Introduction Of Methyl Group Research Articles

Effect of methyl substituent in the fjord region on the conformational stability of aza[5]helicenes

Few derivatives of aza[5]helicenes were synthesized and characterized. Introduction of methyl group in the fjord region of aza[5]helicene gives sufficient conformational rigidity resulting in the formation of stable, resolvable enantiomers. The analysis of dimethyl aza[5]helicene on chiral HPLC columns indicate the presence of resolvable isomers. The compounds 1 and 15were further characterized by single crystal X-ray diffraction and computational analysis while their photophycial properties were studied.

Acridinium Ester Chemiluminescence: Methyl Substitution on the Acridine Moiety.

Methyl groups were introduced on the acridine moiety in chemiluminescent acridinium esters that have electron-withdrawing groups (trifluoromethyl, cyano, nitro, ethoxycarbonyl) at the 4-position on the phenyl ester. The introduction of methyl groups at the 2-, 2,7-, and 2,3,6,7-positions on the acridine moiety shifted the optimal pH that gave relatively strong chemiluminescence intensity from neutral conditions to alkaline conditions. 4-(Ethoxycarbonyl)phenyl 2,3,6,7,10-pentamethyl-10λ4-acridine-9-carboxylate, trifluoromethanesulfonate salt showed long-lasting chemiluminescence under alkaline conditions. Acridinium esters to determine hydrogen peroxide concentration at pH 7-10 were newly developed.

Preventing isomerization of the fused-ring core by introducing a methyl group for efficient non-fullerene acceptors

Two FREAs were synthesized and applied in organic solar cells. The OSC devices based on BTMe-C8-2F exhibited a PCE of 12.72%. The high-yield FREAs were achieved by introducing methyl groups to prevent the isomerization of the fused ring core.

Study on the properties of density, viscosity, excess molar volume, and viscosity deviation of [C2mim][NTf2], [C2mmim][NTf2], [C4mim][NTf2], and [C4mmim][NTf2] with PC binary mixtures

The imidazolium type ionic liquids (ILs) 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ([C2mim][NTf2] and [C4mim][NTf2]) were synthesized. For comparing, the ILs with introduction of methyl group 1-alkyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mmim][NTf2] and [C4mmim][NTf2]) were also prepared. The density and viscosity of the systems composed of above ILs and propylene carbonate (PC) were determined. The determined uncertainties are u(ρ) = 0.00010 g·cm−3 for density and ur(η) = 0.02 for viscosity, respectively. The excess molar volumes, thermal expansion coefficients, viscosity deviations, and a-constant were calculated. According to Redlich−Kister equation, the relationship between excess molar volume, viscosity deviation and mole fraction was fitted. By comparing with the systems of the same ILs in other organic solvents, the above-mentioned properties were discussed and the influence of introduced methylene group and methyl group on the above properties was analyzed.

Structure and mechanism of a dehydratase/decarboxylase enzyme couple involved in polyketide \u03b2-methyl branch incorporation

Complex polyketides of bacterial origin are biosynthesised by giant assembly-line like megaenzymes of the type 1 modular polyketide synthase (PKS) class. The trans-AT family of modular PKSs, whose biosynthetic frameworks diverge significantly from those of the archetypal cis-AT type systems represent a new paradigm in natural product enzymology. One of the most distinctive enzymatic features common to trans-AT PKSs is their ability to introduce methyl groups at positions β to the thiol ester in the growing polyketide chain. This activity is achieved through the action of a five protein HCS cassette, comprising a ketosynthase, a 3-hydroxy-3-methylglutaryl-CoA synthase, a dehydratase, a decarboxylase and a dedicated acyl carrier protein. Here we report a molecular level description, achieved using a combination of X-ray crystallography, in vitro enzyme assays and site-directed mutagenesis, of the bacillaene synthase dehydratase/decarboxylase enzyme couple PksH/PksI, responsible for the final two steps in β-methyl branch installation in this trans-AT PKS. Our work provides detailed mechanistic insight into this biosynthetic peculiarity and establishes a molecular framework for HCS cassette enzyme exploitation and manipulation, which has future potential value in guiding efforts in the targeted synthesis of functionally optimised ‘non-natural’ natural products.

Unveiling the unconventional roles of methyl number on the ring-opening barrier in photocatalytic decomposition of benzene, toluene and o-xylene

The ring-opening reaction is the rate-determining step for photocatalytic decomposition of aromatic VOCs with different methyl number. However, as a key challenge, the intrinsic relationship between the methyl number and ring-opening reaction efficiency has not been revealed. In order to clarify the ring-opening barriers and enhance the photocatalytic efficiency, the photocatalytic degradation pathway was systematically investigated aiming to elucidate the pivotal roles of methyl number on ring-opening mechanisms. The SnO2 is chosen as a photocatalyst to achieve highly efficient and stable photocatalytic degradation of benzene, toluene, and o-xylene respectively. It is unexpected to discover that the photocatalytic degradation performance and quantum efficiency are significantly elevated along with the increase of methyl number, reaching the highest efficiency for o-xylene with two methyl groups. The photocatalytic degradation efficiency of o-xylene on SnO2 is as high as 78.2 %, much higher than that of toluene (63.4 %) and benzene (55.9 %). The introduction of methyl groups could exert great influence on the distribution of electrons on the phenyl ring, enhance the adsorption and activation of benzene rings, and finally reduce the energy barrier of ring-opening reaction. The methyl number in the benzene ring is dominantly responsible for the elevated decomposition efficiency. This work proposes a new concept in mechanistic understanding of VOCs decomposition and propels the application of photocatalytic technology for efficient degradation of aromatic VOCs.

Synthetic dosage lethal (SDL) interaction data of Hmt1 arginine methyltransferase.

The introduction of methyl groups on arginine residues is catalysed by Protein Arginine Methyltransferases (PRMTs). However, the regulatory mechanisms that dictate the levels of protein arginine methylation within cells are still not completely understood. We employed Synthetic Dosage Lethality (SDL) screening in Saccharomyces cerevisiae, for the identification of putative regulators of arginine methylation mediated by Hmt1 (HnRNP methyltransferase 1), ortholog of human PRMT1. We developed an SDL array of 4548 yeast strains in which each strain contained a single non-essential gene deletion, in combination with a galactose-inducible construct overexpressing wild-type (WT) Hmt1-HZ tagged protein. We identified 129 consistent SDL interactions for WT Hmt1-HZ which represented genes whose deletion displayed significant growth reduction when combined with WT Hmt1 overexpression. To identify among the SDL interactions those that were dependent on the methyltransferase activity of Hmt1, SDL screens were repeated using an array overexpressing a catalytically inactive Hmt1(G68R)-HZ protein. Furthermore, an additional SDL control screen was performed using an array overexpressing only the protein tag HZ (His6—HA-ZZ) to eliminate false-positive SDL interactions. This analysis has led to a dataset of 50 high-confidence SDL interactions of WT Hmt1 which enrich eight Gene Ontology biological process terms. This dataset can be further exploited in biochemical and functional studies to illuminate which of the SDL interactors of Hmt1 correspond to factors implicated in the regulation of Hmt1-mediated arginine methylation and reveal the underlying molecular mechanisms.

Methyl-Shield Cu-BTC with High Water Stability through One-Step Synthesis and In Situ Functionalization

Cu-BTC is a copper paddlewheel-based metal–organic framework (MOF) with great potential in gas adsorption and heterogeneous catalysis but has restricted practical applications because of its poor water stability. In this work, we propose a strategy for one-step synthesis and in situ functionalization of isopropanol (IPA)-modified Cu-BTC (Cu-BTC-IPA) with enhanced water stability. Successful incorporation of IPA into Cu-BTC was evidenced by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy spectra. The introduction of methyl groups around unsaturated Cu sites can form a methyl-shielding microenvironment, endowing Cu-BTC-IPA with the ability to maintain the topology structure after being immersed in water even for 4 days. After soaking, Cu-BTC-IPA can preserve 95% of its original Brunauer–Emmett–Teller (BET) surface areas and 90% of its initial CO2 adsorption capacity, while Cu-BTC completely lost its crystallinity. In addition, Cu-BTC-IPA managed to preserve its main crystal structure and 83% of its initial BET surface areas after 12 h of immersion in diluted HCl solution (pH = 3). The improved hydrolysis stability mechanism of Cu-BTC-IPA was investigated using density functional theory calculations. The results suggest that the strategy of incorporating IPA into Cu-BTC is very efficient in enhancing its structure stability against water and worthy of further exploitation in improving the structure stability of other MOFs with open metal sites.

Effect of Ligand Fields on the Reactivity of O2‐Activating Iron(II)‐Benzilate Complexes of Neutral N5 Donor Ligands

Three new iron(II)-benzilate complexes [(N4Py)Fe II (benzilate)]ClO 4 ( 1 ), [(N4Py Me2 )Fe II (benzilate)]ClO 4 ( 2 ) and [(N4Py Me4 )Fe II (benzilate)]ClO 4 ( 3 ) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single crystal X-ray structures reveal a mononuclear six-coordinate iron(II) centre in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4Py Me2 and N4Py Me4 ligands weaker field compared to the parent N4Py ligand. All the complexes ( 1-3 ) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation takes lesser time for the complex of more sterically hindered ligand and follows the order 3 > 2 > 1 . The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C-H bonds. Based on interception studies with external substrates, labelling experiment and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.

Hybrid mesoporous aluminosilicate catalysts obtained by non-hydrolytic sol–gel for ethanol dehydration

Introduction of methyl groups into the highly porous aluminosilicates prepared by non-hydrolytic sol–gel improves the ethylene yields in ethanol dehydration.

Surprising Non-Additivity of Methyl Groups in Drug-Kinase Interaction.

Drug optimization is guided by biophysical methods with increasing popularity. In the context of lead structure modifications, the introduction of methyl groups is a simple but potentially powerful approach. Hence, it is crucial to systematically investigate the influence of ligand methylation on biophysical characteristics such as thermodynamics. Here, we investigate the influence of ligand methylation in different positions and combinations on the drug-kinase interaction. Binding modes and complex structures were analyzed using protein crystallography. Thermodynamic signatures were measured via isothermal titration calorimetry (ITC). An extensive computational analysis supported the understanding of the underlying mechanisms. We found that not only position but also stereochemistry of the methyl group has an influence on binding potency as well as the thermodynamic signature of ligand binding to the protein. Strikingly, the combination of single methyl groups does not lead to additive effects. In our case, the merger of two methyl groups in one ligand leads to an entirely new alternative ligand binding mode in the protein ligand complex. Moreover, the combination of the two methyl groups also resulted in a nonadditive thermodynamic profile of ligand binding. Molecular dynamics (MD) simulations revealed distinguished characteristic motions of the ligands in solution explaining the pronounced thermodynamic changes. The unexpected drastic change in protein ligand interaction highlights the importance of crystallographic control even for minor modifications such as the introduction of a methyl group. For an in-depth understanding of ligand binding behavior, MD simulations have shown to be a powerful tool.

The present state of studies on attractive and amphiphilic multi-functional methylated β-cyclodextrins and their purity measurements

β-Cyclodextrins (β-CD) are widely used in multiple fields such as medicine, agriculture, alimentation, and cosmetics because their hydrophobic cavity enables the formation of inclusion complexes with various organic compounds to improve their performances. There are three types of methylated β-CDs (M-β-CDs) on the market, prepared by the introduction of methyl groups on various sites: 2,3,6-tri-O-methyl-β-CD (TM-β-CD), 2,6-di-O-methyl-β-CD (DM-β-CD), and randomly methyl-β-CD (RM-β-CD). M-β-CDs are now used in medical as well as non-medical systems due to their significant water solubility compared to β-CD and unique amphiphilic property in water and organic solvents despite the possibility of tissue damage from nephrotoxicity. It is important to investigate the degree of substitution of M-β-CDs by methyl groups for further applications in a wide range of fields. Studies investigating the substitution degree of M-β-CDs have been carried out for many years. The aim of this study is to analyze the tendency of substitution number of methyl group in RM-β-CD, as a simpler analysis method. First, we analyzed RM-β-CD with simple methods such as hydrophilic interaction chromatography (HILIC) using a refractive index detector (RID) that is widely used for the high performance liquid chromatography (HPLC) analysis of sugars. After separation, liquid chromatography/electrospray ionization mass spectrometry and fast atom bombardment mass spectrometry measurements were carried out on each fraction. In addition, TM-β-CD and DM-β-CD were also analyzed by reverse phase-HPLC with ODS column.

The influence of the cation type of ionic liquid on the production of nanocrystalline cellulose and mechanical properties of chitosan-based biocomposites

In this paper three newly synthesized imidazolium ionic liquids with different structures of cations were used for hydrolysis of cellulose. It was found that type of the cation has a great influence on particle size and dispersity of produced cellulosic materials. The use of an ionic liquid with a cation with an aliphatic substituent resulted in filler characterized with wide dispersity range and some particles larger than 2 µm. Introduction of methyl group into imidazolium ring was responsible for production of particles below 350 nm. Such particles were obtained also during hydrolysis of cellulose with ionic liquid containing a benzyl substituent with that difference that in this case particles had definitely narrower dispersity range. Moreover, type of the ionic liquid used affected crystallinity degree of the produced celluloses. Produced cellulosic materials were used as fillers for chitosan matrix. A relationship between mechanical properties of polymer composites and the particle size as well as dispersity of cellulose, controlled by chemical modifications of cellulose with innovative ionic liquids was evaluated. Incorporation of filler with established dispersive properties made it possible to form composites characterized by the assumed properties, for example with high values of Young’s modulus, tensile strength or elongation at break. Understanding the dependence between the structure of ionic liquids and dispersive properties of cellulose is an important step toward the design of composite materials with optimal mechanical properties.Graphical abstract

Dioxygen/Hydrogen Peroxide Interconversion Using Redox Couples of Saddle-Distorted Porphyrins and Isophlorins.

Interconversion between dioxygen (O2) and hydrogen peroxide (H2O2) has attracted much interest because of the growing importance of H2O2 as an energy source. There are many reports on O2 conversions to H2O2; however, no example has been reported on O2/H2O2 interconversion. Herein, we describe successful achievement of a reversible O2/H2O2 conversion based on an N21, N23-dimethylated saddle-distorted porphyrin and the corresponding two-electron-reduced porphyrin (isophlorin) for the first time. The isophlorin could react with O2 to afford the corresponding porphyrin and H2O2; conversely, the porphyrin also reacted with excess H2O2 to reproduce the corresponding isophlorin and O2. The isophlorin-O2/porphyrin-H2O2 interconversion was repeatedly proceeded by alternate bubbling of Ar or O2, although no reversible conversion was observed in the case of an N21, N22-dimethylated porphyrin as a structural isomer. Such a drastic change of the reversibility was derived from the directions of inner N H protons in hydrogen-bond formation of the isophlorin core with O2 as well as those of the lone pairs of the inner nitrogen atoms of the porphyrin core to form hydrogen bonds with H2O2. The intriguing isophlorin-O2/porphyrin-H2O2 interconversion was accomplished by introducing methyl groups at the inner nitrogen atoms to minimize the difference of the Gibbs free energy between isophlorin-O2/porphyrin-H2O2 states and the Gibbs activation energy of the interconversion. On the basis of the kinetic and thermodynamic analysis on the isophlorin-O2/porphyrin-H2O2 interconversion using 1H NMR and UV-vis spectroscopies and DFT calculations, we propose the formation of a two-point hydrogen-bonding adduct between the N21, N23-dimethylated porphyrin and H2O2 as an intermediate.

A Mononuclear Nonheme Iron(IV)-Oxo Complex of a Substituted N4Py Ligand: Effect of Ligand Field on Oxygen Atom Transfer and C-H Bond Cleavage Reactivity.

A mononuclear iron(II) complex [FeII(N4PyMe2)(OTf)](OTf)(1), supported by a new pentadentate ligand, bis(6-methylpyridin-2-yl)- N, N-bis((pyridin-2-yl)methyl)methanamine (N4PyMe2), has been isolated and characterized. Introduction of methyl groups in the 6-position of two pyridine rings makes the N4PyMe2 a weaker field ligand compared to the parent N4Py ligand. Complex 1 is high-spin in the solid state and converts to [FeII(N4PyMe2)(CH3CN)](OTf)2 (1a) in acetonitrile solution. The iron(II) complex in acetonitrile displays temperature-dependent spin-crossover behavior over a wide range of temperature. In its reaction with m-CPBA or oxone in acetonitrile at -10 °C, the iron(II) complex converts to an iron(IV)-oxo species, [FeIV(O)(N4PyMe2)]2+ (2). Complex 2 exhibits the Mössbauer parameters δ = 0.05 mm/s and Δ EQ = 0.62 mm/s, typical of N-ligated S = 1 iron(IV)-oxo species. The iron(IV)-oxo complex has a half-life of only 14 min at 25 °C and is reactive toward oxygen-atom-transfer and hydrogen-atom-transfer (HAT) reactions. Compared to the parent complex [FeIV(O)(N4Py)]2+, 2 is more reactive in oxidizing thioanisole and oxygenates the C-H bonds of aliphatic substrates including that of cyclohexane. The enhanced reactivity of 2 toward cyclohexane results from the involvement of the S = 2 transition state in the HAT pathway and a lower triplet-quintet splitting compared to [FeIV(O)(N4Py)]2+, as supported by DFT calculations. The second-order rate constants for HAT by 2 is well correlated with the C-H bond dissociation energies of aliphatic substrates. Surprisingly, the slope of this correlation is different from that of [FeIV(O)(N4Py)]2+, and 2 is more reactive only in the case of strong C-H bonds (>86 kcal/mol), but less reactive in the case of weaker C-H bonds. Using oxone as the oxidant, the iron(II) complex displays catalytic oxidations of substrates with low activity but with good selectivity.

Method for Quantification of Ribonucleotides and Deoxyribonucleotides in Human Cells Using (Trimethylsilyl)diazomethane Derivatization Followed by Liquid Chromatography-Tandem Mass Spectrometry.

Investigation into intracellular ribonucleotides (RNs) and deoxyribonucleotides (dRNs) is important for studies of the mechanism of many biological processes, such as RNA and DNA synthesis and DNA repair, as well as metabolic and therapeutic efficacy of nucleoside analogues. However, current methods are still unsatisfactory for determination of nucleotides in complex matrixes. Here we describe a novel method for the determination of RN and dRN pools in cells based on fast derivatization with (trimethylsilyl)diazomethane (TMSD) followed by quantification using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Derivatization was accomplished in 3 min, and each derivatized nucleotide not only had a sufficient retention on reversed-phase column by introduction of methyl groups but also exhibited a unique ion transition which consequently eliminated mutual interference in LC-MS/MS. Chromatographic separation was performed on a C18 column with a simple acetonitrile-water gradient elution system, which avoided contamination and ion suppression caused by ion-pairing reagents. The developed method was fully validated and applied to the analysis of RNs and dRNs in cell samples. Moreover, results demonstrated that the applicability of this method could be extended to nucleoside analogues and their metabolites and could facilitate many applications in future studies.

Manipulating phosphorescence efficiencies of orange iridium(III) complexes through ancillary ligand control

Two novel orange-emitting iridium (III) complexes (nbi)2Ir (bisq) (1) and (nbi)2Ir (dmbisq) (2) utilizing 2-naphthalen-1-yl-phenyl-1H-benzimidazole as cyclometalated ligands were successfully synthesized and characterized. The effect of substituent groups in the ancillary ligands on their emission properties was systematically investigated. The experimental results indicate that complex 2 modified by introduction of methyl groups into its ancillary ligand exhibited higher photoluminescence and electroluminescence efficiencies than 1 without methyl groups. Such improved emission efficiencies were tentatively attributed to the suppressed intermolecular interactions in the solid state caused by the introduction of the methyl groups. Although the obtained efficiencies herein are not high, this work enlightens us to manipulate the photoluminescence and electroluminescence properties of iridium (III) complexes via reasonable modification in the ancillary ligand.

Factors Affecting Dehydrogenation and Catalytic Activity: Methyl Substituent

Metallocene compound is supported on methylaluminoxane (MAO) and the carrier to form the metallocene catalyst, where (n-BuCp)2ZrCl2 and (1,3-Me,n-BuCp)2ZrCl2 are two typical representatives of the metallocene compounds. The difference in the performances of the two compounds (n-BuCp)2ZrCl2 and (1,3-Me,n-BuCp)2ZrCl2 was calculated by DFT. The introduction of methyl groups led to an increase in the number of Mulliken charge and a decrease in the dipole distance. The results fully confirmed that the methyl group showed an electron-donating effect. The catalyst formed by the metallocene compound (n-BuCp)2ZrCl2 in the olefin polymerization process followed the a-agostic mechanism of ground state and transition state, and dehydrogenation occurred during the polymerization process. In contrast, the catalyst formed by the metallocene compound (1,3-Me,n-BuCp)2ZrCl2 in the olefin polymerization process was based on the Green–Rooney mechanism (hydrogen anion migration), and metal–hydrogen bond and small molecule alkane were formed during the polymerization reaction. However, there were some differences in the mechanism of the homopolymerization and copolymerization when using metallocene catalysts for ethylene polymerization. Ethylene/1-alkene reacted to produce copolymers containing unsaturated bonds, and the results were confirmed by FT-IR analysis. The significant effect of the ligand structure on the metallocene catalyst is beyond imagination, which will lead us to find a suitable ligand structure to meet the high catalytic activity and low hydrogen evolution.

A novel role of metal response element binding transcription factor 2 at the Hox gene cluster in the regulation of H3K27me3 by polycomb repressive complex 2.

Polycomb repressive complex 2 (PRC2) is known to play an important role in the regulation of early embryonic development, differentiation, and cellular proliferation by introducing methyl groups onto lysine 27 of histone H3 (H3K27me3). PRC2 is tightly associated with silencing of Hox gene clusters and their sequential activation, leading to normal development and differentiation. To investigate epigenetic changes induced by PRC2 during differentiation, deposition of PRC2 components and levels of H3K27me3 were extensively examined using mouse F9 cells as a model system. Contrary to positive correlation between PRC2 deposition and H3K27me3 level, down-regulation of PRC2 components by shRNA and inhibition of EZH1/2 resulted in unexpected elevation of H3K27me3 level at the Hox gene cluster despite its global decrease. We found that metal response element binding transcriptional factor 2 (MTF2), one of sub-stoichiometric components of PRC2, was stably bound to Hox genes. Its binding capability was dependent on other core PRC2 components. A high level of H3K27me3 at Hox genes in Suz12-knock out cells was reversed by knockdown of Mtf2.This shows that MTF2 is necessary to consolidate PRC2-mediated histone methylation. Taken together, our results indicate that expression of Hox gene clusters during differentiation is strictly modulated by the activity of PRC2 secured by MTF2.

Effect of methyl substitution on the diketopyrrolopyrrole-based semiconducting polymers for organic thin film transistors

Abstract Two semiconducting polymers, poly[2,5-bis(5-octylpentadecyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-selenophene] (PDPP-Se) and poly[3,6-bis(4-methylthiophen-2-yl)-2,5-bis(5-octylpentadecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-selenophene] (PMDPP-Se) were designed and synthesized. These polymers contain diketopyrrolopyrrole (DPP) and methyl-substituted DPP (MDPP) units as the acceptor building blocks, and selenophene as a counter donor unit. The introduction of methyl groups on the thiophene units flanked by the DPP core substantially affected its optical, electrochemical, and charge-transporting properties. Experimental results revealed that the introduction of electron-donating methyl groups raised the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PMDPP-Se. Interestingly, the PMDPP-Se showed better co-planarity with the adjacent aromatic groups compared to PDPP-Se. Furthermore, the methyl-substituted polymer showed a transition behavior in its thin film morphology and crystal orientation with an increase in the annealing temperature, which induced an M-shape dependence of the field-effect mobility on the annealing temperature. PMDPP-Se recorded a maximum hole mobility μh = 1.31 cm2 V−1 s−1 at optimum phase, which is higher than that of PDPP-Se (μh = 0.86 cm2 V−1 s−1).