Effect Of Geometrical Isomerism Research Articles

Effect of Geometric Isomerism of H12-MDI on the Properties of Polysiloxane–Urethane–Ureas Based on It

New polysiloxane–butylene oxide–urethane–ureas based on α,ω-bis[(3-aminopropyl)diethoxy]oligodimethylsiloxane, oligobutylene oxide, and fractions of dicyclohexylmethane 4,4'-diisocyanate (H12-MDI) with different contents of a trans-trans isomer have been synthesized. The mechanical properties of the films have been tested. It is established that the strength and relative elongation at break increase with the increasing content of the trans-trans isomer.

Effects of geometric isomerism in electron ionization mass spectra of dialkyl 1,4-cyclohexanedicarboxylates.

1,4-Cyclohexanedicarboxylic acid and its esters are widely used as building blocks in the production of polymers and copolymers. The properties of such compounds directly depend on the ratio of cis- and trans-isomers in the starting materials. The identification of such stereoisomers by mass spectrometry can be used for the analysis of complex reactions and pyrolysis mixtures. 1,4-Cyclohexanedicarboxylic acid propyl, isopropyl, butyl, 2-butyl, pentyl, 2-pentyl, 4-methylpentyl, heptyl, octyl, and nonyl esters were synthesized and analyzed by gas chromatography-electron ionization mass spectrometry. The general fragmentation patterns of the synthesized compounds in electron ionization conditions were determined using high-resolution mass spectrometry. The relative response factors for the isomers were established on the basis of NMR and GC-MS data. Regardless of the structure of the alkyl groups, the EI mass spectra of cis- and trans-dialkyl 1,4-cyclohexanedicarboxylates differ very sharply. The stereoselectivity of fragmentation processes is due to the steric proximity of the substituents in the case of cis-isomers. Elemental composition of all ions appearing in the mass spectra of the analytes under study was confirmed by high-resolution mass spectrometry. Despite the perceptible differences in the EI mass spectra of the isomers their ionization efficiencies are close. The possibility of the unambiguous identification of stereoisomeric dialkyl cis and trans 1,4-cyclohexanedicarboxylates on the basis of their EI mass spectra was shown. The differences in mass spectra of the isomers are due to the conformational rigidity of the considered monocyclic molecules, which ensures the unique stereoselectivity of the elimination of neutral molecules owing to the 1,3-cis-diaxial proximity effect.

Effects of geometrical isomerism on emissive behaviour of heteroleptic cyclometalated Ir(III) complexes.

In this study, we report the emissive properties of a heteroleptic cyclometalated Ir(iii) complex, [Ir(bzq)2(PBO)] (bzqH = benzo[h]quinoline; PBOH = 2-(2-hydroxyphenyl)benzoxazole). The complex, [Ir(C^N)2(N^O)], was synthesised and optically resolved using a chiral column. Two geometrical isomers, trans-(N,N) and cis-(N,N) isomers, were obtained as the major and minor products in an enantiopure form, respectively. Their molecular structures were determined using single crystal X-ray analysis. In the crystalline states, the intermolecular C-Hπ interaction between PBO- and an H atom in bzq- was the main factor influencing molecular packing. When the complexes were dissolved in CH2Cl2 and excited at 430 nm under N2 atmosphere, yellow (λmax = 550 nm) and orange emissions (λmax = 570 nm) were observed for the trans-(N,N) and cis-(N,N) isomers, respectively, with the quantum yield higher for the former than the latter.

Cis-Tetrachlorido-bis(indazole)osmium(iv) and its osmium(iii) analogues: paving the way towards the cis-isomer of the ruthenium anticancer drugs KP1019 and/or NKP1339.

The relationship between cis-trans isomerism and anticancer activity has been mainly addressed for square-planar metal complexes, in particular, for platinum(ii), e.g., cis- and trans-[PtCl2(NH3)2], and a number of related compounds, of which, however, only cis-counterparts are in clinical use today. For octahedral metal complexes, this effect of geometrical isomerism on anticancer activity has not been investigated systematically, mainly because the relevant isomers are still unavailable. An example of such an octahedral complex is trans-[RuCl4(Hind)2]-, which is in clinical trials now as its indazolium (KP1019) or sodium salt (NKP1339), but the corresponding cis-isomers remain inaccessible. We report the synthesis of Na[cis-OsIIICl4(κN2-1H-ind)2]·(Na[1]) suggesting a route to the cis-isomer of NKP1339. The procedure involves heating (H2ind)[OsIVCl5(κN1-2H-ind)] in a high boiling point organic solvent resulting in an Anderson rearrangement with the formation of cis-[OsIVCl4(κN2-1H-ind)2] ([1]) in high yield. The transformation is accompanied by an indazole coordination mode switch from κN1 to κN2 and stabilization of the 1H-indazole tautomer. Fully reversible spectroelectrochemical reduction of [1] in acetonitrile at 0.46 V vs. NHE is accompanied by a change in electronic absorption bands indicating the formation of cis-[OsIIICl4(κN2-1H-ind)2]- ([1]-). Chemical reduction of [1] in methanol with NaBH4 followed by addition of nBu4NCl afforded the osmium(iii) complex nBu4N[cis-OsIIICl4(κN2-1H-ind)2] (nBu4N[1]). A metathesis reaction of nBu4N[1] with an ion exchange resin led to the isolation of the water-soluble salt Na[1]. The X-ray diffraction crystal structure of [1]·Me2CO was determined and compared with that of trans-[OsIVCl4(κN2-1H-ind)2]·2Me2SO (2·2Me2SO), also prepared in this work. EPR spectroscopy was performed on the OsIII complexes and the results were analyzed by ligand-field and quantum chemical theories. We furthermore assayed effects of [1] and Na[1] on cell viability and proliferation in comparison with trans-[OsIVCl4(κN1-2H-ind)2] [3] and cisplatin and found a strong reduction of cell viability at concentrations between 30 and 300 μM in different cancer cell lines (HT29, H446, 4T1 and HEK293). HT-29 cells are less sensitive to cisplatin than 4T1 cells, but more sensitive to [1] and Na[1], as shown by decreased proliferation and viability as well as an increased late apoptotic/necrotic cell population.

The Effect of Geometrical Isomerism of 3,5-Dicaffeoylquinic Acid on Its Binding Affinity to HIV-Integrase Enzyme: A Molecular Docking Study.

A potent plant-derived HIV-1 inhibitor, 3,5-dicaffeoylquinic acid (diCQA), has been shown to undergo isomerisation upon UV exposure where the naturally occurring 3trans,5trans-diCQA isomer gives rise to the 3cis,5trans-diCQA, 3trans,5cis-diCQA, and 3cis,5cis-diCQA isomers. In this study, inhibition of HIV-1 INT by UV-induced isomers was investigated using molecular docking methods. Here, density functional theory (DFT) models were used for geometry optimization of the 3,5-diCQA isomers. The YASARA and Autodock VINA software packages were then used to determine the binding interactions between the HIV-1 INT catalytic domain and the 3,5-diCQA isomers and the Discovery Studio suite was used to visualise the interactions between the isomers and the protein. The geometrical isomers of 3,5-diCQA were all found to bind to the catalytic core domain of the INT enzyme. Moreover, the cis geometrical isomers were found to interact with the metal cofactor of HIV-1INT, a phenomenon which has been linked to antiviral potency. Furthermore, the 3trans,5cis-diCQA isomer was also found to interact with both LYS156 and LYS159 which are important residues for viral DNA integration. The differences in binding modes of these naturally coexisting isomers may allow wider synergistic activity which may be beneficial in comparison to the activities of each individual isomer.

Diverse topologies in copper aromatic dicarboxylate coordination polymers containing 3-pyridylmethylnicotinamide: Effect of geometric isomerism and ring substituent

Hydrothermal reaction of copper nitrate and 3-pyridylmethylnicotinamide (3-pmna) with aromatic dicarboxylates has afforded a series of coordination polymers that were structurally characterized via single-crystal X-ray crystallography. [Cu(tere)(3-pmna)]n (1, tere=terephthalate) displays a 3,5-connected 3-D binodal net with uncommon (63)(698) gra topology. {[Cu(iph)(3-pmna)(H2O)]·3H2O}n (2, iph=isophthalate) possesses an extremely rare 4-connected 3-D self-penetrated net with 86tcb topology. [Cu2(nip)2(3-pmna)2]n (3, nip=5-nitroisophthalate) manifests a doubled chain 1-D structure, while increased steric bulk in [Cu(tbip)(3-pmna)]n (4, tbip=5-tert-butylisophthalate) results in a 1-D single chain motif. A significant dependence of the dimensionality and topology of these materials on the part of the carboxylate donor disposition and ring substituent was thus revealed. Thermal properties of these new materials were also investigated.

Effects of Geometric Isomerism and Anions on the Kinetics and Mechanism of the Stepwise Formation of Long-Range DNA Interstrand Cross-Links by Dinuclear Platinum Antitumor Complexes

Reported herein is a detailed study of the kinetics and mechanism of formation of a 1,4-GG interstrand cross-link by the dinuclear platinum anticancer compound [15N][{cis-PtCl(NH3)2}2{mu-NH2(CH2)6NH2}]2+ (1,1/c,c (1)). The reaction of [15N]1 with 5'-{d(ATATGTACATAT)2} (I) has been studied by [1H,15N] HSQC NMR spectroscopy in the presence of different concentrations of phosphate. In contrast with the geometric trans isomer (1,1/t,t), there was no evidence for an electrostatic preassociation of 1,1/c,c with the polyanionic DNA surface, and the pseudo-first-order rate constant for the aquation of [(15)N]1 was actually slightly higher (rather than lower) than that in the absence of DNA. When phosphate is absent, the overall rate of formation of the cross-link is quite similar for the two geometric isomers, occurring slightly faster for 1,1/t,t. A major difference in the DNA binding pathways is the observation of phosphate-bound intermediates only in the case of 1,1/c,c. 15 mM phosphate causes a dramatic slowing in the overall rate of formation of DNA interstrand cross-links due to both the slow formation and slow closure of the phosphate-bound monofunctional adduct. A comparison of the molecular models of the bifunctional adducts of the two isomers shows that helical distortion is minimal and globally the structures of the 1,4 interstrand cross-links are quite similar. The effect of carrier ligand was investigated by similar studies of the ethylenediamine derivative [15N]1-en. A pKa value of 5.43 was determined for the [15N]1,1/c,c-en diaquated species. The rate of reaction of [15N]1-en with duplex I is similar to that of 1,1/c,c and the overall conformation of the final adduct appears to be similar. The significance of these results to the development of "second-generation" polynuclear platinum clinical candidates based on the 1,1/c,c chelate (dach) series is discussed.

Effects of geometric isomerism in dinuclear antitumor platinum complexes on their interactions with N-acetyl-L-methionine

Effects of geometric isomerism in dinuclear antitumor platinum complexes on their interactions with N-acetyl-L-methionine

Effects of geometric isomerism in dinuclear platinum antitumor complexes on aquation reactions in the presence of perchlorate, acetate and phosphate

The aquation and subsequent reactions of the dinuclear Pt antitumor complexes [{trans-PtCl(NH(3))(2)}(2)(mu-NH(2)(CH(2))(6)NH(2))](2+) (1,1/t,t) and [{cis-PtCl(NH(3))(2)}(2)(mu-NH(2)(CH(2))(6)NH(2))](2+) (1,1/c,c) in 15 mM perchlorate, acetate or phosphate solutions were followed at 298 K by [(1)H,(15)N] HSQC 2D NMR spectroscopy. Rate and equilibrium constants for the initial reversible aquation and the subsequent reversible reaction with phosphate or acetate are reported. The rate constant for the first aquation step is two-fold lower for 1,1/c,c than 1,1/t,t but the anation rate constants are similar so that the equilibrium lies further towards the chloro form for the 1,1/c,c compound. A pK (a) value of 6.01+/-0.03 was determined for the diaquated species [{cis-Pt(NH(3))(2)(H(2)O)}(2)(mu-NH(2)(CH(2))(6)NH(2))](4+) (1,1/c,c-3) which is 0.4 units higher than that of the 1,1/t,t compound. The rate constants for the binding of acetate and phosphate to 1,1/t,t are similar, but the rate constant for the reverse reaction is close to ten-fold higher in the case of phosphate so that equilibrium conditions are attained more rapidly (12 h compared with 64 h). On the other hand, for 1,1/c,c the rate constants for the forward and reverse reactions with acetate and phosphate are quite similar so that equilibrium conditions are reached very slowly (80-100 h) and a greater proportion of phosphate-bound species are present. The reduced lability of the bound phosphate for 1,1/c,c is attributed to the formation of a macrochelate phosphate-bridged species which was characterized by (31)P NMR and ESI-MS. The speciation profiles of 1,1/t,t and 1,1/c,c under physiological conditions are explored.

Effects of geometric isomerism in dinuclear antitumor platinum complexes on their interactions with N-acetyl-L-methionine

In this study, the reactions of N-acetyl-L-methionine (AcMet) with [{trans-PtCl(NH(3))(2)}(2)-mu-H(2)N(CH(2))(6)NH(2)](NO(3))(2) (BBR3005: 1,1/t,t 1) and its cis analog [{cis-PtCl(NH(3))(2)}(2)-mu-{H(2)N(CH(2))(6)NH(2)}]Cl(2) (1,1/c,c 2) were analyzed to determine the rate and reaction profile of chloride substitution by methionine sulfur. The reactions were studied in PBS buffer at 37 degrees C by a combination of multinuclear ((195)Pt, {(1)H-(15)N} HSQC) magnetic resonance (NMR) spectroscopy and electrospray ionization time of flight mass spectrometry (ESITOFMS). The diamine linker of the 1,1/t,t trans complex was released as a result of the trans influence of the coordinated sulfur atom, producing trans-[PtCl(AcMet)(NH(3))(2)](+) (III) and trans-[Pt(AcMet)(2)(NH(3))(2)](2+) (IV). In contrast the cis geometry of the dinuclear compound maintained the diamine bridge intact and a number of novel dinuclear platinum compounds obtained by stepwise substitution of sulfur on both platinum centers were identified. These include (charges omitted for clarity): [{cis-PtCl(NH(3))(2)}-mu-NH(2)(CH(2))(6)NH(2)-{cis-Pt(AcMet)(NH(3))(2)}] (V); [{cis-Pt(AcMet)(NH(3))(2)}(2)-mu-NH(2)(CH(2))(6)NH(2)] (VI); [{cis-PtCl(NH(3))(2)}-mu-NH(2)(CH(2))(6)NH(2)-{PtCl(AcMet)NH(3)] (VII); [{PtCl(AcMet)(NH(3))}(2)-mu-NH(2)(CH(2))(6)NH(2)] (VIII); [{trans-Pt(AcMet)(2)(NH(3))}-mu-NH(2)(CH(2))(6)NH(2)-{PtCl(AcMet)(NH(3))] (IX) and the fully substituted [{trans-Pt(AcMet)(2)(NH(3))}(2)-mu-{NH(2)(CH(2))(6)NH(2)] (X). For both compounds the reactions with methionine were slower than those with glutathione (Inorg Chem 2003, 42:5498-5506). Further, the 1,1/c,c geometry resulted in slower reaction than the trans isomer, because of steric hindrance of the bridge, as observed previously in reactions with DNA and model nucleotides.

Effect of geometrical isomerism on the reactivity of 3-hexene on clean Ru(001)

The chemical behaviour of E-3-hexene on clean Ru(0 0 1) was studied by RAIRS, under UHV conditions, and compared to that of its geometrical isomer, Z-3-hexene. It is shown that, above 140 K, E-3-hexene dehydrogenates to 3-hexyne di-σ/π complex, which, by thermal activation above 170 K, undergoes C2–C3 and C4–C5 bond breaking, yielding ethylidyne (CCH3) and ethyne di-σ/π complex. However, while above ∼120 K the Z-isomer is completely decomposed, E-3-hexene is remarkably stable, since a significant fraction of physically adsorbed molecules remain on the Ru(0 0 1) surface up to 240 K. By direct adsorption at high temperatures (e.g. 220 K), the decomposition product detected by RAIRS is ethylidyne and, less clearly, the 3-hexyne di-σ/π complex, co-adsorbed with unreacted E-3-hexene. On the contrary, in the same adsorbing conditions, Z-3-hexene follows a second decomposition path involving CC bond scission, with formation of propylidyne and ethylidyne. These results highlight the importance of geometrical isomerism on the stability and decomposition paths of C6 alkenes on Ru(0 0 1), since it may modify the accessibility of the double bond.

Effect of geometric isomerism in dinuclear platinum antitumor complexes on DNA interstrand cross-linking.

The requirement for novel platinum antitumor drugs led to the synthesis of dinuclear bisplatinum complexes. To understand the molecular mechanisms underlying the biological activity of this new class of platinum cytostatics, modifications of natural DNA and synthetic oligodeoxyribonucleotide duplexes by dinuclear bisplatinum complexes with equivalent monofunctional coordination spheres, represented by the general formula [{cis-PtCl(NH(3))(2)}(2)(H(2)N-R-NH(2)](2+) (1,1/c,c), in which R is a linear alkane chain, butane or hexane, were studied by various biochemical and molecular biology methods. The results indicated that the major adducts of 1,1/c,c complexes in DNA ( approximately 90%) were interstrand cross-links preferentially formed between guanine residues. Besides 1,2 interstrand cross-links (between guanine residues in neighboring base pairs), 1,3 or 1,4 interstrand cross-links were also possible. In the latter two long-range adducts, the sites involved in the cross-links were separated by one or two base pairs. 1,2, 1,3, and 1,4 interstrand cross-links were formed with a similar rate and were preferentially oriented in the 5' --> 5' direction. In addition, the DNA adducts of these complexes inhibited DNA transcription in vitro. Thus, the binding of the 1,1/c, c complexes modifies DNA in a way that is distinctly different from the modification by the antitumor drug cisplatin. In addition, there are significant differences between the dinuclear 1,1/c,c and 1,1/t, t isomers. The results of this work are consistent with the hypothesis and support the view that platinum drugs that bind to DNA in a fundamentally different manner can exhibit different biological properties including the spectrum and intensity of antitumor activity. The intracellular DNA binding of the dinuclear compounds is compared to the results presented here. It has been suggested that differences in cross-link structure may be an important factor underlying their different biological efficiencies.

Energy Increment Method Based on Quantum Chemical Results: A General Recipe for Approximative Prediction of Isomerization and Tautomerization Energies of Pyrimidine and Purine Nucleic Acid Bases and Related Compounds

On the basis of HF/6-31G(d,p) and MP2/6-31G(d,p) quantum chemical computations of fully optimized structures of all isomers of cytosine, isocytosine, uracil, thymine, adenine, guanine, xanthine, and many model compounds, a system of additive energy increments has been derived, from which energies of conversion of geometric isomers (conformers) and tautomers of these nucleic acid bases may be reconstructed within approximately 0.5 kcal/mol. The increments are associated with specific structural fragments perceptible in the conventional structural formula. Physically, they correspond to repulsions between H atoms of −OH, −NH2, and NH substituents and H atoms bound to C or N ring atoms and to attractions between H atoms of such substituents and sp2 lone electron pairs localized at N atoms of the ring systems or of imino substituents. Tautomerization energies associated with displacements of H atoms among ring N atoms were included in the estimation process of the increments. Keto−enol and amino−imino tautomerization energies may be estimated from total electronic energies and increments of conformer conversion energies. The estimates also approximately apply for ΔU° (0) and ΔU° (T0) (free molecules). The extended data set allowed some global structural features of the nucleic acid bases (such as formally aromatic 6-rings), which influence certain increments specifically, to be discerned. The set of increments presented may serve as a basis of a rather general recipe for predictive estimation of conformer and tautomer conversion energies of a wide range of hydroxy- and amino-substituted aromatic nitrogen bases and of effects of geometric isomerism on energetics of intermolecular H bonding involving −OH, −NH2, and NH substituents and protonated keto groups.

Mutagenicity of isomeric alkanediazotates, precursors for ultimate alkylating species of carcinogenic N-nitroso compounds

Alkanediazohydroxides are common key intermediates in carcinogenesis and mutagenesis of N-nitroso compounds, which are widely found in human environment. Mutagenicity of ( E)- and ( Z)-potassium alkanediazotates, as precursors of corresponding alkanediazohydroxides were evaluated to investigate the effect of geometric isomerism and also the effect of alkyl groups on their biological activity. Mutagenicity of N-nitroso- N-alkylureas which spontaneously produce alkanediazohydroxides after non-enzymatic hydrolysis were also tested in comparison to that of the corresponding diazotates and other activated chemical species of N-nitrosamines. When the mutagenicity was assayed in three microbial strains, Salmonella typhimurium TA1535, and Escherichia coli WP2 and WP2 uvrA, the order of mutagenic potency of the compounds with the same alkyl group was as follows; ( E)-diazotates>( Z)-diazotates>nitrosoureas. The effect of alkyl groups on the mutagenic potency was different in Salmonella strain and in E. coli strains, and this result could be explained by the efficiency of O 6-alkylguanine-DNA alkyltransferase. In each bacterial strain, this effect of alkyl groups was similar in mutagenicity induced by ( E)- and ( Z)-diazotates, N-nitroso- N-alkylureas and other activated N-nitrosodialkylamines such as α-hydroxy nitrosamines. The geometrical isomerism affected the mutagenicity of ( E)- and ( Z)-potassium alkanediazotates, and the result suggested that alkanediazohydroxides react through diazonium ions in a cage rather than through free alkyldiazonium ions which have no geometrical isomerism. Our results confirmed that ( E)-potassium alkanediazotates, ( Z)-potassium alkanediazotates and N-nitroso- N-alkylureas all decomposed through diazohydroxides, and that alkanediazohydroxides are the active alkylating species of N-nitroso compounds, and also that the geometrical isomerism is important for carcinogenic N-nitroso compounds to show their biological activity.

Effects of geometric isomerism and ligand substitution in bifunctional dinuclear platinum complexes on binding properties and conformational changes in DNA.

The DNA binding profile of a series of dinuclear platinum complexes [{trans-PtCl-(L)2}2H2N(CH2)nNH2]2+ (L = NH3 or py; 1,1/t,t/NH3 and 1,1/t,t/py, respectively) and [{cis-PtCl-(NH3)2H2N(CH2)nNH2]2+ (1,1/c,c/NH3) was examined to compare the effects of geometrical isomerism and the presence of ligands other than NH3 in the coordination sphere. Steric effects, because of the geometry of the leaving groups cis to the diamine bridge or the presence of planar pyridine ligands, result in diminished binding to calf thymus DNA for these isomers. In contrast, the pyridine derivative shows a distinct binding preference for poly(dG-dC).poly(dG-dC) in comparison to both NH3 isomers. Both NH3 complexes induced the B-->Z transition in poly(dG-dC).poly(dG-dC), but the presence of a pyridine ligand stabilized the B conformation. The bifunctional binding of the NH3 isomers results in unwinding of supercoiled pUC19 plasmid DNA equivalent to cis-DDP, while the unwinding of the pyridine derivative is approximately twice that of the mononuclear trans-[PtCl2(py)2]. DNA-DNA interstrand cross-linking is very efficient for all three agents, but sequencing studies indicated that only the 1,1/t,t/NH3 derivative is capable of forming a (Pt,Pt) intrastrand cross-link to the adjacent guanines of a d(GpG) sequence. The effects on DNA caused by bifunctional binding of dinuclear complexes are compared with those from the mononuclear [PtCl2(NH3)2] isomers. The results are discussed with respect to the antitumor activity of the dinuclear series.

183W NMR spectroscopy of W(VI) imidoaryl and imidoalkyl complexes using inverse detection based on non‐specific long‐range interactions

Abstract183W NMR spectra for a series of octahedral W(VI) imidophenyl, ‘WNPh’ and W(VI) imidoethyl, ‘WNEt,’ complexes were obtained using inverse detection based on non‐specific long‐range interactions. The metal couples to both the ortho and para protons of the NPh moiety (four and six bonds, respectively). The 183W shift is shown to be sensitive to the nature of the ligand and the coordination number. The effect of geometric isomerism on δ183W is shown to be several hundred ppm. Some δ14N and δ15N and 1J(183W,15N) data are reported. A number of new geometric isomers, involving the position of the NR ligand with respect to the remaining ligands, have been identified.

Simultaneous effect of geometrical isomerism and chelate ring size of tris(aminocarboxylato)cobalt(III) complexes on their behaviour in thin-layer chromatography on silica gel and alumina

The simultaneous effects of geometrical isomerism and chelate ring enlargement of octahedral complexes on their R F values obtained by chromatographing twelve isomers of complexes of the general formula [Co(gly) 3-α (β-ala) n ] ( n = 0–3; glyH = glycine; β-alaH = β-alanine) on thin layers of silica gel and alumina by using five monocomponent solvent systems was investigated. It was found that in most instances the effect of the ring size was predominant. Within the series of facial or meridional isomers it was established that with the enlargement of the chelate ring the R F values of the complexes decreased on silica gel but increased on alumina, which was ascribed to the formation of hydrogen bonds of different strengths between the complexes and the adsorbent.

X-Ray Valence-Band Emission Spectra from Square-Planar Complex Compounds of Palladium (II) and Platinum (II)

With a high-resolution two crystal spectrometer, the palladium L β 2,15 emission and chlorine K β emission spectra in fluorescence are measured for square-planar complex compounds K 2 PdCl 4 , (NH 4 ) 2 PdCl 4 , trans -[Pd(NH 3 ) 2 Cl 2 ], [Pd(NH 3 ) 4 ]Cl 2 ·H 2 O, K 2 PtCl 4 , cis - and trans -[Pt(NH 3 ) 2 Cl 2 ]. The result is presented along with the palladium L III absorption-edge and chlorine K absorption-edge spectra of these compounds, reported previously. The effect of the ligand replacement Cl\(^{-}\rightleftarrows\)NH 3 is found in the both emission spectra. The effect of geometrical isomerism is observed in the chlorine K β emission spectra of cis - and trans -[Pt(NH 3 ) 2 Cl 2 ]. The palladium L β 2,15 emission and chlorine K β emission spectra are interpreted in terms of the molecular orbitals of square-planar complexes.

Influence of dietary cis and trans fats on DMH-induced colon tumors, steroid excretion, and eicosanoid production in rats prone to colon cancer.

The effect of geometrical isomerism of dietary fats on colon tumorigenesis was studied in male and female rats of a strain prone to colon cancer (Wistar-Furth-Osaka). The rats were fed purified diets containing either partially hydrogenated corn oil (trans fat) or high-oleic safflower (cis fat) at the 5% level for one week and received a single oral dose of 1,2-dimethylhydrazine. The difference in the fatty acid composition of dietary fats was confined solely to the geometry of octadecenoate. An appropriate level of linoleic acid (2% of total energy) was supplied. After about 60 weeks, neither fat-type nor sex-dependent differences in the incidence of colon and small intestinal tumors was observed. The fecal excretion of neutral but not acidic steroids was higher in male rats fed the trans fat than in those fed the cis fat, but the composition remained almost unchanged. Aortic production of prostacyclin and the plasma concentration of thromboxane B2 were not influenced by dietary fats, although these were significantly higher in females, irregardless of the fat source. Thus, trans fat behaved much like the cis fat in various parameters, except for steroid excretion.

ChemInform Abstract: Effect of Geometrical Isomerism on Metal NMR Chemical Shifts in Octahedral d6 Transition‐Metal Complexes.

ChemInformVolume 19, Issue 15 Physical Organic Chemistry ChemInform Abstract: Effect of Geometrical Isomerism on Metal NMR Chemical Shifts in Octahedral d6 Transition-Metal Complexes. N. JURANIC, N. JURANIC Dep. Chem. Phys. Chem., Univ. Belgrade, 11001 Belgrade, Yugosl.Search for more papers by this author N. JURANIC, N. JURANIC Dep. Chem. Phys. Chem., Univ. Belgrade, 11001 Belgrade, Yugosl.Search for more papers by this author First published: April 12, 1988 https://doi.org/10.1002/chin.198815039AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue15April 12, 1988 RelatedInformation