Chemistry of condensed thiophenes. IV. Acetylation of phenanthro[4,5-bcd]thiophene

Treatment of phenanthro[4,5-bcd]thiophene ( 2 ) with acetyl chloride and aluminum chloride in nitrobenzene gives acetylation of positions ortho and para to the heteroatomic sulfur atom. In separate experiments, mixtures of 1- and 3-acetyl (50% yield, ratio 1.9:1) or of 1,5-, 1,7-, and 3,5-diacetyl (79% yield, ratio 3:1:1) derivatives were obtained. Isolated as isomerically pure products were the 1-acetyl and the 1,5-diacetyl compounds, as well as the oximes of the 1- and 3-acetyl derivatives. Comparison of these results is made with those reported for nitration of 2 , which also occurs ortho and para to the sulfur atom, and with nitration and acetylation of pyrene (the benzolog of 2 ) which substitutes in the corresponding positions.     

A Rational Approach Towards Determination of Optical Ionicity and Non-covalent Interactions in Fullerene-Calix[4]arene Host-Guest Complexes

The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C₆₀ and C₇₀) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the ground state for the C₆₀ and C₇₀ complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for the C₆₀-1 and C₇₀-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C₇₀ preferentially compared to C₆₀ as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C₆₀ and C₇₀) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C₇₀-1 complexation, C₇₀ is directed in an end-on manner rather than the traditional side-on pattern.     

A Spirocyclohexyl Nitroxide Amino Acid Spin Label for Pulsed EPR Spectroscopy Distance Measurements

Site‐directed spin labeling and EPR spectroscopy offer accurate, sensitive tools for the characterization of structure and function of macromolecules and their assemblies. A new rigid spin label, spirocyclohexyl nitroxide α‐amino acid and its N‐(9‐fluorenylmethoxycarbonyl) derivative, have been synthesized, which exhibit slow enough spin‐echo dephasing to permit accurate distance measurements by pulsed EPR spectroscopy at temperatures up to 125 K in 1:1 water/glycerol and at higher temperatures in matrices with higher glass transition temperatures. Distance measurements in the liquid nitrogen temperature range are less expensive than those that require liquid helium, which will greatly facilitate applications of pulsed EPR spectroscopy to the study of structure and conformation of peptides and proteins.     

Intramolecular Ketone-Olefin Radical Cyclization with Low-Valent Titanium Reagent: Synthesis of Benzopyrans

A novel protocol for intramolecular ketyl-olefin radical cyclization with low-valent titanium reagent is outlined. It allows the formation of the benzopyran nucleus from ortho-allyloxy propiophenones as the sole product in moderate yields via intramolecular radical cyclization.     

Isolation and biological evaluation of chromone alkaloid dysoline,a new regioisomer of rohitukine from Dysoxylum binectariferum

The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC₅₀ of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6.     

Synthesis,mesomorphic, photophysical and computational studies of new achiral four-ring unsymmetrical bent-core mesogens and their Copper(II) complexes

New achiral four-ring unsymmetrical bent-core mesogens derived from 2,5-dihydroxybenzaldehyde and their copper(II) complexes have been synthesised as a new design with an imine and ester linkage. These new bent-core molecules resemble hockey-stick shape, which possesses 4-n-alkyloxy chain (4-n-hexyloxy and 4-n-decyloxy) at one end and methyl or methoxy group at the other end of the molecule. The synthesis, spectroscopic characterisation, phase transition temperature and characterisation of phase behaviour are reported. The bent-core molecules exhibited monotropic nematic and smectic A phase depending on the terminal chain length. Interestingly, copper(II) complexes of bent-core molecules displayed monotropic nematic phase. This is the first report on copper(II) complexes of bent-core molecules that exhibited nematic phase. The four-ring bent-core molecule exhibited fluorescence with large stoke shift. The density functional theory calculations of bent-core molecules and their copper(II) complexes are carried out using Gaussian 09 program at B3LYP level to obtain the stable molecular conformation, dipole moment, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energies and bending angle of the compounds. The natural atomic charges and electronic configurations of the atoms of free ligands as well as the complexes have been evaluated.     

rmpM Genosensor for Detection of Human Brain Bacterial Meningitis in Cerebrospinal Fluid

Human brain bacterial meningitis is a life-threatening disease caused mainly by Neisseria meningitidis, lead to damage of the outer membrane covering (meninges) of brain or even death. The usual methods of diagnosis are either time-consuming or have some limitations. The specific rmpM (reduction-modifiable protein M) virulent gene based genosensor is more sensitive, specific, and can detect N. meningitidis directly from the patient cerebrospinal fluid in 30 min including 1-min response time. 5′-Thiol-labeled single-stranded DNA (ssDNA) probe was immobilized onto screen-printed gold electrode (SPGE) and hybridized with denatured (95 °C) single-stranded genomic DNA (ssG-DNA) for 10 min at 25 °C. The electrochemical response was measured by cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance using redox indicators. The sensitivity of the genosensor was 9.5087?(μA/cm²)/ng with DPV and limit of detection was 3 ng/6 μL ssG-DNA. The immobilization of the ssDNA probe and hybridization with ssG-DNA from N. meningitidis was characterized by atomic force microscopy and Fourier transform infrared spectroscopy. The rmpM genosensor was stable for 6 months at 4 °C with 10 % loss in initial DPV current. The advantage of rmpM genosensor is to detect bacterial meningitis simultaneously in multiple patients using SPGE array during an outbreak of the disease.     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

A detailed insight into the optimization of plate and frame heat exchanger design by comparing old and new generation metaheuristics algorithms

The voluminous utilization and application of plate and frame heat exchangers (PFHE) in many industries has accelerated the consumer and designer both to optimize exchanger total cost. Over the last few years, several old and new generation algorithms were employed and exploited to optimize PFHE cost. This study explores the application and performance of three new-generation algorithms Big Bang-Big Crunch (BBBC), Grey Wolf Optimizer (GWO), and Water Evaporation Optimization (WEO) in designing optimally PFHE. Besides, this study also compares the performance of three well-established old generations algorithms namely genetic algorithm (genetics and natural selection), particle swarm optimization (animals behaviour), and differential evolution (population-based) with the above three new algorithms in the optimization of PFHE.Seven design factors are chosen for PFHE optimization: exchanger length on hot and cold sides, height and thickness of fin, length of the fin-strip, fin frequency, and the number of hot side layers. The applicability of the suggested algorithms is assessed using a case study based on published research. Though DE performs the best in this study of design optimization concerning total cost and computational time, the three new-generation meta-heuristic algorithms BBBC, GWO, and WEO also provide the novel scope of application in heat exchanger design optimization and successfully finding the cost of the heat exchanger. According to this study, capital costs increase by 19.5% for BBBC, 24% for GWO, and 7.6% for GWO, but operational costs fall by 9.5% for BBBC and GWO when compared to the best performing algorithm (DE). On the other hand, WEO shows an increase of 32.6% in operational costs. Aside from that, a full analysis of the computing time for each algorithm is also provided. The DE has the quickest run time of 0.09 ?s, while the PSO takes the longest at 33.97 ?s. The rest of the algorithms have nearly identical values. As a result, a good comparison is established in this study, offering an excellent platform for designers and customers to make selections. Additionally, the three new generations algorithms mentioned here were not used earlier for optimization of PFHE and the comparative study illustrates that each of them possesses eat potential for cost optimization and also solving other complex problems.     

Conformational Control of Oligo(p‐phenyleneethynylene)s with Intrinsic Substituent Electronic Effects: Origin of the Twist in Pentiptycene‐Containing Systems

Dependence of the backbone planarity of oligo(p‐phenyleneethynylene)s (OPEs) on the intrinsic electronic character of substituents and on the nature of the solvent has been experimentally demonstrated with a series of center‐symmetrical five‐ring systems, pentiptycene‐pentiptycene‐arene‐pentiptycene‐pentiptycene, differing in the substituents on the central arene. In frozen 2‐methyltetrahydrofuran (MTHF), the adjacent pentiptycene units prefer to be in a mutually twisted orientation when the substituents are electron‐withdrawing (F and amido), resulting in a TPPT or TTTT conformation, whereas a planarized PPPP backbone is favored in the case of electron‐donating substituents (alkyl and alkoxy). The propensity to adopt the PPPP form is generally enhanced by replacing MTHF with either methylcyclohexane or mixed ethanol/methanol as solvent. These observations reveal that the twist between adjacent pentiptycene units in OPEs is a consequence of the electronic rather than steric effects of iptycenyl substituents. The electronic effect of iptycenyl substituents is manifested in decreased phenylene π polarizability as the net effect of both electron‐donating hyperconjugation and an electron‐withdrawing inductive effect. Variable‐temperature electronic absorption and emission spectroscopies are the critical tools for this work. Our findings provide important guidelines for conformational and electronic engineering of OPEs and for the design of novel iptycene‐based organic electronic materials.