Influence Of Substitution Pattern Research Articles

Tetrahydropyridinylidene ammonium salts with arylalkyl and diarylalkyl substitution and their antiprotozoal activity

Tetrahydropyridin-4-ylidene salts with benzyl and dibenzyl substitution showed good antiprotozoal activity. This paper reports the synthesis of analogues with longer side chains. They were investigated for their antiprotozoal activities as well as for their cytotoxicity using microplate assays. The most active compounds showed activity against Trypanosoma brucei rhodesiense in concentrations < 0.06 µM. A series of compounds was active against Plasmodium falciparum NF54 in low nanomolar concentration and exhibited outstanding selectivity. The influence of substitution pattern and chain length on the antiprotozoal potencies were analyzed and structure–activity relationships were given. New compounds were characterized by FT-IR, HRMS, and NMR spectroscopy.Graphical abstract

On the Influence of Substitution Patterns in Thioether‐Based Luminophores with Aggregation‐Induced Emission Properties

AbstractIn this work we present a full study on the influence of substitution patterns in aromatic thioether‐based luminogens with aggregation induced emission properties. To this end nine different compounds, either with nitrile groups in ortho, meta or para positions as well as phenol groups in different positions were synthesized and investigated concerning their photophysical properties. Besides that, eight compounds were obtained as single crystals for X‐ray analysis to get a deeper understanding on the packing parameters, secondary interactions as well their influence on the properties of these compounds. Time dependent density functional theory calculations helped to understand the distribution of the frontier orbitals. Moreover, these nanostructures were analysed concerning their applicability as cellular markers. We could thus show that indeed subtle differences in shape and substitution pattern dramatically influence the photophysical properties as well as cellular uptake of the compounds.

Cover Picture: On the Influence of Substitution Patterns in Thioether‐Based Luminophores with Aggregation‐Induced Emission Properties (ChemistrySelect 4/2018)

Cover Picture: On the Influence of Substitution Patterns in Thioether‐Based Luminophores with Aggregation‐Induced Emission Properties (ChemistrySelect 4/2018)

Diarylamino- and Diarylboryl-Substituted Donor-Acceptor Pyrene Derivatives: Influence of Substitution Pattern on Their Photophysical Properties.

Dianisylamino donor (D) and dimesitylboryl acceptor (A) substituents were introduced at the 1,6- and 2,7-positions of pyrene to demonstrate that the substitution patterns influence the photophysical properties. The different pictures in orbital interactions between the pyrene core and the D-A substituents led to the outcome that 1,6-substituted pyrene derivative 1 had stronger electron-donating and electron-accepting properties in conjunction with a small HOMO-LUMO gap, as compared to the 2,7-substituted derivative. For these pyrene derivatives, modest (ΦF = 0.2) to strong (ΦF = 1.0) fluorescence was detected in degassed organic solvents; 1 exhibited a typical intramolecular charge transfer (ICT) emission obeying energy-gap law, while 2 displayed a moderate inverse energy-gap law, originating from the different substitution patterns. Although theoretical calculations predicted that both 1 and 2 adopt highly twisted ICT excited states (TICT excited states) even in the gas phase, but practically, it was suggested that the observed photophysical properties could be determined by the extent of twist angle of the TICT-like excited state in accordance with the solvent polarity. Moreover, the bulky D-A substituents inhibit the intermolecular direct π-π interactions, thereby resulting in the bright and moderate solid-state emissions for 1 (ΦF = 0.76) and 2 (ΦF = 0.21), respectively.

Thienylphenothiazine integrated pyrenes: an account on the influence of substitution patterns on their optical and electroluminescence properties

A new set of thienylphenothiazine-integrated pyrenes have been prepared by Stille coupling reactions in good yields and characterized by optical, electrochemical, thermal and electroluminescence investigations.

Influence of substitution pattern and enhanced π-conjugation on a family of thiophene functionalized 1,5-dithia-2,4,6,8-tetrazocines

The versatile, one-pot synthesis of a series of π-extended 1,5,2,4,6,8-dithiatetrazocines is described, along with their optoelectronic and structural properties.

Improving Melt Flow of Polyoxymethylene (“High-Speed POM”): Additive Design, Melt Rheology, and In Situ Composition Gradient Formation

Multifunctional isocyanurates are tailored as new additives for improving POM melt flow (“High Speed POM”). In a versatile one-pot synthesis, reacting trimerized hexamethylene diisocyanate with various alcohols and amines, functionalities, branching, and n-alkyl chain length are readily varied. The influence of substitution patterns on POM rheology is investigated. Adding 3 wt% isocyanurate urethane (I3O) together with 0.33 wt% nanosilica increases POM melt flow path by 60%. Large POM stacking boxes are molded at temperatures lowered by 40 K. This markedly enhances cooling and reduces cycle times. Isocyanurate urea (I3N) does not require nanosilica addition. Lubrication mechanisms and the role of in situ gradient formation, as measured by AFM, are studied.

Ruthenium(ii) and rhodium(iii) porphyrin phosphine complexes: influence of substitution pattern on structure and electronic properties

A series of ruthenium(II) and rhodium(III) porphyrin complexes with diphenyl phenylacetylene phosphine (dpap) was synthesised and fully characterised by UV-vis, 1H NMR and 31P{1H} NMR spectroscopy, and in most cases also by single-crystal X-ray diffraction. The substitution pattern of the porphyrin was varied with increasing meso-phenyl substitution, from octa-ethyl porphyrin (OEP), through diphenyl di-ethyl porphyrin (DPP), to tetraphenyl porphyrin (TPP) and 3,5-di-tbutyl tetraphenyl porphyrin (tbTPP). The dpap readily displaces the CO ligand from the parent Ru(CO)(porphyrin) and the iodide from the Rh(I)(porphyrin) to give bis-phosphine complexes M(dpap)2(porphyrin). The UV-vis spectra reveal that some of the complexes are partially dissociated at concentrations of 10−6 M, and the association constants were estimated to be in the range of 106 to 107 M−1 for the first, and 104 to 106 M−1 for the second binding event. The 1H NMR chemical shifts of the complexes vary greatly despite the fact that they display very similar geometries in the solid state, and no correlation could be discerned between the crystal structures and the spectroscopic parameters in solution.

Phthalocyanines as sensitive coatings for QCM sensors: Comparison of gas and liquid sensing properties

The quartz crystal microbalance (QCM) was used to investigate the liquid sensing properties of a set of phthalocyanines (Pcs) which were systematically varied by attaching the substituent 2,2,3,3-tetrafluoropropyloxy to different positions and by introducing a central metal ion (i.e. Ni 2+, Zn 2+, and Cu 2+). The responses to low concentrations of organic compounds such as hydrocarbons and chlorocarbons dissolved in water were recorded. The materials were very sensitive to the tested compounds with detection limits in the lower parts-per-million range and they exhibited a good sensing performance as the sensors have been working fully reversibly and reliably over long periods of time. Besides, the influence of substitution pattern and choice of central metal ion on the liquid sensing properties of Pcs were studied for the first time. The results show that the responses differ notably from each other depending on the modifications made to the Pc. Finally, it is demonstrated that the gas and liquid sensing responses of the materials are highly correlated and can be linked to each other with the help of a basic physical model.

Influence of Substitution Pattern on Solution Behavior of Hydroxypropyl Methylcellulose

Industrially produced hydroxypropyl methylcellulose (HPMC) is a chemically heterogeneous material, and it is thus difficult to predict parameters related to function on the basis of the polymer's average chemical values. In this study, the solution behavior of seven HPMC batches was correlated to the molecular weight, degree of substitution, and substituent pattern. The initial onset of phase separation, so-called clouding, generally followed an increased average molecular weight and degree of substitution. However, the slope of the clouding curve was affected by the substitution pattern, where the heterogeneously substituted batches had very shallow slopes. Further investigations showed that the appearance of a shallow slope of the clouding curve was a result of the formation of reversible polymer structures, formed as a result of the heterogeneous substituent pattern. These structures grew in size with temperature and concentration and resulted in an increase in the viscosity of the solutions at higher temperatures.

Influence of substitution pattern and cation binding on conformation and activity in heparin derivatives.

As model compounds for the biologically important heparan sulfate, eight systematically modified heparin derivatives were studied by synchrotron radiation circular dichroism (SRCD), which is sensitive to uronic acid conformation. Substitution pattern altered uronic acid conformation, even when structural changes were made in adjacent glucosamine residues (e.g. 6-O-desulfation) and did not involve a chromophore. SRCD spectra of these derivatives following conversion to the Na+, K+, Mg2+, Ca2+, Mn2+, Cu2+ and Fe3+ cation forms revealed that almost all substitution/cation combinations resulted in unique spectra, showing that each was structurally distinct. The detailed effects that binding Na+, K+, Mg2+ and Ca2+ ions had on a 2-de-O-sulfated derivative was also studied by NMR, revealing that subtle changes in conformation (by NOE) and flexibility (by T2 measurements) resulted. Conversion to the K+ and Cu2+ ion forms also drastically modified biological activity, from inactive to active, in a cell-based assay of fibroblast growth factor-receptor (FGF2/FGFR1c) signalling and this effect was not reproduced by free cations. These observations could explain the often-contradictory data concerning structure-activity relationships for these derivatives in the literature and, furthermore, argue strongly against the established trend of considering sequence as a complete structural definition. It also provides additional means of modifying the activity of these polysaccharides and suggests a possible additional level of control in biological systems. There are also obvious potential applications for these findings in the biotechnology sphere.

Mass Spectrometry of β-Ketoesters. Some Evidence of Their Tautomerism

Mass spectrometric evidence of tautomerism is reported for beta-ketoesters. The analysis of the corresponding mass spectra has allowed specific assignment of fragment ions to tautomers. The predictive value of this methodology is supported by the influence of substitution pattern of these compounds on these equilibria. Experimental data are strongly supported by Austin Model 1 semiempirical calculations indicating that mass spectrometry could be resourced as a tool for the investigation of tautomerism of neutral species in the gas phase.

New Phenyl-Substituted PPV Derivatives for Polymer Light-emitting Diodes−Synthesis, Characterization and Structure−Property Relationship Study

Three new PPV derivatives with dialkoxyphenyl substituents, BEH2P−PPV, BEH3P−PPV, and BEH4P−PPV have been synthesized. The polymers were characterized by FT-IR, 1H NMR, and elemental analysis. The polymers possess excellent solubility, high molecular weights, high photoluminescence efficiencies and good thermal stability. The influence of substitution pattern on the formation of structural defects has been investigated by measuring the signal due to tolane−bisbenzyl moieties (TBB) in the proton NMR spectra. BEH2P−PPV with a steric phenyl group at the ortho-position on the side phenyl ring shows the lowest amount of TBB, which indicates suitable steric hindrance can be applied to suppress the formation of irregular head-to-head and tail-to-tail linkage in the polymer chains. In addition, the polarity of solvents used for the Gilch polymerization will also affect the amount of irregular structure in the polymers. Polar solvents such as THF will result in polymers with low TBB content. Energy level measurement from cyclic voltammetry revealed that the influences of the substitution pattern on the HOMOs and LUMOs are different. The three polymers possess similar HOMO energy levels while the LUMO of BEH4P−PPV is much higher than that of the other two polymers. Polymer light-emitting diodes fabricated from BEH2P−PPV, BEH3P−PPV, and BEH4P−PPV with the configuration of ITO/PEDOT/polymer/Ba/Al, emitted bright blue-green to green light with the maximum peaks at 496, 488, and 525 nm, respectively. The turn-on electric field and maximum external quantum efficiencies of the diodes are 0.30, 0.50, and 0.42 MV/cm and 0.37%, 0.66%, and 0.25% respectively. The quantum efficiency is mainly determined by the electron injection from the cathode. With the highest luminance, lowest turn-on electric field, and good quantum efficiency as well as negligible structural defects, BEH2P−PPV is the most promising material among the three polymers for polymer light-emitting diodes.

Alkyne metathesis with simple catalyst systems: High yield dimerization of propynylated aromatics; scope and limitations

High yield dimerization of propynylated benzenes and propynylnaphthalene by a mixture of Mo(CO) 6 and 4-chlorophenol at 140 °C in 1,2-dichlorobenzene is reported to give the corresponding disubstituted alkynes. The scope and limitation of the reaction and the influence of substitution pattern and substitution type are discussed. Oxygen or nitrogen carrying substrates metathesize in moderate to good yields and ortho-alkyl substituted examples form the respective tolanes very efficiently.

Photohydrolysis of a Halophenol in Sunlight: Critical Influence of Substitution Pattern

While the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) is comparatively stable in sunlight, its positional isomer, 3,5-dibromo-2-hydroxybenzonitrile, degrades rapidly via a highly selective photoaromatic substitution reaction, illustrating a critical influence of substitution pattern on electronic absorption properties and photochemical behaviour.

Long‐range proton‐carbon coupling constants. Part II—norbornene systems

AbstractLong‐range proton‐carbon coupling constants, nJCH, were measured for some simple norbornene derivatives. Among the influence of substitution pattern, a study of the experimental influence of the double bond in the norbornene skeleton on 2JCH and 3JCH was made, taking into account the previously published experimental data for analogous saturated systems. These experimental data show that structural groups which are several bonds away from the coupling sites, but close in space, can provide important alternative mechanisms for transmission of the heteronuclear coupling.

N=N Vibrational Frequencies and Fragmentation Patterns of Substituted 1-Aryl-3,3-Dialkyl-Triazenes: Comparison with other High-Nitrogen Compounds

The influence of substitution pattern and electronic structure on the N=N stretching frequencies of compounds containing three to six linearly connected nitrogen atoms has been investigated by FT-IR and Raman spectroscopy. For a series of 1-phenyl-3,3-dialkyl-triazenes, Phe-N1=N2-N3 R2, shifts in the two valence vibrations of the triazeno group are studied with respect to the type and position of substituents at the aromatic ring, and for various alkyl substituents at N3. The N1=N2 stretching frequency is lowered by electron-withdrawing substituents at the aromatic ring; this effect is most pronounced for para-positioned substituents. A decrease in the N1=N2 bond order, and of the associated valence vibration, is also observed upon introduction of heavier N3-alkyl substituents, due to an inductive effect. Changes in vibrational frequencies are correlated with characteristic fragmentation patterns in the mass spectra of these compounds, where two degradation routes subsequent to ionization at the nitrogen atoms N1 and N2 have been observed. For the investigated pentazadiene derivatives, a weaker dependence of the N=N vibrational frequencies on the substituents is found. Mass spectra are interpreted in terms of two typical fragmentation pathways, involving a McLafferty rearrangement.

Synthesis and activities of new arylsulfonamido thromboxane A 2 receptor antagonists

New benzoic, benzeneacetic and thiazole-4-acetic acids bearing an arylsulfonamido alkyl or alkylhetero side chain were synthesized and tested in vitro for affinity for human platelet thromboxane A 2 receptors and inhibition of U46619-induced rat aortic ring contraction. Influence of substitution patterns, chain length and presence of heteroatoms were studied and compounds within a 30 nmol range for inhibition of U46619-induced contractions were found. One of the most potent, 2-[(4-chloro-benzenesulfonylaminoethyl)thio] thiazole-4-acetic acid ( VII-4) was orally active (1 mg/kg), as evidenced by the inhibition of U46619-induced platelet aggregation in guinea pigs, ex vivo.

Influence of substitution pattern on the benzenoid transitions: Quantitative evaluation of the electronic and vibrational components from new experimental polarization data

The influence of substitution on the benzenoid 1Lb, 1La and 1B transitions is studied by the technique of linear dichroism in stretched polyethylene films.The total intensity of the 1Lb system is resolved into induced and vibrational components and the influence of various substitution patterns on the magnitude and polarization of both components is analyzed quantitatively. As expected from theoretical considerations, the vibrational components like the induced intensity are found to be strongly affected by the substituent strength and the symmetry of substitution pattern. The previously accepted assumption, according to which the vibrational intensity is regarded as a constant, appears to be completely unrealistic when dealing with cases of strong substituents. A satisfactory quantitative treatment of both weak and strong substituents using the same simple theoretical approach seems possible only if the systematic variations observed in the vibrational intensity are not neglected.A qualitative analysis is given for the 1La, and 1B systems. The results are compared with available theoretical predictions and previous experimental data.Practical implications of the present new experimental information to the study of aromatic optical activity are discussed.