Straight Alkyl Groups Research Articles

Transient Photocurrent Elucidating Carrier Dynamics and Potential of Bulk Heterojunction Solar Cells Fabricated by Thermal Precursor Approach

Transient photocurrents are measured to clarify carrier dynamics in a series of bulk heterojunction solar cells that are composed of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and diketopyrrolopyrrole‐tetrabenzoporphyrin conjugates substituted by straight alkyl groups (Cn‐DPP‐BP), of which the device parameters are largely dependent on the length of the substituted alkyl groups (Cn). The time profile of the observed transients indicates the presence of both unimolecular and bimolecular charge recombination processes in the active layer of the cells. Analysis of the photocurrent decays detected at various bias voltages using a drift model that considers charge extraction by electrodes and charge recombination in the active layer enables elucidation of the charge drift mobility, the initial photocarrier density, and the charge recombination rate constants. The bimolecular recombination rate constant is correlated with Cn and this is the main factor that determines the power conversion efficiency (η) of the Cn‐DPP‐BP:PCBM solar cells. The Cn‐dependent fill factor can be interpreted in terms of the bias voltage dependence of the ratio between the extraction and recombination charges (Qex/Qre). Comparison of η and Qex/Qre at the short‐circuit condition predicts that η for the Cn‐DPP‐BP:PCBM solar cell can be potentially improved up to 6%.

Chiroptical Study of α-Aliphatic Amino Acid Films in the Vacuum Ultraviolet Region

A series of natural circular dichroism (CD) and absorption spectra for films of α-aliphatic amino acids--such as alanine, aminobutyric acid, norvaline, norleucine, valine, leucine, and isoleucine--in the vacuum ultraviolet (VUV) region were observed with the absolute values of optical constants at the undulator-based CD beamline TERAS BL5. Preliminary predictions of some CD spectra were also performed, based on quantum-chemical calculations using the crystal structure. Although the absorption spectra show similar features to each other, significant differences between the CD spectra were found, especially in the 7-8 eV region. The CD spectra of aliphatic amino acids with branched alkyl groups in the side-chain--such as valine, leucine, and isoleucine--exhibit strong negative CD peaks in this energy region. In contrast, the corresponding CD peaks were weak or absent in the spectra of amino acids with straight alkyl groups. Our simple calculation, and the absorption spectra of alkanes, suggest that this difference partly originates from the contribution of the alkyl group. Clear discrepancies between the CD spectra of these amino acids in solutions and those in the solid state were also observed; this is probably caused by the different molecular structures in each state. Our results clearly indicated that CD spectra in the VUV region were very sensitive to the conformations of chiral molecules.

A nuclear magnetic resonance study of the pyridine extraction of coal

Coal extracts prepared using different pyridine extraction methods have been investigated using 13C CP/MAS, 1H CRAMPS and 1H liquid-state nuclear magnetic resonance spectroscopy. The results show that short and straight alkyl groups are transferred preferentially to the extract of the coal, but for the most part, the structural distribution in the extract resembles that of the original coal. Incorporation of the solvents, pyridine and THF, was observed to occur during the extraction procedure and/or the subsequent workup to isolate the extract. The information obtained from the different n.m.r. techniques was complementary.

ChemInform Abstract: Syntheses and the Structures of Carbazole Dioxazines Having Long Straight Alkyl Groups.

ChemInform Abstract: Syntheses and the Structures of Carbazole Dioxazines Having Long Straight Alkyl Groups.

長鎖アルキル基をもつカルバゾールジオキサジン類の合成と構造

長鎖アルキル基 (C6H18～C18H37) をもつカルバゾールジオキサジン類〔Xb～f〕を合成し, その構造や長鎖アルキル基の効果, 色材としての性質について調べた。また, 別途に長鎖アルキル基 (C8H17～C12H25) をもつ線形, 非線形構造のカルバゾールジオキサジン類〔6c～e〕,〔13c～e〕を合成し, 過去の文献に記載されたカルパゾレルジオキサジン〔Xc～e〕との物性を比較した結果, 長鎖アルキル基がある場合でも従来法で得られた〔X〕は線形構造でないことがわかった。長鎖アルキル基の効果は融点あるいは分解点を低下させ, 可視スペクトルの吸収は少し長波長シフトし, とくに〔6c～e〕は有機溶媒への溶解性が増し, 再結晶による精製が可能どなった。色材としてに分散性の向上が認められた。

Investigation of pyridine extracts and residues of coals by solid-state 13C n.m.r. spectroscopy

The 13C n.m.r. technique of cross polarization with magic angle spinning was applied to seven coals in their original states and the components obtained after pyridine extraction. It was observed that for the higher rank coals, short and straight alkyl groups are preferentially transferred to the extracts, while long-chain alkyl groups, branched alkyl groups or alicyclic structures are concentrated in the residues. Aliphatic ether or ester moieties were also observed to be concentrated in the residues. For all coals the computer-generated composite extract-residue spectra differed appreciably from the spectra of the original coals, indicating that some structures may be lost or that some structural conversion may occur during the extraction procedure. It was concluded that caution should be used in trying to determine detailed organic structural information of a coal from data obtained on its pyridine extract.

Investigation of the chemical structures of coking and non-coking coals in original and reductively alkylated solid states via 13C n.m.r. and i.r. spectroscopies

Chemical structures of four Turkish coals in original and reductively alkylated forms were investigated in the solid state by CP/MAS 13C n.m.r. and i.r. spectroscopies. Dilatation properties of these samples were also determined. It was observed that, while the aliphatic parts of the coking coals are mainly composed of short and straight alkyl groups and alicyclic structures, the aliphatic parts of the non-coking coals are to a larger extent composed of branched chains and/or alicyclic structures. It was concluded that ether bonds linking aromatic units are more prominent in the coking coals, whereas in the non-coking coals aromatic-O-aliphatic and/or alicyclic ethers dominate. The degree of condensation of aromatic structures was found to be higher in the coking coals, and the extent of reductive alkylations was higher in comparison with the non-coking coals. Non-coking coals were found to be alkylated preferentially at their phenolic oxygens. Difference spectra were found to be very useful in following organic chemical structural changes that accompany reductive alkylation.