Kazuaki Yamanari

Extraordinary Circularly Polarized Luminescence Activity Exhibited by Cesium Tetrakis(3-heptafluoro-butylryl-(+)-camphorato) Eu(III) Complexes in EtOH and CHCl3 Solutions

The largest CPL activity ever measured was observed for cesium tetrakis(3-heptafluoro-butylryl-(+)-camphorato) Eu(III) complexes in EtOH and CHCl3 solutions substantiating the stereospecific formation of chiral Delta-SAPR-(C4) configuration with the aid of Cs+...FC (fluorocarbon) interactions more clearly than the exciton CD spectra.

Chiroptical spectra of a series of tetrakis((+)-3-heptafluorobutylyrylcamphorato)lanthanide(III) with an encapsulated alkali metal ion: circularly polarized luminescence and absolute chiral structures for the Eu(III) and Sm(III) complexes.

The luminescence and circularly polarized luminescence (CPL) spectra of M(I)[Eu((+)-hfbc)(4)] show a similar behavior to the exciton CD in the intraligand π-π* transitions when the alkali metal ions and solvents are manipulated. There is a difference in susceptibility in solvation toward the alkali metal ions but not toward the Eu(III) ion, as in the case of axially symmetric DOTA-type compounds. The remarkable CPL in the 4f-4f transitions provide much more information on the stereospecific formation of chiral Eu(III) complexes, since CPL spectroscopy is limited to luminescent species and reflects selectively toward helicity of the local structural environment around the lanthanide(III). While in comparison, exciton CD reveals the chiral structural information from the helical arrangement of the four bladed chelates. Of special importance, the observation of the highest CPL activities measured to date for lanthanide(III)-containing compounds (i.e., Eu and Sm) in solution supports the theory that the chirality of lanthanide(III) in the excited state corresponds to that in the ground state, which was derived from the exciton CD.

Cyclic Hexamer with a Cubic Cavity: Crystal Structure of [{Rh(6-Purinethione Ribosido)(Cp*)}6](CF3SO3)6

The stereoselective formation of a pseudo-S6 hexamer resulted from the self-assembling reaction between [Rh(Cp*)(H2 O)3 ]2+ and 6-purinethione riboside (see left structure; Cp*=C5 Me5 ). The schematic representation (right) shows the direction of the coordination to the S6 and N(7) donor atoms. C (clockwise) and A (anticlockwise) indicate the chirality of each unit complex.

Vibrational Circular Dichroism of Δ-SAPR-8-tetrakis[(+)-heptafluorobutyrylcamphorato]lanthanide(III) Complexes with an Encapsulated Alkali Metal Ion

The vibrational circular dichroism (VCD) spectra for Delta-M[Ln((+)-hfbc)(4)] (M(I) = Na, K, Rb, Cs; Ln(III) = La, Eu; abbreviated as M-Ln) and Delta-Cs[Yb((+)-hfbc)(4)] (Cs-Yb) were observed in CDCl(3) solutions. The VCD signs and/or intensities are mostly different from those of the Delta-tris(beta-diketonato) transition-metal complexes. The M-Ln complexes give the strong VCD peak(s) near 1550 cm(-1). These VCD patterns are different from each lanthanide(III) complex, but their intensities change with variation of the alkali metal ion. A positive-negative couplet VCD near 1550 cm(-1) for the Delta-M-La complexes is observed similarly for the Delta-tris(beta-diketonato) complexes, confirming the assignment to the Delta absolute configuration based on the exciton CD. The density functional theory calculated VCD for the two peaks at 1650 and 1550 cm(-1) reproduces the relative intensity and signs of the observed ones for the Delta-M-La(III) complexes.

Important role of CH–π interaction in linkage isomers of bis(2,2′-bipyridine)ruthenium(II) complexes with pyrimidine-2-thione and related ligands

Nine ruthenium(II) complexes containing pyrimidine-2-thione and related ligands were prepared and characterized by elemental analysis, UV/VIS and 1H and 13C NMR spectra: [Ru(L-N,S)(bipy)2]ClO4[HnL = Hpymt (pyrimidine-2-thione), Hmpymt (4-methylpyrimidine-2-thione), Hdmpymt (4,6-dimethylpyrimidine-2-thione), Hapymt (4-aminopyrimidine-2-thione), Hdapymt (4,6-diaminopyrimidine-2-thione), H2tuc(2,3-dihydro-2-thioxo-1H-pyrimidin-4-one, 2-thiouracil), 5-H2mtuc (5-methyl-2-thiouracil), 6-H2mtuc (6-methyl-2-thiouracil) or 6-H2ptuc (6-propyl-2-thiouracil); bipy = 2,2′-bipyridine]. Two linkage isomers, adjacent and remote, exist for all the complexes with unsymmetrical ligands except for apymt. The crystal structure of [Ru(mpymt)(bipy)2]ClO4 was determined. The mpymt ligand co-ordinates through the S2/N3 donors and the complex adopts an adjacent linkage form where the 4-methyl group lies just over one of the bipy chelate rings irrespective of steric hindrance. The CH–π attractive interaction between the 4- or 6-alkyl group of the thione ligand and the π system of bipy affects the isomer ratios in a striking manner.

Synthesis and crystal structures of cobalt(III) complexes containing pyridine-2-selenolato and its oxidation products

Abstract A series of mixed cobalt(III) complexes [Co(pySe)3−n(NN)n]n+ [pySe=pyridine-2-selenolato (1−); NN=1,2-ethanediamine (en) and 2,2′-bipyridine (bpy); n=0, 1 and 2] was prepared. The geometrical preference and trans influence of pySe are fairly different from those of pyridine-2-thiolate. These selenolato complexes were oxidized by peracetic acid to give the corresponding pyridine-2-seleninato (pySeO2) and pyridine-2-selenonato (pySeO3) complexes. The crystal structures of the pySeO2 and pySeO3 complexes revealed that the coordination mode change from an original N,Se-four-membered to the N,O-five-membered chelate ring occurred during oxidation and intramolecular hydrogen bonds between the non-coordinated oxygen of pySeO2 or pySeO3 and the amine protons of en stabilize the N,O-coordination mode.

Cobalt(III) promoted ligand fusion reactions of thiobarbituric acid and 4,6-diamino-2-thiouracil (or 4-amino-2-thiouracil)

Abstract Novel cobalt(III) complexes containing three kinds of assembled ligands, L1L2=dapymt–tbba(2-), tbba–dapymt(1-) and apymt–tbba(1-) (H3tbba=thiobarbituric acid; Hdapymt=4,6-diamino-2-thiouracil; Hapymt=4-amino-2-thiouracil), were prepared from the mixed ligand systems, where L2 indicates the coordinated ligand to the Co(III) ion and L1 is a pendant ligand bonded to L2. These complexes were characterized by UV–Vis absorption spectra and NMR spectroscopy. The crystal structures of [Co(Htbba)(en)2]ClO4·2H2O (2) (en=ethane-1,2-diamine), [Co{dapymt–tbba(2-)}(en)2]ClO4·3H2O (3) and [Co{apymt–tbba(1-)}(en)2](ClO4)Cl·3H2O (5′) revealed that coordination occurs through the S(1) and N(1) donors of tbba and the latter complexes 3 and 5′ have an assembled ligand; a new bond is formed between the C(5) atom of tbba and the S(2) atom of dapymt or apymt. An intramolecular hydrogen bond between O(1) of tbba and NH of en was found in all crystals. An interesting intermolecular π–π stacking interaction was found in 5′.

Complete enantioseparation through supramolecular complex formation between tris(1,3-diaminopropane)cobalt(III) phosphate and β-cyclodextrin, [Co(tn)3]PO4·β-CDX.

The supramolecular complex [Co(tn)(3)]PO(4)·β-CDX (tn = 1,3-diaminopropane; β-CDX = β-cyclodextrin) was prepared through β-CDX, rac-[Co(tn)(3)]Cl(3), and Na(3)PO(4) in a mole ratio of 1:2:2. After one recrystallization process, the circular dichroism spectrum confirmed that complete enantioseparation of [Co(tn)(3)]PO(4) is achieved in this system. X-ray crystal structure analysis reveals the presence of the only Λ-enantiomer in the unit cell and the head-to-head chiral discrimination structure of this system. Thus, we found that the present diastereomer formation with β-CDX affords the very convenient and effective optical resolution procedure of [Co(tn)(3)](3+).

Chiroptical Spectra of Tetrakis (+)-3-Heptafluorobutylrylcamphorate Ln(III) Complexes with an Encapsulated Alkali Metal Ion: Solution Structures as Revealed by Chiroptical Spectra

The preparation of tetrakis((+)-hfbc) lanthanide(III) complexes with an encapsulated alkali metal and ammonium ions M[Ln((+)-hfbc)(4)] (hereafter abbreviated as M-Ln : (+)-hfbc, (+)-heptafluorobutyrylcamphorate; M, ammonium or benzyl ammonium ions as well as alkali metal ions) was reported and discussed. The electronic circular dichroism (CD) spectra in the intraligand π-π* transition of M-Ln were examined in view of the solvent effect. Here, the concentration, alkali metal, and ammonium ion dependences are compared with the solid CD, (5)D(0)←(7)F(0) (Eu(III)) excitation spectra, circularly polarized luminescence, and vibrational circular dichroism. It has been revealed that the dodecahedral eight coordinate DD-8-M-Ln complexes in crystals are equilibrated between the diastereoselectively formed square antiprism eight coordinate SAPR-8-M-Ln and [Ln((+)-hfbc)(3)] in EtOH and CH(3) CN solutions or between the SAPR-8-M-Ln and DD-D(2d) (mmmm)-8-M-Ln complexes in CHCl(3) solution. The observed CD couplets are found to reflect the exciton CD couplets which are useful to determine the four-bladed SAPR-(llll) absolute configuration around the lanthanide(III) ion.

Synthesis and stereochemistry of cobalt(III) complexes containing purine-6-thione and related ligands

Seven cobalt(III) complexes containing five purinethiones [Co(L-N,S)(en)2]n+ and [HnL = H2put = 9H-purine-6(1H)-thione, H2aput = 2-amino-9H-purine-6(1H)-thione, H3tpuo = 3,6-dihydro-6-thioxo-9H-purine-2(1H)-one, H3oput = 2,3-dihydro-2-thioxo-9H-purin-6(1H)-one and H2pzpymt = 1H-pyrazolo[3,4-d]-pyrimidine-4(5H)-thione; en = ethane-1,2-diamine] were thermally or photochemically prepared and characterized by elemental analysis, UV/VIS absorption and 1H and 13C NMR spectra. The crystal structure of [Co(put)(en)2]Cl·2H2O was determined. The put ligand co-ordinates through S6 and N7 forming a five-membered chelate ring. The other purine-6-thione ligands all adopt this mode rather than the four-membered one of N1/S6. Carbon-13 NMR spectroscopy is very useful for the assignment of the above linkage isomers.