Number Of Alkyl Substituents Research Articles

Synthesis and Characterization of Size-Controlled Titania Nanorods through Double Surfactants.

A synthetic technique based on a two-step sol-gel hydrothermal method using cetyltrimethylammonium bromide (CTAB) and triblock copolymer PEO106-PPO70-PEO106 (F127) as double surfactants with the assistance of three amines (ethylamine (EA), diethylamine (DEA), and triethylamine (TEA)) for fabrications of anatase titania nanorods is proposed. The formation and growth mechanisms of TiO2 crystals are described. We discovered that crystal size reduces with an increase in the number of alkyl substituents on the nitrogen of amines because the steric hindrance of the bulky alkyl substituent around nitrogen suppresses the nucleation and crystal growth rate. The size of titania from 80 to 220 nm is modulated with concentrations of EA, DEA, and TEA. The amines are considered as catalysts for morphological evolution of TiO2 crystals. The results indicate that the incorporation of double surfactants (F127-CTAB) has a dual role, acting as a chelating agent for titania against external forces and a capping agent inhibiting the three-dimensional growth of TiO2 crystals.

Theoretical study on the enthalpies of adduct formation between alkyl iodides and chlorine atoms

The equilibrium geometries for the ground state of the adducts formed between alkyl iodides (RI) and chlorine (Cl) atoms were optimized, and the enthalpies of adduct formations (EAFs) were obtained. The EAFs decreased when the number of alkyl substituents on the C atom bonded to I atom was increased. This trend suggests that the amount of charge transferred from the electron-donating alkyl group to ICl increases in accordance with the number of substituents, which results in the stabilization of the adduct. Charge density distribution between the Cl and H atoms was an additional mechanism to stabilize the adducts.

Synthesis of Zn(II) porphyrin dyes and revealing an influence of their alkyl substituents on performance of dye-sensitized solar cells

In this study, the series of A3B-type zinc porphyrin dyes have been synthesized for dye-sensitized solar cells (DSSC). All the received zinc-porphyrin complexes bear different alkyl substituents (none, tert-butyl-, methoxy-, hexyloxy-, dodecyloxy-, a pair of hexyloxy-), bulky electron-donating substituent (diphenylamino) in each of three meso-phenyl rings and carboxylic acid as acceptor/anchoring group. The influence of the number and length of alkyl chains on the photophysical properties and DSSCs photovoltaic performance was investigated, as well as quantum-chemical modeling was carried out. Our results reveal that the alkyl chains length and number affect cell performance. We found that DSSC power conversion efficiency increases with an increase in the length and number of alkyl substituents in the porphyrins. A maximum efficiency of 1.29 % was observed in solar cells with dodecyloxy-substituted zinc porphyrin.

Application of pseudo-diabatic electronic states buried in Hartree–Fock wavefunctions to describe bond dissociation processes

Pseudo-diabatic electronic states buried in Hartree–Fock (HF) wavefunctions are applied to describe bond dissociation processes. The limited variational freedom of HF wavefunctions turns to their own advantage to approximately describe the “diabatic” ionic-pair state or the diabatic biradical state. As an application of the pseudo-diabatic states, CH-bond dissociation processes of normal alkanes and their branched isomers are investigated. Reasonable relationships between the diabatic crossing energies and the number of alkyl substituents on a radical center are obtained in accordance with hyperconjugation theory.

Effect of the Passivating Ligands on the Geometric and Electronic Properties of Au–Pd Nanoalloys

Understanding the interaction of the passivating ligands with the clusters is definitely important for the synthesization of high-quality bimetallic clusters (or “nanoalloys”) by chemical reduction method. In this work, the influence of the ligands (PH3 and PMe3) on the geometric and electronic properties of 55-atom Au–Pd nanoalloys is investigated by density functional theory calculations. It is found that the adsorption of PH3 on the Au-rich clusters can modify the morphology of the cluster and the adsoprtion strength of PH3 can be enhanced by the increase of the concentration of Pd in Au–Pd nanoalloys. Our results also suggest that increasing the number of alkyl substituents from PH3 to PMe3 can greatly enhance the adsoprtion strength of the ligand, but is of little effect on the stability of the cluster. In addition, the increase of the coverage of ligands on Au–Pd nanoalloys can slightly decrease the adsorption strength per ligand, but can significantly increase the stability of the cluster. Our results highlight a fundamental research on the effect of the ligands on the physicochemical properties of nanoalloys, which can be used to guide the synthesization of high-quality nanoalloys in the presence of passivating ligands.

The PF6−n(R)n− anions (R = CH3, C2H5; n = 0–6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands

The PF6−n(R)n− superhalogen anions (where R = CH3, C2H5 and n = 1–6) were investigated at the ab initio OVGF/6-311++G(3df,3pd)//MP2/6-311++G(d,p) level of theory and their electronic and thermodynamic stabilities were compared to those of the reference PF6− system. It is demonstrated that (1) the presence of six substituents bound to the phosphorus atom is an important factor that enables the stability of the PF6−n(R)n− anions; (2) subsequent replacement of the fluorine ligands with alkyl R groups in the PF6− superhalogen anion results in a substantial electronic stability decrease (by 2.38–6.74 eV); (3) when the certain number of alkyl substituents is achieved, the PF6−n(R)n− anions become thermodynamically unstable.

Insight into the Interactions That Control the Phase Behaviour of New Aqueous Biphasic Systems Composed of Polyethylene Glycol Polymers and Ionic Liquids

New polyethylene glycol (PEG)/ionic liquid aqueous biphasic systems (ABS) are presented. Distinct pairs of PEG polymers and ionic liquids can induce phase separation in aqueous media when dissolved at appropriate concentrations. Phase diagrams have been determined for a large array of systems at 298, 308 and 323 K. A comparison of the binodal curves allowed the analysis of the tunable structural features of the ionic liquid (i.e., anionic nature, cationic core, cationic alkyl side chain length and functionalisation, and number of alkyl substituents in the cation) and the influence of the molecular weight of the PEG polymer on the ability of these solutes to induce an ABS. It was observed that contrary to typical ABS based on ionic liquids and inorganic salts, in which the phase behaviour is dominated by the formation of the hydration complexes of the ions, the interactions between the PEG polymers and ionic liquids control the phase demixing in the polymer-type ABS studied herein. It is shown that both the ionic liquids and PEG polymers can act as the salting-out species; that is, it is an occurrence that is dependent on the structural features of the ionic liquid. For the first time, PEG/ionic liquid ABS are reported and insight into the major interactions that govern the polymer/ionic liquid phase behaviour in aqueous media are provided. The use of two different nonvolatile and tunable species (i.e., ionic liquids and PEG polymers) to form ABS allows the polarities of the phases to be tailored. Hence, the development of environmentally friendly separation processes that make use of these novel systems is envisaged.

Highly-controlled regiospecific free-radical copolymerization of 1,3-diene monomers with sulfur dioxide

The free-radical copolymerization of alkyl-substituted 1,3-butadienes with sulfur dioxide using a redox initiating system in toluene at -78 °C produced poly(diene sulfone)s consisting of a highly alternating and 1,4-regiospecific repeating structure, irrespective of the position and number of alkyl substituents, and the highly regioselective propagation via a free radical reaction mechanism is well accounted for by DFT calculations using model reactions.

On the photoreactivity of vitamin K compounds

AbstractRate constants for conversion of vitamin K1‐and K2‐derived 1,3‐quinone methides into 1,2‐quinone methides have been measured in CH3CN solutions in the presence of Brönsted acids and bases. Second‐order rate constants approach the diffusion‐controlled limit and are essentially independent of the (acid or base) strength of the catalyst. On the other hand, rate constants for triplet quenching of 2‐methyl‐3‐undecyl‐1,4‐naphthoquinone, used as model compound, are presented and compared with data for 1,4‐naphthoquinone and 2‐methyl‐1,4‐naphthoquinone. A significant decrease in reactivity is observed as the number of alkyl substituents in the quinoid moiety increases, which is attributed to the concomitant increase in triplet π,π* character. Correlation of rate constants for physical quenching, by aromatic hydrocarbons and dimethylsulfoxide, with the electron affinity of the (ground state) quinone and ionization potential of the quenchers suggests quenching by charge‐transfer interactions. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 839–844, 2008

Water-soluble arene ruthenium complexes containing pyridinethiolato ligands: Synthesis, molecular structure, redox properties and anticancer activity of the cations [(η 6-arene)Ru( p-SC 5H 4NH) 3] 2+

The cationic complexes [(η 6-arene)Ru(SC 5H 4NH) 3] 2+, arene being C 6H 6 ( 1), MeC 6H 5 ( 2), p- i PrC 6H 4Me ( 3) or C 6Me 6 ( 4), have been synthesised from the reaction of 4-pyridinethiol with the corresponding precursor (η 6-arene) 2Ru 2(μ 2-Cl) 2Cl 2 and isolated as the chloride salts. The single-crystal X-ray structure of [ 4](PF 6) 2 reveals three 4-pyridinethiol moieties coordinated to the ruthenium centre through the sulphur atom, with the hydrogen atom transferred from the sulphur to the nitrogen atom. The electrochemical study of 1– 4 shows a clear correlation between the Ru(II)/Ru(III) redox potentials and the number of alkyl substituents at the arene ligand ( E°′ (Ru II/III): 1 > 2 > 3 > 4), whereas the cytotoxicity towards A2780 ovarian cancer cells follows the series 4 > 1 > 3 > 2, the hexamethylbenzene derivative 4 being the most cytotoxic one. The corresponding reaction of the ortho-isomer, 2-pyridinethiol, with (η 6-C 6Me 6) 2Ru 2(μ 2-Cl) 2Cl 2 does not lead to the expected 2-pyridinethiolato analogue, but yields the neutral complex (η 6-C 6Me 6)Ru(η 2-SC 5H 4N)(η 1-SC 5H 4N) ( 5). The analogous complex (η 6-C 6Me 6)Ru(η 2-SC 9H 6N)-(η 1-SC 9H 6N) ( 6) is obtained from the similar reaction with 2-quinolinethiol.

Ferrocenoyl Pyridine Arene Ruthenium Complexes with Anticancer Properties: Synthesis, Structure, Electrochemistry, and Cytotoxicity

Organometallic ruthenium(II) complexes of general formula [Ru(eta(6)-arene)Cl(2)(NC(5)H(4)OOC-C(5)H(4)FeC(5)H(5))], where arene = C(6)H(6) (1), C(6)H(5)Me (2), p-iPrC(6)H(4)Me (3), and C(6)Me(6) (4), and of general formula [Ru(eta(6)-arene)Cl(2)](2)(NC(5)H(4)OOC-C(5)H(4)FeC(5)H(4)-COOC(5)H(4)N), where arene = p-iPrC(6)H(4)Me (5) and C(6)Me(6) (6), have been synthesized and characterized, the molecular structures of these complexes being confirmed by single-crystal X-ray structure analysis of complex 4 as a representative example. The redox properties and in vitro anticancer activities of complexes 1-6 have been studied. All the compounds are moderately cytotoxic toward the A2780 and A2780cisR (cisplatin-resistant) human ovarian carcinoma cell lines. The diruthenium arene complexes 5 and 6 are about twice as active as their mononuclear analogues 3 and 4. Cyclic voltammetry revealed a good correlation of the RuII/RuIII redox potentials of 1-4 and the number of alkyl substituents in the arene ligand.

Effect of alkyl substituents on excited state intramolecular proton transfer dynamics of jet-cooled bis(benzoxazolyl)phenoles

Structural factors affecting the dynamics of the excited state intramolecular proton transfer (ESIPT) are studied for alkyl derivatives of 2,5-bis(2-benzoxazolyl)phenol. Two fluorescence bands with equal decay times are observed in solution, while only one--emitted by the phototautomer--in supersonic jet. All evidence indicates the existence of a potential barrier in the S(1) state. Upon deuteration of the OH group the laser induced fluorescence (LIF) excitation spectra become much sharper as a result of slowing down the proton transfer reaction. Two conformers (rotamers) of each compound in the ground state were detected using hole burning technique. With a help of theoretical calculations three vibrations were identified as the most active ones in reducing the distance between two heavy atoms, N and O, involved in H-bond formation. The widths of (0,0) transitions in LIF excitation spectra decrease with increasing size or number of alkyl substituents at terminal aromatic rings. The corresponding calculated rate constants of ESIPT reaction ( approximately 10(12) s(-1)) decrease approximately three times upon the substituent effect. In contrast, model compound 2,5-bis(2-benzoxazolyl)-4-methoxyphenol (BBMP) with OCH(3) parasubstituent in central ring slows down the ESIPT reaction to such an extent that double, primary and phototautomeric, fluorescences coexist.

Melanocortin subtype 4 receptor agonists: Structure–activity relationships about the 4-alkyl piperidine core

SAR about the piperidine core in a series of MC4R agonists is described. A number of alkyl substituents that furnish compounds with good affinity and functional potency are reported.

Hydrogenation of alkyl-substituted phenols over nickel and palladium catalysts

The hydrogenation of alkyl-substituted phenols in the liquid phase was studied using supported nickel and palladium catalysts (<0.02 mm) in stirred reactor. The distribution of hydrogenation products in the final mixture depends not only on the catalyst used, but also on the reactant structure. The palladium catalyst shows higher selectivity with respect to alkylcyclohexanone formation. Also, the number of alkyl-substituents on the aromatic ring and the steric hindrance of hydroxyl group increases the selectivity of alkylcyclohexanone formation. Products of the hydrogenolytic cleavage were observed during hydrogenations on a nickel catalyst. With the help of molecular modelling (PM3 method) the global energy minima of alkylcyclohexanol isomers were determined. The findings were confirmed by GC–MS, high-energy collision induced decomposition (CID method) and by NMR spectroscopy.

Probes for narcotic receptor-mediated phenomena. 25. Synthesis and evaluation of N-alkyl-substituted (alpha-piperazinylbenzyl)benzamides as novel, highly selective delta opioid receptor agonists.

A series of N-alkyl- and N,N-dialkyl-4-[alpha-[(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl] benzyl]-benzamides were synthesized and evaluated for binding affinities at mu, delta, and kappa opioid receptor subtypes. Several compounds (2e,f,h,i,m) strongly bound to the delta receptor with IC50 values in the nanomolar range. On the other hand, the binding affinities of these compounds for the mu and kappa receptors were in the micromolar or greater range indicating excellent delta opioid receptor subtype selectivities. In this series, two important structure-activity relationships were found for the delta receptor binding affinity. First, the spatial orientation of the alpha-benzylic position influenced the affinities with the alpha R derivatives 2a-n generally showing more than 10-fold greater affinity than the alpha S derivatives 3a-n. Second, the binding affinities were strongly influenced by the number of alkyl substituents on the amide nitrogen. N-Monoalkylbenzamide derivatives 2b-d showed lower affinity than N,N-dialkylbenzamide derivatives 2e-n, and the N-unsubstituted benzamide derivative 2a had the lowest affinity for the delta receptor in the series. The dramatic effect of the amide group substitution pattern on the binding affinity for the delta receptor strongly suggests that the amide function is an important structural element in the interaction of this series of compounds at the delta receptor. Selective compounds in this series were examined for binding affinity in cloned human mu and delta receptors. The results obtained generally paralleled those from the rat brain binding assay. Compounds 2e,f with potent delta binding affinities and high delta selectivities were shown to be delta agonists with high selectivity by studies in the guinea pig ileum (GPI) and mouse vas deferens (MVD) preparations. Compound 2f was the most selective compound in the rat brain and GPI/MVD assays with 1755- and 958-fold delta vs mu selectivity, respectively.

Chair/Twist-Boat Energy Gap in Monocyclic, Conformationally Unconstrained Polyalkylcyclohexanes.

A conformational search procedure (HUNTER), in combination with the MM3(92) program, was used for the exploration of the conformational hypersurface of alkyl-substituted cyclohexanes and for the calculation of their chair/twist-boat (TB) energy gap. The systems studied were conformationally unconstrained polyalkylcyclohexanes (alkyl = methyl, ethyl, isopropyl, and tert-butyl) possessing either geminal and/or vicinal arrangements of the alkyl groups, but differing in the number of alkyl substituents and in their relative disposition (i.e., cis or trans). The calculations indicate that in 1,1,3,3,5,5-hexaisopropylcyclohexane the TB is the lowest energy form. Modification of the cis,trans relationship of vicinal alkyl groups changes the chair/TB energy gap, and in the minimum energy conformation of cis,trans,trans-1,2,3,4-tetraisopropylcyclohexane (23c) and cis,syn,cis-1,2,4,5-tetraisopropylcyclohexane (31c) the cyclohexyl ring adopts a TB conformation. The tetrasubstituted systems cis,syn,cis-1,2-diisopropyl-3,4-dimethylcyclohexane (46), cis,syn,cis-1,4-diisopropyl-2,5-dimethyl-cyclohexane (47), and cis,trans,trans-1,2-diisopropyl-3,4-dimethylcyclohexane (41) are the least crowded monocyclic unconstrained cyclohexanes found in which the TB conformation is of lower energy than the chair form. The present study indicates that two methyls and two isopropyl substituents are sufficient for stabilizing the TB form of a cyclohexyl ring relative to the chair form.

Identification of metalloporphyrins by third-derivative UV/VIS diode array spectroscopy

Qualitative analysis of organic compounds is expedited by third-derivative processing of diode array UV/vis spectra which can locate λ max with ±0.02 nm precision, or 1/100 of the present diode interval. The technique was applied to over 50 metalloporphyrins, primarily geological residues of ancient chlorophyll, and the result suggest broader applicability. Among metalloporphyrins, the Soret band wavelength, λ(Soret), varies with the type of functional group structure on the periphery of the 20-carbon porphyrin chromophore. Distinctive λ(Soret) ranges are defined by exocyclic structure (butano, propano, ethano), or lack thereof (etio). Among etioporphyrins λ(Soret) varies with the number of alkyl substituents

Photocrosslinking of polyimide containing benzophenone unit: The effects of polymer compositions on reaction rates and polymer coil dimensions due to the reaction in solution.

The kinetic parameters and the changes in polymer coil dimensions during the competitive intra- and intermolecular photocrosslinking reactions in THF solution depend on the number of alkyl substituents in the diamine component and the amount of benzoph- enonetetracarboxylic dianhydride(BTDA) in polyimide. When a second orth-alkyl substituent is introduced, the quantum yield for intramolecular reaction, including some side reaction with solvent increases and oppositely the quantum yield for intermolecular reaction decreases. The magnitude of 1/2 and Mw is related to the degree of the competition between intra- and intermolecular crosslinking. The contraction ratio, g, of polymer coils decreases smaller as the amount of BTDA in the polyimide increases.

Inositol Liquid Crystals, X-Ray Diffraction Studies of Their Hydrogen-Bond Supported Supramolecular Mesophases1

Abstract Results of x-ray measurements on the various columnar mesophases of multi-ethers of the naturally occurring stereoisomers myo- and scyllo-inositol are presented. Depending on the number of alkyl substituents at their inositol cores such derivatives show interesting kinds of molecular organization in their liquid-crystalline states. Thus, to the best of our knowledge, the first thermotropic mesophase of tetragonal symmetry exhibited by a low-molecular weight system is described. Vicinal diols and a tetrol of this new group of liquid crystals are coupled within their mesophases by hydrogen bonding networks. In case of scyllo-inositol it could be shown that the number of functionalizations determines the size of this network or the degree of multimerization; columnar mesophases composed of dimers or pentamers were observed. A comparison of stereoisomeric inositol tetraethers (vicinal cis- and trans-diols) clearly revealed stereochemical influences on their liquid-crystalline properties.

ChemInform Abstract: Steric Effects in the UV‐VIS Spectra of Benzylideneanilines. Part 2. Alkyl Derivatives of N‐(4′‐Dimethylaminobenzylidene)‐4‐substituted‐anilines.

AbstractThe effect of the size and number of alkyl substituents on the UV/VIS absorption spectra of the title compounds (I) (26 examples given) is discussed.