Systematic Structure Property Research Articles

Pot- and atom-economic synthesis of oligomeric non-fullerene acceptors via C–H direct arylation

Three long-chain oligomeric acceptors with a stepwise increase in conjugation length are obtained via three successive one-pot reactions and a systematic structure–property–performance relationship study was carried out.

Influence of substituents of Perylenebisimides on the surface energy and wettability: A systematic structure–property relationship analysis

This paper seeks to elucidate the influence on the surface wettability of a variety of substituents located in different positions of the perylene bisimide (PBI) core (ortho versus imide) with distinct electron-donor or -withdrawing character and diverse steric demand, using for this more than 20 planar PBIs. The correlation between the polarity of the individual functional group on the PBI and the surface wettability has been addressed by means of substituent descriptors in terms of Hansch-Fujita π parameter, Hammett σmeta and σpara constants, and steric parameters (Taft-Dubois Es' and Charton υ). With these parameters, a quantitative structure–property relationship (QSPR) analysis has been performed using multivariable linear regression (MLR) fittings. The relationship of Surface Energy, determined by the static contact angle method with three different solvents, to structural properties of PBIs is described. As well, the polar and dispersive contributions have been determined. For planar PBIs, a predominant influence of the substituents in the imide position on the surface wettability has been found despite of the electronic nature and steric hindrance of the substituents simultaneously located in ortho positions. This effect is more pronounced with the longer alkyl substituents at the imide position. This study paves the way for a rational chromophore design considering the on surface behavior, which will ultimately condition the contact and thus their performance in optoelectronic devices.

Highly Breathable Chemically Protective MOF‐Fiber Catalysts

AbstractFibrous composite materials provide distinct advantages in large surface area and enhanced molecular transport through the media, lending themselves to diverse applications. Despite substantial development in synthetic methods, it is still lacking in insights into structure–property relationships that can correlate features of the functional materials to absorptive, transport, and catalytic performance of the composites. Herein, for the first time, a systematic structure–property–function analysis is provided for Zr‐based metal–organic frameworks (MOFs) coated onto polypropylene nonwoven textiles. MOF fraction on the fabric and defect density in MOF microstructures are controlled by an in situ seeded growth, where fiber surfaces are pretreated with metal‐oxide by atomic layer deposition. The best performing MOF‐fiber composite shows a rapid catalytic hydrolysis rate for a chemical warfare agent simulant, p‐nitrophenyl phosphate with t1/2 < 5 min, and a significant permeation restriction of a real agent GD‐vapor through the composite. Of added advantage is the observed moisture vapor transport rate of 15 000 g m−2 day−1 for the composite, which is notably superior to that of other commercially available chemical‐protective fabrics. The chemical‐protective composites realized in this work overcome the breathability/detoxification trade‐off and show promise for the materials to be deployed in a realistic field.

Asymmetric simple unfused acceptor enabling over 12% efficiency organic solar cells

High photovoltaic performance with cost-effective material synthesis and device fabrication are the prerequisite for commercialization of organic solar cells (OSCs). Herein, we conduct a systematic structure–property correlation study on unfused acceptors adopting different frameworks. Dithieno[3,2-b:2′,3′-d]pyrrole (DTP) based A-D1-D-D2-A asymmetric acceptor (DBT-4F) has been screened as a promising acceptor for high-efficient OSCs. Three DTP-based unfused acceptors display strong near-infrared absorption with narrow optical band gap (Egopt < 1.45 eV). Blends of DBT-4F with PBDB-T contribute a champion power conversion efficiency (PCE) of 12.14% due to better miscibility to form homogenous fibrous phase separation. To the best of our knowledge, the PCE is among the highest values for unfused acceptor based binary OSCs in the literature. The excellent performance of DBT-4F is revealed with more efficient photon-harvesting, higher and more balanced charge transport, and less charge recombination in the blends. Our work manifests the great potential of DTP based asymmetric unfused acceptor for developing high-efficient OSCs via rational molecular design.

Direct air capture of CO2 via crystal engineering.

This article presents a perspective view of the topic of direct air capture (DAC) of carbon dioxide and its role in mitigating climate change, focusing on a promising approach to DAC involving crystal engineering of metal–organic and hydrogen-bonded frameworks. The structures of these crystalline materials can be easily elucidated using X-ray and neutron diffraction methods, thereby allowing for systematic structure–property relationships studies, and precise tuning of their DAC performance.

Chitin–clay composite gels with enhanced thermal stability prepared in a green and facile approach

Chitin–clay composite hydrogels were successfully fabricated through a facile alkali and freeze treatment. Systematic structure–property relationships based on different compositions of the composite systems were determined. It was found that addition of clay considerably increased the thermal stability as indicated by increases in initial decomposition temperature compared to pure chitin. The increase in activation energy of degradation calculated by the Coats–Redfern method supported the thermal stabilization. For other properties, clay decrease water content, swelling ratio and porosity of gel materials. The morphology indicated they underwent a transition from clay clusters as the dispersive phase to clay flakes as the matrix. Wide angle X-ray scattering results suggested that clay-hindered crystallization of chitin. Fourier-transform infrared spectroscopy results indicated that freezing induced specific interactions while incorporation of clay-hindered deacetylation. This work provides a simple and green method to prepare chitin–clay composites gel materials.

High-Performance Ambient-Condition-Processed Polymer Solar Cells and Organic Thin-Film Transistors.

Large-scale commercial synthesis of bulk-heterojunction (BHJ) solar cell materials is very challenging and both time and energy consuming. Synthesis of π-conjugated polymers (CPs) with uniform batch-to-batch molecular weight and low dispersity is a key requirement for better reproducibility of high-efficiency polymer solar cells. Herein, a conjugated polymer (CP) PTB7-Th, well known for its high performance, has been synthesized with high molecular weight and low dispersity in a closed microwave reactor. The microwave reaction procedure is known to be more controlled and consumes less energy. The precursors were strategically reacted for different reaction time durations to obtain the optimum molecular weight. All different CPs were well characterized using 1H NMR, gel permeation chromatography (GPC), UV–vis, photoluminescence (PL), electron spin resonance (ESR), and Raman spectroscopy, whereas the film morphology was extensively studied via atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXRD) techniques. The effect of molecular weight on a conventional BHJ solar cell with PC71BM acceptor was investigated to derive systematic structure–property relationships. The CP obtained after 35 min of reaction time and integrated into BHJ devices under ambient conditions provided the best performance with a power conversion efficiency (PCE) of 8.09%, which was quite similar to the results of CPs synthesized via a thermal route. An enhanced PCE of 8.47% was obtained for the optimized polymer (35 min microwave reaction product) when device fabrication was carried out inside a glovebox. The organic thin-film transistor (OTFT) device with the microwave-synthesized CP displayed better hole mobility (0.137 cm2 V–1 s–1) as compared to that with the thermally synthesized CP. This study also proved that the device stability and reproducibility of the microwave-synthesized CP were much better and more consistent than those of the thermally developed CP.

Tailored Combinatorial Microcompartments through the Self‐Organization of Microobjects: Assembly, Characterization, and Cell Studies

AbstractA new concept enables the generation of cell microenvironments by microobject assembly at an water/air interface. As the orientation of 30 μm sized polymer cubes and their capillary force assembly are controlled by the surface wettability, which in turn can be modulated by coating the initially exposed surfaces with gold and self‐assembled monolayers, unique niches in closely packed arrays of cubes with vertex up orientation can be realized. The random assembly of distinctly different cubes, prefunctionalized or surface‐structured exclusively on their top surface, facilitates the parallel generation of different microenvironments in a combinatorial manner, which paves the way to future systematic structure–property relationship studies with cells.

Tailored Combinatorial Microcompartments through the Self-Organization of Microobjects: Assembly, Characterization, and Cell Studies.

A new concept enables the generation of cell microenvironments by microobject assembly at an water/air interface. As the orientation of 30 μm sized polymer cubes and their capillary force assembly are controlled by the surface wettability, which in turn can be modulated by coating the initially exposed surfaces with gold and self-assembled monolayers, unique niches in closely packed arrays of cubes with vertex up orientation can be realized. The random assembly of distinctly different cubes, prefunctionalized or surface-structured exclusively on their top surface, facilitates the parallel generation of different microenvironments in a combinatorial manner, which paves the way to future systematic structure-property relationship studies with cells.

A structure-property study of fluoranthene-cored hole-transporting materials enables 19.3% efficiency in dopant-free perovskite solar cells.

To date, most of the prevailing organic hole-transporting materials (HTMs) used in perovskite solar cells (PVSCs), such as spiro-OMeTAD and PTAA, generally require a sophisticated doping process to ensure their reasonable hole-transporting properties. Unfortunately, the employed dopants/additives and the associated oxidation reactions have been shown to deteriorate the long-term device stability seriously. The exploitation of efficient and stable dopant-free HTMs is thus strongly desired for PVSCs. However, effective molecular design strategies for dopant-free HTMs are still lacking. Thus far, only a few of them yielded comparable performance to their doped counterparts, while their synthetic costs are still high. In this work, a new class of cost-effective small molecule dopant-free HTMs have been developed using readily available fluoranthene as the structural framework. The structure-property correlation of the fluoranthene-based HTMs was carefully investigated by tuning their structural geometry (linear vs. branched), connection between electron-donating and electron-withdrawing moieties (single bond vs. ethylene), and the substitution position of the methoxy side-groups (para- vs. meta-). As a result, the optimized molecule, FBA3, was demonstrated to serve as an efficient dopant-free HTM in a conventional PVSC to deliver an impressive power conversion efficiency of 19.27%, representing one of the best cost-effective dopant-free organic HTMs reported thus far.

Asymmetric multifunctional 3D cell microenvironments by capillary force assembly

The fabrication and characterization of advanced 3D cell culture microenvironments that enable systematic structure–property relationship studies are reported.

Conformationally-restricted bicarbazoles with phenylene bridges displaying deep-blue emission and high triplet energies: systematic structure-property relationships.

The synthesis is reported of twelve new symmetrical carbazole dimers in which the carbazole units are linked via 1,4-phenylene spacers. There are two distinct series of compounds based on the position on the carbazole ring where the phenylene spacer is attached: this is either at carbazole C(3) (series 1a-1f) or at C(2) (series 2a-2f). The central phenylene ring is substituted with either two methyl, two methoxy or two cyano substituents which impart an intramolecular torsional angle between the phenylene and carbazole rings, thereby limiting the extent of π-conjugation between the carbazole units, and raising the triplet energies of the molecules to ET 2.6-3.0 eV, as determined from their phosphorescence spectra at 80 K. Structure-property relationships were studied by UV-vis and fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. A notable observation is that substitution at the 2-position of carbazole (linear conjugation) exerts control over the position of the HOMO, while substitution at the 3-position of carbazole (meta conjugation) allows greater control over the LUMO. X-ray crystal structures are reported for two of the bicarbazoles. Compound 2d is shown to be a suitable host for the sky-blue emitter FIrpic in PhOLEDs, with improved device performance compared to CBP as host.

Synthesis, characterization, and systematic structure–property investigation of a series of carbazole–thiophene derivatives

A series of carbazole–thiophene oligomers linked at the 3,6-positions of the carbazole fragment of 4,4′-bis(carbazol-9-yl)biphenyl (CBP) and 4,4′-bis(carbazol-9-yl)-2,2′-dimethylbiphenyl (CDBP) with systematically elongated molecular lengths were synthesized via the Suzuki–Miyaura and Ullmann coupling reactions. Their electronic properties were studied by UV-Vis, cyclic voltammetry, and theoretical calculations. The coupling of CBP and CDBP with thiophene and bi- and terthiophene residues stabilized the HOMO and LUMO energy levels. The absorption and emission spectra exhibited a gradual red shift. The compounds with oligothiophene units had greatly decreased band gaps compared with CBP and CDBP. Therefore, these units may be introduced into the backbone of π-conjugated small molecules to develop new materials with low band gaps that may have potential applications in optoelectronics.

Structure–Property Relations and Polymorphism in Compressed Methylamines

The structures of a series of the simplest aliphatic amines determined at high pressure by single crystal X-ray diffraction reveal systematic structure property relations involving intermolecular interactions and molecular symmetries. Five new polymorphs have been found: one of methylamine (phase II, space group Fdd2), two of dimethylamine (phase I, space group C2/c and phase II, P21/c), and two of trimethylamine (phase II, space group P21/n and phase III, P21/m). The methylamine and dimethylamine molecules are arranged according to the NH···N hydrogen bonds. The phase diagrams of methylamines have been outlined up to 6 GPa.

Playing with nanosegregation in discotic crown ethers: from molecular design to OFETs, nanofibers and luminescent materials

ABSTRACTDiscotic liquid crystals are promising materials for electronic device applications. Combining extended π-systems with crown ethers may further open access to functional supramolecular hybrid materials. In the present publication, we briefly summarise recent literature developments and focus in a second part on our work in the field of discotic crown ethers. The crown ether derivatives are conveniently accessible by convergent syntheses which allow a high degree of variation with respect to side chains, mesogenic unit, size and symmetry of the crown core, metal complexation and counterion. This set of compounds provides a basis for systematic structure–property relationship investigations. Numerous experimental studies identified factors being crucial for mesophase stabilisation and geometry and furthermore led to novel room-temperature crown ether mesogens. The latter were obtained by congestion of the mesogenic units and even introduction of peripheral δ-methyl branched side chains. The formation of molybdenum clustomesogens and their application as luminescent hybrid materials is also described.

Synthesis and Search for Design Principles of New Electron Accepting Polymers for All-Polymer Solar Cells

New electron withdrawing monomers, thieno[2′,3′:5′,6′]pyrido[3,4-g]thieno[3,2-c]isoquinoline-5,11(4H,10H)-dione (TPTI) and fluorenedicyclopentathiophene dimalononitrile (CN), have been developed and used to form 12 alternating polymers having different monomer combinations: (a) weak donating monomer–strong accepting monomer, (b) weak accepting monomer–strong accepting monomer, (c) weak accepting monomer–weak accepting monomer, and (d) strong donating monomer–strong accepting monomer. It was found that lowest unoccupied molecular orbital (LUMO) energy levels of polymers are significantly determined by stronger electron accepting monomers and highest occupied molecular orbital (HOMO) energy levels by the weak electron accepting monomers. In addition, fluorescent quantum yields of the TPTI-based polymers in chloroform solution are significantly decreased as the LUMO energy levels of the TPTI series of polymers become deeper. The quantum yield was found to be closely related with the photovoltaic properties, which reflects the effect of internal polarization on the photovoltaic properties. Only the electron accepting polymers showing SCLC mobility higher than 10–4 cm2/(V s) exhibited photovoltaic performance in blend films with a donor polymer, and the PTB7:PNPDI (1:1.8 w/w) device exhibited the highest power conversion efficiency of 1.03% (Voc = 0.69 V, Jsc = −4.13 mA/cm2, FF = 0.36) under AM 1.5G condition, 100 W/cm2. We provide a large set of systematic structure–property relationships, which gives new perspectives for the design of electron accepting materials.

Systematic Structure–Property Investigations on a Series of Alternating Carbazole–Thiophene Oligomers

A series of alternating carbazole-thiophene oligomers, namely 2,7-linked carbazole-thiophene oligomers 1, 3, 5, 7, and 9 and 3,6-linked ones 2, 4, 6, 8, and 10, in which the molecular length was systematically elongated, were synthesized by Suzuki-Miyaura coupling reactions. The effects of the conjugation connectivity between the carbazole and thiophene moieties and the molecular length on the electronic, photophysical, and electrochemical properties of 1-10 were comprehensively investigated. In the present oligomer architectures, the connection with thiophene at the 2,7-positions of carbazole ensures π-conjugation to a high extent and high fluorescence quantum yields, while that at the 3,6-positions enhances the donor ability. The increase in the molecular length of the 2,7-linked oligomers effectively extends π-conjugation. The relationship between structural variations and photophysical properties was examined by fluorescence lifetime measurements in detail. The X-ray crystal structure of 6 was also disclosed.

Altering physical properties of pharmaceutical co-crystals in a systematic manner

Systematic structure–property studies on a series of co-crystals of potential cancer drugs with aliphatic dicarboxylic acids were undertaken.

Microstructural characterisation of oxide layer developed by sulphuric anodisation on 2017A alloys

Abstract In this paper, the characteristics of the oxide film formed on the surface of 2017A aluminium alloy by sulphuric oxidation are investigated. Morphological features on the oxide film are studied using scanning electron microscopy. Crystallographic details are obtained using X-ray diffraction. The composition of the oxide layer is estimated using wavelength dispersive X-ray spectrometry and Raman spectroscopy. Through systematic structure–property studies, the microstructure of the oxide layer is identified providing the incorporation of the alloying elements in the inner layer with a copper enrichment at the interface.

Synthesis of organic phosphinic acids and studies on the relationship between their structure and extraction–separation performance of heavy rare earths from HNO3 solutions

Efficient new extractant design relies on systematic structure–property studies. However, systematic structure–property research on extractants of organic phosphinic acids is far from sufficient. To make up for this deficiency, twelve organic phosphinic acid extractants (including nine dialkylphosphinic acids, two dicycloalkylphosphinic acids and one diarylphosphinic acid) were synthesized with free-radical-addition-reaction method and Grignard-reaction method. Reaction rules, advantages and disadvantages of these two methods were discussed respectively. The extraction ability and separation performance of the synthesized organic phosphinic acids for Tm, Yb and Lu from HNO3 solutions were evaluated and compared. For dialkylphosphinic acids the nearer the branched chain moved to P atom, the more reduction generated on the extraction ability. Dialkylphosphinic acids without branched chain in α-C or β-C (e.g. HYY-3, HYY-5, HYY-7 and HYY-9) exhibited strong extraction ability as P507. On the contrary, dialkylphosphinic acids with branched chain in α-C (e.g. HYY-4, HYY-8) and dicyclohexylphosphinic acids exhibited poor extraction ability as Cyanex 272. New compound Di-(2,3-dimethylbutyl)-phosphinic acid (HYY-2) exhibited good extraction ability and separation performance and its separation factors of Lu/Yb, Yb/Tm and Lu/Tm were 1.42, 3.10 and 4.40 respectively, apparently superior to Cyanex 272 (βLu/Yb=1.31, βYb/Tm=3.25, βLu/Tm=4.26).