Thiophene-Fused Isomerism Governs Optoelectronic Properties, Crystal Packing, and Carrier-Transport Characteristics in Dodecyl-Substituted Angular Anthradithiophenes

Natural flavonols exhibit a wide range of pharmacological activities and possess unique dual ESIPT (Excited-State Intramolecular Proton Transfer) fluorescence, making them sensitive to microenvironments. This sensitivity allows for the detection of metal ions, anions, small ligands, and biomacromolecules. However, the diversity in their structure, including the number and position of hydroxyl groups and potential chemical modifications, complicates the relationship between structure and fluorescence, posing challenges for their practical use as fluorescent probes. In this study, we focus on fine-tuning the ESIPT fluorescence, crystal packing, physicochemical properties, and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) characteristics of a series of flavonols. We achieve this by introducing hydroxy, methoxy and benzyl groups at the C3′ and C4′ positions of the 2-phenyl side ring. The photophysical properties of the synthesized flavonols were systematically examined by UV-vis and fluorescence measurements in terms of their structure–property relationship. Our findings indicate that the nature and position of the substituent groups in flavonols can significantly influence their crystal packing in the solid state, tuning contributions of intra- and intermolecular hydrogen bonding and the ESIPT behavior. Lastly, through fluorescence titration and molecular docking calculations, we explored how the introduction of a bulky benzyl moiety and its alteration between C3′ and C4′ positions can influence the binding interactions of flavonols with β-glucosidases. We believe our findings shed light on the structure–fluorescence relationship in flavonols and open up new opportunities for the design of innovative flavonol-based probes.

Organometallic compounds have been studied with X-ray crystallography from their very discovery. Yet structural organometallic chemists were almost exclusively concerned with the molecular structure and stereochemistry of organometallic compounds and clusters rather than with their crystal structures and packing characteristics. The growing importance of crystal engineering and supramolecular chemistry, however, led to interest in the nature of the interactions that bind organometallic molecules into crystals. In part, these interactions are similar to those found in purely organic crystals because the peripheries of these molecules often contain organic residues. Yet molecular features peculiar to organometallic compounds also do lead to distinctive supramolecular characteristics. Most notable among these intermolecular interactions are hydrogen bonds. Organometallic compounds contain a wealth and diversity of hydrogen bonds that are without counterpart in the organic world. These include C–H⋯O bonds to M–CO acceptors, and hydrogen bonds wherein the metal atom itself acts as a donor or as an acceptor. Even more exotic is the dihydrogen bond M1–H⋯H–M2. Despite this variety, all these weak interactions have properties that resemble those of the more familiar hydrogen bonds such as O–H⋯O, N–H⋯O, O–H⋯N and N–H⋯N. Other interactions that are distinctive to organometallic compounds are the agostic interaction to electron deficient metals (C–H)⋯M and the aurophilic interaction Au⋯Au. The Cambridge Structural Database (CSD) is an essential tool in the analysis of weak intermolecular interactions. Since the number of organometallic crystal structures in the CSD is very large, the weakest of intermolecular interactions may be studied with ever-increasing degrees of reliability. Through such analysis one is able to obtain a more complete idea of organometallic crystal architecture. Crystal engineering must pass through the stage of analysis before crystal synthesis can be attempted and organometallic crystal engineering is still in its infancy. However, the progress made so far in understanding the nature of intermolecular interactions in these crystals indicates that one may expect rapid progress in the engineering of organometallic crystals with desired structures and properties.

Electron transporting (n-channel) polymer semiconductors for field-effect transistors are rare. In this investigation, the synthesis and characterization of new electron-depleted N-alkyl-2,2'-bithiophene-3,3'-dicarboximide-based pi-conjugated homopolymers and copolymers containing the 2,2'-bithiophene unit are reported. A novel design approach is employed using computational modeling to identify favorable monomer properties such as core planarity, solubilizing substituent tailorability, and appropriate electron affinity with gratifying results. Monomeric model compounds are synthesized to confirm these properties, and a crystal structure reveals a short 3.43 A pi-pi stacking distance with favorable solubilizing substituent orientations. A family of 10 homopolymers and bithiophene copolymers is then synthesized via Yamamoto and Stille polymerizations, respectively. Two of these polymers are processable in common organic solvents: the homopolymer poly(N-(2-octyldodecyl)-2,2'-bithiophene-3,3'-dicarboximide) (P1) exhibits n-channel FET activity, and the copolymer poly(N-(2-octyldodecyl)-2,2':5',2'':5'',2'''-quaterthiophene-3,3'-dicarboximide) (P2) exhibits air-stable p-channel FET operation. After annealing, P1 films exhibit a very high degree of crystallinity and an electron mobility > 0.01 cm (2) V(-1) s(-1) with a current on-off ratio of 10 (7), which is remarkably independent of film-deposition conditions. Extraordinarily, P1 films also exhibit terracing in AFM images with a step height matching the X-ray diffraction d spacing, a rare phenomenon for polymeric organic semiconductors. Another fascinating property of these materials is the air-stable p-channel FET performance of annealed P2 films, which exhibit a hole mobility of approximately 0.01 cm(2) V(-1) s(-1) and a current on-off ratio of 10(7).

Building upon the previous results on silicon-based homopolymers, the authors have now synthesized and characterized copolymers of these novel materials. The copolymers poly(di-n-butylsilylene-co-di-n- pentylsilylene) (PB-co-PS) and poly(di-n-pentylsilylene-co-di-n-hexylsilylene) (PP-co-HS) were synthesized from solutions containing equal molar concentrations of the two respective monomers. The materials were examined by solution- and solid-state NMR, X-ray diffraction, DSC, and UV spectroscopy to obtain a description of the solid-state structures, phase transitions, and thermochromism of these copolymers. The conformational properties, crystal packing, and UV absorption characteristics of PB-co-PS are found to be the same as those of the two corresponding homopolymers poly(di-n-butylsilylene) (PDBS) and poly(di-n-pentylsilylene) (PDPS). In contrast, the authors find that while the silicon chain conformation of PP-co-HS (either a 7/3 or 9/4 helix) appears similar to that of the PDPS homopolymer, the UV absorption characteristics and the crystal packing differ from those of either of the corresponding homopolymers, PDPS and poly(di-n-hexylsilylene) (PDHS). The results of this study demonstrate that the properties of the polysilylene copolymers are complex and not directly predictable solely on the basis of the corresponding homopolymers.

Texture Development in Cumulate Rocks

A hexaazatrinaphthylene [HAT] is a well‐known halogenated perylene diimide compound recognized for photochemical stability, high electron affinity, easy functionalization, and high conductivity. Based on density functional theory, optoelectronic and charge transport properties of HAT derivatives with electron‐donating, electron‐withdrawing, and push‐pull substituents, were investigated. The impact of substituting electron‐withdrawing groups (EWG), electron‐donating groups (EDG), and push‐pull substituents on various aspects, including molecular structure, frontier molecular orbitals, ionization energy, electron affinity, reorganization energy, crystal packing, and charge carrier mobility, is investigated. A crystal structure simulation method is employed to optimize potential arrangements of crystal packing for the molecules under examination. The presence of EWG, EDG, and push‐pull substitutions significantly affects the energy and distribution of electron density in the frontier molecular orbitals, leading to alterations in the absorption spectrum and charge transport properties. When adding various substituents to the core system, the different crystal packing motifs and varied intermolecular interactions of the examined molecules result in noticeably different transfer integrals. Due to higher hole reorganization energy and weak HOMO orbital overlapping, HAT derivative molecules exhibit better electron mobility. Among the studied molecules, HAT‐F and HAT‐F‐OCH 3 molecules demonstrate better electron mobility with values of 0.49 and 2.36 cm 2 V −1 s −1 , respectively, and established the n‐channel characteristics.

Systematic color tuning of a family of firefly oxyluciferin analogues suitable for OLED applications

While the impact of alkyl side-chain length on the photovoltaic properties of conjugated polymers and their performance in bulk heterojunction (BHJ) solar cells has been studied extensively, analogous studies on pyrrolo-perylene-based polymers have not received adequate attention. To explore these effects, we synthesized two copolymers based on N-annulated pyrrolo-perylene and consisting of cyano group substituents on thiophene vinylene thiophene units with two different alkyl groups of 2-decyltetradecyl and 7-decylnonadecyl, and we studied them with regard to chemical structure and photovoltaic performance. UV-vis spectroscopy and cyclic voltammetry studies showed that variations in alkyl chain length affect crystallization, light absorption, and the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. These factors have a pronounced impact on the morphology of BHJ thin films and their charge carrier separation and transportation characteristics, which, in turn, influences photovoltaic properties.

Bi2Te3 recently emerges as a promising candidate material for the next generation of mid-wave to long-wave infrared photodetection owing to its exceptionally narrow bandgap (approximately 0.2 eV) and the favorable photoelectronic properties. In particular, its topological insulator structure is safeguarded by time-reversal symmetry, leading to electronic structures with distinct surface and bulk states as well as distinctive optoelectronic properties. This study examines the infrared detection mechanism of Bi2Te3 across various thicknesses, aiming to elucidate the transport behavior and characteristics of internal carriers in Bi2Te3 under the complex interplay between the bulk state and surface states. Bi2Te3 films at various thicknesses were synthesized pulsed laser deposition with varied number of pulses which determines the actual thickness. The bandgap and the photoelectric response mechanism of Bi2Te3 at different layer thicknesses were investigated, and the charge carrier transport dynamics across layers were clarified. To summarize, this study offers a theoretical basis for advancing photoelectric detection devices designed to regulate Bi2Te3 at distinct thicknesses.

The molecular shape exerts remarkable effects on solubility, polymorphism, crystal packing and optoelectronic properties – searching for 3D organic semiconductors.

Comprehensive SummaryResearchers investigated the organic optoelectronic materials and facilitated their development in organic light‐emitting diodes (OLEDs), chemo‐ and biosensors, organic solar cells, data storage, and anticounterfeiting devices. Atoms make up molecules through chemical bonds, and molecular aggregates are formed through weak intermolecular interactions. The opto‐electronic performance of these materials depends on not only the properties of the well‐designed molecules with specific function groups, but also their aggregate states. The molecular aggregates in the form of nanoparticles can be applied in biological imaging, and films can be applied to photovoltaic and photodeformable devices, in which, the alignment of optoelectronic molecules can be either an ordered crystalline or an amorphous state. Generally, the crystalline materials could be deeply investigated by single crystal/powder X‐ray diffraction analysis, which could provide the accurate information about molecular conformations, interactions and packing characteristics. It afforded a convenient way to investigate the possible relationship between molecular aggregates and opto‐electronic properties. Among various opto‐electronic materials, organic room temperature phosphorescence (RTP) materials exhibit the extremely sensitive luminescence property to molecular aggregates, even the dynamic properties can be detected by the tiny change of molecular aggregates. Thus, we selected the organic RTP emission as the output information of molecular aggregates, and afforded typical examples to find the possible relation between RTP effect and molecular packing. Accordingly, molecular packing can be adjusted by the external force as light, mechanical force, temperature, electric field, and so on, as well as the molecular structures as the building blocks, and the systematic investigation in the dynamic and static aggregation structures is of great value to the design of various optoelectronic materials. This review discusses the relationship among molecular structures, aggregation behaviors and corresponding optoelectronic properties by a comprehensive summary of recent research in our group, and the concept of molecular uniting set identified characteristic (MUSIC) is afforded. What is the most favorite and original chemistry developed in your research group?The concept of “Suitable Isolation Group” for molecular design of organic second‐order nonlinear optical (NLO) materials. Molecular packing is highlighted as the key point to opto‐electronic materials, which are partially summarized in this mini review to present “MUSIC” in the molecular world.How do you supervise your students?Discussions. We do discussions for science, interests and other topics related to research together, through which to solve the encountered problems.What is the most important personality for scientific research?Curiosity, desire to advance, persistence, sense of urgency, and teamspirit.What are your hobbies? What's your favorite book(s)??Listening to music and reading books, and my favorite book is “Tao Te Ching (道德经)”.Could you please give us some advices on improving Chinese Journal of Chemistry?There are many different approaches to improve CJC, perhaps, to attract and publish good papers is the key, especially those from Chinese authors since the chemistry in China develops rapidly.If you have anything else to tell our readers, please feel free to do so?While pursuing new published exciting papers, it is a very good habit to read related old excellent literatures and the classics.

The p38 MAP kinase pathway is an essential component of numerous cellular signalling networks which are usually activated in response to extracellular environmental stress conditions. In addition to the canonical activation, several alternative activation pathways have been identified for p38; one of these, in which p38 is initially phosphorylated on Tyr323 and consequently autoactivated, is exclusive to T cells and is induced by TCR activation. Intrinsically active and inactive mutants at position 323 have been developed in order to evaluate the structural changes that occur upon TCR-induced activation. In order to promote crystal growth, cross streak-seeding techniques were utilized. This technique has gained popularity in promoting crystal growth when spontaneous nucleation induces critical defects or is being entirely hindered. The crystal characteristics of some mutants were highly similar to those of the wild-type source seeds (form A). In contrast, other mutants crystallized spontaneously with a different space group and molecular packing (form B). One of the active mutants (Y323T) crystallized in both crystal forms, displaying different packing characteristics and significant differences in molecular conformation that were clearly dictated by the source seeds. This implies that the source seeds used in cross streak-seeding could, in some cases, impose bias on the structural outcome of the studied molecule. Such incidents could occur when the conformational freedom permits crystal packing while not reflecting the authentic structure.

A total of 23 benzamides are obtained through a simple reaction between chloro-/bromo-/iodoaniline and trifluoromethylbenzoyl chloride and characterized using single-crystal X-ray diffraction. Crystal structures of three series of benzamides based on N-chlorophenyl–trifluoromethyl–benzamide (nine compounds), N-bromophenyl–trifluoromethyl–benzamide (six compounds), and N-iodophenyl–trifluoromethyl–benzamide (eight compounds) are prepared to analyse the halogen-mediated noncovalent interactions. The influences of Cl/Br/I and trifluoromethyl substituents on the respective interactions are examined in the presence of a strong N—H...O hydrogen bond. This exercise has resulted in the documentation of frequently occurring supramolecular synthons involving halogen atoms in the crystal packing of benzamide molecules in the solid state. In the present study, a detailed quantitative evaluation has been performed on the nature, energetics, electrostatic contributions, and topological properties of short and directional intermolecular interactions derived from the electron density on halogenated benzamides in the solid state. Besides these, the occurrence of three-, two- and one-dimensional isostructurality in halogen (Cl or Br or I) substituted benzamide analogues is also investigated. A `region of co-existence' involving halogen-based intermolecular interactions in the vicinity of the sum of the van der Waals radii has been identified. Thus, the nature of the halogen (effective size), type of interaction and the packing characteristics via presence of additional interactions establish the subtle, yet important, role of cooperativity in intermolecular interactions in crystal packing.

Trifluoromethylated benzanilides, containing C(sp3)–F bonds, have been synthesized and their crystal and molecular structures have been investigated to highlight the significance of weak intermolecular interactions associated with the presence of organic fluorine in a molecule. It is observed that the molecular conformation and packing characteristics are a delicate interplay amongst different intermolecular interactions, namely strong N–H⋯OC, weak C–H⋯OC, C–H⋯F–C, and C–H⋯π H-bonds, along with C–F⋯F–C and C–F⋯π intermolecular interactions in the solid state. All the isomers are associated with variations in crystal packing due to the presence of different supramolecular variants introduced by the presence of a trifluoromethyl group at the ortho, meta and para positions of the phenyl ring. Furthermore, a comparison of the experimental molecular conformation with that obtained from DFT theoretical calculations delineates the significant role of the trifluoromethyl group on the phenyl ring, which results in variations in conformational flexibility associated with the molecule. It has been observed that the –CF3group is associated with rotational disorder in some of the crystalline solids and the overall crystal structure is stabilized by a network of C(sp2)–H⋯F–C(sp3) intermolecular H-bonds and C–(sp3)F⋯F–C(sp3) contacts [the “fluorous effect”] in the crystalline lattice. It is also observed that there also exists a definite relationship between the acidity of the participating hydrogens with the hydrogen bonding characteristics of such weak C–H⋯F–C H-bonds in the crystal.

Crystalline 5′-iodo-5′-deoxyguanosine (I) exists as a pair of solvent-free polymorphs (Ia, Ib) and as a mixed water/methanol solvate (Ic). The solvent-free polymorphs are capable of epitaxial intergrowth to give hybrid crystals that by visual inspection appear to be single crystals (Parkin et al. Cryst. Growth Des. 2016, 16, 6343–6352; hereafter PTGB). To investigate the generality and origin of the unusual polymorphism of the solvent-free forms, we have prepared and characterized the 5′-bromo- and 5′-chloro-5′-deoxyguanosine analogues (II and III, respectively), as well as the pseudohalide derivative 5′-azido-5′-deoxyguanosine (IV). Monoclinic and orthorhombic polymorphs of II (IIa and IIb, respectively) and an orthorhombic form of III all grow from water as small nonsolvated, tightly packed needles or laths. Although IIa is isostructural with the dominant polymorph of I (i.e., Ia in PTGB), all of these crystals (IIa, IIb, III) have similar molecular conformations and packing characteristics to Ia, in which the halogen adopts a gauche conformation relative to the deoxyribose ring oxygen. In spite of having different space group symmetries (P21 for Ia and IIa vs P212121 for IIb and III), the crystal structures of IIb and III are also clearly related to Ia. Unlike I, however, no experimental evidence for conformational polymorphism, or of solvated forms was found for either II or III. Similar to PTGB work on I, density functional theory calculations show that the experimental gauche halide-atom conformations in II and III are ∼2.0 kcal/mol higher in energy than the energy-minimized anti-conformation (which occurs in the minor polymorph of I, i.e., Ib). The 5′-azido analogue (IV) in contrast, crystallized solely as a hydrate, initially forming minuscule irregular shards that were far too small for conventional X-ray analysis. By a process of Ostwald ripening, these shards could be enlarged sufficiently to allow structure determination by X-ray crystallography. The hydrate of IV shares many structural characteristics with Ic, but is much more complicated. It contains four independent molecules of IV (i.e., Z′ = 4, vs Z′ = 2 in Ic), which exhibit a range of distinctly different molecular conformations, as well as five full occupancy water molecules.