Self-Assembly Behavior of Diacetylenic Acid Molecules upon Vapor Deposition: Odd–Even Effect on the Film Morphology

A series of linear carboxylic acids containing diacetylenic units at different positions along the chain (C₁₂H₂₅(C≡C)₂(CH₂)_nCOOH, n=7–11) were vacuum-deposited on clean silica substrates. The morphologies of the initial films after UV irradiation were studied. A clear odd–even effect on the morphology of the initial film was observed in that, depending on the spacer length between the diacetylenic unit and carboxyl head group, rings or dendrites of acid dimer layers were obtained. A molecular dynamic simulation of the aggregation process suggests that two competing intermolecular interactions and thus aggregation directions are involved and modulated by the odd or even carbon chain length. Further modulation of the interaction by substitution of a phenyl group at the terminus of the chain or by changing the carboxyl head group to an amidobenzoic acid head group led to a similar odd–even effect but with different dimensions or trends, which can be rationalized similarly. These results give the opportunity to create aligned conjugated polymer chains of different dimensions through self-assembly for applications in molecular/organic electronics.     

Fatty-acid composition of rat brain lipids. Determined by support-coated open-tubular gas chromatography.

The nonhydroxy fatty acid composition of rat brain lipids (except gangliosides) was determined by support-coated open-tubular (SCOT) gas chromatography. Fatty acids of both odd and even chain lengths ranging from C14 to C26 were detected. Brain lipids contained 49% saturated, 29% monounsaturated, and 22% polyunsaturated fatty acids. Monoenoic fatty acids were mainly of the omega-9 and omega-7 series with minor amounts of omega-10 and amega-11 isomers. Dienes and trienes consisted of omega-6, amega-7, and omega-9 series. Tetraenes were of the omega-6 series. Small amounts of omega-6 and omega-3 pentaenes were detected. The most abundant polyunsaturated fatty acid was 22:6omega-3. The advantages of support-coated open-tubular columns over wall-coated open-tubular columns for the analysis of brain lipid fatty acids are discussed.     

A density functional study on beryllium-doped carbon dianion clusters CnBe2- (n = 4-14)

Making use of the software of molecular graphics, we designed numerous models of C(n)()Be(2-) (n = 4-14). We carried out geometry optimization and calculation on vibration frequency by means of the B3LYP density functional method. After comparison of structure stability, we found that the ground-state isomers of C(n)()Be(2-) (n = 4-14) are linear with the beryllium atom located inside the C(n)() chain. When a side carbon chain is with an even number of carbon atoms, it is polyacetylene-like, whereas when a side chain is with an odd number of carbon atoms, it is cumulene-like. The C(n)Be(2-) (n = 4-14) clusters with an even number of carbon atoms are more stable than that with an odd number of carbon atoms, matching the peak pattern observed in accelerator mass spectrometry (AMS) and Coulomb Explosion Imaging (CEI) investigations of C(n)()Be(2-) (n = 4-14). The trend of such odd/even alternation is explained based on concepts of bonding characteristics, electronic configuration, electron detachment, and incremental binding energy.     

Nanoscopic Imaging of meso‐Tetraalkylporphyrins Prepared in High Yields Enabled by Montmorrilonite K10 and 3 Å Molecular Sieves

We have developed a high‐yielding synthesis of meso‐tetraalkylporphyrins, which previously have been obtained only in lower yields. By employing Montmorrilonite K10 as the acid catalyst and 3 Å molecular sieves as the dehydrating agent, yields that reached 70 % could be achieved with some aliphatic aldehydes. The free‐base porphyrins with decyl ( C10 ) or longer chains were imaged at the single‐molecule level at the solvent/surface interface. Highly oriented pyrolytic graphite (HOPG) was used as a π‐stacking surface, whereas 1‐phenyloctane and 1‐phenylnonane were used as solvents. An odd–even effect was observed from C13 to C16 . For C13 a single‐crystal X‐ray structure allowed an unprecedented insight into how packing from two dimensions is expanded into a three‐dimensional crystal lattice.     

Hydrogen bonding versus van der Waals interactions: competitive influence of noncovalent interactions on 2D self-assembly at the liquid-solid interface

The structures of the self-assembled monolayers of various 4-alkoxybenzoic acids physisorbed at the liquid-solid interface were established by employing scanning tunnelling microscopy (STM). This study has been essentially undertaken to explore the competitive influence of van der Waals and hydrogen-bonding interactions on the process of two-dimensional self-assembly. These acid derivatives form hydrogen-bonded dimers as expected; however, the dimers organise themselves in the form of relatively complex lamellae. The characteristic feature of these lamellae is the presence of regular discommensurations or kinks along the lamella propagation direction. The formation of kinked lamellae is discussed in light of the registry mechanism of the alkyl chains with the underlying graphite substrate. The location of the kinks along a lamella depends on the number (odd or even) of carbon atoms in the alkyl chain. This result indicates that concerted van der Waals interactions of the alkyl chain units introduce the odd/even chain-length effect on the surface-assembled supramolecular patterns. The odd/even effects are retained even upon complexation with a hydrogen-bond acceptor. However, as the solvent is changed from 1-phenyloctane to 1-octanoic acid, the kinked lamellae as well as the odd/even effects disappear. This solvent-induced convergence of supramolecular patterns is attained by means of co-crystallisation of octanoic acid molecules in the 2D crystal lattice, which is evident from high-resolution STM images. The solvent co-adsorption phenomenon is discussed in terms of competing van der Waals and hydrogen-bonding interactions.     

Valence parity renders z(*)-type ions chemically distinct

Here we report that the odd electron z (*) -type ions formed by the electron-based peptide dissociation methods (electron capture or transfer, ECD or ETD) have distinctive chemical compositions from other common product ion types. Specifically, b-, c-, and y-type ions have an odd number of atoms with an odd valence (e.g., N and H), while z (*)-type ions contain an even number of atoms with an odd valence. This tenet, referred to as the valence parity rule, mandates that no c-type ion shall have the same chemical composition, and by extension mass, as a z (*) -type ion. By experiment we demonstrate that nearly half of all observed c- and z (*) -type product ions resulting from 226 ETD product ion spectra can be assigned to a single, correct, chemical composition and ion type by simple inspection of the m/ z peaks. The assignments provide (1) a platform to directly determine amino acid composition, (2) an input for database search algorithms, or (3) a basis for de novo sequence analysis.     

Studies on the odd‐even effect of methylene spacers in poly(pyromellitimide‐ester)s

Three series of poly(pyromellitimide‐ester)s were synthesized from various N,N′‐bis(ω‐hydroxyalkyl)pyromellitimides (HAPMIs) by melt condensation with dicarboxylic acids, including terephthalic acid (TPA), 4,4′‐biphenyldicarboxylic acid (BPDA), and 4,4′‐azobenzenedicarboxylic acid (ABDA). Polymers were characterized by elemental analysis, solubility, inherent viscosity, spectra (IR, ¹H‐NMR, ¹³C‐NMR), and X‐ray diffraction (XRD). Thermal stability and phase transition behaviour were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and hot‐stage optical polarized microscopy (HOPM). The d‐spacings, calculated from XRD data, showed an odd‐even effect with varying numbers of methylene spacers. Crystallinity of polymers decreased in the following order: azobenzene > biphenyl > phenyl polymers. Similarly, DSC‐obtained melting temperatures (T_m's) showed an odd‐even effect, and glass transition temperatures (T_g's) decreased with increasing numbers of methylene spacers. Thermal stability decreased as methylene chain length increased. Thermal stability of polymers occurred in the following order: phenyl > biphenyl > azobenzene polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1755–1761, 1999     

Systematic characterisation of long-chain aliphatic esters of wool wax by gas chromatography-electron impact ionisation mass spectrometry

A detailed structural characterisation of the aliphatic high-molecular-mass esters extracted from raw wool based on high-temperature gas chromatography-electron impact ionisation mass spectrometry is described. The raw wool esters extracted are in the range of C37 to C54 (i.e., molecular mass 550-788). The selected ion chromatogram exhibited four isomers for the esters with an odd number of carbon atoms (i:a, i:n, a:n and n:n) and five for those with an even number of carbon atoms (i:i, a:a, i:n, a:n and n:n). Isomeric structural elucidation is discussed with respect to the long-chain fatty acid and long-chain fatty alcohol structures, on the basis of chromatographic retention behaviour and mass spectral information.     

Odd–Even Alternation in Tautomeric Porous Organic Cages with Exceptional Chemical Stability

Amine‐linked (C−NH) porous organic cages (POCs) are preferred over the imine‐linked (C=N) POCs owing to their enhanced chemical stability. In general, amine‐linked cages, obtained by the reduction of corresponding imines, are not shape‐persistent in the crystalline form. Moreover, they require multistep synthesis. Herein, a one‐pot synthesis of four new amine‐linked organic cages by the reaction of 1,3,5‐triformylphloroglucinol (Tp) with different analogues of alkanediamine is reported. The POCs resulting from the odd diamine (having an odd number of −CH₂ groups) is conformationally eclipsed, while the POCs constructed from even diamines adopt a gauche conformation. This odd–even alternation in the conformation of POCs has been supported by computational calculations. The synthetic strategy hinges on the concept of Schiff base condensation reaction followed by keto–enol tautomerization. This mechanism is the key for the exceptional chemical stability of cages and facilitates their resistance towards acids and bases.     

Effect of polyester zigzag structure on the phase segregation of polyester-based polyurethanes

Polyester-based polyurethanes were synthesized from 4,4′-methylenebis(phenyl isocyanate) (MDI) with butanediol as a chain extender and low molecular weight polyester–diol as a soft segment. Two polyesters were used in the synthesis of polyurethanes. One of the polyesters was synthesized from adipic acid and 1,6-hexanediol, which had an even number of carbon atoms. The other polyester was synthesized from pimelic acid and 1,5-pentanediol, which had an odd number of carbon atoms. The effect of even carbon monomers and odd carbon monomers of polyester soft segments on the phase segregation of soft and hard segments was studied by DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2095–2104, 1999     

Oligo(ethylene imine)-grafted glycidyl methacrylate linear and star homopolymers: Odd–even correlated transfection efficiency

The present study aims to investigate an odd–even effect of the number of ethylene imine units in the side-groups of totally abiotic synthetic polymers on their efficiency in DNA transfection. A library of fifteen polymers was fabricated. Two star homopolymers and one linear homopolymer based on glycidyl methacrylate were synthesized and used as precursors to which five linear oligo(ethylene imine)s (OEI) were grafted. The number of ethylene imine groups of the OEIs was varied. Specifically, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine were used. Each of these fifteen OEI-grafted polymers was evaluated in terms of their efficiency to transfer plasmid DNA encoding firefly luciferase in C2C12 mouse myoblast cells. The transfection efficiency displayed an odd-even pattern, with all OEI-grafted polymers with an odd number of ethylene imine repeating units exhibiting higher transfection efficiency compared with those possessing an even number of ethylene imine repeating units. The odd–even effect was more pronounced for the star polymers with longer arms (degree of polymerization, DP = 100), while in case of the linear polymers, the odd–even effect was only observed for the lowest polymer loading. The cytotoxicity of the OEI-grafted polymers also followed an odd–even pattern, with the OEI-grafted star polymers with an arm DP of 100 and the linear polymers clearly presenting an odd-even effect, while the cytotoxicity of the OEI-grafted star polymers with an arm DP of 20 slightly increased with the number of ethylene imine repeating units.     

Optical diffraction in twisted liquid-crystalline media-phase grating mode

We have calculated the diffraction of light perpendicular to the twist axis in a chiral smectic C liquid crystal. In contrast to a cholesteric liquid crystal, in a chiral smectic C liquid crystal we find extra orders which form the odd orders in the diffraction pattern. For an incident linearly polarized light, at a general azimuth, these odd orders are linearly polarized and the even orders are elliptically polarized. The intensities of the odd orders are always independent of the azimuth of the incident light, while this is possible for even orders only at a particular tilt angle of the chiral smectic C liquid crystal. Also, for the incident vibration parallel or perpendicular to the twist axis the odd orders are polarized in the orthogonal linear state with respect to incident vibration, while the even orders are in the same linear state.     

Infrared intensity and band shape studies on Langmuir-Blodgett films of ω-trieosenoic acid on silicon

We report FT-i.r.-ATR studies on Langmuir-Blodgett films of ω-tricosenoic acid on a silicon substrate as a function of the (odd or even) number of mono-layers. It is shown that the first monolayer has significantly different hydrogen bonding interactions (at the Si/SiO₂ interface) from subsequent (cyclic dimer bound) monolayers. These first layer interactions are found to profoundly influence the v(C=O) band shape and height, but the integrated intensity still increases roughly linearly with increasing thickness. Dichroic effects on our ATR spectra are small (but real), and there is clear evidence of a degree of random variation in the hydrocarbon chain “tilt” (away from the surface normal) as indicated by electron diffraction measurements.     

Chemical oxidation of the components of extraction solutions and critical parameters of heat explosion

Thermochemical interaction of TBP with nitric acid in single-phase organic systems has been studied at the concentrations of HNO₃ 1.4 to 5.6M, in temperature range of 110–140 °C. The termochemical oxidation of TBP includes a number of consecutive and concurrent reactions, such as acid hydrolysis, the oxidation of the TBP hydrolysis products, and TBP destructive oxidation. Some of these reactions can proceed with heat explosion. The limiting temperature (120–130 °C) and acid concentration (2.5 mol/l) at which the oxidation reactions are able to transform to heat explosion have been estimated. The rate constants and activation energies were determined for the reactions presenting a potential hazard.     

直线型CnP^—（n=1～11）结构的理论研究

以激光溅射方法产生了一系列含一个磷原子的碳原子簇负离子．针对其在实验中呈现的奇偶变化规律进行了量子化学从头算研究．在HF／6－311G*水平上（对单重态为RHF，多重态为ROHF）优化了直线型CnP-（n=1～11）键长和能量，计算了相邻簇离子的能量差与成簇碳原子的平均结合能及从CnP-分别解离C、C2、C3、P、CP、C2P等6种通道所需的能量．计算发现，n为奇数的CnP-单重态（1Σ）最稳定，而，n为偶数的簇离子则以三重态（3Σ）的能量较低．所计算的CnP-各结构参数均表现出奇偶交替的变化规律，n为奇数的CnP-相对稳定．     

Layer-by-layer surface freezing of linear alcohols at the graphite/liquid interface

Differential scanning calorimetry (DSC), incoherent elastic neutron scattering, and neutron diffraction are used to demonstrate the presence of adsorbed solid multilayers of linear alcohols at the graphite-liquid alcohol interface. All alcohols studied (C(5)-C(18)) are found to form at least one monolayer. In addition all the even alcohols investigated (C(6)OH to C(18)OH) show multilayer formation. However, only the short odd alcohols (C(5)OH to C(11)OH) clearly exhibit additional features indicating multilayer formation.     

Closed-shell polycyclic aromatic hydrocarbon cations: a new category of interstellar polycyclic aromatic hydrocarbons

Density functional theory has been employed to calculate the harmonic frequencies and intensities of a range of polycyclic aromatic hydrocarbon (PAH) cations that explore both size and electronic structure effects on the infrared spectroscopic properties of these species. The sample extends the size range of PAH species considered to more than 50 carbon atoms and includes several representatives from each of two heretofore unexplored categories of PAH cations: (1) fully benzenoid PAH cations whose carbon skeleton is composed of an odd number of carbon atoms (C(odd) PAHs); and (2) protonated PAH cations (HPAH+). Unlike the radical electronic structures of the PAH cations that have been the subject of previous theoretical and experimental work, the species in these two classes have a 'closed'-shell electronic configuration. The calculated spectra of circumcoronene, C54H18, in both neutral and (radical) cationic form are also reported and compared with those of the other species. Overall, the C(odd) PAHs spectra are dominated by strong CC stretching modes near 1600 cm(-1) and display spectra that are remarkably insensitive to molecular size. The HPAH+ species evince a more complex spectrum consistent with the added contributions of aliphatic modes and their generally lower symmetry. Finally, for both classes of closed-shell cations, the intensity of the aromatic CH stretching modes is found to increase with molecular size far out of proportion with the number of CH groups, approaching a value more typical of neutral PAHs for the largest species studied.     

Above the surface multifragmentation of surface scattered fullerenes

C(60) (-) ions were scattered from a gold surface at impact energies of 80-900 eV. The C(n) (-) fragments abundance distribution (odd and even) and the sharp fragmentation threshold observed, point at a prompt shattering event. The measured angle and energy distributions of the C(n) (-) fragments (n=2-12) provide clear evidence for a multifragmentation process where the superheated fullerenes leave the surface "intact" and disintegrate away from the surface.     

First-principles study on electron transport of carbon dumbbells C60-C(n)-C60

Electronic transport properties of carbon dumbbells, a new type of carbon hybrid nanostructures formed by connecting carbon atomic chains to two fullerenes C(60), are investigated by using nonequilibrium Green's functions in combination with the density-functional theory. Specifically, the transport properties as a function of the carbon chain length n are examined. An obvious metal-insulator-like oscillation has been achieved with the increase of the carbon chain length. When n is even, the device behaves as a metal. In contrast, when n is odd, it behaves as an insulator. It is quite different to the carbon chains directly sandwiched between metallic leads where the low conductance states are observed for even n while the high conductance states are observed for odd n. Such a difference arises from the screening effect of C(60)s.     

The Theoretical and Experimental Studies on Oxidation of Straight Chain Amino Acids in Moderately Concentrated Sulfuric Acid Medium

The kinetics of the permanganic oxidation process of some straight chain amino acids in moderately concentrated sulfuric acid medium have been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions. It is determined that even and odd effects of the number carbon atom in a carbon chain are annihilated when it's the number of carbon atoms is increased more than of three in a noncatalytic oxidation pathway. Thus, rate constants belonging to glycine, l ‐α‐amino‐n‐butyric acid, l ‐norleucine, and l ‐α‐amino‐n‐heptanoic acid satisfy Taft's equation involving the induction factor in the noncatalytic pathway, whereas l ‐α‐amino‐n‐heptanoic acid has an odd number of carbon atom in its chain carbon. On the other hand, in the catalytic pathway, rate constants satisfy Taft' equation including inductive and steric factors, when rate constants belonging to amino acids with an even number of carbon atoms are separated from those with an odd number of carbon atoms. The oxidation process of amino acids in the noncatalytic pathway and those with the even number of carbon atoms in the carbon chain in the catalytic pathway speeds up by an increase in the length of chain that is accompanied with an increase in the carbon chain's electron‐donating characteristic. On the other hand, an increase in the length of the carbon chain is accompanied with more steric hindrance, which counteracts its electron‐donating character, thereby decreasing reaction rate in the catalytic pathway. Finally, amino acid–Mn(II) complexes were studied using a density functional theory method. Results obtained show that such a complex is less stable than reactants, namely it is formed in an endothermic reaction. The number and strength of hydrogen bonding belonging to amino acid is more than those of the amino acid–Mn(II) complex. Besides, it has been illustrated that natural bond orbital analysis and molecular orbital calculations satisfy the findings.