Template-dependent photochemical reactivity of molecular metal oxides.

A combined experimental and theoretical study shows that the photooxidative activity of two isostructural metal oxide clusters depends on their internal templates. To this end, two halide-templated bismuth vanadium oxide clusters [X(Bi(dmso)3 )2 V12 O33 ](-) (X=Cl(-) , Br(-) ) are reported and fully characterized. The two clusters show similar absorption features and illustrate that bismuth incorporation results in increased visible-light absorption.

Cluster-controlled dimerisation in supramolecular ruthenium photosensitizer-polyoxometalate systems.

A supramolecular reaction system is reported where a labile molecular metal oxide cluster enables the unprecedented dimerisation of ruthenium photosensitizers [Ru(L)2(tmbiH2)](2+) (L = 4,4'-di-tert-butyl-2,2'-bipyridine (1a) or 2,2'-bipyridine (1b); tmbiH2 = 5,5',6,6'-tetramethyl-2,2'-bibenzimidazole). In the presence of [Mo8O26](4-) clusters (2) the dimerisation is triggered by the in situ conversion of [Mo8O26](4-) to [Mo6O19](2-) which results in the release of hydroxide ions. Simultaneous deprotonation of the pH-sensitive tmbiH2-ligands starts the dimerisation, resulting in the formation of the dinuclear complex [(Ru(L)2)2(tmbi)](2+) (L = 4,4'-di-tert-butyl-2,2'-bipyridine (3) or 2,2'-bipyridine (4)).

Synthesis and characterization of a trisheteroleptic Ru(II) -based molecular switch.

The synthesis of a trisheteroleptic ruthenium complex [Ru(tb)(dppz)(tmbiH2 )][PF6 ]2 (tb=4,4'-di-tert-butyl-2,2'-bipyridine, dppz=dipyrido[3,2-a:2',3'-c]phenazin, tmbiH2 =5,6,5',6'-tetramethyl-2,2'-bibenzimidazole) is described. In addition, the structural characterisation by means of 1D, 2D (1) H NMR spectroscopy, and mass spectrometry, along with determination of the solid-state structure of the important precursor Ru(tb)(dppz)Cl2 , supports the proposed octahedral coordination geometry. The capability of tmbiH2 to form hydrogen bonds is corroborated by the solid-state structure.

Carbene based photochemical molecular assemblies for solar driven hydrogen generation.

Novel photocatalysts based on ruthenium complexes with NHC (N-heterocyclic carbene)-type bridging ligands have been prepared and structurally and photophysically characterised. The identity of the NHC-unit of the bridging ligand was established unambiguously by means of X-ray structural analysis of a heterodinuclear ruthenium-silver complex. The photophysical data indicate ultrafast intersystem crossing into an emissive and a non-emissive triplet excited state after excitation of the ruthenium centre.

Kinetic studies of the reduction of [Co(dmgH)2(py)(Cl)] revisited: mechanisms, products, and implications.

We report on a mechanistic investigation regarding the reduction of [Co(III)(dmgH)2(py)(Cl)] (dmg = dimethylglyoxime) by several complementary techniques. The reduction of [Co(III)(dmgH)2(py)(Cl)] was initiated by either electrochemical, photochemical, or pulse radiolytical techniques, and the corresponding products were analyzed by ESI mass spectrometry. In addition, all of the rate constants for each step were determined.

A study of acridine and acridinium-substituted bis(terpyridine)zinc(II) and ruthenium(II) complexes as photosensitizers for O2 (1Δg) generation.

The homoleptic zinc(II) and ruthenium(II) metal complexes of bis(tridentate) 9-acridine and 10-methyl-9-acridinium-substituted terpyridines were tested for their suitability as triplet photosensitizers (PS) using the photooxidation of 1,5-dihydroxynaphthalene (DHN) to Juglone as a model reaction. Singlet oxygen (O2(1)Δg) generation is superior or comparable to Ru(bpy)3(2+) for the acridine complexes, whereas the acridinium complexes are ineffective. The molecular structure of the bis(9-(5-([2,2':6',2''-terpyridin]-4'-yl)thien-2-yl)-10-methylacridinium)zinc(II) complex ([Zn(MeATT)2][PF6]4) is determined by X-ray structure analysis, whereas for other complexes DFT calculations were performed for structural parameters to obtain insights into their electronic properties.

Supramolecular assembly of multicomponent photoactive systems via cooperatively coupled equilibria.

Here, we show that the synergistic interplay between two binding equilibria, acting at different sites of a (Zn)phthalocyanine-amidine molecule (Pc1), enables the dissociation of the photoinactive phthalocyanine dimer (Pc1)2 into a three-component system, in which a sequence of light harvesting, charge separation, and charge shift is successfully proven. The aforementioned dimer is assembled by dual amidine-Zn(II) coordination between neighboring Pc1 molecules and gives rise to high association constants (KD ≈ 10(11) M(-1)). Such extraordinary stability hampers the individual binding of either carboxylic acid ligands through the amidine group or pyridine-type ligands through the Zn(II) metal atom to (Pc1)2.

Solution and solid-state interactions in a supramolecular ruthenium photosensitizer-polyoxometalate aggregate.

The intermolecular interactions between a ruthenium-based photosensitizer ([Ru(tbbpy)(2)(biH(2))](2+)) and a molecular metal oxide ([β-Mo(8)O(26)](4-)) are investigated in solution and in the solid state. The supramolecular interactions were studied using (1)H-NMR, UV-Vis and emission spectroscopy, ESI mass spectrometry and single-crystal X-ray diffraction. The formation of supramolecular aggregates was observed both in the crystal lattice and in solution.