Controlling helicene's pitch by molecular tethering

We applied post-cyclization annulation to introduce a series of tethered S-shaped double [4]helicenes in which the intramolecular tether imposes a specific helical handedness. Introducing a tether and then shortening the tether length incrementally increase the pitch angle of [4]helicene, thus enabling a quantitative study of the effects of helicene's pitch on its electronic and (chiro)optical properties.

Advances in the Chemistry of 2,4,6-Tri(thiophen-2-yl)-1,3,5-triazine

Heterocyclic systems are now considered to be an integral part of material chemistry. Thiophene, selenophene, furan, pyrrole, carbazole, triazine and others are some such examples worth mentioning. 2,4,6-Tri(thiophen-2-yl)-1,3,5-triazine is a C3h -symmetric system with thiophene as the donor unit and s-triazine as the acceptor unit. This review gives an insight into the advances made in the thienyl-triazine chemistry over the past two to three decades. The synthetic pathways for arriving at this system and all its important derivatives are provided. The major focus is on the materials synthesized using the thienyl-triazine system, including star molecules, linear and hyperbranched polymers, porous materials and their diverse applications. This review will play a catalytic role for new dimensions to be explored in thienyl-triazine chemistry.

Effect of connectivity variation in Azulene-BODIPY triads and their optoelectronic properties

Azulene is a non-alternant non-benzenoid aromatic hydrocarbon with an inherent dipole moment of 1.08 D providing azulene-containing conjugated systems with a narrow HOMO-LUMO gap. Here we discuss the design, synthesis...

Synthesis of bent-shaped π-extended thienoacenes from 2,5-distannylated 3,4-dialkynethiophene

Bent-shaped thienoacenes show promise as next-generation organic semiconductors. Here we present the synthesis of an air-stable, pure and easily scalable thiophene precursor, 2,5-distannylated-3,4-dialkyne thiophene, starting from 3,4-dialkyne thiophene in quantitative yields. This precursor has been used for the synthesis of a versatile class of syn-thienoacenes comprising up to 13 fused rings, helical acenes and donor-acceptor acenes.

Polycyclic Arene-Fused Selenophenes via Site Selective Selenocyclization of Arylethynyl Substituted Polycyclic Arenes

Arene-fused selenophenes were synthesized by a redox neutral process from arylethynyl substituted polycyclic arenes using selenium powder in refluxing N-methyl-2-pyrrolidone (NMP) with the assistance of the residual water in NMP as a catalytic proton source. The site-selective nature of this selenocyclization produces trans-alkenes as a competitive product, which is dependent on the π-electron donation ability of polycyclic arenes and the kind of arylethynyl group attached to it. DFT calculations were performed to understand the site selectivity in the selenophene formation reaction. The HOMO coefficient on the carbon adjacent to carbon having arylalkyne substituent of the polycyclic arene correlates with the selenocyclization tendency of the substrate. The wavelength of absorption and emission and quantum yield of emission increase with increasing the number of fused benzene rings in the polycyclic unit (from naphthalene to pyrene).

The Effect of Base and Nucleophile on the Nucleophilic Substitution of Methoxytropone Derivatives: An Easy Access to 4- and 5-Substituted Multifunctional Azulenes

The nucleophilic substitution on 3-substituted 2-methoxytropones to form azulenes is dependent on the nucleophile and base employed. With bulkier nucleophiles (ethyl/methyl cyanoacetate), the reaction proceeds with the abnormal nucleophilic substitution irrespective of the base and with smaller nucleophiles (malononitrile), the reaction follows base-dependent normal and abnormal nucleophilic substitution. Thus, the methodologies are developed to selectively obtain 4- and 5-substituted azulenes based on the nature of bases and nucleophiles employed.

Mechanophotonics: Flexible Single-Crystal Organic Waveguides and Circuits

We present the one-dimensional optical-waveguiding crystal dithieno[3,2-a:2',3'-c]phenazine with a high aspect ratio, high mechanical flexibility, and selective self-absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave more like plastic crystals due to significant surface adherence, making them suitable for constructing photonic circuits via micromechanical operation with an atomic-force-microscopy cantilever tip. The flexible crystalline waveguides display optical-path-dependent FL signals at the output termini in both straight and bent configurations, making them appropriate for wavelength-division multiplexing technologies. A reconfigurable 2×2-directional coupler fabricated via micromanipulation by combining two arc-shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals.

Boron difluoride formazanates with thiophene and 3,4-ethylenedioxythiophene capping and their electrochemical polymerization

BF₂ formazanates with thiophene and 3,4-ethylenedioxythiophene capping, prospective candidates for ambipolar semiconductors, have been synthesized and polymerized electrochemically.

Abnormal Nucleophilic Substitution on Methoxytropone Derivatives: Steric Strategy to Synthesize 5-Substituted Azulenes

Azulene is a non-alternant non-benzenoid aromatic system, and in turn, it possesses unusual photophysical properties. Azulene-based conjugated systems have received increasing interest in recent years as optoelectronic materials. Despite the routes available for the preparation of substituted azulene derivatives, there remain few methods that allow regioselective substitution on the seven-membered ring of azulenes due to the subtle reactivity difference among the various positions. This report explores the reactivity of substituted tropolones as the azulene precursors and also provides a new method to create 5-substituted azulenes. The reaction of cyanoacetate enolate with unsubstituted 2-methoxytropone affords azulene through the attack of the nucleophile on the C-2 center (normal pathway). We have observed that 3-substituted 2-methoxytropones undergo steric-guided nucleophilic addition at the C-7 center (abnormal pathway) to afford 5-substituted azulene derivatives. Based on this observation and DFT calculation, a new synthetic strategy is devised for the regioselective synthesis of 5-substituted multifunctional azulenes, which cannot be accessed by any other method.

Effect of heteroatom (S/Se) juggling in donor–acceptor–donor (D–A–D) fused systems: synthesis and electrochemical polymerization

Planarization of donor–acceptor–donor (D–A–D) systems through N-bridges with systematic alteration of S/Se atom(s) resulted in interesting fluorosolvatochromic molecules and their electrochemical polymers.

Effects of calcium soap of rice bran oil fatty acids supplementation alone and with DL-α-tocopherol acetate in lamb diets on performance, digestibility, ruminal parameters and meat quality

Thirty-six Malpura lambs (28 day old and 6.7 ± 0.25 kg BW) were distributed equally in three groups having six males and six female. They were ad libitum fed individually three different experimental diets containing calcium soap of fatty acids (CA-FA) at 0 (T1 ) and 40 (T2 and T3 ) g/kg concentrate up to six months of age. Animals in T3 were supplemented additionally with 40 mg DL-α-tocopherol acetate/kg of concentrate. The roughage moiety included ad libitum dry Prosopis cineraria and fresh Azadirachata indica leaves. All the lambs were allowed to suckle from their dam up to weaning (90 day of age). Supplementation of Ca-FA improved weight gain and feed conversion ratio during both pre- (28-90 days) and post-weaning (91-180 days) phases; however, no effect of DL-α-tocopherol was observed. Metabolic parameters during post-weaning phase revealed non-significant effect on digestibility but improved nitrogen balance in the test groups. The effect on biochemical attributes did not show any significant alteration in ruminal parameters, blood biochemicals and urinary purine derivatives. Carcass traits revealed higher (p < 0.05) dressing yield and loin eye area with Ca-FA supplementation. The value of thiobarbituric reactive substances for nuggets prepared from frozen carcasses revealed significant (p < 0.05) reduction in T3 compared to the other dietary groups. Fatty acid profile of adipose tissue revealed higher (p < 0.001) 9-octadecanoic, 9-12-octadecadienoic, polyunsaturated fatty acids (PUFA), higher ratio of PUFA/saturated fatty acids (SFA), ω-6/ω-3 and lower SFA in Ca-FA-supplemented groups. It is concluded that supplementation of 40 g/kg calcium soap prepared from industrial grade rice bran oil in lamb ration provided additional energy intake, improved N utilization, gain and feed conversion ratio besides improving dressing yield and meat quality with CLA enriched fatty acid profile. DL-α-tocopherol acetate when supplemented at 40 mg/kg feed reduced lipid oxidation of meat products thus improving its keeping quality.

Mandating audio-video recording of informed consent: are we right in enforcing this?

Medicines are the result of experimentation carried out in animals and humans. However, there are numerous instances in the history of medicine where humans were subjected to undue risks and abuses, requiring regulations for their safety. Idea of informed consent has found its presence in medical literature from the times of Hippocratic Oath propagating principles of '...never do harm to anyone' and physician directed care of patients. This was revived in post-world war II era in the form of Nuremberg code and the declaration of Helsinki in response to various debilitating experimentations done on prisoners in concentration camps and elsewhere. Complete information and voluntary participation forms the ethical tenets of these acts and the same has been reflected in various guidelines enacted worldwide, which are sufficient to make sure that patient consent is obtained in fair and just manner. Despite this, there have been undesirable lapses in the conduct of clinical trials. This situation worsens, when intentional lapses in conduct of trial hamper the ability of socially and economically disadvantaged communities in developing countries to make free and informed decision.

Effect of combining viscous fibre with lovastatin on serum lipids in normal human subjects

OBJECTIVES

Soluble fibre supplements are recommended to reduce the levels of low-density lipoprotein cholesterol (LDL-C). Limited information exists on the interaction between fibre and hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). The purpose of the present study was to evaluate the per se effect of psyllium (10 g/day) and lovastatin (20 mg/day) alone and in combination on serum lipids in normal human volunteers.

METHODS

In a 4-week open label, randomised, parallel study, subjects were randomised to receive 20 mg of lovastatin, 10 g of psyllium or 20 mg of lovastatin plus 10 g of psyllium in evening daily. Levels of total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C), TC/LDL-C ratio, LDL-C/HDL-C ratio and triglycerides were determined after 1, 2, 3 and 4 weeks of treatment.

RESULTS

The study group comprised 36 adult, male subjects. All treatments were well tolerated, and after 4 weeks the mean LDL-C, TC and TG levels in the group receiving 20 mg of lovastatin plus 10 g of psyllium fell by 30.88%, 26.88% and 26.21% from baseline, compared with 24.78%, 19.55% and 32.88% in the group receiving 20 mg of lovastatin and 3.58%, 2.90% and 10.95% in the group receiving 10 g of psyllium respectively. Although additive effect was observed in the group receiving combination compared with group receiving lovastatin, the observed difference was not statistically significant. No significant changes from baseline in HDL-C levels occurred.

CONCLUSIONS

Psyllium soluble fibre should be considered as a safe and well-tolerated dietary supplement option to enhance cholesterol lowering.

Emergency surgery in orbital trauma: a neurosurgical view

This study is an analysis of five cases of orbital trauma causing proptosis, paralysis of extraocular muscles with or without associated visual failure. All the cases were treated by a Neurosurgical team. Either a frontal craniotomy or a lateral orbitotomy was performed. Plain X-rays of the skull and Computerised Tomography (C.T. Scanning) were the main investigations. Results were encouraging both functionally and cosmetically. Early diagnosis and an aggressive approach to orbital decompression can achieve good results.