Sono-chemical Synthesis and Mechanism of Dibenz[a,c]anthracene

Planar polycyclic aromatic hydrocarbons have important applications in optoelectronics,environmental chemistry and cancer researches.An improved sono-chemical synthetic procedure of dibenz[a,c]anthracene（D[a,c]A） was reported in this work.The yield was increased to 56% and the resultant was carefully characterized via gas chromatography-electron impact mass spectrometry（GC-EIMS）,matrix assisted laser desorption ionization-time of flight（MALDI-TOF）,1 H NMR,13 C NMR,correlation spectrometry（1 H1 H COSY）,heteronuclear multiple bond correlation（HMBC） and heteronuclear multiple quantum coherence（HMQC）.Based on the characterization data,we proposed a 4-step mechanistic explanation for the formation of D[a,c]A under sono-chemical bis-ortho-Wittig reaction conditions.

Molecular Properties of 9,10-Phenanthrenequinone and Benzil

9,10-Phenanthrenequinone（PQ） and benzil are important a-diketones. This manuscript explains the first comparison of PQ and benzil molecular properties. We have used 1H NMR, 13C NMR, 1H-IH COSY, HMBC, HMQC, UV-Vis absorption and emission, CV and TGA experiments to study PQ and benzil that provided the following novel results. （1） The 1H NMR（CDC13） of PQ show δ 8.19（H1）, 8.02（H4）, 7.72（H3）, 7.47（H2） instead of an earlier reported 8.25（H4）, 8.08（H1）, 7.80（H2）, 7.55（H3）; （2） in the 13C NMR（CDCl3）, the C9/C10（C=O） signal of PQ appears upfield（6 180.3） compared to C9/Cl0（C=O） signal of benzil（6 194.5）, which shows higher electrophilic character（more attractive for nucleophiles） of C9/C10（C=O） of benzil; （3） the first 2max for the UV-Vis absorption and emission of PQ are blue-shifted compared to benzil despite increased conjugation attributed to the different symmetries（C2v for PQ and C2h for Benzil） of the two molecules; （4） the emission spectrum of benzil is broader compared to that of PQ due to slower relaxation of the excited state; （5） The CV study shows that PQ and benzil are good electron acceptors and PQ shows a better reduction process than benzil due to an extra ring that provides stability for the reduced species（mono or diradical anions）; （6） TGA shows the higher thermal stability of PQ than benzil attributed to the presence of phenanthrene unit in PQ.

Synthesis,GC-EIMS,~1H NMR,^(13)C NMR,Mechanistic and Thermal Studies of o-Xylylene-α,α'-bis (triphenylphosphinebromide)

Organophosphorous compounds containing phosphorus as an integral part have been widely used in industry, organic synthesis and optoelectronics, o-Xylylene-a,a＇-bis（triphenylphosphinebromide）（OXBTPPB） is a facile reagent to convert o-quinones（e.g., 9,10-phenanthrenequinone） into polycyclic aromatic hydrocarbons（PAHs）. Herein lies an improved synthetic route to OXBTPPB. The resultant was carefully characterized with GC-EIMS, ^1H NMR, ^13C NMR, spectroscopic techniques. The EIMS shows characteristic peaks at m/z=262.4, 183.3, 108.2, 77.1 attributed to the [C18H15P]^＋, [C12H8P]^＋, [C6H8P]^＋, [C6H5]^＋ ions, respectively. The ^1H and ^13C NMR spectrum shows well resolved peaks and all the hydrogens and carbons were well-assigned via a combined study of ^1H-^1H COSY, HMBC, and HMQC experiments. The mechanism for the formation of OXBTPPB was proposed based on literature and obtained experimental data. Meanwhile, the thermal stability of OXBTPPB was evaluated with TGA analysis, and an onset decomposition temperature（Td） was recorded at 323.6 ℃.

Mechanistic Aspects of Monomer, Polymer Formation, and Synthesis of PQ-Alt-Dialkyl-fluorene Conjugated Copolymer

Suzuki coupling reaction is widely used in the construction of conjugated polymers; however, there is still no report describing the mechanism and coupling of 9,10-phenanthrenequinone（PQ） building blocks via Suzuki reaction because PQ is sensitive to bases and light. Herein is reported the efficient Suzuki coupling of PQ with 9,10-dialkylfluorene with Na2CO3 as basic species and high molecular weight PQ-Alt-Dialkyl-Fluorene conjugated copolymer obtained in an yield of 42%. Based on the characterization data and well-accepted literature, we proposed a step-by-step mechanistic explanation for the formation of the PQ containing alternating conjugated copolymer.

Tailoring Excited State Properties and Energy Levels Arrangement via Subtle Structural Design on D-π-A Materials

The donor-n-conjugated-acceptor （D-n-A） structure is an important design for the luminescent materials be- cause of its diversity in the selections of donor, n-bridge and acceptor groups. Herein, we demonstrate two examples of D-^-A structures capable to finely modulate the excited state properties and arrangement of energy levels, TPA-AN-BP and CZP-AN-BP, which possess the same acceptor and n-bridge but different donor. The investigation of their photophysical properties and DFT calculation revealed that the D-n-A structure with proper donor, n-bridge and acceptor can result in separation of frontier molecular orbitals on the corresponding donor and acceptor with an obvious overlap on the n-bridge, resulting in a hybridized local and charge-transfer （HLCT） excited state with high photoluminescent （PL） efficiencies. Meanwhile, their singlet and triplet states are arranged on corresponding moie- ties with large energy gap between T2 and T1, and a small energy gap between S1 and T2, which favor the reverse intersystem crossing （RISC） from high-lying triplet levels to singlet levels. As a result, the sky-blue emission non-doped OLED based on the TPA-AN-BP reached maximum external quantum efficiency （EQE） of 4.39% and a high exciton utilization efficiency （EUE） of 77%. This study demonstrates a new strategy to construct highly effi- cient OLED materials.

Preparation and electronic characteristics of anionic perylene bisimide films

Neutral perylene bisimides(PBI) are well-known n-type organic semiconductors, with number of challenging electronic properties in their neutral and reduced states. We report the characteristic electronic properties of PBI anionic films. We unexpectedly discovered that pristine PBI dianion film showed p-type character, while oxidized dianion film(dominant neutral state with few radical anions) showed normal n-type semiconductor character based on Seebeck effect measurements. Both kinds of films exhibit high electrical conductivity with a potential for thermoelectric applications. The mechanism of polarity reversal is proposed.

Thermal and Optoelectronic Properties of Anthracene and Dibenz[a,c]Anthracene

The basic characteristics of anthracene（AN） and dibenz[a,c]anthracene（D[a,c]A） derivatives, important semiconductors, were systematically studied. Differential scanning calorimetry（DSC） shows that D[a,c]A has the reversibility of solid and liquid phases. Thermalgravimetric analysis（TGA） shows that D[a,c]A exhibits higher Td（decomposition temperature）, which indicates D[a,c]A, as active layers, should be more suitable to being made into stable devices. D[a,c]A shows blue-shifted UV-Vis absorption and emission despite increased conjugation compared to anthracene due to different symmetries. Both the compounds are planar and show weak blue fluorescence in the tetrahydrofuran（THF） solution and higher fluorescence in the solid-state, due to different energy levels in solution and solid-state, explained via Jablonski diagram.