Influence of carrier ligand NH hydrogen bonding to the O6 and phosphate group of guanine nucleotides in platinum complexes with a single guanine ligand

Coordinated N,N',N"-trimethyldiethylenetriamine (Me3dien) has several possible configurations: two have mirror symmetry (R,S configurations at the terminal nitrogens) and the terminal N-Me's anti or syn with respect to the central N-Me (anti-(R,S) and syn-(R,S) isomers, respectively), and two are nonsymmetrical (R,R and S,S configurations at terminal nitrogens, rac denotes a 1:1 mixture of the two isomers). For each configuration, two Me3dienPtG atropisomers can be formed (anti or syn orientation of central N-Me and G 06, G = guanine derivative), and these can be observed since the terminal N-Me's decrease the rate of G rotation about the Pt-N7 bond. In symmetrical syn-(R,S)-Me3dienPtG derivatives with G = 9-EtG and 3'-GMP, the anti rotamer, which can form O6-NH H-bonds, was slightly favored over the syn rotamer but never more than 2:1. This anti rotamer is also favored by lower steric repulsion between the terminal N-Me's and G O6; thus, the contribution of O6-NH H-bonding to the stability of the anti rotamer could be rather small. With G = 5'-GMP, an O6-NH H-bond in the anti rotamer and a phosphate-NH H-bond in the syn rotamer can form. Only the syn rotamer was detected in solution, indicating that NH H-bonds to 5'-phosphate are far more important than to O6, particularly since steric factors favor the anti rotamer. Interconversion between rotamers was faster for syn-(R,S)- than for rac-Me3dien derivatives. This appears to be determined by a smaller steric impediment to G rotation of two "quasi equatorial" N-Me's, both on one side of the platinum coordination plane (syn-(R,S) isomer), than one "quasi equatorial" and one "quasi axial" N-Me on either side of the coordination plane (rac isomer).     

Rotamer stability in cis-[Pt(diA)G2] complexes (diA = diamine derivative and G = guanine derivative) mediated by carrier-ligand amine stereochemistry as revealed by circular dichroism spectroscopy

Extensive investigations of cis-[Pt(diA)G2] complexes (in which G = a guanine ligand; diA = a single diamine ligand) revealed the types of interactions between the two G ligands and between the G and the cis-amine substituents when diA is a diamine ligand with substituents on each nitrogen atom being a small hydrogen atom and a bulky group able to slow the rotation about the Pt-G bond. All these interactions are shown to apply also when diA = dach (1,2-diaminocyclohexane), even though this chiral primary diamine has only small N-H atoms on each side of the coordination plane. However, a slight difference in the stereochemistry of the two protons (one N-H has "quasi axial" and the other "quasi equatorial" character) is sufficient to induce a significant change in the relative stabilities of the [Pt(dach)G2] deltaHT and lambdaHT rotamers (HT = head-to-tail). The new results show that at acidic and neutral pH the induction of asymmetry from the dach ligand to the HT rotamers is governed by the G-to-G dipole-dipole interaction, which is greater for the six-membered ring of each guanine leaning towards the cis-G. Such a "six-in" canting of the two guanine ligands can be hampered by the steric interaction between the H8 of each guanine and the substituent on the cis-amine that is on the same side of the coordination plane. Such a repulsion is greater for a "quasi equatorial" N-H than for a "quasi axial" N-H. Under basic pH conditions, deprotonation of the guanine N1-H renders the O6 atom a much better hydrogen-bond acceptor; therefore, the stability of the HT rotamers is governed by the hydrogen-bond interaction of guanine O6 and the cis-amine N-H group. Such a guanine O6/N-H cis-amine interaction is stronger for a "quasi axial" than for a "quasi equatorial" N-H group. In the head-to-head (HH) rotamer, in which the electrostatic repulsion between electron-rich O6 atoms, both on the same side of the platinum coordination plane, tends to place the six-membered rings of each guanine further from the cis-guanine and closer to the cis-amine, we can expect better N-H...O6 hydrogen bonding for the "quasi equatorial" N-H groups.     

Synthesis,Structure and Fluorescence of a Copper(II) Complex [Cu_2(bipy)_2(Hpht)_2Cl](Hpht)(bipy=2,2'-Bipyridine,H_2pht=o-Phthalic Acid)

1 INTRODUCTION o-Phthalic acid (H2pht) is a versatile ligand for co-ordinating to metal ions in various modes, such asmonodentate bonding through a carboxylic O atom[1],bidentate fashion via two carboxylic O atoms[2] andtriple coordination through its three carboxylic Oatoms[3], and bridging mode with two or four Oatoms of its carboxylate groups[4]. The coordinationproperties thus allow for the preparation of complex-es with a large variety of architectures, forming iso-lated mono-, di…     

CRYSTAL STRUCTURE OF ADDUCT OF BIS(O,O''''-DIBUTYLDITHIOPHOSPHATO)-NICKEL (II) WITH BIPYRIDYL

<正> Ni[(C8H9O)2PS2]2 bipy, Mr=697.57, triclinic, Ci-Pl, a=9.469(1)A, b=14.638(3)A, c=14.637(2)A, α=69.64(1)° , β=71.16(1)°, r=89.99(1)°, V= 1785.6A3, Z=2, Dc=1.297g.cm-3, Mo kα radiation, λ=0.71073A, F(000)=736e, R=0.081 for 4986 independent reflections. Ni(II) is coordinated by four sulfur atoms and two nitrogen atoms to form a distorted octahedron. The angles between each two among planes N2Ni, NiS(11)S(12) and NiS(21)S(22) are nearly 90°.     

Neglected bidentate sp2 N-donor carrier ligands with triazine nitrogen lone pairs: platinum complexes retromodeling cisplatin guanine nucleobase adducts

Rapid rotation of guanine base derivatives about Pt-N7 bonds results in fluxional behavior of models of the key DNA intrastrand G-G cross-link leading to anticancer activity of Pt(II) drugs (G = deoxyguanosine). This behavior impedes the characterization of LPtG2 models (L = one bidentate or two cis-unidentate carrier ligands; G = guanine derivative not linked by a phosphodiester group). We have examined the formation of LPtG2 adducts with G = 5'- and 3'-GMP and L = sp(2) N-donor bidentate carrier ligands [5,5'-dimethyl-2,2'-bipyridine (5,5'-Me2bipy), 3-(4'-methylpyridin-2'-yl)-5,6-dimethyl-1,2,4-triazine) (MepyMe2t), and bis-3,3'-(5,6-dialkyl-1,2,4-triazine) (R4dt)]. NMR spectroscopy provided conclusive evidence that these LPt(5'-GMP)2 complexes exist as interconverting mixtures of head-to-tail (HT) and head-to-head (HH) conformers. For a given G, the rates of G base rotation about the Pt-N7 bonds of LPtG2 models decrease in the order Me4dt > Et4dt > MepyMe2t > 5,5'-Me2bipy. This order reveals that the pyridyl ring C6 atom + H atom grouping is large enough to impede the rotation, but the equivalently placed triazine ring N atom + N lone pair grouping is sterically less impeding. For the first time, the two possible HH conformers (HHa and HHb) in the case of an unsymmetrical L have been identified in our study of (MepyMe2t)Pt(5'-GMP)2. Although O6-O6 clashes involving the two cis G bases favor the HT over the HH arrangement for most LPtG2-type complexes, the HH conformer of (R4dt)Pt(5'-GMP)2 adducts has a high abundance (approximately 50%). We attribute this high abundance to a reduction in O6-O6 steric clashes permitted by the overall low steric effects of R4dt ligands. Under the reaction conditions used, 3'-GMP forms a higher abundance of the LPt(GMP)2 adduct than does 5'-GMP, a result attributable to more favorable second-sphere communication in the LPt(3'-GMP)2 adduct than in the LPt(5'-GMP)2 adduct.     

Synthesis,characterization and crystal structure of ruthenium(II) polypyridyl complexes

[Ru(bipy)2(5-R-phen)](ClO4)2 complexes have been prepared, where bipy=2,2- bipyridine, phen=1,10-phenanthroline, and R=H, Me, NO2 or NH2. The influence of the different 5- substituted phen on the electron delocalization and ligand-ligand interactions have been investigated by solution n.m.r.. The ligand- ligand interaction has also been observed in the solid state by determining the single crystal structure of [Ru(bipy)2(5- NO2-phen)](ClO4)2. The strong steric interaction between the polypyridyl ligands was relieved neither by the elongation of Ru–N bonds (2.055–2.086Å) nor by increase of N–Ru–N bite angles (77.8–79.4°), but rather by distortion of the coordination sphere by forming specific angles (=2.0, 3.2 and 4.2°) between the polypyridyl ligand planes and coordination planes (N–Ru–N), and larger torsion angles (5.8 and 8.2°) between the two pyridine rings for each bipy.     

Hydrothermal Synthesis and Electrochemical Properties of Complex Cu(CH3C6H4COOH)2(2,2''-bipy)·(H2O)

The title complex has been synthesized by 4-methylbenzoic acid and 2,2'-bipyridine (bipy) in the mixed solvent of water and methanol. It crystallizes in the triclinic system, space group (P1-) with a = 0.7047(3), b = 1.1217(5), c = 1.6718(7) nm, α = 103.826(7), β = 90.772(6), γ = 104.195(6)°, C26H25CuN2O5.50, Mr = 517.02, V = 1.2404(9) nm3, Dc = 1.384 g/cm3, Z = 2, F(000) = 536, μ(MoKα= 0.921 mm-1, R = 0.0782 and wR = 0.2172. Structural analysis shows that the copper atom is coordinated with three oxygen atoms from two 4-methylbenzoic acids and one water molecule together with two nitrogen atoms from 2,2'-bipyridine, giving a distorted square-pyramid coordination geometry. The cyclic voltametric behavior of the complex has also been described.     

新颖无限三股螺旋钴配位聚合物{[Co(4,4′-bipyridine)(4,4′-azobispyridine)2(NCS)2]·H2O}n的合成、结构和性质的研究

The novel complex {[Co(bipy)(azpy)₂(NCS)₂]·H₂O}_n (where bipy=4,4′-bipyridine, azpy=4,4′-azobisp- yridine) has been synthesized and characterized by elemental analyses, IR, UV, thermal analyses, and vari-able-temperature magnetic susceptibility. The crystal (C₃₂H₂₆CoN₁₂OS₂, M_r=717.70) belongs to the orthorhombic, space group Pnna, a=2.21312(16)nm, b=1.40403(10)nm, c=1.14237(8)nm, V=3.5497(4)nm³, Z=4, D_c=1.343g·cm^-3, μ=0.645mm^-1, F(000)=1476, and final R₁=0.0691, wR₂=0.1129 for 231 parameters and 1674 observed reflections [I >2.00σ(I)]. The Co(Ⅱ) atom is, in a distorted octahedral geometry, coordi-nated by six nitrogen atoms from two bridging bipy, two monodentate azpy, and two thiocyanate groups. The bridging ligand bipy links Co(Ⅱ) atoms to form the infinite “rod＂ with terminal coordination azpy ligand acting as sidearms. Unprecedented three parallel interpenetrating two-dimensional (4,4) networks and novel infinite triple helices are formed via hydrogen-bonding interactions. CCDC: 155588.     

Synthesis,Structure and Thermal Property of a Cobalt Supramolecular Complex Containing N-[（4-Carboxyphenyl）-sulfonyl]glycine

Utilizing N-[(4-carboxyphenyl)-sulfonyl]glycine (abbreviated as cbsglyH3),a new cobalt complex [Co(cbsglyH)(bipy)2]3H2O (bipy = 2,2'-bipyridine) has been synthesized under mild conditions and characterized by IR,elemental analysis,thermogravimetric analysis and X-ray diffraction analysis. It crystallizes in the monoclinic system,space group C2/c with a = 34.978(3),b = 12.0437(11),c = 20.0041(19) ,β = 122.2990(10)°,V = 7123.0(11) 3,Z = 8,C29H28CoN5O9S,Mr = 681.55,μ = 0.593 mm-1,Dc = 1.271 Kg/m3,F(000) = 2816,the final R = 0.0434 and wR = 0.1351. The title complex is a monomeric compound which is further assembled by intermolecular hydrogen bonds into a 3-D supramolecular network. Thermogravimetric analysis illustrates that this complex begins decomposing at 100 ℃ and decompounding completely at 560 ℃.     

Hydrothermal Synthesis, Crystal Structure and Electrochemical Properties of the Complex Cu(o-Methylbenzoic acid)2(2,2''-bipy)·(H2O)

The title complex (C26H24CuN2O5, Mr = 508.01) has been synthesized by o-methylbenzoic acid, 2,2'-bipyridine (bipy) and copper perchlorate in the mixed solvent of water and methanol. It crystallizes in orthorhombic, space group P212121 with a = 0.70814(10), b = 1.6953(3),c = 1.9539(3) nm, V= 2.3457(6) nm3, Dc= 1.439 g/cm3, Z= 4,μ = 0.971 mm-1, F(000) = 1052, R= 0.0432 and wR = 0.0860. The structural determination shows that the copper atom is coordinated by three oxygen atoms from two o-methylbenzoic acids and one water molecule together with two nitrogen atoms from 2,2'-bipyridine, giving a distorted square-pyramidal coordination geometry.The cyclic voltammetric behavior of the complex is also discussed.     

Coordination properties of a diarylaza crown ether appended with a luminescent [Ru(bipy)3]2+ unit

The [Ru(bipy)(2)(1)](PF(6))(2) (bipy refers to 2,2'-bipyridine) complex, comprising a ruthenium(II) tris(2,2'-bipyridine) luminophore covalently linked to a di[(o-triethyleneglycoxy)phenyl]amine crown ether 1, has been synthesized and fully characterized. The photophysical properties of this metal complex have been examined in solution at ambient temperature. Luminescence from the metal complex is enhanced significantly in the presence of various adventitious cations, including protons. In particular, Li(+) cations bind to the crown ether, as evidenced by (1)H NMR and luminescence spectroscopy. Cation binding serves to decrease the rate of reductive quenching of the triplet state of the metal complex, thereby increasing the extent of luminescence. The solution-phase conformation of [Ru(bipy)(2)(1)](PF(6))(2), with and without encapsulated Li(+), has been examined by 2-D NMR and by molecular dynamics simulations.     

Synthesis and Crystal Structure of a Fumaratocopper(II) Complex with Bipyridine

The title complex [Cu₂(C₄H₂O₄)₂(bipy)₂(H₂O)₃] · 3H₂O (bipy = 2,2'-bipyridine) was prepared and its crystal structure determined by X-ray diffraction methods. Both Cu(II) atoms of the binuclear complex assume square pyramidal coordination. The fumarate groups display different coordination modes. One fumarate group bridges two Cu(II) ions to form a binuclear complex while another fumarate group terminally coordinates to a Cu(II) atom with one carboxyl group free from coordination. The terminally coordinated fumarate showed unusual disorder, which may be due to an intermolecular H-bonding interaction. Close stacking of bipy rings is observed as verified by the distance of 3.46 Å between parallel ring planes. IR spectra were assigned based on the molecular structure.     

Hydrothermal Synthesis, Crystal Structure and Electrochemical Properties of the Complex Cu(o-Methylbenzoic acid)_2(2,2′-bipy)·(H_2O)

The title complex (C26H24CuN2O5, Mr = 508.01) has been synthesized by o-me- thylbenzoic acid, 2,2′-bipyridine (bipy) and copper perchlorate in the mixed solvent of water and methanol. It crystallizes in orthorhombic, space group P212121 with a = 0.70814(10), b = 1.6953(3), c = 1.9539(3) nm, V = 2.3457(6) nm3, Dc = 1.439 g/cm3, Z = 4, μ = 0.971 mm-1, F(000) = 1052, R = 0.0432 and wR = 0.0860. The structural determination shows that the copper atom is coordinated by three oxygen atoms from two o-methylbenzoic acids and one water molecule together with two nitrogen atoms from 2,2′-bipyridine, giving a distorted square-pyramidal coordination geometry. The cyclic voltammetric behavior of the complex is also discussed.     

Substitution reactions of [MBr(π allyl)(CO)2(LL)] complexes (M = Mo,W; L-L = 2,2 -bipyridine 1,2-bis(diphenylphosphine)ethane) with xanthates and dithiocarbamates

The complexes [MBr(π-allyl)(CO)₂(bipy)] (M = Mo, W, bipy = 2,2′-bipyridine) react with alkylxanthates (M^IRxant), and N-alkyldithiocarbamates (M^IRHdtc) (M^I = Na or K), yielding complexes of general formula [M(S,S)- (π-allyl)(CO)₂(bipy)] (M = Mo, (S,S) = Rxant (R = Me, Et, t-Bu, Bz), RHdtc (R = Me, Et); M = W, (S,S) = Extant). A monodentate coordentate coordination of the (S,S) ligand was deduced from spectral data. The reaction of [MoBr(π-allyl)(CO)₂(bipy)] with MeHdtc and Mexant gives the same complexes whether pyridine is present or not. The complexes [Mo(S,S)(π-allyl)(CO)₂(bipy)] ((S,S) = MeHdtc, Mexant) do not react with an excess of (S,S) ligand and pyridine.No reaction products were isolated from reaction of [MoBr(π-allyl)(CO)₂(dppe)] with xanthates or N-alkyldithiocarbamates.     

Role of cyclometalation in controlling the rates of ligand substitution at platinum(II) complexes

The rates of chloride for triphenylphosphine substitution have been measured in dichloromethane for a series of cyclometalated [Pt(N-N-C)Cl] complexes containing a number of terdentate N-N-C anionic ligands, derived from deprotonated alkyl-, phenyl-, and benzyl-6-substituted 2,2'-bipyridines. These rates have been compared with those of the corresponding [Pt(N-N)(C)Cl] (N-N = 2,2'-bipyridine; C = CH3 or C6H5) complexes having the same set of donor atoms but less constrained arrangements of the ligands. The reactions of the cyclometalated compounds occur as a single-stage conversion from the substrate to the ionic pair [Pt(N-N-C)(PPh3)]Cl products. There is no evidence by 1H and 31P(1H) NMR spectroscopy for the formation of other Pt(II) species or of concurrent ring-opening processes. In contrast, in the monoalkyl- or monoaryl-2,2'-bipyridine complexes, chloride substitution is followed by subsequent slower processes which involve the detachment of one arm of the chelated 2,2'-bipyridine, fast cis to trans isomerization of the cis-[Pt(PPh3)2(eta 1-bipy)(R)]+ transient intermediate, and, eventually, the release of free bipy, yielding trans-[Pt(PPh3)2(R)Cl] (R = Me or Ph). All reactions are first-order with respect to complex and phosphine concentration, obeying the simple rate law kobsd = k2[PPh3]. The values of the second-order rate constant k2 do not seem particularly sensitive to the nature of the bonded organic moiety (alkyl or aryl), to its structure (cyclometalated or not), to the size of the ring, or to the number of alkyl substituents on it. The effects are those foreseen on the basis of an associative mode of activation. The only exception to this pattern of behavior is constituted by the complex [Pt(bipy phi-H)Cl] (bipy phi = 6-phenyl-2,2'-bipyridine), which features a significant rate enhancement with respect to the analogue [Pt(bipy)(Ph)Cl] complex. The results of this work, together with those of a previous paper, suggest that there is not a specific role of cyclometalation in controlling the reactivity, unless an in-plane aryl ring becomes part of the pi-acceptor system of the chelated 2,2-bipyridine, behaving as a cyclometalated analogue of the nitrogen terdentate 2,2':6',2"-terpyridine.     

Hydrothermal Synthesis, Crystal Structure and Fluorescent Property of a Keggin Polyoxometalate [Cu~I(2,2'-bipy)_2]_3[PW~(Ⅵ)_(12)O_(40)]

1 INTRODUCTION Polyoxometalates (POMs) have become a focus of contemporary chemical research due to their structure diversity and potential applications in many areas, such as catalysis[1], photochemistry[2], magnetism[3], etc. In this field, POMs containing Keggin moieties have received considerable attention. A large num- ber of efforts have been given to the decoration of POMs with various transition metal complexes and organic moieties[4]. To date, several compounds con- taining …     

STUDY ON TETRANUCLEAR TRANSITION METAL CLUSTER WITH μ_3-O BRIDGES I . SYNTHESIS AND CRYSTAL STRUCTURE OF [Fe_4O_2(O_2CCH_3)_7(2,2''''-bipy)_2]Cl

INTRODUCTION.The first tetranuelear oxo一bridged manganese eomplex eon-taining〔Mn4OZ〕“+eore was reported on its synthesis,strueture and magnetie proper-ties in 1 987〔‘〕,representing the best available model for the photosynthetie water oxi-dation eentre.In order to find out the relationship of aetivity with eonfiguration ofthis kind of eomplexes,a series of dual oxo一bridged tetranuelear eomplexes have beensynthesized in our laboratory〔2〕.In this paper the aeetato一bridged tetran…     

Crystal Structure and Magnetic Property of a Two-dimensional Manganese Compound [Mn(PhCOO)_2(4,4'-bipyridine)]_n

A new two-dimensional polymeric manganese compound [Mn(PhCOO)2(4,4'-bi-pyridine)]n 1 has been prepared and structurally characterized by X-ray diffraction. The complex crystallizes in space group Pbcn with a = 18.7158(2), b = 11.6919(3), c = 9.4799(2) , V = 2074.42(7) 3, Z = 4, Mr = 453.34, Dc = 1.452 g/cm3, μ = 0.670 mm-1 and F(000) = 932. The final refinement gave R = 0.0458 and wR = 0.1439 for 1358 observed reflections with I > 2σ(I). The complex consists of repeating units of Mn(PhCOO)2(4,4'-bipyridine). Each Mn center is six-coordinated by four carboxylate O atoms of four benzoate anions and two pyridyl N atoms from bipy ligands to furnish a slightly distorted octahedral geometry. The two adjacent Mn atoms are connected by a pair of μ1,3-carboxylate groups to form infinite chains, which are further interlinked by bipy to complete a 2D grid network. The magnetic property of the polymeric complex has also been investigated.     

Synthesis and Structure Characterization of Aqua-（μ2-carbonato-O,O′）-（2,2′-bipyridyl）-copper（Ⅱ） Dihydrate

Under hydrothermal conditions the reaction of cis-aconitic acid with Cu2(OH)2CO3 and bipy (bipy = 2,2'-bipy) in H2O/DMF (3:2) afforded a neutral mononuclear compound [Cu- (bipy)((2-CO3)(H2O)](2H2O, which has been structurally characterized by single-crystal X-ray diffraction analysis. The crystal belongs to triclinic, space group Pī with a = 8.3950(5), b = 8.7974(5), c = 9.4496(3)（A。）, α = 98.270(3), β = 93.014(3), γ = 100.068(3)°, V = 677.83(6) （A。）3, Dc = 1.635 g/cm3, Z = 2, C11H14CuN2O6, Mr = 333.78, μ = 1.637 mm－1, λ(MoKα) = 0.71073 （A。）, F(000) = 342, the final R = 0.0616 and wR = 0.1273 for 1621 observed reflections with I > 2σ(I). The structure of the complex contains a distorted square pyramidal core with a bipy, a carbonate anion and a water molecule coordinating to a CuⅡ atom. The dihedral angle between the two planes composed of N(1)N(2)Cu(1) and O(1)O(3)Cu(1) is 21.73(8)°. The intermolecular hydrogen bonds (O…O) are observed in the crystal structure.     

Bis(2,2′‐bipyridine)iodo­(oxo)tri‐μ3‐sulfido‐tricopper(I)tungsten(VI)

The title nest‐shaped cluster, [Cu₃WIOS₃(C₁₀H₈N₂)₂], has been synthesized by the reaction of (NH₄)₂[WOS₃], CuI and 2,2′‐bipyridine (bipy) in dimethyl­formamide under a purified nitro­gen atmosphere. The cluster has a neutral skeleton containing the bipy ligands, and the central W atom is tetra­hedrally coordinated by three S atoms and one O atom. The three Cu atoms are divided into two different kinds. Two Cu atoms adopt distorted tetra­hedral geometry, with each Cu atom coordinated by two S atoms and the two N atoms of a bipy ligand. The other Cu atom adopts a trigonal mode surrounded by two S atoms and one I atom.