Highly efficient NIR-Ⅱ window photoluminescence up to 1000 nm using heteroatomic fused-ring radicals.

Neutral radicals have the potential to construct pure organic light-emitting diodes (OLEDs) with internal quantum efficiencies reaching 100%. However, neutral radical luminescent materials with emission wavelengths in the second near-infrared (NIR-II) window are rare. Herein, a serial of neutral donor-bridge-acceptor (D-π-A) type radical derivatives are investigated.

Regulating and Predicting the Polyhedral Crystal Morphology in Spirofluorene Molecular Systems.

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.

The combination of skeleton-engineering and periphery-engineering: a design strategy for organic doublet emitters.

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 (D) to the doublet ground state (D) 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.

Hydrogen Migration-Triggered Diradicaloid Singlet-Fission Switch.

We present a theoretical design of the singlet-fission (SF) interconversion between two hydrogen tautomers to attract attention to electronic devices such as switches in the SF field. We develop a tuned π-electron conjugation strategy based on single-hydrogen migration to introduce diradical character and yield low-lying (T) levels. Specifically, these objectives could be accomplished by moving one hydrogen from a dihydrogen-substituted pyrazine-fused ring to another unsubstituted pyrazine-fused ring in tetraazatetracenes.

Self-Assembly of a Phosphate-Centered Polyoxo-Titanium Cluster: Discovery of the Heteroatom Keggin Family.

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 (PO )-centered polyoxo-titanium clusters (PTCs) is presented, PTi and PTi , which display classic heteroatom Keggin and its trivacant structures, respectively. Because Ti has lower oxidate state and larger ionic radius than Mo , W , V , and Nb , additional Ti centres in these PTCs are used to stabilize the resultant heteroatom Keggin structures, as demonstrated by the cooresponding theoretical calculation results.

Exploring the Influence of Halogen Coordination Effect of Stable Bimetallic MOFs on Oxygen Evolution Reaction.

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.

Structural, spectral and magnetic studies of two Co(II)-N-heterocyclic diphosphonates based on multinuclear units.

Two examples of Co(II)-N-heterocyclic coordination polymers based on 1-hydroxyethylidenediphosphonic acid (H5L=CH3C(OH)(PO3H2)2), namely 0.5(H3NCH2CH2NH3)·[Co6(Cl2)(H3L)2(H2L)(HL)(2,2'-bipy)6] 1 and 2(NH4)·[Co3(HL)2(H2O)2(phen)2]·2(H2O) 2, have been solvothermally obtained by introducing the second ligands 2,2'-bipyridine/1,10-phenanthroline (2,2'-bipy/phen) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, TG-DSC. The single-crystal X-ray diffractions show that compound 1 possesses a 0-D structure with hexa-nuclear cluster [Co6(O-P-O)8] built through single/double O-P-O bridges and compound 2 displays a 1-D ladder-like chain structure with magnetic topology building blocks [Co4(O-P-O)4]n.

Two novel Cu(II) diphosphonates: structural, spectral and magnetic studies.

By introducing the second organic N-heterocyclic ligands 2,2'-bipyridine (2,2'-bipy)/1,10-phenanthroline (phen), two mono-/bi-nuclear examples of Cu(II)-diphosphonate coordination polymers based on 1-hydroxyethylidenediphosphonic acid (H5L=CH3C(OH)(PO3H2)2), [Cu(H4L)2(2,2'-bipy)]·H2O 1 and [Cu(H3L)(phen)]2·(HOCH2CH2OH)0.52, have been solvothermally obtained and characterized by powder X-ray diffraction, elemental analysis, IR, TG-DSC. The single-crystal X-ray diffractions show that both the two compounds possess zero-dimensional structures, built from mononuclear unit [CuO4N2]n for 1 and binuclear unit [-Cu-O-P-O-]2n with a double O-P-O bridge for 2 in syn-anti fashion.

Quantum chemical characterization and design of host materials based on phosphine oxide-substituted (triphenylamine) fluorene for (deep) blue phosphors in OLEDs.

We studied the electronic structures of a series of fluorene derivatives (p/mPODPFs and p/mPOAPFs) using density functional theory calculations and investigated their performances as host materials in organic light-emitting diodes from three aspects, i.e. triplet energy, ability of charge injection from neighboring organic layer or electrode, and match of the hosts and the reference guests (FIrpic and FCNIr) for efficient energy transfer (EF).

After the electronic field: structure, bonding, and the first hyperpolarizability of HArF.

In this work, we add different strength of external electric field (E(ext)) along molecule axis (Z-axis) to investigate the electric field induced effect on HArF structure. The H-Ar bond is the shortest at E(ext) = -189 × 10(-4) and the Ar-F bond show shortest value at E(ext) = 185 × 10(-4) au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H-Ar shows downtrend (ranging from 0.

Cyano or o-nitrophenyl? Which is the optimal electron-withdrawing group for the acrylic acid acceptor of D-π-A sensitizers in DSSCs? A density functional evaluation.

We report a DFT, TDDFT and DFTB investigation of the performance of two donor-π-acceptor (D-π-A)-type organic dyes bearing different electron-withdrawing groups (EWG) for dye-sensitized solar cells (DSSCs) to evaluate which EWG is better for an acrylic acid acceptor, i.e., Cyano (-CN) or o-nitrophenyl (o-NO2-Ph).

The origin of the unusual broad and intense visible absorption of tetrathiafulvalene-annulated zinc porphyrazine: a density functional theory study.

The vertical excitation energies of tetrathiafulvalene (TTF)-annulated zinc porphyrazine (ZnPzTTF) were investigated using time-dependent density functional theory (TDDFT) calculations and compared to the experimental UV-vis spectra. To examine the effects of the aza substitutions and TTF groups on the molecular properties, zinc complexes of porphyrin (ZnP), porphyrazine (ZnPz) and tetraTTF-annulated porphyrin (ZnPTTF) were also selected for comparison. It was shown that numerous electronic transitions with TTF-to-porphyrin or porphyrazine charge transfer character exist and the Q band of ZnPzTTF is dominated by TTF-to-porphyrazine charge transfer transition mixed with porphyrazine core unit itself except for classic porphyrazine π→π* transitions.

Functionalized ferrocenes and ferroceniums: synthesis, crystal structures and electrochemical properties based on carbazole/phenothiazine-ferrocene conjugated molecules.

Four new D-pi-D (or D-pi-D-pi-D) complexes 9-ethyl-3-E-((1-ferrocenyl)vinyl)-carbazole (1), 9-ethyl-3,6-E,E-((1,1-diferrocenyl)vinyl)- carbazole(2), 10-ethyl-3-E-((1-ferrocenyl)vinyl)-phenothiazine (3), 10-ethyl- 3,7-E,E- ((1,1-diferrocenyl)vinyl)-phenothiazine (4), have been obtained by solid-phase Wittig reactions and fully characterized. The four complexes were treated with iodine leading to four corresponding [D-pi-A](+) I(3)(-) ferrocenium triiodides (+)I(3)(-) (5), (+)I(3)(-) (6), (+)I(3)(-) (7) and 4(+)I(3)(-) (8), respectively. The results of single crystal X-ray diffraction analysis show that and display better coplanarity between the Fc and carbazole subunits than that between the phenothiazine and ferrocene moieties, which leads to a better pi-electron delocalization.

Various unique coordination patterns of Hg and DFT calculations to determine the formation of a 3-D supramoleculer framework by covalent and noncovalent interactions.

By combining a large pi-conjugated bidentate ligand L: 3,6-dipyrazole-N-ethylcarbazole with HgI(2), an extraordinary supramolecular coordination polymer, [Hg(4)L(2)I(8)](infinity), has been prepared. The crystal structures of the ligand and its coordination polymer were determined by X-ray crystallography, which shows three varied coordination modes especially the rare asymmetric quadruply bridged trinuclear moieties in [Hg(4)L(2)I(8)](infinity). Density functional theory (DFT) calculations (ADF) performed on model dimers show the roles of covalent and noncovalent interactions in establishing the three-dimensional architecture.

Theoretical study on a novel series of fullerene-containing organometallics Fe(eta5-C55X5)2 (X = CH, N, B) and their large third-order nonlinear optical properties.

Geometry structures, electronic spectra, and third-order nonlinear optical (NLO) properties of Fe(eta (5)-C 55X 5) 2 (X = CH, N, B) have first been investigated by time-dependent density functional theory. We analyzed the intramolecular interactions between ferrocene and the C 50 moiety. The calculated electronic absorption spectrum indicates that the short wavelength transitions are ascribed to the C 50 moiety mixed charge transfer transition of ferrocene itself, while the low energy excitation transitions are ascribed to the unique charge transfer transition from ferrocene to C 50 moiety in these systems.