James D. Hoefelmeyer

Naphthalene derivatives peri-substituted by Group 13 elements

Abstract This review focuses on the chemistry of naphthalene derivatives substituted by Group 13 moieties at the peri-positions. Depending on the nature of the Group 13 elements, different synthetic approaches have been considered. 1,8-Diborylated naphthalene complexes are conveniently prepared by metathesis of boron halides or alkoxides with 1,8-dilithionaphthalene. Such complexes can also be obtained by ring opening reaction of 1,8-boron bridged naphthalene species. Owing to the proximity of the boryl moieties, these derivatives are often sterically congested. Gallium and indium derivatives have also been prepared. In this case, however, alternative synthetic approaches have been used. These derivatives can be obtained by reaction of GaCl3 or InCl3 with 1,8-bis(trimethylstannyl)naphthalene. The transmetalation reaction of indium(I) halides with 1,8-bis(halomercurio)naphthalene has also proved useful for the synthesis of naphthalenediylindium complexes. While the development of various applications is still being explored, the 1,8-diborylated naphthalene complexes serve as bidendate Lewis acidic hosts for neutral and anionic guests. Recently, such complexes have also served to provide a scaffold for the formation of radicals that feature intramolecular one-electron σ-bonds.

Reactivity of the dimesityl-1,8-naphthalenediylborate anion: isolation of the borataalkene isomer and synthesis of 1,8-diborylnaphthalenes

The anionic boron peri-bridged naphthalene derivative, namely dimesityl-1,8-naphthalenediylborate (1), undergoes a hydrolysis reaction to afford dimesityl-1-naphthylborane (2) whose structure has been determined. Upon standing at room temperature in toluene for an extended period of time, 1 undergoes a ring expansion reaction to afford 8,10,11a-trimethyl-7-mesityl-11aH-7-boratabenzo[de]anthracene (3). As shown by its crystal structure, compound 3 constitutes a rare example of a borataalkene and features a carbon-boron double bond of 1.475(6) Angstroms incorporated in a conjugated hexa-1-boratatriene system. The reaction of 1 with 9-chloro-9-borafluorene and 5-bromo-10,11-dihydrodibenzo[b,f]borepin results in the formation of diboranes 4 and 5 which bear two different boryl moieties at the peri-positions of naphthalene. These diboranes have been characterized by multinuclear NMR spectroscopy and X-ray single crystal analysis. The boron center of the borafluorenyl moiety is pi-coordinated to the ipso-carbon of a mesityl group with which it forms a contact of 2.730(3) Angstroms. The cyclic voltammogram of 2 in THF shows a quasi-reversible reduction wave at E(1/2)-2.41 V (vs. Fc/Fc+) corresponding to the formation of the radical anion. In the case of diboranes 4, 5 and 1-(dimesitylboryl)-8-(diphenylboryl)naphthalene (6), two distinct waves are observed at E(1/2)-2.14 and -2.56 V for 4, E(1/2)-2.26 and -2.78 V for 5, and E(1/2)-2.41 and -2.84 V for 6. The first reduction wave most likely indicates the formation of a radical anion in which the unpaired electron is sigma-delocalized over the two boron centers.

Exciton migration and charge transfer in chemically linked P3HT–TiO2 nanorod composite

Exciton migration and charge transfer in the chemically linked P3HT–TiO2 nanorod composite (P3HT–Si–nr–TiO2) solution were investigated in comparison with pristine P3HT and physically mixed P3HT/LA–nr–TiO2 solutions. The chemically linked P3HT–Si–nr–TiO2 was made by covalently linking in situ polymerized P3HT onto nr–TiO2 using triethoxy-2-thienylsilane as a linker to replace the initial linoleic acid (LA) capping agent on nr–TiO2. The physically mixed P3HT/LA–nr–TiO2 was prepared by adding ex situ synthesized P3HT into the LA–capped nr–TiO2 solution. In the chemically linked sample, charge transfer from P3HT to TiO2 nanorods was found to occur evidenced by photoluminescence (PL) quenching and ultrafast decay dynamics with a timescale of 0.75 ps. However, both the emission spectra and femtosecond dynamics in physically mixed sample overlapped very well with those from pristine P3HT solution, indicating no PL quenching or charge transfer from P3HT to nr–TiO2. In addition, blue shift in absorbance and PL spectra, larger Stokes shift, and structureless PL spectra found in the chemically linked sample indicated that P3HT formed a more coil-like conformation with more twisted torsion disorders than those in pristine P3HT and physically mixed samples. This is consistent with the femtosecond measurement result that torsional relaxation occurred with a longer decay time and higher amplitude. Moreover, intersystem crossings (ISC) from singlet state (S1) to triplet state (T1) in P3HT of the three samples were all found to occur in a comparable timescale of ∼1 ns and showed no dependence on conformational disorders such as torsional defects.

Synthesis of brookite TiO2 nanorods with isolated Co(II) surface sites and photocatalytic degradation of 5,8-dihydroxy-1,4-naphthoquinone dye

Decomposition of Co2(CO)8 in the presence of ca. 4 nm × 20 nm oleic acid stabilized brookite TiO2 nanorods was performed according to a prior report in the literature in which Co–TiO2 hybrid nanocrystals had been observed. The hybrid nanocrystals could not be duplicated; however, we report a procedure that consistently led to a mixture of blue Co(II)–TiO2 nanorods and Co precipitate. The Co(II)–TiO2 nanorods have single-site Co(II) ions selectively attached to the TiO2 nanocrystal surface. Transmission electron microscopy and powder X-ray diffraction data show the crystal phase and morphology of the nanorod is unchanged on addition of Co(II) and no new crystal phases or particulate domains are associated with the colloid. A combination of UV-visible, X-ray photoelectron, and X-ray absorption spectroscopic analysis indicates Co(II) sites are present on the surface of the TiO2 nanorods in octahedral and tetrahedral coordination in ∼1 : 1 ratio. A mechanism is proposed in which the Co–Co bond of the precursor undergoes heterolysis followed by disproportionation of Co(I) to yield Co(II) and Co(0) precipitate. The Co(II)–TiO2 nanorods were shown to exhibit greater activity than TiO2 nanorods in the degradation of 5,8-dihydroxy-1,4-naphthoquinone dye under visible light irradiation.

Graphitized activated carbon based on big bluestem as an electrode for supercapacitors

Activated carbon based on biochar is an attractive material for energy storage in terms of its high specific capacitance and low cost. The activated carbon samples were based on big bluestem biochar, which is the waste from a thermochemical process optimized for bio-oil production. Sodium bicarbonate, sodium hydroxide and potassium hydroxide were used as reagents to obtain the activated carbon samples. The surface area and pore structure of the activated carbon, characterized by the N2 adsorption–desorption method, were firmly in conjunction with those of the reagents. The high specific surface area (2490 m2 g−1) of the activated carbon was achieved by the activation of potassium hydroxide. Scanning electron microscopy and Raman spectroscopy were used to test the microstructure and crystallographic orientation of the carbon samples. Concerning the G band (1580 cm−1) and the ratio of this with the D band (1338 cm−1), which was 0.55, the Raman spectrum indicated that the potassium hydroxide activated carbon sample contained sp2 carbon. The 2D (2680 cm−1) band showed that this activated carbon has similar properties to multilayer graphene. The cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy were measured after the activated carbon was assembled into supercapacitors. The potassium hydroxide activated carbon sample presented a high specific capacitance of 283 F g−1, and a relatively low inner resistance of 2 ohm.

1,2-Nucleophilic addition of 2-(picolyl)organoboranes to nitrile, aldehyde, ketone, and amide

A series of 2-(picolyl)borane molecules were synthesized as products of the reaction between 2-(picolyl)lithium and R(2)BOMe (R = ethyl, 9-BBN, phenyl, 9-borafluorenyl). The 2-(picolyl)boranes were dimeric; whereas, monomers coordinated to LiOMe could be isolated when the synthesis was carried out in the presence of TMEDA and THF. The 2-(picolyl)boranes undergo reaction with nitriles, ketones, aldehydes, and amides with apparent 1,2-addition of the B-C(picolyl) bond to the unsaturated bond. Theoretical models reveal the presence of a donor orbital on the 2-(picolyl)borane with significant electron density at the benzylic carbon that we conclude was involved in nucleophilic attack on the electrophilic center of unsaturated organic functional groups.

8-Iodo­quinolinium triiodide tetra­hydro­furan solvate

The title compound, C9H7IN+·I3 −·C4H8O, was synthesized from 8-aminoquinoline using the Sandmeyer reaction. The 8-iodoquinolinium cation is essentially planar and the triiodide ion is almost linear. N—H⋯O hydrogen bonds, and intermolecular I⋯I [3.7100 (5) Å] and I⋯H interactions, between the cation, anion and solvent molecules result in the formation of sheets oriented parallel to the (03) plane. Between the sheets, 8-iodoquinolinium and triiodide ions are stacked alternately, with I⋯C distances in the range ∼3.8–4.0 Å.

Self-limiting adsorption of Eu 3+ on the surface of rod-shape anatase TiO 2 nanocrystals and post-synthetic sensitization of the europium-based emission

The surface of oleic acid stabilized rod-shape anatase TiO2 nanocrystals was modified by adsorption of Eu(3+) ions. The Eu(3+) attachment showed Langmuir adsorption behavior, thus the loading of Eu(3+) could be controlled precisely up to surface saturation coverage. The Eu(3+)-TiO2 nanorods show weak Eu(3+) based luminescence. However, addition of thenoyltrifluoroacetone (TTFA) leads to coordination of the ligand to the Eu(3+) centers and the TTFA-Eu(3+)-TiO2 materials exhibit strong Eu(3+) fluorescence sensitized by the TTFA ligand.

8-Iodo-quinolinium chloride dihydrate.

The title compound, C9H7IN+·Cl−·2H2O, was obtained during the synthesis of 8-iodoquinoline from 8-aminoquinoline using the Sandmeyer reaction. The 8-iodoquinolinium ion is almost planar. Solvent water molecules and chloride ions form a hydrogen-bonded chain along the c axis via O—H⋯Cl links. The 8-iodoquinolinium ions, which are packed along the c axis with cationic aromatic π–π stacking (centroid–centroid distance = 3.624 Å), are linked to the chain via N—H⋯O hydrogen bonds.

CHAPTER 2:Nanocatalysis: Definition and Case Studies

Nanocatalysis has emerged as an important area of study from its roots in catalysis, surface science, and solid-state physics. The distinguishing feature in nanocatalysis is the intentional synthesis of uniform, high-quality nanocrystals in which their morphology dictates the electronic structure–surface topology combination. Early fundamental work seeks to establish the specific effects of structure and topology on turnover frequency and selectivity in catalysis. An eventual goal is to engineer nanocrystals for specific catalytic processes.