J. Appl. Cryst.の発刊に際して

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes.

Comprehensive Review in Current Developments of Imidazole‐Based Medicinal Chemistry

Triplet excitons in organic molecules underscore a variety of processes and technologies as a result of their long lifetime and spin multiplicity Organic phosphorescence, which originates from triplet excitons, has potential for the development of a new generation of organic optoelectronic materials and biomedical agents However, organic phosphorescence is typically only observed at cryogenic temperatures and under inert conditions in solution, which severely restricts its practical applications In the past few years, room-temperature-phosphorescent systems have been obtained based on organic aggregates Rapid advances in molecular-structure design and aggregation-behaviour modulation have enabled substantial progress, but the mechanistic picture is still not fully understood because of the high sensitivity and complexity of triplet-exciton behaviour This Review analyses key photophysical processes related to triplet excitons, including intersystem crossing, radiative and non-radiative decay, and quenching processes, to illustrate the intrinsic structure–property relationships and draw clear and integrated design principles The resulting strategies for the development of efficient and persistent room-temperature-phosphorescent systems are discussed, and newly emerged applications based on these materials are highlighted Advances in molecular-structure design and modulation of the aggregation behaviour have enabled much progress in the observation of room-temperature phosphorescence from organic aggregates This Review analyses key photophysical processes related to triplet excitons, illustrating the intrinsic structure–property relationships and identifying strategies to design efficient and persistent room-temperature-phosphorescent systems

Room-temperature phosphorescence from organic aggregates

Photoluminescence (PL), up-conversion PL (UCPL), and phosphorescence are three kinds of phenomena common to light-emitting materials, but it is very difficult to observe all of them simultaneously when they are derived from a single material at room temperature. For the first time, triple-mode emission (that is, PL, UCPL, and room temperature phosphorescence (RTP)) is reported, which relies on a composite of the luminescent carbon dots (CDs) prepared from m-phenylenediamine and poly(vinyl alcohol) (PVA). Moreover, the CDs-PVA aqueous dispersion is nearly colorless and demonstrates promise as a triple-mode emission ink in the field of advanced anti-counterfeiting.

Triple-Mode Emission of Carbon Dots: Applications for Advanced Anti-Counterfeiting

Some 2,6-diarylpiperidin-4-one thiosemicarbazones (1a–8a), obtained from the corresponding 2,6-diarylpiperidin-4-ones (1–8) on oxidative cyclization with H2O2 at 0°C provide 7,9-diaryl-1,2,4,8-tetraaza spiro[4.5]decan-3-thiones (1b–8b) in excellent yields. The structures of these compounds have been established on the basis of their elemental, analytical and spectral data.

Synthesis of 6‐Substituted/Unsubstituted‐7,9‐diaryl‐1,2,4,8‐tetraazaspiro [4.5]decan‐3‐thiones.

In a wide search program toward new and efficient antimicrobial agents, a series of substituted piperidin-4-one oxime ethers (5a-5k) was synthesized and tested for their in vitro antibacterial and antifungal activities. Also, the structures of these oxime ethers and their relative stereochemistries have been investigated by nuclear magnetic resonance spectroscopy. In all the oxime ethers synthesized, the orientation of the N-O bond of the oxime ether moiety syn to C-5 (E-isomer) was deduced based on (1)H NMR and (13)C NMR spectra. It was found that the sterically less hindered compounds, either C-3 (H) and C-5 (H)- or C-3 (Me) and C-5 (H) -substituted ones 5a, 5c, 5d, 5f, 5g, 5i and 5j prefer chair conformation, whereas the sterically more hindered C-3 (Me) and C-5 (Me) -substituted ones 5b, 5e, 5h, and 5k prefer twist-boat conformation. Among the oxime ethers tested, 1,3,5-trimethyl-2,6-diphenylpiperidin-4-one O-(2-chlorophenylmethyl)oxime (5h) exhibited good antibacterial property against Bacillus subtilis, with minimum inhibitory concentration (MIC) closer to that of reference drug, streptomycin. Compounds, 1,3-dimethyl-2,6-diphenylpiperidin-4-one O-(2-chlorophenylmethyl)oxime (5g) and 1,3-dimethyl-2,6-diphenylpiperidin-4-one O-(2-bromophenylmethyl)oxime (5j) showed potent antifungal activity against Aspergillus flavus and Candida-51, respectively. The later compound 5j is more active than the reference drug while the activity of the former one 5g is similar to that of the reference drug, amphotericin B in terms of MIC. The present results may be used as key steps for the construction of novel chemical entities with better pharmacological profiles than standard drugs.

Synthesis, Stereochemistry, and Antimicrobial Evaluation of Substituted Piperidin‐4‐one Oxime Ethers.

https://journals.iucr.org/x/issues/2016/06/00/zq4007/zq4007.pdf

2-Chloro-N-(4-phenyl-1,3-thia­zol-2-yl)acetamide

Aldoximes and ketoximes are effectively deoximated to regenerate the carbonyl compound by an efficient, mild, stable oxidant N-chloro-3-methyl-2,6-diphenylpiperidin-4-one (NCP).

N‐Chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one (NCP) — An Efficient, Mild, Stable Oxidant for Cleavage of Carbon—Nitrogen Double Bonds of Oximes.

In the title piperidine derivative, C21H22Cl2N2O, the piperidine ring adopts a chair conformation. The chloro­phenyl rings are oriented at an angle of 45.59 (14)° with respect to each other. In the crystal, mol­ecules are linked via N—H⋯O hydrogen bonds, forming C(4) chains along [100]. The chains are linked by C—H⋯O hydrogen bonds, forming sheets parallel to the ab plane. Within the sheets, there are N—H⋯π inter­actions present. The crystal studied was refined as an inversion twin.

https://journals.iucr.org/e/issues/2015/11/00/su5218/su5218.pdf

Senthamaraikannan Kabilan

Papers

Synthesis of 6‐Substituted/Unsubstituted‐7,9‐diaryl‐1,2,4,8‐tetraazaspiro [4.5]decan‐3‐thiones.

Synthesis, Stereochemistry, and Antimicrobial Evaluation of Substituted Piperidin‐4‐one Oxime Ethers.

2-Chloro-N-(4-phenyl-1,3-thiazol-2-yl)acetamide

N‐Chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one (NCP) — An Efficient, Mild, Stable Oxidant for Cleavage of Carbon—Nitrogen Double Bonds of Oximes.

Crystal structure of 2-[4(E)-2,6-bis-(4-chloro-phen-yl)-3-ethyl-piperidin-4-yl-idene]acetamide.

Senthamaraikannan Kabilan

Papers

Synthesis of 6‐Substituted/Unsubstituted‐7,9‐diaryl‐1,2,4,8‐tetraazaspiro [4.5]decan‐3‐thiones.

Synthesis, Stereochemistry, and Antimicrobial Evaluation of Substituted Piperidin‐4‐one Oxime Ethers.

2-Chloro-N-(4-phenyl-1,3-thia­zol-2-yl)acetamide

N‐Chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one (NCP) — An Efficient, Mild, Stable Oxidant for Cleavage of Carbon—Nitrogen Double Bonds of Oximes.

Crystal structure of 2-[4(E)-2,6-bis-(4-chloro-phen-yl)-3-ethyl-piperidin-4-yl-idene]acetamide.

2-Chloro-N-(4-phenyl-1,3-thiazol-2-yl)acetamide