Search

Comprehensive Summary: Stability against oxygen is an important factor affecting the performance of organic semiconductor devices. Improving photooxidation stability can prolong the service life of the device and maintain the mechanical and photoelectric properties of the device. Generally, various encapsulation methods from molecular structure to macroscopic device level are used to improve photooxidation stability. Here, we adopted a crystallization strategy to allow 14H‐spiro[dibenzo[c,h]acridine‐7,9′‐fluorene] (SFDBA) to pack tightly to resist fluorescence decay caused by oxidation. In this case, the inert group of SFDBA acts as a "steric armor", protecting the photosensitive group from being attacked by oxygen. Therefore, compared with the fluorescence quenching of SFDBA powder under 2 h of sunlight, SFDBA crystal can maintain its fluorescence emission for more than 8 h under the same conditions. Furthermore, the photoluminescence quantum yields (PLQYs) of the crystalline film is 327% higher than that of the amorphous film. It shows that the crystallization strategy is an effective method to resist oxidation. [ABSTRACT FROM AUTHOR]

Crystallization of organic steric molecules often leads to multiple polyhedral crystal morphologies. However, the relationships among the molecular structure, supramolecular interaction, aggregation mode and crystal morphology are still unclear. In this work, we elaborate two model crystals formed by spiro[fluorene‐9,9′‐xanthene] (SFX) and spiro[cyclopenta[1,2‐b : 5,4‐b′]dipyridine‐5,9′‐xanthene] (SDAFX) to demonstrate the feasibility of morphology prediction by periodic bond chain (PBC) theory based on interaction energy (IE) values in terms of single point energy. With non‐directional van der Waals forces, only one PBC direction is found in SFX crystal, leading to the irregular 1D rod‐like structure. Compared with SFX, the extra N heteroatoms in SDAFX can bring additional hydrogen bonds and some other interactions into the bulky molecular skeletons, inducing 3‐dimensionally oriented PBCs to form the explicit F‐face network in SDAFX which leads to the final octahedral structure. A simple and accurate method has been provided to quantify PBC vector on the supramolecular level in the organic molecular system, and the PBC theory has also been further demonstrated and developed in the morphology prediction of organic spiro‐molecules. [ABSTRACT FROM AUTHOR]

In this work, a series of homoleptic monocyclic and [2]catenanes gold(I) thiolates were studied by DFT and TD-DFT methods to analyze the relationship between structure and property. The results reveal that the increase of Au–S–Au bond angles in Au11 and Au12 makes the [2]catenanes more planar than the monocyclic molecules. The smaller Au⋯Au contacts tighten the overall structure and enhance its geometrical stability. There is a positive correlation between the Au percentage in the frontier molecular orbitals and the orbital energy levels for both monocyclic molecules and [2]catenanes. The HOMO levels of the [2]catenanes are higher than those of the monocyclic molecules, which may be caused by stronger Au⋯Au Pauli repulsion. Differences in size and metallophilic interactions are responsible for the different absorption spectra of the complexes, and the electronic spectral redshift of the [2]catenanes is consistent with their higher HOMO energy levels. The results of energy decomposition analysis indicate that electrostatic interaction and orbital interaction are the main driving forces of molecular formation. In [2]catenanes, Pauli repulsion and steric interaction can be balanced. The calculated results of interaction energy and stabilization energy suggest that [2]catenanes are very stable. The calculated reaction enthalpies indicate that the chemical stabilization of [2]catenanes decreased in the order of Au12, Au11, and Au10. [ABSTRACT FROM AUTHOR]

The emergence and development of radical luminescent materials is a huge breakthrough toward high-performance organic light-emitting diodes (OLEDs) without spin-statistical limits. Herein, we design a series of radicals based on tris(2,4,6-trichlorophenyl)methyl (TTM) by combining skeleton-engineering and periphery-engineering strategies, and present some insights into how different chemical modifications can modulate the chemical stability and luminescence properties of radicals by quantum chemistry methods. Firstly, through the analysis of the geometric structure changes from the lowest doublet excited state (D1) to the doublet ground state (D0) states, the emission energy differences between the BN orientation isomers are explained, and it is revealed that the radical with a smaller dihedral angle difference can more effectively suppress the geometric relaxation of the excited states and bring a higher emission energy. Meanwhile, a comparison of the excited state properties in different radicals can help us to disclose the luminescence behavior, that is, the enhanced luminescent intensity of the radical is caused by the intensity borrowing between the charge transfer (CT) state and the dark locally excited (LE) state. In addition, an efficient algorithm for calculating the internal conversion rate (kIC) is introduced and implemented, and the differences in kIC values between designed radicals are explained. More specifically, the delocalization of hole and electron wave functions can reduce nonadiabatic coupling matrix elements (NACMEs), thus hindering the non-radiative decay process. Finally, the double-regulation of chemical stability and luminescence properties was realized through the synergistic effect of skeleton-engineering and periphery-engineering, and to screen the excellent doublet emitter (BN-41-MPTTM) theoretically. [ABSTRACT FROM AUTHOR]

High-performance luminescent radical-based materials are emerging and are in demand for application in organic light-emitting diodes (OLEDs). Herein, quantum chemistry methods are employed to investigate a series of donor–acceptor (D–A) type monoradical molecules based on the tris(2,4,6-trichlorophenyl)methyl (TTM) acceptor and triarylamine (TPA) donor. The major factors affecting the device performance of the monoradical molecules, including thermodynamic stability, excited state characteristics and luminescence properties, are taken into consideration. The introduction of donor fragments can help to tune the luminescent properties of the monoradical molecule, and furthermore, the electron donating abilities of donor fragments, revealed by molecular Mulliken electronegativity, are negatively associated with both the stability and photoluminescence quantum yield (PLQY). The hybrid transition characteristic formed by the combination of charge transfer (CT) and localized excitation (LE) makes a significant contribution to the luminescence intensity of the monoradical molecules. Comparative analyses can lead us to conclude that monoradical molecules 1, 2, 3, 4, 6 and 8 possess more significant stability and photoluminescence efficiency, and are expected to become high-performance luminescent materials. Finally, our investigations show that in order to enhance the thermodynamic stability and PLQY, it should be appropriately considered to weaken the electron donating ability of donor fragments in the TTM-based D–A type of monoradical molecules by rational chemical modifications. [ABSTRACT FROM AUTHOR]

In a variety of skeletal structures of delayed fluorescence molecular materials, the donor–acceptor–donor (D–A–D) type has been widely considered for improving the efficiency of the reverse intersystem crossing (RISC) process. Herein, three new D–A–D molecules (PTZ-MPS, TPA-MPS and PCz-MPS) bearing 9,9-dimethylthioxanthene-S,S-sulfur dioxide (MPS) as the electron acceptor group are designed and investigated using theoretical calculations. PTZ-MPS shows the feature of the high-lying reverse intersystem crossing process, which is conducive to improving the exciton utilization of organic light-emitting diodes (OLEDs). PTZ-MPS has a much smaller singlet–triplet energy splitting (ΔES1T3 = 0.03 eV) than TPA-MPS (ΔES1T3 = 0.32 eV) and PCz-MPS (ΔES1T3 = 0.59 eV). However, it has a much larger spin–orbital coupling (SOC) strength (〈S1‖ĤSOC‖T3〉 = 1.013 cm−1) than TPA-MPS (〈S1‖ĤSOC‖T3〉 = 0.311 cm−1) and PCz-MPS (〈S1‖ĤSOC‖T3〉 = 0.354 cm−1), which makes it easy to induce a sufficient RISC from the Tn state to the S1 state. The ΔEST and SOC are the two most important factors in determining TADF molecules. Therefore, PTZ-MPS is expected to be a potential high-lying excited state delayed fluorescence material candidate, and our work demonstrates that high-performance TADF materials can also be obtained successfully by designing rational molecules. [ABSTRACT FROM AUTHOR]

Effective protection against photooxidation of organic wide‐bandgap semiconductors is a potential method to afford high efficient deep‐blue emission for full color displays. Herein, the crystallization effect of fluorene‐based blue emitter on suppressing the formation of long‐wavelength green band (g‐band) defect is demonstrated through the model of self‐assembled organic micro/nanocrystals. The selected molecule 2,2'‐bi(9,9‐dipropyl)fluorene (DDC3F), which easily generates strong g‐band emission (green index (Igreen/Iblue) of ≈5 under ultraviolet exposure for 3 h) in amorphous state, shows an excellent spectra stability of deep‐blue emission with a green index of ≈0 and an unchangeable CIE coordination of (0.18, 0.09) in crystalline nanorod morphologies. Such effect of crystallization‐induced stability enhancement can be further extended into other solution‐processing methods such as brushing. Molecular dynamic simulation reveals that crystalline nanorods with compact molecular packing enable to effectively block the diffusion of O2 and H2O molecules, which is crucial to suppress the occurrence of photooxidation reactions. Along with high quantum yield of 87% from crystallization‐induced luminescence enhancement effect, such ultrastable deep‐blue emission on crystalline film can also be maintained in solution‐processing organic light‐emitting diode devices. The supramolecular self‐assembled micro/nanocrystals strategy provides a potential platform to maintain ultrastable color purity in organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

A novel barium(II) coordination polymer (CP), [Ba3(L)2(H2O)4]n1, has been firstly isolated based on organic ligand 1‐[(2′‐carboxybiphenyl‐4‐yl)methyl]‐2‐propylimidazole‐4,5‐dicarboxylic acid (H3L=(HO2C)2(C3N2)(C3H7)CH2(C6H4)(C6H3)CO2H) by hydrothermal technique, and determined by single‐crystal X‐ray diffractions, elemental analysis, IR, powder X‐ray diffractions (PXRD). The Ba(II)‐CP 1 belongs to a novel 2‐D layer structure created from 1‐D serrated chain containing secondary building unit (SBU) [Ba(1)Ba(2)Ba(3)] via carboxylate group linkage. In 1, the ligand L3− gives a variety of coordinated styles, nonadentate: μ2:(η1η1), μ2:(η1η1), μ3:(η2η2) and decadentate: μ1:(η1η1), μ3:(η2η2), μ3:(η1η2), μ3:(η1η2), which is the first reported example. Moreover, the room‐temperature fluorescent measurements show that the Ba(II)‐CP 1 has specific ability to recognize copper(II) ion in aqueous solution by means of fluorescence quenching effect, corresponding obtained quenching constant Ksv=1.18×102 M−1 and the limit of detection LOD=0.274 μM. Fluorescence titration experiment reveals that there is a good linear relationship between copper ion concentration and fluorescence intensity in the concentration range of 2.0×10−6∼5.3×10−6 mol ⋅ L−1. The corresponding linear equation: y=402.41897–0.70486x, and linear correlation coefficient: R2=0.99866 (λex=310 nm and λem=412 nm). [ABSTRACT FROM AUTHOR]

The energy crisis and environmental pollution have forced scientists to explore alternative energy conversion and storage devices. The anodic reactions of these devices are all oxygen evolution reactions (OER), so the development of efficient OER electrocatalysts is of great significance. At the same time, understanding the reaction mechanism of OER is conducive to the rational design of efficient OER electrocatalysts. In general, catalytic active centers play a direct role in OER performance. In this paper, a series of stable bimetallic metal–organic frameworks (MOFs, named as Fe3‐Con‐X2, n=2, 3 and X=F, Cl, Br) with similar structure were synthesized by changing the halogen coordinated with the cobalt metal active center, aiming to investigate the influence of halogen substitution effect on OER performance. It was found that the OER activity of Fe3‐Co3‐F2 is much better than Fe3‐Co2‐Cl2 and Fe3‐Co2‐Br2, indicating that the regulation of the electronegativity change of the coordination halogen atom can regulate the coordination electron structure of the metal active center, thereby achieving effective regulation of OER performance. [ABSTRACT FROM AUTHOR]

Over the past 200 years, the most famous and important heteroatom Keggin architecture in polyoxometalates has only been synthesized with Mo, W, V, or Nb. Now, the self‐assembly of two phosphate (PO43−)‐centered polyoxo‐titanium clusters (PTCs) is presented, PTi16 and PTi12, which display classic heteroatom Keggin and its trivacant structures, respectively. Because TiIV has lower oxidate state and larger ionic radius than MoVI, WVI, VV, and NbV, additional TiIV centres in these PTCs are used to stabilize the resultant heteroatom Keggin structures, as demonstrated by the cooresponding theoretical calculation results. These photoactive PTCs can be utilized as efficient photocatalysts for highly selective CO2‐to‐HCOOH conversion. This new discovery indicates that the classic heteroatom Keggin family can be assembled with Ti, thus opening a research avenue for the development of PTC chemistry. [ABSTRACT FROM AUTHOR]

On the basis of theoretical models and calculations, CN‐substituted difuropyrene systems have been investigated as potential singlet fission (SF) candidates for solar cell applications. Calculations indicate that the fusion of difuran and pyrene in different arrangements could introduce variable diradical properties, and the fused compound ab‐trans‐DFP has moderate diradical character (y0=0.45) while satisfying the main condition (ΔE1) of SF. Furthermore, CN‐substituted ab‐trans‐DFP (substituted at distinct positions) is used to adjust the frontier molecular orbital energy level to satisfy the SF secondary condition (ΔE2). Interestingly, the position of the cyano substituents has almost no effect on the diradical character, which can be explained by the insensitivity of the ring aromaticity to the cyano position. Both time dependent density functional theory (TD‐DFT) and multi‐configurational self‐consistent field (MCSCF) results confirm that the 4‐ and 5‐position cyano‐substituted ab‐trans‐DFP derivatives can satisfy the two energy conditions and may become potential SF candidates. This work provides an effective strategy for the rational design of new suitable diradical SF candidates, and it is expected that more polycyclic aromatic hydrocarbons such as pyrene can achieve SF conditions by chemical modification, such as fusion or substitution, to adjust the diradical character and the vertical excitation energy. [ABSTRACT FROM AUTHOR]

Hyphodontia mollissima is described from Hainan Province, southern China, as a new species. This species is characterized by resupinate, soft corky basidiocarps, poroid hymenophores, a pseudodimitic hyphal system with clamped generative hyphae, presence of both bladder-like and apically encrusted cystidia, and broadly ellipsoid, colorless, thin-walled, smooth basidiospores. Morphologically, H. mollissima except for poroid hymenophores, fits the concept of Palifer. A potential member of Palifer , Hyphodontia erikssonii , resembles H. mollissima by similar two kinds of cystidia and also similar shape and size of basidiospores, but distinctly differs from the latter by having non-poroid hymenophores and a monomitic hyphal system. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT) in combination with non-equilibrium Green's functions, we have investigated the electronic structures, magnetization, and quantum transport properties of zigzag graphene nanoribbons (ZGNRs) functionalized with conventional conductive metal adatoms (Al, Cu, Ag and Au). On the basis of the adsorption energies, our simulation demonstrates that Al and Cu adatoms are chemically bonded with ZGNRs, while the adsorptions for Ag and Au are between weak chemisorption and strong physisorption. The properties of charge transfer and magnetic moment are in reasonable agreement with the previous calculations. The adsorption of metal adatoms induce a net magnetic moment of −1 μB in 6ZGNR–metal systems. On the other hand, the transport studies of metal adatoms adsorbed ZGNRs suggest that the metal adatoms play an important role in the transport properties of devices and exhibit different effects on the transport properties of 6ZGNR-based and 7ZGNR-based devices. The 7ZGNR-based devices show the opposite conductive order in 6ZGNR-based devices. For 6ZGNR-based devices, the transport current in 6ZGNRs can be enhanced effectively by the adsorption of metal adatoms. However, the currents in 7ZGNR functionalized with conductive metal atoms are obviously smaller than that in pristine 7ZGNR, implying that metal adsorptions reduce the electrical conductivity of 7ZGNR-based devices. In contrast to the properties of the bulk materials, the conductivity of 6ZGNR–Al is highest among 6ZGNR–metal systems, which is in agreement with that of single atomic wires of Ag, Al, Au, and Cu. [ABSTRACT FROM AUTHOR]

The example of Co(II)-N-heterocyclic complex based on 1-hydroxyethylidenediphosphonic acid (H5L = CH3C(OH)(PO3H2)2), namely [Co2(H3L)2(2,2′-bipy)2] 1, has been solvothermally isolated using the second ligand 2,2'-bipyridine (2,2'-bipy) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, and thermal gravimetric analyses. The single-crystal X-ray diffractions show that complex 1 possesses a 0-D structure built from binuclear unit [Co2(O–P–O)2] by μ2-(O–P–O) bridge. Then, H-bonding and π–π stacking interactions further expand this 0-D structure into a 3-D supramolecular framework. Fluorescent measurements reveal that the maximum emission peak is centered at 421.5 nm, mainly deriving from intraligand π*–π transition state of the second ligand 2,2'-bipy (λem = 419.5 nm, λex = 235 nm). Magnetism data indicate that 1 exhibits ferromagnetic behavior within binuclear Co(II) unit via μ2-(O–P–O) bridge in syn-anti mode. [ABSTRACT FROM AUTHOR]

By introducing the second ligand 1,10-phenanthroline (phen), three low-dimensional examples of Cd/Zn diphosphonates based on 1-hydroxyethylidenediphosphonic acid (HL = CHC(OH)(POH)), [Cd(HL)(phen)(HO)] 1, {[Zn(HL)(phen)]·2HO} 2 and [Zn(HL)(phen)]·(HOCHCHOH) 3, have been hydro- or solvo-thermally obtained and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, TG-SDTA. The single-crystal X-ray diffractions show that both compounds 1 and 3 display zero-dimensional structures built from binuclear units [M(OPO)] (M = Cd/Zn) via a double O-P-O bridge, and compound 2 possesses one-dimensional fish-bone inorganic chain structure with three types of coordination modes of Zn(II) ions. Then H-bond or/and π- π stacking interactions further expand the low-dimensional structures into the three-dimensional supramolecular frameworks. Fluorescent measurements reveal that the maximum emission peaks (371.5, 391.5 nm for 2 and 376.5, 392.5 nm for 3) of 2-3 have a significant increase in intensity compared to those of the phen ligand ( λ = 362.5, 379 nm, λ = 335 nm), which are mainly caused by intraligand π*- π emission state of the phen ligand. The results of electrochemical measurements indicate the donor ability of 1- 3 has gone up, compared with the ligands (HL and phen). Graphical Abstract: Three examples of CdZn diphosphonates have been hydro- or solvo-thermally obtained. Two Zn(II) diphosphonates with 1,10-phenanthroline indicate a significant increase in intensity of fluorescence. The results of electrochemical measurements indicate the donor ability of Cd/Zn diphosphonates increase, compared with the ligands HL and phen.[InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Four Cd(II)- and Cu(II)-containing coordination polymers (CPs) based on a multidentate N-donor ligand and varied dicarboxylate anions, [Cd(3,3′-tmbpt)(p-bdc)]·2.5H2O (1), [Cd(3,3′-tmbpt)(m-bdc)]·2H2O (2), [Cu(3,3′-tmbpt)(m-bdc)]·H2O (3), and [Cu(3,3′-tmbpt)(p-bdc)]·2H2O (4), where 3,3′-tmbpt = 1 − ((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole,p-H2bdc = 1,4-benzenedicarboxylic acid, andm-H2bdc = 1,3-benzenedicarboxylic acid, have been prepared hydrothermally. The structures of the compounds were determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra and elemental analyses. Compound1exhibits a 3-D twofold interpenetrating framework with a 65·8 CdSO4topology. Compound2is a 2-D layer containing meso-helical chains with a 44·62sql topology. Compound3shows a 1-D → 3-D interdigitated architecture while4displays a 2-D → 3-D interdigitated architecture. The structural differences of the compounds indicate that the dicarboxylate anions and the central metal ions play important roles in the resulting structures of CPs. Optical band gaps and solid-state photoluminescent properties have also been studied. [ABSTRACT FROM PUBLISHER]

Two CdII-containing coordination polymers based on a multidentate N-donor ligand and two structure-related dicarboxylate ions, namely, [Cd2(3,4′-tmbpt)( o-bdc)2] ·2H2O ( 1) and [Cd2(3,4′-tmbpt)2( p-bdc)2] ·6.5H2O ( 2) [3,4′-tmbpt = 1-((1 H-1,2,4-triazol-1-yl)methyl)-3-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole, o-H2bdc = 1,2-benzenedicarboxylic acid, and p-H2bdc = 1,4-benzenedicarboxylic acid], were prepared under hydrothermal conditions. The structures of the two compounds were determined by single-crystal X-ray diffraction analysis and further characterized by infrared spectra (IR) and elemental analysis. Compound 1 is a 3D framework containing infinite Cd-O chains. Compound 2 displays a 2D → 2D interdigitated architecture. The effect of the dicarboxylate ions on the structures of the compounds was discussed. Moreover, the optical bandgaps and photoluminescent properties of the compounds were investigated. [ABSTRACT FROM AUTHOR]

Five inorganic–organic hybrid compounds have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction analyses, infrared spectra, elemental analyses, powder X-ray diffraction, and thermogravimetric analyses. In1, each 2,2ʹ-tmbpt ligand links two Cu(II) ions to generate a highly undulated chain. The chains are further bridged by [SiW12O40]4‒anions to form a layer. Compound2exhibits a 3-D (3,4,5)-connected framework with large channels, in which [SiW12O40]4‒anions are tetradentate linkages. In3, each 2,4ʹ-tmbpt links three Cu(II) ions to form 2-D layers, which are further linked by [SiW12O40]4‒to yield a 3-D (3,4)-connected framework. In4, each 4,4ʹ-tmbpt connects three Cu(II) ions to generate 1-D double chains. In5, [PW12O40]3‒link Cu(II) ions to generate 1-D chains. Compounds1‒5exhibit photocatalytic activities for degradation of methylene blue and rhodamine B. Five inorganic–organic hybrid compounds have been synthesized, and the photocatalytic properties of the compounds have also been studied. [ABSTRACT FROM PUBLISHER]