magnetic properties indicate weak antiferromagnetic interactions of the bridging Ni2+ center and adjacent polyoxovanadate anions, as well as small magnetic anisotropy of the individual Ni2+ centers.

Synthesis of Functionalized Perfluorinated Porphyrins for Improved Spin Switching.

We have established a method to synthesize perfluorinated meso-phenylporphyrins with one phenyl group bearing a substituent in the ortho position. These novel electron-deficient porphyrins are interesting for model enzymes, catalysis, photodynamic therapy, and electron transfer. The key step is the synthesis of an iodine-substituted porphyrin and its Suzuki cross coupling with boronic acid derivatives. We applied the novel strategy to synthesize a highly electron-deficient, azopyridine-substituted Ni-porphyrin that undergoes an improved ligand-driven coordination-induced spin-state switch.

Utilization of mixtures of aromatic N-donor ligands of different coordination ability for the solvothermal synthesis of thiostannate containing molecules.

Utilization of mixtures of differently coordinating aromatic N-donor ligands leads to the formation of the two new compounds {[Ni(phen)2]2Sn2S6}·4,4'-bipy·½H2O I and {[Ni(phen)2]2Sn2S6}·2,2'-bipy II that could be prepared under solvothermal conditions (4,4'-bipy = 4,4'-bipyridine, C10H8N2; phen = 1,10-phenanthroline, C12H8N2; 2,2'-bipy = 2,2'-bipyridine, C10H8N2). In the structures of both compounds Ni-S bond formation is observed which is highly unusual when only bidentate N-donor ligands are applied in the reaction mixture. The detailed analysis of the crystal structure indicates that the presence of 4,4'-bipy and 2,2'-bipy molecules are essential for the stabilization of the arrangement of the constituents. The main structural motif {[Ni(phen)2]2Sn2S6} is arranged generating off center parallel stacking of the phen ligands. The empty spaces between the {[Ni(phen)2]2Sn2S6} moieties are occupied by either 2,2'-bipy (I) or 4,4'-bipy (II) molecules which are oriented towards the phen ligands to form intermolecular π-π interactions.

Rational design of a room temperature molecular spin switch. The light-driven coordination induced spin state switch (LD-CISSS) approach.

Extensive use of quantum chemical calculations has been made to rationally design a molecule whose spin state can be switched reversibly using light of two different wavelengths at room temperature in solution. Spin change is induced by changing the coordination number of a nickel complex. The coordination number in turn is switched using a photochromic ligand that binds in one configuration and dissociates in the other. We demonstrate that successful design relies on a precise geometry fit and delicate electronic tuning. Our designer complex exhibits an extremely high long-term switching stability (more than 20 000 cycles) and a high switching efficiency. The high-spin state is extraordinarily stable with a half-life of 400 days at room temperature. Switching between the dia- and paramagnetic state is achieved with visible light (500 and 430 nm). The compound can also be used as a molecular logic gate with light and pH as input and the magnetic state as non-destructive read-out.

Template-assisted solvothermal synthesis of five copper(I)-thioantimonate(III) composites: crystal structures and optical and thermal properties of (C6N2H18)0.5Cu2SbS3, (C4N3H15)0.5Cu2SbS3, (C8N4H22)0.5Cu2SbS3, (C4N3H14)Cu3Sb2S5, and (C6)N4H20)0.5Cu3Sb2S5.

The novel copper(I)-thioantimonates(III) (C(6)N(2)H(18))(0.5)Cu(2)SbS(3) (I) (C(6)N(2)H(16) = 1,6-diaminohexane), (C(4)N(3)H(15))(0.5)Cu(2)SbS(3) (II) (C(4)N(3)H(13) = diethylenetriamine), (C(8)N(4)H(22))(0.5)Cu(2)SbS(3) (III) (C(8)N(4)H(20) = 1,4-bis(2-aminoethyl)piperazine), (C(4)N(3)H(14))Cu(3)Sb(2)S(5) (IV) (C(4)N(3)H(13) = diethylenetriamine), and (C(6)N(4)H(20))(0.5)Cu(3)Sb(2)S(5) (V) (C(6)N(4)H(18) = triethylenetetramine) were synthesized under solvothermal conditions reacting Sb, Cu, and S with the amines. The compounds I-III belong to the RCu(2)SbS(3) structure family (R = amine) and are built up of trigonal SbS(3) pyramids and two CuS(3) moieties forming 6-membered (6 MR) and 10-membered (10 MR) rings. The rings are condensed yielding single layers which are joined into [Cu(2)SbS(3)](-) double layers via Cu-S bonds. The organic ions are located between the anionic layers, and the shortest interlayer distances are 7.8 Angstroms (I), 7.4 Angstroms (II), and 8.8 Angstroms (III). The structure of the novel inorganic-organic hybrid compound IV contains one SbS(3) group, one SbS(4) unit, two CuS(3) triangles, and one CuS(4) tetrahedron. These units are joined into four-membered (4 MR) and six-membered rings (6 MR) forming a hitherto unknown strong undulated layered (Cu(3)Sb(2)S(5))(-) anion. Anions and cations are arranged in a sandwichlike manner with an interlayer distance of 6.184 A. The new composite V contains an anion with the same chemical composition as compound IV, but the structure exhibits a unique and different network topology which is constructed by two SbS(3) pyramids, two CuS(3) triangles, and one CuS(4) tetrahedron. These units are joined into 6 MR which may be described as an inorganic graphene-like layer or as a 6(3) net. Two such layers are connected via Cu-S bonds into the final double layer. The interlayer distance amounts to 6.44 Angstroms. All compounds decompose in a more or less complex manner when heated in an inert atmosphere.

Pyrolysis of a tubular aromatic compound.

[reaction: see text] In the attempt to close the walls of a small tubular system that is a substructure of a [4,4] armchair nanotube a very unusual rearrangement reaction was observed.

catena-poly[[(acetonitrile-N)dichlorocopper(II)]-mu-2,5-dimethylpyrazine-kappa2N:N'].

In the structure of the title compound, [CuCl2(C2H3N)(C6H8N2)], each Cu2+ cation is surrounded by two 2,5-dimethylpyrazine ligands, one acetonitrile ligand and two Cl- anions within a distorted tetragonal pyramid. The acetonitrile ligand, which forms the apex of the pyramid, the Cu2+ cation and the Cl- anions are all located in general positions, whereas each of the 2,5-dimethylpyrazine ligands is located about a centre of inversion. The 2,5-dimethylpyrazine ligands connect the Cu2+ cations via mu-N:N' coordination to form chains.

Poly[[aquacopper(I)-mu-bromo]-mu-(5-methylpyrazine-2-carboxylato)-kappa3N4:O,N1-[di-aquacopper(II)]-mu-(5-methylpyrazine-2-carboxylato)-kappa3O,N1:N4-[aquacopper(I)-mu-bromo]].

In the structure of the title compound, [Cu3Br2(C6H5N2O2)2(H2O)4], both copper(I) and copper(II) cations are present. The copper(II) cations are located on centres of inversion and are coordinated by two N atoms and two carboxylate O atoms from two symmetry-related 5-methylpyrazine-2-carboxylate anions, with two water molecules completing a distorted octahedron. The copper(I) cations are coordinated by the second N atom of the 5-methylpyrazine-2-carboxylate anion, one water molecule and two bromide anions within a distorted tetrahedron. Each of the bromide anions connects two symmetry-equivalent copper(I) cations to form zigzag-like CuBr chains. These chains are connected by the [diaquabis(5-methylpyrazine-2-carboxylato)]copper(II) complexes, forming corrugated sheets parallel to (100). The CuBr chains and the sheets are connected via O-H...O and O-H...Br hydrogen bonding.

RbCu2VS4.

The reaction of Cu and V in a Rb(2)S(5) melt yields black crystals of rubidium dicopper vanadium tetrasulfide, RbCu(2)VS(4). The structure is comprised of [Cu(2)VS(4)](-) layers within the (010) plane which are separated by Rb(+) cations. The layers consist of a network of edge- and corner-sharing [VS(4)] and [CuS(4)] tetrahedra parallel to (010). The optical band gap was determined as 1.45 eV.

Poly[copper(I)-mu-bromo-mu-2,3-dimethylpyrazine-N:N'].

In the structure of the title compound, [CuBr(C(6)H(8)N(2))](n), each Cu(2+) cation is surrounded by two 2,3-dimethylpyrazine ligands and two Br(-) anions in a distorted tetrahedral arrangement. The Cu(2+) cations and Br(-) anions form (Cu(2)Br(2))(2) rhomboid dimers located around a centre of inversion. The 2,3-dimethylpyrazine ligands connect the Cu(2+) cations in the dimers into sheets parallel to (010).

Poly[copper(II)-mu-pyrazine-mu(3)-squarato].

In the structure of the title compound, [Cu(C(4)O(4))(C(4)H(4)N(2))](n), each copper cation is surrounded by three squarate (3,4-dihydroxy-3-cyclobutene-1,2-dioate) anions and two pyrazine ligands, all of which are located in special positions. The copper cation and all atoms of the squarate anion are located on a mirror plane, whereas the pyrazine ligand is located around a mirror plane which is perpendicular to the ring plane. The cations are connected via the squarate anions and the pyrazine ligands, forming sheets parallel to (001).

A new type of calixarene: octahydroxypyridin.

A new type of calixarene has been synthesised. Like resorcinol and a number of resorcinol derivatives, 2,6-dihydroxypyridine has been proven to form cyclic tetramers in moderate yields with a number of aliphatic and two aromatic aldehydes in acidic media. The problem of the formation of configurational isomers can be reduced by increasing the reaction temperature and time. With electron-rich aromatic aldehydes, 2,6-dihydroxypyridine unexpectedly yields deep-coloured acyclic quinoid systems. The octahydroxypyridine[4]arenes may have a high potential as receptors for molecular recognition and self organisation.

Synthesis of dipolar nitronyl nitroxides

The synthesis of a nitronyl nitroxide radical with a dipolar (mesomeric betaine) unit is reported.