Interaction of Pd(II) and Pt(II) Amino Acid Complexes With Dinucleotides

The interaction of the dinucleotides d(ApG) and d(ApA) with [Pd(aa)Cl(2)], where aa = L- or D-histidine or the methyl ester of L-histidine, and with [Pt(Met)Cl(2)], where Met = L-methionine was studied by (1)H and (13)C NMR and CD measurements. In the case of the L-histidine and L-histidineOMe, the reaction with d(ApG) appeared to give the bifunctional adducts Pd(L-Histidine)N1(1)N7(2) and Pd(L-HisOMe)N1(1)N7(2), but the behavior with D-histidine suggested the formation of the monofunctional adduct Pd(D-His)N7(2). The reaction of L-histidine with d(ApA) seemed to form the bimetallic adduct (L-His)PdN7(1)N7(2)Pd(L-His). The Pt(II)-L-methionine complex in both reactions with d(ApG) and d(ApA) seemed to yield mainly adducts Pt(L-Met)N7(1)N7(2) but the existence of adducts Pt(L-Met)N1(1)N7(2) cannot be ruled out.     

60]fullerene--metal cluster complexes: novel bonding modes and electronic communication

[60]Fullerene can bind a variety of metal clusters via eta(2)-C(60), mu-eta(2):eta(2)-C(60), and mu(3)-eta(2):eta(2):eta(2)-C(60) pi-type bonding modes. Multiple C(60) additions to a single cluster core have also been demonstrated. Modification of the coordination sphere of cluster moieties has resulted in novel transformation of the coordination mode of the C(60) ligand between pi and sigma (mu(3)-eta(1):eta(1):eta(2)-C(60) and mu(3)-eta(1):eta(2):eta(1)-C(60)) types as well as reversible interconversion between mu(3)-eta(2):eta(2):eta(2)-C(60) and mu-eta(2):eta(2)-C(60). The mu(3)-eta(2):eta(2):eta(2)-C(60) metal cluster complexes show remarkable electrochemical stability and an unusually strong electronic communication between C(60) and metal cluster centers.     

Reactions of organic disulfides and gold(i) complexes

Gold-thiolate/disulfide exchange reactions of (p-SC(6)H(4)Cl)(2) with Ph(3)PAu(SC(6)H(4)CH(3)), dppm(AuSC(6)H(4)CH(3))(2), and dppe(AuSC(6)H(4)CH(3)) (2) were investigated. The rate of reactivity of the gold-thiolate complexes with (p-SC(6)H(4)Cl)(2) is: dppm(AuSC(6)H(4)CH(3))(2)> dppe(AuSC(6)H(4)CH(3))(2)>Ph(2)PAu (SC(6)H(4)CH(3)). This order correlates with conductivity measurements and two ionic mechanisms have been evaluated. (1)H NMR experiments demonstrate that in the reaction of dppm(AuSC(6)H(4)CH(3))(2) with (p-SC(6)H(4)Cl)(2), the mixed disulfide, ClC(6)H(4)SSC(6)H(4)CH(3), forms first, followed by the formation of (p-SC(6)H(4)CH(3))(2). The rate law is first order in (pp-SC(6)H (4)Cl)(2) and partial order in dppm(AuSC(6)H(4)CH(3))(2). Results from electrochemical and chemical reactivity studies suggest that free thiolate is not involved in the gold-thiolate/disulfide exchange reaction. A more likely source of ions is the dissociation of a proton from the methylene backbone of the dppm ligand which has been shown to exchange with D(2)O. The implications of this are discussed in terms of a possible mechanism for the gold-thiolate/disulfide exchange reaction.     

Synthesis of the Sulphonate and Phosphonate Derivatives of Mercaptoacetyltriglycine. X-Ray Crystal Structure of Na(2)[ReO(Mercaptoacetylglycylglycylaminomethanesulphonate)].3H(2)O

Mercaptoacetyltriglycine forms complexes with (186/188)Re and (99m)Tc radionuclides that are useful in nuclear medicine because they are substrates of the renal anion transport system. However, the renal clearance of [MO(MAG(3))](2-)(MAG(3) = penta-anionic form of mercaptoacetyltriglycine, M = Re, Tc) complexes are less than ideal. Organic sulphonates are also transported by the renal anion transport system and phosphonates are similar to sulphonates in size and shape. In an effort to develop new ligands that form Re and Tc complexes and have improved renal clearances compared to [MO(MAG(3))](2-) complexes, the sulphonate and phosphonate derivatives of mercaptoacetyltriglycine were synthesized. The dianion [ReO(MAG(2)-AMS)](2-) (MAG(2)-AMS = penta-anionic form of mercaptoacetylglycylglycylaminomethanesulphonic acid) was prepared for characterization by exchange reaction of ReOCl(3)(Me(2)S)(OPPh(3)) and isolated as the disodium salt. The structure of Na(2)[ReO(MAG(2)-AMS)].3H(2)O (6) was determined by X-ray diffraction. The coordination geometry is pseudo square pyramidal, with the nitrogen and sulfur donor atoms forming a square base and the oxo ligand at the apex. The deprotonated sulphonate group has a syn conformation with respect to the oxo ligand. The renal clearances of [(99m)TcO(MAG(2)-AMS)](2-) and [(99m)TcO(MAG(2)-AMP)](3-) were similar in rats and suggest that the difference in total charge between the SO(3) (-) and PO(3) (2-) groups is not important to renal clearance. However, their renal clearances were 40-50% less than that of [(99m)TcO(MAG(3))](2-) suggesting that the size and shape of the large tetrahedral SO(3) (-) and PO(3) (2-) groups of [(99m)TcO(MAG(2)-AMS)](2-) and [(99m)TcO(MAG(2)-AMP)](3-) inhibit recognition by the renal transport system compared to the small planar CO(2) (-) group of [(99m)TcO(MAG(3))](2-).     

Structure Determination and Anti-Inflammatory Activity of some Purine Complexes

Organomercury(II)-purine derivatives of the type, p-MeOC(6)H(4)HgL(1) (I), p-NO(2)C(6)H(4)HgCl(L(2))(II), p-MeC(6)H(4)HgCl(L(3))(III) and p-NO(2)C(6)H(4)HgCl(L(3))(IV) [ HL(1) = theophylline, L(2) = theobromine, L(3) = caffeine] have been synthesised and characterised on the basis of spectral studies (IR, UV, (1)H & (13)C NMR). The complexes have been screened for anti-inflammatory activity.     

Synthesis and "in Vitro" Trypanocidal Activity Evaluation of Some Organo-iron Compounds

Eight organo-iron ferrocene derivatives and arenocenium salts were prepared and evaluated by "in vitro" assay against one strain of Trypanosoma cruzi (Y). Six of the eight organo-iron compounds assayed, piperazinium diferrocenoate 1, eta(6)-(o-xylene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorophosphate 3, eta(6)-(mesitylene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 5, eta(6)-(durene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 6, eta(6)-(rho-chlorotoluene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorphosphate 7 and eta(6)-(chlorobenzene)-eta(5)-(cyclopentadienyl) iron(II) picrate 8 , were poorly active in the "in vitro" assays. Only two compounds 1,1'-(N-pyperidinocarbonyl) ferrocene 2(IC(50)=2.4 mug/mL) and eta(6)-(o-xylene)-eta(5)(cyclopentadienyl) iron(II) picrate 4 (IC(50)=12.08 mug/mL), were more active. Thus, some of the compounds are promising to be used against Chagas' disease as a prophylactic agents.     

Toxicity of Certain Penta-Coordinated Organotin(IV) and Tetra-Coordinated Tin(II) Complexes of Heterocyclic beta-Diketones Against the Larvae of Aedes Aegypti (Liston)

Some organotin(IV) and tin(II) complexes of composition R(3)Sn[R'COC:CON(C(6)H(5))N:CCH(3)] (where R=C(4)H(9), R'=CH(3), C(3)H(5), p-ClC(6)H(4); R=C(6)H(5), R'=C(6)H(5) and p-ClC(6)H(4)) and Sn[p-ClC(6)H(4)COC:CON(C(6)H(5))N:CCH(3)](2) were screened for their toxicity against Aedes aegypti larvae. Organotin(IV) complexes were more active than tin(II) complexes.     

Redox Chemistry and [Au(CN)(2)] in the Formation of Gold Metabolites

The role of hypochlorite ion, which can be generated by the enzyme myleoperoxidase, in the biochemistry of gold(I) anti-arthritic drugs was investigated. Sodium hypochlorite (OCl(-)) directly and rapidly oxidizes AuSTm, Au(CN)(2) (-), AuSTg (gold thioglucose) and auranofin (Et(3)PAuSATg). The resulting gold(III) species were detected by an Ion Chromotography Ion-Pairing technique that was developed to distinguish gold(I) and gold(III). Formation of Au(III) was also demonstrated spectrophotometrically after the conversion to AuCl(4) (-). The reactions of AuSTm, AuSTg, and auranofin are complex and gold(III) appears only after the initial oxidation of the thiolate (and phosphine) ligands.The enzymatic reaction, using MPO with H(2)O(2) and Cl(-) as substrates, leads to slow oxidation of Au(CN)(2) (-), AuSTm or AuSTg. The extent and rate of reaction depend on the concentrations of MPO, H(2)O(2), and Au(I). The continued presence of Au(I) during the initial stages of reaction (oxidation of the thiolates in AuSTm and AuSTg) and the conversion to Au(III) in the latter stages of the reaction were demonstrated. Au(CN)(2) (-), a gold metabolite, binds tightly to serum albumin. Unlike other gold(I) complexes, aurocyanide reacts almost negligibly at Cys-34 via ligand exchange. Instead, there is a strong association (K(1) = 5.5 x 10(4) and K(2) = 7.0 x 10(3); n(1) = 0.8 and n(2) = 3) of intact Au(CN)(2) (-). The full extent of binding is revealed only by equilibrium methods such as NMR or ultrafiltration; the bound gold dissociates extensively on conventional gel-exclusion columns and partially on Penefesky spun columns.The immunological and pharmacological significance of these results are discussed.     

碳包覆对LiNi_(0.5)Mn_(1.5)O_4电化学性能的影响

以蔗糖为碳源,采用溶液沉积-真空热解法制备了LiNi_(0.5)Mn_(1.5)O_4/C复合材料。用热重与差热分析、X射线衍射分析、扫描电镜分析及电化学测试等手段对LiNi_(0.5)Mn_(1.5)O_4/C的微观结构、表面形貌和电化学性能进行了研究。结果表明,蔗糖热分解后在LiNi_(0.5)Mn_(1.5)O_4颗粒的表面包覆形成了一层无定形碳。无定形碳可以有效阻止LiNi_(0.5)Mn_(1.5)O_4颗粒的聚集,增加电极的导电面积,降低电池极化,从而改善LiNi_(0.5)Mn_(1.5)O_4的电化学性能。与未包覆的LiNi_(0.5)Mn_(1.5)O_4粉末相比,LiNi_(0.5)Mn_(1.5)O_4/C复合材料具有更高的可逆容量、更稳定的循环性能和更好的倍率性能。0.2C放电时,LiNi_(0.5)Mn_(1.5)O_4/C复合材料的首次放电容量达到144.8mA.h.g-1,经60次循环后平均每次循环的容量损失仅为0.0081%。而1.0C和2.0C放电时,LiNi_(0.5)Mn_(1.5)O_4/C复合材料的首次放电容量分别保持在131.9mA.h.g-1和122.4mA.h.g-1。     

Synthesis and physiological activity of thiophenes and furans with 3- and 4-methoxyacetophenone derivatives

The synthesis and physiological activity of thiophenes and furans with methoxyacetophenone derivatives were examined. 3-Methoxyacetophenone (1) and 4-methoxyacetophenone (2) were converted, respectively, to the oximes (3) and (4) by oximation with hydroxylamine hydrochloride, and to the primary amines (5) and (6) by reduction with LiAlH(4). The primary amine derivatives were further converted into the thiophene and furan compounds (5a) approximately (5h) and (6a) approximately (6h), respectively. Bioassay of these compounds (5a) approximately (5h) and (6a) approximately (6h) on the germination of lettuce(Lactuca satiba) seeds showed that compound (5b) exhibits growthpromoting activity.     

Fluorescent-magnetic nanocrystals: synthesis and property of YP(x)V(1-x)O4:Eu@GdPO4 core/shell structure

A fluorescent-magnetic YP(x)V(1-x)O(4):Eu@GdPO(4) core/shell nanostructure was prepared by a two-step method. The YP(x)V(1-x)O(4):Eu core was synthesized using a hydrothermal method, and it exhibits strong photoluminescence with the effective doping of phosphorus (P) and europium (Eu) into a YVO(4) matrix. The hydrothermal process provides a hydrophilic and fresh surface for coating GdPO(4) shell. As YP(x)V(1-x)O(4):Eu and GdPO(4) have the similar unit cell parameters, YP(x)V(1-x)O(4):Eu nanoparticles (NPs) were favorably coated by an epitaxial growth of GdPO(4) shell in aqueous phase. The core/shell nanostructure was identified by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The GdPO(4) shell not only possesses the paramagnetic character, but also enhances the photoluminescence efficiency by blocking the non-radiative de-excitation from the VO(4)(3-) groups to the surface quenching sites. These optical and magnetic properties promise outstanding fluorescent-magnetic bifunctional nanomaterials.     

Formation mechanism for hexagonal-structured self-assemblies of nanocrystalline titania templated by cetyltrimethylammonium bromide

Hexagonal-structured self-assemblies of nanocrystalline (anatase) titania templated by cetyltrimethylammonium bromide (C(16)H(33)N(CH(3))(3)Br; CTAB) (Hex-ncTiO(2)/CTAB Nanoskeleton) were formed after mixing of aqueous solutions containing CTAB spherical micelles and titanium oxysulfate acid hydrate (TiOSO(4).xH(2)SO(4).xH(2)O) as a titania precursor in the absence of any other additives. Formation mechanism of the Hex-ncTiO(2)/CTAB Nanoskeleton was examined in terms of the reaction temperature, titania precursor/CTAB mixing ratio, surfactant type, electrostatic interaction, micelle formation and molecular component. We found that crystal growth of crystalline (anatase) titania (polymorphic crystallization) was promoted with higher temperature and lower titania precursor content in aqueous solutions. In addition, we revealed that the crystalline (anatase) titania was formed in polycation, poly(allylamine hydrochloride ([CH(2)CH(CH(2)NH(2))HCl](n); PAH), and formamide (HCONH(2)) solutions. On the other hand, no titania formation was observed in anionic systems such as sodium dodecyl sulfate (CH(3)(CH(2))(11)OSO(3)Na; SDS) and poly(sodium 4-styrenesulfonate ([C(8)H(7)SO(3)Na](n); PSSS). This indicates that hydrolysis reaction of the titania precursor is initiated by not only cations but also nitrogen atoms in molecules and polymers. Hexagonally structure was formed in only cationic surfactant micellar solutions but not in polycation solutions and formamide.     

Anionic Pd(0) and Pd(II) intermediates in palladium-catalyzed Heck and cross-coupling reactions

The anions of PdCl(2)L(2) and Pd(OAc)(2), precursors of palladium(0) used in cross-coupling and Heck reactions, play a crucial role in these reactions. Tricoordinated anionic complexes Pd(0)L(2)Cl(-) and Pd(0)L(2)(OAc)(-) are the effective catalysts instead of the usually postulated Pd(0)L(2) complex. The anion ligated to the palladium(0) affects the kinetics of the oxidative addition to ArI as well as the structure and reactivity of the arylpalladium(II) complexes produced in this reaction. Thus, pentacoordinated anionic complexes are formed, ArPdI(Cl)L(2)(-) or ArPdI(OAc)L(2)(-), the precursor of neutral trans-ArPd(OAc)L(2), instead of the usually postulated trans-ArPdIL(2) complex (L = PPh(3)).     

Metallation of Isatin (2,3-Indolinedione). X-Ray Structure and Solution Behavior of Bis(Isatinato)Mercury(II)

The first X-ray structure of an isatin (2,3-indolinedione, isaH) metal complex, bis(isatinato)memury(II) (C(16)H(8)N(2)O(4)Hg) (1), was determined. (1) was obtained from the reaction of isaH with mercury(II) acetate in methanol. Analogously, treatment of sodium saccharinate and mercury(II) acetate in methanol yielded Hg(saccharinato)(2) (*)0.5CH(3)OH (3). (1) crystallizes in the monoclinic system, space group P2(1)/ a with a = 7.299(1) A, b = 8.192(1) A, c = 11.601(1) A , beta = 105.82(1) degrees , V = 667.4 A(3), Z = 2, D(calc) = 2.452 g cm(-3), MoKalpha radiation(lambda = 0.71073 A), mu = 115.5 cm(-1), F(000) = 460, 21(1) degrees C. The structure was refined on the basis of 2023 observed reflections to R= 0.044. The two deprotonated, non coplanar isa ligands are trans to each other in a head to tail orientation and bound to the Hg through the nitrogen in a linear N-Hg-N arrangement. The Hg atom is at the center of symmetry of the complex and displaced by 0.62 A from the two planes of the isa ligands (tau Hg-N1-C2-O2= -16 degrees ). The Hg-N bond length is 2.015 A. Nopi-aryl-memury(ll)-pi-aryl stacking interaction was observed either in the solid state or in the solution state. The IR, electronic, and (1)H and (13)CNMR spectral data of (1) and (3) suggest binding of the memury to the heterocyclic nitrogen, in agreement with the crystal structure determination of (1).     

Synthesis and physiological activity of ureas and amides with carvone residues

The synthesis and herbicidal activity of ureas and amides with carvone residues were examined. (S)-(+)-(1) and (R)-(-)-Carvone(2) were converted to the respectively, primary amines(3) and (4) by oximation and reduction with LiAlH(4). Primary amine derivatives were further converted into the urea and amide compounds (3a) approximately (3e) and (4a) approximately (4e). The herbicidal activity of products (3a) approximately (3e) and (4a) approximately (4e) towards weeds found in a paddy field and field was measured in the pot. Products (3a) showed a particularly strong inhibitory effect on the growth of Amaranthus retroflexus(AR) and Setaria viridis(SV).     

Controlled synthesis and optical spectroscopy of lanthanide-doped KLaF₄ nanocrystals

KLaF(4), as a good host matrix for trivalent lanthanide (Ln(3+)) ions to fabricate upconversion (UC) or downconversion (DC) phosphors, has been rarely reported. Herein, monodisperse (～10 nm) cubic-phase Ln(3+)-doped KLaF(4) nanocrystals (NCs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of KLaF(4):Ln(3+)/Yb(3+) (Ln = Tm, Ho, Er) NCs were comprehensively surveyed. Particularly, after coating an inert KLaF(4) shell, the green and red UC luminescence intensity of KLaF(4):Er(3+)/Yb(3+) NCs was enhanced ～35 times, and the corresponding UC lifetimes of (4)S(3/2) and (4)F(9/2) levels of Er(3+) were observed significantly prolonged from 42 and 68 μs in core-only NCs to 87 and 136 μs in core/shell counterparts. Furthermore, intense DC luminescence was also achieved in Ce(3+)/Tb(3+) and Eu(3+) doped KLaF(4) NCs, with absolute quantum yields of 39.8% (Tb(3+)) and 17.3% (Eu(3+)). The luminescence lifetimes of (5)D(0) (Eu(3+)) and (5)D(4) (Tb(3+)) were determined to be 4.2 and 4.7 ms, respectively. Water-soluble Ln(3+)-doped KLaF(4) NCs featuring excellent monodispersion, long luminescence lifetime, and high UC/DC efficiency may have versatile and promising applications as luminescent nano-biolabels.     

Chiral platinum(II) metallointercalators with potent in vitro cytotoxic activity

Four platinum(II) metallointercalating complexes of 1,10-phenanthroline (phen) with the chiral ancillary ligands trans-R,R- and trans-S,S-1,2-diaminocyclohexane (R,R- and S,S-dach, respectively), and N,N'-dimethyl-R,R- and N,N'-dimethyl-S,S-1,2-diaminocyclohexane (Me(2)-R,R-dach and Me(2)-S,S-dach, respectively) have been synthesised and characterised. The crystal structure of [Pt(Me(2)-S,S-dach)(phen)](ClO(4))(2)1.5 H(2)O (C(20)H(26)Cl(2)N(4)O(9.5)Pt) has been determined; orthorhombic, space group P2(1)2(1)2(1)(No. 19), a=23.194(8), b=25.131(9), c=8.522(3) A. In vitro cytotoxic assays (IC(50)) in the human bladder cancer cell line 5637 and in the murine leukemia L1210 cell line revealed that [Pt(S,S-dach)(phen)](ClO(4))(2) (0.091 and 0.13 microM, respectively) and [Pt(R,R-dach)(phen)](ClO(4))(2) (0.54 and 1.50 microM, respectively) were more cytotoxic than cisplatin (0.31 and 0.50 microM, respectively) and considerably more cytotoxic than their methylated counterparts, [Pt(Me(2)-R,R-dach)(phen)](ClO(4))(2) and [Pt(Me(2)-S,S-dach)(phen)](ClO(4))(2) (both>23 microM). Chiral discrimination for [Pt(S,S-dach)(phen)](ClO(4))(2) over its R,R-enantiomer was observed in all 13 cancer cell lines investigated. Moreover, [Pt(S,S-dach)(phen)](ClO(4))(2) was more active than cisplatin in all cell lines tested and shows only partial cross-resistance to cisplatin in two cisplatin resistant cell lines.     

Developing Carrier Complexes for "Caged NO": RuCl(3)(NO)(H(2)O)(2) Complexes of Dipyridylamine, (dpaH), N,N,N'N'-Tetrakis (2-Pyridyl) Adipamide, (tpada), and (2-Pyridylmethyl) Iminodiacetate, (pida)

Delivery agents which can carry the {Ru(NO)}(6) chromophore ("caged NO") are desired for vasodilation and for photodynamic therapy of tumors. Toward these goals, complexes derived from [RuCl(3)(NO)(H(2)O)(2)]= (1) have been prepared using dipyridylamine (dpaH) as mono and bis adducts, [Ru(NO)Cl(3)(dpaH)] = (2) and [Ru(NO)Cl(dpaH)(2)]Cl(2) = (3). The dpaH ligands coordinate cis to the Ru(NO) axis.The mono derivative is a model for a potential DNA groove-spanning binuclear complex {[RuNO)Cl(3)](2)(tpada)} = (4) which has two DNA-coordinating Ru(II) centers, photo-labile {Ru(NO)}(6) sites, and a groove-spanning tether moiety.The binuclear assembly is prepared from the tethered dipyridylamine ligand N,N,N',N'-tetrakis(2-pyridylmethyl)adipamide (tpada) which has recently been shown to provide a binuclear carrier complex suited to transporting Ru(II) and Pd(II) agents. A related complex, [Ru(NO)Cl(pida)] = (5) with the {Ru(NO)}(6) moiety bound to (2-pyridylmethyl) iminodiacetate (pida(2-)) is also characterized as a potential "caged NO" carrier. Structural information concerning the placement of the pyridyl donor groups relative to the {Ru(NO)}(6) unit has been obtained from (1)H and (13)C NMR and infrared methods, noting that a pyridyl donor trans to NO+ causes "trans strengthening" of this ligand for [Ru(NO)Cl(pida)], whereas placement of pyridyl groups cis to NO+ causes a weakening of the N-O bond and a lower NO stretching frequency in the dpa-based complexes.     

Cofactor-apoprotein hydrogen bonding in oxidized and fully reduced flavodoxin monitored by trans-hydrogen-bond scalar couplings

Hydrogen bonding plays a key role in the tight binding of the FMN cofactor and the regulation of its redox properties in flavodoxins. Hydrogen bonding interactions can be directly observed in solution by multidimensional heteronuclear NMR spectroscopy through the scalar couplings between donor and acceptor nuclei. Here we report on the detection of intermolecular trans-hydrogen-bond couplings ((h)J) between the flavin ring system and the backbone of Desulfovibrio vulgaris flavodoxin in the oxidized and the two-electron reduced states. For this purpose, experiments are adapted from pulse sequences previously applied to determining (h)J coupling constants in nucleic acid-base pairs and proteins. The resulting (h2)J(N,N), (h4)J(N,N), (h3)J(C,N), and (h1)J(H,N) couplings involve the (15)N(1), (13)C(2), and (15)N(3) nuclei of the pyrimidine moiety of FMN, whereas no such interactions are detectable for (13)C(4) and (15)N(5). Several long-range (15)N-(15)N, (13)C-(15)N, and (1)H-(15)N J-coupling constants within the flavin are obtained as "by-products". The magnitudes of both (h)J and regular J couplings are found to be dependent on the redox state. In general, good correlations between (h)J coupling constants and donor-group (1)H chemical shifts and also crystallographic donor-acceptor distances are observed.     

5-Methoxy, 7-methylbenz[a]anthracene: Crystal Structure of a Planar Weak Carcinogen

Abstract

The crystal and molecular structure of 5-methoxy,7-methylbenz[a]anthracene has been determined by X-ray diffraction at room temperature to an R-index of 0.062 over 936 reflections. The molecule, the first methoxy-substituted methylbenz[a]anthracene to be analysed, is highly planar, with the carbon and oxygen atoms of substituents lying within 0.04 Å of the mean plane of the polycyclic skeleton. Carbon–oxygen bond lengths in the methoxy group are unequal at 1.372(7) and 1.426(9) Å and the C_aromatic–O bond makes dissimilar angles of 113.5(7) and 124.3(7)° at C(5). The shortest C–C bonds are C(5)–C(6) = 1.351(9) at the substituted K-region, C(8)–C(9) = 1.352(9), C(10)–C(11) = 1.362(9) Å, and C(3)–C(4) = 1.361(10) Å. In the unsubstituted bay region, the long beach bond C(13)–C(18) = 1.454(9) Å is flanked by beach bond angles C(12)–C(18)–C(13) = 121.2(6) and C(18)–C(13)–C(1) = 123.1(6)°.