Different Keggin-type polyoxometalates have been synthesized and characterized in order to identify optimized homogeneous catalysts for the selective oxidation of biomass to formic acid (FA) using oxygen as an oxidant and p-toluenesulfonic acid as an additive. Applying the optimized polyoxometalate catalyst system H 8 [PV 5 Mo 7 O 40 ] (HPA-5), a total FA-yield (with respect to carbon in the biogenic feedstock) of 60% for glucose within 8 h reaction time and 28% for cellulose within 24 h reaction time could be achieved. The transformation is characterized by its mild reaction temperature, its excellent selectivity to FA in the liquid product phase and its applicability to a very wide range of biogenic raw materials including non-edible biopolymers and complex biogenic mixtures. † Electronic supplementary information (ESI) available: NMR, UV-Vis and electrochemical spectra recorded from the different HPA-complexes. See

Polyoxometalates (POMs) [1] are an exceptional family of polynuclear molecular oxide anions usually formed by W, Mo, or V.[2] POMs offer a wide range of structures with diverse physical properties, electronic structures, and applications, such as in catalysis, [3] medicine, [4] materials science, [5] or nanotechnology. Heteropolyoxometalates (HPOMs) are a significant and widely explored subset of POMs. Within this class, the choice of the heteroelement not only determines certain physical properties of the cluster, but increasingly has been found to control the range and connectivity of the building blocks.[6] Amongst the structural diversity of HPOMs architectures, Keggin [7] . In general, POMs exhibit significant stability for both the oxidized and oneelectron-reduced form, [9] and the electrochemistry of HPOMs has been extensively studied.[10] In this respect, in an effort to tune the redox properties of POMs, we have been able to engineer clusters that incorporate redox-active anions and expand the classic WD family. [11] Electrochemical studies demonstrated that classic WD anions are reduced through multiple steps of two electrons (at pH 7) without degradation of the heteropoly structure.The process generates reduced species, known as heteropoly blues owing to their characteristic blue color, [12] with the WD structures having two types of metal sites: cap and the belt (Figure 1). In the classic WD structures, these "blue" electrons are delocalized only over the belt metal atoms. [13] NMR spectroscopy experiments on the reduced species show that electron delocalization is restricted to the two hexagonal belts and are completely spin-paired at room temperature. [14] Herein, we present the first Dawson-like {W 18 O 56 XO 6 } clusters (X = I or Te) with localized redox active inner-cluster templates, and we show that these moieties can adopt different oxidation states; for example, IVII/VI or Te VI/V , respectively. To investigate this in detail, we used cyclic voltammetry, UV and EPR spectroscopy combined with experimental comparison to a control, non-heteroatom embedded Dawson-like cluster. We also evaluated the electronic structure of both the oxidized and reduced forms of the clusters using DFT based upon X-ray data of the oxidized forms.[11] As a built-in control we used a

Physicochemical characterization of boron(III) subporphyrazines (SubPzs)--lower subphthalocyanine (SubPc) homologues--has been carried out for the first time. The SubPz macrocycle can act both as an oxidizing and a reducing entity, giving rise to stable radical anion or radical cation species, respectively. SubPzs are luminescent and exhibit fluorescence quantum yields that are in the range known for SubPcs. The peripheral substitution plays a dramatic role with respect to the luminescence properties. Moreover, as with SubPcs, deactivation of the singlet excited state of the SubPzs by intersystem crossing affords long-lived triplet excited states, which are amenable to being used as singlet-oxygen generators. Subporphyrazines are also promising electro- and photoactive materials for molecular photovoltaics.

The phase diagram is an interesting field of research, particularly in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic--N(C) and discotic--N(D)) and one biaxial nematic (N(B)) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I(RE)) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I(RE)-N(C)-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N(C) phase, where the absolute value of the optical birefringence (Deltan is maximum.

Polyoxometalates (POMs) [1] are an exceptional family of polynuclear molecular oxide anions usually formed by W, Mo, or V. [2] POMs offer a wide range of structures with diverse physical properties, electronic structures, and applications, such as in catalysis, [3] medicine, [4] materials science, [5] or nanotechnology. Heteropolyoxometalates (HPOMs) are a significant and widely explored subset of POMs. Within this class, the choice of the heteroelement not only determines certain physical properties of the cluster, but increasingly has been found to control the range and connectivity of the building blocks. [6] Amongst the structural diversity of HPOMs architectures, Keggin [7] [M 12 O 36 (XO 4 )] nÀ and Wells-Dawson (WD) [8] anions [M 18 O 54 (XO 4 ) 2 ] mÀ form a basic set of extensively reviewed geometries, which encapsulate tetrahedral heteroanions such as [SO 4 ] 2À and [PO 4 ] 3À . In general, POMs exhibit significant stability for both the oxidized and oneelectron-reduced form, [9] and the electrochemistry of HPOMs has been extensively studied. [10] In this respect, in an effort to tune the redox properties of POMs, we have been able to engineer clusters that incorporate redox-active anions and expand the classic WD family. These new non-classical Dawson clusters, with the general formula [H n M 18 O 56 -(XO 6 )] mÀ (X = W VI , Te VI , I VII ), embed one octahedral or trigonal prismatic template within the cluster shell. [11] Electrochemical studies demonstrated that classic WD anions are reduced through multiple steps of two electrons (at pH 7) without degradation of the heteropoly structure.The process generates reduced species, known as heteropoly blues owing to their characteristic blue color, [12] with the WD structures having two types of metal sites: cap and the belt (Figure 1). In the classic WD structures, these "blue" electrons are delocalized only over the belt metal atoms. [13] NMR spectroscopy experiments on the reduced species show that electron delocalization is restricted to the two hexagonal belts and are completely spin-paired at room temperature. [14] Herein, we present the first Dawson-like {W 18 O 56 XO 6 } clusters (X = I or Te) with localized redox active inner-cluster templates, and we show that these moieties can adopt different oxidation states; for example, I VII/VI or Te VI/V , respectively. To investigate this in detail, we used cyclic voltammetry, UV and EPR spectroscopy combined with experimental comparison to a control, non-heteroatom embedded Dawson-like cluster. We also evaluated the electronic structure of both the oxidized and reduced forms of the clusters using DFT based upon X-ray data of the oxidized forms. [11] As a built-in control we used a Dawson-like tungstate cage {W 18 O 56 }, where the template is [WO 6 ] 6À (TPA 6 [H 4 W 18 O 56 (WO 6 )], abbreviated as WW 18 ; TPA = tetrapropylammonium), [15] as a reference system to compare directly with the [TeO 6 ] 6À (g*-TPA 7 [H 3 W 18 O 56 (TeO 6 )]/g*-TeW 18 ) [11d] and [IO 6 ] 5À (b*-TPA 6 [H 3 W 18 O 56 (IO 6 )]/b...

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In this work we will use digital images to compute the entropy dependence on temperature of a nematic lyotropic sample. The set of images comprehend the entire temperature range between a reentrant nematic isotropic phase transition, at a low temperature, and a usual nematic isotropic phase transition at a higher temperature. We will show that, inside the nematic phase, the image entropy profile agrees accurately with the entropy given by the Maier-Saupe model. As far as we know, this is the first time that the entropy of a lyotropic nematic phase is evaluated by this method, which introduces a way to measure their macroscopic variables. Namely, being that the entropy is a thermodynamical potential, this result implies that digital images can be used to compute mean values of nematic random variables.