Crystal structure of 2,3-dimethoxy-meso-tetrakis(pentafluorophenyl)morpholinochlorin methylene chloride 0.44-solvate

The title morpholinochlorin, C46H16F20N4O3, was crystallized from hexane/methylene chloride as its 0.44 methylene chloride solvate, C46H16F20N4O3·0.44CH2Cl2. The morpholinochlorin was synthesized by stepwise oxygen insertion into a porphyrin using a `breaking and mending strategy': NaIO4-induced diol cleavage of the corresponding 2,3-dihydroxychlorin with in situ methanol-induced, acid-catalyzed intramolecular ring closure of the intermediate secochlorins bisaldehyde. Formally, one of the pyrrolic building blocks was thus replaced by a 2,3-dimethoxymorpholine moiety. Like other morpholinochlorins, the macrocycle of the title compound adopts a ruffled conformation, and the modulation of the porphyrinic π-system chromophore induces a red-shift of its optical spectrum compared to its corresponding chlorin analog. Packing in the crystal is governed by interactions involving the fluorine atoms of the pentafluorophenyl substituents, dominated by C—H...F interactions, and augmented by short fluorine...fluorine contacts, C—F...π interactions, and one severely slipped π-stacking interaction between two pentafluorophenyl rings. The solvate methylene chloride molecule is disordered over two independent positions around an inversion center with occupancies of two × 0.241 (5) and two × 0.199 (4), for a total site occupancy of 88%.

Oxidation-Induced Detachment of Ruthenoarene Units and Oxygen Insertion in Bis-Pd(II) Hexaphyrin π-Ruthenium Complexes

Two types of new bis-Pd(II) hexaphyrin π-ruthenium complexes are reported. A double-decker bis-Pd(II) hexaphyrin π-ruthenium complex 4 was obtained by oxidation-induced detachment of a ruthenoarene unit from the triple-decker complex 3 and oxygen-inserted triple-decker bis-Pd(II) hexaphyrin π-ruthenium complex 6 was obtained upon treatment of bis-Pd(II) [26]hexaphyrin 5 with [RuCl2(p-cymene)]2 under aerobic conditions. Although π-metal complexation of porphyrinoids often results in decreased global aromaticity due to the enhancement of local 6π aromatic segments, distinct aromatic characters were indicated for 4 and 6 by 1H-NMR spectral and theoretical calculations. These results are accounted for in terms of possible resonance contributors of hexaphyrin di- and tetraanion ligands. Thus, π-metal coordination has been shown to be effective for modulation of the overall aromaticity.

Photoelectrochemical Study of the Delafossite AgNiO2 Nanostructure: Application to Hydrogen Production

AgNiO2 is a semiconductor crystallizing in the delafossite structure; it is prepared by the hydrothermal route, and the photoelectrochemical properties are studied for the first time. The TG/DSC analyses show a low stability not exceeding 290 °C before its reduction into Ag and NiO. The direct bandgap energy of the bulk material is 0.87 eV, due to the d–d transition of Ag+ linearly coordinated. AgNiO2 is chemically stable in the pH region (4–14); a flat band potential of −0.022 VRHE with p-type behavior, inferred to oxygen insertion is reported in KOH solution (10−2 M). The holes density (1.92 × 1022 cm−3) agrees with a semi-metallic behavior. Positive potentials give rise to surface oxidation of AgNiO2 in the diffusion plateau before oxygen evolution. The electrochemical oxygen insertion, investigated by chrono-amperometry, is found to be slow with a diffusion coefficient of ∼8 × 10−16 cm2 s−1. The Nyquist plot exhibits a semicircle centered below the abscissa axis, whose diameter 4200 Ω cm2 decreases down to 760 Ω cm2 under visible illumination. Such results indicate dipolar and multi-relaxation processes and confirm the existence of the optical gap. The conduction band (−0.88 VRHE) derived from Ag+: 4d orbital is more cathodic than the potential of H2O/H2 (∼−0.64 VRHE) level and hydrogen is evolved under visible irradiation. An evolution rate of 1.43 mL g−1 min−1 at pH ∼ 12.8 is obtained with a light-to-chemical energy efficiency of 2.40%.

Mn-catalyzed radical initiated domino transformation of alkynylated cyclohexadienones with TMSN3 and O2 to bicyclic azido alcohols

An efficient cascade radical addition/cyclization/oxygen insertion reaction of alkyne-tethered cyclohexadienones with TMSN3 was carried out under mild conditions to generate bicyclic azido alcohol scaffolds.