Nanocrystalline Copper Coatings Produced by Cold Spraying

Jingchun Liu,Hua Cui,Xianglin Zhou,Jishan Zhang,Xiangkun Wu 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.1

Copper powder was cryomilled for 12 hours to achieve particle size in the range of 2 µm to 25 µm, which powder was subsequently used as feedstock for the deposition of nanocrystalline (nc) Cu coating via cold spraying. The as-milled copper powder was characterized by X-ray diffraction (XRD), scanning electron micros-copy (SEM) and high resolution transmission electron microscopy (HRTEM). The particle size of the cryomilled Cu powder was detected by laser scattering. The microstructure of the coating was analyzed using SEM and scanning transmission electron microscopy (STEM). The XRD and HRTEM analysis showed that the grain size of the cryomilled Cu powder was about 5 to 40 nm. This nanoscale structure was retained after the cold spraying. The nanoindentation analysis showed that the nc Cu coating hardness value reached 3.3GPa, which was higher than that of its coarse grained counterpart.

Phenalenyl-fused porphyrins with different ground states

Zeng, Wangdong,Lee, Sangsu,Son, Minjung,Ishida, Masatoshi,Furukawa, Ko,Hu, Pan,Sun, Zhe,Kim, Dongho,Wu, Jishan Royal Society of Chemistry 2015 Chemical Science Vol.6 No.4

<▼1><P>Fusion of one or two phenalenyl units onto the porphyrin core led to biradicaloids with different ground state, physical property and chemical reactivity.</P></▼1><▼2><P>Materials based on biradicals/biradicaloids have potential applications for organic electronics, photonics and spintronics. In this work, we demonstrated that hybridization of porphyrin and polycyclic aromatic hydrocarbon could lead to a new type of stable biradicals/biradicaloids with tunable ground state and physical property. Mono- and bis-phenalenyl fused porphyrins <B>1</B> and <B>2</B> were synthesized <I>via</I> an intramolecular Friedel–Crafts alkylation-followed-by oxidative dehydrogenation strategy. Our detailed experimental and theoretical studies revealed that <B>1</B> has a closed-shell structure with a small biradical character (<I>y</I> = 0.06 by DFT calculation) in the ground state, while <B>2</B> exists as a persistent triplet biradical at room temperature under inert atmosphere. Compound <B>1</B> underwent hydrogen abstraction from solvent during the crystal growing process while compound <B>2</B> was easily oxidized in air to give two dioxo-porphyrin isomers <B>11a</B>/<B>11b</B>, which can be correlated to their unique biradical character and spin distribution. The physical properties of <B>1</B> and <B>2</B>, their dihydro/tetrahydro-precursors <B>7</B>/<B>10</B>, and the dioxo-compounds <B>11a</B>/<B>11b</B> were investigated and compared.</P></▼2>

Tetrakis(4-<i>tert</i>-butylphenyl) substituted and fused quinoidal porphyrins

Zeng, Wangdong,Lee, Byung Sun,Sung, Young Mo,Huang, Kuo-Wei,Li, Yuan,Kim, Dongho,Wu, Jishan The Royal Society of Chemistry 2012 Chemical communications Vol.48 No.62

<P>4-<I>tert</I>-Butylphenyl-substituted and fused quinoidal porphyrins <B>1</B> and <B>2</B> are prepared for the first time. They show (1) intense one-photon absorption in the far-red/near-infrared region, (2) enhanced two-photon absorption compared with aromatic porphyrin monomers, and (3) amphoteric redox behavior. Their geometry and electronic structure are studied by DFT calculations.</P> <P>Graphic Abstract</P><P>Tetrakis(4-<I>tert</I>-butylphenyl) substituted and fused quinoidal porphyrins are prepared for the first time, which show unique geometry, electronic structure and optical properties. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc33728b'> </P>

Octazethrene and Its Isomer with Different Diradical Characters and Chemical Reactivity: The Role of the Bridge Structure

Hu, Pan,Lee, Sangsu,Park, Kyu Hyung,Das, Soumyajit,Herng, Tun Seng,Gonç,alves, Thé,o P.,Huang, Kuo-Wei,Ding, Jun,Kim, Dongho,Wu, Jishan American Chemical Society 2016 Journal of organic chemistry Vol.81 No.7

<P>The fundamental relationship between structure and diradical character is important for the development of open-shell diradicaloid-based materials. In this work, we synthesized two structural isomers bearing a 2,6-naphthoquinodimethane or a 1,5-naphthoquinodimethane bridge and demonstrated that their diradical characters and chemical reactivity are quite different. The mesityl-or pentafluorophenyl-substituted octazethrene derivatives <B>OZ-M/OZ-F</B> and their isomer <B>OZI-M</B> (with mesityl substituents) were synthesized via an intramolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation strategy from the key building blocks <B>4</B> and <B>11</B>. Our detailed experimental and theoretical studies showed that both isomers have an open-shell singlet ground state with a remarkable diradical character (<I>y</I><SUB>0</SUB> = 0.35 and 0.34 for <B>OZ-M</B> and <B>OZ-F</B>, and <I>y</I><SUB>0</SUB> = 0.58 for <B>OZI-M</B>). Compounds <B>OZ-M</B> and <B>OZ-F</B> have good stability in an ambient environment, while <B>OZI-M</B> has high reactivity and can be easily oxidized to a dioxo product <B>15</B>, which can be correlated to their different diradical characters. Additionally, we investigated the physical properties of <B>OZ-M</B>, <B>OZ-F</B>, and <B>15</B>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2016/joceah.2016.81.issue-7/acs.joc.6b00172/production/images/medium/jo-2016-00172x_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo6b00172'>ACS Electronic Supporting Info</A></P>

Toward Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity

Hu, Pan,Lee, Sangsu,Herng, Tun Seng,Aratani, Naoki,Gonç,alves, Thé,o P.,Qi, Qingbiao,Shi, Xueliang,Yamada, Hiroko,Huang, Kuo-Wei,Ding, Jun,Kim, Dongho,Wu, Jishan American Chemical Society 2016 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.138 No.3

<P>Open-shell singlet diradicaloids display unique electronic, nonlinear optical, and magnetic activity and could become novel molecular materials for organic electronics, photonics, and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this Article, we report our efforts toward a tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties, and chemical reactivity were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introduction of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/antiaromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.</P>

Stable 2D anti-ferromagnetically coupled fluorenyl radical dendrons

Wang, Jian,Kim, Gakhyun,Sandoval-Salinas, Marí,a Eugenia,Phan, Hoa,Gopalakrishna, Tullimilli Y.,Lu, Xuefeng,Casanova, David,Kim, Dongho,Wu, Jishan Royal Society of Chemistry 2018 Chemical Science Vol.9 No.13

<▼1><P>The first class of stable two-dimensional anti-ferromagnetically coupled dendritic polyradicaloids was synthesized, which show polyradical character and unique properties.</P></▼1><▼2><P>We report the first class of stable, two-dimensional (2D) anti-ferromagnetically coupled dendritic polyradicaloids. A kinetically blocked fluorenyl radical was used to build up the first and second generation dendrons <B>FR-G1</B> and <B>FR-G2</B> containing three and seven fluorenyl units, respectively. The neighboring fluorenyl radicals in <B>FR-G1</B> and <B>FR-G2</B> show moderate anti-ferromagnetic exchange interaction, resulting in a doublet and quartet ground state, respectively, with a small doublet–quartet energy gap. From <B>FR-G1</B> to <B>FR-G2</B>, the energy gap decreased and the two-photon absorption was enhanced owing to more extended 2D π-conjugation. Both compounds showed multiple redox waves due to their polyradical character.</P></▼2>

Dibenzoheptazethrene Isomers with Different Biradical Characters: An Exercise of Clar’s Aromatic Sextet Rule in Singlet Biradicaloids

Sun, Zhe,Lee, Sangsu,Park, Kyu Hyung,Zhu, Xiaojian,Zhang, Wenhua,Zheng, Bin,Hu, Pan,Zeng, Zebing,Das, Soumyajit,Li, Yuan,Chi, Chunyan,Li, Run-Wei,Huang, Kuo-Wei,Ding, Jun,Kim, Dongho,Wu, Jishan American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.48

<P><I>Clar’s aromatic sextet rule</I> has been widely used for the prediction of the reactivity and stability of polycyclic aromatic hydrocarbons with a <I>closed-shell</I> electronic configuration. Recent advances in <I>open-shell</I> biradicaloids have shown that the number of aromatic sextet rings plays an important role in determination of their ground states. In order to test the validity of this rule in singlet biradicaloids, the two soluble and stable dibenzoheptazethrene isomers <B>DBHZ1</B> and <B>DBHZ2</B> were prepared by different synthetic approaches and isolated in crystalline form. These two molecules have different numbers of aromatic sextet rings in their respective biradical resonance forms and thus are expected to exhibit varied singlet biradical character. This assumption was verified by different experimental methods, including nuclear magnetic resonance (NMR), electron spin resonance (ESR), superconducting quantum interference device (SQUID), steady-state and transient absorption spectroscopy (TA), and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. <B>DBHZ2</B>, with more aromatic sextet rings in the biradical form, was demonstrated to possess greater biradical character than <B>DBHZ1</B>; as a result, <B>DBHZ2</B> exhibited an intense one-photon absorption (OPA) in the near-infrared region (λ<SUB>abs</SUB><SUP>max</SUP> <I>=</I> 804 nm) and a large two-photon absorption (TPA) cross-section (σ<SUP>(2)</SUP><SUB>max</SUB> = 2800 GM at 1600 nm). This investigation together with previous studies indicates that Clar’s aromatic sextet rule can be further extended to the singlet biradicaloids to predict their ground states and singlet biradical characters.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-48/ja410279j/production/images/medium/ja-2013-10279j_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja410279j'>ACS Electronic Supporting Info</A></P>