Effect Of Alkyl Substituents Research Articles

Dual-response signal under mechanical stimulation: Alkyl substituent effect on the fine-tuning of molecular packing

Mechanical stimulus-responsive materials are generally considered to be closely related to molecular packing in the solid state, underscoring the significance of regulating molecular packing via precise molecular design. In this study, flexible alkyl substituents were employed to adjust the molecular packing. By modifying alkyl substituents, predictable changes in the molecular packing of their derivatives were observed, resulting in adjustable ML properties. The DPA-PYZ-TB with a tert-butyl-side chain exhibited strong ML and MC stimulus response signals. The enhanced ML and MC performance can be attributed to the effective suppression of non-radiation through the helical crystal arrangement and strong intermolecular interactions. The relationship between molecular arrangement and ML/MC properties was validated through analysis of the single crystal structure and corresponding experimental results. This study offers valuable insights into the enigmatic ML process and the development of efficient luminous materials that utilize both MC and ML.

Effect of Alkyl Substituents on Molecular Packing and Luminescence Properties of Crystalline Thioxanthone Derivatives

Effect of Alkyl Substituents on Molecular Packing and Luminescence Properties of Crystalline Thioxanthone Derivatives

Preparation of Highly-Ordered Tetrabenzorporphyrin Films Controlled by Supramolecular Assemblies and Precursor Approach

The control of the orientation and packing structures of small organic semiconductor molecules is the important issue for the improvement of charge carrier mobilities of organic field effect transistors. Tetrabenzoporphyrin (BP) is one of the promising p-type organic semiconductors but solubility in organic solvents is very low. We have developed a precursor approach, where a spun-cast film of soluble precursor, tetra-bicyclo[2.2.2]octadiene-fused porphyrin (CP), was heated to obtain BP crystalline film by in-situ retro-Diels–Alder reaction. However, the obtained BP film is a polycrystalline film and the field-effect transistors (FETs) hole mobilities were 10-1~10-2 cm2V-1s-1[1]. Recently, we reported the effect of alkyl substituents at 5,15-positions of BP for the control of the molecular arrangement. The best performance of OFET hole mobility of 5,15-disubstituted BP was 4.1 cm2V-1s-1 [2, 3].A supramolecular strategy has attracted attentions as the effective method for the control of molecular arrangement in films. We applied the combination of supramolecular assembling method and the precursor approach to prepare well-ordered BP films. 5,15-Bis(p-dodecylamidephenyl)-CP was deposited on the substrate by drop-casting, spin-coating or dip-coating method, followed by the heating to 200 ºC for 10 min to give the corresponding 5,15-bis(p-dodecylamidephenyl)-BP films. The film morphologies of the BP were compared with 5,15-bis(p-dodecyloxyphenyl)-BP, which doesn’t include amide moieties for hydrogen-bonding, using UV-vis absorption spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, and p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) to clarify the effect of amide groups. OFET performance of the BPs will be also discussed to clarify the effect of intermolecular hydrogen bonding interaction.

Tuning Sensing Efficacy of Oligo(phenylenevinylene) Based Chromogenic Probes: Effect of Alkyl Substituents on Metal Ion Detection at Micelle-Water Interface.

In this work, we conducted a comparative analysis of the metal ion sensing capabilities of two pyridine-end oligo p-phenylenevinylene compounds featuring different alkyl substituents (-C4H9 and -C16H33) within a micelle medium. Our findings revealed a correlation between the positioning of the probe molecules within the micelle and the length of the alkyl chains, impacting their self-assembly tendencies and optical characteristics. The compound with shorter alkyl chains demonstrated a superior affinity towards Hg2+ ions, whereas exposure to the compound with longer alkyl substituent resulted in a color-changing response with both Cu2+and Hg2+ ions. Intriguingly, the sensitivity towards Hg2+ ions heightened with increasing alkyl chain length. This trend persisted in non-polar solvents like THF. The capacity to modulate sensing efficacy solely by adjusting the length of the alkyl chains represents a relatively uncommon occurrence in the existing literature. This discovery suggests promising prospects for engineering sensory devices equipped with adaptable sensitivity.

The effect of alkyl substituents in the β-side on the conformation, molecular structure, and copper-oxygen bond strength of bis(β-diketonato)copper(II) complexes by DFT results and experimental vibrational and UV spectra

The effect of alkyl substituents in the β-side on the conformation, molecular structure, and copper-oxygen bond strength of bis(β-diketonato)copper(II) complexes by DFT results and experimental vibrational and UV spectra

Origins of Regioselectivity in CuH-Catalyzed Hydrofunctionalization of Alkenes.

Factors controlling the regioselectivity in alkene hydrocupration were computationally investigated using energy decomposition analysis. The results demonstrate that the Markovnikov-selective hydrocupration with electronically activated mono-substituted olefins is mostly affected by the destabilizing Pauli repulsion, which is due to the electron delocalization effect. The anti-Markovnikov-selective hydrocupration with 1,1-dialkyl-substituted terminal olefins is dominated by the repulsive electrostatic interactions, which is because of the unequal π electron distribution caused by the induction effect of alkyl substituents.

Cover Image

The cover image is based on the Research Article Competition between the stabilizing effects of saturated alkyl substituents and pi bonds on complexes of silver ion (Ag+) with alkenes by Gary W. Breton, https://doi.org/10.1002/poc.4301.

Pyrithione metal (Cu, Ni, Ru) complexes as photo-catalysts for styrene oxide production

Selective photochemical oxidation of styrene was performed in an active acetonitrile medium, using H2O2 with or without ultraviolet (UV) light radiation. Pyrithione metal complexes (M–Pth: M = Cu(II), Ni(II), Ru(II); Pth = 2-mercaptopyridine-N-oxide) were used as catalysts. Catalytic testing measurements were done by varying the time, chemical reaction temperature and H2O2 concentration with or without UV energy. Epoxide styrene oxide (SO), benzaldehyde and acetophenone were the major synthesized products. A high batch rate, conversion and selectivity towards SO was shown in the presence of UV. A minor constant formation of CO2 was observed in the stream. Coordinated Ru-based compounds demonstrated the highest process productivity of SO at 60 °C. The effect of the functional alkyl substituent on the ligand Pth, attached to the specific ruthenium(II) centre, decreased the activity of the substance. Ni-Pth selectively yielded benzaldehyde. The stability of the catalysts was examined by applying nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis coupled with mass spectrometry. Tested metal complexes with pyrithione (M–Pth) exhibited excellent reuse recyclability up to 3 cycles.

Effect of alkyl substituent for cyclohexane on pyrolysis towards sooting tendency from theoretical principle

The fuel structure is an important controlling factor during the process of soot formation. Alkylated cyclohexane is a typical surrogate fuel with more complex structure than alkanes or aromatic fuels. Five alkylated cyclohexanes (i.e., cyclohexane, methylcyclohexane, ethylcyclohexane, 1,3-dimethylcyclohexane, 1,3,5-trimethylcyclohexane) and the n-alkane were selected to investigate the effect of the alkyl substituent on sooting tendency during the pyrolysis process from the theoretical principle. The reaction energy barriers profiles of alkylated cyclohexanes obtained by the density functional theory (DFT) illustrate the length and number of the alkyl substituent will affect the production of alkenes fragments which finally decompose to C2H2 and C3H3 species. The molecular dynamics simulations show the abundance of C2H2 and C3H3 fragments from the initial pyrolysis of fuels will accelerate the sooting tendency, which follow the trend of cyclohexane < methylcyclohexane < ethylcyclohexane ≈ 1,3-dimethylcyclohexane < 1,3,5-trimethylcyclohexane, in agreement with experimental findings. We hope this study can provide a more comprehensive understanding of the effect of fuel structure on sooting tendency and ideas for soot inhibition.

Competition between the stabilizing effects of saturated alkyl substituents and pi bonds on complexes of silver ion (Ag+) with alkenes

AbstractThe coordination of Ag+ ions to alkenes is of both theoretical and practical interest. While much attention has been paid to how the nature of the C=C π bond affects the coordinative process, little attention has been directed toward the effect of saturated side chains on complex stabilization despite experimental evidence suggesting its importance. Calculations employing the M06‐2X DFT functional have revealed that saturated chains can exhibit as powerful a stabilizing effect on Ag+/alkene complex formation as increased alkyl substitution about the C=C bond. Natural bond orbital (NBO) analysis confirms the mechanism of stabilization to be that of agostic interactions of properly‐oriented CH σ‐bonds in the saturated chain with the Ag+ ion. Analysis by the extended transition state energy decomposition approach with the natural orbital for chemical valence method (ETS‐NOCV) and the reduced density gradient (RDG) model were used to better characterize the nature of the interaction as a near equivalent combination of electrostatic and orbital interactions.

Theoretical Investigation of the Effect of Alkylation and Bromination on Intersystem Crossing in BODIPY-Based Photosensitizers.

Halogenated and alkylated BODIPY derivatives are reported as suitable candidates for their use as photosensitizers in photodynamic therapy due to their efficient intersystem crossing (ISC) between states of different spin multiplicities. Spin-orbit couplings (SOCs) are evaluated using an effective one-electron spin-orbit Hamiltonian for brominated and alkylated BODIPY derivatives to investigate the quantitative effect of alkyl and bromine substituents on ISC. BODIPY derivatives containing bromine atoms have been found to have significantly stronger SOCs than alkylated BODIPY derivatives outside the Frank-Condon region while they are nearly the same at local minima. Based on calculated time-dependent density functional theory (TD-DFT) vertical excitation energies and SOCs, excited-state dynamics of three BODIPY derivatives were further explored with TD-DFT surface hopping molecular dynamics employing a simple accelerated approach. Derivatives containing bromine atoms have been found to have very similar lifetimes, which are much shorter than those of the derivatives possessing just the alkyl moieties. However, both bromine atoms and alkyl moieties reduce the HOMO/LUMO gap, thus assisting the derivatives to behave as efficient photosensitizers.

Catalyst Activation and Chain Transfer Agents in Metallocene Catalysts for Ethylene Polymerization: A Computational Investigation

AbstractA density functional theory (DFT) study has been carried out to investigate the effect of various cocatalysts/chain transfer agents (such as Al(R)3, Mg(R)2, (R)Mg(Cl), Zn(R)2, (R)Zn(Cl), B(C6F5)3, and Al(C6F5)3, here, R=alkyl group) on catalyst activation and ethylene polymerization including chain transfer steps using (CpR, R’)2M(Cl)2 (M=Zr, Hf and R, R’=alkyl group) metallocenes. Initially, the catalyst alkylation step (where one of the chlorine atoms of the catalyst is replaced by an alkyl group of the cocatalyst) has been studied using the Al(Me)3, Mg(Me)2, (Me)Mg(Cl), Zn(Me)2, and (Me)Zn(Cl) moieties, and it was observed that the AlMe3 species is more effective for the alkylation step. Furthermore, a modification in the metallocene, such as (CpR, R’)2Zr(Cl)2, where R and R’=H, Me, Et, n‐propyl, iso‐propyl, iso‐butyl, tert‐butyl, and different combinations of those, has been performed to evaluate the effect of different alkyl substituents on the alkylation process, whereby it was found that the mono‐substituted metallocene favors the alkylation in comparison to bi‐substituted metallocene. Moreover, a detailed fundamental understanding of the ion pair formation step was gained by incorporating various steric and electronic factors of different alkyl groups, including fluorinated alkyl group bound on the Cp ligand. These results suggest that only B(C6F5)3 and Al(C6F5)3 activators could form the ion pairs by abstracting a methyl group from the metallocene. Additionally, the ethylene polymerization has also been investigated using B(C6F5)3 or Al(C6F5)3 cocatalyst, where B(C6F5)3 was found to be more effective towards polymerization. Furthermore, the Al(Me)3, Mg(R)2, (Me)Mg(Cl), Zn(R)2, and (Me)Zn(Cl) species have been employed as chain transfer agent (CTA). It has been observed that the magnesium‐ and zinc‐based species are more likely to behave as CTAs, and this process can be improved by changing the alkyl substituents on them. These chemical calculations shed light on catalyst alkylation and ethylene polymerization, including the chain transfer process, in metallocenes.

Substituent-Adjusted Electrochromic Behavior of Symmetric Viologens.

As a promising electrochromic material, viologens have attracted increasing attention due to their high redox activity and adjustable electrochromic capability. In order to investigate the effect of alkyl substituents on electrochromic behavior, four alkyl-substituted viologens and a benzyl-substituted viologen were synthesized, namely 1,1′-dioctyl-4,4′-bipyridinium dibromide (OV), 1,1′-didekyl-4,4′-bipyridinium dibromide (DeV), 1,1′-didodecyl-4,4′-bipyridinium dibromide (DoV), 1,1′-dihexadecyl-4,4′-bipyridinium dibromide (HV), and 1,1′-dibenzyl-4,4′-bipyridinium dibromide (BV). The different photophysical and electrochemical properties of these viologens were attributed to their deviation in spatial structure caused by different substituents. Compared with benzyl-substituted BV, a slight blueshift occurred for the absorption peaks of alkyl-substituted viologens from 262 to 257 nm with the increase in alkyl chain length. Moreover, the first redox couple increased positively, and the dimerization of the compound decreased gradually, accompanied by the decrease in optical contrast and distinct chromatic difference. A comparison of chromatic and optical contrasts indicated that OV had the longest coloring response time (RTc), while it was shortest for HV. The bleaching response time (RTb) of viologen films gradually decreased with the alkyl chain length, and the OV film had the shortest RTb. Furthermore, when increasing the length of the alkyl chain, the cycling stabilities of alkyl viologens increased gradually. In addition, the OV film exhibited the best contrast after 200 continuous cycles.

Viscosity and Density of Two 1-Alkyl-3-methyl-imidazolium Triflate Ionic Liquids at High Pressures: Experimental Measurements and the Effect of Alkyl Chain Length

New measurements of the viscosity of 1-butyl-3-methyl-imidazolium triflate ([BMIM][OTf]) and 1-hexyl-3-methyl-imidazolium triflate ([HMIM][OTf]) have been carried out at high pressures, using a vibrating-wire technique operated in the forced mode of oscillation. The measurements for [BMIM][OTf] have been performed along six isotherms from 298 to 358 K at pressures up to 50 MPa. The viscosity measurements for [HMIM][OTf] have been carried out along five isotherms from 303 to 358 K at pressures up to 50 MPa. The estimated uncertainty of the measurements is less than U(η) = 0.02·η for viscosities up to 68 mPa·s and less than U(η) = 0.026·η for higher viscosities, with a confidence level of 0.95 (k = 2). For both ionic liquids, complementary density measurements have been performed using an Anton Paar HP densimeter in the same temperature and pressure ranges as those used for the viscosity measurements. The density results have an uncertainty smaller than U(ρ) = 0.002·ρ with a confidence level of 0.95 (k = 2). The viscosity results were correlated with the density data using a previously described hard-sphere-based technique. The individual correlations are able to describe the viscosity results for each liquid with an uncertainty smaller than the estimated uncertainty of the experimental data. The effect of alkyl substituents on the viscosity and the density of these ionic liquids has been analyzed. For this purpose, previously published results for the viscosity and density of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) have been considered in addition to the data obtained in the present work for [BMIM][OTf] and [HMIM][OTf].

Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen‐type Schiff base

Salen-type Schiff Bases are a kind of important compounds and are widely used. In order to explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts 63 title compounds were synthesized. Their 1 H NMR and 13 C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δH (CH=N), δC (CH=N), δH (OH) and δC (C-OH)) were studied. The results show that: (1) The alkyl polarizability effect index (PEI) has an important influence on the chemical shifts of the above four atoms, with the increase of PEI, the values of δH (CH=N) and δc (CH=N) decrease, while the values of δH (OH) and δC (C-OH) increase.(2) The influence of substituent X attached to aromatic ring on the chemical shift is related to its position by taking OH or CH=N as reference. As for the effect of substituent on the chemical shifts, the effect of Hammett constant σ(X)-OH and excited-state substituent parameter with OH as reference are different from that of σ(X)-CH=N and with CH=N as reference, and there is a "homoring competition effect" of the substituent. (3) The effect of the cross-interaction between X and OH on the chemical shift is also significantly different due to the different position of X. Quantitative correlation equations against chemical shifts were built for the four atoms, and the stability and prediction ability of the obtained equations were confirmed by leave-one-out cross validation.

Synthesis and properties of fluorinated benzotriazole‐based donor‐acceptor‐type conjugated polymers via Pd‐catalyzed direct CH/CH coupling polymerization

AbstractFluorine substituted benzotriazole (BTz) units have shown great potential in improving various conjugated polymers (CPs)‐based optoelectronic devices' performance. Thus, it is highly expected for the establishment of simple, efficient, and inexpensive accesses to such polymers. In this paper, Pd‐catalyzed direct CH/CH coupling polymerization is first employed for the synthesis of 5,6‐difluorobenzotriazole containing π‐CPs, which fully avoids prefunctionalization of monomers. Under the optimized conditions, a series of donor‐acceptor‐type π‐CPs with excellent regio‐regularity are facilely obtained via the direct CH/CH coupling reaction of 5,6‐difluoro‐2‐(2‐hexyldecyl)‐2H‐BTz with different thiophene analogs. The chemical structure of the as‐synthesized polymers are confirmed by NMR technique including 1H NMR, 19F NMR, and the edited heteronuclear singular quantum correlation and heteronuclear multiple bond correlation spectra as well as comparative study on the same polymers obtained via Stille coupling and direct (hetero)arylation polymerization. Further, their optical properties, electrochemical properties, and thermal stabilities are also carefully explored by UV–Vis absorption spectra, cyclic voltammograms as well as thermogravimetric analysis, respectively. On the basis of density functional theory (DFT) simulation, the effect of alkyl substituents attached to thiophene units on the reactivity and optical performance of the resultant polymers is explained. Our protocol exhibits remarkable advantages in synthetic simplicity, atom‐economy, high efficiency, and excellent regioselectivity of cross‐coupling, providing an alternative synthetic strategy for high‐performance optoelectronic materials.

Alkyl-substituted bis(4-((9H-fluoren-9-ylidene)methyl)phenyl)thiophenes: weakening of intermolecular interactions and additive-assisted crystallization

Effect of alkyl substituents and an additive on crystallization and intermolecular interactions of bis(4-((9H-fluoren-9-ylidene)methyl)phenyl)thiophenes is revealed.

Achieving enhanced ML or RTP performance: alkyl substituent effect on the fine-tuning of molecular packing

By changing the substituted alkyl chain of PIth–C derivatives to well regulate the stacking angles of molecular dimers, and considering the efficient intermolecular interactions, their ML/RTP performance could be well tuned.

Identification of N-Nitrosamines and Nitrogenous Heterocyclic Byproducts during Chloramination of Aromatic Secondary Amine Precursors.

With diminishing pristine water, wastewater-affected waters that contain complex anthropogenic compounds are becoming important sources of drinking water and the compounds will inevitably react with disinfectants to form disinfection byproducts (DBPs). Secondary amines such as diphenylamine (DPA) analogues are considered as potential precursors of N-nitrosamines. In this study, an in situ 14N/15N-labeling and screening workflow was used to systematically investigate the formation of nitrogenous DBPs (N-DBPs) and putative reaction pathways. Twenty-four pairs of N-DBPs were generated and identified from chloramination of DPA through two main pathways, in which chloramines reacted with the amino and phenyl functional groups to form N-nitrosodiphenylamine and monochlorinated 5,10-dihydro-phenazine (Cl-DiH-Phe), respectively. Cl-DiH-Phe could further produce phenazine and the coupling products with another DPA molecule. Selective N-DBP formation was pH and dose-dependent, and the same reactions were observed for additional two aromatic DPA analogues. Effects of alkyl substituents on the formation pathways were investigated using a series of dialkyl and N-alkyl aromatic analogues. Only the amino pathway to form nitrosamines was noticed for dialkyl amines, nevertheless, both the main reactions occurred for N-alkyl aromatic amines. These findings suggested that the reaction with chloramines through a phenyl pathway was likely to be crucial for novel nitrogenous heterocyclic byproducts.

Effect of alkyl substituent on molecular configuration in a Cu(II) complex: Synthesis of Cu and CuO nanoparticles using a single, solid-source precursor

A new hydrazone-type ligand, methyl 4-(pyridine-4yl-methylene) hydrazinecarboxylate (C8H9N3O2; 4-pymc) and its Cu(II) complex [Cu(4-pymc)2(CH3COO)2(H2O)] (1) were prepared and characterized. The structure of 1 comprises monomers in which Cu is five-coordinated with a distorted square pyramidal structure. Oxygen atoms of two monodentate acetate anions and a pair of nitrogen atoms from pyridine rings form the basal plane. The apical position is filled by a water molecule. Further, the TEM images demonstrated successful preparation of both Cu (~35 nm) and CuO (~95 nm) nanoparticles (NPs) using the single source as-prepared Cu(II) complex via a thermal decomposition approach simply by changing the atmospheric conditions (i.e., vacuum and air atmospheres) under which the Cu(II) complex was calcined for 1 h at 400 °C. Furthermore, the TG-DTA studies indicate that 1 underwent endo- followed by exo-thermic decomposition to form CuO as the end residue in an air atmosphere. The production of Cu and CuO NPs was corroborated by powder x-ray diffraction (PXRD) analysis. The sharp and high intensity PXRD peaks of the calcined samples corroborated that the formed NPs had no impurity and high crystallinity. Furthermore, both ligand and Cu(II) complex showed photoluminescence properties. Also, we demonstrated that the prepared 1 can act as a single, solid-source precursor to form both Cu and CuO NPs.