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ABSTRACT: A π-radical ligand (9-[4-(6-oxo-1,5-dimethylverdazyl)phenyl]-10-[5-(2,2'-bipyridyl)ethynyl]anthracene, ) with a photo-excited high-spin quartet state (S = 3/2) and its iron(ii) complex [Fe(){H(2)B(Pz)(2)}(2)] () {H(2)B(Pz)(2)(-) = dihydrobis(1-pyrazolyl)borate} were synthesized as a candidate for a new strategy for spin-crossover compounds exhibiting light-induced excited spin state trapping (LIESST), which is via the photo-excited high-spin state of the π-conjugated aromatic system. Control compounds, ligand and [Fe(){H(2)B(Pz)(2)}(2)] (), in which the verdazyl radical moiety in was removed, were also synthesized. The photo-excited quartet state of the π-radical ligand was confirmed by the time-resolved ESR technique. Temperature dependence of the magnetic behaviors of and were investigated from 5 K to 350 K, showing spin-crossover transition at T(c) = 222 K and at T(c) = 162 K for complexes and , respectively. The transition enthalpies and entropies were determined to be ΔH = 8.09 kJ mol(-1) and ΔS = 36.4 J K(-1) mol(-1) for and to be ΔH = 22.39 kJ mol(-1) and ΔS = 138 J K(-1) mol(-1) for . LIESST phenomena were also observed below ca. 50 K for both complexes. The effects of the attachment of radical moiety are discussed based on the results.
Dalton Transactions 09/2012; 41(43):13465-73. · 3.84 Impact Factor
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Shigenobu Yano,
Hiromi Ohi,
Mizue Ashizaki,
Makoto Obata,
Yuji Mikata,
Rika Tanaka,
Takanori Nishioka, Isamu Kinoshita,
Yuko Sugai,
Ichiro Okura,
Shun-Ichiro Ogura,
Justyna A Czaplewska,
Michael Gottschaldt,
Ulrich S Schubert,
Takuzo Funabiki,
Keiko Morimoto,
Misaki Nakai
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ABSTRACT: Four platinum(II) and palladium(II) complexes with sugar-conjugated bipyridine-type triazole ligands, [Pt(II) Cl(2) (AcGlc-pyta)] (3), [Pd(II) Cl(2) (AcGlc-pyta)] (4), [Pt(II) Cl(2) (Glc-pyta)] (5), and [Pd(II) Cl(2) (Glc-pyta)] (6), were prepared and characterized by mass spectrometry, elemental analysis, (1) H- and (13) C-NMR, IR as well as UV/VIS spectroscopy, where AcGlc-pyta and Glc-pyta denote 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (1) and 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl β-D-glucopyranoside (2), respectively. The solid-state structure of complex 6 was determined by single-crystal X-ray-diffraction analysis. These complexes exhibited in vitro cytotoxicity against human cervix tumor cells (HeLa) though weaker than that of cisplatin.
Chemistry & Biodiversity 09/2012; 9(9):1903-15. · 1.80 Impact Factor
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ABSTRACT: In the title compound, [Ni(3)(C(10)H(22)N(2)S(2))(2)](ClO(4))(2), the complex cation consists of a nickel(II) ion and two [Ni(C(10)H(22)N(2)S(2))] units with an N(2)S(2) tetra-dentate ligand, 3,3'-[1,2-ethane-diylbis(methyl-imino)]bis-(1-propane-thiol-ate). The central Ni(II) ion is located on a crystallographic inversion centre and is bound to the four S atoms of the two [Ni(C(10)H(22)N(2)S(2))] units to form a linear sulfur-bridged trimetallic moiety. The dihedral angle between the central NiS(4) plane and the terminal NiN(2)S(2) plane is 145.71 (5)°. In the [Ni(C(10)H(22)N(2)S(2))] unit, the two methyl groups on the chelating N atoms are cis to each other, and the two six-membered N,S-chelate rings adopt a chair conformation. The Ni-S bond lengths and the S-Ni-S bite angles in the central NiS(4) group are similar to those in the [Ni(C(10)H(22)N(2)S(2))] unit.
Acta Crystallographica Section E Structure Reports Online 03/2012; 68(Pt 3):m307. · 0.35 Impact Factor
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ABSTRACT: The reaction of manganese(II) acetate with a xanthene-bridged bis[3-(salicylideneamino)-1-propanol] ligand, H(4)L, afforded the tetramanganese(II,II,III,III) complex [Mn(4)(L)(2)(μ-OAc)(2)], which has an incomplete double-cubane structure. The corresponding reaction using manganese(II) chloride in the presence of a base gave the tetramanganese(III,III,III,III) complex [Mn(4)(L)(2)Cl(3)(μ(4)-Cl)(OH(2))], in which four Mn ions are bridged by a Cl(-) ion. A pair of L ligands has a propensity to incorporate four Mn ions, the arrangement and oxidation states of which are dependent on the coexistent anions.
Inorganic Chemistry 12/2011; 51(2):766-8. · 4.60 Impact Factor
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ABSTRACT: Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(μ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained.
Chemistry 09/2011; 17(38):10708-15. · 5.93 Impact Factor
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ABSTRACT: Nickel complexes having acetylated glucopyranosyl group incorporated N-heterocyclic carbene (NHC) ligands with methyl or benzyl groups as an N-substituent exhibit two kinds of dynamic behaviours in solution (1)H NMR spectroscopy. One of the dynamic behaviours is attributed to the anti- and syn-rotamers, which occur by the rotation of the unsymmetrical NHC ligands around the axes of the Ni-C bonds. The other is attributed to the diastereomers of the syn-rotamers, which occur by opposite rotation of the imidazolylidene rings and the chiral carbohydrate group incorporated into the NHC ligands. Crystallographic analysis of the nickel complex having the NHC ligand with acetylated glucopyranosyl and benzyl groups as N-substituents showed CH-π interaction between the glucopyranosyl unit of each NHC ligand and the phenyl ring of the other NHC ligand in the complex in the solid state.
Dalton Transactions 07/2011; 40(25):6778-84. · 3.84 Impact Factor
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ABSTRACT: The first example of the diastereoselective synthesis induced by anomeric isomerism of sugar units in ligands of metal complexes was demonstrated. S and R configurations of chiral-at-metal Ir(III) and Rh(III) complexes were selectively obtained by using chelate-type NHC ligands with α- and β-glucopyranosyl units, respectively.
Dalton Transactions 03/2011; 40(18):4826-9. · 3.84 Impact Factor
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ABSTRACT: A thermal reaction of 6-(4''-dibenzothienyl)-2,2'-bipyridine (bpyDBT) with [Ru(3)(CO)(12)] produced a sulfur-bridged triruthenium complex via double carbon-sulfur bond cleavage and CO insertion, while a diiron(I,I) complex containing a thiametallacycle was obtained by a photochemical reaction of bpyDBT with [Fe(CO)(5)].
Dalton Transactions 01/2011; 40(4):785-7. · 3.84 Impact Factor
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ABSTRACT: A reaction of FeCl(2) with tris(2-pyridylthio)methane (tptmH) produced the carbanion complex [Fe(tptm)(CH(3)CN)(2)](FeCl(4)){(C(2)H(5))(3)NH}. When FeI(2) was used instead of FeCl(2), the carbene complex [FeI(pyt)(bptmd)] (pyt = 2-pyridinethiolate, bptmd = bis(2-pyridylthio)methylidene) was isolated. The carbene forms [FeX(pyt)(bptmd)](n+) (n = 1 for X = CH(3)CN, n = 0 for X = I) were observed for [Fe(tptm)(CH(3)CN)(2)](FeCl(4)){(C(2)H(5))(3)NH} and [FeI(pyt)(bptmd)] in chloroform, whereas the carbene-carbanion equilibrium was observed in acetonitrile by NMR measurements. The thermodynamic parameters were evaluated by variable temperature (1)H NMR measurements using the diamagnetic salt [Fe(tptm)(CH(3)CN)(2)]PF(6) for [Fe(tptm)(CH(3)CN)(2)](+)⇆ [Fe(pyt)(bptmd)(CH(3)CN)](+) + CH(3)CN (ΔH = 23 kJ mol(-1), ΔS = 55 J mol(-1) K(-1)).
Dalton Transactions 11/2010; 39(41):9988-93. · 3.84 Impact Factor
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ABSTRACT: In the title compound, [RuCl(C(6)H(6))(C(15)H(17)NS)]PF(6), the cation adopts a three-legged piano-stool structure around the Ru(II) atom with an η(6)-benzene ligand, a chloride ligand and a 2-[2-(tert-butyl-sulfan-yl)phen-yl]pyridine (btppy) ligand. The btppy ligand acts as a N,S-bidentate ligand, forming a six-membered ring, which has an envelope conformation. The S-Ru-N bite angle is 86.76 (9)°, and the dihedral angle between the pyridine and benzene rings in btppy is 39.8 (2)°. The unit cell contains two pairs of racemic diastereomers with (S(Ru),S(S)) and (R(Ru),R(S)) configurations, in which the tert-butyl group on the coordin-ated S atom is distant from the η(6)-benzene ligand.
Acta Crystallographica Section E Structure Reports Online 01/2010; 67(Pt 1):m63. · 0.35 Impact Factor
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Bulletin of The Chemical Society of Japan - BULL CHEM SOC JPN. 01/2010; 83(3).
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ABSTRACT: Two diastereomers of the Schiff base ligand [N,N'-bis(2'-hydroxyphenyl)phenylmethylidene]-1,2-diamino-1,2-diphenylethane (H(2)L) were used for the analyses of the redox behaviour of the copper(ii) complexes [Cu(L(R,R/S,S))] (rac-) and [Cu(L(R,S))] (meso-). Both complexes were structurally characterised by X-ray crystallographic studies and showed square planar geometries. The reduction potential of Cu(II) to Cu(I) for meso- was higher than that for rac-. This is due to the steric effect of the phenyl substituents and the geometrical change in the copper(i) state, which is supported by DFT calculations. A red shift of the absorption spectrum was observed for meso- in the visible region by the change of solvent from dichloromethane to pyridine, while rac- did not show a significant change. The effect of solvent on the reduction potential was found to be relatively small. The geometrical effect is more important for understanding the electrochemical behaviour in this system.
Dalton Transactions 10/2009; · 3.84 Impact Factor
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ABSTRACT: Introduction of a heavy atom into photosensitizers generally facilitates intersystem crossing and improves the quantum yield (Phi(Delta)) of singlet oxygen ((1)O(2)), which is a key species in photodynamic therapy (PDT). However, little information is available about the physiological importance of this heavy-atom effect. The aim of this study is to examine the heavy-atom effect in simple metallochlorins in vitro at the cellular level. 1,3-Dipolar cycloaddition of azomethine ylide to 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato palladium(II) and platinum(II) afforded metallochlorins 4b and 4c in yields of 17.1 and 12.9%, respectively. The Phi(Delta) values increased in the order of 4a (0.28) < 4b (0.89) < 4c (0.92) in C(6)D(6). The photocytotoxicity of 4a, 4b, and 4c was evaluated in HeLa cells at a light dose of 16 J x cm(-2) with lambda > 500 nm and increased in the order of 4a < 4b < 4c at the concentration of 0.5 microM. The photocytotoxicity of 4b and 4c was significantly inhibited by addition of sodium azide, but not D-mannitol, suggesting that (1)O(2) is the major species causing cell death. Our results clearly indicate that 4b and 4c act as efficient (1)O(2) generators due to the heavy-atom effect in a cellular microenvironment as well as in nonphysiological media.
Journal of Medicinal Chemistry 05/2009; 52(9):2747-53. · 4.80 Impact Factor
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Chemistry Letters - CHEM LETT. 01/2009; 38(4):366-367.
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ABSTRACT: Treatment of 4-(2′-pyridyl)dibenzothiophene (PyDBT) with the ruthenium carbonyl cluster [Ru3(CO)12] gave the diruthenium(II) complex [Ru(μ-PyBPT-κ3N,C,S)(CO)2]2 (1), where PyBPT denotes a dianion of 3′-(2′′-pyridyl)-1,1′-biphenyl-2-thiol. The tridentate-N,C,S PyBPT ligand provides a pincer structure consisting of a six-membered thiaruthenacycle and a five-membered azaruthenacycle. The thiolate-containing NCS pincer ligand in 1 is produced by cleavage of a carbon−sulfur bond adjacent to a pyridyl group in PyDBT. The corresponding reactions using 4-(4′-methyl-2′-pyridyl)dibenzothiophene (4-MePyDBT) and 4-(6′-methyl-2′-pyridyl)dibenzothiophene (6-MePyDBT) afforded the diruthenium(II) complexes with the same pincer framework [Ru(μ-4-MePyBPT-κ3N,C,S)(CO)2]2 (2) and [Ru(μ-6-MePyBPT-κ3N,C,S)(CO)2]2 (3), respectively. The much slower formation of 3 certifies the reaction path through the initial coordination of the pyridyl group to Ru or the formation of an N,S-chelate structure. Indeed, PyDBT showed the chelating ability in the ruthenium(II) complex [Ru(η6-C6H6)(PyDBT-κ2N,S)Cl]CF3SO3 (4). Complex 1 contains Ci and C2 symmetrical isomers, 1a and 1b, respectively, which were separated. The latter isomerized to 1a in DMSO-d6 at 80 °C. The stepwise formation of the same NCS pincer ligand was established in the reaction of [Rh(μ-Cl)(CO)2]2 with PyDBT. The facile reaction at room temperature produced the mononuclear rhodium(I) complex cis-[RhCl(CO)2(η1-N-PyDBT)] (5). The isolated complex 5 was converted to the tetranuclear rhodium(I/III/III/I) complex [{Rh(μ-PyBPT-κ3N,C,S)}(μ-Cl)2{Rh(CO)2}]2 (6) at 100 °C for 3 days.
08/2008;
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Makoto Obata,
Asuka Kitamura,
Akemi Mori,
Chiaki Kameyama,
Justyna A Czaplewska,
Rika Tanaka, Isamu Kinoshita,
Toshiyuki Kusumoto,
Hideki Hashimoto,
Masafumi Harada,
Yuji Mikata,
Takuzo Funabiki,
Shigenobu Yano
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ABSTRACT: Novel chelators, i.e., 4-(2-pyridyl)-1,2,3-triazole derivatives, were synthesized by means of Cu(I)-catalyzed 1,3-dipolar cycloaddition and used to prepare luminescent Re(I) complexes [ReCl(CO)(3)(Bn-pyta)], [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] (Bn-pyta = 1-benzyl-4-(2-pyridyl)-1,2,3-triazole, AcGlc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranoside, Glc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl beta-d-glucopyranoside). X-Ray crystallography of Bn-pyta and Glc-pyta indicated an azocompound-like structure while the 1,2,4-triazole isomer has an azine character. [ReCl(CO)(3)(Bn-pyta)] crystallized in the monoclinic system with space group P2(1)/n. Bn-pyta ligand coordinates with the nitrogen atoms of the 2-pyridyl group and the 3-position of 1,2,3-triazole ring, which is a very similar coordinating fashion to that of the 2,2'-bipyridine derivative. The glucoconjugated Re(I) complexes [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] hardly crystallized, and were analyzed by applying extended X-ray absorption fine structure (EXAFS) analysis. The EXAFS analyses suggested that the glucoconjugation at the 1-position of the 1,2,3-triazole makes no influence to the coordinating fashion of 4-(2-pyridyl)-1,2,3-triazole. [ReCl(CO)(3)(Bn-pyta)] showed a blue-shifted maximum absorption (333 nm, 3.97 x 10(3) M(-1) cm(-1)) compared with [ReCl(CO)(3)(bpy)] (371 nm, 3.35 x 10(3) M(-1) cm(-1)). These absorptions were clearly assigned to be the mixed metal-ligand-to-ligand charge transfer (MLLCT) on the basis of time-dependent density functional theory calculation. The luminescence spectrum of [ReCl(CO)(3)(Bn-pyta)] also showed this blue-shifted feature when compared with that of [ReCl(CO)(3)(bpy)]. The luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] was determined to be 8.90 mus in 2-methyltetrahydrofuran at 77 K, which is longer than that of [ReCl(CO)(3)(bpy)] (3.17 micros). The blue-shifted electronic absorption and elongated luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] suggested that 4-(2-pyridyl)-1,2,3-triazole functions as an electron-rich bidentate chelator.
Dalton Transactions 08/2008; · 3.84 Impact Factor
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ABSTRACT: Tris(2-pyridylthio)methane (tptmH) reacts with ZnCl(2) producing the Zn-C containing complex of [ZnCl(tptm)], whose cyclic voltammogram shows an irreversible oxidation peak at 0.2 V vs. E(0')(Fc(+/0)). DFT calculations suggested that 1e(-) oxidation should occur at the tptm ligand resulting in the cleavage of the Zn-C bond, leading to decomposition of the complex.
Chemical Communications 04/2008; · 6.17 Impact Factor
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ABSTRACT: A Copper(2+) complex with a Cu(II)-C bond containing sp(3) configuration was used to investigate the role of strong hydrogen bonds in proton coupled electron transfer (PCET) reactions. The only example of a Cu(II)-C system realized so far is that using tris-(pyridylthio)methyl (tptm) as a tetradentate tripodal ligand. Using this ligand, [CuF(tptm)] and [Cu(tptm)(OH)] have been prepared. The former complex forms supra-molecular arrays of layers of the complex between which hydroquinone is intercalated in the crystalline phase. This hydroquinone intercalation crystal was prepared via the photochemical conversion of quinone during the crystallization process. This conversion reaction probably involves a proton coupled electron transfer process. The nuclear magnetic resonance spectroscopic analysis of the reaction mixture shows the presence of Cu(III) during the conversion reaction. These results strongly suggest the presence of the molecular aggregate of the [CuF(tptm)] complex, water and quinone in the solution phase during the quinone to hydroquinone conversion. The presence of this type of aggregate requires a strong hydrogen bond between the [CuF(tptm)] complex and water. The presence of this particular hydrogen bond is a unique character of such a complex that has the Cu(II)-C bond. This complex is used as a model for photosynthetic water splitting since the photoconversion of quinone to hydroquinone also involves the production of oxygen from water.
Photosynthesis Research 03/2008; 95(2-3):363-71. · 3.24 Impact Factor
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ABSTRACT: A glucopyranoside-incorporated N-heterocyclic carbene iridium complex was synthesized using an Ag complex as a carbene transfer agent. The catalytic ability of the Ir complex, the structure of which was determined by X-ray crystallography, toward H/D exchange reactions involving 2-propanol and cyclohexanol in D2O were examined.
01/2007;
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Ryoko Santo,
Riichi Miyamoto,
Rika Tanaka,
Takanori Nishioka,
Kazunobu Sato,
Kazuo Toyota,
Makoto Obata,
Shigenobu Yano, Isamu Kinoshita,
Akio Ichimura,
Takeji Takui
Angewandte Chemie International Edition 12/2006; 45(45):7611-4. · 13.45 Impact Factor
