Fluorescence modulation of naphthalene containing salicyl hydrazide-based receptor through aggregation-induced emission enhancement approach: Dual detection of lanthanum and cyanide ions in semi-aqueous medium.

The sensing activity of naphthalene containing salicyl hydrazide-based fluorescence receptor has been improved through aggregation-induced enhanced emission mechanism approach in semi-aqueous medium. The receptor has been found to be selective toward La3+ with approximately 70-fold fluorescence enhancement due to a combined effect of keto-enol tautomerism inhibition and chelation enhanced fluorescence with a detection limit of 3.91 × 10-6 M. In addition, the receptor is also able to sense CN- with a detection limit of 3.55 × 10-6 M via deprotonation effect, justifying its multiple analyte sensing behaviour. Hence, the current analytical methodology improves the sensing activity of the probe and also provides a greener alternative for La3+ and CN- detection.

Interaction of ribonucleotides with metal hexacyanocobaltate(III): a possible role in chemical evolution.

It has been proposed that metal cyanide complexes would have acted as effective prebiotic catalysts. Insoluble metal cyanide complexes could have concentrated biomonomers from the dilute prebiotic soup, facilitating certain prebiotic reactions. In the light of the above hypothesis, interaction of four ribonucleotides, namely 5'-AMP, 5'-GMP, 5'-CMP, and 5'-UMP with copper(II)- and cadmium(II) hexacyanocobaltate(III) has been studied. The interaction was found to be maximum at neutral pH. 5'-GMP showed greater interaction with both the metal hexacyanocobaltate(III) while copper(II) hexacyanocobaltate(III) showed greater uptake than cadmium(II) hexacyanocobaltate(III) for all the four ribonucleotides studied. Infrared spectral studies of ribonucleotides, metal hexacyanocobaltate(III) and ribonucleotide - metal hexacyanocobaltate(III) adducts indicated that the nitrogen base and phosphate moiety of ribonucleotides interact with outer divalent metal ion present in the lattice of metal hexacyanocobaltate(III).

Interaction of tryptophan and phenylalanine with metal ferrocyanides and its relevance in chemical evolution.

The interaction of two naturally occurring aromatic alpha-amino acids, namely, tryptophan and phenylalanine, with zinc, nickel, cobalt, and copper ferrocyanides has been studied. Both amino acids showed a high adsorption affinity toward metal ferrocyanides at neutral pH (7.0). Adsorption trends followed the Langmuir adsorption isotherm. Values of the Langmuir constants K(L) and X(m) suggest tryptophan is a better adsorbate than phenylalanine. Zinc ferrocyanide showed the highest adsorption, while the minimum adsorption was found in the case of copper ferrocyanide. Infrared spectral studies of adsorbate, adsorbent, and adsorption adducts indicate that adsorption occurs because of the interaction of adsorbate molecules with outer divalent metal ions present in the lattice of metal ferrocyanides. The present investigation supports the hypothesis that metal ferrocyanides might have concentrated the biomonomers on their surface in primeval seas during the course of chemical evolution.

Adsorption and oxidation of aniline and anisidine by chromium ferrocyanide.

The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.