Natural surfactant mediated bioremediation approaches for contaminated soil.

The treatment of environmental pollution by employing microorganisms is a promising technology, termed bioremediation, which has several advantages over the other established conventional remediation techniques. Consequently, there is an urgent inevitability to develop pragmatic techniques for bioremediation, accompanied by the potency of detoxifying soil environments completely. The bioremediation of contaminated soils has been shown to be an alternative that could be an economically viable way to restore polluted soil. The soil environments have long been extremely polluted by a number of contaminants, like agrochemicals, polyaromatic hydrocarbons, heavy metals, emerging pollutants, etc. In order to achieve a quick remediation overcoming several difficulties the utility of biosurfactants became an excellent advancement and that is why, nowadays, the biosurfactant mediated recovery of soil is a focus of interest to the researcher of the environmental science field specifically. This review provides an outline of the present scenario of soil bioremediation by employing a microbial biosurfactant. In addition to this, a brief account of the pollutants is highlighted along with how they contaminate the soil. Finally, we address the future outlook for bioremediation technologies that can be executed with a superior efficiency to restore a polluted area, even though its practical applicability has been cultivated tremendously over the few decades.

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.

Copper-phenanthroline catalysts for regioselective synthesis of pyrrolo[3',4':3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and of pyrrolo[1,2-a]phenanthrolines under mild conditions.

A new series of pyrrolo[3',4':3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and pyrrolo[1,2-a]phenanthrolines were efficiently built up from an 8-hydroxyquinoline derivative or phenanthroline via 1,3-dipolar cycloaddition reaction involving non-stabilized azomethine ylides, generated in situ from the parent furo[3,2-h]quinoliniums/phenanthroliums, in presence of a copper(II) chloride-phenanthroline catalytic system. The methodology combines general applicability with high yields.

Unichromophoric platinum-acetylides that contain pentiptycene scaffolds: torsion-induced dual emission and steric shielding of dynamic quenching.

The effect of the rigid bulky pentiptycene scaffolds on the photoluminescence, redox properties, and oxygen sensing behavior of unichromophoric Pt-acetylides is reported. When the pentiptycene groups are near the Pt(PBu3)2 center, the Pt-acetylides display both blue fluorescence and green phosphorescence with long phosphorescence lifetimes (90-202 µs) in THF. Their phosphorescence intensity is highly sensitive to molecular oxygen, and the emission color depends on the concentration of not only oxygen but also the complexes, which allows a feasible determination of oxygen in the range of 1-5% air volume. The dynamic quenching rate constants decrease linearly with increasing the number of pentiptycene groups, revealing the steric shielding effect of the peripheral rings of pentiptycene. A dependence of oxidation potential on the number of pentiptycene groups also revealed the steric shielding effect on the electron transfer between the complexes and the electrode. In a PMMA matrix, the dual emissive properties are diminished due to increased phosphorescence and decreased fluorescence intensity, and the phosphorescence lifetimes are significantly increased (up to ∼700 µs), leading to an "on-off" optical response to oxygen concentration. Both the dual emissive properties and long-lived triplet excitons are attributed to diminished spin-orbit couplings caused by twisting and steric shielding of the π-conjugated backbone around the Pt center.

Pentiptycene building blocks derived from nucleophilic aromatic substitution of pentiptycene triflates and halides.

The nucleophilic aromatic substitution (S(N)Ar) reactions of the nitro-substituted pentiptycene triflate 15 with LiBr and LiI and the resulting halides 18 and 19 with N(3)(-), CN(-), and ArS(-) in DMF provide an efficient route toward pentiptycene halides and dihalides and other new pentiptycene building blocks. The reactivity of diaminopentiptycene in Pd-catalyzed C-N coupling reactions is also demonstrated.

(2S,4S)-3-Acryloyl-6-oxo-2-phenyl-perhydro-pyrimidine-4-carboxylic acid.

In the title compound, C(14)H(14)N(2)O(4), the central six-membered ring adopts a twisted boat conformation with the phenyl substituent occupying an orthogonal position [dihedral angle = 86.88 (11)°]. In the crystal, mol-ecules are linked by carboxylic acid-carbonyl O-H⋯O and amide-carbonyl N-H⋯O hydrogen bonds, forming a three-dimensional network.