Hiroaki Kido

Two-color multiphoton dissociation/ionization of jet-cooled CrIII(acac)3 and Cr0(CO)6: appearance energies of Cr atom

Abstract Photodissociation of jet-cooled Cr III (acac) 3 and Cr 0 (CO) 6 has been investigated by two-color multiphoton dissociation/ ionization spectroscopy in which a UV light of 258−242 nm is used for the dissociation and a visible light for the multiphoton ionization of photofragments. The generation of the neutral Cr atom is found in both compounds after two-photon excitation with the UV light. The threshold energies of the two-photon dissociation are determined and the characteristic fragmentations are observed. For Cr III (acac) 3 it is found that no fragment other than the Cr atom is produced by the two-photon dissociation and that the threshold energy for Cr atom generation is about 78500 cm −1 (9.73 eV). The result suggests that the neutral Cr atom originates directly from the super-excited state which is the neutral excited state lying at about 2.27 eV higher than the ionization potential of Cr III (acac) 3 . For Cr 0 (CO) 6 , the production of the coordinatively unsaturated photofragments is found in the photodissociation with the UV light and the sequential mechanism for the Cr atom generation is confirmed.

Preparation and circular dichroism of rhodium(I) complexes containing optically active trans-cyclooctene

Abstract Three new rhodium(I) compounds containing optically active trans -cyclooctene ( trans -C 8 H 14 ) were prepared: [RhL {(+) D - trans -C 8 H 14 } 2 ] (L = acetylacetonate and 1,3-diphenyl-1,3-propanedionate) and [Rh 2 Cl 2 {(+) D - trans -C 8 H 14 } 4 ]. The absorption and circular dichroism spectra were measured and compared with those of [Pt 2 Cl 4 {(-) D - trans -C 8 H 14 } 2 ]. The absolute configuration of coordinated alkenes is correlated with the CD spectra in the wave number regions, (20–30) x 10 3 cm -1 and 40 x 10 3 cm -1 . In the former range the CD sign is the reverse of that of platinum(II)—alkene complexes, but in the latter region the CD signs are equal.

Preparation of a flexible binucleating ligand, xylylene-bridged biscyclam α,α′-bis(1,4,8,11-tetraazacyclotetradecan-6-yl)-p-xylene and structure of its dinickel(II) complex

Abstract A binucleating ligand, xylylene-bridged biscyclam α,α′-bis(1,4,8,11-tetraazacyclotetradecan-6-yl)-p-xylene ((cyclam)2-p-xyl) was prepared from α,α′-dichloro-p-xylene, diethylmalonate and 1,4,8,11-tetraazaundecane in three steps. The second step, aminolytic condensation of the tetraamine was critical. The ligand yielded a dinickel(II) complex (Ni2(cyclam)2-p-xyl](ClO4)4 · 4H2O. X-ray crystal analysis of the complex disclosed opposite and almost perpendicular occupation of the macrocycles to the bridging benzene ring through equatorial connection at the 6-carbons. Crystal data: tetragonal space group P4 2 , a = 15.251(2), c = 9.821(2) A V = 2284.3(6) A 3 Z = 2 . It is anticipated that conformational change in solution due to free rotation around the methylene carbon at the junction puts the macrocycles into face-to-face location with Niue5f8Ni distance of ∼ 7.7 A.

Photodissociation of jet-cooled acetylacetonato complexes of the first transition metals. Free metal generation and fragmentational ionization

Abstract Photodissociation of jet-cooled acetylacetonato complexes of Sc(III), Mn(III), Fe(III), Co(III), Ni(II), Cu(II), Zn(II), Al(III), and Ga(III) is studied by multiphoton dissociation/ionization mass spectroscopy. Efficient generation of the neutral Cu atom from the Cu(II) complex is found to occur after two-photon excitation with UV light. Two-color laser photolysis shows that the Cu atom generation is due to homolytic dissociation of all the metal-ligand bonds occurring in the super-excited state of the Cu(II) complex. The threshold energy of the two-photon dissociation is obtained and the energetics of the photolysis of the Cu(II) complex is given on the basis of the results. For other metal complexes it is found that extensive fragmentational ionization takes place under a similar excitation condition to that of the Cu(II) complex while free metal atom generation does not occur. The characteristic free metal generation occurring in the Cu(II) complex is discussed in connection with the photolysis of the Cr(III) complex which was reported in a previous paper.

Optical Inversion and Substitution of Coordinated Olefins in Optically Active Trans(N)-Chloro-L-Prolinatoolefinplatinum(II) Complexes in Organic Solvents

Optical isomerism due to asymmetric coordination of some olefins such as propylene and trans-2-butene was first studied by Paiaro and Panunzi.l We have synthesized diastereomers of the type trans(Nolefin)[PtCl(L-prol)(olefin)] crystalline,2 and discussed the absolute configuration of coordinated olefins on the basis of circular dichroism (CD) spectroscopy.3 The complexes with such olefins as trans-2-butene and 2-methyl-2-butene gave no change in u.v. absorption and CD in organic solvents such as ethanol, chloroform and acetone. When the same olefin as the ligand was added, the CD changed, the u.v. absorption remaining unchanged. (Figure 1) This fact suggests that only the inversion of the coordinated olefin takes place.