Search

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, 5D0 7F0(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 CH3CN solutions or between the SAPR-8-M-Ln and DD-D2d(mmmm)-8-M-Ln complexes in CHCl3 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. Chirality 24:1055–1062, 2012. © 2012 Wiley Periodicals, Inc.

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.

The X-ray crystal structure of tetrakis (+)-hfbc Pr(III) complex, Na[Pr((+)-hfbc)4]·CH3CN, was compared with that of the corresponding Na–La complex with a pseudo-achiral dodecahedron, and the solution CD spectra were also discussed in the 4f–4f transition in consideration of the exciton CD couplet showing Δ-SAPR-8 configuration in CHCl3.

Six C3 cyclic trinuclear complexes [{M(Cp*)(L)}3]3+ (M = RhIII and IrIII; Cp* = η5–C5Me5) containing adenosine nucleosides [L: adenosine (Hado), 2′-deoxyadenosine (Hdeoado) and 5′-acetyl-2′,3′-isopropylideneadenosine (Haipado)] were prepared and characterized by UV/Vis and circular dichroism (CD) spectra, NMR spectroscopy, electrospray ionization mass spectroscopy and X-ray crystal structure analysis. The isolations of one and/or two diastereomers were successfully carried out for the four systems by second-order asymmetric transformation and/or fractional crystallization. Interestingly, a striking kinetic difference was found between the present RhIII– and IrIII–ado systems. The crystal structure of CCC-[{Rh(Cp*)(ado)}3](CF3SO3)3·2.5H2O·CH3OH revealed that the ado ligand adopts a μ-1κN1:2κ2N6,N7 bridging mode and the three purine rings forming a triangle dome-like cavity can include one methanol molecule into its cavity. The absolute configurations were assigned to these complexes based on the crystal structural result and CD spectral arguments. The RhIII–N-methyl adenosine (HNMeado) system exceptionally gave a di-μ-hydroxy anti-dinuclear structure because of the weak coordination ability of the N(6) donor.

Four palladium(II) complexes [PdX2(L-N,S)] (X=Cl, Br; L: BzSq=benzyl 8-quinolyl sulfide, PheneSq=phenethyl 8-quinolyl sulfide) were prepared. The crystal structure of [PdCl2(BzSq-N,S)] revealed the presence of an intraligand stacking between the phenyl and quinolyl groups of BzSq. This stacking interaction was confirmed even in Me2SO, MeCN and MeNO2. On the other hand, [PdCl2(PheneSq-N,S)] did not show such an intraligand stacking both in the solid and in solutions.

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′.

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.

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.

The aggregation of novel type cobalt(III) surfactants, such as [Co(en)2{NH2(CH2)2S(1-CnH2n+1)}]3+ (n = 6, 8, and 12) and [(en)2Co{NH2(CH2)2 S(CH2)mS(CH2)2NH2}Co(en)2]6+ (m = 8 and 12), was studied in water using multinuclear NMR spectroscopies, 1H NMR self-diffusions, and 1H NMR chemical shifts. The 59Co linewidths of the surfactants were useful to monitor the premicellar and micellar formation. It was revealed that the tripositive mononuclear surfactants have comparable cmc (critical micelle concentration) values to those for the usual monovalent surfactants having the same alkyl chains. The 35Cl longitudinal relaxation rates for the counterions were useful to monitor the two kinds of ionic interactions, i.e., those with the surfactant monomers and with the micelles. We determined the cmcs for the premicellar formation in the hexyl mononuclear and octyl dinuclear complex systems. The determination of this kind of cmc has become possible by using such highly charged complexes as the cystam complex and by ...

Self-assembling reactions between [Rh(η5-C5Me5)(H2O)3]2+ and pyrimidine-2-thionate (pymt) or related ligands [L; mpymt = 4-methyl-pyrimidine-2-thionate(1−), dmpymt = 4,6-dimethylpyrimidine-2-thionate(1−), apymt = 4-aminopyrimidine-2-thionate(1−), dapymt = 4,6-diaminopyrimidine-2-thionate(1−), or mpol = 2-sulfanyl-3-pyridinolate(2−)] were carried out and the products characterized by UV/vis, NMR spectroscopy, electrospray ionization mass spectrometry, and crystal structure analysis. All products are dinuclear rhodium(III) complexes of [{Rh(η5-C5Me5)(L)}2]n+: three crystal structures with mpymt, dmpymt and mpol were determined. The mpymt and dmpymt ligands co-ordinate through a 1κ2N,S∶2κS mode and the two pyrimidine rings are located in cis position, whereas mpol adopts a five-membered chelating mode with 1κ2S,O∶2κS and the two pyrimidine rings are located in trans position. Such structural difference can reasonably be explained by the intramolecular stacking interaction between the two bridging ligands.

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.

A rapid reversible inversion (epimerization) between the Δ-(R,R,R) and Λ-(R,R,R) diastereomers for fac-Δ- and Λ-tris(R-cysteinato-N,S)cobaltate(III) occurs at room temperature in an aqueous solution of each salt. The half-lives for the mutarotation were measured (k = kΛ + kΔ): 80 and 6 minutes at 20 and 40 °C, respectively. The equilibrium constants, K = [Λ-(R,R,R)]/[Δ-(R,R,R)], are 1.2 at 20 °C and 1.0 at 40 °C, which means that the cobalt inversion rate constant kΛ nearly equals kΔ. Eight kinds of metal salts, M3[Co(R-cys-N,S)3] [M = Li+, Na+, K+, Rb+, Cs+; M1/2 = Ca2+, Sr2+, Ba2+], were prepared. It was found that all these salts show a second-order asymmetric transformation under a solid-solution equilibrium at room temperature of the kind first demonstrated for the Ba2+ salt by Arnold and Jackson. The phenomenon led to the Δ-(R,R,R) diastereomer for the salts of Li+, Na+, K+, Rb+, Cs+, Ca2+ and Sr2+, but to the Λ-(R,R,R) diastereomer for Ba2+. These results could be clearly explained by solubility measurements of each diastereomeric salt pair.

The first ligand oxidation of sulfur donors of OC-6-3′2-[Co(pyet)2]+ [pyet = 2-[(2-pyridylmethyl)amino]ethanethiolate (1−)] by molecular dioxygen is attained in the presence of active charcoal. The oxidation products are characterized as one (thiolato)(sulfinato) complex OC-6-3′2-[Co(pyet)(pyesi)]+ (b; 82%), one (thiolato)(sulfenato) complex OC-6-3′2-[Co(pyet)(pyese)]+ (d; 14%) and a mixture of four bis(sulfenato) complexes OC-6-3′2-[Co(pyese)2]+ (h, i, j, and k; 4%), [pyese = 2-[(2-pyridylmethyl)amino]ethanesulfenate (1−); pyesi = 2-[(2-pyridylmethyl)amino]ethanesulfinate (1−)]. It is apparent that the route producing the monosulfinato complex is dominant in the dithiolatocobalt(III) complex as well as in the dithionickel(II) complexes. The isolation of OC-6-3′2-[Co(pyet)(pyese)]+, however, is extremely interesting because this complex is the first example of an oxidation product free from an O2.

The cyclic multinuclear complexes [Co(n)()(L-N,S,N')(n)()(tacn)(n)()](n)()(+) (L = purine-6-thiones; tacn = 1,4,7-triazacyclononane) were synthesized through self-assembly of the mononuclear complex [Co(HL-N,S)Cl(tacn)](+) based on the multidentate bridging ability of purine-6-thione. Three kinds of purine-6-thione ligands were used: 9H-purine-6(1H)-thione (H(2)put), 2-amino-9H-purine-6(1H)-thione (H(2)aput), and 3,6-dihydro-6-thioxo-9H-purin-2(1H)-one (H(3)tpuo). The complexes [Co(n)()(L-N,S,N')(n)()(tacn)(n)()](n)()(+), n = 3 and 4 for put and n = 4 for aput and Htpuo, were characterized by NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and X-ray crystal structure analysis. ESI-MS proved to be a very powerful tool for determining the nuclearity (n value) unambiguously. X-ray crystal structure analyses of [Co(4)(put)(4)(tacn)(4)](CF(3)SO(3))(4).12H(2)O [triclinic, Ponemacr; (No. 2)] and [Co(4)(aput)(4)(tacn)(4)]Cl(4).16H(2)O [monoclinic, C2/c (No. 15)] reveal that all purinethione ligands act as tridentate ligands via S(6)/N(7) chelation and the N(9) bridge and both tetranuclear complexes adopt the cyclic S(4) structure which is stabilized by four intramolecular hydrogen bonds between N(3) and H-N(tacn). The trinuclear complex [Co(3)(put)(3)(tacn)(3)](3+) having the C(1) structure was optically resolved. Stereochemistry for the cyclic molecular boxes containing chiral octahedral ions is developed.

Ternary solubility isotherms of trans(N,t-N)-[Co(leu)(tren)]I2, trans(N,t-N)-[Co(n-leu)(tren)][ClO4]2, and trans(N,t-N)-[Co(n-val)(tren)][ClO4]2 [t-N = tertiary amine nitrogen; leu = leucinate(1−), n-leu = norleucinate(1−), n–val = norvalinate(1−), and tren = tris(2-aminoethyl)amine] were determined at 25 °C. Each isotherm consists of two branches of the solubility curve and one eutectic point; the tie lines do not converge to any apex of the pure enantiomers, but diverge widely. These facts mean that the three complexes simultaneously form a conglomerate and a solid solution. X-Ray crystal analyses were carried out for crystals grown from the three racemic aqueous solutions. All of the crystals were isomorphous to each other in spite of having different amino acidates and counter ions. The crystal structures clearly demonstrated the coexistence of D-amino acidate and L-amino acidate at one site of the crystal lattice, that is, a solid solution. Furthermore, all of the crystals were partially optically ac...

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.

Ternary solubility diagrams of trans(N,t-N)-[Co(n-leu)(tren)]I2 and trans(N,t-N)-[Co(met)(tren)]I2[t-N = tertiary amine nitrogen, n-leu = norleucinate(1-), met = methioninate(1-), and tren = tris(2-aminoethyl)amine] were determined at 25.0 °C. A single isotherm was found; the tie lines do not converge to any apexes of the enantiomers in either system. The solid phases are variable over the entire region from D : L(%) = 100 : 0 to 0 : 100, and both systems form a solid solution. The X-ray crystal structures of trans(N,t-N)-[Co(DL-n-leu)(tren)]I2 (1; D : L = 50 : 50) and trans(N,t-N)-[Co(DL-met)(tren)]I2 (3; D : L = 50 : 50) were determined from 3600 and 4699 reflections to R = 0.036 (Rw = 0.046) and R = 0.045 (Rw = 0.068), respectively: space group P21/c with a = 9.204(4), b = 11.057(2), c = 19.576(3) A, β = 95.95(2)°, and Z = 4 for 1 and space group P21/n with a = 13.032(4), b = 11.210(4), c = 13.535(2) A, β = 92.62(2)°, and Z = 4 for 3. The results confirm the co-existence of the D- and L-amino acidato c...

A room-temperature reaction of Co(CH3CO2)2·4H2O with pyrimidine-2-thione (Hpymt), or eight kinds of their derivatives (mole ratio = 1 : 2.8—3.0) in methanol, was carried out in air. It was found that the substituent group at a 4-position in the pymt skeleton governs the product. The pymt and its derivatives, having an alkyl or an amino group as the 4-substituent, gave tris-type cobalt(III) complexes mer-[Co(N-S)3] in good yields. On the other hand, the 2-thiouracil derivatives, having an oxygen or a sulfur atom as the 4-substituent, produced only bis-type cobalt(II) complexes [Co(N-S)2]. Such different ligand behavior concerns the different electronic structures of the pyrimidine rings. The presence of three linkage isomers in mer-[Co(4-methyl-pymt)3] has been confirmed by 59Co NMR spectroscopy, and an important role of the CH···π attractive interaction has been found.

A novel (μ-peroxo)(μ-thiosulfato) bridged cobalt(III) complex [(tren)Co(μ-O2)(μ-S2O3)Co(tren)]2+ [tren = tris(2-aminoethyl)amine] was prepared. The complex shows a characteristric UV/VIS absorption spectrum and the X-ray crystal structure reveals that the complex has an unprecedented large Co-O-O-Co torsion angle 75.5(2)°.

An unusual red complex [Co(di-Hatuc)(en)2]+ (di-Hatuc = [5-((1′H)-4′-oxo-6′-aminopyrimidin-2′-yl)thio]-6-amino-2-thiouracilate (2−); en = ethane-1,2-diamine) is formed by a simple thermal reaction. This complex has both a intramolecular hydrogen bond and novel linear intermolecular hydrogen bonds, the latter being analogous to hydrogen bonding in nucleic acids.

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 A-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+ . .

Ternary solubility isotherms of trans(N,t-N)-[Co(leu)(tren)]I2 and trans(N,t-N)-[Co(n-leu)(tren)](ClO4)2 (leu = leucinate(1−), n-leu = norleucinate(1−), and tren = tris(2-aminoethyl)amine) at 25 °C consist of two branches of solubility curve and one eutectic point, but the tie lines do not converge to any apex of the pure enantiomers and diverge widely. These facts mean that both racemates form a conglomerate and simultaneously a solid solution. The X-ray crystal analysis of the former iodide (D : L = 63 : 37; space group P32) confirms the existence of this conglomeratic solid solution.

The ternary solubility phase diagrams, [Co(L-leu)(NH3)4]X2–[Co(D-leu)(NH3)4]X2–H2O (leu = leucinate(1−); X = Br and I) were determined at 25 °C. Only one isotherm is obtained in each system and the D:L ratios of the solid phases are variable over entire region from D:L = 100:0 to 0:100. This means that the solid solutions of the enantiomers form in both systems. These phase diagrams are the first examples of solid solutions of metal complexes containing natural amino acids.

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.

cis-K[Co(NO2)4(NH3)2] was first synthesized from hexanitrocobaltate(III) in liquid ammonia and characterized by the elemental analysis and electronic and infrared spectra. The cis structure was confirmed by the X-ray analysis. The anomalous congested contact among three oxygens of three nitro ligands was found in the crystal.

Six new cyclic tetranuclear complexes [[M(Cp*)(L)](4)](4+) and [[Ru(II)(L)(cymene)](4)](4+) [Cp* = eta(5)-C(5)Me(5), cymene = eta(6)-p-MeC(6)H(4)Pr(i); M = Rh(III) and Ir(III); HL = 6-purinethione (H(2)put) and 2-amino-6-purinethione (H(2)aput)] were prepared in a self-assembly manner and characterized by NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray crystal structure analysis. The two crystal structures of [[Rh(Cp*)(H(0.5)put)](4)](CF(3)SO(3))(2) and [[Ir(Cp*)(Haput)](4)](CF(3)SO(3))(4) revealed that they have similar S(4) structures with an alternate chirality array of CACA, and all ligands adopt a mu-1kappaN(9):2kappa(2)S(6),N(7) coordination mode. The orientations of the four bridging ligands are alternately up and down, and they form a central square cavity. Interestingly, the cationic tetramers of the former are stacked up along the c axis, resulting in an infinite channel-like cavity. The driving force of this stacking is due to intermolecular double hydrogen bonds [N(1)-H...N(21) = 2.752(4) A] at both sides of the cavity. In the two Rh(III)- and Ru(II)-H(2)aput systems, it turned out that the dimeric species are dominantly formed in the reaction solutions but finally convert into the tetrameric species.

The stereoselective formation of a pseudo-S

For electronic circular dichroism in the 4f-4f transitions (4f-4f CD) of a series of nine tetrakis ((+)-3-heptafluorobutyrylcamphorato) Ln(III) complexes, Δ-SAPR-8-C(4)(llll) Cs[Ln((+)-hfbc)(4)]·H(2)O (Cs-Ln = Cs-Pr, -Nd, -Sm, -Eu, -Dy, -Ho, -Er, -Tm, -Yb), the spectroscopic observables such as the dissymmetry factor g = Δε/ε values with the intensities (Δε) of the CD components and the molar absorption intensities (ε) in the 4f-4f transitions between the (2S+1)L(J) levels are compared with each other to test the classification of the CD components in the relative order of the observables predicted in terms of the selection rule for 4f-4f transitions. The 4f-4f CD-based chiroptical spectra-structural relationship across the series of Δ-SAPR-8-C(4)(llll) lanthanide(III) complexes is proposed: the signs of the 4f-4f CD or CPL in the hypersensitive transitions are related to the absolute configuration; Ln complexes with a negative CD component have the Δ-configuration around Ln(III) and vice versa.

The novel tris(2-aminoethyl)aminecobalt(III) complex containing a dimerized ligand Hatuc-atuc (6-amino-5-[6-amino-4-oxo-(1H)-pyrimidin-2-yl]thio-2-thioxo-pyrimidin-4-onate(2-)) was prepared. The crystal structure revealed that Hatuc-atuc coordinates through the S/N donors and exhibits the intermolecular π–π stacking and the double N–H···O hydrogen bond interactions.

Two bis(2,2′-bipyridine)ruthenium(II) complexes containing purine-6-thione were prepared. The crystal structure of [Ru(H2put)(bpy)2](ClO4)2·2.5H2O (bpy = 2,2′-bipyridine; H2put = 7H-purine-6(1H)-thione) revealed that the H2put ligand coordinates through the S6/N(7) donors and can form the double N–H···N intermolecular hydrogen bonds in the crystal.

A diastereomer with a C3 cyclic trimer [{Rh(adenosine)(Cp*)}3](CF3SO3) 3, which was obtained selectively by a second-order asymmetric transformation, can include one methanol molecule into its triangle dome-like cavity.

The novel Co(III)-CDX supramolecular complex [Co(en)(3)](2)(CO(3))(3).2(alpha-CDX) (1) was prepared and the circular dichroism spectrum showed that complex 1 is 25% Lambda-rich (Lambda : Delta = 62.5 : 37.5). X-ray crystallography revealed the crystal structure of complex 1 and the reasonable chiral recognition mechanism of this system.

Chromatographic columns prepared from SP-Sephadex C-25 resins and Δ- and Λ-(β-cyclodextrinato)-bis(ethylenediamine)cobalt(III)(1+) chloride have been successfully applied to the optical resolution of cis- and trans-(RS-amino acidato)(nitrilotriacetato)cobaltate(III)(1–) complexes.

The first ligand oxidation of Co(III)-bound thiolates by molecular dioxygen is realized in the presence of active charcoal. Three oxidation products are characterized by UV/VIS absorption and 13C NMR spectra and X-ray crystal analysis.

Ruthenium(II) complexes containing nine pyrimidine-2-thione [Ru(L-N,S)(bpy)2]+ (HL = pyrimidine-2-thione; bpy = 2,2′-bipyridine) are prepared and characterized. Two linkage isomers exist for most of the complexes with unsymmetrical ligands. The isomeric ratios are interpreted by CH/π attractive interaction between the 4- or 6-alkyl group of the thione ligands and the π-system of bpy.

Thermal reaction between trans-[CoCl2(en)2]Cl (en = ethane-1,2-diamine), H2atuc (6-amino-2-thiouracil) and NaOH in the presence of activated charcoal produced two red complexes 1 and 2. The crystal structures of complexes 1 and 2 were determined from 5090 and 4567 reflections to R= 0.048 (R′= 0.052) and 0.055 (0.068), respectively. Complex 1 has the composition [Co(atuc)(en)2]+ where atuc co-ordinates through atoms 2-S and 3-N. Complex 2 has an unusual composition [Co(HL)(en)2]+{H3L = 6-amino-5-[6-amino-4-oxo-(1H)-pyrimidin-2-yl]thio-2,3-dihydro-2-thioxo-(1H)-pyrimidin-4-one}: a new bond is formed between the 5-carbon atom of the co-ordinated atuc and the 2-sulfur atom of an unco-ordinated atuc, that is the atuc is dimerized. This complex has self-associated double intermolecular hydrogen bonds in the crystals in addition to an intermolecular hydrogen bond.

Two kinds of dinuclear cobalt(III) complexes sym-(meso- and rac-)[{Co(en)2}2(µ-ttcy)]X3 and sym-[meso- and rac-)[{Co(en)2}2(µ-dtcy)]X3(en = ethane-1, 2-diamine, H3ttcy = 1,3,5-triazine-2,4,6-trithione, H3dtcy = 4-oxo-1,3,5-triazine-2,6-dithione) have been prepared photochemically from [Co(en)3]Cl3, H3ttcy and NaOH and characterized by elemental analysis, IR, UV/VIS and NMR spectroscopy. The dtcy complexes are formed via a novel desulfurization of the ttcy ligand. Two crystal structures, sym-meso-[{Co(en)2}2(µ-ttcy)][ClO4]3·2H2O and sym-meso-[{Co(en)2}2-(µ-dtcy)]l3·4H2O were determined from 1859 and 4146 reflections to R= 0.056 (R′= 0.060) and R= 0.069 (R′= 0.073), respectively: monoclinic, space group P21/a, a= 14.392(4), b= 14.807(4), c= 14.816(4)A, β= 92.83(3)° and Z= 4; monoclinic, space group P2/c, a= 18.088(3), b= 8.146(6), c= 21.757(3)A, β= 93.25(1)° and Z= 4. The bridging ttcy and dtcy ligands co-ordinate symmetrically through the two N and S donor sets and both complexes are in the meso form. Marked symmetric intramolecular hydrogen bonds N–H ⋯ S[N ⋯ S 3.19(1), 3.21(1)A] were formed between the free sulfur atom of the ttcy and the two amine protons of the en in the ttcy complex.

Three series of mixed-ligand cobalt(III) complexes containing four-membered N,S chelates [CoLn(en)3–n](3–n)+[n= 1 or 2; HL = 2-thiocytocine (4-aminopyrimidine-2-thione, Hapymt), 4,6-diaminopyrimidine-2-thione (4,6-Hdapymt) or 2,4-diaminopyrimidine-6-thione (2,4-Hdapymt); en = ethane-1,2-diamine] have been prepared photochemically and/or thermally and characterized by elemental analysis, UV/VIS absorption, and 1H and 13C NMR spectra. The crystal structure of [Co(apymt)(en)2][ClO4]2 was determined from 1897 observed reflections to R= 0.048 (R′= 0.053): space group Pbca(orthorhombic) with a= 11.849(7), b= 27.551(8), c= 11.201(3)A and Z= 8. The apymt ligand co-ordinates through the N1 and S2 donors and the complex adopts a remote linkage form where the C4 amino group is distant from the en chelate rings. A new type of intramolecular hydrogen bond between the co-ordinated sulfur atom of one dapymt ligand and one of the amino groups of the other dapymt ligand was found in trans-(S)-[Co(4,6-dapymt)(en)2]+ and trans-(S)-[Co(2,4-dapymt)(en)2]+, which is responsible for their relatively high formation yield.

Eight cobalt(III) complexes containing four-membered N,S chelates [CoL(en)2]+ and [Co(HL)(en)2]2+{H2L = 2-thiouracil [2,3-dihydro-2-thioxo-(1H)-pyrimidin-4-one](H2tuc), 5-methyl-2-thiouracil (5Me-H2tuc), 6-methyl-2-thiouracil (6Me-H2tuc) or 2,3-dihydro-2-thioxo-(1H)-quinazolin-4-one (H2quz); en = ethane-1,2-diamine} have been photochemically prepared from robust [Co(en)3]Cl3 and the ligands in moderate yields and characterized by elemental analyses, UV/VIS absorption and NMR spectroscopy. The crystal structure of [Co(tuc)(en)2]ClO4·H2O was determined from 3905 reflections to R= 0.053 (R′= 0.056): space group P(triclinic) with a= 9.489(2), b= 10.968(2), c= 8.640(2)A, α= 101.28(2), β= 115.19(1), γ= 80.61(2)° and Z= 2. The tuc ligand co-ordinates through N and S donors and the complex adopts an adjacent linkage form where the C4 oxygen atom is located near the en chelate ring. A characteristic intramolecular hydrogen bond N–H ⋯ O [N ⋯ O 2.876(8)A and N–H ⋯ O 143.14°] was found between the oxygen atom of the tuc and an amine proton of en, which contributes to the stabilization of the sterically unfavourable adjacent isomer. Proton NMR spectroscopy showed that the hydrogen bond is also present in D2O and (CD3)2SO solutions.

By crystallization of ΔΛ-[Co(aet)(en)2][ClO4]2 in the presence of Δ-Na[Co(edta)]·3H2O or Na2(D-tart)·2H2O [aet = 2-aminoethanethiolate(1–), en = ethylenediamine, edta = ethylenediaminetetraacetate(4–) and D-tart =(RR)-tartrate(2–)] the Δ-aet complex always appears as the first crop. The mechanism can be best explained by use of a ternary solubility isotherm: a shift of the eutectic point on the central racemic line into the optically active region is caused by the active cosolute (or solvent); the larger the shift the higher is the percentage resolution. This isotherm has also clarified that the solubility difference between the enantiomers in the binary system is not relevant to the optical resolution. This resolution mechanism is applicable to conglomerates with rapid racemization rates.

Three series of mixed-ligand cobalt(III) complexes containing four-membered N,S chelates [CoLn-(en)3–n](3–n)+[n= 1, 2 and/or 3; HL = pyrimidine-2-thiol (Hpymt), 4-methylpyrimidine-2-thiol (Hmpymt), or 4,6-dimethylpyrimidine-2-thiol (Hdmpymt); en = ethane-1,2-diamine] have been photochemically prepared from robust [Co(en)3]3+ and the free ligand in moderate yields and characterized by their elemental analyses, UV/VIS absorption and 1H and 13C NMR spectra. The crystal structure of [Co(mpymt)(en)2][ClO4]2 was determined from 3329 reflections to R= 0.043 (R′= 0.062): space group P21/n(monoclinic) with a= 10.122(8), b= 9.003(6), c= 20.35(2)A, β= 100.17(7)° and Z= 4. The mpymt ligand co-ordinates through N and S donors and the complex adopts a remote linkage form where the C4 methyl group is distant from the en chelate rings. The Co–N bond length trans to the sulfur atom is slightly longer (0.013 A) than the cis one.

The binary and ternary solubility diagrams of [Co(CO3)(en)2]Br (en = ethylenediamine) have been determined at 5–70°C. It was found that the bromide exists as a racemic compound dihydrate below 15.0 °C and as an anhydrous conglomerate above this temperature. The conglomerate is kinetically resolved by crystallization in the presence of chiral additives, Δ-[Co(glyO)(en)2]Br2(glyO = glycinate) and Λ-[Co(ox)(en)2]Br (ox = oxalate), at room temperature. The same resolutions utilizing racemization of [Co(CO3)(en)2]Br were also attempted at 40 °C.

[2]-[[(en)2Co{NH2(CH2)2S(CH2)nS(CH2)2NH2}Co(en)2]Cl6]-[α- or β-CDX]-rotaxanes were prepared with partial stereoselectivity and characterized from their absorption and 13C NMR spectra, molar conductance, and elemental analysis (CDX=cyclodextrin; n=8, 10, and 12). The rotaxanes always showed apparently ΔΔ-rich. CD spectra, the highest selectivity (16% ΔΔ-rich) being found in the case of n=10 and α-CDX. The results are related to the direct preparation of [2]-[ΔΔ-[(en)2Co{NH2(CH2)2S(CH2)nS(CH2)2NH2}Co(en)2]Cl6]-[α-CDX]-rotaxanes (n=8, 10, and 12) in relatively higher yields than the corresponding ΛΛ rotaxanes: 3.5% for n=8, 21% for n=10, and 28% for n=12. Inclusion complexes of a new type [Co(en)2{NH2(CH2)2S(CH2)nBr}]Cl3·2(α-CDX) were also isolated (n=10 and 12).

The crystal structure and absolute configuration of diastereomeric molecular compound, d-C4H6O6·(+)500CD[Co{S(O)CH2CH2NH2}3]·H2O, were determined by the X-ray diffraction method. The crystals are orthorhombic with space group P212121, Z=4, and a=13.034(4), b=13.559(6), and c=11.048(8) A. The rifinement of 1724 reflections (Mo Kα radiation) led to R=0.068. The complex molecule has the configuration fac(S)-Λ-(δ,δ,δ)-(R, R, R). All amino groups and the sulfenato oxygen atoms form hydrogen bonds with d-tartaric acid and/or water molecules three-dimensionally, which is responsible for the formation of the novel diastereomeric molecular compound.

Two kinds of four-component solubility isotherms consisting of (Λ-[Co(ox)(en)2]+, Δ-[Co(ox)(en)2]+)–(Cl−, X−)–H2O, where X− stands for Δ-[Co(edta)]− or (R,R)-C4H5O6−, have been determined experimentally at 25 °C. It has been found that neither double salt nor solid solution exists and no configurational activity is observed in these systems. The applications of these phase diagrams to the practical optical resolutions are discussed.

A four-component solubility isotherm consisting of (Λ-[Co(en)3]3+, Δ[Co(en)3]3+)–(Br−,(R,R)-C4H4O62−)–H2O was determined at 25 °C. It was found that three double salts, rac-[Co(en)3]Br3·3H2O, Λ-[Co(en)3]Br(d-C4H4O6)·5H2O, and Λ-[Co(en)3]0.48·Δ-[Co(en)3]0.52(d-C4H4O6)1.5·5H2O and a gelatinous precipitate exist, six invariant points appearing. Application of this phase diagram to practical optical resolutions is discussed. The solubility of each salt in the system was measured in the range 5–65 °C in water, that of Λ and Δ-[Co(en)3](d-C4H4O6)1.5·nH2O being found to be reversed at 42 °C.

The X-ray photoelectron spectroscopic data of 25 cobalt(III) complexes of CoNxS6−x types are reported(x = 6, 5, 4, 3, and 0). The S2p3⁄2 binding energies can readily be distinguished into eight types of sulfur ligands. The S2p3⁄2, Co2p3⁄2, and Nls binding energies are distributed between two extremes; one represents the case of thiolato and sulfenato complexes, and the other sulfinato and sulfito ones. These results are discussed in connection with the structural trans effect.

Two kinds of mixed type cobalt(III) complexes, [(2-aminoethylthio)acetato](L-methioninato)cobalt(III) chloride and [3-(2-aminoethylthio)propionato](L-methioninato)cobalt(III) chloride, have been prepared and chromatographically separated into seven and eight isomers, respectively. The characterization of isomers based on their electronic absorption and 1H NMR spectra leads to the conclusion that there have been obtained four pairs of diastereomers due to the sulfur chirality of the coordinated L-methioninate. The circular dichroism spectra of isomers have been measured and discussed in relation to the absolute configurations. The vicinal CD contribution due to the chiral sulfur atom of L-methioninate has been estimated by applying an additivity rule for the three diastereomeric pairs.