Effect Of Regioisomerism Research Articles

Directional formation of microtubes by soft-template electropolymerization from fully conjugated triphenylamine-based monomers

Microtubular structures have been prepared by soft-template electropolymerization of conjugated organic monomers with the aim to mimic the strong water-adhesive forces of gecko foot or rose petals. Water-saturated solvent of low water solubility (dichloromethane) was used to form a micellar solution stabilized by tetrabutylammonium perchlorate as the electrolyte and the surfactant, in which case the formation of nanotubes was particularly efficient. The studied monomers were built from a triphenylamine core conjugated with three arms differing by their structure and positions: (i) 2- or 3-positions in the thiophene arms or (ii) carbazole arms attached to para, meta or ortho-positions of the benzene ring of the core. The formation of microtubes is due to preferential growth of polymer films and an aggregation of formed polymers/oligolymers in one direction (1D) facilitated by π–stacking interactions. The key factors influencing on the surface morphologies (monomer structures and reactivity, electrodeposition conditions, etc) are discussed. Impressive results have been obtained in studies of carbazole-containing monomers and the effect of regioisomerism in the monomers (the position of the carbazole attachment to the core). Extremely long microtubes (tens to >100 μm length, diameter ≈ 1.0–1.5 μm) were formed on the electrode surface from the monomer N-Ph-p-Cb with the carbazole attachment in the para-position. Wettability analysis showed highly hydrophobic surfaces with apparent contact angles up to 154.0° and extremely strong water adhesion comparable to rose petals or gecko feet. Such coatings can find applications in water-harvesting systems, sensing platforms or electrochemical analyses.

Efficient thermally activated delayed fluorescence emitters with regioisomeric effects for red/near-infrared organic light-emitting diodes

The regioisomeric effect of cyano substituents on the photoluminescence and electroluminescence properties of thermally activated delayed fluorescence molecules is studied.

Perylenediimide regioisomers with tunable physicochemical and charge-transport properties.

Two perylenediimide (PDI) regioisomers with the central core substituted at the ortho (Y-αPDI) and bay (Y-βPDI) areas of the PDIs were successfully prepared. The regioisomeric effects on the physicochemical and charge-transport properties were thoroughly investigated. The results unravel that Y-βPDI shows ambipolar transport with higher mobilities compared to its α-counterpart, which is due to its favourable molecular geometry, stronger intermolecular interaction and improved electron-withdrawing ability.

Regioisomeric effects of dibenzofuran on the properties of boron–nitrogen multiple resonance emissive materials

Regioisomeric effects have a profound impact on the OLED efficiency. DABNA-3-DBF demonstrated enhanced PLQY and a EQEmax of 25.9%, showcasing optimized conjugation for greater performance.

Vacuum-deposited petroporphyrins: Effect of regioisomerism on film morphology

Petroporphyrins are geochemical marker molecules that could provide evidence for the biogenic origin of crude oil. Despite the standing interest in their properties, the structure of the condensed phase has not received due attention so far. Here we report on the optical absorption, microscopic structure and molecular ordering in thin vacuum-deposited films of four closely related compounds of petroporphyrin family (transition metal etioporphyrins) that differ either position of peripheral substituents or by the central metal atom. It is shown that even such minor alteration in the molecular architecture as regioisomerism results in remarkable distinctions in film morphology. The observed structural features can potentially be useful in organic electronics applications.

Enhancing Photovoltaic Performances of Naphthalene‐Based Unfused‐Ring Electron Acceptors upon Regioisomerization

Isomeric effects play a crucial role in regulating electronic properties, molecular packing, and device performance of organic semiconductors. Herein, a series of unfused‐ring electron acceptor (UREA) regioisomers (NOF‐1, NOF‐2, and NOF‐3), which are constructed using 2,6‐α‐, 1,5‐β‐, and 3,7‐β‐type naphthalene cores, are successfully synthesized and characterized. The regioisomeric effects on geometries, photophysics, electrical properties, molecular packing behaviors, charge transport properties, blend film morphologies, and photovoltaic performance are systematically studied. As a result, the PBDB‐T:NOF‐3‐based device delivers a power conversion efficiency (PCE) of 11.58% due to its more balanced charge mobility, efficient exciton dissociation, less charge recombination, and favorable film morphology. These findings encourage further attention to the regioisomeric effects to design high‐performance UREAs.

Effect of Regioisomerism on Processability and Mechanical Properties of Amine/Urea Exchange Based Poly(urea-urethane) Vitrimers

In this paper, three analogous poly(urea-urethane) elastomers were thoroughly characterized to determine the effect of regioisomerism on the processability and mechanical properties of the final ma...

Effect of regioisomerism on the self-assembly, photophysical and gelation behavior of aroylhydrazone based polycatenars: Synthesis and characterization

In this paper we report five series of aroylhydrazone based polycatenars differing from each other in number and position of alkoxy chains on one end of the core; keeping other end the same. A systematic variation in the structures was carried out to understand the effect of position and chain length on the mesophase behavior. In the case of single alkoxy chain at 4-position, there is a transition from Smectic C to Smectic A mesophase during cooling and Smectic A to Smectic C transition in heating cycle in all the homologues except n = 6 & n = 8. In the case of two alkoxy chains at 3-, 5-positions, the compounds are non-mesogenic in nature. On changing the position of alkoxy chains from 3-, 5-positions to 3-, 4-positions, intermolecular forces weaken and these compounds become liquid crystalline and show columnar rectangular mesophase resulting from the effect of regioisomerism. Moving on to the series with three alkoxy chains, it was observed that 2-, 3-, 4-trialkoxy substituted compounds exhibit columnar rectangular mesophase except lower chain length (n = 6 & 8) while 3-, 4-, 5-trialkoxy substituted aroylhydrazones show columnar rectangular mesophase; except n = 10 which shows columnar oblique mesophase. Thus it was established that on increasing density of alkoxy chains around one terminal, mesophase changes from smectic to columnar mesophase. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding. Further, effect of substitution pattern did not show much influence on the photophysical properties of the mesogenic series in solid and solution state. However, the non-mesogenic series showed a different absorption and emission transition from the mesogenic series in solid and solution state. Solid state fluorescence studies show almost similar emission maxima in all the series. However, it was also noticed that non-mesogenic series show maximum red shifted emission maxima in solid state as compared to that of solution. All the series showed good gelation properties with less than 1% CGC (wt%) suggesting the strong ability of molecules to form gel. These H-bonded liquid-crystalline gels have immense potential for applications in emissive displays.

Examining the effect of regioisomerism on the physico-chemical properties of lysophosphatidylethanolamine-containing liposomes using fluoro probes

Lysophospholipids (LysoPLs) receive steadily increasing attention in the area of lipid chemistry and biology. However, the physico-chemical properties of individual LysoPL regioisomers have not yet been investigated. Herein, we report the synthesis of fluoro analogues of lysophosphatidylethanolamines (LPEs) and examine the physico-chemical properties of the LPE regioisomers using chemically synthesized fluoro probes.

Effect of Regioisomerism on the Efficiency of 1-Phenylpyrrole-Type Atropisomeric Amino Alcohol Ligands in Enantioselective Organometallic Reactions

Syntheses of two regioisomeric series of atropisomeric amino alcohols and a comparative study on their application in the enantio­selective addition of diethylzinc to benzaldehyde are reported. Systematic modification of the electronic and steric properties of the functional groups resulted in highly efficient catalyst ligands in both series. Quantum-chemical calculations agreed well with the experimental results of this first systematic comparative study on regioisomeric ­atropisomeric ligands.

The effect of regioisomerism on the photophysical properties of alkylated-naphthalene liquids.

Novel regioisomeric alkylated-naphthalene liquids were designed and synthesized. In the solvent-free liquid state, 1-alkyloxy regioisomers showed excimeric luminescence, whereas 2-alkyloxy analogues exhibited monomer-rich luminescence features. Correlations among the molecular structures and the photophysical, calorimetric, and rheological properties are presented, demonstrating the impact of regioisomerism on the alkylated-chromophore liquid systems.

Regio-isomeric effects in tandem mass spectra of sulfonium cations generated from thiacyclane based sulfonium salts under soft ionization conditions.

The influence of regio-isomerism of even-electron sulfonium ions on tandem electrospray and matrix-assisted laser desorption/ionization mass spectra recorded by using collision-induced dissociation was investigated. The initial organic sulfides belonged to isomeric thiabicyclane series (substituted 7- and 8-thiabicyclo[4.3.0]nonanes, 2- and 3-thiabicyclo[4.4.0]decanes) and phenylthiolanes. To investigate by the abovementioned mass spectrometry methods, the sulfides were preliminary S-alkylated by methyl, ethyl iodides, their deuterated analogs and trialkoxonium tetrafluoroborates to form corresponding sulfonium salts. The latter salts readily gave off corresponding sulfonium cations under abovementioned desorption/ionization conditions and these cations were precursor ions in collision-induced dissociation experiments. The main quantitative and frequently qualitative differences between collision-induced dissociation spectra of isomers were manifested in mass numbers and relative intensities of the ions Alk-S+ = CHR (formal structure) that originated from the destruction of sulfur-containing ring. Corresponding peaks are particularly abundant for cations Alk-S+ = CH2 and their intensities are usually greater than for other C-substituted homologues. Qualitative difference between fragmentation features of 2- and 3-phenylthiolanium cations is that only the latter can eliminate neutral C2H4S molecule.

The effect of regioisomerism on the mesomorphic and photophysical behavior of oxadiazole-based tris(N-salicylideneaniline)s: synthesis and characterization

Two new regioisomeric star-shaped tris(N-salicylideneaniline)s are synthesized and characterized.

Regioisomeric Effects of Donor-Acceptor-Acceptor' Small-Molecule Donors on the Open Circuit Voltage of Organic Photovoltaics.

Donor-acceptor-acceptor' small-molecule donors are synthesized to investigate regioisomeric effects on organic photovoltaic device performance. Cross-conjugation in 2-((7-(N-(2-ethylhexyl)-benzothieno[3,2-b]thieno[3,2-d]pyrrol-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)methylene)malononitrile leads to an increased open-circuit voltage compared with its isomer 2-((7-(N-(2-ethylhexyl)-benzothieno[3,2-b]thieno[2,3-d]pyrrol-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)methylene)malononitrile. A correlation is then established between molecular conjugation length and orbital energies, and hence open-circuit voltage.

Effect of regioisomerism on the self-assembly and photophysical behavior of 1,3,4-thiadiazole-based polycatenars

The effects of regioisomerism on the self-assembly and luminescence of polycatenars have been investigated.

The effect of regioisomerism on the crystal packing and device performance of desymmetrized anthradithiophenes

Chromatographic separation of asymmetric anthradithiophene isomers allows determination of the impact of sulfur orientation on crystal packing and device performance.

The effect of regioisomerism on the solid-state fluorescence of bis(piperidyl)anthracenes: structurally simple but bright AIE luminogens

Bis(piperidyl)anthracenes were developed as structurally simple, bright and colour tuneable AIE luminogens and their emission mechanisms were analysed.

Regioisomeric effects on the electronic features of indenothiophene-bridged D-π-A'-A DSSC sensitizers.

Two D-π-A'-A regioisomers (A-IDT-D and D-IDT-A) featuring 4,4'-di-p-tolyl-4 H-indeno[1,2-b]-thiophene as a π linker (π) between the diarylamino donor (D) and the pyrimidine-cyanoacrylic acid acceptor (A'-A) have been successfully synthesized and characterized as efficient sensitizers for the dye-sensitized solar cells (DSSCs). The different arrangements of the D and A'-A blocks on the unsymmetrical indenothiophene (IDT) core render the dipole of IDT being along (A-IDT-D) or opposite (D-IDT-A) to the direction of intramolecular (donor-to-acceptor) charge transfer, and thus induce variations in the physical properties. The experimental observations correlated well with the theoretical analyses, clearly revealing the trade-off between the molar extinction coefficient (ε) and the S0 →S1 transition energy. As a result, a superior ε value was observed for D-IDT-A, whereas a bathochromic shift in the absorption occurred in A-IDT-D. The larger ε value of D-IDT-A together with its more favorable energy level relative to TiO2 led to a higher power conversion efficiency of 7.41 % for the D-IDT-A-based DSSC, retaining approximately 95 % of the N719-based DSSC efficiency. This work manifests the clear structure-property relationship for the case of donor and acceptor components being connected by an unsymmetrical π linker and provides insights for molecular engineering of organic sensitizers.

Effect of Regioisomerism on the Local Dynamics of Polychlorostyrene

Relaxation properties of three isomers of atactic polychlorostyrene, having the chlorine atom in the ortho, meta, and para positions (P2CS, P3CS, and P4CS, respectively), were measured by mechanical and dielectric spectroscopies and modulated scanning calorimetry. For the α relaxation, the more spatially extended pendant group in P4CS gives rise to steric constraints on the segmental dynamics that cause both the temperature dependence of its relaxation time (i.e., the fragility) and the number of dynamically correlated segments to be largest. For the secondary β-relaxation in P4CS, the chlorophenyl moiety can rotate (spin) without involving the backbone; that is, the motion involves internal degrees of freedom. Consequently, this secondary relaxation is high in frequency and has a weak relaxation strength, especially as measured dielectrically. On the other hand, the pendant group in P2CS cannot reorient without adjustments in position of the backbone segments, causing its β relaxation strength measured m...

Photochemically generated cyclopentane-1,3-diyl triplet diradicals as model systems for the assessment of spin delocalization in heteroaryl-substituted benzyl-type monoradicals through the EPR spectral D parameter

The zero-field D parameters of a comprehensive set of cyclopentane-1,3-diyl triplet diradicals 2 were determined at 77 K in a 2-MTHF glass matrix. The D values were found to be dependent on the heteroaryl substituents in the decreasing order 3-furyl 3-thienyl > 4-pyridyl ≈ 3-N-oxypyridyl > 2-pyridyl ≈ 3-pyridylium > 3-pyridyl ≈ phenyl 2-pyridylium 4-pyridylium 2-furyl 2-thienyl 4-N-oxypyridyl. Good linear correlations were obtained with the reported aα coupling constants (r2 = 0.953) for the benzyl monoradicals 4 and with the semiempirically calculated (PM3) α spin densities (r2 = 0.928) for the cumyl monoradicals 3. To rationalize the observed electronic effects, for convenience the ΔDAr scale was defined as a measure of the spin-delocalizing ability of the different heteroaryl substituents relative to the phenyl group as reference. The hitherto unknown electronic effects of N-oxidation and protonation for the different pyridyl regioisomers as well as the regioisomeric effects of the furyl and thienyl substituents, are experimentally reflected accurately by the changes in the D parameter of the triplet diradicals 2 and explained theoretically with the help of MO calculations for the corresponding monoradicals 3.