Osamu Ishitani

Synthesis and properties of [Ru(tpy)(4,4′-X2bpy)H]+ (tpy=2,2′:6′,2″-terpyridine, bpy=2,2′-bipyridine, X=H and MeO), and their reactions with CO2

Abstract A novel type of hydrido complex [Ru(tpy)(4,4′-X2bpy)H]+ (X=H and MeO) was synthesized. The stronger hydridic character of the complexes compared with [Ru(bpy)2(L)H]+ type complexes (L=CO, PPh3 and AsPh3) was demonstrated by the relatively high chemical shifts of RuH in the 1H NMR spectra and by higher reactivities with CO2. The reactions of [Ru(tpy)(4,4′-X2bpy)H]+ with CO2 occurred at second-order rate constants varying from (4.69±0.02) to (5.51±0.04)×10−3 M−1 s−1 depending on both solvent and X, giving the formato complexes [Ru(tpy)(4,4′-X2bpy)(OCHO)]+ quantitatively. The rate constant was increased with the increase of solvent acceptor number, and the reaction of [Ru(tpy){4,4′-(MeO)2bpy}H]+ with CO2 was found to be 3.6 times faster than that of [Ru(tpy)(bpy)H]+. These results suggest that nucleophilic attack of the hydride ligand to the carbon atom of CO2 is the rate determining step for the formation of the formato complex. The structure of the formato complex [Ru(tpy)(bpy)(OCHO)](PF6) was determined by X-ray crystallographic analysis.

Preparation and characterization of [Re(bpy)(CO) 3L][SbF6] (L = phosphine, phosphite)

A series of rhenium complexes [fac-Re(bpy)(CO)3L][SbF6] (bpy = 2,2′-bipyridine, L = P(nBu)3, PEt3, PPh3, P(OMe)Ph2, P(OiPr)3, P(OEt)3, P(OMe)3, P(OPh)3) has been prepared and characterized by the IR, UV-vis, 1H NMR, 31P NMR, X-ray photoelectron spectroscopy and electrochemical techniques. Variations in the electronic properties, i.e. CO stretching, metal-to-ligand charge transfer transition, and 31P NMR chemical shifts were interpreted on the basis of the electron-acceptor strength of L. However, the redox potential corresponding to [Re(bpy)(CO)3L]+/[Re(bpy−)(CO)3L]showed ‘V-character type’ changes after the increase in the electron-acceptor strength of L. Variation of the P(2p) binding energy of the phosphorus atom indicated that the electronic structure of the coordinated phosphorus atom was strongly influenced by the electronic properties of the directly attached substituents.

Synthesis, spectroscopic characterization, electrochemical and photochemical properties of ruthenium(II) polypyridyl complexes with a tertiary amine ligand

Abstract A series of ruthenium(II) polypyridine complexes were synthesized with a tertiary aliphatic amine ligand, [Ru(4,4′-X2bpy)2(DMAEPy)]2+ (1a; X=H, 2; X=CF3), [Ru(tpy)(N–N)Cl]+ (3a; N–N=DMAEPy, 3c; N–N=DEAEPy) and [Ru(tpy)(DMAEPy)(MeCN)]2+ (4) where DMAEPy=2-(2′-dimethylaminoethyl)-pyridine, DEAEPy=2-(2′-diethylaminoethyl)-pyridine, tpy=2,2′:6′,2″-terpyridine and bpy=2,2′-bipyridine. The spectroscopic, electrochemical and photochemical properties of these complexes are studied and compared to those of the corresponding primary-amine complexes [Ru(bpy)2(AEPy)]2+ (1b) and [Ru(tpy)(AEPy)Cl]+ (3b) where AEPy=2-(2′-aminoethyl)-pyridine. The MLCT bands in the UV–Vis absorption spectra of the tertiary-amine complexes were blue-shifted (8–9 nm), and their redox potentials for the RuII/III couples were more positive than expected (90–100 meV) compared to the corresponding primary-amine complexes. Irradiation of an acetonitrile solution of the complexes causes selective photochemical ligand substitution of the tertiary-amine ligand even under aerated conditions, giving the corresponding solvento complex [Ru(4,4′-X2bpy)2(MeCN)2]2+ or [Ru(tpy)(MeCN)2Cl]+.

Application of an integrated PrepStation–GC-NPD system to automated continuous measurement of formaldehyde and acetaldehyde in the atmosphere

An integrated PrepStation-gas chromatography-nitrogen phosphorus detection (GC-NPD) system was used for the fully automated, continuous, low parts per billion analysis of lower aldehydes in the atmosphere. Analysis involved a solid phase extraction procedure based on the collection of aldehydes from air pumped through a silica gel cartridge impregnated with acidified 2,4-dinitrophenylhydrazine (DNPH). Automated continuous measurements were performed with a typical temporal resolution of 3 h, including 146 min for sampling of air at a constant air flow rate of 0.15 L min(-1) and 34 min for the preparation and extraction of several cartridges. Analysis of samples could be performed in parallel by using previously defined scheduler settings from separate, independent software to operate the PrepStation module. GC-NPD measurements were highly repeatable, and relative standard deviations were < 3.0%. Recoveries for all compounds were 88-101%. DNPH decomposition products did not adversely affect the quantitative determination of aldehyde DNPHs; therefore, it was not necessary to remove excess DNPH reagent. The limits of quantification (10sigma of the blank hydrazones) of formaldehyde and acetaldehyde were 2.2 and 1.2 ppb, respectively, for 21.9 L (0.15 L min(-1) for 146 min) of air sample volume. The integrated PrepStation GC-NPD system gave results comparable to those of the Sep-Pak DNPH silica cartridge method.

High-performance liquid chromatographic characterization of rhenium bipyridine complexes with phosphorus ligands

SummaryThe high-performance liquid chromatography of fourteen rhenium complexes with phosphorus and 2,2′-bipyridine-derivative ligands has been examined. Good separation between these complexes was achieved by use of an ODS column with a 60∶40 (v/v) mixture of MeOH and KH2PO4-NaOH buffer as mobile phase. Linear correlations were observed between the capacity factors of the mono-phosphorus complexes and Fujitas organicity/inorganicity ratios for the phosphorus ligands, revealing that Fujitas organicity/inorganicity parameters are useful for evaluating of the retention behavior of these complexes.

Synthesis of a linear-shaped tetramer and trimers of rhenium(I) diimine complexes

First examples of a linear-shaped tetramer and non-symmetrical trimers of rhenium(I) diimine complexes have been synthesized in good yields, and their UV–vis absorption and emission spectra are reported.

Applications of electrospray mass spectrometry and high performance liquid chromatography in the elucidation of photocatalytic CO2-fixation reactions

Photocatalytic CO 2 -fixation using [Re(bpy)(CO) 3 L]+ [bpy = 2,2′-bipyridine, L = P( n -Bu) 3 (1), PEt 3 (2), PPh 3 (3), P(OMe)Ph 2 (4), P(O i -Pr) 3 (5), P(OEt) 3 (6)]was examined by electrospray mass spectrometry and high performance liquid chromatography. The complexes 1, 2, 4, 5 and 6 remained at close to initial levels during the catalytic CO formation and a formate complex Re(bpy)(CO) 3 OC(O)H (7) was detected after prolonged irradiation. On the other hand, 3 changed completely to solvent (DMF, triethanolamine) complexes with a quantum yield of >>1 before catalytic CO formation, followed by the generation of 7. The ligand exchanges with solvent molecules were explained in terms of a chain reaction mechanism.