The preparation of nanoparticulate RuO 2 supported on mesoporous silica SBA-15 was optimized to achieve a uniform dispersion and confinement of RuO 2 . The supported RuO 2 (NP2) has been used as the catalyst for photoinduced water oxidation with Ru(bpy) 3 2+ as the photosensitizer and S 2 O 8 2− as the sacrificial oxidant. Both NP2 and the previously prepared NP1 achieved O 2 yields (based on S 2 O 8 2−) of 95% and 88% and overall quantum efficiencies of 11.3% and 10.0%, respectively. These benchmark numbers far exceed those of many other metal oxide-based catalysts and previously reported RuO 2 catalysts. In addition, NP2 has been recycled up to five times with minimal loss of activity.

Presented here is the chemistry of Cr(III) alkynyl complexes based on the rac-HMC and meso-HMC ligands (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). Thus far, two pairs of cis/trans-[Cr(rac/meso-HMC)(C2R)2]Cl (R = Ph, C2H/C2SiMe3) complexes have been synthesized from reactions between cis/trans-[Cr(rac/meso-HMC)Cl2]Cl and LiC2R. These complexes were characterized using single crystal X-ray diffraction, UV-vis spectroscopy, FT-IR spectroscopy, and fluorimetry. Single crystal X-ray diffraction studies revealed that these complexes adopt a pseudo-octahedral geometry. The electronic spectra of both the cis- and trans-[Cr(rac/meso-HMC)(C4R')2]Cl (R' = H or SiMe3) complexes exhibit d-d bands with pronounced vibronic progression associated with the asymmetric stretch of the Cr-bound C≡C bonds. All of these complexes are phosphorescent and show structured emissions originating from the ligand field excited states.

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Reported herein are the syntheses and structural and emission spectroscopic characterizations of new Cr(HMC) and Co(cyclam) complexes bearing fluorophore alkynyl ligands, where HMC and cyclam are 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane and 1,4,8,11-tetraazacyclotetradecane, respectively. Two Cr(III) bis-1-ethynylnaphthalene (CNp) complexes, trans-[Cr(HMC)(CNp)]Cl ([1]Cl) and cis-[Cr(HMC)(CNp)]Cl ([2]Cl), were prepared from the reactions between trans/cis-[Cr(HMC)Cl]Cl and lithium 1-ethynylnaphthalene (LiCNp) in yields of 73 and 66%, respectively. Also investigated are Co(cyclam) complexes bearing both CNp and CANT (ANT = 9-anthryl), namely [Co(cyclam)(CAr)Cl]Cl (Ar = ANT ([3]Cl), Np ([4]Cl)), [Co(cyclam)(CNp)(NCCH)](OTf) ([5](OTf)), and [Co(cyclam)(CNp)]OTf ([6]OTf). Complexes [3]Cl (72%) and [4]Cl (67%) were prepared from the reaction between [Co(cyclam)Cl]Cl and MeSiCANT or MeSiCNp, respectively, in the presence of triethylamine. The reaction of [4]Cl with excess silver triflate in CHCN yielded complex [5](OTf) (78%), which was reacted with HCNp in the presence of triethylamine to form complex [6]OTf in 39% yield. Single crystal X-ray diffraction studies of [1], [3], [4], and [6] revealed a pseudo-octahedral geometry around the Cr(III) or Co(III) center with the tetraaza-macrocyclic ligand occupying the equatorial plane and the alkynyl- and/or chloro-ligand occupying the apical positions. The absorption spectra of complexes [1] and [2] display structured d-d bands between 400 and 550 nm, a feature that is absent in the d-d absorption of the Co(III) complexes [3]-[6]. Contrasting emission behaviors were observed: the Cr(III) complexes display metal-centered phosphorescence, while the Co(III) species exhibit ligand-based fluorescence. Time-delayed phosphorescence measurements revealed lifetimes of 447 and 97 μs for [1] and [2] at 77 K, respectively, and a room temperature lifetime of 218 μs for [1].

The synthesis and characterization of four new CrIII–bis(alkynyl) complexes bearing the macrocyclic tetraaza ligand DMC (DMC = 5,12‐dimethyl‐1,4,8,11‐tetraazacyclotetradecane) are reported. Complexes trans‐[Cr(DMC)(C2R)2]X (R = Ph ([1]X), Fc ([2]X), X = Cl, ClO4. C2H ([3]X′); X′ = ClO4, BPh4) and cis‐[Cr(DMC)(C4TMS)2]Cl ([4]Cl) were studied using UV/Vis and FTIR spectroscopy, and their identities were verified with ESI‐MS and elemental analysis. The three trans complexes, [1]Cl, [2](ClO4), and [3](BPh4), were structurally characterized using single‐crystal X‐ray diffraction, which revealed a pseudo‐octahedral geometry around the Cr center with the nitrogen atoms occupying the equatorial plane and the alkynyl ligands residing in the apical positions. Spectroscopic analysis of [1]Cl, [3](BPh4) and [4]Cl shows highly structured d–d bands between 320 and 500 nm. All CrIII complexes reported herein are emissive, and detailed studies were performed for [1]Cl, [3](BPh4), and [4]Cl, yielding phosphorescence lifetimes (77 K) of 380, 358, and 160 µs, respectively, and room temperature quantum yields of 0.01 % for complex [1]Cl and 0.15 % for complex [4]Cl. Voltammetric studies of complex [2](ClO4) indicate a weak but discernible coupling between two ferrocenyl groups across the C2–Cr–C2 bridge.